Drinking Water Treatment, Calco-carbonic Equilibrium and Disinfection

Chapter 20 Calco-carbonic Equilibrium, Correction of Aggressivity and Remineralization 1 20.1 Characteristics of water leading to calco-carbonic equilibrium 2 20.1.1 Chemical equilibria 2 20.1.2 Aggressive water 12 20.1.3 Scaling water 12 20.1.4 Corrosive water 12 20.2 The equilibrium reactions of water’s constituents 15 20.2.1 Equilibrium pH 16 20.2.2 Langelier equation 20 20.3 Hallopeau–Dubin diagram 25 20.4 Indicative criteria to determine the aggressivity or corrosivity of water 29 20.4.1 Indicators of aggressivity: concrete pipelines 29 20.4.2 Corrosivity indicators 32 20.5 The calco-carbonic equilibrium of water 36 20.5.1 Water quality and regulations 38 20.5.2 The correction of aggressivity 38 20.5.3 Aggressivity correction treatments 39 20.6 Remineralization treatments 60 20.6.1 Graphic method 61 20.6.2 Processes for implementing remineralization: chemical reactions in tanks 62 20.7 Characteristics of the various reagents used 85 20.7.1 Lime 85 20.7.2 “Micronized” lime 86 20.7.3 Caustic soda 86 20.7.4 Caustic soda at 50% 87 20.7.5 Caustic soda flakes or grains 87 20.7.6 Sodium carbonate 88 20.7.7 Sodium bicarbonate 89 20.7.8 Calcium carbonate 89 20.7.9 Acticalmag limestone 90 20.7.10 Magno 90 20.7.11 Calcium sulfate 91 20.7.12 Calcium chloride 92 20.7.13 Carbon dioxide 92 20.7.14 Sulfuric acid (90–98%) 93 20.7.15 Hydrochloric acid 94 20.8 References 96 Chapter 21 Disinfection 99 21.1 Microorganisms present in the water 99 21.1.1 Bacteria 99 21.1.2 Indicator microorganisms or test germs 102 21.1.3 Viruses 104 21.1.4 Parasites 105 21.1.5 Micro-algae 107 21.2 Quality of potable water 108 21.2.1 French regulations 108 21.3 General rules of chemical disinfection 110 21.3.1 Disinfection mechanisms 110 21.3.2 The mode of action of chemical disinfectants 111 21.3.3 Inactivation kinetics 112 21.3.4 The notion of Ct 113 21.4 Factors affecting the efficiency of chemical disinfection 117 21.4.1 Contact time 117 21.4.2 Turbidity 118 21.4.3 Presence of oxidizable matter 118 21.4.4 pH 119 21.4.5 Injection mode and injection point 119 21.4.6 Design of the contact tank 119 21.5 Qualities of a good disinfectant 120 21.6 Chlorine disinfection 121 21.6.1 Gaseous chlorine 122 21.6.2 Hypochlorite 124 21.6.3 Chlorine application points 128 21.6.4 Oxidant demand 132 21.6.5 The implementation of chlorination 137 21.6.6 Disinfection performances with chlorine 146 21.6.7 Synthesis of chlorine reactions 148 21.7 Calcium hypochlorite 149 21.8 Chlorine dioxide disinfection 150 21.8.1 Chlorine dioxide preparation 151 21.8.2 Chlorine dioxide performances 155 21.8.3 Dechlorination 157 21.8.4 The advantages of dioxide over chlorine 159 21.8.5 The special case of the use of chlorine dioxide at a station equipped with ozone 160 21.8.6 Advantages and drawbacks of using chlorine dioxide 160 21.9 Chloramination 161 21.9.1 Principle 161 21.9.2 Implementation 163 21.9.3 Performances of monochloramine 164 21.9.4 Dechloramination 165 21.9.5 Advantages and drawbacks of chloramination 166 21.10 Proportion of chlorine in chlorine disinfectants 167 21.11 Disinfection with ozone 168 21.11.1 General remarks on ozone 168 21.11.2 Ozone production 170 21.11.3 Ozone demand 172 21.11.4 The implementation of ozonation 174 21.11.5 Performances of ozone disinfection 181 21.11.6 De-ozonation 183 21.12 Criteria for choosing a chemical disinfection technique 184 21.12.1 Practical implementation of chemical disinfection 184 21.12.2 Comparative efficiency of the main techniques 185 21.13 Another chemical disinfectant used: bromine (Br 2) 187 21.14 Disinfection by ultraviolet radiation 187 21.14.1 General remarks on UV radiation 187 21.14.2 Inactivation mechanisms 189 21.14.3 Lethal dose and inactivation kinetics 190 21.14.4 Implementation 194 21.14.5 UV disinfection design parameters 199 21.14.6 Factors affecting the efficiency of a UV treatment 200 21.14.7 UV radiation performances 204 21.14.8 Photoreactivation 208 21.14.9 Advantages and drawbacks of UV disinfection 209 21.14.10 Conclusions on UV disinfection 209 21.15. Comparative criteria between the various chemical disinfectants 210 21.16 References 212 Chapter 22 Disinfection By-products 217 22.1 General aspects 217 22.2 Reaction by-products 218 22.3 Formation and evolution of chlorination by-products 222 22.4 Kinetics and formation mechanisms 224 22.4.1 Formation kinetics 224 22.4.2 Mechanisms 226 22.4.3 Chlorination of HS 228 22.4.4 Chlorination of carboxylic acids 230 22.4.5 Factors influencing the formation of DBPs 230 22.5 Regulations 238 22.6 Predictive models of CBPs 239 22.7 Removal of THMs and HAAs 240 22.7.1 Aeration 240 22.7.2 Activated carbon 242 22.7.3 Biofiltration 246 22.7.4 High-pressure membranes 246 22.8 The case of nitrosamines and NDMA 247 22.8.1 Nitrosation mechanism with HOCl 247 22.9 Oxidation by-products related to chlorine dioxide 248 22.10 Ozonation by-products 251 22.11 Recommendations 254 22.12 References 255 Chapter 23 Sludge Treatment 261 23.1 Choosing a treatment chain 262 23.2 Characteristics of drinking water sludge 263 23.2.1 The quantity of sludge produced 263 23.2.2 Sludge concentration estimate at different stages of the chain 265 23.2.3 Sludge quality: physical and chemical properties 266 23.3 Handling and storage: shovelable and stackable nature 268 23.4 Different classes of sludge 269 23.4.1 Hydroxide sludge 269 23.4.2 Softening sludge 269 23.4.3 Metal species sludge treatment 270 23.4.4 Biological sludge 270 23.4.5 The case of mixed sludge 270 23.5 Sludge composition depending on the characteristics of raw water 271 23.5.1 Surface water sludge 271 23.5.2 Treatment sludge with coagulants (Fe or Al) 272 23.5.3 Borehole sludge 272 23.6 Thickening of drinking water sludge 273 23.6.1 Function and criteria for choosing a thickener 273 23.6.2 Thickener design 275 23.6.3 Implementation of thickeners 281 23.6.4 Flotation 286 23.7 Drinking water sludge dewatering 288 23.7.1 Plate filter 288 23.7.2 Centrifugation 291 23.7.3 Belt filters 294 23.7.4 Filter bags 295 23.7.5 Drying beds 296 23.7.6 Sludge lagoon treatment 302 23.8 Advantages and drawbacks of the different sludge dewatering treatments 304 23.9 References 305 Chapter 24 The Treatment Chain: Conception and Design 307 24.1 The treatment chain 309 24.2 The definition of a treatment chain 310 24.3 The stages of a treatment chain 313 24.4 The renovation of water treatment plants 315 24.4.1 Adaptation of new goals 316 24.4.2 The choice of treatment technologies 317 24.5 References 324 Chapter 25 The Future of Water 327 25.1 The major elements of the future of water 327 25.2 Will there be enough water? 330 Index 333 Summaries of other volumes 335