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BIOFILM REACTORS
WEF Manual of Practice No. 35
Prepared by the Biofiltn Reactors Task Force of the
Water Environment Federation®
WEF Press
Water Environment Federation Alexandria, Virginia
McGrawHill
New York Chicago San Francisco Lisbon London Madrid
Mexico City Milan New Delhi San Juan Seoul
Singapore Sydney Toronto
Contents
List of Figures xxv
List of Tables xxxiii
Preface xxxvii
Chapter 1 Introduction
1.0 BACKGROUND AND PURPOSE 1
2.0 CHARACTERISTICS OF FIXED-GROWTH PROCESSES 2
3.0 HISTORY 3
3.1 Contact Beds 4
3.2 Trickling Filters 4
3.3 Rotating Biological Contactors 5
3.4 Coupled Trickling Filter/Activated Sludge Process 6
3.5 Biological Filters 7
3.6 Hybrid Processes 7
4.0 ORGANIZATION OF MANUAL 10
5.0 REFERENCES 11
6.0 SUGGESTED READINGS 14
Chapter 2 Biology of Fixed-Growth Process
1.0 INTRODUCTION 17
2.0 CLASSIFICATION OF LIVING ORGANISMS 18
3.0 MICROORGANISMS OTHER THAN BACTERIA 21
3.1 Fungi 22
3.2 Algae 22
3.3 Protozoa 23
3.4 Multicellular Invertebrates 23
vii
viii Contents
3.5 Viruses 24
3.6 Consortia 26
4.0 CHARACTERISTICS OF BACTERIA 26
4.1 Structure of the Bacterial Cell 26
4.2 Chromosome and Plasmids 28
4.3 Cytoplasm 30
4.4 Cell Membrane 30
4.5 Cell Wall 30
4.6 Pili 31
4.7 Flagella 31
4.8 Extracellular Polymeric Substances 31
4.9 Chemical Composition of Cells 32
4.10 Example 1—Theoretical Oxygen Demand of Bacterial Cells 32
4.20.1 Solution 32
4.10.2 Comment 33
5.0 BACTERIAL METABOLISM, NUTRITION, AND RESPIRATION ...
.33
5.1 Energy Source 36
5.2 Chemoheterotrophic Metabolism 36
5.3 Chemoautotrophic Metabolism 38
5.4 Photosynthetic Metabolism 39
5.5 Nutrient Requirements 40
5.6 Bacterial Energy Metabolism 41
5.7 Aerobic Growth and Respiration 42
5.8 Anoxic Conditions and Respiration 43
5.9 Anaerobic Respiration and Fermentative Metabolism 44
5.10 Energetics of Respiration 46
5.11 Example 2—Calculation of Electrode Reduction Potentials
and AG for Half-Reactions 48
5.12 Solution 48
5.13 Co-Metabolism 50
Contents ix
6.0 BACTERIAL GROWTH 51
6.1 The Bacterial Growth Curve 51
6.2 Growth in Mixed Cultures 53
6.3 Enrichment Cultures 53
6.4 Stability of Mixed Cultures 54
6.5 Effects of Environmental Variables 54
7.0 BACTERIAL GROWTH KINETICS IN BIOFILMS 55
7.1 Rate of Bacterial Processes 56
7.2 Note 56
7.3 Physical and Chemical Changes in Biofilms Resultingfrom Growth 59
7.4 Structured Models 59
7.5 Temperature Effects 60
7.6 Example 3—Effect of Temperature on Organic Removal 61
7.7 Solution 61
7.8 Inhibition and Toxicity 63
7.9 Mass-Transfer-Rate Limitations 64
8.0 KEY TRANSFORMATIONS IN BIOFILMS 65
8.1 Chemoheterotrophic Processes 66
8.2 Chemoautotrophic Processes 67
8.3 Biology of Nitrogen Transformations 67
8.4 Denitrification 67
8.5 Aerobic Nitrification 68
8.6 Anoxic Nitrification/Denitrification 69
8.7 Biological Phosphorus Removal 70
8.8 Sulfide and Sulfur Oxidation 71
8.9 Hydrogen Oxidation 71
9.0 FEATURES OF MICROBIAL COMMUNITIES IN BIOFILMS 72
10.0 REFERENCES 74
X Contents
Chapter 3 Trickling Filter and Combined TricklingFilter Suspended-Growth Process Designand Operation1.0 INTRODUCTION 83
2.0 GENERAL DESCRIPTION 84
2.1 Distribution System 84
2.2 Biofilm Carriers 87
2.3 Containment Structure 90
2.4 Underdrain System and Ventilation 90
2.5 Trickling Filter Pumping Stations: Influent and Recirculation 91
2.6 Hydraulic and Contaminant Loading 92
3.0 PROCESS FLOW SHEETS AND BIOREACTOR CONFIGURATION.. .93
3.1 Standard Process Flow Diagrams 93
3.2 Bioreactor Classification 96
3.3 Hydraulic Application: Effect on Media Wetting,Flow Distribution, and Control 98
4.0 VENTILATION AND AIR SUPPLY ALTERNATIVES 100
4.1 Natural Draft 101
4.2 Mechanical Ventilation 102
5.0 TRICKLING FILTER PROCESS MODELS 103
5.1 National Research Council 103
5.2 Galler and Gotaas 105
5.3 Kincannon and Stover 106
5.4 Velz 107
5.5 Schulze 107
5.6 Germain 108
5.7 Eckenfelder 109
5.8 Chartered Institution of Water and
Environmental Management 110
5.9 Logan Trickling Filter Model Ill
Contents xi
5.10 Selecting a Trickling Filter Model 112
5.11 Method for Combining Trickling Filter and
Suspended-Growth Models 113
6.0 PROCESS DESIGN 115
6.1 Combined Carbon Oxidation and Nitrification 115
6.2 Nitrifying Trickling Filters 120
6.2.1 Gujer and Boiler Nitrifying Trickling Filter Model 122
6.2.2 Okey and Albertson Nitrifying Trickling Filter Model 124
6.2.2.1 Application of the Gujer and Boiler Model 126
6.2.2.2 Application of the Albertson and Okey Model 128
6.3 Temperature and Hydraulic Application Effects 131
7.0 DESIGN CONSIDERATIONS 132
7.1 Distribution System 133
7,2.2 Hydraulic Drive Rotary Distributors 134
7.2.2 Electronic or Mechanical Drive Rotary Distributors 136
7.2.3 Optimizing Rotary Distributor Operation 138
7.2 Construction of Rotary Distributors 138
7.3 Trickling Filter Media Selection 139
7.3.2 Depth 141
7.3.2 Structural Integrity 142
7.4 Trickling Filter Pumping Station or Dosing Siphon 144
7.5 Control Mechanisms for Trickling Filter Macro Fauna 144
7.5.1 Operational Strategies and Facility Improvements for Macro Fauna Control.. 145
7.5.2 Spulkraft 147
7.5.3 Flooding 148
7.5.4 Chemical Treatment 149
7.5.5 Physical Control 152
7.6 Trickling Filter Startup 153
7.7 Combined Trickling Filter and Suspended-Growth Processes 155
7.7.2 Activated Biofilter 156
7.7.2 Trickling Filter/Solids Contact 158
xii Contents
7.7.3 Roughing FilterIActivated Sludge 162
7.7.4 Biofilter IActivated Sludge 162
7.7.5 Trickling Filter/Activated Sludge 162
8.0 REFERENCES 163
Chapter 4 Rotating Biological Contactors
1.0 INTRODUCTION 174
2.0 PROCESS DESIGN CONSIDERATIONS 178
2.1 Media Surface Area 179
2.2 pH and Nutrient Balance 180
2.3 Oxygen Transfer 180
2.4 Flow and Loading Variability 182
2.5 Operating Temperature 183
2.6 Solids Production 183
2.7 Toxic and Inhibitory Substances 184
3.0 ROTATING BIOLOGICAL CONTACTOR DESIGN METHODS 184
3.1 Monod Kinetic Model 184
3.2 Second-Order Model 186
3.3 Empirical Model 187
3.4 Manufacturers' Design Curves 189
3.5 Comparison of Model Predictions 190
3.6 Predicted Performance versus Full-Scale Data 191
3.7 Temperature Correction 192
4.0 ROTATING BIOLOGICAL CONTACTOR
NITRIFICATION MODELS 194
5.0 DENITRIFICATION APPLICATION 197
6.0 PHYSICAL DESIGN FEATURES 198
6.1 Physical Layout 198
6.2 Tank Volume 198
6.3 Hydraulics and Flow Control 198
6.4 Media 199
Contents
6.5 Drive Systems 200
6.6 Covers 201
6.7 Biomass Control 201
7.0 ROTATING BIOLOGICAL CONTACTOR DESIGN EXAMPLES... .202
7.1 Secondary Treatment Design Example 202
7.2 Advanced Secondary Treatment Design Example 203
8.0 PROBLEMS AND CORRECTIVE ACTIONS 204
8.1 Inadequate Treatment Capacity 205
8.2 Excessive First-Stage Loadings 205
8.3 Excessive Biomass Growth 206
8.4 Loping of Air-Drive Systems 206
8.5 High Clarifier Effluent Suspended Solids 207
8.6 Corrosion of Media Supports 207
9.0 PILOT-PLANT STUDIES 207
10.0 REFERENCES 208
Chapter 5 Moving-Bed Biofilm Reactors
1.0 INTRODUCTION 212
2.0 MOVING-BED REACTORS 213
3.0 DESIGN CONSIDERATIONS FOR MOVING-BED REACTORS 217
3.1 Carrier Biofilms 218
3.2.3 Carbonaceous Matter Removal 220
3.2.2 High-Rate Designs 220
3.2.3 Normal-Rate Designs 221
3.2.4 Low-Rate Designs 221
3.2.5 Nitrification 224
3.2.6 Denitrification 229
3.2.6.2 Pre-Denitrification Moving-Bed Biofilm Reactors 229
3.2.6.2 Post-Denitrification Moving-Bed Biofilm Reactors 230
3.2.6.3 Combined Pre-/Post-Denitrification Moving-Bed
Biofilm Reactors 230
xiv Contents
3.2 Mixers 231
3.3 Pretreatment 232
4.0 SOLIDS SEPARATION 233
5.0 GENERAL CONSIDERATIONS FOR MOVING-BED
BIOFILM REACTORS 234
5.1 Approach Velocity 234
5.2 Foaming 234
5.3 Media Transfer and Inventory Management 234
6.0 CASE STUDIES 235
6.1 Moa Point Wastewater Treatment Plant, Wellington,New Zealand 235
6.2 Harrisburg Wastewater Treatment Plant, Harrisburg,Pennsylvania 238
6.3 Moorhead Wastewater Treatment Facility, Moorhead,Minnesota (Adapted from Zimmerman et al., 2004) 240
6.4 Williams Monaco Wastewater Treatment Plant, Henderson,Colorado 241
6.5 Klagsham Wastewater Treatment Plant, Malmo, Sweden
(Adapted from Taljemark et al, 2004) 246
6.6 Gardemoen Wastewater Treatment Plant, Gardemoen, Norway 250
7.0 REFERENCES 253
Chapter 6 Hybrid Processes
1.0 OVERVIEW OF INTEGRATED FIXED-FILM
ACTIVATED SLUDGE SYSTEMS 260
1.1 Advantages 261
1.2 Disadvantages 262
2.0 MEDIA TYPES 262
2.1 Fixed-Media Systems 263
2.2 Free-Floating Media Systems 264
2.2.2 Plastic 264
2.2.2 Sponge 264
Contents xv
3.0 HISTORY OF PROCESS 265
4.0 APPLICATION OF INTEGRATED FIXED-FILM
ACTIVATED SLUDGE SYSTEMS 267
4.1 Fixed Media 267
4.2.2 General Requirements 267
4.2.2 Growth on Media 268
4.2.3 Kinetics 269
4.2.4 Worm Growth 270
4.2.5 Media Breakage 270
4.2.6 Dissolved Oxygen Level 270
4.2.7 Mixing 271
4.2.8 Access to Diffusers 271
4.2.9 Odor 271
4.2 Free-Floating Media—Sponge Media 272
4.2.1 General Requirements 272
4.2.2 Screen Clogging 272
4.3 Control of Biomass Growth 273
4.3.2 Loss of Sponges 273
4.3.2 Taking Tank Out-of-Service 274
4.3.3 Loss of Solids 274
4.3.4 Air Distribution System 274
4.3.5 Plastic Media 274
4.3.5.2 General Requirements 274
4.3.5.2 Biomass Growth 275
43.5.3 Media Mixing 276
4.3.5.4 Screens 276
4.3.5.5 Foaming 276
4.3.5.6 Media Replacement 276
4.3.5.7 Taking Tank Out-of-Service 276
4.3.5.8 Worm Growth 277
4.3.5.9 Startup 277
xvi Contents
5.0 PROCESS DESIGN 277
5.1 Introduction 277
5.2 Parameters Influencing Organics Removal in the Biofilm of
Integrated Fixed-Film Activated Sludge Systems 278
5.2.2 Biofilm Flux Rates 278
5.2.2 Removals in Biofilm per Unit of Tank Volume 278
5.3 Parameters Influencing Removals in the Mixed-LiquorSuspended Solids 281
5.4 Interaction Between the Mixed-Liquor Suspended Solids
and the Biofilm 282
5.5 Interaction Between Heterotrophs and Nitrifiers 284
5.6 Design Tools/Procedures 284
5.6.2 Empirical Methods 285
5.6.2.1 Equivalent-Sludge-Age Approach 285
5.6.2.2 Quantity (Length or Web Surface Area) ofMedia Approach 286
5.6.2 Rates Based on Pilot Studies 286
5.6.3 Biofilm Rate Model 287
5.6.3.2 Define Range ofFlux Rates 287
5.6.3.2 Quantify Removal at Different Mixed-Liquor SuspendedSolids Mean Cell Residence Times 287
5.6.3.3 Select Flux Rates Based on Location Along Aerobic Zone 287
5.6.3.4 Calculate the Quantity ofMedia Required 288
5.6.3.5 Additional Analysis to Finalize a Design 288
5.6.3.6 Application ofKinetics-Based Approach with IntegratedFixed-Film Activated Sludge Design Software 288
6.0 CASE STUDIES 288
6.1 Annapolis Water Reclamation Facility, Anne Arundel County,Maryland 288
6.2.2 Original Wastewater Treatment Plant 289
6.2.2 Pilot Study (1993 to 1996) 289
6.1.3 Full-Scale Upgrade for Biological Nutrient Removal (1997 to 2000) 291
6,1.3.2 Pilot Study 291
Contents xvii
6.1.3.2 During Construction (1997 to 2000) 293
6.1.3.3 Post-Construction (2000 to 2003) 299
6.2 Westerly Wastewater Treatment Plant, Westerly, Rhode Island 299
6.2.2 Introduction 299
6.2.2 Description of Original Facilities 299
6.2.3 Description of Upgrade 299
6.2.4 Design Criteria 302
6.2.5 Performance of the Integrated Fixed-Film Activated Sludge System 302
6.2.6 Operational Issues 306
6.2.7 Costs 307
6.3 Broomfield Wastewater Treatment Plant, Broomfield, Colorado ...307
6.3.2 Introduction 307
6.3.2 Full-Scale Plant Results 308
6.4 Colony Wastewater Treatment Plant, Colony, Texas 308
6.4.2 Introduction and Background 308
6.4.2 Changing Design Conditions 316
6.4.3 Plant Construction and Operation 318
6.4.4 System Flexibility 320
6.4.5 Redworm Predation 321
7.0 REFERENCES 321
Chapter 7 Biological Filters
1.0 INTRODUCTION 327
2.0 DESCRIPTIONS OF BIOLOGICALLY ACTIVE FILTER REACTORS
AND EQUIPMENT 329
2.1 Brief History of Biologically Active Filters 329
2.2 Downflow Biologically Active Filter with Sunken Media 331
2.3 Upflow Biologically Active Filter with Sunken Media 334
2.4 Upflow Biologically Active Filter with Floating Media 335
2.5 Moving-Bed, Continuous Backwash Filters 337
2.6 Non-Backwashing, Open-Structure Media Filters 339
xviii Contents
3.0 MEDIA FORUSE IN BIOLOGICALLY ACTIVE FILTERS 341
3.1 Mineral Media 341
3.2 Random Plastic Media 343
3.3 Modular Plastic Media 345
4.0 BACKWASHING AND AIR-SCOURING 345
5.0 BIOLOGICALLY ACTIVE FILTER PROCESS DESIGN 349
5.1 Process Design for Secondary Treatment 351
5.1.1 Volumetric Biochemical Oxygen Demand Loading 351
5.2.2 Hydraulic Loading 351
5.2.3 Backwashing 351
5.2.4 Design Example: Design of a Submerged, Upflow BiologicalAerated Filter System for Secondary Treatment (No Nitrification) 353
5.2.5 Solution 353
5.2 Process Design for Nitrification 355
5.2.1 Influence of Hydraulic Filtration Rates 355
5.2.2 Effect ofProcess Air Velocity 357
5.2.3 Dependence on Loading Conditions 359
5.2.4 Temperature Effects 360
5.2.5 Design Example: Design ofa Submerged, Upflow Biological Aerated
Filter System for Nitrification Following Secondary Treatment 360
5.2.6 Solution 361
5.3 Process Design for Combined Nitrification and Denitrification... 362
5.4 Process Design for Tertiary Denitrification 365
5.4.1 Volumetric Mass Loading 365
5.4.2 Half-Order Kinetic Model 367
5.4.3 Hydraulic Loading 368
5.4.4 Solids Removal and Sludge Production 368
5.4.5 Supplemental Carbon Requirements 369
5.4.6 Tertiary Denitrification Typical Operations Issues and
Corrective Actions 370
5.4.6.2 Excess Backwashing 370
5.4.6.2 Gas (Nitrogen) Accumulation 371
Contents xix
5.4.6.3 Solids Breakthrough 371
5.4.6.4 Nitrate/Nitrite Breakthrough 371
5.4.6.5 Carbon Breakthrough 372
5.4.6.6 Phosphorus Management 372
5.4.6.7 Operation During Peak Flow Events 372
5.5 Phosphorus Removal Considerations for Biologically Active
Filter Processes 373
6.0 DESIGN CONSIDERATIONS 374
6.1 Preliminary and Primary Treatment 374
6.2 Backwash Handling Facilities 374
6.3 Biologically Active Filter Process Aeration 375
6.3.1 Oxygen-Transfer Efficiency 375
6.3.2 Process Air Distribution Systems 377
6.3.3 Process Air Control 377
6.4 Supplemental Carbon Feed Requirements 378
7.0 BIOLOGICALLY ACTIVE FILTER CASE STUDIES 379
7.1 Chemically Enhanced Primary Treatment Followed by
Two-Stage Biologically Active Filter for Total NitrogenRemoval: VEAS Wastewater Treatment Plant, Oslo, Norway ....
379
7.2 Chemically Enhanced Primary Treatment Followed by Three-Stage
Biologically Active Filter for Total Nitrogen Removal: Siene Centre
Wastewater Treatment Plant, Colombes, France 381
7.3 Total Nitrogen Removal in a Single-Stage Biologically Active
Filter: Frederikshavn Wastewater Treatment Plant, Denmark ....
384
7.4 Nitrification and Denitrification: West Warwick,
Rhode Island 387
7.5 Post-Denitrification Sand Filters: Havelock, North Carolina 389
8.0 REFERENCES 391
Chapter 8 New and Emerging Fixed-Film Technologies
1.0 INTRODUCTION 401
2.0 BIOFILM REACTORS WITH SUSPENDED CARRIERS OR
GRANULES 402
XX Contents
2.1 Biofilm Airlift Suspension Reactor 402
2.2 Upflow Anaerobic Sludge Blanket 404
2.3 Expanded Granular Sludge Blanket 404
2.4 Internal Circulation Reactor 404
3.0 ANAMMOX BIOFILM REACTORS 405
4.0 MEMBRANE BIOFILM REACTORS 406
5.0 REFERENCES 408
Chapter 9 Clarification
1.0 INTRODUCTION 414
2.0 SOLIDS-SEPARATION CHOICES 416
3.0 DESIGN APPROACH 417
3.1 Types of Settling Regimes 418
3.1.1 Type I 419
3.1.2 Type II 419
3.1.3 Type III 419
3.1.4 Type IV 419
3.2 Special Considerations for Nutrient Removal Sludges 419
3.3 Clarifier Enhancements 420
3.4 Wastewater Flocculation 422
3.5 Flocculation Criteria 424
3.6 Clarifier Design Details 429
3.6.2 Influent Column 431
3.6.2 Energy-Dissipating Inlet 431
3.6.3 Feed Well (Flocculating Type) 433
3.6.4 Side Water Depth, Clear Water Zone, and Overflow Rate 435
3.6.5 Floor Slope 438
3.6.6 Effluent Weir and Launder 440
3.6.7 Sludge Collectors 443
3.6.8 Sludge Hopper 445
3.7 Rectangular versus Circular Clarifiers 445
Contents xxi
3.8 Design Example 446
3.9 Clarifier Following Moving-Bed Biofilm Reactor, TricklingFilter, Rotating Biological Contactor, and Biotower 448
3.9,2 Secondary (Integrated Fixed-Film Activated Sludge) Clarifiers 451
3.9.2 Sludge Hopper 454
3.9.3 Process Performance 455
3.10 Other Considerations 458
3.20.2 Modeling 458
3.20.2 Interaction with Other Facilities 458
3.20.3 International Practices 458
4.0 REFERENCES 459
Chapter 10 Effluent Filtration
1.0 INTRODUCTION 463
2.0 PROCESS PERFORMANCE 465
3.0 REFERENCES 469
Chapter 11 Development and Application of
Models for Integrated Fixed-Film Activated Sludge,Moving-Bed Biofilm Reactors, Biological Aerated
Filters, and Trickling Filters
1.0 INTRODUCTION 473
2.0 MODELING 478
2.1 Numerical Approach Using Semi-Empirical Equations for
Biofilm (Steady-State and Dynamic Simulation) 478
2.2.2 Ammonium-Nitrogen Uptake Rate 480
2.2.2.2 Ammonium-Nitrogen Uptake Rate by Nitrifiers in Biofilm 480
2.2.2.2 Biofilm Nitrification Rates from Pilot Studies 482
2.2.2.3 Ammonium-Nitrogen Uptake Rate by Nitrifiers in
Mixed-Liquor Volatile Suspended Solids 485
2.2.2.4 Mass Balance for Ammonium-Nitrogen in Each Reactor 490
2.2.2 Chemical Oxygen Demand Removal 494
xxii Contents
2.2.3 Biomass Production 499
2.1.3.1 Mixed-Liquor Volatile Suspended Solids 500
2.2.3.2 Biofilm 501
2.2.4 Fraction ofNitrifiers 502
2.2.5 Denitrification 503
2.2.6 Oxygen 504
2.2 Numerical Approach to Solve One- and Two-Dimensional Biofilm-
Diffusion Models (Steady-State and Dynamic Simulation) 504
2.2.2 Ammonium-Nitrogen 506
2.2.2 Linkage to Equations 11.1 to 11.42 Presented Earlier 508
2.2.3 Chemical Oxygen Demand, Biomass (Volatile and Total SuspendedSolids), Dissolved Oxygen, and NOx-N 510
2.2.4 Biofilm Thickness, Growth, and Fraction Nitrifiers 510
3.0 MODEL APPLICATIONS TO FULL-SCALE FACILITIES 512
3.1 Integrated Fixed-Film Activated Sludge Plant Descriptionand Modeling 513
3.2.2 Integrated Fixed-Film Activated Sludge Plant Description 514
3.2.2 Integrated Fixed-Film Activated Sludge Plant Operation 515
3.2.2.2 Data from December 2006 515
3.2.2.2 Flow and Recycle 515
3.1.2.2.1 Primary Effluent 515
3.1.2.2.2 Aerobic Cells 518
3.1.2.2.3 Secondary/Plant Effluent 518
3.1.2.2.4 Discussion of the Data 518
3.2.3 Modeling Integrated Fixed-Film Activated Sludge in Aquifas 518
3.1.3.1 Results from Aquifas 519
3.2.3.2 Key Inputs to Aquifas Biofilm One-Dimensional Model 526
3.1.3.3 Discussion ofAquifas Model and Accuracy ofResults 526
3.2.4 Modeling in BioWin 527
3.2.4.2 Framework 527
3.2.4.2 Results from BioWin 531
3.1.4.3 Discussion of Results from BioWin 531
Contents xxiii
3.2 Moving-Bed Biofilm Reactor Plant Description and Modeling. ...534
3.2.3 Moving-Bed Biofilm Reactor Modeling with GPS-X 537
3.2.2.1 Introduction 537
3.2.1.2 Example 542
3.2.2 Moving-Bed Biofilm Reactor Modeling with Aquifas 542
3.2.3 Moving-Bed Biofilm Reactor Modeling—General Comments 543
3.2.4 Integrated Fixed-Film Activated Sludge and Moving-Bed BiofilmReactor Modeling—General Observations 552
4.0 REFERENCES 553
INDEX 559
