Water and Wastewater Project Development

Contents

Glossary of terms xiv

Abbreviations and symbols xvi

Chapter 1 Introduction to project development 1

1.1 Scope of the book 1

1.2 An overview of the process of project development 1

1.3 Influencing factors 3

1.4 Planning for the future 4

1.5 Making a decision 5

1.5.1 Mathematical techniques 6

1.6 Risk and uncertainty 7

1.7 Problem – phosphorus removal 7

1.8 Exercises 11

Chapter 2 Justification and development 12

2.1 Introduction 12

2.2 Investment criteria 12

2.3 Defining the need for the project 13

2.4 Design horizons 13

2.5 Changes in loading 14

2.5.1 Estimating changes in loading 14

2.6 Conditions and performance of assets 15

2.7 Legal framework 16

2.7.1 Wastewater and sludge directives 16

2.7.2 Legislation and policy relating to conservation 19

2.8 Methodology for developing the project 19

2.8.1 Evaluation of facts 20

2.8.2 Developing proposals 20

Chapter 3 Kingston Development – a case study 24

3.1 Introduction 24

3.2 Background to the Kingston Development Study 24

3.3 Correspondence file 27

3.4 Data file 49

3.4.1 River quality data 49

3.4.2 Trade flow data 51

3.4.3 Report on Veryan Sewage Treatment Works 52

3.4.4 Report on Teniae Sewage Treatment Works 55

3.4.5 Report on Slade Sewage Treatment Works 56

3.4.6 Report on existing sewerage 60

3.4.7 Report on the water distribution system 64

Chapter 4 Basic concepts 66

4.1 Introduction 66

4.2 The nature of organic matter 66

4.3 Bacteria 66

4.4 Types of bacterial reaction 67

4.5 Application of bacterial reactions 69

4.6 Bacterial growth 69

4.7 Decomposition of nitrogenous and carbonaceous matter 71

4.8 Composition of wasetwater 72

4.9 Concentrations – units 72

4.10 Dissolved oxygen and oxygen demand 73

4.10.1 Problem – variation of BOD with time 74

4.10.2 Problem – kinetics of BOD exerted 75

4.10.3 Problem – kinetics of BOD: 1 75

4.10.4 Problem – kinetics of BOD: 2 75

4.11 Characteristics of wastewater 76

4.12 Summary of parameters 78

Chapter 5 Analysis 81

5.1 Introduction 81

5.2 Units 81

5.2.1 Problem – unit conversion 82

5.3 Mass balance equation 82

5.4 Kinetics of a reaction 83

5.5 Types of reactor 84

5.5.1 Batch reactors 84

5.5.2 Plug flow reactors 85

5.5.3 Problem – effect of an effluent on a river 87

5.5.4 Problem – variation of ammonia-N levels in a river 88

5.6 Continuously stirred reactors 90

5.6.1 Problem – performance of a lagoon 91

5.7 River quality 93

5.7.1 River classification 93

5.7.2 River quality indicators 94

5.7.3 Problem – water quality index 95

5.8 Discharge consents 98

5.8.1 Problem – compliance with a discharge consent 99

5.8.2 Types of characteristic included in the discharge consent 102

5.8.3 Problem – setting the BOD of a consent from dilution data 103

5.8.4 Problem – updating a consent using no deterioration criteria 104

5.9 Dissolved oxygen sag curves 105

5.10 The prediction of DO levels in a river 105

5.10.1 Problem – setting up the Streeter-Phelps equation 106

5.10.2 Problem – application of the Streeter-Phelps equation 107

5.11 Exercises 110

Chapter 6 Design 111

6.1 Introduction 111

Part 1 Estimation of loadings 111

6.2 Estimation of flows and loadings 111

6.3 Estimation of hydraulic loadings in wastewater systems 112

6.3.1 Definition and estimation of dry weather flow 112

6.3.2 Design data for flow rate estimation (sewage) 112

6.3.3 Flow variation 113

6.3.4 Infiltration 114

6.3.5 Combined sewerage 114

6.3.6 Problem – estimation of hydraulic loading 115

6.4 Biological loadings on sewage treatment works 118

6.4.1 Industrial loadings 118

6.4.2 Problem – calculate the BOD load on a treatment works 120

6.5 Estimation of hydraulic loadings in a water supply system 120

Part 2 Treatment process design 121

6.6 Introduction 121

6.7 Wastewater treatment layout 122

6.7.1 Stages of treatment 122

6.8 Sedimentation 124

6.8.1 Theory and design 124

6.8.2 Design data and design notes 127

6.8.3 Types of sedimentation tank 129

6.8.4 Sedimentation in water treatment 129

6.8.5 Problem – design of primary sedimentation tanks 131

6.9 Aerobic biological oxidation – basic concepts 133

6.10 Biological filtration 136

6.10.1 Biological filters 136

6.10.2 Analysis of biological filter performance 138

6.10.3 Biological filters – design summary 140

6.10.4 Biological filters – design notes 142

6.10.5 Problem – design of low-rate filter system 143

6.11 Activated sludge process 146

6.11.1 Layout and design of an activated sludge process 146

6.11.2 Activated sludge – design summary 147

6.11.3 Aeration methods and design of air requirements 148

6.11.4 Design of final sedimentation tanks for activated sludge plants 151

6.11.5 Activated sludge – design notes 152

6.11.6 Problem – design of an activated sludge process 153

6.12 Sludge 159

6.12.1 Properties of sludge 159

6.12.2 Problem – sludge volume change on dewatering 159

6.12.3 sludge stream through a sewage treatment works 160

6.12.4 Methods of dewatering sludges 161

6.12.5 Anaerobic biological oxidation 163

6.12.6 Sludge holding and disposal 165

6.12.7 Sludge – design notes 167

6.12.8 Problem – design of a sludge handling and digestion plant 167

6.13 Tertiary treatment 170

6.14 Nutrient removal 172

6.14.1 Problem – removal of phosphorus by chemical dosing 174

6.14.2 Biological removal of phosphorus 175

6.15 Exercises 175

Chapter 7 Water transfer systems 180

7.1 Introduction 180

7.2 Basic hydraulic analysis 180

7.2.1 Problem – application of the energy principle to a pressure pipeline 183

7.3 Energy losses in pipes 185

7.3.1 Pipe friction 185

7.3.2 Minor head losses 186

7.4 Water hammer 187

7.5 Water supply distribution networks – design notes 188

7.5.1 Problem – derivation of the design of a service reservoir 189

7.5.2 Problem – application of design method 191

7.6 Gravity flow in sewers 192

7.6.1 Theory 192

7.6.2 Design of gravity sewers 192

7.6.3 Design considerations 193

7.7 Pumping and pumping stations 194

7.7.1 Pumping in water supply systems 194

7.7.2 Pumping in sewerage systems 194

7.7.3 Sump size 195

7.7.4 Operational problems in pumping systems 196

7.7.5 Rising mains 196

7.7.6 Problem – design of a pumping station, rising main and gravity sewer 196

7.7.7 Pumping and pumping stations – design summary 200

7.8 Pipe networks – analysis 202

7.8.1 Problem – analysis of a pipe network 204

7.8.2 Pipe networks – design summary 210

7.8.3 Cost estimate 210

7.9 Pipeline construction and renovation 211

7.10 Exercises 213

Chapter 8 Evaluation 215

8.1 Introduction 215

8.2 Risk assessment 215

8.2.1 Definition of risk 215

8.2.2 Risk management and risk assessment 216

8.2.3 Assessment of risk 217

8.3 Qualitative and semi-quantitative risk analysis 217

8.4 Quantitative risk analysis 218

8.4.1 Estimation of probabilities 218

8.4.2 Acceptance criteria 219

8.4.3 Problem – application of the fatal accident rate concept 219

8.5 Network analysis 220

8.5.1 Fault tree analysis 220

8.5.2 Problem – fault tree analysis of an emergency overflow 221

8.5.3 Event tree analysis 221

8.5.4 Problem – event tree analysis of a power supply failure 222

8.5.5 The cost of risk 223

8.6 Financial assessment 224

8.6.1 Cost models 225

8.6.2 Problem – global cost modelling 226

8.6.3 Life-cycle costing 229

8.6.4 Present value techniques 230

8.6.5 Problem – cash flow 231

8.6.6 Sensitivity analysis 234

8.7 Environmental protection and management 236

8.8 Environmental impact assessment 237

8.8.1 Environmental issues 238

8.8.2 Impact rating 240

8.8.3 Problem – semi-quantitative impact analysis 241

8.9 Assessment of performance and condition 244

8.9.1 Evaluation of operational performance 245

8.9.2 Evaluation of physical condition 246

8.9.3 Quantification of condition and performance 246

8.9.4 Water supply systems 247

8.9.5 Sewerage systems 249

8.9.6 Application of risk assessment to transfer systems 249

8.9.7 Assessment of the condition of treatment plants 249

8.9.8 Performance of sewage treatment works 250

8.10 Grading systems 250

8.10.1 Combination of grades 252

8.10.2 Examples of assessments for treatment plants 253

Chapter 9 Optimisation, decision making and prioritisation 256

9.1 Analytical methods of optimisation 256

9.1.1 Problem – cost minimisation for a growth-related situation 256

9.1.2 Problem – optimisation for a unit process 259

9.2 Optimisation by Lagrange multipliers 260

9.2.1 Problem – optimisation using Lagrange multipliers 260

9.3 Linear programming 263

9.3.1 The Simplex method 263

9.3.2 Problem – application of the Simplex method 267

9.3.3 Problem – solution of linear programming using Excel 269

9.3.4 Problem – solution of Problem 9.1.2 using linear programming 269

9.4 Decision making 271

9.4.1 Matched pair analysis 272

9.4.2 Problem – selection of the most appropriate option using matched paired techniques 275

9.5 Prioritisation 277

9.5.1 Introduction 277

9.5.2 Problem – asset condition assessment and prioritisation 277

Chapter 10 Report on the Kingston Development 286

10.1 Introduction 286

10.2 Format of a report 286

10.2.1 Contents 287

10.3 Example of a preliminary appraisal 287

10.4 Example of a detailed appraisal 293

10.5 Exercises 297

10.5.1 River quality 297

10.5.2 Treatment options 298

10.5.3 Sewerage schemes 298

10.5.4 Water supply 298

Appendix 1 Cost estimation 300

Appendix 2 Materials and material performance 306

Appendix 3 Pipe flow charts 315

Index 319