Physicochemical treatment processes

Contents Preface ............................................................................................................................ v Contributors................................................................................................................. xix 1 Screening and Comminution Frank J. DeLuise, Lawrence K. Wang, Shoou-Yuh Chang, and Yung-Tse Hung....................................................................................... 1 1. Function of Screens and Comminutors ....................................................................................................... 1 2. Types of Screens .......................................................................................................................................... 2 2.1. Coarse Screens ................................................................................................................................... 2 2.2. Fine Screens ....................................................................................................................................... 2 3. Physical Characteristics and Hydraulic Considerations of Screens .......................................................... 3 4. Cleaning Methods for Screens ..................................................................................................................... 5 5. Quality and Disposal for Screens ................................................................................................................ 6 6. Comminutors ............................................................................................................................................... 7 7. Engineering Specifications and Experience ................................................................................................ 8 7.1. Professional Association Specifications ............................................................................................ 8 7.2. Engineering Experience .................................................................................................................... 11 8. Engineering Design ................................................................................................................................... 12 8.1. Summary of Screening Design Considerations ............................................................................... 12 8.2. Summary of Comminution Design Considerations ........................................................................ 14 9. Design Examples ....................................................................................................................................... 15 9.1. Example 1: Bar Screen Design ......................................................................................................... 15 9.2. Example 2: Bar Screen Head Loss ................................................................................................... 16 9.3. Example 3: Plugged Bar Screen Head Loss .................................................................................... 17 9.4. Example 4: Screen System Design .................................................................................................. 17 Nomenclature ................................................................................................................................................... 18 References ........................................................................................................................................................ 18 2 Flow Equalization and Neutralization Ramesh K. Goel, Joseph R. V. Flora, and J. Paul Chen............................... 21 1. Introduction ................................................................................................................................................ 21 2. Flow Equalization ...................................................................................................................................... 21 2.1. Flow Equalization Basin Calculations ............................................................................................. 23 2.2. Mixing and Aeration Requirements ................................................................................................. 25 2.3. Mixer Unit ........................................................................................................................................ 26 3. Neutralization ............................................................................................................................................ 28 3.1. pH...................................................................................................................................................... 28 3.2. Acidity and Alkalinity ...................................................................................................................... 29 3.3. Buffer Capacity ................................................................................................................................ 30 3.4. Hardness ........................................................................................................................................... 31 4. Neutralization Practices ............................................................................................................................. 32 4.1. Neutralization of Acidity .................................................................................................................. 32 4.2. Neutralization of Alkalinity ............................................................................................................. 33 4.3. Common Neutralization Treatments ................................................................................................ 34 5. pH Neutralization Practices ....................................................................................................................... 36 5.1. Passive Neutralization ...................................................................................................................... 36 5.2. In-Plant Neutralization ..................................................................................................................... 36 5.3. Influent pH Neutralization ................................................................................................................ 36 5.4. In-Process Neutralization ................................................................................................................. 37 5.5. Effluent Neutralization ..................................................................................................................... 38 5.6. Chemicals for Neutralization ........................................................................................................... 38 5.7. Encapsulated Phosphate Buffers for In Situ Bioremediation ......................................................... 39 6. Design of a Neutralization System ............................................................................................................ 39 7. Design Examples ....................................................................................................................................... 40 Nomenclature ................................................................................................................................................... 43 References ........................................................................................................................................................ 44 3 Mixing J. Paul Chen, Frederick B. Higgins, Shoou-Yuh Chang, and Yung-Tse Hung..................................................................................... 47 1. Introduction ................................................................................................................................................ 47 2. Basic Concepts .......................................................................................................................................... 48 2.1. Criteria for Mixing ............................................................................................................................ 50 2.2. Mixing Efficiency ............................................................................................................................. 52 2.3. Fluid Shear ....................................................................................................................................... 54 3. Mixing Processes and Equipment .............................................................................................................. 55 3.1. Mixing in Turbulent Fields ............................................................................................................... 55 3.2. Mechanical Mixing Equipment ........................................................................................................ 58 3.3. Impeller Discharge ............................................................................................................................ 69 3.4. Motionless Mixers ............................................................................................................................ 71 3.5. Mixing in Batch and Continuous Flow Systems ............................................................................. 73 3.6. Suspension of Solids ......................................................................................................................... 77 3.7. Static Mixer ...................................................................................................................................... 84 4. Design of Facilities .................................................................................................................................... 86 4.1. Pipes, Ducts, and Channels .............................................................................................................. 86 4.2. Self-Induced and Baffled Basins ...................................................................................................... 89 4.3. Mechanically Mixed Systems .......................................................................................................... 90 Nomenclature ................................................................................................................................................... 99 References ...................................................................................................................................................... 100 4 Coagulation and Flocculation Nazih K. Shammas ......................................................................................... 103 1. Introduction .............................................................................................................................................. 103 2. Applications of Coagulation .................................................................................................................... 104 2.1. Water Treatment ............................................................................................................................. 104 2.2. Municipal Wastewater Treatment .................................................................................................. 104 2.3. Industrial Waste Treatment ............................................................................................................ 104 2.4. Combined Sewer Overflow ............................................................................................................ 104 2.5. Factors to be Considered in Process Selection .............................................................................. 105 3. Properties of Colloidal Systems .............................................................................................................. 105 3.1. Electrokinetic Properties ................................................................................................................ 105 3.2. Hydration ........................................................................................................................................ 106 3.3. Brownian Movement ...................................................................................................................... 106 3.4. Tyndall Effect ................................................................................................................................. 106 3.5. Filterability ..................................................................................................................................... 107 4. Colloidal Structure and Stability ............................................................................................................. 107 5. Destabilization of Colloids ...................................................................................................................... 109 5.1. Double-Layer Compression ............................................................................................................ 110 5.2. Adsorption and Charge Neutralization .......................................................................................... 110 5.3. Entrapment of Particles in Precipitate ........................................................................................... 111 5.4. Adsorption and Bridging between Particles .................................................................................. 111 6. Influencing Factors .................................................................................................................................. 112 6.1. Colloid Concentration ..................................................................................................................... 112 6.2. Coagulant Dosage ........................................................................................................................... 112 6.3. Zeta Potential ................................................................................................................................. 112 6.4. Affinity of Colloids for Water ........................................................................................................ 113 6.5. pH Value ......................................................................................................................................... 113 6.6. Anions in Solution .......................................................................................................................... 114 x Contents 6.7. Cations in Solution .......................................................................................................................... 114 6.8. Temperature ................................................................................................................................... 114 7. Coagulants ............................................................................................................................................... 114 7.1. Aluminum Salts ............................................................................................................................... 115 7.2. Iron Salts ......................................................................................................................................... 116 7.3. Sodium Aluminate .......................................................................................................................... 116 7.4. Polymeric Inorganic Salts ............................................................................................................... 117 7.5. Organic Polymers ............................................................................................................................ 117 7.6. Coagulation Aids ............................................................................................................................. 118 8. Coagulation Control ................................................................................................................................ 118 8.1. Jar Test ............................................................................................................................................ 119 8.2. Zetameter ........................................................................................................................................ 120 8.3. Streaming Current Detector ............................................................................................................ 121 9. Chemical Feeding .................................................................................................................................... 121 10. Mixing ...................................................................................................................................................... 122 11. Rapid Mix ................................................................................................................................................ 124 12. Flocculation ............................................................................................................................................. 125 13. Design Examples ..................................................................................................................................... 127 Nomenclature ........................................................................................................................................... 137 References ................................................................................................................................................ 138 5 Chemical Precipitation Lawrence K. Wang, David A. Vaccari, Yan Li, and Nazih K. Shammas ... 141 1. Introduction .............................................................................................................................................. 141 2. Process Description ................................................................................................................................. 142 3. Process Types .......................................................................................................................................... 142 3.1. Hydroxide Precipitation .................................................................................................................. 142 3.2. Sulfide Precipitation ....................................................................................................................... 144 3.3. Cyanide Precipitation ...................................................................................................................... 145 3.4. Carbonate Precipitation .................................................................................................................. 145 3.5. Coprecipitation ............................................................................................................................... 146 3.6. Technology Status ........................................................................................................................... 146 4. Chemical Precipitation Principles ........................................................................................................... 146 4.1. Reaction Equilibria ......................................................................................................................... 146 4.2. Solubility Equilibria ........................................................................................................................ 147 4.3. Ionic Strength and Activity ............................................................................................................ 148 4.4. Ionic Strength Example .................................................................................................................. 149 4.5. Common Ion Effect ......................................................................................................................... 150 4.6. Common Ion Effect Example ......................................................................................................... 150 4.7. Soluble Complex Formation ........................................................................................................... 151 4.8. pH Effect ........................................................................................................................................ 152 4.9. Solubility Diagrams ........................................................................................................................ 152 5. Chemical Precipitation Kinetics .............................................................................................................. 152 5.1. Nucleation ...................................................................................................................................... 153 5.2. Crystal Growth ............................................................................................................................... 153 5.3. Aging .............................................................................................................................................. 154 5.4. Adsorption and Coprecipitation ..................................................................................................... 154 6. Design Considerations ............................................................................................................................. 155 6.1. General ........................................................................................................................................... 155 6.2. Chemical Handling ......................................................................................................................... 155 6.3. Mixing, Flocculation, and Contact Equipment ............................................................................. 156 6.4. Solids Separation ............................................................................................................................ 157 6.5. Design Criteria Summary ............................................................................................................... 157 7. Process Applications ............................................................................................................................... 158 7.1. Hydroxide Precipitation .................................................................................................................. 158 7.2. Carbonate Precipitation .................................................................................................................. 159 7.3. Sulfide Precipitation ....................................................................................................................... 160 7.4. Cyanide Precipitation ...................................................................................................................... 161 7.5. Magnesium Oxide Precipitation ..................................................................................................... 162 Contents xi 7.6. Chemical Oxidation–Reduction Precipitation ............................................................................... 162 7.7. Lime/Soda-Ash Softening .............................................................................................................. 162 7.8. Phosphorus Precipitation ................................................................................................................ 162 7.9. Other Chemical Precipitation Processes ........................................................................................ 163 8. Process Evaluation .................................................................................................................................. 163 8.1. Advantages and Limitations ........................................................................................................... 163 8.2. Reliability ....................................................................................................................................... 164 8.3. Chemicals Required ........................................................................................................................ 165 8.4. Residuals Generated ....................................................................................................................... 165 8.5. Process Performance ....................................................................................................................... 165 9. Application Examples .............................................................................................................................. 165 Nomenclature ................................................................................................................................................. 169 References ...................................................................................................................................................... 170 Appendices ..................................................................................................................................................... 174 6 Recarbonation and Softening Lawrence K. Wang, Jy S. Wu, Nazih K. Shammas, and David A. Vaccari ................................................................................. 199 1. Introduction .............................................................................................................................................. 199 2. Process Description ................................................................................................................................. 199 3. Softening and Recarbonation Process Chemistry ................................................................................... 201 4. Lime/Soda Ash Softening Process .......................................................................................................... 203 5. Water Stabilization .................................................................................................................................. 205 6. Other Related Process Applications ........................................................................................................ 206 6.1. Chemical Coagulation Using Magnesium Carbonate as a Coagulant .......................................... 206 6.2. Recovery of Magnesium as Magnesium Carbonate ...................................................................... 207 6.3. Recovery of Calcium Carbonate as Lime ...................................................................................... 207 6.4. Recarbonation of Chemically Treated Wastewaters ..................................................................... 208 7. Process Design ......................................................................................................................................... 208 7.1. Sources of Carbon Dioxide ............................................................................................................ 208 7.2. Distribution Systems ....................................................................................................................... 210 7.3. Carbon Dioxide Quantities ............................................................................................................. 212 7.4. Step-by-Step Design Approach ...................................................................................................... 212 8. Design and Application Examples .......................................................................................................... 215 Nomenclature ................................................................................................................................................. 226 Acknowledgments ......................................................................................................................................... 227 References ...................................................................................................................................................... 227 7 Chemical Oxidation Nazih K. Shammas, John Y. Yang, Pao-Chiang Yuan, and Yung-Tse Hung................................................................................... 229 1. Introduction .............................................................................................................................................. 229 1.1. Dissolved Oxygen and Concept of Oxidation ............................................................................... 230 1.2. The Definition of Oxidation State .................................................................................................. 231 2. Theory and Principles .............................................................................................................................. 233 2.1. Stoichiometry of Oxidation–Reduction Processes ........................................................................ 234 2.2. Thermodynamics of Chemical Oxidation ...................................................................................... 236 2.3. Kinetic Aspects of Chemical Oxidation ........................................................................................ 240 3. Oxygenated Reagent Systems .................................................................................................................. 243 3.1. Aeration in Water Purification and Waste Treatment ................................................................... 243 3.2. Hydrogen Peroxide and Peroxygen Reagents ............................................................................... 246 3.3. High-Temperature Wet Oxidation ................................................................................................. 248 4. Transition-Metal Ion Oxidation Systems ................................................................................................ 256 4.1. Chromic Acid Oxidation ................................................................................................................ 256 4.2. Permanganate Oxidation ................................................................................................................. 258 5. Recent Developments in Chemical Oxidation ........................................................................................ 261 5.1. Ozone (O3) Processes ..................................................................................................................... 261 5.2. Ultraviolet (UV) Processes ............................................................................................................. 262 5.3. Wet Oxidation ................................................................................................................................ 263 xii Contents 5.4. Supercritical Water Oxidation ........................................................................................................ 264 5.5. Biological Oxidation ....................................................................................................................... 264 6. Examples .................................................................................................................................................. 264 Nomenclature ................................................................................................................................................. 268 References ...................................................................................................................................................... 269 8 Halogenation and Disinfection Lawrence K. Wang, Pao-Chiang Yuan, and Yung-Tse Hung .................... 271 1. Introduction .............................................................................................................................................. 271 2. Chemistry of Halogenation ...................................................................................................................... 274 2.1. Chlorine Hydrolysis ........................................................................................................................ 274 2.2. Chlorine Dissociation .......