Biofilm Reactor Technology and Design

Chapter 13 Biofilm Reactor Technology and Design 1.0 INTRODUCTION: BIOFILMS AND BIOFILM REACTORS IN MUNICIPAL WASTEWATER TREATMENT 13-5 1.1 Biofilm Reactor Compartments 13-8 1.2 Biofilm Processes, Structure, and Function 13-8 1.3 Bulk-Liquid Hydrodynamics 13-10 1.4 Biofilm Development and Detachment 13-12 2.0 BIOFILM REACTOR DESIGN APPROACHES, CONSIDERATIONS 13-15 2.1 Simplified Biofilm Reactor Design Approaches 13-16 2.1.1 Graphical Procedure 13-17 2.1.2 Empirical and Semi-Empirical Models 13-20 2.2 Mathematical Biofilm Models for the Practitioner 13-23 2.2.1 Why Should We Use Biofilm Models as a Design Tool? 13-23 2.2.2 Diffusion and Reaction in a One-Dimensional Biofilm: First- and Zero-Regions in Biofilm Reactors 13-25 2.2.3 Identifying the Rate-Limiting Substrate 13-29 2.2.4 Biofilm Models Used in Engineering Design 13-31 2.2.5 Limitations of Biofilm Models for the Practitioner 13-33 2.2.6 Wastewater Characterization 13-35 3.0 MOVING BED BIOFILM REACTORS 13-36 3.1 General Description 13-38 3.1.1 Plastic Biofilm Carriers 13-39 3.1.2 Media Retention Sieves 13-42 3.1.3 Aeration System 13-43 3.1.4 Mechanical Mixing Devices 13-44 3.2 Process Flow Sheets and Bioreactor Configurations 13-44 3.2.1 Carbon Oxidation 13-45 3.2.2 Nitrification 13-49 3.2.3 Denitrification 13-58 3.2.4 Phosphorus Limitations (Focus on Denitrification) 13-64 3.3 Design Considerations 13-66 3.3.1 Preliminary and Primary Treatment 13-66

3.3.2 Plastic Biofilm Carrier Media 13-66 3.3.3 Aeration System 13-68 3.3.4 Media Retention Sieves 13-70 3.3.5 Mechanical Mixing 13-71 3.3.6 Solids Separation 13-72 4.0 BIOLOGICALLY ACTIVE FILTERS 13-73 4.1 Biologically Activate Filter Configurations 13-74 4.1.1 Downflow with Sunken Media 13-77 4.1.2 Upflow with Sunken Media 13-79 4.1.3 Upflow Biologically Activate Filter with Floating Media 13-81 4.1.4 Moving Bed, Continuous Backwash Filters 13-82 4.1.5 Non-Backwashing, Open-Structure Media Filters 13-84 4.2 Media for Use in Biologically Activated Filter Reactors 13-87 4.3 Backwashing and Air Scouring 13-87 4.4 Biologically Activated Filter Process Design 13-88 4.4.1 Secondary Treatment 13-90 4.4.2 Nitrification 13-94 4.4.3 Combined Nitrification and Denitrification 13-97 4.4.4 Tertiary Denitrification 13-99 4.4.5 Phosphorus Removal Considerations 13-104 4.5 Facility Design Considerations for Biologically Activated Filter Plants 13-105 4.5.1 Preliminary and Primary Treatment 13-105 4.5.2 Backwash Handling Facilities 13-105 4.5.3 Process Aeration 13-106 4.5.4 Supplemental Carbon Feed Facilities 13-109 5.0 EXPANDED AND FLUIDIZED BED BIOFILM REACTORS 13-109 5.1 Fluidized Bed Biofilm Reactor Advantages and Disadvantages 13-112 5.2 Fluidized Bed Biofilm Reactor Technology Status 13-115 5.2.1 History 13-115 5.2.2 Installations 13-115 5.3 Process Design 13-116 5.3.1 Typical Design Parameters 13-116 5.3.1.1 Vertical Flow Velocity 13-116 5.3.1.2 Recirculation 13-117 5.3.1.3 Flow Distribution 13-118 5.3.2 Media 13-120 5.3.3 Biofilm Thickness Control 13-124 5.3.4 Aeration 13-125

5.4 Pilot Testing 13-126 5.5 Fluidized Bed Biofilm Reactor Design Models 13-128 5.6 Design Considerations 13-128 5.6.1 Nitrification 13-128 5.6.2 Tertiary Denitrification 13-129 5.7 Design Example for Denitrification 13-130 5.8 Performance of Fluidized Bed Biofilm Reactor Fauna 13-133 5.9 Process Performance 13-133 5.9.1 Nitrogen Removal Rate 13-133 5.9.2 Temperature 13-135 6.0 ROTATING BIOLOGICAL CONTACTORS 13-136 6.1 Introduction 13-136 6.2 Carbon Oxidation 13-137 6.2.1 Monod Kinetic Model 13-137 6.2.2 Second-Order Model 13-138 6.2.3 Empirical Model 13-138 6.3 Nitrification 13-139 6.4 Media and Media Support Shaft 13-139 6.5 Covers 13-140 6.6 Biofilm Thickness Control 13-140 7.0 TRICKLING FILTERS 13-141 7.1 General Description 13-141 7.1.1 Distribution System 13-142 7.1.2 Biofilm Carriers 13-143 7.1.3 Containment Structure 13-148 7.1.4 Underdrain System and Ventilation 13-148 7.1.5 Trickling Filter Pumping Station 13-149 7.1.6 Hydraulic and Pollutant Loading 13-150 7.2 Process Flow Sheets and Bioreactor Configuration 13-151 7.2.1 Process Flow Diagrams 13-151 7.2.2 Bioreactor Classification 13-153 7.2.3 Hydraulics 13-155 7.3 Oxygen Requirements and Air Supply Alternatives 13-157 7.3.1 Natural Draft 13-158 7.3.2 Forced Ventilation 13-159 7.4 Trickling Filter Design Models 13-160 7.4.1 National Research Council Formula 13-161 7.4.2 Galler and Gotaas Formula 13-163

7.4.3 Kincannon and Stover Model 13-165 7.4.4 Velz Equation 13-165 7.4.5 Schulze Formula 13-166 7.4.6 Germain Formula 13-167 7.4.7 Eckenfelder Formula 13-168 7.4.8 Institution of Water and Environmental Management Formula 13-169 7.4.9 Logan Trickling Filter Model 13-170 7.4.10 Selecting a Trickling Filter Design Model 13-171 7.5 Combined Carbon Oxidation and Nitrification 13-173 7.6 Nitrifying Trickling Filters 13-178 7.6.1 Kinetics and Design Procedures 13-180 7.6.2 Gujer and Boller Model 13-182 7.6.3 Modified Gujer and Boller Model 13-184 7.6.4 Albertson and Okey Model 13-184 7.6.5 Comparisons of NTF Models 13-186 7.6.6 Temperature Effects 13-186 7.6.7 Hydraulic Application 13-187 7.7 Design Considerations 13-188 7.7.1 Distribution System 13-189 7.7.2 Hydraulic Propelled Distributors 13-189 7.7.3 Electronic or Mechanically Driven Distributors 13-190 7.7.4 Other Means for Distributor Speed Control 13-192 7.7.5 Trickling Filter Pumping Station or Dosing Siphon 13-193 7.7.6 Construction of Rotary Distributors 13-193 7.7.7 Filter Media 13-194 7.7.7.1 Media Selection 13-194 7.7.7.2 Filter Media Depth 13-195 7.7.7.3 Structural Integrity 13-196 7.8 Design Examples 13-198 7.8.1 Example 13.1: Biofilter Design for Carbonaceous Biochemical Oxygen Demand Limitations 13-198 7.8.2 Example 13.2: Nitrifying Trickling Filter Design 13-200 7.8.3 Example 13.3: Organic and Hydraulic Loading 13-202 7.8.4 Example 13.4: Biofilter Classification and Distributor Adjustment 13-204 8.0 EMERGING BIOFILM REACTORS 13-205 8.1 Membrane Biofilm Reactors 13-206 8.1.1 Hydrogen-Based 13-207 8.1.2 Oxygen-Based 13-209

8.2 Suspended-Biofilm Reactors 13-210 8.2.1 Reactors Based on Aerobic Granules 13-210 8.2.2 Anammox Biofilm Reactors 13-211 8.2.3 Biofilm Airlift Reactors 13-212 8.2.4 Internal Circulation Reactor 13-213 9.0 REFERENCES 13-214