Treatment of Microbial Contaminants in Potable Water Supplies: Technologies and Costs 9780815512141, 0815512147, 9780815519362

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TREATMENT OF MICROBIAL CONTAMINANTS IN POTABLE WATER SUPPLIES: Technologies and Costs Jerrold J. Troyan Sigurd P. Hansen

William Andrew Inc.

TREATMENT OF MICROBIAL CONTAMINANTS IN POTABLE WATER SUPPLIES

TREATMENT OF MICROBIAL CONTAMINANTS IN POTABLE WATER SUPPLIES Technologies and Costs

by

Jerrold J. Troyan Sigurd P. Hansen CWC-HDR, Inc. Cameron Park, California

NOYES DATA CORPORATION Park Ridge, New Jersey, U.S.A.

Copyright ©1989 by Noyes Data Corporation Library of Congress Catalog Card Numbar: 89-16034 ISBN: 0-8155-1214-7 ISSN: 0090-516X Printed in the United States Published in the United States of Am8l'Ica by Noyes Data Corporation Mill Road, Park Ridge, New Jersey 07656 10987 65432 1

Library of Congress Cataloging-in-Publication Data Troyan, Jerrold J. Treatment of microbial contaminants in potable water supplies : technologies and costs I by Jerrold J. Troyan, Sigurd P. Hansen. p. cm. -- (Pollution technology review, ISSN 0090·516X ; no. 171) Bibliography: p. Includas index. ISBN 0-8155-1214-7 : 1. Drinking water--Puriflcation. 2. Microbial contamination. I. Hansen, Sigurd P. II. Title. III. Series. TD433.T76 1989 628.1'62--dc20 89-16034 CIP

Foreword

This book identifies the best technologies or other means that are generally available, taking costs into consideration, for inactivating or removing microbial contaminants from surface water and groundwater supplies of drinking water. For municipal officials, engineers, and others, the book provides a review of alternative technologies and their relative efficiency and cost. More specifically, it discusses water treatment technologies which may be used by community and noncommunity water systems in removing turbidity, Giardia, viruses, and bacteria from water supplies. While most of the book covers surface water supolies, a brief discussion of disinfection technologies and costs for groundwater supplies is also provided, since disinfection is the best available technology for groundwater systems to comply with coliform regulations. The technologies and actions available to a community searching for the most economical and effective means to comply with microbiological regulations include modification of eXisting treatment systems; installation of new treatment systems; selection of alternate raw water sources; regionalization; and documenting the existence of a high quality source water while implementing an effective and reliable disinfection system, combined with a thorough monitoring program, and maintaining a continuing compliance with all drinking water regulations. It is not the intent of the USEPA to require any system to use a particular technology to achieve compliance with proposed treatment regulations. Instead, the responsibility is retained by the individual water systems to select one or more procedures that are optimal for their particular water supply situation. Whatever technology is ultimately selected by a water supplier to achieve compliance with the requirements must be based upon a case-by-case technical evaluation of the system's entire treatment process, and an assessv

vi

Foreword

ment of the economics involved. However, the major factors that must be considered include: • • • • •

Quality and type of raw source water Raw water turbidity Type and degree of microbial contamination Economies of scale and the potential economic impact on the community being served Treatment and waste disposal requirements

Some methods are more complex or more expensive than others. Selection of a technology by a community may require engineering studies and/or pilotplant operations to determine the level of removal a method wi II provide for that system. Alternative technologies for the removal of microbial contaminants and turbidity are identified because of their adaptability to treatment of drinking water supplies. It is expected that after development and pilot-scale testing, these methods may be technically and economically feasible for specific situations. The information in the book is from Technologies and Costs for the Treatment of Microbial Contaminants in Potable Water Supplies, by Jerrold J. Troyan and Sigurd P. Hansen of CWC·HDR, Inc. for the U.S. Environmental Protection Agency, October 1988. The table of contents is organized in such a way as to serve as a subject index and provides easy access to the information contained in the book. Advanced composition and production methods developed by Noyes Data Corporation are employed to bring this durably bound book to you in a minimum of time. Special techniques are used to close the gap between "manuscript" and "completed book." In order to keep the price of the book to a reasonable level, it has been partially reproduced by photo-offset directly from the original report and the cost saving passed on to the reader. Due to this method of publishing, certain portions of the book may be less legible than desired.

Acknowledgments

Preparation of this document involved important contributions from many people in two consulting engineering firms and the United States Environmental Protection Agency (USEPA), Office of Drinking Water, and Drinking Water Research Division. In fulfillment of a contract with the USEPA, day-to-day work was conducted by CWC-HDR, Inc., with supervision, review, and technical contributions provided by Malcolm Pirnie, Inc. Personnel from Malcolm Pirnie involved in this work were John E. Dyksen, David J. Hiltebrand, and Linda L. Averell. Principal authors from CWC-HDR were Jerrold J. Troyan and Sigurd P. Hansen. Other members of CWC-HDR (which became HDR Engineering, Inc., in April 1989) who contributed to either the technical content or the preparation of the manuscript include: Perri P. Garfinkel judith A. Hinrichs Robert R. Livingston Mark S. Montgomery, Ph.D. I. Jean Wagy Bruce R. Willey

Teresa D. Boon May L. Bray Candice E. Cornell Gordon L. Culp Russell L. Culp Brian A. Davis Marie A. Filippello

In addition, valuable technical review and contributions to the text were provided by USEPA personnel including Stig Regli, Project Manager, Gary S. Logsdon, John C. Hoff, Ph.D., Edwin E. Geldreich, and James J. Westrick.

vii

NOTICE The materials in this book were prepared as accounts of work sponsored by the U.S. Environmental Protection Agency. On this basis the Publisher assumes no responsibility nor liability for errors or any consequences arising from the use of the information contained herein. Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the Agency or the Publisher. Final determination of the suitability of any information or procedure for use contemplated by any user, and the manner of that use, is the sole responsibility of the user. The reader is warned that caution must be exercised when dealing with potentially hazardous materials such as contaminated waters, and expert advice shOUld be sought at all times before implementation of any treatment technologies. viii

Contents and Subject Index

EXECUTIVE SUMMARY 1 Introduction 1 Definition of Technology Categories 2 Most Applicable Technologies 2 Other Applicable Technologies 2 Additional Technologies 2 Background 2 Waterborne Disease Outbreaks 2 Filtration in Community Systems 5 General 6 Effectiveness of Filtration for Removal of Microbial Contaminants 6 Discussion of Most Applicable Technologies 9 Conventional Treatment 9 Direct Filtration 9 Diatomaceous Earth Filtration 9 Slow-Sand Filtration . . . . . . . . . . . • . . . . . . . . . . . . . . . . . 10 Package Plants 10 Disinfection in Community Systems. . . . . . . . 10 11 General Most Applicable Technologies 11 Chlorination 12 Chlorine Dioxide 12 Chloramination 12 Ozonation 13 Small Water Systems 14 Treatment Technologies Applicable to Small Systems 14 Alternatives to Treatment 15 Cost Data 15 ix

x

Contents and Subject Index Groundwater Disinfection Costs. . . . . . . . . . . . . . . . . . . . Surface Water Filtration Cost Calculations Costs of Obtaining an Exception to the Surface Water Filtration Rule Costs for Presently Filtering Systems to Improve Their Disinfection Facilities Cost Range Information Regarding Land, Piping, and Finished Water Pumping

18 18 19 19 19

I.

INTRODUCTION Purpose of the Document. . . . . . . . . . . . . . . . . . . . . . . Definition of Technology Categories Most Applicable Technologies Filtration Disinfection Other Applicable Technologies Filtration Disinfection Additional Technologies

II.

BACKGROUND 29 General 29 29 Waterborne Disease Outbreaks-1946 to 1980 35 Waterborne Disease Outbreaks-1981 to 1983 Problems in Removing Microbial Contamination from Water 39 Supply Sources False Sense of Security 40 Protected Watersheds 40 Turbidity Standard 41 Monitoring Microbial Contaminants 41 Coliforms as Indicator Organisms 41 Turbidity as an Indicator of Water Quality 44 Particle Counting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 46 Treatment for Control of Bacteria and Viruses 46 By-Products of Disinfection 49 Treatment for Control of Giardia and Removal of Turbidity 50 Case Histories 51 Argument for Multiple Barriers 52 Alternative Approaches to Microbial Contaminant Control . . . . 53 Quality Requirements 54 Surface Water Treatment Requirements 55 Conditions When Filtration May Not Be Necessary 55

III. FILTRATION IN COMMUNITY SYSTEMS General Effectiveness of Filtration for Removal of Microbial Contaminants Discussion of Most Applicable Technologies Conventional Treatment

24 24 25 26 27 27 27 27 28 28

58 58 58 61 61

Contents and Subject Index Process Description Laboratory and Pilot Plant Studies Case Histories Montreal Denver Sacramento Direct Filtration Process Description Laboratory and Pilot Plant Studies Case Histories Lake Oswego Virginia Erie County Two Harbors Portola Diatomaceous Earth Filtration Process Description Laboratory and Pilot Plant Studies Slow-Sand Filtration Process Description Laboratory and Pilot Plant Studies Case Histories Denver Water Board Survey of 27 Plants New York State Mcindoe Falls Package Plants Process Description Package Plant Performance IV. DISINFECTION IN COMMUNITY SYSTEMS General Most Applicable Technologies

Chlorination General Performance Laboratory Research and Pilot-Plant Studies Plant-Scale Testing Summary Chlorine Dioxide General Performance Laboratory Research and Pilot Studies Summary Chloramination General Performance Case Histories

xi 61 64 66 66 67 67 67 67 71 74 74 74 74 75 76 76 76 79 80 80 82 83 83 84 89 91 92 92 94 98 98

99 103 103 105 106 118 120 121 121 122 122 125 128 128 129 132

xii

Contents and Subject Index Philadelphia Suburban Water Company (PSWC) 135 Fort Meade, Maryland 135 Summary 135 Ozonation 135 General 135 Performance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140 Laboratory Research and Pilot Plant Studies 140 Plant-Scale Results 142 Summary 143 Other Applicable Technologies 143 Iodine 143 General 143 Performance 145 Laboratory Research 145 NoncommunitY Use 146 Bromine 147 Ultraviolet Radiation 147 Performance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149 Laboratory Research 149 Heat Treatment 151 Additional Technologies 151 153 Disinfection with Filtration. .

V.

SMALL WATER SYSTEMS General . . . . . . . . . . . . . . . . . . CommunitY Systems l\Joncommunity Systems Water Requirements Waterborne Disease Outbreaks Treatment Facilities Used by Small Water Systems Difficulties Specific to Small Systems Treatment Technologies Applicable to Small Systems Filtration Technologies Package Plants Slow-Sand Filters Diatomaceous Earth Filters Ultrafiltration Cartridge Filters Disinfection Technologies Hypochlorination and Gaseous Chlorination Iodination Erosion Feed Chlorinators Ultraviolet Radiation Ozonation Alternatives to Treatment Wells Purified Water Vending Machines

154 154 154 154 154 156 157 157 158 159 159 159 160 160 161 163 163 164 164 165 166 166 166 166

Contents and Subject Index VI. COST DATA

Basis of Costs-General Capital Costs Operation and Maintenance Costs Updating Costs to the Time of Construction Basis of Costs-Process by Process. . . . . . . . . . . . . . . . . . . . . Pumping Package Raw Water Pumping Raw Water Pumping In-Plant Pumping Backwash Pumping Package High-Service Pumping Finished Water Pumping Un thickened Chemical Sludge Pumping Thickened Chemical Sludge Pumping Chemical Feed Basic Chemical Feed Liquid Alum Feed Polymer Feed Sodium HydrOXide Feed Lime Feed Sulfuric Acid Feed Filtration Process Components Rapid Mix Flocculation Rectangular Clarifiers Tube Settling Modules Gravity Filtration Convert Rapid·Sand Filters to Mixed-Media Filters Filter-to-Waste Facilities Slow-Sand Filters Pressure Filtration Contact Basins for Direct Filtration Hydraulic Surface Wash Systems Washwater Surge Basins Automatic Backwashing Filter Clearwell Storage Package Pressure Diatomite Filtration Pressure Diatomite Filters Package Ultrafiltration Plants Package Conventional Complete Treatment Disinfection Processes Chlorine Storage and Feed Systems Chlorine Dioxide Generation and Feed Ozone Generation, Feed, and Contact Chambers Ammonia Feed Facilities Ultraviolet Light Disinfection Solids Handling Processes

xiii 168 168 168 169 171

172 172 174 175 175 176 177 178 178 179 179 180 181 182 183 184 185 186 186 187 188 188 189 190 190 191 192 193 194 194 195 196 196 197 198 199 200 200 202 203 204 205 206

xiv

Contents and Subject Index Sludge Holding Tanks 206 Sludge Dewatering Lagoons 206 Liquid Sludge Hauling 207 Gravity Sludge Thickeners 208 Filter Press 208 Dewatered Sludge Hauling 209 Administration, Laboratory and Maintenance Building 209 Alternatives to Treatment 210 Constructing a New Well 210 Conceptual Design 210 Operation and Maintenance Requirements 211 Bottled Water Vending Machines 211 Conceptual Design 211 Operation and Maintenance Requirements 212 Typical Treatment Costs for Surface Water 212 Filtration 213 Package Complete Treatment 213 Conventional Treatment 213 Conventional Treatment with Automatic Backwashing Filters 213 Direct Filtration 213 Diatomaceous Earth Filtration 214 Slow-Sand Filtration 214 Package Ultrafiltration 223 Disinfection 223 Chlorination 223 Ozone Disinfection 223 Chlorine Dioxide and Chloramination 223 Ultraviolet Light 223 Supplemental Process Costs for Surface Water Treatment 230 Additional Chemical Feed Facilities 230 Modifications to Rapid-Sand Filters 230 Adding Tube Settling Modules 230 Direct Filtration Modifications 239 Additional Filtration Facilities 239 Finished Water Pumping 239 Additional Instrumentation 239 Alternatives to Treatment 248 Cost Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 249

REFERENCES

255

APPENDIX A: GROUNDWATER DISINFECTION COSTS

277

APPENDIX B: SURFACE WATER FILTRATION COST CALCULATIONS

284

Contents and Subject Index

xv

APPENDIX C: COSTS OF OBTAINING AN EXCEPTION TO THE SURFACE WATER FILTRATION RULE

298

APPENDIX D: COSTS FOR PRESENTLY FI LTERI NG SYSTEMS TO IMPROVE THEIR DISINFECTION FACILITIES

314

APPENDIX E: COST RANGE INFORMATION REGARDING LAND. PIPING. AND FINISHED WATER PUMPING

328

ABBREVIATIONS AND SYMBOLS

332

METRIC CONVERSIONS

335

Executive Summary

IIITROOUCTION (SECTI Of( I) This docUlllent assists the Adm nistrator of the U. S. Envi ronmenta 1 Protect i on Agency (EPA) in identifying the best technologies or other means that are generally ava 11 ab 1e. taki ng costs into consi derati on. for i nact ivat i ng or rernovi ng mcrobial contanli nants from surface water and groundwater suppli es of dri nk 1n9 water. For lIIlnicipal officials, engineers, and others, the document provides. a review of alternative technologies and their relative efficiency and cost. "1ore specHi cally, thi s ·docUtllent di scusses water treatment technol ogi es whi ch may be used by COlllll,"i ty and noncOIlIlI.Ini ty water systelllS in removi ng tUl"bi dity. Giardia, viruses. and bacteria fra- water supplies. EPA is currently developing ｴｲ･｡ｾ ･ｮｴ regulations addressi.ng these mcrobiolog.ical concerns. WIli le most of this document is devoted to discussion of surface water suppiles, a brief discussion of disinfection technologies and costs for groundwater supplies is also provided, since disinfection is the best available technology for groundwater systems to comply with the coliform regulations. It is not the intent of EPA to require any system to use a particular technology to achieve compliance with the proposed treatment regulations. Instead. the responsibility is retained by the individual water systems to select ODe or more proc.edures that are optimal for their particular water supply situation. Whichever individual or combination of technologies Is ultimately selected by a water supplier to achieve compliance with the requirements lIIlSt be based upon a caseby-case technical evaluation of the system's enti re treatment process. and an assessment of the economics involved. The information provided in the main document is intended to aid a system in reviewing available technologies for achieving the required reduction in turbidity and microorganisms. It provides the user with an evaluation of the various

2

Treatment of Microbial Contaminants in Potable Water Supplies

methods in use today for the removal of different concentrations of turbidity and microorganisms, as well as relative costs. Definition of Technology Categories Thll methods that can be appli ed for the removal of mi crobi a1 contami nants are divided into three categories: Most Applicable Technologies: Those that are generally available and have a demonstrated removal or control based on experience and studies for most systems subject to the regulations, and for which' reasonable cost estimates can be developed. Other Applicable Technologies: Those additional methods not ｩ､ｾｮｴｦ･､ as generally available, but which may have applicability for some water supply systems ;n consideration of site-specific conditions, despite their greater complexity and cost. Additional·Technologies: Those. experimental or that may be studied for specific situations to lations, and for which insufficient data exist and applicability of the technology for removal

other methods with potential use achieve compliance with the reguto fully evaluate the suitability of microbial contaminants.

BACXGROUIll (SECTION II)

An overview of trends in the incidence of waterborne di sease over the past 40 years, and of the capabilities and limitations of available treatment processes, i ndi cates the need for: (1) constant awareness of a broad spect rum of disease-producing organisms; (2) continuing improvement in microbial detection techniques; and most importantly, (3) proper application and operation of available treatment processes. Waterborne Disease Outbreaks Annual occurrences of outbreaks of waterborne di seases from 1946 to 1980 are shown on Figure 1. The increase in annual outbreak occurrences since 1966 is

Executive Summary

ｾ

«I :II: 4(

a:. 30 IU

...::l«I 0

20

10

0

50

85

eo

es

10

15

80

YI!AR

Figure 1 ANNUAL OCCURRENCE OF WATERBORNE DISEASE OUTBREAKS

3

4

Treatment of Microbial Contaminants in Potable Water Supplies

probably due to both more acthe data collection by federal agencies, and more aggressive investigating and reporting by a few states. 1 The most recent data still lack accuracy due to the absence of Intensive surveillance by many state and local agencies. Reported causative agents for waterborne diseases from 1972 to 1981 are indicated in Table 1. Giardia ranks number one in cases of illness and outbreaks.

TABLE 1.

ETIOLOGY OF WATERBORNE OUTBREAKS IN THE UNITED STATES. 1972-1981

Acute gastrointestinal illness Giardiasis Chemical poisoning Shigellosis Hepatitis A sa 1mone 11 os is Viral gastroenteritis Typhoi d fever Campylobacter gastroenteritis Toxigenic E. coli gastroenteritis Cholera --------TOTAl.

Outbreaks

Cases

183 50 41 22 10

37,069 19,863 3,717 5,105

8 11

1,150

282

4 4 1 1

4,908 222 3,902 1,000 17

335

77 ,235

Source: Reference 2.

An evaluation of water system deficiencies specifically responsible for giardiasis outbreaks is presented in Table 2. It is worth noting that 83.5 percent of the cases li sted in Tab Ie 2 (fi rst three items, surface water systems) occurred in systems that ei ther di d not have I'll trat i on, or in whi ch fil trat ion was ineffective or intermittent. Conceivably, all of these cases could have been avoided if the systems serving them had effective filtration and adequate disinfection. The following paragraphs, and corresponding sections of the main document, describe the technologies and costs necessary to achieve adequate control of pathogenic organisms.

Executive Summary

5

TABLE 2. WATERBORNE OUTBREAKS OF GIARDIASIS ClASSIFIED BY TYPE OF WATER TREATMENT OR WATER SYSTEM DEFICIENCY, 1965 TO 1984 Water Source and Treatment/Deficiency 1. Surface water source, chlorination only· 2. Surface water source, filtration 3. Surface water source, untreated 4. Cross-connection 5. Groundwater. untreated: a. well water source b. spri ng source 6. Groundwater. chlorination only a. well water source b. spri ng source 7. Contamination during main repai r 8. Contamination of cistern 9. Consumption of water from nonpotable-tap 10. Consumption of water while swimming. diving ll. Insufficient information to classify

TOTAL

Outbreaks

Cases

39 15 12 4

12,088 7,440 322 2,220

4

27 44

2

4

126 29 1,313 5 7 90 65

90

23,776

2 2 2 1 1 2

• Includes three outbreaks and 76 cases of 111ness lOhere filtration was 'available but not used. In one outbreak filtration facilities were used intermittently and in two outbreaks filtration facilities were bypassed. Source: Reference 2.

FILTRATION IN COMlNITY SYSTEMS (SECTION III)

At this time. treatment requirements for filtration and disinfection are the best available means for controlling pathogenic organisms. This section provides a description of the characteristics and efficiency of water filtration technologies. The section contains supporting data on each technology In the form of laboratory and pilot-plant studies, and case histories regarding full-scale plant operation. The following paragraphs present a sulirnary of the treatment efficiency of each technology. together with a brief description of each technology.

6

Treatment of Microbial Contaminants in Potable Water Supplies

General Filtration of domestic water supplies 15 the most widely used technique for removing turbidity and microbial contaminants. The removal of suspended particles occurs by strai ni ng through the pores in the fil ter bed, by adsorpti on of the particles to the filter grains, by . sedimentation of particles while in media pores, coagulation (floc growth) while traveling through the pores, and, in the case of slow-sand filters, by biological mechanisms. Effectiveness of Filtration for R8IOval of Microbial Cont..inants Filtration processes provide various levels of microbial contaminant removal. Tables 3 and 4 summarize microbial removal efficiencies determined from field and pilot plant studies completed on a range of filtration ｰｲｯ｣･ｳ ＮＳＬｾ Table 3 includes vi rus removal results by several filtration processes without disinfection. As shown in the table, all of the processes are capable of removing 99 percent of viruses witAout disinfection. Giardia lamblia removal data by conventional treatment, direct filtration, diatomaceous earth filtration, and slow-sand filtration are shown in Table 4. Very high levels Ｈ＾Ｙ Ｎ ｾＩ of Giardia reduction can be achieved by chemical coagulation followed by settling and filtration, or by direct filtration. The importance of coagulation to achieve high levels of Giardia removal is noted for both processes. Diatomaceous earth filtration is also extremely effective in removing Giardia cysts. Slow-sand filtration which relies on biological as well as physical mechanisms to remove microbial contaminants is especially effective in removi ng Giardia cysts. In his review of performance data, Logsdon compared slow-sand filtration, diatomaceous earth filtration, and conventional and direct filtration. 3 Using information from filtration studies at pilot-scale, full-scale, or both, he showed that all of the filtration processes, when properly designed and operated, can reduce the concentration of Giardia cysts by 99 percent or more, if they are treating a source water of suitable quality. Many of the studies also contained Giardia removals of 99.9 percent, agreeing with the values shown in Table 4.

Executive Summary

TABLE 3. REMOVAL EFFICIENCIES OF VIRUSES BY WATER TREATMENT PROCESSES Percent Unit Process

Rl!lIIOul

Slow sand filtration

99.9999 99.B 99.8 91

Operating Par_Urs 0.2 II/hr, U-12"C 0.2 II/hrt 0.4 II/hr, 6"C 0.4 II/hrt With cationic polynltr coat CAtionic ｲｾｬｯｰ Into raw water

Reference 16*

17**

Dlatoaaceous earth ftltratlon

>99.95

Direct filtration

90-99

2-6 gpll/ft2 , 11-19"C

18*

Conventional treatment

99

2-6 gpll/ft2 , 17-19"C

la*

* Ptl ot-scaIe studt es. **Laboratory-scale studies. t No temperature data given. ttNo vi ruses recovered.

tt

7

8

Treatment of Microbial Contaminants in Potable Water Supplies

TABLE 4.

REMOVAL EFFICIENCIES OF GIARDIA LAMBLIA BY WATER TREATMENT PROCESSE-S--------------

Raw Water Concentration

Percent Removal

Operating Par_tel'S

Rapid filtration with coagulation, sed illllntat i on

23-1100/L

96.6-99.9

Min. Alu•• 10 mg/L Opt. pH • 6.5 Filtrat10n rate. 4.9-9.8 ./hr (2.0-4.0 gpm/ft 2)

Direct f1ltration w1th coagulation

20 x 106/L (as slug)

95.9-99.9

Min. allll • 10 mg/L pH rangl • S.6-6.S

48

Fil t. rate • 4.9-9.8 III/hI' (2.0-4.0 gpm/ft 2) NTU • Eff. ｾｕＯｩｮｦＮ (0.02-0.5)/(0.7-1.9) Eff. pool' dur1 ng ri peni ng

Unit Process

- No

coagu!at i on

- With flocculation

95-99

- No coagulation DiatOMaceous earth fl1 tl'at 1on

A1UJII •• 2-5 mg/L PolyMer (Magn1floc 572 CR) • 1.2 mg/L Temp •• SO-lSoC Eff. NTU/inf. NTV • 0.05/1.0 FlIt. Rate· 4.S 18.A lI/hr (2.0-7.75 gpm/ft 2)

10-70 1.5 x 1059.0 x l05L

99-99.99

10 2-10 4/L

>99.9

Reference

5-

6-

6-

Filter aid· 20 mg/L body feed Filt. rate· 2.4 - 9.8 III/hI' (1.0-4.0 gpm/ft 2) Temp •• SO-13°C Eft. NTU/1nf.

7··

"TV • (0.13-

0.16)/( 1.0-2.0} Slow sand filtration

50-5 x l03/L

• laboratory and pilot-scale stud1es. --Laboratory-scale studies. Source: Reference 4.

100

Filt. rate· 0.04 - 0.4 III/hI' Temp. 0·, S°, l7°C (1.0-10 mgad) Eff. "TU/inf. NTU • (3-7)/( 4-10)

8·-

Executive Summary

9

Discussion of Most Applicable Technologies The following methods of filtration are identified as the Most Applicable Technologies and are those most widely used for removal of turbidity and microbial contaminants: • • • • •

Conventional treatment Di rect filtration (gravity and pressure filters) Diatomaceous earth filtration Slow-sand filtration Package plants

Conventi onal Treat-m-Conventional treatment is the most widely used technology for removing turbidity and mi crobia1 contll\li nants frClll surface water suppll es. Convent i ona1 treatment includes the pretreatment steps of chemical coagulation, rapid mixing, flocculation and sedimentation followed by filtration. Direct Filtration-The direct filtration process can consist of anyone of several different process trains depending upon the application. 9 In its most simple form, the process includes only filters (oftentimes pressure units) preceded by chemical coagulant Ilppll cat Ion lind nrl xi ng. Raw water II\lst be of seasona lly uniform qual i ty wi th turbidities routinely less than 5 NTU in order to be effectively filtered by an in-11ne di rect filtration system. A second cOlllllOn configuration of the process includes f10ccculation as pretreatment for the filters, in addition to coagulant application and mixing. Preflocculation results in better performance of certain dua1-medla filter designs on specific water supplies. Diato.aceous Earth Filtration-Diatomaceous earth (DE) filtration. also known as precoat or diatomite filtration, is applicable to direct treatment of surface waters for removal of relatively low levels of turbidity. Oiatomite filters consist of a layer of DE about lIB-inch thick supported on a septum or filter element. The thin precoat layer of DE is subject to cracking and II\lst be supplemented by a continuous-body feed of

10

Treatment of Microbial Contaminants in Potable Water Supplies

diatomite. which is used to maintain the porosity of the filter cake. If no body feed is added. the particles filtered out will build up on the surface of the filter cake and cause rapid increases in head10ss. The problems inherent in maintaining a perfect film of DE between filtered and unfiltered water have restricted the use of diatomite filters for municipal purposes, except under favorable conditions. Slow-Sand Filtration-Slow-sand filters are similar to single-media rapid-rate filters in some respects. yet they differ in a number of important characteristics. In addition to (1) slower flow rates (by a factor of 50 to 100 versus direct filtration for example), slow-sand filters also: (2) function using biological mechanisms instead of physi cal-chemi ca1 mechanisms. (3) have sma 11 er pores between sand particles. (4) do not require backwashing. (5) have longer run times between cleaning. and (6) require a ripening period at the beginning of each run. Package P1ants-Package plants are not a separate technology in pri nci pl e from the precedi ng technologies. They are. however. different enough in design criteria. operation. and maintenance requirements that they are discussed separately in this document. The package plant is designed as a factory-assembled. skid-mounted unit generally incorporating a single. or at the most. several tanks. A complete treatment process typically consists of chemical coagulation. flocculation. settling and filtration. Package plants. for purposes of this document. generally can be applied to flows ranging from about 25.000 gpd to approximately 6 mgd.

nlSINFECTION IN COMMUNITY SYSTEMS (SECTION IV) Section IV provides a description of the process characteristics and inactivation efficiencies of disinfection technologies. The section contains detailed criteria and support i ng data on each technology in the fOrlll of laboratory. pil ot-sca1e. and plant-scale studies. The following paragraphs present a summary of the inactivation efficiency of each technology. together with a brief description of that technology.

Executive Summary

11

General While the filtration processes described in Section III are intended to physically remove microbial contaminants from water supplies, disinfection is specifically used to inactivate or kill these organisms. Sterilization, or the destruction of all organisms in water, Is not considered. Disinfection is most commonly achieved by add1ng oxld1z1ng chemicals to water, but can also be accomplished by phys1cal methods (apply1ng heat or l1gnt), by adding metal ions, or by exposure to rad10act1vlty. Most Appl1uble Technolog1es

The following methods of disinfection are Identified as the Most Applicable Technologies (not necessarily in order of effectiveness), and are those most widely used for destruction of .1crobial contam1nants: • • • •

Chlorination (chlor1ne liquid, gas, and hypochlorite) Chlor1ne d10xide Chloraminat10n Ozonation

The performance of these and other chemi cal disi nfectants can best be descri bed through the use of the C.T product (the product of residual disinfectant, C, in mg/L, and contact t1me, T, In minutes). A detailed descr1ption of the application of the vT concept to disinfection practice has been presented by Hoff. IO The range of concentrations and contact times for different di si nfectants to achieve 99 percent inactivation of h coli, poliovirus. and Giardia cysts are presented in Table 5. As shown by the concentration-time (C. T) products in the table. there Is w1de variation both 1n resistance of a specific organism to the different disinfectants, and in the disinfection requirements for different organisms using a s1ngle di'Sinfectant. In general, however. the C·T products in the tables show that Giardia cysts are the most resistant to disinfection, followed by viruses, whereas h£2lL are the least resistant.

12

Treatment of Microbial Contaminants in Potable Water Supplies

Ch1ori nit 1on-For purposes of disinfection of municipal supplies, chlorine is applied primarily in two foms: as a gaseous element, or as a solid or liquid chlorine-containing hypochlorite compound. Gaseous chlorine is generally considered the least costly form of chl ori ne that can be used in large facllit i es. Ch 1ori ne is sh i pped in cylinders, tank cars, tank trucks, and barges as a liquified gas under pressure. Chlorine confined in a container .ay exist as a gas, as a liquid, or as a mixture of both. Thus, any consideration of liquid chlorine includes consideration of gaseous ch 1or1 ne. Hypochlor1te fOnDS (principally calci\lll or sodium) have been used primarily in small systens (less than 5,000 persons) or in large systems where safety concerns related to handli ng the gaseous form outwei gh economi c concerns. Present day cOlllllercial, high-test cal cillll hypochlorite products cantai n at 1east 70 percent avallable chlorine and are usually shipped in tablet or granular forms. Sodium hypochlorite is provided in solution form. containing 12 percent or 15 percent available chlorine. Chlorine Dioxide-Chlorine dioxide ＨｃｬｾＩ is not widely used as a disinfectant in the United States, though its use for this purpose is relatively common In Europe. Chlorine dioxide cannot be transported because of Its Instability and explosiveness, so ｾｉ ｴｳｾ be generated at the site of application. The most common method for producing C10z is by chlorination of aqueous sodium chlorite (NaC102 ), although the use of sodl \Ill chlorate 15 IIIOre eUi ci ent. For water treatment, chl orl ne di oxi de j s only used In aqueous solutions to avoid potential explosions. In terms of available chlorine, chlorine dioxide has more than 2.5 times the oxidizing capacity of chlorine. However, Its comparat1Ye efficiency as a disinfectant varies with a number of factors. Ch 1or.-1 nati onIn aqueous systems. Chloramines have many ally less effective protozoans at equal

chlorine reacts with ammonia (NH 3 ) to form chloramines. properties different than chlorine. Chloramines are generthan chlorine for Inactivating bacteria, viruses, and dosages and contact times. Conventional practice for

Executive Summary

TABLE 5.

Hi croorganiSllI ｾＮ

col1

SUMMARY OF ｾ T VALUE RANGES FOR· 99 PERCENT INACTIVATION OF VARIOUS MICROORGANISMS BY DISINFECTANTS AT 5°C Free Chlori ne pH 6 to 7

Ozone pH 6 to 7

95-180

0.4-0.75

0.02

1.1-2.5

770-3,700

0.2-6.7

0.1-0.2

0.01-0.05

3,800-6,500_

0.2-2.1

0.006-0.06

§.. lambl1a cysts

47->150

§.. muri s cysts

30-630

ｾｯｵｲ｣･Ｚ

Disinfectant Performed Chlorine Chloramine Dioxide pH 8 to 9 pH 6 to 7

0.034-0.05

Polio 1 Rotavi rus

13

0.5-0.5

7.2-18.5

1.8-2.0

Reference 10

chloramination in the field is to add ammonia to the water first, and chlorine later. Ozonat1011-Ozone is the most potent and effective germicide used in water treatment. Only free residual chlorine can approximate it in bactericidal power, but ozone is far more effective than chlorine against both viruses and cysts. However, since it is highly reactive, ozone does not provide a long-lasting residual in drinking water. In addition, ozone must be produced electrically on-site as it is needed, and it cannot be stored.

14

Treatment of Microbial Contaminants in Potable Water Supplies

SMALL VATER SYSTEMS (SECTION Y) Th Is sect Ion defl nes the characterist Ics of small water systems, and i dent 1f i es and describes filtration, disinfection, and alternative technologies applicable to small systems. In this document, small water systems are defined as those with design capacities less than 1.0 rngd. They may serve either cOllmJnity systems or noncOll1Rlnlty systems, and often have distinctly different characteristics and problems than larger systems. Several surveys of small systems were performed in connection with this report to detenwine characteristics such as system supply capacity, treatment design capacity, average day flow requirements, and system storage capacity.ll,12 The· results of those two surveys, coupled with data collected informally from other small water systems, lead to the definition of flow characteristics for four flow categories for the purposes of this report, as defined in Section VI. The processes and facilities used by existing small water systems to treat water supplies vary about as widely as the range of flows they treat. Treat.-nt TechnologieS Applicable to SINH Syst. . Many of the technologies described in Section III, Filtration, and Section IV, Disinfection, are adaptable to smaller systems. Others, because of such factors as operational complexity, safety considerations, equipment size limitations and cost, are not appropriate for small ｳｹｴｾＮ Filtration technologies that can serve small systems Include:

•

•

• •

•

Package plants Slow-sand filters Diatomaceous earth f11 ters Ultrafiltration Cartridge filters

Executive Summary

15

Disinfection technologies which may be appropriate for small systems include: •

Hypochlorination and gaseous chlorination

• •

Ozonation Iodination (noncommunity systems serving transient populations)

• •

Erosion feed chlorinators Ultraviolet radiation (groundwater systems)

Detail ed descri pt ions of each of these technol ogi es are provi ded in the ma in document. Alternatives to TreatMnt Under certain circumstances. SOllIe SllIIll systems l1llIy have alternatives available to them that are not practical for larger systems. Specifically. it may be possible for a small system to construct a well to provide a groundwater source as either a suppl ement to or a replacement for an existi ng surface water source. Further. some systems may be small enough that pur.tfi ed water vendi ng mach I nes could be used to supply all or a major portion of its water demand. COST DATA (SECTION VI) Capital and operating costs for the technologies in this document are Dased upon updated costs originally presented in several cost documents prepared for EPA.13.1" Construction cost Infonutlon originating from those reports was modified and updated by acquisition of recent cost data. SpecHic details regarding cost calculations for individual processes and process groups are presented In this section and in Appendix B. Description of assumptions and costs for disinfection of groundwater are presented In Appendix A. All costs were prepared for facilities with average flows as shown I n Table 6, selected after a nationa.1 survey of operating treatment plants. 1S Capacities range from 26.000 gpd for the smallest plant to 1.3 billion gpd for the largest. Construction costs are based on plant capacity flow rates shown in the table. whtle operation. maintenance. and chemical use costs are based on average flow rates.

16

Treatment of Microbial Contaminants in Potable Water Supplies

Individual descriptions and costs are presented for the following processes: •

•

•

Pumping Package Raw Water Pumping Raw Water Pumping In-Plant Pumping Backwash PUIlIPing Package Hi gh-Servi ce Pumpi ng Finished Water Pumping Unthickened Chemical Sludge Pumping Thickened Chemical Sludge Pumping Chemi cal Feed Basic Chemical Feed Liquid Alum Feed Po1ytRer Feed Sodium Hydroxide Feed Lime Feed Sulfuric Acid Feed Filtration Process Components Rapid M1 x Flocculation Rectangular Clarifiers Tube Settling Modules Gravity Filtration Convert Rapi d-Sand Fil ters to M1 xed-Medi a Filters Filter-to-Waste Facilities Capping Sand Filters with Anthracite Slow-Sand Fll ters Pressure Filtration Contact Basins for Direct Filtration Hydraul1c Surface Wash Systems Washwater Surge Basins Automatic Backwashing Filter Clearwell Storage

TABLE 6.

Category 1

2 3 4

5 6

1 8

9

10 11 12

PROPOSED AVERAGE PRODUCTION RATE AND PLANT CAPACITIES

Population Range 25 - 100 10'1 - 500 501 - 1,000 1,001 - 3,300 3,301 - 10,000 10,001 - 2S ,000 25,001 - 50,000 50,001 - 15,000 15,001 - 100,000 100,001 - 500,000 500,001 - 1,000,000 >1,000,000

Average Flow (QA)' !gd 0.013 O.04!i

0.133 0.40 1.30

3.25 6.15 11.50 20.00 55.SO 205 650

Surface Water Treat.ent Plant QA as S Capacity, of Plant .gd Capacity 0.026* 0.068* 0.166* 0.500* 2.SO 5.85

SO.O 66.2

SO.O SO.O

52.0 55.6

11.58

58.3

22.86 39.68 109.90 404 1,215

50.3 50.4 50.5 50.7 51.0

m x

CD

n

....c Ｎｾ

*Costs for supply systems in Categories 1-4 include sIgnifIcant supplemental storage volumes. See Section V of maIn document for further details.

en c

3 3


TABLE Z. Tr.. tMftt Processes

SUMMARY OF TOTAL COSTS

CD

4

S

6

I

1

2 3 0.0611 0.1"

O.'SII

Uo

5.115

It.5.

22.86

O.n13

0.04' n.133

0.40

1.ll)

3.U

6.15

11.50

ＰＮｮＲｾ

...o :::J

Total Cost of Tr..teeRt, 4",00II lII110ns SI ze CatjPGryi

9

jU8

ZO.on

10 ln4.9 55.5

11

If

ZOS

650

.....

s:: a C"

404 1.115

(i"

Fllt ...tlonl

iii"

CCllIplete treat_nt pachge phnts Con.entlonal cClllplete treatMnt Con.entlonal treat_ftt "It_ autout Ic hact"ISMn, filters 01 reet flltratlon uslng pressure tllters III reet fllt ...t Ion using g,a.tt, tl Iters p,eceded b, flocculet Ion Direct ftlt,atlon using g'eYlt, fllte,s and contlct blSlns Direct fllt,atlon using dhtouceous e.rth 51 ow-sand flltrat Ion Package ultraflltratlon phnts

941.5

217.4

19'.1

322.1

113.6

12.8 104.1 81.9

52.4 10.3 58.3

131.?

19.1

1511.2

'10.5

131.?

(')

32.0

31.0

28.6

23.6

21.3

31.5

26.3

21.4

19.1

41.7

3'.4

58.11 50.8

61.9 51.6

53.8 49.4

39.3 41.5

48.11

39.2

45.8

36.'

28.2

511.4

46.8

50.5

39.11

llO.9

54.1

44.2

48.0 48.1

672.9

227.2

134.1

66.6

43.1

43.1.

36.1

377.8 455.6

205.1 Z?11.8

133.4 179.2

54.7 1311.4

34.3

28.7

25.3

o :::J lit Ｂｾ:::J II>

:::J

l;/' :::J "'tl

S II>

2: CD

I.

2.

Catego" 'i1tt!9ory I. ｾＵ 2. IIlI 3. 5B1 -

.alues, f.... top to bott_. are .......,. desIgn now (1IgCI). and a.e,a91 flow (1IgCI). P......latlon ,anges fo, lOch Ire: HI. 10Il.001 - 500.1lOO IflO 1. 25.001 - 51l.llIlB 4. 1.001 - 3.3IlB 500 8. 50.flOl - 15.0Il0 5. 3.]1)1 - IIl.llIlB II. 5l1li.001 - l.llOB.OOO 1,Il00 q. 75.001 - 100.000 Ii. 10.001 - ?5.llIlB Ｎｾｉ >1.IlOO.IlOO

Eoch p,ocess g,oup ｉｮ｣ｬｵｾ･ｳ ChMlcal addttlon and ｬ｡ｵｾｨ､ｮｉ liquId and solids ･ｸ｣ｬｵ､･ｾ are r ... "ater p...plng. ｦｴｮｬｳｨｾ ..ater p..... lng. aM dlstnfectlon.

ｨ｡ｮｾｬｴｮｧ

p,ocesses ,equl,ed for operation;

:E II> lit ... CIl

c:

"C

ｾ

ｾＮ

TABLE 7 (Continued) Toto I Cast of Trllt_nt, VI,lllIO 61l1ans Shl Cot"9aryl TrlltMnt Processe,

12]

4

S'

1

II

I

Ih

1I----r2

d.hM

h.MII h.lii'

n.!in

2.m

US

11.5.

22.'"

]9.68

1M.'

404

I,m

0.013

0.045 0.133

0.40

-1.30

3.25

6.75

11.SO

ZO.M

55.5

ZO!i

6SO

otsinfeclll)lil Clllarl .. food focllltll'" Ozone ge..rltl"" loci food! Clllorl .. dlo.lde' CIllarMt nit lorl IJlt ...lolet IIg11t

81.7 51.1 14.1

16.2 27.5 46.1 23.9 11.4

9.7 12.1 16.8 14.4 5.4

4.3 7.0 7.0 6.1

2.8 4.5 4.2 3.6

2.1 3.4 2.9 2.6

1.6 2.6 2.2 2.1

1.3 2.2 1.1 1.6

1.0 1.1 1.3 1.3

0.8 1.4 1.0 1.0

0.7 1.2 0.9 0.9

21.0 0.5

11.0 11.4 21>.2 1/1.7 9.9 /1.3

1.2 8.4 16.5 8.4 7.1> 0.1

2.9 3.0 7.5 4.1 4.1 0.3

2.9 3.0 1'1 2. 1.0 0.3

1.2 1.4 1.1 1.9 0.6 O.l

0.1 0.8 0.9 1.6 /1.4 0.3

0.5 0.6 0.8 1.6 11.3 0.3

0.3 0.4 0.7 1.5 0.3 0.3

0.2 0.3 11.6 1.4 0.2 0.3

0.2 0.2 11.6 1.4 11.2

0.1 0.2 0.5 1.4 0.2

9.4

5.5

l.l

2.1

2.0

1.1

1.1>

1.5

1.5

1.5

ｾＮＵ＾ｉ

23.1>

1119 3?2 In 4l.Z

17.2

Suppl_ntll Procesus Add polyMr flod, /1.3 "9fl Add polyMr feed, 11.5 "9fl Add II .. foed, 10 "9fl Md sodl .. hydrollde feed Add sulfuric Icld food Clpplng rlptd-untl flltlrs ..lth Inthrlc Ite CCNl I Con.erll og rlptd-uocl filters to .1 lId __dll ftlters

35.3 36.4 81.1 3/1.2

m 1. 4. 5.

ntslnfectlon flctllttes IllCludl III requtrod generillon, storlge, loci feed equlpoent; contoct blsln Ind detent ton flctllttes oro ..c1uded. lleslgn flows for Clt"9orlos 1-4 ore, respectholy: 0./lZ6 "'!ld, 0./161I oogd, 0.166 "9d, loci II.SO oogd. noso Is S.II.glL; tncludes hypotlllorito solutton food for Cotegorles 1-3, chlorlno foed Ind cyllndor starlge for Cotegortos 41/1. Inti chlortne feod Inti an-slto storlgo for Cltogortos II Ind 12. nos 0 Is I. 0 109ft.

9: ll8u.ｯａ｜ｩＳｔｨＲＧｾｲｩｴ

It 1./1 ogfl' loci .->nll It 1.0 19ft.

X

CD

g ....

m

en r:::

'C

"2(ii'

'"

or

TA8LE 8. SlJ1MARY

1

DISINFECTION METHOD Chlorine

Ozone

ll:06

,

I

66.9, 30.2 ｾ

,

Ultraviolet Lfght'

lr.J ｾ

12.0 8.7

m:r

61.6

31.6

n:r n:r

321.3 19.7

96.9 10.0

rn:9

45.3 4.1 'Sll:1r

41.8 19.4

23.6 8.1

ｾ

Chloramination'

3 0.133

22.9 19.4

165.1

Chlorine, ｄｩｯｸｴｾ･

2

0.045

116.8 30.2

m:o 61.9 ｾ

ｾ

--o.lT ""ll"":1I

0.013

ｾ

Jr.j

20.2

10.1

20.2"

ro.r

-

GlOUNlllIATER DIS tNFEC TlON COS TS

COST OF TREATMENT. Sue. ｣｡ｴ･ｾｯｲｹ 4 5 6

J.1l6

Kr

0.40

1.30

3.25

6.75

4.1 6.2

3.1 5.4

1.6 3.3

1.1 2.5

Tll":r 15.5

ｾ

1.5

T5:'5""""

T.'S""""

16.8 3.3

6.0 3.7

ｾ

ｾ

4/1 ,ODD

9.5 6.2

8

9

ra

44.Z

11.5

20.0

0.9 2.0

0.8 1.7

10

11

12

m-

ill

55.5

205

r:-m 650

1).6 1.3

0.4 1.0

0.3 0.8

4.9

""ToT

--n

""T.""S"

T:l

r.r

5.n

4.0

3.5

3.1

2.1

1.4

1.2

"5:'0"""'

--..r

"9:1

....,

J.r

3.9 5.4

1.9 3.3

1.2 2.5

rs:r r.r

GAL

3.1 2.4

!:r

2.1 1.6

J.r

ｾ

-

ｾ

.

-r:T

---r.T

T:l

a

1.6 1.3

1.4 1.1

0.9 0.8

0.6 0.5

0.4 0.4

1.0 2.0

0.8 1.1

--r;r ""T.""S"

--r.o

""T.""S"

-r.r

IT

1).6 1.3

0.3 1.0

ｾ

T:j

ｾ

n

0.2 0.8

7.6

---,:r

Costs InclUde a chlorine dosage of 2.0 mg/l with 30...,lnute detention tl .... Chlorine 15 fed as a hypochlorite solution for Cltegorles 1 through 4; cylinder storage and feed Is used for Cltegorles 5 11 and 12. Detention storage 15 provided by a through 10, with on-site tonk storage used In ｳ･ｴｲｾ｡ｃ pressure .essel In Cltegorles 1 and 2. I looped underground pipeline In Cltegorles 3 and 4, and I chlo2 rtne contact basin In Categories 5 through 12. Costs. tncludlng both capitol and O&H. Ire shown as follows: XX.x - dlsl nfect t on generat lon/feed !qut poent l1.:1. - detention storage facilities , zZ.z - toto 1 cost Includes dIrect In-llne ozone Ippllcltlon ot 0 dosoge of 1.0 .,g/l followed by a 5....lnute contact ttme, • asslJOled to be achieved In the transmission line between the well ond the distribution syste",. Includes chlorine dioxIde It I dose of 2.0 .,gl1 with 0 15....lnute detention tlllle. Detention 15 In pressure .essels In Cltegorles 1 and 2. In looped underground pipelines In Cltegorles 3 and 4. and In chlortne ,contact bl5lns In Cotegorles 5 throUgh 12. Costs Ire for a chlorine dose of 1.5 "'9/1. an .....,nh dose of 0.5 '"9/1. and 3D-tlIinute detentton. Chlorine 15 pro.lded 15 a hypochlorite solution In Categories 1 through 4, by cyllnder storege and feed In Cltegorles 5 through 10, Ind Is stored in on-site links tn Cltegorles 11 Ind 12 ........nlo 15 fed as Inhydrous _ I I In Cotegories 1 through 4, Ind 15 aquo ....,.,nh In Cltegorles 5 through 12. Detention Is In pressure .essels In Cltegorles lind Z, In looped underground pipelines tn Cltegorles 3 ond 4. Ind tn , chlorine contlct chombers In Cotegorles 5 through 12. 110 addlttonol detention storage used beyond that bullt tnto the ultravtolet light unit. I

m

X n

(I)

ｾ

c:


..1.

-.!

40

40

.-+

!2: C1l

:E ll> .-+

C1l .... en

r:::

'0

* AGI • Acute gastrointestinal Illness of unknown etiology. Source: Reference 3.

"2-

ro' en

Background

TABLE II-8.

39

WATERBORNE DISEASE OUTBREAKS. BY TYPE OF DEFICIENCY, 1981 TO 1983

Deficiency

1981

Total Outbreaks

1982

1983

3-Year Period 12

Untreated surface water

4

5

3

Untreated groundwater

9

11

12

32

Treatment deficiencies

11 2

14

19

44

5

4

11

Deficiencies in distribution system Miscellaneous

3

3

0

6

Multiple deficiencies

3

2

.J.

7

32

40

40

112

TOTAL Source: Reference 3.

PROBLEMS IN REMOYINli MICROBIAL CONTAMINATION FROM WATER SUPPLY SOURCES The materi a1 just presented on the frequency and severi ty of waterborne d1 sease outbreak s due to transmiss i on of mi crobia1 contami nants through pub 11 c water supplies roughly defines the minimum extent of this public health problem as it is known today. Due to nonrecognition and incomplete reporting of outbreaks of waterbome disease, the nwnber of actual occurrences is believed to be I1llch higher than that presently reported. l With proper appli cati on and use of today I s water treatment technology, di sease outbreaks from public water supplies could virtually be eliminated. There are numerous reasons why this is not presently the case. The statistics on reported outbreaks

of waterborne disease stri ki ngly demonstrate the pri nci pa 1 problem

which currently exists. Water systems either do not have the needed water treatment facilities, the existing water treatment facilities are inadequate, or there has been an interruption 1n the proper operation or use of exist 1ng faci 1i t 1es.

40

Treatment of Microbial Contaminants in Potable Water Supplies

Interruptions In proper operation can be due to lack of adequate system reliabil1ty. nachani cal failure. unant 1ci pated emergency condl t Ions. or operator error. Within ･ｳｾｨｴ general problem categories there are a host of detailed problems which contribute to the present lack of total effectiveness In removing microbes frOlll water. Some of these problems will be presented in the discussions which follow. False sense of security

Public water supplies in the United States have long had the reputation of being excellent with respect to quality and safety. Many protected surface water supply sources have operated successfully in the past with only disinfection treatment. Many do not have backup disinfection equipment for use in times of emergency. To a great extent. the fact that there has never been a recognized prOblem. explains the present lack of III)re extensi've treatment facilities. Many managers of water systems are not convinced of the need for other than minimum treatment (disinfection) of their supplies. because they have not recognized any problems. Times have changed. however. and the known hazards of contamination have significantly Increased In 'recent years. Protected Watersheds-There are several changes affecting the need for treatment of surface water suppl ies. Many protected watersheds and raw water reservoi rs are now opened to the threat of hllllan pollution by the widespread use of trail bikes. four-wheel drive vehicles. and snowmobiles which enable people to reach formerly inaccessib1e areas. However. this hazard of increased opportuni ty for human transml ss i on of nri crobial contllllli nants. is overshadowed by the potential for transmi ss i on of Giardia cysts from beaver and other animals to· man through drinking water. Pluntze. in describing the first waterborne outbreak of giardiasis having strong evidence of animal origin (Camas. Washington. 1976) aptly stated: "This changed forever the time-honored concept of the 'protected' waterShed: I.e., if one could simply keep people out. or at least monitor and control their activities, there would be little likelihood of human waste contaminating the water."6 The cause of the disease 1n camas is presumed to be beavers. not people. "Giardia organi sms can and do Infect many domestic and wild animals, Including cats, dogs, sheep, mice. rats. gerbils. beavers. muskrats. and voles."7

Background

41

On protected watersheds, loggers and recreation1$ts are more easily controlled than beavers and nuskrats, a s i tuat ion whi ch is caus i ng some reassessment concerning the safety of unfiltered surface water suppl ies, even those that have been derived from watersheds which were considered to have maximum .protection from human pathogens. Turbidity Standard-The NlPOWR (National Interill Prillary Drinking Water Regulations) turbidity ·standards of 1.0 NTU (nephelometric turbidity units) has been used for many years to support and justify nontreatment of raw waters of high clarity. The degree of risk involved in this practice is now recognized as being higher than previously estimated, since Giardia and other cysts have been found in unfil tered waters with turbidities less than 1.0 NTU. several examples of th1$ type of occurrence are described in the following pages. Monitoring Microbial cent_inaAts Microbial agents that cause waterborne disease outbreaks are rarely isolated from the water system. 8 Examination of water samples for pathogenic bacteria, viruses, and protozoa 1$ technologically and economically infeasible for many water systems. For example, since one plaque-forming viral unit may be an infective dose for a portion difficult. 9

of the population,

isolating and detecting viruses

is quite

Coliforns IS Indicator'OrganiSlS-The fact that the number of pathogens in water 1$ low, lind that they occur in wide vaMety (requiring different methodologies for detection), imposes a severe restriction on their direct and quantitative detennination in routine water analysis. As a result, it is necessary to resort to indirect evidence of their presence. Indicator organisms provide the substitute evidence. The presence of coliforms in any water sample indicates the potential for recent fecal contamination, which in turn suggests the possible presence of pathogens. In treated water, their relative numbers are primarily used to indicate treatment efficiency. Investigation for the presence of coliform organisms, because of the relatively large numbers present in most waters, offers a practical approach for assessing

42

Treatment of Microbial Contaminants in Potable Water Supplies

treatment efficiency and detecting contamination. A search for specific pathogenic organisms is likely to take longer than coliform determinations, and might be fruitless. IO ,II Moreover, throughout the longer time required to make and confirm the necessary examinations for specific pathogens, people would continue to consume the water.

This delay in determining the hazardous nature of a water

could easily result in a waterborne-disease outbreak. Although the waterworks profession relies on the coliform ·examination to determi ne both treatment effi ci ency and the probabili ty 1evel that di sease-produc i ng microorganisms are present, this test also has its limitations. For example, specific pathogens respond differently to the various treatment processes. Also, it may not be correct to assume that treatment reduces all pathogeni c organi sms to the same. extent that it reduces coliform bacteria. Accumulated evi dence i ndi cates that the bacteria caus i ng typhoi d, paratyphoi d, cholera, and bacillary dysentery do respond to treatment in the same manner as co l.iform bacteria. Some vi ruses and cysts, however, appear. to pers i st in water for longer times than coliforms. Viruses may penetrate through rapid-sand filters more readi ly than col i form bacter! a. Certai n vi ruses and cysts are 'Rore res istant than coliforms to destruction by chlorine disinfection. Recent work reported by Rose, et aI, suggests that enteric viruses can occur at detectable levels in fil tered fi ni shed water whi ch meets current col iform (1/100 mi.) and turbi di ty (1 NTU) standards and contains >0.2 mg/L free chlorine. 12 From these observations, it can be concluded that it is possible for certain pathogenic organisms to survive treatment that apparently removes or destroys all coliform bacteria. Despite this possibility, the record of waterborne-disease outbreaks attributable to properly treated public water supplies, as indicated by coliform absence, supports the use of coli forms as one indicator of the microbiological safety of water. With good filtration and disinfection practices there is an excellent chance of removi ng or i nact i vat i ng any vi rus or Gi ardi a that may be present in the raw water. The limitations of using coliform absence as an indicator of treatment effectiveness are, however, growi ng more apparent. The AWWA Conrnittee on the Status of Waterborne Diseases in the U.S. and Canada (1981) stated the problem as ｾＺｳｷｯｬｦ

Background

43

Coliform organism identification is used as an indication of fecal contcwination of water supplies and is widely employed for routine surveill ance. Negative resul ts are usually interpreted as assurance that the water is free of enteric pathogens. Thi s i nterpretat i on I1lJst be reevaluated, as outbreaks of waterborne di sease have occurred in water systems where coli forms have either not been detected or have not been found to exceed standards. The methods of scwpling for col1forms are limitations in themselves, i.e., coliform samples are not taken continuously, and often very few samples are taken. Finally,

investigations

into

outbreaks

in

Camas,

Hampshire; and six different outbreaks in Colorado, indicate that

coliform

counts

are

poor

or

Washington; from

inadequate

Berlin,

1976 through indicators

New 1982,

regarding

Giardia, since treated water concentrations did not violate bacterial standards, yet outbreaks occurred. 1 ] ＬＱｾ ,lS Several· different tests for coliforms have been used, inclUding total coliform, fecal coliform, heterotrophic plate count (IFC), and others. Regulations to date have conventionally used total coliform counts, and in some cases, fecal coliforms. The use and value of HPC has also been noted by several

authors and

groups. McCabe et al, for example, note that this general bacterial enumeration does not usually have direct health significance, but heavy growths do indicate a potential for ｣ｯｮｴ｡ｭｩｮ｡ｴｩｯｮＮｾＵ

They also cite research findings suggesting that

high plate counts inhibit the growth of coliforms on lab media, thereby observing their ｰｲ･ｳ ｮ｣･ＮｾＵ Geldreich et al, later confirmed this finding, and refined it by noting that the frequency of detection of both total coliform and fecal coliform began decreas i ng after the HPC exceeded about 500/ml. (B) They also found increased difficulty in screening for Salmonella and Shigella serotypes when the HPC exceeded 500/ml. The survey data of Geldreich et al, also included disinfection control results in the distribution system, finding that (a) HPC in distribution lines was controlled to less than 500/ml by maintaining a chlorine residual of 0.3 mg/L, and further, that (b) HPC values less than 10/ml were obtained in more than 60 percent of the distribution systems with chlorine residuals of 0.1 to 0.3 mg/L. Based on these data, the authors recommended establishing an HPC limit of 500/ml

in distribution ｳｹ ｴ･ｭｳＮｾＶ

More recently, the AWWA Committee

44

Treatment of Microbial Contaminants in Potable Water Supplies

on Heterotrophic Plate County bacteria has reconrnended that (a) systems monitor for HPC in fi nl shed waters at a frequency equal to 10 percent of that for total coliform measurement In the distribution system (minimum of 2 samples per month), and that (b) systems provide treatment which achieve HPC concentrations of less than 10/111." 7 Turbfdfty u an Indfcator of Wlter Qua1fty

Measurement of the turbidfty of treated water serves several purposes. Turbidity is a direct indicator of water clarity. Turbidity removal also affords one of the best tests available for the rapid evaluation of the efficiency of the Chemical coagulation and filtration processes In removing particulate matter. In conventional treatment. low turbidity water and effective turbidity removal are necessary to ensure proper disinfection. Particles causing turbidity may interfere with the disinfection processes by coating. adsorbing. or otherwise shielding the ｭｩ｣ｲｯ ｲｧ｡ｮｩｾｳ

from contact with the disinfectant. Experience in the operation of water systems has long ago established the relationship between low finished water turbidities and improved public health statistics. However. recent experience with the increased incidence of giardiasis focuses even more sharply on the necess! ty for mai nt-al ni ng very low fl nished water turbl di ties 1n convent i ana 1 treatment processes to curtail the spread of this disease. although there is some recent data to 1ndi cate that slow-sand fil ters achi eve good cyst remova I wi th finished water turbidities greater than 1 NTU. 16 • 17 As noted by the 1981 AWWA Committee on the Status of Waterborne

ｄｩｳ･｡ Ｚｾ

Turbidity that interferes with disinfection is health related; nowever. fol'llS of turbidity such as iron precipitate or other inorganic matter are not health related. Waterborne disease outbreaks. primarily giardiasis. have occurred in systems where the health-related turbidity 1imi t has not been exceeded. It cannot be ass""ed that meet i ng the turbi dfty l1mi t wf11 prevent waterborne di sease when the raw water source may contal n pathogens. especially Giardia cysts. Under these conditions. safe drinking water can be assured only by properly

Background

45

designed and operated water filtration plants utilizing coagulants or filter aids in addition to disinfection. A principal conclusion of the investigation of the camas. Washington. giardiasis outbreak was that. ••••• turbidity and coliform count alone are inadequate parameters on which to judge the biological quality of filter effluent.· 1l • 1S Karlin and Hopkins made tile following conclusions regarding Colorado giardiasis outbreaks :110 •

Turbidity and bacterial concentrations are poor indicators regarding Giardia--no violations of standards were associated with tllese outbreaks.

•

A turbidity standard of 1 NTU permits many Colorado water treatment systems to discontinue pretreatment when raw water source is 99

2-6 gpm/ft2 , 17-19°C

36*

Diatomaceous earth fil trat ion

>99.95 tt

Direct filtration Conventional treatment

* Pilot-scale studies. Ｊ ｌ｡｢ｯｲ｡ｾｯｲｹＭｳ｣｡ｬ e studi es. t No temperature data given. ttNo viruses recovered. Source: Reference 9

Virus removal achieved by filtration processes are shown in Table III-I. These results, together with others discussed in this section, indicate that filtration without disinfection can remove 99 percent of viruses in water supplies. Giardia lamblia removal data by conventi onal treatment, di rect fil trat ion, di atomaceous earth filtration, and slow-sand filtration are shown in Table III-2. Very high levels Ｈ＾Ｙ Ｎ ｾＩ of ｾ reduction can be achieved by chemical coagulation followed by settling and filtration, or by direct filtration. The importance of coagulation to achieve high levels of ｾ removal is noted for both processes". Diatomaceous earth filtration is also extremely effective in removing Giardia cysts. Slow-sand filtration which relies on biological as well as physical mechanisms to remove microbial contaminants is especially effective in removing Giardia cysts.

60

Treatment of Microbial Contaminants in Potable Water Supplies

REMOVAL EFFICIENCIES OF GIARDIA LAMBLIA BY WATER TREATMENT ｾｅｓ ｅｃｏｒｐ --Operating Percent Raw Water Concent rat ion Removal Parameters

TABLE II 1-2.

Unit Process Rapid filtration with coagulat10n, sed1mentat10n

23-1100/L

96.6-99.9

D1rect f1ltrat1on w1th coagulat10n

-20 x 1()6 /L (as slug)

95.9-99.9

- No coagulat10n

-48

- With flocculation

95-99

- No coagulation

10-70

Oiata-aceous earth filtration

1.5 x 1()S9.0 x lOS /L 1()2 -lOt /L

Slow sand filtration

99-99.99 >99.9

Min. Alum· 10 mg/L Opt. pH • 6.5 Filtration rate· 4.9-9.B m/hr (2.0-4.0 gpm/ft 2 )

5"

M1n.

5"

ｾｬ｡

• 10 mg/L

pH range· 5.6-6.8

Filt. rate· 4.9-9.B m/hr (2.0-4.0 gpm/ft 2 ) Eff. NTU/1nf. NTU • (0.02-0.5)/(0.7-1.9) Eff. poor dur1ng r1 pen1 ng Alu••• 2-5 mg/L Polymer (Magnifloc 572 CR) • 1.2 mg/L Temp•• 50 _18°C Eft. HTU/inf. NTU • 0.0511.0 Filt. Rate· 4.8 18.8 llI/hr ＮＷＭＰｾＲＨ 75 gpm/ftz) F1lter a1d • 20 mg/L body feed Filt. rate· 2.4 - 9.8 m/hr (1.0-4.0 gpm/ft2 ) TIllIIP•• 50 _13°C Eff. NTU/1 nf. HTU • (0.130.16)/(1.0-2.0)

F1lt. rate· 0.04 - 0.4 m/hr Temp. 0°, 5°, 17°C (l.0-10 mgad) Eff. HTU/inf. NTU • (3-7)/(4-10) • Studies included laboratory and pilot-scale work. "'Stud1es were laboratory scale. Source: Reference 1 50-5 x 103 /L

-100

Reference

6"

6" 5.... 7"·

8....

Filtration in Community Systems

61

In a 1ater revi ew of performance data, Logsdon compared slow-sand fil trat ion, diatomaceous earth filtration, and conventional and di rect filtration. 9 Using information from filtration studies at pilot-scale, full-scale, or both. he showed that all of the filtration processes, when properly designed and operated, cysts by 99 percent or more, if they are can reduce the concentration of ｾ treating a source water of suitable quality_ Many of the studjes also contained Giardia reMOvals of 99.9 percent, agreeing with the values shown in Table 111-2. DISCUSSION OF JIIlST APPliCABLE TECHNOl06IES

The following methods of filtration are Identified as the Most Applicable Technol ogi es and are those most wi de ly used for removal of turbi dity and mi crobial contaminants: • • •. • •

Conventional treatment Direct filtration (gravity and pressure filters) Diatomaceous earth filtration Slow-sand filtration Package plants

Conventional Treatment Process Description-Conventional treatment is the most widely used tecnnology for removing turbidity and microbial contalllinants from surface water supplies. Conventional treatment Includes the pretreatment steps of chemical coagulation, rapid mixing, flocculation and Sedimentation followed by filtration. Disinfection is not inclUded in the flow sheet because it 15 discussed separately in the next section of this document. The filters can be either sand, dual-medla, or tri-media. Site-specific conditions will therefore influence the design criteria for each component of a conventional treatment systenl. For the purposes of this document, it is assumed that the processes descri bed here are used for raw waters wi th reI at i ve ly low turbidity, since the need for treatment is more obvious with highly turbid waters.

62

Treatment of Microbial Contaminants in Potable Water Supplies

Figure 111-1 is a flow sheet for a conventional treatment plant. Typically, upon entering the plant, r!W water is coagulated with aluminum sulfate (alum), ferric or ferrous sulfate, ferric chloride, or an organic cationic or anionic coagulant. Following addition of coagulants, the flow is subjected to rapid mixing to provide ｣ ｾ ｬ ･ ｴ dispersion of the coagulant into the raw water. Depending on the type of rapid mixing device, detention times ranging from 3D seconds to 2 minutes are typically provided. Fo 11 owi ng flash mi xi ng, the water enters a baftl ed fl occulat i on bas in where the degree of m1xing is controlled to produce a readily settleable floc. ,Typically, mechanically mixed flocculation basins are designed with detention times ranging from 20 to 45 minutes. Flocculated water 15 then introduced into a sedimentation basin designed with 1 hour to 4 hours of detention time to permit the fl occu lated water to c1ari fy. Sedimentation basin overflow rates range from 500 gpd/ft 2 to 1,400 gpd/ft Z depending on site-specHic conditions. These basins are usually designed with mechanical sludge collectors for continuous- removal of settled solids. In some applications where sludge accumulates slowly due to low raw water turbidity, the basins may be cleaned manually by draining the basin and hosing the collected sludge to the plant sewer. A well designed and operated sedimentation basin should provide a high level of turbidity r'emoval. Effluent from the sedimentation basins, to be treated by rapid-sand filters, should have a turbidity of less than 2 NTU. If dual- or trimedia filters are used, applied water turbidities can be as high as 10 NTU. Water treatment plants using rapid-sand fl1 ters are generally des i gned wi th a filtration rate of 2 gpm/ft 2 • Rapid sand filter media varies in effective size from 0.35 mm to 1.0 mm, with a uniformity coefficient of 1.3 to 1.7. Newer plants using dual- or tri-media filters have a design filtration rate of 4 to 6 gpm/ft 2 • Properly operated and using adequate coagulant dosages, a plant designed around rapid-sand fl1ters is generally capable of producing a low turbidity filtered water approaching a value of 0.1 to 0.2 NTU. Plants using dual- or tri-media filters can genera lly produce a lower fil tered effl uent turbi dity since po lymer

Filtration in Community Systems

t N

.. -

-f ..... D 0)(

,:

.. :I E

i

ｾ

...J

'C.

o

9'" ...

ﾷｩｾi=

Ｚｾ Ｕ

«

z

ｾ｣ｾＮＬ

t-

ii:

UJ

..1«02

Z

> Z

o U

z

ｾ

...2

•ｾ

I

11

..e z

0

....t ｾ

G 1 0° ｾ

0"

;f.....2

e· z ..c .... Io

W>

zc

..I

C.. o0·

C

o o

...z

.• :>

..I

;!;

63

64

Treatment of Microbial Contaminants in Potable Water Supplies

filtration aids are yenerally used to Improve fl1tratlon performance. Polymers are used In multl-medla filters as ｦｾｬｴｲ｡ｩｯｮ aids to counteract the higher sheer forces and depth of penetration caused by the higher appl1 cat Ion rates 1n dua lor trl-media filters. Polymers are not generally effective as filter aids for rapid sand filters. Cleasby et aI, have noted that since Giardia cysts are relatively large (8 to 14 11m long, 7 to 10 11m wide), properly operated and maintained deep-bed granular media filters should remove them efficiently, when used In a conventional water treatment system. 10,11 llboratory and Pilot Pllnt Studtes-Logsdon et aI, have conducted pilot studies showing that removal of Giardia cysts by sedlllM!ntation varied fran 65 to 93 percent and generally was simi Jar to turbidity removal. 12 The authors also concluded that coarse anthracite medi a was less efficient at removing Giardia than granular activated carbon (GAe), sand, or dual-media, at similar bed depths. Conventional treatment with any of the three media, however, provided better .than 99.9 percent removal of Giardia with optimum chemical dosages, as shown In Table III-3. In his review of fl1tration studies, Lin concluded that granular media fl1tratlon processes wi th pretreatment are capable of removing more than 99 percent of influent cysts. 13 He also noted that proper ｣ｯ｡ｾｵｬ｡ｴ ｯｮ Is a necessary key to effective filtration. A p11 ot study was undertaken by the Unl vers i ty of Washl ngton to eva 1uate the removal of Giardia lamblia cysts and cyst-sized particles (7 to 12 11m) by drinkIng water plants. 5 The first phase of the study was devoted to a laboratory-scale evaluation of Giardia removal efficiency by coagulation, flocculation, and mlxedmedia f11tratlon. The third phase Involved on-site testing at Leavenworth and Hoqu1., Washington, with a 20 gpm pilot plant employing coagulation, flocculation, settling, and filtration. Granular media ·f11 tratl on tests yl el ded greater than 99.9 percent remova 1 of spiked cysts under optimum conditions. Both the p110t unit and the field unit established the Importance of a m1 nlmum alum dosage (10 mg/L), an optimum pH range, and i ntermedhte flow rates of 2 to 4 gpm/ft 2 • Eftl uent turbi dl ty and cyst-s 1zed part leI es pass i ng the fl1 ter I ncreased rapid ly when the above condit10ns were not attained or when sudden changes occurred in plant operation.

TABLE 111-3. REMOVAL OF G. HURlS CYSTS DURING TEST SERIES 3· Chlrlcterlstlcs of Filter

Turbidity, ntu Rite

Heldloss Medh GAC GAC GAC Sind Sind Anthracite Anthracite Anthrlctte Dull Mdll

Condition Ripened Ripening Ifter wish Blckwlshed. ripened Ripening Ifter Wish Bickwished. ripened Ripened Rlpenln9 Ifter Wish Bickwished. ripened Ripened

ft

•

4.6-5.2 0.3 0.6-1.4 1.3 1.8-5.6 3.4-4.0 0.2 0.3-0.5 2.0-2.8

1.40-1.58 0.09 0.18-0.43 0.40 0.55-1.71 1.04-1.22 0.06 0.09·0.15 0.61-0.85

.pH settled water - 7.2-7.4; alu. doslge - 24.8 ［ｌＯｾ tCysts dosed to raw wlter continuously; concentration Source: Reference 12

gptlll

ｲｾｬｯｰ

59 ft

_Is

Rlw Miter

2.42 3.04 3.04 2.ft6 2.86 2.92 2.90 2.90 2.90

1.64 2.06 2.06 1.94 1.94 1.98 1.97 1.97 1.97

8.0-9.5 7.7 7.5-8.5 8.1 7.5-8.5 8.0-9.5 7.7 7.5-8.5 7.5-9.5

doslge - 0.095 ｣Ｎｬ ｵ Ｎｴｾ

ＮｌＯｾ

Filtered Mater 0.06-0.08 0.17-0.08 0.06-n.M 0.14-0.13 0.07-0.09 0.10-0.14 0.35-0.13 0.10-0.16 0.06-0.09

Cysts/L FI1tered Appltedt Miter 31 000 31 000 31 000 31 000

31 000 31 000 31 000 31 000 31 000

17 42 13 8.3 5.2 19 35 11

12

Cyst Re-oval Percent 99.94 99.• 86 99.958 99.973 99.983 99.94 99.89 99.96 99.96

"T1 r+

.... Q>

r+

0" ::::l ::::l

b' 3 3 c

::::l

;::+"

-
loo.Ot 6O.0t

--

ＰＮＴｾ

13.0 2.7 1.2 3.3

*Reference 32 tAveraged Values for Day

leI.....11

Effluent

1.8 2.8 9.6 1.5 2.0 2.4 8.5 5.4 0.3 1.2 0.8 0.3 0.3 0.5 0.5 1.2 0.3 1.2 1.0 0.5

'1 ant " Raw

--39.0 40.0 27.0 6.0 3.8 73.0 3.6t 3.8 6.0 70.Ot 25.0t >loo.0t >loo.Ot 8.5t 4.3 4.0t 9.6t 19.1 64.0 8.2

elel Effl

0.2 3.8 2.6 2.4 1.2 0.1 11.0 0.1 0.3 0.5 16.0 3.4 55.0 31.0 2.2 0.4 1.0 1.9 1.1 6.9 1.0

11 t

Pllnt P I: Iel.....11 Illw £ffluent 12.0 4.4

--3.5

2.0 1.2 15.6 3.1 17.2

0.8 2.4 7.0 1.5 0.1 0.5 9.7 2.2 1.9 "TI ｾ

....

...o' Q)

:::J :::J

ｾ

3 3

c

:::J ;:::t" 0
150

cysts

§.. muri s

30-630

cysts

Source:

Reference 2

7.2-18.5

1.8-2.0

CONCENTRATION-CONTACT TIME OF DISINFECTANTS FOR 99 PERCENT Concentration Contact Disinfectant T, .In Mlcroor9anlsms C, I19/L 0.065 0.33 Ozone (1\) L.. Co111 D.0023 1.03 Chlorine Dioxide 0.75 0.50 0.30 0.75 Ｈｃｬｾ ) TABLE IV-2.

Hypochlorous Acid (HDel)

0.1

0.4

0.04

6.0

5

Hypochlorite Ion (OC1-)

1.0

0.92

0.92

10.0

5

Dlchlora.lne (NHC1 2 )

1.0

5.5

5.5

4.5

15

Monochlora.lne

1.0

9.0

5

Ozone (03 )

0.3 0.245

0.13 0.50

0.04 0.12

7.2 7.0

5 24

3°

Chlorine Dioxide (C1Clz )

O.B 0.5

6.8 2.0

5.4 1.0

7.0 7.0

5 25

...0"

Hypoch1orous Acid (HOC1)

0.5

2.1

1.05

6.0

5

ＨｾｃｬＩ

Pollovl rus1

INACTIVATION OF MICROORGANISMS Tl!IIlperature CoT pH °C 0.022 7.2 1 0.002 7.0 12 0.38 5 6.5 0.23 10 6.5

175

175

0

C;;"

....

I1l 0

::J ::J

(")

0

Hypochlorite Ion (OC1-) Dlchlora.lne (NHC1 2 ) Monochloraliine (NHzCl) Giardia lalllbl1a2

Free Chlorine

0.5

21

10.5

10.0

5

3 3

;::to

c:

100

140

14,000

4.5

5

10

90

900

9.0

15

::J

-< en -< ｾ

I1l

3

en

2.5 2.5 2.5

30

47 57

75 118 142

6 7 8

5 5 5

.0 .-

...

TABLE IV-2 (Continued)

0

Disinfectant

HI croorganl SIlS

Concentration C, IIg/L

Contact T, .In

C·T

pH

I\J

Tellperature aC

-l ..... ｾ

Giardia lamblla3

Ozone (OJ)

Giardia IIUrl s3

Ozone

ＩｾＨ

0.15 0.082 0.034 0.48 0.20 0.11

0.97 1.9 5.5 0.95 3.2 5.0

0.15 0.16 0.19 0.46 0.64 0.55

7 7 7 7 7 7

25 25 25 5 5 5

0.18 0.10 0.08 0.70 0.40 0.31

1.3 2.2 3.4 2.5 5.0 6.4

0.24 0.22 0.27 1.8 2.0 2.0

7 7 7 7 7 7

25 25 25 5 5 5

0.03- 0.15 0.11- 0.48

5.5-1.06 5.0-0.94

1.5 - 2.4 1.4 - 2.9 1.0 - 1.9.

236-276 122-227 75-241

496 354 184

5.0 -16.6 3.2' - 9.0

50-182 58-132

848 466

...3 ... III ｾ

:l

....

0

ｾ

o' ..... 0 Q:

-

III

ｾ

... :l

III

ｾＮ

:l

III

... :l

Glardl a lamb11 a't

Ozone

Giardia IlUrlsS

ＩｾＨ

Chi ora.l ne

0.17 0.53

7 7

25 5

7 7 7

3 10

7 8

15 15

I/>

:l

"'0 0

... ｾ

III

ｾ

18

........:E III

Giardia IlUrls(,

ChloraMine

1lI

en c:

"0

1 Reference 2 Reference 3 Reference .. Reference 5 Reference (, Reference

ｾ

3

4 5 6 7. Chloramlnes not preformed. 78. Prefonned chiorallines.

=

-

(ii' I/>

-

Disinfection in Community Systems

103

The use of C·T values to interpret disinfection data has become more prevalent in the 1980's. The 99 percent inactivation level has been used for calculating C·T values in most studies. probably because it is the level at which exponential kinetics (N/N • followed, and if for other levels often observed,

K·T) are usually best approximated. If exponential kinetics were C·T values for 99 percent inactivation were known, C·T values of inactivation could easily be calculated. The ideal is not though, and great care must be· used in any attempts at

extrapolation. The following paragraphs describe the methods and performance of each of the Most Applicable Technologies individually. Chlorination General-The practice of chI ori nation has been used to control the outbreak of di sease since its first continuous application to a New Jersey municipal water supply in 1908. For purposes of disinfection of municipal supplies, chlorine is applied primarily in two forms: as a gaseous element, or as a solid or liquid chlorinecontaining hypochlorite cOlllPound. Gaseous chlorine 15 generally considered the least costly form of chlorine that carr be used in large facilities. Chlorine is shipped in cylinders, tank cars, tank trucks, and barges as a liquified gas under pressure. Chlorine confined in a container may exist as a gas, as a liquid, or as a mixture of both. Thus, any consideration of liquid chlorine includes consideration of gaseous chlorine. Hypochlorite forms (principally calcium or sodium) have been used primarily in small systems (less than 5,000 persons) or in large systems where safety concerns related to handling the gaseous form outweigh economic concerns. Present day corrmercial, high-test calcium hypochlorite products contain at least 70 percent available chlorine and are usually shipped in tablet or granular forms. Sodium hypochlorite is provided in solution form, containing 12 percent or 15 percent available chlorine. When chlorine (Cl 2 ) is dissolved in water, it reacts to form hypochlorous and hydrochloric acids:

104

Treatment of Microbial Contaminants in Potable Water Supplies

This reaction Is essentially complete within a few seconds. The hypochlorous acid Ionizes or dissociates practically Instantaneously into hydrogen and hypochlorite ions: HOC1 : H+ + OCl These reactions represent the basis for use of chlorine In most sanitary app 11 catIons. HOCl and oCl- have considerably different capabilities for destruction of microorgani SInS, and therefore, It 15 Important to know that the two forms exi st in equal percentages (50-50) at about pH 7.5, that the percentage of HOCl Increases nonlinearly (and OCl- decreases) as pH decreases, and that the reverse Is true as pH Increases. Hypochlorite chlorine forms also lonhe In water and yield hypochlorite ions which establishes equilibrium with hydrogen Ions: Ca(OC112 +. 2H2o : 2HOCl + Ca(oH)2 MaOCl

+ ｾｯ

: HOCl

+

MaoH

Only recently has a negative aspect been rea11 zed regardi ng chl ori nation: under some conditions, chlorine reacts with certain organic substances present in some water supply sources to produce tri hal omethanes (TIt4) and other by-products, which may hive carcinogenic effects following continuous exposure over long periods of time. Exposure to these by-products hiS al ready been reduced to a great extent by changes in chlorination practice. These changes include the use of different points of application, the use of lower dosages, the use of chlorine In combination with other oxidants, and removal of precursor organics. In treating waters with high TIt4 production potential where precursor removal Is difficult or expensive, and where other chlorine disinfection by-products become of concern, the use of altemate disinfectants may replace or supplement chlorine In many instances.

Disinfection in Community Systems

105

Perfol'lllnce-There are wide differences in the susceptibllity of various pathogens to chlorine. The general order, from most susceptible to least susceptible, is (1) bacteria, (2) virus, (3) cysts, and (4) bacterial endospores. The destruction of pathogens by chlorination is dependent on a number of factors, including water temperature, pH, contact time, degree of mixing, turbidity, presence of interfering substances, and concentration of chlorine available. Both pH and temperature have a marked effect on the rate of vi rus Id 11 by chI ori ne. For example, several studies show that decreasing the pH from 7.0 to 6.0 reduced the requi red vi rus inactivation time by about 50 percent and that a rise in pH from 7.0 to 8.8 or 9.0 increased the inactivation period about six times. 9 An AWWA Comm1 ttee report i ng on vi rus in water concl uded that "i n the prechl ori nat ion of raw water, any enteric virus so far studied would be destroyed by a free chlorine res idua1 of about 1.0 ppm, provi ded this concentration coul d be mai ntai ned for about 30 minutes and that the virus was not embedded in particulate material-un In a later AWWA committee report it was recommended that these conditions be maintained at a pH of less than 8 to ensure adequate protection from viruses. 76 In general, disinfection by chlorination has been shown to be most efficient with relatively high values of chlorine residual, contact time, C·T prOducts, water temperature, and degree of mixing; combined with relatively low values ·for pH,. turbi dity, and the presence of i nterferi ng substances. As i ndi cated by the C· T product, it is possible to have excellent disinfection with low chlorine residuals, as long as long contact times are used and other factors are beneficial for disinfection. The converse is also true, i.e., high chlorine residuals with shorter contact times may also result in excellent disinfection, within practical ranges of residuals and contact times. The fo 11 owi ng paragraphs present recent data regardi ng disi nfect i on by chI ori ne from laboratory, pilot-plant, and full-scale water treatment plant sources. It is important to keep in mind the many differences between these three test. environments when reviewing the information provided. Contact time, for example, is a critical factor in chlorination efficiencY, and whlle laboratory conditions can sometimes approach theoretical contact times for plug-flow and complete-mixing conditions, plant-scale conditions in contact basins rarely do. Significant

106

Treatment of Microbial Contaminants in Potable Water Supplies

short-ei rcuiting often occurs, reducing contact time, sometimes by as IIIlch as 95 percent. 10 Iotlere uncertai nty exists regardi ng the effect of short-ci rcu i t i ng. tracer studies would be needed to establish real disinfectant contact times. Laboratory Research and Pilot-Plant Studies--Several relationships regarding susceptibility of pathogens to disinfection by chlorine, as well as the effects of varying pH are shown by laboratory data plotted in Figure IV-I. The bacteria ｾ coli and Shigella dysenteriae can be seen to require the lowest contact times and chlorine concentrations for destruction, followed by three viruses (polio, coxsackie Al, and hepatitis A). The ｡｢･ｯｭ｡ｴｮｾ histolytica cyst requires longer contact times and higher concentrations than the bacteria or vi ruses. The di fferences in susceptibility between species of the same type of organism are highlighted by the fact that the bacterium Bacillus anthracis (which forms a spore) . is shown to require greater contact times and concentrations than the vi rus and cysts in this figure. The increased effectiveness of disinfection at lower pH values can be seen by comparing contact time-concentration curves for coxsacki evi rus A2, ｾ histolytica, and ｾ anthracis.

ｾ

coli,

The resistance of 20 different enteric vi ruses to free chlorine was studied by Liu et al. 12 These tests were all conducted under constant conditions of 0.5 mg/L free chlorine, a pH of 7.8, 2°C, using treated Potomac estuary water. As shown in Table IV-3, the least resistant virus was a reovirus requiring 2.7 minutes for a 99.99 percent (4 log) devitalization, and the most resistant was a poliovi rus requiring more than 60 minutes for the same level of devitalization. Correspondi ng C· T factors for these 20 vi ruses range from 1.4 to more than 30 under the constant conditions of this work. Vi rus survival tests have al so been reported by Payment on a vari ety of both laboratory strains and field strains.7 7 These tests were all conducted at a free chlorine residual of 0.4 mg/l, a pH of 7.0, and 5°C. Survival was analyzed at 10. 100, and 1,000 minutes of contact time. Test results (see Table IV-4) show that only two poliovi rus strains of the total of 20 test cultures had reached a 99.99 percent inactivation after 10 minutes (C·T • 4), six poliovirus strains had reached 99.99 percent inactivation after 100 minutes (C·T • 40), and 11 of the 12 polio viruses plus one Coxsackievirus strain (12 out of 20 strains) had reached 99.99 percent inactivation after 1,000 minutes (C.T • 400).

400

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Figure IV-l.

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ell

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10

o

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3

50

100

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o ｾ

II>

5!:

Processes include: Chl!lllcal feed (all_, pol11ll!r, and sodlUll hydroxIde); rapId .Ix and flocculatton; sedlllentatlon; gravIty ftltratlon usIng .bed lledla; backwashtng wIth washwater surge basIns; In-plant pUllplng, and sludge pu.plng and c1earwell storage. CategorIes 5 through 1 I nc1 ude 51 udge dewaterl ng lagoons and liquId sludge haultng. CategorIes 8 through 12 Include gravIty sludge thIckeners, ftlter presses for sludge dewaterIng, and dewatered sludge hauling to landftll disposal. A buIldIng for ad.lnlstratlon, laboratory, and .. tntenance purposes Is Included In all categorIes.

CIl

:E

II> ｾ

ｾ

.... g' CIl

"0 (j)"

'"

TABLE VI-6. ESTIMATED COSTS FOR SURFACE WATER TREATMENT BY CONVENTIONAL TREATMENT WITH AUTOMATIC BACKWASHING FILTERS

g

5 6 7 8 9 10

2.50 5.85 11.59 22.86 39.68 109.90

Average Flow, .gd

1.30 3.25 6.75 11.50 20.00 55.50

Capftal Cost,

$1,000 2,279 3,677 6,792 14,238 20,213 47,920

Operatfon and Mafntenance Cost 4/1,000 gal $I,OOO/yr

149 259 453 745 1,235 2,778

31.5 21.9 18.4 17 .7 16.9 13.7

./1,000 gal 87.9 58.3 50.8 57.6 49.4 41.5

Processes for all categories fnclude chetJllcal feed (alull and polymer); rapfd IIfx and flocculatfon; rectangular clarifiers; contfnuous automatic backwashfng filters, In-plant pullpfng and sludge pumpfng and below-grade c1earwell storage basin. Categories 5 and 6 fnclude sodfUlI hydroxfde feed and slUdge dewatering lagoons. Category 7 Includes ｬ ｦ ｾ feed Instead of HaOH, plus liquid slUdge hauling. Categorl es 8 through 10 I ncl ude gravity sl udge thl ckeners, f11 ter presses for sl udge dewaterl ng, and dewatered slUdge hauling to landfill disposal. A separate building for administration, laboratory, and maintenance purposes Is Included In all categories. ｾ

bl o

'"or

'"..... -..J

.....

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(Xl

...-i 3 CD D>

3 4

5 6 7 8 9 10

CD

TABLE VI-7. ESTIMATED COSTS FOR SURFACE WATER TREATMENT BY DIRECT FILTRATION USING PRESSURE FILTERS

...o

Plant Capacity, d

Average Flow,

o·

0.17 0.50 2.50 5.85 11.59 22.86 39.68 109.90

0.13 0.40 1.30 3.25 6.75 11.50 20.00 55.50

Capital Cost, S1 ODO 896 1,187 2.080 3.118 5,084 11.386 15,684 34,235

::I

...... ｾ

eratlon and Helntenance Cost a r 47.9 60.8 131 213 369 586 853 1;851

100.9 41.7 27.6 17.9 15.0 14.0 11.7 8.4

(3

/1 ODD Qal

0-

322.7 137.2 79.1 48.8 39.2 45.8 36.9 28.2

...ｾ

Processes tnclude chemical feed (aluli. polyMer, and sodiuM hydroxide); horizontal pressure filters; Mixed media; backwashing and surface ｾ｡ｳｨ facilities; ｾ｡ｳｨｷ｡ｴ･ｲ surge basins; below-grade Ｌｬ･ｾ｡｣ and sludge ｰｵｾＱｮｧＮ Categories 3 through 7 include sludge dewatering lagoons with sludge hauling. Categories 8 through 10 include gravity sludge thickeners, filter presses. and dewatered sludge hauling to landfill disposal. Storage Is used to cOllpensate for the ｬｯｾ･ｲ plant capacities In Categories 3 and 4, compared to Table VI-2. The cost of the additional storage is included above. A separate building is Included In Categories 5-10 for ｡､ｾｩｮｬｳｴｲｯＬ laboratory, and Maintenance purposes. .

j;;.

::I D>

3 3· D>

... ::I

en

3· "'tl

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D> CD

......:E D>

CD

ｾ

"tl

'!!.

m·

en

TABLE VI-B. ESTIMATED· COSTS FOR SURFACE WATER TREATMENT BY DIRECT FILTRATION USING GRAVITY FILTERS PRECEDED BY FLOCCULATION

4 5 6 7 8 9 10 11 12

0.50 2.50 5.B5 11.59 22.86 39.68 109.90 404 1.275

Average Flow, "'9 d

Capital Cost, $1.000

Sl.ooolvr

Vl.OOO Qat

V1.000 Qal

0.40 1.30 3.25 6.75 11.50 20.00 55.50 205 650

1,266 2.440 3.B55 6.190 12.244 16.142 31.105 89.368 242.751

70.6 143 240 425 680 1.014 2.289 7.151 22.010

4B.4 30.1 20.2 17 .2 16.2 13.? 10.6 9.6 9.3

150.2 90.5 58.4 46.8 50.5 39.8 28.6 23.6 21.3

Processes Include chemical feed (aluM. polymer. and sodium hydroxide); l-.inute rapid mix basin; mechanical flocculation with 30-lIlnute detention. gravity mixed media filters. backwash and surface wash facilities; washwater surge basin; in-plant pumping and sludge pumping. and below-grade c1earwell storage basins. Sludge dewatering lagoons and sludge hauling are used In Categories 4 through 7. Categories 8 through 12 use gravity sludge thickeners. filter presses, and dewatered sludge hauling to landfill disposal. Storage is used to compensate for the lower plant capacity In Category 4, compared to Table VI-2. The cost of the additional storage Is included above. A separate building for administration. laboratory. and ･｣ｮ｡ ･ｴｮｉｾ Is included in plants In Categories 5 through 12. ｾ

ｾ

...o III

III

I\,) ｾ

co

I'.,) I'.,)

o ｾ

(0

....'"

TABLE VI-9. ESTIMATED COSTS FOR SURFACE WATER TREATMENT BY DIRECT FILTRATION USING GRAVITY FILTERS AND CONTACT BASINS

3

(0 ｾ

....

o -..

Capital Cost, 1,000 4 5 6 7 8 9 10 11 12

0.50 2.50 5.85 11.59 22.86 39.68 109.90 404 1,275

6.40 1.30 3.25 6.75 11.50 20.00 55.50 205 650

1,162 2,242 3,714 6,047 12,060 15,867 30,255 87,025 232,970

s:

Operation and Maintenance Cost $I,OOO/yr ./1,000 gal 55.1 121 212 378 597 875 1,922 5,835 17,897

37.7 25.4 17.9 15.4 14.2 12.0 8.8 7.8 7.6

('i' ..., o

4I 1,OOOoal

C"

ｾ

131.2 80.9 54.7 44.2 48.0 37.5 26.3 21.4 19.1

Processes Include chellical feed (al u_, polywler, and sodl UII hydroxl de); 3O-.1nute detention contact basin; gravity filters using mixed medlai backwash and surface wash facilities; wash water surge basin; In-plant pumpl ng and sl udge pumpklg; and be low-grade c1earwell storage bas In. categories 4 through 7 Include sludge dewatering lagoons and sludge hauling. Categories 8 through 12 Include gravity sludge th Ickeners, fllter presses for sl udge dewaterl ng, anddewatered sl udge haull ng to landfill d15posa 1. Storage 15 used to compensate for the lower plant capacHy for Category 4, compared to Table VI-2. The cost of additional storage 15 Included above. A separate building for administration, laboratory, and maintenance purposes Is Included for plants In Categories 5-12.

?]

... ｾ

III

2, ｾ

III

.... ｾ

'" :;' ."

S III

Q: (0

ｾ

:E (0 ...,

ｾ

en c:

Ｎｾ

TABlE VI-I0. ESTIMATED COSTS FOR SURFACE WATER TREATMENT BY DIRECT FILTRATION USING DIATOMACEOUS EARTH

1 2 3 4 5 6 7 8 9 10

0.026 0.068 0.166 0.50 2.50 5.85 11.59 22.86 39.68 109.90

Average Flow, d

Capttal Cost, $1,000

0.013 0.045 0.130 0.40 1.30 3.25 6.75 11.50 20.00 55.50

221 285 374 570 1,573 2,538 4,433 10,713 15,982 37,733

$I,OOO/yr 6.0 8.0 20.0 30.4 128 214 369 762 1,165 2,730

tIl,OOO gal

tll,OOO Qal

127.0 43.7 42.2 20.8 27.0 18.0 15.0 18.1 16.0 13.5

672.9 227.2 134.7 66.6 66.0 43.1 36.1 48.1 41.7 35.4

Processes include pressure dtatomaceous earth ftltratton untts, dtatomaceous earth feed equtpment; ftltered water storage clearwell; and sludge dewatertng lagoons. A separate admtnlstratton, lab, and matntenance butldlng ts Included In Categortes 5-10. Sludge pu;ps are tncluded tn the package facllittes used tn Categories 1-4, but separate sludge pumping stations are Included tn Categortes 5-10. Categories 8 through 10 tnclude sludge holding tanks, sludge dewatertng wtth filter presses and haul1ng of dewatered soltds to landfill disposal. Storage ts used to compensate for the lower plant capaclttes for Categortes 1-4, compared to Table Vl-2. The cost of additional storage ts Included above.

("')

oen

-+

o

ll>

or

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r-..l

...-l

...3 ... o

... ::l

U>

'S.

...'J ll>

Q: (l)

...:E

ll>

., g> (l)

'0

'2..

Cos ts-are base'd-on-'contact bas' n wi th 30·m1 nute detent ion time.

Ｎｾ

TABLE VI-27. ESTJrIATED COSTS FOR SUPPLEflENTlNG SURFACE WATER TREAHIENT BY ADDING RAPID MIX

Category 1 2 3 4 5 6 7 8 9 10 II 12

PI ant Capacity. mgd

Average Flow. mgd

Capi ta I Cost. Sl.OOO

0.026 0.068 0.166 0.50 2.50 5.85 11.59 22.86 39.68 109.90 404 1.275

0.013 0.045 0.133 0.40 1.30 3.25 6.75 11.50 20.00 55.50 205 650

13.2 17.5 22.5 30.9 47.7 63.7 88.2 139 218 587 2.100 6,670

eration and 11alntenance Cost 1,000/yr Vl.000 gal 2.8 2.9 7.0 7.9 13.3 22.4 38.2 69.2 116 313 1.130 3,540

58.6 17.6 14.7 5.4 2.8 1.9 1.6 1.6 1.6 1.5 1.5 1.5

Tota I Cost, ill,OOO gal 91.3 30. 1 20.3 7.9 4.0 ＲＮｾ

2.0 2.0 I.g I.g 1.8 1.8 (')

0

....en 0 ....

Ql Ql

I')

.:>....

I') ｾ I')

ｾ

CIl ll>

3 CIl

::::l ....

o...... §; n .... o

TABLE VI-2B. ESTltlATEO COSTS FOR SUPPlE/1ENTlNG SURFACE WATER TREATHENT BY AOOIlIG FLOCCULATION

e-

Category 1 2 3 4 5 6 7 8 9 10 II

12

Plant Capaci ty. mgd

Average Flow. mgd

0.026 0.068 0.166 0.50 2.50 5.85 11.59 22.86 39.68 109.90 404 1.275

0.013 0.045 0.133 0.40 1.30 3.25 6.75 11.50 20.00 55.50 205 650

Capita 1 Cost, $1.000 10 18 34 73

217 325 418 537 840 1.830 6,060 19.200

eration and Haintenance Cost I,OOO/yr 411,000 gal 1.0 1.1 2.3 2.7 3.8 5.6 8.7 14.5 22.9 53.9 182 569

21.7 6.9 4.9 1.8 0.8 0.5 0.4 0.4 0.3 0.3 0.2 0.2

Tota 1 Cost. V 1.000 gal 45.2 20.1 13.3 7.7 6.2 ｾ 7 2.3 2.0 1.7 1.3 1.2 1.2

n;'

ｾ

::::l .... ll>

3

5" ll>

::::l .... en ::::l

....ｾ ll>

!2: CIl

:E ll>

....CIl ....

(/)

c:

"C

"!2.

i"

TABLE VI-29. ESTIMATED COSTS FOR SUPPLEMENTING SURFACE WATER TREATMENT BY ADDING RECTANGULAR CLARIFIERS

Cate90ry I 2 3 4 5

6 7 8 9 10 11

12

PI ant Capacity, m9d

Average Flow. m9d

Capi ta I Cost. Sl.OOO

0.026 0.06B 0.166 0.50 2.50 5.85 11.59 22.86 39.68 109.90 404 1.275

0.013 0.045 0.133 0.40 I. 30 3.25 6.75 11.50 20.00 55.50 205 650

2B 46 102 174 435 960 1.930 3.110 5.220 14.300 51,000 162.000

Ope,ation and Maintenance Cost ｾｄＬｉ

1.2 1.4 5.3 6.3 9.2 19.9 37.0 56.8 102 244 858 2,720

ｾＰ ＮｬＯＮ

25.9 8.7 11.2 4.3 2.0 1.7 1.5 1.4 1.4 1.2 1.2 1.2

Tota I Cost. 411,OOO.2l 95.5 41.7 36.4 18.3 12.7 11.2 10.7 10.1 9.8 9.5 9.2 9.2

...ｾ ...0 en

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W

f'.)

t :;l

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Q)

TABLE VI-30.

CD

ESTII1ATED COSTS FOR ADDING ttYDRAUlIC SURFACE WAStt FACILITIES

::l

....

ｾ

Category I 2 3 4 5 6 7 8 9 10 II

12

Plant Capaci ty. ffigd 0.026 0.068 0.166 0.50 2.50 5.85 I I .59 22.86 39.68 109.90 404 1.275

Average Flow, ffigd 0.013 0.045 0.133 0.40 ). 30 3.25 6.75 11.50 20.00 55.50 205 650

Capita I Cost. $1.000 21.6 35.3 43.5 56.4 80.9 114 187 247 360 950 3.310 10.100

Operation and Haintenance Cost SJ .OOO/yr ./1.000 gal 0.6 0.6 1.2 1.4 2.1 3.2 4.8 7.7 II. 7 28.4 101 343

11.8 3.8 2.5 0.99 0.45 0.27 0.20 0.18 0.16 0.14 0.14 0.14

Total Cost. ./1.000 gal 80.1 29.0 13.3 5.5 2.4 1.4 1.1 0.9 0.7 0.7 0.7 0.6

..,n

o

2: ｾ

b'

... ::l

Q)

a.

::l Q)

... ::l

'"::l

"'tl

...o Q)

2: CD

.....,:E Q)

CD

g> "0

-:E.. CD

'"

TABLE VI-31. ESTIHATEO COSTS FOR ADDING FILTER-TO-WASTE FACILITIES

I

2 3 4 5 6 7 8 9 10 11

12 Hote:

0.03 0.07 0.17 0.50 2.50 5.85 11.59 22.86 39.68 109.90 404 1,275

Average Flow, mgd

Capital Cost,

n.ooo

SI.OOO/vr

il1.000 gal

VI.OOO gal

0.01 0.05 0.13 0.40 1.30 3.25 6.75 11.50 20.00 55.50 205 650

2.2 5.6 9.9 16.5 36.4 40.4 54.5 71.5 124 345 759 2,410

0

0 0 0 0 0 0 0 0 0 0 0 0

5.5 4.C 2.4 1.3

0

0 0 0 0 0 0 0 0 0 0

O.g

0.4 0.3 0.2 0.2 0.2 0.1 0.1

Assooes one backwash unit for Category 1, two for Categories 2-4, four for Categories 5-8, six for Category 9, 16 for Category 10, 56 for Category 11, and 118 for Category 12. Costs Include valves and controls, plus 10 ft of pipe and fittings.

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TABLE VI-32. ESTIMATED COSTS FOR FINISHED WATER PUMPING

....-l

...3 ...o CD I\> CD

Plant Capacl ty, Category mgd I 2 3 4 5 6 7 8 9 10 II 12

0.03 0.07 0.17 0.50 2.50 5.B5 11.59 22.86 39.68 109.90 404 1,275

Average Flow, mgd 0.01 0.05 0.13 0.40 I. 30 3.25 6.75 11.50 20.00 55.50 205 650

Capital Cost, $1,000* 22.6 24.6 27.0 33.6 243 457 792 1,215 1,615 5,055 18,150 56,340

ｏｰ･ｲ｡ｴｬｯｮ｟ｾ､

ｍ｡ｬｾｴ･ｮ ｣

SI,OOO/yr 0.7 1.0 2.9 6.3 5B.5 135 272 459 792 2,184 8,048 25,508

Cost ./1,000 gal 14.3 6.1 6.0 4.3 12.3 11.4 II.I 10.9 10.9 10.8 10.8 10.8

::J

Tota I Cost, ./1,000 ga I 70.3 23.7 12.7 7.0 IB.4 16.0 14.9 14.3 13.9 13.7 13.7 13.7

-

ｾ o

o ....

0-

ｾ

Q

... ::J

I\>

3 :i' I\>

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::J "'C

...o I\>

2: CD

.......:E I\> CD

*Assumes'faCtorOfl-:"48tilnes construction cost for sitework, contractors overhead and profit, en9ineerlng, legal and ･ｶｩｴ｡ｲ ｳｩｮ ｾ､｡ costs, and interest during construction. Note: Categories 1 through 4 assume use of package high service pump station (maximum output pressure: 70 psi). Categories 5 through 12 assume use of custom-built finished water pumping station ｯｰ･ｲｾｴｩｮＹ at 300 ft TOH. Costs for other head conditions are included in Appendix E.

en c:

"0

"2CD

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TABLE VI-33.

Category

Plant Capacity. mgd

ｅｓｔｉＧｾｔｅｄ COSTS FOR IHPROVING SURFACE WATER TREATMENT BY ADDING FILTER EFFLUENT TURBIDIfIETERS

Average Flow. mgd

Capital Cost, Sl.DOO

4

0.50

0.40

27.0

5

2.50

1. 30

45.0

6

5.85

3.25

45.0

7

11.59

6.75

81.0

B

22.86

11.50

B1.0

9

39.68

20.00

8l.0

10

109.90

55.50

135

11

404

205

225

12

1,275

650

405

Operation and '·Iaintenance Cost $l.OOO/yr 4/1.000 gal

o o a o o o o o o

Total Cost, Vl.000 gal 2.2 1.1 0.4 0.4 0.2 0.1 0.08 0.04 0.02

Costs Include turbldllneters, samplin9 pumps, piping, and instrumentation. One system assumed installation in clearwell. plus on the effluent lines of two filters in Category 4, four filters in Categories 5 and 6. eight fi lters in Categories 7 through 9. 14 fi Hers in Category la, 24 filters in Category 11. and 44 filters in Category 12. A single complete system would have a capital cost of approximately $g.OOO.

()

o ｾ

...o III III

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248

Treatment of Microbial Contaminants in Potable Water Supplies

TABLE VI-34. ESTIMATED COSTS FOR COAGULANT CONTROL SYSTEM Cost Category

Cost, $

Manufactured equipment* Electrical and instrumentation Installation

$ 9,000 1,000

ｾ

$12,500

Subtotal

ｾ

Miscellaneous and Contingency

$14,400

Construction Cost Engi neeri ng. 1ｾｧ｡ admi ni strat i ve

4,600

1, fi nanci a 1 ,

S19,OOO

TOTAL CAPITAL COST

*Includes coagulant control system, 2-pen recorder, and flow controller. Assumes metering pump already in place. Normal maintenance should average less than $100 per year for entire system.

VI-33 presents costs for filter effluent turbidimeters, while Table VI-34 tabulates the installation cost of a single coagulant control system. This system can be used to monitor the effectiveness of flocculant/coagulant dosages; thereby enabling

plant

operators

to

adjust

chemical

dosage

rates

to

obtain

optimum

performance. Alternatives to Treatment In some cases, it may be more cost-effective for a small water system to choose an alternative course of action. rather than constructing a treatment system. Two examples of such alternatives are either to construct a new well or to

ｰｵｲ｣ｨ｡ｳｾ

and install bottled water vending machines. Costs for designing, constructing, and

operating a well

350 feet deep are presented

in Table VI-35.

Costs

for

implementing use of enough bottled water vending machines to supply the design flow for Categories 1 and 2 are presented in Table VI-36. Assumptions used in estimating costs of these alternatives are those presented on previous pages, including

the

requi rements.

general

basis

of

costs

and

conceptual

design

and

operating

COST SUMMARY A comparison of the total costs of all treatment processes listed in this section is provided in Table VI-37. Values in the table are taken from the last column of the cost table of each treatment process and process group. and are expressed in units of cents per 1,000 gallons.

1'0)

U1

o

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3

CD

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TABLE VI-35.

ESTIMATEO COSTS FOR CONSTRUCTING A NEW WELL

..... ｾ

.. o n

Plant Capacity. Category A1gd I 2 3 4

0.07 0.15 0.34 0.84

Average Flow. mgd 0.01 0.05 0.13 0.40

Capital Cost. Sl.OOO 56 75 115 205

Operation and Maintenance Cost ｲｹＯｏ ＬＱｾ tll,OOO gal 7.8 10.5 15.4 27.0

164.4 63.9 31.7 18.5

Total Cost. 41l.000.9!!. 303.0 117.5 59.5 35.0

C"

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g> ::J

or

Ｎｾ

::J

'"::J lit ::J ""Cl

... o

Costs are for a well 350 feet deep, and Include engineering costs.

'"ｾ

CD

.....'"ｾ CD

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en

TABLE VI-36.

Category

Plant Capacity, mgd

ESTIMATED COSTS FOR PURCHASING AND USING BOTTLED WATER VENDING MACHINES

Average

Flow,

Capita I Cost,

IAgd

$1,000

Operation and Maintenance Cost $I,OOO/yr Vl p OOD gal

Tota I Cost. ill.OOO gal

1

0.07

0.01

215

12.5

263.4

795.5

2

0.\5

0.05

447

26.0

158.3

47B.\

...b' o ... Ul

Ql Ql

'" 01 ｾ

i'.l 01 i'.l

］ｾ ＢＮ］ Ｍｾ

Ｍｾ ｾ］

__________

_

.fAIlLE VI'l'. _SUIt1ARY OF TOTAL COSTS_

.... - ..

--- --

,'.'

----------

Toul Cost of Treallleni •• /1.000 Gallon.

::J

ＱＭ ＭＲ Ｍｬ Ｍ ｃ ＭＵ Ｍ ｩＡｾ ＱＮＭ Ｘ Ｍ ＹＭ ｦｏＭ Ｍｦ

Treot"",nl Processes .

"-- -"1"i

if.Ott>- - -0:-06"8' -O_T66--0:5"0-t:50--5:8S- -n:-5r Ｍ ｩＲＺＸＶＭ ｪＢＹＺＰＸＭ ｦｾＧＭＹｾＴＭｬＬｭ ｾ

0.045 _ 0.1))

0.40

1.30

｟ｾ

6.15 __ ｟ＮｾＺ Ａ

20.00

ｾ(l) ..... '"3 (l)

｟ｾ

__

ｾ

ｾ

.....

o ..... ｾ

..,

()

f ill rot 1002

o

COMIplete IreatllOnl package plAnl. Convenllonal c",aplele Ireal.. nl Conventional treatllent with aulOlllat Ic backwashtn9 fillers Direct ftllratlon using pre.. ure filters Di rect fill ratl on us t ng grav1ly filter. preceded by flocculAtion Direci filtration u.lng grav1ly ftller. and eonuet buln. Direct filtration using dlaloIDaceous e.rth Slow-.and fillration Package ultrafiltration planlS

944.5

2/1.4

195.1

322.1

113.6

2:

12.8 104.1 81.9

52.4 10.3 58.3

58.6 50.8

61.9 51.6

53.8 49.4

39.3 41.5

131.2

19.1

48.8

39.2

45.8

36.9

28.2

150.2

90.5

58.4

46.8

50.5

39.8

28.6

23.6

21.3

'"2. ::J

21.4

19.1

'"ｾ

131.2

80.9

54.1

44.2

48.0

31.5

26.3

612.9

221.2

134.1

66.6

43.1

43.1

36.1

48.1

41.1

35.4

311.8 455.6

205.1 226.8

Ill.4 119.2

54.1 138.4

J4.3

28.1

25.3

32.0

31.0

!!!..

bl ::J .....

'"::J

-c

o .....

'"Q:

I.

2.

Cate90ry cate90ry I. 25 2. 101 3. SOl -

value., frOlll lop 10 bollOl1l, ue numH, design flow (Ilgdl, and average flow (_gdl. Population range. fe- e"h are: 3,300 100 4. 1.001 I. Z5.001 50,000 10. 100;001 - 500,000 500 5. 3,301 10,000 8. 50,001 15,000 II. 500,001 - 1,000.000 1,000 6. 10,001 25,000 9. 15,001 tOO,ODO 12. >1.000,000

Each proce .. group include. ch"",tcal addition and Individual liquid and solid. «eluded are ra" "ater pIM'llling, finished water ｐＢ ＧＴ ｩｮｾＬ and disinfection.

•• _ _ .

0_. __ ._----_._ ••_._- • __ .•.

.

_

ｨ｡ｮ､ｬｩｮｾ

proce.. es required for operalion;

(l)

ｾ

:E

.., en c (l)

-c

"2ｾ

.

.

ｉａＸｬｅｾ｟ｾｬｴｮｵＮ､Ｉ

.

....

.

_

Tot.1 COSI of Tr.OI ...nt. 411.000 G.llons

--1---2------r-----.--- --r-Ir•• t ..nl ｬ Ｎ ｬＢｾＭ ｬｲＮ ｬ｢ ｦ ＭｬｲＮｔＶＢｏｬｉＮｳｯＭ ｲＮｳｯＭ Ｉｾ｡ｳＭ Pro,"ss.s ___________________________ 0.013 _ 0.045 0.1ll 0.40 1.30

--. i!l!f!!j9.°r1'- --8---'- --\0 ---- -W i2 - Ｍｉｔ［ｾｧ --22.86 39.68109".r - 40{"' '£,lIS .gL__ ｾＮＡＺ __ ｾ｟ｾｾ __ 205 . . ｾＵＰ

ｾｮｦＮ｣ｴｾ

Chlorln. f ••d f.clIIlI.s· Ozone gen.r.! Ion .nd f••ds Chlorln. dloxtde' Ch Ior.,.t n.tlonl Ultr •• tol.t light

65.9 109 322 163 43.2

23.6 31.2 8/.1 51.1 \4.\

16.2 21.5 46.\ 23.9 8.4

9.1 12.1 \6.8 14 .4 5.4

4.3 1.0 /.0 6.1

2.8 4.5 4.2 3.6

2.1 3.4 2.9_ 2.6

1.6 2.6 2.2 2.\

1.3 2.2 \./ 1.6

1.0 1.1 1.3 1.3

0.8 1.4 1.0 1.0

0.1 1.2 0.9 0.9

35.3 36.4 8/.1 30.2 21.0 0.5

11.0 11.4 26.2 10.1 g.g 0.3

8.2 8.4 16.5 8.4 1.6 0.3

2.9 3.0 /.5 4.1 4.3 0.3

2.9 3.0 I.g 2./ 1.0 0.3

1.2 1.4 1.1 1.9 0.6 0.3

0./ 0.8 0.9 1.6 0.4 0.3

0.5 0.6 0.8 1.6 0.3 0.3

0.3 0.4 0./ 1.5 0.3 0.3

0.2 0.3 0.6 1.4 0.2 0.3

0.2 0.2 0.6 1.4 0.2

0.1 0.2 0.5 1.4 0.2

9.4

5.5

3.3

2.\

2.0

1./

1.6

1.5

1.5

1.5

Suppl ....nt.1 Proc.S'.s Add poly... r f ••d. 0.3 _gil Add poly.. r f••d, 0.5 .gIL Add .1 ... f.ed, 10 _gil Add sodiu_ hydroxide feed Add sulfuric .cld fe.d C.pping r.pld-und f IIt.rs with .nthr.clt. co. I Con.erllng r.pld-s.nd fillers to _lxed-..dl. ftlt.rs 3.

Olslnf.cllon f.clllties Include .11 required generolton. slorog., '00 f.ed equlpwnt; contact bosln .nd deLenllon f.cllltle,

ore excluded. Design flows for C.tegorles 1-4 ore. respectively: 0.026.gd. 0.068 _gd. 0.166 IIIJd, .nd 0.50 _yd. 4.

Oose Is 5.0 .gIL; Includes hypochlorlle solution feed for C.tegories 1-3, chlorine feed .nd cylinder stor.ge for C.tegorles 410 ••nd chlorIne f.ed .nd on-site stor.ge for C.tegorles II .nd 12. 5. Oose Is 1.0 .gIL. 6. Oose Is 3.0 -gIL. /. Ooses .re chlorin• • t 3.0 IIgll .nd amlllOnl •• t 1.011glL. -_.__ . - --_. __ . -. ... _--------_. - - _. - .. _.- --- ---- --- --- -- -- ---

_

_._-

b' II> ｾ

o

Cll

S

ｾ

U1

W

ｾ TABLE VI-J1 _jContinued)

.

_

--l ....

rot.1 Cost of rre.taent. tll.llOO C.llons Treat.nt Proce§'Ses

ＱﾷＭ ｾ Ｍ ｔｾＭ ＭＢＵ Ｍ Ｍ ｩＡ ｾｦＡ ＮｪｧｯＮＡＱ ＧﾷＭｲ ﾷＭＹＢ Ｍ ﾷｬｏＭ

ｾｰｬ･Ｂ Ｌ｟ｮｴ｡ｬ

- 11

-12

.•(j---.:_8; - -n-:-5"r-"If.sr-19.«iM.9"- --464 -- I,m

ｬｲＮｏｬＮＭｾＮｵｲＭｔｉＢｏｾ

0.013

0.045

0.133

0.40

1.30

ＡＬｬｌＮ｟ｾＮ

11.50

20.00

55.5 __

ｾｄＲ

ｄｾＡ

...ｾ3 ...o

3 CD

::J ....

o ｾ

o .... o

0-

ｾ

b'

::J .... II>

Ｎｾ

::J

II>

....

0

::J

0

'"::J

134.1

1. 1 avg Hr./yr

12.9

11.6 Hr.O

23/1.3

1i.1I Hr.0

62.1

50.0 GPM

54.4

25.0 GPH

6.1

2.0 t'li/yr

.11,000

-l .... CD

""C

o ....

II>

52: CD

1.1 Hr./yr 25'1.0

-

:E

II> .... CD

.... en c:

112.6 56.5

"C

"2CD

5,035.2

'" 474.5

19.3

TABLE R-5. Continued

Process or Factor Sitework, Interface Piping Subsurface Consideration General Contractor's OHSP Engineering Legal, Fiscal, ａｾｬｮ ｳｴｲ｡ｴｬｙ･ Interest Ourlng Construction TOTAL CAPITAL cnST TOTAL, 4/1,000 GALLONS

Oeslgn Parameter

Construction cost, SI,OOO

Operating Parameter

O&H Cost, SI,OOO/yr

Unit Cost, 4/1,000 gallons

::l

Co

x· O:J

en

711;.4

..,t: a;-

23R.A 573.1 'l45.7

n

(II

.....,:E

55.A

ell

6119.2 11,254.2

l> -c -c (II

(II

39.3 58.6

.....,

1')

...o' III

::l ("')

o ｾ

Q

n

5-

...o' ell

::l