Basic Sciences for Sustainable Development: Water and the Environment 9783111071206, 9783111070896

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Ponnadurai Ramasami (Ed.) Basic Sciences for Sustainable Development

Also of interest Basic Sciences for Sustainable Development Volume : Water and the Environment Ponnadurai Ramasami (Ed.),  ISBN ----, e-ISBN ----

Chemical Sciences in the Focus Ponnadurai Ramasami (Ed.),  Set ISBN ---- Volume : Pharmaceutical Applications ISBN ----, e-ISBN ---- Volume : Green and Sustainable Processing ISBN ----, e-ISBN ---- Volume : Theoretical and Computational Chemistry Aspects ISBN ----, e-ISBN ---- Chemistry and Energy From Conventional to Renewable Mark Anthony Benvenuto,  ISBN ----, e-ISBN ----

Green Chemistry and Technology Mark Anthony Benvenuto and George Ruger (Eds.),  ISBN ----, e-ISBN ----

Data Science in Chemistry Artificial Intelligence, Big Data, Chemometrics and Quantum Computing with Jupyter Thorsten Gressling,  ISBN ----, e-ISBN ----

Basic Sciences for Sustainable Development Volume 2: Water and the Environment Edited by Ponnadurai Ramasami

Editors Prof. Dr. Ponnadurai Ramasami University of Mauritius Faculty of Science Department of Chemistry Computational Chemistry Group 80837 RÉDUIT MAURITIUS [email protected]

ISBN 978-3-11-107089-6 e-ISBN (PDF) 978-3-11-107120-6 e-ISBN (EPUB) 978-3-11-107165-7 Library of Congress Control Number: 2022950898 Bibliographic information published by the Deutsche Nationalbibliothek The Deutsche Nationalbibliothek lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the internet at http://dnb.dnb.de. © 2023 Walter de Gruyter GmbH, Berlin/Boston Cover image: intararit / iStock / Getty Images Plus Typesetting: TNQ Technologies Pvt. Ltd. Printing and binding: CPI books GmbH, Leck www.degruyter.com

Preface of the book (volume 2) entitled Basic Sciences for Sustainable Development: Environmental protection and Water Remediation The year 2022 has been declared by the United Nations as the "International Year of Basic Sciences for Sustainable Development". Sustainable development is focused on the UN's 17 Sustainable Development Goals. These require the involvement of basic sciences. This edited book (volume 2) is a collection of ten invited and peer-reviewed contributions from environmental protection and water remediation. Maghanga et al. analysed the applicability of Maerua Subcordata root powder in the removal of fluorides in borehole drinking water. Their results indicate that M. subcordata is a viable plant in fluoride treatment with approximately 68% fluoride removal efficiency. Shikuku and co-workers discussed the recent data on the sources, progress, and challenges in the management of pharmaceutical and personal care products and perand polyfluoroalkyl substances as emerging contaminants in the African continent. The group of Sarkar reviewed the effects of azadirachtin on non-target aquatic over the last three decades. Nyamato and Apollo reported on the solvent extraction of copper(II), zinc(II), cadmium(II), and lead(II) from wastewater using phenoxy-imino/amino ligands. Ganesan et al. addressed the conscientiousness of environmental concepts in sustainable development and ecological conservation. Ganesan and Tharudini = reviewed the role of science in conservation of environment for sustainable development. Ramachandra et al. discussed on changes in land use, land cover patterns of the agrarian district Tumkur in Karnataka State, considering temporal remote sensing data of three decades, using geospatial techniques and modeling. Karthikeyan and co-workers reported on the degradation the mask dyes at the surface of the mask using nano metal oxide silicate photo catalysts. Ganesan et al. elaborated on bio char and its characteristics application and utilization on the environment. The group of ganesan also reported on biotic farming using organic fertilizer for sustainable agriculture. I hope that these chapters of this volume 2 will add to literature and they will be useful references for researchers. Prof. Ponnadurai Ramasami, CSci, CChem. FRSC, FAAS, FICCE, MMast UNESCO Chair in Computational Chemistry, Computational Chemistry Group, Department of Chemistry, Faculty of Science, University of Mauritius, Réduit 80837, Mauritius Visiting Professor, Centre of Natural Product Research, Department of Chemical Sciences, University of Johannesburg, Doornfontein Campus, Johannesburg 2028, South Africa Professor Extraordinarius, Department of Chemistry, University of South Africa, Private Bag X6, Florida 1710, South Africa E-mail address: [email protected] https://doi.org/10.1515/9783111071206-201

Contents Preface V List of contributing authors

XIII

Justin K. Maghanga, Veronica A. Okello, Justine A. Michira, Loice Ojwang, Bancy Mati and Fred K. Segor 1 Fluoride in water, health implications and plant-based remediation 1 strategies 2 1.1 Introduction 4 1.1.1 Plant based remediation strategies 6 1.2 Materials and methods 6 1.2.1 Materials 7 1.2.2 Study area 7 1.2.3 Preparation of the adsorbent 7 1.2.4 Physicochemical analysis 7 1.2.5 Optimization studies 8 1.2.6 Borehole water sample treatments 8 1.3 Results and discussions 8 1.3.1 Distribution of fluorides in Kenya groundwaters 9 1.3.2 Physicochemical water parameters 10 1.3.3 Application of maerua subcordata for water treatment 11 1.3.4 Optimization studies 14 1.3.5 Borehole sample experiments 15 1.4 Conclusions 16 1.4.1 Recommendations 16 References Victor O. Shikuku, Emily C. Ngeno, Joel B. Njewa and Patrick Ssebugere 2 Pharmaceutical and personal care products (PPCPs) and per- and polyfluoroalkyl substances (PFAS) in East African water resources: progress, 21 challenges, and future 21 2.1 Emerging contaminants 21 2.1.1 Introduction 23 2.2 Occurrence of PPCPs in water resources 25 2.3 Per- and Polyfluoroalkyl Substances (PFAS) 25 2.3.1 PFASs properties 26 2.3.2 PFASs exposure routes 26 2.3.3 PFAS in potable water 27 2.3.4 Sludge and wastewater 27 2.3.5 Sediments and suspended solids

VIII

2.3.6 2.4 2.4.1 2.4.2 2.4.3 2.4.4 2.4.5 2.4.6 2.4.7 2.4.8 2.4.9 2.4.10 2.5

Contents

Surface and pore water 28 29 Pollution control of CECs 29 Regulating emissions of CECs into receiving waters 30 Minimizing and/or replacing CECs 30 Proper disposal 31 Technical solutions 31 Intensify technical infrastructural funding Investigate and avail data on CECs’ occurrence, fate, toxicity, persistence, 32 and variability 32 Legislation 33 Institute structures to probe pollution and its repercussions Establish collaborations across stakeholders for pollution 33 abatement 33 Provision of incentives 33 Future perspectives of emerging contaminants 34 References

Prithwish Sarkar, Kishore Dhara and Himadri Guhathakurta 3 Azadirachtin in the aquatic environment: Fate and effects on non-target 39 fauna 39 3.1 Introduction 41 3.1.1 The chemical nature of azadirachtin 42 3.1.2 Fate 42 3.1.3 Mode of use 43 3.1.4 Ecotoxicity 43 3.1.5 Effects 47 3.2 Conclusions 47 3.2.1 From the foregoing it seems safe to assume that 47 References George S. Nyamato and Seth Apollo 4 Removal of heavy metals from wastewater using synthetic chelating 51 agents 51 4.1 Introduction 52 4.2 Materials and methods 53 4.2.1 Extraction experiments 53 4.2.2 Wastewater samples 53 4.3 Results and discussion 54 4.3.1 Nature of metal cation 55 4.3.2 Nature of ligand structure 56 4.3.3 Impact of ligand concentration

Contents

4.3.4 4.4

Real water samples 57 Conclusions 57 References

IX

57

Subbulakshmi Ganesan, Gopalakrishnan Padmapriya and Agampodi Sanduni Anupama De Zoysa 5 Conscientiousness of environmental concepts in sustainable development 61 and ecological conservation 61 5.1 Introduction 62 5.2 Methodology 62 5.2.1 Methodology of preparation of bioplastics 64 5.3 Methodology of making biopesticides 64 5.3.1 Using ginger extracts 65 5.3.2 Using papaya leaves 65 5.4 Methodology of production of biodiesel using algae 65 5.4.1 Bioplastic 66 5.4.2 Biofertilizer 66 5.4.3 Biodiesel: Table 5.3 and Figure 5.4 67 5.4.4 Biopesticides 67 References Subbulakshmi Ganesan and Asha Rajiv 6 Role of science in environmental conservation leading to sustainable 69 development 69 6.1 Introduction 71 6.2 Discussion 73 6.3 Conclusion 74 References T. V. Ramachandra, Bharath Setturu and Vinayaka Bhatta 7 Landscape ecological modeling to identify ecologically significant regions in 75 Tumkur district, Karnataka 76 7.1 Introduction 77 7.2 Materials and methods 77 7.2.1 Study area 79 7.2.2 Methods 83 7.3 Results & discussion 7.3.1 Modeling landscape dynamics and spatial configuration of 83 Tumkur 7.3.2 Prioritization of Ecologically Sensitive Regions (ESRs) for conservation 90 and sustainable development

X

7.4

Contents

Conclusions References

96 97

Balakrishnan Karthikeyan, Antonybaburajan Therasa Alphonsa, Natesan Vijayakumar and Antony Samy Jose Vinoth Raja 8 Role of semiconductor photo catalysts on mask pollution 101 management 101 8.1 Introduction 103 8.1.1 The pandemic and mask use 106 8.1.2 Titanium dioxide and lead oxide semiconductors 109 8.2 Experimental methods 109 8.2.1 Chemicals 109 8.2.2 Sol–gel synthesis of TiO2-SiO2 109 8.2.3 Sol–gel synthesis of PbO-SiO2 109 8.2.4 Photo Reactor Studies 110 8.3 Result and discussion 110 8.3.1 Mask degradation on sun light 110 8.3.2 Photo degradation on mask layer 110 8.3.3 Photo degradation 112 8.4 Summary 113 References Subbulakshmi Ganesan, G. Padmapriya, Izegaegbe Daniel Omoikhoje, J.H. Tharudini, and Sanduni Anupama De Zoysa 9 Biochar: its characteristics application and utilization of on 115 environment 116 9.1 Introduction 117 9.2 Methodology 117 9.2.1 Preparation of biochar: from a variety of raw materials 118 9.2.2 Research on biochar analysis method 119 9.2.3 Biochar modification 122 9.3 Conclusions 123 Terminologies 123 References Subbulakshmi Ganesan 10 Biotic farming using organic fertilizer for sustainable agriculture 125 10.1 Introduction 126 10.2 Organic fertilizers 127 10.3 Climate change and agriculture 127 10.4 Effects of chemical fertilizers on soil health

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Contents

10.5 10.6 10.7 10.8 10.9 10.10 10.11 10.12 10.13

Index

Organic farming methods 128 129 Crop diversity 129 Use of PGPR as biofertilizer Use of legumes for sustainable agriculture 130 Crop rotation 130 Liquid organic fertilizer 131 Advantages of organic fertilizers 131 Disadvantages of chemical fertilizers 132 Conclusion 132 References 135

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List of contributing authors Agampodi Sanduni Anupama De Zoysa Department of Life Science Jain University Bangalore Karnataka India Seth Apollo Department of Physical Sciences University of Embu P.O Box 6-60100 Embu Kenya Vinayaka Bhatta Energy & Wetlands Research Group Center for Ecological Sciences [CES] Bangalore Karnataka India Kishore Dhara Office of the Deputy Director of Fisheries (Research & Training) Freshwater Fisheries Research & Training Centre Directorate of Fisheries Government of West Bengal Kulia, Kalyani, Nadia West Bengal 741235 India Subbulakshmi Ganesan Department of Chemistry Jain University Bangalore Karnataka India E-mail: [email protected] Himadri Guhathakurta Sripat Singh College Jiaganj Murshidabad 742123 India E-mail: [email protected]

https://doi.org/10.1515/9783111071206-202

Balakrishnan Karthikeyan Department of Chemistry Faculty of Science Annamalai University Annamalainagar 608002 Tamil Nadu India E-mail: [email protected] Justin K. Maghanga Taita Taveta University P.O Box 635-80300 Voi Kenya Bancy Mati Jomo Kenyatta University of Agriculture and Technology P.O Box 62000-00200 Nairobi Kenya Justine A. Michira Pwani University P.O Box 195-80108 Kilifi Kenya Emily C. Ngeno Department of Physical Sciences Kaimosi Friends University P.O. Box 385-50309 Kaimosi Kenya Joel B. Njewa Department of Chemistry University of Malawi P.O. Box 280, Zomba Malawi George S. Nyamato Department of Physical Sciences University of Embu P.O Box 6-60100 Embu Kenya E-mail: [email protected]

XIV

List of contributing authors

Loice Ojwang Pwani University P.O Box 195-80108 Kilifi Kenya

Fred K. Segor University of Eldoret P.O Box 1125-30100 Eldoret Kenya

Veronica A. Okello Machakos University P.O Box 136-90100 Machakos Kenya E-mail: [email protected]

Bharath Setturu Energy & Wetlands Research Group Center for Ecological Sciences [CES] Bangalore Karnataka India

Izegaegbe Daniel Omoikhoje Department of Life Science Jain University Bangalore Karnataka India Gopalakrishnan Padmapriya Department of Chemistry Jain University Bangalore Karnataka India T. V. Ramachandra Energy & Wetland Research Group CES TE 15 Centre for Ecological Sciences; and Centre for Sustainable Technologies (Astra); and Centre for infrastructure Sustainable Transportation and Urban Planning [CiSTUP] Indian Institute of Science Bangalore 560012 India E-mail: [email protected] Asha Rajiv Department of Physics Jain University Bangalore Karnataka India Prithwish Sarkar Jangipur College Jangipur Murshidabad 742213 India

Victor O. Shikuku Department of Physical Sciences Kaimosi Friends University P.O. Box 385-50309 Kaimosi Kenya E-mail: [email protected] Patrick Ssebugere Department of Chemistry Makerere University P.O. Box 7062 Kampala Uganda J.H. Tharudini Department of Life Science Jain University Bangalore Karnataka India Antonybaburajan Therasa Alphonsa Department of Chemistry Faculty of Science Annamalai University Annamalainagar 608002 Tamil Nadu India E-mail: [email protected]

List of contributing authors

Natesan Vijayakumar Department of Biochemistry and Biotechnology Faculty of Science Annamalai University Annamalainagar 608002 Tamil Nadu India E-mail: [email protected]

XV

Antony Samy Jose Vinoth Raja Department of Biochemistry and Biotechnology Faculty of Science Annamalai University Annamalainagar 608002 Tamil Nadu India E-mail: [email protected]

Justin K. Maghanga, Veronica A. Okello*, Justine A. Michira, Loice Ojwang, Bancy Mati and Fred K. Segor

1 Fluoride in water, health implications and plant-based remediation strategies Abstract: The high prevalence of dental fluorosis and bone mineralization deficiency as a result of exposure to fluorides has increased in Kenya over the years due to consumption of water with elevated levels of fluoride. The World Health Organization (WHO) provides a guideline of 1.5 mg/L level of fluoride in drinking water. However, majority of studies carried out in Kenya over the last 40 plus years have indicated very high levels of fluoride in drinking water in various regions, with a prevalence in dental fluorosis observed in children and adults living in Rift valley and central regions due to basaltic and volcanic rocks. Unfortunately, this trend of fluoride-induced enamel changes has been observed in other regions such as Nairobi and Machakos which were originally presumed to contain low fluoride levels. This study sought to analyse the applicability of Maerua subcordata root powder (MSRP) in the removal of fluorides in borehole drinking water. Fresh Maerua subcordata roots were peeled to obtain the white flesh, chopped into small pieces, dried and ground into powder. The process parameters varied were; fluoride ion concentration [F−] (0–12 mg/L), adsorbent dosage (0–200 g/L) and equilibration time (30–240 min) [F−] were hence analysed before and after treatment using ion selective electrode (ISE) fluoride meter. Results indicated that MSRP is a viable plant in fluoride treatment with approximately 68% fluoride ion removal efficiency. An MSRP dosage of 200 g/L was found optimal in [F−] reduction while a 2 mg/L [F−] concentration recorded the highest reduction of [F−]. The optimal equilibration time was found to be 30 min. The results can be used to develop a lowcost column for treatment of high fluoride waters in rural areas using MSRP. Borehole samples were treated with MSRP using the optimized conditions; however their reduction levels were lower than the [F−] standards used. It is envisaged that with further modification and/or doping with zero-valent iron nanoparticles, its efficiency will be improved.

*Corresponding author: Veronica A. Okello, Machakos University, P.O Box 136-90100 Machakos, Kenya, E-mail: [email protected] Justin K. Maghanga, Taita Taveta University, P.O Box 635-80300 Voi, Kenya Justine A. Michira and Loice Ojwang, Pwani University, P.O Box 195-80108 Kilifi, Kenya Bancy Mati, Jomo Kenyatta University of Agriculture and Technology, P.O Box 62000-00200 Nairobi, Kenya Fred K. Segor, University of Eldoret, P.O Box 1125-30100 Eldoret, Kenya As per De Gruyter’s policy this article has previously been published in the journal Physical Sciences Reviews. Please cite as: J. K. Maghanga, V. A. Okello, J. A. Michira, L. Ojwang, B. Mati and F. K. Segor “Fluoride in water, health implications and plantbased remediation strategies” Physical Sciences Reviews [Online] 2022. DOI: 10.1515/psr-2022-0123 | https://doi.org/10.1515/ 9783111071206-001

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1 Fluoride in water

Keywords: adsorption; drinking water; fluoride; Maerua subcordata; plant-based remediation.

1.1 Introduction Water is very critical for human survival. However, only 3% is fresh and in a drinkable state even though 70% of the earth is covered with water, and sadly, one in three people globally do not have access to clean drinking water [1]. Limited supply of fresh water can be attributed to high demand, climate change and pollution. The later can be attributed to primary and/or secondary sources of pollution. According to World Health Organisation (WHO), about 3.4 million people die annually due to waterborne diseases. These water pollutants include heavy metals, anions, organic matter, pathogens and other emerging contaminants such as personal care products. Of the various pollutants, fluoride is particularly of great concern since it is a naturally available, necessary element for human life but excess intake can lead to adverse health effects [2]. Fluorine is an element of the halogen family that forms inorganic and organic compounds called fluorides. Fluoride compounds such as fluorspar (CaF2), fluorapatite (Ca5[PO4]3[F,Cl]), topaz (Al2SiO4[F,OH]2) and cryolite [Na3AlF6] occur through geogenic processes such as dissolution of fluorine containing minerals. The ionic form of fluorine is the 13th most abundant element in the earth crust. There are 416 fluoride bearing rock minerals with major primary mineral source being apatite [Ca5(PO4)3F] [3]. Other fluoride containing minerals include fluorite (CaF2), igneous zircon (ZrSiO4), biotite (K(MgFe)3(AlSi3O10)(FOH)2) and hornblende (CaNa)2(Mg,F,Al)5(Al,Si)8O22(OH)2. Fluoride occurrence has also been linked to high Ca levels, presence of thermal waters and volcanic activity. The latter produces magmatic fluorine mainly as hydrogen fluoride (HF) [4]. Regions with K, Mg, Ca and bicarbonate ions (HCO3−) have also been associated with high concentration of fluorides. These regions also tend to have pH levels above 7 [5, 6]. Fluoride ions and fluoride compounds may be produced by manmade processes. These anthropogenic sources have been linked to poor industrial waste disposal, thermal decomposition of coal, oil refining, steel, brick and phosphatic fertilizer manufacturing processes [7, 8]. Fluoride ion (F−) may be deleterious or beneficial to cells or organs [3]. This may depend on the level of intake, enamel development age, and duration of exposure. The dual nature of fluorides poses a great concern to health-care professionals, toxicologists and geo-environmentalists. Exposure to high levels of fluorides in drinking water [9], brick tea [10] and coal-burning [11] have been associated with the development of skeletal and dental fluorosis among other effects [2]. Moreover, acute high-level exposure to fluoride water contamination can lead to seizures and muscle spasms. It is estimated that more than 70 million people suffer from fluorosis worldwide. On the other hand, fluoride produced synthetically is mainly used

1.1 Introduction

3

in drinking water, toothpaste, mouthwashes and various chemical products to prevent fluorosis. This is because fluoride displaces the hydroxide ions from Ca5(PO4)3OH mineral found in bones and teeth to form a much harder and stronger Ca5(PO4)3F resistant to acidic attack. Ironically, too much fluoride can lead to dental fluorosis (1.5–2.0 mg/L) or skeletal fluorosis (4–8 mg/L), which can damage bones and joints, lead to thyroid problems and neurological effects [7]. With high levels of fluorides, the Ca5(PO4)3OH mineral is converted to Ca5F10 plus phosphate ions (PO43−). Harmful effects of fluorides are not only limited to human beings but ecological effects on flora and fauna have been documented [12]. Studies have shown accumulation of fluoride in the plants foliage and livestock forages resulting into decreased plant growth and yield, thus directly affecting agricultural outputs and in turn endangering both humans and animals through the food chain [13]. Furthermore, fluorides also accumulate in insect tissue causing severe damage. D’ Addabbo et al. [14] reported on the impact of volcanoes on amphibian living freshwater organisms. Elsewhere, chronic fluorosis in grazing animals from groundwater or geothermal waters have been reported [15]. This can be attributed to accumulation of fluoride ions (F−) in their bones and into the soft tissue, leading to metabolic malfunction in animals [16]. Socialeconomic implications resulting to a decline in government water supply programs especially in fluoridated areas have been reported [17]. It is therefore important to come up with strategies that will aid in removal of fluorides in drinking water. Studies have indicated regions with high fluoride levels within the Great Rift Valley. These mainly include the Middle East and East African countries. The latter include Kenya, Sudan, Ethiopia, Tanzania and Uganda [3, 18]. In Kenya, fluorspar, apatite and hornblende are found in Kerio Valley, Mirima hills and Central Kenya. In addition, other documented regions with high fluoride levels in Kenya include Turkana, Southern Rift Valley areas, Central and Eastern Regions. A Kenyan survey conducted in 2017 indicated that the mean [F−] across 8 provinces was 4.14 ± 8.63 mg/L. This is higher than the recommended World Health Organization limit of 1.5 mg/L [18]. The highest fluoride reported in ground waters of the volcanic areas of the Nairobi, Rift Valley and Central Provinces was 30–50 mg/L [5]. Certain regions in Kenya have recorded very high fluoride levels. For example, Lake Elementaita (1640 mg/L) and Lake Nakuru (2800 mg/L) have the highest fluoride levels in the world [18]. Sadly, fluorosis and other health issues associated with ingestion of fluoride in drinking water are not only confined to the people living in these regions but noticeable effects have been seen in other surrounding regions too hence raising an important toxicological and geo-environmental concern. Figure 1.1 shows fluoride distribution worldwide as per the WHO permissible level in drinking water. Exposure to fluorides can occur through inhalation via the gastrointestinal tract, from occupational exposure or fuel burning [19, 20]. Absorption can also occur through drinking water [9] or the skin in case of contact with HF. Strong [HF] over 50% can cause immediate, severe, burning pain and a whitish discoloration of the skin which usually proceeds to blister formation [21]. However, since the main route of exposure to fluoride

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1 Fluoride in water

Figure 1.1: Fluoride concentration in groundwater worldwide as per world health organization (WHO) permissible limit for drinking purposes. Adapted from Kumar et al. 2021 [3].

is through drinking water and food, this is a great concern because the majority of people in the developing world use groundwater for cooking and drinking [17]. The recommended total daily fluoride intake from dietary sources and toothpaste ingestion is 0.07 (range, 0.04–0.2) and 0.08 (range 0.05–0.21) mg/kg/day for children 2 years of age from fluoridated and non fluoridated communities, respectively [22]. European Food Safety Authority (EFSA) recommends 0.05 mg/day/kg body weight for prevention of caries [23]. Consumption of fluoride at less than 0.5 mg/L can result into dental caries, and bone mineralization deficiency, while consumption of more than 1 mg/L of fluoride can aggravate cavity formation and dental fluorosis as a result of loss of tooth matrix calcium [24]. The WHO guideline value for fluoride in drinking water is 1.5 mg/L [25]. Balancing the optimum levels for caries prevention especially in fluoridated areas still remains a big challenge. Solutions are thus needed to alleviate these problems through provision of viable and sustainable water supplies and remediation technologies.

1.1.1 Plant based remediation strategies Conventional techniques/methods are available for removal of fluorides from waterbodies with appreciable success. These include, reverse osmosis, nano-filtration, Donnan-dialysis and electrodialysis [26]. These techniques are invasive to the environment, expensive and may not be available in rural communities due to high poverty levels. In addition, commercial coagulants are also limited due to high poverty levels. Therefore, there is a need to develop cheaper environmentally friendly remediation strategies for not only fluorides but also other water and soil contaminants. According to United States Environmental Protection Agency (USEPA) 2008, Green Remediation is defined as “the practice of considering all environmental effects of

1.1 Introduction

5

remedy implementation and incorporating options to maximize net environmental benefit of cleanup actions” [27]. Green remediation strategies offer a viable option and have gained attention in the recent past as they promote global environmental quality. Moreover, the U.S. Environmental Protection Agency’s Greener Cleanup Standard Initiative works to improve the environmental outcome of site cleanups by ensuring/ promoting the minimization of the environmental footprint of site remediation by mitigating the impact to water, natural resources and energy. In addition, green remediation strategies focus on using efficient techniques in managing and protecting surface and groundwater systems. This study thus seeks to employ plant-based removal of fluorides from groundwater bodies. Examples of green remediation strategies include bioremediation which is further divided into microbial bioremediation [3] and phytoremediation [28]. The former uses microorganisms to break down pollutants while the later uses plants. Phytoremediation in essence can take place through a wide range of mechanisms including phytodegradation, phytoaccumulation, phytovolatization and phytostabilization. Several studies have reported on the use of phytoremediation to clean up contaminated soils and water, based on green plants ability to accumulate, degrade, metabolize and immobilize/stabilize pollutants such as heavy metals, organics, anions and personal care products [26–29]. Recently, a review by Yadav et al. [30] reported adsorptive potential of modified plant-based adsorbents for removal of dyes and heavy metals from wastewater. Elsewhere biosorption of fluoride on Neem (Bharali et al.) leaf powder [31] and removal of fluorides using wheat straw, sawdust and activated bagasse carbon of sugarcane through adsorption has been reported [32]. Therefore, application of plant-based seeds, leaves, roots and stem have proven to be viable alternative for treatment of water compared to use of chemicals. These methods are more economical, do not require advanced technical know-how and are environmentally friendly. For example, seeds of Moringa oleifera have been used for treatment of groundwater to remove fluoride ions [33] and as a biocoagulant for drinking water to remove turbidity [34]. Elsewhere a study on the effectiveness of Moringa oleifera tree in purification of drinking water indicated that it is an effective primary coagulant for water treatment [35]. Other bio-coagulants include, neem seed, aloe vera, seeds of Nirmala trees, guar plant and tamarind tree [36]. A study by Suneetha et al. [37] indicated effective adsorption of fluorides using active carbon derived from Vitex negundo plant. Since limited research has been done to investigate the viability of using plants for defluoridation, this work therefore assesses the suitability of Maerua subcordata (M. subcordata) root powder MSRP (Figure 1.2) in the treatment of water to remove fluoride ions. M. subcordata belonging to the family Capparaceae Juss, genus Maerua Forssk is a shrub that grows up to 2 m tall with a woody swollen root. Its native range is North Eastern and Eastern Tropical Africa to DR Congo. In Kenya, the plant is found in the semi-arid south eastern region where its root is considered a famine food also chewed to quench thirst. Local communities also boil it in broth for strength and health. The Pokot and Turkana communities in Kenya refer

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1 Fluoride in water

Figure 1.2: Maerua subcordata (M.S) Plant.

to it as Chepulusuw and Erut respectively. For a complete description of M. subcordata, further information is documented in the Royal Botanical Gardens Kew [38]. In the recent past, M. subcordata shrub was investigated as an alternative sugar source for cheap and efficient bioethanol production in Kenya [39]. Moreover, a study by Hiben et al. [40] showed that its fruit, root, and seed extracts were non-cytotoxic up to 30-g dry weight per litre but the leaf extract exhibited some cytotoxicity and that induction by the root extract was minimal. Other studies have indicated the use of M. subcordata as an herbal medicine for management of malaria symptoms, diabetes, blood pressure, loss of appetite; laxative and abortifacient; food and water purification [40]. Therefore, in this study, standards of fluoride ion (F−) were used for optimization of process parameters while real fluoridated water samples were collected from boreholes located in Thika Area-Upper Tana Basin, Kenya to validate the method. The borehole samples were subjected to treatment by M. subcordata root powder as discussed in the following sections.

1.2 Materials and methods 1.2.1 Materials Fluoride measurements were done using Ion Selective Electrode (ISE) fluoride meter (BANTE A131 ISE) from Bante Instruments, China. NaF standard and TISAB were

1.2 Materials and methods

7

purchased from LabLink Supplies Kenya Ltd. M. subcordata root fibers were obtained from the northern regions of Kenya.

1.2.2 Study area Thika town has a population of 279,429 as per the 2019 population census. The town is a major commerce industrial hub in Kiambu County and lies 42 km NE of Nairobi city near the confluence of the River Chania and River Thika, at 01°03’S 37°05’E. A total of six (6) selected boreholes were sampled within the vicinity of Thika town. Borehole water was collected in 250 mL triple rinsed plastic storage bags and transported to the laboratories for further analysis. Temperature and pH were measured on site. On site parameters were recorded before sampling.

1.2.3 Preparation of the adsorbent Fresh M. subcordata roots were peeled to obtain white flesh, washed in double distilled water then cut into small pieces. They were then dried under sunlight for three days. After the roots were completely dry, they were crushed into fine powder using a mortar and a pestle. The resulting powder was then stored in airtight containers awaiting further analysis and use.

1.2.4 Physicochemical analysis Using the fluoride ISE meter and TISAB (for pH stabilization and prevention of polyvalent ion interferences), the initial and Final [F−] analysis was determined before and after addition of MSRP. Change in the concentration of fluoride ions [F−] was used to determine fluoride removal efficiency. Other physico-chemical analysis was carried out in accordance with standard procedures outlined in APHA (2005) [41]. A blank (distilled water with no fluoride ions) determination was carried out to zero out any background reading to enable us to report accurate values for the compound of interest. Sodium fluoride (NaF) was used as the working F− standard.

1.2.5 Optimization studies This was carried out by varying various process parameters including contact time and adsorbent dosage. For variation in contact time experiments, MSRP dosage of 5 g in 50 mL NaF standard solutions was used with concentrations range: 0, 2, 4, 6, 8, 10 and 12 mg F/L. Equilibration time was varied at 30, 120 and 240 min. Whereas for dosage

8

1 Fluoride in water

studies, 0.5, 3 and 5 g of MSRP was varied in 25 mL NaF standard solution and allowed to equilibrate for 30 min.

1.2.6 Borehole water sample treatments Borehole water samples were treated with MSRP using optimized/selected process conditions then analyzed for fluorides and pH before and after treatment.

1.3 Results and discussions 1.3.1 Distribution of fluorides in Kenya groundwaters Kenya has a total of eight provinces namely; Nairobi, Central, Coast, Eastern, North Eastern, Nyanza, Rift Valley and Western as shown in Figure 1.3. About 80% of the population in Kenya is rural [42]. Interestingly, seven out of the eight provinces have water containing fluoride ions at concentrations that are greater than 1 mg/L (see Table 1.1). This is a concern since studies have indicated that even low levels of water or plasma fluoride exposure is associated with increased risk of dental fluorosis [43].

Figure 1.3: Map of Kenya showing the eight provinces.

1.3 Results and discussions

9

Table .: Provinces known to be endemic for fluoride in Kenya. Province        

Number of water sources

Concentration mg/L

∼; ∼; ∼ ∼; ∼; > ∼; ∼; ∼ ∼; ∼; ∼ ∼; ∼; ∼ ∼; ∼; ∼ ∼; ∼; ∼ ∼

>; .–; ; .–; ; .–; ; .–; ; .–; ; .–; ; .–;