Recent Trends in Constructed Wetlands for Industrial Wastewater Treatment 9819925630, 9789819925636

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Maulin P. Shah   Editor

Recent Trends in Constructed Wetlands for Industrial Wastewater Treatment

Recent Trends in Constructed Wetlands for Industrial Wastewater Treatment

Maulin P. Shah Editor

Recent Trends in Constructed Wetlands for Industrial Wastewater Treatment

Editor Maulin P. Shah Environmental Microbiology Lab Gujarat, India

ISBN 978-981-99-2563-6 ISBN 978-981-99-2564-3 (eBook) https://doi.org/10.1007/978-981-99-2564-3 © The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 This work is subject to copyright. All rights are solely and exclusively licensed by the Publisher, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmission or information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed. The use of general descriptive names, registered names, trademarks, service marks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. The publisher, the authors, and the editors are safe to assume that the advice and information in this book are believed to be true and accurate at the date of publication. Neither the publisher nor the authors or the editors give a warranty, expressed or implied, with respect to the material contained herein or for any errors or omissions that may have been made. The publisher remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. This Springer imprint is published by the registered company Springer Nature Singapore Pte Ltd. The registered company address is: 152 Beach Road, #21-01/04 Gateway East, Singapore 189721, Singapore

Contents

Textile Wastewater Treatment: Possible Approaches with an Emphasis on Constructed Wetlands . . . . . . . . . . . . . . . . . . . . . . . . . . Christy K Benny and Shweta Singh

1

Constructed Wetland for Metals: Removal Mechanisms and Analytical Challenges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ankita Chatterjee and Maulin P. Shah

31

Role of Aerated Constructed Wetlands for Municipal Wastewater Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pooja M. Patil, Rasiya C. Padalkar, Abhijeet R. Matkar, Ranjit Gurav, and Maruti J. Dhanavade

43

Constructed Wetlands for Remediating Organic Hydrocarbons: An Approach for the Sustainable Environmental Cleanup . . . . . . . . . . . . . Ritu Rani, Jitender Rathee, Nater Pal Singh, and Anita Rani Santal

71

Constructed Wetlands as an Effective Tool for Textile Effluent Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bishwarup Sarkar and Sougata Ghosh

91

Constructed Wetland-Microbial Fuel Cell for Wastewater Treatment and Energy Recovery: An Emerging Technology . . . . . . . . . . . 107 Anamika Yadav, Shravankumar S. Masalvad, and Dipak A. Jadhav Aerated Constructed Wetlands for Treatment of Food Industry Wastewater . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 Rym Salah-Tazdaït and Djaber Tazdaït Use of Algae in Wastewater Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 Nermin El Semary Constructed Wetlands: The Traditional System . . . . . . . . . . . . . . . . . . . . . . 177 Adrija Ghosh, Jonathan Tersur Orasugh, and Dipankar Chattopadhyay

v

vi

Contents

The Need for Auto-Tailored Wetlands for the Treatment of Untampered Wastes of Wineries and Breweries . . . . . . . . . . . . . . . . . . . . 197 Bedaprana Roy, Debapriya Maitra, Bidisha Chatterjee, Pallab Ghosh, Jaydip Ghosh, and Arup Kumar Mitra Horizontal Subsurface Flow Constructed Wetlands for Toxic Pollutants Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213 L. E. Amábilis-Sosa, A. Roé-Sosa, J. M. Barrera Andrade, A.d. C. Borja-Urzola, and M. G. Salinas-Juárez Microbial Consortium for the Treatment of Brewery Effluents-Recommendation for Brewery Effluent Treatment in Constructed Wetlands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239 Priya Kannan, Bhargavi Subramanian, Arunmozhi Bharathi Achudhan, Annapurna Gupta, and Lilly M. Saleena In-silico Integration in Environmental Remediation . . . . . . . . . . . . . . . . . . 249 Arunmozhi Bharathi Achudhan, Madhumitha Masilamani, Priya Kannan, and Lilly M. Saleena

Textile Wastewater Treatment: Possible Approaches with an Emphasis on Constructed Wetlands Christy K Benny and Shweta Singh

1 Introduction The textile industry is one of the most water-intensive industries known, contributing significantly to water contamination. The textile processing operation includes various stages such as desizing, scouring, bleaching, mercerizing, dyeing, printing and finishing. The amount and composition of textile wastewater are determined by different parameters, including the processed fabric and process type. Approximately 1,000–3,000 m3 of wastewater is produced after processing about 12–20 tonnes of textiles per day (Ghaly et al. 2014). It contains high levels of colour, COD, BOD, pH, temperature and toxic chemicals (Verma et al. 2012). Dyeing operation accounts for a large portion of the industry’s total wastewater generation. Spent dye bath and wash water are the major sources of dyeing effluents, and the wastewater contains residual dyes, salts, metals, surfactants, etc. (Dos Santos et al. 2007). Azo dyes constitute about 60–70% of total dyes produced and are distinguished by –N=N– chromophore, common in reactive dyes (Manu and Chaudhari 2002). Synthetic dyes are aromatic or heterocyclic compounds with stable and complex structures that make degradation difficult. Textile effluent is highly toxic, and in addition to its unappealing appearance, it has the potential to contaminate local water bodies and soil, posing a risk to the environment and human health. Textile wastewater must be adequately treated before disposal to safeguard the environment and enable recycling of the treated effluent for irrigation or reuse within the industry. Many treatment approaches, such as physico-chemical and biological processes, are developed to treat textile wastewater efficiently and cost-effectively. The main goals of any treatment procedure are to remove synthetic dyes (colour) and other C. K. Benny (B) · S. Singh Department of Civil Engineering, Indian Institute of Technology Guwahati, Guwahati 781039, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. P. Shah (ed.), Recent Trends in Constructed Wetlands for Industrial Wastewater Treatment, https://doi.org/10.1007/978-981-99-2564-3_1

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C. K. Benny and S. Singh

harmful substances from textile effluents. Physico-chemical treatment methods are simple to operate, but they are not always cost-effective and environmentally friendly. High energy consumption and the generation of many by-products and sludge that need further treatment are the bottlenecks of these methods (Bhatia et al. 2017). Biological treatment methods are developed to use the ability of microorganisms (bacteria, algae, fungi, yeasts, etc.) to flourish under various environmental conditions to degrade synthetic dyes and other pollutants. Biological processes are environmentally friendly, economically feasible, and generate less volume of sludge when compared with other techniques. Constructed wetland (CW) is a green wastewater treatment technique that has gotten a lot of attention in the last decade due to its low cost and low energy requirements (Wu et al. 2015). These treatment systems, mainly comprised of substrate, soil, microorganisms, vegetation and water, utilize physical, chemical and biological processes to remove various contaminants or improve the water quality. CWs have been used to treat several types of industrial wastewater over the past few decades, including textile effluents (Saeed and Sun 2013; Shehzadi et al. 2014; Vymazal 2014). This chapter discusses an overview of various treatment technologies for textile effluents, emphasizing constructed wetlands.

2 Textile Wastewater Characteristics Every stage of the textile manufacturing process uses a large quantity of water and chemicals. Water is mainly used for the application of chemicals to fabrics as well as the rinsing of manufactured fabrics. The amount of water varies from industry to industry, depending on the dyeing process and type of fabric used. Unused materials or chemicals from each stage of the textile processes are discharged along with wastewater (process and cleaning wastewater) with high levels of BOD, COD, TSS, TDS, temperature and various other chemicals. The chemical constituents can be synthetic dyes, starch, hydrogen peroxide, acids, alkalis, surfactants, resins, dispersing agents, solvents, enzymes, oils, waxes, etc. (Verma et al. 2012). Metals also contaminate textile wastewater due to the presence of dyes and additives (salts, sodium carbonate, sodium hydroxide, etc.). Adinew (2012) reported that metals like cobalt, copper and chromium are present within the dye chromophores, which cause environmental issues. Figure 1 presents the functions of each processing stage and a list of the numerous pollutants produced. Textile wastewater characteristics vary significantly from industry to industry and are dependent on the type and amount of chemicals used (dyes, acids, bases, surfactants, bleaching agents, etc.); type of textile processes (dyeing, mercerizing, bleaching, etc.); type of fabrics used (cotton, wool, silk, polyester, etc.); machines used (continuous, batch, jet, jiggers, etc.) and season of the year (changes related to fashion) (Pazdzior et al. 2019). Textile wastewater characteristics from the literature are given in Table 1.

Fig. 1 The functions and wastewater constituents of various stages of a textile manufacturing process (Babu et al. 2007; Verma et al. 2012; Holkar et al. 2016)

Textile Wastewater Treatment: Possible Approaches with an Emphasis … 3

1,953

a BDL:

232–990

below detection limit

276–1,379

–

99–350

3.9–11.4

–

320–925

344

172–450

92

7.4–12.9

150–1,200

752–1,120

6.8

–

–

9

–

7.1

7–9

708

368–458

7.8–9.6

806

1,714

–

–

10

COD (mg L−1 )

6.9

BOD (mg L−1 )

pH

–

0.69–13.8

0.47

3.2–8.1

–

0.74

3.84

–

12.5

1.83

Conductivity (mS cm−1 )

–

76–1,777

330

–

50–2,500

–

–

200–260

–

300

Colour (Pt–Co)

–

–

338

90–800

1,000–1,600

–

125

384–452

–

270

Chloride (mg L−1 )

Table 1 Characteristics of textile wastewater studied by various researchers

76–2,200

–

227

216–673

–

–

28

320–380

–

387

SO4 2− (mg L−1 )

–

–

–

0.07–4.01

–

9.3–19

–

0.2–4.5

0.47–50.8

–

–

–

–

5–10

a BDL-1.8

–

1.7

–

NH4 + −N (mg L−1 )

16.8

–

PO4 3− (mg L−1 )

–

1.2–5.6

1.9

20–24

–

–

–

–

3.6

–

NO3 − −N (mg L−1 )

Bulc and Ojstrsek (2008)

Lim et al. (2010)

Almazan-Sanchez et al. (2016)

Shehzadi et al. (2014)

Turhan and Turgut (2009)

Un and Aytac (2013)

Aouni et al. (2012)

Manekar et al. (2014)

Punzi et al. (2015)

Buscio et al. (2015)

References

4 C. K. Benny and S. Singh

Textile Wastewater Treatment: Possible Approaches with an Emphasis …

5

3 Environmental Impacts of Textile Wastewater Textile wastewater causes substantial damage to the environment and human health if disposed without any treatment or with partial treatment. The discharge of textile effluent colourizes surface waterbodies, and local residents may not tolerate an aesthetically displeasing appearance. Colour prevents sunlight penetration into waterbodies, thereby disrupting the photosynthetic function of aquatic plants. Dyes and other contaminants accumulate in soil around the discharge location, and leaching of these pollutants may impact groundwater systems (Khaled et al. 2009). Textile effluent can reduce carbohydrate, protein and chlorophyll contents of plants if used for irrigation. Most dyes and their decomposition products or intermediates are highly toxic to aquatic flora and fauna. Dyes may undergo chemical and biological assimilations, consume dissolved oxygen and intercept re-oxygenation of receiving waterbodies. Dyes can also sequester metal ions, resulting in genotoxicity and microtoxicity. Some studies on azo dyes showed their linkage with cancers of different organs (bladder, spleen, liver, etc.) in model organisms and chromosomal abnormalities in mammalian cells (Bhatia et al. 2017). In a broader sense, prolonged exposure to coloured textile effluents may cause immune suppression, circulatory, respiratory and neurobehavioral disorders presage as allergy, multiple myeloma, autoimmune diseases, leukemia, hyperventilation, vomiting, insomnia, salivation, profuse diarrhea, cyanosis, quadriplegia, jaundice, tissue necrosis, eye and skin infections, etc. (Foo and Hameed 2010). Benzidine, a well-known carcinogen and parent component of most azo dyes, poses a greater threat to living organisms (Golka et al. 2004). It is reported that Malachite Green (MG) can cause serious harm to human immune and reproductive systems (Sudova et al. 2007). Human bladder cancer has been reported to be stimulated by 1-amino-2-naphthol, which is formed by the reduction of Acid Orange 7 (Khan and Banerjee 2010). Amaranth, an azo dye widely used as a food colourant in many countries, was found to be carcinogenic in rats (Andrianova 1970). Dyes can persist in the aquatic environment for a long time due to high photo and thermal stability. For example, Reactive Blue 19 can remain in the water for many years (46 years of half-life) at 25 °C and pH 7.0 (Carmen and Daniela 2012).

4 Textile Wastewater Treatment Textile wastewater must be treated before being discharged into waterbodies as it severely degrades the water quality. Many treatment approaches, such as physicochemical and biological processes, can be used to treat it efficiently.

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C. K. Benny and S. Singh

4.1 Physico-chemical Treatment Methods There are different types of physico-chemical treatment methods such as coagulationflocculation, adsorption, membrane techniques, electrocoagulation and chemical oxidation processes. Some of them are described below and summarized in Table 2. Coagulation-flocculation is the most commonly used treatment method in developed and developing countries, regardless of the large amount of sludge generated that must be treated again. It is a complex process involving various inter-related parameters. Therefore, it is essential to define how well a coagulant will perform under a particular set of conditions. Pre-hydrolysed coagulants such as poly aluminium chloride (PAC), poly aluminium ferric chloride (PAFC), poly ferrous sulphate (PFS) and poly ferric chloride (PFC) are reported to be more effective than metallic salts like aluminium sulphate (alum), ferric chloride and ferric sulphate. They are effective even at low temperatures and produce less sludge volume. The most critical parameters to consider in coagulation are pH, the concentration of applied metal ions (coagulant), mixing speed and time, temperature and retention time (Verma et al. 2012). Various natural coagulants produced by plants or animals have been examined by many researchers (Lea 2010; Mahmoodi et al. 2011). Natural coagulants may also prove their effectiveness if used as coagulant aids along with chemical coagulants (Sanghi et al. 2006). Golob et al. (2005) investigated the coagulation-flocculation process to decolourize textile effluent comprising reactive and acid dyes. They examined the combination of alum with a cationic organic flocculent and obtained almost complete colour removal with a reduction in TOC (50%) and COD (45%). Sanghi et al. (2006) used the water-soluble, non-ionic, high molecular weight seed gums Ipomoea dasysperma (ID) and guar gum (GG) as coagulants to study dye decolourization from synthetic dye solutions. The dye mixture contained Direct Orange (DO), Acid Sandolan Red (ASR) and Reactive Procion Brilliant Blue RS (PBB). ID and GG alone were effective for the decolourization of DO (51 and 65%), and in combination with PAC, colour removals were increased for all kinds of dyes (70–87%). They concluded that plant-based natural coagulants like ID and GG, which are biodegradable and safe for human health, could be used to replace conventional coagulants like PAC. Adsorption is one of the most commonly used removal strategies, owing to its ease of use and insensitivity to toxic pollutants. Even though adsorption generates highquality treated water, the problem lies in selecting the most suitable adsorbent. The use of adsorbents has been restricted due to the issues with regeneration, dumping, sludge production and the cost of the adsorbent (Holkar et al. 2016). Zhong et al. (2011) investigated the use of modified wheat residue (MWR) as a sorbent to remove Reactive Red 24 (RR24) from an aqueous solution. MWR had a maximum sorption capacity of 200 mg g−1 for RR24, comparable to commercial activated carbon. When 2.0 g L−1 of sorbent was utilized, colour removal was above 95% over a dye concentration range of 50–200 mg L−1 . For membrane techniques such as ultrafiltration (UF), nanofiltration (NF) and reverse osmosis (RO), it is necessary to consider the constituents and temperature

Conditions

• Dye removal using water-soluble, non-ionic, high molecular weight seed gums Ipomoea dasysperma (ID) and guar gum (GG) • Dye mixture contained Direct Orange (DO), Acid Sandolan Red (ASR) and Reactive Procion Brilliant Blue RS (PBB)

Coagulation-flocculation • Removal of reactive and acid dyes using alum and cationic organic flocculants

Physico-chemical methods

Type of process References

• Colour removal in the order Sanghi et al. of DO, ASR and PBB dyes (2006) ID alone: 51%, 31%, 20% GG alone: 65%, 45%, 14% ID + a PAC combined: 80%, 87%, 70% GG + PAC combined: 73%, 86%, 75%

• Almost complete reduction Golob et al. of colour (98%) (2005) • TOC reduced by 50%, COD by 45% and biodegradability increased by 50% • Optimum coagulant dosage: 20 mg L−1 • Optimum pH: near to neutral

Results

Table 2 Physico-chemical and biological methods for the treatment of textile wastewater Disadvantages

(continued)

• Simple and • Low decolourization inexpensive efficiency • Convenient and safe • Slow process, poor operations settling and aggregation of • Dewatering qualities precipitates • Large chemical requirement • Excessive sludge production which needs further treatment

Advantages

Textile Wastewater Treatment: Possible Approaches with an Emphasis … 7

• UF followed by RO • Removal after UF: TOC for treating textile 37%, COD 42%, phenols printing wastewater 71%, TP 59%, NH4 + −N containing reactive 66% and colour 63–70% • Final removal after RO: dyes COD 94%, BOD 95%, • Membrane materials: phenols 98%, TOC 85%, tubular ceramic TP 97% and colour 99% membrane module for UF and polyether sulfone membrane of spiral wound type for RO

Membrane separation

References

Sostar-Turk et al. (2005)

• Maximum sorption capacity Zhong et al. of MWR:200 mg g−1 (2011) • 95% RR24 sorption for 50–200 mg L−1 dye level

• Modified wheat residue (MWR) used as sorbent to remove Reactive Red 24 (RR24) dye

Results

Conditions

Type of process

Adsorption

Table 2 (continued) • Difficulties in regeneration • Costly disposal of adsorbent • Excessive maintenance costs • Requirement of pretreatment to reduce suspended solids

Disadvantages

(continued)

• Less space • Expensive requirement • Production of • Removal of all types concentrated sludge of dye • Frequent membrane fouling • Requirement of different pretreatments

• Excellent removal of different types of dyes • Cheap and inexpensive materials • Less sludge generation

Advantages

8 C. K. Benny and S. Singh

Advantages

• Degradation of dye • Colour (95–99%) and COD Sarayu et al. mixture containing removals were effective at (2007) eight reactive dyes pH 10 with concentrations 50–500 mg L−1 using ozone • Semi-batch reactor was used

• Degradation of Reactive Green 19 (RG19) dye using UV/H2 O2

• High cost of electricity • Generation of secondary pollutants • Less electrode reliability

Disadvantages

(continued)

• Removes most of the • Expensive complex organic and • Iron sludge generation inorganic chemicals in Fenton process present in textile effluent • Faster process • No electricity requirement

• Complete decolourization Zuorro and in 20 minute Lavecchia (2014) • TOC removal: 63% in 90 minute • Optimum conditions: UV radiation 1,500 µW cm−2 , H2 O2 concentration 30 mM and pH 6.5

References

Advanced oxidation process (AOP)

Results • Maximum colour removals Ayhan Sengil and • Both soluble and for DB56 and BY28 were Ozdemir (2012) insoluble dyes can 86.2 and 99.9% be removed • Optimum conditions: pH 7, • Less chemical initial dye concentration requirement 100 mg L−1 , current density 10.89 mA cm−2 , salinity 3,000 mg L−1 and distance between electrodes 2.2 cm • 10 minute electrolysis time for colour removal

Conditions

Electro-coagulation (EC) • Removal of colour from solution containing Disperse Blue 56 (DB56) and Basic Yellow 28 (BY28) dyes • Iron electrodes were used

Type of process

Table 2 (continued)

Textile Wastewater Treatment: Possible Approaches with an Emphasis … 9

• 100% decolourization observed within 24 h under pH 8 and temperature 50 °C • Metabolites obtained after biotransformation were naphthalen-1-yldiazene, naphthalene, 1-(2-methylphenyl)-2-phenyldiazene and diphenyldiazene • Optimum conditions: pH 3.0, temperature 30 °C, algae concentration 0.5 g L−1 • Almost complete removal for concentration less than 25 mg L−1 • Decolourization rate increased with increase in temperature (5–45 °C) • Colour removal of 92.4% at pH 9

• Lichen Permelia perlata used for degradation of Solvent Red 24 (SR24) dye • Laccase was responsible for biotransformation

• Acid Red 274 (AR274) removed by Spirogyra rhizopus (green algae) • Batch mode study

• Malachite Green (MG) degraded by Cosmarium species (green algae) • Batch mode study

• Optimum conditions: pH 7 and temperature 37 °C • Decolourization efficiency: 90% at 24 h

• Maximum decolourization 98% on 3rd day • Rate of decolourization decreased with increase in dye concentration

Results

• Degradation of Amido Black 10B dye using white-rot fungus Phanerochaete chrysosporium • Extracellular enzymes lignin peroxidase, manganese peroxidase and laccase responsible for degradation

Conditions

Bacterial biodegradation • Decolourization of Reactive Blue 19 (RB19) using (pure culture) Enterobacter sp. isolated from anaerobic digester • Anaerobic conditions

Algal biodegradation

Fungal biodegradation

Biological methods

Type of process

Table 2 (continued)

(continued)

Holkar et al. (2014)

Daneshvar et al. (2007)

Ozer et al. (2006)

Kulkarni et al. (2014)

Senthilkumar et al. (2014)

References

10 C. K. Benny and S. Singh

Results • 100% RO13 decolourization after 24 h • Degradation products: naphthalene and 6-[(4-chloro-1,3,5-triazin-2-yl) amino]-2-iminonaphthalen-1(2H)-one

Conditions

• Degradation of Reactive Orange 13 (RO13) by isolated bacterial strain Alcaligenes faecalis • Static anoxic conditions

a PAC:

Polyaluminum chloride

• Bacterial mixed culture (six bacterial strains of Bacillus, Lysinibacillus and Ochrobacterium) for decolourization of Reactive Violet 5R (RV5R) • Static conditions

• Optimum conditions: pH 7 and temperature 37 °C • Complete decolourization of RV5R (200 mg L−1 ) within 18 h

Bacterial biodegradation • Degradation of textile effluent and Reactive Orange • Optimum conditions: pH 7 and temperature 30 °C (mixed culture) 16 (RO16) dye using microbial consortium • Complete decolourization of textile effluent and consisting three bacterial species (Pseudomonas) RO16 (100 mg L−1 ) within 48 h • Static anaerobic conditions

Type of process

Table 2 (continued)

Jain et al. (2012)

Jadhav et al. (2010)

Shah et al. (2012)

References

Textile Wastewater Treatment: Possible Approaches with an Emphasis … 11

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C. K. Benny and S. Singh

of wastewater for the choice of filter and its permeability. Membrane separation procedures are expensive and produce waste that must be treated further (Holkar et al. 2016). UF and RO units were employed by Sostar-Turk et al. (2005) to remove reactive dyes from textile printing wastewater. Pollutant levels were dropped after UF, i.e., TOC by 37%, COD by 42%, phenols by 71%, TP by 59%, NH4 + −N by 66% and colour by 63–70%. RF was installed after UF as the measured parameters did not meet the required concentration for discharge into water. After RO, COD was reduced by 94%, BOD by 95%, phenols by 98%, TOC by 85%, TP by 97% and colour by 99%. They concluded that UF followed by RO has been very effective in wastewater treatment after reactive printing. Electrocoagulation (EC) can effectively remove both soluble and insoluble dyes, but the high cost of electricity and the generation of secondary pollutants from chlorinated organics and heavy metals are the key drawbacks. Ayhan Sengil and Ozdemir (2012) examined EC technology for colour removal from a solution containing Disperse Blue 56 (DB56) and Basic Yellow 28 (BY28). The results indicated that dyes were effectively removed when iron electrodes were used as a sacrificial anode. The optimum colour removals for DB56 and BY28 were 86.2 and 99.9%, respectively, under initial pH 7, initial dye concentration 100 mg L−1 , current density 10.89 mA cm−2 , salt concentration 3000 mg L−1 and distance between electrodes 2.2 cm. It was also found that about 10 min of electrolysis time was required to remove the colour from the dye solution. Chemical oxidation methods have the potential to degrade hazardous dyes completely or partially. Advanced oxidation processes (AOPs) are more famous for treating textile effluents among various chemical oxidation methods. AOPs are a highly competitive treatment approach for eliminating organic pollutants that are ineffectively treated by traditional methods due to their limited biodegradability (dyes are chemically or structurally stable and therefore difficult to destroy). AOPs produce hydroxyl radicals that are more powerful than conventional oxidizing agents like potassium permanganate and hydrogen peroxide. AOPs include Fenton chemistry (reaction between Fe+3 and H2 O2 ) and photocatalytic oxidation (activation of semiconductor catalyst using sunlight). Dye degradation can also be achieved using oxidizing agents such as O3 + H2 O2 and UV light + H2 O2 due to the generation of significant quantities of hydroxyl radicles. These methods do not increase the volume of wastewater or produce sludge, but they need a lot of electrical energy (Oller et al. 2011). Sarayu et al. (2007) experimented with the ozonation process to degrade the dye mixture containing eight reactive dyes (concentrations ranging between 50 and 500 mg L−1 ). The authors found that maximum colour and COD removals were attained at pH 10 and an ozone dose of 4.33 mg L−1 for 30 minutes. Decolourization and COD removal rates were decreased as the dye concentrations increased from 200–500 mg L−1 . The release of nitrate, chloride and sulphate indicated oxidation and breakage of functional groups. After the ozonation process, the biodegradability (BOD/COD ratio) of the wastewater increased from 0.196 to > 0.3. The suitability of AOP (UV + H2 O2 ) for the degradation of Reactive Green 19 (RG19) azo dye was examined by Zuorro and Lavecchia (2014). Complete decolourization of the dye

Textile Wastewater Treatment: Possible Approaches with an Emphasis …

13

solution was obtained in about 20 min under optimum conditions, and TOC removal was about 63% in 90 min. They concluded that UV/H2 O2 treatment could be an effective method for removing RG19 from textile effluents.

4.2 Biological Treatment Methods Biological treatment methods are developed to use the ability of microorganisms to thrive under various environmental conditions for the degradation of pollutants. They can degrade toxic synthetic dyes to comparatively less toxic inorganic compounds by breaking bonds (i.e., chromophoric groups) and helping to remove colour. Biological processes are environmentally friendly, economically feasible, and generate a lower volume of sludge compared to physico-chemical treatment methods (Bhatia et al. 2017). Different types of biological methods currently used to treat textile effluents are described in the following section, and the summary is given in Table 2.

4.2.1

Fungal Degradation

Several studies have been conducted to treat textile wastewater using the degradation potential of various fungal species. Senthilkumar et al. (2014) studied the degradation potential of white-rot fungus Phanerochaete chrysosporium for decolourizing synthetic dye bath effluent. The researchers found that Phanerochaete chrysosporium produced extracellular enzymes such as lignin peroxidase, manganese peroxidase and laccase that degraded azo dye molecules. Maximum colour removal (98%) was obtained on the 3rd day under normal conditions, and the required optimized amounts of nutrients were glucose 0.5%, manganese sulphate 0.1% and ammonium salts 0.5%. Moreover, the addition of starch and lignin increased enzyme production and the rate of decolourization. Kulkarni et al. (2014) reported that Lichen Permelia perlata fungi degraded and decolourized (100%) Solvent Red 24 (SR24) dye under optimum conditions of pH 8 and temperature 50 °C. The laccase enzyme produced by P. perlata was responsible for the biodegradation of SR24. Various analytical techniques confirmed the presence of SR24 degradation products such as naphthalen-1-yldiazene, naphthalene, 1-(2-methylphenyl)-2-phenyldiazene and diphenyldiazene.

4.2.2

Algal Degradation

Algae can be found in freshwater and saltwater, and they have been studied extensively as biosorbents. Algae have high biosorption potential due to their large surface area and binding ability. The degradation mechanism of algae involves three steps. Initially, algae utilize dye chromophores to yield algal biomass. Algae transform chromophore material into non-chromophore material, which is finally adsorbed onto

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algal biomass. Ozer et al. (2006) studied the removal of Acid Red 274 (AR274) dye by Spirogyra rhizopus (green algae). The optimum removal conditions were pH 3, temperature 30 °C and algae concentration 0.5 g L−1 . Almost complete removal was obtained for AR274 levels less than 25 mg L−1 due to biocoagulation and biosorption. Daneshvar et al. (2007) studied the potential of Cosmarium species (green algae) for the removal of Malachite Green (MG). Decolourization was affected by dye concentration, algal concentration, pH and temperature. The decolourization rate increased with an increase in temperature for 5–45 °C, and maximum colour removal of 92.4% was obtained at pH 9.

4.2.3

Bacterial Degradation

Bacterial degradation of azo dyes occurs mainly due to the cleavage of azo bonds (–N=N–) by azoreductase enzymes under anaerobic conditions, forming colourless and toxic intermediates (aromatic amines), which can be further degraded by aerobic methods. Lade et al. (2012) evaluated the ability of a consortium containing Aspergillus ochraceus fungi and Pseudomonas sp. bacteria to decolourize and detoxify Rubine GFL dye. Under microaerophilic conditions, the consortium enhanced dye decolourization (95% removal in 30 h) without forming aromatic amines. They also found that bacterial degradation was 37% higher than fungal degradation. Dye degradation can be done using single bacterium cultures and bacterial consortia (an association of two or more bacterial groups). Individual bacterial cultures cannot completely breakdown azo dyes, and the metabolites generated may be toxic aromatic compounds that need further decomposition (Khan et al. 2014). The rate of biodegradation and mineralization of dyes are higher in the mixed culture system due to the synergy of metabolic activities of the bacterial community. A single bacterium culture may attack dye molecules at different places in a mixed culture system or consume intermediate compounds formed by another existing bacterium culture for supplementary dye degradation. One of the major drawbacks of bacterial consortia is that the biodegradation results are difficult to replicate. Physico-chemical operational parameters such as pH, temperature, oxygen, dye concentration, dye structure, carbon and nitrogen sources, amount of electron donor and redox mediator, etc., can influence bacterial degradation (Fig. 2). Some studies regarding the degradation of dyes using pure and mixed bacterial cultures are explained in the following section. Holkar et al. (2014) examined the ability of an isolated Enterobacter sp. bacterial strain to degrade Reactive Blue 19 (RB19) dye. The bacterial strain was isolated from a mixed culture from an anaerobic digester for biogas production. The decolourization efficiency of RB19 was about 90% at 24 h under optimized conditions. The degradation of Reactive Orange 13 (RO13) dye was studied by Shah et al. (2012) using an isolated bacterial strain Alcaligenes faecalis. Noteworthy induction of veratryl alcohol oxidase, tyrosinase and NADH-DCIP reductase enzymes were observed during the decolourization process, which suggested the enzymatic decolourization and degradation of RO13 dye.

Fig. 2 Effect of various physico-chemical parameters on bacterial degradation (Holkar et al. 2016)

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Jadhav et al. (2010) used a microbial consortium consisting of three bacterial species (Pseudomonas) isolated from dye wastewater contaminated sites. Complete decolourization of textile effluent and Reactive Orange 16 (100 mg L−1 ) dye solution were obtained within 48 h at pH 7 and temperature 30 °C in static conditions. Induction of laccase and reductase enzymes during dye decolourization showed their role in biodegradation. The consortium achieved higher removals of colour, BOD, COD and metal ions in much less time than pure cultures, indicating the mutual interaction among various isolates of the microbial consortium. A mixed bacterial culture (composed of six bacterial strains of Bacillus, Lysinibacillus and Ochrobacterium species) was employed to decolourize Reactive Violet 5R (Jain et al. 2012). The bacterial culture grew well in a medium containing low amount of glucose and yeast extract (1 g L−1 ) and decolourized RV5R dye (200 mg L−1 ) within 18 h.

4.2.4

Mechanism of Dye Degradation

Biodegradation of dyes can be achieved under aerobic, anaerobic or a combination of both conditions. The biodegradation process involves various metabolic pathways that affect the process rates and metabolites produced from the parent compounds. It is reported that the initial degradation of azo dyes occurs under anaerobic conditions (Nigam et al. 1996). Dye degradation is thought to be mostly an extracellular process. This hypothesis is supported by the findings that microbial excreted or artificial redox mediators (redox mediators speed up the reaction rate by transporting electrons from electron donors to electron-accepting organic compounds) catalyse the dye degradation process (Keck et al. 1997). Azo dyes do not generate carbon or energy for microbial growth. Therefore, various organic compounds or cosubstrates such as glucose, starch, acetate, ethanol, etc., are required for dye decolourization. Various aromatic compounds are generated after the initial anaerobic stage, which is colourless but potentially hazardous. These intermediates will accumulate under anaerobic conditions (i.e., intermediates resist further anaerobic degradation). Further degradation can only be achieved under aerobic conditions (Pearce et al. 2006). The electron-withdrawing nature of azo linkages hinders the susceptibility of dye molecules to oxidative reactions. However, researchers have identified some bacteria capable of degrading azo dyes under aerobic conditions (Khalid et al. 2008). The number and position of sulfonate and other substituent groups in azo dyes determine the decolourization rate. Khalid et al. (2010) reported that acid dyes show lower colour removal than direct dyes due to the complicated structure of polyaromatic and sulfonate groups. These sulfonate groups will hinder the transfer of dye molecules through the cell membrane. Therefore, the colour reduction will decrease as the number of sulfonate groups increases. Decolourization of azo dyes is also highly dependent on the specificity of enzymes (azoreductase) for various types of azo dyes. It affects the enzyme–substrate complex formation and the ability of the dye molecule to receive an electron and cleave the azo group from the parent molecule.

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Some substitute groups (methyl, sulfo, methoxy and nitro) in the molecule can affect azoreductase activity. According to Nigam et al. (1996), azo dyes containing hydroxyl or amino groups degrade faster than methyl, sulfo, methoxy or nitro groups.

4.2.5

Biological Treatment Systems

Biological treatment systems use bacteria, protozoa and other microorganisms to treat wastewater. A flocculation effect occurs when microorganisms break down organic contaminants for food, allowing the organic matter to settle out of the solution. During the process, a more manageable sludge is formed, which is subsequently dewatered and disposed of as solid waste. Anaerobic, aerobic or both conditions were simulated in biological reactors to treat textile effluents. Manu and Chaudhari (2002) studied the decolourization of 100 mg/L of Acid Orange 7 (AO7) and Reactive Black 8 (RB8) in anaerobic reactors. Colour removal of >99% and COD removal of >90% were achieved in both dye-containing reactors. The authors concluded that no inhibition of methanogenesis was observed for dye concentrations up to 400 mg L−1 for both dyes. Khehra et al. (2006) employed a sequential anoxic/aerobic bioreactor to treat textile wastewater containing 100 mg/L Acid Red 88 (AR88) dye. The method proved quite effective, with dye and COD removals of 98 and 95%, respectively. Because the biological content within the system is active under both anoxic and aerobic conditions, leading to the complete degradation of the dye structure. Muda et al. (2010) treated simulated textile effluents containing 50 mg/L of mixed dyes (Sumifix Black EXA, Sumifix Navy Blue EXF and Synozol Red K-4B) with granular sludge in a single sequential batch reactor under anaerobic and aerobic conditions. Due to high biological activity in the system, COD and ammonium levels were reduced by more than 90%. In contrast, the colour reduction was only 62% due to insufficient adaptation time for recalcitrant dye removal. Spagni et al. (2010) set up a bench-scale system comprising an anaerobic biofilter, an anoxic reactor and an anaerobic membrane bioreactor to treat textile wastewater containing Reactive Orange 16 (RO16) dye (5–37.5 mg L−1 ). The system was effective in colour removal (90%), and the majority of colour removal occurred under anaerobic conditions, while there was a minor increase in colour removal under both anoxic and aerobic conditions. Although aromatic amines are thought to be easily degradable under aerobic conditions, the results show that sulfonated aromatic amines formed under anaerobic conditions are resistant to biodegradation, implying that aromatic amines are still a concern for biological textile wastewater treatment.

5 Constructed Wetlands Constructed wetlands (CWs) are engineered wetlands designed and fabricated to mimic natural wetland systems for treating wastewater. The specific design of a CW improves treatment performance compared to natural systems when conducted

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in a more controlled environment. These systems, mainly comprised of vegetation, substrates, soils, microorganisms and water, utilize complex processes involving physical, chemical and biological mechanisms to remove various contaminants or improve the quality of water (Vymazal 2011). CWs are classified into two categories based on wetland hydrology: free water surface constructed wetlands (FWSCWs) and subsurface flow constructed wetlands (SSFCWs). The FWSCWs are similar to natural wetlands, with a shallow wastewater flow over saturated media. In SSFCWs, wastewater flows horizontally (horizontal flow constructed wetlands, HFCWs) or vertically (vertical flow constructed wetlands, VFCWs) through the media. Another wetland type, known as hybrid constructed wetlands (HCWs), is designed to exploit the advantages of individual wetland systems by combining different types of wetland systems. Enhanced CWs (artificial aerated CWs, baffled flow CWs, hybrid towery CWs, step feeding CWs, etc.) have recently been proposed to intensify the removal processes and minimize the area requirement of CWs (Wu et al. 2015). Constructed wetlands are green and environmentally friendly wastewater treatment method. They have the unique advantage of producing high-quality effluent without the input of fossil fuels and chemicals. CWs can be used for fish cultivation, biomass production, agriculture, recreation, flora and fauna conservation, etc. They can also increase the aesthetic value of the site and enhance the landscape with the presence of water, vegetation and associated wildlife. Compared to conventional wastewater treatment methods, the operation and maintenance of the CW system are easy. Moreover, CWs are cost-effective and energy-efficient. Besides many advantages over traditional treatment technologies, there are some limitations while using this technology in large-scale applications. Land requirements for CWs may be the most limiting factor for their broader application, especially in some regions where land resources are scarce and population density is high. Optimization of parameters becomes difficult when different types of wastewater get mixed in CWs. Periodic harvesting of the biomass is essential to maintain consistent performance. Design criteria for CWs are still in development stage for different kinds of wastewater in different climatic conditions. Moreover, strategies like artificial aeration, step feeding, effluent recirculation, etc., are required to achieve higher removal performance, which increases the lifecycle cost of CWs.

5.1 Constructed Wetlands for Textile Wastewater Treatment Constructed wetlands have previously been used to remove suspended solids, organic matter and nutrients from municipal wastewater and urban runoff. Lately, research interest has shifted to exploring the potential of CW technology for treating different types of industrial wastewater (Tee et al. 2009). Many researchers have investigated the performance of CWs for treating textile wastewater (mostly colour and COD reduction). A brief survey regarding previous works on CWs for treating textile wastewater is described in the following section, and the summary is given in Table 3.

Strategy

Retention time, loading and removal efficiency

References

(continued)

Bulc and Ojstrsek (2008)

• HRT: 0.8–8 days • Removal efficiencies: colour 90%, COD 84%, BOD 66%, TOC 89%, TN 52%, Norganic 87%, SO4 2− 88%, anion surfactant 80% and TSS 93%

Pilot-scale HCW

• Two VFCWs followed by an HFCW • Wetlands filled with coarse sand, fine sand and gravel, and planted with Phragmites australis • Intermittent feeding strategy for VFCWs and continuous feeding for HFCW • Real textile wastewater was used

• HRT: 1.34 days for control unit and 1.45 days for Mbuligwe (2005) planted units • Removal efficiency: Planted units: colour 72–77%, COD 68–73% and SO4 2− 53% Control unit: colour 14%, COD 51% and SO4 2− 15%

• HLR: 2.8–10.8 cm d−1 Davies et al. (2006) • Organic loading: 5.82–26.09 g COD m−2 d−1 • Removal efficiency: colour 99% and COD 86–93%

Davies et al. (2005)

Pilot-scale HFCW • All three wetland beds filled with sand and two beds planted with cattail and cocoyam • Real dye-rich wastewater was used

Pilot-scale VFCW • VFCWs filled with gravel and sandy-clay soil and planted with Phragmites australis • Continuous feeding of synthetic wastewater containing Acid Orange 7

Pilot-scale VFCW • VFCWs filled with gravel and sandy-clay soil and • HRT: 180 minutes planted with Phragmites australis • Organic loading: 21–105 g COD m−2 d−1 • Intermittent pulsed feeding of synthetic wastewater • Removal efficiency: colour 70% and TOC 70% containing Acid Orange 7

Type of wetland

Table 3 Constructed wetlands for the treatment of textile wastewater

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Lab-scale VFCW

• Wetlands filled with gravel, sand, soil and coconut shavings, and planted with Typha domingensis • Bioaugmentation with textile degrading bacteria Microbacterium arborescens and Bacillus pumilus • Real wastewater was used

• HRT: 0–3 days • Removal efficiencies: colour 90%, COD 79%, BOD 77%, TDS 59% and TSS 27% for bioaugmented planted wetland

• VFCW followed by HFCW (two systems) • HLR: 56.6–566 cm d−1 • Wetlands filled with sugarcane bagasse and sylhet • Organic loadings: 9840–19,680 g COD m−2 d−1 sand media, and planted with Phragmites australis, • Removal efficiencies (maximum): colour Dracaena sanderiana and Asplenium platyneuron 93.3–86.6%, COD 88.6–89.3%, BOD 95–96.6%, • Intermittent feeding of real textile wastewater TSS 62.5–37.7%, NH4 + −N 80.5–69.9% and NO3 − −N 72.1–76.6%, for system 1 and system 2, respectively

• HRT: 3–6 days • Removal efficiencies: COD 74–90%, AO7 94–98%, TN 44–67%, TP 12–28%, NH4 + −N 24–99% and NO3 − −N 21–100%

• Wetland units (aerated and non-aerated) filled with gravel and planted with Phragmites australis • Synthetic wastewater containing Acid Orange 7(50–100 mg L−1 ) • Up-flow feeding

Lab-scale HCW

Retention time, loading and removal efficiency

Strategy

Type of wetland

Lab-scale UFCW

Table 3 (continued)

(continued)

Shehzadi et al. (2014)

Saeed and Sun (2013)

Ong et al. (2010)

References

20 C. K. Benny and S. Singh

Lab-scale HCW

Type of wetland

Table 3 (continued) Retention time, loading and removal efficiency

• Two VFCWs followed by an FWSCW (two • HLR: 11.3–22.6 cm d−1 systems) • Removal efficiencies: colour 80.8–89.9%, COD • VFCWs of system 1 filled with sugarcane bagasse, 74.2–73.4%, BOD 80.2–79.6%, TN 57.5–74.2%, biochar, coal and oyster shell. VFCWs of system 2 NH4 + −N 82.1–84.3%, TP 83.3–100% and SO4 2− packed with construction materials, gravel and 52.2–84.1%, for system 1 and system 2, sand, and both FWSCWs filled with sand media respectively • All wetland units were planted with Phragmites australis • Real industrial wastewater (mixture of metal, paper and textile effluents)

Strategy

Saeed and Khan (2019)

References

Textile Wastewater Treatment: Possible Approaches with an Emphasis … 21

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The role of a plant enzyme, peroxidase, in the degradation of Acid Orange 7 (AO7) was studied by Davies et al. (2005) in a pilot-scale vertical flow CW planted with Phragmites australis. The VFCW (0.96 m2 × 0.87 m) was filled with gravel (10 cm bottom layer) and sandy-clay soil (77 cm top layer). The authors found that peroxidase activity was enhanced with an increased AO7 concentration. At an AO7 level of 130 mg L−1 , peroxidase activity was 12.9, 4.3 and 2.1-fold for roots, stems and leaves, respectively. A significant decrease in peroxidase activity was observed for the second increase in concentration (130–700 mg L−1 ). After two days, peroxidase activity returned to the previous level. AO7 and TOC removal efficiencies were about 70%, which indicated AO7 mineralization. They concluded that Phragmites australis has an active role in degrading AO7 and aromatic amines. In another study, Davies et al. (2006) used the same planted VFCW reactor to investigate the aerobic degradation of AO7. The wetland was continuously fed with wastewater containing AO7 dye (127 mg L−1 ) for 48 days, and the dye removal performance was monitored at different hydraulic loads (28–108 L m−2 d−1 ). The authors reported 99% colour removal and 86–93% COD removal for varying inlet organic loads (5.82–26.09 g COD m−2 d−1 ). The AO7 degradation products were sulfanilic acid (SA) and 1amino-2-naphthol (1-amn-2-naph), and these intermediates were further degraded into inorganic compounds (NO3 − and SO4 2− ). The positive redox potential at the outlet and the intermediate degradation led to the conclusion that AO7 was degraded in aerobic conditions. A pilot-scale HFCW was developed by Mbuligwe (2005) for treating real dyerich wastewater, and the role of wetland plants on removal performance was assessed by comparing treatment efficiencies between planted and unplanted wetland units. Three wetland beds (2.85 m in length, 0.6 m in width and 0.6 m in depth) were filled with sand media, and two beds were planted with cattail and cocoyam. An HRT of 1.21 days gave a combined flow rate of 0.53 L min−1 through three CW beds. Colour, COD and sulphate removals in planted units were 72–77%, 68–73% and 53%, respectively. Colour, COD and sulphate removals in unplanted units were 14%, 51% and 15%, respectively. Overall, the planted units attained an average removal of 65–69%, while the unplanted unit achieved only 30% average removal. The authors also reported that sulphate reducing bacteria (SRB) might have played a role in dye decolourization as they convert sulphate to sulphide, which chemically decolourizes dyes. High COD removal efficiency indicated that colour reduction was accompanied by almost complete degradation of dyes and intermediate products. A combination of pilot-scale VFCWs and an HFCW was employed by Bulc and Ojstrsek (2008) for treating real textile wastewater. Two VFCW beds covered 20 m2 (5 m length × 4 m width) each, with a depth of 0.6 m. The HFCW bed covered 40 m2 (8 m × 5 m) with an average depth of 0.5 m. All three beds were filled with coarse sand, fine sand and gravel, and planted with common reed (Phragmites australis). The VFCWs were fed intermittently, whereas the HFCW was fed continuously with real dye-rich wastewater. The average removal efficiencies of the system were colour 90%, COD 84%, BOD 66%, TOC 89%, TN 52%, Norganic 87%, SO4 2− 88%, anion surfactant 80% and TSS 93%, respectively. The results proved that the hybrid CW system

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could offer an optimal solution to meet effective and inexpensive textile wastewater treatment requirements. The removal performances of two lab-scale up-flow constructed wetlands (UFCWs) were compared for treating wastewater containing Acid Orange 7 (AO7) at different AO7 concentrations, HRTs and alternative supplementary aeration (Ong et al. 2010). The wetland reactors (18 cm in diameter and 70 cm in height each) were filled with gravel and planted with Phragmites australis. Influent AO7 concentration was increased from 50 to 100 mg L−1 , and HRT was extended from 3 to 6 days. The aerated wetland reactor outperformed the non-aerated one in removing organic matter, NH4 + −N and aromatic amines. In contrast, colour and NO3 − −N reduction in the non-aerated reactor were better than in the aerated reactor. An increase in AO7 concentration reduced organic degradation and nitrification rate in non-aerated wetland reactor. It also negatively affected the decolourization and denitrification in aerated wetland unit. As the HRT increased to 6 days, the NH4 + −N removal efficiency was significantly enhanced in the non-aerated wetland reactor. The average removal efficiencies were 74–90%, 94–98%, 44–67%, 12–28%, 24–99% and 21– 100% for COD, AO7, TN, TP, NH4 + −N and NO3 − −N, respectively. The pollutant removal efficiencies of two lab-scale hybrid wetland systems treating real textile wastewater were studied by Saeed and Sun (2013). Each system consisted of two treatment stages, i.e., a VF wetland (1.5 m in height and 0.15 m in diameter) followed by an HF wetland (1.01 m in length, 0.45 m in width and 0.7 m in depth). The VF and HF wetlands were filled with sugarcane bagasse and sylhet sand media, respectively, in both systems. Three types of locally available macrophytes, Phragmites australis, Dracaena sanderiana and Asplenium platyneuron were planted in the wetlands. The hydraulic loading was varied in both systems (system 1 56.6–283 cm d−1 and system 2 113.2–566 cm d−1 ). Both systems exhibited almost similar organics and nitrogen removal performances, even though they operated under different hydraulic loading conditions. The authors found that horizontal wetlands were more effective in colour removal. Maximum removal efficiencies in systems 1 and 2 were colour 93.3–86.6%, COD 88.6–89.3%, BOD 95–96.6%, TSS 62.5–37.7%, NH4 + −N 80.5–69.9% and NO3 − −N 72.1–76.6%, respectively. Experiments were conducted on four lab-scale VFCWs to study the influence of inoculation of textile effluent-degrading bacteria (Microbacterium arborescens and Bacillus pumilus) on the degradation of textile effluents (Shehzadi et al. 2014). Three reactors were vegetated with Typha domingensis, and one reactor was left unplanted (as a control unit). Microbacterium arborescens was isolated from the shoot of Typha domingensis and Bacillus pumilus from the root of Pistia. These bacterial strains enhanced the degradation of textile effluents and plant growth-promoting activities. Significant removal efficiencies (colour 90%, COD 79%, BOD 77%, TDS 59% and TSS 27%) were attained by using plants and bacteria within 72 h. The removal performances of two hybrid wetland systems fed with industrial wastewater (a mixture of metal, paper and textile effluents) were compared by Saeed and Khan (2019). Each wetland system comprised two VFCWs (height 1.5 m and diameter 0.15 m each) in series, followed by an FWSCW (length 1.22 m, width 0.61 m and height 0.5 m). The VFCWs of system 1 were filled with biological materials such as sugarcane bagasse,

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biochar, coal and oyster shell. In contrast, VF units of system 2 were packed with construction materials, gravel and sand, and both FWSCWs were filled with sand media. All wetland units were planted with Phragmites australis. The first stage VF wetland of system 1 attained maximum organic and nitrogen removals due to carbon leaching from organic sugarcane bagasse and biochar media. On the other hand, the lack of carbon leaching from the media of the first stage VF wetland of system 2 hindered such removals, which was counterbalanced as the wastewater passed through the second stage VF unit. The results proved that VFCWs were inefficient in colour removal. The overall average removal efficiencies in system 1 and system 2 were colour 80.8–89.9%, COD 74.2–73.4%, BOD 80.2–79.6%, TN 57.5– 74.2%, NH4 + −N 82.1–84.3%, TP 83.3–100% and SO4 2− 52.2–84.1%, respectively. The authors concluded that hybrid systems packed with biological and construction materials were suitable for treating hardly degradable industrial wastewater.

5.2 Design Parameters and Operational Conditions of Constructed Wetlands The design parameters that need to be considered for any type of CW are the choice of substrate media, selection of plant species, hydraulic loading and retention time.

5.2.1

Selection of Substrates

Substrates, also known as media or filling material, are one of the significant components of CWs. They have been widely acknowledged to play a vital role (as a carrier for biofilm development, as a medium for wetland plant growth and as an adsorbent for pollutant immobilization) in CWs, especially for the removal of non-biodegradable pollutants like organic xenobiotics and toxic metals (Yang et al. 2018). Proper substrate selection can enhance the removal efficiencies of CWs. Cost and local availability are the two most important factors determining the choice of substrates. More significantly, the physical (particle size, porosity, specific surface area, hydraulic and electrical conductivities, mechanical strength), chemical (surface charge, chemical stability, toxicity) and biological (electron donor/acceptor) properties of the substrates have to be considered to optimize the system performance. Substrates should be environmentally friendly without causing any secondary pollution to the surrounding environment. They should also have a long lifetime and can be disposed of safely after use. Substrates used in wetlands are broadly categorized into conventional and emerged substrates. Soil, sand and gravel are the most widely used conventional substrates due to their availability and low cost. Wetland systems using conventional substrates may face several problems, such as substrate clogging and low removal performance. These problems lead to the development of emerged

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substrates in CWs. The use of waste products (mainly industrial by-products) as wetland media is also considered to minimize waste disposal problems. In textile wastewater treatment using CW, the organic media can enhance the overall nitrogen and organics removal. It is reported that various organic compounds are required for dye degradation as azo dyes do not yield carbon or energy for microbial growth (Pearce et al. 2006). Saeed and Sun (2013) employed sugarcane bagasse as wetland media for treating textile wastewater. They reported that physical structures (higher porosity) and chemical properties (carbon leaching) of organic sugarcane bagasse media improved nitrogen and organic removal. Saba et al. (2015) stated that an additional supply of carbon and nitrogen is required to biodegrade hardly degradable dyes. The authors used rice husk and biochar as wetland media and attained enhanced dye degradation.

5.2.2

Selection of Plants

Plant selection plays a significant role in CWs as it is involved in many wetland functions and pollutant removal processes. Plants (macrophytes) used in CWs can be categorized into four groups: emergent macrophytes (e.g., Acorus calamus, Carex rostrata, Phragmites australis, Scirpus lacustris and Typha latifolia), floating leaved macrophytes (e.g., Nymphaea odorata and Nuphar lutea), submerged macrophytes (e.g., Myriophyllum spicatum, Ceratophyllum demersum and Rhodophyceae) and freely floating macrophytes (e.g., Lemna minor, Spirodela polyrhiza and Eichhornia crassipes) (Saeed and Sun 2012). For the selection of plants to be used in CWs, the following recommendations can be made: • Use of local and indigenous species • Use of plant species that grow in natural wetlands because their roots are adapted to growing in water-saturated conditions • Plants with an extensive root and rhizome system below ground are preferable • Plants should be able to withstand shock loads and short dry periods Establishing a successful root zone system in the wetland bed is a crucial factor in the application of CW technology for treating high-strength industrial effluents. The survival of macrophytes under strong organic loading and soluble salts (i.e., sodium, sulphate and chloride) is of the highest importance (Billore et al. 2001). Therefore, the negative effect of organic-rich wastewater on macrophytes should be considered. Various macrophytes such as Phragmites australis, Myriophyllum spicatum, Ceratophyllum demersum, Dracaena sanderiana, Asplenium platyneuron, Typha domingensis, Prescaria barbata, etc., have been successfully used in CWs for the treatment of textile wastewater.

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C. K. Benny and S. Singh

Hydraulic Loading and Hydraulic Retention Time

Hydrology is considered one of the most important aspects for regulating wetland operations, and the flow rate needs to be adjusted for effective treatment performance. Hydraulic loading rate (HLR) and hydraulic retention time (HRT) play a crucial role in the removal efficiency of CWs; therefore, the design should be suitable for these parameters. A greater HLR permits wastewater to move through the wetland media at a faster rate, thereby reducing the optimal contact time. At a longer HRT, the microbial population in the CW system may get sufficient contact time to eliminate pollutants (Saeed and Sun 2012). Saeed and Khan (2019) employed two planted wetland systems of the same configuration (VFCW-VFCW-FWSCW) for treating industrial wastewater (a mixture of metal, paper and textile effluents). The HLR varied between 11.3 and 22.6 cm d−1 for both systems. The authors studied the effects of HLR on the removal performance of organics and nitrogen. The organics and nitrogen removals substantially improved in the first stage VFCW of both systems when HLR was decreased from 22.6 to 11.3 cm d−1 , i.e., reduction of HLR increased retention time and associated removals in the first stage wetlands (COD removal increased from 92 to 94% and 90 to 96% in systems 1 and 2, and TN removal increased from 80 to 91% and 84 to 97% in systems 1 and 2, respectively). In contrast, the removals in second and third stage wetlands of both systems showed opposite phenomena, as they operated below optimal removal capacity. Keskinkan and Lugal Goksu (2007) studied the effect of HRT on dye removal performance in a planted lab-scale vertical flow wetland system. The HRT of the system varied from 3 to 18 days. The results indicated that the effluent dye concentrations at HRTs of 9 and 18 days were lower than those at HRTs of 3 and 6 days in the planted wetlands. The average dye removal efficiency in planted wetlands increased from 70 to 96% when the HRT was increased from 9 to 18 days. They also found that the effect of plants was much more important at higher HRT.

6 Conclusions Textile wastewater treatment technologies such as coagulation-flocculation and advanced oxidation processes are not feasible on a large scale because of the high costs and complex processes involved. Developing countries like India may benefit from less energy-intensive textile wastewater treatment systems due to the unavailability of continuous energy supplies. Therefore, it is essential to find an alternative treatment system, such as constructed wetlands, that is cost-effective, less energyintensive, environmentally friendly and simple to operate. The use of CWs for textile wastewater treatment is still at an experimental stage and is not well established. However, CWs are found to be effective in removing colour and other contaminants from textile wastewater. The results rarely cover all seasons, and few works have been conducted on a mixture of various dyes and the reduction of intermediate

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aromatic compounds. Future research should focus on dye degradation mechanisms inside the CW system and resulting toxicity reduction, exploration of novel enhancement technologies (e.g., microbial augmentation), optimization of environmental and operational parameters, comprehensive evaluation of plants and substrates in field trials under real-life conditions and maintenance strategies to ensure the successful and long-term application of full-scale CWs (e.g., plant harvest).

References Adinew B (2012) Textile effluent treatment and decolorization techniques: a review. Bul J Sci Educ 21(3):434–456 Almazan-Sanchez PT, Linares-Hernandez I, Solache-Rios MJ, Martinez-Miranda V (2016) Textile wastewater treatment using iron-modified clay and copper-modified carbon in batch and column systems. Water Air Soil Pollut 227(4):1–14 Andrianova MM (1970) Carcinogenic properties of the red food dyes Amaranth, Ponceau SX and Ponceau 4R. Voprosy Pitaniya 29(5):61–65 Aouni A, Fersi C, Cuartas-Uribe B, Bes-Pia A, Alcaina-Miranda MI, Dhahbi M (2012) Reactive dyes rejection and textile effluent treatment study using ultrafiltration and nanofiltration processes. Desalination 297:87–96 Ayhan Sengil I, Ozdemir A (2012) Simultaneous decolorization of binary mixture of blue disperse and yellow basic dyes by electrocoagulation. Desalin Water Treat 46(1–3):215–226 Babu BR, Parande AK, Raghu S, Kumar TP (2007) Cotton textile processing: waste generation and effluent treatment. J Cotton Sci 11:141–153 Bhatia D, Sharma NR, Singh J, Kanwar RS (2017) Biological methods for textile dye removal from wastewater: a review. Crit Rev Environ Sci Technol 47(19):1836–1876 Billore SK, Singh N, Ram HK, Sharma JK, Singh VP, Nelson RM, Dass P (2001) Treatment of a molasses-based distillery effluent in a constructed wetland in central India. Water Sci Technol 44(11–12):441–448 Bulc TG, Ojstrsek A (2008) The use of constructed wetland for dye-rich textile wastewater treatment. J Hazard Mater 155(1–2):76–82 Buscio V, Marin MJ, Crespi M, Gutierrez-Bouzan C (2015) Reuse of textile wastewater after homogenization-decantation treatment coupled to PVDF ultrafiltration membranes. Chem Eng J 265:122–128 Carmen Z, Daniela S (2012) Textile organic dyes-characteristics, polluting effects and separation/elimination procedures from industrial effluents: a critical overview, vol. 3. IntechOpen, Rijeka, pp 55–86 Daneshvar N, Ayazloo M, Khataee AR, Pourhassan M (2007) Biological decolorization of dye solution containing Malachite Green by microalgae Cosmarium sp. Biores Technol 98(6):1176– 1182 Davies LC, Carias CC, Novais JM, Martins-Dias S (2005) Phytoremediation of textile effluents containing azo dye by using Phragmites australis in a vertical flow intermittent feeding constructed wetland. Ecol Eng 25(5):594–605 Davies LC, Pedro IS, Novais JM, Martins-Dias S (2006) Aerobic degradation of acid orange 7 in a vertical-flow constructed wetland. Water Res 40(10):2055–2063 Dos Santos AB, Cervantes FJ, Van Lier JB (2007) Review paper on current technologies for decolourization of textile wastewaters: perspectives for anaerobic biotechnology. Biores Technol 98(12):2369–2385 Foo KY, Hameed BH (2010) Decontamination of textile wastewater via TiO2 /activated carbon composite materials. Adv Coll Interface Sci 159(2):130–143

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C. K. Benny and S. Singh

Ghaly AE, Ananthashankar R, Alhattab MVVR, Ramakrishnan VV (2014) Production, characterization and treatment of textile effluents: a critical review. J Chem Eng Process Technol 5(1):1000182 Golka K, Kopps S, Myslak ZW (2004) Carcinogenicity of azo colourants: influence of solubility and bioavailability. Toxicol Lett 151(1):203–210 Golob V, Vinder A, Simonic M (2005) Efficiency of the coagulation/flocculation method for the treatment of dyebath effluents. Dyes Pigm 67(2):93–97 Holkar CR, Pandit AB, Pinjari DV (2014) Kinetics of biological decolorisation of anthraquinone based Reactive Blue 19 using an isolated strain of Enterobacter sp. Biores Technol 173:342–351 Holkar CR, Jadhav AJ, Pinjari DV, Mahamuni NM, Pandit AB (2016) A critical review on textile wastewater treatments: possible approaches. J Environ Manage 182:351–366 Jadhav JP, Kalyani DC, Telke AA, Phugare SS, Govindwar SP (2010) Evaluation of the efficacy of a bacterial consortium for the removal of color, reduction of heavy metals, and toxicity from textile dye effluent. Biores Technol 101(1):165–173 Jain K, Shah V, Chapla D, Madamwar D (2012) Decolorization and degradation of azo dye— Reactive Violet 5R by an acclimatized indigenous bacterial mixed cultures-SB4 isolated from anthropogenic dye contaminated soil. J Hazard Mater 213:378–386 Keck A, Klein J, Kudlich M, Stolz A, Knackmuss HJ, Mattes R (1997) Reduction of azo dyes by redox mediators originating in the naphthalene sulfonic acid degradation pathway of Sphingomonas sp. strain BN6. Appl Environ Microbiol 63(9):3684–3690 Keskinkan O, Lugal Goksu MZ (2007) Assessment of the dye removal capability of submersed aquatic plants in a laboratory-scale wetland system using ANOVA. Braz J Chem Eng 24(2):193– 202 Khaled A, El Nemr A, El-Sikaily A, Abdelwahab O (2009) Treatment of artificial textile dye effluent containing Direct Yellow 12 by orange peel carbon. Desalination 238(1–3):210–232 Khalid A, Arshad M, Crowley DE (2008) Accelerated decolorization of structurally different azo dyes by newly isolated bacterial strains. Appl Microbiol Biotechnol 78(2):361–369 Khalid A, Arshad M, Crowley D (2010) Bioaugmentation of azo dyes. In: Biodegradation of Azo Dyes. Springer, Berlin, Heidelberg, pp 1–37 Khan R, Banerjee UC (2010) Decolourization of azo dyes by immobilized bacteria. In: Biodegradation of azo dyes. Springer, Berlin, Heidelberg, pp 73–84 Khan Z, Jain K, Soni A, Madamwar D (2014) Microaerophilic degradation of sulphonated azo dye Reactive Red 195 by bacterial consortium AR1 through co-metabolism. Int Biodeterior Biodegradation 94:167–175 Khehra MS, Saini HS, Sharma DK, Chadha BS, Chimni SS (2006) Biodegradation of azo dye CI Acid Red 88 by an anoxic-aerobic sequential bioreactor. Dyes Pigm 70(1):1–7 Kulkarni AN, Kadam AA, Kachole MS, Govindwar SP (2014) Lichen Permelia perlata: a novel system for biodegradation and detoxification of disperse dye Solvent Red 24. J Hazard Mater 276:461–468 Lade HS, Waghmode TR, Kadam AA, Govindwar SP (2012) Enhanced biodegradation and detoxification of disperse azo dye Rubine GFL and textile industry effluent by defined fungal-bacterial consortium. Int Biodeterior Biodegradation 72:94–107 Lea M (2010) Bioremediation of turbid surface water using seed extract from Moringa oleifera tree. Curr Protoc Microbiol 16(1):1G – 2 Lim SL, Chu WL, Phang SM (2010) Use of Chlorella vulgaris for bioremediation of textile wastewater. Biores Technol 101(19):7314–7322 Mahmoodi NM, Salehi R, Arami M, Bahrami H (2011) Dye removal from coloured textile wastewater using chitosan in binary systems. Desalination 267(1):64–72 Manekar P, Patkar G, Aswale P, Mahure M, Nandy T (2014) Detoxifying of high strength textile effluent through chemical and bio-oxidation processes. Biores Technol 157:44–51 Manu B, Chaudhari S (2002) Anaerobic decolorisation of simulated textile wastewater containing azo dyes. Biores Technol 82(3):225–231

Textile Wastewater Treatment: Possible Approaches with an Emphasis …

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Mbuligwe SE (2005) Comparative treatment of dye-rich wastewater in engineered wetland systems (EWSs) vegetated with different plants. Water Res 39(2–3):271–280 Muda K, Aris A, Salim MR, Ibrahim Z, Yahya A, van Loosdrecht MC, Ahmad A, Nawahwi MZ (2010) Development of granular sludge for textile wastewater treatment. Water Res 44(15):4341–4350 Nigam P, Banat IM, Singh D, Marchant R (1996) Microbial process for the decolorization of textile effluent containing azo, diazo and reactive dyes. Process Biochem 31(5):435–442 Oller I, Malato S, Sánchez-Pérez J (2011) Combination of advanced oxidation processes and biological treatments for wastewater decontamination: a review. Sci Total Environ 409(20):4141–4166 Ong SA, Uchiyama K, Inadama D, Ishida Y, Yamagiwa K (2010) Treatment of azo dye Acid Orange 7 containing wastewater using up-flow constructed wetland with and without supplementary aeration. Biores Technol 101(23):9049–9057 Ozer A, Akkaya G, Turabik M (2006) The removal of Acid Red 274 from wastewater: combined biosorption and biocoagulation with Spirogyra rhizopus. Dyes Pigm 71(2):83–89 Pazdzior K, Bilinska L, Ledakowicz S (2019) A review of the existing and emerging technologies in the combination of AOPs and biological processes in industrial textile wastewater treatment. Chem Eng J 376:120597 Pearce CI, Christie R, Boothman C, von Canstein H, Guthrie JT, Lloyd JR (2006) Reactive azo dye reduction by Shewanella strain J18 143. Biotechnol Bioeng 95(4):692–703 Punzi M, Nilsson F, Anbalagan A, Svensson BM, Jonsson K, Mattiasson B, Jonstrup M (2015) Combined anaerobic-ozonation process for treatment of textile wastewater: removal of acute toxicity and mutagenicity. J Hazard Mater 292:52–60 Saba B, Jabeen M, Khalid A, Aziz I, Christy AD (2015) Effectiveness of rice agricultural waste, microbes and wetland plants in the removal of Reactive Black 5 azo dye in microcosm constructed wetlands. Int J Phytorem 17(11):1060–1067 Saeed T, Khan T (2019) Constructed wetlands for industrial wastewater treatment: alternative media, input biodegradation ratio and unstable loading. J Environ Chem Eng 7(2):103042 Saeed T, Sun G (2012) A review on nitrogen and organics removal mechanisms in subsurface flow constructed wetlands: dependency on environmental parameters, operating conditions and supporting media. J Environ Manage 112:429–448 Saeed T, Sun G (2013) A lab-scale study of constructed wetlands with sugarcane bagasse and sand media for the treatment of textile wastewater. Biores Technol 128:438–447 Sanghi R, Bhattacharya B, Dixit A, Singh V (2006) Ipomoea dasysperma seed gum: an effective natural coagulant for the decolourization of textile dye solutions. J Environ Manage 81(1):36–41 Sarayu K, Swaminathan K, Sandhya S (2007) Assessment of degradation of eight commercial reactive azo dyes individually and in mixture in aqueous solution by ozonation. Dyes Pigm 75(2):362–368 Senthilkumar S, Perumalsamy M, Prabhu HJ (2014) Decolourization potential of white-rot fungus Phanerochaete chrysosporium on synthetic dye bath effluent containing Amido Black 10B. J Saudi Chem Soc 18(6):845–853 Shah PD, Dave SR, Rao MS (2012) Enzymatic degradation of textile dye Reactive Orange 13 by newly isolated bacterial strain Alcaligenes faecalis PMS-1. Int Biodeterior Biodegradation 69:41–50 Shehzadi M, Afzal M, Khan MU, Islam E, Mobin A, Anwar S, Khan QM (2014) Enhanced degradation of textile effluent in constructed wetland system using Typha domingensis and textile effluent-degrading endophytic bacteria. Water Res 58:152–159 Sostar-Turk S, Simonic M, Petrinic I (2005) Wastewater treatment after reactive printing. Dyes Pigm 64(2):147–152 Spagni A, Grilli S, Casu S, Mattioli D (2010) Treatment of a simulated textile wastewater containing the azo-dye reactive orange 16 in an anaerobic-biofilm anoxic-aerobic membrane bioreactor. Int Biodeterior Biodegradation 64(7):676–681 Sudova E, Machova J, Svobodova Z, Vesely T (2007) Negative effects of malachite green and possibilities of its replacement in the treatment of fish eggs and fish: a review. Vet Med 52(12):527

30

C. K. Benny and S. Singh

Tee HC, Seng CE, Noor AM, Lim PE (2009) Performance comparison of constructed wetlands with gravel-and rice husk-based media for phenol and nitrogen removal. Sci Total Environ 407(11):3563–3571 Turhan K, Turgut Z (2009) Decolourization of direct dye in textile wastewater by ozonization in a semi-batch bubble column reactor. Desalination 242(1–3):256–263 Un UT, Aytac E (2013) Electrocoagulation in a packed bed reactor-complete treatment of colour and cod from real textile wastewater. J Environ Manage 123:113–119 Verma AK, Dash RR, Bhunia P (2012) A review on chemical coagulation/flocculation technologies for removal of colour from textile wastewaters. J Environ Manage 93(1):154–168 Vymazal J (2011) Plants used in constructed wetlands with horizontal subsurface flow: a review. Hydrobiologia 674(1):133–156 Vymazal J (2014) Constructed wetlands for treatment of industrial wastewaters: a review. Ecol Eng 73:724–751 Wu H, Zhang J, Ngo HH, Guo W, Hu Z, Liang S, Liu H (2015) A review on the sustainability of constructed wetlands for wastewater treatment: design and operation. Biores Technol 175:594– 601 Yang Y, Zhao Y, Liu R, Morgan D (2018) Global development of various emerged substrates utilized in constructed wetlands. Biores Technol 261:441–452 Zhong QQ, Yue QY, Li Q, Xu X, Gao BY (2011) Preparation, characterization of modified wheat residue and its utilization for the anionic dye removal. Desalination 267(2–3):193–200 Zuorro A, Lavecchia R (2014) Evaluation of UV/H2 O2 advanced oxidation process (AOP) for the degradation of diazo dye Reactive Green 19 in aqueous solution. Desalin Water Treat 52(7– 9):1571–1577

Constructed Wetland for Metals: Removal Mechanisms and Analytical Challenges Ankita Chatterjee

and Maulin P. Shah

1 Introduction Wetlands are natural resources which are highly valuable in wastewater treatment. Human beings have been using wetlands in several ways since their existence. However, the advantages and positive impact of the wetlands on the ecosystem have been recognized in recent years. The applications of wetland systems for wastewater treatment are practiced often. There United States contains around 500 wetland systems for the treatment of municipal, agricultural, and mining wastewater (Kirby 2002). Wetlands are natural systems with great ecological significance, which provide habitats for numerous species and support their life. Constructed wetlands are engineered wetland systems which are planned and constructed for utilization in wastewater treatment. Constructed wetlands are beneficial than the natural wetlands because the wastewater treatment can be carried out in a controlled condition in the constructed wetlands (Vymazal 2010). Constructed wetlands allow the experimental processes in terms of substrate composition, vegetation, and flow pattern to obtain the maximum output. Apart from maintaining the controlled conditions, several other advantages, like, selection of site, size adaptability, regulatory hydraulic motion, and retention time are considered to be important (Vymazal and Kröpfelová 2008). Water pollution caused by chemical contaminants is a major threat to the society. Water pollution occurs when single or multiple components are released into the A. Chatterjee (B) Department of Biotechnology, School Applied Sciences, REVA University, Karnataka Bangalore, India e-mail: [email protected] M. P. Shah Industrial Wastewater Research Lab, Division of Applied and Environmental Microbiology, Enviro Technology Limited, GIDC, Ankleshwar, Gujarat, India e-mail: [email protected]

© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. P. Shah (ed.), Recent Trends in Constructed Wetlands for Industrial Wastewater Treatment, https://doi.org/10.1007/978-981-99-2564-3_2

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water bodies which reduces the quality of water. According to the World Health Organization, water-borne diseases are most common among human beings. Disposal and treatment of wastewater is required much because the pollutants and pathogens present in the wastewater reaches into the lakes and river thereby reducing the quality of drinking water (Vigneswaran et al. 2009).

2 Constructed Wetlands Constructed wetlands are artificially engineered wetlands systems. Wetlands were used in the treatment of wastewater since 1950. However, planned artificial setup of wetland was first operated during the era of 1960s in Germany. Gradually, with passing time, the constructed wetlands and their application in wastewater treatment gained popularity in Europe, North America, and Australia. The formation of constructed wetland began with the idea of vegetation-based environment for the treatment of inland waterways which were exposed to certain pollutants. Since then, the technology related to wastewater treatment is improved and in terms of constructed wetlands several experimental setups are not constructed to find the maximum remediation rate (Vymazal 2011). Constructed wetlands are observed to be categorized based on their design and applications, the most important parameters based on which the constructed wetlands are classified as waste water flow, growth of macrophytes, and path of the wastewater flow. Depending on the growth of macrophytes, constructed wetlands can be freefloating, submerged, and emergent. Two types of constructed wetlands are classified depending on their flow of wastewater, named as, surface flow or free water surface system and subsurface flow or subsurface flow system. In case of surface flow system, the flow of wastewater doesn’t reach the depth and resemble the natural wetlands. However, the subsurface flow system of wetlands can be further classified into vertical flow and horizontal flow (Bapista et al. 2008; Babatunde et al. 2016). At certain times, different systems are combined to make the wetlands more efficient. Figure 1 depicts the classification of constructed wetlands. The constructed wetlands can be classified in four major groups depending on their applications. The groups are discussed below: I.

Constructed Wetlands for Creation of Habitats: These wetlands are constructed for providing habitat for wildlife dwelling. Habitat-constructed wetlands are further categorized as salt marshes, freshwater marshes, saltwater swamps, and freshwater swamps. Freshwater marshes and freshwater swamps are observed to be constructed around high lands considering it to be suitable for the growth of wetland species. Saltwater marshes and swamps, on the other hand, are created near to the estuaries so that the species utilizing saline water can grow in these wetlands. II. Constructed Wetlands for Control of Flood: These artificially prepared wetlands significantly help in controlling flood. Natural flood water is stored in the

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Fig. 1 Classification of constructed wetlands

constructed wetland and can be used to fulfill the agricultural and urban purposes. The plants and microbes present in the constructed wetlands naturally or artificially accomplish the flood control. These systems are constructed at low altitude in landscapes. III. Constructed Wetlands for Aquaculture: Constructed wetlands have been used for rearing aquatic animals, like, prawns, crayfishes, and shrimps. Rice, water chestnuts, and cranberries are certain plants which can tolerate the presence of water are grown in these wetlands. This helps in maintaining a symbiotic relationship between the plants and the aquatic lives. As the growth of the aquatic animals and fishes increases, automatically occurs enhanced growth of the plants due to the release of better nutrients in the wastewater. IV. Constructed Wetlands for Wastewater Treatment: These wetlands are created to treat the wastewater received from various sources. Wetlands are one of the convenient modes of treating sewage water.

3 Description of Constructed Wetland Components The major components of any artificially engineered wetlands are vegetation of the wetland, living organisms, consortium of microbial population, the substrate that supports the vegetation and the water column. There are different aquatic weeds and plants which are used in the treatment of wastewater in the constructed wetlands. Microorganisms obtain nutrients and energy from the contaminated substances to continue their life cycles. The efficiency of the constructed wetlands depends a lot on maintaining the optimum environmental conditions for the growth of microbes. In general, microorganisms grown in constructed wetlands are omnipresent in nature and thus are easily present in the wastewater. Rarely, if required microbes are inoculated in the wetlands for treatment of wastewater (Alexander 1978).

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Fig. 2 Importance of Macrophytes in Constructed Wetlands

The vegetation of the constructed wetlands is important for helping in the attachment of microorganisms. The leaves and the stems of the wetland plants efficiently increases the surface area of microbial binding inside the water column. The plants transport the atmospheric gases deep into the roots to endure anaerobic conditions (Gersberg et al. 1986; Shah 2020). The importance of macrophytes in constructed wetlands is depicted in Fig. 2. It has been observed that various constructed wetlands are created using a certain type of substrate and vegetation combination which efficiently treats wastewater. However, maintaining a particular combination has certain drawbacks due to high operational costs since any pest or microbial interaction can damage the system of monoculture combination. Also, multi-culture system or mixed species would be much more efficient in remediation and resistant toward the pollutants (Brix and Schierup 2020).

4 Heavy Metals Management in the Constructed Wetlands Phytoremediation has always been considered as an effective mode of removal of heavy metals from contaminated soil samples and water bodies. Plants are able to uptake the heavy metals from the wastewater. Thus, the presence of vegetation in the constructed wetlands plays an important role in the remediation of heavy metals contaminants (Aitchison et al. 2000). It has been reported by Yeh et al. in 2009 that constructed wetlands were able to remove significant quantity of zinc and copper present in swine wastewater (Yeh et al. 2009; Shah 2021).

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4.1 Heavy Metal Removal Pathways Followed by Constructed Wetlands The removal processes include a combination of physical and biological mechanisms. These processes are briefly explained below: • Physical Techniques: Physical approaches of heavy metal remediation include filtration, flocculation, and sedimentation. In filtration, solid particles are separated from the liquid medium with the help of the plant roots. The pores and interstitial spaces in the substrates act as a filter in the constructed wetlands during the flow of wastewater through the substrates. Thereby, the solid particles are filtered out (Batool and Saleh 2020). Flocculation increases the settling rate of heavy metal ions suspension by creating a bridge between the flocs and polymers. The combination of flocs with polymers forms larger aggregates of the particles and can easily be suspended. The flow rate and the direction of the wastewater impact the rate of flocculation to a great extent (Hua and Haynes 2016). The process of settling down suspended particles is involved in sedimentation. Thus, the heavy metal ions which are adjoint to the suspended particles can be eliminated by sedimentation (Hua and Haynes 2016). Adsorption is an important phenomenon which follows the principle of attachment of heavy metal ions on adsorbent surfaces. Adsorption can be accompanied with any of the physical processes for enhanced efficiency. However, physical processes of separation are used at a preliminary stage for the removal of heavy metals from waste water because they are unstable in nature and can be affected by the environmental factors. • Chemical Techniques: Chemical approaches of heavy metal treatment includes chemical adsorption, ion exchange, precipitation, and oxidation–reduction reaction. The attachment of the heavy metal ions on the surface of the adsorbents by ionic or covalent bonds. Stability of the new component is strengthened by the formation of the bonds. In some cases, the non-heavy metal ions inhibit the adsorption of heavy metal ions due to the phenomenon of competitive adsorption (Hua et al. 2018; Zhao et al. 2019). Ion exchange, on the other hand, is a reversible approach. The heavy metal ions in the wastewater are exchanged with ions which have identical electrical characteristics on the insoluble solid particles’ surfaces. The constructed wetlands consist of substrates providing metal ions which involves in the ion-exchange mechanism (Guo et al. 2021). Deformation of the substrates during the process, however, affects the rate of ion exchange of heavy metals (Zhao et al. 2019). Apart from adsorption and ion-exchange methods, precipitants like carbonates, sulfides, oxides, hydroxides, and oxyhydroxide are used to treat the heavy metal ions by precipitation reaction (Lizama-Allende et al. 2021). Further, oxidation–reduction is yet another efficient mechanism of controlling heavy metal ions by changing their valency. Redox reactions are carried out by microorganisms and plants present in the constructed wetlands. • Biological Process: Biological ways of treating heavy metals involves both phytoremediation and microbial activities. Plants accumulates, volatizes, and regulates several other techniques to eliminate the heavy metals from waste water.

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The activity of rhizofiltration and phytostabilization is observed to reduce the heavy metals mobility along with the secretion of organic matters (Ali et al. 2020). Siderophores, amino acids, organic acids, and proteins aid in heavy metals chelating and thus the metal ions are converted into lesser or non-toxic forms. Absorption of heavy metals by plants can occur through roots of the plants and further the metal ions are transferred to other tissues of plants. Ion exchange mechanism is one of the common approaches where small fractions of metal ions are transported to the shoots which are removed along with plants shoots harvest (Jacob et al. 2018). Plants also treat the heavy metal ions by phytovolatilization where they transform the metal ions to volatile components which are passed through the plants’ stomata into the atmosphere (Zhao et al. 2020). Root oxygen leakage in plants stimulates the degradation of nutrients followed by the precipitation of heavy metals (Schwindaman et al. 2014). Microorganisms, in the constructed wetlands, metabolize and adsorb the heavy metals on their surfaces. Heavy metal ions act as essential micronutrients for the growth of microorganisms as well as some metal ions are extremely important components of enzymes, pigments, and proteins of the microbes. Accumulation of heavy metals by microbial cells are often observed to occur in the cell walls and cell membranes (Chatterjee et al. 2020). Apart from bioaccumulation, microbial cells attach to heavy metals and carry out biosorption. Precipitation of metals occurs during the interaction of the pollutants with the microbial cells (Dey et al. 2020). Extracellular polymeric substances in the microbes contain different functional groups which are also capable of adsorbing the heavy metals (Yu et al. 2020) (Table 1).

5 Factors Affecting Heavy Metal Removal Processes in Constructed Wetlands The factors which play an important role in reducing heavy metals pollution by the constructed wetlands are discussed in brief below: • pH: Heavy metals exists in ionic state when present at low pH and as then enter any high pH zone, precipitation of heavy metal ions occurs. The pH of the wastewater and anions present influences the precipitation of the heavy metals. Aluminum is observed to precipitate by forming aluminum hydroxide at neutral pH (Hua et al. 2015; Li et al. 2020). pH affects the chemical nature of the heavy metals. The removal of the metal ions by plants is enhanced at low pH because the acidic pH conditions enhance the mobility and solubility of the heavy metal ions, which allows them to be accumulated by the plant roots. Though, this process induces a chance of toxicity in the plants (Mayes et al. 2009; Rahman et al. 2014). In case of microbial activity, pH plays a role in sulfide precipitation by the sulfatereducing bacteria. The sulfate-reducing bacteria requires neutral pH for heavy metals treatment (Guo et al. 2021). Components of the constructed wetlands

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Table 1 Efficient removal of heavy metals by constructed wetlands Heavy metals remediated

Type of constructed wetland

Specific components of the wetland

References

Al, Cd, Cu, Mn, Pb, and Zn

Vertical/reverse-vertical flow (inflow/outflow) constructed wetland

Vegetation: Cyperus alternifolius and Villarsia exaltata

Cheng et al. (2002)

Chromium

Horizontal subsurface flow and vertical flow constructed wetland

Plants, microbial biofilms, Papaevangelou and gravels et al. (2017)

Zn, Cu, and Pb

Subsurface Flow Constructed Wetlands

Substrates: Coke and Gravel

Mengzhi et al. (2009)

Pb, Cr, and Cd

Vertical flow constructed wetland

Vegetation: Phragmites australis

Mohammed and Babatunde (2017)

Zn, Cd, Cr

Horizontal flow constructed wetland

Vegetation: aboveground biomass of Phragmites australis

Vymazal and Bˇrezinová (2016)

Zn, Pb, Cd, Cu

Horizontal Surface flow constructed wetland

Vegetation: Typha latifolia Lim et al. (2003) Support medium: Graded gravel

Zn, Cr, Ni, Cd, Fe, Pb

Vertical flow constructed wetland

Support medium: Loamy Dan et al. (2017) soil, pumice stone Vegetations: Phragmites australis or Juncus effusus

Cu, Zn, Cd

Downflow Subsurface constructed wetland

Substrate: Biochar prepared using walnut shell and sand Drainage layer: gravel Vegetation: Iris pseudoacorus

Chen et al. (2021)

undergo certain changes at higher pH range. The adsorbent surfaces become negatively charged and thus attaches the cationic-charged heavy metal ions. The hydroxyl ions present competes with the oxygen containing ions for adsorption. Thus, at high pH, the heavy metal removal mostly occurs by precipitation and low pH aids in the adsorption of heavy metals (Gomes et al. 2019). • Temperature: Temperature plays important role in the growth of microbes and plants in the constructed wetlands. Low temperatures impact the growth of the plants negatively as the aquatic plants become dormant and wilted leading to inhibition of respiration and photosynthesis. The declined temperature also results in the reduction of the organic matter synthesis and transportation which eventually decreases the plant growth rate (Valipour and Ahn 2016). Low temperature leads to enhanced accumulation of the debris. The reduced microbial count due to low temperature results in decreased microbial decomposition rate (Ma et al. 2017). At high temperature, remediation of heavy metals is observed to increase due to rapid growth of plants and eventually enhances respiration and photosynthesis rate. The precipitation of oxyhydroxide and reduction of sulfate are also

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reported to increase after an increase of temperature. When microbial activities are concerned, the metabolism rate of microbes increases. However, in certain cases, conformational alteration in the ribosome occurs due to extreme temperatures and thus protein synthesis is hampered which might affect the elimination of heavy metals (Thomson et al. 2017). • Heavy Metals Concentration: Constructed wetlands are efficient to remediate heavy metals at low concentrations. This is because higher heavy metal ions concentration has extra ions as compared to the sites of adsorption which remains the same on the substrates. Less concentration of heavy metals can be uptaken by plants and accumulated by microorganism (Guo et al. 2021). Excess concentrations of heavy metals are capable of harming the plants and altering their ultrastructure as well as metabolic rates. Also, the metabolism of the microorganisms is affected by interference of the heavy metals in the regulation of genetic material. The enzymatic activities of the microbes are affected and thereby the growth of microbes is declined (Salama et al. 2019). • Dissolved Oxygen: Dissolved oxygen concentration is related to the degree of oxidation–reduction reaction and the microbial activities. Thus, indirectly the presence or absence of dissolved oxygen in the wastewater affects the heavy metal removal. Adsorption and precipitation reaction mostly occurs when the wastewater contains dissolved oxygen. The functionality of sulfate-reducing bacteria is affected due to the presence of oxygen (Hua and Haynes 2016). • Chemical Oxygen Demand: Increase in chemical oxygen demand stimulates the activity of microorganism affecting the redox system of the constructed wetlands. Microbial cells require organic and inorganic carbon for their growth, metabolic activity, and reproduction. These carbon sources can be supplied to them by the plants as well as organic substrates and pollutants. Thus, the addition of organic carbon helps in improving the bacterial sulfate reduction and thereby enhances plant growth. Altogether, the activity of the constructed wetlands is improved due to this phenomenon (Yu et al. 2019; Chen et al. 2021).

6 Scope of Future Studies The constructed wetlands on treatment of heavy metals equally involve physical, chemical, and biological approaches. However, much detailed studies are required to understand the efficiency of the key factors affecting the treatment. The bioavailability of the heavy metals after the application of the chelators should be studied in order to understand the fate of the heavy metals. The mechanisms followed are required to be understood thoroughly for determining the exchanges of ions occurring due to breaking down of the complex compounds of heavy metals. Cost-effective substrates should be assessed to make the process applicable for large-scale usage. Phytotoxicity and inhibition of microbial activity in certain cases due to increased concentration of heavy metals should be addressed in further studies.

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7 Conclusion Constructed wetlands are already proven to have immense potential for the treatment of municipal and industrial wastewater. This chapter focused on the various mechanisms of heavy metals removal in the constructed wetlands. The factors affecting the removal of the metal ions are discussed thoroughly. It has been found that pH, temperature, concentration of heavy metals, dissolved oxygen and chemical oxygen demand are the few environmental factors which play important role in the remediation technique. For efficient removal of heavy metals, appropriate environmental condition should be maintained for the growth of plants and microorganisms for the biological approach of remediation.

References Aitchison EW, Kelley SL, Alvarez PJ, Schnoor JL (2000) Phytoremediation of 1, 4-dioxane by hybrid poplar trees. Water Environ Res 72(3):313–321 Alexander M (1978) Introduction to soil microbiology. Soil Sci 125(5):331 Ali S, Abbas Z, Rizwan M, Zaheer IE, Yava¸s ˙I, Ünay A, Abdel-Daim MM, Bin-Jumah M, Hasanuzzaman M, Kalderis D (2020) Application of floating aquatic plants in phytoremediation of heavy metals polluted water: a review. Sustainability 12(5):1927 Babatunde AO, Miranda-CasoLuengo R, Imtiaz M, Zhao YQ, Meijer WG (2016) Performance assessment and microbial diversity of two pilot scale multi-stage sub-surface flow constructed wetland systems. J Environ Sci 1(46):38–46 Baptista JD, Davenport RJ, Donnelly T, Curtis TP (2008) The microbial diversity of laboratory-scale wetlands appears to be randomly assembled. Water Res 42(12):3182–3190 Batool A, Saleh TA (2020) Removal of toxic metals from wastewater in constructed wetlands as a green technology; catalyst role of substrates and chelators. Ecotoxicol Environ Saf 1(189):109924 Brix H, Schierup HH (2020) Danish experience with sewage treatment in constructed wetlands. CRC Press. Chatterjee A, Das R, Abraham J (2020) Bioleaching of heavy metals from spent batteries using Aspergillus nomius JAMK1. Int J Environ Sci Technol 17(1):49–66 Chen J, Deng S, Jia W, Li X, Chang J (2021) Removal of multiple heavy metals from miningimpacted water by biochar-filled constructed wetlands: adsorption and biotic removal routes. Biores Technol 1(331):125061 Chen J, Li X, Jia W, Shen S, Deng S, Ji B, Chang J (2021) Promotion of bioremediation performance in constructed wetland microcosms for acid mine drainage treatment by using organic substrates and supplementing domestic wastewater and plant litter broth. J Hazard Mater 15(404):124125 Cheng S, Grosse W, Karrenbrock F, Thoennessen M (2002) Efficiency of constructed wetlands in decontamination of water polluted by heavy metals. Ecol Eng 18(3):317–325 Dan A, Oka M, Fujii Y, Soda S, Ishigaki T, Machimura T, Ike M (2017) Removal of heavy metals from synthetic landfill leachate in lab-scale vertical flow constructed wetlands. Sci Total Environ 15(584):742–750 Dey P, Malik A, Mishra A, Singh DK, von Bergen M, Jehmlich N (2020) Mechanistic insight to mycoremediation potential of a metal resistant fungal strain for removal of hazardous metals from multimetal pesticide matrix. Environ Pollut 1(262):114255 Gersberg RM, Elkins BV, Lyon SR, Goldman CR (1986) Role of aquatic plants in wastewater treatment by artificial wetlands. Water Res 20(3):363–368

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A. Chatterjee and M. P. Shah

Gomes HI, Mayes WM, Whitby P, Rogerson M (2019) Constructed wetlands for steel slag leachate management: partitioning of arsenic, chromium, and vanadium in waters, sediments, and plants. J Environ Manage 1(243):30–38 Guo X, Cui X, Li H, Xiong B (2021) Purifying effect of biochar-zeolite constructed wetlands on arsenic-containing biogas slurry in large-scale pig farms. J Clean Prod 10(279):123579 Hua T, Haynes RJ (2016) Constructed wetlands: fundamental processes and mechanisms for heavy metal removal from wastewater streams. Int J Environ Eng 8(2–3):148–178 Hua T, Haynes RJ, Zhou YF (2018) Potential use of two filter media in constructed wetlands for simultaneous removal of As, V and Mo from alkaline wastewater-batch adsorption and column studies. J Environ Manage 15(218):190–199 Hua T, Haynes RJ, Zhou YF, Boullemant A, Chandrawana I (2015) Potential for use of industrial waste materials as filter media for removal of Al, Mo, As, V and Ga from alkaline drainage in constructed wetlands–adsorption studies. Water Res 15(71):32–41 Jacob JM, Karthik C, Saratale RG, Kumar SS, Prabakar D, Kadirvelu K, Pugazhendhi A (2018) Biological approaches to tackle heavy metal pollution: a survey of literature. J Environ Manage 1(217):56–70 Kirby A (2002) Wastewater treatment using constructed wetlands. Can Water Res J 27(3):263–272 Li Q, Liu J, Gadd GM (2020) Fungal bioremediation of soil co-contaminated with petroleum hydrocarbons and toxic metals. Appl Microbiol Biotechnol 104(21):8999–9008 Lim PE, Tay MG, Mak KY, Mohamed N (2003) The effect of heavy metals on nitrogen and oxygen demand removal in constructed wetlands. Sci Total Environ 301(1–3):13–21 Lizama-Allende K, Ayala J, Jaque I, Echeverría P (2021) The removal of arsenic and metals from highly acidic water in horizontal subsurface flow constructed wetlands with alternative supporting media. J Hazard Mater 15(408):124832 Ma N, Wang W, Gao J, Chen J (2017) Removal of cadmium in subsurface vertical flow constructed wetlands planted with Iris sibirica in the low-temperature season. Ecol Eng 1(109):48–56 Mayes WM, Batty LC, Younger PL, Jarvis AP, Kõiv M, Vohla C, Mander U (2009) Wetland treatment at extremes of pH: a review. Sci Total Environ 407(13):3944–3957 Mengzhi C, Yingying TA, Xianpo LI, Zhaoxiang YU (2009) Study on the heavy metals removal efficiencies of constructed wetlands with different substrates. J Water Resour Prot 14:2009 Mohammed A, Babatunde AO (2017) Modelling heavy metals transformation in vertical flow constructed wetlands. Ecol Model 24(354):62–71 Papaevangelou VA, Gikas GD, Tsihrintzis VA (2017) Chromium removal from wastewater using HSF and VF pilot-scale constructed wetlands: overall performance, and fate and distribution of this element within the wetland environment. Chemosphere 1(168):716–730 Rahman KZ, Wiessner A, Kuschk P, van Afferden M, Mattusch J, Müller RA (2014) Removal and fate of arsenic in the rhizosphere of Juncus effusus treating artificial wastewater in laboratoryscale constructed wetlands. Ecol Eng 1(69):93–105 Salama ES, Roh HS, Dev S, Khan MA, Abou-Shanab RA, Chang SW, Jeon BH (2019) Algae as a green technology for heavy metals removal from various wastewater. World J Microbiol Biotechnol 35(5):1–9 Shah MP (2020) Microbial bioremediation & biodegradation. Springer Shah MP (2021) Removal of refractory pollutants from wastewater treatment plants. CRC Press Schwindaman JP, Castle JW, Rodgers JH Jr (2014) Fate and distribution of arsenic in a processdesigned pilot-scale constructed wetland treatment system. Ecol Eng 1(68):251–259 Thomson B, Hepburn CD, Lamare M, Baltar F (2017) Temperature and UV light affect the activity of marine cell-free enzymes. Biogeosciences 14(17):3971–3977 Valipour A, Ahn YH (2016) Constructed wetlands as sustainable ecotechnologies in decentralization practices: a review. Environ Sci Pollut Res 23(1):180–197 Vigneswaran S, Ngo H, Visvanathan C, Sundarvadivel M (2009) Wastewater recycle, reuse, and reclamation. Conv Water Treat Technol 1(2) Vymazal J (2010) Constructed wetlands for wastewater treatment. Water 2(3):530–549

Constructed Wetland for Metals: Removal Mechanisms and Analytical …

41

Vymazal J (2011) Constructed wetlands for wastewater treatment: five decades of experience. Environ Sci Technol 45(1):61–69 Vymazal J, Bˇrezinová T (2016) Accumulation of heavy metals in aboveground biomass of Phragmites australis in horizontal flow constructed wetlands for wastewater treatment: a review. Chem Eng J 15(290):232–242 Vymazal J, Kröpfelová L (2008) Types of constructed wetlands for wastewater treatment. In: Wastewater treatment in constructed wetlands with horizontal sub-surface flow, pp 121–202 Yeh TY, Chou CC, Pan CT (2009) Heavy metal removal within pilot-scale constructed wetlands receiving river water contaminated by confined swine operations. Desalination 249(1):368–373 Yu G, Peng H, Fu Y, Yan X, Du C, Chen H (2019) Enhanced nitrogen removal of low C/N wastewater in constructed wetlands with co-immobilizing solid carbon source and denitrifying bacteria. Biores Technol 1(280):337–344 Yu G, Wang G, Li J, Chi T, Wang S, Peng H, Chen H, Du C, Jiang C, Liu Y, Zhou L (2020) Enhanced Cd2+ and Zn2+ removal from heavy metal wastewater in constructed wetlands with resistant microorganisms. Biores Technol 1(316):123898 Zhao M, Wang S, Wang H, Qin P, Yang D, Sun Y, Kong F (2019) Application of sodium titanate nanofibers as constructed wetland fillers for efficient removal of heavy metal ions from wastewater. Environ Pollut 1(248):938–946 Zhao Q, Huang JC, He S, Zhou W (2020) Enhancement of a constructed wetland water treatment system for selenium removal. Sci Total Environ 20(714):136741

Role of Aerated Constructed Wetlands for Municipal Wastewater Treatment Pooja M. Patil, Rasiya C. Padalkar, Abhijeet R. Matkar, Ranjit Gurav , and Maruti J. Dhanavade

1 Introduction Water is important for the development of all aspects of society. The well-being and socio-economic progress are mainly depending on water availability. Water could not exhaust and reproduce (Koutsoyiannis 2020), though two-thirds of planet Earth is covered with water; very little water is available for human consumption. In the universe, total amount of water is the same since its formation. Water only gets recycled through a hydrological cycle. The preferences for water consumption are formulated as per the basic needs of human society by the government. The use of water is mainly for drinking, domestic, agriculture, and industrial consumption (Anand 2001). After the consumption of fresh water, it generates wastewater. The consumption of fresh water in various operations lastly produces wastewater. In other words, wastewater is “Used water from any combination of commercial, domestic, agricultural or industrial operations, stormwater/surface runoff, any sewer inflow, sewer seepage, and sewer infiltration” (Tilley 2014). In today’s modern world, urban centers P. M. Patil · R. C. Padalkar Department of Environment Management, Chhatrapati Shahu Institute of Business Education and Research, Kolhapur, India e-mail: [email protected] A. R. Matkar Department of Mechanical Engineering, D. Y. Patil College of Engineering and Technology, Kolhapur, India R. Gurav (B) Ingram School of Engineering, Texas State University, TX San Marcos, USA e-mail: [email protected] M. J. Dhanavade (B) Department of Microbiology, Bharati Vidyapeeth’s Dr. Patangrao Kadam Mahavidyalaya, Sangli, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. P. Shah (ed.), Recent Trends in Constructed Wetlands for Industrial Wastewater Treatment, https://doi.org/10.1007/978-981-99-2564-3_3

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consume water mostly for domestic purposes. This freshwater demand for domestic purposes in urban localities is increasing eventually due to changing lifestyles. Thus 3 R such as reduce, reuse, and recycle must be followed for sustainable water utilization in every consumption venture. In arid and semi-arid areas water is becoming a scarce resource and policymakers are subjected to think about any available sources of water that might be used practically and economically. Considering the present increasing demands of water, exact quantification for water consumption based on various necessary activities. A study shows that 55% of fresh water is used for agriculture, followed by residential which comes under domestic consumption such as washing, bathing, kitchen, flushing, etc. Another major consumption pathway is golf course irrigation. The commercial use of water in restaurants, resorts, swimming pools, etc., consume 4% of fresh water whereas the share of industrial water consumption is 2%, the same amount, i.e., 2% is used for irrigating and maintaining parks and gardens and 1% is used for institutional consumption (Next-generation storyline 2021). The average value of basic water utilization for urban life is 92 L/person/day, for healthy well-being but with restricted use of water. A more practical value is 175 L/person/day with a bit of relaxation on the usage of water (Crouch et al. 2021). Due to the changing development pattern, urban centers are becoming more populous and their demand for fresh water is increasing day by day. This demand needs to be fulfilled in a sustainable manner to maintain harmony in the community and to avoid conflicts over water sharing. In present situation, natural water resources are depleting rapidly, qualitatively, and quantitatively. Water reuse, rainwater harvesting, and water recycling are some of the important solutions to fulfill the increasing water demands. An increase in urban populations and expanded use of domestic water supply and sewerage producing large quantities of municipal wastewater. This municipal wastewater when mixed with natural water bodies or its discharge on land can create problems for public health and the local ecosystem. Discharging urban wastewater in natural water bodies can increase the nutritional content that leads to excessive growth of blue-green algae, depletion of dissolved oxygen, and killing of aquatic animals due to lack of oxygen and eventually resulted into a eutrophicated waterbody (Edokpayi et al. 2017). This heavy discharge of untreated municipality wastewater on land can cause soil pollution and contamination of pathogens in fresh water. With the current emphasis on public health, environment, and water pollution issues, there is an increasing awareness regarding the need to dispose of these wastewater safely and beneficially. Scientifically designed reuse of municipal wastewater reduces the chances of surface water pollution problems. These designs can conserve valuable water resources as well as recover the nutrients from wastewater by growing crops using this water (Pescod 1992). The concept of reuse of water can be implemented at the domestic level with scientifically designed minimum engineering work such as the use of septic tank and the use of its outlet water for gardening purposes, use of settlement chambers at homes, use of bathing water for flushing, etc. These small practices can decrease the need for domestic water per day at some level. Rainwater harvesting is also one of the promising methods for increasing the availability of domestic water in the scariest period. Storing rainwater in underground tanks or

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recharging borewells and groundwater can be helpful for enhancing the ground water table which in return will help in reducing the burden on the exploitation of available surface water sources. Water recycling is another method that includes recycling wastewater by removing the impurities from water and making it again available for agriculture or domestic consumption. Recycling of water is possible from a small scale to a large scale from a centralized to decentralized manner. Municipal wastewater has the potential for recycling as it does not contain hazardous chemicals and can be recycled by using economical techniques (Schaechter 2009; Shah 2020). Hence this book chapter is focused on advanced treatment methods and their recent updates to treat municipality wastewater that can be very applicable to serve the increasing demand of fresh water.

2 Municipal Wastewater The wastewater available at urban centers is municipal wastewater that falls into the low-strength category of waste streams. Low organic strength and high particulate organic matter are the major contents of municipal wastewater (Sikosana et al. 2019). Municipal wastewater generates after the consumption of domestic water, which involves, flushing, washing, bathing, etc. (Metcalf and Eddy 2003). During these processes, nutrients, pathogens, and harmful chemicals get combined with fresh water making it unsuitable for reuse and consumption. The maximum amount of wastewater is produced during the flushing process, then bath and showers. The multisectoral process of adding various sources into municipal wastewater thus it contains a complex composition. The major source of municipal wastewater is water coming out from domestic consumption, followed by various commercial sources such as servicing centers, restaurants, hotels, public toilets, clinics, etc., and then storm water which drains into the sewers in the form of surface runoff. This waste from various sources after mixing makes the composition of municipal wastewater more heterogeneous.

2.1 Types of Municipal Wastewater Based on the major component and origin municipal wastewater is divided into two major categories viz. black water and grey water. Urban centers, towns, and semi-urban demographic units produce municipal wastewater in two forms. One is grey water which includes wastewater from kitchen, washing, baths, gardens, and surface runoff whereas another is black water which contains human fecal waste and harmful pathogens.

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Greywater

Greywater is generated by various domestic activities, but it does not come in contact with feces when open defecation is strictly restricted and proper toilet facilities are available. Dirt, food particles, grease, and some household chemicals may be present in the greywater making it to look dirty. But this dirt can be removed with simple techniques and the nutrients present in this water are beneficial for plant growth. If this water gets mixed with natural water bodies in large quantities, it can create water pollution but when it is used for irrigation and home gardening it can act as liquid fertilizers for the plants (Sustainable water bodies 2020). Greywater, if reused scientifically, then the water scarcity problem can be solved at certain levels in arid regions.

2.1.2

Black Water

Black water mainly contains the water coming out from toilets which includes human fecal matter and urine. It contains harmful pathogens and the contamination of the same in drinking or domestic water can create serious health problems in the society by spreading epidemics like Gastro, Typhoid, Hepatitis, Cholera, etc. (Schweitzer and Noblet 2018). The generation of sewage is calculated based on the fresh water supplied to a particular community. Typically, 85% of fresh water is converted into black water (Samal 2016). The supply of fresh water for communities is based on the type of community. Urban settlements need more freshwater supply than rural settlements because of their mechanized way of living. Similarly, demand for fresh water is much less in developing countries than in developed countries and very low in under-developing countries.

2.2 Vital Contaminants and Sources in Municipal Wastewater Municipal wastewater comprises pollutants from both point and non-point sources. Point sources are those which can be identified, and non-points are those which cannot be identified (Taebi and Droste 2004). Contaminants from point sources entering in municipal wastewater mainly by household activities such as washing, flushing, bathing, kitchen waste, etc. Non-point sources like garden irrigation, surface runoffs, storm water, etc., are discharging pollutants in municipal wastewater. Mixing of these contaminant sources makes municipal wastewater difficult to categorize into types. Generally, the concentration of human origin pollutants is more in municipal wastewater, thus the typical composition of municipal wastewater is like nitrogen (N) 50 mg/L, phosphorus (P) 10 mg/L, and potassium (K) 30 mg/L along with traces of other minor nutrients, carbonates, and bicarbonates (Pescod 1992). The N, P, and K are essential nutrients useful for plant growth and can be made available by the recovery of these nutrients. Other pollution parameters of wastewater are total

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Table 1 Typical composition of wastewater (Samal 2016; Schweitzer and Noblet 2018) Parameters

Concentration Environmental impact mg/L

Suspended solids

200

Increases turbidity of water and reduces light penetration

Nitrogen (N)

40

If concentration get increased in natural waterbody, it increases the algal bloom

Phosphorus (P)

10

Increases algal bloom and responsible for eutrophication

Chloride

50

Increases electrical conductivity and corrosivity of water

Alkalinity (as CaCO3 ) 100

Alkalinity up to 200 mg/L is suitable for drinking purposes

Grease

100

Creates a layer on top of the waterbody which inhibits the penetration of oxygen and light into water

BOD

200

Reflects the amount of biodegradable matter in water. Higher BOD reduces the DO level in water which results in killing of fishes and disturbance in the aquatic food chain

solids, total dissolved solids, suspended solids, grease, BOD, and COD which are also important for deciding the treatment method to follow and the final disposal of wastewater. Final disposal of municipal wastewater is generally practiced in natural water bodies as well as for irrigation purposes (Table 1). The composition of wastewater is based on the sources of wastewater, as the sources vary, the composition will change. More amount of black water will increase the BOD percentage of wastewater. The wastewater coming from commercial sources will increase the grease and suspended solids whereas the percentage of N, P, and K will increase if the sources of wastewater are coming out from agricultural land, i.e., from non-point sources. If this untreated wastewater gets mixed with natural water bodies, these water bodies start accumulating nutrients and pollutants year after year. Once the natural healing capacity and carrying capacity of these water bodies ends, polluted water bodies start causing damage to aquatic ecosystems, eutrophication of lakes, killing of fishes, problems of public health and finally leading to water scarcity (Samal 2016). Various measures are in practice to resolve this water scarcity problem. Reusing and recycling wastewater is important in the present situation. The reuse of wastewater cuts down the absolute demand for fresh water and brings down the cost of water supply for the community. Although recycling adds some new costs to the water supply system but reduces pollution load from a natural water body and also brings down the cost of exploitation of new water resources such as ground water exploration, bringing clean water from far away for an urban community, etc.

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2.3 Current Treatment Methods for Municipal Wastewater Currently implemented wastewater treatment methods at urban centers mainly possess three types including physical, chemical, and biological methods most popularly activated sludge. These methods require large structures and considerable investment in infrastructure. The following are the most used methods for various types of domestic wastewater treatments.

2.3.1

Laundry Drum

The cheapest and simplest method for the reuse of greywater is the laundry drum technique. This technique is nothing but storing wastewater in a large barrel which is attached with a hose at the bottom and then using it for irrigation in the backyard. In areas like California where water use is strictly restricted due to recurrent droughts for many years, this technique can be used effectively. The important thing to remember is that the strict use of biodegradable detergents is very essential. To increase the efficiency of this technique, simple enrichment/neutralization techniques can be adopted to remove the adverse effects of domestic chemicals. To name a few, by testing the pH of stored water with the help of a pH strip, neutralization of water can be achieved by the addition of mild alkali/acid. The basic filter also can be added into the drum such as a sand filter and activated charcoal filter to remove the fine impurities that make water clearer. Keeping the stored water steady for a few hours will help to settle the suspended impurities at the bottom which can, later on, be used for manure making and clear water can be used for irrigation purposes. The dissolved impurities such as carbonates and bicarbonates are not harmful to the plants if used in limited quantities. The greywater coming out of the domestic consumption does not contain higher values of dissolved impurities and thus can be used for irrigation of ornamental, fruits, and avenue plants.

2.3.2

Indoor Greywater Treatment

One more alternative after giving preliminary treatment is the reuse of greywater for the flushing of toilets. The greywater contains more chemicals that are responsible for damaging the flora of septic tanks (Moja and March 2008). Reusing of greywater is more economical and efficient in commercial places like hotels and resorts where the use of water for flushing and washing is commonly more than in houses. With minimum technical advancement in flushing systems by plumbing arrangements the target of decreased consumption of fresh water can be achieved. At large scale such as hotels, resorts, or big townships, the reuse of greywater can be centralized with some basic treatment methods such as filtration, sedimentation, and disinfection. Dilution of freshwater can also be practiced if the concentration of greywater is high in certain parameters. For dilution, purposes rejected water from reverse osmosis flow also can

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be used by considering the TDS levels that are acceptable (Campisano and Modica 2010). Researchers found that filtration and chlorination are necessary treatments allowing the use of greywater effluents for toilet flushing in hotels (Mourad et al. 2011).

2.3.3

Septic Tanks for Black Water

Black water is the domestic wastewater coming out from toilets with more concentration of nutrients along with harmful pathogens (Adhikari and Lohani 2019). The use of septic tanks at the household level to treat black water is a conventional method available in various structures with basic common principles. Septic tanks contain two compartments, the first one is larger which allows sufficient time for scum formation and for suspended solids to settle into the sludge format. A separating wall makes the second compartment smaller which is used for the settlement of minor particles. The settled sludge undergoes anaerobic decomposition which letter converts into fertilizer known as night soil. The disposal of human waste has always been a major issue in cities and fragmented settlements. In developing countries like India, the construction of septic tanks is one of the low-cost methods of disposing human waste (Kunte et al. 2004). There are some concerns in the use of septic tanks and their sludge as fertilizer is the presence of enteric pathogenic bacteria that can cause public health problems. The seepage and percolation losses due to leakage of septic tanks can cause groundwater pollution. To reduce the fear of contaminating freshwater and groundwater by these pathogenic bacteria, improved methods of anaerobic digestion can be used.

2.3.4

Biogas Production

Biogas production from wastewater especially from black water is the process of biochemical conversion of waste into energy. The organic material in the form of sewage gets converted into methane gas which can be used for electricity generation and cooking purposes. In many rural areas, the toilets are attached directly to biogas chambers. Animal waste is also added into the pit which generates a good amount of methane gas and reduces the burden from the central sewage treatment unit. The slurry produced during the process of methanogenesis is completely decomposed organic matter, which has a good amount of N, P, and K along with some micronutrients. This slurry can be used as a soil fertilizer for agricultural applications. In developing countries like India, the use of solid/liquid waste will help to achieve win–win situations by increasing the availability of fuel for cooking purposes in remote areas where people are still dependent on wood for cooking purposes. This biogas will reduce the efforts of people, especially women to collect wood from remote areas (Mirmasoumi et al. 2018).

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Sewage Treatment Plant

Sewage treatment plants are the centralized treatment plants installed in towns, small cities, and metro cities. The sewage is brought down at low elevation points in the settlement area through drainage lines and treated at a large scale by using two or three stages. In these treatment plants, raw municipal sewage undergoes preliminary, primary, and then secondary treatment. In some cases, based on the end-use of treated water additional treatment is given (Use of Reclaimed Water and Sludge in Food Crop Production 1996). The sludge generated in the process should be disposed of properly by using conventional to advanced techniques. The Sun-drying technique is largely in use as it is an economical and feasible solution for all kinds of sewage treatment plants. The dried sludge brick can be used as a fertilizer for agriculture as it contains a good amount of organic matter along with a small amount of N, P, and K. Another use of the dried sludge bricks is for burning instead of using wood during cooking process. It will reduce the burden of firewood and ultimately protect the loss of forest. Hence these sewage treatment plants are highly applicable (Table 2). Table 2 Overview of different treatment methods (Mirmasoumi et al. 2018; Kunte et al. 2004) Treatment method Acceptance of waste

End-use

Type of method

Scale

Laundry Drum

Greywater, Washing outlet

Gardening

Reuse

Small scale, Decentralized &, at domestic level

Indoor greywater use

Greywater, Washing outlet

Flushing, Gardening

Reuse

Small scale, decentralized &, at domestic level

Septic Tank

Black Water

Discharge in waterbody, Soil application

Recycle and reuse

Medium Scale, Domestic level, small settlements, Townships, Apartments

Sewage Treatment Black Water Plant

Discharge in waterbody, Soil application for irrigation

Recycle and reuse

Large Scale, Towns, Cities

Constructed Wetlands

Discharge in waterbody, Soil application for irrigation

Recycle

Large scale, scattered settlements, townships, industrial colonies

Greywater and Black water

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3 Constructed Wetlands (CW) Wetlands are always an important ecological feature in the ecosystem. Wetlands are marshy land flooded with a thin layer of water and occupied by peculiar types of vegetation such as hydrophytes and microphytes. Wetlands act as a sponge for freshwater sources. They receive the water coming out from various natural and anthropogenic sources. These wetlands absorb the impurities, excess nutrients, and release the fresh water in the natural water body. Also, wetlands contribute to water regulations quantitatively. In the summer season, during the shortage of water, it releases the water and during the rainy season, it absorbs the excess water. These principles of wetlands can be used in constructed wetlands for the treatment of different types of wastewater. Artificially constructed wetlands (CWLs) are used to treat storm water, greywater, municipal sewage, and sometimes industrial wastewater. CWLs are useful for land reclamation also after mining, quarrying, etc. CWLs are civil structures that use natural principles of soil, microorganisms, and vegetation to extend secondary treatment to wastewater without percolation of water into groundwater. If the number of suspended particles and debris is more in wastewater then, primary treatment needs to be given for the same. In secondary treatment, the breakdown of complex molecules happens which reduces the chemical and biological load from the wastewater with microbial and Phyto remedial measures. CWLs act as a bio-sorbent for many pollutants like natural wetlands. It removes/reduces the impurities like harmful pathogens, heavy metals, nutrients, etc., and makes the treated water more acceptable to mix in natural freshwater bodies (Patil et al. 2022). The constructed wetland has some benefits over other treatment methods, such as it consumes very low energy for its operation. The energy requirement is for the pumping of water. In the case of aerated wetlands, the energy requirement is a little more to infuse the air into the water through aerators. Another benefit of constructed wetland is it uses technology based on natural principles, is simple to understand, and is manageable with limited resources. One of the important environmental benefits of the wetland is, it provides habitat for aquatic flora and fauna and helps in maintaining groundwater and surface water level. It also acts as a source for water storage in case of water scarcity. Apart from this, the CWLs act as a place for recreation and add aesthetic value to the locality. With the above benefits, CWLs are cost-effective in terms of construction and operation.

3.1 Constructed Wetlands and Their Types The CWLs are divided into various types. The primary classification is done based on the design of the structure and water flow systems. These different types of CWLs are used based on the type of wastewater and its end-use. Depending on the path of flow there are two main types of CWLs (Fig. 1).

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Fig. 1 CWLs and their classification for wastewater treatment

3.1.1

Free Water Constructed Wetlands

Free water CWLs also called surface flow constructed wetlands, these wetlands are having a horizontal flow of water across the roots of plants and flow above from the substrate medium. These wetlands appear like natural swamps. This wetland contains a few centimeters layer of wastewater and requires a large area for treatment. In this method, sometimes mosquito breeding can happen because of the stagnant water above the surface with very less water column. Aerobic digestion of sediments takes place in this process where halophyte plants act as an oxygen pump. These types of wetlands are useful where the wastewater flow rate is highly unpredictable but with minor pollution loads such as storm water surface flow treatments where anaerobic pretreatment is not required (Kilien Water 2019).

Emergent Plant Emergent plants, especially macrophytes are useful in reducing the wind speed which enables sedimentation and helps to settle wastewater faster without re-suspension. These plants also provide a substrate for microorganisms to grow and reduce the organic load present in wastewater. Macrophyte genera like Scirpus, Juncus, Eleocharis, Typha, and Juncus are found more efficient after studying 643 emergent plant-free water constructed wetlands from 43 countries (Vymazal 2013). The most important mechanism in an emergent plant constructed wetland is the submerged part of it which comes in contact with wastewater; the more the submerged biomass, the more will be the efficiency of the system. Emergent plant-free water constructed wetlands are effective in the treatment of wastewater from coal mines, drainage water, agriculture, dairy, and farmland.

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Submerged Plants Plant species that are completely submerged in the water also be used in free water constructed wetlands. Species like Potamagetoncrispus L., Myriophyllum spicatum L., Ceratophyllumdemersum L., Vallisnerianatans, and Hydrilla verticillata are some of the important and efficient submerged plant species especially used for removal of heavy metals like chromium, arsenic, and mercury (Chen et al. 2015). Submerged plants are thin and unstable biomass but it has a more exposed surface area as compared to emergent plants which come in contact with wastewater.

Free Floating Plants Nutrient uptake is one of the important mechanisms in wastewater purification, especially in municipal wastewater. Floating plants play an important role in the removal of nutrients from wastewater. Species like Eichhornia crassipes, Hottoniainflata, Salvinia minima, and Spirodelapolyrhiza are important free-floating species that can be used for municipal wastewater treatment. The use of framed structure for gathered and concentrated plant density is useful for effective treatment. Ecological floating beds (EFB) are structures made up of various materials. This frame-like structure keeps the floating plants together. EFB increases the efficiency of wastewater treatment.

3.2 Subsurface Flow Constructed Wetlands In subsurface flow, water flows from below the substrate medium, without surfacing above. It will allow the wastewater to flow between the roots of the plants. Due to subsurface flow, the system does not attract mosquitoes. A porous layer of gravel above the water flow restricts the odor nuisance in the atmosphere. The wastewater flows through the matrix created by roots which enables the maximum contact of wastewater with microorganisms present at the rhizosphere of a plant.

3.2.1

Vertical Subsurface Flow

A planted filter bed that drains the water at the bottom vertically is a vertical subsurface flow constructed wetland. With the help of a mechanical dosing system, wastewater is poured from above vertically through the filter mesh. The drained water is then collected at the bottom of a drainage pipe. An air pipe is situated below the substratum above the drainage pipe which provides aeration to the vertical flow and microflora. The enhanced aeration increases the rate of decomposition and nitrification of nitrate (Tietz et al. 2007). This method reduces BOD and suspended solids at high rates. It does not create the problem of mosquitoes because of the absence

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of surface water flow. This method is efficient in reducing organic carbon and other nutrients also. This system requires scientific design and expert construction with a steady supply of electricity for the dosing system (Vymazal 2007).

3.2.2

Horizontal Subsurface Flow

About 1% slope is given to the bottom of the constructed wetland and the wastewater flows through the filter media upon which the bacteria can grow. This system is good for removing solids, where facultative and anaerobic bacteria decompose most organics (García et al. 2005). It is a system with a large gravel and sand filter basin with vegetation. This system also does not create mosquito problems as the water flows through the subsurface and does not require an electricity supply. The nutrient removal is low in the system as compared with the vertical flow system and chances of clogging are also there (Suhaib and Bhunia 2022). Thus, it is useful to treat wastewater having less pollution load, such as greywater, bathing water, irrigation runoff, etc.

4 Aerated Constructed Wetlands Aerated CWLs are saturated wetland systems with integrated aeration systems that provide oxygen to microflora. This aerated CWL can cause aerobic decomposition for wastewater purification. The plants are used in these constructed wetlands. Along with soil and connected microorganisms, unwanted components are removed from municipal wastewater. The CWLs are a replica of natural wetlands with the required precaution to avoid the percolation of municipal wastewater into groundwater. This wastewater treatment unit is low cost, compare with other conventional wastewater treatment methods (Jethwa and Bajpai 2016). Though this treatment is economical the major point is that this treatment method needs a large operational area. An installed aeration system releases air bubbles that ascend in an upward direction which enables the gaseous oxygen transferred to a dissolved oxygen state (Nivala et al. 2020). Aerated CWLs are more efficient in pollutant removal than conventional anaerobic wastewater treatment methods. For municipal wastewater treatment, nitrogen/nitrate removal is one of the important objectives. For the removal of nitrate-nitrogen and ammoniacal nitrogen, the nitrification process is essential which requires the presence of oxygen. Horizontal flow constructed wetland with inbuilt aeration pipes enables this oxygen supply to the system. Surface flow constructed wetland is free-flowing water systems that enable contact with atmospheric oxygen and with water. In subsurface wetlands, the induced flow of air is needed to maintain the steady supply of oxygen in wastewater. Aerated constructed wetlands offer high efficiency in wastewater purification with minimum odor and system footprints when scientifically selected plants are used (Nivala et al. 2020).

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4.1 Criteria for Plant Selection in Aerated Constructed Wetlands Many wetlands ecosystem emergent plants can be used for the removal of nutrients in constructed wetlands. Different types of plants can be used in this type of ecosystem such as emergent rooted plants, floating plants, submerged rooted plants, etc. The plants which are able to withstand higher osmotic pressure have high nutrient removal capacity will work more efficiently in the system. Plants like Ecornia, duckweed are effective in nutrient removal along with a reduction in BOD and organic matter. Plant selection can be done based on climate, wastewater characteristics, end-use of treated water, and plant biomass.

4.1.1

Plants Used in Aerated Constructed Wetlands

The aquatic plants like Macrophytes are largely used in CWLs. It includes aquatic angiosperms, ferns, some larger algae, and aquatic mosses. The presence of ample light, water, and nutrients comes mostly from municipal sewage. The net primary productivity of wetlands is very high which ultimately consumes organic matter and other components at higher rates. The process of decomposition is also based on microbial activity and physical processes (Brix 2003). The most frequently used plants in the emergent category are Phragmites australis and Typha angustifolia. In the free-floating category Ecornia spp. and Lemnoideae family plants are mostly in use, whereas in the submerged category, Ceratophyllumdemersum, Heterantheradubia, Hydrilla verticillata are the most used plant species. In the selection of plant species for CWLs, care must be taken while introducing exotic species. Some exotic species can be invasive and able to create serious ecological problems in natural habitats. The species Ecornia has created such disturbances in natural ecology in many places in India as it was introduced as ornamental species and then became an invasive weed in many aquatic ecosystems. Local species which are efficient in nutrient removal and tolerant of high pollution loads are useful in CWLs.

4.1.2

Plant Tolerance to Municipal Wastewater

Plants that are used for numerous pollutant removal in aerated wetlands will undergo environmental stress. Numerous researchers revealed that in extreme circumstances municipal wastewater will surpass the plant tolerance and will limit treatment potential and plant survivorship (Patil et al. 2019a, b). In aerated CWLs, when an excess load of municipal wastewater contains toxic or contaminated pollutants, the method will operate hardly sustainably owing to subsiding the plant survivorship (Almeida et al. 2019). The environmental pollution also causes damage to plants that are present in wetlands, like eutrophication will inhibit the growth of the plant and also disappear the beneficial plants. The excess ammonia in municipal wastewater (MWW)

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will damage the plant physiology and flora will reduce its nutrient uptake capacity. Ammonia will lead to leaf impairment, root lowering, and chromatic symptoms of depression in yields as well as generate oxidative stress articulated through the enrichment in peroxidase and catalase activity. The research has been carried out to identify the plant tolerance ability against numerous wastewaters, these studies revealed that T. latifolia is stressed by an average concentration of ammonia with 155–170 mg/L, despite the S. validus enduring the extreme and risky contaminants present in MWW. The Zornia latifolia wetland plant species can also adapt to the great ammonia concentration present in wastewater (Chang et al. 2014). The MWW with high COD when disposed of in aerated CWLs then the P. australis wetland plant species has altered its normal metabolism. The extreme COD level has also caused obvious physiological variations in P. australis plant species. Other research specified that Sarcocornia fruticosa and Arundo donax have a prospective to treat more salinity concentration in MWW, and also eliminate nitrogen, organics, and phosphorus present in the MWW. The wetland plant species Typha angustata had an outstanding chromium accumulation ability and even persist to 32 mg/L chromium concentration for up to 19–20 days. Moreover, a study of the impending antibiotic effect on aerated wetlands exhibited that P. australis plant species remove and tolerate the concentration of antibiotics that are present in MWW. Consequently, these assessments are not only valuable for the understanding of wetland plant tolerance but also give the opening to select the excellent tolerant fauna species in aerated CWLs for treating MWW efficiently (Bryce et al. 2018).

4.1.3

The Capacity of Plants to Remove Impurities from MWW

Plants that are present in the wetland are considered to be the most crucial factor prompting the quality of water in the wetland. As the crucial biological constituent of aerated CWLs, floras perform as inter medium for decontamination mechanisms by enriching the diversity of elimination procedures and directly consuming phosphorus, nitrogen, and other organic nutrients. The wetland floras can also accumulate hazardous and toxic substances, like antibiotics, heavy metals, and other pollutants that exist in MWW. Earlier the research has been carried out on the plant uptake capacity in aerated CWLs (Huang et al. 2019). The uptake capacity of floras may change according to the retention times, system configurations, wastewater types, loading rates, and climate conditions. In the removal of P and N, the wetland plants have contributed high, respective 25–20% for P and 14–80% for N. The wetland plants have extensively removed emerging contaminants from MWW, like sulphonamides, trimethoprim, and carbamazepine when applies in aerated CWLs. For the removal of heavy metals, Eleocharis acicularis wetland flora is used and it has an excellent capacity to accumulate heavy metals like Pb, Cd, Cu, Ag, Zn, and Ir (Zhao et al. 2018) (Table 3).

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Table 3 Diverse plant species and their pollutant removal efficiency (Bryce et al. 2018; Zhao et al. 2018) Plant name

Media

Contaminant name Removal efficiency (%)

Flax Lily

Sand, Pea gravel, and loamy sand

Total Nitrogen

48–96

NOx

34–60

Total Phosphorus

7–37

Total Phosphorus

7–59

Foxtail Grass Banksia, and Bottlebrush Typha

T. latifolia

Fonthill sand Lockport dolomite

Total Phosphorus

19

Queenston shale

Total Phosphorus

18–29 66

P. australis

Gravels bed associated TSS with aquatic floras BOD

C. lurida

Clay and sand

Total Phosphorus

86

J. effusus

Total Phosphorus

76

D. acuminatum

Total Phosphorus

75

All of the above (Mixed)

Total Phosphorus

83

Ammonia

80

COD

97

BOD

71

Total Nitrogen

87

Common reed (Phragmites australis)

Gravels

Common reed and cattails

Phosphate S. pungens, P.australis, T.angustifolia

Paxton fine sandy loam BOD Total Phosphorus

89

61 70.5 69

TSS

93

Cattail, Club-rush, Heavy Clay Common water plantain, Meadowsweet Yellow flag, Compact rush, Reed canary grass

Total Phosphorus

7–68

Total Nitrogen

8–40

TSS

6–72

Ammonia

50–58

Cattails (Typha latifolia) with Scirpus acutis the borders

Ammonia

50

BOD

35

Total Nitrogen

38

Total Phosphorus

0.34

E. coli

59

Gravel

4.2 Benefits of Aerated Constructed Wetlands Crucial aspects disturbing the treatment performance comprise the plant species, temperature, flow type, hydraulic loading rate (HLR), and substrate characteristics. The HLR, associated with the available space for water flow over the aerated CWLs,

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is the primary characteristic of wastewater treatment. It is revealed that pollutant and contaminant removal in aerated CWLs was enhanced by declining HLR after hydraulic retention time (HRT) applied to the range from 5 to 15 days. An inferior HLR indicates more stable treatment and additional contact time, however, it requires a large land area (Xu et al. 2017). Physical methods like decantation, and sedimentation, play a crucial role in the removal of organic matter from wastewater, but in the winter, these methods are generally not effective. The biological methods are temperature dependent, in the winter season, their pollutant removing efficiency is also reduced. In winter temperature is low, which declines the level of dissolved oxygen in wastewater that results in less organic matter degradation by biological methods. In aerated CWLs, the oxygen availability is more as compared to CWLs which helps in the enhancement of the organic matter degradation process and hence can remove the pollutants efficiently from wastewater. It was revealed that plants can remove contaminants less than 10%, even though it is known to clear out nutrients in less loaded systems. Aerated CWLs plants are playing a significant role in holding their constituents in place, stopping erosion and landscape incorporation. Consequently, artificial aeration seems essential and proficient for high organic load, and municipal WWT (Shen et al. 2015).

4.2.1

The Prominence of Dissolved Oxygen (DO)

In aerated CWLs, for treating MWW, DO plays a substantial role as it upholds microbial activity. Depending upon the MWW properties and operational manipulation, the anoxic and aerobic areas of these aerated CWLs need to be optimized so that there will be instantaneous removal of inorganic nutrient, organic and contaminated materials. The DO has a key role to play in the decomposition of a biological substance by the transformation and mineralization process supported by microorganisms. The aerobic bacteria or microorganisms need oxygen to break the complex or toxic substances and produce carbon dioxide providing biomass and energy for other microorganisms (Resende et al. 2019). In CWLs, predominantly the aerobic microorganisms present near floras roots, where DO level is low so aerated CWLs enhance the level of DO. The DO is a most imperative parameter of water quality. DO is necessary for the existence of fish and the rest of the aquatic species which are present in aerated CWLs. In aerated CWLs for the photosynthesis process DO acts as a byproduct of aquatic flora. Even though in aerated CWLs by heterotrophic bacteria organic material is degraded aerobically and anaerobically contingent on DO level, aerobic decomposition is habitually more imperative than anaerobic decomposition. So, the DO level should be maintained in aerated CWLs to efficiently treat the MWW (Ji et al. 2020).

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59

Chemical Oxygen Demand (COD) Removal

In aerated CWL the HLR is related to COD removal. The COD of MWW will not decrease if HLR is more. The increase in HLR would decrease the interaction time between microbes and MWW, enhance the objectivity of microorganisms off substrate area, and reduce the oxygen availability. In aerated CWLs for COD removal from MWW, DO concentration is a vital part because aerobic degradation is more imperative, it is revealed that reduction in COD concentration was correlated positively with the aeration situation: continuous aeration induces COD removal with high efficacy than intermittent aeration, followed by non-aeration environments, respectively. It is revealed that in the summer season, there was an improvement in COD reduction in planted mesocosms wetlands as associated with unplanted, but on artificial aeration, no effect is seen. In winter, the reduction in COD in aerated wetlands was more significant than in non-aerated CWLs, both for unplanted and planted divisions. In winter the artificially supplemented oxygen counterbalanced the COD removal due to plants dormancy and temperature. When oxidation declines, the concentration of residual inert organic material accumulated raises, and the filtration matrix aggregates change the hydraulic by decreasing biological properties and HRT. The increasing availability of oxygen with artificial aeration reduces hydraulic clogging and enhances mineralization. Thus, aerated CWLs are beneficial, and significant in COD reduction (Yang et al. 2018). It has been considered that biological methods are dependent on the temperature, the change in temperature reduces the solubility of biological matter and activity of organic compounds. Yet, there is a controversial thought that COD elimination is dependent on the temperature. In the research, it is revealed that the efficiency of BOD purification declines when the temperature is low. The MWW is treated in aerated CWLs, and it is reported that the elimination rate of COD is dependent on temperature. The temperature is strongly interacted with eliminating and controlling the level of COD. In the winter season, the efficiency declined by 81% for planted CWLs, and for unplanted 74% decrease in effectiveness is seen. The BOD removal was higher in summer when the temperature is high. Some findings imply that the result of biological compounds is due to the soil microbes, microbial activity, and ability to degrade organic pollutants at low temperatures. It is indicated that the roots of plants and porous media balance the temperature of industrial wastewater and allow the microbes to continue their activity and functions. However, oxygen is a significant factor in treatment. If the concentration of oxygen is less, then the temperature will drop down and it will have a negative impact on the treatment efficiency (Cui et al. 2019).

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Nitrogen Removal

Removal of nitrogen in aerated CWLs arises due to biomass adsorption, volatilization, assimilation, and united with denitrification/nitrification. Denitrification/nitrification is more significant among these methods. Subsequently, denitrification and nitrification both are separate operations which correspondingly require anoxic and aerobic conditions, the nitrification rate impact significantly the total nitrogen removal. In aerated CWL the increase in HLR will decrease the removal effectiveness of nitrogen that exists in MWW. Aeration in CWLs will significantly enhance the availability of oxygen and thus improve the removal of ammonium from MWW. Intermittent aeration is most excellent for the removal of nitrogen, which simplifies denitrification by the temporal and spatial formation in anoxic areas of CWLs. The constant aeration accomplished the maximum nitrification, but the denitrification step is inhibited (Zhuang et al. 2019). The elimination of excessive nitrogen in aerated CWLs is done multiple times and includes ammonification, plant uptake, volatilization, nitrification/denitrification, and matrix adsorption. It has been well revealed that most nitrogen is eliminated by nitrifying and denitrifying bacteria. At root zones, the microbial activity of nitrogen elimination was dependent, and the elimination is much more dependent on the temperature. The MWW treating performance is seasonally cyclical and the temperature has a major effect on organic component reactions which are low at high temperatures. For the nitrification process, the optimum temperature required is within the range of 24–36 °C. The volatilization of ammonia increases 1.4–3.4 times, from 0 to 30 °C with 10 °C each increase in temperature. Similarly, the denitrification rates also get double with a 10 °C temperature rise. Hence, a low temperature will restrain bacterial metabolism, proliferation, and microbial nitrification process (Rehman et al. 2018).

4.2.4

Phosphorous Removal

Elimination of phosphorus from aerated CWLs is an outcome of microbial immobilization, microbial immobilization, porous media adsorption, plant uptake, wetland soil aeration, and water column precipitation. Plant uptake and bacterial activity are significant for phosphate elimination, whereas total phosphate elimination is preliminary related to the precipitation and media retention capacity. The seasonal differences in phosphorus elimination by the circumstance occurred during winter disorder, by decomposed microbial biomass, phosphorus that is discharged from precipitates, which solubilized in water. In the winter season due to the cold climate, the phosphorus elimination is indirectly affected by the availability of oxygen which impacts redox concentration, and the regression represents lower total phosphorus elimination efficiency (Rehman et al. 2018). At lower temperatures below 15 °C the phosphorus removal efficiency declines. However, above 15 °C there is an accountable increase in phosphorus elimination levels. When the phosphorus removal efficiency was compared between the summer and winter seasons, total phosphorus

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removal was 20% more efficient in the summer season as compared with winter. The elimination of phosphorus seemed to be sovereign on temperature if loading rate and contact time differ, hence the inorganic and physical removal methods are chiefly significant for total phosphorus elimination. It has been considered that phosphorus is present in a particulate manner and doesn’t get dissolved in filters that are not saturated by phosphorus or any other elements competing with adoration situates. It has been also concluded that persistent high loading will decrease the phosphorus removal efficiency (Zhuang et al. 2019).

4.2.5

Heavy Metal Removal

The presence of heavy metals in an aquatic water body through municipal wastewater is the primary threat to the ecosystem. Heavy metals can be removed by conventional physicochemical technologies like ion exchange, precipitation, membrane processes, and electrochemical. So, the aforementioned treatments are energy-intensive and expensive. The aerated CWL method is below maintained and low-cost treatment substitute for municipal wastewater, industrial effluent, specifically in developing cities. In aerated CWLs the approximate efficiency of metal removal was 82%, 83%, 55%, and 69% for chromium (Cr), iron (Fe), zinc (Zn), and nickel (Ni), respectively. In the horizontal aerated wetland, the metal removal efficiency (Cu, Zn, Al) of MWW was more than 84%. The metal removal effectiveness is intensely dependent on hydraulic loading rates and influent concentration. It is revealed that the heavy metals Cd, Cu, Ni, Pb, Zn, and Co could be removed readily by aerated CWL’s systems, however the removal of metal efficiency appears to be influenced by the used media types and the wastewater types which is to be treated (Patil and Bohara 2020). The elimination of trace metals is influenced by seasonal variation. Overall plant species variation, plant growth stage, characteristics of elements, metal translocation, and accumulation are the key factors to eliminate metals from various types of wastewater. Mostly in the wetland plants root tissues, the metals are accumulated and fewer concentrations exist in the above-ground portions of the plants. It has been revealed that the heavy metals in wetlands plants are more accumulated in the summer season as compared to winter. The interaction between sediments and plant roots is enhanced during the rising or growing season and declines in winter, where wetland plants decline or stop their metabolic activity. In sediments, the Zn and Pb concentration varies upon seasons, in the month of January it is well-defined, correspondingly during this month the root levels are low, and in the month of May it is prominently decreased. This indicates that the concentration of Zn and Pb in sediments is varied and it is reciprocal to the root variation. From March to September the biomass of roots substantially increases as a response to the increasing temperature, and the concentration of metal in wetlands plants roots followed a similar dissimilarity pattern (Rehman et al. 2018) (Fig. 2).

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Fig. 2 Benefits of aerated constructed wetlands

4.3 Factors Affecting Aerated Constructed Wetland Performance The performance of the aerated CWLs depends on numerous environmental and operational factors like HRT, HLR, temperature, DO, temperature, and pH. The characteristics of wastewater, flow rate, and the concentration of contaminants depend on the removal rate of parameters like total phosphorus, total nitrogen, ammonium, COD, BOD, heavy metals, etc. The abiotic components of aerated CWLs like media and biotic organisms like microorganisms and macrophytes are significant for several mechanisms involved in the treatment of wastewater. At low temperatures, the functioning of organic and inorganic components may get hampered. In the following paragraph, the influence of several environmental and operational factors has been provided (Jia et al. 2020).

4.3.1

Temperature Influence

Temperature plays a crucial role in the competent functioning of microorganisms and macrophytes in aerated CWLs. Therefore, seasonal variation is a principal aspect that considerably affects the organic and nutrient or contaminant removal efficiency in this technique. Extensive research has been carried out to determine the temperature influence on the aerated CWLs treatment method. Aerated CWLs are influenced by weather, a climate that causes frequent patterns in evapotranspiration, microbial activity, and photosynthesis. The seasonal distinct variation in elimination efficiencies observed in several studies accredited to changes in temperature in several seasons. It is revealed that the nutrient removal occurs at optimal temperature 30 °C

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(Li et al. 2020; Shah 2021). The more significant COD reduction was in the spring and summer seasons as compared to the autumn and winter season. The removal of nitrogen efficiencies was 7–11% more for aerated CWLs in summer than in winter. This research revealed that there is a direct association between microbial activity and temperature has the resultant impact on waste removal efficiency. The treatment performance of aerated CWLs in tropical areas has been higher than in cold regions and temperate areas due to temperature variances leading to improved phytoremediation by microbial activity and macrophytes, serving upgraded plant development and growth (Cui et al. 2019).

4.3.2

Macrophytes

In aerated CWL macrophytes are the most essential and used component for wastewater treatment, and their existence distinguishes aerated CWLs from unplanted lagoons or soil filters. The macrophytes are significant and effective in artificial as well as in natural systems. Depending upon the characteristics of water the macrophytes may be varied. During photosynthesis, the produced organic matter by macrophytes is a vitality source of heterotrophic activity. In saturated or waterlogged, macrophytes transport oxygen to microorganisms and the rest of the organisms. The contaminant removal efficiency of planted aerated CWLs has been carried out and it has a valuable role in the removal of different contaminants. The unplanted and plated aerated wetland studied regarding their COD removal efficiencies revealed that planted wetlands have 20% more efficiency to reduce COD than unplanted wetlands. A study on unplanted and planted wetlands in treating wastewater, and it was revealed that planted wetland has better efficiency in treating wastewater than an unplanted wetland. Flora plays several vital roles like root zone oxygen, improving aerobic decomposition, etc. These plants’ operations are often impacted by the adjacent temperature. This infers that the plant species selection based on the weather or climate of the place or site is a crucial feature for the accurate functioning and management of aerated CWLs.

4.3.3

Microorganisms

In the pollutants removal, chemicals, BOD, and COD, microorganisms have a significant role as they degrade or decompose the complex elements present in wastewater. The pollutant removal in aerated CWLs is done through several mechanisms like denitrification, decomposition of organic nitrogen, nitrification, volatilization, stabilization, etc. The microorganisms support mineral, nutrient, and organic pollutant transformation. The several bacterial species not only enhance the system performance but also improve the growth and development of a plant by providing essential nutrients. The dephosphorization and nitrogen-removing microbes remove the total phosphorus and nitrogen from MWW. The primary nutrient removal mechanism in microbes is nitrification, and denitrification, whereas the plant intake is of

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less significance. The nitrogen removal effectiveness from MWW at low temperature is largely inhibited due to curbed activity and the growth of nitrogen removal bacteria. It is observed that microorganisms’ metabolic action is negatively impacted by alteration in temperature. Temperature, waste characteristics, and treatment site are the principal aspect influencing the existence, development, growth, and activity of microbes.

4.3.4

Media

The aerated CW’s treatment performance mostly depends on the effective use of the media. The media or substrate sustenance of the macrophytes offer sites for chemical and biochemical transformations and offer areas for storage of aloof contaminants. The wetland matrix enacts the key role in the removal of contaminant from MWW, as the substrates offer constituents for bioreactors, and surface attachment for microorganisms. In substrate, clogging problems happen due to gravels, leading to flow resistance near inlets. The microbes and macrophytes are also responsible for eradicating a significant amount of contaminants but they are incapable of eradicating a significant portion of phosphorus. From MWW the phosphorus is eliminated through adsorption and sedimentation. The selection of media for the removal of phosphorus from MWW is critical. Various media have diverse characteristics. To prevent clogging more hydraulic conductivity is needed, which minimizes surface space resulting in fewer adsorption sites. Gravels have more hydraulic conductivity, but they remove the low concentrations of phosphorus as the constituents are impermeable and the surface area is low as compared to its volume (Wang et al. 2020). Research is conducted to evaluate the performance of media in terms of COD, TSS, and BOD reduction. Plastic is more effective in reducing the parameters of wastewater than gravel and rubber. Several potential media that have a positive impression on the contaminant removal are polyethylene, zeolite, organic wood mulch, lightweight aggregates, rice husk, peat, slag, alum sludge, etc. For nitrogen and organic matter reduction in aerated CWL, the substrate should contain anaerobic, aerobic pores, and carbon sources in a matrix to assist denitrification, nitrification, and reduction of organics. In media, the particles get accumulated, which reduces the efficiency of treatment by lessening the pore space (Fig. 3).

5 Future Consideration on the Sustainability of Aerated Constructed Wetlands The aerated CWLs have evolved as an efficient technology for the treatment of several wastewaters after years of research and implementation. The aerated CWLs increase the level of DO contributing to lessening clogging and preventing superior flow patterns by mixing and raising the temperature. The contaminant removal efficiency

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Fig. 3 Factors affecting aerated constructed wetlands

from wastewater of aerated CWLs is reliable on the climate, wastewater characteristics, media, and microorganisms so depending on its properties the aerated CWLs structure should be designed and modified accordingly. Looking toward water quality standards for treated wastewater and global water reuse, optimization, and modifications of wetland systems, should be studied future, and extensive investigation is required (Sun et al. 2018). The vegetation which is present in aerated CWLs should have supplementary thermal protection contrary to ice formations. An exhaustive evaluation of alterations between species, climate, and the season is also required. The substrate and plants selection specify in the aerated wetland is a critical issue for the removal of the sustainable contaminants from MWW treatment, more attention must be given to appropriate macrophyte species selection like a rich supply of carbon and oxygen compounds, more biomass production, and more contaminant uptake particularly emerging pollutant like pharmaceuticals compounds and heavy metals, acceptance of great contaminant loadings (Patil et al. 2019a, b). Certain non-conventional aerated wetland media, such as agriculture waste, an industrial byproduct, etc., has more sorption capability and it is advantageous for contaminant removal processes that should be instigated and developed for aerated CWLs. The operation and design factors reveal that the effectual treatment performance is extremely dependent on hydraulic, climate, operation, and environmental conditions. Hence, for treatment optimization extensive research, investigation and modification are essential. The research is going throughout the world regarding aerated CWLs. The innovative strategies and technologies for improved wastewater treatment are essential for the improvement in the quality of water in the future. These strategies and technology include step feeding, tidal operation, microbial augmentation, external carbon addition, a combination of several substrates, allocation of several plants, and

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the hybrid and baffled flow of aerated CWLs (Park et al. 2015). From the research, it is revealed that the nutrients and other contaminants integrated by aerated wetland plants are released into the water body when plants decay and die during the cold climate, which has poor performance in the removal of contaminants in aerated CWLs. Therefore, development and research on suitable plant harvest strategies, recycling, and reclamation of plant resources in aerated CWLs are needed in the present scenario (Jia et al. 2020).

6 Conclusion From extensive research and detailed understanding, it is clear that aerated CWLs are an emerging alternative method that is relevant to various functions, including treatment to MWW, industrial wastewater, strom water, bioremediation, etc. This aerated CWL has become an interesting option in the present situation because of its several useful characteristics such as easy operation and construction, less area requirement, and more importantly less cost. Macrophytes, media, temperature influence, and microorganisms have proved to play a vital role in contaminant removal from wastewater in aerated CWLs. To enhance the wastewater treatment performance, it is essential to explore the relations between plant development conditions and the efficiency of contaminant removal present in wastewater. Increasing the number of plant species will enhance the microorganism’s diversity in the plant’s root, which helps to improve the wastewater treatment performance in a positive manner. After several decades of research and its implementations to treat various wastewater aerated CWLs have become an efficient method. The aerated CWL’s level of DO is increased, it contributes to declining in the clogging problem and avoiding superior flow patterns by merging and rising the temperature. Hence, this detailed information about aerated CWLs for efficient wastewater treatment at a single place can be a major guideline to deal with the rising problem of wastewater and scarcity of fresh water in present situation as well as in the future.

References Adhikari JR, Lohani SP (2019) Design, installation, operation and experimentation of septic tank– UASB wastewater treatment system. Renew Energ 143:1406–1415. https://doi.org/10.1016/j. renene.2019.04.059 Almeida A, Ribeiro C, Carvalho F, Durao A, Bugajski P, Kurek K, Pochwatka P, Jó´zwiakowski K (2019) Phytoremediation potential of Vetiveria zizanioides and Oryza sativa to nitrate and organic substance removal in vertical flow constructed wetland systems. Ecol Eng 138:19–27. https://doi.org/10.1016/j.ecoleng.2019.06.020 Anand PB (2001) Consumer preferences for water supply? An application of choice models to urban India (No. 2001/145). WIDER Discussion Paper.

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Brix H (2003) Plants used in constructed wetlands and their functions. Ministerio das Cidades, Ordenamento do Territ¢rio E Ambiente. https://www.researchgate.net/publication/230563384_ Plants_used_in_constructed_wetlands_and_their_functions Bryce C, Blackwell N, Schmidt C, Otte J, Huang YM, Kleindienst S, Kappler A (2018) Microbial anaerobic Fe (II) oxidation–ecology, mechanisms and environmental implications. Environ Microbiol 20(10):3462–3483. https://doi.org/10.1111/1462-2920.14328 Campisano A, Modica C (2010) Experimental investigation on water saving by the reuse of washbasin grey water for toilet flushing. Urban Water J 7(1):17–24. https://doi.org/10.1080/157306 21003596739 Chang J, Fan X, Sun H, Zhang C, Song C, Chang SX, Gu B, Liu Y, Li D, Wang Y, Ge Y (2014) Plant species richness enhances nitrous oxide emissions in microcosms of constructed wetlands. Ecol Eng 64:108–115. https://doi.org/10.1016/j.ecoleng.2013.12.046 Chen G, Liu X, Brookes PC, Xu J (2015) Opportunities for phytoremediation and bioindication of arsenic contaminated water using a submerged aquatic plant: Vallisneria natans (Lour.) Hara. Int J Phytoremed 17(3):249–255. https://doi.org/10.1080/15226514.2014.883496 Crouch ML, Jacobs HE, Speight VL (2021) Defining domestic water consumption based on personal water use activities. AQUA—Water Infrastruct Ecosyst Soc 70(7):1002–1011. https://doi.org/ 10.2166/aqua.2021.056 Cui H, Yang Y, Ding Y, Li D, Zhen G, Lu X, Huang M, Huang X (2019) A novel pilot-scale tubular bioreactor-enhanced floating treatment wetland for efficient in situ nitrogen removal from urban landscape water: long-term performance and microbial mechanisms. Water Environ Res 91(11):1498–1508. https://doi.org/10.1002/wer.1147 Edokpayi JN, Odiyo JO, Durowoju OS (2017) Impact of wastewater on surface water quality in developing countries: a case study of South Africa. Water Qual:401–416.https://doi.org/10.5772/ 66561 García J, Aguirre P, Barragán J, Mujeriego R, Matamoros V, Bayona JM (2005) Effect of key design parameters on the efficiency of horizontal subsurface flow constructed wetlands. Ecol Eng 25(4):405–418. https://doi.org/10.1016/j.ecoleng.2005.06.010 https://greywateraction.org/greywater-reuse/ https://www.instructables.com/Simple-Laundry-Greywater-System/ http://www.kilianwater.nl/en/constructed-wetlands/solar-powered-water-treatment.html https://www.nextgenstorylines.org/where-does-all-of-our-clean-water-come-from-and-wheredoes-all-of-our-dirty-water-go Huang XF, Ye GY, Yi NK, Lu LJ, Zhang L, Yang LY, Xiao L, Liu J (2019) Effect of plant physiological characteristics on the removal of conventional and emerging pollutants from aquaculture wastewater by constructed wetlands. Ecol Eng 135:45–53. https://doi.org/10.1016/j.ecoleng. 2019.05.017 Jethwa, K.B. and Bajpai, S. 2016. Role of plants in constructed wetlands (CWS): a review. J Chem Pharm Sci 2:4–10. https://www.jchps.com/specialissues/2016%20Special%20Issue% 202/jchps%202%20Kruti%204-10.pdf Ji B, Chen J, Mei J, Chang J, Li X, Jia W, Qu Y (2020) Roles of biochar media and oxygen supply strategies in treatment performance, greenhouse gas emissions, and bacterial community features of subsurface-flow constructed wetlands. Bioresour Technol 302:122890. https://doi. org/10.1016/j.biortech.2020.122890 Jia L, Liu H, Kong Q, Li M, Wu S, Wu H (2020) Interactions of high-rate nitrate reduction and heavy metal mitigation in iron-carbon-based constructed wetlands for purifying contaminated groundwater. Water Res 169:115285. https://doi.org/10.1016/j.watres.2019.115285 Koutsoyiannis D (2020) Revisiting the global hydrological cycle: is it intensifying? Hydrol Earth Syst Sci 24(8):3899–3932. https://doi.org/10.5194/hess-24-3899-2020 Kunte DP, Yeole TY, Ranade DR (2004) Two-stage anaerobic digestion process for complete inactivation of enteric bacterial pathogens in human night soil. Water Sci Technol 50(6):103–108. https://doi.org/10.2166/wst.2004.0365

68

P. M. Patil et al.

Li Y, Guo J, Li H, Song Y, Chen Z, Lu C, Han Y, Hou Y (2020) Effect of dissolved oxygen on simultaneous removal of ammonia, nitrate and phosphorus via biological aerated filter with sulfur and pyrite as composite fillers. Bioresour Technol 296:122340. https://doi.org/10.1016/j. biortech.2019.122340 Metcalf and Eddy, Burton FL, Stensel HD, Tchobanoglous G (2003) Wastewater engineering: treatment and reuse. McGraw Hill. Mirmasoumi S, Ebrahimi S, Saray RK (2018) Enhancement of biogas production from sewage sludge in a wastewater treatment plant: evaluation of pretreatment techniques and co-digestion under mesophilic and thermophilic conditions. Energy 157:707–717. https://doi.org/10.1016/j. energy.2018.06.003 Moja GM, March JG (2008) Monitoring of an indoor pilot plant for osmosis rejection and greywater reuse to flush toilets in a hotel. Desalination 219(1–3):81–88. https://doi.org/10.1016/j.desal. 2007.02.033 Mourad KA, Berndtsson JC, Berndtsson R (2011) Potential fresh water saving using greywater in toilet flushing in Syria. J Environ Manage 92(10):2447–2453. https://doi.org/10.1016/j.jen vman.2011.05.004 Nivala J, Murphy C, Freeman A (2020) Recent advances in the application, design, and operations & maintenance of aerated treatment wetlands. Water 12(4):1188. https://doi.org/10.3390/ w12041188 Park JH, Kim SH, Delaune RD, Cho JS, Heo JS, Ok YS, Seo DC (2015) Enhancement of nitrate removal in constructed wetlands utilizing a combined autotrophic and heterotrophic denitrification technology for treating hydroponic wastewater containing high nitrate and low organic carbon concentrations. Agric Water Manage 162:1–14. https://doi.org/10.1016/j.agwat.2015. 08.001 Patil PM, Bohara RA (2020) Nanoparticles impact in biomedical waste management. Waste Manage Res 38(11):1189–1203. https://doi.org/10.1177/0734242X20936761 Patil PM, Mahamuni PP, Abdel-Daim MM, Aleya L, Chougule RA, Shadija PG, Bohara RA (2019a) Conversion of organic biomedical waste into potential fertilizer using isolated organisms from cow dung for a cleaner environment. Environ Sci Pollut Res 26(27):27897–27904. https://doi. org/10.1007/s11356-019-05795-7 Patil PM, Mahamuni PP, Shadija PG, Bohara RA (2019b) Conversion of organic biomedical waste into value added product using green approach. Environ Sci Pollut Res 26(7):6696–6705. https:// doi.org/10.1007/s11356-018-4001-z Patil R, Zahid M, Govindwar S, Khandare R, Vyavahare G, Gurav R, Desai N, Pandit S, Jadhav J (2022) Chapter 8 - Constructed wetland: a promising technology for the treatment of hazardous textile dyes and effluent. In: Shah M, Rodriguez-Couto S, Biswas J (eds) Development in wastewater treatment research and processes. Elsevier, pp 173–198. https://doi.org/10.1016/ B978-0-323-85583-9.00016-8 Pescod (1992) Wastewater treatment and use in agriculture. FAO, Irrigation and Drainage, Paper 47. Rehman K, Imran A, Amin I, Afzal M (2018) Inoculation with bacteria in floating treatment wetlands positively modulates the phytoremediation of oil field wastewater. J Hazard Mater 349:242–251. https://doi.org/10.1016/j.jhazmat.2018.02.013 Resende JD, Nolasco MA, Pacca SA (2019) Life cycle assessment and costing of wastewater treatment systems coupled to constructed wetlands. Resour Conserv Recycl 148:170–177. https:// doi.org/10.1016/j.resconrec.2019.04.034 Samal SS (2016) Design of Sewage Treatment Plant.https://doi.org/10.9790/1684-1305052531 Shah MP (2020) Microbial bioremediation & biodegradation. Springer Shah MP (2021) Removal of refractory pollutants from wastewater treatment plants. CRC Press Schaechter M (2009) Encyclopedia of microbiology. Academic Press Schweitzer L, Noblet J (2018) Water contamination and pollution. Green Chem. https://doi.org/10. 1016/B978-0-12-809270-5.00011-X

Role of Aerated Constructed Wetlands for Municipal Wastewater …

69

Shen Z, Zhou Y, Liu J, Xiao Y, Cao R, Wu F (2015) Enhanced removal of nitrate using starch/PCL blends as solid carbon source in a constructed wetland. Bioresour Technol 175:239–244. https:// doi.org/10.1016/j.biortech.2014.10.006 Sikosana ML, Sikhwivhilu K, Mountloaki R, Madyira DM (2019) Municipal wastewater treatment technologies: a review. Procedia Manufacturing. 35:1018–1024. https://doi.org/10.1016/j.pro mfg.2019.06.051 Suhaib KH, Bhunia P (2022) Dynamics of clogging in subsurface flow constructed wetlands. J Haz Tox Radioact Waste 26(1):03121004. https://doi.org/10.1061/(ASCE)HZ.2153-5515.0000646 Sun H, Yang Z, Wei C, Wu W (2018) Nitrogen removal performance and functional genes distribution patterns in solid-phase denitrification sub-surface constructed wetland with micro aeration. Bioresour Technol 263:223–231. https://doi.org/10.1016/j.biortech.2018.04.078 Taebi A, Droste RL (2004) Pollution loads in urban runoff and sanitary wastewater. Sci Total Environ 327(1–3):175–184 Tietz A, Kirschner A, Langergraber G, Sleytr K, Haberl R (2007) Characterisation of microbial biocoenosis in vertical subsurface flow constructed wetlands. Sci Total Environ 380(1–3):163– 172. https://doi.org/10.1016/j.scitotenv.2003.11.015 Tilley E (2014) Compendium of sanitation systems and technologies. Eawag. Use of Reclaimed Water and Sludge in Food Crop Production (1996) National Academy Press, Washington, DC, pp 3, 45. Vymazal J (2007) Removal of nutrients in various types of constructed wetlands. Sci Total Environ 380(1–3):48–65. https://doi.org/10.1016/j.scitotenv.2006.09.014 Vymazal J (2013) Emergent plants used in free water surface constructed wetlands: a review. Ecol Eng 61:582–592. https://doi.org/10.1016/j.ecoleng.2013.06.023 Wang Y, Cai Z, Sheng S, Pan F, Chen F, Fu J (2020) Comprehensive evaluation of substrate materials for contaminants removal in constructed wetlands. Sci Total Environ 701:134736. https://doi. org/10.1016/j.scitotenv.2019.134736 Xu D, Xiao E, Xu P, Zhou Y, He F, Zhou Q, Xu D, Wu Z (2017) Performance and microbial communities of completely autotrophic denitrification in a bioelectrochemically-assisted constructed wetland system for nitrate removal. Bioresour Technol 228:39–46. https://doi.org/10.1016/j.bio rtech.2016.12.065 Yang Z, Yang L, Wei C, Wu W, Zhao X, Lu T (2018) Enhanced nitrogen removal using solid carbon source in constructed wetland with limited aeration. Bioresour Technol 248:98–103. https://doi. org/10.1016/j.biortech.2017.07.188 Zhao Y, Cao X, Song X, Zhao Z, Wang Y, Si Z, Lin F, Chen Y, Zhang Y (2018) Montmorillonite supported nanoscale zero-valent iron immobilized in sodium alginate (SA/Mt-NZVI) enhanced the nitrogen removal in vertical flow constructed wetlands (VFCWs). Bioresour Technol 267:608–617. https://doi.org/10.1016/j.biortech.2018.07.072 Zhuang LL, Yang T, Zhang J, Li X (2019) The configuration, purification effect and mechanism of intensified constructed wetland for wastewater treatment from the aspect of nitrogen removal: a review. Bioresour Technol 293:122086. https://doi.org/10.1016/j.biortech.2019.122086

Constructed Wetlands for Remediating Organic Hydrocarbons: An Approach for the Sustainable Environmental Cleanup Ritu Rani, Jitender Rathee, Nater Pal Singh, and Anita Rani Santal

1 Introduction Wastewater generated from various industries has a great concern for the environment. Industrial effluents contain toxic materials such as heavy metals, organic hydrocarbons, polyaromatic hydrocarbons, lubricants, waxes, and other organic compounds (Chand et al. 2022). The wastewater containing aromatic hydrocarbon compounds affects the aquatic ecosystem by decreasing the dissolved oxygen level in the water bodies and increasing the death rate of aquatic organisms, increasing the Biochemical Oxygen Demand (BOD). The petrochemical effluents with organic hydrocarbons made the poor water quality of the Ubeji Creek in the Niger Delta of Nigeria reported by Uzoekwe and Oghosanine (2011). Exposure to highly toxic aromatic hydrocarbons over a long period also affects human health (Zhang et al. 2022). Moreover, these hydrocarbons may even move into the water table and cause biomagnification. There is an urgent need for constructed wetland systems to capitalize on the internal processes used to improve water quality. The constructed wetland system can be converted into natural or artificial ecosystems to clean the environment (Fig. 1). These wetlands are generally constituted of different compartments: soil, microorganisms, biomass, sediments, plants, and effluents loaded with toxic chemicals (Jain et al. 2021). The wetland systems also have a drain field that can be constructed for water filtration and thus return to the environment. The two basic designs for the construction of the wetland systems majorly work for the primary reason: wastewater treatment that is surface flow and subsurface flow. In the subsurface flow constructed wetlands (SSF), the water flow in a horizontal R. Rani · J. Rathee · A. R. Santal (B) Department of Microbiology, Maharshi Dayanand University, Haryana 124001 Rohtak, India e-mail: [email protected] N. P. Singh Centre for Biotechnology, Maharshi Dayanand University, Haryana 124001 Rohtak, India © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. P. Shah (ed.), Recent Trends in Constructed Wetlands for Industrial Wastewater Treatment, https://doi.org/10.1007/978-981-99-2564-3_4

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Fig. 1 Constructed wetland system for remediation of different Organic hydrocarbons (Liu et al. 2021)

manner parallel to the surface or maybe in the vertical direction through the matrix and out of the system, while the water moves above the substrate surface in surface flow wetlands (SF). The wetland systems have been previously studied and reviewed in the sewage treatment plants. In recent years, the application of the constructed wetland systems has become a cost-effective and experimentally proved technology for removing the various organic compounds from the water bodies and underground water (Ayaz et al. 2020; Shah 2020). Therefore, the constructed wetland systems have come with great potential for the remediation of the highly concentrated organic hydrocarbons in the surface water and underground water that significantly affect the environment. Different strategies such as environmental factors have been employed to influence the organic contaminant removal efficiency (Thullner et al. 2018). Several methods (physical, chemical, and biogeochemical processes) with the association and transformation of organic hydrocarbons present in water were evaluated in the constructed wetland systems. The constructed wetland systems are coursed on the performance, whereas the integrated wetlands with microbes or molecular activities had been investigated for the degradation and sorption of the organic hydrocarbons. Various advantages of using constructed wetlands for wastewater treatment have been reported. This method is cheaper and can be easily operated virtually compared to

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the conventional methods. The wetland systems also benefitted from multi-purpose sustainable utilization for swamp fisheries, seasonal agriculture, wildlife conservation, and research purposes. Wetland systems can be alternative or supplementary wastewater treatment systems in developing countries (Araneda et al. 2018; Shah 2021). This book chapter focuses on the critical processes that determine the presence of organic hydrocarbons in constructed wetland systems, intending to improve their pilot studies and various waste treatment methods. It primarily focuses on a few categories of contaminants of global significance, namely organic hydrocarbons, organochlorines, PAHs, and some pharmaceuticals. Overall, degradation is given special attention because it is expected to be a sink of organic chemicals in constructed wetlands.

2 Constructed Wetland Systems Wetlands are generally traditionally built areas between land and water that can be differentiated and characteristics maintained by the plants adapted on the wet soils and the depth of the water table. Wetlands are mainly classified into three types based on their dominant plants such as marshlands, salt, freshwater swamps, and bogs (Deng and Zhao 2015). Swamps are the flooded regions mainly influenced by water-tolerant woody plants; marshlands are influenced by soft-stemmed plants, while bogs have acid-loving plants and bryophytes. For more than 50 years, the constructed wetland systems have been employed for wastewater treatment (Rahman et al. 2020). The wetlands that are constructed with the horizontally subsurface flow (HF) and vertically subsurface flow (VF) were intensively studied. The constructed wetlands technology requires the design, operation, and application of the removal of organic hydrocarbons (Fig. 2) (Langergraber and Dotro 2019). The data represented in Table 1 showed various types of waste materials earlier studied for the constructed wetland capability. The materials such as cork, rice husks, and woodchips had shown maximum filtration mechanisms in the constructed wetland. However, crushed PET bottles did not work in the constructed wetland systems (Table 1).

3 Organic Hydrocarbons and Their Types Organic Hydrocarbons such as polyaromatic hydrocarbons (PAHs) are majorly detectable industrial recalcitrant widely distributed in the various water bodies like lakes, ponds, estuaries, etc. In a recent study, Yan et al. (2022) reported that out of roughly 110 major types of organic pollutants, PAH was the dominant organic contaminant with a concentration of 548–2598 ng/L in the upper reach of the Yellow

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Fig. 2 Various types of constructed wetland to remove organic hydrocarbons from the ecosystem Table 1 Different types of filtration methods are employed on the various waste materials on the constructed wetland systems Waste material

Constructed wetland type

Scale for filtration

Region

Reference

Clay brick fragments Cork granulates Coal slags Snail shells

VF

Microcosm

Portugal

Mateus and Pinho (2020)

Rice husk

HF

Mesocosm

Vietnam

Anh et al. (2020)

Waste bricks

VF-upflow

Microcosms

China

Zhang et al. (2022)

Woodchips Alum sludge

HF (baffled)

Microcosms

China

Yuan et al. (2020)

Coco peat Steel slag Concrete blocks

VF (tidal)

Mesocosm

Bangladesh

Saeed et al. (2020)

Porous slag

Batch CW

Microcosm

China

Liang et al. (2019)

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River, China (Zhao et al. 2015) (Table 2). Furthermore, Liu et al. (2020) reported that the concentration of PAH was up to 670.1 ng/L in the Yarlung Tsangpo river basin, China. There are primarily 16 major organic hydrocarbons that belong to PAHs and have been identified as exceedingly toxic contaminants by the US EPA and the EU, including naphthalene (Naph), acenaphthene (Ace), fluorene (Fl), pyrene, acenaphthylene (Acyl), phenanthrene (Phen), anthracene (Anth), fluoranthene (F), (da Silva Vilar et al. 2021). These PAHs are predominantly observed near the river basin of various countries with the accumulation in the ecosystem (Table 2). Carcinogenic PAHs, Benz(a)anthracene (B[a]A), require special consideration and relatively strict standards than that of other types of PAHs. As a result, nearly equivalent PAH amounts can have a diverse variety of ecological toxic side effects based on the component mix and therefore should be controlled following the specified standards to minimize the major environmental threat. Table 2 Distribution of polyaromatic hydrocarbons in the surface water Surface water location

Duration of water sampling

Various PAHs

Different concentrations of PAHs in surface water (ng/L)

References

The top surface of 2013 Yellow River, China

16

548–2,598

Zhao et al. (2015)

Ogbese River, Nigeria

2015

16

6.25 × 103 –1.393 × 104

Oladoja et al. (2017)

Huai River, China

2015

16

891–1,951

Zhang et al. (2022)

Liaohe River

2011

16

840.50–4,274.73

Wang et al. (2016a, b)

The lower region of 2016 the Yangtze River

13

67.68–573.02

Yan et al. (2022)

Yarlung Tsangpo River, China

2016

16

315.4–670.1

Liu et al. (2020)

Urban River of Shanghai, China

2015

16

71.92–460.53

Liu et al. (2016)

Guanlan River, China

2017

16

1.85–7,124.25

Liang et al. (2019)

Elbe River, Germany

2001–2016

16

73.37–121.28

Li et al. (2019)

Chaobai River system, China

2017–2018

16

55–882

Qiao et al. (2021)

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4 Removal Processes of Various Organic Hydrocarbons in Constructed Wetland In a complex constructed wetland system, various pathways may selectively break down many hydrocarbons from the ecosystem. According to Kadlec (1999), the organic chemical compound throughout the wetlands also undergo volatilization, microbial degradation, sedimentation, sorption, and photochemical oxidation (Table 3). This table lists the physicochemical properties of various organic pollutants for constructed wetland treatment. The following section emphasizes the proper relationship between many physicochemical characteristics and the fate of various pollutants through constructed wetland systems. The different types of organic hydrocarbons are mentioned according to the water-soluble property. The positive (+) and negative (−) symbols are associated with the definite removal mechanism observed by the constructed wetland systems (Table 3). The importance of a particular mechanism varies greatly depending on the type of organic hydrocarbons in the water, the wetland type vertical flow (VF) or horizontal Table 3 Various types of physicochemical processes are involved in the treatment of different types of organic pollutants in the constructed wetland systems Types of organic hydrocarbons

Different processes involved in References the constructed wetlands

Chlorobenzenes (1–2 Cl substituents)

Microbial degradation, volatilization (+), sorption

Keefe et al. (2004)

PCDD, PCDF

Sorption (+), microbial degradation (hypothesized)

Campanella et al. (2002)

PAH (3–6 rings)

Sorption (+), microbial degradation (+), plant uptake and metabolism (−)

Harms et al. (2003)

Fuels: kerosene C9–16, diesel C10–19, heavy fuel oil C20–70

Microbial degradation, sorption, sedimentation, volatilization

Omari et al. (2003)

Ibuprofen

Microbial degradation, sorption

Matamoros et al. (2005)

BTEX

Microbial degradation, volatilization (+), sorption

Wallace and Kadlec (2005)

Chlorinated solvents (1–2 C–atoms)

Plant uptake and metabolism (+), volatilization (+), phytovolatilization, microbial degradation (−), sorption

Kassenga et al. (2004)

Phenol, cresols

Microbial degradation (+), sorption, volatilization (−)

Abira et al. (2005)

PCBs

Sorption (+), microbial degradation, plant uptake, and metabolism (−)

Campanella et al. (2002)

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flow (HF), and operational design based on environmental conditions, retention time, vegetation type mainly within the wetland system, and also on soil matrix (Araneda et al. 2018). The rough estimation of organic hydrocarbon reduction in traditional wastewater treatment has been mainly based on Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) values. However, the proper treatment of organic hydrocarbons in fully constructed wetland systems has already been collaborated on the good establishment. The organic chemical compounds exhibited a wide range of physicochemical properties and a degree of recalcitrance that has not been visible in common contaminants in water located in agricultural and domestic sewage (Deng and Zhao 2015). Evaluating various physicochemical features and physiological activities of certain groups of organic hydrocarbon compounds in terms of their potential capacity and then identifying the results using artificial wetlands could help develop different operating and design methods for constructing wetland (Thawaba and Brahana 2009).

5 Destructive and Non-destructive Methods 5.1 Destructive Methods It involves the degradation of organic hydrocarbons using biological, chemical, physicochemical, or thermal methods. This remediation approach can be in-situ or ex-situ treatment. The destructive methods are used to adsorb, separate, remove, extract, destroy, transform, and then mineralize the various organic compounds into less toxic forms in the environment.

5.1.1

Phytodegradation of Organic Pollutants

The degradation of organic pollutants using plants is known as phytodegradation. In this process, enzymes produced by plants help decompose major organic pollutants. Biochemical changes of various organic contaminants have been demonstrated in a wide variety of plants, which include typically constructed wetland plants such as broad-leaved cattail (Typha latifolia), common reed (Phragmites australis), and some Populus species (Limmer and Burken 2016). The ability of plants to break the organic pollutants is primarily examined by the compound of interest. The P. australis has been shown to have various enzymes that break PCBs with up to three chloride ions, while greater chlorine-based PCBs were not changed easily. The deterioration of solvents with chlorine by blended poplar trees (P. trichocarpa crossed with P. deltoides) and other plants is an outstanding example of organic hydrocarbons’ physiological and metabolic changes using the constructed wetlands (Valujeva et al. 2018). For these pollutants, physiological and metabolic degradation can be quite effective. Phytodegradation is the predominant technique for removing carbon tetrachloride, hexachloroethane, and DDT from wastewater.

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Biodegradation of Organic Hydrocarbons Using Microorganisms

The degree of biodegradation of diverse organic chemical compounds in constructed wetland systems and the kind of biodegradation is thought to be highly impacted by the contaminant’s physicochemical qualities. The rate of organic compound degradation or the recalcitrant nature of a compound always depends on the chemical structure of organic compounds and various functional groups attached to the hydrocarbons. However, the Stockholm Convention categorized all compounds with chlorine substituents as persistent organic pollutants. These compounds can be cleaved through their carbon and chlorine bonds using constructed wetland systems (Imfeld et al. 2009). Various microbial metabolic pathways have been studied to degrade organic pollutants in wetlands. Toxic organic substance disposal is primarily a microbially mediated procedure that could be further subdivided into aerobic and anaerobic biodegradation methods. A few authors reported on the research of removing organic compounds in constructed wetlands, in which some contaminants were attributed to degradation by microbes. The subsequent section can provide a total view of significant pollutant groups. To date, there is a lack of supply of experimental evidence that allows for identifying microbial degradation routes and quantifying important organic deterioration potentials in constructed wetlands. To assess microbial degradation, indirect strategies such as quantification of degradation processes alternatively (sorption, volatilization) are used in the constructed wetlands (Kulshrestha et al. 2020).

Constructed Wetland System for Remediation of Petroleum Hydrocarbons Petroleum hydrocarbons are a large group that consists mainly of naphthalenes, paraffines, polyaromatic and aliphatic hydrocarbons in different amounts, such as 49%, 55.52%, and 3.9%, respectively (Kuppusamy et al. 2020). They are frequently examined as composite parameters in constructed wetland investigation, such as total aromatic and aliphatic hydrocarbons, total petroleum hydrocarbons, and gasoline varieties of organic compounds (Mustapha and Lens 2018). In contrast, the compounds with a high molecular weight observed in wax and tar fragments and most hydrocarbons generally located in fuels are substantially more water-soluble than the PCBs and PAHs (Srogi 2007). These organic pollutants have a high potential for sorption and are usually exceptionally deteriorated; thus, they mineralize in the presence of oxygen. A few authors have reported earlier substantial removal efficiencies of hydrocarbons in well-constructed wetlands (Tietz et al. 2008). Jin and Kelley (2007) investigated the association between the removal of crude oil, the home-grown fungal, and bacterial microflora observed in a constructed wetland. Rahman et al. (2020) confirmed the removal rates of hydrocarbon up to 90% in a constructed wetland system with a quite porous mineral substrate matrix. For the removal of organic hydrocarbons, the sorption methods were designated up to 10% of the reduction, and volatilization was approximated at 25%, degradation by microbes and uptake by the plant were supposed to be 60% of the experiential losses.

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Constructed Wetland System for Remediation of Highly Chlorinated Compounds (PCBs) The PCBs have low bioavailability, low water solubility, and are highly chlorinated (Anyasi and Atagana 2011). Due to these properties, they are known to be recalcitrant and hard to remediate from the environment. Pagé et al. (2015) observed that pine and oak trees are associated with higher mycorrhizal fungi in a polluted area. However, the dechlorination process occurs at slower rates without oxygen. Wetland plants absorb more water than non-wetland plants. These plants have a greater biomass and root system than other plants, which leads to frequent microbial activities for the degradation of chlorinated hydrocarbons.

Constructed Wetland System Used for Remediation of Different Types of Volatile Organic Compounds (VOCs) In previous years, much attention has been drawn to removing chlorinated VOCs from constructed wetlands, such as chlorine-based ethenes and chlorobenzene (CB). Some well-known microbial metabolic pathways for these organic compounds include reductive dechlorination and aerobic oxidation (Ramazani et al. 2018). However, volatilization is perhaps the most probable process of removing contaminants that need to compete with degradation by microbes of different organic compounds. Recently, the reductive dechlorination of tetrachloro-ethene or perchloroethylene (PCE) into trichloro-ethene (TCE), vinyl chloride, and dichloro-ethenes was demonstrated in an upward-flowing VF-CW (Chen et al. 2012). de Guzmán et al. (2018) discovered that microbial mineralization only accounted for about 5% of the marked 14C-Tichloro-ethylene removal in wetland microhabitat cultivated with broad-leaved pussy willow, and volatilization was the ascendent process of removing contaminants (>50%). Braeckevelt et al. (2011) studied cis-DCE reductive dechlorination in vertical flow wetland microhabitats and anaerobic subcultures derived from the previous mechanisms. After a twelve-week operation, more than 90% of the cis-DCE compounds had degraded vinyl chloride within the wetland systems. It was determined that dechlorination by reduction process could take place actively in anaerobic regions adjoining to aerobic zones in a rhizosphere of wetland system (Lee et al. 2009). Under aerobic conditions, chlorobenzene (CB) is degraded selectively through a dioxygenase-catalyzed pathway (Parales et al. 2002). CB could be degraded through dechlorination and metabolized through other anaerobic processes (Tiehm and Schmidt 2011). BTEX molecules, such as chlorinated solvents, are comparatively water-soluble and highly volatile. Microbes can degrade these molecules in anaerobic and aerobic conditions (Farhadian et al. 2008). Degradation efficiencies with 88% have been investigated in BTEX-treated constructed wetlands with inflow concentrations less than 2 mg/L. (Jain et al. 2021). Generally, due to its high solubility in water and high Henry coefficient, the gasoline additive MTBE is widespread in the aquatic environment and has high volatilization prospects in constructed wetlands.

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Furthermore, MTBE has meager microbial degradation rates under anaerobic environments, although degradation mechanisms under different environmental conditions have been mentioned (Attarian and Mokhtarani 2021). According to Pandey et al. (2020), the primary carbon-14 MTBE removal mechanism in the laboratory conditions with poplar plants was restoration and volatilization in 10 days. Similarly, Liu et al. (2021) discovered that 3.5% of the MTBE labeled was enhanced by 14-Carbon Dioxide, representing an insignificant MTBE degradation by bacteria or poplar plants.

5.2 Non-destructive Methods The organic hydrocarbon toxicant concentrations in the aqueous medium can also be reduced using non-destructive methods such as volatilization and sorption, but this may only reorganize the main pollutant in the ecosystem. As a result, the mass transfer of pollutants from the aqueous medium to specific compartments (air and soil) must be carefully examined when assessing the potential ecological hazards.

5.2.1

Phytovolatilization and Volatilization

The direct evaporation of contaminants from the effluents to the atmosphere is called volatilization. Several other wetland trees absorb pollutants via their root system and transmit them to the environment in the form of vapors. This process is known as phytovolatilization (Limmer and Burken 2016). Volatile pollutants are transferred from the water phase to the air. In unsaturated soil regions, diffusion is a means of transport that helps to determine the effective VOC emissions. An elevated Henry coefficient is a unique characteristic feature of many organic pollutants groups that are widely allowed to treat in constructed wetlands, including chlorinated solvents, BTEX (benzene, toluene, ethylbenzene, xylene), and MTBE (methyl tert-butyl ether) compounds (Deeb et al. 2001). Various hydrophilic carbon compounds such as acetone and phenol are expected to have very low direct volatilization and phytovolatilization. On the other hand, Volatilization could be an important technique for removing volatile organic substances, including relatively low chlorine-based benzenes, BTEX compounds, and trichloroethylene (Xianrong et al. 2021). Various processes may result in the release of the particular compound into the atmosphere during constructed wetland treatment of MTBE. The MTBE has high water solubility, moderate Henry coefficient, and strong anaerobic recalcitrance (Deeb et al. 2001). Absorption through the plants’ xylem sap and its successive phytovolatilization by the leaves and stems could be a significant removal process that substantially contributes to pollutant mass loss; furthermore, these plants increase the upward flow of water into the unconfined aquifer, in which augmented volatilization takes place (Pivetz 2001). If the half-lives

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of VOCs in the earth’s atmosphere are civilly limited, as in the case of MTBE at 25 °C for three days, and the danger of the toxic effects is postulated for being low, water-to-atmosphere pollutant transmission in wetlands could be a feasible ideal solution of remediation. However, VOC volatilization can cause pollutant dispersal in the environment and air pollution. The above fact, along with a lack of consistent risk evaluation, presently discourages regulatory phytoremediation acceptance as a VOCs reduction strategy (Vose et al. 2000). Phytovolatilization could be particularly important in processes like SSF, where direct volatilization is hampered by the diffusion of pollutants at a slow rate through the unsaturated zone and by laminar flow in soil regions with water saturation, which may result in a meager amount of mass transmissions. This is because water always remains in direct contact with the atmosphere; therefore, direct contaminant volatilization is roughly estimated to become more prominent in SF wetlands (Kadlec 2009).

5.2.2

Phytoaccumulation of Organic Hydrocarbons

Substantial organic uptake into the root tissues is primarily influenced by the lipophilicity of organic contaminants, as measured by the partition coefficient (Kow) of octanol-solvents. Due to the considerable retention within the epidermal cells of roots, water-insoluble—insoluble organics with a log Kow less than 4 are thought not to be remarkably reabsorbed by the plant cell membrane, and yet exceptional cases may take place. The high affinity of lipophilic PCBs is soaked up by marshes and paddy plants (Khan et al. 2021). Mostly in the presence of a large pollutant absorption by vegetation could also take place by processes such as phytovolatilization and phytoaccumulation. The physiological and metabolic transition could potentially remove organic pollutants from wastewater (Nedjimi 2021). Phytoaccumulation occurs when desorbed toxins are not rapidly degraded or discharged into the atmosphere by the plant, resulting in a concentration inside the root tissues (Yan et al. 2022). The concentration of chlorinated pollutants, such as chlordane and PCDD/Fs, has indeed been researched in species of Cucurbita pepo, which appear to particularly have a unique mechanism for the uptake of such pollutants. The storage of organic contaminants in large amounts in biomass production has been demonstrated for the higher amounts of organic compounds. PCBs with more than two aromatic rings of chlorine and DDT were demonstrated to build up in rice seedlings but still could be located in compartments of the various plant after two months of incubation (Clostre et al. 2014).

5.2.3

Sedimentation and Sorption of Hydrocarbons

The physicochemical attachment of pollutants with the solid substrates, or the dispersion of different varieties of molecules between both the organic matter content and aqueous medium, can result in chemical sorption to soil minerals. The organic carbon

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partition coefficient (Koc), which is explained as the ratio of mass adsorption capacity of pollutant per unit of organic carbon weight and nutrients to the solvent concentration, is an acceptable measurement to be used to analyze the sorption nature of organic materials in soils (Razzaque and Grathwohl 2008). It can be estimated roughly by using the empirical equations from the Kow or can be predicted from the compound’s water solubility (Karickhoff 1981). The variations in the value of Koc for a particular molecule, on the other hand, are influenced by the organic matter’s sorption properties in the soil. According to Grathwohl (1998), there is an empirical correlation between the atomic hydrogen/oxygen proportion in organic substances and the value of Koc. As a result, the magnitude of sorption is determined by the compound’s hydrophobicity and the organic carbon content, its chemical composition, and the structure of organic matter in the soil. Because of the high adsorption capacity of initially non-exposed substances, sorption onto the soil surface would then obviously be greater during the previous stages of constructed wetland operating conditions. The system behaves as a sink for the pollutant as long as no desorption–sorption equilibrium is achieved. Pollutants will still be managed to retain by the reversible adsorption process after effectively managing situations, and there will be no much further net loss of pollutants (Masindi and Muedi 2018). The retention may also accumulate the residence time of pollutants in the constructed wetland and aid biodegradation by increasing access to degrading bacteria (Malaviya and Singh 2012). High sorption procedures may have an adverse influence on pollutant bioavailability. The bioavailability of chemicals in the soil is presently defined as the proportion of the chemical substance which can be absorbed or converted by living creatures anywhere at a time (Pertruzzelli et al. 2020). One of the key factors guiding chemical recalcitrance in soil–sediment systems is the limited systemic absorption of pollutants. Due to slow desorption kinetics, biodegradation could be confined, particularly when dealing with ancient sedimentary rocks. The chemical reactions that sequester harmful byproducts into organic matter, its dispersion into tiny holes, and the integration of non-aqueous stage fluids into semi-rigid films end up causing aging (Huang et al. 2003). Distinct subgroups of the pool of pollutants may exhibit large rates of reduced desorption, as demonstrated by Lee et al. (2003) for dichlorobenzenes. Natural resource proportions in soil conditions influence sorptive interactions with organic molecules, which have been remedied in various aqueous environments. However, this is widely accepted that in saturated soils, water molecules effectively block minerals of clay adsorption sites for organic materials. Sorption seems to be complete due to effective partitioning into specific organic matter in the soil, minimum for substances that are non-polar such as solvents with chlorine (Serrano and Gallego 2006). Sorption has the potential to affect most organic pollutants to some extent. Highly lipophilic toxic organic pollutants (POPs) such as PCDDs, PCBs, PAHs, and extremely chlorobenzene are heavily negatively affected by sorption and thus collect in constructed wetlands sedimentary rocks (Bisht et al. 2015). Due to their hydrophobic nature, pharmaceuticals such as Carbamazepine are thought to be eliminated from the fluid phase via sorptive effects (Löffler et al. 2005). Fuel hydrocarbons have also been proven to have significant high sorption impacts in wetland soils

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with lesser benzenes that are chlorinated (Omari et al. 2003). Sedimentation occurs when pollutant particles interact with particulate (POM) organic matter, collecting mechanical means retained inside the constructed wetland. The sedimentation of polyaromatic hydrocarbons with a concentration range in water solubility from 500 parts per trillion to 1,800 parts per million was investigated near North Georgia pond and river sediments (Karickhoff 1981). In an aquatic environment system, sediments serve as both carriers. Potential sources of organic pollutants such as industrial and urban wastes are frequently discharged into water bodies such as a river and pond by anthropogenic activities, and constructed wetland systems use sedimentation to adsorb the chemical compounds. Mechanical filtration is perhaps the most promising route for the transmission loss of organic materials sorbed to particulates in industrial wastewaters containing a high concentration of POM, as illustrated for industrial effluents and hexachlorobenzene (Schwermer et al. 2018).

6 Metabolic Potentials of Constructed Wetlands for Degradation of Organic Pollutants Constructed wetlands could support a wide range of biogeochemical reactions and environmental factors at the wetland system scale (Imfeld et al. 2009). This function is required for the transformation of organic contaminants. The matter of fact is that the environmental factors impact both the thermal viability of various chemical changes and the activity of soil microorganisms with the enzymatic capability to carry out ideal biochemical processes. Constructed wetlands are complicated bioreactors in many ways, with considerable flow rates of energy and material governing chemical changes throughout temporal and spatial pressure gradients (Shah et al. 2020). These flow rates are especially noticeable in certain regions, like the root system. These fluxes allow for restoring thermodynamic non-equilibrium conditions and initiating various reactions with energy-releasing changes.

6.1 Organic Hydrocarbon Degradation Efficacy of Bacteria in Constructed Wetlands System A range of bacterial species isolated from the differently constructed wetlands and mangrove sediments can digest organic hydrocarbons through metabolic pathways. The most common bacterial species is Pseudomonas, which is accomplished by degrading a wide variety of persistent organic pollutants. Zhuo and Fan (2021)

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reported that three Pseudomonas strains were PHE-degrading strains from sediments, which utilize PHE as the sole carbon source and produce the surfactant compounds that can speedup PHE degradation from 75 to 100% degradation efficiency for 150 mg/L PHE after seven days. Moreover, various bacteria that can produce surfactants aid PAH biodegradation, including Lysobacter sp., Sphingomonas, and Mycobacterium (Wolf et al. 2019). Cyanobacteria are photosynthetic bacteria that generate oxygen through oxygenic photosynthesis using carbon dioxide. Rao et al. (2021) observed a rise in cyanobacterial abundance in a VF constructed wetland treatment of BbF, recognizing their responsibility in giving electron acceptors and polyaromatic compounds degradation. Cyanobacteria can also form good alliances with different microorganisms. Other microorganisms also can form levels of collaboration with cyanobacteria. The combination of manganese-oxidizing bacteria and cyanobacteria improved the efficiency of benzo(b)fluoranthene degradation (Patel et al. 2020). Individual PAH removal can be selectively affected by different microbe species. Pseudomonas sp. can degrade several types of organic hydrocarbons, including, BaA, PHE, naphthalene (NAP), acenaphthene (ACE), and dibenzo(a,h)anthracene (DBA) (Ahmed and Fakhruddin 2018). Under the presence and absence of oxygen conditions, bacterial breakdown of organic hydrocarbons can be done via a succession of enzymes activities driven through dehydrogenase, dioxygenase, and ligninolytic enzymes, as a consequence of changes in the terminal electron acceptor (Imam et al. 2022). Under aerobic conditions, oxygen is the terminal electron acceptor, and organic hydrocarbons can be degraded through the various metabolic actions of various enzymes. Dioxygenase hydroxylates degrade PAHs, resulting in cis-dihydrides (Zeng et al. 2017). The diol intermediates are subsequently converted to pyruvate, acetaldehyde, and other citric acid cycle intermediate compounds before being oxidatively decomposed into carbon dioxide and water. Sulfate, nitrates, and other oxidizing agents participate as terminal electron acceptors for PAH reductions in anaerobic environments (Hamdan et al. 2017). However, each PAH has its biodegradation mechanism. The major mechanism for PHE breakdown is producing 1-hydroxy-2-napthoic acid through a sequence of enzyme processes. The salicylic or phthalic acid metabolic pathways could be followed for degradation. The ring-opening and deoxygenation activities of benzo(k)fluoranthene (BkF) are followed by the naphthoic acid metabolism route (Nowakowski et al. 2017).

6.2 Organic Hydrocarbon Degradation Efficacy of Fungi and Algae in Constructed Wetlands System Organic hydrocarbons in the CWs can be resistant to biodegradation by various fungal species. Mohapatra et al. (2022) reported that the fungal population increase within days could be employed in pilot-scale constructed wetlands to treat an organic

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hydrocarbon containing wastewater and effectively selected fungal species that have biodegradation capabilities for fluoranthene (FLUH). Absidia cylindrospora was perhaps the most effective, with an eradication efficiency of over 80% for FLUH. A selected fungal species, Ulocladium chartarum has a degradation capability that can be induced to increase PAH removal. Usually, PAH-degrading fungi are classed as either ligninolytic and white-rot fungi or non-ligninolytic fungi. The fungi which are non-lignin in nature can degrade PAHs organic hydrocarbons by excreting various enzymes such as monooxygenase, whereas lignin-degrading fungi excrete lignocellulosic peroxidase and manganese peroxidase (Zhuo and Fan 2021). Algae can aid with organic hydrocarbon degradation and conversion; significant research has been done on the algae’s role in the constructed wetland system is quite limited. It is important to note that microbes do not have solitary roles. Indeed, various adsorption and/or biodegradation methods are used by a consortium of different microorganisms and plants within the ecosystem to remove organic hydrocarbons from the constructed wetlands. The photoautotrophic microalgae system can successfully remove organic pollutants, nitrogen, and phosphorus from wastewater as a new way of water treatment. Nitrogen and phosphorus concentrations can be quickly lowered to 2 mg/L and 0.1 mg/L, respectively (Wang et al. 2016a, b). In terms of nitrogen and phosphorus removal, the treatment efficiency outperforms other traditional technologies (such as artificial wetlands) (Li et al. 2020).

7 Conclusions Wetlands have long been utilized to treat agricultural, municipal, and industrial wastewater as ecological purifying systems for organic aromatic compound cleanup worldwide. The biochemical mechanisms involved in removing petroleum aromatic hydrocarbons from processed water and the use of engineered treatment wetlands in this process are, nevertheless, poorly understood. Furthermore, there are significant restrictions to their broader applicability that need to be investigated further. Organic hydrocarbon removal in the constructed wetlands is limited by coupling several mechanisms, including plant absorption, adsorption, metabolism, volatilization, biodegradation, and photodegradation. While engineered wetlands are a very lucrative technique of surface and subsurface water treatment, they are not without their drawbacks. Constructed wetlands with appropriate substrates are also important. The constructed wetlands with the specific substrates also play a crucial role in removing organic hydrocarbons from wastewater, although it is unclear whether the wetland plants and substrates affect the degradation efficiency. Furthermore, research must be conducted to produce a suitable model design that can be interpreted and used to provide collective information on various constructed wetland systems. As a result, there is an urgent need to comprehend the aspects that can influence the elimination of organic hydrocarbons in appropriate habitats with various artificial wetlands.

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References Abira MA, Van Bruggen JJA, Denny P (2005) Potential of a tropical subsurface constructed wetland to remove phenol from pre-treated pulp and papermill wastewater. Water Sci Technol 51(9):173– 176 Ahmed F, Fakhruddin ANM (2018) A review on environmental contamination of petroleum hydrocarbons and its biodegradation. Int J Environ Sci Nat Resour 11(3):1–7 Anh BTK, Van Thanh N, Phuong NM, Ha NTH, Yen NH, Lap BQ, Kim DD (2020) Selection of suitable filter materials for horizontal subsurface flow constructed wetland treating swine wastewater. Water Air Soil Pollut 231(2):1–10 Anyasi RO, Atagana HL (2011) Biological remediation of polychlorinated biphenyls (PCB) in the environment by microorganisms and plants. Afr J Biotechnol 10(82):18916–18938 Araneda I, Tapia NF, Lizama Allende K, Vargas IT (2018) Constructed wetland-microbial fuel cells for sustainable greywater treatment. Water 10(7):940 Attarian P, Mokhtarani N (2021) Feasibility study of aerobic cometabolism biodegradation of MTBE by a microbial consortium: biomass growth and decay rate. J Water Process Eng 44:102338 Ayaz T, Khan S, Khan AZ, Lei M, Alam M (2020) Remediation of industrial wastewater using four hydrophyte species: a comparison of individual (pot experiments) and mix plants (constructed wetland). J Environ Manag 255:109833 Bisht S, Pandey P, Bhargava B, Sharma S, Kumar V, Sharma KD (2015) Bioremediation of polyaromatic hydrocarbons (PAHs) using rhizosphere technology. Braz J Microbiol 46:7–21 Braeckevelt M, Seeger EM, Paschke H, Kuschk P, Kaestner M (2011) Adaptation of a constructed wetland to simultaneous treatment of monochlorobenzene and perchloroethene. Int J Phytoremediation 13(10):998–1013 Campanella BF, Bock C, Schröder P (2002) Phytoremediation to increase the degradation of PCBs and PCDD/Fs. Environ Sci Pollut Res 9(1):73–85 Chand N, Kumar K, Suthar S (2022) Enhanced wastewater nutrients removal in vertical subsurface flow constructed wetland: effect of biochar addition and tidal flow operation. Chemosphere 286:131742 Chen Z, Wu S, Braeckevelt M, Paschke H, Kästner M, Köser H, Kuschk P (2012) Effect of vegetation in pilot-scale horizontal subsurface flow constructed wetlands treating sulphate rich groundwater contaminated with a low and high chlorinated hydrocarbon. Chemosphere 89(6):724–731 Clostre F, Letourmy P, Turpin B, Carles C, Lesueur-Jannoyer M (2014) Soil type and growing conditions influence uptake and translocation of organochlorine (chlordecone) by Cucurbitaceae species. Water Air Soil Pollut 225(10):1–11 da Silva Vilar D, Torres NH, Bharagava RN, Bilal M, Iqbal HM, Salazar-Banda GR, Eguiluz KIB, Ferreira LFR (2021) Emerging contaminants in environment: occurrence, toxicity, and management strategies with emphasis on microbial remediation and advanced oxidation processes. In: Microbe mediated remediation of environmental contaminants. Woodhead Publishing, pp 1–14 de Guzmán GTN, Hapeman CJ, Millner PD, McConnell LL, Jackson D, Kindig D, Torrents A (2018) Using a high-organic matter biowall to treat a trichloroethylene plume at the Beaver Dam Road landfill. Environ Sci Pollut Res 25(9):8735–8746 Deeb RA, Hu HY, Hanson JR, Scow KM, Alvarez-Cohen L (2001) Substrate interactions in BTEX and MTBE mixtures by an MTBE-degrading isolate. Environ Sci Technol 35(2):312–317 Deng Y, Zhao R (2015) Advanced oxidation processes (AOPs) in wastewater treatment. Curr Pollut Rep 1(3):167–176 Farhadian M, Vachelard C, Duchez D, Larroche C (2008) In situ bioremediation of monoaromatic pollutants in groundwater: a review. Bioresour Technol 99(13):5296–5308 Grathwohl P (1998) Basics of sorption and diffusion in soils and sediments. In: Diffusion in natural porous media. Springer, Boston, MA, pp 15–41 Hamdan HZ, Salam DA, Hari AR, Semerjian L, Saikaly P (2017) Assessment of the performance of SMFCs in the bioremediation of PAHs in contaminated marine sediments under different redox

Constructed Wetlands for Remediating Organic Hydrocarbons: …

87

conditions and analysis of the associated microbial communities. Sci Total Environ 575:1453– 1461 Harms H, Bokern M, Kolb M, Bock C (2003) Transformation of organic contaminants by different plant systems. Phytoremediation Transform Control Contaminants, 285–316 Huang W, Yu Z, Fu J (2003) Effects of organic matter heterogeneity on sorption and desorption of organic contaminants by soils and sediments. Appl Geochem 18(7):955–972 Imam A, Suman SK, Kanaujia PK, Ray A (2022) Biological machinery for polycyclic aromatic hydrocarbons degradation: a review. Bioresour Technol 343:126121 Imfeld G, Braeckevelt M, Kuschk P, Richnow HH (2009) Monitoring and assessing processes of organic chemicals removal in constructed wetlands. Chemosphere 74(3):349–362 Jain KR, Desai C, van Hullebusch ED, Madamwar D (2021) Advanced bioremediation technologies and processes for the treatment of synthetic organic compounds (SOCs). Front Bioeng Biotechnol, 871 Jin G, Kelley TR (2007) Characterization of microbial communities in a pilot-scale constructed wetland using PLFA and PCR-DGGE analyses. J Environ Sci Health Part A 42(11):1639–1647 Kadlec RH (1999) Chemical, physical and biological cycles in treatment wetlands. Water Sci Technol 40(3):37–44 Kadlec RH (2009) Comparison of free water and horizontal subsurface treatment wetlands. Ecol Eng 35(2):159–174 Karickhoff SW (1981) Semi-empirical estimation of sorption of hydrophobic pollutants on natural sediments and soils. Chemosphere 10(8):833–846 Kassenga G, Pardue JH, Moe WM, Bowman KS (2004) Hydrogen thresholds as indicators of dehalorespiration in constructed treatment wetlands. Environ Sci Technol 38(4):1024–1030 Keefe SH, Barber LB, Runkel RL, Ryan JN (2004) Fate of volatile organic compounds in constructed wastewater treatment wetlands. Environ Sci Technol 38(7):2209–2216 Khan A, Ali S, Murad W, Hayat K, Siraj S, Jawad M, ..., Khan A (2021) Phytochemical and pharmacological uses of medicinal plants to treat cancer: a case study from Khyber Pakhtunkhwa, North Pakistan. J Ethnopharmacol 281:114437 Kulshrestha K, Aalam T, Khalil N (2020) Municipal wastewater treatment through vertical flow constructed wetlands: a demonstration in tropical climate region. IWRA India J Half Yearly Tech J Indian Geogr Comm IWRA 9(1):3–7 Kuppusamy S, Maddela NR, Megharaj M, Venkateswarlu K (2020) An overview of total petroleum hydrocarbons. Total Petrol Hydrocarbons, 1–27 Langergraber G, Dotro G (2019) Wetland technology: practical information on the design and application of treatment wetlands. IWA Publishing Lee CG, Fletcher TD, Sun G (2009) Nitrogen removal in constructed wetland systems. Eng Life Sci 9(1):11–22 Lee S, Pardue JH, Moe WM, Valsaraj KT (2003) Mineralization of desorption-resistant 1, 4-dichlorobenzene in wetland soils. Environ Toxicol Chem Int J 22(10):2312–2322 Li X, Wu S, Yang C, Zeng G (2020) Microalgal and duckweed based constructed wetlands for swine wastewater treatment: a review. Bioresour Technol, 123858 Li R, Hua P, Cai J, Wang X, Zhu Y, Huang Z, Li P, Wang Z, Bai Y, Hu BX, Zhang J. (2019) A sixteen-year reduction in the concentrations of aquatic PAHs corresponding to source shifts in the Elbe River, Germany, J Clean Prod 223:631–640 Liang Y, Zhu H, Bañuelos G, Xu Y, Yan B, Cheng X. (2019) Preliminary study on the dynamics of heavy metals in saline wastewater treated in constructed wetland mesocosms or microcosms filled with porous slag. Environ Sci Pollut Res 26:33804–33815 Limmer M, Burken J (2016) Phytovolatilization of organic contaminants. Environ Sci Technol 50(13):6632–6643 Liu F, Sun L, Wan J, Shen L, Yu Y, Hu L, Zhou Y (2020) Performance of different macrophytes in the decontamination of and electricity generation from swine wastewater via an integrated constructed wetland-microbial fuel cell process. J Environ Sci 89:252–263

88

R. Rani et al.

Liu J, Yi NK, Wang S, Lu LJ, Huang XF (2016) Impact of plant species on spatial distribution of metabolic potential and functional diversity of microbial communities in a constructed wetland treating aquaculture wastewater. Ecol Eng 94:564–573 Liu M, Cesarz S, Eisenhauer N, Xia H, Fu S, Craven D (2021) Soil quality, leaf litter quality, and microbial biomass interactively drive soil respiration in a microcosm experiment. Soil Org 93(3):181–194 Löffler D, Römbke J, Meller M, Ternes TA (2005) Environmental fate of pharmaceuticals in water/sediment systems. Environ Sci Technol 39(14):5209–5218 Malaviya P, Singh A (2012) Constructed wetlands for management of urban stormwater runoff. Crit Rev Environ Sci Technol 42(20):2153–2214 Masindi V, Muedi KL (2018) Environmental contamination by heavy metals. Heavy Met 10:115– 132 Matamoros V, García J, Bayona JM (2005) Behavior of selected pharmaceuticals in subsurface flow constructed wetlands: a pilot-scale study. Environ Sci Technol 39(14):5449–5454 Mateus DM, Pinho HJ (2020) Evaluation of solid waste stratified mixtures as constructed wetland fillers under different operation modes. J Clean Prod 253:119986 Mohapatra B, Dhamale T, Saha BK, Phale PS (2022) Microbial degradation of aromatic pollutants: metabolic routes, pathway diversity, and strategies for bioremediation. In Microbial Biodegradation and Bioremediation, pp 65–394 Mustapha HI, Lens PN (2018) Constructed wetlands to treat petroleum wastewater. In Approaches in Bioremediation, pp 199–237 Nedjimi B (2021) Phytoremediation: a sustainable environmental technology for heavy metals decontamination. SN Appl Sci 3(3):1–19 Nowakowski M, Rostkowski P, Andrzejewski P (2017) Oxidized forms of polycyclic aromatic hydrocarbons (Oxy-PAHs): determination in suspended particulate matter (SPM). In 15th International Conference on Envrionmental Science and Technology CEST2017_01337 Oladoja NA, Saliu TD, Ololade IA, Anthony ET, Bello GA (2017) A new indigenous green option for turbidity removal from aqueous system. Sep Purif Technol 186:166–174 Omari K, Revitt M, Shutes B, Garelick H (2003) Hydrocarbon removal in an experimental gravel bed constructed wetland. Water Sci Technol 48(5):275–281 Pagé AP, Yergeau É, Greer CW (2015) Salix purpurea stimulates the expression of specific bacterial xenobiotic degradation genes in a soil contaminated with hydrocarbons. PLoS One 10(7):e0132062 Pandey VC, Patel D, Maiti D, Singh DP (2020) Case studies of perennial grasses: phytoremediation (holistic approach). Phytoremediation Potent Perennial Grasses, 337–349 Parales RE, Bruce NC, Schmid A, Wackett LP (2002) Biodegradation, biotransformation, and biocatalysis (B3). Appl Environ Microbiol 68(10):4699–4709 Patel AB, Shaikh S, Jain KR, Desai C, Madamwar D (2020) Polycyclic aromatic hydrocarbons: sources, toxicity and remediation approaches. Front Microbiol 11:2675 Petruzzelli G, Pedron F, Rosellini I (2020) Bioavailability and bioaccessibility in soil: a short review and a case study. AIMS Environ Sci 7(2):208–225 Pivetz BE (2001) Phytoremediation of contaminated soil and ground water at hazardous waste sites. US Environmental Protection Agency, Office of Research and Development, Office of Solid Waste and Emergency Response Qiao W, Li R, Tang T, Zuh AA (2021) Removal, distribution and plant uptake of perfluorooctane sulfonate (PFOS) in a simulated constructed wetland system. Front Environ Sci Eng 15(2):1–11 Rahman ME, Bin Halmi MIE, Bin Abd Samad MY, Uddin MK, Mahmud K, Abd Shukor MY, Sheikh Abdullah SR, Shamsuzzaman SM (2020) Design, operation and optimization of constructed wetland for removal of pollutant. Int J Environ Res Pub Health 17(22):8339 Ramazani A, Oveisi M, Sheikhi M, Gouranlou F, Hanifehpour Y, Joo SW, Aghahosseini H (2018) A review on the destruction of environmentally hazardous chlorinated aromatic compounds in the presence (or without) of nanophotocatalysts. Curr Org Chem 22(15):1554–1572

Constructed Wetlands for Remediating Organic Hydrocarbons: …

89

Rao K, Zhang X, Wang M, Liu J, Guo W, Huang G, Xu J (2021) The relative importance of environmental factors in predicting phytoplankton shifting and cyanobacteria abundance in regulated shallow lakes. Environ Pollut, 117555 Razzaque MM, Grathwohl P (2008) Predicting organic carbon–water partitioning of hydrophobic organic chemicals in soils and sediments based on water solubility. Water Res 42(14):3775–3780 Saeed T, Miah MJ, Khan T, Ove A (2020) Pollutant removal employing tidal flow constructed wetlands: media and feeding strategies. Chem Eng J 382:122874 Schwermer CU, Krzeminski P, Wennberg AC, Vogelsang C, Uhl W (2018) Removal of antibiotic resistant E. coli in two Norwegian wastewater treatment plants and by nano-and ultra-filtration processes. Water Sci Technol 77(4):1115–1126 Shah MP (2020) Microbial bioremediation & biodegradation. Springer Shah MP (2021) Removal of refractory pollutants from wastewater treatment plants. CRC Press Serrano A, Gallego M (2006) Sorption study of 25 volatile organic compounds in several Mediterranean soils using headspace–gas chromatography–mass spectrometry. J Chromatogr A 1118(2):261–270 Shah AI, Dar MUD, Bhat RA, Singh JP, Singh K, Bhat SA (2020) Prospectives and challenges of wastewater treatment technologies to combat contaminants of emerging concerns. Ecol Eng 152:105882 Srogi K (2007) Monitoring of environmental exposure to polycyclic aromatic hydrocarbons: a review. Environ Chem Lett 5(4):169–195 Thawaba S, Brahana J (2009) Constructed wetlands for the pretreatment of drinking water obtained from coal mines Thullner M, Stefanakis AI, Dehestabi S (2018) Constructed Wetlands treating water contaminated with organic hydrocarbons. Constructed Wetlands for industrial wastewater treatment. WileyBlackwell, Chichester, UK Tiehm A, Schmidt KR (2011) Sequential anaerobic/aerobic biodegradation of chloroethenes— aspects of field application. Curr Opin Biotechnol 22(3):415–421 Tietz A, Langergraber G, Watzinger A, Haberl R, Kirschner AK (2008) Bacterial carbon utilization in vertical subsurface flow constructed wetlands. Water Res 42(6–7):1622–1634 Uzoekwe SA, Oghosanine FA (2011) The effect of refinery and petrochemical effluent on water quality of Ubeji Creek Warri, Southern Nigeria. Ethiopian J Environ Stud Manag 4(2):107–116 Valujeva K, Burlakovs J, Grinfelde I, Pilecka J, Jani Y, Hogland W (2018) Phytoremediation as tool for prevention of contaminant flow to hydrological systems. Rural Environ Eng Landsc Archit 1 Vose JM, Swank WT, Harvey GJ, Clinton BD, Sobek C (2000) Leaf water relations and sapflow in eastern cottonwood (Populus deltoides Bartr.) trees planted for phytoremediation of a groundwater pollutant. Int J Phytoremediation 2(1):53–73 Wallace S, Kadlec R (2005) BTEX degradation in a cold-climate wetland system. Water Sci Technol 51(9):165–171 Wang J, Song X, Wang Y, Abayneh B, Ding Y, Yan D, Bai J (2016a) Microbial community structure of different electrode materials in constructed wetland incorporating microbial fuel cell. Bioresour Technol 221:697–702 Wang XX, Wu YH, Zhang TY, Xu XQ, Dao GH, Hu HY (2016b) Simultaneous nitrogen, phosphorous, and hardness removal from reverse osmosis concentrate by microalgae cultivation. Water Res 94:215–224 Wolf DC, Cryder Z, Gan J (2019) Soil bacterial community dynamics following surfactant addition and bioaugmentation in pyrene-contaminated soils. Chemosphere 231:93–102 Xianrong MENG, Song GE, Wei XU, Jiansheng WU, Changning LI (2021) Remediation of chlorohydrocarbon contaminated soil by in-situ electrical resistance heating. Chin J Environ Eng 15(2):669–676 Yan C, Huang J, Cao C, Wang Y, Lin X, Qian X (2022) Response of constructed wetland for wastewater treatment to graphene oxide: perspectives on plant and microbe. J Hazard Mater 422:126911

90

R. Rani et al.

Yuan C, Zhao F, Zhao X, Zhao Y (2020) Woodchips as sustained-release carbon source to enhance the nitrogen transformation of low C/N wastewater in a baffle subsurface flow constructed wetland. Chem Eng J 392:124840 Zeng J, Zhu Q, Wu Y, Chen H, Lin X (2017) Characterization of a polycyclic aromatic ringhydroxylation dioxygenase from Mycobacterium sp. NJS-P. Chemosphere 185:67–74 Zhang Y, Pelletier R, Noernberg T, Donner MW, Grant-Weaver I, Martin JW, Shotyk W (2022) Impact of the 2016 Fort McMurray wildfires on atmospheric deposition of polycyclic aromatic hydrocarbons and trace elements to surrounding ombrotrophic bogs. Environ Int 158:106910 Zhao X, Qiu H, Zhao Y, Shen J, Chen Z, Chen J (2015) Distribution of polycyclic aromatic hydrocarbons in surface water from the upper reach of the Yellow River Northwestern China. Environ Sci Pollut Res 22(9):6950–6956 Zhuo R, Fan F (2021) A comprehensive insight into the application of white rot fungi and their lignocellulolytic enzymes in the removal of organic pollutants. Sci Total Environ 778:146132

Constructed Wetlands as an Effective Tool for Textile Effluent Treatment Bishwarup Sarkar and Sougata Ghosh

1 Introduction The textile industry is one of the primary contributors to water pollution that can potentially create an adverse effect on aquatic biota as well as humans. Textile effluents are mainly composed of toxic dyes, chlorolignin residues, phthalates, heavy metals, high amounts of organic and inorganic materials such as sodium hydroxide, sodium sulphate, calcium chloride, urea, ethyl alcohol, toluene, cyclohexane, propanoic acid, benzene, tetratriacontane, phthalic acid, diacetyl sulphide, hydroxylamine, tyramine, and many more (Talouizte et al. 2020). Therefore, treatment of textile effluents before their discharge is extremely important for avoiding harmful consequences to the environment. Although there are several physicochemical methods for the treatment of textile wastewater some of which include sedimentation, screening, aeration, filtration, floatation, equalization, ion adsorption, chlorination, ozonation, and coagulation, the majority of these methods are quite expensive, often form sludge and toxic byproducts, require high power for operation as well as skilled labour (Sharma and Malaviya 2021). Hence, different biological methods for the treatment of textile wastewater are being investigated since they have the potential to provide costeffective and sustainable approaches for the same. The application of constructed wetlands (CWs) is one such effective wastewater remediation strategy that utilizes the phytoremediation potential of macrophytes along with bacterial degradation of textile pollutants in the presence of sand, gravel, soil, and other materials as substrates (Malaviya and Singh 2012). CWs can facilitate textile effluent remediation in a B. Sarkar College of Science, Northeastern University, Boston, MA, USA S. Ghosh (B) Department of Microbiology, School of Science, RK University, Rajkot, Gujarat, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. P. Shah (ed.), Recent Trends in Constructed Wetlands for Industrial Wastewater Treatment, https://doi.org/10.1007/978-981-99-2564-3_5

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controlled environment, under saturated conditions, and in the presence of a gravitational force. Hence, this chapter elaborates on the effective usage of CWs planted with different macrophytes and augmented with pollutant-degrading bacterial strains for the treatment of textile effluents. Different parameters such as total nitrogen content, electrical conductivity, total organic carbon, chemical oxygen demand, and biological oxygen demand can be effectively reduced using CWs treatments. Moreover, several toxic dyes which are a major component of textile effluent are also efficiently biotransformed into less toxic products after the treatment processes. Further evaluation and standardization of CWs with regards to the duration of the treatment, on-site efficiency, large-scale applicability, and reusability can improve the potential of application of CWs in textile industries for treatment of the wastewater before discharge.

2 Role of CWs In this section, various types of CWs are discussed with their promising role in the removal of refractory pollutants from the wastewater which is summarized in Table 1. Ishaq et al. (2021) reported the treatment of wastewater samples from the textile industry through the construction of an artificial wetland using two plants namely Lemna minor L. and Typha latifolia L. that was supplemented with Hoagland’s solution and exposed to varying concentrations of citric acid and the wastewater samples for evaluation of its phytoextraction potential. Initially, the agronomic traits of the two plants were investigated wherein the growth and biomass of L. minor gradually decreased in the presence of increasing concentrations of wastewater samples. However, the addition of citric acid resulted in 36.66%, 68.75%, 53.33%, and 58.33% increase in the fresh weight, dry weight, leaf area, and height of the 100% wastewater-treated plant, respectively. Similarly, the total chlorophyll, carotenoid content, soluble protein, and soil-plant analysis development (SPAD) value were increased by 53.94%, 100%, 117.52%, and 119.50% after the addition of citric acid in wastewater-treated L. minor plants. Moreover, the activities of superoxide dismutase (SOD), ascorbate oxidase (APX), peroxidase (POD), and catalase (CAT) in wastewater-treated L. minor plants were further increased by 11.40%, 9.68%, 17.45%, and 22.55% after citric acid incorporation. Oxidative damage in L. minor plants was also controlled by citric acid as the electrolytic leakage content was decreased by 16.05% while the malondialdehyde (MDA) and hydrogen peroxide (H2 O2 ) contents were reduced by 25.84% and 15.97%, respectively. Further, the accumulation of Pb, Cu, and Cr by L. minor plants was increased to 120%, 82%, and 80% with a subsequent increase in the concentration of textile effluent that was further enhanced by 96.65%, 107.09%, and 108.75%, respectively, after addition of citric acid. Similar results were obtained in the artificial wetland with T. latifolia with enhanced accumulation of Pb, Cr, and Cu in different parts of the plant after the addition of citric acid. A maximum accumulation of 279%, 240% and 171% of Pb,

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Table 1 CWs for industrial effluent remediation CW design type

Substrate used

Plants/microbes used

Pollutant removed

Reference

–

–

Lemna minor L. and Typha latifolia L.

Cr, Cu, and Pb

Ishaq et al. (2021)

Floating wetpark

–

Fimbristylis dichotoma, Ipomoea aquatica, and Pluchea tomentosa

Orange 3R dye, heavy metals such as Ni, Cr, Mn, Mg, Zn, and Cu

Kadam et al. (2022)

Horizontal flow

Clay soil

Echinodorus cordifolius Reactive Red Noonpui and L. 2 (RR2), Thiravetyan Reactive Red (2011) 120 (RR120), and Reactive Red 141 (RR141) dyes

Horizontal-vertical hybrid flow

Coarse gravel, fine Phragmites australis Cd, Fe, Ni gravel layer, augmented with and other washed river sand Bacillus endophyticus nutrients PISI25, Microbacterium arborescens TYSI04, and Pantoea sp. TYRI15

Hussain et al. (2019)

Horizontal-vertical hybrid flow

Recycled brick and Canna indica sugarcane bagasse

Organics, nitrogen, and phosphorus

Saeed et al. (2018)

Horizontal-vertical hybrid flow

Gravel-sand-tuff

Phragmites australis

Inorganic and Bulc and organic Ojstršek nitrogen, (2008) sulphate

Vertical flow

Gravel

Phragmites australis

BR46 and AB113 dyes

Vertical flow

Rice husk or biochar

Persica barbata augmented with Psychrobacter alimantainus strain KS23

Total nitrogen Saba et al. and (2015) phosphorus, reactive azo Black-5 dye

Vertical flow

Fine gravel, coconut shavings, and soil

Portulaca grandiflora augmented with Pseudomonas putida

Disperse Red BF, Disperse Yellow G, Disperse Bryal Blue, Rubine GFL, and Brown REL dyes

Hussein and Scholz (2017)

Khandare et al. (2013)

(continued)

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Table 1 (continued) CW design type

Substrate used

Plants/microbes used

Pollutant removed

Vertical flow

Coconut shavings

Gaillardia pulchella augmented with Pseudomonas monteilii

REL, Rubine Kabra et al. GFL (RGFL), (2013) SRR, RR, and Green HE4B (GHE4B) dyes

Vertical flow

Coconut shavings, sand, gravel, soil

Typha domingensis augmented with Microbacterium arborescens TYSI04 and Bacillus pumilus PI

Total organic material

Shehzadi et al. (2014)

Vertical flow

Eucalyptus leaves, sawdust, and fly ash

Typha angustifolia and Paspalum scrobiculat

Congo Red, Rubine GFL, Scarlet RR, and Green HE4B

Chandanshive et al. (2017)

Vertical flow

Activated charcoal, eggshells, wood husk, and gravel

Canna indica augmented with E. coli

Inorganic and Jayabalan organic et al. (2020) materials

Vertical flow

Sand, gravel, and zeolite

Canna indica and Typha Yellow 2G angustfolia dye

Dogdu and Yalcuk (2016)

Vertical flow

–

Eichhornia crassipes

Sivakumar et al. (2013)

Chloride, sulphate, and phenols

Reference

Cu, and Cr was observed in the leaves of T. latifolia while 192%, 172%, and 154% of Pb, Cu, and Cr were accumulated in the stem of the plants, respectively. In another recent study, Kadam et al. (2022) demonstrated the efficient dye degradation ability of a constructed wetland. Co-plantation of Fimbristylis dichotoma, Ipomoea aquatica, and Pluchea tomentosa was employed to create a floating wetpark that was further investigated for the removal of Orange 3R dye. The plant consortium was able to remove 84% of 100 mg/L of Orange 3R dye after 48 h of treatment whereas 72%, 70%, and 64% of 100 mg/L of Orange 3R dye were decolourized by F. dichotoma, I. aquatica, and P. tomentosa, respectively. Moreover, higher tolerance of 180 mg/L of Orange 3R dye was achieved in the plant consortia as compared to individual vegetative growth in the constructed wetlands. In addition, the plant consortia demonstrated increased activities of oxidoreductase enzymes after exposure to Orange 3R dye. For instance, enzyme activities of tyrosinase, varatryl alcohol oxidase, lignin peroxidase, riboflavin reductase, laccase, nicotine amide dinucleotide-dichloroindophenol (NADH-DCIP) reductase, and azo reductase were increased by 76%, 85%, 150%, 151%, 171%, 11%, and 241%, respectively, in the root tissues of consortia. Hence, it was assumed that the synergistic enzymatic activities of the three different co-cultured plants resulted in enhanced dye decolourization.

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Microscopic observations of the plant tissues revealed altered morphologies of the root tissues after 50 h of exposure to Orange 3R dye. It was further proposed that dye accumulation was mediated by the root capillary system within 24 h of the treatment process which resulted in the upregulation of oxidoreductase enzymes in the plants which in turn, mineralized the dye molecules into simple products within 48 h of incubation. Scanning electron micrographs (SEM) of the F. dichotoma, I. aquatica, and P. tomentosa plant root tissues also displayed damage after 24 h of incubation in the presence of the dye as evident from Fig. 1. Thereafter, gas chromatography– mass spectrometry (GC-MS) results of the degraded products were used to propose the mechanism of dye degradation wherein Orange 3R was assumed to undergo asymmetric cleavage in presence of azoreductase enzyme that may have resulted in the formation of N-phenylacetamide-2-aminocyclohexa-1,3-dien-1-ol and another intermediate compound both of which may then further undergoes deamination and demethylation followed by degradation to finally form N-phenylformamide and phenol. Moreover, 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay demonstrated 94% viability of HepG2 cells in the presence of biotransformed products of Orange 3R as compared to 72% cell viability in presence of the 1 μg/mL of original dye. The on-field treatment efficacy of the floating wetpark was also evaluated in the presence of textile industry effluent samples which showed 87%, 86%, 75%, 49%, 48%, and 46% reduction in COD, BOD, colour, TSS, total solids (TS), and TDS after 168 h of incubation, respectively. In addition, the plant consortia also reduced the concentration of heavy metals such as Ni, Cr, Mn, Mg, Zn, and Cu by 24%, 29%, 97%, 07%, 44%, and 40%, respectively. Noonpui and Thiravetyan (2011) also evaluated reactive azo dye treatment from textile wastewater samples using a constructed wetland. Echinodorus cordifolius L. was planted in the clay soil with the addition of Hoagland’s solution for plant culture. Three commercial azo dyes, namely, Reactive Red 2 (RR2), Reactive Red 120 (RR120), and Reactive Red 141 (RR141) were used for evaluation of the dye removal potential by the constructed wetland. Initially, maximum removal of 33.39 μmolRR2 kg−1 FW of RR2 was achieved by E. cordifolius L. while 13.35 μmolRR120 kg−1 FW and 10.57 μmolRR141 kg−1 FW of RR120 and RR141 dyes were removed, respectively. Hence, the removal rate of RR2 was better as compared to the other two dyes which were attributed to its smaller size. Thereafter, the application of the synthetic reactive red141 dye wastewater (SRRW141) in the constructed wetland resulted in the reduction of colour, TDS, and conductivity of the same within 7 days under both soil and soil-free conditions. The maximum dye removal efficiency of 98–99% was attained within 6–7 days of treatment under a soil-free system whereas 96–100% of dye degradation efficiency was obtained in the presence of soil within 4– 5 days only. Moreover, the relative growth rate of the plants was higher in presence of soil and SRRW141 due to better root development in the presence of salt molecules (for example, sulphate) which in turn, resulted in efficient dye removal from the wastewater. Additionally, the clay soil used for the growth of E. cordifolia L. was proposed to contribute to dye adsorption and also provide a niche for soil microflora for enzymatic dye degradation. Thereafter, the TDS value of the wastewater sample was reduced by 42% within 7 days of operation while the pH of the system also

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Fig. 1 SEM analysis of roots of F. dichotoma, I. aquatica, and P. tomentosa after Orange 3R exposure at (A1, B1 and C1) 0 h and (A2, B2 and C2) 24 h, respectively (Reprinted with permission from Kadam SK, Tamboli AS, Chandanshive VV, Govindwar SP, Choo YS, hong Pak J [2022]. Construction and implementation of a floating wetpark as an effective constructed wetland for industrial textile wastewater treatment. Journal of Hazardous Materials 424:127710. Copyright © 2021 Elsevier B.V.)

changed from basic to neutral immediately and within 2 days in the presence of soil and under soil-free conditions, respectively. It was further proposed that plants may use their Na+ /H+ antiporter system for exchanging protons and sodium ions from the wastewater samples which may result in such pH changes. In another study, Hussain et al. (2019) compared the textile effluent treatment efficiency of constructed horizontal and vertical flow wetlands (HFCWs and VFCWs) that were composed of coarse gravel, fine gravel layer, washed river sand, and

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augmented with three bacterial endophytes, namely, Bacillus endophyticus PISI25, Microbacterium arborescens TYSI04, and Pantoea sp. TYRI15 with pollutantdegrading ability. In addition, Phragmites australis was also planted in both the wetlands for phytoremediation of the pollutants as shown in Fig. 2. The chemical oxygen demand (COD), biological oxygen demand (BOD), total organic carbon (TOC), total suspended solids (TSS), as well as total dissolved solids (TDS) of the textile effluent were decreased in both HFCWs and VFCWs containing P. australis which was further increased after bacterial augmentation. A more efficient phytoremediation activity was observed in HFCWs compared to VFCWs while the presence of both bacteria and plants resulted in a significant decrease in the COD, BOD, and TOC values from 690, 250, and 120 mg/L to 89, 22, and 8 mg/L, respectively, after 72 h of incubation. Likewise, maximum reduction of nutrients and heavy metals, namely, Cd, Fe, and Ni was demonstrated in vegetated HFCWs containing pollutantdegrading bacterial endophytes. Further, a reduction in the toxicity of the textile effluent was also investigated by conducting a fish toxicity assay in which no toxicity was observed in effluents that were treated using HFCWs supplemented with plants and bacteria. The biomass, as well as the root and shoot lengths of the P. australis, were reduced in the presence of the bleaching wastewater sample wherein the growth inhibition of the plants was higher in the VFCWs as compared to HFCWs. However, inoculation of the bacterial endophytes reduced the stress on the plants and improved the vegetative growth in both the constructed wetlands. Additionally, restriction fragment length polymorphism (RFLP) analysis confirmed the presence of 43%, 56%, and 29% of the inoculated bacterial endophytes in the rhizoplane, root interior, and shoot the interior of the vegetations present in HFCWs, respectively. On the contrary, 37%, 49%, and 31% of the bacterial endophytes were present in the rhizoplane, root interior, and shoot of P. australis plants, respectively. The long-term stability of both the wetlands was maintained for 3 months with retention of maximum remediation potential. Likewise, Saeed et al. (2018) also treated industrial wastewater samples using a hybrid-constructed wetland containing recycled brick media and/or sugarcane bagasse that was planted with Canna indica. Removal of mean organic pollutants was efficient in hybrid systems that ranged from 74.0 to 85.0% whereas nitrogen, TS, phosphorus, and colour removal were in the range of 67.5–80.0, 55.0–95.0, 64.0–89.0, and 46.0–83.0%, respectively. In addition, sugarcane bagasse was used as support material which facilitated the proliferation of microbes that contributed to the removal of pollutants from the wastewater. The total nitrogen removal rate in the presence of such organic substrates was 1.82 g/m2 d as internal carbon formation took place in the system during the operation. Moreover, 89% of phosphorus was efficiently removed from the wastewater primarily due to adsorption by the recycled brick media. Comparative analysis of the two different substrates used for the treatment processes revealed better colour removal ability using recycled brick media whereas higher amounts of sulphate were removed when sugarcane bagasse was added as the substrate into the system. Effluent recirculation resulted in increased BOD and total nitrogen removal in the case of recycled brick media whereas a decrease in the two parameters was observed using sugarcane bagasse.

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Fig. 2 The design and installation of HFCWs and VFCWs at Interloop, Khurianwala, Faisalabad, Pakistan. A, B Schematic representation of HFCWs and VFCWS, respectively; C, D Planting of Phragmites australis in the macrocosms; E P. australis after the operation of CWs for treatment of bleaching effluent (5th month of the experimental period) (Reprinted with permission from Hussain Z, Arslan M, Shabir G, Malik MH, Mohsin M, Iqbal S, Afzal M, 2019. Remediation of textile bleaching effluent by bacterial augmented horizontal flow and vertical flow constructed wetlands: A comparison at pilot scale. Science of the Total Environment 685:370–379. Copyright © 2019 Elsevier B.V.)

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Similarly, Bulc and Ojstršek (2008) also reported the textile effluent treatment ability of constructed wetland augmented with P. australis. A VFCW model containing gravel-sand-tuff was prepared using polyethylene plates and Plexiglas that exhibited a maximum decolouration of 70% of reactive dye after 24 h of treatment. Additionally, 85% of the COD reduction was achieved with a retention time of 24 h. Thereafter, a pilot-scale CW was fabricated with a vertical–horizontal-sub-surface flow (VHSSF) system and augmented with P. australis. The electrical conductivity was decreased by 63% during the treatment along with the reduction in the value of spectral absorption coefficient (SAC) which is indicative of colour removal. Moreover, the COD value of the textile wastewater samples was reduced up to 84% while BOD, TOC, total nitrogen, organic nitrogen, sulphate, anion surfactant, TSS, and colour of the wastewater sample was reduced by 66%, 89%, 52%, 87%, 88%, 80%, 93%, and 90%, respectively. Hence, it was proved that such planted CW systems could offer an inexpensive method for the treatment of textile effluents. Hussein and Scholz (2017) in their study demonstrated the use of VFCWs for the treatment of synthetic wastewater samples containing two different azo dyes namely Acid Blue 113 (AB113) and Basic Red 46 (BR46) that could be useful in textile wastewater treatments. P. australis was planted in the gravel-containing wetland that displayed significant growth in the presence of AB113 as compared to BR46 while longer contact time also increased plant growth. Redox potential and dissolved oxygen (DO) values of both the dyes ranged from 32 to 4 mV and 5.4 to 8.2 mg/L, respectively, which indicated degradation of dye molecules under both aerobic and anaerobic conditions. Moreover, the electrical conductivity of the wetlands increased in the presence of low concentrations of dye molecules while the opposite was observed in the case of high concentrations of both the dyes. The concentration of TSS was also increased when low concentrations of AB113 and BR46 dyes were incorporated in the wastewater sample. Turbidity measurements further demonstrated the removal of 6.8 ± 3.90 mg/L of BR46 dye under low resting and contact times while 224 ± 202.69 mg/L of AB113 dye was effectively removed using planted wetlands. The AB113 dye removal ability of the constructed wetlands was better when planted with P. australis while there was no significant change in the case of BR46 dye removal ability. Removal of nutrients was better (81%) when a high concentration of BR46 dye was added to the synthetic wastewater as well as in the presence of P. australis. Saba et al. (2015) demonstrated the effectiveness of Reactive Black-5 azo dye removal by VFCWs containing rice husk as the substrate and augmented with Psychrobacter alimantainus strain KS23 and planted with Persica barbata. Initially, almost 70% of the dye was removed within 48 h by rice husk which was reduced with increased pH values. Such high dye adsorption in acidic pH was assumed to be a result of strong chemical attraction between the lone pair of electrons present in the dye molecules and Si4+ groups of the rice husk. Further evaluation highlighted the best fit of the Langergren model for the dye adsorption kinetics by the rice husk substrate. Hence, rice husk or its biochar was used as the substratum for the constructed wetland where the pH remained stable while the electrolytic conductivity and TOC increased by 50–60% and 0.054 ± 0.03–2.48 ± 0.24, respectively.

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Moreover, a significant positive correlation was attained between the TDS and electrolytic conductivity of the system that was proposed to be due to the ionic nature of the TDS present in the effluent. Additionally, the TSS and turbidity of the effluent were drastically reduced after 60 days of the treatment. A maximum of 78.7% of total nitrogen was removed using biochar as the substrate for the wetlands along with KS23 augmentation while the total phosphorus content was also decreased to 15 mg/L. The high surface area of the biochar was proposed to facilitate dye adsorption and provide a niche for the bacterial colonization. Moreover, the COD value of the wastewater sample decreased from 672 to 358 mg/L after treatment using microbe inoculated biochar-containing wetlands. The colour of the effluent was also maximally reduced by 90% after 30 days of the treatment process using biochar as the substrate and KS23 addition in the VFCWs that was negatively correlated to COD of the system. Further, no adverse effects on the growth of P. barbata were observed during the entire treatment process which highlighted its resistance towards the dye wastewater. Moreover, the number of leaves, plant height, and leaf area was increased by 53%, 28%, and 52%, respectively. Khandare et al. (2013) also reported textile effluent treatment using a lab-scale phytoreactor planted with Portulaca grandiflora and augmented with soil isolates of Pseudomonas putida. A layer of fine gravels followed by coconut shavings and soil was used as the substrate of the VFCW in this study. American Dye Manufacturers’ Institute (ADMI) method was carried out for analysis of colour removal from the textile effluents after treatment in the phytoreactor containing P. grandiflora and bacterial cultures, wherein 86% of the colour was effectively removed within 48 h of operation. Moreover, the COD, BOD, TOC, turbidity, TDS, and TSS values were reduced by 73, 54, 52, 57, 83, and 71% after 48 h of operation of the phytoreactor augmented with bacteria, respectively. In addition, the Fourier transform infrared (FTIR) spectral analysis of the mixture of dyes treated using the prepared phytoreactor indicated that the parent dye molecules were degraded and new metabolites were formed. The FTIR spectra of wastewater samples treated with bacteriaaugmented phytoreactor demonstrated loss of the majority of functional groups as compared to the peaks of the untreated samples. Further, high-performance thinlayer chromatography (HPTLC) results highlighted maximum degradation of the mixture of dyes after treating with phytoreactor containing bacteria with a decrease in absorbance values of Disperse Red BF, Disperse Yellow G, Disperse Bryal Blue, Rubine GFL, and Brown REL dyes from 432.8, 315.3, 256.3, 39.7, to 30.7, 0.0, 18.4, 0.0, and 7.8 absorbance units after 64 h of operation, respectively. Moreover, after 72 h of operation, only two of the dyes namely Disperse Red BF and Disperse Bryal Blue were present in the dye mixture with a reduced absorbance value of 31.3 and 6.3 absorbance units, respectively. Thereafter, the phytotoxicity of the bacteria augmented phytoreactor treated textile effluent was evaluated wherein only 10% inhibition in Phaseolus mungo and Sorghum vulgare seed germination was observed as compared to 60% and 50% inhibition in the P. mungo and S. vulgare seed germination, respectively, which highlighted reduced toxicity of the effluent after treatment using the prepared VFCW.

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Kabra et al. (2013) also reported a similar study that demonstrated the efficacy of bioreactor containing a consortium of Glandularia pulchella and Pseudomonas monteilii ANK for the treatment of textile effluent and Scarlet RR (SRR) dye mixture. Initially, G. pulchella plants showed 97% decolourization of 50 mg/L of SRR within 72 h of incubation while P. monteilii reduced 85% of the dye solution under similar conditions. However, the plant–bacteria consortium provided 100% decolourization of the SRR dye within 48 h of incubation wherein the rate of decolourization was 1.04 mg/L/h. Enzymatic analysis of both the plants and the bacteria revealed 438% and 842% induction in the activities of lignin peroxidase and DCIP reductase in G. pulchella while 612%, 260%, and 185% induction in laccase, DCIP reductase, and tyrosinase activity was observed in P. monteilii in presence of SRR dye, respectively. Thus, the dye was proposed to be metabolized by the synergistic enzymatic action of both the plants and the bacteria. Further analysis of the degraded products using HPTLC demonstrated complete biotransformation of the dye after treatment in the bioreactor with plant–bacteria consortium that was confirmed by the FTIR spectra. The GC–MS analysis was used to propose two different degradation pathways in which SRR was speculated to undergo asymmetric cleavage by the lignin peroxidase of G. pulchella followed by demethylation, reduction, and deamination to finally form 2-(aminomethyl)quinolin-4(3H)-one and 2-methylquinolin-4(3H)-one. Likewise, laccase produced by P. monteilii was proposed to asymmetrically cleave SRR molecules to form quinolin-4-ol and [2-({[ethyl (methyl)amino]acetyl}amino)-1λ3 chlorinin-4-yl](hydroxy)oxoammonium that undergoes further demethylations and deaminations to form 2-amino-1λ3 -chlorinin-4-yl)(hydroxy)oxoammonium. Moreover, the decolourization of the dye mixture containing REL, Rubine GFL (RGFL), SRR, RR, and Green HE4B (GHE4B) in the bioreactor was very effective with average ADMI removal of 93% after 24 h of operation of the first decolourization cycle. Likewise, 95% ADMI removal was attained after 48 and 60 h treatment of two different textile effluent samples in the bioreactor containing plant–bacteria consortia. Additionally, the average TOC, COD, and BOD removal values of the dye mixture were 74, 70, and 70%, while the values for textile effluent were 72%, 70%, and 67%, respectively. Phytotoxicity analysis then highlighted higher seed P. mungo and S. vulgare germinations in the presence of the treated samples as compared to the untreated effluents and dye mixtures. Shehzadi et al. (2014) also reported improved textile effluent degradation using VFCW planted with Typha domingensis along with endophytic bacterial strains such as Microbacterium arborescens TYSI04 and Bacillus pumilus PIRI3 that had textile effluent-degrading potential. Bacterial inoculation was observed to improve the growth of T. domingensis in the VFCW with improved root and shoot lengths as well as increased biomass production. On the contrary, the addition of textile effluent negatively affected plant growth and development. The wetland was composed of coconut shavings, gravel, and sand along with soil for the growth of T. domingensis plants that significantly reduced the colour and TOC of the effluent which was further improved after bacterial augmentation. The TDS and TSS of the effluent were decreased by 59% and 27%, respectively. The COD and BOD were reduced from 410 and 207 mg/L to 85 and 47 mg/L, respectively, after 72 h operation of the

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VFCW. Further, RFLP analysis of the treated wastewater, rhizospheric soil, as well as the root and shoot of T. domingensis exhibited 62–75% presence of the inoculated bacterial strains highlighting that M. arborescens TYSI04 and B. pumilus PIRI3 were also involved in textile effluent degradation. Additionally, the mutagenicity of the effluent was also reduced after its treatment with planted VFCW which was augmented with the two bacterial strains as well. Constructed wetland having vertical orientation and co-planted with Typha angustifolia and Paspalum scrobiculatum was also demonstrated by Chandanshive et al. (2017) to be an efficient treatment strategy for textile effluents. The drench was supplemented with Eucalyptus leaves, sawdust, and fly ash for the reduction of textile wastewater loss during the treatment process. A significant decrease in the ADMI value, BOD, COD, TDS, and TSS up to 76%, 75%, 70%, 56%, and 46%, respectively, were observed within 96 h of textile effluent treatment in the drenches containing the plant consortia. In addition, the concentration of As, Pb, Cd, and Cr was reduced by 72%, 69%, 71%, and 77%, respectively, whereas the bacterial count in the effluent was 87 ± 2.33 × 10−7 colony-forming units (CFUs) that were higher as compared to the untreated effluents as well as effluents treated with drenches that were planted with individual plants. Moreover, the consortia of plants were also able to effectively decolourize various dyes such as Rubine GFL, Scarlet RR, and Green HE4B by 85%, 79%, and 82%, respectively, within 60 h of operation while 94% of Congo Red dye was effectively degraded within 48 h of treatment. Specific activities of certain oxidoreductase enzymes were also significantly enhanced in the presence of the pollutants. Root tissues of T. angustifolia exhibited 193%, 823%, 492%, and 248% increase in activities of lignin peroxidase, veratryl alcohol oxidase, laccase, and azo reductase, respectively. Similar results were observed in root tissues of P. scrobiculatum as well. Further histological studies of the plant tissues demonstrated accumulation of Congo Red dye in the outer epidermal cells along with cortical area after 24 h of exposure that disappeared after 48 h of exposure because of phytotransformation as evident from Fig. 3. In addition, the concentrations of chlorophyll a, chlorophyll b, and carotenoids were increased by 8, 16, and 15% in the leaves of T. angustifolia, respectively, while P. scrobiculatum leaves exhibited 28, 22, and 21% increase in the chlorophyll a, chlorophyll b, and carotenoids content, respectively. The phytotransformation of Congo Red dye was further confirmed by HPLC that demonstrated different spectral peaks of the degraded products as compared to the original dye molecule. GC–MS result analysis provided a proposed mechanism of Congo Red degradation that involves asymmetric cleavage of the dye molecule by the lignin peroxidase and laccase enzymes of T. angustifolia and P. scrobiculatum to form 1,1’-biphenyl-4,4’-diyldidiazene and sodium 4-amino-3-hydroxynaphthalene1-sulfonate wherein 1,1’-biphenyl-4,4’-diyldidiazene was speculated to undergo desulfonation and deamination to form 1-aminonaphthalen-2-ol and naphthalen-2ol. Thereafter, phytotoxicity analysis exhibited 90% germinations of P. mungo seeds in the presence of the degraded products of Congo Red dye as compared to 30% seed germination in the presence of untreated dye molecules. In another study, vertical sub-surface flow constructed wetlands were used for the treatment of textile effluents (Jayabalan et al. 2020). The wetland prepared in this

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Fig. 3 Anatomy of root of (A) T. angustifolia; and (B) P. scrobiculatum; (A1, B1) control; plants exposed to (A2, B2) Congo Red after 24 h; (A3, B3) 48 h and (A4, B4) normal water (Reprinted with permission from Chandanshive VV, Rane NR, Tamboli AS, Gholave AR, Khandare RV, Govindwar SP, 2017. Co-plantation of aquatic macrophytes Typha angustifolia and Paspalum scrobiculatum for effective treatment of textile industry effluent. Journal of Hazardous Materials 338:47–56. Copyright © 2017 Elsevier B.V.)

study was added with activated charcoal, eggshells, wood husk, and gravel along with Canna indica plantation and E. coli augmentation. COD of the textile effluent after treatment was reduced from 2000 mg/L to 800 mg/L. However, the COD removal rate was subsequently reduced due to the build-up of inorganic matter in the bed which prevented the microbial metabolism for degradation of the components present in the textile effluent. The pH of the planted wetland system was reduced from 8.5 to 6.4 which was attributed to rhizospheric oxidation of the inorganic components of the textile wastewater sample. The BOD value of the effluent was also gradually reduced from 500 mg/L to 310 mg/L because of effective metabolic reactions by the bacterial strains present in the rhizosphere of the wetland. In another report, Yellow 2G azo dye contaminated wastewater was treated in a lab-scale vertical flow constructed wetland layered with sand, gravel, and zeolite for effective removal of colour, organic compounds, and nutrients within 79 days of operation (Dogdu and Yalcuk 2016). Two different plants namely, Canna indica and Typha angustfolia were planted in two different wetlands that showed 99.32 ± 9.95% and 99.43 ± 1.21% colour removal, respectively. The sulphate concentration of the effluent was reduced from 128 mg/L to 67.3 ± 13.01 mg/L and 66.5 ± 11.78 mg/L by the wetlands planted with C. indica and T. angustfolia, respectively. Likewise, the phosphorus concentration also decreased from 2.05 mg/L to 0.25 ± 0.17 and 0.23 ± 0.13 mg/L, respectively. The average concentration of ammonium was reduced from 3.5 mg/L in the untreated effluent sample to 2.1 ± 0.42 and 1.9 ± 0.32 mg/L after treatment in the constructed wetlands having C. indica and T. angustfolia, respectively. However, zeolite was also suggested to facilitate ammonium removal in the process. The average COD of the textile effluent containing Yellow 2G dye of 250 mg/L was also reduced to 97.25 ± 23.94 mg/L and 82.41 ± 20.55 mg/L by the two wetlands, respectively. Evaluation of plant growth and development during the

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treatment processes revealed the death of C. indica plants after 43 days of operation in the VFCW, whereas T. angustfolia was tolerant to the toxicity of the wastewater sample. Further, FTIR spectral analysis revealed the breakage of azo bonds of Yellow 2G dye after treatment in the VFCW. Similarly, Sivakumar et al. (2013) reported the construction of wetland using aquatic macrophytes Eichhornia crassipes that effectively treated textile industry effluents. Activated sludge at varying concentrations was used as the nutrient source in this study that affected the percentage reduction of electrical conductivity, TDS, chloride, sulphate, phenols, BOD, and COD of the textile industry wastewater sample. Increasing the concentration of nutrients to 60 g provided an optimal reduction of electrical conductivity, TDS, chloride, sulphate, phenols, BOD, and COD values by 86.29, 88.54, 80.78, 84.05, 76.36, 90.42, and 91.40%, respectively. Similarly, an optimal effluent: diluent ratio of 10 exhibited maximum removal percentages after 7 days of treatment. Additionally, alkaline conditions of the system with an optimal pH value of 8.0 further displayed an improved reduction of wastewater that was attributed to the increased availability of active sites in Eichhornia crassipes that can enhance adsorption. Finally, another wetland system having E. crassipes was set up for textile wastewater treatment with the optimized conditions of 60 g of nutrient dosage, dilution ratio of 10, pH 8.0, and 6 days of contact time that showed 87.2, 90.2, 82.6, 86.8, 78.5, 91.3, and 92.8% reduction in electrical conductivity, TDS, chloride, sulphate, phenols, BOD, and COD, respectively.

3 Conclusion and Future Perspectives CWs serve as a promising alternative for wastewater treatment on a large scale that exploits both plants and microbes along with their active enzymes. Genetically modified plants can be used for the purpose of high metal accumulation and dye degradation. Further, they can detoxify the end products generated during the metabolic degradation. There are numerous plants such as Gnidia glauca, Litchi chinensis, Platanus orientalis, Barleria prionitis, Plumbago zeylanica, and Gloriosa superba that are reported for their promising bioconversion of metal ions into metal nanoparticles which are biomedically significant (Ranpariya et al. 2021; Shinde et al. 2018). These plants as a whole, their parts, or biochar generated from them can be used in the CWs for the enhancement of the efficiency. Numerous microbes like bacteria, fungi, and algae are reported to remove heavy metals and dyes from the textile effluents. Such microbes can be used in consortium where a mixed population can have more impact on the effluent treatment in CWs. Further, recombinant DNA technology can be employed to generate more effective microbes with high metal reduction, bioconversion, and bioaccumulation properties. Nanotechnological advances have proved to be revolutionary in treating industrial effluents. Several metal and metal oxide nanoparticles are used for photocatalytic dye degradation very effectively. Hence, such nanotechnology-driven mechanisms should be coupled with the CWs where the removal of refractory pollutants can be

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synergistically enhanced. In view of the background, it can be concluded that CWs provide a powerful strategy for the efficient treatment of textile effluent in order to ensure a clean and safe environment.

References Bulc TG, Ojstršek A (2008) The use of constructed wetland for dye-rich textile wastewater treatment. J Hazard Mater 155:76–82 Chandanshive VV, Rane NR, Tamboli AS, Gholave AR, Khandare RV, Govindwar SP (2017) Coplantation of aquatic macrophytes Typha angustifolia and Paspalum scrobiculatum for effective treatment of textile industry effluent. J Hazard Mater 338:47–56 Dogdu G, Yalcuk A (2016) Evaluation of the treatment performance of lab-scaled vertical flow constructed wetlands in removal of organic compounds, color and nutrients in azo dye-containing wastewater. Int J Phytorem 18(2):171–183 Hussain Z, Arslan M, Shabir G, Malik MH, Mohsin M, Iqbal S, Afzal M (2019) Remediation of textile bleaching effluent by bacterial augmented horizontal flow and vertical flow constructed wetlands: a comparison at pilot scale. Sci Total Environ 685:370–379 Hussein A, Scholz M (2017) Dye wastewater treatment by vertical-flow constructed wetlands. Ecol Eng 101:28–38 Ishaq HK, Farid M, Zubair M, Alharby HF, Asam ZU, Farid S, Bamagoos AA, Alharbi BM, Shakoor MB, Ahmad SR, Rizwan M (2021) Efficacy of Lemna minor and Typha latifolia for the treatment of textile industry wastewater in a constructed wetland under citric acid amendment: a lab scale study. Chemosphere 283:131107 Jayabalan JB, Amirthalingam S, Sekar S, Santhanam NK, Manoharan S (2020) Treatment of textile effluent using sub-surface flow constructed wetlands. AIP Conf Proc 2240:130001 Kabra AN, Khandare RV, Govindwar SP (2013) Development of a bioreactor for remediation of textile effluent and dye mixture: a plant–bacterial synergistic strategy. Water Res 47:1035–1048 Kadam SK, Tamboli AS, Chandanshive VV, Govindwar SP, Choo YS, hong Pak J (2022) Construction and implementation of floating wetpark as effective constructed wetland for industrial textile wastewater treatment. J Hazard Mater 424:127710 Khandare RV, Kabra AN, Kadam AA, Govindwar SP (2013) Treatment of dye containing wastewaters by a developed lab scale phytoreactor and enhancement of its efficacy by bacterial augmentation. Int Biodeterior Biodegradation 78:89–97 Malaviya P, Singh A (2012) Constructed wetlands for management of urban stormwater runoff. Crit Rev Environ Sci Technol 42:2153–2214 Noonpui S, Thiravetyan P (2011) Treatment of reactive azo dye from textile wastewater by burhead (Echinodorus cordifolius L.) in constructed wetland: Effect of molecular size. J Environ Sci Health Part A 46:709–714 Ranpariya B, Salunke G, Karmakar S, Babiya K, Sutar S, Kadoo N, Kumbhakar P, Ghosh S (2021) Antimicrobial synergy of silver-platinum nanohybrids with antibiotics. Front Microbiol 11:610968 Saba B, Jabeen M, Khalid A, Aziz I, Christy AD (2015) Effectiveness of rice agricultural waste, microbes and wetland plants in the removal of reactive black-5 azo dye in microcosm constructed wetlands. Int J Phytorem 17:1060–1067 Saeed T, Muntaha S, Rashid M, Sun G, Hasnat A (2018) Industrial wastewater treatment in constructed wetlands packed with construction materials and agricultural by-products. J Clean Prod 189:442–453 Sharma R, Malaviya P (2021) Constructed wetlands for textile wastewater remediation: A review on concept, pollutant removal mechanisms, and integrated technologies for efficiency enhancement. Chemosphere 290:133358

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Shehzadi M, Afzal M, Khan MU, Islam E, Mobin A, Anwar S, Khan QM (2014) Enhanced degradation of textile effluent in constructed wetland system using Typha domingensis and textile effluent-degrading endophytic bacteria. Water Res 58:152–159 Shinde SS, Joshi KA, Patil S, Singh S, Kitture R, Bellare J, Ghosh S (2018) Green synthesis of silver nanoparticles using Gnidia glauca and computational evaluation of synergistic potential with antimicrobial drugs. World J Pharm Res 7(4):156–171 Sivakumar D, Shankar D, Prathima AV, Valarmathi M (2013) Constructed wetland treatment of textile industry wastewater using aquatic macrophytes. Int J Environ Sci 3(4):1223–1232 Talouizte H, Merzouki M, Benlemlih M, Bendriss Amraoui M (2020) Chemical characterization of specific micropollutants from textile industry effluents in Fez City, Morocco. J Chem 2020:3268241

Constructed Wetland-Microbial Fuel Cell for Wastewater Treatment and Energy Recovery: An Emerging Technology Anamika Yadav, Shravankumar S. Masalvad, and Dipak A. Jadhav

1 Introduction On a global scale, sewage is the first and major source of pollution directly to the environment and existing water bodies. About 90–95% of the world’s sewage is produced from civilized areas and directly discharged into the environment in its raw form (Seghezzo 2004). In India, over 70% of home sewage is released into watercourses instead of being properly or completely treated (CPCB 1997). However, nearly all of the wastewater generated from cities and towns in certain developing nations is regularly released into water sources such as rivers and lakes, resulting in immediate or often severe impacts on human health and environmental quality (Seghezzo 2004; Shah 2020). The raw effluent has obvious negative effects on the environment as well as human health. Proper wastewater treatment is critical for sustaining people’s health, preserving the environment’s quality, and, ultimately, fostering economic growth (Kyambadde 2005). According to the rules set by the recent state and central legislative bodies (CPCB 1997), treatment to remove pollutants from wastewater is mandatory in developing countries for avoiding the adverse impacts on the receiving water bodies. The traditional methods of wastewater treatment, i.e., aerobic process and chemical coagulation have been implemented either solely or in combination A. Yadav Department of Agricultural Engineering, Triguna Sen School of Technology, Assam University, Silchar 788011, Assam, India S. S. Masalvad Department of Civil Engineering, Sreenidhi Institute of Science and Technology, Hyderabad 501301, India D. A. Jadhav (B) Department of Environmental Engineering, College of Ocean Science and Engineering, Korea Maritime and Ocean University, 727 Taejong-Ro, Yeongdo-Gu, Busan 49112, Republic of Korea e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. P. Shah (ed.), Recent Trends in Constructed Wetlands for Industrial Wastewater Treatment, https://doi.org/10.1007/978-981-99-2564-3_6

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to control both domestic and industrial wastewater. These methods are energyintensive, which include a large amount of chemicals and generate a large amount of sludge (Jadhav et al. 2014). Due to the increasing population in developing countries, it is urgently needed to create appropriate and effective wastewater treatment methods. Recently, the treatment of residential and industrial wastewater has turned towards high-rate anaerobic methods. Anaerobic procedures provide several benefits over traditional aerobic treatment, including less energy demand for oxygen delivery, reduced sludge generation, and waste-to-energy recovery at the same time. The untreated wastewater causes contamination of groundwater. To choose between different wastewater treatments, simple natural systems need to be given more consideration. There will be no harmful environmental impacts if toxins are removed from wastewater before it is discharged or reused safely. Untreated wastewater in the environment can lead to eutrophication (algae growth in water bodies), low oxygen levels (dangerous for aquatic species), toxic compounds and heavy metal build-up in aquatic water bodies, and human health risks.

1.1 Wetland Wetlands are the marshy areas found in between terrestrial and natural waterways which are saturated with water, either permanently or periodically, as a result, it takes on the attributes of a specific environment. The wetlands are categorized with a broad range of wet environments considering natural wetlands for instant marshes, fens, sloughs, floodplains, and ribbon (riparian) wetlands along stream channels. The boundaries of all these different types of wetland areas including natural, constructed, fresh water, and salt water have unique characteristics. Natural wetlands are designed to offer various advantages, such as improving food and habitat for animals, enhanced water quality, protection against flood, preventing coastal sites from erosion, and providing recreational and scenic opportunities. Wetland plants have a special ability to transfer oxygen into the root zone, resulting in an oxidized rhizosphere. Wetland plant rhizospheres have been found to promote nitrogen removal, whereas the nearby anaerobic region encourages de-nitrification (Xu et al. 2019). The conversion of inorganic compounds into organic compounds, which is the base of the wetland food chain, is supported by receiving resources of nutrients.

1.2 Constructed Wetlands (CWs) CWs are manmade engineered designed systems that are developed and built to help treat wastewater by utilizing natural processes including soil media, wetland plants, and related bacterial associations (Fig. 1). The CW systems are prepared similarly as natural wetlands found in lower regions. These systems can be divided

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into four different forms depending on different categories of the dominant macrophyte, i.e., free-floating leaves, floating leaves, rooted emergent, and submerged macrophytes. Furthermore, the CWs system can also be categorized on the basis of wetland hydrology. The flow of water in subsurface systems is found to be horizontal and vertical on the basis of the direction of flow. These systems are one of the natural treatment processes for wastewater having the ability to generate useful biomass and achieving effective removal of organic matter, nutrients, and even metals present in the wastewater (Steer et al. 2002). CW technology is well-known for being lowenergy and low-maintenance, as well as being simple to use. These characteristics make it useful for wastewater treatment in areas where land availability and pricing are not a constraint. Since from many years, CWs have been employed in the domestic wastewater management. They can handle a wide range of effluents and operate in various unpleasant environmental situations. These practices are majorly adopted to treat the wastewater because CWs use extremely very limited or and less energy, their construction and operating expenses are relatively inexpensive. Plants that flourish in wetlands may absorb CO2 from the atmosphere and reduces the warming effect. CWs have also been demonstrated to have a great potential for removing biorefractory pollutants. Water, energy, and nutrients should be considered as sources of recovery instead of as pollutants in wastewater treatment technology and management. If the wetland system is clubbed with MFC, due to the synergy of both processes, it will offer distinct advantages of reducing retention time required for treatment, and energy in the form of direct electricity and biomass as feedstock for bio-energy production can be harvested. The opportunity to enhance water quality by providing attention to animal habitats has prompted growing investment in the use of CWs for waste management. Sedimentation, filtration, digestion, oxidation, reduction, adsorption, and precipitation are all used to treat industrial effluents in such systems. The CW merged with microbial fuel cell (CW-MFC) technology is becoming more popular, and it’s also a viable solution for treating wastewater and producing power at the same time. Recently, MFC has been widely explored for various applications Fig. 1 Constructed wetland site with vegetation (Source New Indian Express)

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including contaminant removal, energy recovery, biosensor applications, external power source for operating low-power requirement appliances, and so on (Shabani et al. 2021).

2 Components of Wetlands 2.1 Hydrology Hydrology is the study of water on the surface of earth, which is the most essential variable for produce, protection, and development of various types of wetlands (Mitsch and Gosselink 1992). It describes the wetlands’ water profile by permanent or periodic saturation, in which biogeochemical processes occur in wetland areas. Hydrology is the most significant designing aspect for constructed wetlands since it connects all of the functions in wetlands. The success or failure of a created wetland has a significant impact on the design parameters.

2.2 Subgrades, Sediments and Litter Subgrades are the base material of constructed wetland that must be different types of soil and gravel. It provides the structure for holding water up to saturation level in wetland areas. The sediments and litter produce organic matter or compost as a substrate material for a productive wetland. The accumulation of the sediments and litter can reduces the flow velocity and produces a marshy-type area. The importance of including substrates, sediments, and litter in wetlands are: 1. In wetlands, substrates, sediments, and litter can provide a habitat for a variety of living organisms. 2. Water movement through the wetland system is influenced by the permeability of the substrate. 3. The substrates undergo numerous chemical and biological (particularly microbial) changes. 4. Substrates were used to store a variety of pollutants. 5. The amount of organic matter in the wetland grows as trash accumulates. 6. Organic matter is a source of carbon for bacterial activity.

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2.3 Vegetation Used in Wetlands In artificially constructed wetlands, both the types of vascular (higher plants) and non-vascular (algae) plants play an important role in wastewater treatment. The main reason behind the vegetated wetland systems is to provide a sufficient environment for microbial populations. The amount of aerobic microbial habitat in the substrate is increased by plants. Plant and algae enhance the quality of water by raising the dissolved oxygen level of wetlands. Wetland vegetation helps to reduce erosion, pollutant access, and water quality degradation in natural waterways, as well as serving as an appealing study location. Various aquatic plants are commonly employed in a variety of wastewater treatment industries (Wang et al. 2021). A plant helps to increase the process of denitrification and significantly improve the removals rates of ammonia nitrogen (NH4 + –N) through plant absorption that promotes the conditions of water bodies (Saba et al. 2019). Other than the nutrient removal, it is also important to maintain the appropriate level of dissolved oxygen, which is directly related to the process of nitrification and denitrification (Xu et al. 2017; Shah 2021). CWs plants (macrophytes) generally produce in oxygen-depleted water or soil environments. Figure 2 shows how the macrophytes are utilized in CWs and can be categorized into four different types (SAAT 2006). a. Emergent macrophytes required water depths of above 50 cm to grow over the surface of a substrate. These plants are mostly found on water-saturated surfaces or submerged in sediment. Their roots release oxygen into the surrounding rhizosphere, allowing contaminants to be degraded aerobically (Moshiri 1993; Vymazal 2013).

Fig. 2 Macrophyte plants cultivated in CW (SAAT 2006)

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b. Floating-leaved macrophytes are semi-floating-type species growing in wetlands. The root zone section of floating type macrophytes in submerged soil with a water depth of 0.5–3.0 m and the leaves of plant have characteristics to float above the water surface. c. Submerged macrophytes are completely immersed in water. These plants have active respiratory cells for the photosynthesis process and mostly utilizes for the secondary treatment of wastewater (Moshiri 1993). d. Free-floating macrophytes can be found floating freely on the surface of the water. Floating plants can eliminate nitrogen and phosphorus through mixing with plant biomass in the denitrification process. These plants are also able to extract suspended solids.

2.4 Microbes and Bacteria Wetlands are characterized by different types of microbes and their metabolism, which plays a key role in the functioning of wetlands. Microbial biomass serves as a key source of organic carbon and a variety of nutrients. Microorganisms have the ability to convert or recycle the nutrients such as a wide range of organic and inorganic chemicals into insoluble harmful substances. The microbes’ activity can also change the oxidation level of the processing unit that affects the wetland system’s treatment capability. These microbial conversions are aerobic and anaerobic. Microorganisms are inoculated in an anodic compartment of MFCs. In the anode compartment (anaerobic), electrons are generated and transmitted through a proton exchange membrane called exoelectogens (Jadhav et al. 2021). The density, types, and composition of produced microbes and bacteria on the electrode materials in the anaerobic compartment determine the ability of wetland systems to produce electricity. Shewanella and Geobacter are the two most significant exoelectrogens and have been thoroughly researched by authors Biffinger et al. (2007) and Richter et al. (2009). Various other microbes (Proteus mirabilis, Saccharomyces cerevisiae, Escherichia coli, Enterococcus faecium, Shewanella putrefaciens, Actino-bacillus sucinogenes, Enterococcus faecium, etc.) are also capable of providing electrons from organic matter decomposition (Wang et al. 2010). As a result, exoelectrogens produce electricity by oxidizing the organic components in the substrate. Bacteria that developed were likely able to use a number of different types of electron acceptors, but the most fascinating for those of us interested in MFCs were bacteria able to transfer electrons outside the cell. Bacteria can utilize the mediators for effective extracellular electron transfer (EET). Also, through nanowires and cell surfaces to the bacteria are capable of passing electrons from anode to cathode (Huang et al. 2008).

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3 Types of Constructed Wetlands for Wastewater Treatment The CWs system is categorized into several types according to different parameters such as water level, plants, and flow pattern, and its direction is presented in Table 1. CWs can be categorized into 3 subsystems, viz. rooted-emergent, free-floating, and submerged macrophytes based on the living thing living macrophytes for wastewater treatments (Moshiri 1993).

3.1 Free Water Surface Flow Constructed Wetland (FWSF-CW) FWSF-CW is also known as surface flow constructed wetland (SF-CWs). FWSFCW systems integrated with vegetation (natural or planted) serve the treatment capability similar to land-intensive biological treatment systems (Vymazal 2013). These systems have low water depth and low flow velocity. Especially in long channels and narrow passages and ensure plug-flow conditions, the water flow rate can be regulated by the available plants and their parts like stalks and litter. Water flow in FWSF-CW system is mainly horizontal and the water surface is above the substrate. CW systems perform all three processes, i.e., physico-chemical and microbial processes to eliminate various contaminants (Wu et al. 2020). These processes involved various operations such as filtration, sedimentation, adsorption, bioconversion, and uptake through microbes and plants used in wetlands. Microbial decomposition with adherent and free-living bacteria is primarily responsible for the removal of organic substances from waste. The floating plants’ root systems provide an enormous surface area for associated microbes, which enhances the opportunity for organic carbon breakdown. Air turbulence and mixing are reduced by the bulk vegetation on the surface, while suspended materials are removed by gravitation underneath the floating plants’ surface layer. Nutrient removal is significantly more challenging in systems with freefloating plants than plant uptake alone. The nitrification/denitrification method is more successful in removing nitrogen in FWS-CWs. Temperature has a large impact on nitrogen removal (Wang et al. 2021). Nitrogen can also be removed through macrophyte harvesting however the amount of removal is very low. The density of vegetation affects the detention time in FWS-CWs, like the detention time increases with the plant density. Vymazal (2013) found that emergent plants are used in FWSCWs, where the macrophytes have an important role in FWS-CWs. It has been reported that the treatment performance of planted FWS-CWs is superior to vegetated lagoons. However, the treatment performance of FWS-CWs could be affected by the plant species used. Galanopoulos et al. (2013) evaluated a pilot-scale study for FWS-CWs through the direct comparison of two parallel pilot-scale systems, one with plants (Typha latifolia) and one without. FWS-CWs system with plants

Horizontal

Flow

Direction

3

4

Floating-leaved

Free water surface flow

Free-floating

Water level

Plants

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Parameters

S. No.

Table 1 Types of CWs

Submerged

Emergent

Subsurface flow Horizontal

Emergent Vertical Down-flow

Up-flow

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provides a better performance than without plants. El-Sheikh et al. (2010) worked with improving water quality in polluted drains with FWS-CWs at high and low flow rates.

3.2 Subsurface Flow Constructed Wetland (SSF-CWs) SSF-CWs commonly used gravel as the principal media to encourage plant development. The substrate flows vertically/horizontally through the media in biological contact facilitating contaminants deduction from the bulk liquid. It has been proved that they can enhance water quality from influent to effluent. Similar to the FWSCWs system, these systems are also capable to allow treatment through physical, chemical, and biochemical treatment methods (Yadav et al. 2021). The SSF-CWs are divided into 2 sub-types, i.e., horizontal and vertical flow CW.

3.3 Horizontal Flow Constructed Wetland (HF-CW) The HF-CWs allow wastewater to flow horizontally through porous sand media. The wastewater entered from the inlet point to the outlet, which passes through different layers of soil as shown in Fig. 3. The quantity of oxygen generated by roots and rhizomes should be adequate to fulfil the requirement of aerobic decomposition of oxygen-consuming compounds in the wastewater as well as nitrification process, based on the working concept of HF-CWs. The HF-CWs system can be so practicable for secondary-level treatments to treat total suspended solids (TSS). Although nitrogen removal is often less successful until greater hydraulic retention time and sufficient oxygen are available for treatment. Ammonia removal is limited due to a shortage of oxygen in the filtration bed as a result of constant waterlogging. Vymazal and Kropfelova (2008) studied the treatment of wastewater in constructed wetlands with horizontal flow. Phosphorus is predominantly removed from iron and aluminium hydrous oxides by ligand exchange processes. Phosphorus removal through HF-CWs system is not much attentive because of the selected media used for the construction of CWs, such as pea gravel, crushed stones, etc.; generally, it does not comprise a high concentration of iron, aluminium, and calcium (Vymazal and Kropfelova 2008).

3.4 Vertical Flow Constructed Wetland (VF-CW) Seidel (1966) first proposed constructed wetlands (CWs) with vertical flow (VF) as a pre-treatment option with flow beds. VF-CW consists of a flat bed of different layers of sand and gravel with vegetation (Fig. 4). Wastewater is supplied from the top, permeates downward through media, and is gathered through a drainage basin at the

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Fig. 3 Representation of SSF-CW (White 2013)

Fig. 4 Schematic diagram of VF-CW system with components (Vymazal 2010)

bottom. This type of feeding allows for good oxygen transfer and hence is capable of the nitrification process. The VF-CW system is a novel method to treat wastewater through the bed into the root zone according to the effluent quality. The wastewater treatment through aeration of water reaches oxygen diffusion during drops through the bed from the VF-CWs. The system has a number of significant outcomes: (1) aeration and recirculation substantially improve organic matter decomposition, allowing for a

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decreasing system area, which is significant in high-cost land locations; (2) continuous flow of water through VF-CW bed is effective in improving the microbial population as well as dissolving the raw influent with slightly treated wastewater, thereby attenuating possible sharp influent strength fluctuations (Fang et al. 2015). VF-CWs are widely used in household wastewater treatment because of their high chemical oxygen demand (COD) and nitrogen removal efficiency; lower operating costs, increased oxygen transfer capability, high hydraulic loading rate, efficient nutrient elimination, and small size (Langergraber et al. 2009). Within the permissible limits, nitrogen removal rates improve in subsurface flow wetland systems. In comparison to SF-CWs, the SSF-CWs have very high nitrogen removal efficiencies due to a combination of efficient ammonification, uptake by plants, and efficient adsorption of the generated NH4 + –N to the substrates (Annelies et al. 2009). The nitrogen and organics removal methods in SF-CWs are dependent on environmental factors, operating circumstances, and supporting medium, according to Saeed and Sun (2012). The nitrification and denitrification processes are still the main nitrogen removal routes in subsurface flow wetlands, although they are frequently hampered by a shortage of organic carbon. Valerie et al. (2011) demonstrated the results that the VF-CW systems are very effective for the nitrification process and also have great potential for denitrification during wastewater treatment. This method is a low energy intensive for implementing in wetland areas. These systems required less space as compared to HF-CWs. It has a great impact on the environment and surrounding which becomes an important consideration nowadays. CWs might be an excellent solution to recover resources while also lowering environmental concerns. Several studies had been documented on treating different wastewater using CWs, and some of them are given in Table 2.

4 Constructed Wetland-Microbial Fuel Cell System (CW-MFC) CW-MFCs are the bio-electrochemical systems in which nutrients, organic carbon, and trace metals present in the wastewater are removed by the plants hence offering treatment of wastewater (Gupta et al. 2021). Similar to conventional MFC, the CW systems contain two separate zones (aerobic and anaerobic) in all depths of media and water column (Yadav et al. 2021). CW-MFCs have shown to be effective in addressing a number of water quality concerns, with benefits over the natural wetlands, in which particularly the soil media significantly performs as the proton exchange membrane (PEM). This technology is capable of generating electricity from lab-scale sedimentsbased microbial fuel cells (SMFCs) to field scale for a variety of industrial wastewaters (Sajana et al. 2019; Shabani et al. 2021; Dai et al. 2021). Basic knowledge is required to complete betterment and develops MFC energy output. The microorganisms employ different biochemical processes depending on the MFCs’ specific operating conditions. Several researchers worked on the optimization of electrode

Domestic wastewater

Domestic wastewater

Domestic wastewater

Subsurface flow

HS-CW

CW

VF-CW

1.

2.

3.

4.

Domestic wastewater

Type of wastewater

S. Experimental No system

Typha latifolia, Collocasiaesculenta, Gladiolous sp., Iris sp. Thalia Sp

7.5 m × 3.0 m × 0.2 m

Authors

Typhaaugustifolia

63 cm × 45 cm × 40 cm

BOD5 : 89.5%, N: 68.8%, TP: 99.4%, TSS: 89.9%

Scirpus, Sagittaria, Acoruscalamus, Lobeliacarinalis, Asclepiasincarnata and BOD5 : 89%, Pontederiacordata TSS: 79%, Faecal coliform: 74%, Phosphorus: 50%, Ammonia: 16%,

TSS: 94.8%, BOD5 : 82.6%, COD: 72.1%, NH3 –N: 25.6, NO3 –N: 39.4%, TKN: 35.5%

(continued)

Park (2009)

Steer et al. (2002)

Vanier and Dahab (2001)

TSS: 88%, Neralla BOD5 : 90%, et al. FC: 99%, NH3 : (2000) 39%,

Removal efficiency

4.5 m × 5.5 m × 0.46 m

50 m × 25 m T. latifolia, T. domingensis, Scripusacutus, Phragmitescommunis × 0.6 m

Plant species used

Size of the wetland (Length × width × depth)

Table 2 Various CW systems for wastewater treatment and plant species used

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Domestic wastewater

SSF-CW

Integrated VF-CW

VF-CW

VF-CW

5.

6.

7.

8.

Domestic wastewater

Grey water

Domestic wastewater

Type of wastewater

S. Experimental No system

Table 2 (continued)

Arundodonax, Canna indica

1m×1m ×1m

COD: 81.03%, TN: 51.66%, NH4 –N: 42.50%, TP: 68.01%

(continued)

Wu et al. (2013)

Al-Zu’bi et al. (2015)

Filter media

1m×1m × 0.65 m

BOD5 : 94%, COD: 88%, TSS: 90%, Chloride: 48%, Na: 33%

COD: 62.8%, Chang TN: 15.0%, TP: et al. 52% (2012)

Canna indica, T. orientalis, Arundodonax P. cordata

Zhang et al. (2010)

Authors

1m×1m ×1m

Removal efficiency

NH4 –N: 94.4%, BOD5 : 89.1%, TN: 86.0%

Plant species used

3 m × 0.7 m Typhaangustata, Phragmiteskarka, Scirpuslittoralis ×1m

Size of the wetland (Length × width × depth)

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9.

HF/VF-CW

S. Experimental No system

Table 2 (continued)

Dairy wastewater

Type of wastewater

Plant species used

VFCW: T. augustifolia 0.5 m diameter and 1.5 m height, and HFCW: 0.75 m length × 0.25 m breadth × 0.5 m height

Size of the wetland (Length × width × depth) NH4 –N: 53.1% and 66.2%, PO4 −3 : 49.4% and 59.7%, BOD5 : 82.8% and 73%, COD: 25.7% and 35.7%, NO3 –N: 62.9% and 47.5%, SO4 −2 : 47% and 41.1%, and Heavy metals (Fe: 47.3%, Cr: 65.5%, and Ni: 64.8%) for HFCW and VFCW, respectively

Removal efficiency

(continued)

Verma and Suthar (2018)

Authors

120 A. Yadav et al.

Domestic sewage waste

Domestic wastewater

10. CW

11. Hybrid CW (HF/VF-CW)

HF-CW: 1.5 m × 0.4 m × 0.4 m, and VF-CW: 0.6 m × 0.4 m × 0.7 m

Large-scale wetland of length 500 m at different depths of 5 m, 12 m, and 22 m

Size of the wetland (Length × width × depth)

T. latifolia, Hydrillaverticillata, Eichhorniacrassipes, Spirogyra

Sagittarialancifolia, T. dominguensis

Acoruscalamus, Reeds

Plant species used

Wu et al. (2020)

Authors

Faecal coliform: 68%, particulate Phosphorus: 72%, Total phosphorus: 42%, and Nitrogen: 35%

Wang et al. (2021)

Organic matter Vega De removal (COD, Lille et al. BOD5 and (2021) TOC): > 92%, TSS: 88%, Nitrogen: 66%, and Phosphorus: 90%

COD: 10%, NH3 –N: 18%, TN: 15%, and TP: 28%

Removal efficiency

BOD–5 day biological oxygen demand; COD–Chemical oxygen demand; TSS–Total suspended solids; TP–Total phosphorus; TN–Total nitrogen; TKN–Total kjeldahl nitrogen; TOC–Total organic carbon.

12. CW integrated Contaminated Wetland with aquatic runoff/stormwater area: 2 ha macrophytes

Type of wastewater

S. Experimental No system

Table 2 (continued)

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materials, types and combinations of bacteria, and electron transfer in MFCs (Song et al. 2019). Regardless of the fact that the concept of generating electricity produced by microorganisms has been established for almost a century, researchers have only just begun to fully comprehend MFCs (Jadhav et al. 2022b) and they are also focusing on, how to increase their efficiency (Jadhav et al. 2022a). The performance of CWMFC mainly depends on several factors, i.e., the selection of appropriate factors related to the types of microorganism and their density, type of substrate, substrate characteristics, type of flow and its operating mode, retention time (HRT), feeding concentration, thickness of soil media or bed, total depth of soil media, electrode materials, electrode size, surface area of the electrode, IEM, reactor size, type of PEM, experimental operating conditions, and many more (Wang et al. 2017a, b; Huang et al. 2021; Xu et al. 2018).

4.1 Principle of Wastewater Treatment via Microbial Fuel Cell (MFC) MFC is a promising technique that can provide a long-term viable solution towards effective contaminant degradation along with bioelectricity harvesting (Sajana et al. 2019; Shabani et al. 2021; Dwivedi et al. 2022). MFC helps to transform chemical energy to electrical energy through the catalytic activities of anode-respiring bacteria (Jadhav et al. 2017; Sajana et al. 2017). MFCs consist of two electrode compartments, i.e., anodic compartment (anoxic) and cathodic compartment (oxic), separated by proton exchange membrane (PEM) as shown in Fig. 5. The energy production in MFC technology depends on the bacterial activity and originated energy from the oxidation of organic matter in anaerobic condition (Mathuriya et al. 2018). The generated microbe in the anode compartment contains electrogens, anodophilic and electrochemically active bacteria that oxidize the substrate, separating electrons from protons (Jadhav et al. 2019, 2020). Due to microbial degradation of organic substances under anaerobic conditions, the electrons produced are transferred from the anode surface to the cathode through an external electric circuit (Shabani et al. 2021; Dwivedi et al. 2022). The ability of bacteria (Escherichia coli) to generate electric current was first reported in 1911 by British scientist M.C. Potter, but MFCs have appeared in the fuel cell family only within recent decades from the 1990s. This technology is well-known for being lowenergy, low-maintenance, and simple to use (Jadhav et al. 2017). These characteristics make it useful for wastewater treatment in areas where land availability and costs are not a concern. The equations below illustrate the basic reactions occurring in MFCs considering sucrose as an example of a substrate. Anodic reaction: C12 H22 O11 + 13H2 O → 12CO2 + 48H+ + 48e−

(1)

Cathodic reaction: 4H+ + O2 + 4e− → 2H2 O

(2)

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Fig. 5 Schematic representation of the working mechanism of MFC

The sediment MFC is an advancing technology for replacing traditional energy sources with renewable energy sources in wireless sensors, with the potential to provide long-term WSN without the need for battery replacement (Niwa et al. 2020). Shabani et al. (2021) proposed the design and development of an energy-autonomous MFC-based water quality monitoring sensor to measure the COD concentration from natural ponds (Jadhav et al. 2018). It was discovered that the MFC was found to be practical for the simultaneous use of sensors and energy sources. The COD value was calculated with R2 value of 0.94 precision and could be used in natural ponds or aquaculture. Song et al. (2019) developed a sediment MFC system integrated with numerous cathodes deployed at various depths of water for water quality monitoring at various depths of lake water. The linear association with an R2 value of 0.9576 was obtained with current and DO levels of 0–9 mg/l. In recent decades, several authors studied MFC-based biosensor technology, which is gaining popularity due to their ease of use and long-term viability, with applications of monitoring water quality parameters, i.e., dissolved oxygen (DO), pH, nitrite, COD, BOD, toxicants, etc. The MFC-based biosensor technology may also help to detect the air quality parameters, i.e., carbon monoxide and formaldehyde (Klevinskas et al. 2021). The water quality can be managed by utilizing different sensors to measure specific parameter such as temperature, DO, pH, phosphate, nitrate, calcium, and magnesium on a regular basis (Wu et al. 2020). These technologies are primarily designed to fix or detect problems caused by changes in environmental circumstances, which have an impact on water quality.

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4.2 Advantages of CW-MFC The synergizing of the CW treatment technology with the microbial fuel cell has many advantages such as: 1.

CWs have consistently proved their ability to breakdown organic molecules as evaluated through BOD/COD and total dissolved solids (TDS). 2. In long-distance flow, the nutrients gradients may be produced, that is, efficient to the removal of suspended particles and organics present in wastewater. 3. The whole process is highly sustainable and more importantly carbon neutral thus adding no net CO2 into the carbon cycle. 4. The CW systems are expected to eliminate the methane emission which may occur in normal wetland systems when anaerobic conditions prevail. 5. Development of humic acids for nitrogen and phosphorus removal. 6. The electricity produced from the whole process can be exploited to partially meet the power needs to run the wastewater treatment plants. Using this electricity for other domestic purposes may prove unprofitable due to the heavy transmission losses and highly inefficient power distribution systems in the country. 7. Apart from harvesting electricity, some agro plants like water hyacinth or similar high carbohydrate content plants when used in the wetland treatment large amounts of excess biomass can be produced that is used as feedstock for biofuel. 8. In developing countries like India where we are facing the problem of using bio-crops instead of food crops in agricultural farms, this system can prove to be a sustainable solution. 9. The CW systems have very low capital and operational costs. 10. The CW systems are potentially stable, reliable, have high regulatory compliance, productive ecosystem, and manage long-term industrial contamination. 11. Development of the constructed wetlands might be a proper solution for asset recuperation and decreasing natural effects. 12. CW-MFCs can self-generate microbes, are resistant to environmental stress, and can be monitored and controlled in real time.

4.3 Applications of CW-MFC The applications of CW-MFCs in several fields have presented new approaches to extract wastewater’s energy content are presented in Table 3. MFC generates green energy effectively from organic matter in effluent wastewater, eliminating the requirements for energy extraction, filtration, and conversions (Elhenawy et al. 2022).

Substrate

Synthetic wastewater

Azo dye

Synthetic wastewater

Quartz sand

Type of system and mode of operation

Up-flow Membrane-Less MFC (MBR-MFC)

CW-MFC (Vertical down-flow)

Up-flow CW-MFC

CW-MFC (downward flow-continuous mode)

Applications of CW-MFC

Anode and Cathode: carbon fibre felt Plant: –

Anode and Cathode: carbon fibre brush electrode Plant: –

Anode: activated carbon and stainless steel mesh Cathode: air cathode Plant: Ipomoea aquatica

Bioelectricity production, and pollutants removal application

MFC with an algae cathode for generating electricity and removing nutrients from landfill leachate wastewater

Influence of HRT, reactive brilliant red X-3B (ABRX3) %, and COD loading on performance of CW-MFCs

Anode: carbon felt, Cathode: Comparative performance carbon felt, Pt-loaded carbon of different cathode paper and carbon flake electrode materials used in each Up-flow MBR-MFC to see the performance in power generation

Type of electrodes and growing plants

Table 3 Applications of CW-MFC for nutrients removal and energy production

COD: 86% NO3 -N: 87%

COD: 99% NH4 + –N: 651 mg/l TP: 80.28% and 61.46% with 5% algae growth and 10% leachate

COD: 85.66%

COD: 85%

Nutrients removal

Current density: 48.41 mA/m2 Power density: 8.91 mW/m2

Power density: 93 mW/m3

Power density: 61.9 mW/m3

Power density: 0.04 W/m2

Energy production

(continued)

Wang et al. (2017a)

Nguyen et al. (2017)

Fang et al. (2015)

Thung et al. (2015)

Authors

Constructed Wetland-Microbial Fuel Cell for Wastewater Treatment … 125

Electrodes: Granular AC Plant: Schoenoplectuscalifornicus

Anode and Cathode: Group ZVI Plant: Iris rhizomes

Dewatered alum sludge

Synthetic wastewater

Regular Wastewater, ammonium/ nitrate-free

Synthetic wastewater

Synthetic wastewater

CW-MFC (up-flow continuous mode)

CW-MFC (up-flow continuous mode)

CW-MFC (Continuous flow mode)

NP-CW-MFC, CW-MFC, CW

CW-MFC (Vertical up-flow mode)

Anode: AC granules Cathode: SS mesh Plant: Ipomoea aqua

Anode: graphite plate Cathode: magnesium plate Plants: –

Electrodes: C. fibre felt with glass wool partition

Electrodes: (a) C. fibre felt (b) SS mesh (c) Glass wool (d) Ni-foam Plant: Canna indica

Quartz sand

Single-chambered MFC-CW (downward flow-continuous mode)

Type of electrodes and growing plants

Substrate

Type of system and mode of operation

Table 3 (continued) Nutrients removal

COD: 82.2 ± 6.8% to 98.3 ± 2.2% NO3 -N: 98.8 ± 0.5%

Performance-related applications CW-MFC utilizes micro electrolytic processes

COD: 79%

Organic matter removal and COD: 74–87%, nitrogen conversion 69–81% and 62–72% NH4 -N: 62.28 ± 2.12%, 65.98 ± 3.97% and 66.56 ± 3.08%

The effects of microbial population composition on the anode surface

Application on the effect of COD: 88%, vegetation used in NH4 : 89%, CW-MFC NO3 : 78% TP: 94%

Application on the effect of – glass wool separator for electricity production

The effect of electrodes and COD: 49,37, 52,5, substrate concentration on NO3 : 80, 69, 42, energy production 84% for a, b, c, d combination respectively

Applications of CW-MFC

Xu et al. (2018)

P-0.066 W/m2

Power density: 2.03 mW/m2 and 1.32 mW/m2

-

(continued)

Dai et al. (2020)

González et al. (2020)

Power density: 0.628 Wang et al. W/m3 (2019)

Power density: 58.50 Saz et al. (2018) mW/m2

Wang et al. (2017b)

Authors

Current density: 17.3 mA/m2 Power density: 1.78 mW/m2

Energy production

126 A. Yadav et al.

Substrate

CW-MFC (Batch mode) Synthetic municipal wastewater

Type of system and mode of operation

Table 3 (continued)

Electrodes: graphite

Type of electrodes and growing plants Low-power energy harvesting with self-sustainable treatment process

Applications of CW-MFC

Energy production

COD: 82 ± 4% and Power: 0.055 mW 80 ± 6% and 0.04 mW (R1 and R2 microcosm) (R1 and R2 microcosm) TOC: 52 ± 7% and 48 ± 5% (R1 and R2 microcosm) TN:70 ± 2% and 69 ± 2% (R1 and R2 microcosm), NH4 + : 70 ± 2% and 80 ± 3% (R1 and R2 microcosm)

Nutrients removal

Srivastava et al. (2021)

Authors

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4.4 Energy Demand for Effective Contaminant Removal Wastewater treatment technologies are necessary to reduce the harmful impacts of carbon and nutrient compounds on the quality of the environment (Ren et al. 2021). The wastewater treatment process followed a series of operations to treat each particular targeted element. Almost all of these operations spend energy and produce carbon-rich sludge that must be stabilized while they remove their target ingredients from wastewater (Ghadge et al. 2015). The energy requirements for the removal of different nutrients from wastewater and the power generation capacity of CW-MFCs system are presented in Table 4. Wu et al. (2017) effectively enhance the removal efficiency of total nitrogen in an up-flow CW-MFC through aeration and effluent recirculation. The system is closely fitted with electrode materials. The denitrification process and anaerobic ammonium oxidation bacteria are responsible to remove total nitrogen in the bottom layer of the system. Wang et al. (2016) discovered that MFCs may enhance the nitrogen removal rate of open and closed-circuit CW-MFCs (down-flow). Substrates being a key component of CW-MFC is crucial for nitrogen and phosphorus elimination. Larger surface area and porous structural substrates can enhance nitrogen and phosphorus adsorption and encourage microbial growth (Wang et al. 2020). Yakar et al. (2018) worked on different substrates that affected the efficiency of CW-MFCs. In up-flow CW-MFCs, zeolite might be employed to improve nitrogen and phosphorus removal efficiency and bioelectric generation, according to their research. However, whether the greater nitrogen removal efficiency in CWMFCs filled with zeolite is related to the stimulation of functional bacterial communities engaged in nitrogen removal. Recently, Ge et al. (2020) discovered nitrate and nitrite (NO2 – ) removals in a pyrite-based down-flow type CW-MFC. Nitrate as a TEA in the cathode had been successfully used in MFCs (Clauwaert et al. 2007). Wang et al. (2019) found that the MFC can decrease the CW’s relying on carbon sources for denitrification. It was examined that how substrate selection affects the nitrogen reduction technique of CW-MFCs.

5 Advancement in CW-MFC System and Future Perspective Organic matter removal and power generation remain the key use of the CW-MFCs among the many potential applications. CW treatment efficiency has been improved with the use of CW-MFC technology so far. The anode electrode material’s effect on anaerobic oxidation of contaminants and the cathode effect on reducing processes are the major factors. According to the investigations, MFCs have reached remarkable Columbic efficiency and power density (mW/m3 ), under various operating conditions and capacities of the reactor ranging from a few to many thousands. The main reason for this is the substantially larger amount of wastewater exposed compared to the electrode surface area. As a result, the CW-electron MFC’s recovery has

Anode and Cathode: Graphite plate Plant: Phragmites australis Anode and Cathode: Carbon felt Plant: Typha latifolia

Synthetic wastewater

Swine wastewater

Synthetic Wastewater 108 (Horizontal Subsurface flow)

Synthetic wastewater

Swine Slurry

Azo Dye wastewater

3

4

5

6

7

Anode and Cathode: Graphite plate Plant: Glyceria maxima

Anode and Cathode: Graphite plate, Plant: Canna indica

1.4 (VF)

Electrodes: Granular AC Plant: Ipomoea aquatica

8.1 (Simultaneous Anode and Cathode: Up-flow and Down-flow) Graphite Granules Plant: Phragmites australis

Vertical Up-flow

3.7 (Vertical Up-flow)

5.4 (Vertical flow)

Anode and Cathode: Non-catalyzed graphite discs Plant: Eichhornia crassipes

2

24.01 (Gravity flow)

Domestic sewage with fermented distillery wastewater

Electrode materials and Growing plant

1

Liquid capacity (L)

Type of substrate

S. No.

Yadav et al. (2012)

Zhao et al. (2013)

Villasenor et al. (2013)

Oon et al. (2015)

Doherty et al. (2015)

Fang et al. (2016)

0.016 W/m2

0.009 W/m2

0.15 mW/m2

0.006 W/m2

268 mW/m3

852 mW/m3

COD: 80%

COD: 100%, NO3 − : 40% and NH4 + : 91%

COD: 73%

COD: 64% Ammonium: 75% Phosphorous: 85–86% Total Phosphorous: 89–90%

COD: 77%

COD: 75%

(continued)

Venkata Mohan et al. (2011)

224.9 mA/m2

COD: 86.67%, and VFA: 72.32%

Reference

Power /current density

Nutrients removal

Table 4 Energy requirements for removal of different nutrients from wastewater and power generation capacity of CW-MFC systems

Constructed Wetland-Microbial Fuel Cell for Wastewater Treatment … 129

Type of substrate

Municipal Wastewater

Synthetic Greywater

Synthetic wastewater-based ceramsite (CM-A), quartz (CM-B), and zeolite (CM-C)

Swine wastewater

S. No.

8

9

10

11

Table 4 (continued)

6.0 (Horizontal subsurface and Vertical Up-flow)

4.12 (Up-flow and Down-flow mode)

10 (Batch cycle-mode)

35.3 (Vertical subsurface-flow)

Liquid capacity (L)

Anode and Cathode: Stainless steel mesh Plant: Cyperus

Anode and Cathode: Granular graphite Plant: Canna indica

Anode and cathode: Synthetic graphite granules Plant: Phragmitesaustralis

Anode and Cathode: Granular Activated Carbon Plant: Phragmites australis

Electrode materials and Growing plant

CM-A: 120.3 mW/m3 , Zhong et al. (2020) CM-B: 11.3 mW/m3 , and CM-C: 14.2 mW/m3

NH4 + –N: 93.8%, and PO4 3− –P: 99.6%

Ren et al. (2021)

Araneda et al. (2018)

33.52 ± 7.87 mW/m3

COD: 91.7 ± 5.1% Phosphate: 56.3 ± 4.4% Nitrate: 86.5 ± 7.1%

9.0 mW/m3

Song et al. (2017)

0.20 W/m3

COD: 90.45%

COD: 72%, N: 47% and P: 85%

Reference

Power /current density

Nutrients removal

130 A. Yadav et al.

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been reduced (Wang et al. 2016). Ohmic losses have increased due to larger volume responsible for a 2–3 order of magnitude fall in maximum power density. The CWMFC can measure the voltage produced by each unit to provide enough electricity to run low-energy gadgets. The stacked modular CW-MFCs suffer from an unexpected voltage reversal and power overshoot phenomenon (Xu et al. 2017; Tamta et al. 2020). For these conditions, energy extraction is a bit difficult. However, the next generation of CW-MFCs must be investigated with applications of sensor technology for monitoring the specific (physical, chemical, and biological) parameters of raw wastewater. To maintain the ecology and ecosystem, water bodies that get treated water must be regulated and monitored. Electrochemical sensor-dependent analyses that have been created are even more efficient and precise. On-site monitoring data helps ease detection and the implementation of preventative and control actions in a timely manner. The BOD measurement using MFC-based biosensors has been studied in the previous few years (Corbella et al. 2018). Anodic microorganisms are capable to metabolize organics in wastewater to create alternating energy, forming a direct and linear link between degradable organic matter and power generation in MFCs. Bio-sensing applications individually produce current signals besides power generation in MFC without any transducer. Microbes are generally susceptible to pollutants in their surroundings (Chouler et al. 2018). As a result, Xu et al. (2017) presented the first attempt on CW-MFC as a bioelectrochemical sensing and detection device for COD in the range of 0–1 g/l, concluding that for low COD loading (0.1 g/l), the minimum system’s performance (approx. 2 h) is more efficient than for concentrations >200 mg/l, which achieve a constant voltage steady state after 5 h. The signals are also quite near to each other for COD values of more than 700 mg/l, owing to the system’s saturation for substrate use. Electrical signals that were fairly distinct and repeatable were produced around 200 and 700 mg/l. The bio-sensing capabilities of CW-MFC, according to Corbella et al. (2018), is a subjective evaluation system for constant monitoring of inlet water quality, instead of an exact measuring instrument for COD. The sediment MFC (SMFC) is an advancing technology for replacing traditional energy sources with renewable energy sources in wireless sensors, with the potential to provide long-term WSN without the need for battery replacement (Niwa et al. 2020; Sajana et al. 2017). Algar et al. (2020) worked on the micro sensors profile to measure the sediments geochemistry for oxygen, sulphide, and pH. The experiments were compared in SMFC and without MFC. The results indicated better performance of SMFC than without MFC. The result shows it was concluded that the SMFCs can remove sulphide from sediments which might help the benthic ecosystem underneath aquaculture ponds. The pH of sediments varies with the depth. The protons releases due to the oxidation half processes at the anode side resulted in a lower pH at depth in SMFCs. Shabani et al. (2021) proposed the design and development of an energy-autonomous MFC-based water quality monitoring sensor to measure the COD concentration from natural ponds. It was discovered that the MFC was found to be practical for the simultaneous use of sensors and energy sources. The COD value was calculated with R2 value of 0.94 precision and could be used in natural ponds or aquaculture. Song et al. (2019) developed a sediment MFC system integrated with

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numerous cathodes deployed at various depths of water for water quality monitoring. Several researchers have developed highly reliable sensor modules based on MFC power to substitute battery power for long-range sensor applications (Veerubhotla et al. 2019). CW-MFC systems have been developed for low energy production with the power management system that comes up to drive the electrical appliances (Xu et al. 2018). To improve the restricted energy accumulation, a pump unit can be inserted between the MFC and the super-capacitor. In the power management system arrangement, a new component, the transformer, was added to boost the capacitor’s charge storage capability. Power management systems are commonly utilized for different power gadgets. Xu et al. (2018) evaluated the power management system integrated with the bio-cathode CW-MFC to generate energy through producing electrons within the anode capacitor of the CW-MFC system. The study of CW-MFC integrated with power management system provides new ideas for its electrical applications in future research. In another study, the CW systems integrated with electrocoagulation (CW-EC) method can efficiently treat the industrial wastewater containing pollutants removal, i.e., iron, aluminium, dyes, nitrate, ammonium, phosphate, COD, sulphate, and metals (Gao et al. 2016; Liu et al. 2020). The electrolysis of conductive electrodes is the primary concept used by the CW-EC. Liu et al. (2020) showed electrolysis integrating tidal flow-CW for eliminating sulfamethoxazole, and they have concluded that CW-EC has the ability to treat wastewater at full scale. The choice of sacrificial electrodes, on the other hand, must be considered for long-term operation (Gao et al. 2016). According to the findings, electro-dissolution of Fe-ion and in-situ production of Fe2+ -coagulant considerably improved N and P removal. These limited investigations imply that integrating EC into CW has great wastewater treatment potential; nevertheless, more studies are needed to determine its greater applicability, scope and long-term operational practicality.

6 Conclusions The CW-MFC technology is a novel technique for increasing contaminant degradation kinetics and also generating energy simultaneously. It is the innovative practical technology utilized to strengthen the intended process among the many integrated bio-ecological systems to improve the performance. Various CW-MFC designs and process-related elements have been examined at laboratory sizes thus far. However, the technique has yet to be tested in the field for the actual wetland conditions. Such technology has various research gaps which need to be addressed for upscaling the system, and the technology must be optimized before moving toward field demonstrations.

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References Algar CK, Howard A, Ward C, Wanger G (2020) Sediment microbial fuel cells as a barrier to sulfide accumulation and their potential for sediment remediation beneath aquaculture pens. Sci Rep 10. https://doi.org/10.1038/s41598-020-70002-4 Al-Zu’bi Y, Ammari TG, Al-Balawneh A, Al-Dabbas M, Ta’any R, Abu-Harb R (2015) Ablution greywater treatment with the modified re-circulated vertical flow bioreactor for landscape irrigation. Desalination Water Treat 54(1):59–68. https://doi.org/10.1080/19443994.2013. 876673 Annelies MK, Moortel VD, Diederik PL, Rousseau F, Tack MG, Pauw ND (2009) A comparative study of surface and subsurface flow constructed wetlands for treatment of combined sewer over flows: a greenhouse experiment. Ecol Eng 35:175–183 Araneda I, Tapia N, Lizama Allende K, Vargas I (2018) Constructed wetland-microbial fuel cells for sustainable greywater treatment. Water 10(7):940. https://doi.org/10.3390/w10070940 Biffinger JC, Pietron J, Ray R, Little B, Ringeisen BR (2007) A biofilm enhanced miniature microbial fuel cell using Shewanellaoneidensis DSP10 and oxygen reduction cathodes. Biosens Bioelectron 22(8):1672–1679 Chang JJ, Wu SQ, Dai YR, Liang W, Wu ZB (2012) Treatment performance of integrated verticalflow constructed wetland plots for domestic wastewater. Ecol Eng 44:152–159 Chouler J, Cruz-Izquierdo A, Rengaraj S, Scott J, Di Lorenzo M (2018) A screen-printed paper microbial fuel cell biosensor for detection of toxic compounds in water. Biosens Bioelectron 102:49–56. https://doi.org/10.1016/j.bios.2017.11.018 Clauwaert P, Rabaey K, Aelterman P, De Schamphelaire L, Pham TH, Boeckx P, Boon N, Verstraete W (2007) Biological denitrification in microbial fuel cells. Environ Sci Technol 41:3354–3360. https://doi.org/10.1021/es062580r Corbella C, Hartl M, Fernandez-gatell M, Puigagut J (2018) MFC-based biosensor for domestic wastewater COD assessment in constructed wetlands. Sci Total Environ 660. https://doi.org/10. 1016/j.scitotenv.2018.12.347 CPCB (1997) Central pollution control board, Ministry of environmental and forest, Govt. of India Dai MX, Li YX, Li P, Guo W, Qi X, Zhang Y, Kong Q (2020) Constructed wetland-microbial fuel cells enhanced with zero-valent iron for wastewater treatment and power generation. Int Biodeterior Biodegrad 153:105048 Dai Z, Yu R, Zha X, Xu Z, Zhu G, Lu X (2021) On-line monitoring of minor oil spills in natural waters using sediment microbial fuel cell sensors equipped with vertical floating cathodes. Sci Total Environ 782. https://doi.org/10.1016/j.scitotenv.2021.146549 Doherty L, Zhao Y, Zhao X, Wang W (2015) Nutrient and organics removal from swine slurry with simultaneous electricity generation in an alum sludge-based constructed wetland incorporating microbial fuel cell technology. Chem Eng J 266:74–81 Dwivedi KA, Huang SJ, Wang CT (2022) Integration of various technology-based approaches for enhancing the performance of microbial fuel cell technology: a review. Chemosphere 287(3):132–248 Elhenawy S, Khraisheh M, AlMomani F, Al-Ghouti M, Hassan MK (2022) From waste to watts: updates on key applications of microbial fuel cells in wastewater treatment and energy production. Sustainability 14:955. https://doi.org/10.3390/su14020955 El-Sheikh MA, Saleh HI, El-Quosy DE, Mahmoud AA (2010) Improving water quality in polluted drains with free water surface constructed wetlands. Ecol Eng 36:1478–1484 Fang Z, Song HL, Cang N, Li XN (2015) Electricity production from Azo dye wastewater using a microbial fuel cell coupled constructed wetland operating under different operating conditions. Biosens Bioelectron 68:135–141 Fang Z, Song H, Yu R, Li X (2016) A microbial fuel cell-coupled constructed wetland promotes degradation of azo dye decolorization products. Ecol Eng 94:455–463

134

A. Yadav et al.

Galanopoulos C, Sazakli E, Leotsinidis M, Lyberatos G (2013) A pilot-scale study for modeling a free water surface constructed wetlands wastewater treatment system. J Environ Chem Eng 1(4):642–651 Gao Y, Xie Y, Zhang Q, Wang AL, Yu YX, Yang LY (2016) Intensified nitrate and phosphorus removal in an electrolysis -integrated horizontal subsurface-flow constructed wetland. Water Res 108. https://doi.org/10.1016/j.watres.2016.10.033 Ge X, Cao X, Song X, Wang Y, Si Z, Zhao Y, Wang W, Tesfahunegn AA (2020) Bioenergy generation and simultaneous nitrate and phosphorus removal in a pyrite-based constructed wetland-microbial fuel cell. Bioresour Technol 296:122350. https://doi.org/10.1016/j.biortech. 2019.122350 Ghadge AN, Jadhav DA, Pradhan H, Ghangrekar MM (2015) Enhancing waste activated sludge digestion and power production using hypochlorite as catholyte in clayware microbial fuel cell. Biores technol 182:225–231 González ML, Hernández Benítez C, Juarez ZA, Zamudio Pérez E, RamírezCoutiño VÁ, Robles I, Godínez LA, Rodríguez-Valadez FJ (2020) Study of the effect of activated carbon cathode configuration on the performance of a membrane-less microbial fuel cell. Catalysts 10(6):619 Gupta S, Srivastava P, Patil SA, Yadav AK (2021) A comprehensive review on emerging constructed wetland coupled microbial fuel cell technology: potential applications and challenges. Biores Technol 320:124376 Huang LP, Zeng RJ, Angelidaki I (2008) Electricity production from xylose using a mediator-less microbial fuel cell. Biores Technol 99(10):4178–4184 Huang X, Duan C, Duan W, Sun F, Cui H, Zhang S, Chen X (2021) Role of electrode materials on performance and microbial characteristics in the constructed wetland coupled microbial fuel cell (CW-MFC): a review. J Clean Prod 301:126951. https://doi.org/10.1016/j.jclepro.2021.126951 Jadhav DA, Ghadge AN, Ghangrekar MM (2014) Simultaneous organic matter removal and disinfection of wastewater with enhanced power generation in microbial fuel cell. Biores technol 163:328–334 Jadhav DA, Ghosh Ray S, Ghangrekar MM (2017) Third generation in bioelectrochemical system research—a systematic review on mechanisms for recovery of valuable by-products from wastewater. Renew Sustain Energy Rev 76:1022–1031 Jadhav DA, Ghangrekar MM, Duteanu N (2018) Recent progress towards scaling up of MFCs. Microbial Fuel Cell: A Bioelectrochemical System that Converts Waste to Watts 443–457 Jadhav DA, Chendake AD, Schievano A, Pant D (2019) Suppressing methanogens and enriching electrogens in bioelectrochemical systems. Biores Technol 277:148–156 Jadhav DA, Das I, Ghangrekar MM, Pant D (2020) Moving towards practical applications of microbial fuel cells for sanitation and resource recovery. J Water Process Eng 38:101566 Jadhav DA, Mungray AK, Arkatkar A, Kumar SS (2021) Recent advancement in scaling-up applications of microbial fuel cells: from reality to practicability. Sustain Energy Technol Assess 45:101226 Jadhav DA, Park SG, Pandit S, Yang E, Abdelkareem MA, Jang JK, Chae KJ (2022a) Scalability of microbial electrochemical technologies: applications and challenges. Bioresour Technol 126498 Jadhav DA, Chendake AD, Vinayak V, Atabani A, Abdelkareem MA, Chae KJ (2022b) Scale-up of the bioelectrochemical system: Strategic perspectives and normalization of performance indices. Biores Technol 127935. Klevinskas A, Kantminien˙e K, Žmuidzinaviˇcien˙e N, Jonuškien˙e I, Griškonis E (2021) Microbial fuel cell as a bioelectrochemical sensor of nitrite ions. Processes 9. https://doi.org/10.3390/pr9 081330. Kyambadde J (2005) Optimizing processes for biological nitrogen removal in Nakivubo Wetland, Uganda. Royal Institute of Technology, Department of Biotechnology. Ph.D., thesis. Stockholm, Sweden Langergraber G, Rousseau D, Garcia J, Mena J (2009) A general model to describe biokinetic processes in subsurface flow constructed wetlands. Water Sci Technol 59(9):1687–1697

Constructed Wetland-Microbial Fuel Cell for Wastewater Treatment …

135

Liu X, Wang Y, Lu S, Liu Y, Zhao B, Xi B, Guo X, Guo W, Zhang J (2020) Intensified sulfamethoxazole removal in an electrolysis-integrated tidal flow constructed wetland system. Chem Eng J 390:124545. https://doi.org/10.1016/j.cej.2020.124545 Mathuriya AS, Jadhav DA, Ghangrekar MM (2018) Architectural adaptations of microbial fuel cells. Appl microbiol biotechnol 102:9419–9432 Mitsch WJ, Gosselink JG (1992) Wetlands. Van Nostrand Reinhold, New York Moshiri GA (1993) Constructed wetlands for water quality improvement. Lewis Publishers, Boca Raton, FL Neralla S, Weaver RW, Lesikar BJ, Persyn RA (2000) Improvement of domestic wastewater quality by subsurface flow constructed wetlands. Bioresour Technol 75:19–25 Nguyen HTH, Kakarla R, Min B (2017) Algae cathode microbial fuel cells for electricity generation and nutrient removal from landfill leachate wastewater. Int J Hydrog Energy 42:29433–29442 Niwa M, Pan Z, Shimamoto S (2020) IoT Sensor network powered by sediment microbial fuel cell. In: 2020 IEEE 17th Annual Consumer Communications and Networking Conference, CCNC. https://doi.org/10.1109/CCNC46108.2020.9045606 Oon Y, Ong S, Ho L, Wong Y, Oon Y, Lehl HK, Thung W (2015) Hybrid system up-flow constructed wetland integrated with microbial fuel cell for simultaneous wastewater treatment and electricity generation. Bioresour Technol 186:270–275 Park WH (2009) Integrated constructed wetland systems employing alum sludge and oyster 196 shells as filter media for P removal. Ecol Eng 35:1275–1282 Ren B, Wang T, Zhao Y (2021) Two-stage hybrid constructed wetland-microbial fuel cells for swine wastewater treatment and bioenergy generation. Chemosphere 128803 Richter H, Nevin KP, Jia H, Lowy DA, Lovley DR, Tender LM (2009) Cyclic voltammetry of biofilms of wild type and mutant Geobacter sulfurreducens on fuel cell anodes indicates possible roles of OmcB, OmcZ, type IV pili, and protons in extracellular electron transfer. Energy Environ Sci 2(5):506–516 SAAT (2006) Subsurface flow and free water surface flow constructed wetland with magnetic field for leachate treatment. University Teknologi Malaysia, Johor Bahru Saba B, Khan M, Christy AD, Kjellerup BV (2019) Microbial phyto-power systems—a sustainable integration of phytoremediation and microbial fuel cells. Bioelectrochemistry 127:1–11. https:// doi.org/10.1016/j.bioelechem.2018.12.005 Saeed T, Sun G (2012) A review on nitrogen and organics removal mechanisms in subsurface flow constructed wetlands: dependency on environmental parameters, operating conditions and supporting media. J Environ Manage 112:429–448 Sajana TK, Ghangrekar MM, Mitra A (2017) Influence of electrode material on performance of sediment microbial fuel cell remediating aquaculture water. Environ. Eng Manag J 16:421–429. https://doi.org/10.30638/eemj.2017.042 Sajana TK, Pandit S, Jadhav DA, Abdullah-Al-Mamun M, Fosso-Kankeu E (2019) Sediment microbial fuel cell for wastewater treatment: a new approach. In: Nano and bio-based technologies for wastewater treatment: prediction and control tools for the dispersion of pollutants in the environment, pp 303–337. https://doi.org/10.1002/9781119577119.ch9 Saz Ç, Türe C, Türker OC, Yakar A (2018) Effect of vegetation type on treatment performance and bioelectric production of constructed wetland modules combined with microbial fuel cell (CW-MFC) treating synthetic wastewater. Environ Sci Pollut Res 25(9):8777–8792 Seghezzo L (2004) Anaerobic treatment of domestic wastewater in subtropical regions. Ph.D. thesis, Wageningen University, Wageningen, the Netherlands Seidel K (1966) Reinigung von GewässerndurchhöherePflanzen. Naturwissenschaften 53:289–297 Shabani F, Philamore H, Matsuno F (2021) An energy-autonomous chemical oxygen demand sensor using a microbial fuel cell and embedded machine learning. IEEE Access 9:108689–108701. https://doi.org/10.1109/ACCESS.2021.3101496 Shah MP (2020) Microbial bioremediation & biodegradation. Springer Shah MP (2021) Removal of refractory pollutants from wastewater treatment plants. CRC Press

136

A. Yadav et al.

Song H, Zhang S, Long X, Yang X, Li H, Xiang W (2017) Optimization of bioelectricity generation in constructed wetland-coupled microbial fuel cell systems. Water 9:185 Song N, Yan Z, Xu H, Yao Z, Wang C, Chen M, Zhao Z, Peng Z, Wang C, Jiang HL (2019) Development of a sediment microbial fuel cell-based biosensor for simultaneous online monitoring of dissolved oxygen concentrations along various depths in lake water. Sci Total Environ 673:272–280. https://doi.org/10.1016/j.scitotenv.2019.04.032 Srivastava P, Belford A, Abbassi R, Asadnia M, Garaniya V, Yadav AK (2021) Low-power energy harvester from constructed wetland-microbial fuel cells for initiating a self-sustainable treatment process. Sustainable Energy Technol Assess 46:101282. https://doi.org/10.1016/j.seta. 2021.101282 Steer D, Fraser L, Boddy J, Seibert B (2002) Efficiency of small constructed wetlands for subsurface treatment of single-family domestic effluent. Ecol Eng 18(4):429–440 Tamta P, Rani N, Yadav A (2020) Enhanced wastewater treatment and electricity generation using stacked constructed wetland–microbial fuel cells. Environ Chem Lett 18. https://doi.org/10. 1007/s10311-020-00966-2. Thung WE, Ong SA, Ho LN, Wong YS, Oon YL, Oon YS, Lehl HK (2015) Simultaneous wastewater treatment and power generation with innovative design of an up-flow membrane-less microbial fuel cell. Water Air Soil Pollut 226:165 Valerie JF, Mihelcic JR, Gierke JS (2011) Life cycle assessment of vertical and horizontal flow constructed wetlands for wastewater treatment considering nitrogen and carbon greenhouse gas emissions. Water Res 45(5):2073–2081 Vanier SM, Dahab MF (2001) Star-up performance of a subsurface-flow constructed wetland for domestic wastewater treatment. Environ Technol 22(5):587–596 Veerubhotla R, Nag S, Das D (2019) Internet of Things temperature sensor powered by bacterial fuel cells on paper. J Power Sources 438:226947 Vega De Lille MI, Hernández Cardona MA, Tzakum Xicum YA, Giácoman-Vallejos G, QuintalFranco CA (2021) Hybrid constructed wetlands system for domestic wastewater treatment under tropical climate: Effect of recirculation strategies on nitrogen removal. Ecol Eng 166:106243 Venkata Mohan S, Mohanakrishna G, Chiranjeevi P (2011) Sustainable power generation from floating macrophytes based ecological microenvironment through embedded fuel cells along with simultaneous wastewater treatment. Bioresour Technol 102:7036–7042 Verma R, Suthar S (2018) Performance assessment of horizontal and vertical surface flow constructed wetland system in wastewater treatment using multivariate principal component analysis. Ecol Eng 116:121–126 Villasenor J, Capilla P, Rodrigo MA, Canizares P, Fernandez FJ (2013) Operation of a horizontal subsurface flow constructed wetland-microbial fuel cell treating wastewater under different organic loading rates. Water Res 47(17):6731–6738 Vymazal J (2010) Constructed wetlands for wastewater treatment. Water 2:530–549 Vymazal J (2013) Emergent plants used in free water surface constructed wetlands: a review. Ecol Eng 61:582–592. Plants in constructed, restored and created wetlands Vymazal J, Kropfelova L (2008) Wastewater treatment in constructed wetlands with horizontal sub-surface flow. Ecol Eng 25:478–490 Wang CT, Chen WJ, Huang RY (2010) Influence of growth curve phase on electricity performance of microbial fuel cell by Escherichia coli. Int J Hydrog Energy 35:7217–7223 Wang J, Song X, Wang Y, Abayneh B, Li Y, Yan D, Bai J (2016) Nitrate removal and bioenergy production in constructed wetland coupled with microbial fuel cell: establishment of electrochemically active bacteria community on anode. Biores Technol 221:358–365. https://doi.org/ 10.1016/j.biortech.2016.09.054 Wang J, Song X, Wang Y, Bai J, Bai H, Yan D, Cao Y, Li Y, Yu Z, Dong G (2017a) Bioelectricity generation, contaminant removal and bacterial community distribution as affected by substrate material size and aquatic macrophyte in constructed wetland-microbial fuel cell. Biores Technol 245:372–378. https://doi.org/10.1016/j.biortech.2017.08.191

Constructed Wetland-Microbial Fuel Cell for Wastewater Treatment …

137

Wang J, Song X, Wang Y, Zhao Z, Wang B, Yan D (2017b) Effects of electrode material and substrate concentration on the bioenergy output and wastewater treatment in air-cathode microbial fuel cell integrating with constructed wetland. Ecol Eng 99:191–198. https://doi.org/10.1016/j.eco leng.2016.11.015 Wang J, Wang W, Xiong J, Li L, Zhao B, Sohail I, He Z (2021) A constructed wetland system with aquatic macrophytes for cleaning contaminated runoff/storm water from urban area in Florida. J Environ Manage 280:111794 Wang X, Tian Y, Liu H, Zhao X, Wu Q (2019) Effects of influent COD/TN ratio on nitrogen removal in integrated constructed wetland-microbial fuel cell systems. Bioresour Technol 271:492–495. https://doi.org/10.1016/j.biortech.2018.09.039 Wang Y, Cai Z, Sheng S, Pan F, Chen F, Fu J (2020) Comprehensive evaluation of substrate materials for contaminants removal in constructed wetlands. Sci Total Environ 701:134736. https://doi. org/10.1016/j.scitotenv.2019.134736 Wu H, Gao X, Wu M, Zhu Y, Xiong R, Ye S (2020) The efficiency and risk to groundwater of constructed wetland system for domestic sewage treatment—a case study in Xiantao, China. J Cleaner Prod 123384 Wu SQ, Chang JJ, Dai Y, Wu ZB, Liang W (2013) Treatment performance and microorganism community structure of integrated vertical flow constructed wetland plots for domestic wastewater. Environ Sci Pollut Res 20:3789–3798 Wu S, Lv T, Lu Q, Ajmal Z, Dong R (2017) Treatment of anaerobic digestate supernatant in microbial fuel cell coupled constructed wetlands: evaluation of nitrogen removal, electricity generation, and bacterial community response. Sci Total Environ 15:339–346. https://doi.org/10.1016/j.sci totenv.2016.11.138 Xu D, Xiao E, Xu P, Zhou Y, He F, Zhou Q, Xu D, Wu Z (2019) Performance and microbial communities of completely autotrophic denitrification in a bioelectrochemically-assisted constructed wetland system for nitrate removal Bioresour. Technol 228:39–46 Xu L, Zhao Y, Tang C, Doherty L (2018) Influence of glass wool as separator on bioelectricity generation in a constructed wetland-microbial fuel cell. J Environ Manage 207:116–123. https:// doi.org/10.1016/j.jenvman.2017.11.035 Xu L, Zhao Y, Wang T, Liu R, Gao F (2017) Energy capture and nutrients removal enhancement through a stacked constructed wetland incorporated with microbial fuel cell. Water Sci Technol 76(1):28–34. https://doi.org/10.2166/wst.2017.168 Yadav AK, Dash P, Mohanty A, Abbassi R, Mishra BK (2012) Performance assessment of innovative constructed wetland-microbial fuel cell for electricity production and dye removal. Ecol Eng 47:126–131 Yadav A, Jadhav DA, Ghangrekar MM, Mitra A (2021) Effectiveness of constructed wetland integrated with microbial fuel cell for domestic wastewater treatment and to facilitate power generation. Environ Sci Pollut Res J. https://doi.org/10.1007/s11356-021-17517-z Yakar A, Türe C, Türker OC, Vymazal J, Saz Ç (2018) Impacts of various filtration media on wastewater treatment and bioelectric production in up-flow constructed wetland combined with microbial fuel cell (UCW-MFC). Ecol Eng 117:120–132. https://doi.org/10.1016/j.eco leng.2018.03.016 Zhang L, Zhang L, Liu Y, Shen Y, Liu H, Xion Y (2010) Effect of limited artificial aeration on constructed wetland treatment of domestic wastewater. Desalination 250:915–920 Zhao YQ, Collum S, Phelan M, Goodbody T, Doherty L, Hu YS (2013) Preliminary investigation of constructed wetland incorporating microbial fuel cell: batch and continuous flow trials. Chem Eng J 229:364–370 Zhong F, Yu C, Chen Y, Wu X, Wu J, Liu G, Zhang J, Deng Z, Cheng S (2020) Nutrient removal process and cathodic microbial community composition in integrated vertical-flow constructed wetland â microbial fuel cells filled with different substrates. Front Microbiol 11:1896. https:// doi.org/10.3389/fmicb.2020.01896

Aerated Constructed Wetlands for Treatment of Food Industry Wastewater Rym Salah-Tazdaït

and Djaber Tazdaït

1 Introduction Water man-made pollution has reached alarming levels in recent years despite the considerable efforts of governments worldwide to treat daily life sewage and wastewater resulting from different industries. Water pollution effects on the environment essentially include (1) algal blooms caused by water contamination with inorganic nutrients, such as fertilizers, which eventually can induce eutrophication, and (2) the toxic effects of heavy metals and xenobiotics on human health and aquatic organisms (Tazdaït and Salah-Tazdaït 2021; Salah-Tazdaït and Tazdaït 2022). Food processing industries generate effluents with non-negligible quantities of non-food materials and waste with different compositions and different pollution and biodegradation characteristics. They contain different types of combinations of suspended and/or dissolved substances. These effluents are recognized as significant sources of aquatic pollution. Some of them, such as those of the dairy industry, are easily biodegradable. On the contrary, high cellulosic-containing effluents are less or even non-biodegradable. Other effluents, such as those of slaughterhouses and meat, poultry, and seafood industries, can contain chemical (pesticide residues) and biological (antibiotics and hormones) contaminants with negative human health impacts. Food processing effluents are diverse; they include fruit processing effluents, R. Salah-Tazdaït (B) · D. Tazdaït Bioengineering and Process Engineering Laboratory (BIOGEP), National Polytechnic School, Algiers, Algeria e-mail: [email protected] D. Tazdaït e-mail: [email protected]; [email protected] D. Tazdaït Faculty of Sciences, Department of Natural and Life Sciences, Algiers 1 University—Benyoucef Benkhedda, Algiers, Algeria © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. P. Shah (ed.), Recent Trends in Constructed Wetlands for Industrial Wastewater Treatment, https://doi.org/10.1007/978-981-99-2564-3_7

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dairy industry wash water, slaughterhouse wash water, water serving for washing vegetables, etc. Most of the food processing wastewater is characterized by high dissolved solids and particles in suspension concentrations and high BOD (biological oxygen demand) and COD (chemical oxygen demand) rates (Abdel-Wahaab et al. 2020; Shah 2020; Roets-Dlamini et al. 2022). In addition, food processing effluents contain organic (urea, proteins, nucleotides, amino acids) and inorganic (ammonia) nitrogen, polyphenols, lipids, carbohydrates, acids, alkalis, chlorides, phosphorus, etc., and, in the case of slaughterhouses effluents, a large variety of pathogenic and non-pathogenic microorganisms, parasites and cysts (Hatam-Nahavandi et al. 2015). Because food processing effluents are extremely biodegradable, thanks to their content in various primary substrates, they can be easily and effectively biodegraded by heterotrophic aerobic/anaerobic microorganisms present in the biological wastewater treatment systems. The wastewater effluents treatment approach predominantly in use today is based on an integrated civil-engineered facility known as a wastewater treatment plant, which combines physical, chemical, and biochemical processes to treat organic and inorganic pollutants in effluents received from various sources (hospitals, industries, agricultural activities, etc.) (Sanderson et al. 2019). However, despite their effectiveness in attaining high water quality levels, wastewater treatment plant processes have the drawback of having high operation and maintenance costs. Constructed wetlands (CWs) are a good substitute or an addition to traditional wastewater treatment plants. They present a technically feasible and cost-effective solution for treating large volumes of highly contaminated effluents. This ecoefficient and friendly technology is widely used in treating different wastewater effluents throughout the world. CWs are engineered systems that use natural reed beds and microorganisms within a given ecosystem area to aerobically transform wastewater charged with organic and inorganic contaminants into reusable water of high physical–chemical quality with no requirements for chemical treatments. The maintenance and operating expenses of the system are minimal. In this system, richly diverse populations of microorganisms, including mycorrhizal fungi, bacteria, and protozoa, inhabit the soil matrix and plant roots. The microorganisms and the plants (through enzymatic catalysis inside tissues) within the wetlands have been found to degrade a broad variety of organic pollutants present in liquid wastes into innocuous compounds. The system is doted with an aeration system, which creates an aerobic environment, thus increasing the biochemical activity of the microorganisms. According to the US EPA, CWs are the seat of different physical, chemical, and biochemical processes, including (1) precipitation of particles in suspension, (2) filtration and chemical precipitation through the soil matrix, (3) transformation through chemical reactions (4) physisorption, and ion exchange on the plants and the soil matrix (5) biodegradation and biotransformation of toxic compounds by microorganisms and plants (phytoremediation) (6) assimilation of nutrients by microorganisms and plants, and (7) elimination of pathogenic organisms mainly through natural predation. However, CWs harbor some drawbacks, such as a large area requirement,

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seasonal efficiencies variations, and biological populations’ sensitivity to the toxic effects of xenobiotics such as pesticides. According to the type of flow regime, CWs are traditionally classified into surface flow, subsurface flow, and multistage systems (Vymazal 2019). In the surface flow wetlands, the water level is above the soil matrix. This type of wetlands is shallow basins with a substrate (soil or other medium) harboring the vegetation. Subsurface flow wetlands are basins in which the water surface is below the substrate (gravel, sand and rocks) through which it flows. In this case, the pattern of the flow regime can be horizontal or vertical. The aim of this chapter focused on describing (1) the aerated constructed wetlands (CWs) types, (2) the types of wastewater from food industries, (3) the biochemical mechanisms for the microbial biodegradation of food industry wastewater in CWs, (4) the mechanisms of phytoremediation of food industry wastewater in CWs, and (5) the Factors influencing food industry wastewater treatment in CWs.

2 Constructed Wetlands (CWs) Types Constructed wetlands generally consist of filter beds of gravel, pozzolana, or even sand. Plants adapted to these water conditions and playing the role of depolluting species are introduced and then colonize this environment by developing an important root system. Wastewater treatment is then carried out using a combination of physical, chemical, and biological processes. In particular, sedimentation processes, precipitation, adsorption on soil particles, or even assimilation by plants and microbiological transformations (Makopondo et al. 2020). The design of a constructed wetland is subject to several constraints, including the nature of the soil, the level of filling in the wetland, the area of the tributary basin, and the area of land available. Therefore, relatively thorough investigations concerning these different parameters are necessary before establishing a constructed wetland. Wastewater treatment by constructed wetlands can be classified according to the type of plants and the type of water flow. We can then find constructed wetlands composed of emergent plants, submerged or semi-aquatic plants, or even floating plants. Constructed wetlands can be horizontal or vertical flow. The selection of the type of flow mainly depends on the pollutant to be treated, the geographical location of the site, and the cost of treatment (Parde et al. 2021).

2.1 Free Water Surface Constructed Wetland This type of constructed wetland is a natural wetland characterized by an open water basin containing floating, emergent, and submerged plants growing in lagoons or shallow ponds over organic or sandy soils. The polluted influent water flows slowly

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through the macrophytes for a maximum pollutant uptake and a UV degradation (Fig. 1a). The biological and physicochemical processes observed in this type of constructed wetland are very close, even comparable to those of natural wetlands. It is the least expensive to implement and adapts well to tropical and subtropical climates because the water to be treated is in direct contact with the warm ambient air, thus promoting the purification of wastewater. The drawback of this system is that it requires a high implantation surface. This type of constructed wetland is effective in eliminating organic matter in the degradation and elimination of suspended solids through their filtration and sedimentation. The reduction rates obtained are close to 70% for suspended solids, chemical oxygen demand (COD), biochemical oxygen demand (BOD), and pathogens. Nitrogen removal efficiency is typically 40%–50% (Ma et al. 2020; Makopondo et al. 2020; Shah 2021; Baldovi et al. 2021; Xu et al. 2021; Allen et al. 2022).

2.2 Horizontal Flow Constructed Wetland The horizontal flow constructed wetland is the most frequently encountered. This type of constructed wetland, known as a reed bed system, treats domestic wastewater and industrial water. The feeding of horizontal flow constructed wetlands is generally carried out with a secondary or tertiary effluent. The wastewater flows horizontally in the bed (sand, gravel, or crushed rock) of the constructed wetland (Fig. 1b) and undergoes aerobic and anaerobic conditions. This constructed wetland is widely used in countries with cold climates because the wastewater to be treated passes below the surface and is, therefore, less sensitive to freezing. The nitrogen reduction rate with this type of constructed wetland is close to 45%, and that of total phosphorus is around 65%. In addition, this constructed wetland type allows abatement rates close to 75 and 66% for BOD and COD, respectively. Organic materials are easily degradable. On the other hand, this type of constructed wetland has limitations for eliminating suspended solids requires more land area than vertical flow constructed wetland (Al-Ajalin et al. 2020; Jamwal et al. 2021; Sethulekshmi and Chakraborty 2021).

2.3 Vertical Flow Constructed Wetland This type of constructed wetland consists of several layers of gravel whose grain size increases with the depth of the filter. The surface layer (made up of gravel or sand) allows a good distribution of the effluents, while the bottom of the basin (made up of coarse gravel) allows the drainage of the treated effluents (Fig. 1c). This constructed wetland is effective for the treatment of suspended solids, organic matter, and also microbial pollution. However, the treatment of nitrogen pollution (in particular denitrification) can be limited due to the high dissolved oxygen level.

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Vertical flow constructed wetland feeding can be done with primary effluent. The saturated vertical flow constructed wetland makes it possible to obtain respective reduction rates of 89% and 82% for the BOD and the COD. This system removes organic matter at 75–93% rates. This effective elimination is attributable to a more significant transfer of dissolved oxygen from the surface layer to the depth. On the other hand, denitrification occurs very little in this system. Concerning the elimination of total phosphorus, an abatement rate of 60% was obtained. This percentage of phosphorus elimination is further improved if the filtering mass is made of materials based on iron, calcium, aluminum, and/or magnesium (Chu et al. 2022; Venditti et al. 2022; Verma et al. 2022; Zheng et al. 2022). The French vertical flow constructed wetland is a type of vertically constructed wetland arranged in two stages (Fig. 1d). The construction cost is cheaper than those of a vertical flow constructed wetland with the same removal efficiency and negligible variations due to changes in climate and the hydraulic loading (Kania et al. 2019).

2.4 Hybrid Constructed Wetland A hybrid constructed wetland combines vertical flow constructed wetland and horizontal flow constructed wetland, associated in series (Fig. 1e). The arrangement of hybrid constructed wetland units enhances removal efficiency as per aerobic or anaerobic conditions. For example, there is good nitrification in the vertical filters, which are well-oxygenated, and good denitrification in the horizontal filters, where the anoxic conditions necessary for this reaction are found (Xiong et al. 2022).

2.5 Baffled Subsurface Flow Constructed Wetland The baffled subsurface flow constructed wetland consists of a vertical baffle along the width of the wetland to obtain better hydraulic efficiencies with a long contact time between the media and the wastewater (Fig. 1f). This system is particularly interesting for nitrogen removal from wastewater (Zhao et al. 2016).

2.6 Aerated Constructed Wetland Aerated constructed wetland is a horizontal flow constructed wetland with an aeration system (aerators) to fulfill the oxygen requirement (Fig. 1g). It has low energy consumption and is recommended for treating municipal and food industry wastewater (Li et al. 2021a).

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2.7 Multi-Tropic Free Flow Engineered Wetland Multi-tropic free flow engineered wetland is a constructed wetland with floating aquatic plants growing in the wastewater (Fig. 1h). It is recommended to remove phosphates and nitrogen (Parde et al. 2021).

3 Types of Wastewater from Food Industries The industry is the human activity that generates the most wastewater. Industrial wastewater includes all the water that is, in principle, discharged by the factory into the external environment after contributing to manufacturing, cleaning, transport, and cooling. In general, they consist of: manufacturing water, cooling circuit water, floor and machine-washing water, and discharges from general services. The composition and concentration of industrial effluents are extremely variable depending on the type of industry. Thus, each industrial operation generates specific quantities and qualities of wastewater that can contain considerable loads of pollutants. Industries belonging to the food sector are classified among those that generate the most wastewater with high dissolved and suspended organic loads. Several industrialists

Fig. 1 Constructed wetland types. a Free water surface constructed wetland. b Horizontal flow constructed wetland. c Vertical flow constructed wetland. d French vertical flow constructed wetland. e Hybrid constructed wetland. f Baffled subsurface flow constructed wetland. g Aerated constructed wetland. h: Multi-tropic free flow engineered wetland

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reject wastewater with a high rate of fats, phosphorus, nitrogen, and sodium chloride. During production, certain activities, such as cleaning, periodically release acids and bases, causing pH problems. Generally, releases do not contain metals and are considered biodegradable (Germain et al. 2022; Shrivastava et al. 2022). Wastewater from food industries can have several origins:

3.1 Beverage Production Industry Wastewater The production of carbonated and alcoholic beverages is an important economic link in many countries. Beer is the fifth most-consumed drink in the world after tea, carbonates, milk, and coffee. However, this activity generates large volumes of effluent loaded with pollutants throughout the year. The pollutant load of brewery effluents mainly contains organic matter from processing activities. The nature of the pollutants and the volumes of water discharged vary according to the stages of the industrial process. The use of different raw materials and the variation of the rinsing operations of tanks, bottles, and sanitation production facilities, lead to great variability in the effluents discharged. It is reported that the carbonaceous organic matter contained in this brewery wastewater is biodegradable, as it is composed mainly of sugar, starch, ethanol, fatty acids, and solid matter, with a BOD/COD ratio of around 0.5–0.75. Significant pH variations have been demonstrated in brewery effluents due to the amount of chemicals (caustic soda, phosphoric acid, nitric acid) used for cleaning and disinfection. The nitrogen contents present in the effluents of breweries depend above all on the dosage of raw material and the yeast. High phosphorus concentrations are usually the result of the use of detergents during cleaning activities (Manyuchi et al. 2018; Ashraf et al. 2021).

3.2 Slaughterhouses and Meat Industries’ Wastewater The pollution flows generated by this industry depends primarily on: the type of meat (cattle, pigs, sheep, poultry, etc.) and the processes found downstream of the slaughterhouse. The tripe-gut workshops and the emptying of stercorary matter, present in the majority of the meat industries, alone reject more than 50% of the pollution. This depends on: • The importance of the gutting workshop for ungulate slaughterhouses. Washing stomachs and intestines can correspond to nearly 20% of total BOD and 15% of nitrogen emissions and therefore contributes significantly to the organic content of effluents. Pathogens can also be found in the rumen or intestines.

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• Blood recovery rate (blood in a liquid state, COD: 400 g.L¯1 , BOD: 200 g.L¯1 , NK: 30 g.L¯1 ). Among all liquid waste generated by slaughterhouses, blood has the highest COD. • Auxiliary workshops such as hide processing, salting, and canning use a large quantity of salt (NaCl) and generate chloride concentrations. The BOD load of these workshops is around 10 to 20 g per kg of the finished product. • The mode of the evacuation of stercorary matter. • Fats are present in large quantities. The high contents of suspended solids sometimes encountered correspond to nonbiodegradable fibrous cellulosic materials. Depending on the workshops, the water used can be cold, hot (90 °C), or mixed (45 °C). The fats (mainly derived in ungulates from the processes of evisceration and washing of the intestines) present in large quantities are more or less emulsified depending on the temperature of the water and the presence of surfactant (cleaning agent). The presence of a processing workshop: feathers (poultry) bringing sulfides, blood, or gelatin (pigs), which generate organic loads and suspended solids. Tanneries workshops include a common pre-treatment of the skins by soaking, liming in a lime bath with the addition of sulfides, and rinsing; the effluent can contain up to 3/4 of the pollution load. The subsequent phase of the treatment is the tanning, causing mineral pollution (NaCl brine and alums, mainly). The rejects contain protein colloids, fats, hairs, dyes, chlorides, and sulfides from liming (Bingo et al. 2021; Kanafin et al. 2022).

3.3 Dairy Industries’ Wastewater The manufacturing processes implemented on-site and the nature of the product formed are therefore at the origin of the releases. They are usually integrated factories and thus produce various products with various discharges: • Pasteurization and bagging: milk losses, diluted washing water with highly variable pH. • Cheese factories and casein factories: a rejection of whey deproteinized but rich in lactose. • Butter factories: a rejection of buttermilk, low in fat but rich in lactose and protein. Serum and buttermilk are increasingly the subjects of complementary treatments. • Protein recovery by ultrafiltration. • Demineralization and recovery of lactose from sera by electrodialysis, thereby reducing the pollution of these discharges. Dairy effluents are very readily biodegradable, resulting in a COD/BOD ratio ranging from 1.5 to 2.

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Given their low pollutant load, the recovery and recycling of cooling water and condensates can be easily applied. Cleaning operations are generally governed by automated programs, which often include extensive rinsing of an alkaline (soda) or acid (phosphoric, nitric acid, etc.) nature. This causes significant daily variations in pH, from 2 to 12, and flow (cleaning at the end of the day, start-up of installations, etc.). Their volume depends on recycling (cooling and recovery of condensates), i.e. from 1 to 6 L.L−1 of treated milk (Mohebrad et al. 2022).

3.4 Starch Factory Wastewater Starch factories extract starch from cassava tubers and potatoes and mainly from richer cereals (wheat, maize, rice). In the latter case, the pollution comes from water evaporation and consists of volatile organic acids. Notable pollution in soluble proteins can also come from the workshop of the glucose factory if it exists. The nature of the effluents depends on the specific treatments of the raw materials after the common washing. The potato contains 12 to 20% starch, 70 to 80% water, and a lot of protein. Wastewater from the potato industry may correspond to the following workshops: • common: washing and transporting tubers (soil and plant debris), peeling with soda or steam (high concentrations of recoverable pulp and starches and proteins); • specific: production of French fries and crisps (significant quantities of fat), bleaching (high BOD). Some characteristics of this wastewater can be noted: • A high rate of organic matter, readily biodegradable; • An increase in COD and BOD levels through the hydrolysis and fermentation of, among other things, reduced sugars, volatile acids, and aldehydes. • The presence of nitrogen, urea, and ammonia is due to compounds generated by protein degradation (Chen et al. 2022).

4 Biochemical Mechanisms for the Microbial Biodegradation of Food Industry Wastewaters in CWs Constructed wetlands can provide an environment in which a large variety of heterotrophic microorganisms and some photoheterotrophic microalgae carry out complete biodegradation (mineralization) of virtually all organic compounds present in food wastewaters through sequential enzymatic-mediated biochemical reactions, thus serving as growth substrates. Biodegradation through mineralization refers to

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the breakdown of organic compounds into inorganic constituents (H2 O, CO2 , NH3 , etc.). The first reaction which occurs in CWs is the hydrolysis by extracellular enzymes (proteases, lipases, glycosidases) of organic polymers, including proteins, carbohydrates, and fats, which liberate peptides, sugars (simple and complex), fatty acids (stearic, palmitic, myristic, etc.), and glycerol. The peptides are further degraded intracellularly to yield amino acids. These molecules then penetrate the cells before they enter the different central metabolic pathways (Entner–Doudoroff, Embden-Meyerhof-Parnas, and Pentose phosphate pathways) to serve cell growth and proliferation (Fig. 2). It is worth noting that although the majority of microalgae are autotrophs, some species, such as Scenedesmus obliquus and Chlorella vulgaris, are capable of growing Sugars (glucose, fructose, mannose, etc.)

Entner–Doudoroff pathway

Embden-MeyerhofParnas patway

Pentose phosphate pathway

Glyceraldehyde-3-phosphate

Amino acids (lysine, glutamate, arginine, etc.)

Glycerol

Pyruvate Decarboxylase and monooxygenase pathways

Steroids

Acetyl CoA

Krebs and glyoxilate cycles

β-oxidation

Fatty acids

Energy for cell growth

Fig. 2 Microorganisms-mediated catabolic pathways of major organic compounds present in food processing effluents

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heterotrophically (mixotrophic microalgae) in the darkness using a variety of carbon compounds, including glucose, glycerol, organic acids, lipids, for cell synthesis (Perez-Garcia et al. 2011). Other microalgae, such as Agmenellum quadruplicatum, are photoheterotrophs, which means that they are capable of using glycerol as a carbon source even under light conditions and in the absence of CO2 (Lambert and Stevens Jr. 1986). The composition of the food wastewaters varies according to the type of industry. The efficiency of CWs in removing organic compounds, ammonia, and suspended solids can be evaluated by measuring the BOD5 /COD ratio, which reflects the biological degradability. The food wastewaters, such as those from abattoirs, meat processing, and dairies, have BOD5 /COD ratios greater than 0.5 and have thus high biological degradability, while those with low ratios, such as pulp and paper wastewaters, are hardly biodegradable (Skrzypiec and Gajewska 2017). Besides, the phosphorus removal efficiency in CWs can be evaluated by determining the P/BOD5 ratio.

4.1 Nitrogen Removal Some food processing effluents such as aquaculture and seafood processing industry, abattoirs, and meat processing industry are characterized by high contents of nitrogen in both organic (amino acids, pyrimidines, purines, urea, chitin) and inorganic (ammonia, nitrate, nitrite) forms, reaching up to 2629 mg/L nitrate, 2925 mg/L ammonium, and 275.64 mg/L Kjeldahl nitrogen (Noukeu et al. 2016). In CWs, organic nitrogen compounds are metabolized aerobically and anaerobically by heterotrophic microorganisms into ammonia through either oxidation (nucleotides, amino acids), or hydrolysis (urea, chitin). This process, called ammonification, is known to occur in a variety of aerobic (Pseudomonas, Micrococcus, Bacillus, etc.), anaerobic (Wolinella, Clostridium, etc.) bacteria, and microscopic saprotrophic fungi, such as Rhodotorula, Mucor, and Mortierella (Kharitonov et al. 2022). In the case of amino acids degradation, ammonia can be produced in the cells through decarboxylase and monooxygenase pathways. The resulting ammonia can be reductively assimilated as a nitrogen source by bacteria, cyanobacteria, and some yeasts through the ATP-dependent glutamine synthetase/glutamate synthase pathway yielding glutamate, which serves as an amino donor to produce amino acids, purine, and pyrimidine bases of nucleic acids. On the other hand, ammonia can aerobically undergo a sequence of oxidative reactions leading to nitrate formation. This process, called nitrification, is catalyzed by two distinct groups of chemolithoautotrophs bacteria, namely ammonia-oxidizing bacteria, such as Nitrosolobus, Nitrosospira, Nitrosovibrio, and Nitrosomonas, and nitrite-oxidizing bacteria, such as Nitrospira, Nitrococcus, Nitrobacter. The nitrate resulting from the nitrification process or already present in the food processing wastewaters can return to its most reduced form (ammoniacal form) through a process called nitrate immobilization or assimilatory nitrate reduction,

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which occurs in bacteria, plants, fungi, and algae, or be anaerobically reduced into gaseous nitrogen through the denitrification process. This process is considered to be very effective in removing nitrate and total nitrogen in tidal flow CWs when heterotrophic nitrification-aerobic denitrification bacteria are added (Tan et al. 2021). Many studies have reported the inefficiency of wetlands for nitrogen removal, especially when nitrogen loading is significant. In a study by Gutiérrez-Sarabia et al. (2004), the efficiency of a full-scale free surface-flow CW in treating abattoir wastewater with a moderate biodegradability index (0.44) was assessed. The CW used had a surface of 1144 m2 , a hydraulic retention time (HTR) of 10.6 days, and was planted with Typha latifolia (cattail) and Phragmites australis (reed) at a density of 4 plants/m2 . The authors reported that the system was poorly efficient in nitrogen removal, with organic nitrogen removal of about 51% and ammonia–nitrogen removal of only 9%. In an attempt to treat wastewater from a small slaughterhouse, Soroko (2007) reached a maximum total nitrogen removal percentage in the range of 85.7% to 96.6% by applying recirculation in a hybrid system consisting of a vertical flow CWs (filled with fine gravel and sand) and a horizontal flow CW planted with Phragmites australis (common reed). Besides, the authors reported that recirculation also resulted in significant removal efficiency of nitrate from the effluent. Several studies have attempted to enhance the nitrogen removal efficiency in CWs by adding different carbon substrates. In a recent study by Zhou et al. (2022), the effect of three different carbon substrates (common reed litter (Phragmites), sucrose, and hydroponic kale residues) on the nitrogen removal efficiency in vertical flow constructed wetlands was evaluated. The study clearly demonstrated that the best effect on nitrogen removal efficiency was obtained following the application of sucrose and common reed litter. The laters exhibited almost the same effect in improving nitrate (98.3% and 99.8%, respectively) and total nitrogen (84.9% and 93.5%, respectively) removal. In a study evaluating the effect of grain size, retention time, and depth on ammonia–nitrogen removal from slaughterhouse wastewater in a vertical subsurface flow CW at a flow rate of 41 ml/min, it was found that the system was effective in achieving ammonia–nitrogen removal with an increase in substrate size at longer retention time (5 days) and at deep gravel mesocosm (0.8 m depth) (Mburu et al. 2019).

4.2 Phosphorus Removal Phosphorus is an essential mineral for life. It is one of the five elements (hydrogen, carbon, nitrogen, oxygen, and phosphorus) necessary for the growth of terrestrial and aquatic plants and all microorganisms. If it is not adequately removed, high concentrations of phosphorus could pollute aquatic media by accelerating the growth of algae, thus depriving fish and other aquatic life of oxygen, causing what is caused eutrophication.

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It is, therefore, crucial to reducing phosphorus inputs into aquatic environments by applying and improving its treatment in CWs processes. High phosphorus contents are usually found in different food processing effluents, such as those from vegetable oils processing (olive mill wastewater, for instance), with phosphorus loads that can reach up to 416-fold the admissible norm (Dutournié et al. 2019), especially when phosphoric acid is overused during the degumming of vegetable oils. In food processing effluents, phosphorus is present in varied forms, including inorganic (polyphosphates, orthophosphates), organic, dissolved, and particulate (attached to suspended solids). Total phosphorus includes dissolved and particulate phosphorus and also refers to mineral and organic phosphorus. The phosphoric ions (PO4 3− , HPO4 2− , H2 PO4 − ), which are considered entirely bioavailable, are the primary forms of dissolved phosphorus. Phosphorus removal in CWs occurs through different processes, including sorption to the substratum, chemical precipitation by using iron, aluminium or calcium salts, microbial accumulation, and biological assimilation. Brix et al. (2001) reported that phosphate removal in subsurface flow constructed wetlands occurs mainly through sorption on the substratum. The organic phosphorus found in the food wastewaters consists mainly of phospholipids (phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine, phosphatidylglycerol, and phosphatidylinositol), nucleotides. These organic forms of phosphorus are transformed into their bioavailable forms assimilable by plants and microorganisms thanks to the catabolic activities of the indigenous heterotrophic microorganisms called phosphate solubilizing microorganisms, including bacteria (Pseudomonas, Rhizobium, etc.) and fungi (Trichoderma, Penicillium, etc.) (Kalayu 2019). For instance, phospholipids’ biodegradation (mineralization) is initiated by extracellular enzymes, namely phospholipases. These phosphate uptake microorganisms assimilate phosphate to sustain their growth, and the excess phosphorus is enzymatically transformed into polyphosphate by PolyP kinase and is intracellularly accumulated in the form of insoluble granules. Polyphosphate is involved in a wide variety of physiological functions, such as the stress adaptation process (Alcántara et al. 2014) and phosphorus storage function (Neville et al. 2022). There have been many studies that evaluated the performance of CWs in treating phosphorus-rich food effluents such as those from the slaughterhouse industry, which is known to generate high levels of various organic compounds and pathogens that have a negative impact on both surface and groundwaters. In one study conducted by Keerthana and Thivyatharsan (2018), the efficiency of phosphate removal from slaughterhouse wastewater in small-scale CW grown with young Typha latifolia (cattail) was evaluated. The substratum used consisted of three superposed layers of chopped Coir fiber, medium-sized gravel, and fine sand, and different retention times values ranging from 3 to 9 days were tested. The obtained results showed that the removal of phosphate in the system was very efficient, reaching 85.8% after 9 days of treatment. In another study, Carreau et al. (2012) studied the performance of a free water surface CW treating abattoir wastewater generated by a small farm in Great Village, Nova Scotia (Canada) was monitored for a year. The CW consisted of two units built in series with a total surface of 58.5 m2 , a residence time of 111 days, and

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was mainly overgrown with transplanted broad-leaved Typha latifolia. The authors reported that in addition to having achieved very high organic substances removal (BOD5 (95%) and total suspended solids (72%)), they also monitored a significant removal percentage of total phosphorus (88%) and soluble reactive phosphorus (97%). Besides, it was observed that, overall, removal efficiencies were the highest during the growing season of the plants used.

5 Mechanisms of Phytoremediation of Food Industry Wastewater in CWs Wastewater treatment technique by plants appeared in Europe from the West with the work of SEIDEL (the 1950s), who showed that the reed of the chairmen Scirpus lacustris is capable of retaining large quantities of substances organisms from contaminated water. The system developed by SEIDEL includes a series of beds made up of sand or gravel supporting submerged aquatic vegetation, which has been most commonly used, and in the majority of cases, the vertical flow constructed wetland (Vymazal 2010). A constructed wetland consists of a basin designated properly to contain water, a substrate, and, often, vascular plants. These constituents can be manipulated in the construction of a wetland. Other important components, such as microbial communities and invertebrates, will develop naturally. The components of a constructed wetland are: • Water: Constructed wetland forms when water is directed into a deep depression and where an impermeable surface layer prevents water from seeping into the ground. A constructed wetland can be built almost anywhere in the landscape by forming the surface of the ground to collect water by sealing the basin to retain water. Hydrology is the most important factor in the design of a constructed wetland because it links all the functions in the constructed wetland, and it is often the primary factor in the success or failure of a constructed wetland (Wu et al. 2022). • Substrate, sediment, and detritus Substrates used to build a constructed wetland include soil, sand, gravel, rocks, and organic materials such as compost. Sediments and detritus accumulate in the filter due to low water viabilities and typical high productivity. Substrates, sediments, and detritus are important for several reasons: • They support many organisms living in the constructed wetland; • The permeability of the substrate influences the movement of water through the constructed wetland; • Several biological transformations (especially microbial) take place in the substrate;

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• Substrates provide storage for many contaminants; and • The accumulation of detritus increases the amount of organic matter in the constructed wetland. Organic matter provides sites for material exchange and microbial attachment; it is a source of carbon. The physical and chemical characteristics of soils and other substrates are altered when they are overwhelmed. In a saturated substrate, water replaces atmospheric gases in the pore spaces, and microbial metabolism consumes available oxygen. As soon as oxygen is consumed, it can be replaced more quickly by diffusion from the atmosphere, and the substrates become anoxic (without oxygen). This reducing medium is important in removing pollutants such as nitrogen and metals (Kataki et al. 2021; Manthiram Karthik and Philip 2021, Ravichandran and Philip 2022). • Microorganisms Microorganisms include bacteria, yeasts, fungi, protozoa, and bark algae. Microbial biomass is a major carbon sink organic with several nutrients. The microbial activity consists of: • Transform a large number of organic and inorganic substances into harmless or insoluble solutions; • Alter the reduction/oxidation (redox) conditions of the substrate and thus influence the capacity of constructed wetlands processes; and • It is involved in the recycling of nutrients. Some microbial transformations are aerobic (i.e. require free oxygen), and others are anaerobic; they can function under both aerobic and anaerobic conditions depending on the change in environmental conditions. The microbial community of a constructed wetland can be influenced by toxic substances, such as pesticides and heavy metals, and care should be taken to prevent such chemicals from being introduced at concentrations detrimental (Kataki et al. 2021; Ravichandran and Philip 2022). • Animals Constructed wetlands provide a habitat for a rich diversity of invertebrates and vertebrates. Invertebrate animals, such as insects and worms, contribute to the process by breaking up the waste and consuming the organic matter; the larvae of many insects are aquatic and consume significant amounts of materials during their larval stages, which can last for several years. Invertebrates also perform several ecological roles; for example, dragonfly nymphs are important predators of mosquito larvae. Although invertebrates are the most important animals in breeding water quality, constructed wetlands also attract a variety of amphibians, turtles, birds, and mammals (Q. Li et al. 2021a, b; Wang et al. 2021). • Vegetation Both vascular plants (tall plants) and non-vascular plants (algae) are important in constructed wetlands. Photosynthesis by algae increases the dissolved oxygen

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content in the water, which in turn affects the reactions of nutrients and metals. Vascular plants contribute to the treatment of wastewater and water runoff in different ways: • They stabilize the substrates and limit the flow. • They slow down the speed of the water, allowing suspended matter to file. • They remove carbon, nutrients, and trace elements and incorporate them into plant tissues. • They transfer gases between the atmosphere and the sediments. • Oxygenated macrosites in the substrate are created by the escape of oxygen from the upper surfaces of plant structures. • Root systems and their stems provide sites for microbial attachment. • They create detritus when they die and rot. Constructed wetlands are often planted with submerged vegetation, which develops with their roots in the substrate, and their stems and leaves appear on the water surface. Common emergent plants used in filter beds include rushes, reeds, and several broadleaf species. The absorption of metal ions is effective by algae or other higher plants. The filtration of fine particles in suspension is achieved through tangles of roots or plant apparatus immersed. Macrophytes contribute indirectly to the degradation of suspended volatile matter in the raw effluent; • The growth of roots and rhizomes allows the regulation of initial hydraulic conductivity. The small grain size of the substrate (sand or gravel) and the significant contribution amount of organic matter is conducive to filter clogging. The growth of the parties’ roots limits these risks by forming tubular pores and the roots that develop. However, in a horizontal flow constructed wetland, one should not expect a hydraulic conductivity superior to that of the original materials. • The foliar cover is a thermal regulator that impacts yield purifiers in cold climates. • Small amounts of oxygen from the aerial parts are released at the apex of the rootlets of the plants. Still they are insufficient to contribute alone to the satisfaction of the oxygen requirements of bacterial biomass, responsible for degradation. • Root development increases the attachment surface to develop microorganisms and precipitation reactions. At this increase in active surface, there is certainly also added a still very poorly documented factor of stimulation of the activity, or even the diversity and density of microorganisms, involved in various ways in purification processes. The root tissues and their exudates are likely to constitute more hospitable niches for microorganisms than inert mineral substrates. The role of plant metabolism (assimilation of nutrients) more or less affects the treatment according to the surfaces involved. If for vertical planted filters assimilation is negligible, the larger surfaces involved in the horizontal flow constructed wetland can lead to levies that can reasonably be taken into account in the balance sheets, but which should be at a maximum of 20% for nitrogen and 10% for phosphorus. These

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elements are not directly exportable in biomass that can be cut but are also trapped in the root system (Kataki et al. 2021; Kulshreshtha et al. 2022; Ravichandran and Philip 2022).

6 Factors Influencing Wastewaters Treatment in CWs As a full-fledged ecosystem, the CW performance may be affected by various factors that include but are not limited to temperature, pH, oxygen content, substratum type, presence of xenobiotics and heavy metals. All these factors can affect the physiological and growth status of the indigenous organisms/microorganisms involved in the treatment. In fact, many studies have reported that the microorganisms involved in the removal treatment can be affected by the presence of pollutants. Accordingly, particular interest should be focused on deepening the study of the magnitude of the effects of eubiotics and xenobiotics on the functioning of CWs. In a recent study, Cao et al. (2022) investigated the stress effect of polyvinyl pyrrolidone-coated silver nanoparticles on the microorganisms implied in phosphorus and nitrogen removal in a laboratory-scale vertical flow constructed wetland vegetated with Iris pseudacorus (yellow iris). The authors demonstrated that both the richness and the composition of the microbial community of the WC were negatively affected by the silver particles. On the other hand, the presence of silver particles induced a significant decrease in the removal percentage of total phosphorus, ammonia–nitrogen, and total nitrogen, very likely through gene inhibition. Besides, although much research has been done on antibiotics removal by CWs, many studies suggested that antibiotics also negatively impact the normal functioning of CWs by affecting, among others, (1) the mechanisms of nutrient removal, such as those of nitrogen and phosphorus, and organic matter, (2) the structural and functional composition of the bacterial community, (3) the diversity of eukaryotic organisms, such as Metazoa and Chloroplastida, and (4) the plant’s physiology, such as root growth and leave’s chlorophyll content (Ohore et al. 2022).

7 Conclusions Increasing population growth and economic development, particularly in developing countries, leads to increasing volumes of either untreated or partially treated domestic and industrial wastewater, including food processing effluents, which pose a severe threat to humans and ecological habitats. There is thus an urgency to solve the problem with solutions that should be low-cost and eco-friendly. One proposed solution is to use CWs, which are small risk-free wastewater treatment units that use natural biological activities to detoxify effluents or make them less toxic. They are designed so that the bottom of the systems is waterproofed to avoid any contamination of the ground from polluted water, and they require limited manual intervention. This

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cost-effective and eco-friendly technology offers a promising solution that could achieve very high treatment efficiency and even provide a clean water supply in both developed and developing nations, yet some limitations exist, such as poor efficiency for phosphorus and nitrogen removal and susceptibility to chemical and biological contaminants. In order to address this, further improvements in process engineering and in comprehending biochemical, microbiological, and physiological processes that occur in CWs are needed both in a laboratory and in situ scales. Besides, governments throughout the world should financially support both the widespread of this sustainable technology and fundamental and applied research initiatives aiming at its improvement. Acknowledgements The authors wish to thank the editor for his guidance and helpful comments. They are also thankful to Miss Mélissa TAZDAÏT for her help in drawing the figures in this chapter.

References Abdel-Wahaab R, Abou Taleb EM, Ibrahim, MS, Mohamed OA (2020) Potential of food processing wastewater treatment for reuse. Egypt J Chem, 63(7):2661–2672. https://doi.org/10.21608/ejc hem.2019.19515.2190 Al-Ajalin, Fayeq Abdel Hafez, Mushrifah Idris, Siti Rozaimah Sheikh Abdullah, Setyo Budi Kurniawan, and Muhammad Fauzul Imron (2020) Effect of wastewater depth to the performance of short-term batching-experiments horizontal flow constructed wetland system in treating domestic wastewater. Environ Technol Innov 20(November):101106. https://doi.org/10.1016/j. eti.2020.101106 Alcántara C, Blasco A, Zúñiga M, Monedero V (2014) Accumulation of polyphosphate in Lactobacillus spp. and its involvement in stress resistance. Appl Environ Microbiol 80(5):1650–1659. https://doi.org/10.1128/AEM.03997-13 Allen DJ, Farrell M, Huang J, Reynolds C, Rupasinghe M, Mosley LM (2022) Long-term water quality response to increased hydraulic loadings in a field-scale free water surface constructed wetland treating domestic effluent. J Environ Manage 311:114858. https://doi.org/10.1016/j.jen vman.2022.114858 Ashraf Adil, Racchana Ramamurthy, Eldon RRene (2021) Wastewater treatment and resource recovery technologies in the brewery industry: current trends and emerging practices. Sustain Energy Technol Assess 47(October):101432. https://doi.org/10.1016/j.seta.2021.101432 Baldovi Aldrew Alencar, André Ribeiro de Barros Aguiar, Roseli Frederigi Benassi, Jan Vymazal, Tatiane Araujo de Jesus (2021) Phosphorus removal in a pilot scale free water surface constructed wetland: hydraulic retention time, seasonality and standing stock evaluation. Chemosphere 266(March):128939. https://doi.org/10.1016/j.chemosphere.2020.128939 Bingo MN, Njoya M, Basitere M, Ntwampe SKO, Kaskote E (2021) Performance evaluation of an integrated multi-stage poultry slaughterhouse wastewater treatment system. J Water Process Eng 43:102309. https://doi.org/10.1016/j.jwpe.2021.102309 Brix H, Arias CA, del Bubba M (2001) Media selection for sustainable phosphorus removal in subsurface flow constructed wetlands. Water Sci Technol 44(11–12):47–54. https://doi.org/10. 2166/wst.2001.0808 Cao C, Huang J, Yan, and C. -N. (2022) Unveiling changes of microbial community involved in N and P removal in constructed wetlands with exposing to silver nanoparticles. J Hazard Mater 432:128642. https://doi.org/10.1016/j.jhazmat.2022.128642

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Carreau R, VanAcker S, VanderZaag AC, Madani A, Drizo A, Jamieson R, Gordon RJ (2012) Evaluation of a surface flow constructed wetland treating abattoir wastewater. Appl Eng Agric 28(5):757–766. https://doi.org/10.13031/2013.42416 Chen Qijue, Quanming Ding, Wen Li, Jing Deng, Qinlu Lin, Juan Li (2022) Enhanced treatment of organic matters in starch wastewater through bacillus subtilis strain with polyethylene glycolmodified polyvinyl alcohol/sodium alginate hydrogel microspheres. Bioresour Technol 347 (March):126741. https://doi.org/10.1016/j.biortech.2022.126741 Chu Yifan, Wei Liu, Qiyang Tan, Lingli Yang, Jinmei Chen, Lin Ma, Yi Zhang, Zhenbin Wu, Feng He (2022) Vertical-flow constructed wetland based on pyrite intensification: mixotrophic denitrification performance and mechanism. Bioresour Technol 347 (March):126710. https:// doi.org/10.1016/j.biortech.2022.126710 Dutournié P, Jeguirim M, Khiari B, Goddard M-L, Jellali S (2019) Olive mill wastewater: from a pollutant to green fuels, agricultural water source, and bio-fertilizer. Part 2: water recovery. Water 11:768. https://doi.org/10.3390/w11040768 Germain S, Marie F, Faure K, Saunier E, Lerestif J-M, Heinisch S (2022) On-Line 2D-RPLC x RPLC – HRMS to assess wastewater treatment in a pharmaceutical plant. J Pharm Biomed Anal 208:114465. https://doi.org/10.1016/j.jpba.2021.114465 Gutiérrez-Sarabia A, Fernández-Villagómez G, Martínez-Pereda P, Rinderknecht-Seijas N, PoggiVaraldo HM (2004) Slaughterhouse wastewater treatment in a full-scale system with constructed wetlands. Water Environ Res 76(4):334–343. http://www.jstor.org/stable/25045791 Hatam-Nahavandi K, Mahvi AH, Mohebali M, Keshavarz H, Mobedi I, Mostafa Rezaeian M (2015) Detection of parasitic particles in domestic and urban wastewaters and assessment of removal efficiency of treatment plants in Tehran, Iran. J Environ Health Sci Eng 13(4):1–13. https://doi. org/10.1186/s40201-015-0155-5 Jamwal P, Raj AV, Raveendran L, Shirin S, Connelly S, Yeluripati J, Richards S, Rao L, Helliwell R, Tamburini M (2021) Evaluating the performance of horizontal sub-surface flow constructed wetlands: a case study from southern India. Ecol Eng 162:106170. https://doi.org/10.1016/j.eco leng.2021.106170 Kalayu G (2019) Phosphate solubilizing microorganisms: promising approach as biofertilizers. International Journal of Agronomy. Article ID 4917256:1–7. https://doi.org/10.1155/2019/491 7256 Kanafin Yerkanat N, Ardak Makhatova, Kulyash Meiramkulova, Stavros G. Poulopoulos (2022) Treatment of a poultry slaughterhouse wastewater using advanced oxidation processes. J Water Process Eng 47(June):102694. https://doi.org/10.1016/j.jwpe.2022.102694 Kania M, Gautier M, Imig A, Michel P, Gourdon R (2019) Comparative characterization of surface sludge deposits from fourteen french vertical flow constructed wetlands sewage treatment plants using biological, chemical and thermal indices. Sci Total Environ 647:464–473. https://doi.org/ 10.1016/j.scitotenv.2018.07.440 Kataki S, Chatterjee S, Vairale MG, Dwivedi SK, Gupta DK (2021) Constructed wetland, an ecotechnology for wastewater treatment: a review on types of wastewater treated and components of the technology (macrophyte, biolfilm and substrate). J Environ Manage 283:111986. https:// doi.org/10.1016/j.jenvman.2021.111986 Keerthana K, Thivyatharsan R (2018) Constructed wetland for slaughterhouse wastewater treatment. AGRIEAST: J Agric Sci 12(1):7–15. http://doi.org/https://doi.org/10.4038/agrieast.v12i1.47 Kharitonov S, Shchegolkova N, Alexandrova A, Saynchuk A, Michel P, Maciejewski K, Gautier M, Gourdon R, Semenov M, Krasnov G (2022) Taxonomic diversity of fungi and bacteria in Azoé-NP® vertical flow constructed wetlands. Water 14(5):698. https://doi.org/10.3390/w14 050698 Kulshreshtha NM, Verma V, Soti A, Brighu U, Gupta AB (2022) Exploring the contribution of plant species in the performance of constructed wetlands for domestic wastewater treatment. Bioresource Technology Reports. 18:101038. https://doi.org/10.1016/j.biteb.2022.101038 Lambert DH, Stevens SE Jr (1986) Photoheterotrophic growth of Agmenellum quadruplicatum PR-6. J Bacteriol 165(2):654–656. https://doi.org/10.1128/jb.165.2.654-656.1986

158

R. Salah-Tazdaït and D. Tazdaït

Li J, Zheng L, Ye C, Ni B, Wang X, Liu H (2021a) Evaluation of an intermittent-aeration constructed wetland for removing residual organics and nutrients from secondary effluent: performance and microbial analysis. Biores Technol 329:124897. https://doi.org/10.1016/j.biortech.2021.124897 Li Qiangang, Zeqing Long, Hongjie Wang, Guangming Zhang (2021b) Functions of constructed wetland animals in water environment protection—A critical review. Sci Total Environ 760:144038. https://doi.org/10.1016/j.scitotenv.2020.144038 Ma Zhen, Yuanlai Cui, Changqiang Guo, Yufeng Luo, Di Wan, Linhua Ma, Yonghong Shu, Fangping Liu (2020) Consistency analysis of the optimal combination of free water surface constructed wetland design optimization over different seasons. Ecol Eng 155:105928 Makopondo ROB, Rotich LK, Kamau CG (2020) Potential use and challenges of constructed wetlands for wastewater treatment and conservation in game lodges and resorts in Kenya. Sci World J 2020:1–9. https://doi.org/10.1155/2020/9184192 Manthiram Karthik R, Philip L (2021) Sorption of pharmaceutical compounds and nutrients by various porous low cost adsorbents. J Environ Chem Eng 9(1):104916. https://doi.org/10.1016/ j.jece.2020.104916 Manyuchi MM, Mbohwa C, Muzenda E (2018) Anaerobic treatment of opaque beer wastewater with enhanced biogas recovery through acti-zyme bio augmentation. S Afr J Chem Eng 26:74–79. https://doi.org/10.1016/j.sajce.2018.10.002 Mburu C, Kipkemboi J, Kimwaga R (2019) Impact of substrate type, depth and retention time on organic matter removal in vertical subsurface flow constructed wetland mesocosms for treating slaughterhouse wastewater. Phys Chem Earth 114:102792. https://doi.org/10.1016/j.pce.2019. 07.005 Mohebrad B, Ghods G, Rezaee A (2022) Dairy wastewater treatment using immobilized bacteria on calcium alginate in a microbial electrochemical system. J Water Process Eng 46:102609. https://doi.org/10.1016/j.jwpe.2022.102609 Neville N, Roberge N, Jia Z (2022) Polyphosphate kinase 2 (PPK2) enzymes: structure, function, and roles in bacterial physiology and virulence. Int J Mol Sci 23(2):670. https://doi.org/10.3390/ ijms23020670 Noukeu NA, Gouado I, Priso RJ, Ndongo D, Taffouo VD, Dibong SD, Ekodeck GE (2016) Characterization of effluent from food processing industries and stillage treatment trial with Eichhornia crassipes (Mart.) and Panicum maximum (Jacq.). Water Resources and Industry. 16:1–18. https:// doi.org/10.1016/j.wri.2016.07.001 Ohore OE, Liu W, Qin Z, Sanganyado E, Wang Y, Jiao X, Wang Z (2022) Ecological impact of antibiotics on bioremediation performance of constructed wetlands: microbial and plant dynamics, and potential antibiotic resistance genes hotspots. J Hazard Mater 424:127495. https:// doi.org/10.1016/j.jhazmat.2021.127495 Parde D, Patwa A, Shukla A, Vijay R, Killedar DJ, Kumar R (2021) A review of constructed wetland on type, treatment and technology of wastewater. Environ Technol Innov 21:101261. https:// doi.org/10.1016/j.eti.2020.101261 Perez-Garcia O, Escalante FME, de-Bashan, L. E., and Bashan, Y. (2011) Heterotrophic cultures of microalgae: metabolism and potential products. Water Res 45:11–36. https://doi.org/10.1016/j. watres.2010.08.037 Ravichandran MK, Philip L (2022) Assessment of the contribution of various constructed wetland components for the removal of pharmaceutically active compounds. J Environ Chem Eng 10(3):107835. https://doi.org/10.1016/j.jece.2022.107835 Roets-Dlamini Y, Moonsamy G, Lalloo R, Ramchuran S (2022) Use of bacillus spp in the bioremediation of fats, oils and greases (FOG’s), and other waste substrates in food processing effluents. Biocatal Agric Biotechnol 42:102351. https://doi.org/10.1016/j.bcab.2022.102351 Salah-Tazdaït R, Tazdaït D (2022) Phyto and microbial remediation of heavy metals and radionuclides in the environment, an eco-friendly solution for detoxifying soils. Routledge, United Kingdom

Aerated Constructed Wetlands for Treatment of Food Industry Wastewater

159

Sanderson H, Brown RS, Hania P, McAllister TA, Majury A, Liss SN (2019) Antimicrobial resistant genes and organisms as environmental contaminants of emerging concern: Addressing global public health risks. In: Roig Benoit, Weiss Karine, Véronique Thireau (ed) Management of emerging public health issues and risks, Academic Press, 147–187. https://doi.org/10.1016/ B978-0-12-813290-6.00007-X Sethulekshmi S, Chakraborty S (2021) Textile wastewater treatment using horizontal flow constructed wetland and effect of length of flow in operation efficiency. J Environ Chem Eng 9(6):106379. https://doi.org/10.1016/j.jece.2021.106379 Shah MP (2020) Microbial bioremediation & biodegradation. Springer Shah MP (2021) Removal of refractory pollutants from wastewater treatment plants. CRC Press Shrivastava V, Ali I, Marjub MM, Rene ER, Soto AMF (2022) Wastewater in the food industry: treatment technologies and reuse potential. Chemosphere 293:133553. https://doi.org/10.1016/ j.chemosphere.2022.133553 Skrzypiec K, Gajewska MH (2017) The use of constructed wetlands for the treatment of industrial wastewater. J Water Land Devt 34 (VII–IX): 233–240. https://doi.org/10.1515/jwld-2017-0058 Soroko M (2007) Treatment of wastewater from small slaughterhouse in hybrid constructed wetlands systems. Ecohydrol Hydrobiol 7(3–4):339–343. https://doi.org/10.1016/S1642-359 3(07)70117-9 Tan X, Yang Y-L, Li X, Gao Y-X, Fan X-Y (2021) Multi-metabolism regulation insights into nutrients removal performance with adding heterotrophic nitrification-aerobic denitrification bacteria in tidal flow constructed wetlands. Sci Total Environnent 796:149023. https://doi.org/ 10.1016/j.scitotenv.2021.149023 Tazdaït D, Salah-Tazdaït R (2021) Polycyclic aromatic hydrocarbons: toxicity and bioremediation approaches. In: Joshi Sanket J, Deshmukh Arvind, Sarma Hemen (eds) Biotechnology for sustainable environment, Singapore: Springer, 289–316. https://doi.org/10.1007/978-981-161955-7_12. United States Environmental Protection Agency (US EPA) Constructed Wetlands Handbooks (Volumes 1): A Guide to Creating Wetlands for Agricultural Wastewater, Domestic Wastewater, Coal Mine Drainage and Stormwater in the Mid-Atlantic Region. https://www.epa.gov/sites/def ault/files/2015-10/documents/constructed-wetlands-handbook.pdf Venditti S, Brunhoferova H, Hansen J (2022) Behaviour of 27 selected emerging contaminants in vertical flow constructed wetlands as post-treatment for municipal wastewate. Sci Total Environ 819:153234. https://doi.org/10.1016/j.scitotenv.2022.153234 Verma V, Soti A, Kulshreshtha NM, Rampuria A, Brighu U, Gupta AB (2022) Strategies for enhancing phosphorous removal in vertical flow constructed wetlands. J Environ Manage 317:115406. https://doi.org/10.1016/j.jenvman.2022.115406 Vymazal Jan (2010) Constructed wetlands for wastewater treatment. Water 2(3):530–549. https:// doi.org/10.3390/w2030530 Vymazal J (2019) Constructed wetlands for wastewater treatment. In: Fath Brian (ed) Encyclopedia of Ecology, Elsevier, 14–21. https://doi.org/10.1016/B978-0-12-409548-9.11238-2 Wang Xiaoou, Jun Bai, Yimei Tian, Tao Wang, Xiaoxuan Zhou, Changping Zhang (2021) Synergistic effects of natural ventilation and animal disturbance on oxygen transfer, pollutants removal and microbial activity in constructed wetlands. Chemosphere 283:131175. https://doi.org/10. 1016/j.chemosphere.2021.131175 Wu Yanfeng, Jingxuan Sun, Y. Jun Xu, Guangxin Zhang, Tao Liu (2022) Projection of future hydrometeorological extremes and wetland flood mitigation services with different global warming levels: A case study in the Nenjiang river basin. Ecol Indic 140:108987. https://doi. org/10.1016/j.ecolind.2022.108987 Xiong Chunhui, Qiwen Li, Nora Fungyee Tam, Xiaomeng Zhang, Yiping Tai, Ruitai Wu, Lingjie Huang, Jan Vymazal, Yunv Dai, Yang Yang (2022) The combination sequence effect on nitrogen removal pathway in hybrid constructed wetlands treating raw sewage from multiple perspectives. Sci Total Environ 833:155200. https://doi.org/10.1016/j.scitotenv.2022.155200

160

R. Salah-Tazdaït and D. Tazdaït

Xu Duo, Huiwen Bai, Zhaoxin Li, Shan Lu, Zilong Cheng, Xiaoqiang Shen, Hao Wang (2021) Acclimation of phytoplankton to diverse environmental variables at the initial operation stage of a free water surface constructed wetland. J Clean Prod 317:128442. https://doi.org/10.1016/ j.jclepro.2021.128442 Zhao Jinhui, Yaqian Zhao, Zhihuan Xu, Liam Doherty, Ranbin Liu (2016) Highway runoff treatment by hybrid adsorptive media-baffled subsurface flow constructed wetland. Ecol Eng 91:231–239. https://doi.org/10.1016/j.ecoleng.2016.02.020 Zheng Y, Wang Z, Cao T, Yang D, Liu Y, Sun Z, Chen R, Dzakpasu M, Wang XC (2022) Enhancement effects and pathways of nitrogen removal by plant-based carbon source in integrated vertical flow constructed wetlands. J Water Process Eng 47:102734. https://doi.org/10.1016/j. jwpe.2022.102734 Zhou T, Liu J, Lie Z, Lai DYF (2022) Effects of applying different carbon substrates on nutrient removal and greenhouse gas emissions by constructed wetlands treating carbon-depleted hydroponic wastewater. Biores Technol. https://doi.org/10.1016/j.biortech.2022.127312

Use of Algae in Wastewater Treatment Nermin El Semary

1 Introduction Water is essential for life. However, there are many places that suffer from a lack of water and drought. Therefore, water is a very valuable commodity and water resources need to be preserved and their use must be maximized. Unfortunately, pollution has damaged many of these water supplies and wastewater needs to be recycled to meet the urgent and pressing demand. To preserve water resources pollutants need to be removed. Pollutants can be organic and inorganic including hazardous heavy metals. Heavy metals are considered as inorganic pollutants that pose a threat as they cannot be decomposed and they accumulate in aquatic organisms causing poisoning. Several studies have emerged looking at ways to treat water from these heavy elements (Gadd 1990). According to Gadd (1990), Bio-removal of heavy metals is mainly via their accumulation by the use of biological material, thereby allowing the recovery and/or the ecofriendly disposal. Sewage water contains solids and liquids coming mainly from household waste, human waste, as well as industrial waste (Sonune and Ghate 2004). Sewage water also contains pathogenic organisms that can cause many diseases such as typhoid, cholera, and dysentery in addition to fungi (Chahal et al. 2016). Environmentally speaking, the discharge of wastewater into water bodies leads to N. El Semary (B) Al Bilad Bank scholarly chair for food security in Saudi Arabia, Deanship of Scientific Research, Vice presidency for Graduate Studies and Scientific Research, King Faisal University, Al Ahsa 31982, Saudi Arabia e-mail: [email protected] Biological Sciences Department, College of Science, King Faisal University, Al Ahsa 31982, Saudi Arabia Botany and Microbiology Department, Faculty of Science, Helwan University, Ain Helwan, Helwan, Cairo 11795, Egypt © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. P. Shah (ed.), Recent Trends in Constructed Wetlands for Industrial Wastewater Treatment, https://doi.org/10.1007/978-981-99-2564-3_8

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contaminating the coastal lines and the spread of many pathogens, in addition to unpleasant odors. Indeed, Naidoo and Olaniran (2013) reported that mis-treated wastewater effluent can pose a threat as a source of microbial pollution of water resources. Due to the current interest in protecting the environment, restrictions have been increased on sewage disposal. Wastewater has to be treated thoroughly prior to being disposed of (European Commission 2007; Hendriks and Langeveld 2017) especially TN (total nitrogen) and TP (total Phosphate) to reduce eutrophication (Schindler et al. 2008) and subsequent harmful algal blooms and pollution.

2 Wastewater Treatments Wastewater treatment is a process by which solids are partially removed and changed by decomposition from organic solids to mineral or relatively stable organic solids (Sonune and Ghate 2004). It usually includes three main stages: Primary treatment: Sometimes called physical treatment, which involves the removal of suspended large particles and sand. The main target is to remove the majority of settleable solids (https://www.engineeringarticles.org/primary-treatm ent-of-wastewater/). Wastewater is passed through a series of screens that separate solid and particulate organic and inorganic materials. The effluent is allowed to settle where Solids settle to the bottom of the reservoir and the effluent is either discharged or drawn off for further treatment. Secondary treatment: This treatment involves the aeration in which atmospheric oxygen is dissolved in sewage water for the respiration of aerobic bacteria. This in turn plays an important role in the removal of biodegradable organic matter through bacterial decomposition (Samer 2015; https://www3.epa.gov/npdes/pubs/mstr-ch3. pdf). This treatment uses naturally occurring biological processes where the level of oxygen is changed at different stages in order to produce aerobic and anaerobic environments. 1. Aerobic Treatment: This treatment is a biological treatment where aerobic bacteria respires and use oxygen to break down organic matter and remove nitrogen and phosphorus (https://www.veoliawatertechnologies.co.uk/technolog ies/aerobic-treatment). The technologies involved include a. b. c. d.

Activated Sludge Process (ASP)/Extended Aeration System (EAS) Sequential Batch Reactor (SBR) Moving Bed Bio Film Reactor (MBBR) Membrane Bioreactor (MBR).

2. Anaerobic Treatment: Anaerobic treatment is a process where wastewater material is broken down by microorganisms in the absence of oxygen. The most

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commonly used anaerobic technology is Anaerobic Sludge Blanket Reactor (UASB) (Samer 2015). Tertiary treatment: It is the in-depth treatment that aims at reaching the permissible values of pollutants. It involves physical–chemical treatment, or combined biological-physical treatment. Tertiary treatment is used when to obtain higherquality effluent. The treatment involves the disinfection of pathogenic microorganisms. Several tertiary treatment processes include: 1. Effluent polishing: This treatment is intended for the removal of suspended solids from secondary effluent. It is usually performed using granular media filters. 2. Biological Phosphorus removal: Secondary biological treatment usually removes about 20% of phosphorus, thereby necessitating additional treatments. Chemical precipitation is the most commonly used process that can remove up to 90% of the phosphorus. This is achieved by adding either iron or aluminum as chloride or sulfate salts but with Fe2+ or Fe+ salts being the most e commonly used. At near-neutral pH, iron forms insoluble fer rice phosphate (or ferric hydroxide-phosphate complexes. that precipitate and are removed as sludger) (Bunce et al. 2018).

3 Use of Algae in Wastewater Treatment The use of algae in wastewater treatment dates back to the 1970s initially intended to use algae in tertiary treatment (McGriff and McKenney 1971; Shelef et al. 1978). Ponds were established for further treatment of secondary effluent (McGriff and McKinney 1972). Nonetheless, the removal of nutrients by algae from settled sewage was more efficient than the activated sewage process thereby favoring the use of algae in the secondary rather than tertiary treatment process (Tam and Wong 1989). Microalgae offer an efficient wastewater treatment due to their ability to assimilate carbon, (nitrogen and phosphorus (del Morales-Amaral et al. 2015). In addition they possess the ability to remove heavy metals (Kumar et al. 2015), as well as some toxic organic compounds (Matamoros et al. 2015). Furthermore, microalgae evolve oxygen during photosynthesis thereby supplying free aeration. This oxygen is also used by heterotrophic bacteria in respiration, allowing them to proliferate and biodegrade organic matter. In addition, photosynthetic microalgae can fix CO2 thereby decreasing global warming (Gupta et al. 2015). Indeed, it is estimated that 1 kg of dry algal biomass uses about 1.83 kg of CO2 (Chisti 2007). The Biological nutrient removal (BNR) systems are based mainly on the processes of autotrophic nitrification, heterotrophic denitrification, and enhanced biological phosphorus removal in order to meet regulations that necessitate the reduction in total nitrogen and

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total phosphorus concentrations in the effluent before the water can be discharged (Ahn et al. 2010) in order to reduce eutrophication (Hendriks and Langeveld 2017). Hence, algae can provide a holistic approach that aims at limiting effluent Phosphorus and nitrogen. In addition, algae can remove heavy metals that are accumulating in sludge thereby reducing the health risk if this sludge is used as soil fertilizer Singh and Agrawal (2008). Previous investigations aimed at selecting the best stage for mass microalgal cultivation for wastewater treatment included that of Bohutskyi et al. (2016) who investigated replacement of chemical fertilizers with nutrients from primary and secondary wastewater effluents and anaerobic digestion centrate. Moreover, microalgae, represent an ecofriendly sustainable alternative to conventional biological treatment (Singh et al. 2015; Oswald 2003). In addition the use of microalgae in wastewater treatment is cost-effective (Almomani et al. 2019) as it will serve both oxygenation and nutrient removal (Mohsenpour et al. 2021 and references therein). Microalgae treatment process is introduced mainly at two points; PSW (primary sewage wastewater) or secondary treatment effluent (STE). Indeed, it is more economical and ecofriendly to directly treat PSW with algae where primary sewage wastewater has more optimum nutrient concentrations to support microalgal growth as compared to STE (Mohsenpour et al. 2021). Interestingly, primary wastewater effluent despite possessing a high level of bacterial contamination but proved to be the best growth medium for microalgal cultivation than nutrient-scarce secondary effluent. Indeed, Bohutski et al. (2016) concluded that unsterilized primary and secondary wastewaters were suitable substrates for the cultivation of Chlorella and Scenedesmus strains.

4 Algal Bioremediation for Municipal Sewage Wastewater According to Gupta et al. (2016) municipal wastewater treatment system include (1) wastewater before to primary settling, (2) wastewater post primary settling, (3) wastewater after activated sludge, and (4) concentrated wastewater generated during sludge centrifuge called centrate. Municipal water contains less nitrogen and Phosphorus than industrial and agricultural wastes. Centrate is usually re-circulated back for further purification which adds more energy cost-effective. However, centrate obtained after anaerobic digestion of activated sludge is a rich source of P and N that favor microalgal cultivation (del Morales-Amaral et al. 2015). Utilizing centrate by microalgae allows the nitrogen and phosphorus in it to be used thereby reducing the number of stages required as well as reducing costs (Sepúlveda et al. 2015).

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5 Oxidation/Algal/Aeration ponds One of the biological systems utilized is the oxidation/aeration ponds. It is a secondary treatment technology that accelerates the natural filtration of wastewater by biological treatment that mostly involves interactions between microorganisms such as bacteria and algae. It removes phosphorus, and nitrogen from wastewater before it is discharged. Several researchers have studied municipal wastewater treatment by microalgae in units such as high-rate algal ponds (HRAPs) (Benemann et al. 1980; Matamoros et al. 2015; Oswald 1988). Microalgae can be used either in suspension or by immobilization (Cai et al. 2019; de-Bashan and Bashan 2010). Growing algae in aerated, ponds can raise the Biological oxygen demand and total soluble salts) levels in the final effluent. Surface blooms, turbidity, and s unpleasant odors are all caused by excessive algal growth which can be problematic. If the algae are present in the drinking water supply. Park et al. (2011), emphasized on factors that enhance the yield of algal biomass which include CO2 supply, control of grazers, and bio-flocculation in addition to cultivation systems and energy consumption. In congruence with this, Stephenson et al. (2010) and Jorquera et al. (2009) reported that the majority of the energy consumed was in the cultivation where mixing in photobioreactors by required more energy than mixing via paddlewheels in high rate algal ponds (HRAP). Recently, more advanced High rate algal ponds (HRAP) were used for the treatment of municipal wastewater in places with good solar radiation. HRAP is more beneficial both environmentally and economically in terms of CO2 sequestration (Kohlheb et al. 2020). Among the various groups of microalgae used in these systems are, Chlorophytes (e.g.Chlorella, Scenedesmus, Botryococcus) which are widely used for the wastewater treatment (Cabanelas et al. 2013).

5.1 Some of the Most Common Algal Species Used in Wastewater Treatments Algae that use both light energy to drive photoautotrophy as well as using organic carbon to drive heterotrophy are called Mixotrophic algae. The rationale behind the use of mixotrophic microalgae to treat wastewater lies in their ability to utilize organic and inorganic carbon, as well as inorganic N and P in wastewater for their growth, resulting in reductions in the concentration of these elements in the water thereby algal growth allows nutrient removal in wastewater (Chawla et al. 2020). Also Microalgae can use both organic nitrogen (e.g., urea) and inorganic nitrogen (ammonium/ammonia) as well as nitrite and nitrates (Ross et al. 2018). The principal advantage of incorporating microalgae into wastewater treatment is the generation of O2 through photosynthesis which is necessary for heterotrophic bacteria to biodegrade organic matter. Interestingly, the use of algae granules in synthetic wastewater has been reported to be highly efficient for the removal of

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phosphorus and its recovery from the Phosphorus-rich algae biomass (Cai et al. 2019). In addition, to being efficient for CO2 sequestration and nutrient removal from wastewater, microalgae represents a potential source of energy generation (Arun et al. 2020).

5.2 Below are Some Examples of Microalgae That have been Used in Wastewater Treatment 5.2.1

Chlorella

The green algal genus Chlorella was widely used in wastewater treatment with abilities to remove nitrogen and phosphorus with different capacities according to the species of Chlorella species used as well as whether there was mixing with bacteria or not (Wang et al. 2022 and references therein). For example, Chlorella vulgaris showed a removal rate of nitrogen and phosphorus on wastewater from Pig slurry at 54–98 and 42–89, respectively and biological oxygen demand of 98% within a period of 4.5 days. Whereas Chlorella pyrenoidosa showed a removal rate of N and P on wastewater from settled domestic waste of 93.9 and 80 in a time period of 13 days. Many recent reports including; Cabanelas et al. (2013) using Chlorella vulgaris; Sforza et al. (2014) using Chlorella protothecoides and Mahdy et al. (2016) using Chlorella vulgaris all reported similar findings. Choi (2016) reported 88% biological oxygen demand, 82% TN (total nitrogen), and 54% TP (total phosphorus) removal from initial concentrations in brewery effluent by C. vulgaris. Chlorella minutissima grown in wastewater have higher growth rates of 380 mg L−1 under heterotrophic conditions compared to 73 mg L−1 under phototrophic conditions in raw sewage (Bhatnagar et al. 2010). Other microalgal species were examined for their bioremediation potential including Chlamydomonas sp., Nanochloropsis sp., Dunaliella sp., Spirulina sp. and Botryococcu sp. (Cuellar-Bermudez et al. 2015; Gonçalves et al. 2017). Most of the studies showed that green algae, in particular Chlorella, are better assimilators of nutrients. Chlorella is highly capable of mixotrophy. Indeed, Wang et al. (2010a, b) used anaerobic digested dairy manure for the cultivation of oil-rich green microalgae Chlorella sp. Wang et al. (2010a), showed that Chlorella sp. can use ammonium or nitrate indicating its flexibility in wastewater treatment. Mixing Chlorella with the diatom alga Nitzchia and bacteria in an algal–bacterial symbiosis has resulted in a very rapid removal rate of N (97%) and to a lesser extent P (74%) with great enhancement in BOD at (97%) and (89%) for COD (chemical oxygen demand) within a period of 10 h indicating the importance of using microbial consortium for fast and effective nutrients removal (McGriff and McKinney 1972). In agreement with this, Su et al. (2011) Valigore et al. (2012) and García et al. (2017) all showed the effectiveness of using an algal–bacterial consortium in wastewater treatment.

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5.2.2

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A consortium of microalga Desmodesmus communis, and bacteria e in effluents showed that enriching primary effluent with CO2 , gave higher biomass productivity compared with the non-enriched algal consortium. D. communis cultures reached also a better nutrient removal efficiency compared with the algal consortium culture, with almost complete removal of ammonia and phosphorous. Moreover, biomass composition was richer in polysaccharides and total fatty acids as the ammonia concentration in the water decreased. The Anaerobic digestion of this biomass with such as composition is suggested to be the most suitable for biofuel generation. Sánchez-Zurano et al. (2021) treated primary urban wastewater in outdoor raceways with microalgae-bacteria consortia dominated by Scenedesmus almeriensis.]. Optimum dilution rates for nutrient removal and highest biomass productivity were 0.3–0.5/day. while minimizing nitrifying bacteria. Whangchenchom et al. (2014) reported that growing algae on wastewater would also give valuable products such as lipids and pigments. Moreover, cultivation microalgae in wastewater was found to reduce chemical oxygen demand in wastewater by 39.89–73.37%. With regard to the utilization of algal biomass for biofuel production. Several reports exist on the subject. According to Álvarez-Díaz et al. (2015), the microalga Scenedesmus obliquus when cultured in batch wastewater maintained at the stationary phase with different conditions of CO2 , light and salinity showed an improvement in the lipid content. CO2 had the highest impact on increasing lipid content followed by light presence and salt presence. The x-3 fatty acids content increased with CO2 and light presence acting solely. Nevertheless, when both factors acted together the interaction impact was negative. The x-3 eicosapentaenoic acid content of the oil from S. obliquus slightly exceeded the 1% maximum to be used as biodiesel source (EU normative). Therefore, blending the resulting oil with other oils or the selective extraction of the x-3 fatty acids from S. obliquus oil can presumably improve oil quality. Acevedo et al. (2017) used domestic wastewater as a substrate to obtain microalgal biomass and allow nutrient removal. Biological treatment with microalgae provided aeration, and reduced both operating costs and the risk of volatilization of contaminants. It also provided oxygen to the bacteria for the degradation of organic compounds. They further grew Scenedesmus sp. synthetic wastewater with different concentrations of N and P. Synthetic water of low and medium concentration had higher removal percentages of nitrogen and phosphorus, For real domestic water, the removal was 65% for phosphorus and 80% for nitrogen. This suggests that Scenedesmus sp. can be used for removing nutrients while growing for other applications.

6 Algal/Bacterial Consortium The amount of oxygen is low in water contaminated with sewage. The reason is that heterotrophic bacteria use oxygen in respiration and energy generation for growth.

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Oxygen is provided by algae during photosynthesis which facilitates the bacterial biodegradation of organic matter in sewage. Waste products include ammonia, nitrates, and phosphates, which are directly used as nutrients for algae. Carbon dioxide generated during bacterial respiration is taken up by algae during photosynthesis. Therefore, a mutual stimulation of growth of algae and bacteria exists while the rate of decomposition of organic matter rises. Undesirable appearance, color and foul smell of undissolved matter changes into soluble, odorless, colorless inorganic compounds. Microalgae use ammonia and phosphate directly for cell growth and metabolic activities (Falkowski and Raven 2007; Borowitzka et al. 2016). As a result, microalgal treatment lowers greenhouse gas emission rate where most of N is used instead of forming oxides of nitrogen. Indeed, negligible emission of N2 O by microalgae was detected (Guieysse et al. 2013; Fagerstone et al. 2011). Furthermore, wastewater treated by an algal–bacterial consortium allows removal of Phosphorus and nitrogen in a single phase treatment which is a cost- and energyeffective (Sturm and Lamer 2011; Gouveia et al. 2016).

7 The Use of Algae of Favorable Characteristics in Wastewater Treatment According to Priyadharshini et al. (2021), employing algal species with high flocculation capacity is most favorable in wastewater treatment as well as biofuel generation Algae with high adsorption affinities are recommended microplastics removal. In addition, the algal biomass generated during the treatment of wastewater possesses high protein and lipid contents making them excellent candidates for biofuel, food, and animal feed industries. In complete congruence, Shahid et al. (2019) indicated that microalgal cultivation using wastewater gives the highest carbon fixation rate and the fastest biomass productivity among all bio-remediators. Moreover, the biomass produced contains valuable metabolites including omega-3-fatty acids, pigments, amino acids, and high sugar content and the biomass remaining after their extraction can be either directly transformed to energy or can be used to produce. Gentili (2014) studied the simultaneous increase in growth and lipid production for biofuel generation, where several microalgae were grown on mixed municipal and industrial for the production of biomass and lipids. All algal strains grew in all wastewater mixtures; however, Selenastrum minutum gave the highest biomass and lipids yields. Nitrogen and phosphorus removal were high and the ammonium removed was used in algal growth. Interestingly, lipid content was negatively correlated to the nitrogen concentration in all algal biomass. To enhance carbon availability in the wastewater, an external supply in the form of CO2 or bicarbonate salts is used (Kesaano et al. 2015; Razzak et al. 2013; Cragg et al. 2011). Shen et al. (2015) used S. obliquus for the remediation of total nitrogen from artificial wastewater at different CO2 : air ratios Most of the total nitrogen was removed within two days at 5% CO2 . Where they found that. CO2 supply in the range of 1–6% is optimum

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for microalgal growth and nutrient removal (Yao et al. 2015; Qi et al. 2017; Hu et al. 2012). Concentrations above that value reduce the beneficial effect of CO2 , and would be inhibitory on microalgal respiration (Sforza et al. 2012). CO2 tolerance is strain-dependent (Zhao and Su 2014).

7.1 Euglena sp. Mahapatra et al. (2013) investigated the use of Euglena sp. for the purpose of biofuel production and treatment of wastewater. The alga was isolated from the sewage treatment plants and was tested for its nutrient removal capability. Compared to other algae, Euglena sp. showed faster growth rates with high biomass production at high concentrations of ammonium and organic carbon. Extensive growth of the alga was observed in untreated wastewater as well as maximum nutrient removal with high lipid accumulation rate. GC-Mass indicated the presence of high contents of palmitic, linolenic, and linoleic acids thereby adding to biodiesel quality. All the aforementioned attributes make Euglena sp. a rich candidate for biofuel production in wastewater.

8 Microalgal Biofilm Boelee et al. (2011) investigated the potential of microalgal biofilms as an effluent post-treatment where they were grown in flow cells with different nutrient loads under continuous light. Microalgal biomass showed high rates of uptake for phosphorus and nitrogen thereby verifying the feasibility of using microalgal biofilm in nutrient removal.

9 The Various Biotechnological Benefits that Result from Microalgal-Based Wastewater Treatment According to Gupta et al. (2016) and references therein, the production of several organic solvents such as methane, acetone, butanol, and ethanol by anaerobic digestion makes microalgal wastewater treatment feasible (Tartakovsky et al. 2015). In addition, hydrogen and bioelectricity can be produced from wastewater by combinations of microbial fuel cells) (ElMekawy et al. 2014). Furthermore, lipids obtained from harvested microalgae can be used for biodiesel production by trans-esterification (Chisti 2007). Moreover, Microalgal biomass contains pigments, enzymes, vitamins, and many valuable metabolites for commercial use in nutraceutical and cosmetic industry (Borowitzka 2013).

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10 The Use of Algal Biomass Resulting from the Treatment of Wastewater in Biofuel Generation Mahapatra et al. (2013) reported that growing algae in mixotrophic nutrition offers an effective removal of N and P from domestic wastewater without any pretreatment. This is particularly important in developing countries that need feasible solutions for wastewater treatment. This can also serve for the remediation of freshwater resources and reduce eutrophication. Furthermore, the biomass of algae after the treatment of wastewater can be further exploited for the purpose of biofuel production. Euglena sp. with high biomass productivities accumulate substantial lipids in the cells while removing nutrients from wastewater. The constituents of the algal oil were similar to the vegetative feedstock oils, indicating the suitability as biofuel for energy production. The percentage of C16–C18 fatty acids was ~ 97% which are essential desirable fatty acids (e.g. palmitic, stearic, oleic, and linolenic acids) for biofuel properties (Knothe 2005, 2008). The removal of nutrients and the production of desirable biofuel from the algal biomass offers a double benefit where nutrients are recycled and algal biomass produced is converted to biofuel. This also helps in reducing global warming via the consumption of carbon in photosynthesis and the release of oxygen. Wang et al. (2010a, b) reported that digested dairy manure, in addition to CO2 , proved to be a useful carbon source for mixotrophic Chlorella. Fatty acid profiles showed that octadecadienoic acid (C18:2) and hexadecanoic acid (C16:0) were the two most abundant fatty acids. Concerning the conditions that favor the lipid high productivity together with an adequate removal rate of N and P, Woertz et al. (2009) investigated lipid productivity and nutrient removal by green algae grown during the treatment of dairy farm and municipal wastewaters supplemented with carbon dioxide. The results from both types of wastewater treatment suggest that CO2 -supplemented algae cultures can simultaneously remove dissolved nitrogen and phosphorus to low levels while generating a feedstock potentially useful for liquid biofuel production.

10.1 Modifications of the System to Shift it Toward Biofuel Production Cabanelas et al. (2013) added glycerol. The mixotrophic production of lipids can generate high-quality biodiesel. The whole process can be further modified for the production of other biofuels (e.g. methane and bio-ethanol) in a biorefinery scenario. Ye et al. (2020) used eight species of microalgae (five Scenedesmus and three Desmodesmus) that were isolated from water and soil in the Hexi Corridor region, China, and. The strains showed different affinities to wastewater with Scenedesmus sp. HXY2 growing well at high total organic carbon and ammonia conditions showing

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the highest nutrient removal efficiency The proportion of unsaturated fatty acids (60.07%) derived from this green algal strain indicated that its lipids were suitable for biodiesel production.

11 Biological Method for Removing Heavy Metals from Water Biological methods rely on the use of naturally occurring processes, as many microorganisms participate in the cycling of toxic heavy metals. Algae as well as other microorganisms play a large role in the remediation of heavy metal ions in the environment. Organic compounds are released from growing cells as well as from biodegradation products of various sources, which act as complexing agents for metal ions, thus reducing metal toxicity. Metal ions can bind to components of the algal cell wall. During the growth of algae, various metabolic processes occur, such as photosynthesis, respiration, nutrient absorption, and others, all of which affect the balance between free metal ions and associated forms, as well as between precipitation and redissolution in the aquatic environment. Algae thriving in metal-contaminated sites possess intracellular mechanisms that enable them to counteract the toxic effects of metals. These types may be used for biological treatment in large water bodies polluted with low concentrations of metal ions (Igiri et al. 2018; Paliwal et al. 2018).

12 Algae Absorption Biosorption involves a combination of positive and negative transport mechanisms starting with the dissemination of metal ions on the surface of the microbial cell. When the metal ion spreads on the surface of the cell, it will bind to the sites on the cell surface that show chemical attraction to this metal. This step contains a number of accumulation processes. To include absorption and ion exchange, coordination, and removal process. Differences between types of algae in terms of heavy metal and microscopic sedimentation. In general, such uptake as the volume change and modification of the metallic ion-coating capacity is rapid and reversible, and is not a limiting factor in the removal of the metal ion. Absorption into the cell structure, depending on the biosynthesis, is often followed by a process of mineral encapsulation where the division, sex, and type of algae occurs. Acknowledgements Professor El Semary would like to express her gratitude for the financial support funded by the Bank Al Bilad Scholarly chair for food security in Kingdom of Saudi Arabia, Deanship of Scientific research, Vice Presidency for Graduate Studies and Scientific research, King Faisal University, AlAhsa, post code: 31982, KSA. Chair grant number: 107.

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References Acevedo S, Peñuela GA, Pino NJ (2017) Biomass production of Scenedesmus sp. and removal of nitrogen and phosphorus in domestic wastewater. Ing y compet 19(1):185–193 Ahn JH, Kim S, Park H, Rahm B, Pagilla K, Chandran K (2010) N2 O emissions from activated sludge processes, 2008−2009: results of a national monitoring survey in the United States. Environ Sci Technol 44:4505–4511 Almomani F, Judd S, Bhosale RR, Shurair M, Aljaml K, Khraisheh M (2019) Integrated wastewater treatment and carbon bio-fixation from flue gases using Spirulina platensis and mixed algal culture. Process Saf Environ Prot 124:240–250 Álvarez-Díaz PD, Ruiz J, Arbib Z, Barragán J, Garrido-Pérez MC, Perales JA (2015) Wastewater treatment and biodiesel production by Scenedesmus obliquus in a two-stage cultivation process. Bioresour Technol 181:90–96 Arun S, Sinharoy A et al (2020) Algae based microbial fuel cells for wastewater treatment and recovery of value-added products. Renew Sust Energ Rev 132 Article 11004 Boelee NC, Temmink H, Janssen M, Buisman CJN, Wijffels RH (2011) Nitrogen and phosphorus removal from municipal wastewater effluent using microalgal biofilms. Water Res 45(18):5925– 5933 Benemann JR, Koopman B, Weissman J, Goebel R (1980) Development of microalgae harvesting and high rate pond technologies in California. In: Shelef G, Soeder CJ (eds) Algae biomass production and use. Elsevier/North-Holland Biomedical Press, Amsterdam, pp 457–495 Bhatnagar A, Bhatnagar M, Chinnasamy S, Das K (2010) Chlorella minutissima—a promising fuel alga for cultivation in municipal wastewaters. Appl Biochem Biotechnol 161:523–536 Bohutskyi P, Chow S, Ketter B, Shek C, Yacar D, Tang Y, Zivojnovich M, Betenbaugh M, Bouwer E (2016) Phytoremediation of agriculture runoff by filamentous algae poly-culture for biomethane production, and nutrient recovery for secondary cultivation of lipid generating microalgae. Bioresour Technology 222:294–308. https://doi.org/10.1016/j.biortech.2016.10.013 Borowitzka MA (2013) High-value products from microalgae—their development and commercialisation. J Appl Phycol 25:743–756 Borowitzka MA, Beardall J, Raven J (2016) The physiology of microalgae. Springer International Publishing, Germany Bunce J, Ndam E, Ofiteru I, Moore A, Graham D (2018) A Review of phosphorus removal technologies and their applicability to small-scale domestic wastewater treatment systems. Front Environ Sci 6. https://www.frontiersin.org/article/. https://doi.org/10.3389/fenvs.2018.00008 Cabanelas ITD, Ruiz JZ, Arbib FA, Chinalia C, Garrido-Pérez F, Rogalla I, Nascimento A, Perales JA (2013) Comparing the use of different domestic wastewaters for coupling microalgal production and nutrient removal. Bioresour Technol 131:429–436 Cai W, Zhao Z et al (2019) Algae granulation for nutrients uptake and algae harvesting during wastewater treatment. Chemosphere 214:55 Chahal C, van den Akker B, Young F, Franco C, Blackbeard J, Monis P (2016) Pathogen and particle associations in wastewater: significance and implications for treatment and disinfection processes. Adv Appl Microbiol 97:63–119 Chawla P, Malik A et al (2020) Selection of optimum combination via comprehensive comparison of multiple algal cultures for treatment of diverse wastewaters. Environ Technol Innov 18 Article 100758 Chisti Y (2007) Biodiesel from microalgae. Biotechnol Adv 25:294–306 Choi H (2016) Parametric study of brewery wastewater effluent treatment using Chlorella vulgaris. Microalgae. 21:401–408 Cragg RJ, Heubeck S, Lundquist TJ, Benemann JR (2011) Algal biofuels from wastewater treatment high rate algal ponds. Water Sci Technol 63:660 Cuellar-Bermudez SP, Garcia-Perez JS, Rittmann BE, Parra-Saldivar R (2015) Photosynthetic bioenergy utilizing CO2 : an approach on flue gases utilization for third generation biofuels. J Clean Prod 98:53–65

Use of Algae in Wastewater Treatment

173

de-Bashan LE, Bashan Y (2010) Immobilized microalgae for removing pollutants: review of practical aspects. Bioresour Technol 101(6):1611–1627. https://doi.org/10.1016/j.biortech.2009. 09.043 del Morales-Amaral M, Gómez-Serrano C, Acién FG et al (2015) Production of microalgae using centrate from anaerobic digestion as the nutrient source. Algal Res 9:297–305 ElMekawy A, Hegab HM, Vanbroekhoven K, Pant D (2014) Techno-productive potential of photosynthetic microbial fuel cells through different configurations. Renew Sustain Energy Rev 39:617–627 European Commission (2007) Pursuant to article 16 of regulation (EC) No 648/2004 of the European Parliament and of the Council of 31 March 2004 on detergents, concerning the use of phosphates. http://www.parliament.bg/pub/ECD/69232COM_2007_234_EN_ACTE_f.pdf Fagerstone KD, Quinn JC, Bradley TH, De Long SK, Marchese AJ (2011) Quantitative measurement of direct nitrous oxide emissions from microalgae cultivation. Environ Sci Technol 45:9449– 9456 Falkowski PG, Raven JA (2007) Aquatic photosynthesis, 2nd edn. Princeton University Press, New Jersey, USA Gadd GM (1990) Accumulation of metals by microorganisms and algae. In: Rehm KJ (ed) Biotechnology handbook 6b special microbial processes. Weinheim: VCH Verlagsgesselschaft García D, Alcántara C, Blanco S, Pérez R, Bolado S, Muñoz R (2017) Enhanced carbon, nitrogen and phosphorus removal from domestic wastewater in a novel anoxic-aerobic photobioreactor coupled with biogas upgrading. Chem Eng J 313:424–434 Gentili FG (2014) Microalgal biomass and lipid production in mixed municipal, dairy, pulp and paper wastewater together with added flue gases. Biores Technol 169:27–32 Gonçalves AL, Pires JCM, Simões M (2017) A review on the use of microalgal consortia for wastewater treatment. Algal Res 24:403–415 Gouveia L, Graça S, Sousa C, Ambrosano B, Ribeiro EP, Botrel PC, Neto AF, Ferreira CMS (2016) Microalgae biomass production using wastewater: treatment and costs scale-up considerations. Algal Res 16:167 Guieysse B, Plouviez M, Coilhac M, Cazali L (2013) Nitrous oxide (N2 O) production in axenic Chlorella vulgaris microalgae cultures: evidence, putative pathways, and potential environmental impacts. Biogeoscience 10:6737–6746 Gupta PL, Lee SM, Choi HJ (2015) A mini review: photobioreactors for large scale algal cultivation. World J Microbiol Biotechnol 31:1409–1417 Gupta PL, Lee SM, Choi HJ (2016) Integration of microalgal cultivation system for wastewater remediation and sustainable biomass production. World J Microbiol Biotechnol 32:139 Hendriks ATWM, Langeveld JG (2017) Rethinking wastewater treatment plant effluent standards: nutrient reduction or nutrient control? Environ Sci Technol 51:4735–4737 Hu B, Min M, Zhou W, Li Y, Mohr M, Cheng Y, Lei H, Liu Y, Lin X, Chen P, Ruan R (2012) Influence of exogenous CO2 on biomass and lipid accumulation of microalgae Auxenochlorella protothecoides cultivated in concentrated municipal wastewater. Appl Biochem Biotechnol 166:1661–1673 Igiri E, Okoduwa SIR, Idoko GO, Akabuogu EP, Adeyi AO, Ejiogu IK (2018) Article toxicity and bioremediation of heavy metals contaminated ecosystem from tannery wastewater: a review. J Toxicol 2018. Article ID 2568038, 16. Review Bernard. https://doi.org/10.1155/2018/2568038 Jorquera O, Kiperstok A, Sales EA, Embiruçu M, Ghirardi ML (2009) Comparative energy lifecycle analyses of microalgal biomass production in open ponds and photobioreactors. Bioresour Technol 101:1406–1413. https://doi.org/10.1016/j.biortech.2009.09.038 Kesaano M, Gardner RD, Moll K, Lauchnor E, Gerlach R, Peyton BM et al (2015) Dissolved inorganic carbon enhanced growth, nutrient uptake, and lipid accumulation in wastewater grown microalgal biofilms. Bioresour Technol 180:7–15. https://doi.org/10.1016/j.biortech. 2014.12.082 Knothe G (2005) Dependence of biodiesel fuel properties on the structure of fatty acid alkyl esters. Fuel Process Technol 86:1059–1070

174

N. El Semary

Knothe G (2008) “Designer” biodiesel: optimizing fatty ester composition to improve fuel properties. Energy Fuel 22:1358–1364 Kohlheb N, van Afferden M et al (2020) Assessing the life-cycle sustainability of algae and bacteriabased wastewater treatment systems: high-rate algae pond and sequencing batch reactor. J Environ Manag 264:Article 110459 Kumar KS, Dahms HU, Won EJ, Lee JS, Shin KH (2015) Microalgae–a promising tool for heavy metal remediation. Ecotoxicol Environ Saf Mahapatra DM, Chanakya HN, Ramachandra TV (2013) Euglena sp. as a suitable source of lipids for potential use as biofuel and sustainable wastewater treatment. J Appl Phycol 25:855–865 Mahdy A, Ballesteros M, González-Fernández C (2016) Enzymatic pretreatment of Chlorella vulgaris for biogas production: influence of urban wastewater as a sole nutrient source on macromolecular profile and biocatalyst efficiency. Bioresour Technol 199:319–325 Matamoros V, Gutiérrez R, Ferrer I et al (2015) Capability of microalgae-based wastewater treatment systems to remove emerging organic contaminants: a pilot-scale study. J Hazard Mater 288:34– 42 McGriff EC, McKenney RE (1971) Activated algae: a nutrient process. Water Sew Works 118:377 McGriff EC, McKinney RC (1972) The removal of nutrients and organics by activated algae. Water Res 6(10):1155 Mohsenpour SF, Hennige S, Willoughby N, Adeloye A, Gutierrez T (2021) Integrating micro-algae into wastewater treatment: a review. Sci Total Environ 752:142168 Naidoo S, Olaniran AO (2013) Treated wastewater effluent as a source of microbial pollution of surface water resources. Int J Environ Res Public Health 11(1):249–270 Oswald WJ (1988) Micro-algae and waste-water treatment. In: Borowitzka MA, Borowitzka LJ (eds) Micro-algal biotechnology. Cambridge University Press, Cambridge, pp 305–328 Oswald WJ (2003) My sixty years in applied algology. J Appl Phycol 15:99–106 Paliwal R, Gusain P, Saun B, Uniyal S, Khanna R, Bhutiani R (2018) Algal potential for inorganic and organic pollutants decontamination algal potential for inorganic and organic pollutants decontamination. Water Biol:207–217 Park JBK, Craggs RJ, Shilton AN (2011) Wastewater treatment high rate algal ponds for biofuel production. Biores Technol 102(1):35–42 Priyadharshini SD, Babu P, Manikandan S, Subbaiya R, Govarthanan M, Karmegam N (2021) Phycoremediation of wastewater for pollutant removal: a green approach to environmental protection and longterm remediation. Environ Pollut 290:117989. https://doi.org/10.1016/j.env pol.2021.117989 Qi F, Xu Y, Yu Y, Liang X, Zhang L, Zhao H, Wang H (2017) Enhancing growth of Chlamydomonas reinhardtii and nutrient removal in diluted primary piggery wastewater by elevated CO2 supply. Water Sci Technol 75:2281–2290 Razzak SA, Hossain MM, Lucky RA, Bassi AS, de Lasa H (2013) Integrated CO2 capture, wastewater treatment and biofuel production by microalgae culturing—a review. Renew Sust Energy Rev 27:622–653 Ross ME, Davis K et al (2018) Nitrogen uptake by the macro-algae Cladophora coelothrix and Cladophora parriaudii: influence on growth, nitrogen preference and biochemical composition. Algal Res 30:1 Samer M (2015) Biological and chemical wastewater treatment processes. Wastewater Treat Eng IntechOpen. https://doi.org/10.5772/61250 Sánchez-Zurano A, Lafarga T, Morales-Amaral MD et al (2021) Wastewater treatment using Scenedesmus almeriensis: effect of operational conditions on the composition of the microalgaebacteria consortia. J Appl Phycol 33:3885–3897 Schindler DW, Hecky RE, Findlay DL, Stainton MP, Parker BR, Paterson MJ, Beaty KG, Lyng M, Kasian SEM (2008) Eutrophication of lakes cannot be controlled by reducing nitrogen input: results of a 37-year whole-ecosystem experiment. Proc Natl Acad Sci 105:11254–11258 Sepúlveda C, Acién FG, Gómez C et al (2015) Utilization of centrate for the production of the marine microalgae Nannochloropsis gaditana. Algal Res 9:107–116

Use of Algae in Wastewater Treatment

175

Sforza E, Cipriani R, Morosinotto T, Bertucco A, Giacometti GM (2012) Excess CO2 supply inhibits mixotrophic growth of Chlorella protothecoides and Nannochloropsis salina. Bioresour Technol 104(2012):523–529 Sforza E, Ramos-Tercero EA, Gris B, Bettin F, Milani A, Bertucco A (2014) Integration of Chlorella protothecoides production in wastewater treatment plant: from lab measurements to process design. Algal Res 6:223–233 Shahid A, Malik S, Zhu H, Xu J, Nawaz MZ, Nawaz S, Asraful Alam M, Mehmood MA (2019) Cultivating microalgae in wastewater for biomass production, pollutant removal, and atmospheric carbon mitigation; a review. Sci Total Environ 20(704):135303 Shelef G, Moraine R, Oron G (1978) Photosynthetic biomass production from sewage. Ergeb Der Limnol 2:3–14 Shen Q-H, Jiang J-W, Chen L-P, Cheng L-H, Xu XH, Chen HL (2015) Effect of carbon source on biomass growth and nutrients removal of Scenedesmus obliquus for wastewater advanced treatment and lipid production. Bioresour Technol 190(2015):257–263 Singh RP, Agrawal M (2008) Potential benefits and risks of land application of sewage sludge. Waste Manage 28:347–358 Singh B, Bauddh K, Bux F (2015) Algae and environmental sustainability, 1st edn. Springer India, New Delhi Sonune A, Ghate R (2004) Developments in wastewater treatment methods. Desalination 167:55–63 Stephenson AL, Kazamia E, Dennis JS, Howe CJ, Scott SA, Smith AG (2010) Life-cycle assessment of potential algal biodiesel production in the United Kingdom: a comparison of raceways and air-lift tubular bioreactors. Energy Fuel 24:4062–4077 Sturm BSM, Lamer SL (2011) An energy evaluation of coupling nutrient removal from wastewater with algal biomass production. Appl Energy 88:3499 Su Y, Mennerich A, Urban B (2011) Municipal wastewater treatment and biomass accumulation with a wastewater-born and settleable algal-bacterial culture. Water Res 45:3351–3358 Tam NFY, Wong YS (1989) Wastewater nutrient removal by Chlorella pyrenoidosa and Scenedesmus sp. Environ Pollut 58:19–34 Tartakovsky B, Lebrun FM, Guiot SR (2015) High-rate biomethane production from microalgal biomass in a UASB reactor. Algal Res 7:86–91 Valigore JM, Gostomski PA, Wareham DG, O’Sullivan AD (2012) Effects of hydraulic and solids retention times on productivity and settleability of microbial (microalgal-bacterial) biomass grown on primary treated wastewater as a biofuel feedstock. Water Res 46:2957–2964 Wang L, Li Y, Chen P, Min M, Chen Y, Zhu J, Ruan RR (2010a) Anaerobic digested dairy manure as a nutrient supplement for cultivation of oil-rich green microalgae Chlorella sp. Bioresour Technol 101:2623–2628 Wang L, Min M, Li Y, Chen P, Chen Y, Liu Y, Wang Y, Ruan R (2010b) Cultivation of green algae Chlorella sp. in different wastewaters from municipal wastewater treatment plant. Appl Biochem Biotechnol 162:1174–1186 Wang S, Yin C, Yang Z, Hu X, Liu Z, Song W (2022) Assessing the potential of Chlorella sp. for treatment and resource utilization of brewery wastewater coupled with bioproduct production. J Clean Prod 367:132939. https://doi.org/10.1016/j.jclepro.2022.132939 Whangchenchom W, Chiemchaisri W, Tapaneeyaworawong P, Powtongsook S (2014) Wastewater from instant Noodle factory as the whole nutrients source for the microalga Scenedesmus sp. cultivation. Environ Eng Res 19:283–287. https://doi.org/10.4491/eer.2014.s1.007 Woertz I, Feffer A, Lundquist T, Nelson Y (2009) Algae grown on dairy and municipal wastewater for simultaneous nutrient removal and lipid production for biofuel feedstock. J Environ Eng 135:1115–1122 Yao L, Shi J, Miao X (2015) Mixed wastewater coupled with CO2 for microalgae culturing and nutrient removal. PLoS One 10(9). Article e0139117. https://www.engineeringarticles.org/pri mary-treatment-of-wastewater/, https://www3.epa.gov/npdes/pubs/mstr-ch3.pdf, https://www. intechopen.com/chapters/49024, (https://www.veoliawatertechnologies.co.uk/technologies/aer obic-treatment)

176

N. El Semary

Ye S, Gao L, Zhao J, An M, Wu H, Li M (2020) Simultaneous wastewater treatment and lipid production by Scenedesmus sp. HXY2. Bioresour Technol 302:122903. https://doi.org/10.1016/ j.biortech.2020.122903 Zhao B, Su Y (2014) Process effect of microalgal-carbon dioxide fixation and biomass production: a review. Renew Sust Energ Rev 31:121–132. https://doi.org/10.1016/j.rser.2013.11.054

Constructed Wetlands: The Traditional System Adrija Ghosh, Jonathan Tersur Orasugh, and Dipankar Chattopadhyay

1 Introduction Constructed wetlands (CW) can be defined as wetlands artificially made in areas for various purposes including the most attractive one i.e. wastewater treatment. It exploits the potential of plants to carry oxygen to their roots and surrounding wastewater. Thus, the most important component of a CW is wetland vegetation. Though there exist other methods for eradication of pollutants, wetland plants are used most of the time. Different plant tissues play different roles. The aerial plant tissues help in insulation (cold climate), reduce wind velocity, and store nutrients. The plant tissues in water help in filtering out debris, and help in sedimentation, nutrient uptake, and aerobic degradation. The roots and rhizomes are colonized by bacteria and microorganisms. They also help in nutrient uptake and aerobic degradation. They prevent clogging. The next component of a CW is the supporting media for plants. The most common media for supporting vegetation in a CW is coarse and fine gravel. They primarily store the biotic and abiotic components of the CW. They promote filtration. Fine and coarse gravel exhibit high hydraulic conductivity. Other than these, microorganisms are also an important component of CW. A. Ghosh · J. T. Orasugh (B) · D. Chattopadhyay (B) Department of Polymer Science and Technology, University of Calcutta, Kolkata 700 009, India e-mail: [email protected] D. Chattopadhyay e-mail: [email protected] J. T. Orasugh Department of Chemical Sciences, University of Johannesburg, Doorfontein, Johannesburg 2028, South Africa Department of Textile Technology, Kaduna Polytechnic, Tudun-Wada, Kaduna, Nigeria DST-CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria 0001, South Africa © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. P. Shah (ed.), Recent Trends in Constructed Wetlands for Industrial Wastewater Treatment, https://doi.org/10.1007/978-981-99-2564-3_9

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The removal of pollutants by CWs takes place through physical, chemical, and biological processes. The physical process involves retardation of wastewater flow by plants, leading to sedimentation of suspended solids. The support media acts as a filter bed and aids in the physical removal of these solids. Chemical processes involve a chemical reaction between substances leading to their precipitation. Atmospheric gases and sunlight facilitate the degradation of organic pesticides and the removal of pathogens. While biological processes that aid in the eradication of pollutants are photosynthesis, respiration, nitrification/denitrification, fermentation, and phosphorus removal (Sundaravadivel and Vigneswaran 2001). CWs have many advantages over conventional wastewater treatment techniques. They do not require any mechanical parts or chemicals. The raw materials used for this method are renewable sources like sunlight and wind. It has comparatively less maintenance requirements. They emit less greenhouse gases. They do not produce sludge as a by-product. They have a higher lifetime around 25–30 years. Most importantly, they have aesthetic appeal. It is a comparatively new technique and has started grabbing the attention of researchers as more interest is paid toward solving environmental issues (Stefanakis 2018).

2 History 2.1 Early Stage of Development Dr. Käthe Seidel was the pioneer in using vegetation-based systems for the development of inland waterways which were highly impacted by factors like overfertilization or sewage pollution. During that period, experts relied upon only the use of physical and chemical methods for wastewater treatment. The biological methods applied were limited to only the use of bacteria. Dr. Seidal conducted various tests by using wetland plants to treat wastewater from several sources such as dairy and livestock. She was successful in growing macrophytes in wastewater from several sources. In 1974, the first horizontal flow constructed wetland (HF CW) was operated in Germany for treating municipal sewage. In the year 1967, the first free water surface CW (FWS CW) was operated in the Netherlands. During this period several kinds of research were carried out for treating municipal wastewater using coastal lagoons or cypress wetlands. In the 1970s the idea of CWs spread through sluggishly in Europe and North America (Vymazal 2011).

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2.2 Period 1980–2000 In the 1980s the notion of CWs was the highlight of many international conferences held in the USA and Europe. In the early 1980s, researchers in Australia conducted pilot-scale experiments to analyze the impact of subsurface CWs on wastewater from various sources. The mid-1980s marked proliferating use of CWs in South Africa. Around 30 CWs were either under operation or construction by 1990. These systems were used for the treatment of domestic sewage along with industrial and agricultural wastewater. During this period, several experiments were performed in Brazil which included the use of hyacinths along with CWs which could be categorized as vertical upflow CWs. The installment of India’s first CW was reported in 1995. Juwakar et al. (1995) pioneered the installment of a CW in Sainik School, Bhubaneswar, Odisha which included the use of emergent macrophytes. By the end of the twentieth century, CWs were used widely across the world. Though a majority of them were still used for the treatment of municipal wastewater. In the last decade of the twentieth century, CWs were certified in a few countries. In the year 2000, International Water Association produced a report on its efficiency, design, and operation gaining more acceptance among professionals to it (Vymazal 2011).

3 Types of Constructed Wetland 3.1 Types of CW Based on Hydrology CWs can be broadly classified into two categories depending upon their hydrologyfree water surface constructed wetland and subsurface constructed wetland. Figure 1 represents these two types of CWs schematically.

3.1.1

Free Water Surface Flow (FWS)

Typical FWS CWs can be identified as shallow basins or channels that have appropriate mediums like soil for breeding of rooted macrophytes. The design of such wetlands aims at the treatment of wastewater through contact with a reactive biological surface. Here basically the organic components of wastewater are eradicated through bacterial metabolism. These bacteria are either living in the roots of rhizomes in the case of free-floating macrophytes or in the stems of rooted macrophytes. On the hand, the suspended solids are removed by gravity sedimentation or filtration through vegetation. Macrophytes assist in this process by preventing waterlogging and wind turbulence. Nitrogen is generally eliminated through the process of nitrification followed by denitrification and ammonia volatilization in presence of high pH.

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Fig. 1 Schematic representation of (a) free water surface flow and (b) subsurface flow constructed wetland (Reproduced with copyright permission from Dubey and Sahu [2014], Spring Journals, 2022)

However, phosphorus retention is less in these wetlands due to inadequate contact between water and soil adsorbing phosphorus (Gauss and Ledent 2008; Vymazal 2022).

3.1.2

Subsurface Flow (SSF)

Vertical Flow (VF) VF CWs can be characterized as a porous bed in which water is supplied in the vertical direction. They can be categorized into three types: downflow, upflow, and fill and drain. VF CWs are mostly operated with a downflow unit. The original purpose of introducing these was to treat anaerobic effluents. Yet horizontal flow (HF) CWs gained much more attention than VF CWs due to the high operation and maintenance needs. They are needed to be pumped with wastewater sporadically. Initially, a large batch of water is supplied over the wetlands which leads to water percolation through the sand. The next batch is supplied once the bed is free from water. This process provides adequate diffusion of oxygen into the bed. Thus this type of VF CWs are

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much more aerobic than HF CWs and are appropriate for nitrification. They are also efficient in the eradication of organic and suspended matters in effluents. While its shortcomings include inadequate removal of phosphorus and unsuitable conditions for the denitrification process. Downflow VF CWs require much less land area for installation than HF CWs. They have the potential of treating wastewater from various sources. Although they are frequently used to treat domestic and municipal effluents. The second type of VF CWs is one that operates with upflow unit. Here, the water is generally supplied below the filter which progresses up to the filtration bed. They bestow the same conditions for wastewater treatment as HF CWs because of the saturation of the filtration bed. The third type of VF CWs is known as “fill and drain” and the process involves alternating upflow and downflow. This leads to a cycle of saturation and unsaturation of the land resulting in the efficient removal of both ammonia and nitrates (Vymazal 2022).

Horizontal Flow (HF) HF CWs can be characterized as porous filtration beds planted with emergent macrophytes and supplied with pretreated wastewater under them. These filtration beds are a system with an arrangement of aerobic, anoxic, and anaerobic zones. Aerobic zones are basically narrow zones adjoining macrophytes that provide aerobic conditions supplying oxygen to the substrate. The filtration bed is generally separated from the neighboring area by an impermeable layer. The filtration media generally consists of either washed gravel or compressed rock. Macrophytes in CWs provide appropriate conditions for the removal of pollution. They supply substrates for attached bacteria and confiscate nutrients from wastewater which are eradicated through harvesting. The most commonly used macrophytes for this purpose are Common reed, cattails, bulrush, and yellow flag. HF CWs are highly efficient in the removal of organic matter and suspended matter in wastewater. Organic matter is eradicated via both anaerobic and aerobic degradation. However, due to the presence of a narrow zone for aerobic decomposition, the anaerobic process dominates over it. Thus, HF CWs possess an appropriate environment for denitrification. Contrary to VF CWs, they are inefficient for nitrification and volatilization due to the absence of a free water surface. Also, it shows inadequate phosphorus removal which can be enhanced by including filter media of higher sorption capability. Though they need to be replaced at regular intervals for maintaining their rate of phosphorus removal. Installation of HF CWs generally involves high capital cost than surface flow CWs but its operation and maintenance costs are low (Vymazal 2022).

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Hybrid CWs

Hybrid CWs are a system that involves the use of different types of CWs to gain their cumulative benefits, especially efficient nitrogen removal. They generally combine the HF and VF CW systems. Installation of such wetlands requires expert construction knowledge, experience, and supervision. They are land extensive in nature. Yet they have higher efficiency in wastewater treatment (Vymazal 2022). Table 1 represents different types of Cs and their pollutant removal efficiency.

3.2 Types of CW Based on Macrophytic Growth CWs can be widely classified based on the kind of macrophytes that are grown on it (Fig. 2). Submerged macrophytes develop entirely underwater. They are rooted at the bottom. They might have flowers that extend above the water surface. Floating leaved macrophytes are also rooted on the bottom but they have their leaves and flowers above the water surface. Free floating macrophytes are not rooted and float on the water surface. On the other hand, emergent macrophytes are generally woody or herbaceous plants that have most of their body parts above the water surface. Few macrophyte species are commonly planted in CWs as represented in Table 2.

4 Construction of CW 4.1 Site Selection Once the decision of installing a CW is taken, the site is then selected for this purpose. Availability of the required amount of land size and its easy accessibility are two important factors for site selection. It also depends on the way chosen to dispose of wastewater post-treatment. The use of the site should follow the community views concerning odors, vectors, aesthetic and environmental effects. Proper characterization of soil is important. This includes the evaluation of soil depth, its composition, erosion potential, and topography. The next step is the characterization of surface and groundwater. The depth and quality of groundwater need to be evaluated for assessing its possible applications.

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Table 1 Pollutant removal efficiency of various types of CWs Country

Type of CW

Source of wastewater

Removal efficiency (%)

References

Iran

Horizontal sub-surface flow

Glass industry

BOD5 = 90, COD = 90, TSS = 99

Gholipour et al. (2020)

India

Horizontal sub-surface flow

Hospital wastewater

COD = 94, MLSS = 97, TSS = 98, BOD5 = 96

Khan et al. (2020)

Italy

Multistage

Winery wastewater

COD = 81, TSS = 69

Milani et al. (2020)

Pakistan

Vertical flow

Textile wastewater

COD = 81, BOD = 72, TDS = 32

Hussain et al. (2018)

Canada

Vertical flow

Winery wastewater

COD = 99, TSS = 98

Schouten and Glasbergen (2011)

USA

Subsurface-flow

Winery wastewater

COD = 98, TSS = 97

Shepherd et al. (2001)

Greece

Vertical flow

Olive mill wastewater

COD = 70

Herouvim et al. (2011)

Tunisia

Re-circulating horizontal flow

Textile wastewater

COD = 92

Haddaji et al. (2019)

Ethiopia

Horizontal sub-surface flow

Tannery wastewater

BOD5 = 96.42, COD = 96.91

Aregu et al. (2021)

Spain

Horizontal sub-surface flow

Tannery wastewater

TP = 78, Cr = 48

García-Valero et al. (2020)

Ethiopia

Subsurface-flow

Floriculture

TSS = 90, TP = 93, Engida et al. (2020) COD = 76

Venezuela

Horizontal sub-surface flow

Tannery wastewater

COD = 96, Cr = 99 Ramírez et al. (2019)

Peru

Hybrid

Tannery wastewater

BOD5 = 98, COD = 97, TSS = 97, TDS = 33

Zapana et al. (2020)

Malaysia

Subsurface-flow

Pulp and paper wastewater

COD = 66.1, SS = 87.2

Yusoff et al. (2019)

Malaysia

Vertical surface-flow

Palm oil mill

COD = 62.2, TSS = Ujang et al. (2021) 88.1

Morocco

Vertical flow

Olive oil and municipal wastewater

COD = 91

Ghadraoui et al. (2020)

Nigeria

Vertical subsurface flow

Petrochemical

BOD = 68, COD = 65, TDS = 54

Mustapha et al. (2015)

Thailand

Vertical surface-flow

Swine wastewater

BOD = 94

Klomjek (2016)

India

Hybrid

Dairy farm wastewater

BOD = 98.3, TSS = Sharma et al. (2021) 97.9 (continued)

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Table 1 (continued) Country

Type of CW

Source of wastewater

Removal efficiency (%)

References

Argentina

Horizontal sub-surface flow

Dairy farm wastewater

BOD = 57.9, COD = 68.7

Schierano et al. (2020)

COD chemical oxygen demand, BOD biochemical oxygen demand, TSS total suspended solids, TDS total dissolved solids, Cr chromium removal efficiency

Fig. 2 Schematic representation of (a) free-floating, (b) submerged, (c) floating leaved, and (d) emergent macrophytes (Reproduced with copyright permission from Kataki et al. [2021], Elsevier, 2021)

4.2 Pretreatment Earlier, the condition of pretreatment was not considered necessary. But following the experience gathered over the years, preliminary and primary treatment of the wetland is performed before wastewater treatment. Preliminary treatment entails screening of coarse solids while primary treatment involves the eradication of heavier solids and reduction of organic matter. Septic tanks, stabilization ponds, and sedimentation tanks help in achieving primary treatment.

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Table 2 Common macrophyte species planted in CWs (Reproduced with copyright permission from Kataki et al. [2021], Elsevier) S. no.

Plant species

Type

Distribution

Area reported

Remark

1

Phragmites australis

Perennial, floating

Global

Throughout temperate and tropical regions

Most widely used macrophyte, Efficient for N, P, BOD, COD, organic removal, Metal tolerant, High biomass production, Highly invasive

2

Typha latifolia Typha angustifolio

Emergent, perennial

Temperate parts of the northern hemisphere, South Africa, America, Australia

Spain, Portugal, USA, Mexico, Greece, Italy

Suitable particularly for high organic matter and ammonia-N load, High biomass yield, Have suitable thermal properties, Metal tolerant, Invasive, Low methane flux

3

Lepironia articulata

Evergreen perennial, emergent

South pacific

Malaysia

High removal performance for BOD, COD, Available N, Suspended solid and turbidity

4

Cymbopogon citratus

Evergreen, emergent

Throughout South East Asia

India

High COD, TSS, TN, TP removal, Have Antimicrobial properties

5

Pennisetum purpureum

Perennial, emergent

Tropical

India, Thailand, China, India

High COD, TSS, TN, TP removal, Low nutrient requirement, Very high yielding

6

Pennisetum americanum

Emergent

Asia, Africa, USA

Thailand, China, Brazil

High fresh yield, High BOD, TN, COD, pH reduction, Have competitive uses

7

Vetiveria zizanioides

Emergent

Throughout South East Asia

Thailand, India, South Africa

High Cr removal efficiency, Suitable for TN, Ammonia, TSS, COD reduction, Fast growing (continued)

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Table 2 (continued) S. no.

Plant species

8

Type

Distribution

Area reported

Remark

Cyperus papyrus Perennial, emergent

Tropical

Thailand, High productivity, Peru, Uganda, better performance China, Italy for BOD, COD, Ammonia N, TP, Coliform due to adventitious roots, Low methane flux

9

Canna Indica

Emergent

In many tropical China, India, areas Vietnam, Denmark

High ROL, greater Fe plaque formation, tolerance high contaminant load, and better removal of TN, TP, and COD, high nutrient uptake capability and root activity in saline water

10

Potamogeton crispus

Perennial, submerged

Europe, Asia, North America

China

Enhance suitable bacterial proportion (ammonia oxidizing bacteria), high oxygenation capacity, High removal efficiencies of COD

11

Salicornia bigelovii

Succulent

America, South Asia, South Africa

China, UK, Iran, Israel

High salinity tolerant, suitable for high ammonia rich waste

12

Heliconia rostrata

Emergent

Tropical

Brazil, Denmark

Efficient for emergent pollutant removal (ibuprofen and caffeine compounds)

13

Eichornia crassipes

Free floating

Throughout the world

India, China, Sri Lanka, Brazil, Argentina,

Excellent accumulator of heavy metal Cd, Cu, Al, High productivity, Reported for emerging pollutant removal, Highly invasive (continued)

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Table 2 (continued) S. no.

Plant species

Type

Distribution

Area reported

Remark

14

Phragmites carca

Emergent

Throughout India, South Tropical and Africa, temperate region Pakistan

Suitable for BOD, COD, TN, TP removal

15

Colocasia esculenta

Perennial, emergent

Tropical

India, Colombia

Suitable for metal uptake

16

Typha domingensis

Perennial, emergent

Throughout temperate and tropical regions

India, Brazil, Argentina

High metal (Hg) accumulator, can be grown in metal contaminated waste, High productivity

17

Cyperus flabelliformis

Emergent

South East Asia, China, High ROL capacity Africa, Arabia Thailand, Iran and high nutrient removal capacity

18

Kandelia candel

Evergreen, mangrove

South Asia, South East Asia

China, Mexico, USA

Salinity tolerant, Toxicity resistant (Cd, Mn)

19

Arundo donax

Emergent

Southern USA

India, Morocco, Malaysia, Portugal, Italy, Greece

High biomass yield, High energy yield, high methane production, salinity tolerant, versatile crop with multiple applications

20

Scripus validus

Perennial, emergent

Throughout Asia, USA, Europe

USA, Mexico

High root and stem production, High ROL, not invasive, high tolerance to nutrients, Establish readily

21

Acorus calamus

Emergent

North temperate hemisphere and tropical Asia

China, Thailand

High O2 release from root, Effective for multiple contaminant removal, longer growth period, Tolerate high strength wastewater

22

Scirpus cyperinus

Perennial, emergent

USA, Europe

USA

High metal uptake, Highly invasive (continued)

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Table 2 (continued) S. no.

Plant species

Type

Distribution

Area reported

Remark

23

Cyperus alternifolius

Emergent

Global

Germany, Italy

Heavy metal phytoremediation, especially for Cu, as well as for Mn and Zn

24

Veronica serpyllifolia

Perennial, emergent

Global

China

Good Zn, Pb accumulator, high ROL and Fe plaque formation

25

Myriophyllum aquaticum

Submerged Global except or emergent Antarctica

China

Good N removal efficiency, High organic exudates release, Tolerate high strength wastewater, Endangered in some parts, Metal tolerant

26

Pistia stratiotes

Free floating

Pan tropical and subtropical

India, Nigeria, Cameroon, Pakistan, The Netherlands

Good accumulator of several heavy metals, Efficient in ammonia-N and TN removal, Enrich microbial growth

27

Leptochloa fusca Perennial, emergent

Global

Pakistan

High biomass, high growth rate, Good for metal removal, solid and organics

28

Eleocharis dulcis Emergent

South East Asia, China, Africa, Australia Australia, Malaysia

Good uptake of Fe and Mn, Reported to have significant Uranium uptake capacity

29

Juncus effusus

Emergent

Global

Tolerant to wet, dry condition, Reported for good removal efficiency for As and ibuprofen, Good P uptake capacity

30

Saggitaria latifolia

Emergent

Global

China, USA, Germany, New Zealand

Aggressive colonizer, High evapo-transpiration (continued)

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Table 2 (continued) S. no.

Plant species

Type

31

Scirpus pungens/validus

Emergent

32

Zizania latifolia

Perennial, Emergent

33

Cladophora

34

Distribution

Area reported

Remark

USA

Fast colonizer, Drought tolerant, High pollutant removal, High N removal

Global

China

High methane flux, Relatively lower nutrient removal, Invasive

Submerged algae

Global

China

Good for removal of Mn

Brachiaria mutica

Emergent

Tropical areas

Vietnam, Pakistan

Good for COD, BOD, Cr removal due to good plant endophyte interaction, Capable of growing fast under high N load

35

Najas guadalupensis

Submerged

USA

USA

Good for P uptake

37

Glyceria maxima Perennial, emergent

North temperate zone of Europe and Asia, USA

Czech Republic, Ireland, New Zealand, Poland

Halophytic, Can remove ammonia-N, Nitrate-N, organic-N, Ortho-P, High nutrient requirement and can thrive in eutrophic environments, Highly productive, arenchymatous, invasive

38

Phalaris arundinacea

Perennial, emergent

Wide (Europe, Asia, Africa, America)

Czech Republic, Newyork

High biomass yield, Good metal removal (Cr, Cd, Zn, Ni)

39

Miscanthus x giganteus

Perennial, terrestrial

Global

Germany, Italy

High energy yield, Biomass yield, Good uptake of Fe, Cu, Zn, Low evapo-transpiration, Low nutrient requirement (continued)

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Table 2 (continued) S. no.

Plant species

Type

Distribution

40

Bassia indica

Terrestrial

Western Israel Mediterranean to Eastern Asia

Salt tolerant, so good for salt phytoremediation, (Na, K)

41

Sarcocornia fruticosa

Emergent

Global (coastal saline habitat)

Portugal

Salinity tolerant, Suitable for high salinity wastewater such as tannery wastewater

42

Iris pseudacorus Perennial, emergent

North temperate zones to North America, Asia

Spain, Czech Republic, Mexico, China, Iran

Reported to remove silver nanoparticles, Good removal of TN, ammonia-N, nitrate-N, COD, High aeration, nitrification capacity

43

Acorus calamus

North temperate hemisphere and tropical Asia

China

Reported for petroleum containing wastewater, Good bacterial enrichment capacity, Grows well in high load (N) water, Longer growth period, High root aeration capacity

Emergent

Area reported

Remark

4.3 Configuration The configuration of a wetland influences its hydrologic features which in turn influences the pollutant removal process. An ideal CW cell should consist of graded bed slops for easy movement of water and facilitate self-draining. It should have the potential of varying operation water depth. The apposite length-to-breadth ratio of the CW system is a required condition. Also, an appropriate arrangement of flow distribution devices at the inlet and collection devices at the outlet of each cell is required.

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4.4 Inlet Structure, Feeding Arrangements, and Outlet Structures Inlet structures play an important role in uniform flow distribution in CW cells. Wetlands with large length-to-width ratio help in the proper utilization of the wetland area. Use of sawtooth weirs aid in the effective distribution of flow. However, these are expensive to construct. Outlets have similar structures as inlets. Outlets collect the effluent, prevent clogging, monitor the depth of water, and help in sampling and flow monitoring.

4.5 Vegetation Planting Vegetation planting is an important aspect as the CW will not perform efficiently till the vegetation is well established. The choice of plant species depends upon the source and components of the influent wastewater. It is ideal to select plants that would exhibit a high growth rate and have both horizontal and vertical root systems. The early spring season is the idyllic time for planting the most commonly used wetland species Phragmites and Typha.

4.6 Establishment of Vegetation The basic requirements for establishment of vegetation in CW are same as required by normal plants to grow. Water, nutrient, and light are the three major factors for the establishment of vegetation. While water and nutrients can be provided, light is a completely natural source. Fluctuating water level is not good for healthy vegetation cover. Too much water causes difficulties in the establishment of vegetation. Excess depth of water limits the availability of oxygen at their roots. Maintaining the level of water during the early growth period is extremely important. As the plants grow, their potential to carry oxygen to their root also increases. The water level can be increased accordingly. However, too much water should not be allowed till the plants grow to a certain height and have shoots with leaves above the water column.

5 Operation and Maintenance There is a very less number of operational factors that can be managed to influence the performance of a CW. The first and most important one is managing the level of water. This can in turn have an impact on residence time, macrophytes diversity and growth, and oxygen diffusion. Manually lowering the water level allows efficient diffusion of

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oxygen to wetland sediments and the roots of plants. This promotes plants growth. Another parameter than be controlled is flow rate. It can be controlled while treating municipal or industrial effluents. The methods used can be pretreatment, parallel wetland cells, and recirculation. Monitoring flow rate influences the hydraulic and pollutant loading. Flow rate can be reduced to control increasing loadings (Beharrell 2004). Maintenance of CWs involves the management of issues related to sediments, litter, vegetation, and breeding vectors. To maintain the hydraulic condition of wetland, built-up sediments should be eradicated. These sediments should be treated as polluted fill. Continuous deposition of heavy metals in sediments may lead to a reduced amount of these substances downstream. In wetlands treating mine drainage the concern is always regarding the bio-accumulation of toxins in the wetland food chain, ultimately affecting the fauna and human health. Another aspect of managing CWs is litter management. Litter screens can be used to remove a considerable amount of litter coming into stormwater wetlands. These screens should be cleaned periodically. If litters and debris are not cleaned regularly, these areas of wetland will show poor performance due to increased hydraulic pressure on macrophytes. Eradication of litter supports wildlife habitats. The third important step of management is to sustain the existence of preferred species of wetland plants. Monitoring the water level can help in maintaining plant diversity in the CWs. Reducing the level of water can help in the recovery of unhealthy plants. Removal of weeds and pests affecting the health of wetland plants can help in managing the wetland vegetation. Surface water CWs are breeding grounds for mosquitoes. The use of sprinklers, larvicides and regular draining of wetlands help to manage the population of mosquitoes. Algal growth should also be maintained. Use of algicides is not advised as it may pollute the water. While steps like reducing water stability, shading, and nutrient removal can be taken to control the algal growth (Beharrell 2004).

6 CW Biotreatment Kinetics To describe the degradation process in the CW, researchers have investigated the use of various kinetics modeling approaches such as first-order kinetics, the constant stirred tank reactor (CSTR), Monod kinetics, as well as Monod-CSTR kinetics. A previous study, for example, looked at the removal rates of TPH, BOD5 , NO3 -N as well as COD, from wastewater using CW planted with Eichhornia crassipes (Agarry 2018). Their results showed that the removal constant rates R2 for BOD5 , TPH NO3 N, as well as COD were in the range of 0.89 to 0.99 (Gajewska and Skrzypiec 2018). The estimated area-based first-order (K − C) along with the first-order (K − C∗) removal rate constants of BOD5 (k A ) in vegetated VSF-CW remained 0.12 and 0.16 md1, respectively (Agarry 2018). The area-based first-order (K – C)-CSTR removal rate constant was revealed to be 0.57 m per day, whereas the Monod-CSTR kinetics maximum removal rate (K max ) and multiple Monod-CSTR kinetics (K max ) in the vegetated VSF-CW were found to be 3.27 as well as 3.47 gm−2 day−1 , respectively.

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The k A (first-order K – C) and kA (first-order K − C∗) for COD removal in the vegetated VSF-CW were 0.07 and 0.11 m day−1 , respectively, while the k A (firstorder CSTR flow), K max (Monod-CSTR), and K max (multiple Monod-CSTR) were 0.21 m day−1 , 4.12 gm−2 day−1 , and 4.35 gm−2 day−1 , respectively. Previous research has shown that the first-order CSTR model is insufficiently precise to describe BOD5 and NO3 -N removal. The Monod-CSTR model, on the other hand, demonstrated a high match between the model and the test results (Saeed and Sun 2011). The mathematical model (J = k.C) can describe contaminant removal. The rate (k) is affected by wetland area, flow volume, and temperature. The rate coefficient denotes the rate of contaminant degradation (Saeed and Sun 2011). The second equation in Table 3 describes the relationship between degradation and constructed wetland inflow and outflow. The water flow in the constructed wetland cannot be described by either the Plug Flow (PF) or the Continuous Stirred Tank Reactor (CSTR) models (CSTR). The Tank-in-Series (TIS) model, which takes into account background concentration and the time effect on the process, has been found to be the best model for describing constructed wet lands (Gajewska and Skrzypiec 2018). To describe contaminant removal in wetlands, a single equation can be formed by combining non-ideal flow and background concentration (Saeed and Sun 2011). This equation is denoted by P − k − C∗, where P represents pollutant weathering, k represents first-order kinetics, as well as C∗ represents non-zero background concentration. Monod kinetics can be combined with CSTR to create a model that describes the relationship between inlet and outlet concentrations via the limiting substrate’s half saturation constant and maximum pollutant rates. Multiple Monod kinetics, which assumes multiple substrates that limit the rate of contaminant degradation, can be used to express the reactions in constructed wetlands. The kinetics equations in Table 3 can be used in the design of constructed wetlands.

7 Advantages, Limitations, and Future Prospects of a CW CWs are less expensive to build compared to other wastewater treatment techniques. Costs related to their operation and maintenance are also low. It is a periodic process. They provide shelter for many wetland organisms and add aesthetic value to open spaces. They can support water recycling sustainably. On the other hand, there are various limitations in their construction. They require a larger amount of land in comparison to conventional wastewater treatment systems. Its efficiency is comparatively low. Also, its efficiency may vary with seasonal changes. Due to such fluctuations in performance, the effluent quality might not meet strict quality standards at all times. Toxic chemicals hamper the biological components, which in turn affects the efficiency. Maintaining the water level in CWs is also challenging (Omondi and Navalia 2020). CWs can not only help in treating wastewater from different origins but also help to reduce the greenhouse effect. The plants in the CW can use carbon which is a major composition of greenhouse gases. CWs provide shelter to many plants,

q(Cin −Cout )(Cout1 +Chalf1 )(Cout2 +Chalf2 ) Cout1 Cout2

out = −K max ( CChalf + Cout )

Cin −Cout τ

K3 =

= e(−kt)

= e(−kv t)

Cout Cin

(C−C ∗ ) (Ci −C ∗ )

= e(−kA / q)

K 3 : maximum areal pollutant removal rate K 3 , g m−2 day−1 Chalf1 , Chalf2 : half saturation constant of limiting substrates Cout1 , C out2 : the outlet concentrations of limiting substrates

τ : hydraulic retention time C half : half saturation constant of limiting substrate K max : maximum pollutant removal rates

C: effluent concentration Ci: influent concentration C*: background concentration

K v : account for time C out : effluent concentration C in : influent concentration

q: is the hydraulic loading rate (m day−1 ) k A : the decomposition constant in m day−1

J: is the contaminant removal per unit area gm−2 day−1 C: contaminant concentration (gm−3 ) k: rate coefficient m day−1

J =k·C

Cout Cin

Parameters

Equation

_

Combination of Continuous Stirred Tank Reactor (CSTR) and Monod kinetics

Combination of non-ideal flow and background concentration (Pollutant weathering, first-order kinetics, and non-zero background concentration)

First-order equation (uses the hydraulic residence time (HRT, t)

First-order equation

_

Description

Table 3 Kinetics equations that are used in CWs. Reproduced with permission from Hassan et al. (2021) MDPI

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birds, and microorganisms. Many plants and animals have the potential to thrive in contaminated water and contribute toward the ecological cycle. CWs can also act as a source of renewable energy. Dry mass generated from CWs post-treatment of wastewater can yield around 170–360 L of methane per kilogram of it. Bioenergy produced from CW can be used as a replacement for fossil fuels. Integration of microbial fuel cells (MFC) into CW promotes its use for both wastewater treatment and energy production. More research work is needed to be conducted to evaluate the potential of macrophytes to interact with micro- and nano plastics along with endocrine-disrupting chemicals such as polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) (Hassan et al. 2021).

8 Conclusion CW is an environment-friendly, cost-effective technique that can be used for wastewater treatment. With proper design and planning, CWs have the potential to treat both organic and inorganic components present in wastewater from different origins. Halophytes and microorganisms assist in the wastewater reclamation process. However, there are several limitations associated with this process like the requirement of large surface area or inconsistent performance which needs to be addressed. More research should be done toward exploring its ability to treat emerging pollutants or wastewater harboring antibiotic-resistant bacteria.

References Agarry SE et al (2018) Biotreatment of petroleum refinery wastewater in vertical surface-flow constructed wetland vegetated with Eichhornia crassipes: lab-scale experimental and kinetic modelling. Environ Technol 41(14):1793–1813 Aregu MB, Asfaw SL, Khan MM (2021) Developing horizontal subsurface flow constructed wetland using pumice and Chrysopogon zizanioides for tannery wastewater treatment. Environ Syst Res 10(1):1–13 Beharrell M (2004) Operation and maintenance for constructed wetlands. Wetlands Ecosystems in Asia. Elsevier, pp 347–359 Dubey A, Sahu O (2014) Phragmites australis (Marsh Plant) as wastewater treatment material. Int J Agri Res Rev 1:48–55 El Ghadraoui A et al (2020) Treatment of olive mill and municipal wastewater mixture by pilot scale vertical flow constructed wetland. Desalin Water Treat 198:126–139 Engida T et al (2020) Analysis of constructed wetlands technology performance efficiency for the treatment of floriculture industry wastewater, in Ethiopia. J Water Process Eng 38:101586 Gajewska M, Skrzypiec K (2018) Kinetics of nitrogen removal processes in constructed wetlands. In: E3S Web of Conferences. EDP Sciences. García-Valero A et al (2020) Treatment of wastewater from the tannery industry in a constructed wetland planted with Phragmites australis. Agronomy 10(2):176 Gauss M, Ledent S (2008) Constructed wetlands: a promising wastewater treatment system for small localities. Word Bank Office, Lima, Peru.

196

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Gholipour A, Zahabi H, Stefanakis AI (2020) A novel pilot and full-scale constructed wetland study for glass industry wastewater treatment. Chemosphere 247:125966 Haddaji D et al (2019) A re-circulating horizontal flow constructed wetland for the treatment of synthetic azo dye at high concentrations. Environ Sci Pollut Res 26(13):13489–13501 Hassan I et al (2021) Wastewater treatment using constructed wetland: current trends and future potential. Processes 9(11):1917 Herouvim E et al (2011) Treatment of olive mill wastewater in pilot-scale vertical flow constructed wetlands. Ecol Eng 37(6):931–939 Hussain Z et al (2018) Treatment of the textile industry effluent in a pilot-scale vertical flow constructed wetland system augmented with bacterial endophytes. Sci Total Environ 645:966–973 Juwarkar A et al (1995) Domestic wastewater treatment through constructed wetland in India. Water Sci Technol 32(3):291–294 Kataki S et al (2021) Constructed wetland, an eco-technology for wastewater treatment: a review on various aspects of microbial fuel cell integration, low temperature strategies and life cycle impact of the technology. Renew Sustain Energy Rev 148:111261 Khan NA et al (2020) Horizontal sub surface flow constructed wetlands coupled with tubesettler for hospital wastewater treatment. J Environ Manage 267:110627 Klomjek P (2016) Swine wastewater treatment using vertical subsurface flow constructed wetland planted with Napier grass. Sustainable Environ Res 26(5):217–223 Milani M et al (2020) Treatment of winery wastewater with a multistage constructed wetland system for irrigation reuse. Water 12(5):1260 Mustapha HI, Van Bruggen J, Lens P (2015) Vertical subsurface flow constructed wetlands for polishing secondary Kaduna refinery wastewater in Nigeria. Ecol Eng 84:588–595 Omondi DO, Navalia AC (2020) Constructed wetlands in wastewater treatment and challenges of emerging resistant genes filtration and reloading. In: Inland Waters-Dynamics and Ecology, IntechOpen. Ramírez S et al (2019) Investigation of pilot-scale constructed wetlands treating simulated pretreated tannery wastewater under tropical climate. Chemosphere 234:496–504 Saeed T, Sun G (2011) Kinetic modelling of nitrogen and organics removal in vertical and horizontal flow wetlands. Water Res 45(10):3137–3152 Schierano MC et al (2020) Horizontal subsurface flow constructed wetland for tertiary treatment of dairy wastewater: removal efficiencies and plant uptake. J Environ Manage 272:111094 Schouten G, Glasbergen P (2011) Creating legitimacy in global private governance: the case of the Roundtable on Sustainable Palm Oil. Ecol Econ 70(11):1891–1899 Sharma PK et al (2021) Biopurification of dairy farm wastewater through hybrid constructed wetland system: groundwater quality and health implications. Environ Res 200:111426 Shepherd HL, Grismer ME, Tchobanoglous G (2001) Treatment of high-strength winery wastewater using a subsurface-flow constructed wetland. Water Environ Res 73(4):394–403 Stefanakis AI (2018) Constructed wetlands for industrial wastewater treatment. Sundaravadivel M, Vigneswaran S (2001) Constructed wetlands for wastewater treatment. Crit Rev Environ Sci Technol 31(4):351–409 Ujang FA et al (2021) Removal behaviour of residual pollutants from biologically treated palm oil mill effluent by Pennisetum purpureum in constructed wetland. Sci Rep 11(1):1–12 Vymazal J (2011) Constructed wetlands for wastewater treatment: five decades of experience. Environ Sci Technol 45(1):61–69 Vymazal J (2022) The historical development of constructed wetlands for wastewater treatment. Land 11(2):174 Yusoff MFM et al (2019) Performance of continuous pilot subsurface constructed wetland using Scirpus grossus for removal of COD, colour and suspended solid in recycled pulp and paper effluent. Environ Technol Innov 13:346–352 Zapana JS et al (2020) Treatment of tannery wastewater in a pilot scale hybrid constructed wetland system in Arequipa, Peru. Int J Environ Sci Technol 17(11):4419–4430

The Need for Auto-Tailored Wetlands for the Treatment of Untampered Wastes of Wineries and Breweries Bedaprana Roy , Debapriya Maitra , Bidisha Chatterjee, Pallab Ghosh, Jaydip Ghosh , and Arup Kumar Mitra

1 Introduction In today’s world environmental issue is an important factor. It is closely intertwined with the socioeconomic impact. Industries are placing more importance in creating eco-friendly or biodegradable waste products. The waste generated by industries is treated either mechanically or in a natural system to minimise the waste production before releasing them into the environment. One such industry is the winery and brewery industry in the food sector. The two most well known and consumable liquors are wine and beer. Every year 250 million hectolitre of wine and 1.34 billion hectolitre of beer is produced worldwide. Both the wineries and the breweries generate large amount of effluents at various stages of processing. These effluents have to be treated appropriately before releasing them into the natural environment to avoid any hazardous impact (Masi et al. 2018). A winery produces approximately 2 L of wastewater and an average of about 5– 10 g of chemical oxygen demand (COD) during manufacturing of 1 L of wine. The organic constituents of the wastewater from winery mainly consist of soluble sugar, high molecular weight compounds like phenol, lignin, various kinds of alcohols, recalcitrant and acids and tannins. Ethanol and sugars (like fructose and glucose) make up almost 90% of the organic matter. The wastewater produced depends on factors like grape variety and vinification condition. However, the phenolic content in wastewater of winery mainly consists of phenolic acids, anthocyanin, glycosides of flavonoids and catechins (Masi et al. 2018). A brewery produces wastewater in the range of 3–10 L while producing 1 L of beer. The wastewater contains high amount of organic from dissolved carbohydrates B. Roy (B) · D. Maitra · B. Chatterjee · P. Ghosh · J. Ghosh · A. K. Mitra Department of Microbiology, St. Xavier’s College (Autonomous), Kolkata, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. P. Shah (ed.), Recent Trends in Constructed Wetlands for Industrial Wastewater Treatment, https://doi.org/10.1007/978-981-99-2564-3_10

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and alcohol from waste beer. The suspended solids mainly consist of yeast, maize and malt. The raw material and the quantity of yeast determine the nitrogen and phosphorous content in the effluent. The effluent has a low heavy metal concentration along with acidic pH (Masi et al. 2018). The organised sector of the liquor industry has various techniques to treat the wastewater produced during the manufacture of wine and beer. They use various anaerobic as well as aerobic treatment procedures. If the effluent is directly released into the environment it can pose a serious threat to the sustainability. As we have seen earlier that the effluent contains high amount of organic waste. When these are released into the waterbody and wetland it enhances the biological oxygen demand (BOD). This in turn reduces the dissolved oxygen in the wetland waterbody. Thus making it susceptible for eutrophication. In India a large section of the unorganised wineries and breweries have no defined protocols and techniques for the disposal of their effluent. One way to solve this problem is the application of microbial bioremediation through auto-tailored or constructed wetlands. Wetlands are natural ecosystems that are home to various species of flora and fauna. Natural wetlands have various functions like groundwater enrichment, flood control, sediment trapping, heat storage and release and carbon dioxide absorption (Stefanakis et al. 2014). Nowadays, there has been a shift from natural wetlands to constructed wetlands. The primary reliance of a natural treatment system, on natural components or natural processes, for effluent treatment without the involvement of intensive external energy defines the constructed or auto-tailored wetlands. They have greater potential for exploitation of the different natural processes in a controlled and closed environment for benefit of mankind, cost efficiency and environmental utilisation. This has popularised the concept of constructed wetlands both in the scientific field and marketing field (Stefanakis 2016). The constructed wetlands have the potential to mimic and thereby enhance the function of natural wetlands. Although they have similar functions as natural wetlands yet they are ecologically more sustainable. These auto-tailored wetlands have a higher potential for flood control, biodiversity restoration and improvement of water quality (Ghermandi et al. 2010). In this chapter we will learn about the various nature of the effluents from wineries and breweries along with techniques for their environment friendly disposal. We will also see the harmful impacts of the improper disposal of the effluents. We will study about microbial remediation of the waste manufactured by wineries and breweries followed by the concept of auto-tailored wetland and its social, economic and environmental impact.

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2 Nature of the Effluents of Wineries and Breweries and Their Disposal Systems Wineries and breweries generate enormous amounts of waste which are largely disposed in agricultural fields and water bodies. The unorganised sector does not take care of the disposal systems or look into the sustainable ways of using the generated waste. Organic wastes are produced in large amounts such as the spent hops and malts. These can be easily reutilised as animal feed or for the enrichment of agricultural soils as they easily degraded (Table 1). The excessive amounts of waste generated is one of the principal challenges faced in this context. In India, small scale unorganised breweries are widely prevalent whose waste productions are not accounted for. For example, beer production can have various kinds of waste productions such as water, spent grains, spent hops, turb, yeast, caustic and acid cleaners and waste beer. All these wastes have high BOD values and total suspended solids. Their chemical compositions, presence of acids, alkalis, etc., make their disposal very complicated and of sincere concern (Fig. 1). As we understand from the figure, a small brewery which has the capacity of brewing 1,500 L of wine or beer thrice a week is expected to produce around 2 tons of just spent grains each week. This spent grain is subject to microbial spoilage that doesn’t only pollute the soil but also the water bodies surrounding it. Management of these wastes especially by the unorganised sectors of the brewing industries is rarely achieved. The liquid wastes such as the washing water, yeast, cleaning chemicals and spoiled beer which are discharged together require vigorous processing before discharge into the environment.

2.1 Brewery Sludge One of the main components discharged from breweries that can directly spoil the water bodies and need proper treatment before its disposal is the “brewery sludge”. Though categorically the disposal of brewery sludge is much easier than most of the other components of winery waste, complications arise due to its varied composition. The components may vary widely with respect to pH that ranges from 2 to 10 and Table 1 The generalised composition of brewery wastes (Thomas and Rahman 2006) Types of waste generated

Solid wastes per cent (w/w)

Carbon content (% Dry solids)

Nitrogen content (% Dry solids)

C/N ratio

Brewery sludge

16

36

7

5

Brewery Spent Grain (BSG)

24

53

2

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Yeast

10

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Fig. 1 Wastes generated from production of beer

prohibits its direct discharge into the environment. A huge variation is also observed regarding the suspended solids parameter which can range from 0 to 2,500 mg per litre. The COD levels might also be as high as 6,000. Treatment of these sludges involves a trickling filtration process that constitutes of 3 segments. First a screening tank, second a settling tank and third a digester that can be anaerobic or aerobic in nature. The digesting tank will contain the materials that are digested organically which mix them soluble in water and thus ready for discharge into the environment (Driessen and Vereijken 2003). Though these processes are carried out in the authorised unorganised sectors of the winery and brewery industries across India, little or no information is available so as to throw light upon waste treatment and disposal of these industries in the unorganised sectors. Dumping of the brewery waste sludge in landfills is a commonly observed process of waste disposal but is not environment friendly. The main reason behind it being the change in the physicochemical properties of the soil such as salinity, pH, C/N ratio, etc., around the landfill may greatly hamper agricultural activities (Thomas and Rahman 2006).

2.2 Brewery Solid Waste The solid waste from the wineries and breweries mainly includes the spent grain that mostly contains residual sugars, proteins, vitamins and minerals that make them very high in the nutrient content. These wastes can be utilised in the agricultural sector as

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animal feed and fertilisers for the soil There have been numerous studies, depicting enhanced plant growth when brewery spent grains were applied to agricultural soils (Stocks et al. 2002).

2.3 Distillery Wastewater The nature of the wastewater depends on the kind of wine or alcohol being produced because of the specificity of the raw materials. It has been observed that almost 88% of the used molasses end up to be wastes. Cane molasses used as a substrate for wine production contain compounds of low molecular weight such as lactic acid, acetic acid, ethanol, glycerol, etc. Generally, effluents from distilleries have brown coloured and acidic nature and the organic substance content is based on the raw materials used. The pH values range from 3.5 to 5.0 which are harmful for various life forms. The distillery water also has recalcitrant properties due to the existence of melanoidins which also in port the characteristic brown colour to the effluents. These compounds are also known to have antioxidant properties which have negative impact in the treatment process of these effluents. Sugarcane molasses-based distillery effluents contain sodium (500 ppm), potassium (2,500 ppm), magnesium (98 ppm), manganese (259 ppm), zinc (273 ppm), copper (396 ppm) and some other heavy metals. They are also rich in different types of sugars, total sugar content approximately being 2.8%. Melanoidines in the cane molasses are polymers that have both low to high molecular weights which are products of a non-enzymatic browning reaction called the Maillard reaction amongst reducing sugars and amino compounds. Melanoidins are not easily degraded as their structures are also not completely known. 6 to 7% Melanoidins degradation is achieved during the conventional effluent treatment processes (Gonzalez et al. 2000) and almost no degradation occurs when it comes to the unorganised sector of these industries. The antioxidant properties of these compounds have a toxic effect on the microbes carrying out their degradation. Apart from this, the effluents also contain colour imparting chemicals such as caramels, phenolics and even melanins. Cane molasses contain more phenolics whereas beet molasses has higher melanin content (Godshall 1999). The distillery wastewater also contains polyphenol compounds that are extremely toxic in nature and resist biodegradation of these winery effluents due to their antibacterial potential. Polyphenol concentrations in the winery wastewaters maybe as high as 474 mg per litre. Removal of these polyphenolic compounds is of prime importance when it comes to the effluent treatment as they pose serious threats to human health. Human beings exposed to around 1,300 mg per litre of polyphenolic compounds can show symptoms of diarrhoea, mouth sores, dark urine, etc. These effluents also contain certain sugar decomposition products such as tannins, anthocyanins and certain xenobiotic compounds (Pandey et al. 2003). The unpleasant odour in the effluents is mainly contributed by the organic compounds such as indoles, skatoles

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and even some sulphur compounds (Garg and Sharma 2016). Disposal of these effluents produced obnoxious smell and is extremely hazardous to human health with high pollution potential (Mahimaraja and Bolan 2004).

3 The Harmful Impacts of Inappropriate Disposal of the Effluents from the Local Wineries and Breweries The effluents from the Breweries and the Wineries generally consist of different types of organic compounds like sugar, starch, ethanol as well as varieties of other components which are enriched in nutrients. Although majority of them are biodegradable in nature still they can be a cause for different types of environment pollution. Many of the local breweries do not possess well designed and sophisticated effluent disposal systems as a result of which the incidence rate of pollution from these sectors is very high. When the effluents from the breweries and wineries are discharged into the water bodies it results in an increase in the Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD) as well as the amount of dissolved solids in the water. It makes the water unsuitable for drinking, irrigation, agricultural purpose, aquatic life and also poses a great risk to human health (Odigie 2014). In case of the Beer factories the wastewater consists of a large amount of suspended organic solid particles. Since the effluents contain high amount of nutrients so they can cause eutrophication if they get mixed in the water bodies which are near to the factories. This phenomenon mainly reduces the ecological balance in the water bodies. The transparency of the aquatic system reduces to a great extent because of the thick green scum due to heavy algal growth. The level of dissolved oxygen gradually reduces after the onset of eutrophication due to respiration of algae as well as decreased sunlight penetrance which ultimately leads to death of the fishes and other aquatic organisms. This gives rise to an anaerobic environment which favours the growth of different anaerobic microbes. The metabolism reactions in these microbes release different types of reducing gases like H2 S, Mercaptan, CH4 and NH3 which reduce the quality of the water in terms of taste and smell. Several toxic compounds are secreted by the algal members which can cause inflammation in the Gastrointestinal tract in humans and cattle if they consume the water directly (Qin 2018). Not only the water bodies but also the soil of a particular region gets affected where the effluents are discharged off. Sometimes these effluents contain traces of toxins which get mixed with the soil. These harmful chemicals are directly absorbed by the plants and they get accumulated in the plant tissues which not only affect the plant but also a threat to the livestock and humans who depend on them. The activity of the microorganisms present in the soil also gets hampered due to the toxic chemicals present in the effluents (Chukwuma and Anayo 2020). The brewery effluents contain significant concentrations of heavy metals like Pb, Cu, Cd, Co, Ni, Zn, Cr which leads to deterioration of river water (Ipeaiyeda and Onianwa 2009).

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In Asia and South America, the production of ethanol from the cane sugar molasses constitutes a major industry. From these industries the most complex and troublesome effluent that is discharged is known as Spent Wash. It is highly organic in nature and constitutes around 12–15 times of the volume of the alcohol produced. It has got high values of BOD and COD (Aishwarya et al. 2014). So, when these types of effluent get mixed in the water bodies it becomes highly polluted. In a case study the physicochemical properties of the effluent from Mohan Meakin Breweries Ltd. Ghaziabad, Uttar Pradesh, India was studied along with its effects on soil and the crops like pea and wheat. It was found that the effluent was acidic in nature and had high levels of BOD and COD. It was recorded that when 100% of the effluents were used in the fields the germination rate of wheat and pea were restricted to 90% and 80% respectively. The germination rate became better when the amount of effluents was reduced to 50% and 25% (Shivajirao 2012). This study clearly indicates that the yield of the crop plants reduces to a great extent because of the effluents. It has been widely seen that whenever the effluents are discharged in the fields they percolate through the soil and pollute the groundwater. Begum (2008) mentioned that high concentrations of sodium in the effluents of the brewing industry lead to the pollution of the groundwater since the effluents easily reach to the water level by means of leaching. Disposal of distillery effluents on land has been found to be extremely hazardous to soil health and vegetation. Some reports suggest decrease in the rates of seed germination and complete inhibition of germination as well. They may also cause deficiency in the amount of soil manganese and damage in agricultural crops (Agrawal and Pandey 1994). In a study with Vigna mungo, distillery effluent even at concentrations as low as 5% (v/v) cause inhibition in seed germination and stunted growth (Kannabiran and Pragasam 1993). Protein and carbohydrate content in the seeds and activities of significant enzymes such as alkaline phosphatase, and ATPase also decreased considerably. Disposing these effluents in the soil without keeping track can have detrimental effects on the groundwater. Alterations can occur in the physicochemical properties (EC, pH, etc.) of the groundwater due to leaching of organic and inorganic compounds can make it unfit for use (Jain et al. 2005). Seed germination was seen to decrease in five crops, in a study by Ramana et al. (2002) when subjected to increasing concentrations of the effluents (Patel and Jamaluddin 2018).

4 Microbial Remediation of the Wastes of Wineries and Breweries and the Concept of Auto-Tailored Wetlands Alcohol production and subsequent wastewater generation have been turning into a major global concern for the past few decades. This comes with a special concern for India, as reportedly, India is the second largest producer of alcohol in Asia, and

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that too, based on the accounted distillation sectors of the country. As per the reports of Patel and Jamaluddin (2018), the accounted distillation sector of India has around 319 distillation units with a production capacity of around 3.25 billion litres of liquor. And as for the unaccounted distilleries in India, the numbers are expected to grow far higher. A report from the central pollution control board placed the accounted distilleries as one of the top 17 polluting industries. Again, it does not need special mention that if the unaccounted sectors are added even roughly, the figures would increase exponentially. The wastewater generated from wineries and breweries contains a rich cocktail of tannins, complex carbohydrates, polysaccharides and proteins in an aqueous mixture along with various phenolic compounds, colouring agents, acids like citric, tartaric, lactic, malic, acetic, etc., microbes and yeasts. Reports from Mahajan et al. (2010), state that pollutants generated from the production of 1 m3 wine are equivalent to the daily sewage waste production of 100 person. In the wastewater generating arena, brewery is another sector that takes the lead. It is roughly estimated that around 3–10 L of waste effluent are generated for the production of 1 L of beer (Simate et al. 2011; Braeken et al. 2004). Normally, the wastewater from breweries and wineries is discharged directly into various nearby water bodies or sometimes into municipal sewage canals. Pre-treating the effluents before draining them into sewage systems has been practised recently in some places, while, some distilleries have their own wastewater treatment plants. But when it comes to the unaccounted breweries and wineries of the country, the presence of such an effluent disposal system seems to be a pretty farfetched idea. This is where the concept of constructed wetlands and utilisation of the microbial inhabitants of the ecosystem for bioremediating the wastewater effluents come to play. Wetlands, also known as nature’s kidney, are areas where anaerobic conditions are developed and used for remediation or filtration of various pollutants by soil saturation over a long period of time. Constructed or auto-tailored wetlands are engineered wetland ecosystems that are used for effective remediation of various effluents. In fact, a number of different processes undergo in these constructed wetland systems which lead to the successful remediation of effluents, like, increased sorption, hydrolysis of various kinds, microbial and macrophytic filtration, oxidation of ionic and metallic compounds, precipitation, iron chelation or binding of oxides of Fe, etc. (Hussain et al. 2018). For constructing auto-tailored system in effective removal of winery and brewery effluent, a critical role would be played by the plant–microbial interaction taking place in the wetland ecosystem. Apart from that, the flow of water, the nature of soil and the kinetics of surface flow are also a few of the other major factors in determining the rate of remediation by constructed ecosystems. Generally, auto-tailored wetlands are categorised according to various criteria like, hydrologically subsurface flow and surface flow types, macrophytic free-flowing, submerged or emergent type (as per Brix 1994 classification), and as per flow path, horizontal and vertical type. The surface flow auto-tailored wetlands are characterised by their dense vegetation and typically have a water depth of around 0.4 m. Sometimes open water flow sources are also incorporated into these models. However, in these cases, care should be taken to maintain optimal hydraulic levels and enhance wildlife balance. Normally a hydraulic

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Fig. 2 A diagrammatic representation of the different parameters of auto-tailored wetlands and their construction

loading rate of 0.7 and 5.0 cm. d–1 is maintained in a regular constructed surface flow auto-tailored wetland (Fig. 2). The main advantage of using a surface flow model is that it is extremely simple in its design and it is low in its operational costs. However, it requires a large land area, and is greatly affected by various physical parameters like temperature, flocculation, odour, mosquito infestations etc. (Hassan 2021). Again, the subsurface flow model of the auto-tailored wetland is based on the Seidel (1967) engineering model. This type of model is prevalent in many European countries and is gaining fame worldwide. Here, first a bed of soil or gravel is placed, which is utilised by the rooted emergent plants as a substrate. Here, by mechanical force or by the action of gravity, the water flows either horizontally or vertically. In the bed substrate, the mechanically flowing wastewater is treated by a range of facultative microorganisms, especially the rhizospheric microbes living on the root surface of the macrophytes. Generally, in these types of wetland models, the bed depth ranges between 0.6 and 1 m while the bed strata bottom is slanted in a way to minimise any overlanding of water flow. According to Hassan et al. (2021), the design of this type of wetland model is kind of complex, and requires sedimentation units like pumps and tanks. However, the advantage of this setup is that it requires much less area than a surface model. It also has more sorption sites, greater tolerance of temperatures, especially cold, less odour, less pest infestation and fewer clogging issues than a surface setup (Fig. 3). The role played by aquatic macrophytes in constructed wetland remediation is immense. Based on their morphology and physiology, Vymazal et al. (1998) categorised these macrophytes into three subclasses, which are:

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Fig. 3 Aerobic and anaerobic digestion by the microbial communities in subsurface flow autotailored wetland model

• The emergent macrophytes like Acorus calamus, Typha latifolia growing on saturated soil or in submerged soil conditions with a water level of around 0.5 m below the surface and having a rich sediment deposition near the roots with a water covering of at least 1.5 m. • The freely floating leaved macrophytes comprises of plant species like Nymphaea odorata, and Nuphar lutea where the plant roots are submerged in sediment and shallow waters of depth range nearing 0.5–3 m. These kinds of free-floaters have aerial leaves. The free-floater macrophytes are the ones that are not rooted to the soil bed at the bottom of the wetland. Examples of these kinds of macrophytes include Lemna minor, Spirodela polyrhiza and Eichhornia crassipes. • The last subclass comprises the submerged macrophytes, which are present all across the photic zones of the wetland and mostly comprise vascular angiospermic species. Plants like Myriophyllum spicatum, Ceratophyllum demersum are found in deeply constructed wetlands with a water depth of about 10 m and hydrostatic pressure as high as 1 atm. In these submerged macrophytic habitats, non-vascular algal growth like that from the group Rhodophyceae can be seen but on the lower limits of the photic zones, mostly up to a range of 200 m. Another type of constructed wetland model is the hybrid type model, where, a multistage system is employed for treating the waste effluents in different designated units. A common example for such of wetland model is where a specific unit has been designed for aerobic reactions, while other units are designated for anaerobic reactions (Saeed and Sun 2012). According to the nature of aeration or induced air flow in the wetland it can be either horizontal flow system or vertical flow system. Normally the auto-tailored wetlands are characterised by shallow water and slow water flow, however, the rate of water flow and increased retention time between the effluents

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plays a critical role in designing of the wetland model. The flow velocity is also critical as it provides the time for microorganisms to degrade or remediate contaminants from the effluent. The mechanism by which microbes, mainly in their consortial form, control the bioavailability incite two different school of thoughts. Some researchers believe in bacterial degradation of contaminants without any requirement for desorption (Ortega-Calvo et al. 2015). While others believe that the bacteria first desorb the contaminants and then degrade it (Biosurfactants Reports 2021). Therefore, while designing a wetland a careful measurement for all the parameters is extremely crucial. It needs to be kept in mind, that the efficacy of constructed wetlands varies with respect to various parameters like its location, the climatic conditions, the nature of effluents, water depth, nature of microorganisms and plant species used in the construct (Brovelli et al. 2011). Generally, to construct a surface flow wetland the basin slope is made between 3:1 and 5:1 while filling up the lower bottom with impervious media components. These setups have a retention time of 3 to 5 days. These models are ideal for a loading capacity of BOD and TSS 20–30 mg/L and 45– 50 kg/ha/day respectively. Again, subsurface flow models, which are more efficient in treating large molecular effluents (viz. brewery and winery wastewater), the range of loading capacity of BOD and TSS ranges around 7 to 16 g/m2 / day and 20 g/m2 /day. As per the hydraulic conductivity is concerned, it varies according to various studies. For a subsurface flow model, the range varies from 1,400–2,800 m/day to 1,000 m/day for the initial 30% stretch of the model. It should be mentioned here that with the ageing and continuous clogging of the water channels, the porosity of the system is drastically compromised (Ávila et al. 2014; Baptestini et al. 2017). For constructing a vertical flow system, the inflow needs to be passed through a filtration system which can be prepared by charcoal, clay, gravel, etc. In these setups temperature plays a pivotal role and their detention time can be changed effectively by altering the number of cells in operations for that day or by altering the water depth. For the horizontal flow setup, the system relies on flow of gravity. This type of flow system requires time to be fully functional and has a hefty reliance on the hydraulic setups. In this setup the water flow should be such that it is always above the surface of the bed layer of the wetland (Bakhshoodeh et al. 2017). In a horizontal flow model, care should be taken for the degradation of the top surface layer of the wetland so that it can profusely support aerobic degradation, while, the lower layers should support profuse anaerobic degradation (Al-Baldawi et al. 2013). The role of microorganisms in these wetland models is tricky. It is believed that the degradation and transformation of the contaminants is done by the microbes present in the wetland ecosystem. In case of the aerobic digestion system, the organic pollutants are the electron donors, while the oxygen in the auto-tailored wetland acts as the electron acceptor system. Therefore, in this process the pollutants are decomposed producing some daughter compounds of the original pollutants. The shallow flow of water in the wetland setup is an arena that enables smooth aerobic digestion by the microbes. Whereas the reverse scenario happens in case of anaerobic digestion. Here, the pollutant acts as the electron acceptor while the CO2 generated in the system acts as the electron donor. In these degradation reactions other organic compounds like nitrates, nitrites, sulphates or carbonates, etc., also act as electron acceptors. Some

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bacteria like Pseudomonas falva, Alcaligenes faecalis, etc., are known for aerobic denitrification. Strains like Albidiferax sp., Candidatus nitrosotenuis, Nitrosomonas sp., etc., are known for their nitrification properties (Hassan et al. 2021). The use of anaerobic digestion is in particular popular for the winery industry, as suggested by Dobelamnn and Müller (2000) due to the rich presence of organic content in the effluent. Again, use of specific plant species for targeted remediation of contaminants can also be practised in case of distillery effluents. For example, use of plants like Phragmites australis for reducing the TSS and COD of wastewater effluents or use of Brachiaria arrecta, B. mutica, etc., for effective in reduction of BOD, COD, nitrogen and phosphorus levels, etc., Scirpus validus in removal of benzoic acids and other halogenated organic compounds, Phragmites spp. for removing aniline, nitrobenzene, nitrophenols, sulphonilic acid and other aromatic compound, etc. The list of macrophytes and microbes in bioremediating large aromatic hydrocarbons is far and wide but the exact mechanism taking place within these auto-tailored wetlands is unknown. Few researchers have established the kinetics of these biotreatments and have proposed various phyto-kinetic models like the first-order kinetics model, or the CSTR model also known as constant stirred tank-based reactor model or the Monod kinetics model, or the combination of the CSTR and Monod model, etc. However, details of these models still require substantial research works. But it can be concluded that with the help of creating a successful auto-tailored wetland, the problem of effluent disposal can be minimised to a considerable extent.

5 The Impact of Auto-Tailored Wetlands for Remediation of Winery and Brewery Waste on the Social, Economic and Environmental Milieu Inappropriate management of wastewater is hazardous for both mankind and the environment. It can lead to the deterioration of the biodiversity, natural flexibility and the ability of nature to provide the basic needs of mankind. The industrial effluents of wineries and breweries leading up to 90% are directly discharged into the waterbody without any prior treatment causing eutrophication, a major global concern in today’s world. In developing countries like India wastewater management has to be done keeping in mind both the quality and the economic condition. The transfer of technology from developed countries to developing countries usually remains unsuccessful. Therefore, people are shifting to constructed or auto-tailored wetlands for wastewater management from industries (Moller et al. 2012). The application of constructed wetland in effluent treatment is more popular in developing countries. The treatment technology includes chemical, physical, natural and biological processes. They can easily adapt to the local environmental and climatic conditions. In comparison to the conventional technologies the auto-tailored wetlands require low financial investment, low operation and maintenance cost and do not require highly skilled operators (Moller et al. 2012).

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The social perception of auto-tailored wetland is crucial for its eventual application. The important criteria for social and environmental impact depends on the various principles and values that people correlate to natural environment. The proper identification of ecological and economic importance of a specific area helps in the successful utilisation of the natural ecosystem. It also depends on how these communities present in these areas create a balance between their social values and priorities. But it is possible that different values may have a relation with the environment. This includes aesthetics, biology, economics and recreation (Alikhani et al. 2021). Understanding the relation between environmental and social values helps to strategise regarding information exchange and incentive schemes (Sterner 2010). Environmental assessment is usually carried out irrespective of the social arrangement. However, people have learnt to maintain social rules for the restoration of the ecosystem along with their preservation (Alikhani et al. 2021). Wetlands in general provide us with various recreational activities. The financial gain obtained from these recreational activities can be easily used for the maintenance and conservation of wetlands. The activities include swimming, hiking, fishing and wildlife viewing (Moeltner and Woodward 2009). There are some people who visit these wetlands only because of the presence of the recreational activities and therefore they hold these wetlands in greater importance and show great respect for these nature-based ecosystems. Thus, recreational activities can motivate people to maintain the wetlands. Thus, wetlands are a source of financial gain because of the variety of recreational activities. It includes walking, swimming, trapping, bird watching and boating. The aquatic activities play hand in physical and mental health of people (Alikhani et al. 2021). Urban sustainability amidst urban development requires proper planning and management of natural resources. In certain areas, like constructed wetlands, these natural resources help in the improvement of the environment such as biodiversity increment, water quality improvement and climate change mitigation (McInnes 2014). Earlier wetlands have been destroyed for the expansion of cities. So it has become a matter of great importance to protect the natural resources of the wetlands (Davidson 2014). Wetlands have the potential to maintain the ecosystem. Thereby they are a natural solution to various challenges of the modern world such as social, economic and environmental (Thorslund et al. 2017). The East Kolkata Wetland is a Ramsar site. Aquaculture is practised in this wetland. The wetland is utilised for the treatment of industrial effluents which are then used for aquaculture and agriculture. So, the efficiency of the wetlands can be enhanced with proper planning. These wetlands are also used for flood control (Roy Basu et al. 2020). The above information helps us to conclude that constructed wetlands possess numerous properties that attach an ecological importance to the treatment of effluents. The two most important criteria for the treatment planning in constructed wetlands were low level of energy consumption and use of biodegradable resources (soil, plants, gravel and sand) for its making (Stefanakis 2016). Certain important criteria have to be taken into account for considering a technology as eco-friendly such as successful treatment, validity, absence of by-products, low consumption of energy,

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using renewable resources, recycling/reusing materials, negligible use of chemicals and environmental stability (Brix 1999). It should be a closed cycle resulting in the reuse of the materials for the sustenance of the environment. Another important aspect of environmental impact is the health sector. It is of utmost importance because it will determine the risk of exposure to various pathogenic microbes and hazardous chemicals. However, it has been observed that the constructed wetlands are capable of successfully removing microorganisms from the effluent (Stefanakis 2016). Constructed Wetlands have a low risk of ecosystem and aquatic life degradation due to efficient treatment procedures. Moreover, it is constructed with natural raw materials easily and globally available along with negligible amount of nonbiodegradable materials. Therefore, raw material generation does not enhance pollution. The facilities use minimum energy as mentioned earlier which saves natural resources since they are non-renewable. They produce very low level of green-house gases and therefore is not an issue for global warming (Stefanakis et al. 2014).

6 Conclusion In this chapter, we discussed about the conditions of the unorganised sector of the distillery industries and their enormous waste generation. A detailed study on the winery wastes makes its pollution potentially extremely prominent. Therefore, a solution to this particular problem lies in the construction of auto-tailored wetlands that can serve as a remedial mechanism not only for winery and brewery but can be modified to naturally remediate different types of wastes and effectively reduce pollution. Thus, justifying the name “auto-tailored”. Not only is this an efficient process, but it also has extremely low energy consuming solution to pollution remediation. Auto-tailored wetlands also cause no harm to aquatic ecosystems and use all biodegradable resources for its functioning. Thus it is an innovative solution for remediating pollutants without interfering with the natural ecosystem of a waterbody.

References Agrawal CS, Pandey GS (1994) Soil pollution by spent wash discharge: depletion of manganese (II) and impairment of its oxidation. J Environ Biol 15:49–53 Aishwarya P et al (2014) Impact of brewery industry effluents on soil enzyme activities. Int J Curr Microbiol App Sci 3(10):686–692 Al-Baldawi I, Abdullah SRS, Anuar N, Suja F, Idris M (2013) Performance assessment of pilot horizontal sub-surface flow constructed wetlands for removal of diesel from wastewater by Scirpus grossus. Water Sci Technol 68:2271–2278 Alikhani S, Nummi P, Ojala A (2021) Urban wetlands: a review on ecological and cultural values. Water 13:3301. https://doi.org/10.3390/w13223301 Ávila C, Nivala J, Olsson L, Kassa K, Headley T, Mueller RA, Bayona JM, García J (2014) Emerging organic contaminants in vertical subsurface flow constructed wetlands: influence of media size, loading frequency and use of active aeration. Sci Total Environ 494–495:211–217

The Need for Auto-Tailored Wetlands for the Treatment of Untampered …

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Bakhshoodeh R, Alavi N, Majlesi M, Paydary P (2017) Compost leachate treatment by a pilot-scale subsurface horizontal flow constructed wetland. Ecol Eng 105:7–14 Baptestini GCF, Matos AT, Martinez MA, Borges AC (2017) Hydraulic conductivity variability in horizontal subsurface flow constructed wetlands. Eng Agríc 37:333–342 Begum A (2008) Study on the quality of water in some streams of Cauvery River. E-J Chem 5(2):377–384 Biosurfactants-types. Sources and applications. https://scialert.net/abstract/?doi=jm.2015.181.192. Accessed 29 Aug 2021 Braeken L, Van der Bruggen B, Vandecasteele C (2004) Regeneration of brewery waste water using nanofiltration. Water Res 38(13):3075–3082 Brix H (1994) Functions of macrophytes in constructed wetlands. Wat Sci Techn 29(4):71–78 Brix H (1999) How green are aquaculture, constructed wetlands and conventional wastewater treatment systems? Water Sci Technol 40(3):45–50. https://doi.org/10.1016/S0273-1223(99)004 18-7 Brovelli A, Carranza-Diaz O, Rossi L, Barry DA (2011) Design methodology accounting for the effects of porous medium heterogeneity on hydraulic residence time and biodegradation in horizontal subsurface flow constructed wetlands. Ecol Eng 37:758–770 Chukwuma OH, Okpara DA (2020) Unsustainable management of wastewater and brewing effluents: the impacts on socioeconomy and environment, Lagos and Niger Delta region, Nigeria. E3S Web of Conferences. Vol. 211. EDP Sciences Davidson NC (2014) How much wetland has the world lost? Long-term and recent trends in global wetland area. Mar Freshw Res 65:934–941 Dreissen W, Vereijken T (2003) Recent developments in biological treatment of brewery effluent. The institute and guild of brewing convention, Livingstone, Zambia Garg UK, Sharma C (2016) Electrocoagulation: promising technology for removal of fluoride from drinking water—a review. Biol Forum Int J 8(1):248–254 Ghermandi A, Van den Bergh JCJM, Brander LM, De Groot HLF, Nunes P (2010) Values of natural and human-made wetlands: a meta-analysis. Water Res 46(W12516) Godshall MA (1999) Removal of colorants and polysaccharides and the quality of white sugar. In: Proceedings of sixth international symposium organized by association Andrew van Hook (AvH), Reims, 25 March 1999, pp 28–35 Gonzalez T, Terron MC, Yague S, Zapico E, Galletti GC, Gonzalez AE (2000) Pyrolysis/gas chromatography/ mass spectrometry monitoring of fungal biotreated distillery wastewater using Trametes sp. I-62 (CECT 20197). Rapid Commun Mass Spectrum 14:1417–1424 Hassan I Chowdhury SR, Prihartato PK, Razzak SA (2021) Wastewater treatment using constructed wetland: current trends and future potential. Processes, 9:1917. https://doi.org/10.3390/pr9 111917 Hussain F, Mustafa G, Zia R, Faiq A, Matloob M, Shah H, Raza A, Irfan J (2018) Constructed wetlands and their role in remediation of industrial effluents via plant-microbe interaction—a mini review. J Bioremediat Biodegrad 9:447. https://doi.org/10.4172/2155-6199.1000447 Ipeaiyeda AR, Onianwa PC (2009) Impact of brewery effluent on water quality of the Olosun river in Ibadan, Nigeria. Chem Ecol 25(3):189–204 Jain N, Bhatia A, Kaushik R, Kumar S, Joshi HC, Pathak H (2005) Impact of post methanation distillery effluent irrigation on ground water quality. Environ Mon Assess 110:243–255 Kannabiran B, Pragasam A (1993) Effect of distillery effluent on seed germination, seedling growth and pigment content of Vigna mungo (L.) Hepper (C.V.T.9). Geobios 20:108–112 Mahajan C, Narkhede S, Khatik V, Jadhav R, Attarde S (2010) Wastewater treatment at winery industry. Asian J Environ Sci 4(2):258–265 Mahimaraja S, Bolan NS (2004) Problems and prospects of agricultural use of distillery spentwash in India. Super Soil, 3rd Australian New Zealand Soils Conference, University of Sydney, 5–9 December 2004

212

B. Roy et al.

Masi F, Rizzo A, Bresciani R (2018) Treatment of wineries and breweries effluents using constructed wetlands. In: Constructed wetlands for industrial wastewater treatment, 1st edn, pp 95–104. https://doi.org/10.1002/9781119268376.ch4 McInnes RJ (2014) Recognising wetland ecosystem services within urban case studies. Mar Freshw Res 65:575–588 Moeltner K, Woodward R (2009) Meta-functional benefit transfer for wetland valuation: making the most of small samples. Environ Resour Econ 42:89–108 Moller KA, Fryd O, Neergaard AD, Magid J (2012) Economic, environmental and socio economic sustainability of three constructed wetlands in Thailand. Environ Urban 24(1):305–323. https:// doi.org/10.1177/0956247811434259 Odigie JO (2014) Harmful effects of wastewater disposal into water bodies: a case review of the Ikpoba river, Benin city, Nigeria. Trop Freshw Biol 23:87 Ortega-Calvo J-J, Harmsen J, Parsons JR, Semple KT, Aitken MD, Ajao C, Eadsforth C, GalayBurgos M, Naidu R, Oliver R et al (2015) From bioavailability science to regulation of organic chemicals. Environ Sci Technol 49:10255–10264 Pandey RA, Malhotra A, Tankhiwale S, Pande S, Pathe PP, Kaul SN (2003) Treatment of biologically treated distillery effluent—a case study. Int J Environ Study 60:263–275 Patel S, Jamaluddin (2018) Treatment of distillery waste water: a review. Int J Theor Appl Sci 10(1):117–139 Qin R (2018) The characteristics of beer industrial wastewater and its influence on the environment. IOP Conf Ser Earth Environ Sci 170(3). Ramana S, Biswas AK, Singh AB (2002) Effect of distillery effluent on some physiological aspects of maize. Biores Technol 84:295–297 Roy Basu A, Bharat GK, Chakraborty P, Sarkar S (2020) Adaptive co-management model for the East Kolkata wetlands: a sustainable solution to manage the rapid ecological transformation of a peri-urban landscape. Sci Total Environ 698:134203 Saeed T, Sun G (2012) A review on nitrogen and organics removal mechanisms in subsurface flow constructed wetlands: dependency on environmental parameters, operating conditions and supporting media. J Environ Manag 112:429–448 Seidel K (1967) Über die Selbstreinigung natürlicher Gewässer. Naturwissenschaften 63:286–291 Shivajirao PA (2012) Treatment of distillery wastewater using membrane technologies. International Journal of Advanced Engineering Research and Studies 1(3):275–283 Simate G, Cluett J, Iyuke S, Musapatika E, Ndlovu S, Walubita L, Alvarez A (2011) The treatment of brewery wastewater for reuse: State of the art. Desalination. https://doi.org/10.1016/j.desal. 2011.02.035 Stefanakis AI (2016) Constructed wetlands: description and benefits of an eco-tech water treatment system (1st ed.). IGI Global, pp 281–303 Stefanakis AI, Akratos CS, Tsihrintzis VA (2014) Vertical flow constructed wetlands: ecoengineering systems for wastewater and sludge treatment, 1st edn. Elsevier Publishing, Amsterdam Sterner, T (2010) Policy instruments for environmental and natural resource management. Routledge Stocks C, Barker AJ, Guy S (2002) The composting of brewery sludge. J Inst Brew 108:452–458 Thomas KR, Rahman PKSM (2006) Brewery wastes. Strategies for sustainability: a review. Asp Appl Biol 80:147–153 Thorslund J, Jarsjo J, Jaramillo F, Jawitz JW, Manzoni S, Basu NB, Chalov SR, Cohen MJ, Creed IF, Goldenberg R et al (2017) Wetlands as large-scale nature-based solutions: status and challenges for research, engineering and management. Ecol Eng 108:489–497 Vymazal J, Brix H, Cooper P, Haberl R, Perfler R Laber J et al (1998) Removal mechanisms and types of constructed wetlands. Backhuys

Horizontal Subsurface Flow Constructed Wetlands for Toxic Pollutants Removal L. E. Amábilis-Sosa , A. Roé-Sosa , J. M. Barrera Andrade, A.d. C. Borja-Urzola , and M. G. Salinas-Juárez

1 Introduction Constructed wetlands are flooded systems that mimic natural processes occurring in a natural wetland but under controlled conditions. One of the major applications of constructed wetlands is wastewater treatment, due to the physical, chemical, and biological mechanisms that favor the pollutants degradation and their subsequent removal from water. The high level of control enables researchers and engineers to modify the treatment facilities, defining the package media, vegetation, size, location, retention time, hydraulic pathways, and flow pattern (Vymazal and Kröpfelová 2008). Indeed, there are two types of constructed wetlands according to the flow direction: vertical flow constructed wetlands (VFCW) and horizontal flow constructed wetlands (HFCW). Each has specific features, which are considered for specific purposes. L. E. Amábilis-Sosa CONACyT - Instituto Tecnológico de Culiacán, Juan de Dios Bátiz 310, C.P. 80220, Culiacán Sinaloa, Mexico A. Roé-Sosa Universidad Tecnológica de Culiacán, Carretera Imala Km 2, C.P. 80014, Culiacán Sinaloa, México J. M. B. Andrade Lab.Catálisis y Materiales, ESIQIE–Instituto Politécnico Nacional, Zacatenco, 07738 Mexico City, Mexico A.d. C. Borja-Urzola Facultad de Ciencias Básicas Y Biomédicas, Universidad Simón Bolívar, Carrera 59 # 59-65, Barranquilla, Colombia M. G. Salinas-Juárez (B) Facultad de Estudios Superiores Zaragoza, Universidad Nacional Autónoma de México, Batalla 5 de mayo, Esquina Fuerte de Loreto, Col. Ejército de Oriente, Iztapalapa C.P. 09230 Mexico City, Mexico e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. P. Shah (ed.), Recent Trends in Constructed Wetlands for Industrial Wastewater Treatment, https://doi.org/10.1007/978-981-99-2564-3_11

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For instance, it is considered that vertical flow promotes the aerobic process, while horizontal flow supports the anaerobic/anoxic mechanisms. In HFCW wastewater flows horizontally, from the inlet until the outlet zone, through a filter formed by gravel, sand, or rock. Emergent plants, knowns as macrophytes, are planted in the bed. Since the horizontal flow constructed wetland is a subsurface wetland, the water level is conserved below the Surface. The saturated condition in HFCW predominantly generates anaerobic processes; the contact of wastewater with the matrix material and with the biological components, such as plant roots and biofilm, leads to the degradation and subsequent removal of a variety of pollutants, for example, organic and inorganic toxic compounds (Hussain et al. 2019; Langergraber et al. 2017). The mechanisms responsible for removal are chemical and biochemical interactions, and physical, such as filtration and sedimentation. In this way, the diverse physicochemical properties in a wetland affect concurrently the removal of pollutants from wastewater. These properties are oxygen concentration, temperature, pH, ionic strength, pollutants concentration and their chemical nature, carbon and nutrients availability, and the number of electron donors, as well as redox mediators (Masi et al. 2019). Among these properties, pH value, ionic strength, and oxidation–reduction potential in soil are affected by flooding. Soils can experience a buffer effect from substances produced as a result of reduction reactions in inundation, and a temporary increase of ions concentration might be obtained with flooding. Redox potential is associated with oxygen concentration and transport, including diffusion from the atmosphere through the layers of soil, chemical consumption, and their release from roots in wetlands. Redox potential indicates the electron availability in the wetland, which is related to the availability, interaction, and reactions among the chemical species in the media, losing and gaining electrons. Consequently, redox potential expresses if the soil or aquatic environment tends to reduce or oxidize substances (Vymazal and Kröpfelová 2008; Shah 2020). Ionic strength, pH, and redox potential are key factors for the chemical transformations, precipitation, adsorption to soil particles, assimilation by the plant tissue, and microbial transformations taking place in HFCW (Vymazal and Kröpfelová 2008; Langergraber et al. 2017). Constructed wetlands, mainly horizontal, have been investigated and used for water treatment for more than fifty years. Over time, components, materials, configuration, and operational conditions have evolved, significantly improving the efficiencies obtained. Nowadays, the elimination of an extensive range of pollutants has been studied successfully in constructed wetlands. This chapter aims to exhibit the capacity of horizontal subsurface flow constructed wetlands for the treatment of toxic compounds by displaying several investigations performed successfully on this topic. Therefore, this chapter provides basic and general information about the main removal mechanisms occurring in HFCW for recalcitrant organic compounds elimination (pesticides, pharmaceuticals, dyes), heavy metals, and acid mine drainage. Finally, a future technical perspective in this field of constructed wetlands is given.

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2 Performance of Horizontal Subsurface Constructed Wetlands for Toxic Organic Compounds Toxic organic compounds include various types of chemical substances such as pharmaceutical and personal hygiene products, pesticides, microplastics, endocrine disruptors, dyes, etc. Many of these substances are considered as emerging pollutants, which indicates that environmental regulations are inexistent or scarce compare with other pollutants. However, their persistence, contribution to environmental deterioration, and human health are currently under investigation (Ahmad et al. 2022). Due to the technological advances developed in the recent decade about preconcentration of contaminants at trace levels, the analytical instrumentation has made it possible to detect their presence in surface and groundwater (Borrull et al. 2020; Valenzuela et al. 2020). The origin of pharmaceutical, agricultural, and dyes compounds is attributed to domestic sewage, wastewater from hospitals and pharmaceutical manufacturers, agricultural wastewater, and industrial effluent, respectively (Li et al. 2014; Shah, 2021; Ravikumar et al. 2022). The persistence and mobility of organic compounds in the environment, as well as in wetlands, depends on their chemical and physical properties: distributions constant (KD ), octanol–water coefficient (Kow ), solubility, Pka, and molecular mass. It has been reported that toxic organic compounds with a molecular mass greater than 358.60 g/mol tend to resist the removal process (Ravikumar et al. 2022; Yan et al. 2022). In addition to the chemical structure, bioavailability affects the removal efficiency of organic compounds by HFCW. Pharmaceuticals and pesticides are normally found in low concentrations in domestic, hospital, and agricultural water, and therefore the microbes can have problems with using these substrates (Tran et al. 2013). The following sections discuss a little about the main mechanisms that occur in HFCW when they are used to remove pharmaceutical compounds, pesticides, and dyes.

2.1 Pharmaceutical Compounds In literature, the main pharmaceutical contaminants that have been studied and removed using HFCW are diclofenac, ibuprofen, ketoprofen, naproxen, salicylic acid, sulfamethoxazole, triclosan, atenolol, clofibric acid, and carbamazepine (Carranza-Diaz et al. 2014; Delgado et al. 2020; Jing et al. 2021; Lancheros et al. 2019; Zhang et al. 2018). The HFCW has been less efficient in the removal of ibuprofen and amoxicillin (Li et al. 2014). The high organic load in the domestic, hospital, and agricultural waters can explain the limited removal of the organic compounds in wetlands, in special pharmaceutical compounds. This can be attributed to the increased oxygen consumption by the system and the prevalence of reducing conditions (Carranza-Diaz et al. 2014). The

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interactions between abiotic components improve the sorption mechanisms in the HFCW. It has been reported that the sorption mechanisms between pharmaceutical compounds and package media involve physical interactions such as dipole–dipole, Van der Waals forces, hydrogen bonds, and ion exchange processes. These interactions depend on the pH and other conditions in the wetland (Dordiov and Carvalho 2013). For example, Carranza-Diaz et al. (2014) reported that carbamazepine can be removed using HFCW by hydrophobic interactions with the package media (π–π interactions, electrostatic forces, and others) and aerobic degradation, and Delgado et al. (2020) reported that the main mechanism to remove recalcitrant compounds, like carbamazepine, is the bacterial biodegradation. Other parameters that have been reported to affect the efficiency of the HFCW are the specific area of package material and plants. It is because the high specific area may favor the sorption of pharmaceutical compounds and the microbial community growth (Carranza-Diaz et al. 2014; Jing et al. 2021; Rajan et al. 2019). The greater removal of pharmaceutical compounds is related to high temperature and strong solar irradiation in summer. In consequence, environmental conditions are another factor that affects the performance of the wetland (Dordio et al. 2010; Li et al. 2014). The environmental conditions in summer improve the growth of plants and the development of microbial activity in the rhizomes (Zhang et al. 2018). The most frequently used vegetation is Typha ssp. and Phragmites spp. In the case of Typha ssp., some organic compounds with Log Kow between 0.5 and 3 can pass through cell membranes and move into and within plant tissues by diffusion (Dordio et al. 2011). Delgado et al. (2020) removed carbamazepine and sildenafil using a planted polyculture macrophytes and grave. The plants used were Heliconea Zingiberales and Cyperurs Haspan. The carbamazepine and sildenafil were removed with 97% of efficiency. So, the macrophytes played an active role in the elimination of pharmaceutical compounds with Kow less than 2.75 and the planted polyculture promotes a grader microorganism diversity. Pharmaceutical compounds, like sildenafil and carbamazepine, show an affinity for the package media. For this reason, the principal removal mechanism is sorption. In this way, the sorption allows long retention of the compound, and the plants and microorganisms can biodegrade it. The removal of pharmaceutical compounds can be affected by the additional release of electron donors and oxygen from the plant roots. For this reason, plant depth is important if the aim is the prevalence of reductive conditions in the HFCW (Carranza-Diaz et al. 2014).

2.2 Pesticides Pesticide distribution, in the different components of the CWs (water, package media, and plants), is a complex process affected by the physicochemical properties of the pesticides (Dordio and Carvalho 2013; Wu et al. 2017). In addition, the solubility, the octanol/water distribution coefficient (Kow ), and the soil/water distribution coefficient

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(Koc ) can determine the performance and removal efficiency of the CWs (Vymazal and Bˇrezinová 2015). The physical and chemical properties of pesticides and the porosity of package media are the main parameters affecting the adsorption of pesticides in CWs. The zeolite addition as a package media increases the fluopyram absorption on porous media by 72% (Parlakidis et al. 2022). Pesticides can be removed from CWs by sedimentation, photolysis, hydrolysis, adsorption, microbial degradation, and plant absorption; therefore, it is important to optimize the removal process to achieve a synergy between all CWs components. In HFCW anoxic or anaerobic conditions prevail due to the position of the package media. The water level remains below the surface and the aeration is limited, because of this there are no conditions to occur photolysis (Papaevangelou et al. 2017b; Parlakidis et al. 2022). In HFCW hydraulic plays an important role, especially the hydraulic retention time (HRT), because it determines the retention of the pesticides on the plants or packages media. A prolonged residence time improves the effectiveness of sedimentation and sorption processes because is possible that the sedimentation of suspended solids and biofilms formation increase (Romain et al. 2015; Vymazal and Bˇrezinová 2015). Pesticides can be removed by plant uptake and by sedimentation or/and adsorption on package media (Parlakidis et al. 2022). Plants have a positive effect on the removal of systematic pesticides. In the case of HFCW, the removal of pesticides is attributed to the adsorption and absorption processes that can occur in the plant uptake and root system. Studies showed that the presence of plants might improve the sorption process of the pesticides onto package media. This is probably because the presence of plants increases the hydraulic resistance time, which prolongs the contact time and interactions between package media and contaminants (Wang et al. 2020). In addition, the presence of plants changes the pH of the wetlands system. Therefore, depending on the chemical and physical properties of the pesticides, some mechanisms of sorption can be improved. The plants can provide sediment bed stabilization and the growth of attached microbes. Plants species such as Phragmites australis, Typha latifolia, and Typha angustifolia are most widely used in HFCW to remove pesticides (Malyan et al. 2021). In some cases, plants compete with package media to carry out the adsorption process of pesticides. Parlakidis et al. (2022) reported that the zeolite competed with the phragmites australis and Thypa latifolia to remove fluopyram (Log Kow = 3.3). The phytoaccumulation in the plant depends on the octanol/water partition coefficient of pesticides. Pesticides with Log Kow between 3.0 and 4.0 have more tendency to be accumulated and transported in plant tissues. In some cases, the package media can compete with the plant for pesticide removal. For this reason, package media are an alternative to removing hydrophobic compounds. Parlakidis et al. (2022) reported that 25% of zeolite as a porous media and 75% gravel reduced the phytoaccumulation of fluopyram in HFCW and removed it with an efficiency of 62.06% compared to 100% gravel that only removed 36.10%. The low removal efficiencies of organic compounds in biological wastewater treatment processes might be attributed, in some cases, to the presence of halogens,

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such as chlorine and fluorine, because they are stronger electron-withdrawing. Also, the distribution constant of the pesticide can be related to the low removal efficiency. The compounds with bearing electron-donating functional groups, such as hydroxyl and amine, can be removed with high efficiency by HFCW (Tran et al. 2013). Matamoros et al. (2007) reported that used a hydraulic loading rate of 36 mm/d and hydraulic retention time of 5–6 days, the reductive halogenation of highly chlorinated compounds, such as pentachlorophenol (Log Kow = 5.12), lindane (Log Kow = 3.72), pentachlorobenzene (Log Kow = 5.17), and endosulfan (Log Kow = 3.84), can occur in an HFCW. The authors concluded that the HFCW are efficient to remove, complete or partial, chloride pesticides. Halogenated pollutants can be removed with high efficiency because in the HFCW the anoxic or anaerobic conditions prevail, and the reductive dehalogenation might occur. Microbiological degradation can be affected by the chemical structure of pesticides. For example, pesticides with rings of organic aromatic compounds and longchain tend to break down less easily than straight-chain structures. Additionally, the presence of halogens also increases their environmental persistence, making them recalcitrant compounds (Gikas et al. 2018b). In the example of herbicides, due to its toxicity, does not serve as an energy source for the growth of microorganisms. As a consequence, communities of bacteria are added to the HFCW, which helps the growth of microorganisms in plants and, therefore, biodegrades the pesticide. Pseudomonas putida strains have been used in HFCW since they increase crop yield, provide protection against pathogens, improve tolerance to abiotic stress, and enhance xenobiotic biodegradation and metal chelation (Parlakidis et al. 2022). Bacillusniabensis have also been used in an HFCW, for the elimination of triazophos, to improve the enzymatic capacity of plants, protect it from changes in environmental conditions and improve microbial growth (Wu et al. 2016). Plants can suffer phytotoxicity. Gikas et al. (2018a) reported an HFCW planted with phragmites australis to remove terbuthylazine (Log Kow = 3.4). The remotion was 73.7% compared to Thypa latifolia which only removed 58.4%. Thypa latifolia is more susceptible to phytotoxicity, concentrations of terbuthylazine have been found in roots, leaves, and shoots of both plants, being higher in Thypa latifolia. The sorption of terbuthylazine on the HFCW package media is mainly dependent on the organic matter content, as lipophilicity is the most important property that regulates the uptake of non-ionized herbicides. The pH values influence the absorption processes uptake by plant material (Gikas et al. 2018a). As mentioned above, pesticides with different physicochemical properties can be removed from agricultural or residual wastewater by HFCW. The principal pesticides removed are simazine, alachlor, chlorpyriphos, pentachlorobenzene, pentachlorophenol, endosulfan, diuron, lindane, mecoprop, fluopyram, boscalid, smetolachlor, terbuthylazine, chlorpyrifos, and chlorothalonil (Agudelo et al. 2012; Gikas et al. 2018a, b; Matamoros et al. 2007; Papaevangelou et al. 2017b; Parlakidis et al. 2022; Rìos-Montes et al. 2017). The literature shows that HFCW is a lowcost and efficient treatment to remove pesticides from agricultural waters, but it is necessary to study the contributions of each wetland component in the pesticide removal process. Operational conditions and efficiency can be varied depending on

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the physicochemical properties of the pesticide. This is because pesticides can be removed under aerobic and anaerobic conditions. For example, some pesticides with similar chemical properties to mecoprop (Log Kow = –0.87) can be degraded in aerobic conditions and pentachlorobenzene tends to be retained in the gravel, due to its higher Log Kow (5.12). Removal through plant uptake and sorption by the root system of plants could be expected for a systematic herbicide like diuron (Log Kow = 2.80) (Matamoros et al. 2007).

2.3 Treatment of Wastewater with Textile Dyes in HFCW Discharges of wastewater containing synthetic dyes produce a substantial environmental impact (Haddaji et al. 2019; Masi et al. 2019). Generally, synthetic dyes are toxic, carcinogenic, and mutagenic substances. Besides, these are released into wastewater at high concentrations from production processes (Hussain et al. 2018). Textile operations, for instance, produce large quantities of wastewater during fabric and clothes manufacture. These wastes contain diverse chemical compounds such as dyes, detergents, pigments, salts, heavy metals, sulfates, chlorides, and others, generally resulting in colored effluents that prevent light infiltration in the water bodies that receive them (Hussain et al. 2018; Masi et al. 2019). The lack of light affects aquatic life and the natural biologic cycles; as a result, the photosynthetic activity and dissolved oxygen decrease in water (Hussain et al. 2018; Masi et al. 2019; Tee et al. 2015). Azo dyes are compounds with one or more azo groups, molecules with a double nitrogen bond. Azo dyes are the most broadly used synthetic dyes in industrial processes, particularly in the textile industry. Between 60 and 80% of the worldwide produced reactive dyes are based on azo compounds (Masi et al. 2019; Tee et al. 2015). The azo dyes advantages, such as the simplicity and cost-effectiveness of their synthesis, their stability, and the variety of colors available make them highly demanded (Tee et al. 2015). In addition to their use in the textile industry, they are extensively used in the paper, food, leather, cosmetics, and pharmaceutical industries. The toxicity of azo dyes is low, but the separation of the azo bond leads to toxic by-products, such as aromatic amines, which are considered mutagenic and carcinogenic (Haddaji et al. 2019; Tee et al. 2015). Although azo molecules resist degradation by their exposure to tensides, sunlight, or oxidizing agents (Masi et al. 2019), some conventional processes have been applied to degrade and remove dyes from wastewaters. Thereby, conventional methods, such as coagulation, flocculation, advanced oxidation processes, photodegradation, and ozone treatment present various disadvantages, for example, the greater use of chemicals, or the toxic sludge generation. Consequently, these technologies are usually not affordable, considering the high cost of maintenance and operation (Hussain et al. 2019). Moreover, the removal is not always complete, and some residual dye is released in the effluent, containing approximately 1 mg/L of dye or some chromophore groups, leading to a still colored discharge or some toxic by-products

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(Haddaji et al. 2019; Masi et al. 2019). Physical methods do not degrade the molecules of dye; they just transfer them to a solid phase. In the case of biological treatment, it has been found that the azo bond is separated under an anaerobic process, but aromatic amines are the product. In many cases, it is applied as an additional aerobic process to decompose aromatic amines. For this reason, biological processes are proposed in a sequence of biological stages, using anaerobic and aerobic processes for having the total degradation of azo compounds in water. These concurrent operations are usually found in a constructed wetland, where oxygen is found in aerobic zones, while the same system encloses anaerobic sections (Tee et al. 2015). One reasonable proposal is the use of different types of constructed wetlands, taking advantage of the particular characteristics of each type, for example, using the anaerobic dominance in horizontal wetlands, and the typical aerobic conditions of vertical flow wetlands. Whatever the arrangement in a wetland, diverse physicochemical parameters affect concurrently the dyes biological removal from wastewater. For instance, oxygen presence, temperature, pH, dye concentration, chemical structure, carbon and nitrogen availability, electron donors, and redox mediator are involved in biochemical mechanisms of degradation (Masi et al. 2019). In the following paragraphs, some cases are presented, where the degradation and removal of azo dyes are studied, adding some biological components to the horizontal constructed wetland, and modifying the structure or the operational conditions of this conventional system. A pilot-scale HFCW was inoculated with three endophytic bacterial strains, improving the efficiency of dye degradation and plant growth (Hussain et al. 2018). The HFCW was inoculated with a consortium of endophytic bacteria, planted with the Leptochloa fusca species, and fed with effluent from the textile industry. The system removes organic and inorganic pollutants; on average, a COD removal of 85% and a BOD removal of 78% were reported within 48 h of treatment. Endophytic bacteria remained in the system, proving their resistance to the toxicity of the water. The authors suggest that bacteria grow in the textile effluent developing molecular mechanisms to proliferate. As well as bacteria, L. fusca demonstrated resistance to wastewater toxicity. Similarly, endophytic bacteria were investigated in an HFCW to evaluate their contribution to the treatment of a textile effluent (Hussain et al. 2019). The effluent originated in the bleaching process. Thus, the effluent did not include dyes but contained all the chemicals required for the preliminary stages of the dyeing process. The study compared the performance of an HFCW against a vertical flow constructed wetland, both of them were augmented with endophytic bacteria. So, the efficiency of the augmented strategy was evaluated. The pilot-scale system had a volume of 1 m3 , was planted with Phragmites australis, and inoculated with bacterial strains capable of pollutant degradation and plant growth-promoting. The results exhibited a better performance of the HFCW than the VFCW for most of the pollutants analyzed, proving to be a better alternative for a bleaching discharge. The augmented strategy improved the treatment efficiency, and inoculated bacteria persisted in water and plants. Organic matter was removed according to the 89% of COD, 91% of BOD, and 96% of TOC removal, besides the toxicity reduction was detected in the effluent.

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To achieve a hybrid arrangement, with a sequence of anaerobic and aerobic conditions, a baffled and a conventional HFCW, planted and unplanted, were tested and compared for the removal of Acid Orange 7 (AO7) (Tee et al. 2015). A set of baffles was installed in an HFCW to create more aerobic, anoxic, and anaerobic environments within the same wetland. The hydraulic retention time applied was 5, 3, and 2 days, when treating domestic wastewater with an AO7 concentration of 300 mg/L. The planted baffled unit was found to achieve 100%, 83%, and 69% AO7 removal for the HRT of 5, 3, and 2 days, respectively. The highest removal was obtained for the 5 days of HRT and the lowest removal for the 2 days of hydraulic retention time. The efficiency of the conventional HFCW was about 30% lower than the baffling system. The baffles installed lead to significant contact with all the components and the zones. Thus, the longer interactions with microbes, roots, and redox components were accountable for the AO7 removal. Hence, oxidation and reduction mechanisms were developed with no more land use. Considering the processes needed to remove azo dyes completely, the combination of aerobic-anoxic-anaerobic zones was beneficial for degradation. A pilot-scale HFCW was studied with an operational adjustment, to improve the removal of nutrients and toxic compounds (Haddaji et al. 2019). The idea of this experiment was to extend the contact time of wastewater with the wetland components. The desired contact was obtained by recirculating the effluent through the HFCW until this wastewater achieves the expected quality. The HFCW was allocated in a greenhouse, planted with Typha domingensis; the intake includes the amaranth azo dye, that was used in the synthetic wastewater fed with different concentrations: 10, 15, 20, and 25 mg/L. The pilot-scale HFCW had a flow rate of 10 L/s, and a hydraulic retention time of 3 h was established. The main objective of the study was to evaluate the phytoremediation capability of the Typha domingensis species. According to the results, a 92 ± 0.14%, discoloration was achieved, in addition, to removals of 56 ± 1.12%, of organic matter (COD), 92 ± 0.34%, of nitrates, and 97 ± 0.17% of ammoniacal nitrogen were accomplished. The analysis conducted indicated the degradation of azo dye amaranth 98%. Additional tests were carried out to analyze the enzyme activities, concluding that enzyme activities increased during the amaranth treatment. Therefore, the primary mechanism for discoloration was attributed to the defense system of the T. domingensis species, which activates the antioxidative enzymes. A hybrid system was used to study dye removal from the discharge of a wastewater treatment plant (Masi et al. 2019). The system consisted of a pilot plant designed to treat up to 9 m3 /d, with a 20 m2 aerated HFCW, planted with Phragmites australis, and a 21 m2 aerated FWS planted with Typha latifolia, Miriophyllum sp., and Potamogetum sp. Intermittent and continuous aeration modes were used in both wetlands. The operation of the pilot plant lasts 11 months, during which the inlet dye concentration was about 1–5 mg/L. Different hydraulic retention times were studied: 1.2, 2.6, and 3.5 days. Results show regular biodegradation of organic matter and nutrients, but the whole aerobic biological treatment did not degrade the residual dye. The additional aeration did not contribute to the dye removal as was expected; the residual dye seemed to resist the aerobic degradation. However, the authors still recommend

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using wetlands for dye treatment but consider a better design with a longer hydraulic retention time and improving the adsorption capacity by biological material. Another strategy applied in constructed wetlands for increasing the treatment efficiency is implementing a fuel cell into the wetland. This implementation aims to take advantage of the redox conditions resulting from the aerobic, anoxic, and anaerobic zones in wetlands using a fuel cell that leads to electrochemical reactions. Power production is obtained as an added value to the wastewater treatment in these systems. However, most of the microbial fuel cells-constructed wetlands tested for dye degradation have been conducted in systems with the vertical flow, probing Methylene blue, Reactive brilliant red, Methyl orange, Acid red 18, Acid Orange 7, and Congo red. In all these experiments, high removals of dye were achieved (60 and 96%), with different hydraulic retention time and with different values of power production (Oon et al. 2020).

3 Heavy Metals and Acid Mine Drainage Controlled by Horizontal Subsurface Constructed Wetlands Over the years, water pollution problems have worsened, presenting different types of pollutants such as pesticides, heavy metals, drugs, and dyes, among others. As there is a wide range of pollutants, the following section is presented the case of treating heavy metals in HFCW. Heavy metals can come from different effluents for which they must be treated depending on the source where they are generated. In the case of acid mine drainage, apart from the heavy metals, they also contain high pH values and sulfates, which may cause damage to the environment by contaminating the water and the soil.

3.1 Treatment of Industrial Effluents Containing Heavy Metals In the case of heavy metals from different industry effluents, there are several cases because most heavy metals are toxic to living beings in low concentrations. Hexavalent chromium is one of the most dangerous elements and has been treated using HFCW where it has been found that vegetation (Phragmites australis) greatly increases the removal of this pollutant, reporting a removal of 87%. This removal was due to the accumulation of microorganisms (Sultana et al. 2015) and in another case, the adsorption and removal of hexavalent chromium were directly linked to the package media (Papaevangelou et al. 2017a), the pH value did not vary greatly, the concentration of hexavalent chromium varied in a range of 0.5–10 mg /L. Refinery effluents are more complex to treat due to the mix of pollutants they contain. The treatment was given to effluent from a refinery that contains iron,

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manganese, aluminum, zinc, copper, nickel, lead and chromium, phenols, and organic matter. Graded, washed silica sand and clay were used as package media. Clay allows for plant establishment in the silica soil. The plant used in the HFCW was Cyperus alternifolius. Air was injected into the system and under aerobic conditions, the wetland was able to remove 96% Fe, part of the Mn (38–92%), Al (63–73%), and Zinc (99%) which precipitated as oxyhydroxides. Similarly, other metal ions such as Cu (61–80%), Ni (70–85%), Pb (96–99%), and Cr (63–92%) were eliminated through co-precipitation. The removal of metal ions was due to adsorption on the package media, the vegetation (roots), air/water interactions, uptake, and assimilation in vegetation biomass. The HFCW was efficient in the removal of metal ions under the selected package media systems and with an HRT of 1.3 days (Mozaffari et al. 2021). Another metallic ion with a high degree of toxicity is lead, which is found in different industrial effluents. The capacity of an HFCW in the elimination of this pollutant was tested, finding the optimal operating conditions to eliminate 37 mg/L of the 50 mg/L of the initial concentration, with a 32-days HRT and without air injection. The vegetation used in this wetland was Scirpus grossus. The removal of lead was by adsorption in the package media and the vegetation (Tangahu et al. 2022). Arsenic is a metalloid with a high degree of toxicity for living beings, researchers have looked for the most appropriate and effective treatment to eliminate it from the water bodies where it is present. This pollutant has been treated using an HFCW system, where the package media was varied. Zeolite and limestone were used and P. australis as vegetation. The values achieved were the removal of arsenic and iron of 96% and lead of 94% when limestone was used due to the buffering effect of the pH value where it reached a value of 7.1. Using the zeolite as package media, the pH value reached a value of 3.8, the influent had an acidic pH value. The effect of the vegetation in the removal of metal ions is minimal, this is not the main factor to consider in this particular treatment system. Arsenic removal was mainly due to co-precipitation and adsorption of iron oxyhydroxides formed by increasing the pH value (Lizama-Allende et al. 2021). Mercury is a metal ion with a high degree of toxicity and causes different effects on the health of living beings, it is found in some industrial-type effluents and the treatment of this pollutant was tested using an HFCW. More than 90% was removed, mainly due to the action of the package media. For this case, granular biochar was used. Several types of bacteria that are resistant to mercury toxicity were found: Arenimonas, Lysobacter, Micropruina, Hydrogenophaga (Chang et al. 2022).

3.2 Pollution from Mining Activities Treatment Over the years, mining has been a very profitable industry due to the benefits of mineral exploitation, however, the extraction process produces a large number of pollutants such as chemical agents, and minerals, found in the same deposit. All

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these substances are put together in a single place called tailings dams, they do not have a structure that supports weather changes, so they are likely to cause disasters in the environment because they can contaminate water bodies and groundwater near the area. These environmental problems are difficult to treat because, over the years, the water manages to generate the dissolution of metal ions found in the rocks and produces the acid mine drainage. This mixture of metal ions causes serious diseases to living beings and even death. This type of effluents has been treated by different methodologies and among them are wetlands. Some advantages, and future applications of wetlands, reported in different works will be exposed. An effluent with an extremely acidic pH value (2.2) from a coal mine was treated, in this condition, several metal ions were found: Fe, Al, Mn, Zn, Co, Ni, and Cr. In addition, there were high concentrations of sulfates. Gravel was used as package media; this provokes the precipitation and adsorption of the different metal ions. The hydraulic retention time was 7 days. High removal percentages were achieved: Fe (73%), Al (79%), Zn (98%), Co (95%), Ni (99%), and Cr (100%), however, Mn only reached a removal of 21%. In the case of sulfates, the elimination of the 74% conforming sulfidogenesis pathway was achieved. The prominence of acidophilic sulfate-reducing bacteria (Desulfosporosium meridiei) was revealed. In turn, the removal of 85% of the COD from the effluent was achieved at the end of the treatment using an HFCW (Singh and Chakraborty 2022). The extraction of minerals is a very particular process, defined by the place where the deposit is located, and a variety of minerals can be located at that point, so the residues produced (mining tailings) will vary according to the elements that compose them. The acid drainage of a mine extracting gold was studied. In this case, the pH value was too acidic, for this reason, the use of an active nanomaterial MgO was implemented as a first step in the treatment of this type of effluent. The attenuation of the pH value was achieved, even leading to alkaline values. This modification in the effluent resulted in the precipitation of most of the metal ions that were present, such as Mn (96%), Fe (95%), Zn (92%), Al (92%), Ni (88%), and Cu (80%). Three wetland arrangements were used, and the third was to provide a polishing touch to the already treated water, this was an HFCW. Vetiveria zizaniodies were used in the wetlands as vegetative species and common soil from the area as package media. In this case, the highest concentrations of metal ions were eliminated in the first stage, however, the effluent maintains concentrations that exceed the values stipulated in the environmental laws. For this reason, an extra treatment was sought so that the effluent is within the parameters. In this case, it was found that this type of wetland was able to reduce the concentration of iron, manganese, and zinc. Nickel was completely removed from the effluent. Studies were carried out to know the content of metals in the vegetative material, however, only iron and zinc were found in a greater proportion in both, roots and leaves (Nguegang et al. 2022).

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4 Innovations in Horizontal Subsurface Constructed Wetlands for Toxic Compounds Removal The physicochemical properties of toxic compounds (specifically their chemical structure) are responsible for their persistence in the environment. In environmental terms, these facts represented an opportunity to innovate treatment systems. As in any project, there are stages of maturity, where large-scale are the highest. In this case, we refer to the application of the HFCW-based treatment system. There is much information on wastewater treatment with toxic compounds or industrial wastewater but at the basic science level. At the prototype level, only laboratory-scale HFCW innovations are available. This situation is not unique to wetland systems. On the contrary, the versatility and interaction of such systems’ biotic and abiotic components have allowed innovations in vegetation type (combination of two or more species), package media, presence of previously adapted or tolerant microorganisms, and biofilm from a biosystem approach (Parlakidis et al. 2022). An example of this last innovation is the electrochemical wetlands with the implementation of a microbial fuel cell in a wetland. There is even a diversity of constructed wetland-microbial fuel cell configurations. In the 1990s, some innovations emerged to reduce the disadvantages of constructed wetlands, mainly the large extensions of land required (derived from long HRT or low organic loads). Later, in the 2000s, innovation in HFCW was focused on efficient nitrogen and phosphorus removal. In the last ten years, the innovations have been concentrated on reducing emerging toxic pollutants, both organic (e.g., drugs, dyes, pesticides) and inorganic (i.e., heavy metals).

4.1 Artificial Aeration Aeration has been used as a biostimulation of the bacterial community in CW and in soil bioremediation. Aeration generates a certain degree of internal water recirculation, which eliminates dead zones, a disadvantage of CW. In addition, reaeration increases the rate of biodegradation, thus improving the removal of organic compounds. Lui et al. (2019) identified from 32 studies that biodegradation of organophosphorus pesticide residues is the primary removal pathway in CW, followed by vegetation assimilation. Both mechanisms are correlated with the amount of dissolved oxygen available in the aqueous medium (Roé-Sosa et al. 2019). Indeed, the concentration of dissolved oxygen determines the processes of nitrification, denitrification, and cellular storage of phosphorus in wastewater. Precisely as these processes occur, it indicates the chemical breakdown of pesticides and pharmaceuticals containing nitrogen and phosphorus in their structure.

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4.2 Electrochemically Assisted Constructed Wetlands The improved HFCW with an electrochemical implementation is based on the aforementioned aerobic-anoxic-anaerobic condition changes. Microbial fuel cells are based on reduction–oxidation reactions. An anode chamber or section oxidizes organic matter under anaerobic conditions to release protons and electrons. Electrons are transferred to the cathode via an external electrical circuit. Protons migrate to the cathode contained in the aerobic section through a selective membrane that separates the two reactions. In the cathode section, electrons and protons react with oxygen to produce water. In addition, both chambers are connected by employing a resistor, which allows power to be obtained from the electron transfer. Thus, HFCW is configured so that anaerobic oxidation reactions take place in the anode chamber, and an oxygen reduction reaction occurs in the cathode section. In effect, biodegradation of organic matter (volatile pollutants and rhizospheric exudates) is performed to release electrons and protons (Kabutey et al. 2019). Considering the operational and economic advantages of HFCW, the most widely used electrochemical wetlands are based on dispensing with the membrane and using the package media instead (Ramírez-Vargas et al. 2018). Recently, investigations in Microbial fuel cells—Constructed wetlands, are focusing in the improvement of the treatment efficiency. Several pollutants have been tested with promising results. An electrical current is obtained, but this is not the main objective of the systems.

4.3 Novel Package Materials Package material is one of the most important components and one that the most influences the efficiency of HFCW. Although package media has the function of being a support for the growth and development of plants and biofilm (Dordio and Carvalho 2013), it can participate in sorption processes, due to its characteristics and its chemical and physical affinity with toxic compounds, and the microbial community structures (Li et al. 2014; Zhang et al. 2018). Also, is important to consider other factors such as its source, cost, hydraulic feasibility, porosity, lifetime, and the possibility to be recycled (Wang et al. 2020; Yang et al. 2018). Since package media has a different capacity for contaminants removal, specific package media should be selected considering the contaminants compounds. In the case of toxic compounds, like drugs, pesticides, dyes, and metals, package media selection could depend on the physicochemical properties of the pollutants. For example, non-polar organic compounds have a greater affinity for package media rich in organic matter such as soil, compost, etc. These compounds interact with package media primarily through hydrophobic interactions. In the case of polar and ionic compounds, they interact with the package media, mainly by electrostatic interactions

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or ion exchange, being graves, clays, or zeolites are the most used due to their removal efficiency (Li et al. 2014). The problem with the affinity between package material and toxic compounds is that it affects the hydraulic permeability of the HFCW. For this reason, packages media with greater porosity are required to improve the performance of the HFCW. Because the package media also influences the cost and sustainability of the CWs, the use of bio-package media is proposed. For instance, Biochar is a low-cost, eco-friendly, and reusable alternative (Deng et al. 2021), and has been the subject of much research in the last decade, mainly because of its benefits for agriculture. Additionally, biochar has an excellent capacity to interact with various pollutants and support high abundances of functional microbes (Deng et al. 2021). The physicochemical characteristics of biochar give it the property of retaining nutrients and water for vegetation. Furthermore, its molecular structure is characterized by the high content of phenolic and chelating groups that allow it to retain by sorption a wide range of toxic pollutants (Zhang et al. 2018). HFCW with Biochar as package media can be a novel alternative to employing carbon materials with high efficiency, cost-effective, environmentally friendly, and sustainable systems for wastewater treatment. Another important consideration to using biochar is that improves macrophyte growth and mitigates greenhouse gas emissions (Deng et al. 2021). Concerning the benefits of biochar on microorganisms that develop a biofilm on HFCW, biochar has a surface area that exceeds any conventional average package by some orders of magnitude (Amabilis-Sosa et al. 2018). However, this large surface area is because the interstices measure less than 0.1 μm. That is, bacterial cells have no chance to grow in the interstices of the biochar because they measure at least 0.45 μm. However, the bacterial biofilm could establish itself in the occluded porosity of the biochar, maximizing the sorption of toxic contaminants by incorporating biosorption (Siatecka and Oleszczuk 2022). Jing et al. (2021) reported the use of a superabsorbent polymer (SAP), a crosslinked hydrophilic polymer to remove hydrophilic pesticides. The pesticide sorption in this package media was related to the ionization state and water solubility of the pesticides. The pesticides studied were imidacloprid, metalaxyl, propiconazole, bentazone, and glyphosate. This package increases hydraulic retention time and improves biodegradation. The efficient or remotion was >93% for glyphosate and propiconazole. In this study, a batch retention experiment was used, and the authors reported that the enhanced pesticide removal can be ascribed to pesticide retention by SAP and an increase in pesticide retention time in CW. Package media, like SAP, can be used in the treatment of agricultural water because it is a low-cost material and can remove pesticides such as glyphosate and propiconazole. Since it is a package media with greater pore volume and surface area, the size in HFCW can be reduced, and at the same time, hydraulic residence time can be increased (Jing et al. 2021). Natural materials and agricultural waste have become excellent alternatives in the HFCW due to their low cost and effectiveness in removing contaminants in comparison with synthetic material (Wang et al. 2020). Future investigations need to

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consider how hydraulic residence time can be affecting wetland saturation and the active sites of the package media. Another innovation in package materials, considered only the mineralogical composition for ion exchange. For example, the volcanic rock contains up to 39% Fe and 13% Al, which are slightly acidic conditions that favor ion exchange with Zn, Cd, Pb, and Cu in solution (Bazúa-Rueda et al. 2020). Likewise, package materials from karst areas contain high CaCO3 and MgCO3 , forming chelators that precipitate the solution’s heavy metals. Table 1 shows specifications and removal efficiencies of HFCW with different innovations for the treatment of toxic effluents or with the presence of toxic compounds. This table shows the diversity of both innovations and compounds or toxic effluents in which HFCW have demonstrated technical feasibility. On the other hand, most of the investigations shown in Table 1 refer to laboratoryscale HFCW and none to full-scale. When it comes to full-scale HFCW, the geometry and available area are limiting factors for the configuration of any treatment system, especially non-mechanized. Therefore, innovations should also focus on increasing the removal of kinetic parameters, which ultimately translates into a smaller treatment area (Ortiz-Marin et al. 2022). By exploring the advantages of package media, it is possible a reduction in HFCW areas. However, different treatment steps are required in biological processes, which are usually opposite in configuration. For organic matter removal and nitrification, aerobic conditions are desirable. Conversely, conversion to molecular nitrogen by denitrification requires anaerobic conditions. Thus, a “module” is required for each treatment stage. Based on the above, some HFCW has demonstrated removal or stabilization of effluents with toxic compounds and implemented at full-scale (Pat-Espadas et al. 2018; Roé-Sosa et al. 2019; Vystavna et al. 2017). In different parts of the world, those HFCW are based on more basic innovation aspects than those shown for laboratory-scale HFCW (Table 1). HFCW at full-scale incorporate in their design and configuration pH, and redox variations derived, in turn, from simple depth variations. Roé-Sosa et al. (2019) evaluated the performance of HFCW for the treatment of agricultural wastewater (concentrated agricultural drainage). The wastewater contained higher values of 30 and 15 mg/L, N and P, respectively, but most of these compounds were in pesticide molecules or their by-products. The variation in wetland depth and respective thermodynamic calculations (for oxygen saturation/dissolution) generated different treatment zones. These zones had different pH and redox potential values, leading to nitrification, denitrification, and phosphate sequestration, reducing nutrients by 65% on average. It should be noted that this nutrient reduction was correlated with a 200% increase in the biodegradability of the treated water. Another relevant case of full-scale success and practically without innovations is Ji et al. (2020), who evaluated the removal of 12 pharmaceuticals present in hospital wastewater. The HFCW was assessed for three years. As the operation time elapsed, the HRT decreased, and the removal of 9 of the 12 drugs was also higher. This reduction in HRT was due to a higher density in the roots of the vegetation that became increasingly more developed, in addition to the maturation of the biofilm

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Table 1 Subsurface horizontal flow constructed wetlands with physical, chemical, and/or biological innovations for treating wastewater with toxic characteristics (Original to the author) Wastewater/pollutants

Innovation

Design aspects and Removal application scale efficiency

Aeration and recirculation application

HRT 1.4 d Front aeration Laboratory with plug-flow

Pesticide-contaminated Biochar-amended Cyperus water systems + alternifolius chips Integrated as biochar recirculating feedstock Laboratory

Comments

BOD: Up to TP removal was 30% more the same as efficient than without aeration without aeration TN: 2.5 times more efficient than without aeration 54–85 TKN

Organophosphates and organoclorates pesticides

Contaminated groundwater/heavy metals

Biochar-amended Bamboo as biochar 75–97% systems feedstock

Cr and Pb Fe- biochar Nitrate reduction of 87%

Slurry in pig farms/heavy metals

Biochar-amended Coconut shell as systems and biochar feedstock zeolite + chlorella (biosorbent)

As: 35.4–83.9% Zn: 8.15–23.7%

As, Zn as representative metals

Diesel oil refinery wastewater

A vertical CW incorporated

L × B × H= 0.6 m × 0.4 m × 0.35 m Laboratory

BTEX: 86–97%

The vertical wetland had the same dimensions as the horizontal wetland but was 0.8 m deep

Groundwater contaminated with benzene and MTBE

A floated system incorporated

HRT = 6 d L × B × H = 5.0 × 1.1 m × 0.6 m Pilot

Benzene: 24%–100% MTBE: 16%–93%

Sections planted with Phragmites australis and unplanted

Antibiotic in waters

Microbial fuel cell integrated

HRT = 1 d Laboratory

SMX: Drugs levels were 99.7%–100% in μg/L TC: 99.6%–99.8%

Antibiotics leakage and methane emission

Microbial fuel cell integrated

Planted with More than Acorus tatarinowii 90% of SDZ ManganeManganse and CIP ore was used as package material Laboratory

A decline in methane fluxes (by 15.29%) was also observed in CW-MFC compared with CW (continued)

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Table 1 (continued) Wastewater/pollutants

Innovation

Design aspects and Removal application scale efficiency

Comments

Azo dye (Methyl orange)

Microbial fuel cell integrated

Granular activated Up to 87% carbon as cathode and anode. Anode in contact with stainless steel mesh HRT = 3 d Laboratory

MPD of glucose and MO CWMFC were 0.688 W m−3 and 0.081 W m−3

Abbreviations SMX = sulfamethoxazole; TC = tetracycline; SDZ = sulfadiazine; CIP = ciprofloxacin; MTBE = methyl tert-butyl ether; BTEX = Benzene, Toluene, Ethylbenzene and Xylene; BOD = Biochemical Oxygen Demand; CW = Constructed Wetland; TP= Total Phosphorus; TN = Total Nitrogen; TKN = Total Kjeldahl Nitrogen

(Amabilis-Sosa et al. 2015). The growth of the microbial biofilm can obstruct the interstices of the middle package, leading to clogging. Clogging seems to be a disadvantage of HFCW, but an HFCW designed under the suitable hydraulic and kinetic considerations does not have to clog. On the contrary, some innovations for toxic effluent treatment have used specific media packages. Yang et al. (2018) collected ten years of research (since 2008) on the advantages and specifications of package media and the different toxic compounds that can remove. The package media investigated were alum sludge, apatite material, calcite, ceramsite, and tire chips. Depending on the contaminants, removal mechanisms such as ion exchange and electron donor substrates were described. But what is remarkable is that the review of all investigations indicates that clogging always depended on hydraulic aspects that are extensively studied for full-scale HFCW. One factor that, despite its obviousness, is not mentioned in the use of any CW, is the effect of temperature. Given the aspect of phytoremediation and temperature dependence for bacterial kinetics, it would seem those CW are only efficient in the tropics. However, Ji et al. (2020) investigated in detail direct and indirect modifications (some innovations) in HFCW overcoming the system’s stress at low temperatures. Direct improvements include bacterial inoculums (bioaugmentation) and package media with specific biochar incursion properties. For indirect improvements, insulation and heat preservation (greenhouse build-up) and artificial aeration (a type of natural attenuation used in soil bioremediation) have been identified. In summary, full-scale HFCW designed with all the appropriate hydraulic, thermodynamic, and kinetic parameters is technically feasible for treating effluents containing toxic compounds, leading to interactions among vegetation, microorganisms, and package media. Of course, the wastewater must be characterized and evaluated under treatability tests. As mentioned, the chemical variety of toxic compounds present in wastewater makes water characterization necessary for the design and

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Fig. 1 Flow diagram for using HFCW to treat toxic effluents. This Figure summarizes the description of HFCW innovation but emphasizes that the ultimate objective is large-scale implementation. (Original to the author) (Abbreviations BOD, Biochemical oxygen demand; COD, Chemical oxygen demand; HFCW, horizontal flow constructed wetland)

configuration of HFCW. Figure 1 shows a flow diagram contributing to decisionmaking when using HFCW to treat toxic effluents. This figure summarizes the above description of HFCW innovation but emphasizes that the ultimate objective is large-scale implementation.

5 Conclusions In summary, full-scale HFCW designed with all the appropriate hydraulic, thermodynamic, and kinetic parameters is technically feasible for treating effluents containing toxic compounds. These specifications are related to the physicochemical properties of flooding soil, such as pH, ionic strength, hydraulic conductivity, oxygen concentration, temperature, pollutant concentration and its chemical nature, carbon and nutrients availability, the number of electron donors, as well as redox mediators, and all these parameters concurrently govern the pollutants removal mechanisms. Toxic pollutants removal requires the appropriate interaction between biotic and abiotic components. On one side, vegetation and bioaugmentation are analyzed to improve the assimilation and uptake of toxic compounds by plants. On the other side,

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the selection of package media influences significantly processes such as adsorption, the buffer effect, and the precipitation phenomenon. Similarly, aeration intervenes in the rate of biodegradation, thus improving the removal of organic compounds. These aspects are considered for future studies in the field of heavy metals, drugs, pesticides, and pharmaceutical removals by HFCW. HFCW is an advisable option for textile wastewater treatment. The dyes complexity requires the application of distinct mechanisms, which are found in wetlands. However, some design and operational modifications manage to improve the treatment efficiency. In this way, the trend suggests that a longer contact among biotic and abiotic components leads to better interactions and thus, to better pollutant removal. Therefore, handling the aerobic/anaerobic/anoxic zones by the configuration and design modifications in HFCW, and operational adjustments such as longer HRT, are being applied and studied to apply them at full-scale for synthetic dye removal. Pollution caused by metal ions is one of the most serious problems. In addition, it is an overly complex problem since the effluents may contain more than one metal and different chemical agents, thus complicating their treatment. An alternative to attack and solve this serious pollution problem is wetlands which are easy to install, with package media from the same place where they are found, endemic plants, and can be adapted with other treatment systems to obtain an effluent within the parameters set in the different environmental Law regulations. Wetlands have different elements that give some valuable properties: susceptible support material to carry out adsorption, bacterial conglomerates that may be able to remove the organic matter and metal ions to trap and transform them into more innocuous products, and material vegetative that through its roots can provide the ideal conditions for the development of bacterial conglomerates and the leaves and stems where these metal ions can be adsorbed, translocating and eliminating them from the effluent. In this way, excellent results can be obtained in the treatment of metal ions and the chemical agents that are in the effluents, providing a viable, economical, effective, and efficient alternative in the removal and treatment of complex effluents. As in different areas of engineering, innovations arise in response to the needs of society. In treating toxic compounds by HFCW, innovations related to package media, electrochemical assistance, aeration, and bioaugmentation have become widespread. These innovations have enabled the efficient treatment of toxic compounds in wastewater, including emerging pollutants in concentrations even in trace levels. However, the application of these innovations has only taken place at a laboratory-scale, which limits the maturity of engineering projects for wastewater treatment. Nevertheless, there are several pilot and successful full-scale case studies. Full-scale HFCW efficiently remove toxic compounds from wastewater when all climatic, hydraulic, and overall design aspects are addressed. During the first months of operation, the efficiencies are not as high. However, once the vegetation develops, the synergy of bacteriapackage-media-vegetation shows high removal efficiencies of toxic compounds from the wastewater. When the concentrations of toxic compounds are very high (tens of parts per million), CW can still be efficient by coupling with pretreatment according to the characteristics of the wastewater.

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Specific analytical determinations (e.g., chromatography) are not always feasible to implement. However, toxicity and biodegradability (BOD/COD) are reliable indicators to assess the level of treatment of pollutants. Thus, establishing levels of both indicators related to the type of innovation is required. For innovative HFCW to be scalable and represent an engineered solution to point sources of toxic compounds, future research should focus on establishing an HFCW guideline based on the toxicity and biodegradability levels of the water to be treated.

References Agudelo CRM, Jaramillo ML, Peñuela G (2012) Comparison of the removal of chlorpyrifos and dissolved organic carbon in horizontal sub-surface and surface flow wetlands. Sci Total Environ 431:271–277. https://doi.org/10.1016/j.scitotenv.2012.05.045 Ahmad HA, Ahmad S, Cui Q, Wang Z, Wei H, Chen X, Ni S-Q, Ismail S, Awad HM, Tawfik A (2022) The environmental distribution and removal of emerging pollutants, highlighting the importance of using microbes as a potential degrader: a review. Sci Total Environ 809:151926. https://doi.org/10.1016/j.scitotenv.2021.151926 Amabilis-Sosa LE, Arroyo-Ginez M, Pérez-González R, Roé-Sosa A, Ramírez-Burgos LI, DuránDomínguez-de-Bazúa M del C (2018) Effect of support media on heavy metals removal in constructed wetlands: inoculated with metallotolerant strains. In: Artificial or constructed wetlands. A suitable technology for sustainable water management. CRC Press, Boca Ratón. https://doi.org/10.1201/9781315184265 Amabilis-Sosa LE, Siebe C, Moeller-Chávez G, del Durán-Domínguez-de-Bazúa M, C, (2015) Accumulation and distribution of lead and chromium in laboratory-scale constructed wetlands inoculated with metal-tolerant bacteria. Int J Phytoremediation 17(11):1090–1096. https://doi. org/10.1080/15226514.2015.1021953 Bazúa-Rueda ER, Bernal-González M, Amábilis-Sosa LE, Cano-Rodríguez MI, García-Gómez RS, Ramírez-Burgos LI, Salgado-Bernal I, Sánchez-Tovar SA, Solís-Fuentes JA, del DuránDomínguez-de-Bazúa M, C, (2020) Mining, water and society: recycling of mining effluents as a social solution to the use of water in Mexico. In: Otazo-Sánchez EM, Navarro-Frómeta AE, Singh VP (eds) Water availability and management in Mexico. Springer International Publishing, Cham, pp 389–411 Borrull J, Colom A, Fabregas J, Borrull F, Pocurull E (2020) Liquid chromatography tandem mass spectrometry determination of 34 priority and emerging pollutants in water from the influent and effluent of a drinking water treatment plant. J Chromatogr A 1621:461090. https://doi.org/ 10.1016/j.chroma.2020.461090 Carranza-Diaz O, Schultze-Nobre L, Moeder M, Nivala J, Kuschk P, Koeser H (2014) Removal of selected organic micropollutants in planted and unplanted pilot-scale horizontal flow constructed wetlands under conditions of high organic load. Ecol Eng 71:234–245. https://doi.org/10.1016/ j.ecoleng.2014.07.048 Chang J, Peng D, Deng S, Chen J, Duan C (2022) Efficient treatment of mercury(II)-containing wastewater in aerated constructed wetland microcosms packed with biochar. Chemosphere 290:133302. https://doi.org/10.1016/j.chemosphere.2021.133302 Delgado N, Bermeo L, Hoyos DA, Peñuela GA, Capparelli A, Marino D, Navarro A, CasasZapata JC (2020) Occurrence and removal of pharmaceutical and personal care products using subsurface horizontal flow constructed wetlands. Water Res 187:116448. https://doi.org/10. 1016/j.watres.2020.116448

234

L. E. Amábilis-Sosa et al.

Deng S, Chen J, Chang J (2021) Application of biochar as an innovative substrate in constructed wetlands/biofilters for wastewater treatment: performance and ecological benefits. J Clean Prod 293:126156. https://doi.org/10.1016/j.jclepro.2021.126156 Dordio A, Carvalho AJP (2013) Constructed wetlands with light expanded clay aggregates for agricultural wastewater treatment. Sci Total Environ 463–464:454–461. https://doi.org/10.1016/ j.scitotenv.2013.06.052 Dordio A, Carvalho AJP, Teixeira DM, Dias CB, Pinto AP (2010) Removal of pharmaceuticals in microcosm constructed wetlands using Typha spp. and LECA. Bioresour Technol 101(3):886– 892. https://doi.org/10.1016/j.biortech.2009.09.001 Dordio AV, Belo M, Martins Teixeira D, Palace Carvalho AJ, Dias CMB, Picó Y, Pinto AP (2011) Evaluation of carbamazepine uptake and metabolization by Typha spp., a plant with potential use in phytotreatment. Bioresour Technol 102(17):7827–7834. https://doi.org/10.1016/j.biortech. 2011.06.050 Gikas GD, Pérez-Villanueva M, Tsioras M, Alexoudis C, Pérez-Rojas G, Masís-Mora M, LizanoFallas V, Rodríguez-Rodríguez CE, Vryzas Z, Tsihrintzis VA (2018a) Low-cost approaches for the removal of terbuthylazine from agricultural wastewater: constructed wetlands and biopurification system. Chem Eng J 335:647–656. https://doi.org/10.1016/j.cej.2017.11.031 Gikas GD, Vryzas Z, Tsihrintzis VA (2018b) S-metolachlor herbicide removal in pilot-scale horizontal subsurface flow constructed wetlands. Chem Eng J 339:108–116. https://doi.org/10.1016/ j.cej.2018.01.056 Haddaji D, Ghrabi-Gammar Z, Hamed KB, Bousselmi L (2019) A re-circulating horizontal flow constructed wetland for the treatment of synthetic azo dye at high concentrations. Environ Sci Pollut Res 26(13):13489–13501. https://doi.org/10.1007/s11356-019-04704-2 Hussain Z, Arslan M, Malik MH, Mohsin M, Iqbal S, Afzal M (2018) Integrated perspectives on the use of bacterial endophytes in horizontal flow constructed wetlands for the treatment of liquid textile effluent: phytoremediation advances in the field. J Environ Manage 224:387–395. https:// doi.org/10.1016/j.jenvman.2018.07.057 Hussain Z, Arslan M, Shabir G, Malik MH, Mohsin M, Iqbal S, Afzal M (2019) Remediation of textile bleaching effluent by bacterial augmented horizontal flow and vertical flow constructed wetlands: a comparison at pilot scale. Sci Total Environ 685:370–379. https://doi.org/10.1016/ j.scitotenv.2019.05.414 Ji M, Hu Z, Hou C, Liu H, Ngo HH, Guo W, Lu S, Zhang J (2020) New insights for enhancing the performance of constructed wetlands at low temperatures. Bioresour Technol 301:122722. https://doi.org/10.1016/j.biortech.2019.122722 Jing Y, Krauss M, Zschieschang S, Miltner A, Butkovskyi A, Eggen T, Kästner M, Nowak KM (2021) Superabsorbent polymer as a supplement substrate of constructed wetland to retain pesticides from agricultural runoff. Water Res 207:117776. https://doi.org/10.1016/j.watres.2021.117776 Kabutey FT, Zhao Q, Wei L, Ding J, Antwi P, Quashie FK, Wang W (2019) An overview of plant microbial fuel cells (PMFCs): configurations and applications. Renew Sustain Energy Rev 110:402–414. https://doi.org/10.1016/j.rser.2019.05.016 Lancheros JC, Madera-Parra CA, Caselles-Osorio A, Torres-López WA, Vargas-Ramírez XM (2019) Ibuprofen and Naproxen removal from domestic wastewater using a horizontal subsurface flow constructed wetland coupled to ozonation. Ecol Eng 135:89–97. https://doi.org/10. 1016/j.ecoleng.2019.05.007 Langergraber G, Dotro G, Nivala J, Rizzo A, Stein, OR (2017) Wetland technology (Vol. 7) in biological wastewater treatment series treatment. International Water Association, London Li Y, Zhu G, Ng WJ, Tan SK (2014) A review on removing pharmaceutical contaminants from wastewater by constructed wetlands: design, performance and mechanism. Sci Total Environ 468–469:908–932. https://doi.org/10.1016/j.scitotenv.2013.09.018 Liu T, Xu S, Lu S, Qin P, Bi B, Ding H, Liu Y, Guo X, Liu X (2019) A review on removal of organophosphorus pesticides in constructed wetland: performance, mechanism and influencing factors. Sci Total Environ 651:2247–2268. https://doi.org/10.1016/j.scitotenv.2018.10.087

Horizontal Subsurface Flow Constructed Wetlands for Toxic Pollutants …

235

Lizama-Allende K, Ayala J, Jaque I, Echeverría P (2021) The removal of arsenic and metals from highly acidic water in horizontal subsurface flow constructed wetlands with alternative supporting media. J Hazard Mater 408:124832. https://doi.org/10.1016/j.jhazmat.2020.124832 Malyan SK, Yadav S, Sonkar V, Goyal VC, Singh O, Singh R (2021) Mechanistic understanding of the pollutant removal and transformation processes in the constructed wetland system. Water Environ Res 93(10):1882–1909. https://doi.org/10.1002/wer.1599 Masi F, Rizzo A, Bresciani R, Martinuzzi N, Wallace SD, Van Oirschot D, Macor F, Rossini T, Fornaroli R, Mezzanotte V (2019) Lessons learnt from a pilot study on residual dye removal by an aerated treatment wetland. Sci Total Environ 648:144–152. https://doi.org/10.1016/j.sci totenv.2018.08.113 Matamoros V, Puigagut J, García J, Bayona JM (2007) Behavior of selected priority organic pollutants in horizontal subsurface flow constructed wetlands: a preliminary screening. Chemosphere 69(9):1374–1380. https://doi.org/10.1016/j.chemosphere.2007.05.012 Mozaffari M-H, Shafiepour E, Mirbagheri SA, Rakhshandehroo G, Wallace S, Stefanakis AI (2021) Hydraulic characterization and removal of metals and nutrients in an aerated horizontal subsurface flow “racetrack” wetland treating primary-treated oil industry effluent. Water Res 200:117220. https://doi.org/10.1016/j.watres.2021.117220 Nguegang B, Masindi V, Msagati Makudali TA, Tekere M (2022) Effective treatment of acid mine drainage using a combination of MgO-nanoparticles and a series of constructed wetlands planted with Vetiveria zizanioides: a hybrid and stepwise approach. J Environ Manage 310:114751. https://doi.org/10.1016/j.jenvman.2022.114751 Oon Y-L, Ong S-A, Ho L-N, Wong Y-S, Dahalan FA, Oon Y-S, Teoh T-P, Lehl HK, Thung W-E (2020) Constructed wetland–microbial fuel cell for azo dyes degradation and energy recovery: influence of molecular structure, kinetics, mechanisms and degradation pathways. Sci Total Environ 720:137370. https://doi.org/10.1016/j.scitotenv.2020.137370 Ortiz-Marin AD, Bandala ER, Ramírez K, Moeller-Chávez G, Pérez-Estrada L, Ramírez-Pereda B, Amabilis-Sosa LE (2022) Kinetic modeling of UV/H2O2, UV/sodium percarbonate, and UV/potassium peroxymonosulfate processes for albendazole degradation. React Kinet Mech Catal 135(2):639–654. https://doi.org/10.1007/s11144-021-02152-z Papaevangelou VA, Gikas GD, Tsihrintzis VA (2017a) Chromium removal from wastewater using HSF and VF pilot-scale constructed wetlands: overall performance, and fate and distribution of this element within the wetland environment. Chemosphere 168:716–730. https://doi.org/10. 1016/j.chemosphere.2016.11.002 Papaevangelou VA, Gikas GD, Vryzas Z, Tsihrintzis VA (2017b) Treatment of agricultural equipment rinsing water containing a fungicide in pilot-scale horizontal subsurface flow constructed wetlands. Ecol Eng 101:193–200. https://doi.org/10.1016/j.ecoleng.2017.01.045 Parlakidis P, Mavropoulos T, Vryzas Z, Gikas GD (2022) Fluopyram removal from agricultural equipment rinsing water using HSF pilot-scale constructed wetlands. Environ Sci Pollut Res 29(20):29584–29596. https://doi.org/10.1007/s11356-021-15373-5 Pat-Espadas AM, Loredo Portales R, Amabilis-Sosa LE, Gómez G, Vidal G (2018) Review of constructed wetlands for acid mine drainage treatment. Water 10(11):1685. https://doi.org/10. 3390/w10111685 Rajan RJ, Sudarsan JS, Nithiyanantham S (2019) Microbial population dynamics in constructed wetlands: review of recent advancements for wastewater treatment. Environ Eng Res 24(2):181– 190. https://doi.org/10.4491/eer.2018.127 Ramírez-Vargas CA, Prado A, Arias CA, Carvalho PN, Esteve-Núñez A, Brix H (2018) Microbial electrochemical technologies for wastewater treatment: principles and evolution from microbial fuel cells to bioelectrochemical-based constructed wetlands. Water 10(9):1128. https://doi.org/ 10.3390/w10091128 Ravikumar Y, Yun J, Zhang G, Zabed HM, Qi X (2022) A review on constructed wetlands-based removal of pharmaceutical contaminants derived from non-point source pollution. Environ Technol Innov 26:102504. https://doi.org/10.1016/j.eti.2022.102504

236

L. E. Amábilis-Sosa et al.

Rìos-Montes KA, Casas-Zapata JC, Briones-Gallardo R, Peñuela G (2017) Optimal conditions for chlorothalonil and dissolved organic carbon in horizontal subsurface flow constructed wetlands. J Environ Sci Health Part B 52(4):274–281. https://doi.org/10.1080/03601234.2016.1273005 Roé-Sosa A, Rangel-Peraza JG, Rodríguez-Mata AE, Pat-Espadas A, Bustos-Terrones Y, DiazPeña I, Vu CM, Amabilis-Sosa LE (2019) Emulating natural wetlands oxygen conditions for the removal of N and P in agricultural wastewaters. J Environ Manage 236:351–357. https://doi. org/10.1016/j.jenvman.2019.01.114 Romain V, Sylvie D, David B (2015) Water residence time and pesticide removal in pilot-scale wetlands. Ecol Eng 85:76–84. https://doi.org/10.1016/j.ecoleng.2015.09.040 Shah MP (2020) Microbial bioremediation & biodegradation. Springer Shah MP (2021) Removal of refractory pollutants from wastewater treatment plants. CRC Press Siatecka A, Oleszczuk P (2022) Mechanism of aging of biochars obtained at different temperatures from sewage sludges with different composition and character. Chemosphere 287:132258. https://doi.org/10.1016/j.chemosphere.2021.132258 Singh S, Chakraborty S (2022) Biochemical treatment of coal mine drainage in constructed wetlands: influence of electron donor, biotic–abiotic pathways and microbial diversity. Chem Eng J 440:135986. https://doi.org/10.1016/j.cej.2022.135986 Sultana M-Y, Chowdhury AKMdMB, Michailides MK, Akratos CS, Tekerlekopoulou AG, Vayenas DV (2015) Integrated Cr(VI) removal using constructed wetlands and composting. J Hazard Mater 281:106–113. https://doi.org/10.1016/j.jhazmat.2014.06.046 Tangahu BV, Sheikh Abdullah SR, Basri H, Idris M, Anuar N, Mukhlisin M (2022) Lead (Pb) removal from contaminated water using constructed wetland planted with Scirpus grossus: optimization using response surface methodology (RSM) and assessment of rhizobacterial addition. Chemosphere 291:132952. https://doi.org/10.1016/j.chemosphere.2021.132952 Tee H-C, Lim P-E, Seng C-E, Mohd Nawi MA, Adnan R (2015) Enhancement of azo dye acid orange 7 removal in newly developed horizontal subsurface-flow constructed wetland. J Environ Manage 147:349–355. https://doi.org/10.1016/j.jenvman.2014.09.025 Tran NH, Urase T, Ngo HH, Hu J, Ong SL (2013) Insight into metabolic and cometabolic activities of autotrophic and heterotrophic microorganisms in the biodegradation of emerging trace organic contaminants. Bioresour Technol 146:721–731. https://doi.org/10.1016/j.biortech.2013.07.083 Valenzuela EF, de Paula FGF, Teixeira APC, Menezes HC, Cardeal ZL (2020) A new carbon nanomaterial solid-phase microextraction to pre-concentrate and extract pesticides in environmental water. Talanta 217:121011. https://doi.org/10.1016/j.talanta.2020.121011 Vymazal J, Bˇrezinová T (2015) The use of constructed wetlands for removal of pesticides from agricultural runoff and drainage: a review. Environ Int 75:11–20. https://doi.org/10.1016/j.env int.2014.10.026 Vymazal J, Kröpfelová L (2008) Wastewater treatment in constructed wetlands with horizontal sub-surface flow. Springer Science & Business Media Vystavna Y, Frkova Z, Marchand L, Vergeles Y, Stolberg F (2017) Removal efficiency of pharmaceuticals in a full scale constructed wetland in East Ukraine. Ecol Eng 108:50–58. https://doi. org/10.1016/j.ecoleng.2017.08.009 Wang Y, Cai Z, Sheng S, Pan F, Chen F, Fu J (2020) Comprehensive evaluation of substrate materials for contaminants removal in constructed wetlands. Sci Total Environ 701:134736. https://doi. org/10.1016/j.scitotenv.2019.134736 Wu J, Feng Y, Dai Y, Cui N, Anderson B, Cheng S (2016) Biological mechanisms associated with triazophos (TAP) removal by horizontal subsurface flow constructed wetlands (HSFCW). Sci Total Environ 553:13–19. https://doi.org/10.1016/j.scitotenv.2016.02.067 Wu J, Li Z, Wu L, Zhong F, Cui N, Dai Y, Cheng S (2017) Triazophos (TAP) removal in horizontal subsurface flow constructed wetlands (HSCWs) and its accumulation in plants and substrates. Sci Rep 7(1):5468. https://doi.org/10.1038/s41598-017-05874-0 Yan J, Hu X, Chen M, Zhang J, Guo F, Vymazal J, Chen Y (2022) Meta-analysis of the removal of trace organic contaminants from constructed wetlands: conditions, parameters, and mechanisms. Ecol Eng 178:106596. https://doi.org/10.1016/j.ecoleng.2022.106596

Horizontal Subsurface Flow Constructed Wetlands for Toxic Pollutants …

237

Yang Y, Zhao Y, Liu R, Morgan D (2018) Global development of various emerged substrates utilized in constructed wetlands. Bioresour Technol 261:441–452. https://doi.org/10.1016/j.bio rtech.2018.03.085 Zhang L, Lyu T, Ramírez Vargas CA, Arias CA, Carvalho PN, Brix H (2018) New insights into the effects of support matrix on the removal of organic micro-pollutants and the microbial community in constructed wetlands. Environ Pollut 240:699–708. https://doi.org/10.1016/j.env pol.2018.05.028

Microbial Consortium for the Treatment of Brewery Effluents-Recommendation for Brewery Effluent Treatment in Constructed Wetlands Priya Kannan, Bhargavi Subramanian, Arunmozhi Bharathi Achudhan, Annapurna Gupta, and Lilly M. Saleena

1 Introduction Brewery industries are known to be the most conventional industries that produce beverages like wine, beer, and other alcoholic beverages. It contributes a significant role to the revenue of the country. In the field of agro-sector industries, the beverage industry is the one that produces the products of the best quality economically. Nonetheless, beverage production requires a large quantity of water and other raw materials such as barley, grains, yeast, etc., which releases the spent grains, yeast surplus, and other by-products while mashing, fermentation, etc. Beer production generates approximately 4–10 L of wastewater with the output of 1 L of beer (Bodike and Thatikonda 2014). The brewery effluents tend to release into the running stream, ponds, lakes, or other natural environments, which may cause pollution to the groundwater and even the soil (Englande et al. 2015). It is not advised to release the effluent into the environment without undergoing bioremediation procedures because this could significantly impact human health and pollute the environment. Treatment is required before releasing into nature since the wastewater has a high concentration of organic compounds such as soluble starch, ethanol, and a low pH that leads to high levels of biological oxygen demand and chemical oxygen demand. The untreated or partially treated effluent disposal into the water bodies can cause severe pollution problems since the effluents contain organic compounds that require oxygen for degradation. Excessive nutrients such as nitrogen and phosphorus in the released effluent could also cause algal bloom and disturb the water body ecosystem. Adopting appropriate treatment procedures at breweries is essential to reducing pollution and addressing environmental and public health issues. Wastewater from the brewery plants has discharged straightaway into the natural P. Kannan · B. Subramanian · A. B. Achudhan · A. Gupta · L. M. Saleena (B) Department of Biotechnology, SRM Institute of Science and Technology, Kattankulathur, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. P. Shah (ed.), Recent Trends in Constructed Wetlands for Industrial Wastewater Treatment, https://doi.org/10.1007/978-981-99-2564-3_12

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water bodies, lakes, oceans, rivers, the pre-treatment plant, or the brewery effluent treatment plant (Bodike and Thatikonda 2014). Regardless of the fact that the raw materials used in the brewing process are harmless, the brewery effluents typically contain organic components which are readily biodegradable, primarily composed of sugars, soluble starch, ethanol, volatile fatty acids, etc., and these are expressed in terms of BOD/COD ratio. Meanwhile, the solids in the brewery wastewater consist of spent grains, kieselguhr, yeast surplus, and the leftover trub, expressed in TSS (Total Suspended Solids) (Simate et al. 2011). To remediate the industrial effluents, we can adopt several methods such as physical, chemical, and biological. Physical treatment involves the removal of floating solid particles, while chemical treatment is associated with using flocculants/coagulants or adjusting the pH of the industrial sewage. Compared to other treatment methods, bioremediation with microorganisms has no detrimental effect on the environment and humankind unless it employs rare pathogenic organisms (Nagda et al. 2022). The basic reasons for adopting biological treatment methods are microbes are used for the effluent treatment, the process is inexpensive, and the levels of BOD/COD removal efficacies are around 80–90% (Sathya et al. 2022). By choosing biological treatment, the treated wastewater is recycled for use in leisure activities, agriculture, and other industrial processes (Gorfie et al. 2022). However, some treatment facilities encounter complications when using biological processes to treat water, such as persistent foaming and scum problems, unpleasant odors, failure to manage BOD/COD levels, excessive sludge formation, etc. Both aerobic and anaerobic mechanisms can be involved in the process of treatment. However, most firms consider the anaerobic technique effective for handling brewery effluents. The majority of industries in India use an aeration system after an up-flow anaerobic sludge reactor (Shao et al. May 2008). When the biological treatment procedure is finished, the water is safe to release into the water body because the standards for water quality have been met. In a constructed wetland that resembles natural wetlands, artificial wetlands were found to be the most cost-effective and environmentally beneficial technique for treating industrial effluents. Constructed wetlands resemble a natural wetland with all the natural microbial community, plants, sand, or gravel acting as filters to separate the dissolved solids (Alayu and Leta 2021). These components could be optimized by several processes examined on the laboratory scale. According to the nature of effluents and the stage at which they must be treated, every parameter in these artificial wetlands, including pH, temperature, the required microbial community, filters like sand or gravel, etc., could be altered. The treatment of brewery effluent in constructed wetlands is inexpensive (Vymazal Dec. 2014). This chapter deals with incorporating the desirable microbial consortium for treating brewery effluent on a laboratory scale which can be expanded to be treated in a constructed wetland.

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2 Microbial Community Used for the Effluent Treatment 2.1 Microalgae Consortium Microalgae have been revealed to remove the pollutants tremendously and were able to decompose and use the heavy metals and other compounds as their nutritive sources (Cuellar-Bermudez et al. Jun. 2017). Consequently, microalgae would be used to treat wastewater which has highly perilous compounds to the environment but is nourishing to them. Besides, microalgae-bacteria systems show synergistic activity owing to the release of carbon dioxide in the oxidation process of organic pollutants degradation, which is used in the photosynthetic activity of the algae. As an outcome, the energy expended for the photosynthetic process is reduced, showing an industrial significance (Brown 1984). Microalgal-bacterial-based systems are a viable alternative treatment approach considering the increased rates of organic and inorganic pollutants remediation provided by the synergistic action of photosynthetic microorganisms and bacteria. Photobioreactors were used in the batch mode to treat the brewery effluent by the consortium of cyanobacteria and heterotrophic bacteria and were done in a laboratory-scale set-up with a small working volume. The photobioreactor was inoculated with 10% of the consortium as seed inoculum. The growth rate of the cyanobacterial-bacterial consortium was monitored by the temperature and pH of the biologically treated effluent sample. Among the microbial consortium, the dominant organism was the filamentous cyanobacterium Leptolyngbya sp., which was in aggregate form cyanobacterium, which holds the relative biomass of about 85%, and a second cyanobacterium which held the relative biomass of 5%, was identified to be Chroococcus-like in the culture. The aggregation is achieved with an important process of the cells, known as Extracellular polymeric substance formation (EPS). EPS formation significantly enables the cells to adhere to each other. This ability of the cells to generate aggregates with the help of various factors provided in the substrate (wastewater) sometimes protects the cells from being vulnerable (More et al. 2014) (Salim et al. 2014). As a result, these consortium aggregates influenced by the filamentous cyanobacterium Leptolyngbya sp. would undergo efficient bioremediation. The brewery effluents have been collected from various stages, such as raw sludge and primary or secondary treated brewery wastewater. These effluent samples were allowed to sediment to remove large particulate matter from the sludge. The researchers gathered the brewery’s untreated raw wastewater from the plant’s inlet before beginning any treatment and collected the other effluent sample from the outlet of the brewery’s secondary wastewater treatment plant, which was the biologically treated brewery effluent via the activated sludge process. It is always recommended to filter the effluent samples to remove the suspended solids. Generally, the filter with a pore size of 0.45 µm filters the suspended solids while the filtrate serves as the source of nutrients for the microbial consortium. The filtrate was analyzed initially

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for the determination of its toxic potential based on the presence of dissolved chemical oxygen demand (2272.00 ± 294 mg/L) and other ions such as nitrate (NO3–N 31.02 ± 6.05 mg/L), nitrite (NO2 –N 0.23 ± 0.02 mg/L), ammonium (NH4+ 4.02 ± 1.05 mg/L), orthophosphate (PO4 4.76 ± 1.01 mg/L), total phosphorus (P) (4.76 ± 1.01 mg/L), total nitrogen (100.18 ± 2.04 mg/L), and the initial pH of the effluent filtrate. These characterizations can be analyzed according to the standard protocols developed by American Public Health Association (APHA) and Water Environment Federation (WEF) (Papadopoulos et al. 2021). To identify the optimum condition, the initial inoculum was studied to understand the optimal growth conditions with varying pH values, temperatures, and inoculum size. Optimum conditions were applied to assess the biomass concentration, biodegradation of the toxic compounds, and the presence of other native bacteria in the wastewater, which would compete and contaminate the cyanobacterial consortium. Based on the growth rate of the preferred microbial consortium, studies reported that the degradation increases with the increase in the inoculum size by 20% in the culture. Furthermore, the change in optimal temperature to about 72 °C for 15 min certainly quick pasteurization has reportedly shown to reduce the native bacteria contamination. After biotreatment of brewery effluent, the efficacies of the microbial consortium in reducing the toxicity and removing the pollutant were estimated by the conventional procedures. The soluble chemical oxygen demand was noted to be removed for about 95.25%, while other ions, as previously described with their initial values, were predominantly removed as follows: total nitrogen (10.04 mg/L) efficiently removed of about 90.14%, nitrate (NO3 –N 6.17 ± 0.57 mg/L) about 80.11%, nitrite (NO2 – N 0.09 ± 0.01 mg/L) for 60.43%, ammonium (NH4+ 0.32 ± 0.02 mg/L) removed effectively about 92.23%, orthophosphate (PO4 1.25 ± 0.97 mg/L) up to 73.73, total phosphorus (P) (1.35 ± 0.23 mg/L) up to 72.62% was removed. Thus, the final concentrations of the pollutants present in the biologically treated brewery wastewater were within the bounds of the authority prescribed. The microalgae consortium produces more carbohydrates used for biofuel production. Furthermore, EPS production of this majored filamentous cyanobacterium enhances the aggregation of cells. Thus, the cyanobacterial consortium paves a massively favorable for the large-scale treatment of the brewery effluents (Papadopoulos et al. 2020a). The overall process of brewery effluent treatment is illustrated in Fig. 1.

2.2 Electrocoagulation Treatment and Cyanobacterial Cultivation For the two-step treatment of Brewery sewage, electrocoagulation (EC) and cyanobacteria-based culturing are preferred in order to create a suitable substitute for traditional activated sludge technology in industrial applications. Untreated wastewater samples were taken from the brewing company equalization tank and

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Fig. 1 Illustration of the overall course of brewery effluent treatment and applications of the treated wastewater

stored at −20 ºC while being analyzed for physicochemical characteristics such as Chemical Oxygen Demand, Soluble Chemical Oxygen Demand, and Total Kjeldahl Nitrogen.BW was pretreated with EC in magnetically stirred batch reactors with three distinct electric current densities applied by connecting the electrodes parallel to a DC-controlled power supply under galvanostatic operation at a constant temperature of 25 ºC. Using a variety of electrode materials (Al and Fe), EC was used as a pre-treatment technique to reduce density and make organic pollutants suitable for photosynthetic cultivation (Moussa et al. 2017). During the EC tests, 5 mL samples were obtained and allowed to settle in falcon tubes for 30 min. After the Electrocoagulation treatment, the wastewater was allowed to sediment for 30 min to allow for sludge separation and precipitation. The supernatant was then gathered and used to cultivate cyanobacteria. A microbial consortium dominated by the cyanobacterium Leptolyngbya sp. was cultivated in order to degrade to less toxic pollutants and produce biomass that could be used for commercial purposes (Taton et al. 2012). In order to maintain the biomass suspension, the electrochemically pre-processed brewery effluent is treated in photobioreactors under batch process with cyanobacteria that were continuously magnetically agitated. Experiments were carried out in non-sterile circumstances with constant light. A microbial consortium of cyanobacteria is used as the inoculum, cultivated in BW till the biomass concentration reaches half of the total volume. Throughout the studies, residual soluble Al and Fe concentrations were evaluated to identify potential secondary pollution sources and the Leptolyngbya-based microbial community’s capacity for bioremediation. Total suspended solids (TSS) elimination was reported as 100% using Al or Fe electrodes, whereas BW decolorization was around 88% using Al and 80% using Fe electrodes after 30 min of treatment. The supernatant collected by the

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electrochemical treatment is employed as the medium for a fifteen-day cyanobacteria culture. Research says the cyanobacterial consortium eliminated up to 90% of s-COD and 60% of inorganic contaminants and residual metals from the EC treatment. The combined procedure was incredibly effective in removing pollutants, with removal rates of 89.1%, 100%, 89.4%, 98.5%, 91.6%, and 100% of the original NO3 (Papadopoulos et al. 2020b).

2.3 Treatment Using Scendesmus Obliquus Microalgae, Scendesmus obliquus is used to treat brewery effluents in a bubblecolumn photobioreactor concurrent with carbon dioxide fixation. Scendesmus obliquus has been observed to be an acclimatizing organism that can survive in the high pollutant level of the sewages, while its biomass could be used as the feed substrate for the production in other agro sectors industries like biofuel, biogas, biofertilizers, etc. (Gupta et al. 2016). This approach was considered the promising conversion of potentially toxic pollutants and recycling biomass in a low-cost method. Since the energy and aeration (oxygen) desired for the other pollutant degrading organisms like aerobic bacteria would be provided by the microalgae making it desirable for fewer demands for external sources of energy or nutritive supplies. Furthermore, Scendesmus obliquus can fix the carbon dioxide, which in turn helps to reduce the greenhouse effect by releasing industrial effluents (Nagda et al. 2022). The effluent has been allowed for sedimentation as it may contain a large amount of sludge for 24 h. Photobioreactor was used for the treatment of brewery sewage with a microbial consortium comprised of Scendesmus obliquus with an algal symbiont to bacteria, i.e., Chlorella sp., as the sewage was continuously fed after the culture had reached a stationary state on the 17th day through the tubes maintained at a total volume of 5 L while effluent was fed by 6% to the microalgae with elevated carbon dioxide with the aeration rate of 0.1 L/L/min obtained as a result of effluent purification, therefore there would be no challenges for any other supplemental sources. There was a continuous illumination of 3 fluorescent lamps fixed sideways of the photobioreactor (Vonshak 1986). 29.4 ± 1.4 mg/L was found to be the initial concentration of ammonia (NH3 ), 72.8 ± 1.4 mg/L for total nitrogen (TN), 37.75 mg/L for phosphate (PO4 ), and the total chemical oxygen demand measured to be 226 ± 0 mg/L with the initial pH as 8.85. After treating the brewery effluent with the microbial consortium, the final concentrations of the pollutants removed are estimated using the standard protocols. The final pollutant concentration was determined based on the different hydraulic retention times (HRT) expressed in days (d), defined as the average time the feed effluent was in contact with the bioreactor. Out of different HRT between 2.1 and 10.4 d, the pollutant removal efficiency is within the range of the legally allowed limit to be vented out into a natural surrounding other than the HRT 2.1 days. To elaborate, HRT at 2.1 showed an efficient pollutant removal for about 71.4% for ammonia, 73.1% for total nitrogen, 6.1% for phosphorus, and 55.8% for COD, but

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at a dilution rate of 0.48 which does not satisfy the legal limit to discharge into the natural environment. The other HRT (days/d) noted were 3.5, 5.3, 6.5, 8.7, and 10.4, in which 10.4 d exhibited the maximum ammonia removal of about 92.9%, while a maximum of total nitrogen removal happened at 3.5 d and 10.4 d with an efficiency of 88.5%, maximum phosphorus elimination found on 10.4 d with 40.8% and the total organic load removal was on 3.5 d HRT with 61.9% moreover at all dilution rates except for phosphorus at 0.10 dilution (Ferreira et al. 2017).

3 Conclusion Many methods and organisms are employed to treat the brewery effluent to reduce or remove the organic and inorganic substances or convert the pollutants to benign and make them ready to introduce into the environment. It is necessary to contemplate the course of time for effluent collection from the production plant to the treatment plant. Certainly, the collection of the brewery effluent should be focused on the time of either batch or continuous manufacturing of wine, beer, and other beverages rather than other processes like CIP and SIP processes of the industry. Henceforth, it would be worthwhile if the collected wastewater during the manufacturing period since the organic and inorganic compounds would be released at the peak during the production time other than during the cleaning and sterilization course. The predominant advantage of the biological treatment of the brewery effluent with microbial consortium would be that they utilize all the carbon, nitrogen, and other nutrients in the effluent and convert them into less toxic or complete pollutant removal. Consequently, the wastewater would become pollution-free and can be discharged into nature. The resultant biomass is also valuable as the feed for sustainable energy sources such as biogas, bioethanol, organic fertilizers, etc. The wastewater reaches the benchmark only when the dissolved pollutants are removed to a certain level as endorsed by the government. It is proven that the incorporation of microbial consortium into the artificially constructed wetlands to treat the beverage industry effluents would be accelerated when it is optimized on a bench scale. Further, the operational cost would also be economical as it does not require any energy outsourcing, and since its technology is understandable, it could be operated even by a lay person. Though treating the brewery wastewater in the constructed wetlands has tremendous fruitful welfare to the man-kind and other life forms, it comes up with liability. The major drawback for the industrial effluent treatment would be the highest retention time which hinders the amount of wastewater from being treated in the stipulated time when compared to the conventional method of effluent treatment by activated sludge process, which provides a maximum pollutant removal within 4–6 h.

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References Alayu E, Leta S (2021) Post treatment of anaerobically treated brewery effluent using pilot scale horizontal subsurface flow constructed wetland system. Bioresour Bioprocess 8(1). https://doi. org/10.1186/s40643-020-00356-0 Bodike R, Thatikonda, SR (2014) Biotreatment of brewary effluent using pseudomonas species [Online]. www.iosrjournals.orgwww.iosrjournals.org8 Brown R (1984) Relationships between suspended solids, turbidity, light attenuation, and algal productivity. Lake Reservoir Manage 1(1):198–205. https://doi.org/10.1080/074381484093 54510 Cuellar-Bermudez SP et al (2017) Nutrients utilization and contaminants removal—A review of two approaches of algae and cyanobacteria in wastewater. Algal Res (24):438–449. https://doi. org/10.1016/j.algal.2016.08.018 Englande AJ, Krenkel P, Shamas J (2015) Wastewater treatment & water reclamation✩, in reference module in earth systems and environmental sciences. Elsevier. https://doi.org/10.1016/b978-012-409548-9.09508-7 Ferreira A (2017) et al Scenedesmus obliquus mediated brewery wastewater remediation and CO2 biofixation for green energy purposes. Of Clean Prod 165:1316–1327. https://doi.org/10.1016/ j.jclepro.2017.07.232 Gorfie BN, Tuhar AW, shiberu Keraga A, Woldeyohannes AB (2022) Effect of brewery wastewater irrigation on soil characteristics and lettuce (Lactuca sativa) crop in Ethiopia. Agric Water Manag (269):107633. https://doi.org/10.1016/J.AGWAT.2022.107633 Gupta SK, Ansari FA, Shriwastav A, Sahoo NK, Rawat I, Bux F (Mar.2016) Dual role of Chlorella sorokiniana and Scenedesmus obliquus for comprehensive wastewater treatment and biomass production for bio-fuels. J Clean Prod 115:255–264. https://doi.org/10.1016/J.JCLEPRO.2015. 12.040 More TT, Yadav JSS, Yan S, Tyagi RD Surampalli RY Extracellular polymeric substances of bacteria and their potential environmental applications (2014) J Environ Manag (144):1–25. Academic Press. https://doi.org/10.1016/j.jenvman.2014.05.010 Moussa DT, El-Naas MH, Nasser M, Al-Marri MJ (2017) A comprehensive review of electrocoagulation for water treatment: potentials and challenges. J Environ Manag 186:24–41. Academic Press. https://doi.org/10.1016/j.jenvman.2016.10.032 Nagda A, Meena M, Shah MP (2022) Bioremediation of industrial effluents: a synergistic approach. J Basic Microbiol 62(3–4):395–414. John Wiley and Sons Inc. https://doi.org/10.1002/jobm.202 100225 Papadopoulos KP et al (2020a) Brewery wastewater treatment using cyanobacterial-bacterial settleable aggregates. Algal Res 49. https://doi.org/10.1016/j.algal.2020.101957 Papadopoulos, KP, Economou CN, Tekerlekopoulou AG, Vayenas Dv (2020b) Two-step treatment of brewery wastewater using electrocoagulation and cyanobacteria-based cultivation. J Environ Manag 265. https://doi.org/10.1016/j.jenvman.2020.110543 Papadopoulos KP, Economou CN, Tekerlekopoulou AG, Vayenas Dv (2021) A cyanobacteria-based biofilm system for advanced brewery wastewater treatment. Appl Sci (Switz) 11(1):1–13. https:// doi.org/10.3390/app11010174 Salim S, Kosterink NR, Tchetkoua ND, Wacka Vermuë, MH, Wijffels RH (2014) Mechanism behind autoflocculation of unicellular green microalgae Ettlia texensis. J Biotechnol 174(1):34–38. https://doi.org/10.1016/j.jbiotec.2014.01.026 Sathya K, Nagarajan K, Carlin Geor Malar G, Rajalakshmi S, Raja Lakshmi P (2022) A comprehensive review on comparison among effluent treatment methods and modern methods of treatment of industrial wastewater effluent from different sources. Appl Water Sci 12(4). Springer Science and Business Media Deutschland GmbH. https://doi.org/10.1007/s13201-022-01594-7 Shao X, Peng D, Teng Z, Ju X (2008) Treatment of brewery wastewater using anaerobic sequencing batch reactor (ASBR). Biores Technol 99(8):3182–3186. https://doi.org/10.1016/j.biortech. 2007.05.050

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Simate GS et al (2011) The treatment of brewery wastewater for reuse: state of the art, Desalination 273(2–3):235–247. https://doi.org/10.1016/j.desal.2011.02.035 Taton A (2012) et al Gene transfer in Leptolyngbya sp. strain BL0902, a cyanobacterium suitable for production of biomass and bioproducts. PLOS One 7(1). https://doi.org/10.1371/journal. pone.0030901 Vonshak A (1986) Laboratory techniques for the cultivation of microalgae (1st edn). Taylor & Francis Group Vymazal J (2014) Constructed wetlands for treatment of industrial wastewaters: a review. Ecol Eng 73:724–751. https://doi.org/10.1016/J.ECOLENG.2014.09.034

In-silico Integration in Environmental Remediation Arunmozhi Bharathi Achudhan, Madhumitha Masilamani, Priya Kannan, and Lilly M. Saleena

1 Introduction Recently, modern days and rapid industrialization has made a drastic change in modern equipment and modern solutions to many human problems that came alongside the issue of waste generation. These wastes contain chemical compounds that are generated and used in our daily lives on a daily basis, and they are eventually emitted into the atmosphere once the work is done. Because of expanding industrialization and urbanization, the amount of chemicals generated and emitted has risen sharply (Singh et al. 2016). Environmental contamination and xenobiotic pollution pose serious risks to the ecosystem and eventually threaten life. Xenobiotics are dangerous because they persist in the environment, contaminate food systems, and raise a number of health issues (Atashgahi et al. 2018). Prolonged exposure to heavy metals and xenobiotics in the environment poses a major hazard to life. These effects of the xenobiotics are long-term; hence treating and getting rid of them is crucial. Treating the hazardous chemical compounds being released into the environment into simpler molecules using various techniques is called the remediation of chemicals. Bioremediation and chemical remediation can treat these Xenobiotic compounds. When treated, chemical remediation yields fairly enough safe compounds and ends up complementing more chemicals. Bioremediation is a promising technique to remediate heavy metals and toxic compounds present in contaminated lands and water existing in the environment. In bioremediation, pollutants are biologically converted into non-toxic molecules to reduce pollution. Generally, microbes, including parasites and other protists, always metabolize organic matter to decompose waste material in areas overburdened with natural waste materials. Bacteria that utilize the A. B. Achudhan · M. Masilamani · P. Kannan · L. M. Saleena (B) Department of Biotechnology, SRM Institute of Science and Technology, Kattankulathur, Tamil Nadu, India e-mail: [email protected] © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2023 M. P. Shah (ed.), Recent Trends in Constructed Wetlands for Industrial Wastewater Treatment, https://doi.org/10.1007/978-981-99-2564-3_13

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metabolic breakdown of xenobiotics as an energy source include aerobic and anaerobic microorganisms (Singh et al. 2014). The microbial removal of the xenobiotics is preferred over the conventional methods due to its lower cost and higher efficiency. Numerous variables, including diversity of microorganisms, abundance, and coding genes, are important to biodegradation and how organisms react to environmental toxins. The enzyme involved is a major factor in the efficiency of xenobiotics catabolism by microbiological organisms. Numerous studies have been conducted to identify the microorganisms capable of degrading substances unique to the enzymes they create (Table 1). There are many enzymes that have been identified and utilized in bioremediation, such as monooxygenase, dioxygenase, reductase, deaminase, dehalogenase, laccase, etc. (Bhandari et al. 2021). Due to their structure and characteristics, these biocatalysts may increase the reaction rate and degradation efficiency. Many biocatalysts have been sourced from microorganisms that are found to have better activity and efficiency. Apart from enzyme sources, the microorganism as a whole is also used in the bioremediation process to remove xenobiotics from the environment effectively (Table 2). Bioremediation in constructed wetlands is better in remediating toxic compounds by microbial remediation. Constructed wetlands are man-made ecosystems that optimize the biological, physical, and chemical processes mimicking natural wetland systems to treat wastewater, mine drainage, and other waterways (Hassan et al. 2021). Table 1 Enzymes involved in xenobiotics degradation with their microbial sources Microorganisms

Enzymes

Applications

Pseudomonas putida F6

Cell-free extracts laccase Degradation of synthetic dyes

Streptomyces cyaneus

Cell-free extracts laccase Oxidation of micropollutants such as BPA, DFC, and MFA

Geobacillus thermocatenulatus

Cell-free extracts laccase Decolorization of textile dyes

Bacillus megaterium

Purified P450

Hydroxylation of PCCDs

Mycobacterium species

Cell-free extracts P450

Biodegradation of morpholine

Bacillus sp; Geobacillus

Purified amylase

Starch Liquefaction

Ochrobactrum and Pseudomonas sp. TL

Purified dehalogenase

Degradation of halogen acids & TBBPA

Sphingobacterium sp. strain S2

cell-free extracts lipase

Degradation of PLA

Pseudomonas putida

cell-free extracts dehydrogenase

Catabolism of 2,4-xylenol

Streptomyces thermoviolaceus

cell-free extracts protease

Deproteinization of crustacean wastes

Bacillus pumilus

cell-free extracts lipase

Degradation of oil containing industrial wastewater

Ancylobacter aquaticus

Cell-free extracts dehalogenase

Degradation of TBP

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Table 2 Removal of Xenobiotics from the Environmental by microbial Degradation Microorganisms

Compounds

Removal efficiency

Bacillus fusiformis & Deuteromycete ligninolytic fungal strains

Naphthalene

Effective—69%, Degraded via o-phthalic acid and benzoic acid

Shewanella putrefaciens & Bacillus sphaericus

Pyridine

Effective—75%

T. versicolor

Sulfur brown GD

Effective—49.5%

Coriolopsis gallica

Reactive Black 5

Effective—78.2%

Bacillus salamalaya 139SI

Crude oil waste

Effective—88%

Bacillus pumilus B12

Poly-lactic acid

Degrade polylactic acid film within 48 h by the release of L-lactate monomers

T. pubescens

Acid black 172

Effective—68.84%

Cyathus bulleri

Succinimidyl ester

Effective—90%

White Rot fungi (Strain RYNF13)

Phenanthrene

Effective—68%

Ganoderma Lucidum 00,679

Disperse Navy blue HGL

Effective—93.4%

Ganoderma lucidum

Phenanthrene and Pyrene (PAH)

Effective—99.65%

Bacillus subtilis BM-1

Fluorene

Degrade 86% of 50 mg/L fluorine within 21 days

Bacillus megaterium

Azo dye

Decolorized 98% dye

Bacillus cereus WD-2

Prochloraz -manganese

90.7% degradation at pH 8

Constructed wetlands can treat wastewater efficiently, cost-effectively, and environmentally soundly while serving as wildlife habitats. Microbes have evolved numerous strategies for surviving in contaminated environments when subjected, and they are known to use various detoxifying mechanisms such as bioaccumulation, biosorption, biomineralization, and biotransformation, which can be used for bioremediation in artificial wetlands (Hussain et al. 2018). Bioinformatic strategies, including pathway prediction systems, toxicity prediction, databases, and protein structure prediction tools, are needed to determine the fate of environmental contaminants in the wetland fields beforehand. The current chapter goes into detail about the collection of all databases, tools, and servers that help with in-silico study and prediction of chemical toxicity as well as the clarification of likely microbial breakdown pathways.

2 What Role Does Bioinformatics Play in Bioremediation? The biodegradation of the chemicals depends on understanding the selectivity, microbial and toxic kinetics, and physiological response factors. Chemical characterization

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supports microbial exposure, bioaccumulation, and compound toxicity by providing information on the fate and transport of toxic compounds together with any possible intermediates generated. However, the traditional and conventional techniques of bioremediation need prolonged exposure and analysis and high expenditures while producing modest results (Sarkar et al. 2005). It took a long time to complete the experiments to enhance the procedures. As a result, researchers created computational, system biological, and bioinformatics tools to support their plans and investigations. The catabolic processes of many chemical compounds with complicated structures were also resolved, as were the techniques used to produce less toxic and simpler molecules. The procedures and approaches become more effective as a result. Data and information like names, synonyms, “SMILES” codes, molecular weight, chemical formula, chemical structure graphic, actual three-dimensional structure in PDB format, the melting point, d-point boiling, solubility, density, evaporation rate, and more are available in bioinformatics databases (Pazos et al. 2005). These tools can be employed right from the starting stage of the degrading mechanism. The amount of toxicity necessary to harm or to cause lethality to the microorganism that is degrading must be determined in order to maintain the population of degrading organisms. In order to evaluate chemical toxicity, in-silico methods are utilized. Additionally, bioinformatics tools may screen pollutants for degradation sensitivity to certain known enzymes. Numerous databases and bioinformatic tools have comprehensive lists of the microbial strains used in bioremediation and detailed lists of microbial enzymes produced by the diverse species engaged in bioremediation (Bhandari et al. 2021; Mojtaba Mousavi et al. 2021). Suppose any novel bacteria deviating from existing microbes involved in the degrading process is discovered. In that case, it can be validated using phylogenetic analysis, making the organisms with differing qualities stand out. There are already a number of databases and prediction tools/approaches available to help plan and execute bioremediation. By doing away with the requirement for fundamental laboratory tests, and the in-silico method speeds up the degradation pathway prediction and saves time (Kleinman et al. 2014). The combination of bioinformatics and biodegradation facilitates the comparison, evaluation, and validation of genetic and genomic data and the worldwide understanding of molecular biology’s revolutionary components. It gives researchers a platform to create efficient computational methods for environmental and human health, and it helps with examining and categorizing biological pathways and networks, which are essential components of environmental remediation on a more comprehensive level. Bioremediation in constructed wetlands is better in remediating toxic compounds by microbial remediation. These constructed wetlands are provided with the suitable conditions and environment for the microbial growth and conditions needed for the degradation and removal of the compounds (Oscar Omondi and Caren Navalia 2021). Bioinformatic strategies, including pathway prediction systems, toxicity prediction, databases, and protein structure prediction tools, are needed to determine the fate of environmental contaminants in the wetland field beforehand (Fig. 1). It gives researchers a platform to create efficient computational methods for environmental and human health, and it helps with examining and categorizing biological pathways and networks (Jaiswal and Shukla 2020).

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Fig. 1 Integration of bioinformatics in bioremediation

3 Toxicity Prediction In our daily lives, we are exposed to a variety of chemical compounds, including organic compounds, skincare products, medications, and other chemicals. These compounds are potentially mutagenic, carcinogenic, or poisonous in nature, lot of these substances are reported to produce adverse medication responses, non-acute and subacute poisoning that causes allergic responses, paralysis, or even death in longer exposure. The experimental methods for predicting molecule toxicity are time-consuming and labor-intensive, hence the machine learning methodologies are imposed to build new toxicity prediction methods. Several models have been created in recent years that employ computational programs to estimate the toxicity of chemical substances (Oscar Omondi and Caren Navalia 2021). Understanding the hazardousness of the compound level of a compound could be much helpful for the bioremediation process. Here are some Publicly available models used to predict the toxicity of the compound,

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• ToxiM (Toxicity Prediction Tool for Small Molecules)—For the purpose of toxicity, solubility, and permeability forecasting of tiny compounds, this server (http:// metagenomics.iiserb.ac.in/ToxiM/) would be a very valuable and dependable resource (Sharma et al. 2017). • SuperToxic (http://bioinformatics.charite.de/supertoxic)—SuperToxic is a vast database of toxicological information that combines toxicity ratings with chemical, structural, and functional data. The potential toxicity of drugs that have not yet been verified can be characterized and estimated using features like similarity screening and substructure search. Reducing the amount of animal testing might be beneficial (Schmidt et al. 2008). • Sarah Nexus (https://www.lhasalimited.org/products/sarah-nexus.htm)—It is a statistical software tool that gives you accurate mutagenicity predictions (Bossuyt et al. 2018). • VirtualToxLab (https://pharma.unibas.ch/de/research/research-groups/comput ational-pharmacy-2155/research/virtualtoxlab/)—For predicting the hazardous potential of medications, chemicals, and natural materials (cardiotoxicity, certain components of carcinogenicity, and endocrine and metabolic disruption) (Vedani et al. 2012). • Toxicity Estimation Software Tool (https://www.epa.gov/chemical-research/tox icity-estimation-software-tool-test)—Its uses molecular structures that can be used to forecast an organic compounds acute toxicity (Vedani et al. 2015). • TOPKAT (https://www.toxit.it/en/services/software/topkat)—Using this technique, it is possible to forecast a chemical’s ecotoxicity, mutagenicity, and reproductive/developmental toxicity (Prival 2001). • Ecological Structure Activity Relationships (ECOSAR) (https://www.epa. gov/tsca-screening-tools/ecological-structure-activity-relationships-ecosar-pre dictive-model)—Using computational structure–activity relationships, estimate that industrial chemicals can be hazardous to aquatic organisms including fishes, aquatic invertebrates, green algae, and aquatic plants in three different ways: acutely (short-term), chronically (long-term), and delayed (Reuschenbach et al. 2008). • ToxiPred (https://webs.iiitd.edu.in/raghava/toxipred/)—a user-friendly application server for analyzing the toxicity of small chemical compounds in aqueous solutions in T. pyriformis (Mishra et al. 2013). Biodegradative databases store and maintain information about chemical biodegradation, such as xenobiotic-degrading microorganisms, toxic chemical metabolic breakdown pathways, enzymes, and genes involved in biodegradation. Table 3 explains the tools and databases that play a pivotal role in the area of bioremediation and their significance along with the address link required for access to the database.

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Table 3 Databases associated with bioremediation Biodegradation databases

Significance in bioremediation Link

University of Minnesota Biocatalysis/Biodegradation Database (UMBBD)

Provides information on the molecular mechanisms and biotransformation principles, enzymes, genes, and reactions involved in the microbial degradation of xenobiotic substances

Oxygenase Database (OxDBase)

Give details on the aromatic https://webs.iiitd.edu.in/rag ring-hydroxylating hava/oxdbase/ dioxygenases (ARCD) that are responsible for destroying pesticides

Pathway Genome Database (BioCyc)

Make knowledge on the biology and genetics of microbial degradation accessible

https://www.hsls.pitt.edu/obrc/ index.php?page=URL110018 8151

https://biocyc.org/

https://metacyc.org/ Metabolic Pathway Database Predict metabolic pathways (MetaCyc) and reconstruction of catabolic pathways Biodegradation Explains how metabolic Network—Molecular pathways are dynamically Biology Database (Bionemo) regulated and how transcription factors are involved in degradation processes

http://bionemo.bioinfo.cnio.es/

4 UM-BBD (University of Minnesota Biocatalysis/Biodegradation Database) The UM-BBD is a biodegradation database found at (http://umbbd.ethz.ch/). Microorganisms, biotransformation processes, genes, enzymes, and the complexity of microbial metabolisms are all represented in this database (Ellis et al. 1999). This database primarily emphasizes xenobiotic chemical metabolic pathways, which are available in both text descriptions and graphic representations. Pathways are a network of multistage process, enzymatic reactions that start with a starting molecule and then go through intermediates. The UM-BBD metabolic route page of a certain molecule contains all known pathways for that drug and information on the microorganisms and enzymatic activities in its breakdown. Two enzymatic mechanisms are involved in the microbial breakdown of benzonitrile. Nitrilase converts benzonitrile straight into benzoate and ammonia via the nitrilase route. In the second process, nitrile hydratase and amidase work together to complete this conversion. Microorganisms (Rhodococcus rhodochrous J1, Klebsiella pneumoniae) that are involved in benzonitrile degradation are also listed. A separate HTML link was also generated

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Fig. 2 Graphical pathway map for Benzonitrile Degradation at the UM-BBD

for the benzonitrile pathway (http://eawag-bbd.ethz.ch/bzn/bzn_map.html) (Fig. 2). The UM-BBD database currently contains (1) 219 microbial degradation pathways; (2) 1503 chemical kinetics; (3) 993 enzymatic reactions; (4) 543 microbes; (5) 250 biotransformation principles; (6) 50 functional groups; and (7) 76 naphthalene 1, 2- dioxygenase reactions and (8) 109 toluene dioxygenase reactions. This database contains data on genes and enzymes that involved in the processes of xenobiotic degradation and is linked to ExPASy, BRENDA, Enzyme, and NCBI.

5 OxDBase—Database of Biodegradative Oxygenases OxDBase (https://webs.iiitd.edu.in/raghava/oxdbase/help.html) is a database introduced by the Council of scientific and industrial research—Institute of Microbial Technology in Chandigarh, India, that database server stores maintain data about oxygenase gathered from scientific literature and the database information. The foremost essential enzymes implicated in the aerobic breakdown of aromatic compounds are oxygenase (Nozaki and Ishimura 1974). Monooxygenases and dioxygenases are the two main forms of oxygenases. Monooxygenases enable the incorporation of one molecular oxygen atom into the substrates, whereas dioxygenases catalyze the incorporation of two molecular oxygen atoms into the substrates (Esmaeel and Alfatlawi 2022). Dioxygenases come in two different varieties: aromatic ring hydroxylating dioxygenases (ARHD) and aromatic ring cleavage dioxygenases (ARCD). While ARCD catalyzes ring cleavage, ARHD is in charge of aromatic ring hydroxylation. Extradiol and intradiol are the two further divisions of ARCDs (Fig. 3). While intradiol ARCDs only cleave rings between two hydroxyl groups, extradiol cleaves rings between hydroxylated carbons and neighboring non-hydroxylated carbons (Chakraborty et al. 2014). This database carries information on almost 240 oxygenases involved in the biodegradation of xenobiotic contaminants, including both dioxygenases and monooxygenases. The EC number, synonym, reaction in which

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Fig. 3 Mechanism of Oxygenase enzymes

they were involved, Family and subfamily, Structure and Gene link, and research reference are all included in the enzyme sections. The sections also included links to external databases such as BRENDA, KEGG LIGAND, ENZYME, NCBI, PDB structure, Pubmed database, and UM-BBD, which featured significant relevant information. It is vital to degrade toxic compounds, and this database will aid in the purpose of environmental remediation (Fig. 4) and it is easy to use and expands our knowledge of aromatic compound aerobic degradation (Arora et al. 2009).

6 Biocyc and Metacyc The Bioinformatics Research Group at SRI International created this database, which is extremely beneficial for Xenobiotic degradation studies and other scientific research. BioCyc (http://biocyc.org/) provides the repository or acquisition of Pathway/Genome Databases. It consists of 20,055 Pathway/Genome Databases (PGDBs) for model eukaryotes and thousands of microorganisms, along with software tools for analyzing them. It is a comprehensive database with curated information from 130,000 publications. The entire genome and projected metabolic pathway for a single organism are contained in each PGDB, and MetaCyc serves as a reference collection for the pathway tool, a program that predicts metabolic pathways (Karp et al. 2018). The predicted metabolic cycle includes a list of all the metabolites, enzymes, and reactions. Additionally, anticipated operons, transporters, and pathway-hole fillers are all covered by Biocyc PGDBs. A variety of tools, including

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Fig. 4 OxDBase potential applications and their uses

gene expression analysis, metabolomics analysis, and other big dataset analysis, are available for querying and analyzing PGDBs on BioCyc pathway tool-based internet sites. A range of visualization tools are available, including metabolic-pathway graphs and zoomable diagrams illustrating each organism’s complete metabolic pivot table (Paley and Karp 2021). MetaCyc (https://metacyc.org/) incorporates experimentally confirmed metabolic activity and enzyme data from the scientific literature. It is a unique resource in domains such as genome analysis, metabolism, and metabolic engineering since it exclusively contains experimentally identified pathways and enzymes and because it tightly integrates data and research papers (Karp et al. 2002). MetaCyc includes both major and secondary metabolic pathways as well as the metabolites, processes, enzymes, and genes related to them (Caspi et al. 2018). The goal of MetaCyc is to record a representative sample of each experimentally described pathway in order to catalogue the universe of metabolism. There are presently 2937 pathways, 17,780 reactions, and 18,124 metabolites in MetaCyc. The online encyclopedia of metabolism aids metabolomics research, evaluates metabolic pathways in sequenced genomes, and enables metabolic engineering via enzyme databases. Some of the MetaCyc applications are useful in predicting the cycle of xenobiotic degradation. Using both BioCyc and MetaCyc for remediating the toxic pollutant by understanding the genome which can degrade and the enzymatic pathway which provides the suitable condition to clear the xenobiotic compounds (Caspi et al. 2018).

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7 Bionemo Bionemo is the abbreviation of tool, Biodegradation Network-Molecular Biology Database (Arora and Bae 2014). The bionemo database uses metabolic, genetic, and regulatory data to link and connect the biochemical processes, which include the transformation of the substrate into products. The entities in the bionemo are linked to comparable external databases like NCBI, UniProt, Pfam, and UM-BBD, much like in other databases. Enzymatic complexes, which are related biochemical reactions that take place throughout the transformation and are also concluded along the pathways they undergo, comprise the majority of the Bionemo. The sequence entries for the biodegradation genes, as well as the transcription and regulatory functions those genes carry, are likewise included in Bionemo. In order to analyze the catalytic mechanism of enzymes, also aids in the development of sequence alignments for proteins. Hence with the toxins in industrial effluents, provided by the toxic compound name, the results will be displayed with the query match categorized into reactions, pathways, enzymatic complexes, and compounds. On proceeding with the pathway that initiates with the toxic compound, a graphical representation of the biotransformation of the toxic compound is displayed. Each node in the graphical representation contains information about the source of the website from which it is extracted, an additional list of complexes that are capable of carrying out the reaction, and also the user can select the gene and protein sequences. This helps us in the further experiments of modification accordingly. These tools may be used to better understand the degradation pathways for toxic compounds found in industrial effluents (Trigo et al. 2008). Additionally, this may be used and exploited for genetic editing techniques. This curated tool can be accessed using http://bionemo.bioinfo.cnio.es. The Bionemo database summary lists the following: Pathways—145, Reactions—945 (with related complex—324), Enzymatic complexes—537, Proteins—1107, Microbial species—234, Transcription units—212, Transcription factors—90, Effectors— 90, TF DNA Binding sites—128, Promoters—100. This database has several layers of rational information about nearly all biochemical aspects related to biodegradation which can be employed widely in the field of bioremediation (Carbajosa et al. 2009).

8 Methods Involved in NGS for Xenobiotic Degradation Bioinformatics techniques are being designed to develop structured collections of authenticated information of genomes upto date, rather than the every simple wet-lab result reported in the literature. Next-generation sequencing (NGS) refers to newer methods for sequencing that have been developed like Roche/454, Illumina/Solexa, Ion torrent, Oxford Nanopore, and others that are commercially accessible NGS technology (McCombie et al. 2019; Tan et al. 2015). The process begins with the

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creation of long/short reads, which are subsequently separated from the contaminated read and aligned with the reference genome. A variety of software programs, including SSAKE, SOAPdenovo, AbySS, SPAdes, and Velvet, are used for genome sequence assembly in the latter stage, which is crucial for NGS technology. After the sequence reads being put together into contigs, the next step involves gene prediction and functional annotation. The most widely used gene prediction method for microbial systems is Frag gene scan, GLIMMER (Gene Locator and Interpolated Markov ModelER), which uses interpolated Markov models to identify the coding region on the microbial genome. To find homologous genes, manually the inspection and evaluation of the predicted coding area sequence are done and the automatic annotation software is also used. There are several automated systems for bacterial annotation, including RAST, BASys, WeGAS, AGes, and PIPA. NGS has sparked a revolution in biodegradation and bioremediation. Microbial genomics examines the full bacterial genomes to find genes involved in biodegradation and other metabolic activities. With the aid of NGS technology, the entire genomes of various xenobiotic-degrading bacteria may be sequenced. Using gene predictions, a large number of xenobioticdegrading genes can also be discovered and annotated in the microbial genomes. The outcomes of in-silico analysis of the bacterial genome include the identification of metabolic pathways for xenobiotic biodegradation and a full understanding of the microbial metabolic network (Breton-Deval et al. 2020). The genomes of xenobioticdegrading bacteria can be used to predict various metabolic pathways when a range of xenobiotic compounds are present. For example, the entire genome of Cupriavidus necator JMP134 (previously known as Ralstonia eutropha, Strain JMP134) has been sequenced, along with 300 multiple genes that encode enzymes involved in the degradation of various xenobiotic compounds and ring cleavage pathways of many aromatic compounds (Lykidis et al. 2010).

9 Conclusion Bioremediation is a biological process that takes significant time, but is a suitable waste treatment process for contaminated environments like soil, water, etc. Organisms that have the capacity to use the contaminants as the substrate for energy sources and survival are a vital resource in bioremediation. The microbial population often is under control and eventually decreases as the compounds degrade and when the organisms run out of the substrate. Also, the treated contaminants often result in harmless products along with water, low amounts of carbon dioxide, and cell biomass. Yet they are limited to biodegradable substances generally. Not all chemicals degrade quickly and completely. The other concern associated with biodegradation is the byproduct generated in the process which can be hazardous compounds at times. For the purpose of providing data on chemical compounds and their biodegradation, several databases have been curated. These databases allow users to get information depending on the area of individual research interests. For example,

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individuals can use chemicals, and Enzymatic databases to get data on the toxicity, metabolic pathway, risk evaluation, and environmental aspects of substances. A number of bioinformatics methods have been created to find chemical toxicity. These tools can be used by users to anticipate the toxicity of compounds. Additionally, a number of pathway prediction models are available to forecast the degradation routes for compounds for which there is no existence of literature on such pathways. The development of bioinformatics tools for the purpose of bioremediation has been benefitted greatly along with metabolic engineering techniques. The only concern with the hypothesized paths predicted using the tool is that they have not yet been empirically verified yet. The only research gap existing is the break between the computationally predicted pathways and the actual experimental models. Since there are no experimental data to support the hypothesis produced by the tool, it can be utilized by the user to get the general idea about the pathways, mechanism, end product, and toxicity level and also the tool can be used for the forecasting prediction mechanisms. Experimental research should be done in the future to validate and verify the hypothesized pathways and bridge the knowledge gap. NGS has been used to sequence the genomes of many bacteria and other microbes that digest xenobiotics, and the annotated sequence data has been used to pinpoint the genes and enzymes so far engaged in biodegradation. Future research on the genetics of biodegradation can be done in genetic modification and alterations using molecular techniques and bioinformatics tools to enhance the standard of existing resources.

References Arora PK, Bae H (2014) Integration of bioinformatics to biodegradation. Biol Proced Online 16:1– 10. https://doi.org/10.1186/1480-9222-16-8 Arora PK, Kumar M, Chauhan A, Raghava GP, Jain RK (2009) OxDBase: a database of oxygenases involved in biodegradation. BMC Res Notes 2:1–8. https://doi.org/10.1186/1756-0500-2-67 Atashgahi S, Shetty SA, Smidt H, de Vos WM (2018) Flux, impact, and fate of halogenated xenobiotic compounds in the gut. Front Physiol 9(July):1–18. https://doi.org/10.3389/fphys.2018. 00888 Bhandari S et al (2021) Microbial Enzymes used in bioremediation. J Chem 2021(February):1–17. https://doi.org/10.1155/2021/8849512 Breton-Deval L, Sanchez-Reyes A, Sanchez-Flores A, Juárez K, Salinas-Peralta I, Mussali-Galante P (2020) Functional analysis of a polluted river microbiome reveals a metabolic potential for bioremediation. Microorganisms 8(4):1–14. https://doi.org/10.3390/microorganisms8040554 Carbajosa G, Trigo A, Valencia A, Cases I (2009) Bionemo: molecular information on biodegradation metabolism. Nucleic Acids Res 37(SUPPL_1):598–602. https://doi.org/10.1093/nar/ gkn864 Caspi R et al (2018) The MetaCyc database of metabolic pathways and enzymes. Nucleic Acids Res 46(D1):D633–D639. https://doi.org/10.1093/nar/gkx935 Chakraborty J, Jana T, Saha S, Dutta TK (2014) Ring-Hydroxylating oxygenase database: a database of bacterial aromatic ring-hydroxylating oxygenases in the management of bioremediation and biocatalysis of aromatic compounds. Environ Microbiol Rep 6(5):519–523. https://doi.org/10. 1111/1758-2229.12182

262

A. B. Achudhan et al.

Ellis LBM, Douglas Hershberger C, Wackett LP (1999) The University of Minnesota Biocatalysis/Biodegradation database: specialized metabolism for functional genomics. Nucleic Acids Res 27(1):373–376 Esmaeel JR, Alfatlawi MAA (2022) Monooxygenase and dioxygenases by bacterial specific enzymes network. Int J Health Sci (Qassim) 6(May):10215–10222. https://doi.org/10.53730/ ijhs.v6ns1.7420 Hassan I, Chowdhury SR, Prihartato PK, Razzak SA (2021) Wastewater treatment using constructed wetland: current trends and future potential. Processes 9(11):1–27. https://doi.org/10.3390/pr9 111917 Hussain F et al (2018) Constructed wetlands and their role in remediation of industrial effluents via plant-microbe interaction—a mini review. J Bioremediat Biodegrad 9(4):1–7. https://doi.org/ 10.4172/2155-6199.1000447 Jaiswal S, Shukla P (2020) Alternative strategies for microbial remediation of pollutants via synthetic biology. Front Microbiol 11(May):1–14. https://doi.org/10.3389/fmicb.2020.00808 Karp PD, Riley M, Paley SM, Pellegrini-Toole A (2002) The MetaCyc database. Nucleic Acids Res 30(1):59–61. https://doi.org/10.1093/nar/30.1.59 Karp PD et al (2018) The BioCyc collection of microbial genomes and metabolic pathways. Brief Bioinform 20(4):1085–1093. https://doi.org/10.1093/bib/bbx085 Kleinman MH et al (2014) In Silico prediction of pharmaceutical degradation pathways: a benchmarking study. Mol Pharm 11(11):4179–4188. https://doi.org/10.1021/mp5003976 Lykidis A et al (2010) The complete multipartite genome sequence of Cupriavidus necator JMP134, a versatile pollutant degrader. PLoS ONE 5(3):e9729. https://doi.org/10.1371/journal.pone.000 9729 McCombie WR, McPherson JD, Mardis ER (2019) Next-generation sequencing technologies. Cold Spring Harb Perspect Med 9(11):a036798. https://doi.org/10.1101/cshperspect.a036798 Mishra NK, Singla D, Agarwal S, Raghava GPS (2013) ToxiPred: a server for prediction of aqueous toxicity of small chemical molecules in T. Pyriformis. J Transl Toxicol 1(1):21–27. https://doi. org/10.1166/jtt.2014.1005 Mojtaba Mousavi S et al (2021). Recent Advances in Enzymes for the Bioremediation of Pollutants. https://doi.org/10.1155/2021/5599204 Nozaki M, Ishimura Y (1974) Oxygenases. Microb Iron Metab: 417–444. https://doi.org/10.1016/ b978-0-12-515250-1.50021-7 Oscar Omondi D, Caren Navalia A (2021) Constructed wetlands in wastewater treatment and challenges of emerging resistant genes filtration and reloading. Inl Waters Dyn Ecol, August, 2021. https://doi.org/10.5772/intechopen.93293 Paley S, Karp PD (2021) The BioCyc Metabolic Network Explorer. BMC Bioinform 22(1):1–6. https://doi.org/10.1186/s12859-021-04132-5 Pazos F, Guijas D, Valencia A, De Lorenzo V (2005) MetaRouter: bioinformatics for bioremediation. Nucleic Acids Res 33(suppl_1):D588–D592. https://doi.org/10.1093/nar/gki068 Prival MJ (2001) Evaluation of the TOPKAT system for predicting the carcinogenicity of chemicals. Environ Mol Mutagen 37(1):55–69. https://doi.org/10.1002/1098-2280(2001)37:1%3c55:: AID-EM1006%3e3.0.CO;2-5 Reuschenbach P, Silvani M, Dammann M, Warnecke D, Knacker T (2008) ECOSAR model performance with a large test set of industrial chemicals. Chemosphere 71(10):1986–1995. https:// doi.org/10.1016/j.chemosphere.2007.12.006 Sarkar D, Ferguson M, Datta R, Birnbaum S (2005) Bioremediation of petroleum hydrocarbons in contaminated soils: Comparison of biosolids addition, carbon supplementation, and monitored natural attenuation. Environ Pollut 136(1):187–195. https://doi.org/10.1016/j.envpol. 2004.09.025 Schmidt U et al (2008) SuperToxic: a comprehensive database of toxic compounds. Nucleic Acids Res 37:295–299. https://doi.org/10.1093/nar/gkn850

In-silico Integration in Environmental Remediation

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Sharma AK, Srivastava GN, Roy A, Sharma VK (2017) ToxiM: a toxicity prediction tool for small molecules developed using machine learning and chemoinformatics approaches. Front Pharmacol 8(November):1–18. https://doi.org/10.3389/fphar.2017.00880 Singh R, Singh P, Sharma R (2014) Microorganism as a tool of bioremediation technology for cleaning environment: a review. Proc Int Acad Ecol Environ Sci 4(1):1–6 Singh A, Prasad SM, Singh RP (2016) Plant responses to xenobiotics. Springer, Singapore, pp 1–346. https://doi.org/10.1007/978-981-10-2860-1 Tan BF, Ng C, Nshimyimana JP, Loh LL, Gin KYH, Thompson JR (2015) Next-generation sequencing (NGS) for assessment of microbial water quality: current progress, challenges, and future opportunities. Front Microbiol 6(September):1027. https://doi.org/10.3389/fmicb.2015. 01027 Trigo A, Valencia A, Cases I (2008) Systemic approaches to biodegradation Biodegradation: a systemic process. https://doi.org/10.1111/j.1574-6976.2008.00143.x Van Bossuyt M et al (2018) Performance of in silico models for mutagenicity prediction of food contact materials. Toxicol Sci 163(2):632–638. https://doi.org/10.1093/toxsci/kfy057 Vedani A, Dobler M, Smieško M (2012) VirtualToxLab—a platform for estimating the toxic potential of drugs, chemicals and natural products. Toxicol Appl Pharmacol 261(2):142–153. https:// doi.org/10.1016/j.taap.2012.03.018 Vedani A, Dobler M, Hu Z, Smieško M (2015) OpenVirtualToxLab—a platform for generating and exchanging in silico toxicity data. Toxicol Lett 232(2):519–532. https://doi.org/10.1016/j.tox let.2014.09.004