Biology of wastewater treatment

BIOLOGY OF
WASTEWATER TREATMENT
Imperial College Press
ICP
University of Dublin, Ireland
N. F. Gray
Second Edition
BIOLOGY OF
WASTEWATER TREATMENT
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Copyright © 2004 by Imperial College Press

BIOLOGY OF WASTEWATER TREATMENT (2nd Edition)
January 19, 2004 14:33 World Scientific Biology of Wastewater Treatmen t (New Edition) bwt
Acknowledgements
Acknowledgement is gratefully made to the authors and publishers of ma-
terial that has been redrawn, reset in tables, reproduced directly or repro-
duced with minor modifications. The exact sources can be derived from the
references. For permission to reproduce copyright material thanks are due
to the following copyright holders:
Chapter 1
International Water Supply Association: Table 1.4a
Office of Water Services (Ofwat): Tables 1.10a, 1.10b
Water Services Association of England and Wales: Table 1.4b
Chapter 2
Anglian Water: Table 2.1
Blackwell Science Publishers: Fig. 2.23
Cambridge University Press: Table 2.6
Chartered Institution of Water and Environmental Management:
Tables 2.4, 2.5; Figs. 2.15, 2.22, 2.26, 2.27
Edward Arnold (Publishers) Ltd.: Figs. 2.14, 2.16
Ellis Horwood Ltd.: Figs. 2.19, 2.20, 2.21
IWA Publishing: Fig. 2.6
John Wiley and Sons Ltd: Fig. 2.17
Dr H.J. Kiuru: Fig. 2.6
Mr J. Lynch, County Engineer, Kildare County Council: Fig. 2.10
McGraw Hill Inc.: Figs. 2.3, 2.4
WRc plc: Table 2.7; Fig. 2.28
v
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vi Acknowledgements
Chapter 3

Academic Press: Tables 3.9, 3.10, 3.12
Applied Science Publishers: Tables 3.13, 3.14
Blackwell Science Publishers: Figs. 3.21, 3.25
Chartered Institution of Water and Environmental Management:
Table 3.5
Controller of Her Britannic Majesty’s Stationary Office: Fig. 3.14
CRC Press: Table 3.18
Elsevier: Table 3.11
John Wiley and Sons Inc.: Table 3.6
McGraw-Hill Inc.: Table 3.17; Figs. 3.2, 3.17, 3.19
Prentice Hall Inc.: Figs. 3.3, 3.5, 3.16, 3.18, 3.20, 3.27
Dr T. Stones: Table 3.4
D. Reidal Publishers: Table 3.16
Water Environment Federation: Table 3.2; Fig. 3.24
Chapter 4
Academic Press: Table 4.18; Figs. 4.1, 4.21
Blackwell Science Publishers: Fig. 4.13
British Ecological Society: Table 4.17; Figs. 4.27, 4.28
British Standard Institution: Tables 4.5, 4.7
Chartered Institution of Water and Environmental Management:
Table 4.21; Figs. 4.22, 4.25, 4.26, 4.31, 4.34, 4.40, 4.43, 4.49
Ellis Horwood Ltd.: Figs. 4.46, 4.47
Elsevier: Tables 4.14, 4.15, 4.19; Fig. 4.36
IWA Publishing: Figs. 4.41, 4.44, 4.48
John Wiley and Sons Inc.: Fig. 4.42
Dr M.A. Learner: Tables 4.3, 4.4
Open University Press: Table 4.9
Dr I.L. Williams: Fig. 4.15
WRc plc: Figs. 4.37, 4.39
Chapter 5

Academic Press: Tables 5.2, 5.26, 5.28, 5.29, 5.30; Figs. 5.1, 5.12, 5.18b,
5.60, 5.79, 5.80, 5.83, 5.90, 5.91, 5.96
Biwater Treatment Ltd.: Fig. 5.18a
Blackwell Science Publishers: Figs. 5.92, 5.93
Carborundum Abrasives GB Ltd.: Fig. 5.23
C.E.P. Consultants, Edinburgh: Figs. 5.30, 5.31, 5.48
Chartered Institution of Water and Environmental Management:
Tables 5.11, 5.25, 5.31; Figs. 5.14, 5.24, 5.25, 5.28, 5.88, 5.98
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Acknowledgements vii
Ellis-Horwood Ltd.: Figs. 5.16, 5.33, 5.51, 5.52, 5.62, 5.63, 5.73, 5.77
Elsevier: Tables 5.17, 5.24; Figs. 5.89, 5.112
IWA Publishing: Tables 5.12, 5.32; Figs. 5.15, 5.34, 5.53
John Wiley and Sons Inc.: Fig. 5.11
Mr G. O’Leary: Figs. 5.21, 5.22
Editor of Oikos: Fig. 5.90
Rosewater Engineering Ltd.: Figs. 5.26, 5.27
Dr J.P. Salanitro, Shell Development Co: Figs. 5.4, 5.81
Simon Hartley Ltd.: Table 5.8; Figs. 5.17, 5.20
TNO Research Institute for Environmental Hygiene, Delft: Fig. 5.60
Water Environment Federation: Table 5.21; Figs. 5.2, 5.5, 5.66,
5.72, 5.76, 5.103
Water Research Commission, South Africa: Tables 5.13, 5.15, 5.16, 5.19,
5.20; Figs. 5.9, 5.67, 5.71, 5.74
Chapter 6
Academic Press: Figs. 6.9, 6.21, 6.22
Editor, American Journal of Botany: Fig. 6.14
British Standards Institution:Fig.6.3
Carl Bro Consultants, Leeds (Lagoon Technology International, Leeds):
Tables 6.15, 6.16, 6.17, 6.19

Chartered Institution of Water and Environmental Management:
Table 6.21, 6.22; Figs. 6.23, 6.24, 6.25, 6.26
CRC Press: Table 6.13; Figs. 6.8, 6.10, 6.12
Elsevier: Table 6.6
IWA Publishing, London: Table 6.20; Fig. 6.16
McGraw-Hill Inc.: Fig. 6.2
National Standards Agency of Ireland:Fig.6.4
Pergamon Press (Elsevier): Fig. 6.17
Springer, Wien: Table 6.3
University of Pennsylvania Press: Tables 6.5, 6.8; Figs. 6.11, 6.13
US Department of Agriculture: Fig. 6.1
US Environmental Protection Agency: Table 6.2
Dr J. Vymazal: Table 6.10
Water Environment Federation: Tables 6.4, 6.7
WorldHealthOrganization, Geneva: Table 6.18
WRc plc: Tables 6.12, 6.14; Fig. 6.15
Chapter 7
Academic Press: Table 7.3
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viii Acknowledgements
Chartered Institution of Water and Environmental Management:
Figs. 7.1, 7.2, 7.12, 7.16; Table 7.2, 7.4, 7.5, 7.10
Editor of Food Technology: Tables 7.11, 7.14
Ellis Horwood Ltd.: Table 7.9
Elsevier: Table 7.13
Institution of Engineers in Ireland: Tables 7.6, 7.8
IWA Publishing: Figs. 7.3, 7.17; Table 7.12
Oklahoma State University, Stillwater:Fig.7.7
Texas State department of Health, Austin:Fig7.8
WRc plc:Fig.7.6

Chapter 8
Cambridge University Press: Tables 8.23, 8.25
Chartered Institution of Water and Environmental Management:
Figs. 8.1, 8.2, 8.5, 8.6, 8.7, 8.12, 8.13, 8.13, 8.16;
Tables 8.16, 8.24, 8.28
Ellis Horwood Ltd.: Tables 8.6, 8.7
European Commission: Table 8.15
IWA Publishing: Figs. 8.14, 8.15; Tables 8.3, 8.10, 8.11, 8.12, 8.26; 8.27,
8.29, 8.30
John Wiley and Sons Inc.: Fig. 8.4
McGraw-Hill Inc.: Table 8.5
National Board for Science and Technology, Dublin:
Figs. 8.9, 8.10, 8.11; Table 8.2, 8.21
National water Council: Tables 8.13, 8.32, 8.33
Open University Press: Table 8.1
Oslo and Paris Commissions: Fig. 8.17; Table 8.35, 8.36
Water Research Commission, South Africa: Table 8.31
WRc plc: Fig. 8.3; Tables 8.17, 8.18, 8.19, 8.20, 8.22, 8.34, 8.40, 8.43
Chapter 9
Academic Press:Fig.9.17
American Public Health Association: Fig. 9.3
American Society of Civil Engineers:Fig.9.22
American Society for Microbiology: Table 9.43; Figs. 9.4, 9.5, 9.12
Americam Water Works Association: Figs. 9.1, 9.11
Blackie & Co.: Figs. 9.24, 9.27
Blackwell Science Publishers: Tables 9.6, 9.23
Carl Bro Consultants, Leeds (Lagoon Technology International, Leeds):
Fig. 9.18
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Acknowledgements ix

Chartered Institution of Water and Environmental Management:
Tables 9.4, 9.5, 9.57
Controller of Her Britannic Majesty’s Stationary Office: Table 9.20.
DEFRA, London: Table 9.49
Ellis Horwood Ltd.: Table 9.52
Elsevier: Tables 9.3, 9.29; Figs. 9.15, 9.21
Editor, Environmental Health Perspectives: Table 9.54
Environmental Sanitation Information Centre, Bangkok: Table 9.33
European Commission: Tables 9.16, 9.17, 9.30, 9.31, 9.32, 9.34
IWA Publishing: Tables 9.11, 9.26, 9.46, 9.47, 9.50, 9.51, 9.53; Fig. 9.6
John Wiley and Sons Inc.: Tables 9.9, 9.10, 9.27, 9.58;
Figs. 9.7, 9.13, 9.23
John Wiley and Sons Ltd.: Tables 9.22, 9.44; Figs. 9.26
Editor, Journal of Hygiene, Cambridge: Tables 9.35, 9.48
Kluwer Academic Publishers: Table 9.45
McGraw-Hill Inc.: Fig. 9.10
Pergamon Press (Elsevier): Fig. 9.20
Van Nostrand Reinhold, New York: Tables 9.55, 9.56
Water Environment Federation: Tables 9.15, 9.24; Fig. 9.19
WorldHealthOrganization, Geneva: Table 9.18
WRc plc: Tables 9.2, 9.19,9.36, 9.37, 9.38, 9.39, 9.42 ; Fig. 9.16
US Environmental Protection Agency: Table 9.7, 9.8
Chapter 10
Academic Press: Tables 10.4, 10.13, 10.15; Figs. 10.2, 10.19
American Society for Microbiology: Tables 10.23, 10.25
Applied Science Publishers: Table 10.7
British Sugar Corporation Ltd.: Fig. 10.1
Editor of Biotechnology Bulletin: Table 10.1
Blackwell Science Publishers: Table 10.3; Fig. 10.13
Cambridge University Press: Fig. 10.3

Centre Europen d’Etudes des Polyphosphates: Table 10.5
Chartered Institution of Water and Environmental Management:
Tables 10.19, 10.26; Figs. 10.8, 10.9, 10.10, 10.11, 10.29, 10.38
Dr A.D. Wheatley: Table 10.6
Ellis Horwood Ltd.: Table 10.8; Figs. 10.27, 10.28
Elsevier: Tables 10.20, 10.24, 10.29; Figs. 10.6, 10.22, 10.23, 10.24, 10.25,
10.26, 10.30, 10.35, 10.36
Professor Isumi Hirasawa: Fig. 10.5
IWA Publishing: Figs. 10.32, 10.37
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x Acknowledgements
John Wiley and Sons Ltd: Table 10.12; Fig. 10.15
Marcel Dekker Inc: Tables 10.21, 10.22
Nature Press: Tables 10.9, 10.10; Fig. 10.4
National Institute of Agricultural Engineering, Silso: Tables 10.17, 10.18
Pergamon Press (Elsevier): Tables 10.12, 10.14; Fig. 10.14
Purdue University: Fig. 10.33
Surveyor Magazine: Fig. 10.12
Chapter 11
Dr Annelies Balkema: Table 11.1
Chartered Institution of Water and Environmental Management:
Fig. 11.1
Elsevier: Tables 11.2, 11.4, 11.5; Fig. 11.5
IWA Publishing: Tables 11.4, 11.6, 11.7, 11.8, 11.9, 11.10, 11.11, 11.12,
11.13; Figs. 11.2, 11.3, 11.4, 11.6
I would also like to thank Dr Anne Kilroy for permission to reproduce
jointly published material in chapter 3.
January 19, 2004 14:33 World Scientific Biology of Wastewater Treatmen t (New Edition) bwt
Contents
Acknowledgements v

Preface to the Second Edition xvii
1 How Nature Deals with Waste 1
1.1. Introduction 1
1.1.1. Thewastewaterproblem 1
1.1.2. Legislation . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. NatureofWastewater 14
1.2.1. Sources and variation in sewage flow . . . . . . . . . 15
1.2.2. Composition of sewage . . . . . . . . . . . . . . . . . 26
1.2.3. Otherwastewaters 47
1.3. Micro-organisms and Pollution Control . . . . . . . . . . . . . 55
1.3.1. Nutritional classification . . . . . . . . . . . . . . . . 56
1.4. MicrobialOxygenDemand 63
1.4.1. Self purification . . . . . . . . . . . . . . . . . . . . . 63
1.4.2. Biochemicaloxygendemand 93
1.4.2.1. Thetest 93
1.4.2.2. Methodology . . . . . . . . . . . . . . . . . 101
1.4.2.3. Factors affecting the test . . . . . . . . . . 112
1.4.2.4. Sources of error . . . . . . . . . . . . . . . 124
2 How Man Deals with Waste 133
2.1. Basic Treatment Processes . . . . . . . . . . . . . . . . . . . . 133
2.1.1. Preliminary treatment . . . . . . . . . . . . . . . . . 138
2.1.2. Primary treatment . . . . . . . . . . . . . . . . . . . 146
xi
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xii Contents
2.1.3. Secondary treatment . . . . . . . . . . . . . . . . . . 147
2.1.4. Tertiarytreatment 148
2.1.5. Examples of treatment plants . . . . . . . . . . . . . 148
2.2. Sedimentation 151
2.2.1. The settlement process . . . . . . . . . . . . . . . . . 151

2.2.2. Design of sedimentation tanks . . . . . . . . . . . . . 157
2.2.3. Performance evaluation . . . . . . . . . . . . . . . . . 163
2.3. Secondary (Biological) Treatment . . . . . . . . . . . . . . . . 173
2.4. TertiaryandAdvancedTreatment 178
2.4.1. Tertiarytreatment 179
2.4.2. Advanced wastewater treatment . . . . . . . . . . . . 190
3 The Role of Organisms 191
3.1. StoichiometryandKinetics 191
3.1.1. Stoichiometry 195
3.1.2. Bacterialkinetics 204
3.1.3. TheBODtest 217
3.2. EnergyMetabolism 223
3.3. Aerobic Heterotrophic Micro-organisms . . . . . . . . . . . . . 230
3.3.1. Theorganisms 230
3.3.2. Nutrition 245
3.3.3. Environmental factors . . . . . . . . . . . . . . . . . . 253
3.3.4. Inhibition 257
3.4. Anaerobic Heterotrophic Micro-organisms . . . . . . . . . . . 259
3.4.1. Introduction 259
3.4.2. Presence in the treatment plant . . . . . . . . . . . . 260
3.4.3. Anaerobic digestion . . . . . . . . . . . . . . . . . . . 262
3.4.4. Sulphide production . . . . . . . . . . . . . . . . . . . 271
3.4.5. Denitrification 272
3.4.6. Redoxpotential 275
3.5. AutotrophicMicro-organisms 277
3.5.1. Introduction 277
3.5.2. Nitrification . . . . . . . . . . . . . . . . . . . . . . . 282
3.6. Assessing Treatability, Toxicity, and Biodegradability . . . . . 290
3.6.1. Introduction 290
3.6.2. Biochemicaltests 291

3.6.3. Bacterialtests 297
3.6.4. Other approaches . . . . . . . . . . . . . . . . . . . . 317
3.6.5. Continuous simulation tests . . . . . . . . . . . . . . 320
3.6.6. Conclusion 324
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Contents xiii
4 Fixed-Film Reactors 325
4.1. Percolating Filters . . . . . . . . . . . . . . . . . . . . . . . . 326
4.1.1. Design and operation . . . . . . . . . . . . . . . . . . 330
4.1.2. Process modifications . . . . . . . . . . . . . . . . . . 356
4.1.3. The organisms and their ecology . . . . . . . . . . . . 364
4.1.4. Factors affecting performance . . . . . . . . . . . . . 417
4.1.5. Nitrifyingfilters 440
4.2. Rotating Biological Contactors . . . . . . . . . . . . . . . . . 441
4.3. Submerged Fixed Film Systems . . . . . . . . . . . . . . . . . 450
4.3.1. Introduction 450
4.3.2. Fluidised bed reactors . . . . . . . . . . . . . . . . . . 451
4.3.3. Biological aerated flooded filters . . . . . . . . . . . . 455
4.3.4. Submerged aerated filters . . . . . . . . . . . . . . . . 460
4.3.5. Movingbedbiofilmreactor 462
5 Activated Sludge 465
5.1. Flocculation 469
5.2. Operating Factors . . . . . . . . . . . . . . . . . . . . . . . . . 477
5.2.1. Processcontrol 477
5.2.1.1. Mixed liquor suspended solids . . . . . . . 477
5.2.1.2. Sludge residence time or sludge age . . . . 478
5.2.1.3. Plant loading . . . . . . . . . . . . . . . . . 479
5.2.1.4. Sludge settleability . . . . . . . . . . . . . . 483
5.2.1.5. Sludge activity . . . . . . . . . . . . . . . . 484
5.2.1.6. Recirculation of sludge . . . . . . . . . . . 487

5.2.2. Factors affecting the process . . . . . . . . . . . . . . 488
5.2.3. Aeration methods . . . . . . . . . . . . . . . . . . . . 496
5.2.3.1. Surface aeration . . . . . . . . . . . . . . . 497
5.2.3.2. Air diffusion . . . . . . . . . . . . . . . . . 504
5.2.3.3. Testing aerators . . . . . . . . . . . . . . . 511
5.3. ModesofOperation 516
5.3.1. Conventional activated sludge processes . . . . . . . . 517
5.3.1.1. Plug-flow systems . . . . . . . . . . . . . . 519
5.3.1.2. Completely mixed systems . . . . . . . . . 528
5.3.1.3. Sequencing batch reactor technology . . . . 530
5.3.2. Extendedaeration 532
5.3.2.1. Oxidationditches 532
5.3.2.2. Packaged plants . . . . . . . . . . . . . . . 539
5.3.3. High-rate activated sludge processes . . . . . . . . . . 541
5.3.3.1. A–B process . . . . . . . . . . . . . . . . . 543
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xiv Contents
5.3.4. Advanced activated sludge systems . . . . . . . . . . 544
5.3.4.1. ICI Deep Shaft

process 545
5.3.4.2. Pure oxygen systems . . . . . . . . . . . . 548
5.4. SludgeProblems 556
5.4.1. Deflocculation 558
5.4.2. Pin-pointfloc 560
5.4.3. Foaming 561
5.4.4. Filamentousbulking 569
5.4.5. Identifyingproblems 583
5.4.6. Non-filamentous bulking . . . . . . . . . . . . . . . . 592
5.4.7. Denitrification 592

5.5. Ecology 593
5.5.1. Bacteria 596
5.5.2. Fungi 599
5.5.3. Protozoa . . . . . . . . . . . . . . . . . . . . . . . . . 599
5.5.4. Othergroups 615
5.6. NutrientRemoval 618
5.6.1. Denitrification 622
5.6.2. Phosphorusremoval 628
6 Natural Treatmen t Systems 641
6.1. LandTreatment 643
6.1.1. Purification process . . . . . . . . . . . . . . . . . . . 644
6.1.2. On-site subsurface infiltration . . . . . . . . . . . . . 646
6.1.3. Slow rate land application . . . . . . . . . . . . . . . 651
6.1.4. Rapid infiltration land treatment systems . . . . . . . 654
6.1.5. Overlandflow 656
6.2. Macrophyte-BasedSystems 658
6.2.1. Algae and submerged macrophytes . . . . . . . . . . 660
6.2.2. Floating macrophytes . . . . . . . . . . . . . . . . . . 663
6.2.3. Emergentmacrophytes 673
6.3. Stabilisation Ponds . . . . . . . . . . . . . . . . . . . . . . . . 697
6.3.1. Anaerobic ponds and lagoons . . . . . . . . . . . . . 700
6.3.2. Oxidationponds 704
6.3.3. Aeration lagoons . . . . . . . . . . . . . . . . . . . . . 731
7 Anaerobic Unit Processes 735
7.1. Introduction 735
7.2. Flow-ThroughSystems(Digestion) 743
7.2.1. Combinedsystems 744
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Contents xv
7.2.2. Digestion 754

7.3. ContactAnaerobicSystems 777
7.3.1. Anaerobic activated sludge process . . . . . . . . . . 779
7.3.2. Sludgeblanketprocess 781
7.3.3. Staticmediafilterprocess 783
7.3.4. Fluidised and expanded media . . . . . . . . . . . . . 790
8 Sludge Treatment and Disposal 793
8.1. Sludge Characteristics and Treatment . . . . . . . . . . . . . . 793
8.1.1. Treatmentoptions 798
8.1.2. Disposal options . . . . . . . . . . . . . . . . . . . . . 819
8.2. LandDisposal 829
8.2.1. Sludge disposal to land sites . . . . . . . . . . . . . . 829
8.2.2. Sludge utilisation to farmland . . . . . . . . . . . . . 834
8.3. SeaDisposal 864
8.3.1. Introduction 864
8.3.2. Legislative control . . . . . . . . . . . . . . . . . . . . 866
8.3.3. Dumpingsites 871
8.3.4. Environmentalimpact 872
9 Public Health 885
9.1. DiseaseandWater 885
9.2. Water-BorneDiseases 888
9.2.1. Introduction 888
9.2.2. Bacteria 889
9.2.3. Viruses 906
9.2.4. Protozoa . . . . . . . . . . . . . . . . . . . . . . . . . 914
9.2.5. Parasiticworms 929
9.3. IndicatorOrganisms 931
9.3.1. Escherichia coli and coliforms . . . . . . . . . . . . . 941
9.3.2. Faecalstreptococci 953
9.3.3. Faecal coliform/faecal streptococci (FC/FS) ratio . . 959
9.3.4. Clostridium perfringens . . . . . . . . . . . . . . . . . 962

9.3.5. Bacteriophage . . . . . . . . . . . . . . . . . . . . . . 964
9.3.6. Bifidobacteria 967
9.3.7. Rhodococcusspp 968
9.3.8. Heterotrophic plate count bacteria . . . . . . . . . . . 969
9.3.9. Other indicator organisms . . . . . . . . . . . . . . . 971
9.3.10. Chemical indicators . . . . . . . . . . . . . . . . . . . 974
9.4. Hazards Associated with Wastewater and Sludge . . . . . . . 976
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xvi Contents
9.4.1. Waterpollution 976
9.4.2. LandPollution 996
9.4.3. Atmospheric pollution . . . . . . . . . . . . . . . . . 1008
9.4.4. Antibiotic resistance in enteric bacteria . . . . . . . . 1011
9.5. Removal of Pathogenic Organisms . . . . . . . . . . . . . . . . 1013
9.5.1. Environmental factors and survival . . . . . . . . . . 1013
9.5.2. Treatment processes . . . . . . . . . . . . . . . . . . . 1021
9.5.3. Sterilization and disinfection methods . . . . . . . . . 1040
10 Biotechnology and Wastewater Treatment 1057
10.1. The Role of Biotechnology . . . . . . . . . . . . . . . . . . . . 1057
10.2. Resource Reuse . . . . . . . . . . . . . . . . . . . . . . . . . . 1060
10.2.1. Fertiliser value . . . . . . . . . . . . . . . . . . . . . . 1060
10.2.2. Reuse of effluents . . . . . . . . . . . . . . . . . . . . 1061
10.2.3. Metal recovery . . . . . . . . . . . . . . . . . . . . . . 1067
10.2.4. Phosphorus recovery . . . . . . . . . . . . . . . . . . 1078
10.3. Biological Conversion . . . . . . . . . . . . . . . . . . . . . . . 1083
10.3.1. Bio-energy . . . . . . . . . . . . . . . . . . . . . . . . 1083
10.3.2. Single-cell protein and biomass . . . . . . . . . . . . . 1099
10.3.3. Composting . . . . . . . . . . . . . . . . . . . . . . . 1124
10.4. Environmental Protection . . . . . . . . . . . . . . . . . . . . 1154
10.4.1. Breakdown of recalcitrants . . . . . . . . . . . . . . . 1155

10.4.2. Bioscrubbing . . . . . . . . . . . . . . . . . . . . . . . 1160
10.4.3. Bioaugmentation . . . . . . . . . . . . . . . . . . . . 1164
10.4.4. Immobilised cells and biosensors . . . . . . . . . . . . 1169
11 Sustainable Sanitation 1179
11.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1179
11.2. The Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . 1180
11.3. Sustainable Options . . . . . . . . . . . . . . . . . . . . . . . . 1190
11.3.1. Source contamination . . . . . . . . . . . . . . . . . . 1190
11.3.2. Treatment . . . . . . . . . . . . . . . . . . . . . . . . 1196
11.3.3. Final disposal . . . . . . . . . . . . . . . . . . . . . . 1203
11.4. Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . 1212
References 1219
Index 1395
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Preface to the Second Edition
Since writing the first edition of Biology of Wastewater Treatment the
wastewater industry has changed quite dramatically. While the basic con-
cepts remain the same, the processes and the industry that design, build
and operate treatment systems have all radically altered. So why has waste-
water technology changed so much since 1990? In Europe the introduction
and rapid implementation of the Urban Wastewater Treatment Directive
has to be a major factor. Nutrient removal, especially biological phosphorus
removal, is now commonplace. This in turn has forced us back to the use of
the original batch reactor designs for activated sludge. The large increase
in sludge production has required the development of integrated disposal
strategies linked with better recovery and reuse technologies. The rapid
expansion of wastewater treatment is allowing manufacturers to experiment
with new innovative designs and processes, and for the first time in nearly
half a century new sewage treatment plants are being built rather than
existing plants merely being upgraded or retrofitted. Privatisation in the

UK has also been hugely influential bringing into play the often-conflicting
factors of cost, especially operational cost, and accountability. Better regu-
lation and control in all countries, coupled with better process management
has resulted in better treatment overall. The concept of sustainability has
also become an important factor, although it is still to have any real in-
fluence on long-term design or planning. Growing urbanization, climate
change, and new analytical techniques that are constantly allowing us to
identify new pollutants and understand the fate of others during treatment
and subsequently in receiving waters, have all significantly influenced the
wastewater industry. However, many fear that wastewater treatment will
xvii
January 19, 2004 14:33 World Scientific Biology of Wastewater Treatmen t (New Edition) bwt
xviii Preface
eventually reach crisis point where existing technologies will prove to be
too expensive and energy dependent to be able to satisfy all the needs of
a modern society. Also, long-term planning is difficult with legislation and
regulation constantly changing. So now is the time to stand back and take
a new look at the whole concept of the wastewater cycle from production
at the household level through to treatment. Our highly diluted waste-
waters, heavily contaminated with metals, pharmaceutical drugs, oestro-
gen mimicking compounds, more varied and dangerous pathogens, and an
alarmingly wide range of trace organic compounds is simply too difficult
to treat effectively in a manner that is going to be sustainable. Rather
than developing better and more efficient process designs we need to start
by looking at the basic concepts of treatment and redesign the system as
though starting from scratch. For, example new separation technologies
and water reuse at the household level is reducing wastewater loadings.
New advances with in-sewer treatment have been very successful in reduc-
ing organic loads to treatment plants and at the same time creating a more
treatable wastewater entering the wastewater treatment plant. Localised

treatment plants rather than centralized systems are now thought to be
more efficient. Removing pollutants at source rather than at the treatment
plant is making effluents and sludges in particular less hazardous. What
is clear is that wastewater treatment will have to become a joint venture
between all the stakeholders, with every person having to take some re-
sponsibility for their waste.
I have tried to retain as much of the original text as possible, but due to
the rapid changes that have occurred over the past decade then considerable
revision was necessary. All sections have been updated with many expanded
to reflect the new importance or popularity of processes. There is also a new
chapter on sustainability.
It is often forgotten by environmentalists, and the public in general,
what an important role wastewater treatment plays in protecting both the
environment and the health of the public. Without it there would be no
development and growth, without it our environment and our very lives
would be at risk. It is a huge credit to all those involved in the industry
that this vital service is carried out in such a discreet and professional
manner. For all those of you who have made it your career, thank you. For
those who would like to, then welcome and I hope that you will also find it
equally as rewarding and exciting as I have.
Nick Gray
TCD
January 2004
January 19, 2004 14:33 World Scientific Biology of Wastewater Treatmen t (New Edition) bwt
‘To you it’s just crap, to me it’s bread and butter.’
Spike Milligan
Recollections of the latrine orderly
January 19, 2004 14:33 World Scientific Biology of Wastewater Treatmen t (New Edition) bwt
1
How Nature Deals with Waste

1.1. Introduction
1.1.1. The wastewater problem
Each day, approximately 1×10
6
m
3
of domestic and 7×10
6
m
3
of industrial
wastewater is produced in the UK. This, along with surface runoff from
paved areas and roads, and infiltration water, produces over 20 × 10
6
m
3
of wastewater requiring treatment each day. To cope with this immense
volume of wastewater there were, in 1999, some 9260 sewage treatment
works serving about 95% of the population (Water UK 2001). The size
of these plants varies from those serving small communities of < 100, to
plants like the Crossness Sewage Treatment Works operated by Thames
Water which treats the wastewater from over 1.7 million people living in a
240 km
2
area of London.
In terms of volume or weight, the quantity of wastewater treated annu-
ally in the UK far exceeds any other product (Table 1.1) including milk,
steel or even beer (Wheatley 1985), with vast quantities of wastewater gen-
erated in the manufacture of most industrial products (Fig. 1.1). The cost
of wastewater treatment and pollution control is high, and rising annually,

not only due to inflation but to the continuous increase in environmental
quality that is expected. During the period 1994–1999, the ten main water
companies in England and Wales invested £16.55bn into its services. Over
half of this was on wastewater provision. In the year 1998/1999, £1.9bn
was spent on new wastewater treatment plants alone as compliance with
the European Union Urban Wastewater Treatment Directive continues. The
industry is extremely large, with the income for these water companies for
1
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2 How Nature Deals with Waste
Table 1.1. The quantity of sewage treated in the UK far exceeds
the quantity of other industrial products processed. Comparative
values are based on 1984 sterling values (Wheatley 1985).
Product Tonnes/annum (×10
6
)Price(£/tonne)
Water as sewage 6500 0.10
Milk 16 25
Steel 12 300
Beer 6.6280
Inorganic fertilizer 3.3 200
Sugar 1.0350
Cheese 0.2 1300
Baker’s yeast 0.1 460
Citric acid 0.015 700
Penicillin 0.003 45000
Fig. 1.1. Tonnes of water required in the manufacture of some products that produce
organic effluents.
1998/1999 in excess of £6,000m with operating costs approaching £4,000m
(Water UK 2001).

There are two fundamental reasons for treating wastewater: to prevent
pollution, thereby protecting the environment; and, perhaps more impor-
tantly, protecting public health by safeguarding water supplies and prevent-
ing the spread of water-borne diseases (Sec. 2.1).
The safe disposal of human excreta is a pre-requisite for the supply of
safe drinking water, as water supplies can only become contaminated where
disposal is inadequate. There are many infectious diseases transmitted in
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Introduction 3
excreta, the most important being the diarrhoeal diseases cholera, typhoid,
and schistosomiasis. The faeces are the major source of such diseases with
few infections, apart from schistsosomiasis, associated with urine. Among
the most common infectious water-borne diseases are bacterial infections
such as typhoid, cholera, bacillary dysentery, and gastro-enteritis; viral in-
fections such as infectious hepatitis, poliomyelitis, and various diarrhoeal
infections; the protozoal infections cryptosporidiosis, giardiasis, and amoe-
bic dysentery, and the various helminth infections such as ascariasis, hook-
worm, and schistosomiasis (bilharzia). Although the provision of clean wa-
ter supplies will reduce the levels of infection in the short term, in the
long term it is vital that the environment is protected from faecal pollution
(Feachem and Cairncross 1993; Mara 1996). Adequate wastewater treat-
ment and the disinfection of water supplies has effectively eliminated these
water-borne diseases from developed countries, but they remain endemic in
many parts of the world, especially those regions where sanitation is poor or
non-existent (Chap. 9). In developed countries where there are high popula-
tion densities, such as the major European cities, vast quantities of treated
water are required for a wide variety of purposes. All the water supplied
needs to be of the highest quality possible, although only a small propor-
tion is actually consumed. To meet this demand, it has become necessary to
utilise lowland rivers and groundwaters to supplement the more traditional

sources of potable water such as upland reservoirs (Gray 1997). Where the
water is reused on numerous occasions, as is the case in the River Severn
and the River Thames Sec. 10.2.2, adequate wastewater treatment is vital
to ensure that the outbreaks of waterborne diseases that were so prevalent
in the eighteenth and nineteenth centuries do not reoccur (Chap. 9).
In terms of environmental protection, rivers are receiving large quan-
tities of treated effluent while estuaries and coastal waters have vast
quantities of partially or completely untreated effluents discharged into
them. Although in Europe, the Urban Wastewater Treatment Directive
has caused the discharge of untreated wastewater to estuarine and coastal
waters to be largely phased out. Apart from organic enrichment endan-
gering the flora and fauna due to deoxygenation, treated effluents rich in
oxidised nitrogen and phosphorus can result in eutrophication problems.
Where this is a particular problem, advanced or tertiary wastewater treat-
ment is required to remove these inorganic nutrients to protect rivers and
lakes (Sec. 2.4). Environmental protection of surface waters is therefore a
major function of wastewater treatment. In 1998, 30% of all rivers surveyed
in England and Wales (12,241 km) were classified as having doubtful, or
worse, quality (i.e. class D, E and F using the Environment Agency General
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4 How Nature Deals with Waste
Table 1.2. The river quality in England and Wales based on the Environment
Agency GQA systems.
River length (%) in each quality grade
ABCDEFTotalkm
Chemical GQA
1988–1990 17.7 30.1 22.8 14.412.72.3 34161
1993–1995 26.8 32.7 21.3 10.28.10.9 40227
1994–1996 27.1 31.5 21.2 10.48.81.0 40804
Biological GQA

1990 24.031.621.6 9.87.35.7 30001
1995 34.631.618.4 8.15.41.9 37555
Nutrient GQA
1990 8.017.710.213.128.022.9 23003
1993–1995 14.7 22.6 11.0 13.127.311.0 34864
Quality Assessment (GQA) chemical classification system) (Environment
Agency 1998; Gray 1999; Water UK 2001) (Table 1.2). As in Ireland, there
is an increasing trend in eutrophication of surface waters (EPA 2000). The
cost of rehabilitating rivers, as was seen with the River Thames in the pe-
riod 1960–1980, is immense. The River Mersey for example, now Britain’s
most polluted river, will cost an estimated £3,700m over the next quarter
of a century to raise to a standard suitable for recreation (Department of
the Environment 1984).
1.1.2. Legislation
Environmental legislation relating to wastewater treatment and receiv-
ing water quality is based largely on quality standards that are related
to suitability of water for a specific use, the protection of receiving
waters, or emission limits on discharges. Standards are usually manda-
tory with maximum permissible concentrations based on health criteria
or environmental quality standards. Table 1.3 lists the key Directives
concerning the aquatic environment that govern legislation in countries
(Member States) comprising the European Union. The principal Direc-
tives are those dealing with Surface Water (75/440/EEC), Bathing Waters
(76/160/EEC), Dangerous Substances (76/464/EEC; 86/280/EEC), Fresh-
water Fish (78/659/EEC), Ground Water (80/68/EEC), Drinking Water
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Introduction 5
Table 1.3. EU Directives concerning inland waters by year of introduction.
1973
Council Directive on the approximation of the laws of the Member States relating to

detergents (73/404/EEC)
Council Directive on the control of biodegradability of anionic surfactants (73/405/EEC)
1975
Council Directive concerning the quality required of surface water intended for the ab-
straction of drinking water in the Member States (75/440/EEC)
1976
Council Directive concerning the quality of bathing waters (76/160/EEC)
Concil Directive on pollution caused by certain dangerous substances discharged into
the aquatic environment (76/464/EEC)
1977
Council decision establishing a common procedure for the exchange of information on
the quality of surface in the Community (77/795/EEC)
1978
Council Directive on titanium oxide waste (78/178/EEC)
Council Directive on quality of fresh waters needing protecting or improvement in order
to support fish life (78/659/EEC)
1979
Council Directive concerning the methods of measurement and frequencies of sampling
and analysis of surface water intended for the abstraction of drinking water in the Mem-
ber States (79/869/EEC)
Council Directive in the quality required for shellfish wates (79/923/EEC)
1980
Council Directive on the protection of ground water against pollution caused by certain
dangerous substances (80/68/EEC)
Council Directive on the approximation of the laws of the Member States relating to the
exploitation and marketing of natural mineral waters (80/777/EEC)
Council Directive relating to the quality of water intended for human consumption
(80/778/EEC)
1982
Council Directive on limit values and quality objectives for mercury discharges by the

chlor-alkali electrolysis industry (82/176/EEC)
Council Directive on the testing of the biodegradability of non-ionic surfactants
(82/883/EEC)
Council Directive on the monitoring of waste from the titanium oxide industry
(82/883/EEC)
1983
Council Directive on limit values and quality objectives for cadmium discharges
(83/513/EEC)
1984
Council Directive on limit values and quality objectives for discharges by sectors other
than the chlor-alkali electrolysis industry (84/156/EEC)
Council Directive on limit values and quality objectives for discharges of hexachlorocy-
clohexane (84/491/EEC)
1985
Council Directive on the assessment of the effects of certain public and private projects
on the environment (85/337/EEC)
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6 How Nature Deals with Waste
Table 1.3. (Continued)
1986
Council Directive on the limit values and quality objectives for discharge of cer-
tain dangerous substances included in List I of the Annex to Directive 76/464/EEC
(86/280/EEC)
1987
Council Directive on the preventation and reduction of environmental pollution by as-
bestos (87/217/EEC)
1988
Council Directive amending Annex II to the Directive 86/280/EEC on limit values and
quality objectives for discharges of certain dangerous substances included in List I of the
Annex to Directive 76/464/EEC (88/347/EEC)

1990
Council Directive amending Annex II to the Directive 86/280/EEC on limit values and
quality objectives for discharges of certain dangerous substances included in List I of the
Annex to Directive 76/464/EEC (90/415/EEC)
1991
Council Directive concerning urban waste water treatment (91/271/EEC)
Council Directive concerning the protection of waters against pollution caused by nitrates
from agricultural sources (91/676/EEC)
1992
Council Dirrective on pollution by waste from the titanium oxide industry (92/112/EEC)
1996
Council Directive on integrated pollution prevention control (96/61/EEC)
1998
Council Directive on the quality of water intended for human consumption (98/83/EEC)
2000
Council Directive establishing a framework for community action in the field of water
policy (00/60/EC)
(80/778/EEC), Urban Waste Water Treatment (91/271/EEC), Nitrates
(91/676/EEC), Integrated Pollution Prevention Control (96/61/EEC), and
Water Framework (00/60/EEC). The Directive controlling sewage sludge
disposal to agricultural land (86/278/EEC) is discussed in Chap. 8. In most
Directives both guide (G) and imperative, or mandatory, (I) values are
given. The G values are those which Member States should be working to-
wards in the long term. In most cases, nationally adopted limit values are
the I values although occasionally more stringent values are set.
The Dangerous Substances Directive (76/464/EEC) requires licensing,
monitoring and control of a wide range of listed substances discharged
to the aquatic environment. List I (Black List) substances have been se-
lected mainly on the basis of their toxicity, persistence and potential for
bioaccumulation. Those that are rapidly converted into substances that are

biologically harmless are excluded. List II (Grey List) substances are consid-
ered to be less toxic, or the effects of which are confined to a limited area
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Introduction 7
Table 1.4. List I and List II substances defined by the EU Dangerous Substances Di-
rective (76/464/EEC).
List no. 1 (‘black list’)
Organohalogen compounds and substances which may form such compounds in the
aquatic environment
Organophosphorus compounds
Organotin compounds
Substances, the carcinogenic activity of which is exhibited in or by the equatic environ-
ment (substances in List 2 which are carcinogenic are included here)
Mercury and its compounds
Cadmium and its compounds
Persistent mineral oils and hydrocarbons of petroleum
Persistent synthetic substances
List no. 2 (‘grey list’)
The following metalloids/metals and their compounds:
Zinc, copper, nickel, chromium, lead, selenium, arsenic, antimony, molybdenum, tita-
nium, tin, barium, beryllium, boron, uranium, vanadium, cobalt, thalium, tellurium,
silver
Biocides and their derivatives not appearing in List 1
Substances which have a deleterious effect on the taste and/or smell of products for
human consumption derived from the aquatic environment and compounds liable to
give rise to such substances in water
Toxic or persistent organic compounds of silicon and substances which may give rise to
such compounds in water, excluding those which are biologically harmless or are rapidly
converted in water to harmless substances
Inorganic compounds of phosphorus and elemental phosphorus

Non-persistent mineral oils and hydrocarbons of petroleum origin
Cyanides, fluorides
Certain substances which may have an adverse effect on the oxygen balance, particularly
ammonia and nitrites
which is dependent on the characteristics and location of the water into
which they are discharged (Table 1.4). Member States are in the process of
establishing environmental quality standards (EQS) for surface and ground
waters. These will be used as maximum permissible concentrations in wa-
ters receiving discharges containing such compounds (Table 1.5).
Water policy in the EU has recently been rationalized into three key
Directives: Drinking Water (80/778/EEC), Urban Waste Water Treatment
(91/271/EEC), and the Water Framework Directive (2000/60/EEC).
The Water Framework Directive (2000/60/EEC) brings together the ex-
isting Directives on water quality of surface fresh water, estuaries, coastal
waters and ground water. It covers all aspects of aquatic ecology and wa-
ter quality, including the protection of unique and valuable habitats, the
protection of drinking water resources and the protection of bathing wa-
ters. It achieves this by managing all water resources within River Basin