Waste sites as biological reactors : characterization and modeling

Where and how wastes disappear, and how the environment is affected by the process, are issues that affect cities and towns around the world. Recent investigations have convincingly shown that waste poses water, air, and public health dangers that necessitate highly efficient engineered controls. An inexpensive, effective, method for assessing impacts and risks of a system and devising management plans is to develop mathematical and quantitative models that are sufficiently representative to allow examination of physical systems as units subject to environmental factors.

Providing detailed coverage of the biological, chemical, and physical characteristics of solid waste sites, Waste Sites as Biological Reactors: Characterization and Modeling describes the parameters required to understand, model, and assess the capacity of a waste disposal site as an open biodegradation system. The authors present original analyses of waste and reactor kinetics, decomposition, temperature, and moisture effects, and heat properties. They discuss landfill gas and leachate chemicals generation with detailed composition and property data. Tables and figures provide easy access to the information, and the authors explore various site management options.

The simplicity, ugliness, and beauty of a waste disposal site confronts us with a microcosm of nature at its most basic, yet functioning in its most elegant form. Where and how wastes disappear and how the environment is affected are issues of concern to cities and towns around the world. Waste Sites as Biological Reactors: Characterization and Modeling deconstructs the mystery of the waste site in such a way that it can be modeled using familiar tools and the information obtained can then be applied to site remediation.

Chapter 1 Introduction	p. 1
The Nature and Control of Waste Disposal Sites	p. 1
The Bioreactor Concept	p. 3
Reactor Configurations of Relevance to Practical Description of a Waste Site	p. 4
The Waste Site as a Biological Reactor	p. 8
Chapter 2 Physical Characteristics of Waste Sites	p. 13
Waste Site Biological Reactor Concepts	p. 13
Basic Physical Characteristics of Solid Media	p. 13
Determination of Mean Particle Size	p. 14
Particle Size Distribution Approaches to Finding Mean Size of Porous Media	p. 14
Grain Size Statistics vs. Age of Wastes	p. 20
Packed Bed Porosity, Hydraulic Conductivity and Permeability	p. 20
Porosity of a Waste Site	p. 21
An Approach to Determining Porosity of A Packed Bed of Mixed Particle Types	p. 23
Density and Other Properties of Mixed Soil and Waste Materials	p. 25
Applicability of Conductivity and Permeability Relations for Packed Beds	p. 25
Permeability k of a Mixed Porous Media	p. 30
Permeability (k) Correction for Packed Bed Flow	p. 32
Correction of Packed Column Pressure Drop for Wall Effects	p. 35
Corrections for Pressure Drop Relations for Fluid Flow through a Waste Site	p. 38
Waste Site Particle Properties: Size and Shape	p. 38
Characterization of Surface Area and Related Physical Properties of Wastes	p. 44
Specific Surface Areas of Solid Materials From Liquid or Gas Sorption Isotherms	p. 44
Equivalence Between BET and GAB Water Adsorption Models	p. 50
Areas from Nitrogen, Vapor Adsorption vs. Moisture Sorption	p. 50
Relationship between Water Activity and Other Moisture Characteristic Terms	p. 51
Range of Adsorption in Solid Materials and Water Availability to Organisms	p. 51
Determination of Solid Structure Characteristics from Adsorption Data	p. 54
Example	p. 56
The Relation between Specific Surface Area and Sphericity of Waste Particles	p. 57
Example	p. 65
Particle Shape Considerations	p. 66
Application to Mixtures of Granular Materials	p. 70
Application of Particle-based Properties to the Kinetic Modeling of Reactors	p. 71
Chapter 3 Characterization of Disposed Wastes: Physical and Chemical Properties and Biodegradation Factors	p. 73
Determination of Physical and Chemical Characteristics of Wastes	p. 73
MSW Composition vs. Landfill Layer Depth or Age: Data for Initialization	p. 74
Individual Wastes and Characteristics	p. 75
Characteristics of Paper Wastes	p. 75
Characteristics of Food Wastes	p. 77
Characteristics of Yard Wastes	p. 78
Characteristics of Plastics Wastes	p. 79
Plastics Deterioration in Waste Sites	p. 83
Chemical Deterioration of Plastics	p. 85
Biological Deterioration of Plastics	p. 85
Effect of Physical Structure of Plastic on Degradability	p. 86
Organisms Involved in Plastics Biodegradation	p. 86
Variation of Degradation with Plastic Type	p. 87
Effect of Plastics Biodegradability Test Method on Published Results	p. 88
Effect of Air or Oxygen Content on Plastics Degradation	p. 90
Plastics Deterioration Rates	p. 91
Landfill Leachate and Landfill Gas Characteristics	p. 91
Landfill Leachate	p. 94
Leachate Organics	p. 95
Leachate BOD/COD Ratio as an Indicator of Biological Treatability	p. 96
Hazardous or Toxic Compounds in Waste Site Leachates	p. 97
Chapter 4 Waste Site Ecology	p. 101
Influence of the Waste Site Environment on Types of Organisms Present	p. 102
Species Competition for Food at a Waste Site	p. 103
The Range of Organisms at Waste Sites	p. 104
Organisms Found in Compost Piles	p. 104
Trophic Relations and Environmental Factors Determining Organisms at Waste Sites	p. 106
Influence of Site Environmental Factors on Organism Types	p. 113
The Waste Site as an Environment for Organisms	p. 114
Definition of Impact of Organisms at Disposed Waste Site	p. 117
Organisms Reported at Landfills, Dumps and Other Waste Sites: Considerations	p. 118
Waste Site Scavengers	p. 119
Bears	p. 122
Other Large Animals at Waste Sites	p. 123
Small Animals	p. 123
Waste Removal Impact of Animals at Disposal Sites	p. 124
Birds	p. 127
Waste Removal by Insects and Soil Mesofauna	p. 130
Impact of Worms and Nematodes	p. 131
Springtails (Collembola)	p. 134
Waste Site Microorganisms: Fungi, Yeast and Bacteria	p. 137
Soil Fungi	p. 137
Landfill Bacteria	p. 141
Summary	p. 141
Chapter 5 Moisture and Heat Flows	p. 143
Moisture as a Control of Processes in the Waste Site	p. 143
Water Film Thickness on Solid Materials under Sorption Regime	p. 145
Method I for Liquid Film Thickness Determination	p. 147
Correction of Errors in Calculation of t by Method I	p. 148
Method II for Moisture Film Thickness	p. 149
Water Potential vs. Water Activity of Soils and Solid Porous Materials	p. 149
The Issue of Mixed Water Saturation or Varied Water Potential in Wastes	p. 153
Maximum Moisture Sorption by a Material	p. 154
Effect of Waste Moisture Content on Soil Organisms	p. 156
Water Availability to Organisms	p. 160
Hydraulic Conductivity	p. 161
Capillary Effects in Waste Sites	p. 163
Theory	p. 164
Waste Site Moisture Retention Characteristics	p. 166
Full Range Moisture Capillarity	p. 167
Middle Moisture Content Range	p. 168
Moist to Saturation or Wet Moisture Content Section of Curve	p. 169
Moisture Retention Curve in the Dry Range for Landfilled Waste	p. 169
Boundary Conditions	p. 170
Estimation of Constants Full-Range (Wet to Dry) Moisture Capillarity Relations	p. 170
Reliability of Estimated Values	p. 173
Relevance of the Lower Curve Junction to Bioreactor Simulation	p. 173
Development of Moisture Capillarity-Hydraulic Conductivity Relationships	p. 175
Dry Range Logarithmic Curve Section, for [theta subscript j] [greater than or equal] [theta] [greater than or equal] 0	p. 175
Medium Moisture Range, Power Law Curve, for [theta subscript i] [greater than or equal] [theta] [greater than or equal] [theta subscript j]	p. 176
Saturated-to-Mid Range (Parabolic) Curve, [theta subscript i] [greater than or equal] [theta] [greater than or equal] [theta subscript j]	p. 177
Summary of Extended Range Conductivity Relationships	p. 178
Moisture Inflow and Moisture Balance	p. 179
Locations Used for Landfill Cover Moisture Impact Simulations	p. 179
Microorganism Rate vs. Water Content and Water Activity	p. 180
Limitations of Applying Water Potential Concepts	p. 182
Models of Water Content vs. Water Potential	p. 182
Limitations of Models of Water Retention vs. Humidity	p. 183
Discussion	p. 186
Chapter 6 Heat Generation and Transport	p. 189
Introduction	p. 189
The Heat Model	p. 191
Viscous Energy Dissipation	p. 191
Definition of Waste Site System Heat Capacity	p. 192
Heat Content of System: Landfill Gas or Air as Saturating Fluid	p. 194
The Volumetric Heat Generation Term q'''	p. 195
Heat Impact of Moisture Uptake and Flows	p. 195
Heat Effect of Moisture Evaporation	p. 197
Evaporation Enhancement Due to Thermal Gradient in Pore Structure	p. 198
Temperature vs. Water Vapor Diffusion, Latent Heat and Density Variation	p. 200
Water Vapor Diffusion	p. 200
Latent Heat of Vaporization	p. 201
Water Vapor Density Variation	p. 201
Other Data for Evaluating D[subscript A], [xi] and [characters not reproducible] [subscript rho v]/[characters not reproducible]T VS. Temperature (T)	p. 202
Definitions of Waste Site System Tortuosity	p. 203
Tortuosity as a Function of Particle Flatness	p. 204
Tortuosity as a Function of Particle Surface Properties	p. 208
Energy Balance at Atmospheric Boundary of Bioreactor	p. 209
Net Solar Radiation	p. 210
Effect of Surface Albedo	p. 212
Incoming Longwave Radiation	p. 212
Outgoing Longwave Radiation	p. 214
Latent Heat Flow of a Bioreactor System	p. 214
Temperature Variation with Depth	p. 215
Sensible Heat Flow from the Bioreactor System	p. 215
Development of the Heat Generation Model	p. 215
Solution to the Heat Equation	p. 216
Heat Equation	p. 216
Temperature at the Waste Site Surface	p. 218
Variables of the Heat Generation Model	p. 223
Landfill Thermal Conductivity K[subscript m]	p. 223
Thermal Conductivity and Diffusivity Values	p. 224
Estimating the Mean Thermal Conductivity of Mixed Waste Materials	p. 224
Chapter 7 The Kinetics of Decomposition of Wastes	p. 229
Introduction	p. 229
Anaerobic and Aerobic Decomposition Patterns	p. 229
Anaerobic Decomposition	p. 230
The Anaerobic Decomposition Process	p. 231
Waste Hydrolysis by Soil Organisms	p. 231
Determination of the Hydrolysis Rates of Organic Solid Materials	p. 232
Practical Forms of the Hydrolysis Relationship	p. 233
Anaerobic and Aerobic Regimes and Lag Time	p. 234
Hydrolysis Products in Anaerobic Decomposition	p. 235
Hydrolysis Products Use for Aciodgenic Biomass Growth and Acid Generation	p. 237
Acid Production in Anaerobic Operation	p. 238
Acetic Acid Generation	p. 238
Methane Generation	p. 239
Carbon Dioxide (CO[subscript 2]) Generation	p. 239
Total GAS Output	p. 240
Gas in Management Scenarios	p. 241
Decomposition PROCESS Sensitivity to pH	p. 242
Improvement of Reactor Liquid Phase pH	p. 242
Approaches to Incorporating the Effect of pH on Decomposition Kinetics	p. 244
Ion Concentration Inhibition	p. 244
Mechanistic Models of pH Effect	p. 245
Models for Effect of Product Inhibition and Incorporating pH Effect	p. 246
Assumptions for Mass Balance Model for Anaerobic Decomposition	p. 248
Leachate or Gas Recycle as Anaerobic Bioreactor Options	p. 249
The Kinetics of Aerobic Decomposition at a Waste Site	p. 249
Aerobic Hydrolysis	p. 250
The Change from Anaerobic to Aerobic Regimes	p. 251
Lag Time for Aerobic Reactor Decomposition	p. 251
Aerobic Hydrolysis Product Generation, Incorporation and Use	p. 253
Use of Hydrolysis Products for Growth of Acidogenic Biomass and Acid Formation	p. 253
Basic Relations for Oxygen-Limited Growth	p. 253
Oxygen as a Limiting Substrate in Aerobic Kinetics	p. 254
Oxygen Solubility in Water or Liquid	p. 257
Oxygen Transport Considerations	p. 259
The Oxygen Consumption Term R(O)	p. 259
Change of Oxygen Concentration with Waste Site Depth	p. 260
Oxygen Transport and Consumption in a Column Waste Site Reactor	p. 260
Diffusivity Coefficients for Liquid and Gas Solutes	p. 264
Practical Waste Site Parameters for Diffusion	p. 264
A Stoichiometric Approach to Decomposition	p. 266
The Stoichiometry of Decomposition of Wastes	p. 267
Development of a General Stoichiometric Relationship	p. 268
The Dependence of the Stoichiometric Relationship on f[subscript s] and Yield Factor Y[subscript x/s]	p. 269
Reactor Considerations for f[subscript s]	p. 270
Definition of Residence Time t[subscript s]	p. 272
The Fraction of Substrate Energy Stored in the Biomass	p. 274
Accuracy of the Value of [gamma subscript b]	p. 274
The Energy Expression	p. 276
Other Discussions of the Yield Term Y[subscript ave,e] for the Energy Expression	p. 277
Cell Mass Yield Factor Y[subscript X/S] from Chemical Oxygen Demand (cod)	p. 278
Yield Estimation from Oxygen Consumption	p. 279
The Value of Y[subscript X/O]	p. 279
Use of f[subscript s] Values to Estimate Water Production from Aerobic Decomposition	p. 281
CO[subscript 2] Produced, O[subscript 2] Required and Heat Produced During Aerobic Decomposition	p. 282
The Stoichiometry of Anaerobic Decomposition of Solid Wastes	p. 283
Water Consumption During Anaerobic Decomposition Process	p. 284
Carbon Dioxide, Methane and Hydrogen Sulfide from Anaerobic Decomposition	p. 284
Methane Production from Stoichiometric Anaerobic Decomposition	p. 284
Hydrogen Sulfide Production	p. 284
Stoichiometric Heat Production During the Anaerobic Decomposition Reaction	p. 285
Values of Decomposition Kinetic Constants	p. 286
Chapter 8 Decomposition Issues	p. 291
Introduction	p. 291
Waste Site Models Of Previous Waste Site Studies	p. 291
Landfill Soil Sampling Studies	p. 297
Organics vs. Landfill Depth	p. 297
Landfill Soil Microorganism Studies	p. 298
Mass Transfer Considerations	p. 304
Sherwood Number	p. 305
Application of Transport Model to Gas Flux	p. 308
Gas-Liquid Transfers	p. 308
Mass Flux	p. 309
Removal of Chemical in Liquid Film	p. 310
Application of Transport Model to Gas Chemicals Flux	p. 311
Biodegradation Rates for Waste Site Organic Chemicals	p. 312
Partitioning Between Gas and Liquid	p. 312
Waste Site Settlement	p. 313
Chapter 9 Sensitivity Analysis and Conclusions	p. 321
Introduction	p. 321
Information in Database for MSW Fractions as Substrate	p. 322
Range of Anaerobic and Hydrolysis Rates	p. 323
Chemical Characterization of Waste Fractions	p. 323
Moisture Sorption Factors for Municipal Waste Materials	p. 324
Moisture Response of Materials to the Environment	p. 325
Testing Approach	p. 327
Other Properties Estimated for the Database	p. 328
Constants for Aerobic and Anaerobic Decomposition	p. 328
Soil Moisture Content	p. 329
Moisture Inflow Effect of Cover	p. 329
Temperature as a Decomposition Factor	p. 329
Biofiltration Effect	p. 330
Settlement Effect	p. 330
Discussion	p. 330
Moisture Input	p. 331
Conclusions	p. 331
Recommendations	p. 332
Appendix 1 Waste Properties	p. 333
Appendix 2 Landfill Gas Properties	p. 347
References	p. 355
Index	p. 367

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