Wastewater Treatment and Technology

Contents

Chapter 1. Introduction 1

Pollution, 1

Controlling pollution, 3

Consents, 3

Urban pollution management, 10

Treatment, 14

Basic biology, 14

Bacteria, 16

Protozoa, 21

Viruses, 23

References, 23

Chapter 2. Pre-treatment 25

Preliminary processes, 25

Screens, 25

Grit removal, 29

Storm water, 32

Primary settlement, 34

Hydro-dynamic separators, 41

Sea outfalls, 41

References, 43

Chapter 3. Trickling filters 44

Introduction, 44

Biofilm, 45

Media, 47

Wastewater treatment and technology

Ventilation, 48

Distributors, 49

Operation of trickling filters, 50

Modes of operation, 50

Settlement tanks, 55

Performance, 55

Operational problems, 56

Ponding, 56

Flies, 57

Spring sloughing, 58

Temperature, 58

High-rate filters, 60

Plastic media, 60

High-rate filtration, 60

Low-rate filtration, 63

Models, 64

References, 65

Chapter 4. Activated sludge process 67

Introduction, 67

Process variables, 70

Organic loading rate, 70

Sludge age, 71

Hydraulic retention time, 72

Aeration plant design, 73

Aeration devices, 73

Aerator efficiencies, 77

Oxygen transferred by aerators, 79

Oxygen requirements, 79

Optimization of aeration efficiency, 80

Dissolved oxygen control, 82

Hybrid aeration, 83

Sludge settleability, 85

Design of final settlement tanks, 87

Aeration tank configuration, 90

Sludge production, 93

Sludge wastage rate, 94

Sludge recycle rate, 94

Operational problems, 95

Filamentous species, 95

Bulking, 99

Foam formation, 103

Mathematical models, 105

Sequence for design, 107

References, 108

Chapter 5. Bio-oxidation – other aspects 113

Introduction, 113

Biological contactors, 113

Submerged filters, 117

Biological aerated filters, 118

Submerged aerated filters, 122

Deep shaft process, 122

Sequencing batch reactors, 126

Use of pure oxygen, 128

Open tanks, 130

Covered aeration tanks, 133

Oxygen supply, 135

Oxidation ditches, 137

Reed beds, 142

Membrane reactors, 145

Odours and odour control, 148

General overview, 148

Odour measurement, 149

Dealing with odours, 150

References, 154

Chapter 6. Nutrient removal 160

Introduction, 160

Nitrogen removal, 161

Nitrification, 161

De-nitrification, 164

Phosphorus removal, 168

Chemical phosphorus removal, 168

Biological phosphorus removal, 173

Phosphorus recovery, 178

References, 180

Chapter 7. Tertiary treatment 183

Introduction, 183

Solids’ removal, 183

Lagoons, 183

Wastewater treatment and technology

Grass plots, 184

Upflow clarifiers, 186

Microstrainers, 187

Rapid gravity filters, 188

Deep bed filters, 192

Upflow sand filters: the Dynasand filter, 193

Reed beds, 194

Disinfection, 195

Chlorine, 196

Ozone, 198

Ultraviolet radiation, 200

References, 202

Chapter 8. Sludge handling and disposal 204

Introduction, 204

Sludge thickening, 209

Gravity thickening, 209

Centrifugation, 210

Belt thickeners, 211

Dissolved air flotation, 212

Sludge rheology, 213

Anaerobic digestion, 216

Essential elements, 216

Design and operation, 218

Dual digestion, 223

Enhancing anaerobic digestion, 225

Thermophilic digestion, 227

Enzymatic hydrolysis, 227

Enhanced treatment options, 228

Aerobic digestion, 228

Lime treatment, 230

De-watering, 230

Filter press, 231

Belt press, 236

Sludge disposal, 237

Disposal to agricultural land, 237

Incineration, 241

Landfill, 245

Composting, 245

Thermal drying, 247

References, 249

Chapter 9. Anaerobic digestion of wastewaters 253

Introduction, 253

Microbiology, 253

Reactor design, 255

Contact digester, 255

Anaerobic filter, 257

Upflow sludge blanket reactor, 258

Expanded and fluidized bed digesters, 263

Anaerobic baffled reactor, 264

To digest or not to digest, 265

Costs, 265

Comparison with aerobic processes, 265

Basic considerations, 266

Modes of operation, 268

Prevalence of anaerobic digestion, 269

References, 270

Chapter 10. Industrial wastewater treatment 273

Introduction, 273

Integrated pollution control, 274

Industrial wastewaters, 275

Biological treatment, 275

Enhanced biological treatment, 282

Physico-chemical treatment, 284

Enhanced oxidation, 289

Recovery, 291

Agricultural industry, 294

References, 297

Chapter 11. The future 302

Trace organics, 302

Endochrine disrupting chemicals, 302

Toxicity, 304

Sewage biosolids, 305

Activated sludge process, 312

References, 315

Index 319