ENERGY CONSERVATION IN WATER AND WASTEWATER TREATMENT FACILITIES. WEF Manual of Practice No. 32. Prepared by the Energy.

Transcription

1 ENERGY CONSERVATION IN WATER AND WASTEWATER TREATMENT FACILITIES WEF Manual of Practice No. 32 Prepared by the Energy Conservation in Water and Wastewater Treatment Facilities Task Force of the Water Environment Federation WEF Press Water Environment Federation Alexandria, Virginia Mc Grauu Hill New York Chicago San Francisco Lisbon London Madrid Mexico City Milan New Delhi San Juan Seoul Singapore Sydney Toronto

2 Preface List of Figures List of Tables xxiii xxvii xxix Chapter 1 Energy Efficiency INTRODUCTION ROLE OF MANAGEMENT Monitoring Resources ENERGY AND POWER CLIMATE CHANGE Water Environment Federation Resolution on Climate Change Greenhouse Gas Overview Sources of Greenhouse Gas Emissions Computing Greenhouse Gas Emissions IDENTIFYING ENERGY CONSERVATION MEASURES RANKING AND IMPLEMENTATION OF ENERGY CONSERVATION MEASURES CASE STUDIES California Energy Commission Gloversville-Johnstown Joint Wastewater Treatment Facility REFERENCES SUGGESTED READINGS 17 vii

3 viii Contents Chapter 2 Utility Billing Procedures and Incentives INTRODUCTION COST-SAVING OPPORTUNITIES Obtain, the Most Favorable Tariff Install High-Efficiency Transformers Shave Peak Demand and Transfer Loads Improve the Power Factor Install High-Efficiency Motors ELECTRICITY Billing Charges Customer Energy Demand Power Factor Adjustment Miscellaneous Charges and Surcharges Fuel-Cost Adjustment Regulatory Fees State and Local Taxes Transmission Voltage Standby Service Nonfirm Power Supply Other Rate Structures Flat Demand Rate Flat Energy Rate Incentives to "Load Shift" and "Peak Shave" Electric Service Options Alternative Energy Sources Cogeneration Facilities SAMPLE ELECTRIC BILLS NATURAL GAS BILLING Rate Structures Unbundled Utility Service 32

4 ix Transportation Pipeline Direct Rates Gas Transportation Agreement Seasonal Pricing Incentive Computing Thermal Consumption UTILITY RATE AND SERVICE OPTIONS 36 Chapter 3 Electric Motors and Transformers THE NEED FOR EFFICIENT MOTOR DESIGN Motors as Part of a System Components of Common Motors MEASUREMENT OF ELECTRICAL CHARACTERISTICS Voltage Amperage Power Factor Resistance and Insulation Power Slip OPERATING POWER Service Factor TYPES OF ELECTRIC MOTORS Three-Phase Motors Squirrel Cage Wound Rotor Synchronous Motors Single-Phase Induction Motors Direct Current Motors CONVENTIONS FOR SPECIFYING MOTOR PERFORMANCE Definition of Efficiency Test Procedures MATCHING MOTORS TO LOAD 52

5 X Contents 7.0 STANDARDS FOR ENERGY-EFFICIENT MOTORS Energy Policy Act of Department of Energy Energy Efficiency and Renewable Energy Program U.S. Environmental Protection Agency Independent Energy Companies International Motor Standards National Electrical Manufacturers Association National Electrical Manufacturers Association Premium Motors Program Institute of Electrical and Electronic Engineers Test Standards for Energy-Efficient Motors Consortium for Energy Efficiency MotorMaster Motor Management Motor Records Motor Failure Motor Repairs Selection of a Motor Repair Facility Transformers REFERENCES ADDITIONAL RESOURCES 65 Chapter 4 Pumps PUMPING PRINCIPLES Pump Characteristic Curves Best Efficiency Point System Head Curve Operating Point Relationship of Best Efficiency Point and Operating Point ENERGY PRINCIPLES Pump Efficiency Energy Consumption 77

6 xi 2.3 Multiple Operating Points Measuring Pump System Efficiency Demand Charge REDUCING ENERGY USE AND COST DISCHARGE HEAD Measuring Pump Head System Head Friction Deterrriining Head Loss Low Flows Pipe Restrictions PRICE OF ENERGY PUMP EFFICIENCY DRIVE EFFICIENCY MOTOR EFFICIENCY LIFE CYCLE COSTING OPERATION AND MAINTENANCE PRACTICES FLOW METER CALIBRATION VERIFICATION REFERENCES SUGGESTED READINGS 98 Chapter 5 Variable Controls INTRODUCTION TYPES OF VARIABLE CONTROLS Indirect Control Control of the Driver Motors Engines Motor Control Adjustable-Speed Drives or Variable-Speed Drives Variable-Frequency Drives 205

7 xii Contents Low-Voltage Drives Medium-Voltage Drives Scalar Versus Vector Control Scalar Vector Motor Compatibility Other Technologies Harmonics Description Other Sources ofharmonics in Plants Effect on Efficiency Harmonics Mitigation Methods Motor-Bearing Damage Common-Mode Noise Speed Control Considerations for Pumps, Blowers, and Compressors BLOWERS AND COMPRESSORS OPTIMIZATION OF PUMP OPERATION Affinity Laws Drive Energy Savings Measurements REFERENCES 123 Chapter 6 Energy Use In Water Treatment Plants GENERAL OVERVIEW RAW WATER INTAKES RAW WATER PUMPING AND CONVEYANCE PRETREATMENT: COAGULATION, FLOCCULATION, AND SEDIMENTATION Flash Mix Flocculation Sedimentation High-Rate Clarification Dissolved Air Floatation 136

8 xiii 5.0 TASTE AND ODOR CONTROL Air Stripping Ozone FILTRATION Gravity Filtration Membrane Filtration Low-Pressure Membrane Filtration (Micrqfiltration/Ultrafittration) Low-Pressure Reverse Osmosis and Nanofiltration (Brackish Water Desalination) DISINFECTION Chlorine Gas Bulk Sodium Hypochlorite On-Site Hypochlorite Generation Ultraviolet Systems HIGH-SERVICE PUMPING WATER PLANT RESIDUALS MANAGEMENT Gravity Thickeners Belt Filter Press Centrifuges Membrane Concentrate Disposal REFERENCES 158 Chapter 7 Energy Use in Wastewater Treatment Processes PRELIMINARY AND PRIMARY TREATMENT Screening Influent Wastewater Pumping Opportunitiesfor Energy Reduction Grit Removal PRIMARY TREATMENT Conventional Chemically Enhanced Primary Sludge Pumping 168

9 xiv Contents 3.0 SECONDARY TREATMENT Activated Sludge Processes Dissolved Oxygen Operating Levels Secondary Clarification Membrane Bioreactor Process Anoxic-Zone Mixing Fixed-Film Processes Online Instrumentation DISINFECTION Chlorination/Dechlorination Ultraviolet Disinfection ADVANCED WASTEWATER TREATMENT Granular Media Filtration Activated Carbon Adsorption Chemical Treatment Nutrient Removal Processes Side-Stream Nitrogen Removal Processes Post-Aeration MISCELLANEOUS ENERGY USES REFERENCES SUGGESTED READINGS 190 Chapter 8 Aeration Systems DETERMINING OXYGEN REQUIREMENTS Impact of Process Configuration, Nitrification, Denitrification, and Phosphorus Removal TYPES OF AERATION EQUIPMENT Surface Low-Speed Aerators High-Speed Aerators Aspirating Aerators Brush Aerators Disk Aerators 299

10 xv 2.2 Submerged Diffusers Coarse Bubble Fine Pore Sparger Turbines Submerged Aerator Mixers Static Tubes Jet Aerators U-Tube Aerators DESIGN CONSIDERATIONS Oxygen Transfer Efficiency Mixing Diffuser Flux Rate Alpha Beta System Costs OPERATIONAL CONSIDERATIONS Waste Loading Distribution Step-Feed/Complete-Mix Modes Mixed Liquor Dissolved Oxygen Process Monitoring and Control Dissolved Oxygen Management in Membrane Bioreactor Systems Fouling of Porous Diffusers Diffuser Cleaning Air-Side Fouling Liquid-Side Fouling DIFFUSED-AERATION CASE HISTORIES Batesville, Arkansas Beloit, Wisconsin Palmyra, Wisconsin MECHANICAL AERATION CONTROL Submergence Adjustment 221

11 xvi Contents 6.2 Speed Adjustment On-Time Adjustment Mechanical Aerator Maintenance and Troubleshooting REFERENCES SUGGESTED READINGS 225 Chapter 9 Blowers APPLICATION CONSIDERATIONS Effects of Compressibility Common Blower Types Blower Power Requirements Blower and System Curves Effect of Inlet Conditions Other Considerations POSITIVE-DISPLACEMENT BLOWERS Operating Principles Control Techniques Application Considerations Operating Limits MULTI-STAGE CENTRIFUGAL BLOWERS.'.,; 245 / 3.1 Operating Principles Control Techniques Application Considerations : Operating Limits SINGLE-STAGE CENTRIFUGAL BLOWERS Operating Principles Control Techniques Application Considerations Operating Limits BLOWER SYSTEM RETROFIT OPPORTUNITIES Automatic Controls Additional Energy Conservation Measures 256

12 xvii 6.0 REFERENCES 258 Chapter 10 Solids Processes INTRODUCTION Recycle Streams Energy-Saving Opportunities in the Treatment of Recycle Flows Process Removals Thickening Optimization ANAEROBIC DIGESTION PROCESSES Temperature Class A Anaerobic Digestion Staged Anaerobic Digestion Two-Phase Digestion Torpey Process Co-Digestion Processes Pretrearment of Sludge Gas Composition Energy Consumption in Conventional Digesters Digester Heating Requirements Energy Requirementsfor Sludge Heaters and Recirculation Pumping Mixing Energy Energy Recovery AEROBIC DIGESTION Energy-Saving Opportunities Autothermal Aerobic Digestion INCINERATION Feasibility of Incineration Air Emissions Process Stability Multiple-Hearth Furnace Fluidized-Bed Furnace Heat Requirements 288

13 xviii Contents Heat Losses Associated with Water Wastewater Solids Energy Autogenous Combustion Electrical Energy Use Energy Recovery DRYERS Purpose Energy Use REFERENCES 296 Chapter 11 Energy Management ENERGY MANAGEMENT PLAN OVERVIEW Energy Management Plan Energy Awareness Understanding Energy Use Available Energy Computer Modeling Tracking Utility Consumption and Costs Communicate Value of Energy Awareness ENERGY-EFFICIENT DESIGN Energy Consumption Minimization Understanding Your Energy Bill Design Approach to Acknowledge the Value of Energy Efficiency Energy Efficiency Education Life Cycle Cost Analysis Gather Data Treatment Process Sub-Metering Develop a Baseline Consumption for Your Facility Develop a Benchmark Consumption for Your Facility Data Trending Analyze Data Pump Systems Aeration Process Solids Handling Process 323

14 xix 2.6 Developing an Energy Management Plan Implementation Plan Modify Operations Peak Electric Demand Reduction Flow Equalization Wastewater Water Priority Load Shedding Demand-Side Management Communicate the Value of the Energy Management Plan BENEFICIAL USE OF RENEWABLES Biogas Wind Solar Biomass Hydro Turbines Fuel Cells ON-SITE ENGINE OR POWER UTILIZATION Engine-Driven Pump Power-Generating System Traditional 4.3 Power-Generating System Synchronized Transfer Scheme 326 Transfer Scheme Power-Generating System Parallel with Utility ON-SITE GENERATION OPTIONS Using Emergency Backup Generators for Peak Shaving Distributed Generation Installing Cogeneration Units Using Biogas, Sludge, and Other Byproducts of the Wastewater Treatment Process as Fuels Feasibility Evaluation Ranking ofproject Objectives Facility Factors Design Factors 331

15 aa? Economic Factors Operational Factors ^ Environmental Factors FINANCING APPROACHES Project Financing 33^ 6.2 Revenue Bonds 33^ 6.3 Conventional Bank Financing 33? 6.4 Lease Financing 33^ Direct Financing Lease Leveraged Lease 33S Operating Lease 33S Conditional Sale Lease Certificates of Participation Tax-Exempt Leases Sale-Leaseback Lease Financing Considerations Energy Services Contracting Utility Services Contracting Grants/Rebates Privatization Joint Ownership and/or Development Shared Savings PROFILE OF ENERGY REQUIREMENTS REFERENCES SUGGESTED READINGS 345 Appendix A Agencies and Organizations 347 Appendix B Equations for Converting from English Units to Metric Units 349

16 xxi Appendix C Estimates of Electricity Used in Wastewater Treatment 351 Appendix D Electricity Basics ALTERNATING CURRENT VOLTAGE VOLTAGE DROP 356 Index 359