Anaerobic Sewage Treatment: Optimization of process and physical design of anaerobic and complementary processes

Cover
Copyright
Contents
Preface
Authors
Acknowledgements
Symbols and Abbreviations
Contents in Brief
Chapter 1: Sewage characteristics and treatment systems
	1.1 Introduction
	1.2 Impact of Inadequate Sewage Treatment
	1.3 Effluent Standards and Treatment Objectives
	1.4 Sewage Treatment Systems
		1.4.1 Preliminary treatment
		1.4.2 Primary treatment
		1.4.3 Secondary treatment
		1.4.4 Tertiary treatment
	1.5 Sewage Characteristics
		1.5.1 Flow rate
		1.5.2 Measurement of organic material
	1.6 Comparison of Measurement Parameters
Chapter 2: Organic material & bacterial metabolism
	2.1 Bacterial Metabolism
		2.1.1 Anabolism
		2.1.2 Oxidative catabolism
		2.1.3 Fermentative catabolism or anaerobic digestion
	2.2 Conversion Processes in Biological Treatment
		2.2.1 Conversions in aerobic systems
		2.2.2 Conversions in anaerobic systems
	2.3 Anaerobic Digestion of Organic Material
		2.3.1 Hydrolysis
		2.3.2 Acidogenesis
		2.3.3 Acetogenesis
		2.3.4 Methanogenesis
		2.3.5 Thermodynamic considerations
	2.4 Competing Processes
	2.5 Influence of Environmental Factors
		2.5.1 Temperature
		2.5.2 pH in the reactor
		2.5.3 Toxic compounds and inhibitors
		2.5.4 Nutrients
	2.6 Mass Balance of Organic Material
Chapter 3: Anaerobic sewage treatment systems: process design and performance
	3.1 Introduction
	3.2 Classic Anaerobic Treatment Systems
		3.2.1 The septic tank
		3.2.2 The anaerobic lagoon
	3.3 Modern Anaerobic Treatment Systems
		3.3.1 The anaerobic contact process (ACP)
		3.3.2 The anaerobic filter (AF)
		3.3.3 Fluidized and expanded bed (FB, EB)
		3.3.4 The upflow anaerobic sludge blanket reactor (UASB)
		3.3.5 The anaerobic reactor with a fluidized sludge bed: (RALF)
		3.3.6 Comparison of treatment systems
	3.4 Properties of UASB Sludge
		3.4.1 Sludge composition
		3.4.2 Biological sludge properties
		3.4.3 Sludge settleability
	3.5 Start-Up of UASB Reactors Treating Sewage
		3.5.1 Start-up without seed sludge
		3.5.2 Start-up procedures with seed sludge
	3.6 Steady-State Behaviour
		3.6.1 Effect of the feed COD concentration
		3.6.2 Performance in terms of organic material removal
		3.6.3 Volumetric loading rate
		3.6.4 Sludge concentration profile
		3.6.5 Specific sludge production
		3.6.6 Specific organic sludge loading rate
		3.6.7 Floating solids
	3.7 Presence of Sulphate in Municipal Sewage
	3.8 Influence of UASB Operation
		3.8.1 Parallel versus series operation of UASB reactors
		3.8.2 Excess sludge discharge strategy
		3.8.3 Settleable solids return from the anaerobic effluent into the reactor
	3.9 Key Process Design Parameters for UASB Reactor Performance
		3.9.1 Influence of the GLS separator design quality on UASB performance
		3.9.2 Empirical model for UASB performance based on sludge age
		3.9.3 Temperature influence on the empirical model
	3.10 Process Design Procedure using the Anaerobic Sludge Age
	3.11 Productive Use of the Heating Potential from the Biogas
Chapter 4: UASB reactor design guidelines
	4.1 Introduction
	4.2 Construction Aspects Affecting UASB Performance
		4.2.1 Design and engineering issues
		4.2.2 Operational and maintenance issues
		4.2.3 Undeliverable expectations of UASB performance
	4.3 Design Aspects of the UASB Reactor
		4.3.1 Reactor dimensions
		4.3.2 Gas–Liquid–Solid (GLS) separator
		4.3.3 Biogas deflector
		4.3.4 Influent distribution system
		4.3.5 Effluent collection system
		4.3.6 Sludge sampling and discharge
		4.3.7 Scum removal
		4.3.8 Biogas collection
		4.3.9 Reactor cover and ventilation
	4.4 Reactor Design Procedure
	4.5 Anaerobic Reactor with External Settler
	4.6 Small-Scale UASB Designs
		4.6.1 UASBb with two bi-phase separators
		4.6.2 UASBc with conical three-phase separator
		4.6.3 Geometry of the three phase separator UASBr
Chapter 5: Value and stability of the pH in anaerobic digesters
	5.1 Introduction
	5.2 Weak Acid–Base Systems
	5.3 Buffer Index
	5.4 The Carbonic System
		5.4.1 Alkalinity
		5.4.2 Acidity
		5.4.3 Ionic equilibrium
		5.4.4 Measuring alkalinity
	5.5 Reactor pH and Alkalinity Demand
		5.5.1 Mass balance of inorganic carbon and methane
		5.5.2 pH calculation in buffered wastewaters
		5.5.3 Alkalinity demand in wastewaters without enough buffer capacity
	5.6 Phase Equilibria in Anaerobic Digesters
		5.6.1 Liquid–gas equilibrium
		5.6.2 Liquid–solid equilibrium
Chapter 6: Biogas generation in anaerobic digesters
	6.1 Introduction
	6.2 Solubility of Gases
	6.3 Biogas Production
		6.3.1 Methane production potential
		6.3.2 Carbon dioxide
		6.3.3 Water vapour
		6.3.4 Nitrogen
		6.3.5 Oxygen
		6.3.6 Ammonium
		6.3.7 Hydrogen sulphide
	6.4 Calculation Procedure for Biogas Production and Composition
		6.4.1 Low sulphate concentration
		6.4.2 High sulphate concentration
	6.5 Treatment of Sulphide Produced in Anaerobic Digesters
		6.5.1 Sulphide in biogas
		6.5.2 Sulphide removal from the effluent
		6.5.3 Hydrogen sulphide in the air used for odour collection
	6.6 Biogas Collection
	6.7 Generation of Electrical Energy from Biogas
	6.8 Greenhouse Gas Emissions and Carbon Footprint
	6.9 Loss of Methane in the Effluent
Chapter 7: Dewatering, Dehydration and drying of sludge
	7.1 Introduction
	7.2 Sludge Production and Composition
	7.3 Mechanical Sludge Dehydration
		7.3.1 Belt filter press
		7.3.2 Decanter centrifuges
		7.3.3 Filter press
	7.4 Natural Sludge Drying
		7.4.1 Types of sludge drying beds
		7.4.2 Experimental determination of required percolation and evaporation time of open sludge drying beds
		7.4.3 Determination of time required for evaporation in covered beds
		7.4.4 Determination of time required for evaporation in open beds with sludge tilling
		7.4.5 Design and optimization of drying beds
	7.5 Influence of Rainfall on Drying Bed Productivity
	7.6 Thermal Sludge Drying and Incineration
Chapter 8: Aerobic post-treatment of anaerobic effluents
	8.1 Introduction
	8.2 Types of Aerobic Treatment
		8.2.1 Activated sludge systems (AS)
		8.2.2 Biofilter (BF)
		8.2.3 Submerged aerobic filter (SAF)
	8.3 Modelling of Aerobic Post-Treatment
		8.3.1 Steady-state AS model applied to aerobic post-treatment
		8.3.2 Validation of the steady-state model for digested sewage
		8.3.3 Modelling the sequential batch reactor (SBR)
		8.3.4 Optimization procedure for aerobic post-treatment
	8.4 Integration of the Combined Anaerobic–Aerobic Treatment System
		8.4.1 Potential for reduction of total treatment volume
		8.4.2 Feasibility of energy self-sufficiency
		8.4.3 Potential for reduced sludge production
		8.4.4 Feasibility of aerobic sludge stabilization in the anaerobic reactor
	8.5 Nutrient Removal after Anaerobic Pre-Treatment
		8.5.1 Nitrogen removal from effluent with low content of organic material
		8.5.2 Phosphorus removal from effluent with low content of organic material
Chapter 9: Post-treatment of digested sewage in polishing ponds
	9.1 Introduction
	9.2 Post-Treatment in Polishing Ponds
	9.3 Pathogen Removal in Polishing Ponds
		9.3.1 Kinetics of thermotolerant bacteria decay
		9.3.2 Decay of thermotolerant bacteria in sequential batch ponds
	9.4 Transfer Ponds
	9.5 Factors that Influence the value of the Decay Constant
	9.6 Organic Material and Suspended Solids Removal in Polishing Ponds
	9.7 pH Variation and Nitrogen Removal in Ponds
		9.7.1 Carbon dioxide removal
		9.7.2 Ammonium removal
		9.7.3 Model of the kinetics of CO2 and NH3 removal by desorption
		9.7.4 Experimental determination of the desorption constants for CO2 and NH3
		9.7.5 Model for pH in sequential batch polishing ponds
	9.8 Phosphorus Removal in Polishing Ponds
	9.9 Applicability of Polishing Ponds
		9.9.1 Pre-treatment
		9.9.2 Complementary treatment
Chapter 10: Spreadsheet design of anaerobic and complementary treatment plants
	10.1 Design of the UASB Reactor for Sewage Treatment
	10.2 Design of the Biphasic UASB Reactor (UASBb)
	10.3 Design of the UASB Reactor with Conical Separator (UASBc)
	10.4 Design of the Conventional Reactor (UASBr) Including the Complementary Treatment Units
		10.4.1 Block 1: Wastewater characterization
		10.4.2 Block 2: Applied organic load and calculation of the anaerobic digestion efficiency
		10.4.3 Block 3: Dimensioning of the UASB reactor and phase separator elements
		10.4.4 Block 4: Design verification (lines 83–97, Table 10.10)
		10.4.5 Block 5: Special devices in the UASB reactor (Lines 98–145, Table 10.11)
		10.4.6 Block 6: Flow and composition of the generated biogas (lines 146–166, Table 10.12)
		10.4.7 Block 7: Design of sludge drying beds
		10.4.8 Block 8: Post-treatment of anaerobic effluent in polishing lagoons
		10.4.9 Block 9: Post-treatment in the activated sludge system in SBR configuration
	10.5 Application Examples
Appendix A1: Anaerobic biodegradability, specific methanogenic activity and sludge stability
Appendix A2: Sludge settleability
References