This page intentionally left blank Drinking Water Quality
This textbook provides a comprehensive review of the problems associated with the supply of drinking water in the developed world. Since the first edition of this book was published there have been enormous changes in the water industry, especially in the way drinking water is perceived and regulated. Water companies and regulators have been presented with numerous new challenges – global warming has seriously affected the sustainability of water supplies as well as impacting water quality; advances in chemical and microbial analysis have revealed many new contaminants in water that were previously undetectable or unknown; and recent terrorist attacks have demonstrated how vulnerable water supplies could be to contamination or disruption. This new edition is an overview of the current and emerging problems, and what can be done to solve them. It has been completely updated, and includes the new WHO Revised Drinking Water Guidelines.
Drinking Water Quality is an ideal textbook for courses in environmental science, hydrology, environmental health, and environmental engineering. It also provides an authoritative reference for practitioners and professionals in the water supply industry.
N. F. GRAY is a Professor at the Centre for the Environment at Trinity College, Dublin. He has worked in the area of water technology for 30 years, and is internationally known as a lecturer and author in water quality and pollution control. His research specializes in the operational problems associated with supplying drinking water and treating wastewaters.
Drinking Water Quality Second Edition
N. F. Gray University of Dublin CAMBRIDGE UNIVERSITY PRESS Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore, São Paulo
Cambridge University Press The Edinburgh Building, Cambridge CB2 8RU, UK Published in the United States of America by Cambridge University Press, New York www.cambridge.org Information on this title: www.cambridge.org/9780521878258
© N. F. Gray 1994, 2008
This publication is in copyright. Subject to statutory exception and to the provision of relevant collective licensing agreements, no reproduction of any part may take place without the written permission of Cambridge University Press. First published in print format 2008
ISBN-13 978-0-511-39371-6 eBook (EBL)
ISBN-13 978-0-521-87825-8 hardback
ISBN-13 978-0-521-70253-9 paperback
Cambridge University Press has no responsibility for the persistence or accuracy of urls for external or third-party internet websites referred to in this publication, and does not guarantee that any content on such websites is, or will remain, accurate or appropriate. Contents
Preface page xiii Acknowledgements xvi
Part I Introduction to water supply
1 The water business 3 1.1 Introduction 3 1.2 Water consumption 3 1.3 Acceptable water quality 7 1.4 Water utilities 10 1.5 Water conservation 18 1.6 Conclusions 33 References 35
2 Drinking water standards and risk 37 2.1 Introduction 37 2.2 Development of quality standards 37 2.3 Risk assessment in the development of health-based targets 39 2.4 Water safety plans 42 2.5 Drinking water standards 52 2.6 Conclusions 63 References 64
3 A quick guide to drinking water problems 65 3.1 Introduction 65 3.2 The problems 66 3.3 Conclusions 72 References 73
Part II Problems with the resource
4 Sources of water 77 4.1 Introduction 77 4.2 The water cycle 77 4.3 Surface waters: lakes, reservoirs and rivers 80
v vi Contents
4.4 Groundwater sources 89 4.5 Other sources of water 99 4.6 Conclusions 112 References 114
5 Nitrate and nitrite 116 5.1 Sources in water 116 5.2 Water quality standards 119 5.3 Effect on consumers 120 5.4 Nitrate in groundwaters 123 5.5 Nitrate in surface waters 125 5.6 Control of high-nitrate water 126 5.7 Conclusions 132 References 134
6 Pesticides and organic micro-pollutants 137 6.1 Organic micro-pollutants 137 6.2 Pesticides 139 6.3 Industrial solvents 156 6.4 Polycyclic aromatic hydrocarbons 160 6.5 Removal of organic contaminants from drinking water 162 6.6 Conclusions 163 References 165
7 Endocrine-disrupting compounds and PPCPs 169 7.1 Introduction and definitions 169 7.2 Pharmaceutical and personal care products (PPCPs) 171 7.3 Oestrogen and fertility 174 7.4 Conclusions 177 References 179
8 Odour and taste 181 8.1 Introduction 181 8.2 Standards and assessment 181 8.3 Classification 183 8.4 Odour-causing substances of natural origin 185 8.5 Man-made odour-causing substances 188 8.6 Conclusions 188 References 189
9 Metals 191 9.1 Iron 191 9.2 Manganese 193 9.3 Arsenic 194 9.4 Other metals 196 9.5 Removal by treatment 198 Contents vii
9.6 Conclusions 199 References 200
10 Hardness and total dissolved solids 203 10.1 Introduction 203 10.2 Chemistry of hardness 203 10.3 Standards 205 10.4 Health aspects 206 10.5 Conclusions 207 References 208
11 Algae and algal toxins 210 11.1 Introduction 210 11.2 Problems associated with algae 210 11.3 Standards 213 11.4 Treatment 213 11.5 Conclusions 214 References 215
12 Radon and radioactivity 217 12.1 Introduction 217 12.2 Radon 218 12.3 Non-radon radionuclides 219 12.4 Standards and treatment 220 12.5 Conclusions 222 References 223
13 Pathogens 225 13.1 Introduction 225 13.2 Protozoa 225 13.3 Viruses 229 13.4 Bacteria 231 13.5 Unusual sources of contamination 235 13.6 Conclusions 237 References 239
Part III Problems arising from water treatment
14 Water treatment 245 14.1 Introduction 245 14.2 Unit processes 246 14.3 Process selection 260 14.4 How problems arise 261 14.5 Conclusions 267 References 268 viii Contents
15 Aluminium and acrylamide 270 15.1 Aluminium 270 15.2 Acrylamide 277 15.3 Conclusions 278 References 279
16 Odour and taste 282 16.1 Source of odour and taste problems 282 16.2 Removing odours and tastes 283 16.3 Conclusions 285 References 285
17 Fluoridation 286 17.1 Introduction 286 17.2 Fluoride addition 287 17.3 Fluoridation and health 289 17.4 Fluoridation and public opinion 291 17.5 Who is at risk 292 17.6 Conclusions 293 References 295
18 Disinfection by-products 297 18.1 Formation 297 18.2 Standards 300 18.3 Health risks 301 18.4 Prevention of by-product formation 302 18.5 Conclusions 303 References 304
19 Monitoring and removal of pathogens 307 19.1 Introduction 307 19.2 Monitoring pathogens 307 19.3 Measurement and standards 308 19.4 Heterotrophic plate counts 313 19.5 Removal of pathogens 314 19.6 Disinfection 316 19.7 Conclusions 317 References 320
Part IV Problems arising in the distribution network
20 The distribution network 325 20.1 Introduction 325 20.2 Service reservoirs 325 20.3 Water mains 327 Contents ix
20.4 Service pipes 328 20.5 Conclusions 332 References 333
21 Aesthetic quality 334 21.1 Odour and taste 334 21.2 Discolouration and iron 335 21.3 Sediment and turbidity 338 21.4 Conclusions 340 References 340
22 Asbestos 342 22.1 The nature of asbestos 342 22.2 Health effects and standards 344 22.3 Asbestos cement distribution pipes 345 22.4 Conclusions 346 References 348
23 Coal-tar linings and polycyclic aromatic hydrocarbons 350 23.1 Introduction 350 23.2 Conclusions 351 References 352
24 Animals on tap 353 24.1 Microbial slimes in distribution pipes 353 24.2 Water supplies 355 24.3 Common species and remedial measures 356 24.4 Sampling water mains for animals 361 24.5 Microbial pathogens and invertebrates 362 24.6 Conclusions 363 References 364
25 Pathogens in the distribution system 366 25.1 Introduction 366 25.2 Microbial contamination 366 25.3 Control 369 25.4 Drinking water security 370 25.5 Conclusions 370 References 371
Part V Problems in household plumbing systems
26 Household plumbing systems 375 26.1 Entry to the home 375 26.2 Plumbing systems 375 x Contents
26.3 Water Byelaws and regulations 380 26.4 Conclusions 381 References 381
27 Corrosion and metal contamination from pipework and fittings 382 27.1 Introduction 382 27.2 Corrosion 382 27.3 Lead 387 27.4 Copper 400 27.5 Zinc 403 27.6 Conclusions 403 References 404
28 Micro-organisms, fibres and taste 407 28.1 Micro-organisms in plumbing systems 407 28.2 Fibres, including asbestos 410 28.3 Odour and taste 411 28.4 Conclusions 412 References 413
Part VI The water we drink
29 Alternatives to tap water 417 29.1 Introduction 417 29.2 Bottled water 417 29.3 Point-of-use water treatment 428 29.4 Water harvesting 436 29.5 Conclusions 438 References 441
30 Water security in the twenty-first century 442 30.1 Introduction 442 30.2 Vulnerability assessment 444 30.3 Developing security plans 444 30.4 The emergency response plan 447 30.5 Conclusions 450 References 451
31 Final analysis 453 31.1 Introduction 453 31.2 Complaints 454 31.3 Public perception of drinking water quality 455 31.4 The quality of drinking water 457 Contents xi
31.5 Water usage and conservation 460 31.6 Water conflict 461 31.7 Drinking water in developing countries 461 31.8 Conclusions 465 References 468
Appendix 1 EC Drinking Water Directive (98/83/EEC) quality parameters 469 Appendix 2 US National Primary and Secondary Drinking Water Standards of the US Environmental Protection Agency (2006) 471 Appendix 3 World Health Organization drinking water guide values for chemicals of health significance. Health-related guide values have not been set for a number of chemicals that are not considered hazardous at concentrations normally found in drinking water, although some of these compounds may lead to consumer complaints on aesthetic grounds. These are listed in Table 2.6 488 Appendix 4 Major pesticides and their degradation (breakdown) products with their relative toxicity limits in drinking water. The toxicity is based on limits set originally by the Federal Health Authority in the former Federal Republic of Germany (Miller et al., 1990), where category A pesticides should not exceed 1 mgl 1, category B 3 mgl 1 and category C 10 mgl 1 492 Appendix 5 EC Water Framework Directive (2000/60/EC) Priority Substances 496 Appendix 6 List I and List II substances covered by the EC Dangerous Substances Directive (76/464/EEC) 498 Appendix 7 The USEPA second Drinking Water Contaminant Candidate List (CCL) published in February 2005 499 Glossary 501 Index 508
Preface to the second edition
Since writing the first edition there have been enormous changes in the water industry especially in the way drinking water quality is perceived and regulated. That first edition was written at the same time as the 1993 revision of the World Health Organization (WHO) guidelines as published, which has subsequently resulted in the revision of all the major drinking water standards, including those covering the European Union and the USA. That early edition reflected those changes. So the preparation of this new edition was timed to coincide with the publication, late in 2004, of the latest revision of the drinking water guidelines by the WHO, which has adopted a more rigorous health-based approach in setting guidelines. These new guidelines have been used as the basis of this new edition. The problems associated with global warming leading to regional changes in climate and water availability are seriously affecting sustainability of supplies as well as seriously impacting on quality. Advances in chemical and microbial analysis have revealed that water contains many new contaminants that were previously undetectable or unknown, constantly presenting water utilities and regulators with new challenges. Also the recent terrorist attacks have demonstrated how vulnerable water supplies are to contamination or disruption. Thus, while the existing risks remain and need to be dealt with on a day-to-day basis, these new problems require innovative technical and management solutions. The aim of this new edition is to give an overview of the current and emerging problems and what can be done to solve them. This new edition has been extensively updated and expanded using a different framework. It now comprises of 31 chapters clustered into 5 distinct parts, each dealing with a separate element of the water supply chain. Part I. Introduction to water supply comprises of three introductory chapters. The first deals with the fundamentals of the water industry: how much water is used; what is required by consumers in terms of quality; and the operation, management and regulation of the water utilities. The remainder of the chapter looks at the new management approaches to water supply, in particular water demand management, and how water conservation is becoming an integral part of sustaining future supplies. The second chapter reviews how drinking water standards are developed and the role of risk assessment in that process. Water safety plans are now the basis for achieving good quality and maintaining
xiii xiv Preface to the second edition
supplies and this is discussed in detail. The chapter also explores how guidelines and standards have changed over the past 15 years. Part I closes with a quick overview of the problems relating to drinking water quality, where those problems arise within the supply chain and where more information can be accessed within this text. Part II. Problems with the resource examines in depth the water quality problems that arise within water resources due to natural and man-made influences. Chapter 4 is a brief overview of how quality varies due to land use and natural geology, comparing surface and ground waters. The remaining chapters look at each group of potential contaminants in turn examining the source, effects on consumers and appropriate solutions. There are separate chapters dealing with nitrate and nitrite; organic micro-pollutants including pesticides, industrial solvents and polycyclic aromatic hydrocarbons; endocrine- disrupting (oestrogen-mimicking) compounds, pharmaceutical and personal care products; odour and taste; metals including iron, manganese, arsenic and other heavy metals; hardness; algae and algal toxins; radon and non-radon radionuclides; and pathogens. Part III. Problems arising from water treatment looks at how the very action of improving water quality can itself cause significant aesthetic and occasionally health-related problems. After a brief review of treatment technology and how problems arise, there are individual chapters dealing with the main issues: flocculants such as aluminium and acrylamide; odour and taste; the contentious issue of fluoridation; disinfection by-products including trihalomethanes; and pathogen removal. Part IV. Problems arising in the distribution network deals specifically with the transport of water from the treatment plant to the consumer, which can seriously affect water quality. The design and management of service reservoirs, the mains and the individual service pipe that connects individual households to the network are explained. Chapters dealing with aesthetic quality, asbestos, bitumen and coal-tar linings, the remarkable variety of animals, both large and small, that live in the network and occasionally pop out of the tap, and finally the problems of biofilm development and pathogens within the mains are all dealt with in detail. After all this the water is still very susceptible to contamination from our own household plumbing and storage system. Part V. Problems in household plumbing systems explains how household systems work and follows with specialist chapters on corrosion, including lead contamination, pathogens, such as Legionella and Mycobacter- ium, and other quality problems. Part VI. The water we drink deals with a number of consumer-related issues. The first chapter deals with alternatives to tap water and includes detailed sections on bottled water, point-of-use and point-of-entry treatment systems and other sources of water such as rainwater harvesting and water reuse. I said at the beginning that much has changed in the water industry in the developed world. What hasn’t changed is the number of people facing water scarcity in Preface to the second edition xv
developing countries, leading to poverty, starvation, serious illness and frequently death. After decades of dedicated and life-saving work by agencies such as WaterAid, the situation continues to worsen, driven by the dual problems of climate change and conflict. Water security in the twenty-first century looks at the problem of terrorism and ensuring water is protected more effectively from deliberate or accidental contamination or interruption. The final chapter gives an overview of drinking water quality and how climate change will affect it over the coming decades. Each chapter in the book concludes with a brief discussion of the relevance of the specific problems for consumers and suppliers alike. There are also a number of appendices giving drinking water standards in Europe, USA, as well as the new WHO guidelines and much else. In this text I have attempted to provide a cohesive and comprehensive introduction to the water supply industry and the supply chain, which I hope will be equally useful to engineers, scientists, managers and even the general consumers who wants to know more about the water they drink. The text has been designed to give you an integrated overview of drinking water quality and to act as a reference guide. It should be used in conjunction with the Internet where very detailed information can be accessed and for that reason key URLs have been given where appropriate in the text. The royalties from this text have been donated to WaterAid (www.wateraid. org.uk), which is an international non-governmental organization (NGO) dedicated to the provision of safe drinking water, sanitation and hygiene education to the world’s poorest communities. As you turn on your tap and safe clean water pours out, remember that this really is something very special and that it has given us the wonderful society in which we live today. If you can help WaterAid in giving this gift to others then thank you. Acknowledgements
I am very grateful to the very many people who have kindly provided me with information. I would especially like to thank any publishers or organizations who have given their permission to reproduce, or to modify, copyright material in this text.
xvi PART I INTRODUCTION TO WATER SUPPLY
Chapter 1 The water business
1.1 Introduction The water supply industry is vitally important not only to maintain the health of the community, but for the sustainability of industry, business and agriculture. Without adequate water supplies our present society would never have evolved, and our lives today would be unrecognizable. Our dependence on treated water is now incalculable, and threats to that supply are comparable to the worst natural and man-made disasters. The volumes of water consumed each day by agriculture, industry and the public are vast, requiring an enormous infrastructure to satisfy the demand. Like the other service providers, electricity, telephone and gas, the water utilities deliver their product to the home, which requires a network of distribution pipes to service each household, but unlike the other utilities these are stand alone local or regional networks, rather than integrated national supply networks. In England and Wales there are 26 private water companies that together supplied 52.7 million consumers in 2004/5 with 15 807 million litres (Ml d 1) of water each day. Sixty-eight per cent of this came from surface waters and the remainder (32%) from groundwater. It requires 1344 plants to treat this volume of water, which is supplied to consumers via 326 471 km of distribution mains. When this is broken down by region, the greatest demand is in the south-east and north-west regions, which have the largest populations. However, the areas of highest demand do not normally correspond to the areas where adequate water resources are to be found, so shortages occur. The current demand for potable water in England and Wales has stabilized and is currently at 91% of the peak demand recorded in 1990/1 (Table 1.1).
1.2 Water consumption Water demand varies significantly between countries due to differences in culture, climate and economic wealth (Smith and Ali, 2006). The demand for water also varies over the 24-hour period. This is known as the diurnal variation, with peak usage in the UK occurring between 07.00 and 12.00 and from
3 4 Table 1.1 Water supplied to the public distribution system 1990/1–2004/5. Adapted from Defra (2006) with permission from Defra