Introduction ix
Chapter 1. Urban Wastewater Composition 1
1.1. Main physicochemical parameters of raw wastewater 1
1.1.1. Suspended solids 3
1.1.2. Organic matter indicators 5
1.1.3. Nitrogen 15
1.1.4. Phosphorus 19
1.1.5. Micropollutants 20
1.1.6. Parametric influence in the treatment system 24
1.2. Microbiological parameters: pathogenic organisms and indicators of fecal contamination 25
1.2.1. Bacteria 29
1.2.2. Enteric viruses 31
1.2.3. Enteric protozoa 32
1.2.4. Helminth eggs 32
1.2.5. Fecal contamination indicators: assessment in treated wastewater 34
1.3. References 38
Chapter 2. Processing Unit Operations 43
2.1. Background. 43
2.2. Design principles for treatment plants 45
2.3. Unit operations 48
2.3.1. Pretreatment 51
2.3.2. Primary treatment 52
2.3.3. Secondary treatment 52
2.3.4. Effluent clarification and discharge 54
2.3.5. Additional treatments 54
2.3.6. Sludge treatment 58
2.4. References 62
Chapter 3. Estimation of Pollutant Loadings 65
3.1. Water consumption 65
3.2. Estimated discharges 66
3.2.1. Wastewater flows 67
3.2.2. Peak flows 68
3.2.3. Number of population equivalents (PE) 69
3.2.4. Maximum and minimum flow rates 71
3.3. Pollutant loads 74
3.3.1. Relationship between load and concentration 74
3.3.2. Pollutant loads in BOD, N and P 75
3.4. References 76
Chapter 4. Pretreatments 79
4.1. Screening 79
4.1.1. Manual screens 80
4.1.2. Mechanical screens 81
4.1.3. Screen calculation 83
4.1.4. Screen implementation 89
4.2. Comminution 89
4.3. Sieving 90
4.3.1. Pressure washing sieves 90
4.3.2. Mechanical waste discharge sieves 90
4.4. Sand removal 91
4.4.1. Calculation for aerated sand trap 100
4.5. Oil and grease removal 100
4.5.1. Grease separators 101
4.5.2. Aerated grease and oil trap 101
4.6. References 105
Chapter 5. Primary Settling 107
5.1. General principles 107
5.2. Conical or cylindricalâ"conical static settler 109
5.3. Horizontal flow settler 110
5.3.1. Dimensioning of horizontal settlers 111
5.4. Circular settlers 117
5.4.1. Example design of a primary settler 120
5.5. Design of primary mechanized settlers 123
5.5.1. Rectangular settler 123
5.5.2. Circular settler 124
5.6. Performance of conventional primary settlers 125
5.6.1. Settler depth 128
5.7. Lamellar settlers 129
5.7.1. Theory and general principles 130
5.7.2. Dimensioning basics for lamellar settlers 133
5.8. References 174
Chapter 6. Biological Treatment with Activated Sludge 179
6.1. Background information on microbial organisms 179
6.2. Operating principle 181
6.3. Theoretical bases of aerobic treatment 182
6.3.1. Organic matter (biological oxygen demand) evolution in the presence of bacterial mass 182
6.3.2. Analytical interpretation 184
6.4. Traditional design methods 192
6.4.1. Complete mix 194
6.4.2. Plug flow 211
6.4.3. Comparison between the two systems 213
6.4.4. Oxygen requirements for carbon pollution 213
6.5. Operating parameters 221
6.5.1. Sludge losses: causes and consequences 221
6.5.2. Role of nutrients 223
6.5.3. MI 223
6.5.4. DI 224
6.5.5. Sludge redox potential (Rh) 224
6.5.6. Effect of temperature 225
6.5.7. Effect of pH 226
6.5.8. Effect of some toxicants 226
6.5.9. Sludge settling issues 227
6.6. Activated sludge ecology 230
6.7. Aeration of activated sludge tanks 233
6.7.1. O2 transfer 233
6.7.2. Influence of some factors on Cs and KLa 236
6.7.3. Aeration systems 243
6.7.4. Surface aerators 249
6.7.5. Deep-water aerators 252
6.7.6. Conditions of use of aeration systems 253
6.7.7. Aerator design 257
6.7.8. Using pure oxygen 277
6.8. Activated sludge processing technology 278
6.8.1. Conventional activated sludge 278
6.8.2. Contact stabilization 284
6.8.3. Full mixing 286
6.8.4. Sequencing batch reactor 287
6.8.5. Bioring process 289
6.9. Examples of dimensioning the activated sludge process 291
6.9.1. Example 1: calculation of a low load aeration tank 291
6.9.2. Example 2: calculation of an aeration tank fed under medium loading 293
6.9.3. Example 3: population of 3,000,000 inhabitants 295
6.9.4. Example 4: population of 12,500 inhabitants 302
6.10. References 307
Index 313
