Chapter 16 Physical and Chemical Processes for Advanced Wastewater Treatment 1.0 PROCESS SELECTION CONSIDERATIONS 16-6 2.0 SECONDARY EFFLUENT FILTRATION 16-6 2.1 Background 16-6 2.1.1 Goals 16-8 2.1.2 Applications 16-8 2.1.3 Process Flow Diagram 16-8 2.2 Design Considerations 16-9 2.2.1 Secondary Effluent Characteristics 16-9 2.2.2 Filtered Effluent Quality Characteristics 16-10 2.2.3 Filtration Removal Mechanisms 16-10 2.2.4 Filter Medium Properties 16-11 2.2.5 Backwash Requirements 16-11 2.2.6 Site Requirements 16-11 2.2.7 Hydraulic Requirements 16-12 2.2.8 Filter Controls and Appurtenances 16-12 2.2.9 Pretreatment/Use of Filtration (Chemical) Aids 16-13 2.2.10 Design Optimization 16-14 2.2.11 Protective Structures 16-15 2.2.12 Typical Design Deficiencies 16-15 2.3 Technology Types 16-16 2.3.1 Depth Filtration 16-17 2.3.1.1 Granular Media Filtration 16-17 2.3.1.2 Granular Media Selection and Characteristics 16-19 2.3.1.3 Granular Medium Filtration Technology Types 16-22 2.3.1.4 Compressible Medium Filtration 16-51 2.3.2 Disc Filtration 16-57 2.3.2.1 Fully Submerged Disc Filters 16-57 2.3.2.2 Partially Submerged Disc Filters 16-63 2.3.2.3 Other Emerging Disc Filters 16-66
3.0 ACTIVATED CARBON ADSORPTION 16-66 3.1 Process Description 16-67 3.2 Application 16-69 3.2.1 Tertiary Treatment 16-69 3.2.2 Chemical 16-71 3.3 Design Considerations 16-71 3.3.1 Wastewater Quality 16-71 3.3.2 Carbon Characteristics 16-72 3.3.3 Types of Carbon Adsorption Units 16-74 3.3.3.1 Upflow Columns 16-74 3.3.3.2 Downflow Columns 16-74 3.3.3.3 Fixed and Expanded Beds 16-75 3.3.3.4 Countercurrent Adsorption 16-75 3.3.4 Unit Sizing 16-75 3.3.5 Backwashing 16-77 3.3.6 Valve and Piping Requirements 16-78 3.3.7 Instrumentation 16-79 3.3.8 Control of Biological Activity 16-79 3.3.9 Carbon Transport 16-80 3.3.10 Carbon Regeneration 16-82 3.3.10.1 Carbon Dewatering 16-83 3.3.10.2 Regeneration Furnace 16-83 4.0 CHEMICAL TREATMENT 16-84 4.1 Phosphorus Precipitation 16-85 4.1.1 Phosphorus Removal Methods 16-86 4.1.2 Precipitants 16-86 4.1.2.1 Lime 16-86 4.1.2.2 Alum 16-90 4.1.2.3 Sodium Aluminate 16-92 4.1.2.4 Ferric Chloride 16-94 4.1.3 Solids Considerations 16-96 4.2 ph Adjustment 16-97 4.2.1 Neutralization of Acidity 16-98 4.2.1.1 Lime Alkalies 16-99 4.2.1.2 Sodium Alkalies 16-99 4.2.2 Neutralization of Alkalinity 16-103 4.2.2.1 Sulfuric Acid 16-104 4.2.2.2 Hydrochloric Acid 16-104
4.2.2.3 Acid System Design Considerations 16-105 4.3 Rapid Mixing 16-105 4.3.1 Impeller Mixers 16-105 4.3.1.1 Turbine Mixers 16-106 4.3.1.2 Propeller Mixers 16-106 4.3.2 Other Mixing Devices 16-107 4.3.3 Fluid Regimes 16-108 4.3.4 Design Considerations 16-109 4.3.4.1 Power Requirements 16-109 4.3.4.2 Laboratory Scale-Up 16-111 4.3.4.3 Batch and Continuous Systems 16-111 4.3.4.4 Hydraulic Retention Time 16-112 4.3.4.5 Vessel Geometry 16-112 4.3.4.6 High- and Low-Speed Mixers 16-112 4.3.4.7 Propeller and Turbine Mixers 16-112 4.3.4.8 Mixer Mounting 16-113 4.3.4.9 Top-Entering Turbines and Side-Entering Propeller Mixers 16-113 4.3.4.10 Single-Propeller and Multipropeller Mixers 16-113 4.3.5 Chemical Feed Systems 16-113 4.3.5.1 Dry Feed 16-116 4.3.5.2 Solution Feed 16-118 5.0 MEMBRANE PROCESSES 16-119 5.1 Process Description 16-119 5.1.1 Low-Pressure Membranes: Microfiltration and Ultrafiltration 16-120 5.1.2 High-Pressure Membranes: Nanofiltration and Reverse Osmosis 16-121 5.1.3 Electrical Current-Driven Membranes 16-124 5.1.4 Nanocomposite-Membrane Processes 16-126 5.1.5 Forward Osmosis 16-127 5.1.6 Membrane Bioreactor 16-128 5.1.7 Autotrophic Membrane-Biofilm Reactor (MBfR) 16-128 5.2 Process Objectives 16-129 5.3 Pretreatment 16-130 5.3.1 Scale Control 16-131 5.3.1.1 Acid Addition 16-131 5.3.1.2 Scale-Inhibitor Addition 16-132 5.3.1.3 Softening with a Strong Acid Cation Exchange Resin 16-132 5.3.1.4 Lime Softening 16-132
5.3.1.5 Preventive Cleaning 16-133 5.3.1.6 Adjusting Operating Variables 16-133 5.3.2 Colloidal Fouling Prevention 16-133 5.3.2.1 Media Filtration 16-134 5.3.2.2 Inline Filtration 16-134 5.3.2.3 Coagulation/Flocculation 16-134 5.3.2.4 Cross-Flow Microfiltration/Ultrafiltration 16-134 5.3.3 Biological Fouling Prevention 16-135 5.3.3.1 Chlorination 16-135 5.3.3.2 Dechlorination 16-136 5.3.3.3 Sodium Metabisulfite 16-136 5.3.3.4 Chloramination 16-136 5.3.3.5 Shock Treatment 16-136 5.3.3.6 Microfiltration/Ultrafiltration 16-137 5.3.3.7 Ozone 16-137 5.3.3.8 Ultraviolet Irradiation 16-137 5.3.3.9 Advanced Oxidation 16-137 5.4 Membrane Systems 16-137 5.5 Membrane Module Configuration 16-144 5.6 Membrane Separation by Microfiltration or Ultrafiltration 16-144 5.7 Reverse Osmosis 16-144 5.8 Reject/Brine Disposal Requirements 16-148 5.8.1 Disposal to Surface Water 16-149 5.8.2 Deep-Well Injection 16-149 5.8.3 Evaporation Ponds 16-149 5.8.4 Evaporation to Dryness and Crystallization 16-149 5.8.5 Local Brine Management (Brine Lines) 16-149 5.8.6 Blending with Other Streams 16-150 5.8.7 Brine Recovery Reverse Osmosis 16-150 6.0 AIR STRIPPING FOR AMMONIA REMOVAL 16-150 6.1 Process Description 16-150 6.2 Design Considerations 16-153 6.2.1 Tower Packing 16-153 6.2.2 Loading 16-154 6.2.3 Air-to-Water Ratio 16-154 6.2.4 Temperature 16-154 7.0 AMMONIA REMOVAL BY BREAKPOINT CHLORINATION 16-155 7.1 Process Theory 16-155
7.2 Design Considerations 16-157 8.0 EFFLUENT REOXYGENATION 16-158 8.1 Cascade Reoxygenation 16-159 8.2 Mechanical/Diffused Air Reoxygenation 16-160 8.3 Relationship to Other Unit Processes 16-161 8.4 References and Design Procedures 16-161 9.0 REFERENCES 16-161