Page 13 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

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9.3.2.3 NOM Removal by Metal Coagulatants...................................................................... 197
9.3.2.4 Organics in Wastewaters ............................................................................................ 199
9.3.2.5 Coagulation of Synthetic Organics............................................................................. 199
9.4 Double Layer Theory .............................................................................................................................. 200
9.4.1 Double Layer Description .......................................................................................................... 200
9.4.1.1 Beginning.................................................................................................................... 200
9.4.1.2 Surface Charge............................................................................................................ 200
9.4.1.3 Gouy–Chapman Model............................................................................................... 200
9.4.1.4 Fixed Layer................................................................................................................. 200
9.4.1.5 Effect of Ionic Strength of Solution ........................................................................... 200
9.4.1.6 Electrostatic Potentials................................................................................................ 201
9.4.1.7 DLVO Theory............................................................................................................. 201
9.5 Trivalent Metal Ions: Reactions with Water ........................................................................................... 202
9.5.1 Aluminum and Ferric Ions ......................................................................................................... 203
9.5.1.1 Waters of Hydration ................................................................................................... 203
9.5.1.2 Expressing Concentrations.......................................................................................... 203
9.5.1.3 Liquid Alum................................................................................................................ 204
9.5.2 Alkalinity.................................................................................................................................... 204
9.5.2.1 Role of Alkalinity as a Buffer .................................................................................... 204
9.5.2.2 Effect of Alkalinity on Demand for Alum ................................................................. 204
9.5.2.3 Effect of Alum on pH................................................................................................. 204
9.5.3 Reactions between Alum=Ferric Iron and Water ....................................................................... 205
9.5.3.1 Beginning.................................................................................................................... 205
9.5.3.2 Sequential Hydrolysis Reactions ................................................................................ 205
9.5.3.3 Species Equilibrium.................................................................................................... 206
9.5.3.4 Coagulation Zones ...................................................................................................... 209
9.5.3.5 Spreadsheet Construction of Coagulation Diagrams.................................................. 209
9.5.3.6 Polynuclear Species .................................................................................................... 210
9.5.3.7 Summary of Alum Speciation .................................................................................... 210
9.6 Synthetic Aluminum Polymers................................................................................................................ 210
9.6.1 Characteristics of PACl .............................................................................................................. 210
9.6.1.1 Description of PACl ................................................................................................... 210
9.6.1.2 Electrophoretic Mobility: Comparing Alum and PACl.............................................. 210
9.7 Zeta Potential, Charge Density, and Streaming Current Potential.......................................................... 211
9.7.1 Basic Notions of Electrophoretic Mobility ................................................................................ 211
9.7.2 Mathematical Relations for Electrophoresis............................................................................... 211
9.7.2.1 Electrophoresis............................................................................................................ 211
9.7.2.2 Zeta Potential .............................................................................................................. 212
9.7.3 Measured Zeta Potentials ........................................................................................................... 214
9.7.3.1 Typical Zeta Potentials ............................................................................................... 214
9.7.4 Colloid Titration ......................................................................................................................... 215
9.7.5 Streaming Current Monitor ........................................................................................................ 215
9.8 Physical Models....................................................................................................................................... 216
9.8.1 Jar Tests...................................................................................................................................... 216
9.8.2 Bench Scale Filters..................................................................................................................... 217
9.8.3 Pilot Plants.................................................................................................................................. 218
9.8.3.1 Independent Variables ................................................................................................ 218
9.8.3.2 Dependent Variables................................................................................................... 218
9.8.3.3 Pilot Plant Design ....................................................................................................... 218
9.9 Polymers .................................................................................................................................................. 218
9.9.1 Definitions .................................................................................................................................. 218
9.9.2 Characteristics of Polymers........................................................................................................ 219
9.9.2.1 Charge Concentration ................................................................................................. 219
9.9.2.2 Specific Gravity .......................................................................................................... 219
9.9.3 Polymers in Wastewater Treatment............................................................................................ 219
9.9.3.1 Sludge Conditioning ................................................................................................... 219