Basic Water Treatment Sixth edition

Contents Foreword to the sixth edition ix
Preface xi
About the authors xiii
1 Introduction and structure of the British and
Irish water industries 1
1.1 Introduction 1
1.2 Structure and regulation of the water industry
in the United Kingdom and Ireland 4
References 8
2 Quality of water 9
2.1 Origin and type of impurities 9
2.2 River and source quality 14
2.3 Potable-water standards 15
2.4 Key water quality parameters 20
2.5 Microbiological parameters 22
2.6 Concluding comments 24
References 24
3 Overview of water treatment 27
3.1 Introduction 27
3.2 Water safety plans 28
3.3 Conventional water treatment 34
3.4 Modern water treatment 35
3.5 Overview of processes and process selection 36
3.6 Typical process streams 36
3.7 Raw and treated water quality 38
3.8 Developing world treatment 40
3.9 Future treatment processes 42
3.10 Greenhouse gases (GHGs) 44
References 44
4 Preliminary treatment 45
4.1 Coarse intake screens 45
4.2 Raw water storage 45
4.3 Algae, algal control, and reservoirs 47
4.4 Fine screens 50
4.5 Pre-chlorination 55
4.6 Aeration 55
4.7 Algal treatment 57
4.8 Pre-settlement basins 58
References 59
5 Coagulation and flocculation 61
5.1 Introduction 61
5.2 Definitions – coagulation and flocculation 63
5.3 Types of destabilisation 63
5.4 Coagulation and flocculation – process
variables 64
5.5 Types of rapid mixers (for coagulation) 66
5.6 Types of rapid mixers 67
5.7 Types of flocculator 68
5.8 Jar testing 69
5.9 Enhanced coagulation 70
5.10 Coagulants and coagulant aids 70
5.11 Coagulation with iron and aluminium salts 71
5.12 Other coagulants 76
5.13 Which coagulant? 76
5.14 Other chemicals used in coagulation
and flocculation 77
5.15 Control of coagulation and flocculation 79
5.16 Chemical storage and dosing 80
5.17 The future of coagulation? 82
References 82
6 Clarification 85
6.1 Theory and principles of clarification 85
6.2 Clarifier selection and design considerations 97
References 120
7 Filtration 121
7.1 Introduction 121
7.2 Types of granular filter 121
7.3 Granular filtration theory 122
7.4 Practical aspects 124
7.5 Coagulation prior to filtration 124
7.6 Rapid sand filters 125
7.7 Modes of operation 135
7.8 Pressure filters 138
7.9 Slow sand filters 139
7.10 Other filters 143
References 145
8 Activated carbon adsorption 147
8.1 Introduction 147
8.2 Activated carbon 147
8.3 Design of activated carbon absorption
systems 151
8.4 Practical aspects of GAC adsorbers 154
8.5 Recent developments in adsorption 155
Reference 155
9 Membrane processes 157
9.1 Introduction 157
9.2 Reverse osmosis 159
9.3 Microfiltration and ultrafiltration 166
9.4 The future 167
References 168
10 Other processes 169
10.1 Introduction 169
10.2 Ozonation 169
10.3 Advanced oxidation processes (AOPs) 173
10.4 Ion exchange 174
10.5 Water softening 177
10.6 Removal of iron and manganese 182
10.7 Nitrate removal 184
10.8 Air stripping 185
10.9 Arsenic treatment 187
10.10 Final water conditioning 188
10.11 Desalination 190
References 191
11 Disinfection 193
11.1 Introduction 193
11.2 Disinfection during treatment 194
11.3 Theory of chemical disinfection 195
11.4 Chlorination 196
11.5 Required chemical disinfectant dose and
contact time 201
11.6 Ultraviolet disinfection 202
11.7 Ozonation 205
11.8 Other methods of disinfection 205
11.9 Sodium hypochlorite and OSEC systems 207
11.10 Chlorine contact tank 208
References 209
12 Waterworks wastes and sludge 211
12.1 Introduction 211
12.2 Expression of sludge quantities 212
12.3 Estimation of sludge quantities 213
12.4 Rules of thumb 215
12.5 Treatment options 216
12.6 Disposal 221
References 221
13 Private water supplies 223
13.1 Legal requirements in the UK 223
13.2 Treatment objectives 225
13.3 Risk assessment 225
13.4 The source 226
13.5 Treatment 226
13.6 Conclusions 231
References 231
14 The sizing of water treatment plants 233
14.1 Introduction 233
14.2 Water supply 233
14.3 Components of demand 235
14.4 Domestic demand and projection 235
14.5 Non-household use 236
14.6 Losses from water systems 237
14.7 Measurement of leakage 237
14.8 Demand management 237
14.9 Available water resources 238
14.10 Water resource planning 239
14.11 Sizing the deployable output of a water
treatment works 239
References 240
15 Reuse of water 243
15.1 Introduction 243
15.2 Planned reuse for potable supply 243
15.3 Direct reuse at Windhoek (Du Pisani, 2005) 244
15.4 Planned indirect potable reuse 245
15.5 Direct non-potable domestic reuse 248
References 248
Appendix 1 Sample calculations 249
Appendix 2 Comparison of drinking water quality
standards 257
Appendix 3 Glossary 261
Appendix 4 SI units and basic conversion factors 269
Index 271