United States Office of Water EPA-821 -R-13-002
Environmental Protection Washington, DC 20460 April 2013
Agency
&EPA Technical Development
Document for the Proposed
Effluent Limitations
Guidelines and Standards
for the Steam Electric Power
Generating Point Source
Category
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vvEPA
United States
Environmental Protection
Agency
Technical Development Document for the
Proposed Effluent Limitations Guidelines
and Standards for the Steam Electric
Power Generating Point Source Category
EPA-821-R-13-002
April 2013
U.S. Environmental Protection Agency
Office of Water (4303T)
Washington, DC 20460
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Acknowledgements and Disclaimer
This document was prepared by the Environmental Protection Agency. Neither the United States
Government nor any of its employees, contractors, subcontractors, or their employees make any
warrant, expressed or implied, or assume any legal liability or responsibility for any third party's
use of or the results of such use of any information, apparatus, product, or process discussed in
this report, or represents that its use by such party would not infringe on privately owned rights.
Questions regarding this document should be directed to:
U.S. EPA Engineering and Analysis Division (4303T)
1200 Pennsylvania Avenue NW
Washington, DC 20460
(202) 566-1000
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Table of Contents
TABLE OF CONTENTS
Page
SECTION 1 BACKGROUND 1-1
1.1 Legal Authority 1-1
1.2 Clean Water Act 1-1
1.2.1 Best Practicable Control Technology Currently Available (BPT) 1-3
1.2.2 Best Conventional Pollutant Control Technology (BCT) 1-3
1.2.3 Best Available Technology Economically Achievable (BAT) 1-3
1.2.4 New Source Performance Standards (NSPS) 1-4
1.2.5 Pretreatment Standards for Existing Sources (PSES) 1-4
1.2.6 Pretreatment Standards for New Sources (PSNS) 1-4
1.3 Regulatory History of the Steam Electric Power Generating Point Source
Category 1-5
1.3.1 Summary of Current ELGs Discharge Requirements and
Applicability 1-5
1.3.2 Detailed Study of the Steam Electric Power Generating Point Source
Category 1-8
1.3.3 Other Statutes and Regulatory Requirements Affecting Management
of Steam Electric Power Generating Wastewaters 1-9
SECTION 2 SUMMARY OF PROPOSED REGULATION 2-1
2.1 Summary of Proposed Revisions to Discharge Requirements 2-1
2.2 Revisions to Applicability Provision and Specialized Definitions 2-4
SECTION 3 DATA COLLECTION ACTIVITIES 3-1
3.1 Steam Electric Power Generating Detailed Study 3-1
3.2 Engineering Site Visits 3-2
3.3 Questionnaire for the Steam Electric Power Generating Effluent Guidelines 3-4
3.4 Field Sampling Program 3-7
3.4.1 On-Site Sampling Activities 3-8
3.4.2 CWA 308 Monitoring Program 3-14
3.5 EPA and State Sources 3-15
3.5.1 NPDES Permits and Fact Sheets 3-16
3.5.2 State Groups and Permitting Authorities 3-16
3.5.3 1974 and 1982 Technical Development Documents for the Steam
Electric Power Generating Point Source Category 3-16
3.5.4 CWA Section 316(b) - Cooling Water Intake Structures Supporting
Documentation and Data 3-17
3.5.5 Office of Air and Radiation 3-18
3.5.6 Office of Research and Development 3-18
3.5.7 Office of Solid Waste and Emergency Response 3-19
3.6 Industry-Submitted Data 3-19
3.6.1 Self-Monitoring Data 3-19
3.6.2 NPDES Form 2C 3-20
3.7 Technology Vendor Data 3-20
3.8 Other Sources 3-21
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TABLE OF CONTENTS (Continued)
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3.8.1 Utility Water Act Group 3-21
3.8.2 Electric Power Research Institute 3-21
3.8.3 Department of Energy (DOE) 3-22
3.8.4 Literature and Internet Searches 3-23
3.8.5 Environmental Groups and Other Stakeholders 3-23
3.9 Protection of Confidential Business Information 3-23
3.10 References 3-23
SECTION 4 STEAM ELECTRIC INDUSTRY DESCRIPTION 4-1
4.1 Overview of Electric Generating Industry 4-1
4.1.1 Electric Generating Industry Population 4-2
4.1.2 Applicability of Steam Electric Power Generating Effluent
Guidelines 4-3
4.2 Steam Electric Generating Industry 4-4
4.2.1 Steam Electric Generating Process 4-6
4.2.2 Combined Cycle Systems 4-7
4.2.3 Integrated Gasification Combined Cycle Systems 4-10
4.2.4 Demographics of the Steam Electric Power Generating Industry 4-12
4.3 Steam Electric Wastestreams Evaluated for New or Additional Controls in
the Proposed ELGs 4-19
4.3.1 Fly Ash Transport Water 4-19
4.3.2 Bottom Ash Transport Water 4-23
4.3.3 Flue Gas Desulfurization Wastewater 4-27
4.3.4 Flue Gas Mercury Control Wastewater 4-33
4.3.5 Landfill and Impoundment Leachate and Runoff 4-34
4.3.6 Gasification Wastewater 4-37
4.3.7 Metal Cleaning Waste 4-38
4.4 Steam Electric Wastestreams Not Evaluated for New or Additional Controls
in the Proposed ELGs 4-39
4.4.1 Condenser Cooling Water 4-40
4.4.2 Coal Pile Runoff 4-41
4.4.3 Selected Low Volume Waste Sources 4-42
4.4.4 Selective Catalytic Reduction and Selective Non-Catalytic Reduction
Wastewater 4-43
4.4.5 Carbon Capture Wastewater 4-44
4.5 References 4-46
SECTION 5 INDUSTRY SUBCATEGORIZATION 5-1
5.1 Subcategorization Factors 5-1
5.2 Analysis of Subcategorization Factors 5-1
5.2.1 Age of Plant or Generating Unit 5-2
5.2.2 Geographic Location 5-2
5.2.3 Size 5-2
5.2.4 Fuel Type 5-3
5.3 References 5-3
11
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TABLE OF CONTENTS (Continued)
Page
SECTION 6 WASTEWATER CHARACTERIZATION AND POLLUTANTS OF CONCERN 6-1
6.1 FGD Wastewater 6-1
6.2 Ash Transport Water 6-8
6.2.1 Fly Ash Transport Water 6-8
6.2.2 Bottom Ash Transport Water 6-8
6.2.3 Ash Transport Water Characteristics 6-9
6.3 Combustion Residual Landfill and Impoundment Leachate 6-12
6.4 Flue Gas Mercury Control Wastewater 6-17
6.5 Gasification Wastewater 6-18
6.6 Metal Cleaning Waste 6-20
6.7 Identification of Pollutants of Concern 6-24
6.7.1 FGD Wastewater Pollutants of Concern 6-27
6.7.2 Ash Transport Water Pollutants of Concern 6-28
6.7.3 Combustion Residual Leachate Pollutants of Concern 6-29
6.7.4 Gasification Wastewater Pollutants of Concern 6-31
6.7.5 Flue Gas Mercury Control Wastewater Pollutants of Concern 6-32
6.7.6 Nonchemical Metal Cleaning Wastes Pollutants of Concern 6-33
6.8 References 6-34
SECTION 7 TREATMENT TECHNOLOGIES AND WASTEWATER MANAGEMENT
PRACTICES 7-1
7.1 FGD Wastewater Treatment Technologies and Management Practices 7-1
7.1.1 Surface Impoundments 7-3
7.1.2 Chemical Precipitation 7-4
7.1.3 Biological Treatment 7-9
7.1.4 Vapor-Compression Evaporation System 7-13
7.1.5 Constructed Wetlands 7-16
7.1.6 Design/Operating Practices Achieving Zero Discharge 7-17
7.1.7 Other Technologies Under Investigation 7-19
7.2 Fly Ash Handling, Management, and Treatment Technologies 7-22
7.2.1 Wet Sluicing System 7-24
7.2.2 Wet Vacuum Pneumatic System 7-25
7.2.3 Dry Vacuum System 7-26
7.2.4 Pressure System 7-27
7.2.5 Combined Vacuum/Pressure System 7-28
7.2.6 Mechanical System 7-29
7.3 Bottom Ash Handling, Management, and Treatment Technologies 7-29
7.3.1 Wet Sluicing System 7-32
7.3.2 Mechanical Drag System 7-33
7.3.3 Remote Mechanical Drag System 7-34
7.3.4 Dry Vacuum or Pressure System 7-36
7.3.5 Vibratory Belt System 7-37
7.3.6 Mechanical System 7-38
7.3.7 Complete Recycle System 7-38
7.4 Combustion Residual Leachate 7-39
7.5 Flue Gas Mercury Control Wastewater Treatment Technologies 7-41
in
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TABLE OF CONTENTS (Continued)
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7.6 Gasification Wastewater Treatment Technologies 7-42
7.6.1 Vapor-Compression Evaporation System 7-43
7.6.2 Cyanide Destruction 7-43
7.7 Metal Cleaning Waste Treatment Technologies and Management Practices 7-43
7.8 References 7-48
SECTION 8 TECHNOLOGY OPTIONS CONSIDERED AS BASIS FOR REGULATION 8-1
8.1 Proposed Regulatory Options 8-1
8.1.1 BPT/BCT 8-1
8.1.2 Description of the Proposed BAT/NSPS/PSES/PSNS Options 8-2
8.1.3 Rationale for the Proposed BAT Technology 8-23
8.1.4 Rationale for the Proposed Best Available Demonstrated
Control/NSPS Technology 8-37
8.1.5 Rationale for the Proposed PSES Technology 8-40
8.1.6 Rationale for the Proposed PSNS Technology 8-43
8.1.7 Consideration of Future FGD Installations on the Analyses for the
ELG Rulemaking 8-44
8.2 Timing of New Requirements 8-46
8.3 References 8-47
SECTION 9 ENGINEERING COSTS 9-1
9.1 Introduction 9-1
9.2 Steam Electric Technology Option Cost Bases 9-3
9.2.1 FGD Wastewater 9-3
9.2.2 Fly Ash Transport Water 9-4
9.2.3 Bottom Ash Transport Water 9-4
9.2.4 Combustion Residual Leachate 9-5
9.2.5 Gasification Wastewater 9-6
9.2.6 Flue Gas Mercury Control Wastewater 9-6
9.2.7 Nonchemical Metal Cleaning Wastes 9-6
9.3 Steam Electric Compliance Cost Methodology 9-6
9.4 Steam Electric Cost Model 9-8
9.4.1 Input Data to Technology Cost Modules 9-10
9.4.2 Industry Assumptions/Factors 9-12
9.4.3 Technology Cost Modules 9-13
9.4.4 Model Outputs 9-14
9.5 Costs Applicable to All Wastestreams 9-14
9.5.1 Compliance Monitoring Costs 9-15
9.5.2 Transportation Costs 9-16
9.5.3 Disposal Costs 9-17
9.5.4 Impoundment Operation Costs 9-17
9.5.5 Impoundment BMP Costs 9-18
9.6 FGD Wastewater 9-19
9.6.1 Chemical Precipitation 9-19
9.6.2 Biological Treatment 9-22
9.6.3 Vapor-Compression Evaporation 9-26
iv
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TABLE OF CONTENTS (Continued)
Page
9.6.4 Estimated Industry-Level Costs for FGD Wastewater by Treatment
Option 9-27
9.6.5 Compliance Costs Associated with Planned FGD Systems 9-29
9.7 Ash Transport Water 9-29
9.7.1 Fly Ash Transport Water 9-30
9.7.2 Bottom Ash Transport Water 9-34
9.7.3 Estimated Industry-Level Costs for Ash Handling Conversions 9-39
9.8 Combustion Residual Landfill Leachate 9-41
9.9 Summary of National Engineering Costs 9-42
9.10 Compliance Costs for New Sources 9-44
9.11 References 9-47
SECTION 10 POLLUTANT LOADINGS AND REMOVALS 10-1
10.1 General Methodology for Estimating Pollutant Removals 10-2
10.2 Wastestream Pollutant Characterization and Data Sources 10-4
10.2.1 FGD Wastewater Characterization 10-5
10.2.2 Ash Transport Water Characterization 10-16
10.2.3 Baseline and Post-Compliance Combustion Residual Leachate
Characterization 10-19
10.3 Wastewater Flow Rates for Baseline and Post-Compliance Pollutant
Loadings 10-21
10.3.1 FGD Wastewater Flow Rates for Pollutant Loadings 10-22
10.3.2 Ash Transport Water Flow Rates for Pollutant Loadings 10-22
10.3.3 Combustion Residual Landfill Leachate Flow Rates for Pollutant
Loadings 10-23
10.4 Baseline and Post-Compliance Pollutant Loadings and TWPE Results 10-23
10.4.1 FGD Wastewater Loadings and TWPE 10-23
10.4.2 Ash Transport Water Loadings and TWPE 10-26
10.4.3 Combustion Residual Landfill Leachate Loadings and TWPE 10-29
10.4.4 Pollutant Loadings and Removals for Regulatory Options 10-31
10.5 References 10-32
SECTION 11 POLLUTANTS SELECTED FOR REGULATION 11-1
11.1 Selection of Regulated Pollutant for Direct Dischargers 11-1
11.1.1 FGD Wastewater 11-1
11.1.2 Fly Ash Transport Water 11-5
11.1.3 Bottom Ash Transport Water 11-5
11.1.4 Combustion Residual Leachate 11-5
11.1.5 Gasification Wastewater 11-6
11.1.6 Flue Gas Mercury Control Wastewater 11-6
11.1.7 Nonchemical Metal Cleaning Wastes 11-6
11.2 Regulated Pollutant Selection Methodology for Indirect Dischargers 11-10
11.2.1 Methodology for Determining BAT Percent Removals 11-12
11.2.2 Methodology for Determining POTW Percent Removals 11-12
11.2.3 Results of POTW Pass-Through Analysis 11-13
11.3 References 11-15
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TABLE OF CONTENTS (Continued)
Page
SECTION 12 NON-WATER QUALITY ENVIRONMENTAL IMPACTS 12-1
12.1 Energy Requirements 12-1
12.2 Air Emissions Pollution 12-4
12.3 Solid Waste Generation 12-11
12.4 Reductions in Water Use 12-13
12.5 References 12-14
SECTION 13 LIMITATIONS AND STANDARDS: DATA SELECTION AND CALCULATION 13-1
13.1 Data Selection 13-1
13.1.1 Data Selection Criteria 13-1
13.1.2 Data Selection for Each Technology Option 13-3
13.1.3 Combining Data from Multiple Sources within a Plant 13-6
13.2 Data Exclusions and Substitutions 13-6
13.2.1 Data Exclusions 13-6
13.2.2 Data Substitutions 13-7
13.3 Data Aggregation 13-8
13.3.1 Aggregation of Field Duplicates 13-8
13.3.2 Aggregation of Overlapping Samples 13-9
13.4 Data Editing Criteria 13-9
13.5 Overview of Limitations 13-10
13.5.1 Objectives 13-10
13.5.2 Selection of Percentiles 13-11
13.5.3 Compliance with Limitations 13-11
13.6 Calculation of the Limitations 13-13
13.6.1 Calculation of Option Long-Term Average 13-13
13.6.2 Calculation of Option Variability Factors and Limitations 13-14
13.6.3 Adjustment for Autocorrelation Factors 13-14
13.7 Transfers of the Limitations 13-15
13.7.1 Transfer of Arsenic and Mercury Limitations from Chemical
Precipitation to Leachate 13-16
13.7.2 Transfer of Arsenic and Mercury Limitations from Chemical
Precipitation to Biological Treatment for FGD Wastewater 13-16
13.8 Summary of the Limitations 13-17
13.8.1 Summary of the Plant-Specific Long-Term Average and Variability
Factors for Each Treatment Technology Option for FGD and
Gasification Wastewaters 13-18
13.8.2 Summary of the Option Long-Term Averages, Option Variability
Factors, and Limitations for Each Treatment Technology Option for
FGD, Gasification, and Leachate Wastewaters 13-21
13.9 Engineering Review of the Limitations 13-23
13.9.1 Comparison of Limitations to Effluent Data Used As Basis for the
Limitations 13-23
13.9.2 Comparison of Proposed Limitations to Influent Data 13-28
13.10 References 13-28
SECTION 14 REGULATORY IMPLEMENTATION 14-1
vi
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TABLE OF CONTENTS (Continued)
Page
14.1 Implementation of the Limitations and Standards 14-1
14.1.1 Timing 14-1
14.1.2 Applicability of NSPS/PSNS 14-1
14.1.3 Legacy Wastes 14-2
14.1.4 Monitoring Requirements 14-13
14.2 Analytical Methods 14-18
14.3 Upset and Bypass Provisions 14-18
14.4 Variances and Modifications 14-19
14.4.1 Fundamentally Different Factors Variances 14-20
14.4.2 Economic Variances 14-21
14.4.3 Water Quality Variances 14-21
14.4.4 Thermal Discharge Variances 14-22
14.4.5 Net Credits 14-22
14.4.6 Removal Credits 14-22
14.5 References 14-24
APPENDIX A - SURVEY DESIGN AND CALCULATION OF NATIONAL ESTIMATES
APPENDIX B - MODIFIED DELTA-LOG NORMAL DISTRIBUTION
Vll
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List of Tables
List of Tables
Page
1-1 Current Effluent Guidelines and Standards for the Steam Electric Power
Generating Point Source Category 1-6
3-1 List of Site Visits Conducted During the Detailed Study and Rulemaking 3-3
3-2 Number of Plants in Each Fuel Classification in the Survey Sample Frame Used
to Identify Survey Recipients 3-6
3-3 Selection Criteria for Plants Included in EPA's Sampling Program in the United
States 3-11
3-4 Analytical Methods Used for EPA's Sampling Program 3-12
4-1 Distribution of U.S. Electric Generating Plants by NAICS Code in 2007 4-3
4-2 Distribution of Prime Mover Types for Plants Regulated by the Steam Electric
Power Generating Effluent Guidelines 4-14
4-3 Distribution of Fuel Types Used by Steam Electric Generating Units 4-16
4-4 Distribution by Size of Steam Electric Capacity and Plants Regulated by
the Steam Electric Power Generating Effluent Guidelines 4-18
4-5 Distribution by Size of Steam Electric Generating Units Regulated by
the Steam Electric Power Generating Effluent Guidelines 4-18
4-6 Fly Ash Collection Practices in the Steam Electric Industry 4-19
4-7 Fly Ash Handling Practices in the Steam Electric Industry 4-21
4-8 Conversions of Wet Fly Ash Sluicing Systems Since 2000 4-23
4-9 Bottom Ash Handling Practices in the Steam Electric Industry 4-25
4-10 Conversions of Bottom Ash Sluicing Systems Since 2000 4-27
4-11 Types of FGD Scrubbers in the Steam Electric Industry 4-30
4-12 Characteristics of Coal- and Petroleum Coke-Fired Generating
Units with FGD Systems 4-30
4-13 Leachate Collection at Coal and Petroleum Coke Plants 4-36
4-14 Age of Impoundment or Landfill Collecting Leachate 4-36
4-15 Destination of Leachate in Steam Electric Industry 4-37
4-16 Cooling Water Discharge Average Flow Rates Reported in the
Steam Electric Industry 4-41
4-17 Selected Low Volume Waste Sources in the Steam Electric Industry 4-42
4-18 Carbon Capture Wastewater 4-Day Average Concentration Data 4-45
6-1 FGD Slurry Slowdown Flow Rates 6-2
6-2 FGD Wastewater Discharge at Steam Electric Power Plants by January 1, 2014 6-5
6-3 Average Pollutant Concentrations in Untreated FGD Wastewater 6-5
viii
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List of Tables
List of Tables (Continued)
Page
6-4 Fly Ash Transport Water Flow Rates 6-8
6-5 Bottom Ash Transport Water Flow Rates 6-9
6-6 Ash Wastewater Discharge at Steam Electric Power Plants 6-10
6-7 Fly Ash Transport Water Characteristics 6-11
6-8 Leachate Generation in the Steam Electric Industry 6-13
6-9 Landfill Leachate Discharged by Coal- and Petroleum Coke-Fired Power Plants in
2009 6-14
6-10 Untreated Landfill Leachate Concentrations 6-15
6-11 Untreated Impoundment Leachate Concentrations 6-16
6-12 Mercury Concentrations in Fly Ash with and without ACI Systems 6-18
6-13 Untreated Gasification Wastewater Concentrations 6-19
6-14 Metal Cleaning Waste Generation Frequency Reported in the Steam Electric
Survey 6-21
6-15 Metal Cleaning Wastewater Flow Rates Reported in the Steam Electric Survey 6-23
6-16 Baseline Values for Steam Electric Industry POCs 6-26
6-17 Pollutants of Concern - FGD Wastewater 6-27
6-18 Pollutants of Concern -Ash Transport Water 6-29
6-19 Pollutants of Concern -Landfill Leachate 6-30
6-20 Pollutants of Concern - Impoundment Leachate 6-31
6-21 Pollutants of Concern - Gasification Wastewater 6-31
6-22 Pollutants of Concern - Flue Gas Mercury Control Wastewater 6-33
6-23 Pollutants of Concern -Nonchemical Metal Cleaning Wastes 6-34
7-1 Destination of Metal Cleaning Wastewaters 7-46
8-1 Steam Electric Regulatory Options 8-4
8-2 Summary of Pass Through Analysis 8-41
9-1 Technology Costs Modules Used to Estimate Compliance Costs 9-9
9-2 Number of Plants Expected to Incur Compliance Costs by Wastestream and
Regulatory Option 9-10
9-3 Estimated Industry-Level Costs for FGD Wastewater Based on Oil-Fired Units
and Units 50 MW or Less Not Installing Technology Basis 9-28
9-4 Estimated Industry-Level Costs for FGD Wastewater Based on Oil-Fired Units
and Units at Plants with a Total Plant-Level Wet Scrubbed Capacity of Less Than
2,000 MW Not Installing Technology Basis 9-29
IX
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List of Tables
List of Tables (Continued)
Page
9-5 Estimated Industry-Level Costs for Fly Ash Handling Conversions Based on Oil-
Fired Units and Units 50 MW or Less Not Installing Technology Basis 9-40
9-6 Estimated Industry-Level Costs for Bottom Ash Handling Conversions Based on
Oil-Fired Units and Units 50 MW or Less Not Installing Technology Basis 9-40
9-7 Estimated Industry-Level Costs for Bottom Ash Handling Conversions Based on
Oil-Fired Units and Units 400 MW or Less Not Installing Technology Basis 9-41
9-8 Estimated Industry-Level Costs for Combustion Residual Leachate Based on Oil-
Fired Units and Units 50 MW or Less Not Installing Technology Basis 9-42
9-9 Technology Options and Other Costs Included in the Estimated Compliance Costs
for Each Regulatory Option 9-43
9-10 Cost of Implementation by Regulatory Option [In millions of pre-tax
2010 dollars] 9-43
9-11 NSPS Compliance Cost Scenarios Evaluated for the Proposed Rule 9-45
9-12 Estimated Industry-Level NSPS Costs 9-46
10-1 POTW Removals 10-3
10-2 Data Sets Used in the FGD Loadings Calculation 10-6
10-3 Average Effluent Pollutant Concentrations for FGD Surface Impoundments 10-8
10-4 Average Effluent Pollutant Concentrations for One-Stage Chemical Precipitation
System 10-10
10-5 Average Effluent Pollutant Concentrations for One-Stage Chemical Precipitation
System with Biological Treatment 10-13
10-6 Average Effluent Pollutant Concentrations for One-Stage Chemical Precipitation
System with Vapor-Compression Evaporation 10-15
10-7 Average Effluent Pollutant Concentration for Ash Impoundment Systems 10-18
10-8 Average Pollutant Concentrations Untreated Landfill Leachate 10-20
10-9 Industry-Level FGD Wastewater Loadings Excluding BOD, COD, TDS, and TSS
and Based on Oil-Fired Units and Units 50 MW or Less Not Installing
Technology Basis 10-25
10-10 FGD Wastewater Pollutant Removals Based on Oil-Fired Units and Units 50 MW
or Less Not Installing Technology Basis 10-25
10-11 Industry-Level FGD Wastewater Loadings Excluding BOD, COD, TDS, and TSS
and Based on Oil-Fired Units and Plants with a Total Wet Scrubbed Capacity of
Less Than 2,000 MW Not Installing Technology Basis 10-26
10-12 FGD Wastewater Pollutant Removals Based on Oil-Fired Units and Plants with a
Total Wet Scrubbed Capacity of Less Than 2,000 MW Not Installing Technology
Basis 10-26
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List of Tables
List of Tables (Continued)
Page
10-13 Industry-Level Ash Impoundment Loadings by Type of Impoundment Excluding
BOD, COD, TDS, and TSS 10-28
10-14 Fly Ash and Bottom Ash Pollutant Removals Based on Oil-Fired Units and Units
50 MW or Less Not Installing Technology Basis 10-28
10-15 Bottom Ash Pollutant Removals Based on Oil-Fired Units and Units 400 MW or
Less Not Installing Technology Basis 10-29
10-16 Industry-Level Combustion Residual Landfill Leachate Loadings Excluding
BOD, COD, TDS, and TSS and Based on Oil-Fired Units and Units 50 MW or
Less Not Installing Technology Basis 10-30
10-17 Combustion Residual Landfill Leachate Pollutant Removals Based on Oil-Fired
Units and Units 50 MW or Less Not Installing Technology Basis 10-31
10-18 Estimated Pollutant Removals by Regulatory Option Based on Oil-Fired Units
and Units 50 MW or Less Not Installing Technology Basis 10-31
11-1 Pollutants Considered for Regulation for Direct Dischargers (BAT/NSPS): FGD
Wastewater 11-3
11-2 Pollutants Considered for Regulation for Direct Dischargers (BAT/NSPS):
Combustion Residual Leachate 11-8
11-3 Pollutants Considered for Regulation for Direct Dischargers (BAT/NSPS):
Gasification Wastewater 11-9
11-4 POTW Pass-Through Analysis (FGD Wastewater) - PSES/PSNS 11-14
11-5 POTW Pass-Through Analysis (Combustion Residual Leachate) - PSES/PSNS 11-14
11-6 POTW Pass-Through Analysis (Gasification Wastewater) - PSES/PSNS 11-15
12-1 Industry-Level Energy Requirements by Regulatory Option 12-2
12-2 Summary of IPM Emissions Factors by NERC Region and Across Steam Electric
Plants 12-6
12-3 MOBILE6.2 and California Climate Action Registry
Transportation Emission Rates 12-8
12-4 Industry-Level Air Emissions Associated with Auxiliary Electricity and
Transportation by Regulatory Option 12-9
12-5 Industry-Level Net Air Emissions For the Preferred Regulatory Options 12-10
12-6 Electric Power Industry Air Emissions 12-11
12-7 Industry-Level Solid Waste Increases by Regulatory Option 12-13
12-8 Industry-Level Process Water Reduction by Regulatory Option 12-14
12-9 Wastewater Discharge at Steam Electric Power Plants 12-14
13-1 Aggregation of Field Duplicates 13-9
XI
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List of Tables
List of Tables (Continued)
Page
13-2 Summary of Autocorrelation Values Used in Calculating the
Limitations for Biological Treatment Technology Option for FGD Wastewater 13-15
13-3 Plant-Specific Results for Chemical Precipitation as the
Technology Basis for FGD Wastewater 13-18
13-4 Plant-Specific Results for Biological Treatment as the Technology Basis for FGD
Wastewater 13-19
13-5 Plant-Specific Results for Vapor-Compression Evaporation
(Crystallizer Condensate) as the Technology Basis for FGD Wastewater 13-20
13-6 Plant-Specific Results for Vapor-Compression Evaporation (Vapor-Compression
Evaporator Condensate) as the Technology Basis for Gasification Wastewater 13-21
13-7 Proposed Option Long-Term Averages, Option Variability Factors,
and Limitations for Each of the FGD, Gasification, and Leachate Technology
Options 13-22
xn
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List of Figures
List of Figures
Page
4-1 Types of U.S. Electric Generating Plants 4-1
4-2 Steam Electric Process Flow Diagram 4-8
4-3 Combined Cycle Process Flow Diagram 4-9
4-4 IGCC Process Flow Diagram 4-11
4-5 Plant-Level Fly Ash Handling Systems 4-22
4-6 Plant-Level Bottom Ash Handling Systems 4-26
4-7 Typical FGD Systems 4-28
4-8 Plants Operating Wet FGD Scrubber Systems 4-32
4-9 Capacity of Wet Scrubbed Units by Decade 4-33
4-10 Diagram of Landfill Leachate Generation and Collection 4-35
6-1 Distribution of FGD Wastewater Treatment Systems among the 117
Plants Discharging FGD Wastewater by January 1, 2014 6-7
7-1 Distribution of FGD Wastewater Treatment/Management Systems
Among 145 Plants Currently Operating Wet FGD Systems orPlanned Wet
FGD Systems Operating by 2014 7-3
7-2 Process Flow Diagram for a Hydroxide and Sulfide Chemical Precipitation
System 7-8
7-3 Process Flow Diagram for an Anoxic/Anaerobic Biological Treatment System 7-11
7-4 Chemical Precipitation and Softening Pretreatment for FGD Wastewater Prior to
Vapor-Compression Evaporation 7-14
7-5 Process Flow Diagram for a Vapor-Compression Evaporation System 7-15
7-6 Distribution of Fly Ash Handling Systems for Coal-, Petroleum Coke-
and Oil-Fired Units in the Steam Electric Industry 7-23
7-7 Distribution of Fly Ash Handling System Types Other Than Wet
Sluicing for Coal-, Petroleum Coke-, and Oil-fired Units Reported in the
Steam Electric Survey 7-24
7-8 Schematic of Dry Vacuum, Pressure, and Combined Vacuum/Pressure System 7-27
7-9 Pressure System Airlock Valve 7-28
7-10 Distribution of Bottom Ash Handling Systems for Coal-, Petroleum
Coke-, and Oil-Fired Units Reported in the Steam Electric Survey 7-31
7-11 Distribution of Bottom Ash Handling System Types Other Than Wet Sluicing for
Coal-, Petroleum Coke-, and Oil-Fired Units Reported in the Steam Electric
Survey 7-31
7-12 Bottom Ash Dewatering Bin System 7-33
7-13 Mechanical Drag System 7-34
xiii
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List of Figures
List of Figures (Continued)
Page
7-14 Remote Mechanical Drag System 7-35
7-15 Water Flow Inside the Remote Mechanical Drag System Trough 7-36
7-16 Dry Vacuum or Pressure Bottom Ash Handling System 7-37
7-17 Vibratory Bottom Ash Handling System 7-38
7-18 Distribution of Treatment Systems for Leachate from Landfills
and Impoundments Containing Combustion Residual Wastes 7-40
14-1 Legacy FGD Wastewater Treatment Scenario (Regulatory Options 3 and 4a) 14-4
14-2 Legacy Fly Ash Transport Water Treatment Scenario (Regulatory Options 3a, 3b,
3, and4a) 14-5
14-3 Complete Recycle Fly Ash Transport Water Treatment Scenario (Regulatory
Options 3a, 3b, 3, and 4a) 14-6
14-4 Partial Recycle Bottom Ash Transport Water Treatment Scenario (Regulatory
Option 4) 14-7
14-5 Legacy Fly Ash Transport Water Combined with Bottom Ash Transport Water
Treatment Scenario (Regulatory Options 3a, 3b, and 3) 14-9
14-6 Legacy Fly Ash Transport Water Combined with Bottom Ash Transport Water
Treatment Scenario (Regulatory Option 4) 14-10
14-7 Legacy FGD Wastewater and Fly Ash Transport Water Combined with Bottom
Ash Transport Water Treatment Scenario (Regulatory Option 3) 14-12
14-8 Legacy FGD Wastewater and Fly Ash Transport Water Combined with Bottom
Ash Transport Water Treatment Scenario (Regulatory Option 4) 14-13
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Section 1 - Background
SECTION 1
BACKGROUND
This section provides background information on the development of revised effluent
limitations guidelines and standards (ELGs) proposed for the Steam Electric Power Generating
Point Source Category (Steam Electric Category). Sections 1.1 and 1.2 discuss the legal authority
and regulatory background for the proposed rule. Section 1.3 presents a history of Steam Electric
Category rulemaking activities.
In addition to this report, the proposed Steam Electric ELGs are supported by a number
of reports including:
• Environmental Assessment for the Proposed Effluent Limitations Guidelines and
Standards for the Steam Electric Power Generating Point Source Category, Document
No. 821-R-13-003. This report summarizes the environmental and human health
improvements that result from implementation of the proposed ELGs.
• Benefits and Cost Analysis for the Proposed Steam Electric Effluent Limitations
Guidelines and Standards for the Steam Electric Power Generating Point Source
Category, Document No. EPA-821-R-13-004. This report summarizes the monetary
benefits and societal costs that result from implementation of the proposed ELGs.
• Regulatory Impact Analysis for Proposed Effluent Limitations Guidelines and
Standards for the Steam Electric Power Generating Point Source Category (RIA),
Document No. EPA-821-R-13-005. This report presents a profile of the steam electric
industry, a summary of the costs and impacts associated with the regulatory options,
and an assessment of the proposed ELGs impact on employment and small
businesses.
The proposed effluent limitation guidelines and standards for the Steam Electric Power
Generating Point Source Category are based on data generated or obtained in accordance with
EPA's Quality Policy and Information Quality Guidelines. EPA's quality assurance (QA) and
quality control (QC) activities for this rulemaking include the development, approval and
implementation of Quality Assurance Project Plans for the use of environmental data generated
or collected from sampling and analyses, existing databases and literature searches, and for the
development of any models, which used environmental data.
1.1 LEGAL AUTHORITY
EPA is proposing revisions of the ELGs for the Steam Electric Category (40 Code of
Federal Regulations (CFR) 423) under the authority of Sections 301, 304, 306, 307, 308, 402,
and 501 of the Clean Water Act, 33 U.S.C. 1311, 1314, 1316, 1317, 1318, 1342, and 1361.
1.2 CLEAN WATER ACT
Congress passed the Federal Water Pollution Control Act Amendments of 1972, also
known as the Clean Water Act (CWA), to "restore and maintain the chemical, physical, and
biological integrity of the Nation's waters." 33 U.S.C. 1251(a). The CWA establishes a
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Section 1 - Background
comprehensive program for protecting our nation's waters. Among its core provisions, the CWA
prohibits the discharge of pollutants from a point source to waters of the U.S. except as
authorized under the CWA. Under section 402 of the CWA, discharges may be authorized
through a National Pollutant Discharge Elimination System (NPDES) permit. The CWA also
authorizes EPA to establish national technology-based effluent limitations guidelines and
standards (ELGs) for discharges from categories of point sources.
The CWA authorizes EPA to promulgate nationally applicable pretreatment standards
that restrict pollutant discharges from facilities that discharge wastewater indirectly through
sewers flowing to publicly owned treatment works (POTWs), as outlined in section 307(b) and
(c), 33 U.S.C. 1317(b) and (c). EPA establishes national pretreatment standards for those
pollutants in wastewater from indirect dischargers that may pass through, interfere with, or are
otherwise incompatible with POTW operations. Generally, pretreatment standards are designed
to ensure that wastewaters from direct and indirect industrial dischargers are subject to similar
levels of treatment. See CWA section 301(b), 33 U.S.C. 1311(b). In addition, POTWs are
required to implement local treatment limits applicable to their industrial indirect dischargers to
satisfy any local requirements. See 40 CFR 403.5.
Direct dischargers (i.e., those discharging directly to surface waters) must comply with
effluent limitations in NPDES permits. Indirect dischargers, who discharge through POTWs,
must comply with pretreatment standards. Technology-based effluent limitations in NPDES
permits are derived from effluent limitations guidelines (CWA sections 301 and 304, 33 U.S.C.
1311 and 1314) and new source performance standards (CWA section 306, 33 U.S.C. 1316)
promulgated by EPA, or based on best professional judgment (BPJ) where EPA has not
promulgated an applicable effluent guideline or new source performance standard (CWA section
402(a)(l)(B), 33 U.S.C. 1342(a)(l)(B)). Additional limitations based on water quality standards
are also required to be included in the permit in certain circumstances. CWA section
301(b)(l)(C), 33 U.S.C. 1311(b)(l)(C). The ELGs are established by regulation for categories of
industrial dischargers and are based on the degree of control that can be achieved using various
levels of pollution control technology.
EPA promulgates national ELGs for major industrial categories for three classes of
pollutants: (1) conventional pollutants (i.e., total suspended solids (TSS), oil and grease (O&G),
biochemical oxygen demand (BODs), fecal coliform, and pH), as outlined in CWA section
304(a)(4) and 40 CFR 401.16; (2) toxic pollutants (e.g., toxic metals such as arsenic, mercury,
selenium, and chromium; toxic organic pollutants such as benzene, benzo-a-pyrene, phenol, and
naphthalene), as outlined in section 307(a) of the Act, 40 CFR 401.15 and 40 CFR part 423
appendix A; and (3) non-conventional pollutants, which are those pollutants that are not
categorized as conventional or toxic (e.g., ammonia-N, phosphorus, and total dissolved solids).
EPA bases ELGs on the performance of control and treatment technologies. The
legislative history of CWA section 304(b), which is the heart of the effluent guidelines program,
describes the need to press toward higher levels of control through research and development of
new processes, modifications, replacement of obsolete plans and processes, and other
improvements in technology, taking into account the cost of controls. Congress has also stated
that EPA need not consider water quality impacts on individual water bodies as the guidelines
are developed; see Statement of Senator Muskie (October 4, 1972), reprinted in Legislative
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Section 1 - Background
History of the Water Pollution Control Act Amendments of 1972, at 170. (U.S. Senate,
Committee on Public Works, Serial No. 93-1, January 1973.)
There are four types of standards applicable to direct dischargers (plants that discharge to
surface waters), and two standards applicable to indirect dischargers (plants that discharge to
POTWs). The following sections summarize these guidelines and standards.
1.2.1 Best Practicable Control Technology Currently Available (BPT)
Traditionally, EPA defines BPT effluent limitations based on the average of the best
performances of facilities within the industry, grouped to reflect various ages, sizes, processes, or
other common characteristics. EPA may promulgate BPT effluent limits for conventional, toxic,
and non-conventional pollutants. In specifying BPT, EPA looks at a number of factors. EPA first
considers the cost of achieving effluent reductions in relation to the effluent reduction benefits.
The Agency also considers the age of equipment and facilities, the processes employed,
engineering aspects of the control technologies, any required process changes, non-water quality
environmental impacts (including energy requirements), and such other factors as the
Administrator deems appropriate. See CWA section 304(b)(l)(B). If, however, existing
performance is uniformly inadequate, EPA may establish limitations based on higher levels of
control than what is currently in place in an industrial category, when based on an Agency
determination that the technology is available in another category or subcategory, and can be
practically applied.
1.2.2 Best Conventional Pollutant Control Technology (BCT)
The 1977 amendments to the CWA required EPA to identify additional levels of effluent
reduction for conventional pollutants associated with BCT technology for discharges from
existing industrial point sources. In addition to other factors specified in section 304(b)(4)(B),
the CWA requires that EPA establish BCT limitations after consideration of a two-part "cost
reasonableness" test. EPA explained its methodology for the development of BCT limitations in
July 9, 1986 (51 FR 24974). Section 304(a)(4) designates the following as conventional
pollutants: BODs, TSS, fecal coliform, pH, and any additional pollutants defined by the
Administrator as conventional. The Administrator designated O&G as an additional conventional
pollutant on July 30, 1979 (44 FR 44501; 40 CFR 401.16).
1.2.3 Best Available Technology Economically Achievable (BAT)
BAT represents the second level of stringency for controlling direct discharge of toxic
and nonconventional pollutants. In general, BAT ELGs represent the best available economically
achievable performance of facilities in the industrial subcategory or category. As the statutory
phrase intends, EPA considers the technological availability and the economic achievability in
determining what level of control represents BAT. CWA section 301(b)(2)(A), 33 U.S.C.
131 l(b)(2)(A). Other statutory factors that EPA considers in assessing BAT are the cost of
achieving BAT effluent reductions, the age of equipment and facilities involved, the process
employed, potential process changes, and non-water quality environmental impacts, including
energy requirements and such other factors as the Administrator deems appropriate. CWA
section 304(b)(2)(B), 33 U.S.C. 1314(b)(2)(B). The Agency retains considerable discretion in
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Section 1 - Background
assigning the weight to be accorded these factors. Weyerhaeuser Co. v. Costle, 590 F.2d 1011,
1045 (D.C. Cir. 1978). Generally, EPA determines economic achievability based on the effect of
the cost of compliance with BAT limitations on overall industry and subcategory financial
conditions. BAT may reflect the highest performance in the industry and may reflect a higher
level of performance than is currently being achieved based on technology transferred from a
different subcategory or category, bench scale or pilot plant studies, or foreign plants. American
Paper Inst. v. Train, 543 F.2d 328, 353 (D.C. Cir. 1976); American Frozen FoodInst. v Train,
539 F.2d 107, 132 (D.C. Cir. 1976). BAT may be based upon process changes or internal
controls, even when these technologies are not common industry practice. See American Frozen
Foods, 539 F.2d at 132, 140; Reynolds Metals Co. v. EPA, 760 F.2d 549, 562 (4th Cir. 1985);
California & Hawaiian Sugar Co. v. EPA, 553 F.2d 280, 285-88 (2nd Cir. 1977).
1.2.4 New Source Performance Standards (NSPS)
NSPS reflect effluent reductions that are achievable based on the best available
demonstrated control technology (BADCT). Owners of new facilities have the opportunity to
install the best and most efficient production processes and wastewater treatment technologies.
As a result, NSPS should represent the most stringent controls attainable through the application
of the BADCT for all pollutants (that is, conventional, non-conventional, and toxic pollutants).
In establishing NSPS, EPA is directed to take into consideration the cost of achieving the
effluent reduction and any non-water quality environmental impacts and energy requirements.
CWA section 306(b)(l)(B), 33 U.S.C. 1316(b)(l)(B).
1.2.5 Pretreatment Standards for Existing Sources (PSES)
Section 307(b), 33 U.S.C. 1317(b), of the Act calls for EPA to issue pretreatment
standards for discharges of pollutants to POTWs. PSES are designed to prevent the discharge of
pollutants that pass through, interfere with, or are otherwise incompatible with the operation of
POTWs. Categorical pretreatment standards are technology-based and are analogous to BPT and
BAT effluent limitations guidelines, and thus the Agency typically considers the same factors in
promulgating PSES as it considers in promulgating BAT. The General Pretreatment Regulations,
which set forth the framework for the implementation of categorical pretreatment standards, are
found at 40 CFR part 403. These regulations establish pretreatment standards that apply to all
non-domestic dischargers. See 52 FR 1586 (January 14, 1987).
1.2.6 Pretreatment Standards for New Sources (PSNS)
Section 307(c), 33 U.S.C. 1317(c) of the Act calls for EPA to promulgate PSNS. Such
pretreatment standards must prevent the discharge of any pollutant into a POTW that may
interfere with, pass through, or may otherwise be incompatible with the POTW. EPA
promulgates PSNS based on best available demonstrated control technology (BADCT) for new
sources. New indirect dischargers have the opportunity to incorporate into their facilities the best
available demonstrated technologies. The Agency typically considers the same factors in
promulgating PSNS as it considers in promulgating NSPS.
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Section 1 - Background
1.3 REGULATORY HISTORY OF THE STEAM ELECTRIC POWER GENERATING POINT
SOURCE CATEGORY
This section presents a brief history of Steam Electric Category rulemaking activities.
Section 1.3.1 discusses the existing steam electric industry wastewater discharge regulations.
Section 1.3.2 discusses the Detailed Study of the Steam Electric Category. Section 1.3.3
discusses other statutes and regulatory requirements affecting this industry.
1.3.1 Summary of Current ELGs Discharge Requirements and Applicability
The CWA establishes a structure for regulating discharges of pollutants to surface waters
of the United States. As part of the implementation of the CWA, EPA issues ELGs for industrial
dischargers. EPA first issued ELGs for the Steam Electric Category in 1974 with subsequent
revisions in 1977 and 1982. The Steam Electric ELGs are codified at 40 CFR 423 and include
limitations for the following wastestreams:
• Once-through cooling water;
• Cooling tower blowdown;
• Fly ash transport water;
• Bottom ash transport water;
• Metal cleaning wastes;
• Coal pile runoff; and
• Low-volume waste sources, including but not limited to, wastewaters from wet
scrubber air pollution control systems, ion exchange water treatment systems, water
treatment evaporator blowdown, laboratory and sampling streams, boiler blowdown,
floor drains, cooling tower basin cleaning wastes, and recirculating house service
water systems (sanitary and air conditioning wastes are not included) [40 CFR
423.11(b)].
Table 1-1 summarizes the current ELGs, which are applicable to:
".. .discharges resulting from the operation of a generating unit by an establishment
primarily engaged in the generation of electricity for distribution and sale which
results primarily from a process utilizing fossil-type fuel (coal, oil, or gas) or nuclear
fuel in conjunction with a thermal cycle employing the steam water system as the
thermodynamic medium." [40 CFR 423.10]
The ELGs do not apply to discharges from generating units that primarily use a nonfossil
or nonnuclear fuel source (e.g., wood waste, municipal solid waste) to power the steam electric
generators, nor do they apply to generating units operated by establishments that are not
primarily engaged in generating electricity for distribution and sale.
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Section 1 - Background
Table 1-1. Current Effluent Guidelines and Standards for the Steam Electric Power Generating Point Source Category
Wastestream
All Wastestreams
Fly Ash
Transport
Bottom Ash
Transport
Low Volume
Wastes
Once -Through
Cooling
Cooling Tower
Blowdown
Coal Pile Runoff
BPTa
pH: 6-9 S.U. b
PCBs: Zero discharge
TSS: 100mg/L;30mg/L
Oil & Grease: 20 mg/L; 15
mg/L
TSS: 100 mg/L; 30 mg/L
Oil & Grease: 20 mg/L; 15
mg/L
TSS: 100 mg/L; 30 mg/L
Oil & Grease: 20 mg/L; 15
mg/L
Free Available Chlorine: 0.5
mg/L; 0.2 mg/L
Free Available Chlorine: 0.5
mg/L; 0.2 mg/L
TSS*: 50 mg/L instantaneous
maximum
BATa
PCBs: Zero discharge
Total Residual Chlorine:
For any plant with rated
electric generating capacity >
25 MW: 0.20 mg/L
instantaneous maximum;
For any plant with rated
electric generating capacity <
25 MW, equal to BPT
Free Available Chlorine: 0.5
mg/L; 0.2 mg/L
126 Priority Pollutants: No
detectable amount, except:
Chromium, total: 0.2 mg/L; 0.2
mg/L
Zinc, total: 1.0 mg/L; 1.0 mg/L
NSPSa
pH: 6-9 S.U. b
PCBs: Zero discharge
Zero discharge
TSS: 100 mg/L; 30 mg/L
Oil & Grease: 20 mg/L; 15
mg/L
TSS: 100 mg/L; 30 mg/L
Oil & Grease: 20 mg/L; 15
mg/L
Total Residual Chlorine:
For any plant with rated
electric generating capacity >
25 MW: 0.20 mg/L
instantaneous maximum;
For any plant with rated
electric generating capacity <
25 MW, equal to BPT
Free Available Chlorine: 0.5
mg/L; /0.2 mg/L
126 Priority Pollutants: No
detectable amount, except:
Chromium, total: 0.2 mg/L; 0.2
mg/L
Zinc, total: 1.0 mg/L; 1.0 mg/L
TSS*: 50 mg/L instantaneous
maximum
PSES and PSNSa
PCBs: Zero discharge
Zero discharge
(PSNS only)
No limitation for PSES
126 Priority Pollutants: Zero
discharge, except:
Chromium: 0.2 mg/L; 0.2 mg/L
Zinc: 1.0 mg/L; 1.0 mg/L
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Section 1 - Background
Table 1-1. Current Effluent Guidelines and Standards for the Steam Electric Power Generating Point Source Category
Wastestream
BPTa
BATa
NSPSa
PSES and PSNSa
Chemical Metal
Cleaning Wastes
Non-chemical
Metal Cleaning
Wastes
TSS: 100mg/L;30mg/L
Oil & Grease: 20 mg/L; 15
mg/L
Copper: 1.0 mg/L; 1.0 mg/L
Iron: 1.0 mg/L; 1.0 mg/L
Copper: 1.0 mg/L; 1.0 mg/L
Iron: 1.0 mg/L; 1.0 mg/L
Reserved
TSS: 100 mg/L; 30 mg/L
Oil & Grease: 20 mg/L; 15
mg/L
Copper: 1.0 mg/L; 1.0 mg/L
Iron: 1.0 mg/L; 1.0 mg/L
Reserved
Copper: 1.0 mg/L (daily
maximum)
Reserved
Source: [40 CFR Part 423].
a -The limitations for TSS, oil & grease, copper, iron, chromium, and zinc are presented in the table as daily maximum (mg/L); 30-day average (mg/L). For all
effluent guidelines, where two or more wastestreams are combined, the total pollutant discharge quantity may not exceed the sum of allowable pollutant quantities for
each individual wastestream. BPT, BAT, and NSPS allow either mass- or concentration-based limitations.
b -The pH limitation is not applicable to once-through cooling water.
Free Available Chlorine: 0.5 mg/L; 0.2 mg/L - 0.5 mg/L instantaneous maximum, 0.2 mg/L average during chlorine release period. Discharge is limited to 2
hrs/day/unit. Simultaneous discharge of chlorine from multiple units is prohibited. Limitations are applicable at the discharge from an individual unit prior to
combination with the discharge from another unit.
Total Residual Chlorine: 0.20 mg/L instantaneous maximum. Total residual chlorine (TRC) = free available chlorine (FAC) + combined residual chlorine (CRC).
TRC discharge is limited to 2 hrs/day/unit. TRC is applicable to plants >25 MW, and FAC is applicable to plants <25 MW. The TRC limitation is applicable at the
discharge point to surface waters of the United States and may be subsequent to combination with the discharge from another unit.
126 Priority Pollutants: zero discharge -126 priority pollutants from added maintenance chemicals (refer to App. A to 40 CFR 423). At the permitting authority's
discretion, compliance with the zero-discharge limitations for the 126 priority pollutants may be determined by engineering calculations, which demonstrate that the
regulated pollutants are not detectable in the final discharge by the analytical methods in 40 CFR part 136.
TSS*: 50 mg/L instantaneous maximum on coal pile runoff streams. No limitation on TSS for coal pile runoff flows >10-year, 24-hour rainfall event.
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Section 1 - Background
1.3.2 Detailed Study of the Steam Electric Power Generating Point Source Category
Section 304 of the CWA requires EPA to periodically review all effluent limitations
guidelines and standards to determine whether revisions are warranted. In addition, Section
304(m) of the CWA requires EPA to develop and publish, biennially, a plan that establishes a
schedule for the review and revision of promulgated national effluent guidelines required by
Section 304(b) of the CWA. During the 2005 annual review of the existing effluent guidelines
for all categories, EPA identified the regulations governing the steam electric power generating
point source category for possible revision. At that time, publicly available data reported through
the NPDES permit program and the Toxics Release Inventory (TRI) indicated that the industry
ranked high in discharges of toxic and nonconventional pollutants. Because of these findings,
EPA initiated a more detailed study of the category to determine if the effluent guidelines should
be revised.
During the detailed study, EPA collected information on wastewater characteristics and
treatment technologies through site visits, wastewater sampling, a data request that was sent to a
limited number of companies, and various secondary data sources (Section 3 summarizes these
data collection activities). EPA focused these data collection activities on certain discharges from
coal-fired steam electric power plants (referred to in this report as "coal-fired power plants").
Based on the data collected, EPA determined that most of the toxic loadings for this category are
associated with metals and certain other constituents, such as selenium, present in wastewater
discharges, and that the wastestreams contributing the majority of these pollutants are associated
with ash handling and wet flue gas desulfurization (FGD) systems. EPA also identified several
wastestreams that are relatively new to the industry (e.g., carbon capture wastewater), and
wastestreams for which there is little characterization data (e.g., gasification wastewater). See
Section 4 and Section 7 for more information on these practices.
During the study, EPA found that the use of wet FGD systems to control sulfur dioxide
(862) emissions has increased significantly since the last revision of the effluent guidelines in
1982 and it is projected to continue increasing in the next decade as power plants take steps to
address federal and state air pollution control requirements. EPA also found that FGD
wastewaters generally contain significant levels of metals and other pollutants and that advanced
treatment technologies are available to treat the FGD wastewater; however, most plants were
employing surface impoundments designed primarily to remove suspended solids from FGD
wastewater.
EPA also determined that technologies are available for handling the fly ash and bottom
ash generated at a plant without using any water or at least eliminating the discharge of any
transport water. EPA found that the fly ash and bottom ash transport waters generated from wet
systems at coal-fired power plants are created in large quantities and contain significant
concentrations of metals, including arsenic and mercury. Additionally, EPA determined that
some of the metals are present primarily in the dissolved phase, and generally are not removed in
the surface impoundments that are used to treat these wastestreams. Based on these findings,
EPA determined that there are technologies readily available to reduce or eliminate the discharge
of pollutants contained in fly ash and bottom ash transport water.
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Section 1 - Background
Finally, EPA determined that FGD and ash transport wastewaters contain pollutants that
can have detrimental impacts to the environment. EPA reviewed publicly available data and
found documented environmental impacts that were attributable to discharges from surface
impoundments or discharges from leachate generated from landfills containing coal combustion
residues. EPA determined that there are a number of pollutants present in wastewaters generated
at coal-fired power plants that can impact the environment, including metals (e.g., arsenic,
selenium, mercury), total dissolved solids (IDS), and nutrients. EPA found the interaction of
coal combustion wastewaters with the environment has caused a wide range of harm to aquatic
life.
Overall from the detailed study, EPA found that the industry is generating new
wastestreams that during the previous rulemakings either were not evaluated or were evaluated
to only a limited extent due to insufficient characterization data. Such wastestreams include FGD
wastewater, flue gas mercury control (FGMC) wastewater, carbon capture wastewater, and
gasification wastewaters. EPA also found that these wastestreams, as well as other combustion-
related wastestreams at power plants (e.g., fly ash and bottom ash transport water, leachate)
contain pollutants in concentrations and mass loadings that are causing documented
environmental impacts and that treatment technologies are available to reduce or eliminate the
pollutant discharges.
Upon completing the detailed study in 2009, EPA determined that the current regulations
have not kept pace with the significant changes that have occurred in this industry over the last
three decades. EPA's analysis of the wastewater discharges associated with steam electric power
generation led the Agency to announce, in September 2009, plans to revise the effluent
guidelines.
1.3.3 Other Statutes and Regulatory Requirements Affecting Management of Steam
Electric Power Generating Wastewaters
EPA is taking action to reduce emissions, discharges, and other environmental impacts
associated with steam electric power plants. These actions, which are being implemented by
several different EPA offices (i.e., Office of Air and Radiation (OAR), Office of Solid Waste and
Emergency Response (OSWER), Office of Water (OW)), include establishing new regulatory
requirements which may affect the generation and composition of wastewater discharged from
steam electric power plants. This section provides a brief overview of these statutes and
regulatory requirements.
1. Mercury and Air Toxics Standards (MATS)
When the CAA was amended in 1990, EPA was directed to control mercury and
other hazardous air pollutants from major sources of emissions to the air. For power
plants using fossil fuels, the amendments required EPA to conduct a study of
hazardous air pollutant emissions. CAA Section 112(n)(l)(A). The CAA amendments
also required EPA to consider the study and other information and to make a finding
as to whether regulation was appropriate and necessary. In 2000, the Administrator
found that regulation of hazardous air pollutants, including mercury, from coal- and
oil-fired power plants was appropriate and necessary. 65 FR 79825 (Dec. 20, 2000).
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Section 1 - Background
EPA published the final MATS rule on February 16, 2012. 77 FR 9304. The rule
established standards that will reduce emissions of hazardous air pollutants including
metals (e.g., mercury, arsenic, chromium, nickel) and acid gases (e.g., hydrochloric
acid, hydrofluoric acid). Steam electric power plants may use any number of
practices, technologies, and strategies to meet the new emission limits, including
using wet and dry scrubbers, dry sorbent injection systems, activated carbon injection
systems, and fabric filters.
2. Cross-State Air Pollution Rule (CSAPR)
EPA promulgated the CSAPR in 2011 to require 28 states in the eastern half of the
United States to significantly improve air quality by reducing power plant emissions
of SC>2, nitrogen oxides (NOX) and/or ozone-season NOX that cross state lines and
significantly contribute to ground-level ozone and/or fine particle pollution problems
in other states. The emissions of 862, NOX and ozone-season NOX addressed by the
CSAPR react in the atmosphere to form PM2.5 and ground-level ozone and are
transported long distances, making it difficult for a number of states to meet the
national clean air standards that Congress directed EPA to establish to protect public
health. The U.S. Court of Appeals for the D.C. Circuit stayed the CSAPR on
December 30, 2011, and on August 21, 2012, issued an opinion vacating the rule and
ordering EPA to continue administering the Clean Air Interstate Rule. EME Homer
City Generation, L.P. v. EPA, 696 F.3d 7 (D.C.Cir. 2012). On March 29, 2013, the
United States filed a petition asking the Supreme Court to review the D.C. Circuit
decision.
3. Greenhouse Gas Emissions for New Electric Utility Generating Units
On April 13, 2012, the EPA proposed new source standards of performance under
CAA section 111 for emissions of carbon dioxide (CO2) for fossil-fuel-fired
electricity generating units. 77 FR 22392. The proposed requirements, which apply
only to new sources, would require new plants greater than 25 megawatts (MW) to
meet an output-based standard of 1,000 pounds of CO2 per MW-hour of electricity
generated. EPA based this proposed standard on the performance of natural gas
combined cycle technology because EPA and others project that even without this
rule, for the foreseeable future, new fossil-fuel-fired power plants will be built with
that technology. New coal- or petroleum coke-fired generating units could meet the
standard by using carbon capture and storage of approximately 50 percent of the CO2
in the exhaust gas when the unit begins operating or by later installing more effective
carbon capture and storage to meet the standard on average over a 30-year period.
EPA is evaluating the public comments received on the proposal and has not
determined a schedule at this time for taking final action on the proposed rule.
4. Cooling Water Intake Structures (CWA Section 316(b))
Section 316(b) of the CWA, 33 U.S.C. 1326(b), requires that standards applicable to
point sources under section 301 and 306 of the Act require that the location, design,
construction, and capacity of cooling water intake structures reflect the best
technology available to minimize adverse environmental impacts. Each year, these
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Section 1 - Background
facilities withdraw large volumes of water from lakes, rivers, estuaries or oceans for
use in their facilities. In the process, these facilities remove billions of aquatic
organisms from waters of the United States each year, including fish, fish larvae and
eggs, crustaceans, shellfish, sea turtles, marine mammals, and other aquatic life. The
most significant effects of these withdrawals are on early life stages offish and
shellfish through impingement (being pinned against intake screens or other parts at
the facility) and entrainment (being drawn into cooling water systems).
In November 2001, EPA took final action on regulations for cooling water intake
structures at new facilities that have a design intake flow greater than 2 million
gallons per day (MOD) and that have at least one cooling water structure that uses at
least 25 percent of the water it withdraws for cooling purposes. See 40 CFR 125.81.
EPA's requirements provide a two-track approach. Under Track 1, the intake flow at
facilities that withdraw greater than 10 MGD is restricted to a level commensurate
with the level that may be achieved by use of a closed-cycle recirculating cooling
system. Facilities withdrawing greater than 10 MGD located in areas where fisheries
need additional protection must also use technology or operational measures to
further minimize impingement mortality and entrainment. For facilities with intakes
of less than 10 MGD, the cooling water intake structures may not exceed a fixed
intake screen velocity and the quantity of intake is restricted. Under Track 2, a facility
may choose to demonstrate to the permitting authority that other technologies will
reduce the level of adverse environmental impacts to a level that would be achieved
under Track 1.
In March 2011, EPA proposed standards to reduce injury and death offish and other
aquatic life caused by cooling water intake structures at existing power plants and
manufacturing facilities. The proposed rule would subject existing power plants and
manufacturing facilities withdrawing in excess of 2 MGD of cooling water to an
upper limit on the number offish destroyed through impingement, as well as site-
specific entrainment mortality standards. Certain plants that withdraw very large
volumes of water would also be required to conduct studies for use by the permit
writer in determining site-specific entrainment controls for such facilities. Finally,
under the proposed rule, new generating units at existing power plants would be
required to reduce the intake of cooling water associated with the new unit, to a level
which could be attained by using a closed-cycle cooling system. EPA is continuing
analysis and is in the process of addressing comments and finalizing the rule.
5. Coal Combustion Residuals (CCR) Proposed Rule
CCRs are residues from the combustion of coal in steam electric power plants and
include materials such as coal ash (fly ash and bottom ash) and FGD wastes. CCRs
are currently exempt from the requirements of subtitle C of the Resource
Conservation and Recovery Act (RCRA), which governs the disposition and
management of hazardous wastes. Potential environmental concerns regarding the
management and disposal of CCR include pollution leaching from surface
impoundments and landfills contaminating ground water and natural resource
damages and risks to human health caused by structural failures of surface
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Section 1 - Background
impoundments, like that which occurred at the Tennessee Valley Authority's plant in
Kingston, Tennessee, in December 2008. The spill, which flooded more than 300
acres of land with CCR and contaminated the Emory and Clinch rivers, emphasized
the need for national standards to address risks associated with the disposal of CCR.
On June 21, 2010, EPA co-proposed regulations that included two approaches to
regulating the disposal of CCRs generated by electric utilities and independent power
producers. Under one proposed approach, EPA would list these residuals as "special
wastes," when destined for disposal in landfills or surface impoundments, and would
apply the existing regulatory requirements established under subtitle C of RCRA to
such wastes. Under the second proposed approach, EPA would establish new
regulations applicable specifically to CCRs under subtitle D of RCRA, the section of
the statute applicable to solid (i.e., non-hazardous) wastes. Under both approaches,
CCR that are beneficially used would remain exempt under the Bevill exclusion. EPA
has not yet taken final action on the proposed CCR regulations.
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Section 2- Summary of Proposed Regulation
SECTION 2
SUMMARY OF PROPOSED REGULATION
This section presents a brief summary of the proposed revisions to the ELGs. Section 2.1
summarizes the proposed revisions to discharge requirements and Section 2.2 describes the
proposed revisions to the applicability provision and specialized definitions.
2.1 SUMMARY OF PROPOSED REVISIONS TO DISCHARGE REQUIREMENTS
The proposed Steam Electric rule would revise the technology-based ELGs at 40 CFR
423 for certain wastewater discharges associated with the operation of new and existing
generating units within the Steam Electric Category. The current regulations, which were last
updated in 1982, do not adequately address the toxic pollutants being discharged and have not
kept pace with changes that have occurred in the electric power industry over the last three
decades. The development of new technologies for generating electric power (e.g., coal
gasification) and the widespread implementation of air pollution controls (e.g., flue gas
desulfurization (FGD), selective catalytic reduction (SCR)) have altered existing or created new
wastewater streams at many power plants. Therefore, EPA is proposing to establish new or
additional requirements for wastewaters associated with these new or altered wastestreams.
EPA is proposing to establish new requirements for BAT, NSPS, PSES, and PSNS for
certain wastestreams, described below, for the Steam Electric ELGs. EPA is not proposing new
BCT nor new BPT requirements as part of this proposed rulemaking. Section 8 describes the
technology options considered for each wastestream as the basis for the regulations, as well as
the combination of technology options/wastestreams that comprise the regulatory options
considered for the rulemaking. As described in Section 8, EPA is considering several options in
this rulemaking and has identified four preferred alternatives (i.e., Regulatory Options 3a, 3b, 3,
and 4a) for regulation of existing discharges (i.e., BAT and PSES requirements) for the proposed
revisions to the ELGs. EPA is also proposing Regulatory Option 4 for the new NSPS and PSNS
requirements. The preferred alternatives for the proposed ELGs are summarized below.
Discharges Directly to Surface Water from Existing Facilities
For existing sources that discharge directly to surface water, with the exception of oil-
fired generating units and small generating units (i.e., 50 MW or smaller), under one preferred
alternative for BAT (referred to as Option 3a) the proposed rule would establish BAT for
wastestreams from these sources that include:
• "Zero discharge" effluent limit for all pollutants in fly ash transport water and
wastewater from flue gas mercury control systems;
• Numeric effluent limits for mercury, arsenic, selenium and TDS in discharges of
wastewater from gasification processes;
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Section 2- Summary of Proposed Regulation
• Numeric effluent limits for copper and iron in discharges of nonchemical metal
cleaning wastes;l and
• Effluent limits for bottom ash transport water and combustion residual leachate from
landfills and surface impoundments that are equal to the current Best Practicable
Control Technology Currently Available (BPT) effluent limits for these discharges
(i.e., numeric effluent limits for TSS and oil and grease.
Under a second preferred alternative for BAT (referred to as Option 3b), the proposed
rule would establish numeric effluent limits for mercury, arsenic, selenium, and nitrate-nitrite in
discharges of FGD wastewater from certain steam electric facilities (those with a total plant-level
wet scrubbed capacity of 2,000 MW or greater).2 All other proposed Option 3b requirements are
identical to the proposed Option 3a requirements described above.
Under a third preferred alternative for BAT (referred to as Option 3), the proposed rule
would establish numeric effluent limits for mercury, arsenic, selenium, and nitrate-nitrite in
discharges of FGD wastewater, with the exception of small generating units (i.e., 50 MW or
smaller). All other proposed Option 3 requirements are identical to the proposed Option 3a
requirements described above.
Under a fourth preferred alternative for BAT (referred to as Option 4a), the proposed rule
would establish "zero discharge" effluent limits for all pollutants in bottom ash transport water,
with the exception of all generating units with a nameplate capacity of 400 MW or less (for those
generating units that are less than or equal to 400 MW, the proposed rule would set BAT equal to
BPT for discharges of pollutants found in the bottom ash transport water). All other proposed
Option 4a requirements are identical to the proposed Option 3 requirements described above.
In addition, for oil-fired generating units and small generating units (i.e., 50 MW or
smaller) that are existing sources and discharge directly to surface waters, under the four
preferred alternatives for regulation of existing sources, the proposed rule would establish
effluent limits (BAT) equal to the current BPT effluent limits for the wastestreams listed above.3
Discharges to POTWs from Existing Facilities
For discharges from existing sources to POTWs, EPA is proposing to establish PSES that
are equal to the proposed BAT, with the following exceptions:
1 As described in Section VIII, EPA is proposing to exempt from new copper and iron BAT limitations any existing
discharges of nonchemical metal cleaning wastes that are currently authorized without iron and copper limits. For
these discharges, BAT limits would be set equal to BPT limits applicable to low volume wastes.
2 Total plant-level wet scrubbed capacity is calculated by summing the nameplate capacity for all of the units that
are serviced by wet FGD systems.
3 As described in Section VIII, one of the preferred options would increase this threshold for purposes of discharges
of pollutants in bottom ash transport water only, to 400 MW or less.
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Section 2- Summary of Proposed Regulation
• Numeric standards for discharges of nonchemical metal cleaning wastes would be
established only for copper;4
• Under Options 3a, 3b, and 3 for PSES, EPA is not proposing to establish pretreatment
standards for discharges of bottom ash transport water. Under Option 4a, EPA is not
proposing to establish pretreatment standards for discharges of bottom ash transport
water for generating units with a nameplate capacity of 400 MW or less;5 and
• Other than the pretreatment standards for nonchemical metal cleaning wastes, EPA is
not proposing to establish pretreatment standards for existing sources for discharges
from existing oil-fired units and small generating units (i.e., 50 MW or smaller).
Discharges Directly to Surface Water from New Sources
For all generating units that are new sources and discharge directly to surface waters,
including oil-fired generating and small generating units, the proposed rule would establish
NSPS that include:
• Numeric standards for mercury, arsenic, selenium, and nitrate-nitrite in discharges of
FGD wastewater;
• Maintaining the current "zero discharge" standard for all pollutants in fly ash
transport water for direct dischargers;
• Establishing "zero discharge" standards for all pollutants in bottom ash transport
water and wastewater from flue gas mercury control systems;
• Numeric standards for mercury, arsenic, selenium, and TDS in discharges of
wastewater from gasification processes;
• Numeric standards for mercury and arsenic in discharges of combustion residual
leachate; and
• Numeric standards for TSS, oil and grease, copper, and iron in discharges of
nonchemical metal cleaning wastes.
Discharges to POTWs from New Sources
For generating units that are new sources and discharge to POTWs, including oil-fired
generating units and small generating units, EPA is proposing to establish PSNS that are equal to
the proposed NSPS, except that the PSNS would also establish a "zero discharge" standard for
all pollutants in fly ash transport water (the current NSPS already includes a zero discharge
standard for pollutants in fly ash transport water), and the PSNS would not include numeric
standards for TSS, oil and grease, or iron in discharges of nonchemical metal cleaning wastes.
4 As described in Section VIII, EPA is proposing to exempt from new copper PSES standards any existing
discharges of nonchemical metal cleaning wastes that are currently authorized without copper limits. For these
discharges, the regulations would not specify PSES.
5This is because, as explained in Section VII, EPA generally does not establish pretreatment standards for
conventional pollutants (e.g., TSS and oil and grease) because POTWs are designed to treat these conventional
pollutants.
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Section 2- Summary of Proposed Regulation
EPA is also proposing to add provisions to the ELGs that would prevent facilities from
circumventing the new effluent limitations guidelines and standards. The proposed provision
would do the following:
• Generally require that compliance with the effluent limits applicable to a particular
wastestream be demonstrated prior to mixing the treated wastestream with other
wastestreams; and
• Establish requirements that prevent moving effluent produced by a process operation
for which there is a zero discharge effluent limit/standard, to another process
operation for discharge under less stringent requirements.
In addition to the proposed requirements, EPA is also considering establishing the
following provisions to the ELGs:
• Establish best management practices (BMP) requirements that would apply to surface
impoundments containing coal combustion residuals (e.g., ash ponds, FGD ponds);
and
• Establish a voluntary program that would provide incentives for existing power plants
that dewater and close their surface impoundments containing combustion residuals
and for power plants that eliminate the discharge of all process wastewater (excluding
cooling water discharges).
2.2 REVISIONS TO APPLICABILITY PROVISION AND SPECIALIZED DEFINITIONS
In addition to the proposed revisions to the discharge requirements, EPA is proposing
certain modifications to the applicability provision for the ELGs. These are not substantive
modifications that would alter which generating units are regulated by the ELGs. These units
have been traditionally regulated by the exiting ELGs. Instead, the proposed modifications would
remove potential ambiguity present in the current regulatory text. The changes include:
• Clarification that certain facilities, such as certain municipal-owned facilities, which
generate and distribute electricity within a service area (such as distributing electric
power to municipal-owned buildings), but which use accounting practices which are
not commonly thought of as a "sale" are nevertheless subject to the ELGs;
• Clarification that "primarily," as used in 423.10, refers to those operations where the
generation of electricity is the predominant source of revenue and/or principal reason
for operation;
• Clarification that fuels derived from fossil fuel are within the scope of the current
ELGs; and
• Clarification that combined cycle systems, which are generating units composed of
one or more combustion turbines operating in conjunction with one or more steam
turbines, are subject to the ELGs.
In addition to the proposed revisions discussed above, EPA is proposing revisions to
certain existing specialized definitions, as well as inclusion of new specialized definitions. The
proposed revisions to existing specialized definitions (with revisions underlined) are:
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Section 2- Summary of Proposed Regulation
(b) The term low volume waste sources means, taken collectively as if from one
source, wastewater from all sources except those for which specific limitations are
otherwise established in this part. Low volume waste sources include, but are not
limited to, the following: wastewaters from ion exchange water treatment systems,
water treatment evaporator blowdown, laboratory and sampling streams, boiler
blowdown, floor drains, cooling tower basin cleaning wastes, recirculating house
service water systems, and scrubber air pollution control systems whose primary
purpose is particulate removal. Sanitary wastes, air conditioning wastes, and
wastewater from carbon capture or sequestration systems are not included in this
definition.
(e) The term fly ash means the ash that is carried out of the furnace by the gas stream
and collected by a capture device such as a mechanical precipitator, electrostatic
precipitator, and/or fabric filter. Economizer ash is included in this definition when it
is collected with fly ash. Ash is not included in this definition when it is collected in
wet scrubber air pollution control systems whose primary purpose is particulate
removal.
The proposed new specialized definitions are:
(n) The term flue gas desulfurization (FGD) wastewater means any process
wastewater generated specifically from the wet FGD scrubber system, including any
solids separation or solids dewatering processes.
(o) The term flue gas mercury control (FGMC) wastewater means any process
wastewater generated from an air pollution control system installed or operated for
the purpose of removing mercury from flue gas. This includes fly ash collection
systems when the particulate control system follows the injection of sorbents or
implementation of other controls to remove mercury from flue gas. Flue gas
desulfurization systems are not included in this definition.
(p) The term transport water means any process wastewater that is used to convey fly
ash, bottom ash, or economizer ash from the ash collection equipment, or boiler, and
has direct contact with the ash.
(q) The term gasification wastewater means, taken collectively as if from one source,
wastewater from all sources associated with the gasification process or related
chemical recovery processes at an integrated gasification combined cycle operation.
Gasification wastewater includes, but is not limited to, slag handling wastewater, fly
ash stream, sour/grey water (which consists of condensate from gas cooling, as well
as other wastestreams), CCVsteam stripper wastewater, air separation unit blowdown,
and sulfur recovery unit blowdown.
(r) The term combustion residual leachate means leachate from onsite landfills or
surface impoundments (e.g., ponds) containing combustion residuals. Leachate
includes liquid, including any suspended or dissolved constituents in the liquid that
has percolated through or drained from waste or other materials emplaced in a
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Section 2- Summary of Proposed Regulation
landfill, or that pass through the containment structure (e.g., bottom, dikes, berms) of
a surface impoundment. Leachate also includes the terms seepage, drains, leak, and
leakage, which are generally used in reference to leachate from an impoundment.
(s) The term oil-fired unit means a generating unit that uses oil as the primary or
secondary fuel source and does not use a gasification process or any coal or
petroleum coke as a fuel source. This definition does not include units that use oil
only for start up or flame-stabilization purposes.
(t) The term sufficiently sensitive analytical method means a method that ensures the
sample-specific quantitation level for the wastewater being analyzed is at or below
the level of the effluent limitation.
(u) The term nonchemical metal cleaning waste means any wastewater resulting from
the cleaning of any metal process equipment without chemical cleaning compounds,
including, but not limited to, boiler tube cleaning, boiler fireside cleaning, and air
preheater cleaning.
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Section 3- Data Collection Activities
SECTION 3
DATA COLLECTION ACTIVITIES
EPA collected and evaluated information and data from various sources in the course of
developing the proposed effluent limitations guidelines and standards (ELGs) for the Steam
Electric Power Generating Point Source Category (Steam Electric Category). EPA used these
data to develop the industry profile, determine the applicability of the rule, evaluate industry
subcategorization, and determine wastewater characteristics, technology options, compliance
costs, pollutant loading reductions, and non-water quality environmental impacts. This section
discusses the following data collection activities as they relate to technical aspects of this
proposed rulemaking:
• Steam Electric Power Generating Detailed Study (Section 3.1);
• Engineering site visits (Section 3.2);
• Questionnaire for the Steam Electric Power Generating Effluent Guidelines (Section
3.3);
• Field sampling program (Section 3.4);
• EPA and state sources (Section 3.5);
• Industry-submitted data (Section 3.6);
• Technology vendor data (Section 3.7);
• Other data sources (Section 3.8); and
• Protection of confidential business information (Section 3.9).
3.1 STEAM ELECTRIC POWER GENERATING DETAILED STUDY
EPA conducted a detailed study of the steam electric power generating industry between
2005 and 2009. During the study, EPA collected data about the industry by performing the
following activities:
• Conducted 34 site visits and six wastewater sampling episodes at steam electric
power plants;
• Distributed a questionnaire to collect data from nine companies (operating 30 coal-
fired power plants);
• Reviewed publicly available sources of data; and
• Coordinated with EPA program offices, other government organizations (e.g., state
groups and permitting authorities), and industry and other stakeholders.
EPA's Steam Electric Power Generating Point Source Category: Detailed Study Report
provides an overview of the steam electric power generating industry and its wastewater
discharges, and the data collection activities and analyses conducted during EPA's detailed study
[U.S. EPA, 2009b]. The study focused largely on discharges associated with coal ash handling
operations and wastewater from flue gas desulfurization (FGD) air pollution control systems
3-1
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Section 3- Data Collection Activities
because these sources are responsible for the majority of the toxic pollutants currently discharged
by steam electric power plants.
EPA also evaluated wastewater from coal pile runoff, condenser cooling, equipment
cleaning, and leachate from landfills and surface impoundments. Additionally, EPA reviewed
information on integrated gasification combined cycle (IGCC) operations and carbon capture
technologies. EPA also identified wastewaters from flue gas mercury control systems and
regeneration of the catalysts used for Selective Catalytic Reduction (SCR) NOx controls as
potential new wastestreams that warrant attention.
EPA used the information collected during the detailed study to select plants with
different technology bases for site visits, support the development of the Questionnaire for the
Steam Electric Power Generating Effluent Guidelines (Steam Electric Survey), select plants to
receive the questionnaire, and select plants for EPA's sampling program during the rulemaking.
Additionally, EPA used the data collected during the detailed study to develop an industry
profile and supplement the findings from the survey and sampling program (i.e., Form 2C data
provided by the industry trade association). The remainder of Section 3 provides additional
details regarding the data used from the study.
3.2 ENGINEERING SITE VISITS
EPA conducted a site visit program to gather information on the types of wastewaters
generated by steam electric power plants, and the methods of managing these wastewaters to
allow for recycle, reuse, or discharge. EPA focused data gathering activities primarily on FGD
wastewater treatment and management of ash transport water at coal- and petroleum coke-fired
power plants because the FGD and ash transport water streams are the primary sources of
pollutant discharges from the industry. EPA also conducted site visits at oil-, gas-, and nuclear-
fueled power plants to better understand the plant operations, the wastewaters generated, and the
types of treatment systems used. EPA conducted 65 site visits at steam electric power plants in
22 states between December 2006 and February 2013. The Agency conducted three additional
site visits in Italy in April 2011 to obtain information on their FGD wastewater treatment
systems. Table 3-1 summarizes the site visits conducted. The list of site visits excludes EPA
sampling episodes and EPA audits of CWA 308 sampling described in Section 3.4.
The purpose of the site visits was to collect information about each site's electric
generating processes, wastewater management practices, and treatment technologies, and to
evaluate each plant for potential inclusion in EPA's sampling program. To identify potential
candidate plants for site visits, EPA used information from EPA's Office of Air and Radiation
(OAR) and data provided by the Utility Water Act Group (UWAG), and other sources to
determine the types of operations at power plants. During the detailed study, EPA used the
UWAG data in conjunction with information from other sources, including publicly available
plant-specific information, state and regional permitting authorities, and the Study data request,
to identify plants to contact and obtain additional details regarding the plants' operations. During
the rulemaking effort, EPA identified potential site visit candidates based on information
provided in the survey (i.e., plant operating characteristics). From the information obtained
during these contacts, EPA selected plants for site visits.
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Section 3- Data Collection Activities
The specific objectives of these site visits were to:
• Gather general information about each plant's operations;
• Gather information on pollution prevention and wastewater treatment/operations;
• Evaluate whether the plant was appropriate to include in the sampling program;
• Gather plant-specific information to develop sampling plans; and
• Select and evaluate potential sampling points.
Table 3-1. List of Site Visits Conducted During the Detailed Study and Rulemaking
Plant Name, Location
Yates, Georgia
Wansley, Georgia
Widows Creek, Alabama
Conemaugh, Pennsylvania
Homer City, Pennsylvania
Pleasant Prairie, Wisconsin
Bailly, Indiana
Seminole, Florida
Big Bend, Florida
Cayuga, New York
Mitchell, West Virginia
Cardinal, Ohio
Bruce Mansfield, Pennsylvania
Roxboro, North Carolina
Belews Creek, North Carolina
Marshall, North Carolina
Mount Storm, West Virginia
Harrison, West Virginia
Mountaineer, West Virginia
Gavin, Ohio
Deely, Texas
Clover, Virginia
JK Spruce, Texas
Fayette Power Project/Sam Seymour, Texas
Ghent, Kentucky
Trimble County, Kentucky
Cane Run, Kentucky
Mill Creek, Kentucky
Brandon Shores, Maryland
Kenneth C Coleman, Kentucky
Gibson, Indiana
Month/Year of Site Visit
Dec 2006
Dec 2006
Dec 2006; Sept 2007
Feb2007;Aug2012
Feb 2007; Aug 2007; Aug 2012
Apr 2007; Mar 20 10
Apr 2007
Apr 2007; Jan 2013
Apr 2007; Jul 2007
May 2007
May 2007; Oct 2007
May 2007; Oct 2007; Feb 2010
Oct 2007
Mar 2008
Mar 2008; Oct 2008
Mar 2008
Sept 2008
Sept 2008
Sept 2008; Jan 2009
Sept 2008
Oct 2008
Oct 2008
Oct 2008
Oct 2008
Dec 2008
Dec 2008
Dec 2008
Dec 2008
Jan 2009; Mar 2010
Feb 2009
Feb 2009
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Section 3- Data Collection Activities
Table 3-1. List of Site Visits Conducted During the Detailed Study and Rulemaking
Plant Name, Location
Paradise, Kentucky
Wabash River, Indiana
Miami Fort, Ohio
Covanta, Virginia
Chesterfield, Virginia
Karn-Weadock, Michigan
Kinder Morgan Power, Michigan
Monroe, Michigan
Allen, North Carolina
Cape Fear, North Carolina
Catawba, South Carolina
HB Robinson, South Carolina
FP&L Sanford, Florida
Polk, Florida
Fort Martin, West Virginia
Hatfield's Ferry, Pennsylvania
Keystone, Pennsylvania
Dickerson, Maryland
Dallman, Illinois
Duck Creek, Illinois
latan, Missouri
Edwardsport, Indiana
Torrevaldaliga Nord, Italy
Monfalcone, Italy
Frederico II (Brindisi), Italy
FP&L Manatee, Florida
Wateree, South Carolina
McMeekin, South Carolina
Month/Year of Site Visit
Feb 2009
Feb2009;Aug2010
Apr 2009; Mar 20 10
Jul 2009
Sept 2009
Sept 2009
Sept 2009
Sept 2009
Oct 2009
Oct 2009
Oct 2009
Oct 2009
Oct 2009
Oct 2009
Feb 20 10
Feb 20 10
Feb 20 10
Mar 20 10
Apr 20 10
Apr 20 10
Apr 20 10
Mar 20 11
Apr 20 11
Apr 20 11
Apr 20 11
Nov2011
Jan 20 13
Jan 20 13
3.3
QUESTIONNAIRE FOR THE STEAM ELECTRIC POWER GENERATING EFFLUENT
GUIDELINES
The principal source of information and data used in developing the ELGs is the industry
response to the survey distributed by EPA under the authority of Section 308 of the Clean Water
Act (CWA), 33 U.S.C. 1318. EPA designed the industry survey to obtain technical information
related to wastewater generation and treatment, and economic information such as costs of
wastewater treatment technologies and financial characteristics of potentially affected
companies. The responses were used to evaluate pollution control options for establishing
revisions to the ELGs for the Steam Electric Category.
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Section 3- Data Collection Activities
EPA developed an Information Collection Request (ICR) entitled Questionnaire for the
Steam Electric Power Generating Effluent Guidelines (Steam Electric Survey). The survey was
approved by the Office of Management and Budget (OMB) in May 2010 (OMB Control No.
2040-0281).
The survey comprised the following nine parts:
• Part A: Steam Electric Power Plant Operations
• Part B:FGD Systems
• Part C: Ash Handling
• Part D: Pond/Impoundment Systems and Other Wastewater Treatment Operations
• Part E: Wastes from Cleaning Metal Process Equipment
• Part F: Management Practices for Ponds/Impoundments and Landfills
• Part G: Leachate Sampling Data for Ponds/Impoundments and Landfills
• Part H: Nuclear Power Generation
• Part I: Economic and Financial Data
Part A gathered information on all steam electric generating units at the surveyed plant,
the fuels used to generate electricity, air pollution controls, cooling water, ponds/impoundments
and landfills used for coal combustion residues (CCR), coal storage and processing, and outfalls.
Parts B through I collected economic data and detailed technical information on certain aspects
of power plant operations, including requiring some plants to collect and analyze wastewater
samples.
In order to identify the population of plants that would be candidates to receive the
survey, EPA first created a sample frame consisting of all fossil- and nuclear-fueled steam
electric power plants in the United States that reported operating under NAICS code 22, and their
corresponding generating units. NAICS code 22 (Utilities) comprises establishments engaged in
providing the following utility services: electric power, natural gas, steam supply, water supply,
and sewage removal. Because power generation was not the primary purpose of some of the
plants in this NAICS code (i.e., sewage removal plants), EPA removed them from the sample
frame.
The resulting sample frame consisted of information obtained from databases that are
maintained by the Energy Information Administration (EIA), a statistical agency of the U.S.
Department of Energy (DOE) that collects information on existing electric generating plants and
associated equipment to evaluate the current status and potential trends in the industry. The
source of the information came primarily from the 2007 Electric Generator Report (Form EIA-
860) and was supplemented by information collected by Form EIA-923 and a survey conducted
by EPA's Office of Solid Waste and Emergency Response (OSWER) [U.S. EPA, 2009a]. In
addition, EPA identified two plants that started operations after 2007 and obtained information
about them from Internet searches.
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Section 3- Data Collection Activities
Collectively, the data sources provided key frame information for each steam electric
power plant with a NAICS code of 22, such as county, state, North American Electric Reliability
Council (NERC) region, business size (small or non-small), and regulatory status (e.g., regulated
by public service commission). Also included in the data sources were the number of each type
of generating unit operated at the plant, an identifier that specified the fuel classification of each
generating unit for the plant, and an identifier based on the fuel classifications of the generating
units (e.g., coal, gas-combined cycle, nuclear). In addition, the OSWER survey results and the
EIA-923 data set provided information on the presence of surface impoundments and landfills at
the plant along with the materials that were stored or disposed of in the impoundment/landfill.
EPA also used data for each generating unit reported in the EIA-860 data set classified as a
steam electric generating unit, such as prime mover and fuel (fossil or nuclear), nameplate
capacity (in megawatts (MW)), unit fuel classification, and the plant where the generating unit is
housed. The sample frame contained information on 1,197 plants containing 2,571 generating
units that were potentially within the scope of the Steam Electric ELGs.
To minimize the burden on the respondents, EPA grouped plants into strata based on fuel
classification so that an efficient stratified sampling scheme could be used.6 This sampling
strategy allowed for different sampling rates across the strata. Depending on the amount or type
of information it required for the rulemaking, EPA solicited information either from all plants
within a stratum (i.e., a census or "certainty" stratum) or from a random sample of plants within
a stratum (i.e., probability sampled stratum). As a result, the survey was distributed to all coal-
and petroleum coke-fired power plants and a sample of the rest of the steam electric industry,
including oil-fired, gas-fired, gas-combined cycle, and nuclear power plants. Table 3-2 presents
the number of plants in each fuel classification (i.e. strata) included in the sample frame used to
identify survey recipients.
Table 3-2. Number of Plants in Each Fuel Classification in the Survey Sample Frame Used
to Identify Survey Recipients
Fuel Classification
Coal
Petroleum coke
Oil
Gas
Nuclear
Combination3
Number of Facilities
495
9
43
555
63
32
a - EPA used the "combination" designation for plants that have at least two generating units that have different
unit-level designations (e.g., oil, gas, nuclear), but do not have any coal or petroleum coke units.
The survey comprised several sections that were tailored to address specific processes,
data needs, or types of power plants. Parts A and I of the survey were sent to all sampled plants;
6 EPA classified plants into the fuel categories to develop the sample frame of all fossil- and nuclear-fueled steam
electric power plants in the United States. EPA further developed plant-level fuel classifications based on a
hierarchy of the type of units operating at the plant; therefore, some plants may operate units that burn other types of
fuel in addition to the fuel under which they are classified. Plants that operated coal- or petroleum coke-fired units
were classified as coal or petroleum coke regardless of other fuels at the plant. For example, a plant classified as
coal will have coal-fired unit(s) at the plant, but may also have oil- fired, gas-fired, or nuclear unit(s).
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the remaining sections were sent to sampled plants according to their fuel classification.
Specifically, in addition to Parts A and I, all coal- and petroleum coke-fired power plants
received Parts B, C, D, and H. A subsample of coal- and petroleum coke-fired power plants also
received Parts E, F, and G. The sampled plants in the oil-fired and combination strata received
Parts A, B, C, D, E, H, and I.7 The sampled plants in the gas-fired, gas-combined cycle, and
nuclear power strata received Parts A, E, H, and I.
Most parts of the survey focused on gathering information from all coal- and petroleum
coke-fired power plants. Therefore, all plants with a fuel classification of coal or petroleum coke
were selected with certainty (i.e., probability of selection equal to one), except for Parts E, F, and
G. In addition, for strata with 10 or fewer plants, EPA included all plants in the sample, and at
least 10 plants were sampled within strata containing more than 10 plants. As such, all regulated
and nonregulated combination plants (except gas-fired and gas-combined cycle) were selected
with certainty. For the remaining no regulated and regulated plants with plant fuel classifications
of gas, gas-combined cycle, oil, nuclear, and combination (gas and gas-combined cycle), EPA
randomly selected 30 percent of the plants to receive the survey while adhering to the 10 plant
minimum per stratum. Based on this sampling design, 733 plants were selected to receive the
survey. This total includes 495 coal-fired, 9 petroleum coke-fired, 20 oil-fired, 167 gas-fired, 20
nuclear power plants, and 22 combination power plants.
EPA received 733 completed surveys, including those from 53 plants that certified that
they were not and did not have the capability to be engaged in steam electric power production,
would be retired by December 31, 2011, or did not generate electricity in 2009 by burning any
fossil or nuclear fuels.8 Because responses were received for all 733 sampled plants (including
those 53 plants that were not required to complete the remainder of the survey), there were no
plants that were considered non-respondents, thus the response rate is 100 percent.
EPA then developed weighting factors to represent the entire industry on a national level
from the data provided by the 733 plants that received the survey. Because coal- and petroleum
coke-fired plants were selected with certainty, EPA did not weight the responses for the majority
of data because all plants were represented. However, because EPA sent only Parts E, F, and G
of the survey to a probability sample of coal- and petroleum coke-fired plants, the Parts E, F, and
G data were weighted to represent the entire industry. In addition, data collected from the
probability-sampled strata for other fuel types were weighted to represent the entire industry. All
survey data presented in this document have been weighted to represent the entire industry,
unless otherwise noted.
3.4 FIELD SAMPLING PROGRAM
Between July 2007 and April 2011, EPA conducted a sampling program at 17 different
steam electric power plants in the United States and Italy to collect wastewater characterization
7 For the purpose of the survey, combination power plants mean plants that do not operate generating units fueled by
coal or petroleum coke and have at least two generating units that have different unit-level fuel classifications (e.g.,
gas and oil, gas and gas-combined cycle).
8 At the time EPA developed the survey, EPA used 2011 as the cutoff year for retirements because the plants would
be retired before the proposed rule was published.
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Section 3- Data Collection Activities
data and/or treatment performance data associated with FGD wastewater, fly ash and bottom ash
wastewater, and wastewater from gasification and carbon capture processes. EPA also obtained
sampling data for surface impoundment and landfill leachate collection and treatment systems at
39 plants, as required by Part G of the Steam Electric Survey (described in Section 3.3). This
leachate sampling is not included in the following description of the field sampling program.
EPA's field sampling program began during its detailed study and continued throughout
this rulemaking effort. During the study, EPA conducted one- or two-day sampling episodes at
six plants to characterize untreated wastewaters generated by coal-fired power plants, as well as
to obtain a preliminary assessment of treatment technologies and best management practices for
reducing pollutant discharges. The types of wastewaters sampled during the detailed study were
untreated and treated FGD wastewater, fly ash wastewater, and bottom ash wastewater. See the
Steam Electric Power Generating Point Source Category: Final Detailed Study Report for
additional information on the sampling program completed during the detailed study [U.S. EPA,
2009b].
Following completion of the detailed study, EPA conducted a sampling program at steam
electric power plants to collect wastewater characterization data and treatment performance data
associated with FGD wastewater and to collect data for other emerging wastestreams for which
characterization data were not available (i.e., carbon capture and gasification wastewaters). As
part of this sampling program, EPA conducted on-site sampling activities (i.e., samples were
collected directly by EPA), as well as requiring some plants to collect samples for EPA (i.e.,
CWA 308 monitoring program). The following sections present information on the selection of
plants sampled, the wastewater treatment systems sampled, and the sampling process for field
sampling conducted following the completion of the detailed study.
3.4.1 On-Site Sampling Activities
3.4.1.1 United States
EPA conducted four-day sampling episodes at seven U.S. plants to obtain the following:
1) wastewater characterization data and 2) wastewater treatment technology performance data.
EPA used these data in combination with other industry-supplied data to evaluate wastewater
discharges resulting from steam electric power plants and to evaluate technology options for
handling and treating these wastewaters. The sampling program primarily focused on the
wastewaters associated with the operation of wet FGD systems. EPA collected information to
characterize the untreated FGD scrubber purge wastewater, as well as treated FGD wastewater
from chemical precipitation and biological treatment systems.
The sampling characterized the wastewaters generated by wet FGD scrubbers and the
treatment performance of the systems used to treat the FGD scrubber purge wastewaters. EPA
also collected field quality control (QC) samples consisting of bottle blanks, field blanks,
equipment blanks, and duplicate samples, and laboratory QC samples used for matrix
spike/matrix spike duplicate analyses.
EPA's sampling program also collected data in order to perform an engineering
assessment of the design, operation, and performance of treatment systems at steam electric
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power plants. Specifically, EPA collected information regarding system design and day-to-day
operation.
EPA considered the following characteristics to select plants for sampling:
• Coal-Fired Boilers: All of the plants selected for the sampling program were coal-
fired plants because the wastestreams of interest for the sampling program data
objectives are associated with coal-fired power plants.
• Wet FGD System: EPA evaluated wastewaters generated from wet FGD systems and
the treatment of these wastewaters. EPA considered the following selection criteria
regarding FGD systems:
Type of FGD Wastewater Treatment System: The primary factor for selection was
the type of wastewater treatment system being operated to treat FGD wastewater.
EPA selected plants operating the following types of wastewater treatment
systems, which are the basis for the technology options:
• Chemical precipitation;
• Biological treatment; and
• Vapor-compression evaporation.
- Age of FGD Wastewater Treatment System: EPA collected samples from
wastewater treatment systems that reached steady-state operation. EPA sampled
FGD wastewater treatment systems that had been operating for at least six months
and that plant staff considered the system to have reached a pseudo-steady state
condition past the initial commissioning period.
Type of FGD System: EPA considered the type of FGD system operated by the
plant (e.g., limestone forced oxidation, lime inhibited oxidation) when selecting
plants for sampling. Plants generating FGD scrubber wastewater typically operate
limestone forced oxidation (LSFO) FGD systems. The LSFO system has the
capability of producing wallboard-grade gypsum, but it typically requires a purge
stream that needs to be treated prior to discharge.9
• NOX Controls: EPA considered whether the plants operate a selective catalytic
reduction (SCR) system or a selective noncatalytic reduction (SNCR) system.
Although these NOX control systems do not generate a specific wastewater stream,
their operation may affect the FGD wastewater characteristics as well as the fly ash
and associated fly ash sluice water characteristics.
• Power Load Cycling: EPA considered a plant's load cycling (i.e., baseload, cycling,
peaking) because the production load could potentially affect the FGD wastewater
9 EPA did not select any plants operating inhibited oxidation FGD systems or once-through FGD systems for
sampling after completion of the detailed study because EPA did not identify any plants that operate these systems
and also operate a chemical precipitation or biological treatment system. The wastewater pollutants present in these
systems are similar to those generated by LSFO systems because the scrubbing process will capture the same types
of pollutants from the flue gas. The technologies used to treat wastewater from a recirculating LSFO FGD system
would also be effective at treating the wastewater from inhibited oxidation or once-through LSFO FGD systems.
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Section 3- Data Collection Activities
characteristics Most of the plants selected for sampling were baseload plants;
however, plants with cycling units were also selected.
• Type of Coal: EPA considered the type of coal that the plant burns and selected
plants burning different types of coal because the types and concentration of metals
present in the FGD wastewater could differ based on the fuel source. Most of the
plants sampled burn bituminous coal because the majority of plants with wet FGD
systems burn bituminous coal; however, EPA also sampled wastewater at plants that
burn subbituminous coal.
EPA selected and conducted sampling activities at the following plants in the U.S.:
• Duke Energy Carolina's Belews Creek Steam Station;
• We Energies' Pleasant Prairie Power Plant;
• Duke Energy's Miami Fort Station;
• Duke Energy Carolina's Allen Steam Station;
• Mirant Mid-Atlantic, LLC's Dickerson Generating Station;
• RRI Energy's Keystone Generating Station; and
• Allegheny Energy's Hatfield's Ferry Power Station.
All of the selected plants operate chemical precipitation wastewater treatment systems to
treat their FGD wastewater. The treatment systems at Belews Creek, Allen, and Dickerson also
include a biological treatment stage following the chemical precipitation. Table 3-3 presents the
selection details for each sampled plant.
The pollutants selected for analysis reflected the current understanding of FGD
wastewaters, including contributions from the fuel, scrubber sorbents, treatment chemicals, and
other sources. Table 3-4 lists the analytical methods that EPA used for each analyte. In addition
to these analytes, EPA collected field measurements at all sampling points including temperature
and pH.
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Table 3-3. Selection Criteria for Plants Included in EPA's Sampling Program in the United States
Plant Name
Belews Creek
Pleasant Prairie
Miami Fort
Allen
Dickerson
Keystone
Hatfield's Ferry
Selection Criteria
Coal-Fired
Boilers
Yes
Yes
Yes
Yes
Yes
Yes
Yes
FGD Treatment System
Chemical
Precipitation
Yes13
Yes2'4
Yes2
Yes13
Yesu
Yes2
Yes2
Biological
Yes5
No
No
Yes5
Yes6
No
No
Type of FGD
System
LSFO
LSFO
LSFO
LSFO
LSFO
LSFO
LSFO
NOx
Controls
SCR
SCR
SCR
SNCR
SNCR
SCR
SNCR
Power Load
Cycling
Baseload
Baseload
Baseload
Cycling
Cycling
Baseload
Baseload
Type of Coal
Eastern Bituminous
Subbituminous
(Powder River Basin)
Eastern Bituminous
Bituminous
Eastern Bituminous
Eastern Bituminous
Bituminous,
Subbituminous
(Powder River Basin)
Commercial-
Grade Gypsum
By-product
Yes
Yes
Yes
Yes
Yes
No
No
1 - The chemical precipitation system at these plants include hydroxide precipitation and iron coprecipitation, but do not include sulfide precipitation as part of
the process.
2 - The chemical precipitation system at these plants include hydroxide precipitation, sulfide precipitation, and iron coprecipitation.
3 - The chemical precipitation system at these plants precede a biological treatment stage.
4 - Two-stage chemical precipitation treatment. All other sampled plants use one-stage chemical precipitation.
5 - Anoxic/anaerobic biological system primarily designed to remove selenium.
6 - Sequencing batch reactor (SBR) primarily designed for nutrient removal (nitrification/denitrification).
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Section 3 - Data Collection Activities
Table 3-4. Analytical Methods Used for EPA's Sampling Program
Parameter
Method Number
Classical*
Biochemical oxygen demand (BOD5)
Chemical oxygen demand (COD)
Total suspended solids (TSS)
Total dissolved solids (TDS)
Sulfate
Chloride
Ammonia as nitrogen
Nitrate/nitrate as nitrogen
Total Kjeldahl nitrogen (TKN)
Total phosphorus
Total cyanide
SM5210B
EPA 4 10.4
SM 2540 D
SM 2540 C
EPA 300.0
EPA 300.0
EPA 350.1
EPA 353.2
EPA 351.2
EPA 365.1
SM4500CNE
Total and Dissolved Metals
Mercury
Hexavalent chromium (dissolved only)
Antimony, arsenic, cadmium, chromium, copper, lead, manganese, nickel,
selenium, silver, thallium, and vanadium
Aluminum, barium, beryllium, boron, calcium, cobalt, iron, magnesium,
molybdenum, sodium, tin, titanium, and zinc1
EPA 163 IE
EPA 218.6
EPA 200.8 with collision cell
EPA 200.7
a - Zinc was analyzed using EPA Method 200.8 with collision cell for the Belews Creek, Pleasant Prairie, Miami
Fort, and Allen sampling episodes, but was analyzed by EPA Method 200.7 for the Dickerson, Keystone, and
Hatfield's Ferry sampling episodes. EPA changed methods because it was observing high concentrations of zinc in
the influent and effluent samples that were more suited for analysis by EPA Method 200.7.
EPA collected representative samples at the influent and effluent of the FGD wastewater
treatment systems and, where applicable, the mid-point of the FGD treatment system (i.e.,
effluent from chemical precipitation system prior to biological treatment). EPA collected 24-hour
composite samples at the mid-point and effluent sampling points for all analytes except mercury
and cyanide. At the mid-point and effluent sampling points, EPA collected cyanide as a single
grab sample and mercury as four individual grab samples over the 24-hour period (i.e., a grab
sample collected every six hours). All influent samples were collected as grab samples.
Sampling episode reports describing the sample collection activities and the analytical
results from the seven on-site sampling episodes are included in the rulemaking record. [ERG,
2012a-2012g]
3.4.1.2
Italy
In April 2011, EPA conducted a three-day sampling episode at Enel's Federico II Power
Plant (Brindisi), located in Brindisi, Italy. The purpose was to characterize untreated FGD
scrubber purge and treated FGD wastewater from an FGD wastewater treatment system
consisting of chemical precipitation followed by mechanical vapor-compression evaporation.
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Section 3 - Data Collection Activities
The mechanical vapor-compression evaporation system used a falling-film brine concentrator to
produce a concentrated wastewater stream and a reusable distillate stream. The concentrated
wastewater stream was further processed in a forced-circulation crystallizer, in which a solid
product was generated along with a reusable condensate stream.
In addition to collecting the samples of untreated FGD scrubber purge and treated FGD
wastewater, EPA also collected field QC samples consisting of bottle blanks, field blanks,
equipment blanks, field duplicate samples, and laboratory QC aliquots used for matrix
spike/matrix spike duplicate analyses.
Brindisi was selected by EPA for sampling because it operates a one-stage chemical
precipitation system followed by softening and a two-stage vapor-compression evaporation
system for the treatment of FGD wastewater. The following are the characteristics of the Brindisi
plant:
• The plant is a coal-fired power plant;
• The plant operates limestone forced oxidation wet FGD systems on all four units;
• The plant operates a segregated FGD wastewater treatment system, which includes
the following steps:
- Settling,
- Equalization,
- Lime, sodium sulfide, and caustic soda addition (pH adjustment/metal hydroxide
precipitation),
- Ferric chloride addition,
- Polyelectrolyte addition,
- Clarification,
- Ferrous chloride and soda ash addition (softening),
- Clarification,
- Evaporation (brine concentrator),
- Crystallization; and
• The plant operates selective catalytic reduction (SCR) systems on all four units.
EPA collected samples for the same list of analytes listed in Table 3-4, except for
excluding the following analytes either because of holding time considerations or time
constraints for the sampling event:
• BODS;
• Total cyanide; and
• Dissolved metals (all analytes).
EPA also collected field measurements at all sampling points including temperature and
pH.
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EPA collected representative samples of the influent to the FGD wastewater treatment
system, the distillate from the brine concentrator, and the condensate from the crystallizer. EPA
collected six-hour composite samples at the brine concentrator and crystallizer sampling points
for all analytes except mercury. At the brine concentrator and crystallizer sampling points, EPA
collected mercury as three individual grab samples over the six-hour period (i.e., a grab sample
collected every two hours). EPA collected all analytes at the influent to the FGD wastewater
treatment system as one-day grab samples.
A sampling episode report describing the sample collection activities and the analytical
results from this sampling episode are included in the rulemaking record. [ERG, 2012h]
EPA also requested that a second plant in Italy, A2A's Centrale di Monfalcone
(Monfalcone), collect one-day grab samples. Monfalcone operates a chemical precipitation
followed by vapor-compression evaporation system to treat FGD wastewater. Monfalcone
personnel collected samples of the FGD influent to wastewater treatment, the distillate from the
brine concentrator, and the condensate from the crystallizer. Site visit notes and the
corresponding analytical results are included in the rulemaking record. [ERG, 2013]
3.4.2 CWA 308 Monitoring Program
EPA required a subset of steam electric power plants to collect samples that were used to
supplement the EPA on-site sampling program. Each of the seven plants selected for the on-site
sampling program (except for the Italian plant) were required to participate in the CWA 308
monitoring program so EPA could evaluate the variability associated with the FGD wastewaters
treatment systems performance.
For those seven plants, in addition to the samples collected by EPA during the four-day
on-site sampling event, EPA required the plants to collect four sets of samples over a four- or
five-month period. The samples were collected directly by the plants and shipped to EPA-
contracted laboratories for analysis.
EPA required four additional plants (not sampled by EPA) to participate in its CWA 308
monitoring program. These plants were selected to obtain data about operations or treatment
systems because EPA did not have existing data for these processes or treatment technologies.
EPA obtained data from the following four plants:
• Tampa Electric Company's Polk Station (first of only two currently operating
integrated gasification combined cycle (IGCC) plants);
• Wabash Valley Power Association's Wabash River Station (second of only two
currently operating IGCC plants);
• Appalachian Power Company's Mountaineer Plant (only plant operating a carbon
capture system that is of interest to EPA); and
• Kansas City Power & Light's latan Station (only plant in United States operating a
one-stage vapor-compression evaporation system for treatment of FGD wastewater).
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Section 3 - Data Collection Activities
For these four plants, EPA required the plants to collect four consecutive days of samples
at two to four locations specifically identified for each plant. The sample locations were
identified to characterize gasification wastewaters, carbon capture wastewaters, and the treatment
of FGD wastewater and gasification wastewater by vapor-compression evaporation systems.
EPA used the same four-consecutive-day sampling approach that was used for EPA's on-site
sampling program (as described in Section 3.4.1). These samples were collected directly by the
plants and shipped to EPA-contracted laboratories for analysis.
A report describing the results from the CWA 308 monitoring program is included in the
rulemaking record. [ERG, 2012i]
3.5 EPA AND STATE SOURCES
EPA collected information from databases, publications, and state groups and permitting
authorities, including the following sources discussed below:
• Information on current and proposed permitting practices for the steam electric
industry from a review of selected National Pollutant Discharge Elimination System
(NPDES) permits and accompanying fact sheets;
• Input from EPA and state permitting authorities regarding implementation of the
existing Steam Electric Power Generating ELGs;
• Background information on the steam electric industry from documents prepared
during the development of the existing Steam Electric Power Generating ELGs (i.e.,
the 1974 and 1982 rulemakings);
• Information from a survey of the industry conducted in support of the CWA section
316(b) Cooling Water Intake Structures rulemaking;
• Information from EPA's OAR, including Integrated Planning Model (IPM)
projections based on recent air rules (i.e., Cross-State Air Pollution Rule (CSAPR)
and Mercury and Air Toxics Standards (MATS));
• Information from EPA's Office of Research and Development (ORD) characterizing
CCRs and the potential leaching of pollutants from CCRs stored or disposed of in
landfills and surface impoundments;
• Information from EPA's Office of Research and Development (ORD) characterizing
CCRs and the potential leaching of pollutants from CCRs stored or disposed of in
landfills and surface impoundments
• Data provided by the North Carolina Department of Environment and Natural
Resources for one plant that operates an anoxic/anaerobic biological treatment system
for FGD wastewater; and
• Information collected by EPA's OSWER, regarding surface impoundments or other
similar management units that contain CCRs at power plants and other information
gathered in support of the proposed rule for regulating CCRs under the Resource
Conservation and Recovery Act (RCRA).
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EPA's Office of Water (OW) has coordinated its efforts with ongoing research and
activities being undertaken by the EPA offices listed above. In addition, EPA's OW has also
coordinated with the Office of Enforcement and Compliance Assurance (OECA) and EPA
regional offices to gather further information on the industry.
3.5.1 NPDES Permits and Fact Sheets
The CWA requires direct dischargers (i.e., industrial facilities that discharge process
wastewaters from any point source into receiving waters) to control their discharges according to
ELGs and water-quality-based effluent limitations included in NPDES permits. EPA collected
and reviewed selected NPDES permits and, where available, accompanying fact sheets to
confirm or help clarify information reported in the survey responses.
3.5.2 State Groups and Permitting Authorities
Throughout the detailed study and rulemaking, EPA interacted with states and EPA
regional permitting authorities, such as when contacting and visiting steam electric power plants.
EPA also solicited input and suggestions from states and permitting authorities on specific steam
electric power plant characteristics, ICR development, and implementation of the Steam Electric
Power Generating ELGs. EPA hosted a webcast seminar in December 2008 to review
information on wastewater discharges from power plants for NPDES permitting and
pretreatment authorities. The webcast provided an update on EPA's review of the current ELGs
(40 CFR 423) and presented information on pollutant characteristics and treatment technologies
for wastewater from FGD scrubbers. During the webcast, state and interstate approaches for
managing steam electric power plant wastewaters were shared by representatives from
Wisconsin, North Carolina, and the Ohio River Valley Water Sanitation Commission
(ORSANCO).
In November 2009, EPA held conference calls with states and EPA permitting authorities
to discuss development and input for the ICR [ERG, 2009]. Additionally, EPA held a joint
Federalism/Unfunded Mandates Reform Act (UMRA) consultation meeting in October 2011 to
request input regarding the Steam Electric Power Generating ELGs [U.S. EPA, 201 lb].
EPA participated in periodic conference calls with ORSANCO during the rulemaking to
discuss treatment technologies for managing wastewaters from steam electric power plants.
Additionally, EPA coordinated with the state of North Carolina to obtain long-term
characterization data from Progress Energy Carolinas' Roxboro Steam Electric Plant for the
FGD wastewater treatment influent, FGD impoundment effluent, and biological treatment
effluent, as well as ash impoundment effluent data [NCDENR, 2011].
3.5.3 1974 and 1982 Technical Development Documents for the Steam Electric Power
Generating Point Source Category
Two documents prepared by EPA during previous rulemakings for the Steam Electric
Category have provided useful information for the current rulemaking. These documents are the
1974 Development Document for Effluent Limitations Guidelines and New Source Performance
Standards for the Steam Electric Power Generating Point Source Category (referred to in this
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Section 3 - Data Collection Activities
report as "the 1974 Development Document") (U.S. EPA, 1974) and the 1982 Development
Document for Effluent Limitations Guidelines and Standards and Pretreatment Standards for the
Steam Electric Point Source Category (referred to in this report as "the 1982 Development
Document") (U.S. EPA, 1982). These development documents contain findings, conclusions,
and recommendations on control and treatment technology relating to discharges from steam
electric power plants. During this rulemaking, EPA used the information presented in the 1974
and 1982 Development Documents for historical background on the Steam Electric Power
Generating ELGs and for information on sources of pollutants and wastewater characteristics.
3.5.4 CWA Section 316(b) - Cooling Water Intake Structures Supporting Documentation
and Data
For the CWA section 316(b) Cooling Water Intake Structures rulemaking, EPA
conducted a survey of steam electric utilities and steam electric non-utilities that use cooling
water, as well as facilities in four other manufacturing sectors: Paper and Allied Products
(Standard Industrial Classification (SIC) code 26), Chemical and Allied Products (SIC code 28),
Petroleum and Coal Products (SIC code 29), and Primary Metals (SIC code 33). The survey
requested the following types of information:
• General plant information, such as plant name, location, and SIC codes;
• Cooling water source and use;
• Design and operational data on cooling water intake structures and cooling water
systems;
• Studies of the potential impacts from cooling water intake structures conducted by the
facility; and
• Financial and economic information about the facility.
Although the Section 316(b) survey was used to create guidelines for cooling water
intake structures, the cooling water system information collected in the survey was also useful
for this rulemaking effort. EPA used the information provided by the Section 316(b) survey in
the following analyses:
• Identifying plant-specific cooling water sources (e.g., specific rivers, streams);
• Identifying industrial non-utilities;
• Identifying the type of cooling systems used by plants;
• Linking EIA plant information to the Toxic Release Inventory (TRI) and Permit
Compliance System (PCS) discharges; and
• Determining plant-specific wastewater dilutions associated with cooling water prior
to discharge for the Environmental Assessment (EA) analyses associated with the
rulemaking effort.
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3.5.5 Office of Air and Radiation
EPA's OAR works to control air pollution and radiation exposure and takes action on
climate change by developing regulations under the Clean Air Act (CAA), and developing
national programs and technical policies. OAR relies on the Integrated Planning Model (IPM) for
some of its analyses of the effects of policies on the electric power sector. IPM is an engineering-
economic optimization model of the electric power industry, which generates least-cost resource
dispatch decisions based on user-specified constraints such as environmental, demand, and other
operational constraints. The model uses a long-term dynamic linear programming framework
that simulates the dispatch of generating capacity to achieve a demand-supply equilibrium on a
seasonal basis and by region. In addition to existing capacity, the model also considers new
resource investment options, including capacity expansion at existing plants, as well as
investment in new plants. The model is dynamic in that it is capable of using forecasts of future
conditions to make decisions for the present. IPM Version 4.10 MATS (IPM V4.10) incorporates
in its analytic baseline the expected compliance response for the following air regulations
affecting the power sector: the final Mercury and Air Toxics Standards (MATS) rule; the final
Cross-State Air Pollution Rule (CSAPR); regulatory SO2 emission rates arising from State
Implementation Plans; Title IV of the Clean Air Act Amendments; NOx SIP Call trading
program; Clean Air Act Reasonable Available Control Technology requirements and Title IV
unit specific rate limits for NOx; the Regional Greenhouse Gas Initiative; Renewable Portfolio
Standards; New Source Review Settlements; and several state-level regulations affecting
emissions of SO2, NOx, and Hg that were either in effect or expected to come into force by 2017.
Thus, IPM V4.10 projects the characteristics of electricity generation for various "plant
types" in the future, considering the expected impacts of regulations [U.S. EPA, 201 la]. EPA
used the output from the MATS policy case for run year 2015 to identify potential future wet
FGD scrubber installation that may not be accounted for in the survey responses. EPA used these
data to inform a "future" profile of the industry, which is discussed in Section 8.1.7.
3.5.6 Office of Research and Development
EPA's ORD is evaluating the impact of air pollution controls on the characteristics of
CCRs. Specifically, ORD is studying the potential cross-media transfer of mercury and other
metals from flue gas, fly ash, and other residuals collected from coal-fired boiler air pollution
controls and disposed of in landfills or impoundments. The key routes of release being studied
are leaching into ground water or subsequent release into surface waters, re-emission of mercury,
and bioaccumulation. ORD is also examining the use of CCRs in asphalt, cement, and wallboard
production.
The goal of the research is to better understand potential impacts from disposal practices
and beneficial use of CCRs. The research evaluates life-cycle environmental tradeoffs that
compare beneficial use applications with and without using CCRs. The outcome of this research
will help to identify potential management practices of concern where environmental releases
may occur, such as developing and applying a leach testing framework that evaluates a range of
materials and the different factors affecting leaching for the varying field conditions in the
environment.
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Section 3 - Data Collection Activities
EPA's OW consulted with the ORD on the status and findings of current research
assessing the potential for CCRs to impact water quality. Additionally, during EPA's sampling
program, OW collected samples of CCR landfill leachate from several of the plants for
characterization analysis by ORD.
3.5.7 Office of Solid Waste and Emergency Response
On June 21, 2010, EPA proposed the Hazardous and Solid Waste Management System:
Identification and Listing of Special Wastes; Disposal of Coal Combustion Residuals from
Electric Utilities (i.e., the CCR rule) (75 FR 35128; June 21, 2010). The proposed rule would
regulate coal ash to address the risks from the disposal of the wastes generated by electric
utilities and independent power producers. EPA used data collected by EPA's OSWER to
supplement the data collected for the ELGs. EPA also used costing methodologies developed by
EPA's OSWER in some of the costing approaches for the proposed ELGs, if appropriate.
As part of the proposed CCR rule development, EPA's OSWER issued Information
Request Letters to electric utilities that have surface impoundments or similar management units
that contain CCRs. EPA's OSWER identified the recipients of the request letters based on plants
that potentially operate CCR surface impoundments identified from data compiled in DOE's EIA
databases. However, the EIA data do not include information about waste disposal practices for
those plants with a nameplate electric generating capacity of less than 100 MW. Additionally, the
EIA data excludes information about impoundments at plants that use the impoundment as an
interim step (e.g., to dewater ash or other CCR solids), but ultimately dispose of the CCRs in an
on-site landfill or off site. Therefore, OSWER may not have identified the plants operating these
types of impoundments as potential recipients. As such, data collected by the OSWER survey
underestimates the total number of CCR impoundments nationwide.
As explained in Section 1.3.3, because the CCR rule has not been finalized, EPA cannot
factor in with certainty how any operational changes associated with any final CCR rule may
impact the analyses for the proposed ELGs. Therefore, the analyses presented for the proposed
ELGs represent current industry operations, without implementation of new requirements
contemplated by the CCR rule. Rather, EPA conducted a sensitivity analyses to see how any
final CCR rule might impact the analyses for the proposed ELGs. See DCN SE02123.
3.6 INDUSTRY-SUBMITTED DATA
EPA obtained information on steam electric processes, technologies, wastewaters, and
pollutants directly from the industry through self-monitoring data, as well as NPDES Form 2C
data.
3.6.1 Self-Monitoring Data
EPA requested self-monitoring data from Duke Energy's Belews Creek Steam Station
and Allen Steam Station to evaluate the treatment efficiency and pollutant characteristics of
wastewater discharged from FGD wastewater treatment systems that incorporate both chemical
precipitation and biological treatment (Duke Energy, 201 la and 201 Ib). EPA also used these
data to supplement the data from the EPA sampling program.
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Section 3 - Data Collection Activities
3.6.2 NPDES Form 2C
UWAG and EPA coordinated efforts to create a database of selected NPDES Form 2C
data from UWAG's member companies. Form 2C (or an equivalent form used by a state
permitting authority) is an application for a permit to discharge wastewater that must be
completed by industrial facilities (including manufacturing, commercial, mining, and
silvicultural operations). This form includes facility information, data on facility outfalls, process
flow diagrams, treatment information, and intake and effluent characteristics.
The Form 2C database contains information about the outfalls of coal-fired power plants
that receive FGD, ash handling, or coal pile runoff wastestreams. EPA received Form 2C data
from UWAG for 86 plants in late June 2008 [UWAG, 2008]. UWAG did not include data on
other outfalls, such as separate outfalls for sanitary wastes, cooling water, landfill runoff, and
other wastestreams, in the database. The database does not include Form 2C information for
plants that have neither a wet FGD system nor wet fly ash handling. For example, if a plant has
no wet FGD system and the plant's only wet ash handling is for bottom ash transport, UWAG
did not include its information in the database. EPA used the Form 2C data for developing a
preliminary industry profile and the survey, but these outfall data were eventually superseded by
the data received in response to the survey.
3.7 TECHNOLOGY VENDOR DATA
EPA gathered data from technology vendors through presentations, conferences,
meetings, and email and phone contacts regarding the technologies used in the industry. The data
collected informed the development of the detailed study, the industry survey, and technology
costs and loadings estimates. Between 2007 and 2012, EPA participated in multiple technical
conferences and reviewed the papers presented.
To gather FGD wastewater treatment information for the cost analyses, EPA contacted
companies that manufacture, distribute, or install various components of chemical precipitation
and biological wastewater treatment systems and vapor-compression evaporation. The vendors
provided the following types of information for EPA's analyses:
• Operating details;
• Performance data;
• Equipment used in the system;
• Capital cost information on a component level and system level;
• Operating and maintenance costs; and
• Equipment and system energy requirements.
To gather information on handling of fly ash and bottom ash, EPA also contacted several
ash handling and ash storage vendors. The vendors provided the following types of information
for EPA's analyses:
• The type of fly ash and bottom ash handling systems available for handling ash dry or
in closed-loop recycle;
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Section 3 - Data Collection Activities
• Equipment and modifications required to convert wet fly ash and bottom ash handling
systems to dry handling or closed-loop recycle systems;
• Equipment that can be reused as part of the conversion from wet to dry handling or in
a closed-loop recycle system;
• Outage time required for the different types of ash handling systems;
• Maintenance required for each type of system;
• Operating data for each type of system;
• Equipment and installation capital costs for fly ash and bottom ash conversion;
• The specifications for the types of ash storage available for the different types of
handling systems;
• The equipment and installation capital costs associated with the storage of fly ash and
bottom ash; and
• Operating and maintenance costs for fly ash and bottom ash handling systems.
To obtain additional information on FGD treatment systems and fly ash and bottom ash
conversions, EPA held meetings, conference calls, and site visits with treatment and ash vendors.
3.8 OTHER SOURCES
EPA obtained additional information on steam electric processes, technologies,
wastewaters, pollutants, and regulations from sources including trade associations, the Electric
Power Research Institute (EPRI), DOE, the U.S. Geological Survey (USGS), UWAG, and
literature and Internet searches.
3.8.1 Utility Water Act Group
UWAG is an association of over 200 individual electric utilities and four national trade
associations of electric utilities: the Edison Electric Institute, the National Rural Electric
Cooperative Association, the American Public Power Association, and the Nuclear Energy
Institute. UWAG's purpose is to participate on behalf of its members in EPA's rulemakings
under the CWA. Specifically, EPA coordinated with UWAG on collecting information on power
plant characteristics to support site visit selection, discussing wastewater sampling approaches
and recommendations, laboratory analytical methods, reviewing the questionnaire for clarity,
reviewing the questionnaire mailing list to confirm plants and mailing addresses, and collecting
existing permit data. At the invitation of individual plants, UWAG representatives also collected
split samples during EPA's on-site sampling and CWA 308 monitoring programs and
participated in most site visits.
3.8.2 Electric Power Research Institute
EPRI is a research-oriented trade association for the steam electric industry. EPRI
conducts research funded by the steam electric industry and has extensively studied wastewater
discharges from FGD systems. The trade association provided EPA with the following reports
that summarize the data collected during several EPRI studies:
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Section 3 - Data Collection Activities
• Flue Gas Desulfurization (FGD) Wastewater Characterization: Screening Study
(EPRI, 2006a);
• EPRI Technical Manual: Guidance for Assessing Wastewater Impacts of FGD
Scrubbers (EPRI, 2006b);
• The Fate of Mercury Absorbed in Flue Gas Desulfurization (FGD) Systems (EPRI,
2005);
• Update on Enhanced Mercury Capture by Wet FGD: Technical Update (EPRI, 2007);
• PISCES Water Characterization Field Study, Sites A-G (EPRI, 1997b-2001);
• Selenium Removal by Iron Cementation from a Coal-Fired Power Plant Flue Gas
Desulfurization Wastewater in a Continuous Flow System - A Pilot Study (EPRI,
2009a); and
• Laboratory and Pilot Evaluation of Iron and Sulfide Additives with Microfiltration for
Mercury Water Treatment (EPRI, 2009b).
The EPRI reports provided EPA with background information regarding the
characteristics of FGD wastewaters and the sampling techniques used during the program. These
reports also provided EPA with information regarding the characteristics of discharges from fly
ash and bottom ash impoundments and the respective percentage of loadings from ash
impoundments containing both fly ash and bottom ash. Additionally, the EPRI reports provided
information on the treatment technologies available to treat FGD and ash wastewaters, including
findings from pilot-study evaluations.
EPRI also participated in meetings with EPA and provided comments on EPA's planned
data collection activities, including the survey and the sampling program.
3.8.3 Department of Energy (DOE)
DOE is the department of the United States government responsible for energy policy.
EPA used information on electric generating plants from DOE's EIA data collection forms.
The Agency used information from two of EIA's data collection forms: Form EIA-860,
Annual Electric Generator Report, and Form EIA-923, Power Plant Operations Report. Form
EIA-860 collects information annually from all electric generating facilities that have or will
have a nameplate capacity of 1 MW or more and are operating or plan to be operating within five
years of filing this form.10 The data collected in Form EIA-860 are associated only with the
design and operation of generators at facilities [U.S. DOE, 2007a and 2009a]. Form EIA-923
collects information from electric power plants and combined heat and power plants in the
United States that have a total generator nameplate capacity greater than 1 MW. The form asks
where the generator(s), or the facility in which the generator(s) resides, and if it is connected to
10 DOE defines the generator nameplate capacity as the maximum rated output of a generator under specific
conditions designated by the manufacturer. Generator nameplate capacity is usually indicated in units of kilovolt-
amperes (kVA) and in kilowatts (kW) on a nameplate physically attached to the generator. More generally,
generator capacity is the maximum output, commonly expressed in MW, that generating equipment can supply to
system load, adjusted for ambient conditions.
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Section 3 - Data Collection Activities
the local or regional electric power grid and has the ability to draw power from the grid or
deliver power to the grid. The data collected in Form EIA-923 are associated with the operation
and design of the entire facility [U.S. DOE, 2007b and 2009b]. EPA used these data to help
identify the industry the sample frame for the Steam Electric Survey. Additionally, EPA used
these data to supplement Steam Electric Survey data, such as age of the generating units, which
was not included in the survey.
3.8.4 Literature and Internet Searches
EPA conducted literature and Internet searches to obtain information on various aspects
of the steam electric process, both for plants regulated by the ELGs and certain operations
outside the scope of the regulations for which EPA evaluated whether they could/should be
covered by the ELGs. The objectives of these searches included characterizing wastewaters and
pollutants originating from these steam electric processes, the environmental impacts of these
wastewaters, and applicable regulations. EPA also used the Internet searches to identify or
confirm reports of planned plant/unit retirements or reports of planned unit conversions to dry or
closed-loop recycle ash handling systems. EPA used industry journals, reference texts about the
industry, and company press releases obtained from Internet searches to inform the industry
profile and process modifications occurring in the industry.
3.8.5 Environmental Groups and Other Stakeholders
EPA received information from several environmental groups and other stakeholders as
part of public comments submitted for the 2006 and 2008 Effluent Guidelines Plans, the survey,
and in other discussions during the detailed study and rulemaking. In general, the information
highlighted environmental concerns associated with the pollutants present in steam electric
power plant wastewaters, and technological controls for reducing or eliminating pollutant
discharges from FGD and ash handling systems.
3.9 PROTECTION OF CONFIDENTIAL BUSINESS INFORMATION
Certain data in the rulemaking record have been claimed as confidential business
information (CBI). The Agency has withheld CBI from the public docket in the Federal Docket
Management System. In addition, the Agency has withheld from disclosure some data not
claimed as CBI because the release of these data could indirectly reveal CBI. Furthermore, EPA
has aggregated certain data in the public docket, masked plant identities, or used other strategies
to prevent the disclosure of CBI. The Agency's approach to CBI protection ensures that the data
in the public docket both explain the basis for the proposed rule and provide the opportunity for
public comment, without compromising data confidentiality.
3.10 REFERENCES
1. Duke Energy. 201 la. Industry Provided Sampling Data from Duke Energy's Allen Steam
Station. (17 August). DCN SE01809
2. Duke Energy. 201 Ib. Industry Provided Sampling Data from Duke Energy's Belews
Creek Steam Station. (17 August). DCN SE01808
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Section 3 - Data Collection Activities
3. Eastern Research Group (ERG). 2009. Memorandum to Ron Jordan, US EPA. "Outreach
Calls for the Proposed Steam Electric ICR." (25 February). DCN SE00203.
4. Eastern Research Group (ERG). 2012a. Final Sampling Episode Report, Duke Energy
Carolinas' Belews Creek Steam Station. (13 April). DCN SE01305.
5. Eastern Research Group (ERG). 2012b. Final Sampling Episode Report, We Energies'
Pleasant Prairie Power Plant. (13 April). DCN SE01306.
6. Eastern Research Group (ERG). 2012c. Final Sampling Episode Report, Duke Energy
Miami Fort Station. (13 April). DCN SE01304.
7. Eastern Research Group (ERG). 2012d. Final Sampling Episode Report, Duke Energy
Carolinas' Allen Steam Station. (13 April). DCN SE01307.
8. Eastern Research Group (ERG). 2012e. Final Sampling Episode Report, Mirant Mid-
Atlantic, LLC's Dickerson Generating Station. (13 April). DCN SE01308.
9. Eastern Research Group (ERG). 2012f. Final Sampling Episode Report, Allegheny
Energy's Hatfield's Ferry Power Station. (13 April). DCN SE01310.
10. Eastern Research Group (ERG). 2012g. Final Sampling Episode Report, RRI Energy's
Keystone Generating Station. (13 April). DCN SE01309.
11. Eastern Research Group, Inc. (ERG). 2012h. Final Site Visit Notes and Sampling
Episode Report for Enel's Power Plants. (8 August). DCN SE02013.
12. Eastern Research Group (ERG). 2012L Final Power Plant Monitoring Data Collected
Under Clean Water Act Section 308 Authority ("CWA 308 Monitoring Data"). (30 May).
DCN SE01326.
13. Eastern Research Group (ERG). 2013. Final Monfalcone Site Visit Notes. (11 March).
DCN SE03795 and SE03796.
14. Electric Power Research Institute (EPRI). 1997b - 2001. PISCES Water Characterization
Field Study, Sites A-G Palo Alto, CA. DCN SE01818 through SE01823.
15. Electric Power Research Institute (EPRI). 2005. The Fate of Mercury Absorbed in Flue
Gas Desulfurization (FGD) Systems. 1009955. Palo Alto, CA. (March). DCN SE01814.
16. Electric Power Research Institute (EPRI). 2006a. Flue Gas Desulfurization (FGD)
Wastewater Characterization: Screening Study. 1010162. Palo Alto, CA. (March). DCN
SE01816.
17. Electric Power Research Institute (EPRI). 2006b. EPRI Technical Manual: Guidance for
Assessing Wastewater Impacts of FGD Scrubbers. 1013313. Palo Alto, CA. (December).
Available online at: http://www.epriweb.com/public/000000000001013313.pdf. Date
accessed: 16 May 2008. DCN SE01817.
18. Electric Power Research Institute (EPRI). 2007. Update on Enhanced Mercury Capture
by Wet FGD: Technical Update. 1012673. Palo Alto, CA. (March). DCN SE01815.
19. Electric Power Research Institute (EPRI). 2009a. Laboratory and Pilot Evaluation of Iron
and Sulfide Additives with Microfiltration for Mercury Water Treatment. 1016813. Palo
Alto, CA. (March). DCN SE00409A3.
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Section 3 - Data Collection Activities
20. Electric Power Research Institute (EPRI). 2009b. Selenium Removal by Iron
Cementation from a Coal-Fired Power Plant Flue Gas Desulfurization Wastewater in a
Continuous Flow System - Pilot Study. 1017956. Palo Alto, CA. (July). DCN
SE00409A2.
21. NCDENR. 2011. North Carolina Department of Environment and Natural Resources
(NCDENR) State Provided Sampling Data From North Carolina's Progress Energy
Roxboro Plant. (26 June). DCN SE01812.
22. U.S. DOE. 2007a. U.S. Department of Energy. Annual Electric Generator Report
(collected via Form EIA-860). Energy Information Administration (EIA). The data files
are available online at: http://www.eia.gov/electricity/data/eia860/index.html. DCN
SE02014.
23. U.S. DOE. 2007b. U.S. Department of Energy. Power Plant Operations Support
(collected via Forms EIA-906/920/923). Energy Information Administration (EIA). The
data files are available online at: http://www.eia.gov/electricity/data/eia923/. DCN
SE02015.
24. U.S. DOE. 2009a. U.S. Department of Energy. Annual Electric Generator Report
(collected via Form EIA-860). Energy Information Administration (EIA). The data files
are available online at: http://www.eia.gov/electricity/data/eia860/index.html. DCN
SE01805.
25. U.S. DOE. 2009b. U.S. Department of Energy. Power Plant Operations Support
(collected via Form EIA-923). Energy Information Administration (EIA). The data files
are available online at: http://www.eia.gov/electricity/data/eia923/. DCN SE02030.
26. U.S. EPA. 1974. Development Document for Effluent Limitations Guidelines and New
Source Performance Standards for the Steam Electric Power Generating Point Source
Category. Washington, D.C. (October). DCN SE02917.
27. U.S. EPA. 1982. Development Document for Effluent Limitations Guidelines and
Standards and Pretreatment Standards for the Steam Electric Point Source Category.
EPA-440-1-82-029. Washington, DC. (November). DCN SE02931.
28. U.S. EPA. 2009a. Office of Solid Waste and Emergency Response (OWSER), Summary
Results from the 2009 OSWER Information Request. DCN SE02032.
29. U.S. EPA. 2009b. Steam Electric Power Generating Point Source Category: Final
Detailed Study. EPA 821-R-09-008. Washington, D.C., (October). DCN SE00003.
30. U.S. EPA. 201 la. Office of Air and Radiation (OAR). Integrated Planning Model (IPM)
2015 MATS Policy Case Output. (December). DCN SE02047.
31. U.S. EPA. 2011b. Steam Electric ELGRulemaking - UMRA and Federalism
Implications: Consultation Meeting. (11 October). DCN SE03286 and SE03287.
32. Utility Water Act Group (UWAG). 2008. UWAG Form 2C Effluent Guidelines
Database. (30 June). DCNs SE02918 and SE02918A1.
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Section 4 - Steam Electric Industry Description
SECTION 4
STEAM ELECTRIC INDUSTRY DESCRIPTION
Electricity is produced by converting mechanical, chemical, and/or fission energy into
electrical energy, and may or may not involve the use of steam. This section provides an
overview of the various types of electric generating processes operating in the United States and
describes more fully the categories of processes regulated by the Steam Electric Power
Generating effluent limitations guidelines and standards (ELGs). Section 4.1 generally describes
the electric generating industry, including demographics of the steam electric industry; Section
4.2 describes the steam electric power generating process; Section 4.3 describes the wastestreams
generated by the steam electric industry that were evaluated for new or additional controls in the
proposed ELGs; and Section 4.4 describes the wastestreams generated by the steam electric
industry that were not evaluated for new or additional controls in the proposed ELGs.
4.1 OVERVIEW OF ELECTRIC GENERATING INDUSTRY
This section describes the types of plants that compose the overall electric generating
industry as well as the definition of the Steam Electric Power Generating Point Source Category
(Steam Electric Category). As shown in Figure 4-1, the plants regulated by the Steam Electric
Power Generating ELGs are only a portion of the electric generating industry.
Electric Generating Plants
Electric Generating Industry
(Utilities and Non-Utilities)
Industrial Non-Utilities
Non-Steam Electric
Power Generation
Steam Electric
Power Generation
Fossil or Nuclear Steam Electric
Generating Plants
(Steam Electric Power Generating
Point Source Category)
Non-Fossil and Non-Nuclear
Steam Electric Generating Plants
Figure 4-1. Types of U.S. Electric Generating Plants
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Section 4 - Steam Electric Industry Description
4.1.1 Electric Generating Industry Population
In general, the companies generating electrical power are categorized as one of the
following types:
• Utility: Any entity that generates, transmits, and/or distributes electricity and recovers
the cost of its generation, transmission and/or distribution assets and operations,
either directly or indirectly, through cost-based rates set by a separate regulatory
authority (e.g., state Public Service Commission), or is owned by a governmental unit
or the consumers that the entity serves. According to the Department of Energy
(DOE)'s Energy Information Administration (EIA), plants that qualify as
cogenerators or small power producers under the Public Utility Regulatory Policies
Act are not considered electric utilities [U.S. DOE, 2012b].
• Non-Industrial Non-Utility: Any entity that generates, transmits, and/or sells
electricity, or sells or trades electricity services and products, where costs are not
established and recovered by a regulatory authority. Non-utility power producers
include, but are not limited to, independent power producers, power marketers and
aggregators, merchant transmission service providers, self-generation entities, and
cogeneration firms with Qualifying Facility Status [U.S. DOE, 2012b]. Like utilities,
the primary purpose of non-industrial non-utilities is producing electric power for
distribution and/or sale.
• Industrial Non-Utility: Industrial non-utilities are similar to non-industrial non-
utilities except their primary purpose is not distributing and/or selling electricity. This
category includes electric generators that are located at industrial plants such as
chemical manufacturing plants or paper mills. Industrial non-utilities typically
provide most of the electrical power they generate to the industrial operation with
which they are located, although they may also provide some electric power to the
grid for distribution and/or sale.
This section presents available demographic data and other information for the electric
generating industry, excluding industrial non-utilities. EPA analyzed the available demographic
information using EIA data for the year 2009 (Form EIA-860) [U.S. DOE, 2009] and U.S.
Census Bureau data collected in the 2007 Economic Census [USCB, 2007]. EPA used the 2009
EIA data because data collected from the steam electric industry via EPA's Questionnaire for the
Steam Electric Power Generating Effluent Guidelines (survey) represents plant-level operations
in 2009 and the 2007 Census data because, as a 5-year census, it is the most recent year for
which data are available. Together, these sources provide the most recent and comprehensive set
of power plant data available. EPA identified electric generating plants in the EIA database as
those reporting North American Industrial Classification System (NAICS) code 22 - Utilities.n
The 2007 Economic Census data include more specific industry sector information at the six-
digit NAICS code level.
11 NAICS code 22 - Utilities is defined as establishments providing the following utility services: electric power,
natural gas, steam supply, water supply, and sewage removal. Excluded from this sector are establishments primarily
engaged in waste management services [USCB, 2007].
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Section 4 - Steam Electric Industry Description
EPA also examined the data on operations that electric generating plants reported to the
EIA in 2009. Form EIA-860 contains records for 15,169 steam and nonsteam electric generating
units having at least one megawatt (MW) of capacity operated at 5,300 facilities for calendar
year 2009 [U.S. DOE, 2009]. Because the EIA data also include units at industrial non-utilities,
they overestimate the number of units and plants that may be considered part of the electric
generating industry.
According to the Economic Census, there were 1,934 electric generating plants in the
United States in 2007, 69 percent (1,327 plants) of which were characterized primarily as using
fossil or nuclear fuel [USCB, 2007]. These data include both steam and non-steam-electric
generating processes. Table 4-1 presents the distribution of plants among each of the electric
generating NAICS codes. The Economic Census includes all facilities reporting under NAICS
code 22. As a result, it includes entities categorized by DOE as utilities and non-industrial non-
utilities, but does not include industrial non-utilities.
Table 4-1. Distribution of U.S. Electric Generating Plants by NAICS Code in 2007
NAICS Code - Description
22 1 1 1 1 - Hydroelectric Power Generation
22 1 1 12 - Fossil Fuel Electric Power Generation
22 1 1 1 3 - Nuclear Electric Power Generation
221119 - Other Electric Power Generation (includes conversion of other forms of energy,
such as solar, wind, or tidal power, into electrical energy)
22111 - Electric Power Generation (Total)
Plants
295
1,248
79
312
1,934
Source: U.S. Census, [USCB, 2007].
4.1.2 Applicability of Steam Electric Power Generating Effluent Guidelines
Industrial non-utilities are not included within the scope of the existing Steam Electric
Power Generating ELGs because they are not primarily engaged in producing electricity for
distribution and/or sale.12 As described above, these industrial non-utilities typically are
industrial plants that produce, process, or assemble goods, and the electricity generated at these
plants is an ancillary operation used to dispose of a by-product or for cost savings.
Because industrial non-utilities are not included in the applicability of the Steam Electric
Power Generating ELGs, EPA has excluded them from the discussion of the U.S. electric
generating industry for the purposes of this document. Therefore, information presented on
plants composing the electric generating industry includes only the utilities and the non-
industrial non-utilities. Although the transmission and distribution entities are included in the
definition of utilities and non-industrial non-utilities, they are not included in the Steam Electric
12 The applicability of the Steam Electric Power Generating Point Source Category (40 CFR 423.10) states the
following: "The provisions of this part are applicable to discharges resulting from the operation of a generating unit
by an establishment primarily engaged in the generation of electricity for distribution and sale which results
primarily from a process utilizing fossil-type fuel (coal, oil, or gas) or nuclear fuel in conjunction with a thermal
cycle employing the steam water system as the thermodynamic medium."
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Section 4 - Steam Electric Industry Description
Category; therefore, this document presents information only on the plants and NAICS codes
associated with the generation of electricity.
As shown in Figure 4-1, the electric generating industry can be further broken down
based on the type of prime mover used to generate electricity. EIA defines a prime mover as the
engine, turbine, water wheel, or similar machine that drives an electric generator or a device that
converts energy to electricity directly (e.g., photovoltaic solar and fuel cell(s)) [U.S. DOE,
2012a]. Because the Steam Electric Power Generating ELGs are applicable only to plants
generating electricity using a "thermal cycle employing the steam water system as a
thermodynamic medium," EPA categorized the prime movers into "steam electric" and "non-
steam-electric" categories. The steam electric generating units include steam turbines and
combined cycle systems (see Sections 4.2.1 and 4.2.2 for more details on these types of units).
The non-steam-electric generating units include, but are not limited to, stand-alone combustion
turbines, internal combustion engines, fuel cells, and wind turbines.
The final criterion for a plant to meet the applicability of the Steam Electric Power
Generating ELGs is that it must primarily utilize a fossil or nuclear fuel to generate the steam
used in the turbine. Fossil fuels include coal, oil, or gas, and fuels derived from coal, oil, or gas
such as petroleum coke, residual fuel oil, and distillate fuel oil. Fossil fuels also include blast
furnace gas and the product of gasification processes using fossil-based feedstocks such as coal,
petroleum coke, and oil. Examples of nonfossil/nonnuclear fuels used by some steam electric
power plants include pulp mill black liquor, municipal solid waste, and wood solid waste.
4.2 STEAM ELECTRIC GENERATING INDUSTRY
EPA identified the subset of electric generating plants in the EIA database that use steam
electric processes as those operating at least one prime mover that utilizes steam. The following
electric generating unit or prime mover types specified in the EIA database are included in the
steam electric industry:
• Steam turbine;
• Combined cycle system - steam turbine portion; and
• Combined cycle system - combustion turbine portion.13
Within each prime mover category, electric generating units are also classified by type of
unit based on how often the units are in operation. Units can be classified as baseload, peaking,
cycling, or intermediate. Baseload units produce electricity at an essentially constant rate and
typically run for extended periods, peaking units operate during peak-load periods, cycling units
generally operate in a routine cycle (i.e., only operating during the day), and intermediate units
produce electricity on an as needed basis operating more frequently than peaking units but less
frequently than baseload units.
13 Although the combustion turbine portion of the combined cycle system does not use steam to turn the turbine, the
combined cycle system does use steam associated with the steam turbine portion; therefore, both portions are
included in the analysis because the entire combined cycle system is covered under the Steam Electric Power
Generating ELGs.
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Section 4 - Steam Electric Industry Description
The subset of steam electric power plants that are regulated by the Steam Electric Power
Generating ELGs use a fossil or nuclear fuel as the primary energy source for the steam electric
generating unit. In analyzing the EIA data, EPA included plants using the following EIA-defined
nuclear and fossil (or fossil-derived) fuel types:
• Anthracite coal;
• Bituminous coal:
• Lignite coal;
• Subbituminous coal;
• Coal synfuel;
• Waste/other coal;
• Petroleum coke;
• No. 1 Fuel Oil;
• No. 2 Fuel Oil;
• No. 4 Fuel Oil;
• No. 5 Fuel Oil;
• No. 6 Fuel Oil;
• Diesel Fuel;
• Jet fuel;
• Kerosene;
• Oil-other and waste oil (e.g., crude oil, liquid by-products, oil waste, propane (liquid),
rerefined motor oil, sludge oil, tar oil);
• Natural gas;
• Blast furnace gas;
• Gaseous propane;
• Other gas; and
• Nuclear (e.g., uranium, plutonium, thorium).
Using the criteria for the prime mover type and energy source described above for all
plants (utilities and non-industrial non-utilities) reporting a NAICS code of 22 to EIA in 2009,
EPA identified 1,179 steam electric power plants potentially subject to the Steam Electric Power
Generating ELGs. In analyzing the EIA energy source data for the purpose of this report, EPA
limited the analysis to identify only plants/units that reported one of the above energy sources as
a "primary" or "secondary" energy source in the 2009 EIA data.14 The 1,179 plants operate an
14 For the purposes of this analysis, EPA included only plants/units based on the "secondary" energy source when it
was reported as a type of coal or petroleum coke For example, if a generating unit reported the "primary" energy
source as municipal solid waste and the "secondary" energy source as coal, the plant was included in the analysis;
however, if the generating unit reported the "secondary" energy source as natural gas, then the plant would not have
been included in the analysis.
4-5
-------
Section 4 - Steam Electric Industry Description
estimated 3,341 stand-alone steam electric generating units or combined cycle systems, which
have a total generating capacity of 778,000 MW [U.S. DOE, 2009].
4.2.1 Steam Electric Generating Process
Steam electric power plants generate electricity using a process that includes a steam
generator (i.e., boiler), a steam turbine/electrical generator, and a condenser. Figure 4-2
illustrates the stand-alone steam electric process, in which a combustible fuel is used as the
energy source to generate steam. The Steam Electric Power Generating ELGs regulate
wastewater discharged by those steam electric power plants that use fossil-type fuel (e.g., coal,
oil, or gas) or nuclear fuel to generate the steam. As shown in Figure 4-2, fuels are fed to a boiler
where they are combusted to generate steam. Boilers and their associated subsystems often
include components to improve thermodynamic efficiency by boosting steam temperature and
preheating intake air using superheaters, reheaters, economizers, and air heaters. The hot gases
from combustion (i.e., the flue gas) leave the steam generator subsystem and pass through
paniculate collection and the sulfur dioxide (862) scrubbing system (if present), and then are
emitted through the stack. Natural gas-fired units typically do not operate these types of air
pollution controls. The high-temperature, high-pressure steam leaves the boiler and enters the
turbine generator where it drives the turbine blades as it moves from the high-pressure to the
low-pressure stages of the turbine. The spinning of the turbine blades drives the linked generator,
producing electricity. The lower-pressure steam leaving the turbine enters the condenser, where
it is cooled and condensed by the cooling water flowing through heat exchanger (condenser)
tubes. The water collected in the condenser (condensate) is returned to the boiler where it is
again converted to steam [Babcock & Wilcox, 2005].
Combusting coal, petroleum coke, and oil in steam electric boilers produces a residue of
noncombustible fuel constituents, referred to as ash. Some of the ash consists of very fine
particles that are light enough to be entrained in the flue gas and carried out of the furnace and is
commonly known as fly ash. The heavier ash that settles in the furnace or is dislodged from
furnace walls is collected at the bottom of the boiler and is referred to as bottom ash.
Combusting fossil fuels also generates pollutants in the flue gas (e.g., nitrogen oxides,
SC>2, carbon dioxide (CO2)) that, if not removed, would be emitted to the atmosphere. Therefore,
many plants operate air pollution control technologies that remove these pollutants from the flue
gas. The following are some of the common air pollution control technologies used in the
industry and the pollutant they are primarily used to control:
• Electrostatic precipitator (ESP): fly ash/particulate matter;
• Flue gas desulfurization (FGD): SC>2;
• Selective catalytic reduction (SCR): nitrogen oxides;
• Selective non-catalytic reduction (SNCR): nitrogen oxides; and
• Flue gas mercury controls (FGMC): mercury.
The nuclear-fueled steam electric process is similar to the steam/water system described
above. The nuclear system differs from the non-nuclear system in three key ways: fuel handling,
nuclear fission within the reactor core instead of the boiler as the heat source for producing
4-6
-------
Section 4 - Steam Electric Industry Description
steam, and no air pollution control equipment. No fuel is combusted and no ash is generated in a
nuclear-fueled steam electric process. Instead, heat transferred from the reactor core creates
steam in boiling water reactors or creates superheated water in pressurized-water reactors. The
steam turbine/electric generator and condenser portions of the nuclear-fueled steam electric
process are the same as those described for the stand-alone steam electric process [U.S. DOE,
2012c].
4.2.2 Combined Cycle Systems
Some steam electric power plants operate one or more combined cycle systems fueled by
fossil or fossil-type fuels to produce electricity. A combined cycle system comprises one or more
combustion turbine electric generating units operating in conjunction with one or more steam
turbine electric generating units. Combustion turbines, which typically are similar to jet engines,
commonly use natural gas as the fuel, but may also use oil. Exhaust gases from combustion are
sent directly through the combustion turbine, which is connected to a generator to produce
electricity. The exhaust gases exiting the combustion turbine still contain useful waste heat, so
they are directed to heat recovery steam generators (HRSGs) to generate steam to drive an
additional turbine. The steam turbine is also connected to a generator (which may be a different
generator or the same generator that is connected to a combustion turbine) that produces
additional electricity. Thus, combined cycle systems use steam turbine technology to increase the
efficiency of the combustion turbines. Figure 4-3 illustrates the combined cycle system process.
Steam electric units within combined cycle systems operate almost identically to stand-
alone steam electric units, except without the boiler. In a combined cycle system, the combustion
turbines and HRSGs functionally take the place of the boiler of a stand-alone steam electric unit.
The other two major components of steam electric generating units within combined cycle
systems, the steam turbine/electric generator and steam condenser, are virtually identical to those
of stand-alone steam electric units. Thus, the wastewaters and pollutants generated from both
types of systems are the same. However, the wastewaters of the combined cycle units are more
closely associated with gas-fired steam electric units, and therefore do not typically generate ash
or FGD wastewaters. The wastewaters generated from combined cycle units typically include
cooling water, boiler blowdown, metal cleaning wastes, and steam condensate water treatment
wastes.
4-7
-------
Section 4 - Steam Electric Industry Description
oo
^
Fuel . Boiler
(e.g., coal, oil, or gas) ~
T
Boiler
Slowdown
Coal
Storage
>
Gas to
Atmosphere
t
FGD Wet ^ Flue Gas
Scrubber Desulfurization Wastes
,A
FIU6GaS > Coition t Fly Ash Sluice
System (if wet handling system)
High Pressure Steam
~i ^^^^ f — ~X Electric
I"" „, / \ Generator
Steam ^j \
< Turbine *\^ 7 Chemical
/ -OR-
V "> M Coolln5 Water Recirculating System
Condensate ^-^^(^
^ !
1 V 1
i \ Cnnlinn /
1 \ Tower / ....
^ \ / 1 Equipment
TT r~i~J Cleaning
r >r
± Bottom Ash Boiler Feedwater Make-up 1
f Handling System Treatment Water T ^
Runoff 1 1 Slowdown Chemical Metal
1 1 Addition Cleaning
T T Wastes
Bottom Ash Sluice Waste
(if wet handling system) (Treatment Residuals)
Figure 4-2. Steam Electric Process Flow Diagram
-------
Section 4 - Steam Electric Industry Description
Fuel (e.g., gas, oil, or
gasified coal)
Metal
Cleaning
Wastes
vo
Steam
Turbine
Cycle
Heat Recovery
Steam Generator
(HRSG)
Boiler Feedwater
Treatment
Boiler
Slowdown
T
r
Electric
Generator
Once-through Cooling Water
Once-through Discharge
-OR-
Recirculating System
Waste
(Treatment Residuals)
Make-up
Water
Slowdown
Chemical
Addition
Figure 4-3. Combined Cycle Process Flow Diagram
-------
Section 4 - Steam Electric Industry Description
4.2.3 Integrated Gasification Combined Cycle Systems
Integrated gasification combined cycle (IGCC) systems combine gasification technology
with both gas turbine and steam turbine power generation (i.e., combined cycle power
generation). In an IGCC system, a gasifier converts carbon-based feedstock (e.g., coal or
petroleum coke) into a synthetic gas ("syngas"). The syngas is cleaned of particulates, sulfur, and
other contaminants and is then combusted in a high-efficiency combustion gas turbine/generator.
An HRSG then extracts heat from the combustion turbine exhaust to produce steam and drive a
steam turbine/generator. IGCC plants can achieve higher thermodynamic efficiencies, emit lower
levels of criteria air pollutants, and consume less water per MW than traditional coal combustion
power plants. Like typical combustion power plants, solid wastes and wastewater are generated
from the gasification process.
DOE's National Energy Technology Laboratory (NETL) Gasification World Database
reports two commercial-scale IGCC systems located in the United States — the 262-MW Wabash
River IGCC Repowering Project (Wabash River) in Indiana and the 250-MW Tampa Electric
Polk Power Station IGCC Project (Polk) in Florida. Other U.S. power companies are
investigating or planning IGCC systems at new or existing plants, such as Duke Energy's
Edwardsport Station in Knox County, Indiana, which has an IGCC unit under construction that
was expected to begin commercial operation sometime in 2012 [Duke Energy, 2012].
EPA has conducted site visits at each of the three plants identified above. Figure 4-4
presents a general process flow diagram for an IGCC system. The specific gas preparation and
by-product recovery operations at the plants may vary, but each uses the same general electric
generating process. For example, Polk operates a sulfuric acid plant to recover sulfur, while
Wabash River uses the Claus process to generate an elemental sulfur product [ERG, 2009c;
ERG, 2011].
4-10
-------
Section 4 - Steam Electric Industry Description
Sweet
Syngas
Equipment
Cleaning
>,
Metal
Cleaning
Waste
Coal/
Petroleum
Coke Pile
Runoff
Exhaust Gases
Cooling
>• Water
Heat Recovery Steam
Generator (HRSG)
Electric
Generator
Figure 4-4. IGCC Process Flow Diagram
-------
Section 4 - Steam Electric Industry Description
4.2.4 Demographics of the Steam Electric Power Generating Industry
In 2010, EPA's Office of Water administered the Steam Electric Information Collection
Request (ICR) (Steam Electric Survey) to power plants believed to be subject to the Steam
Electric Power Generating ELGs. As described in Section 3.3, EPA distributed the survey to all
coal- and petroleum-coke fired plants identified in the 2007 EIA and a statistically sampled
subset of steam electric power plants burning other types of fuel, including oil-fired, gas-fired,
and nuclear power plants. EPA obtained information on specific aspects of power plant operation
for the 2009 calendar year.15 The survey also requested information about planned steam electric
generating units, treatment systems, and other improvements or modifications through the year
2020. EPA uses data from the Steam Electric Survey throughout this report to describe the
current state of the steam electric industry and to make predictions on the general direction of the
industry in the near future. This section presents demographic data and other information to
characterize the steam electric industry based on data obtained through the 2009 EIA and EPA's
Steam Electric Survey.
Table 4-2 presents the distribution of the types of steam electric prime movers used by
plants subject to the Steam Electric Power Generating ELGs using both the 2009 EIA data and
EPA's Steam Electric Survey. The table includes the numbers of plants, electric generating units,
and capacity for each type of steam electric prime mover. The number of electric generating
units represents the number of generators/turbines used to generate electricity and does not
necessarily relate to the number of boilers. The number of plants, units, and capacity in the steam
electric industry generated from the Steam Electric Survey are based on values reported in the
survey, which were scaled up to represent the industry as a whole using the industry-weighting
factors discussed in Section 3.3.
As shown in Table 4-2, the Steam Electric Survey estimates are lower than the 2009 EIA
data estimates. Based on EIA data, the industry had 1,179 plants operating at least one steam
electric generating unit powered by a fossil or nuclear fuel in 2009. The weighted survey data
indicate that the industry had 1,079 plants operating at least one steam electric generating unit in
2009.16 As described in Section 3.3, the survey captured data from plants identified using 2007
EIA data but responses reflect data for the 2009 production year. The steam electric industry is
dynamic; the discrepancies between survey data and the 2009 EIA could be due to new
installations, unit fuel conversions, plant/unit retirements. In addition, the Steam Electric Power
Generating ELGs are not applicable to all units generating electricity. Units that do not burn
fossil fuels or plants with a primary purpose other than generating electricity do not fall under the
applicability of the Steam Electric ELGs. Therefore, EPA used the weighted survey results for
the remainder of the analyses in this document to represent the steam electric industry in 2009.
15 EPA is using January 1, 2014 as the baseline for the proposed ELG because 2014 is the year that EPA expects to
promulgate the final rule. The data presented in this section represent 2009 conditions, unless otherwise noted,
because the data are based on responses collected from the Steam Electric Survey.
16 The weighted survey initially indicated that there were 1,088 power plants operating at least one steam electric
generating unit powered by a fossil or nuclear fuel. However, upon further inspection, the data indicated that only
1,079 of these plants operated at least one steam electric generating unit in 2009.
-------
Section 4 - Steam Electric Industry Description
Based on the Steam Electric Survey data, the majority (66 percent) of the steam electric
power produced by the plants subject to the ELGs is generated using stand-alone steam turbines,
which are also the most prevalent type of steam electric prime mover used. Table 4-3 presents
the distribution of fossil and nuclear fuels used to power each type of steam electric prime
mover. The number of electric generating units represents the number of generators/turbines
used to generate electricity and is not equal to the number of boilers. The vast majority (93
percent) of these generating units burn at least some amount of either coal or gas. Coal is the
most common primary fuel type for stand-alone steam turbines, while gas is the primary fuel for
nearly all combined cycle systems. Oil-fired units are not very prevalent in the industry,
accounting for roughly only 3 to 4 percent of the total number of generating units and capacity.
Table 4-4 presents the steam electric capacity, as well as the number of steam electric
power plants distributed by overall plant capacity.l Table 4-4 includes the stand-alone steam
turbines and all the combined cycle system turbines (i.e., combined cycle steam turbine,
combined cycle single shaft, and combined cycle combustion turbine) in the number of steam
electric power plants and steam electric capacity. According to the weighted Steam Electric
Survey data, the largest capacity plants (>500 MW) comprise over 60 percent of all steam
electric power plants and 90 percent of the steam electric generating capacity for all plants
regulated by the ELGs. Based on the weighted Steam Electric Survey data, most steam electric
power plants are either gas- or coal-fired and have a generating capacity greater than 500 MW.
Table 4-5 presents the steam electric industry broken out by size of the generating units.
Table 4-5 includes the stand-alone steam turbines and the all the combined cycle steam turbines.
To determine the size of the combined cycle generating units, EPA added the capacity for all
combined cycle turbines (i.e., combined cycle steam turbine, combined cycle single shaft, and
combined cycle combustion turbine) for each turbine identified for the specific generating unit.
There are 281 generating units with a capacity of 50 MW or less (13 percent of all steam electric
generating units); however, only 71 coal- or petroleum coke-fired generating units have a
capacity of 50 MW or less (3.2 percent of all coal- or petroleum coke-fired generating units). The
281 generating units account for only 1.1 percent of the total capacity associated with the steam
electric industry.
Stand-alone steam turbines are more prevalent than combined cycle units within the
steam electric industry. These stand-alone steam turbines are generally larger units, with 70
percent having a capacity of 500 MW or greater. In most cases, stand-alone steam turbines will
burn coal- or petroleum-coke as either a primary or a secondary fuel. Of the total steam electric
capacity, stand-alone steam turbines burning coal or petroleum coke account for 70 percent.
17 The overall plant capacity includes all electric power generated by the plant, including electricity produced using
non-steam generators and through the use of non-fossil/non-nuclear energy sources.
-------
Section 4 - Steam Electric Industry Description
Table 4-2. Distribution of Prime Mover Types for Plants Regulated by the Steam Electric Power Generating Effluent
Guidelines
Steam Electric Prime Movers
Stand-Alone Steam Turbine
Combined Cycle Systems °
Combined Cycle Steam Turbine d
Combined Cycle Single Shaft (steam
and combustion turbines shaft as single
shaft)6
Combined Cycle Combustion Turbine
Total
2009 EIA
Number of
Plants a
787
(67%)
438
(37%)
416
22
411
1,179
(100%)
Number of
Electric
Generating Units
1,868
(76%)
599
(24%)
550
49
1,013
2,467f
(100%)
Total Steam or
Combined Cycle
Turbine Capacity
(MW)
555,000
(71%)
224,000
(29%)
81,100
9,570
134,000
780,000
(100%)
Steam Electric Survey
Number of
Plants a
716
(66%)
408
(38%)
408
404
1,079
(100%)
Number of
Electric
Generating Units
l,640b
(74%)
573
(26%)
573
570
2,214f
(100%)
Total Steam or
Combined Cycle
Turbine Capacity
(MW)
528,000
(71%)
213,000
(29%)
87,700g
125,000g
741,000
(100%)
Source: Steam Electric Survey, [ERG, 2013]; 2009 EIA, [U.S. DOE, 2009].
Note: Capacity values are rounded to three significant figures.
Note: The number of plants, units, and capacity in the steam electric industry generated from the Steam Electric Survey are based on values reported in the
survey, which were scaled up to represent the industry as a whole using the industry-weighting factors discussed in Section 3.3.
a - Because a single plant may operate multiple electric generating units of various prime mover types, the number of plants by prime mover type is not additive.
There are 1,179 plants (according to the 2009 EIA) or 1,079 plants (according to the steam electric survey) in the industry that operate at least one steam electric
generating unit powered by either fossil or nuclear fuel.
b - One generating unit operating a stand-alone steam turbine was reported as burning only wood. This unit is not included in the count of generating units
because it does not meet the applicability of the steam electric ELGs.
c - Due to the nature of the EIA data, EPA was able to identify the number of combined cycle turbines (i.e., prime movers), but could not discern the number of
actual combined cycle systems. EPA estimated the number of combined cycle systems reported in EIA by adding the number of combined cycle steam turbines
and the number of single shaft turbines. Typically, there are multiple combustion turbines to a single steam turbine in a combined cycle system; therefore, EPA
believes this methodology better represents the number of combined cycle systems than simply adding the number of combined cycle combustion and steam
turbines. For the Steam Electric Survey data, the plants reported the combined-cycle-system-level information directly.
-------
Section 4 - Steam Electric Industry Description
d - One plant in the 2009 EIA database reported using a fossil fuel for its combined cycle steam turbine and a non-fossil/non-nuclear fuel for its three combined
cycle combustion turbines. EPA included the combined cycle steam turbine from this plant in the table, but did not include the combined cycle combustion
turbines using fuels not covered by the ELGs.
e - EIA data differentiate among types of combined cycle turbines, with a separate designation for single shaft turbines (steam and combustion turbines sharing a
single shaft). EPA's Steam Electric Survey does not differentiate between types of combined cycle systems; single shaft turbines are included as combined cycle
systems in the survey.
f - EPA estimated the total number of electric generating units as the sum of the stand-alone steam turbines and the estimated number of combined cycle
systems. EPA did not sum the total number of turbines.
g - From the survey data, EPA was not able to categorize the combined cycle systems as a combined cycle steam turbine, a combined cycle single shaft, or a
combined cycle combustion turbine. Seven plants (17 units) identified operating a combined cycle system but provided only the steam turbine capacity. The 2009
EIA data identifies these units as single-shaft turbines. The total capacity of these units, steam turbine and combustion turbine capacity, is accounted for under
combined cycle steam turbines.
-------
Section 4 - Steam Electric Industry Description
Table 4-3. Distribution of Fuel Types Used by Steam Electric Generating Units
Fossil or Nuclear Fuel a
Coal:
Anthracite Coal
Bituminous Coal
Subbituminous Coal
Lignite Coal
Coal Synfuel
Waste/Other Coal
Blend c
Petroleum Coke
Oil:
No. 1 Fuel Oil
No. 2 Fuel Oil
No. 4 Fuel Oil
No. 5 Fuel Oil
No. 6 Fuel Oil
Diesel Fuel
Jet Fuel
Kerosene
Waste Oil/Other Oil
Blend c
Gas:
Natural Gas
Blast Furnace Gas
Gaseous Propane
Other Gases
Blend c
Stand-Alone Steam Turbines
Number of
Plants
455-465
1
209
145
10-15
0
17
106
8
55-65
0
1-5
1
0
15-20
o
3
0
0
0
32
171
111
0
0
0
0
Number of Electric
Generating Units
1,080-1,090
1
497
310
10-20
0
18
240
;;
70-85
0
1-5
1
0
20-30
3
0
0
0
46
367
367
0
0
0
0
Total Turbine
Capacity (MW)
328,000-330,000
128
144,000
109,000
7,000-8,000
0
1,660
66,700
751
22,500-23,500
0
200-300
210
0
12,500-13,500
1,480
0
0
0
8,430
71,500
71,500
0
0
0
0
Combined Cycle Steam Turbines b
Number of
Plants
2
0
1
0
0
0
0
1
;
5-10
0
0
0
0
0
4
0
1-5
0
0
400
395
0
0
0
5
Number of Electric
Generating Units
2
0
1
0
0
0
0
1
;
5-15
0
0
0
0
0
7
0
1-5
0
0
562
556
0
0
0
5
Total Turbine
Capacity (MW)
427
0
101
0
0
0
0
326
334
1,400-1,900
0
0
0
0
0
438
0
1,000-1,500
0
0
210,000
210,000
0
0
0
537
-------
Section 4 - Steam Electric Industry Description
Table 4-3. Distribution of Fuel Types Used by Steam Electric Generating Units
Fossil or Nuclear Fuel a
Nuclear
Total
Stand-Alone Steam Turbines
Number of
Plants
66
716 d
Number of Electric
Generating Units
99
1,640
Total Turbine
Capacity (MW)
104,000
528,000
Combined Cycle Steam Turbines b
Number of
Plants
0
408 d
Number of Electric
Generating Units
0
573
Total Turbine
Capacity (MW)
0
213,000
Source: Steam Electric Survey [ERG, 2013].
Note: Certain cells contain ranges of values to protect the release of information claimed confidential business information (CBI).
Note: Capacity values are rounded to three significant figures.
Note: The number of plants, units, and capacity in the steam electric industry generated from the Steam Electric Survey are based on values reported in the
survey, which were scaled up to represent the industry as a whole using the industry-weighting factors discussed in Section 3.3.
a - Units were first classified by fuel group based on the following hierarchy: coal, oil, gas, and nuclear For example, if a unit burns both coal and gas then it was
categorized as coal, even if coal was reported as generating less electricity compared to other fuel groups. Units were then categorized by the type of fuel burned.
b - The Steam Electric Survey identifies combined cycle systems, which include at least one steam turbine and one combustion turbine.
c - The 'blend' category identifies units that burn more than one type of fuel within the fuel group. For example, for a generating unit that burns coal, a blend coal
unit burns at least two different types of coal.
d - Because a single plant may operate multiple electric generating units burning various types of fuel, the number of plants by fuel type is not additive. There
are 716 plants responding to the survey that operate at least one stand-alone steam turbine powered by either fossil or nuclear fuel. There are 408 plants
responding to the survey that operate at least one combined-cycle system powered by either fossil or nuclear fuel.
-------
Section 4 - Steam Electric Industry Description
Table 4-4. Distribution by Size of Steam Electric Capacity and Plants Regulated by
the Steam Electric Power Generating Effluent Guidelines
Total Steam Electric Capacity
(MW)b
Percentage of Capacity
Number of Plants
Percentage of Plants
Overall Plant Capacity Range"
0-100
MW
5,040
0.7%
103
9.6%
100-200
MW
9,410
1.3%
88
8.2%
200-300
MW
11,300
1.5%
72
6.6%
300-400
MW
17,600
2.4%
79
7.3%
400-500
MW
17,100
2.3%
61
5.7%
>500 MW
680,000
91.8%
676
62.7%
Total
741,000
100%
1,079
100%
Source: Steam Electric Survey, [ERG, 2013].
Note: Capacity values are rounded to three significant figures.
Note: The number of plants and total steam electric capacity includes the stand-alone turbines and the combined
cycle systems.
Note: The number of plants and capacity in the steam electric industry are based on values reported in the survey,
which were scaled to represent the industry as a whole using the industry-weighting factors discussed in Section 3.3.
a - Overall plant steam electric capacity includes electricity produced by only steam electric generating units.
Electricity generated by non-steam-electric electric units and those using non-fossil/non-nuclear energy sources is
not included.
b - The capacity presented within each size distribution is based on the overall plant steam electric capacity.
Table 4-5. Distribution by Size of Steam Electric Generating Units Regulated by
the Steam Electric Power Generating Effluent Guidelines
Total Steam Electric
Capacity (MW) a
Percentage of Capacity
Number of Steam Electric
Generating Units
Percentage of Steam
Electric Generating Units
Unit Capacity Range
0-50
MW
8,010
1.1%
281
12.7%
50-100
MW
23,200
3.1%
305
13.8%
100-200
MW
65,700
8.9%
445
20.1%
200-300
MW
62,200
8.4%
247
11.2%
300-400
MW
72,200
9.7%
207
9.3%
400-500
MW
55,700
7.5%
124
5.6%
>500
MW
454,000
61.3%
605
27.3%
Total
741,000
100%
2,214
100%
Source: Steam Electric Survey, [ERG, 2013].
Note: Capacity values are rounded to three significant figures.
Note: The number of plants, number of steam electric generating units, and total steam electric capacity include the
stand-alone turbines and the combined cycle systems.
Note: The number of units and capacity in the steam electric industry are based on values reported in the survey,
which were scaled to represent the industry as a whole using the industry-weighting factors discussed in Section 3.3.
a - The capacity presented within each size distribution is based on the capacity at the unit level.
4-18
-------
Section 4 - Steam Electric Industry Description
4.3 STEAM ELECTRIC WASTESTREAMS EVALUATED FOR NEW OR ADDITIONAL CONTROLS
IN THE PROPOSED ELGs
This section describes the wastestreams generated by steam electric power plants for
which EPA evaluated new or revised discharge requirements for the proposed ELGs. Section 4.4
discusses other wastestreams generated by the steam electric industry that EPA did not evaluate
for new or revised discharge requirements in the proposed ELGs.
4.3.1 Fly Ash Transport Water
Depending on the boiler design, as much as 70 to 80 percent of the ash from a pulverized
coal furnace consists of fly ash. Certain boiler designs, such as cyclone boilers, produce
relatively small amounts of fly ash, approximately 20 to 30 percent. Many plants transport fly
ash from the boiler using water as the motive force, known as sluicing. This section presents an
overview of fly ash transport water generated by the steam electric industry.
As discussed in Section 4.2.1, flue gas contains entrained fly ash as it leaves the boiler.
Steam electric units employ three main particulate collection methods to remove fly ash from the
flue gas: electrostatic precipitators (ESPs), baghouses, and venturi-type wet scrubbers. Of the
approximately 1,100 coal-, petroleum coke-, and oil-fired units collecting fly ash, 97 percent
utilize one of these three collection methods. The remaining 3 percent identified some other type
of particulate collection system. Table 4-6 presents the number of coal-, petroleum coke-, and
oil-fired units utilizing each of these collection methods and each is described below.
Table 4-6. Fly Ash Collection Practices in the Steam Electric Industry
Fly Ash Collection Method
ESP
Baghouse
Baghouse and ESP
Wet Scrubber
Other
Total
Number of
Plants
335
143
5-15
5-15
20
508-528"
Number of Coal- and Petroleum
Coke-Fired Steam Electric Units
816
220
10-15
15-25
12
1,080-1,100"
Number of Oil-Fired
Steam Electric Units
5-10
0
2
0
9
26-31
Source: Steam Electric Survey, [ERG, 2013].
Note: Certain fields contain ranges of values to protect the release of information claimed CBI.
Note: The number of plants, units, and capacity in the steam electric industry are based on values reported in the
survey, which were scaled to represent the industry as a whole using the industry-weighting factors discussed in
Section 3.3.
a - 15 coal-fired generating units at 9 plants identified no fly ash collection method. These plant and unit values are
included in the count of total plants and units collecting fly ash.
To remove the fly ash particles from the flue gas, many plants operate electrostatic
precipitators (ESPs). ESPs use high voltage to generate an electrical charge on the particles
contained in the flue gas. The charged particles then collect on a metal plate with an opposite
electric charge. Additionally, some plants may use agglomerating agents, such as ammonia,
4-19
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Section 4 - Steam Electric Industry Description
which help small charged ash particles form larger agglomerates that are more readily attracted
to the charged plates, improving the removal efficiency of the ESPs. As the particles begin to
layer on the metal plates, the plates are tapped/rapped to loosen the particles, which fall into
collection hoppers. ESPs can remove 99.9 percent of fly ash from the flue gas [Babcock &
Wilcox, 2005]. These types of systems are the most common type of fly ash collection system
used in the steam electric industry. Of the approximately 1,100 coal-, petroleum coke-, and oil-
fired units in the industry collecting fly ash in the steam electric survey, about 830 units (75
percent) utilize an ESP system [ERG, 2013].18
Plants may also use other particulate control technologies, such as baghouse filters. A
baghouse system contains several compartments, each containing fabric filter bags that are
suspended vertically in the compartment. The bags can be quite long (e.g., 40 feet) and small in
diameter [Babcock & Wilcox, 2005]. The reverse air system is the baghouse configuration most
commonly used by steam electric power plants. In this system, the flue gas enters into the
various compartments and is forced to flow into the bottom of the fabric filter bags. The flue gas
passes through the fabric filter, but the fly ash particulates cannot pass and are captured on the
inside walls of the baghouse. As the baghouses collect more particulates, the layer of particulates
becomes thicker and help to remove more particulates from the flue gas. After a specified period
of time or once the pressure drop in the baghouse reaches a high set point, the plants reverse the
flow in the compartments and send clean flue gas from the outside of the fabric filter bags to the
inside, which dislodges the particulates. The particulates are captured in hoppers at the bottom of
the compartment [Babcock & Wilcox, 2005]. Of the approximately 1,100 coal-, petroleum coke-,
and oil-fired generating units that reported collecting fly ash from flue gas, about 235 units use
baghouse filters (22 percent) [ERG, 2013].19
After the ESP or baghouse deposits the fly ash into the hoppers, the plant can either
handle the fly ash in a dry or wet fashion. In either system, dry fly ash is initially drawn away
from the hoppers using a vacuum to pneumatically transport the ash. Plants operating a dry fly
ash handling system pneumatically transfer the fly ash from the hopper to a fly ash storage silo
and then dispose of the ash. Plants operating a wet fly ash handling system use water as the
motive force to transport the fly ash from the hopper to a surface impoundment. Section 7.2
discusses the different ash handling methods used in the steam electric industry in more detail.
Additionally, between fifteen and twenty-five generating units use venturi-type wet
scrubbers to remove fly ash from the flue gas [ERG, 2013]. Venturi scrubbers contain a tube
with flared ends and a constricted middle section. The flue gas enters from one of the flared ends
and approaches the constricted section. A liquid slurry stream is added to the scrubber just prior
to or at the constricted section. As the flue gas enters the constricted section, its pressure and
velocity increases, which causes the gas and liquid slurry to mix. The greater the pressure drop in
the scrubber, the better the mixing, and the better the reaction rate, which increases the
particulate removal efficiency. However, venturi scrubbers must be operated at high pressure
drops to remove the same level of particulates as ESPs, making their operation costs higher than
18 This includes 10 to 15 generating units that use a combination system that incorporates an ESP and baghouse
filters to remove particulates from the flue gas.
19 This includes 10 to 15 generating units that use a combination system that incorporates an ESP and baghouse
filters to remove particulates from the flue gas.
4-20
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Section 4 - Steam Electric Industry Description
ESPs [Babcock & Wilcox, 2005; U.S. EPA, 2010]. Based on the proposed revisions to the
specialized definitions, described in Section 2.2, EPA does not consider the ash collected by
venture scrubbers as fly ash, and therefore, the water generated by these systems is not
considered fly ash transport water.
Table 4-7 presents the fly ash handling practices used by plants operating coal-,
petroleum coke-, and oil-fired generating units. Approximately one-fourth of the plants operating
coal-fired generating units handle at least a portion of their fly ash with a wet sluicing system. A
small percentage of oil-fired units, approximately 20 percent, also wet sluice fly ash. In most
cases, plants manually remove the fly ash from these oil-fired units by methods such as scraping
the ash out of the boiler. In general, oil-fired units produce much less fly ash than coal-fired
units. For example, oil-fired units responding to the survey produced an average of just over 60
tons of fly ash per year per unit, compared to over 60,000 tons per year for an average coal-fired
unit.
Table 4-7. Fly Ash Handling Practices in the Steam Electric Industry
Fly Ash Handling
Wet-Sluiced
Handled Dry or Removed in
Scrubber a
Handled Either Wet or Dry b
No Handling System Reported
Total
Number of
Plants
57
(11%)
344
(67%)
81
(16%)
31
(6%)
514
Coal- and Petroleum Coke-
Fired Steam Electric Units
Number of
Units
205
713
168
10
1,096
Capacity
(MW)
47,000
(14%)
222,000
(67%)
59,000
(18%)
2,370
(1%)
330,000
Oil-Fired Steam
Electric Units
Number of
Units
10-15
10-15
1-5
61
80-95
Capacity
(MW)
7,500-10,000
(33%)
2,500-5,000
(17%)
500-1,500
(3%)
11,400
(44%)
21,900-27,900
Source: Steam Electric Survey, [ERG, 2013].
Note: Certain fields contain ranges of values to protect the release of information claimed CBI.
Note: Capacity values are rounded to three significant figures.
Note: The number of plants, units, and capacity in the steam electric industry are based on values reported in the
survey, which were scaled to represent the industry as a whole using the industry-weighting factors discussed in
Section 3.3.
a - EPA considered all transport methods other than wet sluicing as dry fly ash transport.
b -These units have both wet and dry handling systems for removing fly ash from the boiler and can operate either
system as needed.
Most plants operating wet fly ash handling systems are located east of the Mississippi
River. Figure 4-5 provides a distribution of the three categories of fly ash handling practices
presented in Table 4-7. Each symbol represents the plant-level fly ash handling system. The
figure only includes the plants for which responses were provided in the Steam Electric Survey
(i.e., the figure does not represent the weighted numbers). Plants categorized as 'wet and dry
handling' operate some units at the plant with wet fly ash handling systems and other units at the
4-21
-------
Section 4 - Steam Electric Industry Description
plant with dry fly ash handling systems, or in some instances operate both a wet and a dry fly ash
handling system for an individual generating unit.
* O Oj «i Q ou . O
C°'°%^°0 fC^9-(
Type of Fly Ash Transport System at Plant Li
• Wet Handling • Wet and Dry Handlir
O Dry Handling
it Level
ing
Source: Steam Electric Survey, [ERG, 2013].
Figure 4-5. Plant-Level Fly Ash Handling Systems
In 1982, EPA promulgated new source performance standards (NSPS) that prohibited
new sources from discharging wastewater pollutants in fly ash transport water. Not surprisingly,
EPA has found that the steam electric units generating wet fly ash transport water tend to be
older units (e.g., more than 30 years old), while most units built since the NSPS were
promulgated are outfitted with dry fly ash handling systems.
EPA identified several plants that have installed dry fly ash handling systems, either to
replace the preexisting wet handling system or to operate as a parallel system. Table 4-8 presents
the number of units converted from wet fly ash handling to dry fly ash handling since 2000. Each
plant and unit is classified by the type of dry system installed, which include wet vacuum
pneumatic systems, dry vacuum systems, pressure systems, and combined vacuum and pressure
systems. Each of these dry fly ash handling systems is described in Section 7. Data from the
Steam Electric Survey show that power companies converted at least 115 units at over 45 plants
to dry fly ash handling systems since 2000. Power companies also reported that they are planning
4-22
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Section 4 - Steam Electric Industry Description
to convert an additional 61 units to dry handling systems by the year 2020. The reasons cited for
installing the dry handling systems include environmental remediation (i.e., discharges from the
fly ash impoundments caused environmental impacts), economic opportunity (e.g., revenues
from sale of fly ash), and the need to replace ash impoundments approaching full storage
capacity. Because dry fly ash handling practices do not generate fly ash transport water,
converting to a dry system eliminates the discharge of fly ash transport water and the pollutants
contained therein. In addition, it reduces the amount of intake water the plant uses and eliminates
the need for an impoundment to store the fly ash transport water. Section 6.2 presents additional
information on the amount of fly ash transport water generated and discharged by the steam
electric industry and the pollutant characteristics of the transport water.
Table 4-8. Conversions of Wet Fly Ash Sluicing Systems Since 2000
Type of Dry Fly Ash Handling
System Installed
Wet Vacuum System (pneumatic) a
Dry Vacuum System b
Pressure System °
Combined Vacuum/Pressure System d
Total e
Number of Plants
1-5
24
5-10
18
45 - 55 (35 - 42%)
Number of Units
1-5
50
15-25
36
85-115(26-35%)
Capacity
(MW)
2,000-3,000
9,400
7,500-10,000
15,800
34,700 - 38,200 (38-42%)
Source: Steam Electric Survey, [ERG, 2013].
Note: Certain fields contain ranges of values to protect the release of information claimed CBI.
Note: Capacity values are rounded to three significant figures.
Note: The number of plants, units, and capacity in the steam electric industry are based on values reported in the
survey, which were scaled to represent the industry as a whole using the industry-weighting factors discussed in
Section 3.3.
Note: Approximately 33 of these units also wet sluiced a portion of the fly ash in 2009.
a - One of these units also wet sluiced a portion of the fly ash in 2009.
b - Twelve of these units also wet sluiced a portion of the fly ash in 2009.
c - Four of these units also wet sluiced a portion of the fly ash in 2009.
d - Sixteen of these units also wet sluiced a portion of the fly ash in 2009.
e - The percentages are based on the number of systems conducting any wet sluicing operations (wet sluicing
systems and wet and dry systems) in 2000 prior to any conversions (excluding units that have retired since that
time).
4.3.2 Bottom Ash Transport Water
As much as 70 to 80 percent of the ash from a pulverized coal furnace consists of fly ash.
The remaining 20 to 30 percent is bottom ash. Cyclone boilers, and other boiler designs, can
produce a larger percentage of bottom ash, upwards of 70 to 80 percent. Like fly ash, bottom ash
can be transported from the boiler using water. This section presents an overview of bottom ash
transport water generated by the steam electric industry.
Heavy bottom ash particles collect in the bottom of the boiler. The sloped walls and
opening at the bottom of the boiler allow the bottom ash to feed by gravity to the bottom ash
4-23
-------
Section 4 - Steam Electric Industry Description
hoppers positioned below the boiler. The bottom ash hoppers are connected directly to the boiler
bottom to prevent any boiler gases from leaving the boiler. Depending on the size of the boiler,
there may be more than one bottom ash hopper running along the opening of the bottom of the
boiler. Most bottom ash hoppers are filled with water to quench the hot bottom ash as it enters
the hopper. Once the bottom ash hoppers have filled with bottom ash, a gate at the bottom of the
hopper opens and the ash is directed to grinders to grind the bottom ash into smaller pieces. From
the hopper, bottom ash can be handled in a wet or dry fashion.
Plants operating a wet bottom ash handling system sluice the ground ash with water to an
impoundment or a dewatering bin. Because bottom ash particles are heavier than fly ash
particles, they more easily separate from the sluice water. Some plants operate large surface
impoundments for bottom ash, while others use a system of relatively small impoundments
operating in series and/or parallel. Other plants operate dewatering bin systems, in which they
use a tank-based settling operation to separate the bottom ash solids from the transport water. A
dewatering bin system generally consists of at least two bins; while one bin is receiving bottom
ash, the other bin is decanting the water from the collected bottom ash material. Excess water in
the bin flows over a weir, leaving the dewatering bin. Plants can reuse this overflow water
directly as bottom ash transport water, send it to an ash impoundment for additional settling, or
discharge it directly to surface water.
Most coal and petroleum coke plants operate wet bottom ash handling systems, as
described above; however, a substantial number of plants operate a completely dry bottom ash
handling system or a system that does not generate ash transport water (e.g., mechanical drag
system). As seen in Table 4-9, 112 plants handle at least a portion of their bottom ash dry.20
These 112 plants represent 22 percent of plants operating a coal-, petroleum coke-, or oil-fired
generating unit. Approximately 20 percent of all coal- and petroleum coke-fired generating units
use dry bottom ash handling systems. The most common type of dry ash handling system used in
the steam electric industry is the mechanical drag chain system. The plant uses a drag chain to
remove the bottom ash out of the boiler. The bottom ash is dewatered as the drag chain pulls the
bottom ash up an incline, draining the water back to the boiler. The plant then conveys the
bottom ash to a nearby collection area from which it is loaded onto trucks and either sold for
beneficial use or stored on site in a landfill. Section 7.3 provides more detail on dry and closed-
loop recycle bottom ash handling systems.
20For the purpose of this report, dry bottom ash handling systems includes all systems that do not generate bottom
ash transport water, which includes completely dry bottom ash handling systems, mechanical drag systems, and
other mechanical removal systems (e.g., scraping of bottom ash from boiler). Complete recycle and remote
mechanical drag systems are considered wet sluicing systems.
4-24
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Section 4 - Steam Electric Industry Description
Table 4-9. Bottom Ash Handling Practices in the Steam Electric Industry
Bottom Ash Handling
Wet-Sluiced
Handled Dry a
Handled Either Wet or Dry
No Handling System
Reported
Total
Number of
Plants
335 (65%)
101 (20%)
11(2%)
69 (13%)
516
Coal- and Petroleum Coke-Fired
Steam Electric Units
Number of
Units
863
214
6
12
1,096
Capacity
(MW)
286,000 (87%)
39,900 (12%)
2,610 (1%)
1,400 (<1%)
330,000
Oil-Fired Steam Electric Units
Number of
Units
0-5
30-35
0
57
80-95
Capacity
(MW)
0-250 (1%)
10,000-15,000
(51%)
0
11,500(48%)
21,900 - 27,900b
Source: Steam Electric Survey, [ERG, 2013].
Note: Certain fields contain ranges of values to protect the release of information claimed CBI.
Note: Capacity values are rounded to three significant figures.
Note: The number of plants, units, and capacity in the steam electric industry are based on values reported in the
survey, which were scaled to represent the industry as a whole using the industry-weighting factors discussed in
Section 3.3.
a - Dry bottom ash handling systems include all systems that do not generate bottom ash transport water, which
includes completely dry bottom ash handling systems, mechanical drag systems, and other mechanical removal
systems (e.g., scraping of bottom of boiler).
b - Total capacity does not include the capacity of three oil units that did not report generating bottom ash.
Table 4-9 shows that 67 percent of plants (79 percent of coal- and petroleum coke-fired
generating units) wet sluice all or part of the bottom ash produced. Figure 4-6 shows all plants
producing bottom ash in 2009 in the United States with the type of bottom ash handling system
identified by different colored symbols. The figure only includes the plants for which responses
were provided in the Steam Electric Survey (i.e., the figure does not represent the weighted
numbers)
4-25
-------
Section 4 - Steam Electric Industry Description
Type of Bottom Ash Transport System at Plant Level
• Wet Handling • Wet and Dry Handling
O Dry Handling
Source: Steam Electric Survey,[ERG, 2013].
Figure 4-6. Plant-Level Bottom Ash Handling Systems
Table 4-10 presents the number of plants within the industry that converted wet sluicing
bottom ash operations since 2000. The units and plants are classified by type of dry system
installed. Steam electric plants use mechanical drag systems, dry vacuum systems, dry pressure
systems, or a handful of other dry handling methods. Each of these handling technologies is
discussed further in Section 7. These units represent approximately three percent of the total
number of steam electric units that were wet sluicing bottom ash in 2000. Power companies
reported plans to convert an additional 67 units to dry or closed-loop recycle bottom ash
handling systems by the year 2020.
Bottom ash transport water is typically directed to an on-site ash impoundment for
treatment, as described earlier in this section. Steam electric units generate this water
intermittently; the frequency depends upon hopper size and the operation of the boiler. Section
6.2 discusses in more detail the amount of bottom ash transport water generated and discharged
by the steam electric industry and the pollutant characteristics of the transport water.
4-26
-------
Section 4 - Steam Electric Industry Description
Table 4-10. Conversions of Bottom Ash Sluicing Systems Since 2000
Type of Dry Bottom Ash
Handling System Installed
Mechanical Drag System
Dry Vacuum System
Dry Pressure System
Other
Total a
Number of Plants
10-15
1-5
0
1-5
12 - 25 (3 - 7%)
Number of Units
15-20
5-10
0
1-5
21 - 35 (2 - 4%)
Capacity
(MW)
6,500-7,500
250-500
0
100-300
6,850 - 8,300 (3%)
Source: Steam Electric Survey, [ERG, 2013].
Note: Certain fields contain ranges of values to protect the release of information claimed CBI.
Note: Capacity values are rounded to three significant figures.
Note: The number of plants, units, and capacity in the steam electric industry generated from the Steam Electric
Survey are based on values reported in the survey, which were scaled to represent the industry as a whole using the
industry-weighting factors discussed in Section 3.3
a - The percentages are based on the number of systems conducting any wet sluicing operations (wet sluicing
systems and wet and dry systems) in 2000 (excluding units that have retired since that time).
4.3.3 Flue Gas Desulfurization Wastewater
To meet air quality requirements, many power plants that burn coal use a variety of FGD
scrubber systems to control SC>2 emissions from flue gas generated in the plant's boiler. These
systems are classified as "wet" or "dry." For the purposes of this rulemaking, "wet" FGD
systems are those that use a sorbent slurry and that generate a water stream that exits the FGD
scrubber absorber. Figure 4-7 presents a simplified diagram of typical wet and dry FGD systems.
4-27
-------
Section 4 - Steam Electric Industry Description
Reagent Slurry
Gas to Stack
Sorbent Slurry Makeup
Flue Gas
Dry FGD
Scrubber
Gas to Particulate
Collector and Stack
FGD Reagent Slurry
Flue Gas
Wet FGD FGD Solids
Scrubber Separation
Recycle
FGD Scrubber
> Purge to
FGD Slurry Wastewater
Slowdown Treatment
Dry FGD System
Recirculating Wet FGD System
Gas to Stack
Sorbent Slurry Makeup
FGD Reagent Slurry
Flue Gas
Wet FGD
Scrubber
FGD Slurry
. Discharge to
Wastewater
Treatment
Single Pass Wet FGD System
Figure 4-7. Typical FGD Systems
In dry FGD scrubbers, alkaline reagent slurry is introduced into the hot flue gas stream.
The slurry passes through an atomizer and enters the scrubber as a fine mist of droplets. In the
scrubber, 862 is absorbed as the slurry is evaporated and the flue gas is cooled. Dry FGD
scrubbers typically remove between 80 and 90 percent of the SC>2 which is less than a wet FGD
system. The amount of water in the reagent slurry is controlled such that it evaporates almost
completely in suspension [Babcock & Wilcox, 2005]. Although dry FGD scrubbers use water in
their operation, the water in most systems evaporates and they generally do not discharge
wastewater. Of the 72 dry FGD plants, 23 generate wastewater during operation and only 2
discharge to a surface water. Wastewater may also be generated during cleaning operations. Of
the 72 dry FGD plants, 31 generate wastewater from cleaning operations and only 4 discharge
any cleaning wastewater [ERG, 2013]. Dry FGD systems generate smaller, less frequent
quantities of wastewater from their operation/cleaning compared to the FGD wastewater from
wet systems. EPA did not evaluate the wastewater generated from these dry FGD systems as part
of the rulemaking and they would not be subject to the FGD wastewater requirements in the
proposed ELGs.
Wet FGD scrubber systems can remove over 90 percent of the SO2 in the flue gas, and in
some cases can remove up to 99 percent. In wet FGD scrubbers, the flue gas stream contacts a
4-28
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Section 4 - Steam Electric Industry Description
liquid stream containing a sorbent, which causes the mass transfer of pollutants from the flue gas
to the liquid stream. The sorbents typically used for 862 absorption are lime (Ca(OH)2) or
limestone (CaCCb), which react with the sulfur in the flue gas to form calcium sulfite (CaSCb).
Scrubbers can be operated with forced, inhibited, or natural oxidation systems. In forced
oxidation systems, the CaSCb is fully oxidized to produce gypsum (CaSC>4» 2H2O). During the
scrubbing process, metals and other constituents that were not removed from the flue gas stream
by the ESPs may transfer to the scrubber slurry and leave the FGD system via the scrubber
blowdown (i.e., the slurry stream exiting the FGD scrubber that is not immediately recycled back
to the spray/tray levels). The scrubber blowdown is typically intermittently transferred from the
FGD scrubber to the solids separation process. As a result, FGD scrubber purge (i.e., the
wastestream from the FGD scrubber system that is transferred to a wastewater treatment system
or discharged) is also usually intermittent [ERG, 2013].
Table 4-11 presents the distribution of wet and dry FGD systems reported in the Steam
Electric Survey operating in 2009 or planned to be operating by January 1, 2014. Table 4-12
shows the total scrubbed capacity of the steam electric units serviced in those systems.21 There
are 401 FGD systems, servicing 458 coal-fired steam electric generating units, reported to be
online by January 1, 2014.22 Of these 401 systems, 311 generate a slurry stream and are
considered "wet" FGD systems for the purposes of this rulemaking. Wet FGD systems service
78 percent of scrubbed generating units, representing 84 percent of the total industry scrubbed
capacity. These wet systems typically use a limestone slurry with forced oxidation and service
generating units burning bituminous coal. Often, plants also operate SCR systems on these
generating units to control NOX emissions (see Section 4.4.4).
Steam electric power plants operating wet FGD systems are located throughout the
United States; the largest number is on the eastern United States where more bituminous coal-
fired steam electric power plants are located. Figure 4-8 shows the location of all wet scrubbed
FGD systems located at the plants noted in Table 4-12. The figure only includes the plants for
which responses were provided in the Steam Electric Survey (i.e., the figure does not represent
the weighted numbers).
21 The total scrubbed capacity includes electric power generated by only those steam electric units serviced by an
FGD system.
22 Recent air regulations and new state requirements have resulted in the installation of new wet FGD scrubbers.
EPA tried to look ahead to account for these additional wet FGD scrubbers and therefore, because the EPA expects
to promulgate the final ELG in 2014, EPA used January 1, 2014 as the baseline for this ELG.
4-29
-------
Section 4 - Steam Electric Industry Description
Table 4-11. Types of FGD Scrubbers in the Steam Electric Industry
Type of Scrubber
Circulating Dry
Jet Bubbling Reactor
Mechanically Aided
Packed
Spray
Spray /Tray
Spray Dryer
Tray
Venturi
Other3
No Information b
"Wet" FGD Systems
Number of Plants
0
10-15
0
2
77
58
1
1
10
7
2
Number Electric
Generating Units
0
30-40
0
4
159
118
1
1
23
15
2
"Dry" FGD Systems
Number of
Plants
11
0
1
1
1-5
0
50
0
1 -5
5-10
0
Number of Electric
Generating Units
11
0
1
2
1-5
0
69
0
1 -5
7-12
0
Source: Steam Electric Survey, [ERG, 2013].
Note: Certain fields contain ranges of values to protect the release of information claimed CBI.
Note: A plant may operate multiple electric generating units that may use different types of FGD systems; therefore,
the sum of plants may be greater than the total number of plants with FGD systems.
a - The types of scrubber systems classified as 'other' include Advatech Double contact flow scrubbers and dry
sodium injection.
b - Insufficient information is available to classify these units/plants in a specific category.
Table 4-12. Characteristics of Coal- and Petroleum Coke-Fired Generating
Units with FGD Systems
Total
Wet FGD Systems
Number of
Plants
145
Number
Electric
Generating
Units
352
Scrubbed
Capacity a
(MW)
175,000
Dry FGD Systems
Number of
Plants
72
Number of
Electric
Generating
Units
97
Scrubbed
Capacity a
(MW)
31,800
Coal Type
Bituminous
Subbituminous
Lignite
Petroleum Coke
Other/Waste Coal
Blend b
No Information °
83
27
5-10
1-5
0-5
33
4
196
65
10-15
1-5
0-5
81
4
101,000
34,900
5,000-6,000
100-200
0-250
33,300
2,420
28
28
2
0-5
1-5
8
1-5
40
38
3
0-5
1-5
10
5-10
8,730
16,300
1,320
0-150
500-1,000
1,880
2,600-3,000
Type of Oxidation System
Forced Oxidation
Inhibited Oxidation
112
17
272
34
138,000
19,600
1-5
2
5-10
3
800-1,200
1,480
4-30
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Section 4 - Steam Electric Industry Description
Table 4-12. Characteristics of Coal- and Petroleum Coke-Fired Generating
Units with FGD Systems
Natural Oxidation
No Information or NA d
Wet FGD Systems
Number of
Plants
23
2
Number
Electric
Generating
Units
47
3
Scrubbed
Capacity a
(MW)
19,000
860
Dry FGD Systems
Number of
Plants
5-10
61
Number of
Electric
Generating
Units
5-15
80
Scrubbed
Capacity a
(MW)
2,200-2,600
27,100
Sorbent
Lime
Limestone
Magnesium-Enhanced Lime
Magnesium Oxide
Soda Ash
Sodium Hydroxide
Other
No Information d
10-15
121
10-15
0
3
0
5
1-5
30-40
288
25-35
0
9
0
14
5-10
9,500-10,500
146,000
15,500-16,500
0
1,880
0
6,940
3,000-4,000
56
13
0-5
0
0
0
14
1
74
18
0-5
0
0
0
23
1
24,800
6,070
0-250
0
0
0
6,340
46
NOX Controls e
SCR
SNCR
None/Other (no
SCR/SNCR)
No Information d
99
13-23
56
2
203
35-40
110
2
117,000
11,500-12,500
45,700
900
27
12
30-40
5
32
14
45-50
5
13,200
4,070
13,500-14,000
1,250
Source: Steam Electric Survey, [ERG, 2013].
Note: Certain fields contain ranges of values to protect the release of information claimed CBI.
Note: Capacity values are rounded to three significant figures.
Note: All 145 wet scrubbed plants and 72 dry scrubbed plants are included in each of the categories presented in this
table. Because a plant may operate multiple electric generating units that may represent more than one type of
operation in each specific category, the sum of the plants, units, and capacity for each category may be greater than
the total.
Note: This table does not account for any plants or units that have identified a retirement between 2009 and January
1,2014.
a - The scrubbed capacities represent the reported nameplate capacity for only those units serviced by a scrubber.
b - A coal blend is any combination of two or more different types of coal.
c - The current profile includes planned units whose coal type is not yet available.
d - Insufficient information is available to classify these units/plants in a specific category.
e - Some of the NOX information included in this category is associated with NOX systems that are planned or under
construction.
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Section 4 - Steam Electric Industry Description
Plants Operating Wet FGD Systems
O Plants Operating Wet FGD Systems
Source: Steam Electric Survey, [ERG, 2013].
Figure 4-8. Plants Operating Wet FGD Scrubber Systems
As shown in Table 4-12, limestone forced oxidation systems are the most common
scrubbers reported in the survey. Plants that generate gypsum using limestone forced oxidation
systems can market the gypsum for use in building materials (e.g., wallboard), while plants that
do not generate gypsum or only partially oxidize the CaSCb must dispose of their scrubber
solids, typically in landfills or impoundments [U.S. EPA, 2006]. Plants that produce a saleable
product, such as gypsum, may rinse the product cake to reduce the level of chlorides in the final
product and reuse or potentially treat and discharge the wash water along with the FGD scrubber
purge. Both sludge by-products (gypsum and CaSOs) typically require dewatering prior to sale,
disposal, or processing for reuse. The dewatering process used by plants that generate CaSCb
typically consists thickeners used in conjunction with centrifuges. The dewatering process used
by plants that generate gypsum typically consists of hydrocyclones used in conjunction with
vacuum filters (either drum or belt). Additionally, some plants may send the FGD blowdown
directly to a pond where the FGD solids are scooped out of the pond with a backhoe and stacked
on the side of the pond (referred to as "stacking"). The stacking operation is more commonly
used by plants generating gypsum, whereas most plants sending FGD wastewater with CaSCb
just let the solids accumulate in the pond. These dewatering processes generate a wastewater
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Section 4 - Steam Electric Industry Description
stream that the plant likely needs to treat before it is discharged or reused. In the case of the
plants sending the FGD blowdown directly to a pond, the pond system is typically the only
treatment employed prior to discharge. Section 6.1 provides more detail on the amount of FGD
wastewater generated by wet FGD systems.
The installation of wet FGD systems reported in Table 4-12 dates back to 1972. Figure
4-9 shows the total scrubbed capacity of wet FGD systems by decade starting with the 1970s.
The figure includes all 311 wet FGD systems identified as operating by January 1, 2014, but it
does not include retired units that may have operated with wet FGD systems. Therefore, while
the Steam Electric Survey shows an increase in the total wet scrubbed capacity from 1970 to
2010 of 123,000 MW, the actual increase may not be as large because by not including retired
units that may have been scrubbed, the scrubbed capacity for earlier years may not be fully
represented in the data set. However, based on previous discussions with industry
representatives, EPA found that most power companies installed the FGD systems on the largest
and newest generating units in their fleets, which are the generating units that are least likely to
retire. Therefore, EPA believes that the amount of scrubbed capacity that has been retired over
this 45-year period is likely minimal. If that is the case, then the data reasonably reflect the
increased use of wet scrubbed FGD systems over the last 45 years.
200000
g- 180000
§ 160000
140000
120000
100000
1970-1980 1980-1990 1990-2000 2000-2010
Year of FGD System Installation
2010-2014
Source: Steam Electric Survey, [ERG, 2013].
Figure 4-9. Capacity of Wet Scrubbed Units by Decade
Section 6.1 contains information on FGD wastewater characteristics and treatment.
4.3.4 Flue Gas Mercury Control Wastewater
In response to recent Clean Air Act (CAA) rules and other state regulations requiring
limits on air emissions of mercury and other air toxics, plants are beginning to install new
systems to improve removals of mercury from flue gas emissions, beyond those previously
achieved by paniculate control systems to remove fly ash. These systems are relatively new to
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Section 4 - Steam Electric Industry Description
the steam electric industry. According to responses to the Steam Electric Survey, there are
generally two types of systems being used to control flue gas mercury emissions:
• Adding oxidizers to the coal prior to combustion, so that the wet FGD system
removes the oxidized mercury; and
• Injecting activated carbon into the flue gas, which adsorbs the mercury and is
captured in a downstream paniculate removal system.
Using the oxidizers does not generate a new wastewater stream, but it may increase the
mercury concentration in FGD wastewater because oxidized mercury is more easily removed by
the FGD system. However, the activated carbon injection system can generate a new
wastestream at a plant, depending on the location of the injection. If the injection occurs
upstream of the primary particulate removal system, then the mercury-containing carbon (i.e.,
FGMC waste) will be collected and handled the same way as the fly ash; therefore, if the fly ash
is wet sluiced, then the FGMC wastes are also wet sluiced. In this case, adding the FGMC wastes
to the fly ash can increase the pollutant concentration in the fly ash transport water. Section 6.4
provides more detail on how adding FGMC waste affects the characteristics of fly ash. If the
injection occurs downstream of the primary parti culate removal system, then the plant will need
a secondary particulate removal system, typically a fabric filter, to capture the FGMC wastes.
Plants typically inject the carbon downstream of the primary particulate collection system if they
plan to market the fly ash because adding the FGMC wastes makes the fly ash unmarketable. In
this situation, the FGMC wastes, which would be collected with some carry-over fly ash, could
be handled either wet or dry.
Based on the responses to the survey, there are approximately 120 currently installed
FGMC systems, with an additional 40 new installations planned. Approximately 90 percent of
the currently operating FGMC systems are dry systems that do not generate or affect any
wastewater streams. Approximately six percent of the currently operating systems are wet
systems. The type of handling system (e.g., wet or dry handling) is unknown for the remaining
four percent of the systems.
4.3.5 Landfill and Impoundment Leachate and Runoff
Combustion residuals comprise a variety of wastes from the combustion process,
including fly ash and bottom ash from coal-, petroleum coke- or oil-fired units; boiler slag; FGD
solids (e.g., gypsum and calcium sulfite); FGMC wastes; and other wastewater treatment solids
associated with fuel combustion wastewater. Combustion residuals may be stored at the plant in
on-site landfills or impoundments. When a landfill or impoundment has reached its capacity, it
will typically be closed (i.e., covered) to protect against environmental release of the pollutants
contained in the waste. However, these landfills or impoundments may continue to generate
leachate.
Leachate is the liquid that drains or leaches from a landfill or an impoundment. Figure
4-10 presents a diagram depicting the generation and collection systems for landfill leachate and
stormwater. The two sources of landfill leachate are precipitation that percolates through the
waste deposited in the landfill and the liquids produced from the combustion residual placed in
the landfill. In addition to leachate, stormwater that contacts the landfill wastes and flows over
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Section 4 - Steam Electric Industry Description
the landfill may be contaminated. Leachate and contaminated stormwater contain heavy metals
and other contaminants through the contact with the combustion residuals. Section 6.3 further
discusses the characteristics of leachate.
Leachate to
Collection Pond
o G o 4 Clay Lmer/vegitation
^ A A 1-.L .\ n A
Figure 4-10. Diagram of Landfill Leachate Generation and Collection
In a lined landfill, the leachate collected from the landfill typically flows through a
collection system consisting of ditches and/or underground pipes. From the collection system,
the plant transports the leachate to a collection impoundment. The stormwater collection systems
typically consist of one or more small collection impoundments surrounding the landfill area.
Plants may collect the leachate and stormwater in separate impoundments or combine them
together in the same impoundment(s). Some plants discharge the effluent from these collection
impoundments, while other plants send the collection impoundment effluent to the ash
impoundment. Sixty-three percent of the combustion residual landfills reported in the Steam
Electric Survey are lined. Impoundments may also have liners and collection systems similar to
the landfills; 51 percent of the combustion residual impoundments reported in the Steam Electric
Survey are lined. Unlined impoundments and landfills do not collect leachate migrating away
from the impoundment/landfill, which can potentially cause ground water and/or drinking water
contamination.
Table 4-13 presents the number of plants burning coal or petroleum coke that reported
collecting leachate from an impoundment or landfill containing combustion residuals in the
Steam Electric Survey. Approximately 100 plants reported collecting landfill leachate from
approximately 110 existing (i.e., active or inactive) landfills containing combustion residuals,
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Section 4 - Steam Electric Industry Description
while approximately 50 plants reported collecting leachate from existing combustion residual
impoundments. Another 40 plants reported collecting leachate from both combustion residual
landfills and impoundments.
Table 4-13. Leachate Collection at Coal and Petroleum Coke Plants
Type of Leachate Collection
Leachate Collection from Landfills Only
Leachate Collection from Impoundments Only
Leachate Collection from both Landfills and
Impoundments
Number of Coal
and Petroleum
Coke Plants
90-100
40-50
30-40
Number of
Combustion
Residual
Landfills
100-110
NA
30-40
Number of
Combustion
Residual
Impoundments
NA
80-90
60-70
Source: Steam Electric Survey, [ERG, 2013].
Note: Certain fields contain ranges of values to protect the release of information claimed CBI.
Note: Only active and inactive landfills and impoundments are shown in the table.
The majority of landfills installed since 2000 collect leachate. Table 4-14 presents a
distribution of each management unit (impoundment or landfill) collecting leachate and the year
of installation. Table 4-14 includes data from 283 landfills and 1,100 impoundments. A small
percentage of lined landfills do not collect leachate; however, a large percentage of lined
impoundments do not collect leachate. Table 4-14 shows that 18 percent of all lined landfills and
74 percent of all lined impoundments do not collect leachate.
Table 4-14. Age of Impoundment or Landfill Collecting Leachate
Management
Unit Installation
Year
2000 to Present
1990 to 2000
1980 to 1990
Before 1980
Landfills a
Total
66
53
102
59
Number
Lined
55
33
60
31
Number Collecting
Leachate
51
24
49
22
Impoundments b
Total
88
96
308
593
Number
Lined
77
74
231
180
Number Collecting
Leachate
30
18
34
66
Source: Steam Electric Survey, [ERG, 2013].
Note: The number of impoundments and landfills in the steam electric industry are based on values reported in the
survey, which were scaled to represent the industry as a whole using the industry-weighting factors discussed in
Section 3.3.
a - Three landfills did not provide sufficient date or liner/leachate collection information to be included in this
analysis.
b - Fifteen impoundments did not provide sufficient date or liner/leachate collection information to be included in
this analysis.
Once collected, the landfill or impoundment leachate can be recycled back into the
management unit, recycled elsewhere within the plant, or discharged. Table 4-15 presents the
destination of leachate generated from impoundments and landfills. This table includes only
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Section 4 - Steam Electric Industry Description
those impoundments and landfills reported as producing leachate in Part F of the Steam Electric
Survey. The survey data show that at least 28 percent of the impoundment and landfill leachate is
returned to the management unit.23 Most of the returned leachate originates from impoundments.
Nearly half of the impoundment leachate systems return the leachate back to the impoundment
from which it leached. Plants generally discharge landfill leachate directly after collection, or
treat the leachate on site and then discharge after treatment.
Table 4-15. Destination of Leachate in Steam Electric Industry
Destination
Returned to Management Unit (impoundment or
landfill) or Recycled Within the Plant
On-Site Treatment System
Discharged
Other b
Total c
Number of Impoundments a
48 (47%)
6 (6%)
35 (34%)
21 (20%)
103
Number of Landfills
35 (28%)
23 (18%)
86 (68%)
23 (18%)
126
Source: Steam Electric Survey, [ERG, 2013].
Note: The number of impoundments and landfills in the steam electric industry are based on values reported in the
survey, which were scaled to represent the industry as a whole using the industry-weighting factors discussed in
Section 3.3.
a - Respondents did not provide a leachate destination of any kind for seven impoundments. These impoundments
are not represented in the table.
b - "Other" includes perimeter drain with no flow, underground mine pool, and underground injection.
c - Total number of impoundments and landfills is not additive because leachate may have more than one
destination. For example, it is possible for leachate from one impoundment to be both treated and discharged.
4.3.6 Gasification Wastewater
IGCC plants generate wastewater from the gasification process, in which a fuel source
(e.g., coal or petroleum coke) is subjected to high temperature and pressure to produce a
synthetic gas that is used as the fuel for a combined cycle generating unit. As described in
Section 4.2.3, the specific processes used to generate the synthetic gas and clean that gas prior to
combustion vary to some degree at the currently operating IGCC plants; however, each of these
processes require purging wastewater from the process to remove chlorides and other
contaminants from the system. Pollutants that may be present in the gasification wastewater
include selenium, chromium, arsenic, and cyanide.
As shown in Figure 4-4, there are several wastewater streams generated as part of the
IGCC process. Additionally, there may be other wastewaters generated at IGCC plants that are
not included in Figure 4-4. The following is a list of the key wastewaters that may be generated
at IGCC plants:
Part F of EPA's Steam Electric Survey requested information on the management practices of both impoundments
and landfills containing fuel combustion residuals This section included questions related to the collection and
treatment of leachate from both types of management units. As described in Section 3.3, Part F of the questionnaire
was sent only to a probability sampled stratum of coal- and petroleum coke-fired plants.
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Section 4 - Steam Electric Industry Description
• IGCC-specific wastewaters:
Slag handling wastewater;
- Fly ash and water stream;
Sour/grey water (which consists of condensate generated for gas cooling, as well
as other wastestreams);
- CCVsteam stripper wastewater;
- Air separation unit blowdown; and
Sulfur recovery unit blowdown.
• General power plant wastewaters:
Blowdown from the heat recovery steam generator blowdown;
- Coal/petroleum coke pile runoff;
- Metal cleaning wastes;
- Raw water filtration backwash;
- Demineralizer system rej ect; and
- Cooling water.
Depending on the set-up at the plant, most of the general power plant wastewaters would
be handled similarly to how they are treated at conventional pulverized coal-fired power plants.
Additionally, the slag handling wastewater and the fly ash and water stream may be handled
similarly to the fly and bottom ash transport water streams at conventional pulverized coal-fired
power plants (i.e., transferred to a surface impoundment prior to discharge). Otherwise, these
streams may be recycled back to the slurry preparation system and sent back to the gasifier. The
other IGCC-specific wastewaters are treated in a vapor-compression brine concentrator at both of
the currently operating IGCC plants. See Section 6.5 for more information on the characteristics
of IGCC wastewater.
4.3.7 Metal Cleaning Waste
The Steam Electric Power Generating ELGs define metal cleaning waste as "any
wastewater resulting from cleaning [with or without chemical cleaning compounds] any metal
process equipment, including, but not limited to, boiler tube cleaning, boiler fireside cleaning,
and air preheater cleaning." [See 40 CFR 423.11]. Plants use chemicals to remove scale and
corrosion products that accumulate on the boiler tubes and retard heat transfer. The major
constituents of boiler cleaning wastes are the metals of which the boiler is constructed, typically
iron, copper, nickel, and zinc. Boiler firesides are commonly washed with a high-pressure water
spray against the boiler tubes while they are still hot. Fossil fuels with significant sulfur content
will produce sulfur oxides that adsorb on air preheaters. Water with alkaline reagents is often
used in air preheater cleaning to neutralize the acidity due to the sulfur oxides, maintain an
alkaline pH, and prevent corrosion. The types of alkaline reagents used include soda ash, caustic
soda, phosphates, and detergent.
The frequency of metal cleaning activities can vary depending on the type of cleaning
operation and individual plant practices. Some operations occur as often as several times a day,
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Section 4 - Steam Electric Industry Description
while others occur once every several years. Soot blowing, the process of blowing away the soot
deposits on furnace tubes, generally occurs once a day, but some units do this as often as several
hundred times a day. While 83 percent of units responding to the survey use steam or service air
to blow soot, some plants may generate wastewater streams. Air heater cleaning is another
frequent cleaning activity. Sixty-six percent of the units perform this operation at least once
every two years, while other units perform this cleaning task very infrequently, only once every
40 years. Generally, plants use intake or potable water to clean the air heater [ERG, 2013].
The following is a list of all the metal cleaning wastes that were reported in response to
the Steam Electric Survey:
• Air compressor cleaning;
• Air-cooled condenser cleaning;
• Air heater cleaning;
• Boiler fireside cleaning;
• Boiler tube cleaning;
• Combustion turbine cleaning (combustion portion and/or compressor portion);
• Condenser cleaning;
• Draft fan cleaning;
• Economizer wash;
• FGD equipment cleaning;
• Heat recovery steam generator cleaning;
• Mechanical dust collector cleaning;
• Nuclear steam generator cleaning;
• Precipitator wash;
• SCR catalyst soot blowing;
• Sludge lancing;
• Soot blowing;
• Steam turbine cleaning; and
• Superheater cleaning.
4.4 STEAM ELECTRIC WASTESTREAMS NOT EVALUATED FOR NEW OR ADDITIONAL
CONTROLS IN THE PROPOSED ELGs
This section describes the wastestreams generated by steam electric power plants for
which EPA did not evaluate new or revised discharge requirements for the proposed ELGs.
Section 4.3 discusses other wastestreams generated by the steam electric industry the EPA did
evaluate for new or revised discharge requirements in the proposed ELGs.
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Section 4 - Steam Electric Industry Description
4.4.1 Condenser Cooling Water
As discussed in Section 4.2.1, the steam electric process uses cooling water to condense
the steam generated in the boiler; this steam turns the turbines and generates electricity. Because
plants are generally generating electricity continuously, plants must provide a constant flow of
cooling water to maintain steam condensation and a low pressure in the condenser. Steam
electric power plants typically use either once-through or recirculating cooling water systems to
condense the steam from the process. Approximately 96 percent of the electric generating units
serviced by a cooling system use one of these two types of systems: once-through systems
service approximately 52 percent of generating units and recirculating systems service roughly
44 percent. The remaining 4 percent use other methods, most commonly dry cooling systems.
Recirculating systems service roughly 500 coal- or petroleum coke-fired steam electric
generating units [Steam Electric Survey]. In a recirculating cooling system, the heated water is
sent to a cooling tower to lower its temperature. Plants periodically add fresh water to the
cooling water system to make up for evaporative losses. As cooling water evaporates in the
cooling tower, dissolved minerals in the water remain behind in the system and increase in
concentration over time. To prevent the concentrations of these minerals from building up to
unacceptable levels, plants must discharge some of the water, referred to as "cooling tower
blowdown," periodically to purge the minerals from the system.
As the cooling water passes through the condenser, microbiological species (e.g.,
bacterial slimes and algae) stick to and begin growing on the condenser tubes. Steam electric
power plants use biocides, such as sodium hypochlorite, sodium bromide, or chlorine gas, to
control biofouling on the condenser tubes and cooling tower packing material. Plants may also
use chlorine or other antimicrobials, or other methods (e.g., mechanical, thermal) to control
macroorganisms.
Once-through cooling systems service roughly 740 coal- or petroleum coke-fired steam
electric generating units [ERG, 2013]. In these systems, the cooling water is withdrawn from a
body of water, flows through the condenser, and is discharged back to the body of water.
Once-through cooling systems discharge at a significantly higher flow rate than
recirculating systems. Table 4-16 provides the average cooling water blowdown rates for each
type of cooling system reported in the Steam Electric Survey. Recirculating systems generate
blowdown at a rate of approximately 113 MGD, roughly 30 percent of the flow rate generated by
once-through systems. Cooling water blowdown is generally a continuous flow, occurring
24 hours per day and 365 days per year.
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Section 4 - Steam Electric Industry Description
Table 4-16. Cooling Water Discharge Average Flow Rates Reported in the
Steam Electric Industry
Type of Cooling
Water System
Recirculating b
Once-Through
Other c
Total
Number of Cooling
Systems
950
666
128
1,744
Number of
Generating Units
Serviced
1,192
1,108
120
2,420
Capacity of
Generating Units
(MW)
321,000
298,000
26,700
645,700
Average Wastewater
Discharge or Blowdown
per System
(MGD) a
113
3,730
194
1,570
Source: Steam Electric Survey, [ERG, 2013].
Note: Capacity values and wastewater generation rate are rounded to three significant figures.
Note: The number of plants, units, and capacity in the steam electric industry generated from the Steam Electric
Survey are based on values reported in the survey, which were scaled to represent the industry as a whole using the
industry-weighting factors discussed in Section 3.3.
a - The average wastewater flow rate per system is calculated from data provided in the Steam Electric Survey. EPA
did not include any cooling system with incomplete cooling water flow data.
b - Fifteen generating units (twelve plants) selected 'other' for the type of cooling system servicing the units. Two
units (one plant) operate a natural draft cooling system and the remaining thirteen units (eleven plants) operate a
closed loop cooling system. All eight of these units are classified as recirculating systems.
c - Systems classified as 'Other' include dry cooling systems, cooling impoundments, noncontact systems, two-pass
systems, and those systems that did not specify a type of cooling system.
Once-through cooling water and cooling tower blowdown may contain the following
pollutants, often in low concentrations, as a result of chlorination and corrosion/erosion of the
piping, condenser, and cooling tower materials: chlorine, iron, copper, nickel, aluminum, boron,
chlorinated organic compounds, suspended solids, brominated compounds, and nonoxidizing
biocides.
4.4.2 Coal Pile Runoff
According to the Steam Electric Survey, 99 percent of coal-fired plants store or process
coal on site. Coal-fired power plants receive coal via train, barge, or truck. The coal is unloaded
in a designated area and conveyed to an outdoor storage area, referred to as the coal pile. Power
plants generally store between 25 and 40 days' worth of coal in the coal pile, but this varies by
plant. Some coal-fired plants may have more than one coal pile, depending where the boilers are
located and whether the plants use or blend different types of coal. Rainwater and melting snow
contacting the coal pile generates a wastestream that contains pollutants from the coal, referred
to as coal pile runoff.
Coal pile runoff from the coal-fired power industry generates approximately 3.5 million
gallons of wastewater per year [ERG, 2013]. The quantity of runoff at each plant depends upon
the amount of precipitation, the physical location and layout of the pile, and the extent to which
water infiltrates the ground underneath the pile. As a result, individual flows are often infrequent,
with the average plant generating coal pile runoff a total of 131 days per year [ERG, 2013]. Coal
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Section 4 - Steam Electric Industry Description
pile runoff is usually collected in a runoff impoundment during or immediately after times of
rainfall.
EPA collected data on the pH of coal pile runoff impoundments during several site visits
to coal-fired steam electric power plants. The pH of coal pile runoff holding impoundments
ranges from 2.8 to 8.5 S.U. In general, coal pile runoff impoundments containing other
wastewaters, specifically limestone pile runoff, have a higher pH because the limestone pile
runoff neutralizes the acidity of the coal pile runoff [ERG, 2008a - 2008e, 2008g; ERG, 2009a,
2009b, 2009d-2009f].
4.4.3 Selected Low Volume Waste Sources
Low volume waste sources, as currently defined by the existing Steam Electric Power
Generating ELGs, include a variety of wastestreams, such as wastewater associated with wet
scrubber air pollution control systems, ion exchange water treatment systems, water treatment
evaporator blowdown, laboratory and sampling streams, boiler blowdown, floor drains, cooling
tower basin cleaning wastes, and recirculating house service water systems. See 40 CFR 423.11.
The proposed ELGs would remove specific wastewaters from this collective group of low
volume waste sources. As discussed in Section 8.1.1, EPA is proposing to exclude FGD
wastewater, combustion residual leachate, and carbon capture wastewater from the low volume
waste source category. Plants typically combine low volume wastes with other plant wastewaters
for treatment, often in surface impoundments. In some cases, low volume wastewaters can be
recycled within the plant. Table 4-17 shows the distribution of some of the low volume
wastestreams. This table includes the number of plants generating each waste and the minimum
and maximum flows as reported in the Steam Electric Survey.
Table 4-17. Selected Low Volume Waste Sources in the Steam Electric Industry
Type of Wastestream
Ion Exchange Wastewater
Boiler Blowdown
Evaporator Blowdown
Floor Drains
Number of Plants a
134
164
1
220
Minimum Flow b (GPY)
2,590
3,790
1,830,000
12,000
Maximum Flow b (GPY)
60,400,0000
616,000,000
1,830,000
10,500,000,000
Source: Steam Electric Survey, [ERG, 2013].
Note: Wastewater flow rates are rounded to three significant figures.
Note: The table presents a subset of wastestreams that survey responses clearly identified and for which flows were
reported.
Note: The number of plants in the steam electric industry generated from the Steam Electric Survey are based on
values reported in the survey, which were scaled to represent the industry as a whole using the industry-weighting
factors discussed in Section 3.3.
a - The number of plants reported as generating each wastestream is based on the total number of plants listing the
specific wastestream as an influent to an impoundment or wastewater treatment system in the Steam Electric Survey
and then weighted to represent all plants within the Steam Electric Industry. This includes commingled streams or
streams for which a flow rate was not provided.
b - Minimum and maximum flows do not include flow rates for commingled streams. This data only represents the
flow rates that were reported in the Steam Electric Survey.
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Section 4 - Steam Electric Industry Description
4.4.4 Selective Catalytic Reduction and Selective Non-Catalytic Reduction Wastewater
SCR and selective noncatalytic reduction (SNCR) are technologies used to control
nitrogen oxide (NOX) emissions in the flue gas from the boiler. Based on survey responses, EPA
identified 426 plants operating at least one SCR system and an additional 97 plants operating at
least one SNCR system. In SCR, ammonia (NH3) is injected into the flue gas upstream of a
catalyst, such as vanadium or titanium. The NOX in the flue gas (comprising mainly nitrogen
monoxide (NO) with lesser amounts of nitrogen dioxide (NC^)) reacts with the NFL? in the
presence of oxygen and the catalyst to form nitrogen and water. SNCR utilizes either ammonia
or urea injected into the flue gas within a specific temperature zone. As with SCR technologies,
the NOX in the flue gas reacts with the reducing agent, either ammonia or urea, in the presence of
oxygen to form nitrogen and water.
In addition to forming nitrogen and water, a fraction of the SC>2 in the flue gas may be
oxidized to sulfur trioxide (863), and other side reactions may produce ammonium sulfate
((NFL^SO/t) and ammonium bisulfate (NFLjHSO/O as by-products. These by-products can foul
and corrode downstream equipment. The extent to which they form depends upon various factors
within the process, including the sulfur content of the coal used in the boiler and the amount of
excess NFL? in the system. Unreacted NFL? in the flue gas from the SCR/SNCR is commonly
termed ammonia slip [Babcock & Wilcox, 2005].
Plants may use different SCR/SNCR configurations based on the particular operations of
the system, including placing the SCR/SNCR upstream of the air heater and other emission
control devices such as a FGD scrubber and/or particulate removal device (e.g., ESP).24
Although the SCR/SNCR does not produce a wastestream during operation, it can affect the
characteristics of fly ash transport water, air heater wash water, and FGD wastewater. As
previously explained, unreacted NFFj and SC>3 by-product can create (NFL^SCM and NFLjHSCM,
which can deposit in the air heater and must be removed through periodic washes. The collection
of the (NH4)2SO4 and NFLjHSCM affect the characteristics of the air heater wash water and also
lead to more frequent washing. The fly ash transport water characteristics can be affected by the
SCR operation because ammonia that passes unreacted through the SCR/SNCR may attach to the
particulates in the flue gas and be removed from the flue gas in the air pollution control
equipment (e.g., ESP, baghouse, FGD scrubber). Because ammonia is soluble, if the ash
collected from the particulate removal device is handled with a wet system (e.g., wet sluicing),
then the ammonia will likely partition into the wastewater and be discharged from the plant
[Wright, 2003].
In addition to affecting fly ash transport water and FGD wastewater characteristics, SCR
systems could potentially need associated other cleaning operations that generate a wastestream,
including catalyst regeneration wastewater and wastewater from washing the catalyst bed.
According to survey responses, no plants reported generating SCR catalyst regeneration
wastewater in 2009. Three plants reported generating wastewater from washing the SCR catalyst
bed. Catalyst bed washing occurs infrequently, from twice per year to once every six years, and
generates up to 1,080,000 gallons of wastewater per event. The plants reported commingling the
24 The air heater utilizes the heat contained in the flue gas to increase the temperature (via heat exchange) of the air
injected into the boiler for combustion.
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Section 4 - Steam Electric Industry Description
catalyst bed wash water with other wastestreams and treating them on site prior to discharge
[ERG, 2013].
4.4.5 Carbon Capture Wastewater
Due to potential future regulations on carbon dioxide (CO2) emissions, many steam
electric power plants are considering alternatives available for reducing carbon emissions.
There are three main approaches for capturing the CO2 associated with generating
electricity: postcombustion, precombustion, and oxyfuel combustion.
• In post-combustion capture, the CC>2 is removed after the fossil fuel is combusted.
• In precombustion capture, the fossil fuel is partially oxidized, such as in a gasifier.
The resulting syngas (CO and H2) is shifted into CC>2 and more H2 and the resulting
CO2 can be captured from a relatively pure exhaust stream before combustion takes
place.
• In oxyfuel combustion, also known as oxycombustion, the fuel is burned in oxygen
instead of air. The flue gas consists of mainly CC>2 and water vapor; the latter is
condensed through cooling. The result is an almost pure CC>2 stream that can be
transported to the storage, or sequestration, site and stored.
After capture, the plant would transport CC>2 to a suitable sequestration site. Approaches
under consideration include the following:
• Geologic sequestration (injection of the CC>2 into an underground geologic
formation);
• Ocean sequestration (typically injecting the CO2 into the water column at depths to
allow dissolution or at deeper depths where the CO2 is denser than water and would
form CO2 "lakes"); and
• Mineral storage (where CO2 is exothermically reacted with metal oxides to produce
stable carbonates).
Based on preliminary information regarding these technologies, EPA believes these
systems may result in new wastestreams at steam electric power plants that will need to be
addressed. However, as these technologies are currently in the early stages of research and
development and/or pilot testing, the industry has little information on the potential wastewaters
generated from carbon capture processes.
As part of EPA's sampling program, EPA obtained analytical data from two
wastestreams generated from a post-combustion carbon capture pilot-scale system. The pilot-
scale system was based on Alstom's chilled ammonia process. This carbon capture process
generated a few wastewater bleed streams, two of which were analyzed as part of EPA's
sampling program. The first stream, a pilot validation facility (PVF) bleed stream, is a purge
stream that removes ammonium sulfate from the process. During sampling activities, the PVF
bleed stream flow rate ranged from 800 to 5,100 gallons per day (gpd). The second stream, flue
gas condensate, is a condensate stream generated from cooling the flue gas, which condenses the
4-44
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Section 4 - Steam Electric Industry Description
water vapor present. The flow rate of the flue gas condensate stream ranged from 2,600 to 9,900
gpd during sampling. Table 4-18 presents the concentrations of the pollutants measured during
the EPA sampling program. The concentrations presented are the 4-day average concentrations.
According to plant personnel, for a full-scale system, a plant would transfer the PVF
bleed stream to a crystallizer, producing a solid particulate product which could be used as a
fertilizer [Lohner, 2010]. The condensate from the evaporation process could be reused in other
plant processes or discharged.
Table 4-18. Carbon Capture Wastewater 4-Day Average Concentration Data
Analyte
Unit
4-Day Average Concentration
PVF Bleed Stream
Flue Gas Condensate
Classical*
Ammonia
Nitrate Nitrite as N
Nitrogen, Total Kjeldahl
Biochemical Oxygen Demand
Chemical Oxygen Demand
Chloride
Sulfate
Cyanide, Total
Total Dissolved Solids
Total Suspended Solids
Phosphorus, Total
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
26,800
8.98
42,800
ND (14.7)
88.8
NQ (300)
163,000
1.20
163,000
27.3
0.155
<383
1.80
740
<3.65
NQ (20.0)
NQ (6.75)
1,050
ND (0.100)
1,050
<6.75
NQ (0.0500)
Total Metals
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ng/L
ug/L
450
2.65
40.0
57.5
ND (2.00)
13,000
NQ (4.00)
24,000
1,540
73.3
400
4,380
7.78
15,800
965
3,530
2,630
NQ (200)
ND (2.00)
NQ (4.00)
NQ (20.0)
ND (2.00)
1,540
ND (4.00)
< 2,390
<17.5
NQ (20.0)
14.9
2,020
NQ (2.00)
1,990
101
1,060
NQ (40.0)
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Section 4 - Steam Electric Industry Description
Table 4-18. Carbon Capture Wastewater 4-Day Average Concentration Data
Analyte
Nickel
Selenium
Silver
Sodium
Thallium
Tin
Titanium
Vanadium
Zinc
Unit
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
4-Day Average Concentration
PVF Bleed Stream
4,530
4,900
ND (2.00)
16,000
2.30
ND (200)
NQ (20.0)
19.0
293
Flue Gas Condensate
27.5
128
ND (2.00)
NQ (10,000)
ND (2.00)
ND (200)
NQ (20.0)
NQ (10.0)
NQ (40.0)
Source: CWA 308 Monitoring, [ERG, 2012].
< - Average result includes at least one value measured below the quantitation limit. (Calculation uses !/2 the
sample-specific quantitation limit for values below the quantitation limit).
ND - Not detected (number in parenthesis is the quantitation limit).
NQ - Analyte was measured below the quantitation limit for all four results (number shown in parenthesis is the
average quantitation limit), but at least one result was measured above the method detection limit.
Note: Concentrations are rounded to three significant figures.
According to the survey responses, there are no full-scale carbon capture systems
operating in the industry. There are, however, two pilot-scale systems that have been in
operation, the one for which EPA collected the analytical data presented in Table 4-18 (currently
shut down and inactive) and another one that has been decommissioned. Additionally, several
plants reported in their survey responses that they are planning to install a pilot-scale carbon
capture system and some plants even reported plans to install full-scale systems.
In March 2012, EPA proposed a Carbon Pollution Standard for New Power Plants (FR
Doc No: 2012-7820), which would set national limits on the amount of carbon pollution future
power plants can emit. The proposed carbon pollution standard does not apply to existing plants
or those permitted to begin construction by 2013. The proposed rule will allow future plants to
choose to burn any fossil fuel to generate electricity, but would require these plants to
incorporate technologies to reduce the carbon dioxide emissions to meet a standard of 1,000
pounds of CC>2 per megawatt-hour. This rule will likely have the greatest impact on coal-,
petroleum coke-, and oil-fired plants because new natural gas combined cycle units should be
able to meet the proposed standard without additional CC>2 controls [U.S. EPA, 2012].
4.5 REFERENCES
1. Babcock & Wilcox Company. 2005. Steam: Its Generation and Use. 41st edition. Edited
by J.B. Kitto and S.C. Stultz. Barberton, Ohio. DCN SE02919.
2. Eastern Research Group (ERG). 2008a. Final Site Visit Notes: Appalachian Power
Company's Mountaineer Plant. (11 September). DCN SE02070.
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Section 4 - Steam Electric Industry Description
3. Eastern Research Group (ERG). 2008b. Final Site Visit Notes: Kentucky Utilities
Company's Ghent Generating Station. (19 December). DCN SE02079.
4. Eastern Research Group (ERG). 2008c. Final Site Visit Notes: Louisville Gas and
Electric Company's Cane Run Station. (11 December). DCN SE02082.
5. Eastern Research Group (ERG). 2008d. Final Site Visit Notes: Louisville Gas and
Electric Company's Mill Creek Station. (December 12). DCN SE02083.
6. Eastern Research Group (ERG). 2008e. Final Site Visit Notes: Louisville Gas and
Electric Company's Trimble County Station. (10 December). DCN SE02080.
7. Eastern Research Group (ERG). 2009a. Final Site Visit Notes: Alleghany Energy's
Harrison Power Station. (20 January). DCN SE02069.
8. Eastern Research Group (ERG). 2009b. Final Site Visit Notes: CPS Energy's Calaveras
Power Station. (29 October). DCN SE02076.
9. Eastern Research Group (ERG). 2009c. Final Site Visit Notes: Duke Energy's Wabash
River Generating Station. (12 October). DCN SE02095.
10. Eastern Research Group (ERG). 2009d. Final Site Visit Notes: Fayette Power
Project/Sam Seymour Power Station. (30 October). DCN SE02077.
11. Eastern Research Group (ERG). 2009e. Final Site Visit Notes: Ohio Power Company's
Gavin Plant. (19 January). DCN SE02072.
12. Eastern Research Group (ERG). 2009f. Final Site Visit Notes: Tennessee Valley
Authority's Paradise Fossil Plant. (20 September). DCN SE02101.
13. Eastern Research Group (ERG). 2009g. Final Site Visit Notes: Western Kentucky
Energy's Kenneth C. Coleman Station. (23 February). DCN SE02094.
14. Eastern Research Group (ERG). 2011. Final Site Visit Notes: TECO Energy's Polk
Power Station. (2 March). DCN SE00071.
15. Eastern Research Group (ERG). 2012. Final Power Plant Monitoring Data Collected
Under Clean Water Act Section 308 Authority ("CWA 308 Monitoring Data"). (30 May).
DCN SE01326.
16. Eastern Research Group (ERG). 2013. Steam Electric Technical Questionnaire Database
("Steam Electric Survey"). (19 April). DCN SE01958.
17. Lohner, Tim. 2010. Email to Ron Jordan of U.S. EPA from Tim Lohner of AEP. (6
December). DCN SE01335.
18. USCB. 2007. U.S. Census Bureau. Electric Power Generation, Transmission, and
Distribution: 2007 Economic Census Utilities Industry Series. Document and data are
available online at: http://www.census.gov/econ/census07/. DCN SE01802.
19. U.S. EPA. 1982. Development Document for Effluent Limitations Guidelines and
Standards and Pretreatment Standards for the Steam Electric Point Source Category.
EPA-440-1-82-029. Washington, DC. (November). DCN SE02933.
20. U.S. DOE. 2006. U.S. Department of Energy. Introduction to Nuclear Power. Energy
Information Administration (EIA). Available online at:
4-47
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Section 4 - Steam Electric Industry Description
http://www.eia.doe.gov/cneaf//page/intro.html. Date accessed: August 2006. DCN
SE01803.
21. U.S. DOE. 2009. U.S. Department of Energy. Annual Electric Generator Report
(collected via Form EIA-860). Energy Information Administration (EIA). The data files
are available online at: http://www.eia.doe.gOv/cneaf//page/eia860.html. DCN SE01805.
22. Wright, Thomas. 2003. "SCR Operation Optimization: SO3 Removal to Optimize
Catalyst Life & NHa Distribution in Wastewater." In: Proceedings from the Selective
Catalytic/Non-Catalytic Reduction Conference. Chattanooga, TN. (October 30). DCN
SE02934.
23. U.S. DOE. U.S. Department of Energy. Energy Efficiency and Renew able Energy -
Geothermal Technologies Program. Available online at:
http://www 1. eere. energy. gov/al/faqs. html and
http://www 1.eere.energy.gov//powerplants.html. DCN SE01804.
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Section 5 - Industry Sub categorization
SECTION 5
INDUSTRY SUBCATEGORIZATION
This section presents information about factors EPA considered in evaluating whether
different limitations or standards are warranted for certain facilities in the steam electric power
generating point source category. Section 5.1 describes why EPA considers factors that could
lead to establishing different requirements for certain facilities in the point source category and
presents background on the industry categorization established in the 1974 and 1982 ELG
rulemakings. Section 5.2 presents the factors considered in detail and reviews the analyses EPA
performed to review whether subcategorization was necessary to the revisions proposed.
5.1 SUBCATEGORIZATION FACTORS
The CWA requires EPA to consider a number of different factors when developing ELGs
for a particular industry category (Section 304(b)(2)(B), 33 U.S.C. § 1314(b)(2)(B)). For BAT,
in addition to the technological availability and economic achievability, these factors are the age
of the equipment and plants, the process employed, the engineering aspects of the application of
various types of control techniques, process changes, the cost of achieving such effluent
reduction, non-water quality environmental impacts (including energy requirements), and such
other factors the Administrator deems appropriate. One way EPA may take these factors into
account, where appropriate, is by dividing a point source category into groupings called
"subcategories." Regulating a category by subcategory, where determined to be warranted,
ensures that each subcategory has a uniform set of ELGs that take into account technology
availability and economic achievability and other relevant factors unique to that subcategory.
The current Steam Electric ELGs do not divide plants or process operations into
subcategories, although they do include different effluent requirements for cooling water
discharges from generating units smaller than 25 MW generating capacity [U.S. EPA, 1974; U.S.
EPA, 1982]. For this proposed rule, EPA evaluated whether different effluent requirements
should be established for certain facilities within the steam electric power generating point
source category using information from responses to the industry surveys, site visits, sampling,
and other data collection activities (see Section 3 for more details). EPA performed analyses to
assess the influence of age, size, fuel type, and geographic location on the wastewaters
generated, discharge flow rates, pollutant concentrations, and treatment technology availability at
steam electric power plants to determine whether subcategorization was appropriate.
5.2 ANALYSIS OF SUBCATEGORIZATION FACTORS
EPA performed analyses to assess the influence of age, size, fuel type, and geographic
location on the wastewaters generated at steam electric power plants and the availability of
technologies to manage those wastewaters. The following sections summarize the analyses
performed as part of the subcategorization reevaluation. For additional information on the
specific analyses performed as part of the reevaluation, see the memorandum entitled
"Subcategorization Memorandum" [ERG, 2013a].
5-1
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Section 5 - Industry Sub categorization
5.2.1 Age of Plant or Generating Unit
EPA analyzed the age of the power plants and the generating units included in the scope
of the rule. EPA determined that the age of the plant by itself does not in general impact the
wastewater characteristics, the processes in place, or the ability to install the treatment
technologies evaluated as part of this rulemaking [ERG, 2013a]. Therefore, EPA did not
establish subcategories based solely on the age of the plant or generating unit for this proposed
rule.
5.2.2 Geographic Location
EPA analyzed the geographic location of power plants included in the scope of the rule.
EPA determined that the geographic location of the plant by itself does not affect the wastewater
characteristics, the processes in place, or the ability to install the treatment technologies
evaluated as part of this rulemaking. During its evaluation, EPA did find that wet FGD systems,
both wet and dry fly ash handling systems, and both wet and dry bottom ash handling systems
are located throughout the United States, as illustrated in Section 4. Additionally, the location of
the plant does not affect the plant's ability to install the treatment technologies evaluated as part
of this rulemaking. For example, a plant in the southern United States will be able to install and
operate the chemical precipitation and biological treatment system proposed as the BAT
technology basis for FGD wastewater. Because of the warm climate, plants in locations such as
this may find it necessary to install heat exchangers to keep the FGD wastewater temperature at
ideal operating conditions during the summer months. EPA's approach for estimating
compliance costs takes such factors into account. Based on the information in the record
regarding the current geographic location of the various types of systems generating the
wastewaters addressed by this rulemaking and engineering knowledge of the operational
processes and candidate BAT/NSPS treatment technologies, EPA determined that subcategories
based on plant location are not warranted.
5.2.3 Size
EPA analyzed the size (i.e., nameplate generating capacity in MW) of the steam electric
generating unit and determined that it is an important factor influencing the volume of the
discharge flow from the plant. Typically, as the size of the generating unit increases, the
discharge flows of ash transport water generally increase. In general, this is to be expected
because the larger the generating unit, the more fuel it consumes, which generates more ash, and
uses more water in the water/steam thermodynamic cycle [ERG, 2013b]. Although the volume of
the wastewater increases with the size of the generating unit, the pollutant characteristics of the
wastewater generally are unaffected by the size of the generating unit and any variability
observed in wastewater pollutant characteristics does not appear to be correlated to generating
capacity.
As a result of its evaluation, EPA believes that, in certain circumstances, it would be
appropriate to apply different limits for a class of existing generating units or plants based on
size. Section 8 discusses in greater detail EPA's proposal for applying different standards to
certain existing units and plants.
5-2
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Section 5 - Industry Sub categorization
5.2.4 Fuel Type
The type of fuel (e.g., coal, petroleum coke, oil, gas, nuclear) used to create steam most
directly influences the type and number of wastestreams generated. For example, gas and nuclear
power plants typically generate cooling water, metal cleaning wastes (both chemical and
nonchemical), and other low volume wastestreams, but do not generate wastewaters associated
with air pollution control devices (e.g., fly ash and bottom ash transport water, FGD wastewater).
Coal, oil, and petroleum-coke power plants may generate all of those wastewaters. The
wastestream that is most influenced by fuel selection is the ash transport water because the
quantity and quality of ash generated from oil-fired units is different from that generated from
coal- and petroleum coke-fired units. Additionally, the quantity and quality of ash differs based
on the type of oil used in the boiler. For example, heavy or residual oils such as No. 6 fuel oil
generate fly ash and may generate bottom ash, but lighter oils such as No. 2 fuel oil may not
generate any ash.
From an analysis of responses to the Steam Electric Survey, EPA determined that 74
percent of the steam electric units in the industry burn more than one type of fuel (e.g., coal and
oil, coal and gas). Some of these plants may burn only one fuel at a specific time, but burn both
types of fuels during the year. Other plants may burn multiple fuels at the same time. In cases
where facilities burn multiple fuels at the same time, it would be impossible to separate the
wastestreams by fuel type [ERG, 2013b].
EPA did not identify any basis for subcategorizing gas-fired and nuclear generating units.
These generating units generally manage nonchemical metal cleaning wastes in the same manner
as other steam electric generating units, and the proposed requirements for this wastestream
would establish limitations and standards that are equal to current BPT limitations for existing
direct dischargers.25 Furthermore, the gas-fired and nuclear generating units do not generate the
other six wastestreams addressed by this rulemaking. However, based on responses to the Steam
Electric Survey, there are some oil-fired units that generate and discharge fly ash and/or bottom
ash transport water. For these reasons, EPA looked carefully at oil-fired units. As a result, EPA
believes that, in certain circumstances, it is appropriate to apply different limits to existing oil-
fired generating units. Section 8 discusses in greater detail EPA's proposal for applying different
standards to certain existing oil-fired units.
5.3 REFERENCES
1. Eastern Research Group (ERG). 2013a. Steam Electric Technical Questionnaire Database
("Steam Electric Survey"). (19 April). DCN SE01958
2. Eastern Research Group (ERG). 2013b. Memorandum to the Steam Electric Rulemaking
Record. Subcategorization Memorandum." (19 April). DCN SE02127.
3. U.S. EPA. 1974. Development Document for Effluent Limitations Guidelines and New
Source Performance Standards for the Steam Electric Power Generating Point Source
Category. Washington, D.C. (October). DCN SE02917.
25 As described in Section 8, EPA is proposing to exempt from new copper and iron BAT limitations any existing
discharges of nonchemical metal cleaning wastes that are currently authorized without iron and copper limits. For
these discharges, BAT limits would be set equal to BPT limits applicable to low volume wastes.
5-3
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Section 5 - Industry Sub categorization
4. U.S. EPA. 1982. Development Document for Effluent Limitations Guidelines and
Standards and Pretreatment Standards for the Steam Electric Point Source Category.
EPA-440-1-82-029. Washington, DC. (November). DCN SE02933.
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Section 6 - Wastewater Characterization and Pollutants of Concern
SECTION 6
WASTEWATER CHARACTERIZATION AND POLLUTANTS OF
CONCERN
This section summarizes information gathered from survey data, EPA sampling data,
Clean Water Act (CWA) 308 sampling data, and industry-submitted sampling data on
wastewater generation practices associated with the steam electric industry. Sections 6.1 through
6.6 provide details on only those wastestreams for which EPA evaluated new or revised
discharge requirements for the proposed ELGs, those discussed in Section 4.3, including flue gas
desulfurization (FGD) wastewater, ash transport water, combustion residual landfill leachate,
flue gas mercury control (FGMC) wastewater, gasification wastewater, and metal cleaning
waste. Each section provides detail on wastewater generation rates and provides characterization
data for the untreated process wastewater, where available. Section 6.7 identifies the pollutants
of concern (POCs) related to this rulemaking.
6.1 FGD WASTEWATER
Wet FGD scrubber systems are classified into two categories, recirculating wet FGD
systems and single pass wet FGD systems, as shown in Figure 4-7. In a recirculating system,
most of the FGD slurry at the bottom of the scrubber is recirculated back within the scrubber and
occasionally a blowdown stream is transferred away from the scrubber, called FGD slurry
blowdown. The slurry blowdown stream undergoes solid separation and the wastewater is either
recycled back to the scrubber or transferred to a wastewater treatment system as FGD scrubber
purge. In a single pass system, all of the FGD slurry at the bottom of the scrubber is leaves the
scrubber without recirculating the slurry within the system. FGD wastewater can include the
FGD scrubber purge from a recirculating systems, the FGD slurry from single pass systems, any
gypsum wash water, and water generated from the solids dewatering process. This section
describes the amount of FGD wastewater generated by FGD systems at coal-fired power plants
within the steam electric industry and discusses the characteristics of FGD wastewater.
As described in Section 4.3.3, the FGD wastewater generated by wet FGD systems needs
to be removed to purge chlorides from the system. This FGD wastewater is typically generated
intermittently. The factors that can affect the characteristics and flow rate of the FGD wastewater
include the type of coal, scrubber design and operating practices, solids separation process, and
solids dewatering process used at the plant, which are discussed below.
The type of coal burned at the plant can affect the FGD wastewater flow rate. Generally,
burning a higher sulfur coal will require a higher FGD wastewater flow from the system. Higher
sulfur coals produce more sulfur dioxide in the combustion process, which in turn increases the
amount of sulfur dioxide removed in the FGD scrubber. As a result, more solids are generated in
the reaction in the scrubber, which increases frequency at which FGD wastewater is removed
from the system and transferred to treatment.
Likewise, the use of a high chlorine coal can increase the volume and frequency of the
FGD wastewater generated by the system. Many FGD systems are designed with materials
resistant to corrosion for specific chloride concentrations. The chlorine present in the coal leads
to chlorides present in the FGD systems. As the FGD system recirculates the water in the system,
6-1
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Section 6 - Wastewater Characterization and Pollutants of Concern
the chlorides build up within the scrubber. The plant will have to purge some of the wastewater
to remove the chlorides from the system as the chloride concentration in the scrubber begins
approaching the maximum allowable limit for the specific material of construction of the FGD
system. In the United States, FGD scrubbers are generally constructed of alloys that are designed
to withstand a chloride concentration of 20,000 parts per million (ppm) or more. The larger the
maximum allowable chloride concentration in the scrubber, the lower the FGD wastewater flow
rate; however, this lower purge rate leads to additional cycling in the scrubber, which increases
the pollutant concentrations in the FGD wastewater [Babcock and Wilcox, 2005].
Table 6-1 summarizes the FGD slurry blowdown generated by the steam electric industry
in 2009 as reported in the Questionnaire for the Steam Electric Power Generating Effluent
Guidelines (Steam Electric Survey). On average, a steam electric power plant generates 1.2
million gallons per day (MGD) of FGD slurry blowdown. As described above, the FGD slurry
blowdown undergoes dewatering before being transferred to treatment or recycled back to the
scrubber.
Table 6-1. FGD Slurry Blowdown Flow Rates
Number of
Plants
Average Flow
Rate
Median Flow
Rate
Range
of Flow Rate
Flow Rate per Plant
Gallons per day (gpd)/plant
137
1,220,000
598,000
3,300-22,000,000
Source: Steam Electric Survey, [ERG, 2013b].
Note: Flows are rounded to three significant figures.
Note: Two plants are missing data and are therefore not included in the count of plants presented in this table. An
additional six (6) plants identified plans for a future FGD system that will generate FGD blowdown. These future
FGD systems are also not included in the count of plants represented in this table.
The pollutant concentrations in FGD wastewater vary from plant to plant depending on
the coal type, the sorbent used, the materials of construction in the FGD system, the FGD system
operation, the level of recycle within the absorber, and the air pollution control systems operated
upstream of the FGD system. The fuel (coal or petroleum coke) is the source of most of the
pollutants that are present in the FGD wastewater (i.e., the pollutants in the coal are likely to be
in the FGD wastewater). The sorbent used in the FGD system also introduces pollutants into the
FGD wastewater and, therefore, the type and source of the sorbent used affects the pollutant
concentrations in the FGD wastewater.
The materials of construction in the FGD system and the FGD system operation affect the
types of pollutants in the wastewater, as well as their concentrations. Using organic acid
additives contributes to higher concentrations of biochemical oxygen demand (BODs) in the
FGD wastewater. Additionally, the type of oxidation the FGD system uses (i.e., forced oxidation,
inhibited oxidation, natural oxidation) can affect the form of the pollutants present in the FGD
wastewater. According to the Electric Power Research Institute (EPRI), forced oxidation systems
produce most of the selenium present as selenate (Se+6) whereas natural and inhibited oxidation
systems produce most of the selenium present as selenite (Se+4) [EPRI, 2006]. The FGD
wastewater characteristics presented later in this section represent data from plants operating
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Section 6 - Wastewater Characterization and Pollutants of Concern
forced oxidation systems. EPA focused the sampling program on plants operating forced
oxidation systems for the following reasons:
Most plants operating natural or inhibited oxidations systems do not discharge FGD
wastewater because they either operate complete recycle systems or because the water is
evaporated in evaporation ponds or during a pozzolonic reaction.
Selenate is the form of selenium that is more difficult to treat; therefore, if the technology
option selected as the basis for the ELGs can remove the selenate, it will also be able to remove
the selenite. Additionally, the biological treatment process used as the basis for Regulatory
Options 3 and 4 reduces both selenate and selenite to its elemental form; therefore, the form of
selenium present in the wastewater does not impact the removals achieved by the preferred
options.
The materials of construction and the other FGD system operations can also affect the
concentration of pollutants in the FGD wastewater because they affect the amount of recycle
within the system, which in turn, affects the rate at which the FGD wastewater is generated. For
example, during the detailed study, EPA collected samples from the Tennessee Valley
Authority's Widows Creek Fossil Plant (Widows Creek), which operates once-through FGD
systems. These FGD systems do not cycle the wastewater within the system, thereby generating
FGD scrubber purge continuously and at a much larger flow rate compared to plants that do
recirculate the FGD water. However, based on the data collected from the Widows Creek
sampling episode and the data collected during EPA's sampling program, the FGD scrubber
purge that is generated in the once-through systems is at lower concentrations compared to plants
that recirculate the water. While the concentrations are lower, the concentrations of the pollutants
of concern are still at treatable levels for the FGD wastewater treatment system. Because of the
larger flow rate associated with these systems, EPA evaluated costs for these plants to recirculate
some of the FGD water back to the FGD system, as long as the materials of construction in the
FGD system would be able to handle the buildup of additional chlorides. For more information
on this analysis, see Section 4.4.3 of EPA's Incremental Costs and Pollutant Removals for
Proposed Effluent Limitation Guidelines and Standards for the Steam Electric Power Generating
Point Source Category Report.
The air pollution controls operated upstream of the FGD system can also affect the
pollutant concentrations in the FGD wastewater. For example, if a plant does not operate a
particulate collection system (e.g., electrostatic precipitator, or ESP) upstream of the FGD
system, the FGD system will act as the particulate control system and the FGD blowdown
exiting the scrubber will contain fly ash and other particulates. As a result, the FGD wastewater
will likely contain increased concentration of pollutants associated with the fly ash, such as
arsenic and mercury. Based on responses to the Steam Electric Survey, EPA determined that
there are approximately 15 to 25 coal- and petroleum coke-fired generating units that operate
without a particulate collection system prior to the FGD system. EPRI collected data from a plant
that has a generating unit with this configuration as well as a generating unit that operates an
ESP prior to its FGD system. Using the data from the EPRI report representing the FGD influent
from these two different units, EPA determined that the concentrations of mercury, nitrate/nitrite,
and total suspended solids (TSS) are higher in FGD influent for the generating unit that operates
the ESP; however the concentration of arsenic is higher for the unit without the ESP [EPRI,
6-3
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Section 6 - Wastewater Characterization and Pollutants of Concern
r\r
1998a; EPRI, 1998b]. However, based on the information from the EPA sampling program,
EPA determined that arsenic is treated to low levels in the technology selected as the proposed
FGD wastewater treatment system, regardless of the influent concentrations entering the system.
Research conducted by EPA's Office of Research and Development (ORD) has observed
that using postcombustion nitrogen oxide (NOX) controls (e.g., selective catalytic reduction
(SCR) and selective noncatalytic reduction (SNCR)) is correlated to an increased fraction of
chromium in coal combustion residues (CCR) (including FGD wastes) being oxidized to
hexavalent chromium (Cr+6). Hexavalent chromium is a more soluble and more toxic form of
chromium than the trivalent chromium (Cr+3) usually measured in CCRs. This could explain why
ORD has observed increased teachability of chromium when postcombustion NOX controls are
operating [U.S. EPA, 2008]. As part of EPA's sampling program, it collected samples from four
plants operating SCRs at the time of the sampling episodes, one plant operating SNCRs at the
time of the sampling episodes, and two plants that were not operating the SCR/SNCR at the time
of the sampling episode. EPA compared the influent FGD wastewater characteristics from these
plants to evaluate whether the operation of the NOX control systems lead to higher concentrations
of certain pollutants. EPA found that none of the plants had detectable concentrations of
hexavalent chromium in the influent FGD wastewater samples, except for one of the plants that
was not operating its SCR/SNCR. Additionally, EPA found that the concentrations of ammonia
and nitrate/nitrite are not significantly different for the plants operating NOX controls compared
to the plants not operating NOX controls.27 While the ammonia and nitrate/nitrite concentrations
were higher for some of the plants operating NOX controls compared to the plants not operating
NOX controls, there were also plants operating NOX controls that had lower concentrations of
ammonia and nitrate/nitrite compared to plants not operating NOX controls.
Table 6-2 summarizes the FGD wastewater discharged by the steam electric industry in
2009 as reported in the Steam Electric Survey. By January 1, 2014, 117 coal- and petroleum
coke-fired plants will discharge FGD wastewater.28 Collectively, these plants are expected to
discharge 23.7 billion gallons of FGD wastewater per year, with an average total industry daily
discharge of 65 MGD (0.6 MGD per plant). The amount of FGD wastewater discharged by the
steam electric industry is less than the amount of blowdown generated by the industry, presented
in Table 6-1, due to plants recycling the blowdown within the FGD scrubber as FGD preparation
water and in other non-FGD plant processes. Table 6-2 also presents the distribution of FGD
wastewater discharged based on type of coal used. Based on data from the Steam Electric
Survey, the highest average discharge of FGD wastewater occurs from plants with FGD systems
servicing units burning lignite coal.
26 The EPRI report does not include data for selenium; therefore, EPA could not evaluate if the selenium
concentrations are higher with or without an ESP. Regardless, the biological treatment system selected as the
proposed FGD wastewater treatment technology is capable of removing selenium, even at high concentrations.
27 EPA evaluated the ammonia and nitrate/nitrite concentrations because ammonia is injected into the flue gas as
part of the operation of the SCR/SNCR operation; therefore, EPA had hypothesized that there might be higher
concentrations of these pollutants in the FGD wastewater for plants operating these systems.
28
By January 1, 2014, EPA estimates that there will be approximately 145 plants generating FGD wastewater from
wet FGD systems; however, only 1 17 of these plants will discharge to a surface water or POTW.
6-4
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Section 6 - Wastewater Characterization and Pollutants of Concern
Table 6-2. FGD Wastewater Discharge at Steam Electric Power Plants by January 1, 2014
Total
Number of Plants
Discharging
117
Total Discharged FGD
Wastewater Flow
(gpd)
65,000,000
Coal Type a
Bituminous
Subbituminous
Lignite
Petroleum Coke
Blend b
68
15-20
1-5
1-5
23-28
41,000,000
5,000,000
4,000,000
15,000
15,400,000
Average Discharged FGD
Wastewater Flow
(gpd/plant)
559,000
600,000
275,000
800,000
3,000
620,000
Source: Steam Electric Survey, [ERG, 2013b].
Note: Wastewater flow rates are rounded to three significant figures.
Note: The FGD wastewater flow was estimated for 27 plants. Details on the methodology for estimating FGD
wastewater flow rates are provided in EPA's Incremental Costs and Pollutant Removals for Proposed Effluent
Limitation Guidelines and Standards for the Steam Electric Power Generating Point Source Category (DCN
SE01957).
a - Coal type classification is based on the types of coal burned in the units serviced by the wet FGD systems at each
plant.
b - Plants operating wet FGD systems servicing units that burn two or more different coal types are classified as
'blend'.
EPA collected data as part of its sampling program, described in Section 3.4, to
characterize the FGD wastewater from steam electric power plants. EPA's Office of Water (OW)
also collected additional self-monitoring data from Duke Energy Carolinas' Belews Creek and
Allen Steam Stations and Progress Energy Carolinas' Roxboro Steam Electric Plant. EPA used
its sampling data and plant self-monitoring data to characterize the untreated FGD wastewater
generated by the steam electric industry. Table 6-3 presents the average pollutant concentrations
of the influent to the FGD wastewater treatment systems (i.e., downstream of the solids
separation/solids dewatering processes). As shown in the table, FGD wastewater contains
significant concentrations of chloride, total dissolved solids (TDS), nutrients, and metals,
including bioaccumulative pollutants such as arsenic, mercury, and selenium. Some metals, such
as boron, magnesium, manganese, and sodium, are largely present in the dissolved phase.
Table 6-3. Average Pollutant Concentrations in Untreated FGD Wastewater
Analyte
Unit
Average Total Concentration
Classicals
Ammonia
Nitrate Nitrite as N
Nitrogen, Total Kjeldahl
Biochemical Oxygen Demand
Chemical Oxygen Demand
Chloride
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
6.35
74.9
39.6
9.38
367
7,740
6-5
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Section 6 - Wastewater Characterization and Pollutants of Concern
Table 6-3. Average Pollutant Concentrations in Untreated FGD Wastewater
Analyte
Sulfate
Cyanide, Total
Total Dissolved Solids
Total Suspended Solids
Phosphorus, Total
Analyte
Unit
mg/L
mg/L
mg/L
mg/L
mg/L
Unit
Average Total Concentration
8,140
0.764
28,600
16,800
3.19
Average Total
Concentration
Average Dissolved
Concentration
Metals
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Chromium (VI)
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Silver
Sodium
Thallium
Tin
Titanium
Vanadium
Zinc
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
332,000
22
489
2,850
17
291,000
159
3,250,000
1,300
NA
310
784
764
323
3,630,000
107,000
411
313
1,880
4,490
9
275,000
27
184
4,840
1,450
5,380
37,200
6
10
321
3
266,000
128
2,100,000
380
5
225
88
52,600
6
3,400,000
106,000
78
185
1,230
1,980
1
265,000
16
130
734
18
2,290
Source: EPA Sampling Data, [ERG, 2012a - 2012g];Progress Energy Data, [NCDENR, 2011]; Duke Energy Data,
[Duke Energy, 201 la-201 Ib].
NA - Not applicable. Samples were not analyzed for this particular analyte.
Note: Concentrations are rounded to three significant figures.
6-6
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Section 6 - Wastewater Characterization and Pollutants of Concern
As indicated in Table 6-2, 117 plants discharge FGD wastewater. More than half (54
percent) of the 117 plants that discharge FGD wastewater use surface impoundments to treat the
FGD wastewater prior to discharging it to a surface water or publicly owned treatment works
(POTW). Surface impoundments are designed to remove particulates from wastewater by means
of gravity. The use of more advanced wastewater treatment systems, such as chemical
precipitation and biological treatment, is increasing to a limited extent due to more stringent
effluent limit requirements some states have imposed on a site-specific basis. Figure 6-1 shows
the distribution of FGD wastewater treatment systems currently used in the steam electric
industry. All 117 steam electric power plants discharging FGD wastewater by January 1, 2014
are represented in the figure. Based on information provided in the Steam Electric Survey, EPA
classified each plant's FGD wastewater treatment system based on the highest level of treatment
into the following hierarchy: surface impoundment; any type of chemical precipitation system; a
9Q
biological treatment system (either anoxic or anaerobic); or other. Section 7 provides more
detail on the variety of FGD wastewater treatment technologies currently used in the steam
electric industry.
Other
Biological (12 Plants. 10%)
(Anoxic/Anaerobic)
(5 plants, 5
Settling Pond
i'63 plants. 54K)
1
Chenrical Precipitation
(36 plants, 31%)
Source: Steam Electric Survey., [ERG, 2013b]
Figure 6-1. Distribution of FGD Wastewater Treatment Systems among the 117
Plants Discharging FGD Wastewater by January 1, 2014
29 'Other' refers to some level of FGD wastewater treatment beyond a surface impoundment, but not classified as
either a chemical precipitation system or biological treatment systems. Those types of systems classified as 'other'
include, but are not limited to, constructed wetlands, aerobic biological reactors, vapor-compression evaporation, ion
exchange, and resin absorption.
6-7
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Section 6 - Wastewater Characterization and Pollutants of Concern
6.2 ASH TRANSPORT WATER
As described in Section 4.3, plants often use water to remove fly and bottom ash from the
particulate removal systems and boiler, respectively. This ash transport water can be reused as
ash transport water or sent to treatment, typically in an on-site impoundment, and then
discharged. This section presents an overview of the amount of fly ash and bottom ash transport
water generated at coal-fired power plants within the steam electric industry. This section also
discusses the characteristics of fly ash and bottom ash transport water and the amount of ash
transport water that is discharged to surface water.
6.2.1 Fly Ash Transport Water
Fly ash transport water is one of the largest flows generated at coal-fired power plants.
Many of the large baseload units generate enough fly ash that they operate fly ash transport water
systems continuously, while some smaller units and peaking units typically generate less fly ash,
and therefore, may operate fly ash transport water systems intermittently.30'31 Table 6-4 presents
the fly ash transport water flow rates generated by plants. The fly ash transport water flow rate is
the flow rate of the fly ash transport water from the sluicing system to the impoundment, and
does not necessarily represent the fly ash discharge flow rate from the plant. The industry
generated 128 billion gallons of fly ash transport water in 2009, with the average plant
generating 4.2 MOD.
Table 6-4. Fly Ash Transport Water Flow Rates
Flow Rate
per Plant
gpm/plant
gpd/plant
gpy /plant
Number of Plants"
137
137
137
Average Flow Rate
5,980
4,230,000
953,000,000
Median Flow Rate
2,730
2,140,000
389,000,000
Range of Flow Rate
10 - 226,000
4,000 - 35,700,000
80,000 - 9,200,000,000
Source: Steam Electric Survey. [ERG, 2013b].
Note: Wastewater flow rates are rounded to three significant figures.
Note: The number of plants generating transport water are based on values reported in the Steam Electric Survey,
which were scaled to represent the industry as a whole using the industry-weighting factors discussed in Section 3.3.
a - A total of 141 plants wet sluiced fly ash in 2009. Four plants did not provide sufficient data to determine the
plant-level fly ash transport water flow rate.
6.2.2 Bottom Ash Transport Water
Bottom ash transport water is an intermittent stream from steam electric units. The
bottom ash transport water flow rates are typically not as large as the fly ash transport water flow
rates. However, bottom ash transport water is still one of the larger volume wastestreams for
steam electric power plants. Table 6-5 presents the bottom ash transport water flow rates
30 A baseload unit is defined as a unit normally operating to produce electricity at an essentially constant rate. The
unit will typically run for extended periods of time.
31 A peaking unit is defined as a unit normally used only during peak-load periods of electricity demand or to
replace the loss of another generating unit.
6-8
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Section 6 - Wastewater Characterization and Pollutants of Concern
reported by the industry. The bottom ash transport water flow rate is the flow rate of the bottom
ash transport water from the sluicing system to the impoundment, and does not necessarily
represent the bottom ash discharge flow rate from the plant. While there are significantly more
plants producing bottom ash transport water than those producing fly ash transport water, the
average daily flow rate per plant is 40 percent less than the average fly ash transport water flow
rate presented in Table 6-4. The industry generated 255 billion gallons of bottom ash transport
water in 2009, with the average plant generating 2.5 MGD.
Table 6-5. Bottom Ash Transport Water Flow Rates
Flow Rate
per Plant
gpm/plant
gpd/plant
gpy /plant
Number of Plants"
327
328
326
Average Flow Rate
6,200
2,490,000
785,000,000
Median Flow Rate
3,310
1,020,000
296,000,000
Range of Flow Rate
2-119,000
3,200 - 34,600,000
608,000 - 10,800,000,000
Source: Steam Electric Survey, [ERG, 2013b].
Note: Wastewater flow rates are rounded to three significant figures.
Note: The number of plants generating transport water are based on values reported in the Steam Electric Survey,
which were scaled to represent the industry as a whole using the industry-weighting factors discussed in Section 3.3.
a - The number of plants listed indicate the total number of plants providing sufficient data to determine the bottom
ash transport water flow rate. In 2009, 346 plants wet sluiced bottom ash but not all plants provided transport water
flow rate information.
6.2.3 Ash Transport Water Characteristics
Fly ash and bottom ash transport water are typically treated in large surface impoundment
systems. Plants operating both wet fly ash and wet bottom ash handling systems often
commingle the two transport water streams, along with other wastestreams, within the same
surface impoundment system. Plants operating only one wet ash handling system (e.g., fly ash or
bottom ash, but typically bottom ash) may treat the ash transport water in surface impoundments,
which often receive other plant wastewaters. Some plants recycle part or all of the impoundment
effluent, but most plants discharge this impoundment overflow. Untreated ash transport waters
contain significant concentrations of TSS and metals. The effluent from ash impoundments
generally contains low concentrations of TSS; however, metals are still present in the
wastewater, predominantly in dissolved form.
Impoundments are designed to remove particulates from wastewater by gravity. The fly
ash, bottom ash, and other solids (e.g., FGD solids) settle out of the wastewater to the bottom of
the impoundment. To accomplish this, the wastewater must reside in the impoundment long
enough to settle the desired particle size. Impoundments can effectively reduce TSS in ash
transport water, particularly bottom ash transport water, which contains relatively dense ash
particles. Because impoundments remove solid particulates, they may also effectively remove
some metals from fly ash transport water when the metals are present in suspended particulate
form.
Impoundment overflow or discharge flow rates are not the same as ash transport water
flow rates. The ash transport water flow rate is the flow rate of the transport water from the
6-9
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Section 6 - Wastewater Characterization and Pollutants of Concern
sluicing system to the impoundment, while the impoundment overflow or discharge flow is the
flow rate of the water that is leaving the impoundment (e.g., discharged, recycled).
Impoundments typically receive wastestreams in addition to bottom ash and fly ash (e.g., boiler
blowdown, cooling water, low volume wastewater). In addition, there are factors acting to reduce
the impoundment overflow rate, including impoundment losses from infiltration through the
bottom of the impoundment or retaining dikes, evaporation, and amount of recycle from the
impoundment back to the plant for reuse. Table 6-6 presents the amount of fly ash and bottom
ash wastewater discharged in 2009, whereas Table 6-4 and Table 6-5 present the fly ash and
bottom ash transport water generation flow rates. On average, a single plant discharges
approximately 2.4 MOD of fly ash transport water and approximately 1.8 MOD of bottom ash
transport water. Therefore, on average, the Steam Electric Category discharges approximately 57
percent of all fly ash transport water generated and 71 percent of all bottom ash transport water
generated. Section 7 discusses various impoundment management practices in place in the
industry.
Table 6-6. Ash Wastewater Discharge at Steam Electric Power Plants
Type of Wastewater
Fly Ash
Bottom Ash
Number of Plants
Discharging
95
245
Total Wastewater
Discharged
(2009, million gallons/year)
81,100
157,000
Average Wastewater
Discharge Flow Rate
(gpd/plant)
2,390,000
1,760,000
Source: Steam Electric Survey, [ERG, 2013b].
Note: The number of plants and discharge flow rates in the steam electric industry are based on values reported in
the Steam Electric Survey, which were scaled to represent the industry as a whole using the industry-weighting
factors discussed in Section 3.3.
Note: 76 plants combine their fly and bottom ash sluice streams into one impoundment or impoundment system,
identified as a combined ash impoundment. All 76 plants discharging combined ash wastewater were included in the
table and counted as both fly ash and bottom ash dischargers. For these plants, a median percentage of total sluice
flow for both fly and bottom ash sluice was calculated and used to calculate a fly and bottom ash contribution for all
combined ash wastewater flows. The median fly ash wastewater contribution is 61.1 percent and the median bottom
ash contribution is 38.9 percent.
Note: Wastewater flow rates are rounded to three significant figures.
The design, operation, and maintenance of impoundments in the steam electric industry
varies by plant/company. As described above, impoundments are designed to remove TSS;
therefore, the size of the impoundment depends upon the combined flow rate of the influent
wastestreams, as well as the settling properties of the solids in the wastestreams. Some plants
may add chemicals to the impoundments effluent to control the pH of the discharge. The current
Steam Electric Power Generating ELGs limit the pH of discharged wastestreams to a range of
6.0 to 9.0 S.U. Common chemicals used to control the pH in impoundments are sodium
hydroxide and hydrochloric acid.
EPA did not collect data representing fly ash or bottom ash transport water entering an
impoundment during the sampling program for the rulemaking. However, during EPA's detailed
study of the industry, EPA collected a wastewater sample representing the influent to a fly ash
impoundment; the analytical results are presented in Table 4-18. Based on these samples, fly ash
6-10
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Section 6 - Wastewater Characterization and Pollutants of Concern
transport water contains significant concentration of metals, including arsenic, calcium, and
titanium. Some metals are primarily present in the dissolved phase, such as boron, molybdenum,
and selenium.
Table 6-7. Fly Ash Transport Water Characteristics
Analyte
Unit
Average Concentration
Classicals
Ammonia As Nitrogen (NH3-N)
Nitrate/Nitrite (NO3-N + NO2-N)
Total Kjeldahl Nitrogen (TKN)
Biochemical Oxygen Demand (BOD)
Chloride
Hexane Extractable Material (HEM)
Silica Gel Treated HEM (SGT-HEM)
Sulfate
Total Dissolved Solids (TDS)
Total Phosphorus
Total Suspended Solids (TSS)
Analyte
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
Unit
0.17
2.65
1.01
ND (2.00)
56.8
7.00
6.00
1,110
662
4.03
23,400
Average Total
Concentration
Average Dissolved
Concentration
Metals (EPA Method 200.7)
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Chromium (VI)
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Sodium
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
Mg/L
320,000
ND (81.2)
1,520
5,060
71.5
2,790
39.6
204,000
1,300
NA
381
964
298,000
786
35,100
1,120
2.31
333
739
ND (20.3)
69,900
283
ND (20.0)
86.8
164
ND (5.00)
1,380
ND (5.00)
94,800
ND (10.0)
5.00
ND (50.0)
ND (10.0)
ND (100)
ND (50.0)
15,200
40.3
ND (0.200)
243
ND (50.0)
16.6
64,400
6-11
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Section 6 - Wastewater Characterization and Pollutants of Concern
Table 6-7. Fly Ash Transport Water Characteristics
Analyte
Thallium
Titanium
Vanadium
Yttrium
Zinc
Unit
ug/L
ug/L
ug/L
ug/L
ug/L
Average Concentration
ND (40.6)
24,900
2,340
521
1,220
ND (10.0)
ND (10.0)
70.7
ND (5.00)
ND (10.0)
Metals (EPA Method 1638, 1631E)
Antimony
Arsenic
Cadmium
Chromium
Chromium (VI)
Copper
Lead
Mercury
Nickel
Selenium
Thallium
Zinc
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
33.1
519
9.51
569
NA
719
260
1.16
291
ND (200)
43.6
720
17.4
80.7
ND (1.00)
ND (80.0)
NA
ND (20.0)
ND (0.500)
0.00055
ND (100)
21.2
3.1
ND (50.0)
Source: Cardinal SER, [ERG, 2008].
NA - Not applicable. No data for this analyte were available specific to the impoundment type.
ND - Not detected (number in parenthesis is the reporting limit). The sampling episode report for the plant contains
additional sampling information, including analytical results for analytes measured above the detection limit, but
below the reporting limit (i.e., J-values).
Note: Concentrations are rounded to three significant figures.
6.3 COMBUSTION RESIDUAL LANDFILL AND IMPOUNDMENT LEACHATE
As discussed earlier, plants generating FGD wastewater and ash transport water generally
send the wastewater to a surface impoundment or wastewater treatment system. Solids resulting
from FGD wastewater treatment system are typically transferred to a landfill for disposal. The
FGD solids and ash sent to the surface impoundments may be stored permanently in the
impoundment or dredged from the impoundment and transferred to a landfill. Additionally,
plants may place dry ash, both fly ash and bottom ash, and FGD residuals (i.e., gypsum or
calcium sulfite) in a landfill. These combustion residuals stored in the landfills and
impoundments can contaminate the water that contacts the residuals in these management units.
As discussed in Section 4.3.5, leachate is the liquid that drains or leaches from a landfill or
impoundment. Leachate, which includes contaminated stormwater, that has come into contact
with combustion residual solids deposited in an impoundment or a landfill, contains heavy
metals and other contaminants. The following section describes the amount of leachate estimated
to be generated by the steam electric industry and the characteristics of these wastestreams.
6-12
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Section 6 - Wastewater Characterization and Pollutants of Concern
EPA's Steam Electric Survey included a section, Part F, that requested information on the
management practices of both impoundments and landfills containing combustion residuals. Part
F of the survey included questions related to the collection and treatment of leachate from both
types of management units. As described in Section 3.3, EPA sent Part F only to a statistically
sampled stratum of coal- and petroleum coke-fired plants (97 plants). EPA used the responses to
Part F of the survey along with the appropriate survey weights for Part F to estimate the number
of plants in the industry generating leachate from impoundments and landfills containing
combustion residuals. Table 6-8 presents the estimated number of plants generating leachate in
the steam electric industry from either an impoundment or a landfill. Based on the reported
leachate generation rates and the survey weights for Part F, EPA estimates that the steam electric
industry generates approximately 6.6 billion gpy of combined impoundment and landfill
leachate.
Table 6-8. Leachate Generation in the Steam Electric Industry
Type of
Wastewater
Total Landfill
Leachate a
Total Impoundment
Leachate c
Management Unit
Status
Total
Active/Inactive
Planned
Retired
Total
Number of
Plants
92"
84
1
5-10
66
Total Wastewater Generated
(2009, million gallons/year)
2,210
2,200
2
17
4,000
Average Wastewater
Generation Rate
(gpd/plant)
60,400
65,500
6,220
5,950
236,000
Source: Steam Electric Survey, [ERG, 2013b].
Note: Wastewater flow rates are rounded to three significant figures.
Note: Part F of the Steam Electric Survey was distributed to 97 plants. The responses from these plants were
weighted to reflect the portion of plants generating leachate in the industry. Weighted, these 97 plants represent 384
coal- and petroleum coke-fired stream electric plants.
Note: The number of plants generating leachate are based on values reported in the Steam Electric Survey, which
were scaled to represent the industry as a whole using the industry-weighting factors discussed in Section 3.3.Note:
For presentation purposes, EPA used leachate generation from the Steam Electric Survey reported in gpy to
calculate the total wastewater generated in 2009. Leachate flow can fluctuate significantly from day to day based on
rainfall; therefore, EPA believes it is more appropriate to use the values estimated by the plants instead of using the
average gpd and number of days generating leachate to calculate the yearly flow. To calculate the average
wastewater generation rate, EPA used leachate generation reported in gpd as a rough estimate of the average
leachate generation per day.
a - Eighteen (18) plants reported operating a leachate collection system but did not provide the amount of leachate
collected in 2009. These plants are not included in the number of plants or used when calculating the average
wastewater generated in Table 6-8.
b - The number of plants in each landfill status category is not additive. Some plants may operate more than one
landfill, each with a different status (active/inactive, retired, or planned).
c - Nine plants reported operating a leachate collection system but did not provide the amount of leachate collected
in 2009. These plants are not included in the number of plants or used when calculating the average wastewater
generated in Table 6-8. All impoundment leachate reported in the survey is from active/inactive impoundments (i.e.,
plants did not report leachate from closed/retired impoundments).
6-13
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Section 6 - Wastewater Characterization and Pollutants of Concern
The leachate collected from impoundments/landfills is generally transferred to a
collection impoundment. The effluent from these collection impoundments can be discharged,
sent to a holding impoundment, or sent to further treatment such as a constructed wetland
system. Only a small percentage of the leachate collected from combustion residual
impoundments/landfills is treated by means other than a surface impoundment: 9 percent of
impoundment leachate and 24 percent of landfill leachate. Section 7.4 provides more detail on
the types of leachate treatment technologies [ERG, 2013b].
As discussed previously in Section 4.3.5, nearly 50 percent of impoundment leachate
generated in the industry is returned directly to the impoundment (or recycled within the plant).
An additional 9 percent is treated on site in some fashion prior to being discharged. Forty-one
percent of plants discharge leachate from impoundments without any further treatment.
The majority of landfill leachate is discharged to surface water without prior treatment
(68 percent of landfills generating leachate). As shown in Table 4-15, the remaining 32 percent
of landfills return the leachate back to the landfill or treat the leachate on site prior to discharge.
Table 6-9 presents the number of coal- and petroleum coke-fired plants that discharging landfill
leachate in 2009. The table separates the amount of leachate discharged by active or inactive
landfills from the amount discharged by retired landfills. Data from the Steam Electric Survey
indicate a significant difference between the amount of leachate discharged by landfills classified
as active or inactive and the amount discharged by landfills classified as retired. The survey
defined a retired landfill as a landfill that will never accept additional waste and an inactive
landfill as a landfill that is currently not receiving waste, but might in the future. Retired landfills
likely discharge less leachate compared to active and inactive landfills because many retired
landfills are partially or completely capped/covered, thereby reducing the amount of precipitation
entering the landfill.
Table 6-9. Landfill Leachate Discharged by Coal- and Petroleum Coke-Fired
Power Plants in 2009
Type of Wastewater
Active/Inactive Landfill Leachate
Retired Landfill Leachate
Number
of
Plants
100-105
5-10
Total Wastewater
Discharged
(2009, million gallons/year)
2,200
17
Average Wastewater
Flow Rate
(gpd/plant)
54,000
6,180
Source: Steam Electric Survey, [ERG, 2013b].
Note: Ranges are provided to protect CBI data. Wastewater flow rates are rounded to three significant figures.
Note: The number of plants and discharge flow rates in the steam electric industry are based on values reported in
the Steam Electric Survey, which were scaled to represent the industry as a whole using the industry-weighting
factors discussed in Section 3.3.
As part of the Steam Electric Survey, EPA requested that a subset of plants provide
sampling data for leachate collected at the plant. EPA used these data to characterize the
untreated landfill leachate discharged by the steam electric industry. In response to the survey,
EPA obtained sampling data from 22 active fuel combustion residual landfills, four inactive fuel
6-14
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Section 6 - Wastewater Characterization and Pollutants of Concern
combustion residual landfills, and seven retired landfills. Table 6-10 presents the average
pollutant concentration for each type of landfill. Combustion residual landfill leachate contains
high concentration of metals, such as boron, calcium, chloride, and sodium, similar to FGD and
ash wastewaters. The metals in the leachate are generally at lower concentrations than those seen
in FGD wastewater and ash transport water, but still at treatable levels above the quantitation
limit. As expected, the leachate from active landfills generally has larger concentrations of
metals compared to inactive and retired landfills.
Table 6-10. Untreated Landfill Leachate Concentrations
Analyte
Units
Untreated Active
Landfill
Concentration
Untreated Inactive
Landfill
Concentration
Untreated Retired
Landfill
Concentration
Classical*
Chloride
Sulfate
TDS
TSS
ug/L
ug/L
ug/L
ug/L
542,000
1,910,000
3,860,000
41,400
11,100
1,070,000
1,670,000
4,210
149,000
881,000
1,660,000
13,800
Metals
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Silver
Sodium
Thallium
Tin
Titanium
Vanadium
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
5,030
4.6
46
57
1.9
20,500
2.7
481,000
4.9
84
10
59,000
1.4
115,000
4,360
1.4
1,880
69
74
0.68
327,000
1.3
11
17
3,240
100
4.9
10
50
0.47
3,640
1.9
386,000
1.6
3.8
1.7
95
0.47
33,700
355
0.01
995
43
84
0.42
16,700
0.96
13
15
6.2
87
1.1
41
37
1.1
10,100
0.73
303,000
3.4
7.6
2.4
5,700
0.83
21,800
1,280
13
702
16
46
1.03
66,200
0.92
33
11
69
6-15
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Section 6 - Wastewater Characterization and Pollutants of Concern
Table 6-10. Untreated Landfill Leachate Concentrations
Analyte
Zinc
Units
ug/L
Untreated Active
Landfill
Concentration
154
Untreated Inactive
Landfill
Concentration
58
Untreated Retired
Landfill
Concentration
38
Source: Steam Electric Survey, [ERG, 2013b].
Note: Concentrations are rounded to three significant figures.
In response to the survey, EPA obtained sampling data from 20 leachate impoundments.
Table 6-11 presents the average pollutant concentration for the 20 impoundments. Combustion
residual impoundment leachate contains high concentrations of metals, such as calcium, chloride,
and sodium, similar to FGD and ash wastewaters. The metals present in the leachate are
generally at lower concentrations than those seen in FGD wastewater and ash transport water,
but still at treatable levels above the quantitation limit.
Table 6-11. Untreated Impoundment Leachate Concentrations
Analyte
Units
Average Untreated Impoundment Concentration
Classical*
Chloride
Sulfate
Total Dissolved Solids
Total Suspended Solids
ug/L
ug/L
ug/L
ug/L
251,000
1,242,000
2,380,000
9,230
METALS
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
213
0.96
20
55
0.51
22,800
5.1
291,000
1.8
8.1
2.7
7,070
0.51
123,000
2,170
0.19
208
21
152
6-16
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Section 6 - Wastewater Characterization and Pollutants of Concern
Table 6-11. Untreated Impoundment Leachate Concentrations
Analyte
Silver
Sodium
Thallium
Tin
Titanium
Vanadium
Zinc
Units
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
Average Untreated Impoundment Concentration
0.63
145,000
0.67
105
7.1
3.9
301
Source: Steam Electric Survey, [ERG, 2013b].
Note: Concentrations are rounded to three significant figures.
6.4 FLUE GAS MERCURY CONTROL WASTEWATER
As described in Section 4.3.4, there are two types of systems used for FGMC: addition of
oxidizers to the coal prior to combustion and injection of activated carbon into the flue gas, after
combustion. Adding the oxidizers does not generate a new wastewater stream, but it may
increase the concentration of mercury in the FGD wastewater because the oxidized mercury is
more easily removed by the FGD system. Activated carbon injection (ACT) systems, however,
have the potential to generate a new wastestream, depending on the location of the injection. If
the injection occurs upstream of the primary parti culate removal system, then the mercury-
containing carbon (i.e., FGMC waste) will be collected and handled the same way as the fly ash;
therefore, if the fly ash is wet sluiced, then the FGMC wastes are also wet sluiced. When the
activated carbon is injected downstream of the primary parti culate removal system, the FGMC
waste must be collected in a separate particulate removal system, typically a fabric filter
baghouse. Residual fly ash that passes through the primary particulate removal system may also
be captured.
The FGMC waste/fly ash can either be handled using a wet sluicing system or handled in
a dry fashion. There are 15 plants with at least one ACT system injecting carbon downstream of
the primary particulate removal system. Six of these plants identified the FGMC system as
planned, with an installation date after 2009. Of these fifteen plants, only one plant plans to
handle the FGMC waste using a wet sluicing system; however, this plant will send the FGMC
transport water to a zero discharge impoundment, where the impoundment overflow will be
reused for fly ash, bottom ash, and FGMC transport water. EPA does not have any sampling data
on wastewater characteristics of the FGMC transport water or the characteristics of FGMC waste
[ERG, 2013b].
For ACT systems in which the carbon is injected upstream of the primary particulate
control system, the FGMC waste is collected with fly ash. Again, this can be handled either wet
or dry, depending on how the plant is handling the fly ash. There are 58 plants with at least one
ACT system injecting carbon upstream of the primary particulate system. Fourteen of these plants
identified the FGMC system as planned, with an installation date after 2009. Of these 58 plants,
five (three with current systems and two with planned systems) reported handling the FGMC
waste using a wet sluicing system. EPA does not have any sampling data on the wastewater
6-17
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Section 6 - Wastewater Characterization and Pollutants of Concern
characteristics of the FGMC transport water associated with these wet systems; however, ORD
evaluated the effects of these ACT systems on the characteristics of fly ash and determined that
these systems substantially increase the total mercury content of the fly ash [U.S. EPA, 2006].
EPA does not have any sampling data demonstrating how the added mercury in the fly ash
affects the characteristics of the fly ash transport water.
ORD looked at six plants, four operating ACT systems and two operating brominated ACT
systems.32 ORD collected fly ash from these plants, with and without FGMC waste, and
analyzed the fly ash for mercury, arsenic, and selenium. ORD concluded that, of the three
constituents analyzed, FGMC waste significantly affects only the mercury concentration of fly
ash. Five of the six plants showed an increase in the mercury concentration of fly ash with
FGMC waste as compared to fly ash alone [U.S. EPA, 2006]. Table 6-12 shows the distribution
of mercury concentrations at each of the six plants.
Table 6-12. Mercury Concentrations in Fly Ash with and without ACI Systems
Plant
Brayton Point
Pleasant Prairie
Salem Harbor
Facility C
St. Clair a
Facility L (Run 1) a
Facility L (Run 2) a
Mercury (EPA Method 3052)
Fly Ash Only
(ng/g)
651
158
529
16
111
13
20
With ACI
(ng/g)
1,530
1,180
412
1,151
1,163
38
71
Percent
Increase
135%
648%
-22%
7,094%
949%
190%
252%
Mercury (EPA Method 7473)
Fly Ash Only
(ng/g)
582
147
574
11
NT
NT
NT
With ACI
(ng/g)
1,414
1,177
454
1,090
NT
NT
NT
Percent
Increase
143%
701%
-21%
9,810%
NA
NA
NA
Source: [U.S. EPA, 2006]
Note: ORD analyzed mercury using two different analytical methods, EPA Method 3052 and EPA Method 7473.
Both results are shown in the table.
NT - Not tested.
NA - Not applicable.
a - Plant operates a brominated activated carbon injection system.
6.5 GASIFICATION WASTEWATER
As discussed in Section 4.3.6, the gasification process creates a number of different
wastewater streams, some of which are specific to the integrated gasification combined cycle
(IGCC) process (e.g., air separation unit blowdown) and others that are similar to general power
plant wastewaters (e.g., cooling water). The IGCC-specific wastewaters are generally combined,
sometimes along with other plant wastewaters, and collectively referred to as grey water or sour
water. The sour water is sent to a steam stripper, sometimes called a sour water treatment unit,
which essentially distills the wastewater and produces a sweet water stream and recycle slurry
The chloride content of flue gas can affect the performance of activated carbon systems, low chloride
concentrations can yield low mercury removal. Some plants with low chloride levels utilize brominated activated
carbon as a sorbent to increase the amount of mercury captured [U.S. EPA, 2006].
6-18
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Section 6 - Wastewater Characterization and Pollutants of Concern
stream that is reused in slurry preparation. Figure 4-4 depicts the general process flow diagram
for the IGCC process. Although it has been treated by steam stripping, the sweet water stream is
still contaminated with elements from the gasification process, such as selenium, chromium, and
arsenic. The sweet water may also be contaminated with various other metals formed in the
gasification unit, such as selenocyanate. These metals are not known to be generated in
traditional coal-fired boilers.
EPA collected data as part of the CWA 308 monitoring program described in Section
3.4.1 from two plants operating IGCC systems. Both plants, Tampa Electric Company's Polk
Station (Polk) and Wabash Valley Power Association's Wabash River Station (Wabash River),
treat their gasification wastewater with a vapor-compression evaporation system. Both plants
sampled the influent streams transferred to the vapor-compression evaporation system and the
distillate/condensate(s) from the systems. EPA used the data from both plants to characterize
untreated gasification wastewater. Table 6-13 presents the average concentrations of the
untreated gasification wastewater. The table provides the individual average concentrations for
the two plants, as well as the average for both plants combined. For both plants, the gasification
wastewater represents a combination of multiple wastestreams, but because the plants operate
slightly different processes, they are not the same wastestreams at both plants.
Table 6-13. Untreated Gasification Wastewater Concentrations
Analyte
Units
Polk
Concentration
Wabash River
Concentration
Average Polk and
Wabash River
Concentration
Classical*
Ammonia
Nitrate Nitrite as N
Nitrogen, Kjeldahl
Biochemical Oxygen Demand
Chemical Oxygen Demand
Chloride
Sulfate
Total Dissolved Solids
Total Suspended Solids
Phosphorus, Total
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
175
0.09
603
7.7
101
1,300
2,750
4,575
16
0.47
35
0.05
65
205
823
1,050
11
4,225
2.0
0.19
105
0.07
334
106
462
1,175
1,380
4,400
8.9
0.33
Metals
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
11,475
363
280
118
14
38,250
4.1
19,450
4.0
100
1.0
4
10
1.0
34,750
2.0
783
4.0
5,788
182
142
64
7.3
36,500
3.0
10,116
4.0
6-19
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Section 6 - Wastewater Characterization and Pollutants of Concern
Table 6-13. Untreated Gasification Wastewater Concentrations
Analyte
Cobalt
Copper
Cyanide, Total
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Silver
Sodium
Thallium
Tin
Titanium
Vanadium
Zinc
Units
ug/L
ug/L
mg/L
ug/L
ug/L
ug/L
ug/L
ng/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
Polk
Concentration
10
2.0
1.4
2,115
18
5,325
238
70
49
4,950
1,278
1.0
1,675,000
254
100
19
280
77
Wabash River
Concentration
10
2.0
2.3
1,140
1.0
200
10
4.3
20
2.0
920
1.0
1,850,000
3
100
10
16
20
Average Polk and
Wabash River
Concentration
10
2.0
1.8
1,628
10
2,763
124
37
35
2,476
1,099
1.0
1,762,500
129
100
15
148
49
Source: CWA 308 Monitoring Data, [ERG, 2012h].
6.6 METAL CLEANING WASTE
As discussed in Section 4.3.7, metal cleaning wastes are generated during the cleaning of
metal process equipment and can consist of chemical and non-chemical cleaning operations.
There are several different types of metal cleaning wastes (identified in Section 4.3.7) and the
frequency of generation varies among the different types of metal cleaning wastes. Table 6-14
presents the minimum, median, and maximum frequency of the generation for each of the metal
cleaning wastes, broken out between chemical and nonchemical operations. Air heater cleaning
and soot blowing are both examples of cleaning activities that do not use chemicals; between 98
and 100 percent of all units conducting these cleaning operations use no chemicals during the
cleaning operations.33 Boiler tube cleaning generally involves the addition of chemicals and
typically occurs less often than once a year. Fifty-nine percent of the units identified as
conducting boiler tube cleaning do so once every 10 or more years.
EPA compared the frequency information reported in the Steam Electric Survey to data
included in the 1974 Technical Development Document (TDD) to determine if the industry has
From the responses to the Steam Electric Survey, EPA determined that 98 percent of units conducting air heater
cleaning operations and 100 percent of units blowing soot (that use water) do not use chemical addition in the
cleaning process.
6-20
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Section 6 - Wastewater Characterization and Pollutants of Concern
changed the frequency with which they conduct metal cleaning operations. The 1974 TDD
contains frequency information for three metal cleaning operations: air heater cleaning, boiler
fireside cleaning, and boiler tube cleaning. For air heater cleaning, the 1974 TDD frequency data
ranges from once per month to four times per year, which is generally more frequent compared
to the data from the Steam Electric Survey. For boiler fireside cleaning, the 1974 TDD frequency
data ranges from eight times per year to twice per year, which is comparable to the frequency
data from the Steam Electric Survey. For boiler tube cleaning, the 1974 TDD frequency data
ranges from twice per year to once every eight years, which is also comparable to the frequency
data from the Steam Electric Survey. Therefore, EPA determined that the industry is still
performing these cleaning operations at a similar frequency compared to when the Agency
initially set the BPT standards for metal cleaning wastes.
In addition to frequency, the volume of wastewater generated also varies among the
different types of metal cleaning wastes. Table 6-15 provides the minimum and maximum flow
rates associated with each of these cleaning operations. The 1974 TDD contains flow rate
information for air heater cleaning, boiler fireside cleaning, and boiler tube cleaning. For air
heater cleaning, the 1974 TDD flow rates ranges from 43,000 to 600,000 gallons per event,
which is within the range reported in the Steam Electric Survey. For boiler fireside cleaning, the
1974 TDD flow rate data ranges from 24,000 to 720,000 gallons/event, which is within the range
reported in the Steam Electric Survey. For boiler tube cleaning, the 1974 TDD flow rate data
ranges from 13,900 to 150,000 gallons/event, which is also within the range reported in the
Steam Electric Survey. While all of these are within the ranges reported in the Steam Electric
Survey, EPA noted that the maximum value reported in the Steam Electric Survey was
significantly higher (i.e., an order of magnitude) for each of these cleaning operations. However,
based on these results, EPA found that the industry is still generating similar quantities of
wastewater from these cleaning operations compared to when the Agency initially set the BPT
standards for metal cleaning wastes.
The 1974 and 1982 TDD contain characterization data for metal cleaning wastewaters.
Tables A-V-5, A-V-6, and A-V-20 in the 1974 TDD contain characterization data associated
with boiler tube cleaning, air preheater cleaning, and boiler fireside cleaning [U.S. EPA, 1974].
Tables V-68 through V-73 in the 1982 TDD contain characterization data and wastewater flow
rate data boiler fireside and air preheater cleaning [U.S. EPA, 1982].
Table 6-14. Metal Cleaning Waste Generation Frequency Reported in the Steam Electric
Survey
Type of Wastestream
Minimum Frequency
(i.e., Least Frequent)
Median Frequency
Maximum Frequency
(i.e., Most Frequent)
Nonchemical Cleaning Operations
Air Compressor Cleaning
Air-Cooled Condenser Cleaning
Air Heater Cleaning
Boiler Fireside Cleaning
Boiler Tube Cleaning
NA
a
Once Every 40 Years
Once Every 30 Years
Once Every 10 Years
NA
a
Once Every Year
Once Every Year
Once Every 1-2 Years
NA
a
1 1 Times Every Day
Twice Every Day
Twice Every Year
6-21
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Section 6 - Wastewater Characterization and Pollutants of Concern
Table 6-14. Metal Cleaning Waste Generation Frequency Reported in the Steam Electric
Survey
Type of Wastestream
Combustion Turbine Cleaning
(Combustion)
Combustion Turbine Cleaning
(Compressor)
Condenser Cleaning
Draft Fan Cleaning
Economizer Cleaning
FGD Equipment Cleaning
Heat Recovery Steam Generator Cleaning
Mechanical Dust Collector Cleaning
Nuclear Steam Generator Cleaning
Precipitator Wash
SCR Catalyst Soot Blowing
Sludge Lancing
Soot Blowing
Steam Turbine Cleaning
Superheater Cleaning
Minimum Frequency
(i.e., Least Frequent)
Twice Every Year
Once Every Year
a
Once Every Four Years
Once Every 50 Years
a
NA
Once Every 10 Years
NA
Once Every 10 Years
Three Times Every Year
Once Every 4-5 Years
Once Every 10 Years
Once Every 10 Years
NA
Median Frequency
Once Every Three Days
Once Every Two Days
Once Every Year
Once Every Year
Once Every Three years
a
NA
Once Every Four Years
NA
Once Every Three Years
Three Times Every Year
Once Every Three Years
Once Every Day
Once Every 7 Years
NA
Maximum Frequency
(i.e., Most Frequent)
Once Every Two Days
2-3 Times Every Day
Once Every Year
Once Every Year
Once Every Year
Once Every Day
NA
Once Every Year
NA
Once Every Year
Three Times Every Year
Once Every 1-2 Years
600 Times Every Day
Three Times Every Year
NA
Chemical Cleaning Operations
Air Compressor Cleaning
Air-Cooled Condenser Cleaning
Air Heater Cleaning
Boiler Fireside Cleaning
Boiler Tube Cleaning
Combustion Turbine Cleaning
(Combustion)
Combustion Turbine Cleaning
(Compressor)
Condenser Cleaning
Draft Fan Cleaning
Economizer Cleaning
FGD Equipment Cleaning
Heat Recovery Steam Generator Cleaning
Mechanical Dust Collector Cleaning
Nuclear Steam Generator Cleaning
Precipitator Wash
SCR Catalyst Soot Blowing
Sludge Lancing
Twice Every Year
NA
Once Every Two Years
Once Every 10 Years
Once Every 50 Years
Once Every 8 Years
Once Every 10 Years
Once Every 30 Years
Once Every 3-4 Years
NA
Once Every Day
Once Every 40 Years
NA
a
NA
NA
NA
Twice Every Year
NA
Twice Every Month
a
Once Every 10 Years
Twice Every Year
Twice Every Year
Once Every 25 Years
Once Every 3-4 Years
NA
Once Every Day
Once Every 40 Years
NA
a
NA
NA
NA
Twice Every Year
NA
Twice Every Month
a
Once Every Two Years
Three Times Every
Month
Once Every Two Days
a
Once Every 3-4 Years
NA
Once Every Day
Once Every 10 Years
NA
a
NA
NA
NA
6-22
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Section 6 - Wastewater Characterization and Pollutants of Concern
Table 6-14. Metal Cleaning Waste Generation Frequency Reported in the Steam Electric
Survey
Type of Wastestream
Soot Blowing
Steam Turbine Cleaning
Superheater Cleaning
Minimum Frequency
(i.e., Least Frequent)
NA
Once Every 30 Years
Once Every 37 Years
Median Frequency
NA
Once Every Four Years
Once Every 37 Years
Maximum Frequency
(i.e., Most Frequent)
NA
Once Every Year
Once Every 37 Years
Source: Steam Electric Survey, [ERG, 2013b].
Note: This table presents data gathered from only the subset of plants that were required to complete Part E of the
survey.
NA - Not applicable. The cleaning operation was not reported in the Steam Electric Survey for the type of chemical
usage (i.e., nonchemical or chemical cleaning).
a - Data were removed from certain cells to protect the release of information claimed confidential business
information.
Table 6-15. Metal Cleaning Wastewater Flow Rates Reported in the Steam
Electric Survey
Type of Wastestream
Minimum Flow
(Gallons per Event)
Maximum Flow
(Gallons per Event)
Nonchemical Cleaning Operations
Air Compressor Cleaning
Air-Cooled Condenser Cleaning
Air Heater Cleaning
Boiler Fireside Cleaning
Boiler Tube Cleaning
Combustion Turbine Cleaning (Combustion)
Combustion Turbine Cleaning (Compressor)
Condenser Cleaning
Draft Fan Cleaning
Economizer Cleaning
FGD Equipment Cleaning
Heat Recovery Steam Generator Cleaning
Mechanical Dust Collector Cleaning
Nuclear Steam Generator Cleaning
Precipitator Wash
SCR Catalyst Soot Blowing
Sludge Lancing
Soot Blowing
Steam Turbine Cleaning
Superheater Cleaning
NA
a
0
0
0
0
0
4,800
5,000
5,000
15
NA
180,000
NA
9,000
11,900
0
0
0
NA
NA
a
8,000,000
4,500,000
250,000
1,800
5,000
a
169,000
2,640,000
a
NA
3,000,000
NA
16,800,000
11,900
800
200,000
2,000,000
NA
Chemical Cleaning Operations
6-23
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Section 6 - Wastewater Characterization and Pollutants of Concern
Table 6-15. Metal Cleaning Wastewater Flow Rates Reported in the Steam
Electric Survey
Type of Wastestream
Air Compressor Cleaning
Air-Cooled Condenser Cleaning
Air Heater Cleaning
Boiler Fireside Cleaning
Boiler Tube Cleaning
Combustion Turbine Cleaning (Combustion)
Combustion Turbine Cleaning (Compressor)
Condenser Cleaning
Draft Fan Cleaning
Economizer Cleaning
FGD Equipment Cleaning
Heat Recovery Steam Generator Cleaning
Mechanical Dust Collector Cleaning
Nuclear Steam Generator Cleaning
Precipitator Wash
SCR Catalyst Soot Blowing
Sludge Lancing
Soot Blowing
Steam Turbine Cleaning
Superheater Cleaning
Minimum Flow
(Gallons per Event)
20
NA
2,700
0
0
0
0
25,000
100
NA
10
0
NA
a
NA
NA
NA
NA
1,500
39,000
Maximum Flow
(Gallons per Event)
20
NA
80,000
50,000
2,000,000
11,000
10,000
a
100
NA
15
231,000
NA
a
NA
NA
NA
NA
20,000
39,000
Source: Steam Electric Survey, [ERG, 2013b].
Note: This table presents data gathered from only the subset of plants that were required to complete Part E of the
survey.
NA - Not applicable. The cleaning operation was not reported in the Steam Electric Survey for the type of chemical
usage (i.e., nonchemical or chemical cleaning).
a - Data were removed from certain cells to protect the release of information claimed confidential business
information.
6.7 IDENTIFICATION OF POLLUTANTS OF CONCERN
Constituents present in combustion wastewater are primarily derived from the parent
carbon feedstock (e.g., coal, petroleum coke). A number of these constituents have the potential
to cause environmental harm depending on the mass pollutant loadings, wastewater
concentration, and how organisms are exposed to them in the environment. EPA conducted a
field sampling program as part of the detailed study and rulemaking efforts for the Steam
Electric Power Generating ELGs to characterize the wastewater generated by the industry. The
analytes selected for analysis reflect EPA's current understanding of power plant wastewaters,
including contributions from scrubber sorbents, treatment chemicals, and other sources. Section
3.4.1 discusses the analytes evaluated in the EPA sampling program.
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Section 6 - Wastewater Characterization and Pollutants of Concern
EPA primarily used the analytical data from the sampling episodes to identify the
pollutants of concern (POCs) considered for this rulemaking. From the list of analytes sampled,
EPA eliminated from consideration all pollutants that were never detected in untreated
wastewater samples. EPA then reviewed its data from untreated wastewater samples from
individual wastestreams to identify pollutants detected at greater than or equal to 10 times the
baseline value in at least 10 percent of all untreated process wastewater samples.34 This criterion
ensures that the pollutant was present in sufficient concentrations at sites where EPA evaluated
treatment performance. This is used as a screening tool to identify those pollutants that are
quantified in a wastestream at sufficient frequency and at treatable levels. Using 10 times the
baseline value as a screening threshold can facilitate evaluations of treatment system
performance and efficacy, since it ensures the influent concentrations are high enough to more
readily quantify the degree of pollutant removal resulting from treatment processes such as
chemical or biological removal. However, the criterion is less applicable in cases where the
technology basis results in complete removal of all pollutants present, such as would occur under
the technology options considered for fly ash transport water, bottom ash transport water, and
FGMC wastewater. For these "zero discharge" technologies, confirmation that a pollutant is
present in the wastestream at quantifiable levels may be sufficient to identify a pollutant as a
pollutant of concern. Additionally, in past effluent guidelines rulemakings, EPA has determined
that a lower threshold (e.g., 5 times the baseline value) was the appropriate criterion for
identifying pollutants of concern. For example, see Section 7 of the Technical Development
Document for the Final Effluent Limitations Guidelines and Standards for the Meat and Poultry
Products Point Source Category (40 CFR 432) (EPA-821-R-04-011).
EPA used the baseline values that were developed for the 2000 Centralized Waste
Treatment (CWT) Industry Effluent Limitations Guidelines for this analysis. The baseline values
are generally equal to the nominal quantitation limit identified for the analytical method for a
pollutant. For the CWT ELGs, the Agency made several exceptions to this general rule if it
determined that reliable measurements of a pollutant could be made at a lower level, or if the
nominal quantitation limit could not be reasonably achieved, or if a single baseline value had to
be selected when a pollutant had multiple nominal quantitation limits. Generally, the CWT ELGs
used the instrument detection limit for EPA Method 1620 as the basis for the metals baseline
values, with some exceptions. For the steam electric proposed ELGs, EPA analyzed the samples
using EPA Methods 200.7, 200.8 with collision cell, and 163 IE. Each of these methods are
capable of achieving quantitation limits that are lower than the baseline values from CWT.
However, EPA used the CWT baseline values, in most cases, as a more conservative value for
the analysis. EPA did make a couple of exceptions and used the minimum level for mercury
defined in EPA Method 163 IE (i.e., 0.5 ng/L). Additionally, EPA used 2.0 ug/1 for arsenic,
which is based on a method detection limit study conducted by EPA [CSC, 2013]. Table 6-16
presents the baseline values used for the identification of POCs associated with the proposed
Steam Electric ELGs.
34 This approach is consistent with the process EPA used to identify pollutants of concern for many categories. EPA
takes this approach to ensure the pollutants are present at treatable levels.
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Section 6 - Wastewater Characterization and Pollutants of Concern
Table 6-16. Baseline Values for Steam Electric Industry POCs
Analyte
Unit
Baseline Value
Classical* or Conventionals
Ammonia as Nitrogen
Biochemical Oxygen Demand
Chemical Oxygen Demand
Chloride
Nitrate/Nitrite
Total Cyanide
Total Dissolved Solids
Total Phosphorus
Total Sulfide
Total Suspended Solids
ug/1
ug/1
ug/1
ug/1
ug/1
ug/1
ug/1
ug/i
"g/1
"g/1
50.0
2,000.0
5,000.0
1,000.0
50.0
20.0
10,000.0
10.0
1,000.0
4,000.0
Metals
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Phosphorus
Potassium
Selenium
Sodium
Sulfur
Thallium
Titanium
Vanadium
Zinc
ug/1
ug/1
ug/1
ug/1
ug/1
ug/1
ug/1
ug/1
ug/1
ug/1
ug/1
^g/1
ug/1
^g/1
^g/1
ng/1
^g/1
ug/1
^g/1
^g/1
^g/1
^g/1
ug/1
^g/1
^g/1
^g/1
^g/1
200.0
20.0
2.0
200.0
5.0
100.0
5.0
5,000.0
10.0
50.0
25.0
100.0
50.0
5,000.0
15.0
0.5
10.0
40.0
1,000.0
1,000.0
5.0
5,000.0
1,000.0
10.0
5.0
50.0
20.0
Source: Development Document for Effluent Limitations Guidelines and Standards for the Centralized Waste
Treatment Industry, [EPA, 2000]; EPA Method 163 IE; [CSC, 2013]
6-26
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Section 6 - Wastewater Characterization and Pollutants of Concern
For some pollutants, EPA did not have a baseline value identified from the 2000 CWT
ELGs. For these pollutants, EPA used the sample-specific method detection limit (MDL) for the
analysis. For some wastestreams (e.g., ash transport water), there were pollutants that did not
have a baseline value nor a sample-specific MDL; therefore, these pollutants were not included
in the analysis and were not identified as a POC for the specific wastestream. Finally, for some
wastestreams, EPA identified pollutants as POCs because they were identified as POCs for the
wastestream during previous rulemakings. Using the criteria described above, EPA developed
lists of POCs for each fuel combustion wastewater: FGD wastewater, fly ash transport water,
bottom ash transport water, landfill combustion residual leachate, impoundment combustion
residual leachate, FGMC wastewater, gasification wastewater, and nonchemical metal cleaning
wastes. The following sections identify the POCs for each wastestream. The POCs identified for
each wastestream are used only as the basis for the selection of regulated pollutants, described in
Section 11.
6.7.1 FGD Wastewater Pollutants of Concern
EPA reviewed untreated wastewater data from seven steam electric power plants
operating FGD wastewater treatment systems (total of seven sampling points and 28 samples) to
identify POCs for FGD wastewater; see Table 6-17. EPA identified 35 POCs using the criteria
presented in Section 6.7.
Table 6-17. Pollutants of Concern - FGD Wastewater
Pollutant Group
Conventional Pollutants
Priority Pollutants
Nonconventional Pollutants
Pollutant of Concern
Oil and Grease3
Total Suspended Solids
Antimony
Arsenic
Beryllium
Cadmium
Chromium
Copper
Cyanide
Lead
Mercury
Nickel
Selenium
Thallium
Zinc
Aluminum
Ammonia
Barium
Boron
Calcium
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Section 6 - Wastewater Characterization and Pollutants of Concern
Table 6-17. Pollutants of Concern - FGD Wastewater
Pollutant Group
Nonconventional Pollutants
Pollutant of Concern
Chemical Oxygen Demand
Chloride
Cobalt
Iron
Magnesium
Manganese
Molybdenum
Nitrate/Nitrite
Nitrogen Total, Kjeldahl
Phosphorus
Sodium
Sulfate
Titanium
Total Dissolved Solids
Vanadium
Source: EPA Sampling Data, [ERG, 2012a-2012g]; [ERG, 2013a].
a - EPA did not analyze its field sampling data for oil and grease. Rather, since the existing steam electric ELGs
currently contain BPT limitations applicable to FGD wastewater for oil and grease, EPA already has data from the
existing rulemaking demonstrating oil and grease is also a pollutant of concern in FGD wastewater.
6.7.2 Ash Transport Water Pollutants of Concern
EPA sampled untreated fly ash sluice at one plant during the steam electric detailed
study. EPA reviewed the untreated fly ash transport water data from this plant (one sampling
point and one sample) to identify POCs for fly ash transport water. Table 6-18 lists the POCs
identified for fly ash transport water. EPA identified 24 POCs using the criteria presented in
Section 6.7. EPA also identified selenium as a POC for fly ash transport water based on a study
conducted at Belews Lake that linked fish kills to selenium accumulation in the lake associated
with discharges from a power plant, as well as other documented instances of harm caused by
discharges of selenium in ash transport water [Lemly, 1985]. As discussed above in Section 6.7,
the criterion EPA used as a screening tool to identify pollutants of concern is less applicable in
cases where the technology basis results in complete removal of all pollutants present, such as
would occur under the technology options considered for fly ash transport water, bottom ash
transport water, and FGMC wastewater. For these "zero discharge" technologies, confirmation
that a pollutant is present in the wastestream at quantifiable levels may be sufficient to identify a
pollutant as a pollutant of concern. Based on the information in the record for selenium in ash
transport water, EPA identified it as a pollutant of concern.
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Section 6 - Wastewater Characterization and Pollutants of Concern
Table 6-18. Pollutants of Concern - Ash Transport Water
Pollutant Group
Conventional Pollutants
Priority Pollutants
Nonconventional Pollutants
Pollutant of Concern
Oil and Grease3
Total Suspended Solids
Arsenic
Beryllium
Chromium
Copper
Lead
Mercury
Nickel
Selenium
Zinc
Aluminum
Barium
Boron
Calcium
Chloride
Iron
Manganese
Molybdenum
Nitrate/Nitrite
Sodium
Titanium
Total Dissolved Solids
Vanadium
Yttrium
Source: [ERG, 2008]; [ERG, 2013a].
a - EPA did not analyze its field sampling data for oil and grease. Rather, since the existing steam electric ELGs
currently contain BPT limitations applicable to fly ash transport water for oil and grease, EPA already has data from
the existing rulemaking demonstrating oil and grease is also a pollutant of concern in fly ash transport water.
Constituents present in ash, and therefore ash transport water, are primarily derived from
the type of coal/petroleum coke burned; therefore, as discussed in Section 6.2.3, EPA expects
that the bottom ash transport water will have the same constituents that are found in the fly ash
transport water. For this reason, the POCs for bottom ash transport water are identical to those of
fly ash transport water.
6.7.3 Combustion Residual Leachate Pollutants of Concern
As part of the Steam Electric Survey, EPA required a subset of plants to sample their
leachate from impoundments and landfills containing combustion residual. EPA reviewed the
untreated landfill and impoundment leachate data collected from the survey responses to identify
6-29
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Section 6 - Wastewater Characterization and Pollutants of Concern
POCs for landfill leachate and POCs for impoundment leachate. Table 6-19 lists the POCs
identified for combustion residual landfill leachate using the criteria presented in Section 6.7.
Table 6-19. Pollutants of Concern - Landfill Leachate
Pollutant Group
Conventional Pollutants
Priority Pollutants
Nonconventional Pollutants
Pollutant of Concern
Oil and Grease3
Total Suspended Solids
Arsenic
Mercury
Selenium
Aluminum
Boron
Calcium
Chloride
Iron
Magnesium
Manganese
Molybdenum
Sodium
Sulfate
Total Dissolved Solids
Source: Steam Electric Survey , [ERG, 2013b]; [ERG, 2013a].
a - The landfill leachate samples were not analyzed for oil and grease (O&G). Rather, since the existing steam
electric ELGs currently contain BPT limitations applicable to combustion residual leachate for O&G, EPA already
has data from the existing rulemaking demonstrating O&G is also a pollutant of concern in combustion residual
leachate.
Table 6-20 lists the POCs identified for combustion residual impoundment leachate using
the criteria presented in Section 6.7.
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Section 6 - Wastewater Characterization and Pollutants of Concern
Table 6-20. Pollutants of Concern - Impoundment Leachate
Pollutant Group
Conventional Pollutants
Priority Pollutants
Nonconventional Pollutants
Pollutant of Concern
Oil and Grease3
Arsenic
Mercury
Boron
Calcium
Chloride
Iron
Magnesium
Manganese
Molybdenum
Sodium
Sulfate
Total Dissolved Solids
Source: Steam Electric Survey, [ERG, 2013b]; [ERG, 2013a].
a - The impoundment leachate samples were not analyzed for O&G. Rather, since the existing steam electric ELGs
currently contain BPT limitations applicable to combustion residual leachate for O&G, EPA already has data from
the existing rulemaking demonstrating O&G is also a pollutant of concern in combustion residual leachate.
6.7.4 Gasification Wastewater Pollutants of Concern
EPA sampled wastewater streams at two plants operating IGCC generating units as part
of the CWA 308 sampling program discussed in Section 3.4. EPA reviewed the untreated
wastewater data from these two stream electric power plants (5 sampling points and 20 samples)
to identify POCs for IGCC wastewater.
EPA identified 20 POCs for gasification wastewater. Table 6-21 lists the POCs EPA
identified using the criteria discussed in Section 6.7.
Table 6-21. Pollutants of Concern - Gasification Wastewater
Pollutant Group
Conventional Pollutants
Priority Pollutants
Nonconventional Pollutants
Pollutant of Concern
Biochemical Oxygen Demand
Antimony
Arsenic
Cyanide
Mercury
Nickel
Selenium
Thallium
Aluminum
Ammonia
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Section 6 - Wastewater Characterization and Pollutants of Concern
Table 6-21. Pollutants of Concern - Gasification Wastewater
Pollutant Group
Nonconventional Pollutants
Pollutant of Concern
Boron
Chemical Oxygen Demand
Chloride
Iron
Manganese
Nitrate/Nitrite
Nitrogen Total, Kjeldahl
Sodium
Sulfate
Total Dissolved Solids
Source: CWA 308 Monitoring Data, [ERG, 2012h]; [ERG, 2013a].
6.7.5 Flue Gas Mercury Control Wastewater Pollutants of Concern
As described in Section 6.4, for ACT systems, the activated carbon can either be injected
upstream or downstream of the primary particulate removal system. When the activated carbon is
injected upstream of the primary parti culate removal system, the FGMC waste is captured with
the fly ash removed by the system. When the activated carbon is injected downstream of the
primary particulate removal system, the FGMC waste must be collected in a separate particulate
removal system, typically a fabric filter baghouse, and residual fly ash that passes through the
primary particulate removal system may also be captured in the system.
The FGMC waste/fly ash from either of these configurations can be handled using either
a wet sluicing system or dry handling system. Based on responses to the Steam Electric Survey,
EPA determined that more plants are operating ACT systems injecting the carbon upstream of the
primary particulate removal system compared to downstream injection. Additionally, EPA
determined that there are more plants operating wet sluicing systems for upstream carbon
injection compared to downstream injection. Based on these data, EPA determined that the
majority of plants generating FGMC wastewater are collecting the FGMC waste with the bulk of
the fly ash removed from the flue gas. Therefore, because EPA does not have any sampling data
specific to FGMC wastewater, EPA assumed that the pollutants of concern associated with
FGMC wastewater will be the same as those for fly ash transport water. Based on this
assumption, EPA identified 25 POCs associated with FGMC wastewater. Table 6-22 lists the
POCs identified for FGMC wastewater, which is the same as the list for fly ash transport water,
presented in Table 6-18.
6-32
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Section 6 - Wastewater Characterization and Pollutants of Concern
Table 6-22. Pollutants of Concern - Flue Gas Mercury Control Wastewater
Pollutant Group
Conventional Pollutants
Priority Pollutants
Nonconventional Pollutants
Pollutant of Concern
Oil and Grease
Total Suspended Solids
Arsenic
Beryllium
Chromium
Copper
Lead
Mercury
Nickel
Selenium
Zinc
Aluminum
Boron
Barium
Calcium
Chloride
Iron
Manganese
Molybdenum
Nitrate/Nitrite
Sodium
Titanium
Total Dissolved Solids
Vanadium
Yttrium
Source: [ERG, 2008]; [ERG, 2013a].
6.7.6 Nonchemical Metal Cleaning Wastes Pollutants of Concern
As part of the 1974 rulemaking, EPA collected characterization data associated with
chemical and nonchemical metal cleaning wastes. Based on the data collected during that
rulemaking, EPA determined that TSS, oil and grease (O&G), copper, and iron were pollutants
of concern for metal cleaning waste warranting regulation. As such, EPA set BPT limitations for
these four pollutants in discharges of metal cleaning wastes, including both nonchemical and
chemical cleaning wastes, as shown in Table 1-1. For additional information regarding the
pollutants that may be present in nonchemical metal cleaning wastes, see the 1974 Development
Document for Effluent Limitations Guidelines and New Source Performance Standards for the
Steam Electric Power Generating Point Source Category [U.S. EPA, 1974].
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Section 6 - Wastewater Characterization and Pollutants of Concern
Based on this assessment, EPA determined that TSS, O&G, copper, and iron are POCs
for nonchemical metal cleaning wastes. Table 6-23 presents the four POCs for nonchemical
metal cleaning wastes.
Table 6-23. Pollutants of Concern - Nonchemical Metal Cleaning Wastes
Pollutant Group
Conventional Pollutants
Priority Pollutants
Nonconventional Pollutants
Pollutant of Concern
Oil & Grease
Total Suspended Solids
Copper
Iron
Source: [U.S. EPA, 1974].
6.8 REFERENCES
1. Babcock & Wilcox Company. 2005. Steam: Its Generation and Use. 41st edition. Edited
by J.B. Kitto and S.C. Stultz. Barberton, Ohio. DCN SE02919.
2. Computer Sciences Corporation (CSC). 2013. Results of the ICP/MS Collision Cell
Method Detection Limit Studies in the Synthetic Flue Gas Desulfurization Matrix. (16
January). DCN SE03872.
3. Duke Energy. 201 la Industry Provided Sampling Data from Duke Energy's Belews
Creek Steam Station. (17 August). DCN SE01808.
4. Duke Energy. 201 Ib Industry Provided Sampling Data from Duke Energy's Allen Steam
Station. (17 August). DCN SE01809.
5. Eastern Research Group (ERG). 2008. Final Sampling Episode Report, Buckeye Power
Company's Cardinal Power Plant. (August 26). DCN SE02107.
6. Eastern Research Group (ERG). 2012a. Final Sampling Episode Report, Duke Energy
Carolinas' Belews Creek Steam Station. (13 April). DCN SE01305.
7. Eastern Research Group (ERG). 2012b. Final Sampling Episode Report, We Energies'
Pleasant Prairie Power Plant. (13 April). DCN SE01306.
8. Eastern Research Group (ERG). 2012c. Final Sampling Episode Report, Duke Energy
Miami Fort Station. (13 April). DCN SE01304.
9. Eastern Research Group (ERG). 2012d. Final Sampling Episode Report, Duke Energy
Carolinas' Allen Steam Station. (13 April). DCN SE01307.
10. Eastern Research Group (ERG). 2012e. Final Sampling Episode Report, Mirant Mid-
Atlantic, LLC's Dickerson Generating Station. (13 April). DCN SE01308.
11. Eastern Research Group (ERG). 2012f Final Sampling Episode Report, Allegheny
Energy's Hatfield's Ferry Power Station. (13 April). DCN SE01310.
12. Eastern Research Group (ERG). 2012g. Final Sampling Episode Report, RRI Energy's
Keystone Generating Station. (13 April). DCN SE01309.
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Section 6 - Wastewater Characterization and Pollutants of Concern
13. Eastern Research Group (ERG). 2012h. Final Power Plant Monitoring Data Collected
Under Clean Water Act Section 308 Authority ("CWA 308 Monitoring Data"). (30 May).
DCN SE01326.
14. Eastern Research Group (ERG). 2013a. Memorandum to the Steam Electric Rulemaking
Record: Pollutants of Concern Memorandum. (19 April). DCN SE02124.
15. Eastern Research Group (ERG). 2013b. Steam Electric Technical Questionnaire Database
("Steam Electric Survey"). (19 April). DCN SE01958.
16. Electric Power Research Institute (EPRI). 1998a. PISCES Water Characterization Field
Study, Sites D Report. TR-108892-V1. Palo Alto, CA. (August). DCN SE01820.
17. Electric Power Research Institute (EPRI). 1998b. PISCES Water Characterization Field
Study, Sites D Appendix. TR-108892-V2. Palo Alto, CA. (August). DCN SE01820A1.
18. Electric Power Research Institute (EPRI). 2006. Flue Gas Desulfurization (FGD)
Wastewater Characterization: Screening Study. 1010162. Palo Alto, CA. (March). DCN
SE01816.
19. Lemly, D.A., 1985. Toxicology of Selenium in a Freshwater Reservoir: Implications for
Environmental Hazard Evaluation and Safety. Ecotoxicology and Environmental Safety,
10: 314-338. DCN SE01363.
20. NCDENR. 2011. North Carolina Department of Environment and Natural Resources
(NCDENR). State Provided Sampling Data from North Carolina's Progress Energy
Roxboro Plant. (26 June). DCN SE01812.
21. U.S. EPA. 1974. Development Document for Effluent Limitations Guidelines and New
Source Performance Standards for the Steam Electric Power Generating Point Source
Category. Washington, D.C. (October). DCN SE02917.
22. U.S. EPA. 1982. Development Document for Effluent Limitations Guidelines and
Standards and Pretreatment Standards for the Steam Electric Point Source Category.
EPA-440-1-82-029. Washington, DC. (November). DCN SE02933.
23. U.S. EPA, 2000. Development Document for Effluent Limitations Guidelines and
Standards for the Centralized Waste Treatment Industry. (August). DCN SE02920.
24. U.S. EPA Office of Research and Development. 2006. Characterization of Mercury-
Enriched Coal Combustion Residues from Electric Generating Utilities using Enhanced
Sorbents for Mercury Control. (February). DCN SE01339.
25. U.S. EPA. 2008. Characterization of Coal Combustion Residues from Electric Utilities
Using Wet Scrubbers for Multi-Pollutant Control. EPA-600-R-08-077. (July). Available
online at: http://www.epa.gov/nrmrl/pubs/600r08077/600r08077.pdf. DCN SE02921.
6-35
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Section 7- Treatment Technologies and Wastewater Management Practices
SECTION 7
TREATMENT TECHNOLOGIES AND WASTEWATER
MANAGEMENT PRACTICES
This chapter provides an overview of treatment technologies and wastewater
management practices at steam electric power plants for flue gas desulfurization (FGD)
wastewater, fly ash and bottom ash handling, combustion residual landfill leachate, gasification
wastewater, and flue gas mercury control (FGMC) wastewater.
7.1 FGD WASTEWATER TREATMENT TECHNOLOGIES AND MANAGEMENT PRACTICES
During the Steam Electric Power Generating study and rulemaking, EPA identified 145
steam electric power plants that generate FGD wastewater. Of these plants, 117 (81 percent)
discharge FGD wastewater after treatment. EPA identified and investigated wastewater treatment
systems operated by steam electric power plants discharging FGD wastewater, as well as
operating/management practices that plants use to reduce the pollutants associated with
discharge of FGD wastewater. A list of the treatment technologies and management practices,
including a brief description of each, are included below. This section provides a detailed
description of each of the treatment technologies and management practices listed below.
• Surface Impoundments: Surface impoundments (e.g., settling ponds) remove
particulates from wastewater by means of gravity. Impoundments are typically sized
to reduce total suspended solids (TSS) and allow for a certain residence time within
the impoundment.
• Chemical Precipitation: In chemical precipitation systems, the wastewater is treated
in tank-based systems. Chemicals are added to enhance the removal of suspended
solids and to remove dissolved solids, particularly metals. The precipitated solids are
then removed from solution by coagulation/flocculation followed by clarification
and/or filtration.
• Biological Treatment: Power plants can also treat FGD wastewater using biological
treatment systems. EPA identified three types of biological treatment systems
currently used to treat FGD wastewater, including aerobic/anaerobic sequencing
batch reactors (target removals of organics and nutrients), fixed-film bioreactors
(target removals of nitrogen compounds and selenium), and suspended growth
systems (target removals of selenium and other metals).
• Vapor-Compression Evaporation System: This type of system uses a falling-film
evaporator (or brine concentrator) to produce a concentrated wastewater stream and a
distillate stream to reduce wastewater by 80 to 90 percent (with a pretreatment step)
and similarly reduce the discharge of pollutants. The concentrated wastewater may be
further processed in a crystallizer or spray dryer.
• Constructed Wetlands: Constructed wetlands are engineered systems that use natural
biological processes involving wetland vegetation, soils, and microbial activity to
reduce the concentrations of metals, nutrients, and TSS in wastewater.
• Design/Operating Practices Achieving Zero Discharge: EPA identified four
design/operating practices available enabling plants to eliminate the discharge of
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Section 7- Treatment Technologies and Wastewater Management Practices
FGD wastewater: 1) several variations of complete recycle, 2) evaporation
impoundments, 3) conditioning dry fly ash, and 4) underground injection.
• Other Technologies Under Investigation: EPA identified several other technologies
that have been evaluated for treatment of FGD wastewater, including iron
cementation, reverse osmosis, absorption media, ion exchange, and electro-
coagulation. Other technologies under lab oratory-scale study include polymeric
chelates, taconite tailings, and nano-scale iron reagents.
Most plants currently discharging FGD wastewater use surface impoundments for
treatment; however, the use of more advanced wastewater treatment systems is increasing due to
more stringent requirements imposed by some states and regions on a site-specific basis. Figure
7-1 shows the distribution of FGD wastewater management/treatment technologies reported in
the Questionnaire for the Steam Electric Power Generating Effluent Guidelines (Steam Electric
Survey) for the 145 plants that reported using a wet FGD scrubber system in 2009 or planning to
operate one by January 1, 2014. Because the majority of the FGD wastewater management/
treatment technologies are surface impoundments, chemical precipitation systems, biological
treatment, or zero discharge, EPA grouped the vapor-compression evaporation and constructed
wetlands with the "Other" technologies for Figure 7-1. For the purpose of Figure 7-1, to identify
the different treatment systems reported in the Steam Electric Survey, EPA grouped the systems
into the following categories:
• Surface Impoundments: This grouping includes systems comprising of one or more
impoundments where the impoundment is the only treatment unit. This grouping also
includes impoundments with chemical addition to control pH levels prior to
discharge. This grouping does not include systems containing impoundments as
treatment units in a more advanced treatment system (i.e., chemical precipitation,
biological treatment). This grouping does not include systems that achieve zero
discharge of FGD wastewater.
• Chemical Precipitation: This grouping includes systems using hydroxide and/or
sulfide precipitation as the treatment mechanism. This grouping also includes systems
using surface impoundments in combination with chemical precipitation systems and
systems with chemical precipitation in combination with aerobic biological treatment
for BODs removal or biological treatment designed for nutrient removal (i.e., not
designed for heavy metals removal). This grouping does not include systems with
chemical precipitation and anoxic/anaerobic biological treatment systems. This
grouping does not include systems that achieve zero discharge of FGD wastewater.
• Biological Treatment: This grouping includes systems using anoxic/anaerobic or
suspended growth biological treatment systems designed for the removal of heavy
metals. This grouping includes systems that also include surface impoundments
and/or chemical precipitation treatment units in combination with the biological
system. This grouping does not include systems that achieve zero discharge of FGD
wastewater.
• Other: This grouping includes systems using constructed wetlands or vapor-
compression evaporation treatment units. This grouping includes systems that also
include surface impoundments in combination with the constructed wetland/vapor-
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Section 7- Treatment Technologies and Wastewater Management Practices
compression evaporation system. This grouping does not include systems that achieve
zero discharge of FGD wastewater.
Zero Discharge: This grouping includes all FGD wastewater treatment systems that
achieve zero discharge, regardless of the treatment units (e.g., surface impoundments,
chemical precipitation) used to treat the wastewater prior to reuse. Chemical
precipitation systems using aerobic biological treatment to remove BOD were
classified as chemical precipitation; and
Zero Discharge
(28 plants,
Settling Pond
Other '• is; plsrts. 44:-:.i
(12 plants, 8%)
Biological
(Anoxic/Anaerobic)
(6 pi ants, 4%)
Cheirical Precipitation
(36 plants. 25%)
Source: Steam Electric Survey [ERG, 2013g]
Figure 7-1. Distribution of FGD Wastewater Treatment/Management Systems
Among 145 Plants Currently Operating Wet FGD Systems or Planned Wet
FGD Systems Operating by 2014
7.1.1 Surface Impoundments
Surface impoundments are designed to remove particulates from wastewater using
gravity sedimentation. For this to occur, the wastewater must stay in the impoundment long
enough for particles to fall out of suspension before being discharged from the impoundment.
The size and configuration of surface impoundments varies by plant; some surface
impoundments operate as a system of several impoundments, operated in series or in parallel,
while others consist of one large impoundment. Plants typically size the impoundments to
provide enough residence time to reduce the total suspended solids (TSS) levels in the
wastewater to a target concentration and to allow for a certain lifespan of the impoundment
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Section 7- Treatment Technologies and Wastewater Management Practices
based on the expected rate of solids buildup within the impoundment. Coal-fired power plants do
not typically add treatment chemicals to surface impoundments, other than to adjust the pH of
the wastewater before it exits the impoundment to bring it into compliance with National
Pollutant Discharge Elimination System (NPDES) permit limits.
Surface impoundments can reduce the amount of TSS in the wastewater discharge
provided sufficient residence time. In addition to TSS, surface impoundments can also reduce
some specific pollutants in the paniculate form to varying degrees in the wastewater discharge.
However, surface impoundments are not designed to reduce the amount of dissolved metals in
the wastewater. The FGD wastewater entering a treatment system contains significant
concentrations of several pollutants in the dissolved phase, including manganese, selenium, and
boron. These dissolved metals are not largely removed by the FGD wastewater surface
impoundments [ERG, 2008]. Additionally, the Electric Power Research Institute (EPRI) has
reported that adding FGD wastewater to ash impoundments reduces the settling efficiency of the
impoundment leading to increased TSS concentrations and therefore, increased concentrations of
other pollutants (e.g., metals), due to gypsum particle dissolution occurring in the impoundment
[EPRI, 2006]. EPRI has also reported that the FGD wastewater includes high loadings of volatile
metals that can affect the solubility of metals in the ash impoundment, thereby potentially
increasing the effluent metal concentrations [EPRI, 2006].
EPA compiled data for the 145 plants operating wet FGD systems, or planned wet FGD
systems operating by 2014, and the wastewater treatment systems used to treat the FGD
wastewaters generated. Based on these data, surface impoundments are the most commonly used
systems for managing FGD wastewater (approximately 44 percent). Most of these plants transfer
the FGD wastewater directly to a surface impoundment that also treats other wastestreams,
specifically fly and/or bottom ash transport water. Approximately 23 percent of plants managing
FGD wastewater with surface impoundments transfer the FGD wastewater to a segregated
surface impoundment specifically designated to treat FGD wastewater [ERG, 2013g]. These
plants either discharge the FGD wastewater effluent directly to surface waters from the
segregated FGD surface impoundment (with or without commingling with cooling water or other
large volume wastes streams) while others transfer the effluent to another impoundment,
potentially containing other combustion residual wastes (i.e., ash), for further settling and
dilution.
EPA has also identified plants that transfer the FGD wastewater to a surface
impoundment for initial solids removal and then pump the wastewater to a chemical precipitation
system or a biological treatment system for further treatment. As previously mentioned, because
these surface impoundments are treatment units in a more advanced wastewater treatment
system, EPA classifies these plants as "chemical precipitation" or "biological" rather than
"surface impoundments," respectively.
7.1.2 Chemical Precipitation
In a chemical precipitation wastewater treatment system, plants add chemicals to the
wastewater to alter the physical state of dissolved and suspended solids to help settle and remove
the solids. The specific chemical(s) used depends upon the type of pollutant requiring removal.
EPA identified 40 steam electric power plants using chemical precipitation systems to treat FGD
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Section 7- Treatment Technologies and Wastewater Management Practices
wastewater. Power plants commonly use the following three types of systems to precipitate
metals out of FGD wastewater:
• Hydroxide precipitation (40 plants);
• Iron coprecipitation (38 plants); and
• Sulfide precipitation (33 plants).
In a hydroxide precipitation system, plants add lime (calcium hydroxide) to elevate the
pH of the wastewater to a designated set point, helping precipitate metals into insoluble metal
hydroxides that can be removed by settling or filtration. Sodium hydroxide can also be used in
this type of system, but it is more expensive than lime and, therefore, not as common in the
industry.
Thirty-eight power plants use iron coprecipitation as a way to increase the removal of
certain metals in a hydroxide precipitation system. Plants can add ferric (or ferrous) chloride to
the precipitation system to coprecipitate additional metals and organic matter.35 The ferric
chloride also acts as a coagulant, forming a dense floe that enhances settling of the metals
precipitate in downstream clarification stages.
Sulfide precipitation systems use sulfide chemicals (e.g., trimercapto-s-triazine (TMT),
Nalmet® 1689, sodium sulfide) to precipitate and remove heavy metals, similar to the set of
metals removed in hydroxide precipitation. Plants operating sulfide precipitation systems can use
TMT, Nalmet® 1689, MetClear™, sodium sulfide, or other sulfide chemicals in the system. The
plants may test several different sulfide chemicals to determine the one most appropriate for their
treatment system. Sulfide precipitation can also provide more optimal removal of metals with
lower solubilities, such as mercury, than hydroxide precipitation or hydroxide precipitation with
iron co-precipitation. The EPA sampling data suggest that adding organosulfide to the FGD
wastewater can reduce dissolved mercury concentrations to the tens of parts per trillion [ERG,
2012b]. Sulfide precipitation is more effective than hydroxide precipitation in removing metals
with low solubilities because metal sulfides have lower solubilities than metal hydroxides.
Because sulfide precipitation is more expensive than hydroxide precipitation, plants usually use
hydroxide precipitation first to remove most of the metals, and then sulfide precipitation to
remove the remaining low solubility metals. This configuration overall requires less sulfide,
thereby reducing the expense for the bulk metals removal.
FGD wastewater chemical precipitation systems may include various stages of lime,
sulfide, and ferric chloride addition, as well as clarification stages. Some plants add all three
chemicals (i.e., lime, ferric chloride, and organosulfide) to a single reaction tank, whereas other
plants add the chemicals to separate tanks. The plants operating separate tanks may be targeting
different pH set points within the system for optimal precipitation of certain metals. For example,
We Energies' Pleasant Prairie Power Plant (Pleasant Prairie) adds hydrated lime to its FGD
wastewater in the first reaction tank of the treatment system, raising the pH from 5.5 to 8.5 S.U.
to precipitate soluble metals as insoluble hydroxides and oxyhydroxides. After primary
35 The remainder of this section discusses the use of ferric chloride, as ferrous chloride is not commonly used in the
steam electric industry. However, ferrous chloride could also be used in the place of ferric chloride.
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Section 7- Treatment Technologies and Wastewater Management Practices
clarification, the wastewater flows to a second reaction tank and the plant adds organosulfide and
hydrochloric acid, which drops the pH to around 7 S.U. Pleasant Prairie determined that adding
the organosulfide at a neutral pH removed more mercury compared to operating at a more basic
pH level [ERG, 2013c].
During its site visit program, EPA determined that the majority of steam electric power
plant permits include only TSS, pH, and oil and grease (O&G) limitations for FGD wastewater
based on the current Steam Electric ELGs BPT limits for low volume wastewater. For this
reason, 63 plants (44%) operate surface impoundments, as discussed previously, to remove TSS.
However, some steam electric power plant permits include limitations for specific metals due to
state or regional regulations or local limitations. Most effluent limits in NPDES permits for FGD
wastewater (other than TSS and O&G) are water-quality-based effluent limitations (WQBELs)
to meet applicable water quality standards. In these cases, a number of plants have opted to
install chemical precipitation systems designed and operated to target the specific metal or
metals included in the permit. For example, if the plant has a mercury effluent limitation, they
are more likely to operate sulfide precipitation, rather than just hydroxide precipitation or a
surface impoundment if they had only a limitation for TSS.
One example of a treatment system operating to meet only the BPT-based limitations for
TSS, pH, and O&G was AEP's Mountaineer plant, which operates a chemical precipitation
system to treat its FGD wastewater. In 2008, one year after the start-up of the FGD scrubbers and
the FGD wastewater treatment system, the plant went through a permit renewal process and the
state proposed to add a limit for mercury. Based on the proposed mercury limitations in the new
permit, AEP conducted a pilot study evaluating three different technologies that could be
installed as additional treatment downstream of the currently operating chemical precipitation
system. Mountaineer conducted the pilot study from July through December 2008. During the
first three months of the study, the mercury concentrations of the chemical precipitation system
effluent feeding the pilot tests averaged 1,300 parts per trillion (ppt). None of the three
technologies achieved the target effluent concentrations for the pilot testing. Therefore, AEP
took steps to optimize the solids removal in the chemical precipitation system, including adding
additional polymers and organosulfide. Using these optimization steps, AEP noted that "[t]he
combination of supplemental coagulation and organosulfide addition consistently yielded
approximately 80 percent of additional mercury reduction..." within the chemical precipitation
system [AEP, 2010].
In some cases, plants may experience a spike in concentrations for certain metals in their
untreated FGD wastewater, likely based on changes in fuels or operating conditions within the
FGD scrubber. EPA's data demonstrate that well operated systems maintain their chemical
precipitation effluent concentrations because they actively monitor their untreated wastewater for
target concentrations of certain metals allowing them to adjust the operation of the chemical
precipitation system, as necessary. Plants that actively monitor their untreated FGD wastewater
would be able to identify these excursions and adjust the chemical addition rates to treat the
wastewater to the required permit limitation. Some plants actively monitor the influent to the
treatment system and adjust chemical addition by including an equalization tank with a 24-hour
holding time as the first step in the treatment system. Alternatively, plants could monitor the
effluent prior to discharge to make sure that they are in compliance before discharge. For
example, Pleasant Prairie monitors the effluent from the system daily by collecting and analyzing
7-6
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Section 7- Treatment Technologies and Wastewater Management Practices
samples using an in-house Method DMA 80 mercury analyzer. The analyzer can generate results
in approximately six minutes [Michel, 2012]. The plant uses the mercury analyzer to alert
operators when mercury concentrations are at levels close to the plant's mercury permit limit;
therefore, the operators can adjust the system (e.g., chemical feed rates) to achieve additional
mercury removal. When the concentrations are close to the permit limits, the plant begins
discharging in the wastewater in batches. The plant transfers the wastewater to the effluent
storage tank and when the tank is full, the plant collects a sample of the wastewater to confirm it
is below the permit limit. Once the plant confirms the concentration is lower than the limit, the
plant discharges the wastewater from the effluent tank [ERG, 2013c].
Figure 7-2 presents a process flow diagram for a chemical precipitation system using
hydroxide precipitation, sulfide precipitation, and iron coprecipitation to treat FGD wastewater.
This system is designed to remove heavy metals and organic matter. A chemical precipitation
system with no sulfide precipitation stage would be similar, but without the sulfide addition
reaction tank.
For the system illustrated by Figure 7-2, the plant transfers the FGD wastewater from the
plant's solid separation/dewatering process to an equalization tank. This tank equalizes the
intermittent flows, allowing the plant to pump a constant flow of wastewater through the
treatment system. The equalization tank also receives wastewater from a filtrate sump, which
includes water from the gravity filter backwash and filter press filtrate.
The FGD wastewater is transferred in a continuous flow from the equalization tank to
reaction tank 1, where the plant adds hydrated lime to raise the pH of the wastewater from
between 5.5 - 6.0 S.U. to between 8.0 - 10.5 S.U. to precipitate the soluble metals as insoluble
hydroxides and oxyhydroxides. The reaction tank also desaturates the remaining gypsum in the
wastewater, which prevents gypsum scale formation in the downstream wastewater treatment
equipment.
From reaction tank 1, the wastewater flows to reaction tank 2, where the plant adds
organosulfide or inorganic sulfide. Plants can also reconfigure the treatment system by adding
the organosulfide upstream of the hydroxide precipitation step or adding a clarification step
between the two chemical addition steps.36
From reaction tank 2, the wastewater flows to reaction tank 3, where the plant adds ferric
chloride to the wastewater for coagulation and coprecipitation. The effluent from reaction tank 3
flows to the flash mix tank, where the plant adds polymer to the wastewater prior to transferring
it to the clarifier. Alternatively, the plant can add polymer directly to the wastestream as it enters
the clarifier or reaction tank 3. The polymer acts to flocculate fine suspended particles in the
wastewater.
36 Some plants may have a clarification step between reaction tank 1 and reaction tank 2 to remove the hydroxide
precipitates from the wastewater prior to adding organosulfide. In addition, plants may adjust the pH prior to sulfide
addition to target the removal of different metals.
7-7
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Section 7- Treatment Technologies and Wastewater Management Practices
FGD Wastewater
oo
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OkO
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I
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o
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• Wastewater Flow
Intermittent Wastewater Flow
Figure 7-2. Process Flow Diagram for a Hydroxide and Sulfide Chemical Precipitation System
-------
Section 7- Treatment Technologies and Wastewater Management Practices
The clarifier settles the solids that were initially present in the FGD wastewater as well as
the additional solids (precipitate) formed during the chemical precipitation steps. The system
may also include a sand filter to further reduce solids, as well as metals attached to the solids.
The system transfers the backwash from the sand filters to a filtrate sump and recycles it back to
the equalization tank at the beginning of the treatment system.
The plant collects the treated FGD wastewater in a holding tank and either discharges it
directly to surface waters or, in most cases, commingles it with other wastestreams prior to
discharge.
The plant transfers the solids that settle in the clarifier (clarifier sludge) to the sludge
holding tanks, after which the sludge is dewatered using a filter press. The plant then disposes of
the dewatered sludge, or filter cake, in an on-site landfill, and transfers the filtrate from the filter
press to a sump and recycles it back to the equalization tank at the beginning of the treatment
system.
7.1.3 Biological Treatment
Biological wastewater treatment systems use microorganisms to consume biodegradable
soluble organic contaminants and bind much of the less soluble fractions into floe. Pollutants
may be reduced aerobically, anaerobically, and/or by using anoxic zones. Based on the
information EPA collected during the rulemaking, steam electric power plants use two main
types of biological treatment systems to treat FGD wastewater: aerobic systems to reduce
biochemical oxygen demand (BODs) and anoxic/anaerobic systems to remove metals and
nutrients. These systems may consist of fixed film or suspended growth bioreactors, and operate
as conventional flow-through or as sequencing batch reactors (SBRs). This section describes the
wastewater treatment processes for each of these systems. These biological treatment processes
are typically operated downstream of a chemical precipitation system or a solids removal system
(e.g., clarifier, surface impoundment).
7.1.3.1 Aerobic Biological Treatment
Some plants operate aerobic biological treatment systems to reduce BODs in their FGD
wastewater. In a conventional flow-through design, the system continuously feeds the
wastewater to the aerated bioreactor. The plant may add chemicals to the wastewater before it
enters the bioreactor to adjust the pH levels and, in certain climates, feed the wastewater through
a heat exchanger to maintain a certain temperature to make sure the microorganisms are
operating at optimal levels [ERG, 2007]. The microorganisms in the reactor use the dissolved
oxygen from the aeration to digest the organic matter in the wastewater, thus reducing the BODs.
The digestion of the organic matter produces sludge, which the plant may dewater with a vacuum
filter to better manage its ultimate disposal. The treated wastewater from the system overflows
out of the reactor.
An SBR is a type of activated sludge treatment system that can reduce BODs and, when
operated to create anoxic zones under certain conditions, can also reduce nitrogen compounds
through nitrification and denitrification. Plants often operate at least two identical reactors
sequentially in batch mode. The treatment in each SBR consists of a four-stage process: fill,
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Section 7- Treatment Technologies and Wastewater Management Practices
aeration and reaction, settling, and decant. While one of the SBRs is settling and decanting, the
other SBR is filling, aerating, and reacting.
As an aerobic system, the SBR operates as follows. The filling stage of the SBR involves
transferring the FGD wastewater into a reactor that contains some activated sludge from the
previous reaction batch. During the aeration and reaction stages, the reactor is aerated and the
microorganisms reduce the BOD5 by digesting the organic matter in the wastewater. During the
settling phase, the plant stops aeration and the solids in the SBR settle to the bottom. The plant
then decants the wastewater off the top of the SBR and transfers it to surface water for discharge
or to additional treatment or reuses it in plant processes without further treatment. Additionally,
the plant removes and dewaters some of the solids from the bottom of the SBR, but retains some
of the solids in the SBR to keep microorganisms in the system.
7.1.3.2 Anoxic/Anaerobic Biological Treatment
Some coal-fired power plants use anoxic/anaerobic biological systems to reduce certain
pollutants (e.g., selenium, mercury, nitrates) more effectively than has been possible with surface
impoundments, chemical precipitation, or aerobic biological treatment processes. Figure 7-3
presents a process flow diagram for an anoxic/anaerobic biological treatment system. The
microorganisms in this system are susceptible to high temperatures in excess of 105 °F [Pickett,
2005]. Because of this susceptibility, some plants cool the FGD wastewater prior to entering the
biological system using heat exchangers or cooling impoundments. Based on data from EPA
sampling episodes, these plants generally include those in geographic locations with sustained
periods of maximum ambient temperatures greater than 90 °F [U.S. EPA, 2013].
7-10
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Section 7- Treatment Technologies and Wastewater Management Practices
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Section 7- Treatment Technologies and Wastewater Management Practices
anoxic zone (negative ORP) where denitrification as well as chemical reduction of selenium
(both selenate and selenite) occur [Pickett, 2006; Sonstegard, 2010]. The system maintains a pH
level in the bioreactor between 6.0 and 9.0 S.U. because extreme high or low pH levels could
affect the performance of the microbes and potentially allow nondesirable microbes to propagate
[ERG, 2012a].
When the microorganisms reduce the selenate and selenite to elemental selenium, it
forms nanospheres that adhere to the cell walls of the microorganisms. Because the activated
carbon bed retains the microorganisms within the bioreactor, the elemental selenium is
essentially fixed to the activated carbon until it is removed from the system. The microorganisms
can also reduce other metals, including arsenic, cadmium, and mercury, by forming metal
sulfides within the system [Pickett, 2006].
The bioreactor system typically contains multiple bioreactor cells. For example, the Duke
Energy Carolinas' Allen Steam Station and Belews Creek Steam Station have two stages of
bioreactor cells in series, as shown in Figure 7-3, but both stages of bioreactors contain multiple
cells in parallel. Plants usually require multiple bioreactors to provide the necessary residence
time to achieve the specified removals.
Periodically, the bioreactor must be backflushed to remove the solids and inorganic
materials that have accumulated within it. The flushing process involves flowing water upward
through the system, which dislodges the particles fixed within the activated carbon. The water
and solids overflow out of the top of the bioreactor and are removed from the system. This flush
water contains elevated levels of solids, with selenium adhered to it [Pickett, 2006], and will
likely need to be treated prior to discharge. Some plants send the backflush water to the
beginning of the chemical precipitation wastewater treatment system so that the system can
remove the solids (and adhered selenium) within the clarifier. Other plants transfer the backflush
water to a surface impoundment where the solids (and adhered selenium) settle out [ERG, 2010;
Jordan, 2008].
As the microorganisms denitrify the wastewater, nitrogen and carbon dioxide gases form,
which periodically build up and form pockets within the bioreactor. As a result, water flows
through channels, reducing microbial contact and increasing head-loss across the bioreactor, an
overall negative effect on the system [Sonstegard, 2010]. To remove these gas pockets, plants
occasionally perform a degassing operation by transferring water backwards through the cells,
similar to a backflush, but the flush is only long enough for the gas to "burp" out of the system
[Allen SER]. The system flush is long enough to lift the biomatrix and release entrained gases,
but short enough to avoid flushing any water out of the bioreactor [Sonstegard, 2010].
One plant has pilot tested another type of anoxic/anaerobic biological treatment system
that consists of suspended growth flow-through bioreactors instead of fixed-film bioreactors.
Both designs share the fundamental processes that lead to nitrification/denitrification and
reduction of metals in anoxic and anaerobic environments. Based on the results of the pilot test,
in January 2012, the plant commissioned a full-scale suspended growth bioreactor system to treat
FGD wastewater [ERG, 2013f].
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Section 7- Treatment Technologies and Wastewater Management Practices
Plants can also operate SBRs to achieve anoxic/anaerobic conditions. The SBR operation
is similar to the aerobic biological treatment system described above; however, the aeration stage
would be followed by periods of air on, air off, which creates aerobic zones for nitrification and
anoxic zones for denitrification to remove the nitrogen in the wastewater. According to the
treatment system vendor, SBR systems will denitrify the wastewaters, but the ORP in the system
is not managed at levels conducive to reducing metals. Therefore, these SBR systems will not
remove selenium (and other metals) as effectively as the fixed-film or suspended growth
bioreactor systems.
7.1.4 Vapor-Compression Evaporation System
Mechanical evaporators in combination with a final drying process can significantly
reduce the quantity of wastewater pollutants and volume discharged from certain process
operations at various types of industrial plants, including steam electric power plants, oil
refineries, and chemical plants. One type of evaporation system uses a falling-film evaporator
(also referred to as a brine concentrator) to produce a concentrated wastewater stream (i.e., brine)
and a reusable distillate stream. The concentrated wastewater stream may be further processed in
a crystallizer or spray dryer, in which the remaining water is evaporated. When used with a
crystallizer or spray dryer, this process generates a distillate stream and a solid by-product that
can then be disposed of in a landfill.
Steam electric power plants most often use vapor-compression evaporation systems to
treat wastestreams such as cooling tower blowdown and demineralizer waste; however, in 2009,
one plant in the United States began to operate a vapor-compression evaporation system to treat
FGD wastewater [ERG, 2013g]. Two other plants in the United States have installed, or are in
the process of installing, this technology [Jacobs Consultancy, 2012; Loewenberg, 2012].
Additionally, four coal-fired power plants in Italy are treating FGD wastewater with vapor-
compression evaporation systems [Rao, 2008; Veolia Water Solution, 2007]. Two other plants in
Italy also installed vapor-compression evaporation systems but subsequently determined that off-
site disposal is more economical.
Before entering the vapor-compression evaporation system, FGD wastewater is usually
pretreated to remove calcium and magnesium salts, as shown in Figure 7-4. Calcium and
magnesium salts in the FGD wastewater can pose difficulties for the forced-circulation
crystallizer. To prevent this, plants can pretreat the FGD wastewater using chemical precipitation
and a lime-softening process upstream of the brine concentrator. With water softening, the
magnesium and calcium ions precipitate out of the wastewater and are replaced with sodium
ions, producing an aqueous solution of sodium chloride that can be more effectively treated with
a forced-circulation crystallizer [Shaw, 2008]. See Section 7.1.2 for more specific information on
chemical precipitation systems.
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Section 7- Treatment Technologies and Wastewater Management Practices
Sodium
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Wastewater Prior to Vapor-Compression Evaporation
Figure 7-5 presents a process flow diagram for a vapor-compression evaporation system.
When a vapor-compression evaporation system is used to treat FGD wastewater, the first step is
to adjust the pH of the FGD wastewater to approximately 6.5 S.U. Additionally, some plants add
an antiscalant to the wastewater prior to the evaporation system [ERG, 2012d]. Following pH
adjustment, the FGD wastewater goes through a heat exchanger to bring the wastestream to its
boiling point. From the heat exchanger, the wastewater stream is sent to the deaerator, where the
noncondensable materials such as carbon dioxide and oxygen, are vented to the atmosphere
[ERG, 2012d].
From the deaerator, the wastestream enters the sump of the brine concentrator. Brine
from the sump is pumped to the top of the brine concentrator and enters the heat transfer tubes.
While falling down the heat transfer tubes, part of the solution is vaporized and then compressed
and comes in contact with the shell side of the brine concentrator (i.e., the outside of the tubes).
With the temperature difference between the compressed vapor and the brine solution, the
compressed vapor transfers heat to the brine solution, which flashes to a vapor, and the
compressed vapor cools and condenses as distilled water [ERG, 2012d].
The condensed vapor (i.e., distillate water) can be recycled back to the FGD process,
used in other plant operations (e.g., boiler make-up water), or discharged. If the plant uses the
distillate for other plant operations that generate a discharge stream (e.g., used as boiler make-up
and ultimately discharged as boiler blowdown), then the FGD process/wastewater treatment
system is not truly zero discharge. Therefore, operating a vapor-compression evaporation system
does not guarantee that the FGD process/wastewater treatment system achieves zero discharge.
The concentrated brine slurry from the brine concentrator tubes falls into the sump and is
recycled with the feed (FGD wastewater) to the top of the brine concentrator. Typically, the plant
continuously withdraws a small amount from the sump and transfers it to a final drying process.
To prevent scaling within the brine concentrator because of the gypsum in the FGD wastewater,
the brine concentrator is seeded with calcium sulfate. The calcium salts preferentially precipitate
onto the seed crystals instead of the tube surfaces of the brine concentrator. If the treatment
system is preceded by chemical precipitation and softening, the brine concentrator can typically
concentrate the FGD scrubber purge five to 10 times, which reduces the inlet FGD scrubber
purge water volume by 80 to 90 percent [Shaw, 2008]. However, without pretreatment, the brine
7-14
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Section 7- Treatment Technologies and Wastewater Management Practices
Deaerator
Vent to
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Figure 7-5. Process Flow Diagram for a Vapor-Compression Evaporation System
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Section 7- Treatment Technologies and Wastewater Management Practices
concentrator is not as effective because of boiling point rise (the increase in energy required to
concentrate the wastewater stream because of the additional calcium and magnesium salts or
other solids in the wastewater). For example, one plant operates only a clarifier prior to the
vapor-compression evaporation system. The brine concentrator reduces the inlet FGD scrubber
purge water volume only up to 53 percent [ERG, 2012c].
Plants typically consider three options for eliminating the brine concentrate: (1)
evaporating the brine in a brine crystallizer; (2) evaporating the brine in a spray dryer; or (3)
using the brine to condition (add moisture to) dry fly ash or other solids and disposing of the
mixture in a landfill.
Plants may use brine concentrators to treat a wastestream other than FGD wastewater
(e.g., cooling tower blowdown). For these non-FGD systems, the plant typically sends the
concentrated brine from the sump to a forced-circulation crystallizer to evaporate the remaining
water from the concentrate and generate a solid product for disposal.
Coal-fired power plants can avoid having to operate the chemical precipitation
pretreatment process by using a spray dryer to evaporate the residual wastestream from the brine
concentrator. Because the material generated from this process is hygroscopic (i.e., readily taking
up and retaining moisture), the solid residual from the spray dryer is typically bagged
immediately and disposed of in a landfill. Alternatively, the plant can combine the concentrated
brine wastestream with dry fly ash or other solids for disposal in a landfill. To do this, the plant
must generate enough dry fly ash to mix with the brine; otherwise, there will be brine remaining
that the plant must handle.
7.1.5 Constructed Wetlands
A constructed wetland treatment system is an engineered system that uses natural
biological processes involving wetland vegetation, soils, and microbial activity to achieve
reductions in the concentrations of metals, nutrients, and TSS in wastewater. A constructed
wetland typically consists of several cells that contain bacteria and vegetation (e.g., bulrush,
cattails, peat moss), which the steam electric plant selects based on the specific pollutants
targeted for removal. The vegetation completely fills each cell and produces organic matter (i.e.,
carbon) used by the bacteria. The bacteria reduce metals in the aqueous phase of the wastewater,
such as mercury and selenium, to their elemental state. The metals removed by the bacteria will
partition into the sediment, where they either accumulate or are absorbed by the vegetation in the
wetland cells [EPRI, 2006; Rogers, 2005].
High temperature, chemical oxygen demand (COD), nitrates, sulfates, boron, and
chlorides in the wastewater can adversely affect constructed wetlands' performance. To avoid
this, plants typically dilute the FGD wastewater with service water before it enters the wetland to
reduce the temperature of the wastewater and concentration of chlorides and other pollutants,
which can harm the vegetation in the treatment cells. Plants typically maintain the chlorides in a
constructed wetland treatment system below 4,000 mg/L. Because most plants operate their FGD
scrubber system to maintain chloride levels within a range of 10,000 - 20,000 ppm, they would
need to dilute the FGD wastewater prior to transferring it to a wetland system. EPA identified
three plants operating constructed wetlands to treat FGD wastewater. EPA has observed that
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these steam electric power plants tend to operate the FGD system at lower concentrations of
chlorides (e.g., 1,000 to 10,000 ppm). To do this, the plants purge FGD wastewater from the
system at a higher flow rate than they otherwise would do if operating the FGD system at a
higher chloride concentration level.
7.1.6 Design/Operating Practices Achieving Zero Discharge
During its engineering site visit program, EPA observed that some of the plants operating
wet FGD systems designed and/or managed the FGD system to eliminate the discharge of FGD
wastewater. EPA identified 28 plants (19%) achieving zero discharge of FGD wastewater. Based
on information collected as part of the Steam Electric Survey, EPA identified five design/
operating practices available to prevent the FGD wastewater discharge:
• Variations of complete recycle;
• Evaporation impoundments;
• Underground injection;
• Operation of both wet and dry FGD scrubber systems; and
• Dry fly ash conditioning.
This section discusses each of these practices below.
Complete Recycle
Most plants do not recycle their treated FGD wastewater within the FGD system because
of the elevated chloride levels in the treated effluent. Some plants, however, completely recycle
the FGD wastewater within the system without using a wastewater purge stream to remove
chlorides. Such plants generally do not produce a saleable solid product from the FGD system
(e.g., wallboard-grade gypsum). Because the plant is not selling the FGD solid by-product, and
therefore, is most likely disposing of it in a landfill, it has no specific chloride specifications for
the material. Therefore, the plant can operate the FGD system and solids separation/dewatering
process such that the moisture retained with the landfilled solids contains sufficient chlorides that
the plant does not need a separate wastewater purge stream. Transferring the FGD solids to the
landfill essentially serves as the chloride purge from the system.
From the information provided in the Steam Electric Survey, EPA determined that, of the
145 plants operating wet FGD systems, approximately 16 operate complete recycle systems and
do not discharge any FGD wastewaters to surface waters. Of these 16 plants, nine operate natural
or inhibited oxidation system, which generate calcium sulfite instead of calcium sulfate, and are
therefore more likely to dispose of the solids in a landfill.
Evaporation Impoundments
EPA identified approximately 10 plants located in the southwestern United States that use
evaporation impoundments to avoid discharging any FGD wastewaters to surface waters.
Because of the warm, dry climate in this region, the plants can transfer the FGD wastewater to
one or more impoundments where the water evaporates. The evaporation rate from the
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impoundments at these plants is greater than or equal to the flow rate of the FGD wastewater and
amount of direct precipitation entering the impoundments; therefore, there is no discharge.
Conditioning Dry Fly Ash
Many plants that operate dry fly ash handling systems need to add water to the fly ash to
suppress dust or improve handling and/or compaction characteristics. EPA identified six plants
that use FGD wastewater to suppress dust around landfills or to moisture condition fly ash prior
to landfill disposal [ERG, 2013g]. Another plant, discussed in Section 7.1.4, uses a vapor-
compression evaporation system in combination with conditioning dry fly ash to prevent
discharging FGD wastewater [ERG, 2013b]. The plant uses the vapor-compression evaporation
system to reduce the volume of the FGD wastewater and then mixes the concentrated brine
slurry with dry fly ash and disposes of it in a landfill.
Combination of Wet and Dry FGD Systems
Operating combined wet and dry FGD systems on the same unit or at the same plant can
eliminate the scrubber purge associated with the wet FGD process. The dry FGD process
involves atomizing and injecting wet lime slurry, which ranges from approximately 18 to 25
percent solids, into a spray dryer. The water contained in the slurry evaporates from the heat of
the flue gas within the system, leaving a dry residue that is removed from the flue gas by a fabric
filter (i.e., baghouse) [Babcock and Wilcox, 2005]. By operating a combination wet and dry
FGD system, the plant can use the FGD wastewater associated with the wet FGD system as
make-up water for the lime slurry feed to the dry FGD process, thereby eliminating the FGD
wastewater [McGinnis, 2009].
From its data collection activities, EPA identified three plants expected to operate dry and
wet FGD systems in combination on existing or planned units, eliminating the need to discharge
the wastewater associated with the wet FGD system [ERG, 2013g].
Underground Injection
Underground injection is a technique used to dispose of wastes by injecting them into an
underground well, an alternative to discharging wastewater to surface waters. One plant began
using underground injection to dispose of FGD wastewater in 2007, but it has not been
successful. Due to unexpected pressure issues and problems with building the wells due to
geological formations encountered (unrelated to the characteristics of the FGD wastewater), the
plant has not been able to continuously inject the wastewater. The plant operates a chemical
precipitation system as pretreatment for the injection system.37 When it is not injecting the FGD
wastewater, the plant transfers the effluent from the chemical precipitation system to the cooling
lake, which does not discharge to surface water (e.g. zero discharge) [ERG, 2013 A; ERG,
2013g]. Another plant also began injecting the FGD wastewater underground in 2010 [ERG,
2013g]. Underground injection is currently managed under the Underground Injection Control
(UIC) program. Underground disposal of FGD wastewater constitutes zero discharge to waters
of the United States.
Plant operates an iron coprecipitation system.
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7.1.7 Other Technologies Under Investigation
EPRI is conducting industry-funded studies to evaluate and demonstrate technologies that
can potentially remove trace metals from FGD wastewater. EPRI conducted pilot- and full-scale
optimization field studies on some technologies already used by coal-fired power plants to treat
FGD wastewater, such as chemical precipitation (organosulfide and iron coprecipitation),
constructed wetlands, and an anoxic/anaerobic biological treatment system. EPRI is also
conducting laboratory- and pilot-scale studies for other technologies that can potentially remove
metals from FGD wastewaters, which include iron cementation, reverse osmosis, absorption
media, ion exchange, and electro-coagulation. EPA discusses each of these technologies below.
Iron andSulfide Additives with Micro filtration
EPRI conducted bench- and pilot-scale testing of a process to aid in removing mercury
from FGD wastewater. This process involved iron coprecipitation (e.g., ferric chloride addition)
and organosulfide addition, common in currently operating chemical precipitation systems, but
added microfiltration to determine if that would improve solids removal over conventional
clarification and media filtration. Microfiltration typically targets removing particles between 0.1
and 2 microns. Incorporating sludge recirculation theoretically increases particle size of the
resulting precipitates, resulting in better solids removal in conjunction with microfiltration. EPRI
determined that adding microfiltration may help remove fine-particle mercury that passes
through media filters [EPRI, 2009a].
Iron Cementation
EPRI conducted bench-scale testing of the metallic iron cementation treatment
technology as a way to remove all species of selenium from FGD wastewater. EPRI believes this
process may also effectively remove mercury. The iron cementation process consists of
contacting the FGD wastewater with an iron powder, which reduces selenium to its elemental
form (i.e., cementation). The pH of the wastewater is then raised to form metal hydroxides, and
the wastewater is filtered to remove the precipitated solids. The iron powder used in the process
is separated from the wastewater and recycled back to the cementation step. From the initial
studies, EPRI concluded that the metallic iron cementation approach is promising for treating
FGD wastewater for multiple species of selenium, including selenite, selenate, and other
unknown selenium compounds [EPRI, 2008b].
EPRI continued its study of iron cementation by specifically designing a pilot-scale
system to remove selenium and installing the prototype at a plant burning coal from the powder
river basin with FGD wastewater containing high levels of total dissolved solids (TDS), sulfate,
magnesium, nitrate/nitrite-nitrogen, and selenium. Additionally, EPRI evaluated the
effectiveness of the pilot-scale treatment system under continuous flow conditions. The study
showed that iron cementation does reduce selenium, specifically at a lower pH and a greater
hydraulic retention time. EPRI stated that increasing the hydraulic retention time improves the
dissolution of the metallic selenium ion. The study results also show that selenium removal and
iron dissolution are directly related; however, the pilot-scale system was unable to duplicate the
selenium removal levels observed in the previous bench-scale testing described above. Under
ideal operating conditions, the bench-scale testing showed that iron cementation reduced
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Section 7- Treatment Technologies and Wastewater Management Practices
dissolved selenium to less than 0.05 mg/L; however, the pilot-scale testing's lowest selenium
effluent concentration was 0.159 mg/L. Additionally, EPRI also evaluated mercury removals
from a limited data set. EPRI found that mercury was significantly reduced (by a range of 84 to
97 percent) in the iron reactor [EPRI, 2009b].
Reverse Osmosis
Reverse osmosis systems are currently in use at steam electric power plants, usually to
treat boiler make-up water or cooling tower blowdown wastewaters. EPRI identified a high-
efficiency reverse osmosis (HERO™) process that operates at a high pH, allowing the system to
treat wastewaters with high silica concentrations without scaling or membrane fouling because
silica is more soluble at higher pHs. The wastewater undergoes a water-softening process to raise
its pH before entering the HERO™ system.
Although the HERO™ system is currently in use in the industry to treat steam electric
power plant cooling tower blowdown wastewater, its use for FGD wastewater is potentially
limited due to the osmotic pressure of the FGD wastewater resulting from the high
concentrations of chlorides and IDS [EPRI, 2007]. Although many plants may not be able to use
the HERO™ system to treat FGD wastewater, some plants with lower TDS and chloride
concentrations may be able to. The HERO™ system is of particular interest for treating boron in
FGD wastewaters because boron becomes ionized at an elevated pH and, therefore, could be
removed using a reverse osmosis system [EPRI, 2007].
Sorption Media
The drinking water industry uses sorption media to remove arsenic from the drinking
water. Because of its success at removing similar pollutants found in FGD wastewater,
specifically arsenic, EPRI reviewed sorption media technologies to determine whether they are
applicable for treating FGD wastewater. These sorption processes adsorb pollutants onto the
media's surface area using physical and chemical reactions. EPRI determined the most effective
adsorbents are metal-based single-use products, which can be disposed of in nonhazardous
landfills. EPRI also determined granular ferric oxide or hydroxide- and titanium-based oxides are
the most prevalent adsorbent at the time of the study. Ferric- and titanium-based media
effectively remove both common forms of arsenic (arsenate and arsenite) and selenium (selenite)
over a wide pH range [EPRI, 2007].
EPA identified one plant that treats its FGD wastewater with a chemical precipitation
system followed by a full-scale treatment unit that uses cartridge filters in combination with two
sets of adsorbent media specifically designed to enhance removals of metals. After passing
through three sets of cartridge filters (3-micron, 1-micron, and then 0.2 micron), the FGD
wastewater passes through a carbon-based media that adsorbs mercury, and then through a ferric
hydroxide-based media that adsorbs arsenic, chromium, and other metals. The adsorbent media
reportedly achieves a maximum effluent concentration of 14 parts per trillion for mercury.
[Smagula, 2010]
According to Siemens, the vendor of the adsorption media technology used in the full-
scale operation, the capital costs for a system including the two sets of adsorption media could
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Section 7- Treatment Technologies and Wastewater Management Practices
range from $200,000 to $2,000,000 dollars, depending on the flow rate, influent concentrations,
and system configurations. Siemens estimates that the O&M costs for the carbon-based media
are approximately $2 per 1,000 gallons treated and the O&M costs for the ferric hydroxide media
are approximately $1 per 1,000 gallons treated. [Schultz, 2013]
Ion Exchange
Ion exchange systems are currently in use at power plants to pretreat boiler make-up
water. Ion exchange systems remove specific constituents from wastewater; therefore, the system
can target specific metals to be removed. The ion exchange resin works by substituting one ion
for another on a specific resin, which must be replaced or regenerated when full [AEP, 2010].
The typical metals targeted by ion exchange systems include boron, cadmium, cobalt, copper,
lead, mercury, nickel, uranium, vanadium, and zinc. Although the ion exchange process does not
generate any residual sludge, it does generate a regenerant stream that contains the metals
stripped from the wastewater [AEP, 2010].
In 2008, a pilot test was performed that evaluated mercury removals from filtration and
ion exchange. The system was successful in removing trace mercury from FGD wastewater;
however, the filtration process and not the ion exchange system removed most of the colloidal
mercury [Goltz, 2009]. Additionally, EPA identified one plant that tested two ion exchange
resins for treating FGD wastewater, specifically mercury removal. The plant determined that
while the resin can remove dissolved mercury, it is not effective at removing particulate or
colloidal mercury [AEP, 2010].
EPA identified one plant that has installed ion exchange systems to treat FGD
wastewater. This plant operates a full-scale ion exchange system that selectively targets the
removal of boron, in conjunction with a chemical precipitation treatment stage to remove
mercury and other metals, and an anaerobic biological treatment stage to remove selenium
[ERG, 2013f].
Electro-Coagulation
Electro-coagulation uses an electrode to introduce an electric charge to the wastewater,
which neutralizes the electrically charged colloidal particles allowing them to precipitate out of
solution. These systems typically use aluminum or iron electrodes, which dissolve into the
wastestream during the process. The dissolved metallic ions precipitate with the other pollutants
in the wastewater and form insoluble metal hydroxides. EPRI believes additional polymer or
supplemental coagulants may need to be added to the wastewater depending on the specific
characteristics. These systems are typically used to treat small wastestreams, ranging from 10 to
25 gpm, but may also be able to treat wastestreams of up to 50 or 100 gpm [EPRI, 2007].
Other Technologies
EPA obtained only limited information on other technologies under laboratory-scale
study, including polymeric chelates, taconite tailings, and nano-scale iron reagents. In addition,
EPRI is investigating various physical treatment technologies, primarily to remove mercury,
including filtration [EPRI, 2008a].
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1.2 FLY ASH HANDLING, MANAGEMENT, AND TREATMENT TECHNOLOGIES
During the Steam Electric Power Generating study and rulemaking, EPA identified and
investigated fly ash handling systems operated by coal-, petroleum coke-, and oil-fired steam
electric power plants to collect and convey fly ash, that are designed to minimize or eliminate the
discharge of pollutants in fly ash handling transport water. As part of the proposed rulemaking,
EPA considered chemical precipitation for the treatment of fly ash transport water. However,
EPA has not identified any plants using this treatment technology to treat fly ash transport water,
although EPA has reviewed two literature sources that describe laboratory- or pilot-scale tests
using the technology. Upon reviewing the discharge flow rate for fly ash transport water;
however, EPA determined that the capital and operating and maintenance (O&M) costs
associated with treatment were comparable to the costs of converting to dry handling
technologies, despite being less effective at removing pollutants. Therefore, EPA did not select
chemical precipitation as a treatment technology option for fly ash in this proposed rule. A list of
the fly ash handling technologies evaluated by EPA, including a brief description of each, are
included below. This section describes in detail the fly ash handling technologies listed below.
• Wet Sluicing Systems: These systems convey fly ash wet using water-powered
hydraulic vacuums that pull the fly ash from the hopper to a separator/transfer tank,
where the fly ash combines with the transport water flowing through the sluice pipes.
Plants usually direct the resulting sluice to a surface impoundment.
• Wet Vacuum Pneumatic Systems: These systems convey dry fly ash to a silo using
water-powered hydraulic pumps to withdrawal fly ash from the hopper and filter-
receivers to collect the fly ash dry.
• Dry Vacuum Systems: System that uses a mechanical exhauster to move air, below
atmospheric pressure, to pull the fly ash from the hoppers and convey it directly to a
silo.
• Pressure Systems: These systems convey dry fly ash to a silo using air produced by a
positive displacement blower directly to a silo.
• Combined Vacuum/Pressure Systems: These systems use a dry vacuum system to pull
ash from the hoppers to a transfer station, where is introduced to a high pressure
conveying line that conveys the dry ash directly to a silo.
• Mechanical Systems: Manual or systematic systems plant's operating units with a low
volume of fly ash operate remove fly ash from the hopper.
Coal-, petroleum coke-, and oil-fired power plants use particulate control technologies
such as electrostatic precipitators (ESPs), baghouse filters, or venturi-type wet scrubbers to
remove fly ash particles from the flue gas. Section 4 discusses the various types of fly ash
collection methods used in the Steam Electric Industry. After collection, fly ash particles transfer
to hoppers where plants transport fly ash via wet sluicing, dry handling, or a combination of both
to its next destination. From information provided in the Steam Electric Survey, EPA determined
that 481 coal-, petroleum coke-, and oil-fired power plants, corresponding to 1,074 coal- and
petroleum coke-fired units and 30 oil-fired units, generate fly ash. Most of these plants
(approximately 70 percent) currently transport fly ash from all of their coal-, petroleum coke-, or
oil-fired steam electric generating units using dry handling systems or other processes that do not
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Section 7- Treatment Technologies and Wastewater Management Practices
require wet sluicing. As shown in Figure 7-6, approximately 19 percent of coal- and petroleum
coke-fired units operate wet sluicing only systems to collect fly ash, whereas half of the oil-fired
units operate wet sluicing systems. Based on survey responses, the numbers of plants wet
sluicing fly ash will decline by 2014. From survey data, EPA identified nine plants
(corresponding to 18 coal-fired units) operating wet sluicing systems that will convert from wet
to all dry handling operations by January 2014. Additionally, from publicly available data, ERG
identified another eight plants, corresponding to 39 coal-fired units, that announced they will
convert from wet to all dry handling operations [ERG, 2013d]. Plants operating dry handling
systems typically sell the collected fly ash to available markets or condition it with moisture
prior to disposal in a landfill. For Figure 7-6, EPA grouped each coal- petroleum coke-, and oil-
fired generating unit into one of the following three categories based on the type of fly ash
handling system operated by the unit:
• Units with wet sluicing systems only;
• Units with any other type(s) of handling system listed above (excluding wet sluicing);
and
• Units that have multiple fly ash handling systems, including wet sluicing.
Middling (165.15'.)
Coal- ami Pelrokum Cokc-Klml I'nlts
Oil-Flm) Vnih
Source: Steam Electric Survey [ERG, 2013g].
Figure 7-6. Distribution of Fly Ash Handling Systems for Coal-, Petroleum Coke-
and Oil-Fired Units in the Steam Electric Industry
Based on information provided in the Steam Electric Survey, the number of plants
installing fly ash handling systems other than wet sluicing systems on new units, or converting
existing units, is increasing due to their ability to market fly ash and reduce water consumption.
Excluding wet sluicing systems, the most common type of fly ash handling system currently in
operation is the dry vacuum system (approximately 49 percent of non-wet-sluicing systems).
Figure 7-7 shows the distribution of fly ash handling systems, excluding any units with wet
sluicing systems only or units with combination wet and dry handling systems, reported in the
Steam Electric Survey for coal-, petroleum coke-, and oil-fired units. EPA grouped other
handling systems, mechanical systems, and a combination of multiple systems, excluding wet
sluicing, as "Other/Mechanical" in Figure 7-7.
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Section 7- Treatment Technologies and Wastewater Management Practices
CWltt Medunicd
(10. :!••>
C'ofll and Petitileiim Coke Fired I'nits
oil E iml t nils
Source: Steam Electric Survey [ERG, 2013g],
Figure 7-7. Distribution of Fly Ash Handling System Types Other Than Wet
Sluicing for Coal-, Petroleum Coke-, and Oil-fired Units Reported in the
Steam Electric Survey
The following sections discuss fly ash handling systems currently operating in the
industry, including wet sluicing systems and systems that minimize or eliminate the need for fly
ash transport water.
7.2.1 Wet Sluicing System
In a wet sluicing system, water-powered hydraulic vacuums create the vacuum for the
initial withdrawal of fly ash from the hoppers. The vacuum pulls the ash to a separator/transfer
tank, where the fly ash combines with the transport water flowing through the sluice pipes. The
sluice pipes transfer the resulting fly ash slurry to an ash impoundment. Section 6.2.3 describes
wet sluicing operations in the steam electric industry in more detail.
Fly ash transport water is typically treated in large surface impoundments, either
completely separate from or commingled with other combustion residual wastes. Impoundments
vary in size, capacity, age, and most impoundments receive other plant wastewater (e.g., boiler
blowdown, cooling water, low volume wastewater). Plants typically size the impoundments to
provide enough residence time to reduce the TSS levels in the wastewater to meet the discharge
requirement and to allow for a certain lifespan of the impoundment based on the expected rate of
solids buildup within the impoundment.
Surface impoundments can reduce the amount of TSS in the wastewater discharge
provided sufficient residence time. In addition to TSS, surface impoundments can also reduce
some specific pollutants in the particulate form to varying degrees in the wastewater discharge.
However, surface impoundments are not designed to reduce the amount of dissolved metals in
the wastewater. While most plants discharge the overflow from the surface impoundment, some
plants reuse a portion, or all, of the surface impoundment effluent as make-up for the fly ash
transport water system. Additionally, some plants reuse the effluent for other plant operations. In
these cases, much like discharged ash transport water, recycled transport water is often treated
only via settling. Some plants, however, also have pH control systems to adjust the pH of the
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Section 7- Treatment Technologies and Wastewater Management Practices
impoundment or the impoundment effluent stream to mitigate the potential for corrosion of the
boiler and ash handling equipment.
Power plants operate and maintain the impoundments in varying ways. For example,
some plants constantly remove settled ash solids from the impoundment inlet and stack them on
the sides of the impoundment to dewater and build up the height of the impoundment.
Alternatively, some plants periodically dredge the impoundment to remove the ash from the
bottom and transfer the solids off site for disposal or to an on-site landfill, or use the solids to
build up the height of the impoundment. Finally, some plants may not dredge the impoundment,
but leave the ash in the impoundment permanently and, when the impoundment reaches its
capacity, build a new ash impoundment and decommission the old impoundment.
7.2.2 Wet Vacuum Pneumatic System
Wet vacuum pneumatic systems are fly ash handling systems that use water-powered
hydraulic vacuums to create the vacuum for the initial withdrawal of fly ash from the hoppers,
similar to wet sluicing systems. However, the fly ash is not directed to a separator/transfer tank
and is not combined with the water flowing through the sluice pipes. Instead, the fly ash is
captured by a filter-receiver (i.e., bag filter with a receiving tank) placed before the junction
where the fly ash would have been mixed with the sluice water. Wet vacuum pneumatic systems
are able to convey dry ash up to 50 tons per hour (tph) and 500 feet [Mooney, 2010]. From the
filter-receiver tank, the system deposits the fly ash into a silo. The silo receiving the ash is
equipped with an exhauster that displaces the air from the vacuum created by the hydraulic pump
and a baghouse filter that captures the fly ash in the silo.
From the silo, the fly ash is either sold to an available market or moisture conditioned and
sent to a landfill. For unloading the ash for sale or conditioning, silos are usually equipped with
dry unloaders, wet unloaders, or a combination of unloading equipment for each disposal
method. The dry unloaders are conical shaped spouts, with a vacuum system to control fugitive
dust. The system loads the ash, with a moisture content of less than one percent, from the spout
into vacuum-sealed trucks, which transport the ash to the market destination. Wet unloaders use
pugmills to simultaneously unload the fly ash and increase the moisture content of the ash by
conditioning it with water. Pugmills condition the fly ash to between 15 and 20 percent moisture
before it is unloaded into uncovered dump trucks. Responses in the Steam Electric Survey show
that plants use the following types of water to moisture condition fly ash at silo locations:
• Raw intake water;
• Intake water that is treated prior to use;
• Cooling tower blowdown;
• General runoff;
• Floor drain wastewater;
• Leachate;
• Recycled process water;
• FGD wastewater; and
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Section 7- Treatment Technologies and Wastewater Management Practices
• Bottom ash transport water.
After moisture conditioning and loading, the trucks transport the ash to the landfill. Some
silos are equipped with both wet and dry unloading capabilities for flexibility with the fly ash
market.
The wet vacuum pneumatic system is not commonly installed on new units; however, the
system is attractive to plants that are converting existing units from wet to dry fly ash handling
because it allows the plants to reuse the existing vacuum source. The bag filters used to collect
the fly ash prior to mixing with the vacuum water are unable to remove 100 percent of the fly
ash; therefore, a small amount of fly ash contaminates the water generated from the system.
Different from fly ash transport water associated with wet sluicing systems, whose purpose is to
transport ash to an impoundment or other treatment, the purpose of the wet vacuum pneumatic
vacuum water is strictly to create the vacuum to move the ash to the silo, and not to transport the
ash to other locations outside of the system. While this stream is contaminated with a small
amount of carryover fly ash, according to survey responses, most plants operating this type of
system transfer the wastewater to an impoundment and reuse the overflow in the wet vacuum
pneumatic system.
7.2.3 Dry Vacuum System
Dry vacuum systems use a mechanical exhauster to move air, below atmospheric
pressure, to pull the fly ash from the hoppers and convey it directly to a silo. Dry vacuum
systems can convey dry ash up to 60 tph and typically up to 1,000 feet [Mooney, 2010]. From
discussions with fly ash handling vendors, EPA determined that some dry vacuum systems can
convey ash up to 1,500 feet (at 30 to 50 tph), depending on capacity requirements, line
configuration, and plant altitude [McDonough, 2011]. The fly ash empties from the hoppers into
the conveying system via a material handling valve. Similar to the silo configuration described in
Section 7.2.2, the silo is equipped with an aeration system and baghouse filter to receive the fly
ash from the hopper. From the silo, the plant either sells the fly ash or disposes of it in a landfill.
The unloading procedures described in Section 7.2.2 also apply to the dry vacuum system. See
Figure 7-8 for a schematic of a typical dry vacuum fly ash handling system set-up.
Dry vacuum systems have fewer components than pressure systems, allowing for more
flexibility for installing them under existing hoppers. Dry vacuum systems can also start and stop
automatically during operation, due to the components and nature of the vacuum system.
Vacuum systems maintain cleaner operations than other conveyance methods because any leaks
simply pull ambient air into the system [Babcock and Wilcox, 2005].
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Section 7- Treatment Technologies and Wastewater Management Practices
Storage, Fluidiiing &
Withdrawal Systems
Vacuum Systems
One-Way
SK'" Valve Line
Graphic reprinted with permission from FLSmidth Inc. [FLSmidth, 2012].
Figure 7-8. Schematic of Dry Vacuum, Pressure, and Combined Vacuum/Pressure System
7.2.4 Pressure System
A pressurized system uses air produced by a positive displacement blower to convey ash
directly from the hoppers to a silo. Each hopper collecting ash is equipped with airlock valves
that transfer the fly ash from low pressure to high pressure in the conveying line, shown in
Figure 7-9. The airlock valves are transfer points that accept ash at a low pressure, separate it
from the air pressure in the bottom of the hoppers, and then release the ash to the high pressure
conveying line [Babcock and Wilcox, 2005]. Once in the conveying line, the system transports
the fly ash directly to the silo. Because of the high-pressure air, the aeration system at the silo is
less sophisticated than those used for wet vacuum pneumatic systems (Section 7.2.2), because a
vacuum is not involved in the operation. From the silo, the plant either sells the fly ash or
disposes of it in a landfill. The unloading procedures described in Section 7.2.2 also apply to the
pressure system. See Figure 7-8 for a schematic of a typical pressure fly ash handling system set-
up.
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Section 7- Treatment Technologies and Wastewater Management Practices
To Flyash
Hopper
Aeration Stone
To
• Conveying
Pipe
Equalizer Valve
Upper Chamber
Aeration Stone
Cut-off Gate
Lower Chamber
Lower Gate
Conveying Pipe
(Intake Tee)
Graphic reprinted with permission from Steve Stultz [Babcock and Wilcox, 2005].
Figure 7-9. Pressure System Airlock Valve
Plants use pressure systems to convey more ash longer distances compared to a dry
vacuum systems: 100 tph of fly ash for distances up to 5,000 feet [Mooney, 2010]. Depending on
the conveying capacity requirements, pressurized systems can convey ash up to 8,000 feet
[McDonough, 2011]. The airlock valves (see Figure 7-9) at the bottom of the hoppers, however,
require a significant amount of available headspace for installation; therefore, not all plants
currently operating wet sluicing systems would be able to easily install pressure systems without
significant capital investment to raise the bottom of the hopper. Additionally, pressure systems
are not able to stop and start automatically because airlock valves require manual stop and
restart. Pressure systems can also experience leaks of fine ash particulates, usually at the piping
joints due to the high pressure in the conveying line [Babcock and Wilcox, 2005].
7.2.5 Combined Vacuum/Pressure System
Combined vacuum/pressure fly ash handling systems utilize both dry vacuum and
pressure systems. A mechanical exhauster moves air, below atmospheric pressure, to pull the fly
ash from the hoppers, similar to the dry vacuum system. After a short distance, approximately
800 feet or less, the system directs the fly ash to an intermediate transfer vessel, such as a filter
separator, where it transfers the ash from the vacuum (low pressure) to ambient pressure. From
the filter separator, the system transfers the fly ash to airlock valves that convey the ash to the
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high pressure conveying line. This conveying line can convey ash up to 8,000 feet [McDonough,
2011] directly to a silo. Because the second portion of the combination system is a pressure
system, the aeration system at the silo is less sophisticated than for a dry vacuum system, as
described above for the pressure system. From the silo, the plant either sells the fly ash or
disposes of it in a landfill. The unloading procedures described in Section 7.2.2 also apply to the
combined vacuum/pressure system. See Figure 7-8 for a schematic of a typical combined
vacuum/pressure fly ash handling system set-up.
Plants use combination systems to transport fly ash longer distances than vacuum systems
alone can, while retaining the space advantages of the dry vacuum system (i.e., no additional
headspace required under the hopper). Manual stop and restart is still required to transfer fly ash
from the vacuum to the pressure system. Additionally, leaks of fine ash particles will also occur
at the piping joints due to the high-pressure portion of the system [Babcock and Wilcox, 2005].
7.2.6 Mechanical System
Mechanical fly ash handling systems usually service units that generate a low volume of
fly ash. These units are usually oil-fired units, which typically produce less ash than coal-fired
units. Mechanical systems include any manual or systematic approach to removing fly ash.
Based on responses to the Steam Electric Survey, the systems include periodic scheduled
cleanings of the boiler or manual removal. Manual removal procedures include scraping the sides
of the boilers with sprayers or shovels, then collecting and removing the fly ash to an
intermediate storage destination or sending it to a landfill.
EPA is also aware of one plant that retrofitted an oil unit with a mechanical system that
included collecting fly ash with vactor trucks. A vactor truck is a vacuum with a portable pump
to collect the fly ash from the roll-off dumpster. The collection system includes vacuum piping
that transports fly ash in the bottom of the hoppers to a roll-off vacuum container. For plants with
multiple hoppers, the fly ash is conveyed to the roll-off vacuum container one hopper at a time
by closing the valves below the other hoppers. A vactor truck connects to the roll-off container,
vacuums the fly ash to the truck, and disposes of the fly ash off site. Steam electric power plants
can operate this system themselves or contract the vactor truck operation and off-site disposal to
an outside vendor [ERG, 2013g].
7.3 BOTTOM ASH HANDLING, MANAGEMENT, AND TREATMENT TECHNOLOGIES
During the Steam Electric Power Generating study and rulemaking, EPA identified and
investigated bottom ash handling systems operated by coal-, petroleum coke-, and oil-fired steam
electric power plants to collect and convey bottom ash, that are designed to minimize or
eliminate the discharge of pollutants associated with bottom ash transport water. As part of the
proposed rulemaking, EPA considered chemical precipitation for the treatment of bottom ash
transport water. However, upon reviewing the discharge flow rate for bottom ash transport water,
EPA determined that the capital and O&M costs associated with treatment were comparable to
the costs of converting to dry handling or closed-loop recycle technologies, despite being less
effective at removing pollutants. Therefore, EPA did not select chemical precipitation as a
treatment technology option for bottom ash in this proposed rule. A list of the bottom ash
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Section 7- Treatment Technologies and Wastewater Management Practices
handling technologies evaluated by EPA, including a brief description of each, are included
below. This section describes in detail the bottom ash handling technologies listed below.
• Wet Sluicing Systems: These systems convey bottom ash wet from a quench bath
underneath the boiler via slurry lines. Plants usually direct the resulting sluice to a
surface impoundment.
• Mechanical Drag System: These systems are located directly underneath the boiler.
The bottom ash is collected in a water quench bath. A drag chain conveyor pulls the
bottom ash out of the water bath on an incline to dewater the bottom ash.
• Remote Mechanical Drag System: These systems transport bottom ash using the same
processes as wet sluicing systems to a remote mechanical drag system. A drag chain
conveyor pulls the bottom ash out of the water bath on an incline to dewater the
bottom ash.
• Dry Vacuum or Pressure System: These systems transport bottom ash from the boiler
to a dry hopper without using any water. Air is percolated through the ash to cool it
and combust unburned carbon. Cooled ash then drops to a crusher and is conveyed
via vacuum or pressure to an intermediate storage destination.
• Vibratory Belt System: Bottom ash deposits on a vibratory conveyor trough, where
the ash is air cooled and ultimately moved through the conveyor deck to an
intermediate storage destination.
• Mechanical Systems: Manual or systematic systems plant's operating units with a low
volume of bottom ash operate remove bottom ash from the hopper.
• Complete Recycle: Manual or systematic systems plant's operating units with a low
volume of fly ash operate remove fly ash from the hopper.
From information provided in the Steam Electric Survey, EPA determined that 510 coal-,
petroleum coke-, petroleum coke-, and oil-fired power plants, corresponding to 1,083 coal- or
petroleum coke-fired units and 33 oil-fired units, generate bottom ash. Figure 7-10 shows a
distribution of the coal-, petroleum coke-, and oil-fired units based on their type of bottom ash
handling system(s). For this figure, the systems are grouped into the following three categories:
• Units with wet sluicing systems only;
• Units with systems that eliminate bottom ash transport water; and
• Units with multiple bottom ash handling systems, including wet sluicing.
Approximately 72 percent of the 510 steam electric power plants mentioned above
currently operate wet sluicing handling systems on all steam electric generating units that
produce bottom ash. The remaining plants currently operate systems other than wet sluicing
systems, exclusively or in combination with wet sluicing systems. As shown in Figure 7-10,
approximately 80 percent of coal- and petroleum coke-fired units use only wet sluicing systems
to handle bottom ash, whereas over 95 percent of oil-fired units use systems that do not use
bottom ash transport water. From survey data, EPA expects approximately eight plants,
corresponding to 15 coal-fired units, that operate wet sluicing systems to convert from wet to dry
or closed-loop recycle systems by January 2014. Additionally, from publicly available data, EPA
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Section 7- Treatment Technologies and Wastewater Management Practices
expects another 11 plants, corresponding to 59 coal-fired units, to convert from wet to dry or
closed-loop complete system systems [ERG, 2013d]. After collecting the ash, plants can sell
dewatered or dry bottom ash or send it to a landfill.
System Only
Systems that Do N0I
UseTViniport Water
Coal and Petroleum Coke Fired I nils
Source: Steam Electric Survey [ERG, 2013g].
Figure 7-10. Distribution of Bottom Ash Handling Systems for Coal-, Petroleum
Coke-, and Oil-Fired Units Reported in the Steam Electric Survey
Information provided in the Steam Electric Survey and vendor data shows the number of
plants installing mechanical drag systems on new units is increasing [McDonough, 2011]. From
the Steam Electric Survey and EIA data, approximately 70 percent of steam electric generating
units that began operating in the last ten to 25 years are installing handling systems other than
wet sluicing. Of those systems, 55 percent are mechanical drag systems [ERG, 2013g]. Figure
7-11 shows the distribution of bottom ash handling systems, excluding units with any wet
sluicing systems, reported in the Steam Electric Survey for coal-, petroleum coke-, and oil-fired
units. Steam electric generating units with more than one type of bottom ash handling system,
excluding wet sluicing systems, or other mechanical systems were included as "Other" in Figure
7-11.
Coal- and Petroleum Coke-Fired Vnils
Oil-Fired Units
Source: Steam Electric Survey [ERG, 2013g].
Figure 7-11. Distribution of Bottom Ash Handling System Types Other Than Wet Sluicing
for Coal-, Petroleum Coke-, and Oil-Fired Units Reported in the Steam Electric Survey
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Section 7- Treatment Technologies and Wastewater Management Practices
Steam electric generating units that produce bottom ash collect the ash particles in
hoppers, or other types of collection equipment, directly below the boilers. Generally, boilers are
sloped inward and have an opening at the bottom to allow the bottom ash to feed by gravity into
the ash collection system (i.e., hoppers or the trough of a mechanical drag system). The
following sections discuss current bottom ash wet sluicing systems in the industry in addition to
those that minimize or eliminate the discharge of bottom ash transport water.
7.3.1 Wet Sluicing System
In a wet sluicing system, bottom ash hoppers are filled with water to quench the hot
bottom ash as it enters the hopper. Once the hoppers are full of bottom ash, a gate at the bottom
of the hopper opens and the ash is directed to grinders to grind the bottom ash into smaller pieces
(Babcock & Wilcox, 2005). As the gates at the bottom of the hoppers open, they release the
bottom ash and water, emptying the water quench bath in the hopper. Once the gates are closed,
the bottom of the hopper fills with water. Because of the batch style process, bottom ash removal
is not continuous.
After the bottom ash passes through the grinder, the system feeds the bottom ash to the
conveying line. The plant then dilutes the bottom ash with water to approximately 20 percent
solids (by weight) and pumps the bottom ash slurry to an impoundment or a dewatering bin for
solids removal. Section 6.2.3 describes wet sluicing operations in the steam electric industry in
more detail.
Similar to fly ash transport water, bottom ash transport water is typically treated in large
surface impoundments, either completely separate from or commingled with other combustion
residual wastes. See Section 7.2.1 for more information on how plants typically maintain ash
impoundments.
As stated above, the bottom ash slurry can either be transferred to an impoundment or a
dewatering bin. For dewatering bin systems, plants usually operate two dewatering bins so that
while one bin fills, the other is dewatered and the ash is unloaded into trucks or rail cars. As the
bins fill with bottom ash transport water, the particulates are contained at the bottom of the bin.
Excess water in the bin flows over a serrated overflow weir, leaving the dewatering bin. At the
top of the bin, an underflow baffle prevents finer parti culates from floating out of the bin with
the overflow [Babcock & Wilcox, 2005]. As the dewatering bin continues to receive bottom ash
transport water, it eventually reaches its solids loading capacity, at which time the plant directs
the bottom ash transport water to another dewatering bin and begins the decant process in the
first bin. The bottom ash transport water exiting the top of the bin and the water that is decanted
from the bin prior to removing the solids, can either overflow to additional settling tanks or be
pumped to a surface impoundment. Figure 7-12 presents a diagram of a dewatering bin system
with additional settling tanks after the dewatering bins.
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Graphic reprinted with permission from United Conveyor Corporation [UCC, 2009].
Figure 7-12. Bottom Ash Dewatering Bin System
7.3.2 Mechanical Drag System
Mechanical drag systems collect bottom ash from the bottom of the boiler, similar to the
description above for the wet sluicing system. Because of the shape of the boiler, explained
above, the bottom ash is gravity fed through the opening at the bottom of the boiler, through a
transition chute, and into a water-filled trough. The water bath in the trough quenches the hot
bottom ash as it falls from the boiler and seals the boiler gases. The drag system comprises a
drag chain with a parallel pair of chains. The chains are attached with crossbars at regular
intervals along the bottom of the water bath and move in a continuous loop towards the far end
of the bath. At the far end, the drag chain begins moving up an incline, which dewaters the
bottom ash by gravity, draining the water back to the trough as the bottom ash moves upward.
Because the bottom ash falls directly into the water bath from the bottom of the boiler and the
drag chain moves constantly on a loop, bottom ash removal is continuous. The dewatered bottom
ash is often conveyed to a nearby collection area, such as a small bunker outside the boiler
building, from which it is loaded onto trucks and either sold or transported to a landfill. See
Figure 7-13 for a diagram of a mechanical drag system.
Because the trough has a water bath, the mechanical drag system does generate some
water (i.e., residual water that collects in the storage area as the bottom ash continues to
dewater). This wastewater, however, is typically completely recycled back to the quench water
bath. Additionally, EPA does not consider this wastewater to be transport water because the
transport mechanism is the drag chain, not the water.
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Section 7- Treatment Technologies and Wastewater Management Practices
Mechanical drag systems come in various standard widths and require little headspace
under the boiler; however, the system may not be suitable for all boiler configurations. For
example, existing boilers located below grade are usually surrounded with support columns and
positioned close to the floor with the sluice lines 1 to 2 feet above the ground. A mechanical drag
system would be difficult to install with such space limitations. Mechanical drag systems are not
able to combine and collect bottom ash from multiple boilers and generally need a straight exit
from the boiler to the outside of the building. These systems may also be susceptible to
maintenance outages because bottom ash fragments fall directly on to the drag chain.
•-^%K-;
•rrX '-v: r-^'."?''
•"" '•***'-
^••-fS-:^.
Graphic reprinted with permission from United Conveyor Corporation [UCC, 2009].
Figure 7-13. Mechanical Drag System
7.3.3 Remote Mechanical Drag System
Remote mechanical drag systems collect bottom ash using the same operations and
equipment as wet sluicing systems at the bottom of the boiler. However, instead of sluicing the
bottom ash directly to an impoundment, the plant pumps the bottom ash transport water to a
remote mechanical drag system. This type of system has the same configuration as a mechanical
drag system; however, it has additional dewatering equipment in the trough and is not located
under the boiler, but rather in an open space on the plant property. See Figure 7-14 for a diagram
of a remote mechanical drag system. Plants can use this system when converting existing bottom
ash handling systems where space or other limitations limit the changes that can be made to the
bottom of the boiler. Currently, one U.S. plant is operating and another plant is installing a
remote mechanical drag system. The second system is scheduled to begin operating in 2013
[McDonough, 2012b].
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Section 7- Treatment Technologies and Wastewater Management Practices
Graphic reprinted with permission from United Conveyor Corporation [McDonough, 2012a].
Figure 7-14. Remote Mechanical Drag System
The plant pumps the bottom ash transport water from the sluice pipes into the trough of
the remote mechanical drag system. Similar to dewatering bins (see Section 7.3.7), an underflow
baffle prevents the finer particles from exiting the trough with the overflow. As shown in Figure
7-15, the excess transport water in the trough flows over a serrated overflow weir, leaving the
remote mechanical drag system. The plants collect this overflow water in a basin/sump and reuse
it in the bottom ash handling system. Because of the chemical properties of bottom ash sluice,
some plants may have to install a pH adjustment system to treat the overflow prior to recycle to
prevent scaling and fouling in the system. Similar to the mechanical drag system, the drag chain
conveys the ash to a collection area and the plant then sells the ash or disposes of it in a landfill.
The settled bottom ash is removed from the trough using the same drag system described
in Section 7.3.2. The bottom ash can be loaded directly onto trucks and either sold or transported
to a landfill. Remote mechanical drag systems are larger than mechanical drag systems located at
the bottom of the boiler, for comparative units, because the remote systems receive excess water
that must be separated from the bottom ash. Additionally, the remote mechanical drag systems
can service multiple units [Fleming, 2011].
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Section 7- Treatment Technologies and Wastewater Management Practices
Incoming Sluice Pipe
To Settling
Basin/Tank
Graphic reprinted with permission from Clyde Bergemann
Power Group [CBPG, 2012].
Figure 7-15. Water Flow Inside the Remote Mechanical Drag System Trough
The remote mechanical drag system essentially combines a mechanical drag system and a
dewatering bin. However, because the remote mechanical drag system is located away from the
boiler and is close to the ground, unlike a traditional dewatering bin, there is little increase in the
total dynamic head requirements on the existing pumps and no additional water requirements
compared with a traditional wet sluicing system. Also, because the remote mechanical drag
system is not located underneath the boiler and the bottom ash particles have already been
through a grinder, these systems require less maintenance than mechanical drag systems
[Fleming, 2011]. The plant then sells the ash or disposes of it in a landfill. Unlike the mechanical
drag system, remote mechanical drag systems are not located at the bottom of the boiler and
therefore requires water to transport ash to the system. The water associated with the remote
mechanical drag system is ash transport water because, like a sluicing system, the water is the
transport mechanism that moves the bottom ash away from the hoppers.
7.3.4 Dry Vacuum or Pressure System
Dry vacuum or pressure bottom ash handling systems transport bottom ash from the
bottom of the boiler into a dry hopper, without using any water. The system percolates air into
the hopper to cool the ash, combust additional unburned carbon, and increase the heat recovery
to the boiler. Periodically, the grid doors at the bottom of the hopper open to allow the ash to
pass into a crusher that crushes the bottom ash into smaller pieces. The system then conveys the
crushed bottom ash by vacuum or pressure to an intermediate storage facility [UCC, 2009].
Figure 7-16 presents a typical dry vacuum or pressure bottom ash handling system.
Dry vacuum or pressure systems eliminate water requirements and improve heat recovery
and boiler efficiency. These systems are also less complicated to retrofit to existing units because
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Section 7- Treatment Technologies and Wastewater Management Practices
there are less structural limitation (e.g., headspace requirements below the boiler) and the
systems can be installed to collect bottom ash from multiple boilers (e.g., one intermediate
storage facility for multiple units). The plant then sells the ash or disposes of it in a landfill.
Graphic reprinted with permission from United Conveyor Corporation [UCC, 2009].
Figure 7-16. Dry Vacuum or Pressure Bottom Ash Handling System
7.3.5 Vibratory Belt System
Vibratory belt systems feed bottom ash by gravity from the bottom of the boiler directly
to a vibratory conveyor trough supported by coil springs, which reduce the stress of impact from
the falling bottom ash. The vibratory conveyor produces an oscillatory toss-and-catch motion,
transporting bottom ash in a series of successive throws. With each throw, the ash moves up and
forward onto the conveyor deck. Controlled forced draft air enters through the vibratory
conveyor deck to cool, suspend, and enhance oxidation of unburned carbon. The forced draft air
surrounds the entire ash surface creating a fluidized bed of ash, which is conveyed to an
intermediate storage destination. The plant then sells the ash or disposes of it in a landfill [UCC,
2009]. See Figure 7-17 for the layout of a vibratory bottom ash handling system.
The vibratory system eliminates water requirements and has the lowest power
consumption of all other bottom ash handling systems. Additionally, unlike other bottom ash
handling systems, the vibratory system does not have any moving or hinged joints that can
become damaged from falling boiler slag, decreasing the chance of unscheduled outages for
maintenance [UCC, 2009].
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Section 7- Treatment Technologies and Wastewater Management Practices
Graphic reprinted with permission from United Conveyor Corporation [UCC, 2009].
Figure 7-17. Vibratory Bottom Ash Handling System
7.3.6 Mechanical System
Similar to fly ash handling systems, mechanical bottom ash handling systems usually
service units that generate low volumes of bottom ash, or handle fly and bottom ash together.
These units are usually oil-fired units, which typically produce less ash than coal-fired units.
Mechanical systems include any manual or systematic approach to removing bottom ash. Based
on responses to the Steam Electric Survey, the systems can include periodic scheduled boiler
cleanings or manual ash removal. Both procedures involve scraping the sides of the boilers with
sprayers or shovels, then collecting and removing the bottom ash to an intermediate storage
destination. Some plants store the manually collected ash in an ash impoundment, while others
sell or dispose of the ash in a landfill.
7.3.7 Complete Recycle System
Complete recycle bottom ash systems transport bottom ash via water, using the same
process as wet sluicing systems, but all the water that leaves the system is recycled back to the
bottom of the boiler and/or used as make-up to the bottom ash sluicing system. Because the
bottom ash is hot and evaporates a portion of the water in the quench bath, the bottom ash
sluicing system is a net consumer of water, which allows the system to completely reuse all the
water along with a make-up stream. The complete recycle system can operate using several
different configurations. The most common configuration in the industry is to operate with
dewatering bins (described in Section 7.3.1) with the overflow pumped to an impoundment and
the overflow from the impoundment being pumped back to the bottom ash sluice system. There
are also several other configurations that achieve complete recycle using tank-based systems that
do not include impoundments. These tank-based systems can either use dewatering bins or a
remote MDS. For a dewatering bin complete recycle system, the overflow and decant are
transferred to additional settling tanks prior to being recycled back to the bottom ash sluice
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Section 7- Treatment Technologies and Wastewater Management Practices
system, as shown in Figure 7-12. In the settling tank, a large percentage of the fine ash carryover
settles to the bottom and is pumped to the dewatering bin for removal. The plant directs the
overflow from the settling tank to the surge tank, where recirculation pumps return the water to
the existing bottom ash handling system or as make-up water to the quench water bath. For a
remote MDS complete recycle system, the overflow water is collected in a sump prior to being
recycled back to the bottom ash sluice system. Fine ash that carries over into the sump will
collect at the bottom of the sump and the plant will need to collect this material occasionally and
dispose of it off site or in a landfill.
Some complete recycle systems may need to add chemical treatment, specifically pH
control, for the overflow/decant water because of the chemical properties in the water. The
chemical treatment may be necessary to eliminate any scaling or fouling caused by the recycled
water.
Plants that install complete recycle systems on existing wet sluicing units can reuse all of
the existing wet sluicing equipment. These systems also allow plants to handle bottom ash from
multiple boilers. However, because of the amount of equipment and water these systems use,
complete recycle systems have the highest equipment, maintenance, and power consumption
requirements of all other bottom ash handling systems.
Alternatively, plants can achieve complete recycle systems using impoundment systems.
Some plants discharge the ash to an impoundment, or series of impoundments, to settle and then
return all effluent from the impoundment, or impoundment system, to the boiler to use as
transport water. These plants often add additional make-up water to the system to compensate for
any water lost due to evaporation or water retained in the ash.
7.4 COMBUSTION RESIDUAL LEACHATE
During the rulemaking, EPA identified and investigated wastewater treatment systems
and management practices in use by steam electric power plants to treat leachate collected from
landfills and impoundments containing combustion residual wastes. From industry profile
information and leachate characterization data, described in Sections 4.3.5 and 6.3, EPA
determined that combustion residual leachate from landfills and impoundments includes similar
types of constituents as FGD wastewater. However, EPA determined that concentrations of the
constituents in combustion residual leachate are generally lower than in FGD wastewater,
especially for TDS. Based on this characterization of the wastewater, EPA believes that certain
treatment technologies identified for FGD wastewater, as described in Section 7.1, could also be
used to treat leachate from landfills and impoundments containing combustion residual wastes.
Additionally, EPA used information from the Steam Electric Survey, site visits, and
industry profile to identify wastewater treatment systems and management practices currently
used, or considered, to treat and manage combustion residual landfill and impoundment leachate.
The wastewater treatment technologies that EPA identified to treat combustion residual leachate
include:
• Surface impoundments;
• Chemical precipitation;
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Section 7- Treatment Technologies and Wastewater Management Practices
• Biological treatment (anoxic/anaerobic system with fixed film bioreactors); and
• Constructed wetlands.
In the Steam Electric Survey, EPA requested a subset of coal-fired power plants to
provide information on combustion residual leachate treatment systems and management
practices used in the industry. From the treatment information received, EPA determined that
surface impoundments are the most commonly used system to treat combustion residual leachate
from landfills and impoundments [ERG, 2013g]. Figure 7-18 shows the distribution of
combustion residual leachate treatment technologies reported in the Steam Electric Survey or
determined by EPA through industry contacts, for the 29 plants that reported treatment systems
for combustion residual landfill and impoundment leachate.
Biological
Treatment
Surface
Impoundments
Constructed
Wetlands
Source: Steam Electric Survey [ERG, 2013g, WVDEP, 2010].
Figure 7-18. Distribution of Treatment Systems for Leachate from Landfills
and Impoundments Containing Combustion Residual Wastes
Additionally, EPA investigated the management practices for combustion residual
leachate from landfills and impoundments. From information in the Steam Electric Survey, EPA
determined that 14 plants collect their combustion residual landfill leachate and use it as water
for moisture conditioning dry fly ash prior to disposal or dust control around dry unloading areas
and landfills.38 EPA also identified one plant that uses the collected leachate as truck wash and
routes it back to an impoundment at the plant.
EPA also identified different management practices for combustion residual
impoundment leachate. From the Steam Electric Survey, EPA identified approximately 36
percent of plants collecting combustion residual impoundment leachate recycle the leachate
directly back to the impoundment from which it was collected. In this case, because the
EPA also identified three additional plants that use leachate for moisture conditioning fly ash and/or dust control;
however, EPA was unable to determine if the wastewater is combustion residual landfill or impoundment leachate.
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wastewater originated from the impoundment, the collection system is essentially just capturing
a portion of the impoundment wastewater and EPA does not consider the wastewater recycled
directly back to the impoundment as a new wastestream entering the pond. Instead, EPA
considers it to be the same as the wastewater that is already contained within the impoundment
system. However, if any of this collected wastewater is transferred to any other process or
operation, then EPA would consider this a new wastestream that is subject to the proposed
effluent limitations for combustion residual leachate. EPA also determined that seven plants
collect their combustion residual impoundment leachate and use it as water for moisture
conditioning dry fly ash prior to disposal or dust control around dry unloading areas and
landfills.39
7.5 FLUE GAS MERCURY CONTROL WASTEWATER TREATMENT TECHNOLOGIES
During the rulemaking, EPA identified and investigated wastewater treatment systems
operated by steam electric power plants to treat wastewater generated from FGMC, as well as
operating/management practices used to reduce the wastewater discharge. As described in
Section 4.3.4, the installation of these systems is relatively new to the industry.
Generally, there are two types of FGMC systems, addition of oxidizers to the coal prior
to combustion, and injection of activated carbon into the flue gas upstream or downstream of the
primary particulate control system. FGMC systems that add oxidizers simply collect the oxidized
mercury with the wet FGD system. This does not generate a new wastewater stream; however, it
may increase the concentration of mercury in the FGD wastewater because the oxidized mercury
is more easily removed by the FGD system.
In activated carbon injection (ACI) systems, the steam electric power plant injects
activated carbon either before or after primary particulate control. If activated carbon is injected
prior to the primary particulate control system, the adsorbed mercury is collected with the fly ash
and handled according to the technologies described in Section 7.2, including wet sluicing.
However, if the activated carbon is injected after the primary particulate control system, the plant
must install a different handling system to handle the FGMC waste. Similar to Section 7.2, these
systems include:
• Wet Sluicing System: These systems use water-powered hydraulic vacuums to create
the vacuum for the initial withdrawal of fly ash from the hoppers. The FGMC waste
is combined with the water used to create the vacuum and then pumped to an ash
impoundment.
• Wet Vacuum Pneumatic System: These systems use water-powered hydraulic
vacuums to create the vacuum for the initial withdrawal of fly ash from the hoppers,
similar to wet sluicing systems; however, the fly ash is directed to a silo and is not
combined with the water flowing through the sluice pipes.
39 EPA also identified three additional plants that use leachate for moisture conditioning fly ash and/or dust control;
however, EPA was unable to determine if the wastewater is combustion residual landfill or impoundment leachate.
7-41
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Section 7- Treatment Technologies and Wastewater Management Practices
• Dry Vacuum System: These systems use a mechanical exhauster to move air, below
atmospheric pressure, to pull the fly ash from the hoppers and convey it directly to a
silo.
• Pressure System: These systems use air produced by a positive displacement blower
to convey ash directly from the hopper to a silo.
• Combined Vacuum/Pressure System: These systems first utilize a dry vacuum system
to pull ash from the hoppers to a transfer station, and then use a positive displacement
blower to convey the ash to a silo.
• Mechanical System: These systems include any manual or systematic approach to
removing fly ash, such as scraping the sides of the boilers with sprayers or shovels,
then collecting and removing the fly ash to an intermediate storage destination or
disposal.
Based on responses to the Steam Electric Survey, EPA identified 73 power plants that
operate ACT systems. As discussed in Section 6, 15 of these power plants inject the activated
carbon downstream of the primary parti culate removal system and the remaining 58 plants inject
the activated carbon upstream of the paniculate removal system [ERG, 2013g]. The following
describes how these plants handle their FGMC wastes:
• Of the downstream ACT systems, only one plant handles the FGMC waste wet. The
plant identified a planned FGMC system and indicated that the waste will be sluiced
to a zero discharge impoundment from which solids are landfilled and wastewater is
recycled within the plant;
• The remaining 14 downstream ACT systems handle the FGMC waste dry;
• Of the upstream ACT systems, five plants handle the FGMC waste wet. These plants
indicated that the waste will be wet sluiced to an impoundment from which solids are
landfilled and wastewater is potentially discharged;40
• The remaining 53 upstream ACT systems handle the FGMC waste dry.
7.6 GASIFICATION WASTEWATER TREATMENT TECHNOLOGIES
During the rulemaking, EPA identified and investigated wastewater treatment systems
operated by steam electric power plants to treat wastewater generated at IGCC plants from the
gasification process, as well as operating/management practices used to reduce the wastewater
discharge. This section describes the following technologies:
• Vapor-compression evaporation system; and
• Cyanide destruction.
EPA is aware of two plants that currently operate IGCC units in the United States, and
another plant that is scheduled to begin commercial operation in 2012. All three of these plants
40 Four of these plants do not discharge any flue gas mercury control wastewater; however, one plant does discharge
the flue gas mercury control wastewater. This one plant has the capability to handle the fly ash and FGMC waste
using a dry system, but sometimes uses the wet system instead.
7-42
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Section 7- Treatment Technologies and Wastewater Management Practices
currently treat or plan to treat the IGCC wastewaters with vapor-compression evaporation
systems. One of these plants plans to install a cyanide destruction system in addition to a vapor-
compression evaporation system.
7.6.1 Vapor-Compression Evaporation System
As described in Section 7.1.4, plants can use vapor-compression evaporation systems to
treat FGD wastewater and cooling tower blowdown. Additionally, the plants currently operating
IGCC units are using vapor-compression evaporation systems to treat the IGCC wastewaters
generated. The treatment system set-up is the same as that described for treating FGD
wastewater, as discussed in Section 7.1.4; however, unlike the system used to treat FGD
wastewater, the gasification wastewater does not require the pretreatment chemical precipitation
and softening steps.
This vapor-compression evaporation system uses a falling-film evaporator (or brine
concentrator) to produce a concentrated wastewater stream and a distillate stream. The
concentrated wastewater stream may be further processed in a crystallizer, spray dryer, or rotary
drum dryer, in which the remaining water is evaporated, generating a solid waste product and
potentially a condensate stream. The plant can reuse the distillate and condensate streams or
discharge them to surface waters. Figure 7-5 presents a process flow diagram for a vapor-
compression evaporation system.
7.6.2 Cyanide Destruction
Because the wastewaters from the IGCC process can contain different cyanide
contaminants (e.g., selenocyanate) formed in the gasification unit, one steam electric power
plants plans to use cyanide destruction to treat both the distillate and condensate effluent streams
from the vapor-compression evaporation system. Cyanide destruction treatment involves adding
sodium hypochlorite (i.e., bleach) to the wastewater in mixing tanks and providing enough
residence time for the bleach to completely react with the cyanide present.
7.7 METAL CLEANING WASTE TREATMENT TECHNOLOGIES AND MANAGEMENT
PRACTICES
During the rulemaking, EPA identified the potential for revising the ELGs to include
BAT/NSPS/PSES/PSNS limitations for nonchemical metal cleaning wastes as part of this
rulemaking. The rationale for this potential revision is described in Section 8.1.2.7. EPA
reviewed information reported in response to the Steam Electric Survey to evaluate the
management practices used to manage and treat chemical and nonchemical metal cleaning
wastes.
Table 7-1 presents a summary of the destinations reported as receiving metal cleaning
wastes, broken out by the type of cleaning operation, based on the information reported in
response to the Steam Electric Survey.
The Steam Electric Survey data indicate that, to a large extent, chemical and nonchemical
metal cleaning wastes are managed in similar fashion. For example, both types of wastes may be
discharged by plants to surface water or POTWs, as reported for 39 percent of nonchemical
7-43
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Section 7- Treatment Technologies and Wastewater Management Practices
metal cleaning wastes and 17 percent of chemical metal cleaning wastes. Both types of wastes
are evaporated during the cleaning operation at some plants (29 percent for chemical metal
cleaning wastes; 10 percent for nonchemical metal cleaning wastes). Other disposal methods are
also used for both types of wastes, including offsite treatment, disposal wells, landfilling, and
other techniques (46 percent for chemical metal cleaning wastes; 29 percent for nonchemical
metal cleaning wastes).
The Steam Electric Survey data also indicate that treatment practices for chemical and
nonchemical metal cleaning wastes are similar. Chemical precipitation was reported as the type
of onsite treatment system for both chemical and nonchemical metal cleaning wastes (8 percent
and 11 percent, respectively). Surface impoundments were also used to treat both types of
wastes, with impoundments being used more frequently for nonchemical metal cleaning wastes.
This is to be expected since nonchemical cleaning (i.e., without the use of chemical compounds)
is likely to remove fewer pollutants from metal process equipment, resulting in lower pollutant
concentrations in the wastewater and, therefore, would more easily meet the current BPT effluent
limits with surface impoundments (i.e., gravity settling). The data from the Steam Electric
Survey indicate, however, that some chemical metal cleaning wastes are also sufficiently treated
by surface impoundments.
EPA has also conducted a review of permits to identify how discharges of nonchemical
metal cleaning wastes are being regulated in NPDES permits. To conduct this permit review,
EPA used responses to the Steam Electric Survey to identify plants that reported generating
chemical and nonchemical metal cleaning wastes. EPA provided the listing of these plants to the
EPA Regional offices and asked them to review permits for the following:
1. How is the metal cleaning waste handled at the plant? Is there any distinction
between chemical cleaning waste and nonchemical cleaning waste? If so, what are
the limits for each?
2. How is the nonchemical cleaning waste handled at the plant, as metal cleaning
waste or low-volume waste? What is the limit used?
3. If the non-chemical cleaning waste is handled as low-volume waste, what is the
basis for this assumption? Does the factsheet make any specific reference to the
1975 EPA "Jordan Memo" or provide other justification?
EPA's Regional offices reviewed permits for 56 steam electric power plants, 45 of which
are for plants believed to generate nonchemical metal cleaning wastes, based on responses to the
Steam Electric Survey. For the 45 plants believed to generate nonchemical metal cleaning
wastes, EPA determined the following:
• 64 percent of the plants either do not discharge metal cleaning wastes or have to
comply with effluent limits for copper and iron;
• Permits for 27 percent of the plants do not include effluent limits for copper and iron;
and
7-44
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Section 7- Treatment Technologies and Wastewater Management Practices
• Permits for nine percent of the plants do not include enough information to determine
whether the plant already operates in a manner that would be in compliance with the
proposed BAT limitations.
See the memorandum entitled "Nonchemical Metal Cleaning Waste Permit Review" for
additional details on the permit review and a compilation of the data received from the EPA
Regional offices [ERG, 2013e].
7-45
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Section 7- Treatment Technologies and Wastewater Management Practices
Table 7-1. Destination of Metal Cleaning Wastewaters
Cleaning Operation
Non-Chemical Cleaning Operations
Air Compressor Cleaning
Air-Cooled Condenser Cleaning
Air Heater Cleaning
Boiler Fireside Cleaning
Boiler Tube Cleaning
Combustion Turbine Cleaning (Combustion)
Combustion Turbine Cleaning (Compressor)
Condenser Cleaning
Draft Fan Cleaning
Economizer Cleaning
FGD Equipment Cleaning
Heat Recovery Steam Generator Cleaning
Mechanical Dust Collector Cleaning
Nuclear Steam Generator Cleaning
Precipitator Wash
SCR Catalyst Soot Blowing
Sludge Lancing
Soot Blowing
Steam Turbine Cleaning
Superheater Cleaning
Chemical Cleaning Operations
Air Compressor Cleaning
Air-Cooled Condenser Cleaning
Air Heater Cleaning
Boiler Fireside Cleaning
Boiler Tube Cleaning
Combustion Turbine Cleaning (Combustion)
Immediately
Recycled
Back to
Plant
4%
NA
C
6%
6%
0%
0%
0%
C
0%
0%
C
NA
0%
NA
0%
0%
0%
0%
0%
NA
2%
0%
NA
0%
0%
2%
0%
Transferred to Onsite Treatment System
Surface
Impoundment
58%
NA
C
72%
70%
30%
0%
2%
37%
64%
69%
35%
NA
50%
NA
100%
0%
44%
22%
9%
NA
17%
0%
NA
46%
0%
21%
0%
Chemical
Precipitation
11%
NA
C
15%
10%
15%
0%
0%
0%
64%
69%
0%
NA
93%
NA
11%
0%
0%
4%
9%
NA
8%
0%
NA
0%
0%
12%
0%
Constructed
Wetland
<1%
NA
C
<1%
0%
0%
0%
0%
0%
36%
0%
0%
NA
0%
NA
0%
0%
0%
0%
0%
NA
0%
0%
NA
0%
0%
0%
0%
Other3
2%
NA
C
3%
2%
4%
0%
7%
0%
36%
6%
0%
NA
7%
NA
2%
0%
44%
<1%
0%
NA
12%
100%
NA
54%
44%
11%
19%
Discharged
to Surface
Water or
POTW
39%
NA
C
51%
50%
41%
0%
7%
61%
0%
69%
0%
NA
50%
NA
42%
0%
0%
11%
26%
NA
17%
0%
NA
8%
0%
13%
54%
Evaporated
During
Cleaning
Operation
10%
NA
C
5%
<1%
26%
50%
78%
11%
0%
0%
0%
NA
0%
NA
0%
100%
0%
25%
0%
NA
29%
0%
NA
0%
0%
41%
0%
Other
Disposal
Method"
29%
NA
C
21%
29%
19%
50%
9%
21%
36%
19%
0%
NA
0%
NA
14%
0%
14%
45%
43%
NA
46%
0%
NA
92%
100%
37%
43%
-------
Section 7- Treatment Technologies and Wastewater Management Practices
Table 7-1. Destination of Metal Cleaning Wastewaters
Cleaning Operation
Combustion Turbine Cleaning (Compressor)
Condenser Cleaning
Draft Fan Cleaning
Economizer Cleaning
FGD Equipment Cleaning
Heat Recovery Steam Generator Cleaning
Mechanical Dust Collector Cleaning
Nuclear Steam Generator Cleaning
Precipitator Wash
SCR Catalyst Soot Blowing
Sludge Lancing
Soot Blowing
Steam Turbine Cleaning
Superheater Cleaning
Unknown
All Cleaning Operations
Immediately
Recycled
Back to
Plant
2%
29%
0%
NA
0%
0%
NA
0%
NA
NA
NA
NA
0%
0%
7%
3%
Transferred to Onsite Treatment System
Surface
Impoundment
1%
C
100%
NA
50%
0%
NA
0%
NA
NA
NA
NA
29%
100%
11%
41%
Chemical
Precipitation
0%
0%
0%
NA
0%
0%
NA
0%
NA
NA
NA
NA
8%
0%
12%
10%
Constructed
Wetland
0%
0%
0%
NA
0%
0%
NA
0%
NA
NA
NA
NA
0%
0%
0%
<1%
Other3
11%
0%
0%
NA
50%
0%
NA
100%
NA
NA
NA
NA
18%
0%
12%
6%
Discharged
to Surface
Water or
POTW
30%
0%
100%
NA
0%
0%
NA
100%
NA
NA
NA
NA
13%
100%
40%
30%
Evaporated
During
Cleaning
Operation
9%
17%
0%
NA
0%
13%
NA
0%
NA
NA
NA
NA
27%
0%
7%
17%
Other
Disposal
Method"
52%
17%
0%
NA
0%
100%
NA
0%
NA
NA
NA
NA
61%
0%
42%
36%
Source: Steam Electric Survey, [ERG, 2013g].
Note: The percentages reported for each cleaning operation may sum to greater than 100% in some cases because all destinations for metal cleaning wastewater
are identified. In some cases, wastewater can be treated and then discharged.
NA - Not applicable. The cleaning operation was not reported in the Steam Electric Survey for the type of chemical usage (i.e., nonchemical or chemical
cleaning).
a - Other treatment systems include filtration, zero liquid discharge treatment, reverse osmosis, clarification, oil/water separation, and brine concentrator.
b - Other disposal methods include offsite treatment, evaporated in another generating unit, hazardous waste disposal, third-party disposal, mixed with fly ash
and landfilled, and deep injection well.
c - Data were removed from certain cells to protect the release of information claimed confidential business information.
-------
Section 7- Treatment Technologies and Wastewater Management Practices
7.8 REFERENCES
1. AEP. 2010. American Electric Power Mercury Removal Effectiveness Report. (29
January). DCN SE02008.
2. Babcock & Wilcox Company. 2005. Steam: Its Generation and Use. 41st edition. Edited
by J.B. Kitto and S.C. Stultz. Barberton, Ohio. DCN SE02919.
3. Clyde Bergemann Power Group (CBPG). 2010. "Bottom Ash Conversion Options and
Economics." Diagram: ASHCON™ RSSC Design Concept." (December). DCN
SE02037.
4. Eastern Research Group, Inc. (ERG). 2007. Final Engineering Site Visit Report for EME
Homer City Generation L.P.'s Homer City Power Plant. (9 August). DCN SE02057.
5. Eastern Research Group, Inc. (ERG). 2008. Final Sampling Episode Report, Tennessee
Valley Authority's Widows Creek Fossil Plant. (26 August). DCN SE02105.
6. Eastern Research Group, Inc. (ERG). 2010. Final Sampling Plan, Duke Energy Carolinas'
Belews Creek Steam Station. (27 May). DCN SE00502.
7. Eastern Research Group, Inc. (ERG). 2012a. Final Sampling Episode Report, Duke
Energy Carolinas' Allen Steam Station. (13 March). DCN SE01307.
8. Eastern Research Group, Inc. (ERG). 2012b. Final Sampling Episode Report, Allegheny
Energy's Hatfield's Ferry Power Station. (13 March). DCN SE01310.
9. Eastern Research Group, Inc. (ERG). 2012c. Final Power Plant Monitoring Data
Collected Under Clean Water Act Section 308 Authority ("CWA 308 Monitoring Data").
(30 May). DCN SEO1326.
10. Eastern Research Group, Inc. (ERG). 2012d. Final Site Visit Notes and Sampling
Episode Report for Enel's Power Plants. (8 August). DCN SE02013.
11. Eastern Research Group, Inc. (ERG). 2013a. Final Site Visit Notes for Duke Energy's
Gibson Generating Station (11 March). DCN SE03622.
12. Eastern Research Group, Inc. (ERG). 2013b. Final Site Visit Notes for Kansas City
Power & Light's latan Generating Station. (16 March). DCN SE03727.
13. Eastern Research Group, Inc. (ERG). 2013c. Final Site Visit Notes for We Energies'
Pleasant Prairie Power Plant. (6 April). DCN SE00312.
14. Eastern Research Group (ERG). 2013d. Memorandum to Steam Electric Rulemaking
Record. "Changes to Industry Profile for Steam Electric Generating Units for Steam
Electric Effluent Guidelines Proposed Rule." (28 January). DCN SE02033.
15. Eastern Research Group, Inc. (ERG). 2013e. Memorandum to the Steam Electric
Rulemaking Record: Nonchemical Metal Cleaning Waste Permit Review. (19 April).
DCN SE03902.
16. Eastern Research Group, Inc. (ERG). 2013e. Site Visit Notes for GenOn Energy's
Conemaugh Generating Station. (16 March). DCN SE03756.
17. Eastern Research Group, Inc. (ERG). 2013f. Steam Electric Technical Questionnaire
Database ("Steam Electric Survey"). (19 April). DCN SE01958.
7-48
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Section 7- Treatment Technologies and Wastewater Management Practices
18. Electric Power Research Institute (EPRI). 2006. EPRI Technical Manual: Guidance for
Assessing Wastewater Impacts ofFGD Scrubbers. 1013313. Palo Alto, CA. (December).
Available online at: http://www.epriweb.com/public/000000000001013313.pdf. Date
accessed: 16 May 2008. DCN SE01817.
19. Electric Power Research Institute (EPRI). 2007. Treatment Technology Summary for
Critical Pollutants of Concern in Power Plant Wastewaters. 1012549. Palo Alto, CA.
(January). Available online at:
http://www.epriweb.com/public/000000000001012549.pdf Date accessed: 26 June 2008.
DCN SE02922.
20. Electric Power Research Institute (EPRI). 2008a. Environment Quick News: A Monthly
Report from EPRI's Environment Sector. Program 56: Effluent Guidelines and Water
Quality Management. Available online at:
http://mydocs.epri.com/docs/CorporateDocuments/Newsletters/ENV/QN-2008-02/ENV-
QN-2008-02.pdf. Date accessed: 16 May 2008. DCN SE02923.
21. Electric Power Research Institute (EPRI). 2008b. Program on Technology Innovation:
Selenium Removal from FGD Wastewaters Using Metallic Iron Cementation. Available
online at: http://my.epri.com/portal/server.pt?Abstract_id=000000000001016191. Date
accessed: 16 May 2008. DCN SE02924.
22. Electric Power Research Institute (EPRI). 2009a. Laboratory and Pilot Evaluation of Iron
and Sulfide Additives with Microfiltration for Mercury Water Treatment. 1016813. Palo
alto, CA. (March). DCN SE00409A3.
23. Electric Power Research Institute (EPRI). 2009b. Selenium Removal by Iron
Cementation from a Coal-Fired Power Plant Flue Gas Desulfurization Wastewater in a
Continuous Flow System - Pilot Study. 1017956. Palo Alto, CA. (July). DCN
SE00409A2.
24. Fleming, Craig, et al. 2011. Telephone conversation with Craig Fleming, Gary Mooney,
and Ron Grabowski, Clyde Bergemann Power Group, Ron Jordan, U.S. EPA and
Elizabeth Sabol and TJ Finseth, Eastern Research Group, Inc. "Conversion Costs for Wet
to Dry Bottom Ash Handling Systems."(22 June). DCN SE02020.
25. FLSmidth, Inc. 2012. Fly Ash Handling Illustration. (October). DCN SE02038.
26. Goltz, Robert, et al. 2009. Trace Mercury Removal from Flue Gas Desulfurization
Wastewater. DCN SE02041.
27. Jacobs Consultancy. 2012. New Hampshire Clean Air Project Final Report Prepared for
New Hampshire Public Utilities Commission. (10 September). SE02011.
28. Jordan, Ron. 2008. Site Visit Notes: Progress Energy Carolinas' Roxboro Steam Electric
Plant. (7 July). DCN SE02064.
29. Loewenberg, Matthias. 2012. Zero-Liquid Discharge System at Progress Energy Mayo
Generation Station. DCN SE02027.
30. McDonough, Kevin. 2011. Telephone and email communication with Kevin
McDonough, United Conveyor Corporation (UCC), and Elizabeth Sabol, Eastern
Research Group, Inc. "Wet to Dry Ash Handling Conversions - Fly and Bottom."
(April). DCN SE02017.
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Section 7- Treatment Technologies and Wastewater Management Practices
31. McDonough, Kevin. 2012a. Letter from Kevin McDonough, UCC, to Jezebele Alicea,
EPA, RE: Copyright Permission Request - United Conveyor Corporation (UCC®). (27
November). DCN SE02968.
32. McDonough, Kevin. 2012b. Teleconference Notes between Kevin McDonough & Mike
Kippis, United Conveyor Corporation, Ron Jordan and Jezebele Alicea-Virella, EPA, and
TJ Finseth and Elizabeth Sabol, Eastern Research Group, Inc. "Bottom Ash Handling
Conversions in the Industry." (May). DCN SE02016.
33. McGinnis, Gregory, et al. 2009. "Cliffside 6 Integrated Emissions Control System."
Power Engineering. (28 April). Available on-line at:
http://pepei.pennnet.com/display_article/3 58960/67 ARTCL/none/none/l/Cliffside-6-
Integrated-Emissions-Control-System/. DCN SE02925.
34. Michel, Tim. 2012. Telephone conversation with Michel Tim of Milestone, Inc. and
Kavya Kasturi, Eastern Research Group, Inc. "Milestone's Direct Mercury Analyzers."
(27 March). DCN SE02031.
35. Mooney, Gary. 2010. Telephone and email communication with Gary Mooney, Clyde
Bergemann Power Group, Inc. and Elizabeth Sabol, Eastern Research Group, Inc.
"Conversion from Wet to Dry Ash Handling Systems - Fly and Bottom." (18
November). DCN SE01825A69.
36. Pickett, Tim, et al. 2005. ABMet® Biological Selenium Removal from FGD Wastewater.
(March). DCN SE02039.
37. Pickett, Tim, et al. 2006. "Using Biology to Treat Selenium." Power Engineering.
(November). Available online at:
http://pepei.pennnet.com/display_article/278443/6/ARTCL/none/none/Using-Biology-to-
Treat-Selenium/. Date accessed: May 16, 2008. DCN SE02926.
38. Rao, M.N. 2008. Aquatech International Corporation. ZLD Systems Installed for ENEL
Power Plants in Italy. International Water Conference. (27 - 29 October). DCN SE02927.
39. Rogers, John, et al. 2005. Specifically Designed Constructed Wetlands: A Novel
Treatment Approach for Scrubber Wastewater. (September). DCN SE02928.
40. Schultz, Shelly. 2013. Teleconference Notes between Timothy Peschman, Adam
Szczeniak, & Jennifer Ellis, Siemens Industry Inc., and TJ Finseth and Shelly Schultz,
Eastern Research Group, Inc. "Discussion of Merrimack Station System Operation and
Costs." (2 January). DCN SE03901.
41. Smagula, William. 2010. Letter from William H. Smagula, Public Service Company of
New Hampshire, to John King, Office of Ecosystem Protection (U.S. EPA). "Public
Service Company of New Hampshire Merrimack Station, Bow, New Hampshire
Response to Informal EPA Request for Supplemental Information about Planned State-
of-the-Art FGD Wastewater Treatment System." (8 October). SE02010.
42. Shaw, William A. 2008. "Benefits of Evaporating FGD Purge Water." Power. (March).
59-63. Available online at:
http://www.powermag.com/powerweb/archive_article.asp?a=60-
F_WM&y=2008&m=march. Date accessed: March 14, 2008. DCN SE02929.
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Section 7- Treatment Technologies and Wastewater Management Practices
43. Sonstegard, Jill, et al. 2010. ABMet®: Setting the Standard for Selenium Removal.
(October). DCN SE02040.
44. United Conveyor Corporation (UCC). 2009. Wet-to-Dry Conversion: Bottom Ash & Fly
Ash Systems. DCN SE02042.
45. U.S. EPA. 2013. Incremental Costs and Pollutant Removals for Proposed Effluent
Limitation Guidelines and Standards for the Steam Electric Power Generating Point
Source Category Report. (19 April). DCN SE01957
46. Veolia Water Solution & Technologies Company. 2007. "HPD Awarded Flue Gas
Desulfurization (FGD) Effluent Treatment for Monfalcone Coal-Fired Generating
Station." News Release. (16 January). DCN SE02930.
47. WVDEP. 2010. National Pollutant Discharge Elimination System Permit for American
Electric Power's Mountaineer Plant (WV0048500). (6 August). DCN SE02009.
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Section 8 - Technology Options Considered as Basis for Regulation
SECTION 8
TECHNOLOGY OPTIONS CONSIDERED AS BASIS FOR
REGULATION
This section presents the technology options considered by EPA as the basis for the
proposed effluent limitations guidelines and standards (ELGs) for the Steam Electric Power
Generating Point Source Category. EPA developed technology options for the following
limitations and standards:
• Best Practicable Control Technology Currently Available (BPT);
• Best Available Technology Economically Achievable (BAT);
• New Source Performance Standards (NSPS);
• Pretreatment Standards for Existing Sources (PSES); and
• Pretreatment Standards for New Sources (PSNS).
EPA is not developing Best Conventional Pollutant Control Technology (BCT)
limitations for this point source category.
EPA's technology options incorporate pollutant control technologies that are
demonstrated in the steam electric industry, minimize water use, and result in minimal non-water
quality environmental impacts. While EPA establishes ELGs based on a particular set of in-
process and end-of-pipe treatment technology options, EPA does not require a discharger to use
these technologies. Rather, the technologies that may be used to treat wastewater are left entirely
to the discretion of the individual plant operator, as long as the plant can achieve the numerical
discharge limitations and standards, as required by Section §301(b) of the Clean Water Act
(CWA). Direct and indirect dischargers can use any combination of process modifications, in-
process technologies, and end-of-pipe wastewater treatment technologies to achieve the ELGs.
8.1 PROPOSED REGULATORY OPTIONS
This section discusses the regulatory options evaluated for the proposed revisions to the
ELGs for each wastestream. EPA selected the technology bases for each wastestream for which
it is proposing revisions to the regulation from the technologies described in Section 7. Section
8.1.1 describes BPT/BCT. The overall technology bases for the development of BAT, NSPS,
PSES, and PSNS are discussed in Section 8.1.2. Sections 8.1.3 through 8.1.6 discuss the
rationale for the selected technologies for each regulation. Sections 8.1.7 discusses
considerations made by EPA related to future FGD installations.
8.1.1 BPT/BCT
EPA is not proposing to revise the BPT effluent guidelines or establish BCT effluent
guidelines for the proposed rulemaking because the same wastestreams would be controlled at
the proposed BAT/BADCT (NSPS) level of control. EPA is proposing to remove FGD
wastewater, FGMC wastewater, gasification wastewater, and leachate from the definition of low-
volume wastes. As a result, EPA is making a structural adjustment to the text of the regulation at
JM
-------
Section 8 - Technology Options Considered as Basis for Regulation
40 CFR 423 to add paragraphs that list these four wastestreams by name, along with their
applicable effluent limitations. The reformatted regulatory text for these four wastestreams
includes BPT effluent limits, which are the same as the current BPT effluent limits for low
volume wastes.
8.1.2 Description of the Proposed BAT/NSPS/PSES/PSNS Options
EPA is proposing to revise or establish BAT, BADCT (NSPS), PSES, and PSNS that
may apply to discharges of seven wastestreams: FGD wastewater, fly ash transport water, bottom
ash transport water, combustion residual leachate, nonchemical metal cleaning wastes, and
wastewater from FGMC systems and gasification systems. Section 7 describes the treatment
technologies and operational practices that EPA reviewed during the development of this
proposed rule. From these, EPA identified a subset of technologies (treatment processes and
operational practices) that were most promising as candidate BAT/BADCT options. For the
proposed ELGs, EPA is presenting eight main regulatory options (i.e., Option 1, Option 3a,
Option 2, Option 3b, Option 3, Option 4a, Option 4, and Option 5) that represent different levels
of pollutant removal associated with different wastewater streams (i.e., each succeeding option
from Option 1 to Option 5 would achieve more reduction in discharges of pollutants to waters of
the U.S). Table 8-1 summarizes the eight main regulatory options, which are described in the
following paragraphs.
EPA is also proposing to add provisions to the ELGs that would prevent facilities from
circumventing applicable ELGs. The proposed provisions would clarify the acceptable
conditions for discharge of reused process wastewater and establish effluent monitoring
requirements.
EPA is considering establishing BMPs that would apply to surface impoundments (i.e.,
ponds) that receive, store, dispose of, or are otherwise used to manage coal combustion residuals
including FGD wastes, fly ash, bottom ash (which includes boiler slag), leachate, and other
residuals associated with the combustion of coal to prevent uncontrolled discharges from these
impoundments as described in Section 8.1.2.9.
As part of its consideration of technological availability and economic achievability for
all regulatory options, EPA considered the magnitude and complexity of process changes and
new equipment installations that would be required at facilities to meet the requirements of the
rule. EPA proposes that certain limitations and standards being proposed for existing sources
would not apply until July 1, 2017 (approximately three years from the effective date of this
rule).
EPA is also considering establishing, as part of the BAT for existing sources, a voluntary
incentive program that would provide more time for plants to implement the proposed BAT
requirements if they adopt additional process changes and controls that would provide significant
environmental protections beyond those achieved by the preferred options in the proposed rule.
Power plants would be granted two additional years (beyond the time described above in the
preceding paragraph) if they also dewater, close and cap all CCR surface impoundments at the
facility (except combustion residual leachate impoundments), including those surface
impoundments located on non-adjoining property that receive CCRs from the facility. A power
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Section 8 - Technology Options Considered as Basis for Regulation
plant participating in the voluntary incentive program could continue to operate surface
impoundments for which combustion residual leachate was the only type of CCR solids or
wastewater contained in the impoundment. Power plants would be granted five additional years
(beyond the time described above in the preceding paragraph) if they eliminate discharges of all
process wastewater to surface waters, with the exception of cooling water discharges.
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Section 8 - Technology Options Considered as Basis for Regulation
Table 8-1. Steam Electric Regulatory Options
Wastestreams
FGD
Wastewater
Fly Ash Transport
Water
Bottom Ash
Transport Water
Leachate
FGMC
Wastewater
Gasification
Wastewater
Nonchemical Metal
Cleaning Wastes41
Technology Basis for BAT/NSPS/PSES/PSNS
Regulatory Options
1
Chemical
Precipitation
Impoundment
(Equal to BPT)
Impoundment
(Equal to BPT)
Impoundment
(Equal to BPT)
Impoundment
(Equal to BPT)
Evaporation
Chemical
Precipitation
3a
BPJ
Determination
Dry handling
Impoundment
(Equal to BPT)
Impoundment
(Equal to BPT)
Dry handling
Evaporation
Chemical
Precipitation
2
Chemical
Precipitation +
Biological
Treatment
Impoundment
(Equal to BPT)
Impoundment
(Equal to BPT)
Impoundment
(Equal to BPT)
Impoundment
(Equal to BPT)
Evaporation
Chemical
Precipitation
3b
Chemical
Precipitation +
Biological Treatment
for units at a facility
with a total wet-
scrubbed capacity of
2,000 MW and more;
BPJ determination for
<2,000 MW
Dry handling
Impoundment
(Equal to BPT)
Impoundment
(Equal to BPT)
Dry handling
Evaporation
Chemical
Precipitation
3
Chemical
Precipitation
-I- Biological
Treatment
Dry handling
Impoundment
(Equal to
BPT)
Impoundment
(Equal to
BPT)
Dry handling
Evaporation
Chemical
Precipitation
4a
Chemical
Precipitation +
Biological
Treatment
Dry handling
Dry handling/
Closed loop (for
units >400 MW);
Impoundment
(Equal to BPT)(for
units <400 MW)
Impoundment
(Equal to BPT)
Dry handling
Evaporation
Chemical
Precipitation
4
Chemical
Precipitation +
Biological
Treatment
Dry handling
Dry handling/
Closed loop
Chemical
Precipitation
Dry handling
Evaporation
Chemical
Precipitation
5
Chemical
Precipitation +
Evaporation
Dry handling
Dry handling/
Closed loop
Chemical
Precipitation
Dry handling
Evaporation
Chemical
Precipitation
oo
41 As described in Section 8.1.3, EPA is proposing to exempt from new copper and iron BAT limitations any existing discharges of nonchemical metal cleaning
wastes that are currently authorized without iron and copper limits.
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Section 8 - Technology Options Considered as Basis for Regulation
8.1.2.1 FGD Wastewater
Addressing the variety of pollutants present in FGD wastewater typically requires several
stages of treatment to remove the suspended solids, particulate and dissolved metals, and other
pollutants present. Historically, power plants have relied on surface impoundments to treat FGD
wastewater because NPDES permits generally focused on controlling suspended solids for this
wastestream. Surface impoundments are the technology basis for the current BPT effluent limits
(last revised in 1982) for steam electric power plants. In recent years, physical/chemical
treatment systems and other more advanced systems have become more widely used as effluent
limits for metals and other pollutants have been included in permits, in nearly all cases driven by
the need to utilize such technologies to meet water quality-based effluent limits (WQBELs)
established to meet applicable water quality standards in the receiving waters. At present, a
number of steam electric plants either use chemical precipitation or chemical precipitation and
biological treatment to control discharges of FGD wastes. However, surface impoundments
continue to be the predominant technology used to treat FGD wastewater, with 54 percent of
plants that discharge FGD wastewater relying on this technology alone (i.e., not including the
plants that use surface impoundments as pretreatment for more advanced treatment). In addition,
it is common for plants to commingle the surface impoundment FGD effluent with wastestreams
of significantly higher flows (e.g., ash transport water and cooling water) because the higher-
flow wastestreams dilute the FGD wastewater so that the resulting pollutant concentrations in the
combined wastestream do not exceed the applicable water quality-based effluent limitations.
Surface impoundments use gravity to remove solid particles (i.e., suspended solids) from
the wastewater. Metals in FGD wastewater are present in both soluble (i.e., dissolved) and
particulate form. Some metals, such as arsenic, are often present mostly in particulate form; these
usually can be removed to a substantial degree by a well-operated settling process that has a
sufficiently long residence time. However, other pollutants, such as selenium, boron, and
magnesium, are present mostly in soluble form and are not effectively and reliably removed by
wastewater surface impoundments. For metals present in both soluble and particulate forms
(such as mercury), surface impoundments will not effectively remove the dissolved fraction.
Furthermore, the conditions present in some surface impoundments can create chemical
conditions (e.g., low pH) that convert particulate forms of metals to soluble forms, which would
not be removed by the gravity settling process in the surface impoundment. Additionally, EPRI
(a technical research organization funded by the electric power industry) has reported that adding
FGD wastewater to surface impoundments used to treat ash transport water (i.e., ash ponds) may
reduce the settling efficiency in the impoundments due to gypsum particle dissolution, thus
increasing the effluent TSS concentrations. EPRI has also reported that the FGD wastewater
includes high loadings of volatile metals, which can increase the solubility of metals in surface
impoundments, thereby leading to increased levels of dissolved metals and resulting in higher
concentrations of metals in the discharge from surface impoundments [EPRI, 2006].
During the summer, some surface impoundments become thermally stratified. When this
occurs, the top layer of the impoundment is warmer and contains higher levels of dissolved
oxygen, whereas the bottom layer of the impoundment is colder and can have significantly lower
levels of oxygen and may develop anoxic conditions. Typically, during fall, as the air
temperature decreases, the upper layer of the impoundment becomes cooler and more dense,
thereby sinking and causing the entire volume of the impoundment to circulate. Solids that have
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Section 8 - Technology Options Considered as Basis for Regulation
collected at the bottom of the impoundment may become resuspended due to such mixing,
increasing the concentrations of pollutants discharged during the turnover period. Seasonal
turnover effects largely depend upon the size and configuration of the surface impoundment.
Smaller, and especially shallow, surface impoundments likely do not experience turnover
because they do not have physical characteristics that promote thermal stratification. However,
some surface impoundments are large (e.g., greater than 300 acres) and deep (e.g., greater than
10 meters deep) and likely experience some degree of turnover.
Technologies more advanced than surface impoundments exist and that are more
effective at removing both soluble (i.e., dissolved) and particulate forms of metals, as well as
other pollutants such as nitrogen compounds and IDS. Because many of the pollutants of
concern for FGD wastewater are present in dissolved form and would not be removed by surface
impoundments, and because of the relatively large mass loadings of these pollutants (e.g.,
selenium, dissolved mercury) discharged by the FGD wastestream, EPA explored other
technologies that would be more effective at removing these pollutants of concern and is co-
proposing three options that would include such technologies. However, for reasons discussed in
Section 8.1.3, EPA is also co-proposing options under which some or all facilities would
continue, for the purposes of the ELGs, to be subject to the BPT requirements based on surface
impoundments for treatment of FGD wastewater. Under these options, BAT would be left to a
site-specific determination. For the reasons discussed above and in Section 8.1.3, EPA does not
believe that surface impoundments represent best available demonstrated control technology for
controlling pollutants in FGD wastewater. Therefore, none of the regulatory options for NSPS
presented in this proposal are based on the performance of surface impoundments for FGD
wastewater.
The technology basis for the effluent limitations and standards for FGD wastewater in
Option 1 is physical/chemical treatment consisting of the following: chemical
precipitation/coprecipitation (employing the combination of hydroxide precipitation, iron
coprecipitation, and sulfide precipitation). Option 1 also incorporates the use of flow
minimization for plants with high FGD discharge flow rates (i.e., greater than 1,000 gpm) and
FGD system metallurgy and operating practices that can accommodate an increase in chlorides
(e.g., scrubber systems constructed of non-metallic materials or corrosion-resistant metal alloys,
or systems operating with absorber chloride concentrations substantially below the design
chloride limit). The flow minimization at these plants would be achieved by either reducing the
FGD purge rate or recycling a portion of their FGD wastewater.
Physical/chemical treatment (i.e., chemical precipitation) is used to remove metals and
other pollutants from wastewater. Chemicals are added to the wastewater in a series of reaction
tanks to convert soluble metals to insoluble metal hydroxide or metal sulfide compounds, which
precipitate from solution and are removed along with other suspended solids. An alkali, such as
hydrated lime, is typically added to adjust the pH of the wastewater to the point where metals
precipitate out as metal hydroxides (typically referred to as hydroxide precipitation). Chemicals
such as ferric chloride are often added to the system to increase the removal of certain metals
through iron coprecipitation. The ferric chloride also acts as a coagulant, forming a dense floe
that enhances settling of the metal precipitate in the downstream clarification stage. Coagulants
and flocculants are often added to facilitate the settling and removal of the newly formed solids.
Plants trying to increase removals of mercury and other metals will also include sulfide addition
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Section 8 - Technology Options Considered as Basis for Regulation
(e.g., organosulfide) as part of the process. Adding sulfide chemicals in addition to hydroxide
precipitation provides even greater reductions of heavy metals due to the very low solubility of
metal sulfide compounds, relative to metal hydroxides. Sulfide precipitation is widely used in
Europe and multiple locations in the United States have installed this technology. Forty U.S.
power plants (34 percent of plants discharging FGD wastewater) include physical/chemical
treatment as part of the FGD wastewater treatment system; more than half of these plants (28
percent of plants discharging FGD wastewater) use both hydroxide and sulfide precipitation in
the process.
The technology basis for the effluent limitations and standards for FGD wastewater in
Options 2, 3b (for units located at facilities with a total wet-scrubbed capacity of 2,000 MW or
more), 3, 4a, and 4 is chemical precipitation/coprecipitation (the same technology basis under
Option 1) used in combination with anoxic/anaerobic biological treatment designed to optimize
removal of selenium.42 As is the case for Option 1, these BAT options also incorporate the use of
flow minimization for plants with high FGD discharge flow rates (i.e., greater than 1,000 gpm)
and FGD system metallurgy and operating practices that can accommodate an increase in
chlorides. The flow minimization at these plants would be achieved by either reducing the FGD
purge rate or recycling a portion of their FGD wastewater.
Physical/chemical treatment systems are capable of achieving low effluent concentrations
of various metals and the sulfide addition is particularly important for removing mercury;
however, this technology is not effective at removing selenium, nitrogen compounds, and certain
metals that contribute to high concentrations of TDS in FGD wastewater (e.g., bromides, boron).
Six power plants in the U.S. are operating FGD treatment systems that include a biological
treatment stage designed to substantially reduce nitrogen compounds and selenium.43 Other
industries have also used this technology to remove selenium and other pollutants. These systems
use anoxic/anaerobic bioreactors optimized to remove selenium from the wastewater. The
bioreactor alters the form of selenium, reducing selenate and selenite to elemental selenium,
which is then captured by the biomass and retained in treatment system residuals. The conditions
in the bioreactor are also conducive to forming metal sulfide complexes to facilitate additional
removals of mercury, arsenic, and other metals. The information in the record for this proposed
rule demonstrates that the amount of mercury and other pollutants removed by the biological
treatment stage of the treatment system, above and beyond the amount of pollutants removed in
the chemical precipitation treatment stage preceding the bioreactor, can be substantial. In
addition, the anoxic conditions in the bioreactor remove nitrates by denitrification and, if
necessary, the biological processes can be modified to include a step to nitrify and remove
ammonia. Four of these six plants precede the biological treatment stage with physical/chemical
treatment; thus, the entire system is designed to remove suspended solids, particulate and
dissolved metals, soluble and insoluble forms of selenium, and nitrate and nitrite forms of
nitrogen. The other two plants operating anoxic/anaerobic bioreactors to remove selenium
precede the biological treatment stage with surface impoundments instead of chemical
42 This value is calculated by summing the nameplate capacity for all of the units that are serviced by wet FGD
systems.
43 A seventh plant is scheduled to begin operating a biological treatment system for selenium removal next year.
Another plant is installing a similar treatment system to remove selenium in discharges of combustion residual
leachate [ERG, 2013c].
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Section 8 - Technology Options Considered as Basis for Regulation
precipitation. While the treatment systems at these two plants would be less effective at
removing metals (including many dissolved metals) than the plants utilizing chemical
pretreatment, they nevertheless show the efficacy of biological treatment for removing selenium
and nitrate/nitrite from FGD wastewater. Three percent of the plants discharging FGD
wastewater use chemical precipitation followed by anaerobic biological treatment to treat this
wastewater, which is the technology basis for Options 2, 3b (for units located at facilities with a
total wet-scrubbed capacity of 2,000 MW or more), 3, 4a, and 4.
The technology basis for the effluent limitations and standards for FGD wastewater in
Option 5 is chemical precipitation/coprecipitation used in combination with vapor-compression
evaporation. Physical/chemical treatment systems can achieve low effluent concentrations for a
number of pollutants, and reduce concentrations even further when combined with biological
treatment systems. However, these technologies have not been effective at removing substantial
amounts of boron and pollutants such as sodium and bromides that contribute to high
concentrations of TDS. Another FGD wastewater treatment technology that can address these
more recalcitrant pollutants, as well as removing the pollutants treated by physical/chemical and
biological technologies, is vapor-compression evaporation. This technology uses an evaporator
to produce a concentrated wastewater stream and a reusable distillate stream. The concentrated
wastewater stream is either disposed of or further processed to produce a solid by-product and
additional distillate. The plant can reuse the distillate stream as makeup water. Two U.S. plants
and four Italian plants are operating this technology to treat FGD wastewater from their coal-
fired generating units.44
For Option 3a and Option 3b (for units located at facilities with a total wet-scrubbed
capacity of less than 2,000 MW), EPA is proposing not to characterize a technology basis for
effluent limitations and standards applicable to discharges of pollutants in FGD wastewater at
this time. As illustrated above, there is a wide range of technologies currently in use for reducing
pollutant discharges associated with FGD wastewater, and research continues in the development
of additional technologies to treat FGD wastewater (see Section 7.1.7 for more information on
emerging technologies). The more advanced technologies (those that reduce the most pollutants)
reflect recent innovations in the area of treatment of FGD wastewater. EPA expects this trend to
continue and, therefore, under Option 3a and Option 3b (for units located at facilities with a total
wet-scrubbed capacity of less than 2,000 MW), effluent limitations representing BAT for
discharges of FGD wastewater would be determined on a site-specific best professional
judgment (BPJ) basis. Under Options 3a and Option 3b (for units located at facilities with a total
wet-scrubbed capacity of less than 2,000 MW), pretreatment program control authorities would
need to develop local limits to address the introduction of pollutants in FGD wastewater by
steam electric plants to the POTWs that cause pass through or interference, as specified in 40
C.F.R. 403.5(c)(2).
EPA is proposing that certain limitations and standards being proposed for existing
sources would apply to discharges of FGD wastewater generated on or after the date established
by the permitting authority that is as soon as possible within the next permit cycle after July 1,
2017. FGD wastewater generated prior to that date (i.e., "legacy" wastewater) from existing
direct dischargers would remain subject to the existing BPT effluent limits. For indirect
44 A third U.S. plant is currently installing a vapor-compression evaporation system to treat the FGD wastewater.
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Section 8 - Technology Options Considered as Basis for Regulation
dischargers, EPA is proposing that PSES for FGD wastewater would apply to FGD wastewater
generated after a date determined by the control authority that is as soon as possible beginning
July 1, 2017. EPA considered subjecting legacy FGD wastewater to the proposed BAT and PSES
requirements. However, as explained above, FGD wastewater and its associated pollutants are
typically sent to surface impoundments for treatment prior to discharge. These surface
impoundments often contain other plant wastewaters, such as fly ash or bottom ash transport
water, coal pile runoff, and/or low volume wastes. According to data provided by the industry
survey, 78 percent of surface impoundments that receive FGD wastewater also receive fly ash
and/or bottom ash transport water. EPA does not have the data to demonstrate that the
technologies identified above represent BAT for legacy FGD wastewater. As such, EPA is not
proposing BAT requirements associated with discharges of legacy FGD wastewater generated
prior to the date established by the permitting authority (for direct dischargers) or control
authority (for indirect dischargers). As proposed, discharges of legacy FGD wastewater by
existing direct dischargers would remain subject to the existing BPT effluent limits; however,
under some of the proposed options, EPA is also considering setting the BAT effluent limitations
for legacy FGD wastewater that has not been mixed with non-legacy wastes equal to the existing
BPT effluent limits. See Section 14.1.3 for additional information.
8.1.2.2 Fly Ash Transport Water
Under Options 1 and 2, BAT effluent limitations for fly ash transport water would be set
equal to the current BPT effluent limitations, based on the technology of gravity settling in
surface impoundments to remove suspended solids. The current effluent guidelines for existing
sources include BPT effluent limits for the allowable levels of TSS and oil and grease in
discharges of fly ash transport water. The BPT effluent limits are based on the performance of
surface impoundments, which when well-designed and well-operated can effectively remove
suspended solids, including pollutants such as particulate forms of certain metals when
associated with the suspended solids.
Under Options 3a, 3b, 3, 4a, 4, and 5, EPA would establish "zero discharge" effluent
limitations and standards for discharges of pollutants in fly ash transport water, based on the use
of dry fly ash handling technologies. The dry handling technologies for fly ash are described in
Section 7. Although surface impoundments can be effective at removing particulate forms of
certain metals and other pollutants, they are not designed for, nor are they effective at, removing
other pollutants of concern such as dissolved metals and nutrients. The concentrations of
pollutants that remain in the ash impoundment effluent following gravity settling, in combination
with the large volumes of fly ash transport water discharged to surface waters (2.4 MGD on
average per discharging plant), results in a large mass loading of pollutants of concern being
discharged from surface impoundments. Furthermore, as described in Section 8.1.2.1, surface
impoundments can be susceptible to seasonal turnover that degrades pollutant removal efficacy,
and co-managing FGD and ash wastes in the same impoundments can lead to increased pollutant
discharges.
Dry handling technologies are the technology basis for the current fly ash NSPS/PSNS
requirements, which were promulgated in 1982. All generating units built since then have been
subject to a "zero discharge" standard. Some existing units have also converted to dry handling
technologies. Due to the NSPS discharge standard or economic or operational factors,
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Section 8 - Technology Options Considered as Basis for Regulation
approximately 66 percent of coal- and petroleum coke-fired generating units that produce fly ash
currently operate dry fly ash transport systems, while another 15 percent operate both wet and
dry fly ash transport systems. The remaining 19 percent operate only wet fly ash transport
systems. In cases where a unit has both wet and dry handling operations, the wet handling system
is typically used as a backup to the dry system. Effluent limitations and standards based on dry
ash handling would completely eliminate the discharge of pollutants in fly ash transport water.
EPA considered basing one or more regulatory options for fly ash transport water on
chemical precipitation treatment technology, with numeric effluent limits for discharges of the
wastestream to surface waters. EPA has not identified any facilities using this treatment
technology to treat fly ash transport water, although EPA has reviewed two literature sources that
describe laboratory- or pilot-scale tests using the technology. Upon reviewing the discharge flow
rates for fly ash transport water, however, EPA determined that the costs associated with
treatment using chemical precipitation were higher than the cost of the dry handling technology
upon which Options 3a, 3b, 3, 4a, 4, and 5 are based, despite being less effective at removing
pollutants. Because the costs for chemical precipitation treatment are higher than the cost for
converting to dry handling technologies, and chemical precipitation removes fewer pollutants,
EPA did not include chemical precipitation treatment as part of the regulatory options for fly ash
transport water in this proposed rule [ERG, 2013b].
EPA is proposing that the limitations for existing sources based on Options 3a, 3b, 3, 4a,
4, or 5 would apply to discharges of fly ash transport water generated after the date established
by the permitting authority that is as soon as possible within the next permit cycle after July 1,
2017. For indirect dischargers, EPA is proposing that PSES for fly ash would apply to the fly ash
transport water generated after a date determined by the control authority that is as soon as
possible beginning July 1, 2017. Fly ash transport water generated by existing direct dischargers
prior to that date (i.e., "legacy" wastewater) would remain subject to the existing BPT effluent
limits. EPA considered subjecting legacy fly ash transport water (i.e., the fly ash transport water
generated prior to the date established by the permitting authority, as described above) to the
proposed BAT zero discharge requirement. As explained above, currently fly ash transport
wastewater and the associated pollutants are sent to surface impoundments for treatment prior to
discharge. The technology basis identified for the proposed zero discharge requirement
eliminates the generation of the fly ash wastewater but does not eliminate fly ash transport
wastewater that has already been transferred to a surface impoundment. Furthermore, the
technologies identified as the basis for fly ash transport water discharge requirements have not
been demonstrated for the legacy fly ash transport wastewater that has already been generated.
As such, EPA is not proposing BAT or PSES requirements for discharges of legacy fly ash
transport water generated prior to the date established by the permitting authority or control
authority. As proposed, discharges of legacy fly ash transport water by existing direct
dischargers would remain subject to the existing BPT effluent limits; however, EPA is also
considering whether to set the BAT effluent limitations for legacy fly ash transport water equal
to the existing BPT effluent limits. See Section 14.1.3 for additional information.
8.1.2.3 Bottom Ash Transport Water
Under Options 1, 3a, 2, 3b, 3, and 4a (for units less than or equal to 400 MW), effluent
limitations and standards for bottom ash transport water would be set equal to the current BPT
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Section 8 - Technology Options Considered as Basis for Regulation
effluent limitations, based on the technology of gravity settling in surface impoundments to
remove suspended solids. The 1982 effluent guidelines for existing sources include BPT effluent
limits for the allowable levels of TSS and oil and grease in discharges of bottom ash transport
water. The BPT effluent limits are based on the performance of surface impoundments, which
when well-designed and well-operated can effectively remove suspended solids, including
pollutants such as particulate forms of certain metals when associated with the suspended solids.
Although surface impoundments can be effective at removing particulate forms of metals
and other pollutants, they are not designed for nor are they effective at removing other pollutants
of concern such as dissolved metals and nutrients. The concentrations of pollutants that remain in
the wastestream at the ash impoundment effluent, in combination with the large volumes of
bottom ash transport water discharged to surface waters, results in a large mass loading of
pollutants of concern being discharged from surface impoundments. Effluent limitations and
standards based on the technologies used as the basis for Options 4a (for units more than 400
MW), 4, and 5 would completely eliminate the discharge of pollutants in bottom ash transport
water.
Under Options 4a (for units more than 400 MW), 4, and 5, EPA would establish "zero
discharge" effluent limitations and standards for discharges of pollutants in bottom ash transport
water, based on either using bottom ash handling technologies that do not require transport water
or managing a wet-sluicing bottom ash handling system so that it does not discharge bottom ash
transport water or pollutants associated with the bottom ash transport water. These technologies
for handling bottom ash are described above in Section 7. About 80 percent of coal- and
petroleum coke-fired units generating bottom ash operate wet bottom ash transport systems,
while approximately 20 percent operate systems that eliminate the use of transport water. Most,
but not all, of the wet bottom ash transport systems discharge to surface waters. In cases where a
plant has both wet and dry handling operations, the wet handling system is typically used as a
backup to the dry system. In the case of bottom ash handling systems, the term "dry" is typically
used to refer to a process that does not use water as the transport medium to sluice the bottom
ash to a CCR impoundment. In some cases, a "dry" bottom ash system may be entirely dry and
avoid all use of water. Many dry bottom ash systems, however, include a water bath at the
bottom of a boiler in which the bottom ash is dropped and cooled, and then the bottom ash is
mechanically dragged out of the boiler along a conveyor belt and deposited in a pile adjacent to
the building housing the boiler. The bottom ash conveyed out of the water bath will be damp
because the ash particles retain some moisture from the water bath and small volumes of water
will typically drain from the standing bottom ash pile. The water draining from the pile is usually
collected in a sump and either returned to the water bath below the boiler or managed as low
volume waste. Such mechanical drag systems are considered as one available technology that
may be used to achieve proposed limitations and standards under Options 4a (for units >400
MW), 4, and 5. Other technologies serving as the basis for limitations and standards proposed
under Options 4a (for units >400 MW), 4, and 5 are completely dry bottom ash systems, remote
mechanical drag systems, and impoundment-based systems that are managed to eliminate the
discharge of all bottom ash transport water and the associated pollutants.
In developing the technologies that serve as the basis for the regulatory options with
respect to bottom ash transport water, EPA considered basing one or more options on chemical
precipitation treatment technology, with numeric effluent limitations or standards for discharges
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Section 8 - Technology Options Considered as Basis for Regulation
of the wastestream to surface waters. Upon reviewing the discharge flow rates for bottom ash
transport water, however, EPA determined that the costs associated with treatment were
comparable to the cost of the technologies upon which Options 4a (for units more than 400
MW), 4, and 5 are based, despite being less effective at removing pollutants. Because the costs
for chemical precipitation treatment were found to be higher than the cost for converting to dry
handling or closed loop technologies, and the treatment technology removes fewer pollutants,
EPA did not include chemical precipitation treatment as part of the regulatory options for bottom
ash in this proposed rule [ERG, 2013b].
EPA is proposing that certain BAT limitations for existing sources under Options 4a (for
units more than 400 MW), 4, or 5 would apply to discharges of bottom ash transport water
generated after the date established by the permitting authority or control authority that is as soon
as possible within the next permit cycle after July 1, 2017. For indirect dischargers, EPA is
proposing that PSES for bottom ash transport water would apply to bottom ash transport water
generated after a date determined by the control authority that is as soon as possible beginning
July 1, 2017. Bottom ash transport water generated by existing direct dischargers prior to that
date (i.e., "legacy" wastewater) would remain subject to the existing BPT effluent limits. EPA
considered subjecting legacy bottom ash transport water (i.e., the bottom ash transport water
generated prior to the date established by the permitting authority or control authority to the BAT
and PSES zero discharge requirement considered under Options 4a (for units more than 400
MW), 4, and 5. As explained above, currently, bottom ash transport wastewater and the
associated pollutants are sent to surface impoundments for treatment prior to discharge. The
technology bases identified above for Options 4a (for units more than 400 MW), 4, and 5
eliminate the generation of the bottom ash wastewater but do not eliminate bottom ash transport
wastewater that has already been transferred to a surface impoundment. The technologies
identified as the basis for bottom ash transport water discharge requirements under Options 4a
(for units more than 400 MW), 4, and 5 have not been demonstrated for the legacy bottom ash
transport wastewater that has already been generated and do not represent BAT/PSES with
respect to legacy bottom ash wastewater. As such, under Options 4a (for units more than 400
MW), 4, and 5 EPA would not establish BAT or PSES requirements for discharges of legacy
bottom ash transport water generated prior to the date established by the permitting authority. As
proposed, discharges of legacy bottom ash transport water by existing direct dischargers would
remain subject to the existing BPT effluent limits; however, EPA is also considering whether to
set the BAT effluent limitations for legacy bottom ash transport water equal to the existing BPT
effluent limits. See Section 14.1.3 for additional information.
8.1.2.4 Leachate from Surface Impoundments and Landfills Containing Combustion
Residuals
Under Options 1, 3a, 2, 3b, 3, and 4a, effluent limitations and standards for leachate from
surface impoundments and landfills containing combustion residuals would be set equal to the
current BPT effluent limitations, based on the technology of gravity settling in surface
impoundments to remove suspended solids. Leachate is currently included under the definition
of low volume wastes, which are regulated by effluent limits for TSS and oil and grease based on
surface impoundments designed to remove suspended solids. EPA is proposing that under
Options 1, 3 a, 2, 3b, 3, and 4a, the rule would remove leachate from the definition of low volume
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wastes at 40 CFR 423.1 l(b) and would set BAT effluent limits for leachate equal to BPT limits
for TSS and oil and grease (i.e., the current effluent limits for low volume wastes).
The technology basis for effluent limitations and standards for leachate under Options 4
and 5 is chemical precipitation/coprecipitation. This same technology is the basis for BAT
Option 1 for FGD wastewater. Properly designed and operated surface impoundments can
effectively remove suspended solids, including pollutants such as particulate forms of certain
metals when associated with the suspended solids. However, since surface impoundments are not
designed for, nor are they effective at, removing other pollutants of concern such as dissolved
metals, EPA used chemical precipitation/coprecipitation as the technology basis for combustion
residual leachate for Options 4 and 5. Physical/chemical treatment systems are capable of
achieving low effluent concentrations of various metals and are effective at removing many of
the pollutants of concern present in leachate discharges to surface waters. The pollutants of
concern in leachate are the same pollutants that are present in, and in many cases are also
pollutants of concern for, FGD wastewater, fly ash transport wastewater, bottom ash transport
water, and other combustion residuals. This is to be expected since the leachate itself comes from
landfills and surface impoundments containing the combustion residuals and those wastes are the
source for the pollutants entrained in the leachate. Given the similarities present among the
different types of wastewaters associated with combustion residuals, combustion residual
leachate will be similarly amenable to chemical precipitation treatment. The treatability of
pollutants such as arsenic and mercury using chemical precipitation technology is also
demonstrated by technical information compiled for ELGs promulgated for other industry
sectors. See, e.g., the TDDs supporting the ELGs for the Landfills Point Source Category (EPA-
821-R-99-019) and the ELGs for the Metal Products and Machinery Point Source Category
(EPA-821-B-03-001). However, as is the case when treating FGD wastewater, this technology is
not effective at removing selenium, boron and certain other parameters that contribute to total
dissolved solids (e.g., magnesium, sodium).
EPA also considered developing a regulatory option that, for leachate, would be based on
the technology of chemical precipitation/coprecipitation used in conjunction with
anoxic/anaerobic biological treatment. This is the same technology used as the basis for effluent
limitations and standards for FGD wastewater under Options 2, 3b (for units at facilities with a
total wet-scrubbed capacity of 2,000 MW or more), 3, 4a, and 4. EPA has reviewed this
technology as a potential basis for effluent limitations and standards for leachate. The
microorganisms used in the bioreactors for the biological treatment technology for FGD
wastewater are resilient and have shown that they operate effectively under varying conditions
that occur in FGD system and the FGD wastewater treatment system. However, leachate flows
can be more variable than FGD wastewater and, more importantly, may be too intermittent to
facilitate reliable and consistent biological treatment. Such variations are easily accommodated
in a chemical precipitation treatment system, but may be difficult to manage in a biological
treatment system reliant on healthy and sustainable populations of microorganisms.
If EPA did finalize BAT effluent limits developed under Options 4 or 5 (although these
options are not the preferred options included in the proposed rule), EPA's intent is that these
limits would apply to discharges of leachate generated after the date established by the
permitting authority that is as soon as possible within the next permit cycle after July 1, 2017.
For indirect dischargers, PSES for leachate would apply to leachate generated after a date
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determined by the control authority that is as soon as possible beginning July 1, 2017. Leachate
generated by existing direct dischargers prior to that date (i.e., "legacy" leachate wastewater)
would remain subject to the existing BPT effluent limits. EPA considered subjecting legacy
leachate wastewater to the proposed BAT and PSES limitations and standards. However,
although some plants use relatively small surface impoundments to treat leachate and these
impoundments would contain relatively small volumes of legacy leachate wastewater, other
plants send leachate to relatively large surface impoundments that also contain other plant
wastewaters, such as fly ash or bottom ash transport water, cooling water, and/or other low
volume wastes. EPA does not have the data to demonstrate that the technologies identified above
represent BAT for legacy combustion residual leachate. As such, EPA would not expect to
finalize BAT requirements associated with discharges of legacy combustion residual leachate
(i.e., the leachate generated prior to the date established by the permitting authority or control
authority). As proposed, discharges of legacy combustion residual leachate by existing direct
dischargers would remain subject to the existing BPT effluent limits; however, EPA is also
considering whether to set the BAT effluent limitations for legacy combustion residual leachate
that has not been mixed with non-legacy wastes equal to the existing BPT effluent limits. See
Section 14.1.3 for additional information.
8.1.2.5 FGMC Wastewater
Under Options 1 and 2, effluent limitations and standards for FGMC wastewater would
be set equal to the current BPT effluent limitations, based on the technology of gravity settling in
surface impoundments to remove suspended solids. Like leachate, FGMC wastewater is
currently included under the definition of low volume wastes, with effluent limits for TSS and oil
and grease based on surface impoundments designed to remove suspended solids. EPA is
proposing that under all options, FGMC wastewater would be removed from the definition of
low volume wastes at 40 CFR 423.1 l(b). Under Options 1 and 2, BAT effluent limits for FGMC
wastewater would be set equal to BPT limits for TSS and oil and grease (i.e., the current effluent
limits for low volume wastes).
As discussed in Section 4.3.4, some plants inject dry sorbents (e.g., activated carbon) into
the flue gas stream to reduce mercury emissions from the flue gas. Mercury adsorbs to the
sorbent particles, and these mercury-enriched sorbents are then removed from the flue gas using
a fabric filter or ESP. The sorbent can be injected upstream of the primary parti culate collector,
in which case the mercury-enriched sorbent is collected with the majority of the fly ash.
Alternatively, the sorbent can be injected downstream of the primary parti culate collector and
collected with a much smaller amount of fly ash (i.e., the fly ash that passed through the primary
collector) in a smaller, dedicated secondary paniculate collector such as a fabric filter. In either
case, the plant collects the mercury-enriched sorbents along with fly ash. Because of this, the
BAT technology basis for FGMC wastewater in this proposal is identical to the BAT technology
basis for fly ash.
Under Options 3a, 3b, 3, 4a, 4, and 5, EPA would establish "zero discharge" effluent
limitations and standards for discharges of pollutants in FGMC wastewater based on using dry
handling technologies to store and dispose of fly ash without utilizing transport water. The dry
handling technologies that would be used for FGMC wastes are identical to the dry fly ash
handling technologies described in Section 7.2. Although surface impoundments can effectively
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remove particulate forms of metals and other pollutants, they are not designed for nor are they
effective at removing other pollutants of concern such as dissolved metals and nutrients. Effluent
limits based on dry handling would completely eliminate the discharge of pollutants in FGMC
wastewater.
EPA is also aware of some plants that add oxidizers to the coal prior to burning the coal
in the boiler. This chemical addition oxidizes the mercury present in the flue gas, which allows
the plant to remove mercury more readily from the flue gas in the wet FGD system. EPA did not
evaluate separate treatment technologies for the use of oxidizers to control flue gas mercury
emissions because using oxidizers does not generate a separate FGMC wastewater.
To the extent that a power plant generates FGMC wastewater before any BAT zero
discharge limitation were to apply, the proposed BAT limitations under Options 3a, 3b, 3, 4a, 4,
and 5 would apply to discharges of FGMC wastewater generated after the date established by the
permitting authority that is as soon as possible within the next permit cycle after July 1, 2017.
For indirect dischargers, EPA is proposing that PSES for FGMC wastewater would apply to
FGMC wastewater generated after a date determined by the control authority that is as soon as
possible beginning July 1, 2017. As proposed, legacy FGMC wastewater generated by existing
direct dischargers prior to that date would remain subject to the existing BPT effluent limits;
however, EPA is also considering whether to set the BAT effluent limitations for legacy FGMC
wastewater equal to the existing BPT effluent limits. EPA considered subjecting legacy FGMC
wastewater to the proposed BAT/PSES zero discharge requirements. As described in Section 7.5,
although most FGMC wastes are managed using dry handling systems, EPA has identified six
plants that manage their FGMC waste with systems that use water to transport the waste to
surface impoundments. The technology basis identified for the proposed zero discharge
requirement eliminates the generation of the FGMC wastewater by implementing certain process
changes that do not use water to transport the FGMC waste; however, it does not eliminate the
already-generated FGMC wastewater that has already been transferred to and stored in a surface
impoundment. The technologies that underlie Regulatory Options 3a, 3b, 3, 4a, 4, and 5 do not
represent BAT or PSES for the control of pollutants from legacy FGMC wastewater and would
not allow FGMC wastewater that has already been generated to comply with a zero discharge
requirement. As such, EPA is not proposing BAT or PSES requirements associated with
discharges of legacy FGMC wastewater generated prior to the date established by the permitting
authority or control authority. However, EPA is considering whether to set the BAT effluent
limitations for legacy FGMC wastewater equal to the existing BPT effluent limits. See Section
14.1.3 for additional information.
8.1.2.6 Gasification Wastewater
The technology basis for the effluent limitations for all eight regulatory options for
gasification wastewater is vapor-compression evaporation. Two operating IGCC plants in the
U.S. currently use this technology, and a third IGCC plant that is scheduled to begin commercial
operation soon will also use it to treat gasification wastewater. Like leachate and FGMC
wastewater, gasification wastewater is currently included under the definition of low volume
wastes, with effluent limits for TSS and oil and grease based on surface impoundments designed
to remove suspended solids. EPA considered using surface impoundments as the technology
basis for one or more of the regulatory options for gasification wastewater. However, surface
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impoundments are not effective at removing the pollutants of concern present in gasification
wastewater. In addition, one of the currently operating IGCC plants formerly used a surface
impoundment to treat its gasification wastewater and the impoundment effluent repeatedly
exceeded NPDES permit limits established to protect water quality. Because of the demonstrated
inability of surface impoundments to remove the pollutants of concern and the current industry
practice of operating vapor-compression evaporation to treat the gasification wastewater at all
U.S. IGCC plants, EPA determined that surface impoundments do not represent BAT level of
control.
In addition to the vapor-compression evaporation technology that is the basis for all BAT
and BADCT/NSPS options for gasification wastewater, EPA considered also including cyanide
treatment as part of the technology basis for one or more options. EPA notes that the
Edwardsport IGCC plant that is scheduled to soon begin commercial operation includes cyanide
destruction as one step in the treatment process for gasification wastewater. However, EPA
currently does not have sufficient gasification wastewater data with which to calculate effluent
limits based on the performance of cyanide treatment as part of a BAT/BADCT (NSPS)
regulatory option. A possible approach to resolve this would be to transfer effluent limits for
cyanide from an ELG for another industry sector. Alternatively, EPA may obtain effluent data
from the gasification wastewater treatment system for the Edwardsport IGCC unit once it begins
commercial operation and use these data to calculate effluent limitations for cyanide.
8.1.2.7 Nonchemical Metal Cleaning Wastes
The technology basis for the effluent limitations for all eight regulatory options for
nonchemical metal cleaning wastes is chemical precipitation. Separation processes in the
physical/chemical treatment, along with chemical addition when needed to facilitate coagulation
and settling of suspended solids, would effectively remove TSS and oil and grease to effluent
concentrations below the limitations included in the proposed rule. In addition, treatment
chemicals added to adjust pH to precipitate dissolved metals or to facilitate
flocculation/coagulation are effective at removing copper and iron to effluent concentrations
below the proposed limitations, in addition to reducing the concentrations of other pollutants
present in nonchemical metal cleaning wastes.
The current ELG relies on three key terms specific to metal cleaning waste: "metal
cleaning waste," "chemical metal cleaning waste," and "nonchemical metal cleaning waste." The
regulation includes a definition of the broadest term, "metal cleaning waste," as "any wastewater
resulting from cleaning [with or without chemical cleaning compounds] any metal process
equipment, including, but not limited to, boiler tube cleaning, boiler fireside cleaning, and air
preheater cleaning." 40 CFR 423.1 l(d). Thus, this definition includes any wastewater generated
from either the chemical or nonchemical cleaning of metal process equipment. In addition, the
regulation also defines "chemical metal cleaning waste" as "any wastewater resulting from
cleaning of any metal process equipment with chemical compounds, including, but not limited
to, boiler tube cleaning." See 40 CFR 423.1 l(c). The regulation also includes, but does not
expressly define the term "nonchemical metal cleaning waste" when it states that it has
"reserved" the development of BAT ELGs for such wastes. See 40 CFR 423.13(f). Although the
regulation provides no definition of "nonchemical metal cleaning waste," it is clear from the
definitions of metal cleaning waste and chemical metal cleaning waste that nonchemical metal
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cleaning waste is any wastewater resulting from the cleaning of metal process equipment without
chemical cleaning compounds.
The current ELGs include BPT effluent limits for the allowable levels of TSS, oil and
grease, copper and iron in discharges of metal cleaning waste, which includes both chemical and
nonchemical metal cleaning wastes. Although the current BPT effluent limits apply to
nonchemical metal cleaning wastes, EPA has found that some discharges of nonchemical metal
cleaning waste are authorized pursuant to permits incorporating limitations based on BPT
requirements for low volume wastes and, therefore, do not have iron and copper limits. The
information EPA has collected to date indicates many facilities are not discharging nonchemical
metal cleaning wastewater or have copper and iron limits (see Section 7.7 for more information).
The current ELGs do not include BAT/NSPS requirements for the broadly defined
category of metal cleaning wastes; however, they do include BAT/NSPS for chemical metal
cleaning waste. EPA has not promulgated BAT/NSPS for nonchemical metal cleaning waste.
Similarly, although the current ELGs do not include PSES/PSNS for metal cleaning waste, they
do include PSES/PSNS for chemical metal cleaning waste. EPA has not promulgated
PSES/PSNS for nonchemical metal cleaning waste. An overview of the ELGs and existing
limitations for metal cleaning waste, including chemical and nonchemical metal cleaning waste,
is included in Table 1-1.
As described above, EPA found that some discharges of nonchemical metal cleaning
waste are authorized pursuant to permits incorporating limitations based on BPT requirements
for low volume wastes and, therefore, do not have iron and copper limits. Because the potential
costs for dischargers to comply with iron and copper limits is not known, EPA is proposing to
provide an exemption from new copper and iron limitations or standards for existing discharges
of nonchemical metal cleaning wastes from generating units that are currently authorized without
iron and copper limits. For these discharges, BAT limitations for nonchemical metal cleaning
waste would be set equal to BPT limitations for low volume waste, and the regulations would not
specify PSES.
EPA is also considering setting BAT for nonchemical metal cleaning waste equal
to the metal cleaning waste BPT for all nonchemical metal cleaning wastes (i.e., no exemption
for discharges of nonchemical metal cleaning wastes currently authorized without iron and
copper limits) and, for PSES, to establish copper standards for all discharges of nonchemical
cleaning wastes. As part of this approach, EPA is evaluating whether some plants would incur
costs to comply with the current BPT standards
8.1.2.8 Anti-Circumvention Provision
EPA is proposing to add provisions to the regulations that would prevent facilities from
circumventing the effluent limitations guidelines and standards. The proposed provisions would
do three things, as described below.
First, the anti-circumvention provision would require that compliance with the new
effluent limits applicable to a particular wastestream (e.g., FGD, gasification wastewater,
leachate) be demonstrated prior to use of the wastewater in another plant process that results in
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surface water discharge or mixing the treated wastestream with other wastestreams. Under 40
CFR 122.45(h), in situations where an NPDES permit effluent limitations or standards imposed
at the point of discharge are impractical or infeasible, effluent limitations or standards may be
imposed on internal wastestreams before mixing with other wastestreams or cooling water
streams. Limitations on internal wastestreams may be necessary, such as in situations where the
wastes at the point of discharge are so diluted as to make monitoring impracticable, or the
interferences among pollutants would make detection or analysis impracticable. Many power
plants combine FGD wastewater and other power plant wastewaters with ash transport water
and/or cooling water prior to discharge, which can dilute the wastewaters by several orders of
magnitude prior to the final outfall. In addition, surface impoundments typically contain a variety
of wastes (e.g., ash transport water, coal pile runoff, landfill/impoundment leachate) that when
mixed with the FGD wastewater or gasification wastewater may make the analysis to measure
compliance with technology-based effluent limits impracticable. Because of the high degree of
dilution and the number of wastestream sources containing similar pollutants, effluent limits and
monitoring requirements for certain internal wastestreams (e.g., FGD wastewater, combustion
residual leachate, gasification wastewater) are necessary to ensure appropriate control of the
pollutants present in the wastewater.
Second, the anti-circumvention provision would establish requirements intended to
prevent steam electric power plants from circumventing the effluent limits and standards by
moving effluent produced by a process operation for which there is a zero discharge effluent
limit/standard to another process operation for discharge under less stringent requirements than
intended by the steam electric ELGs. For example, several options (including Option 3a)
considered in this rulemaking would establish a zero discharge requirement for pollutants in fly
ash transport water and FGMC wastewater. If this option were selected for the final rule, the
anti-circumvention provisions would allow power plants to recycle/reuse these wastestreams in
ash transport processes or other plant processes, but only to the extent that the plants do not
discharge any pollutants associated with flue gas mercury controls or transporting fly ash. The
presence of a zero discharge wastestream in a process that ultimately discharges to surface water
(e.g., use of fly ash transport water as FGD absorber make-up water in a scrubber that discharges
FGD wastewater) would not be in compliance with the effluent limit.
Last, the anti-circumvention provisions would expressly require permittees to use
analytical EPA-approved methods that are sufficiently sensitive to provide reliable quantified
results at levels necessary to demonstrate compliance with the effluent limits proposed by this
rulemaking when such methods are available. EPA's detailed study and the field sampling for
this rulemaking demonstrate that the use of sufficiently sensitive analytical methods is critically
important to detecting, identifying, and measuring the concentrations of pollutants present in
power plant wastewaters. Where EPA has approved more than one analytical method for a
pollutant, the Agency expects that permittees would select methods that are able to quantify the
presence of pollutants in a given discharge at concentrations that are low enough to determine
compliance with effluent limits, when such methods are available. Facilities should not use a less
sensitive or less appropriate method, thus masking the presence of a pollutant in the discharge,
when an EPA-approved method is available that can quantify the pollutant concentration at the
lower levels needed for demonstrating compliance. For purposes of the proposed anti-
circumvention provision, a method is "sufficiently sensitive" when the sample-specific
quantitation level for the wastewater being analyzed is at or below the level of the effluent
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limitation.45 Allowing plants to use insufficiently sensitive analytical methods for compliance
monitoring purposes when EPA-approved sufficiently sensitive methods are available could
result in an undetected exceedance of the effluent limits.
8.1.2.9 BMPs for CCR Surface Impoundments
EPA is considering establishing BMPs for plant operators to conduct periodic inspections
of active and inactive surface impoundments and to take corrective actions where warranted.
This requirement would apply to direct dischargers. For new sources, EPA would be relying on
CWA section 306, which authorizes the promulgation of standards of performance for new
sources. For existing sources, EPA would be relying on CWA section 304(e), which authorizes
BMPs supplemental to ELGs for toxic or hazardous pollutants to control plant site runoff,
spillage or leaks, sludge or waste disposal, and drainage from raw material storage which the
Administrator determines are associated with or ancillary to the industrial process and may
contribute significant amounts of pollutants to the nation's waters. And CWA section 402(a) (2)
authorizes the imposition of conditions, which would include BMPs and monitoring
requirements, necessary to ensure compliance with all other applicable requirements. EPA's
regulation at 40 CFR 122.44(k) implements these authorities. Specifically, 40 CFR 122.44(k)
allow for NPDES permits to require the use of BMPs to control and abate the discharge of toxic
pollutants. Existing regulations at 40 CFR 122.41(e) further require that NPDES permittees
properly operate and maintain all facilities and systems of treatment and control used to achieve
compliance with their permits. Using CWA authority, EPA could establish the BMPs as part of
the ELGs (BAT and NSPS) codified at 40 CFR part 423, and thus these BMPs would be
implemented through NPDES permits. Structural integrity requirements that seek to reduce the
potential for catastrophic releases from surface impoundments could, alternatively, be
established using RCRA authority. The BMPs under consideration in this rulemaking are similar
to the structural integrity inspection and corrective active requirements proposed in the CCR
rulemaking, but do not include closure requirements that were proposed as part of the CCR
rulemaking.
The Agency believes that the BMP requirements being considered by the Agency in this
rulemaking and in the CCR rulemaking are critical to ensure that the owners and operators of
surface impoundments become aware of any problems that may arise with the structural stability
of the surface impoundment before they occur and, thus, prevent catastrophic releases, such as
those that occurred at Martins Creek, Pennsylvania and TVA's Kingston, Tennessee facility.
The BMPs being considered by EPA in this rulemaking would require, first, that
inspections be conducted every seven days by a person qualified to recognize specific signs of
structural instability and other hazardous conditions by visual observation and, if applicable, to
monitor instrumentation such as piezometers. If a potentially hazardous condition develops, the
owner or operator shall immediately take action to eliminate the potentially hazardous condition;
notify the Regional Administrator or the authorized State Director; and notify and prepare to
evacuate, if necessary, all personnel from the property that may be affected by the potentially
hazardous condition(s). Additionally, the owner or operator must notify state and local
45 For the purposes of this rulemaking, EPA is considering the following terms related to analytical method
sensitivity to be synonymous: "quantitation limit," "reporting limit," "level of quantitation," and "minimum level."
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emergency response personnel if conditions warrant so that people living in the area down
gradient from the surface impoundment can evacuate. Reports of inspections are to be
maintained in the facility operating record.
Second, to address the integrity of surface impoundments, EPA would establish BMPs
for CCR surface impoundments similar to those promulgated for coal slurry impoundments
regulated by the Mine Safety and Health Administration (MSHA) at 30 CFR 77.216. Although
the MSHA regulations are applicable to coal slurry impoundments at coal mines and not to the
impoundments containing CCR at power plants, there are sufficient similarities between coal
slurry and CCR impoundments for the MSHA regulations to be used as a model for the BMP
requirements being considered for the ELG rule. Facilities using CCR impoundments would
need to (1) submit to EPA or the authorized state plans for the design, construction, and
maintenance of existing impoundments, (2) submit to EPA or the authorized state plans for
closure, (3) conduct periodic inspections by trained personnel who are knowledgeable in
impoundment design and safety, and (4) provide an annual certification by an independent
registered professional engineer that all construction, operation, and maintenance of
impoundments is in accordance with the approved plan. When problematic stability and safety
issues are identified, owners and operators would be required to address these issues in a timely
manner.
In developing these possible structural integrity BMP requirements, EPA sought advice
from the federal agencies charged with managing the safety of dams in the United States. Many
agencies in the federal government are charged with dam safety, including the U.S. Department
of Agriculture (USD A), the Department of Defense (DOD), the Department of Energy (DOE),
the Nuclear Regulatory Commission (NRC), the Department of Interior (DOI), and the
Department of Labor (DOL), MSHA. EPA looked particularly to MSHA, whose charge and
jurisdiction appeared to EPA to be the most similar to the Agency's in this context. MSHA's
jurisdiction extends to all dams used as part of an active mining operation and their regulations
cover "water, sediment or slurry impoundments" so they include dams for waste disposal,
freshwater supply, water treatment, and sediment control. In fact, MSHA's current impoundment
regulations were created as a result of the dam failure at Buffalo Creek, West Virginia on
February 26, 1972. (This failure released 138 million gallons of stormwater run-off and fine coal
refuse, and resulted in 125 persons killed, another 1,000 injured, over 500 homes completely
destroyed, and nearly 1,000 others damaged.)
MSHA has nearly 40 years of experience writing regulations and inspecting dams
associated with coal mining. MSHA's regulations are comprehensive and directly applicable to
the dams used in surface impoundments at coal-fired utilities to manage CCRs. EPA believes
that, based on the record compiled by MSHA for its rulemaking, and on MSHA's 40 years of
experience implementing these regulations, the requirements being considered in this rulemaking
would substantially reduce the potential for catastrophic release of CCRs from surface
impoundments, as occurred at TVA's facility in Kingston, Tennessee, and would generally meet
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RCRA's objective to ensure the protection of humans and the environment.46 Thus, EPA is
considering establishing BMPs that would be modeled on MSHA regulations in 30 CFR Part 77.
MSHA's regulations for coal slurry impoundments apply to those impoundments at coal
mines, which impound water, sediment or slurry to an elevation of more than five feet and have a
storage volume of 20 acre-feet or more and those coal slurry impoundments that impound water,
sediment, or slurry to an elevation of 20 feet or more. The BMPs being considered for the ELG
rule would apply to all CCR impoundments at steam electric power generating facilities,
regardless of height and storage volume. EPA is also considering variations on BMPs for the
ELGs, including, but not limited to, different inspection frequencies or limitations on the
applicability of BMPs that more closely mirror the applicability of the MSHA regulations.
8.1.2.10 Voluntary Incentive Program for Power Plants that Close CCR
Impoundments or Eliminate All Process Wastewater Dischargers (Except
Cooling Water
EPA is considering establishing, as part of the BAT for existing sources, a voluntary
incentive program that provides more time for plants to implement the proposed BAT
requirements if they adopt additional process changes and controls that provide significant
environmental protections beyond those achieved by the preferred options for this proposed rule.
The development of advanced process changes and controls is a critical step toward the Clean
Water Act's ultimate goal of eliminating the discharge of pollutants into the Nation's waters. See
CWA Section 101(a)(l). Section 301(b)(l)(C) demands that BAT result in "reasonable further
progress toward the national goal of eliminating the discharge of pollutants." EPA intends that,
for any BAT option that is ultimately selected as part of any final ELG rule, such option would
represent "reasonable further progress," while the voluntary incentives program is designed to
continue progress toward achieving the national goal of the Act. In addition, Section 104(a)(l) of
the Act gives the Administrator authority to establish national programs for the prevention,
reduction, and elimination of pollution, and it provides that such programs shall promote the
acceleration of research, experiments, and demonstrations relating to the prevention, reduction,
and elimination of pollution. The voluntary incentives program being considered for the
proposed rule would effectively accelerate the research into and use of controls and processes
intended to prevent, reduce, and eliminate pollution because it would increase the number of
plants choosing to close and cap CCR surface impoundments and eliminate discharges of all
process wastewater (except cooling water) to surface waters.
This voluntary program would establish two levels, or "tiers," of advanced technology
performance requirements which would be incorporated into the NPDES permits for the facilities
that participate in the program. Under Tier 1, power plants would be granted two additional years
(beyond the time described below in Section 8.2) if they also dewater, close and cap all CCR
surface impoundments (except for those impoundments containing only combustion residual
46 On December 22, 2008, the retention wall of a coal ash impoundment at Tennessee Valley Authority's Kingston
Plant collapsed, which resulted in a massive release of CCRs directly into the Emory River and its tributaries. The
Emory River joins to the Clinch River and then converges with the Tennessee River, a major drinking water source
for populations downstream. This failure released over a billion gallons of fly ash and bottom ash, which
impacted over 100 properties, destroyed three homes, and ruptured a gas line resulting in the evacuation of 22
residents.
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leachate) at the facility, including those surface impoundments located on non-adjoining property
that receive CCRs from the facility. A power plant participating in the Tier 1 program could
continue to operate surface impoundments for which combustion residual leachate is the only
type of CCR solids or wastewater contained in the impoundment. In general, power plants
accepted in the Tier 1 incentives program would first convert ash handling operations to dry
handling or closed-loop tank-based systems and FGD wastewater treatment operations to tank-
based systems, as described above in Section 7. This first step would eliminate new contributions
of CCRs (solids and wastewater) to the surface impoundments. The plants would then dewater
the impoundments by draining or pumping the wastewater from the impoundments, in
compliance with the ELGs and other requirements established in their NPDES permits. Upon
completing the dewatering operations, plants would then stabilize the contents and close and cap
the impoundments consistent with state requirements and any other additional requirements that
may be established by EPA as part of the Tier 1 incentives program or other applicable
requirements.
Under Tier 2, power plants would be granted five additional years (beyond the time
described below in Section 8.2) if they eliminate the discharge of all process wastewater to
surface waters, with the exception of cooling water discharges. The Tier 2 incentives would not
be available to power plants that eliminate direct discharge to surface water by sending the
wastewater to a POTW. A plant accepted into the Tier 2 incentives program would ultimately
need to manage its processes and wastewater in a manner that implements a coordinated
approach toward wastewater minimization, treatment and reuse. To achieve Tier 2 status, these
plants would eliminate all process wastewater discharges (except cooling water) by reducing the
amount of wastewater generated and preferentially using recycled wastewater to meet water
supply demands. To accomplish this, Tier 2 plants would conduct engineering assessments of the
processes that generate wastewater and identify opportunities to eliminate or reduce the amount
of wastewater they generate. These plants would also assess the processes that use water and
determine how they could use recycled wastewater in those processes, as well as the degree of
treatment that may be needed to enable such reuse. Based on responses to the industry survey,
EPA has identified a number of steam electric power plants that currently discharge no process
wastewater. In addition, two of the plants that EPA visited in Italy previously discharged process
wastewater, but have implemented wastewater treatment and process changes, including
wastewater recycle, that now allow them to operate without discharging any process wastewater
except for their cooling water.
The primary objective of this program is to encourage individual power plants to install
advanced pollution prevention technologies or make process changes that would further reduce
releases of toxic pollutants to the environment beyond the limits that would be set by the
proposed rule. The voluntary incentive program being considered is designed to promote
improvements that, in concert with other environmental practices, make significant progress
toward achieving EPA's vision of the "power plant of the future" - one which will have a
minimum impact on the environment. This program would give power plants a platform to
advance the research and development of technologies and processes that promote water
conservation and water recycling and provide greater environmental protection. EPA has
conducted site visits at power plants that have implemented processes that eliminate the use of
water or recycle process wastewater to a substantial degree. Furthermore, as noted above, EPA
observed operations at power plants that implemented process modifications and treatment
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technologies that eliminated all discharges of process wastewater with the exception of their
cooling water. Implementing such practices at other power plants would dramatically reduce
discharges of toxic and other pollutants. These practices would also substantially reduce the
amount of water consumed or used by the plant, which could be an important consideration for
addressing water availability and other concerns. In exchange for providing additional time for
power plants to comply with the proposed BAT limitations, the program would lead to superior
effluent quality and greater environmental protection.
Participation in the program would be voluntary and it would be available only to
existing power plants that discharge directly to surface waters. Power plants would have until
July 1, 2017 (approximately 3 years after promulgation of the final ELGs) to commit to the
program and submit a plan for achieving the Tier 1 or Tier 2 requirements. Once a power plant
enrolls in the program, the NPDES permitting authority would develop specific discharge limits
and key milestones consistent with that tier.
Power plants enrolled in the program would ultimately be agreeing to adopt NPDES
permit limits that are more stringent than those that would be required by the proposed and final
BAT in exchange for additional time to comply with their new effluent limitations. These power
plants and their corporate owners would also receive public recognition for their commitment to
increased environmental protection.
EPA considered including features of the Tier 1 and Tier 2 incentives as part of the
options for the proposed rule. However, although EPA has observed these practices in operation
and they are available for at least a portion of the industry, the degree of complexity will vary
from plant to plant and EPA does not have the site-specific information that could be used to
sufficiently assess how that complexity may affect the engineering challenges and costs that
plants would encounter.
8.1.3 Rationale for the Proposed BAT Technology
BAT represents the best available economically achievable performance of facilities in an
industrial subcategory or category taking into account factors specified in the CWA. The CWA
factors considered in assessing BAT are the cost of achieving BAT effluent reductions, the age
of equipment and facilities involved, the process employed, potential process changes, and non-
water quality environmental impacts, including energy requirements and such other factors as the
Administrator deems appropriate. See Section 304(b)(2)(B). In addition to technological
availability, economic achievability is also a factor considered in setting BAT. See Section
301(b)(2)(A).
After considering all of the technologies described in Section 7, in light of the factors
specified in Section 304(b)(2)(B) and Section 301(b)(2)(A) of the CWA, as appropriate, EPA is
putting forth four preferred alternatives for BAT. These four preferred alternatives primarily
differ in that some would establish more environmentally protective BAT requirements for
discharges from two of the wastestreams from existing sources. Under the first preferred
alternative, EPA is proposing to establish BAT effluent limits based on the technologies
specified in Option 3a. With the exception of oil-fired generating units and small generating
units (i.e., 50 MW or smaller), the proposed rule under Option 3a would:
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• Establish a "zero discharge" effluent limit for all pollutants in fly ash transport water
and FGMC wastewater;
• Establish numeric effluent limits for mercury, arsenic, selenium, and TDS in
discharges of gasification wastewater;
• Establish numeric effluent limits for copper and iron in discharges of nonchemical
metal cleaning wastes;47
• Establish BAT effluent limits for bottom ash transport water and combustion residual
leachate that are equal to the current BPT effluent limits for these discharges (i.e.,
numeric effluent limits for TSS and oil and grease; and
• BAT for discharges of FGD wastewater would continue to be determined on a site-
specific basis.
Under the second preferred alternative for BAT, EPA is proposing to establish BAT
effluent limits based on the technologies specified in Option 3b. With the exception of oil-fired
generating units and small generating units (i.e., 50 MW or smaller), the proposed rule under
Option 3b would:
• Establish numeric effluent limits for mercury, arsenic, selenium, and nitrate-nitrite in
discharges of FGD wastewater for units located at plants with a total wet-scrubbed
capacity of 2,000 MW or more;48'49
• Establish a "zero discharge" effluent limit for all pollutants in fly ash transport water
and FGMC wastewater;
• Establish numeric effluent limits for mercury, arsenic, selenium, and TDS in
discharges of gasification wastewater;
• Establish numeric effluent limits for copper and iron in discharges of nonchemical
metal cleaning wastes;50 and
• Establish BAT effluent limits for bottom ash transport water and leachate that are
equal to the current BPT effluent limits for these discharges (i.e., numeric effluent
limits for TSS and oil and grease).
Under the third preferred alternative for BAT, EPA is proposing to establish BAT
effluent limits based on the technologies specified in Option 3. In addition to the requirements
47 As described later in this section, EPA is proposing to exempt from new BAT copper and iron limitations existing
discharges of nonchemical metal cleaning wastes that are currently authorized under their existing NPDES permit
without iron and copper limits. For these discharges, BAT limits would be set equal to BPT limits for low volume
waste.
48 Total plant-level wet-scrubbed capacity is calculated by summing the nameplate capacity for all of the units that
are serviced by wet FGD systems.
49 For units below the 2,000 MW threshold, BAT would continue to be determined on a site-specific basis.
50 As described later in this section, EPA is proposing to exempt from new BAT copper and iron limitations existing
discharges of nonchemical metal cleaning wastes that are currently authorized under their existing NPDES permit
without iron and copper limits. For these discharges, BAT limits would be set equal to BPT limits for low volume
wastes.
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described for Option 3b, the proposed rule would establish the same numeric effluent limits as in
Option 3b for mercury, arsenic, selenium, and nitrate-nitrite in discharges of FGD wastewater
from units located at all steam electric facilities, with the exception of oil-fired generating units
and small generating units (i.e., 50 MW or less).
Under the fourth preferred alternative for BAT (Option 4a), in addition to the
requirements described for Option 3, the proposed rule would establish "zero discharge" effluent
limits for all pollutants in bottom ash transport water from units greater than 400 MW.
For oil-fired generating units and small generating units (i.e., 50 MW and smaller) that
are existing sources, under all four preferred options, EPA is proposing to set the BAT effluent
limits equal to the current BPT effluent limits for copper and iron for nonchemical metal
cleaning wastes, and for TSS and oil and grease for five of the six wastestreams listed above
(i.e., FGD wastewater, fly ash transport water, FGMC wastewater, leachate from landfills and
surface impoundments containing combustion residuals, and gasification wastewater).51 EPA is
proposing Options 3a, 3b, 3 and 4a as the preferred BAT regulatory options because its analysis
to this date suggests that they are all technologically available, economically achievable, and
have acceptable non-water quality environmental impacts. However, EPA is putting forth a range
of options as candidates for BAT in order to enhance the Agency's understanding of the pros
and cons of each of these options in light of the statutory factors through the public comment
process and intends to evaluate this information and how it relates to the factors specified in the
CWA. As discussed above in Section 7 and 8.1.2, the data in EPA's record and its analysis to
date suggests that all four options are technologically available. EPA's record indicates that the
technologies comprising Options 3a, 3b, 3, and 4a are well-demonstrated and have been
employed at a subset of existing power plants.
Under all of the preferred options, the technology basis for fly ash transport water is dry
handling. All generating units built in the 30 years since the ELGs were last revised in 1982 have
been subject to a zero discharge standard for the pollutants in fly ash transport water, in nearly all
cases installing dry fly ash handling technologies to comply with the standard. In addition, many
other generating units that could discharge their fly ash transport water upon meeting a TSS
effluent limit have instead retrofitted the dry fly ash handling technology to meet operational
needs or for economic reasons. Approximately 40 percent of the plants that were operating wet-
sluicing systems in 2000 have converted generating units to dry fly ash (approximately 115
generating units at 45 power plants). Another 61 generating units are slated to convert to dry fly
ash handling by 2020. Based on data collected by the industry survey, approximately 66 percent
of coal- and petroleum coke-fired generating units handle all fly ash with dry technologies.
Another 15 percent of coal- and petroleum coke-fired generating units have both wet and dry fly
ash handling systems (typically, the wet system is a legacy system that the plant has not
decommissioned following retrofit with a dry system). Only 19 percent of coal- and petroleum
coke-fired generating units exclusively use a wet fly ash handling system. Furthermore, some of
these plants with wet fly ash handling systems manage the ash handling process so that they do
51 As described later in this section, EPA is proposing to exempt from new BAT copper and iron limitations existing
discharges of nonchemical metal cleaning wastes that are currently authorized under their existing NPDES permit
without iron and copper limits. For these discharges, BAT limits would be set equal to BPT limits for low volume
waste.
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Section 8 - Technology Options Considered as Basis for Regulation
not discharge fly ash transport water. As a result, EPA determined that only 13 percent of coal-
fired power plants would incur costs to comply with a BAT zero discharge requirement for fly
ash transport water.
Power plants recently began installing FGMC systems either to comply with state
requirements or to prepare for emissions limits established by the MATS rule. Plants using
sorbent injection systems (e.g., activated carbon injection) typically handle the spent sorbent in
the same manner as their fly ash. Nearly all plants with FGMC systems use dry handling
technologies. Only a few plants use wet systems to transport the spent sorbent to disposal in
surface impoundments. Based on the industry survey, the plants using wet handling systems
currently operate them as closed-loop systems and do not discharge FGMC wastewater to
surface waters, or have the capability to do so. These plants could continue to operate these wet
systems as closed-loop systems, or could convert to dry handling technologies by managing the
fly ash and spent sorbent together in a retrofitted dry system (the wastes are currently managed
together in the impoundments) or by installing dedicated dry handling equipment for the FGMC
wastes similar to the equipment used for fly ash.
The technology basis for control of discharges of FGD wastewater under Options 3b (for
units located at plants with a total wet-scrubbed capacity of 2,000 MW or more), 3, and 4a is
chemical precipitation followed by anaerobic biological treatment. Four power plants, or
approximately three percent of wet-scrubbed power plants that discharge FGD wastewater
already have the Options 3b (for units located at plants with a total wet-scrubbed capacity of
2,000 MW or more), 3, and 4a BAT technology in place. Under Options 3b (for units located at
plants with a total wet-scrubbed capacity of 2,000 MW or more), 3, and 4a, in addition to other
new requirements that would be established, numeric limits would be established for toxic
discharges including arsenic, mercury, and selenium from FGD wastewater.
The technology used as the basis for FGD wastewater treatment under Options 3b (for
units at plants with a total wet-scrubbed capacity of 2,000 MW or more), 3, and 4a has been
tested at power plants for more than 10 years and full-scale systems have been operating at a
subset of plants for 5 years. The biological treatment processes used in the bioreactor portion of
the treatment technology have been widely used in many industrial applications for decades both
in the U.S. and internationally. Five steam electric power plants operate fixed-film
anoxic/anaerobic biological treatment systems to treat FGD wastewater and another operates a
suspended growth biological treatment system that targets removal of selenium.52 Other power
plants are considering installing the biological treatment technology to remove selenium and at
least one plant is moving forward with construction [ERG, 2013c]. In addition, four additional
power plants currently operate anaerobic biological treatment systems for their FGD wastewater,
indicative that this is available technology. EPA is aware of industry concerns with the feasibility
of biological treatment at some power plants. Specifically, industry has asserted that the efficacy
of these systems is unpredictable, and is subject to temperature changes, high chloride
concentrations, and high oxidation reduction potential in the absorber (which may kill the
treatment bacteria). EPA's record to date does not support these assertions, but is interested in
additional information that addresses these concerns.
Four of the six operate the biological treatment systems in combination with chemical precipitation.
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More than one-third of plants that discharge FGD wastewater utilize chemical
precipitation (in some cases, also using additional treatment steps). As noted above, four power
plants currently operate chemical precipitation systems in combination with anaerobic biological
treatment systems. The chemical precipitation treatment processes included in the FGD
wastewater technology basis for these options are used at 24 percent of steam electric power
plants that discharge FGD wastewater (and another 11 percent of plants also use chemical
precipitation systems that could be upgraded to this technology basis) and also at thousands of
industrial facilities nationwide, including Metal Products and Machinery facilities, Iron & Steel
manufacturers, and metal finishers [U.S. EPA, 2003; U.S. EPA, 2002; U.S. EPA, 1983].53
Option 3b proposes limitations based on this technology for units at the largest plants (as
determined by a 2,000 MW total wet-scrubbed capacity threshold), and BAT for the control of
discharges of FGD wastewater from units at plants below this threshold would continue to be
determined on a site-specific basis. For FGD wastewater only, EPA believes any threshold
should be based on a plant level rather than a unit level because many plants currently use a
single FGD treatment systems to service multiple units. Additionally, EPA determined that wet-
scrubbed capacity is an appropriate metric because it only reflects units that are generating FGD
wastewater. For example, a plant could have a total plant nameplate generating capacity of 3,500
MW, but only have a wet-scrubbed capacity of 200 MW if only one of its units is wet-scrubbed.
EPA is putting forth this option as a preferred option based on an assumption that these facilities
are more able to achieve these limits based on economies of scale. These largest facilities will
likely also be able to absorb the costs of installing and operating the chemical precipitation and
anaerobic biological treatment systems on which the FGD wastewater limitations are based. For
these reasons, as well as those specified above related to current innovation and treatment trends,
Option 3b proposes that BAT effluent limitations for discharges of FGD wastewater would
continue to be determined on a site-specific basis for units at facilities below the 2,000 MW
threshold.
The fourth preferred alternative for this proposed rule, Option 4a, in addition to the
requirements that would be established under Option 3, would eliminate discharges of pollutants
in bottom ash transport water from units greater than 400 MW. The technology basis for bottom
ash for the zero discharge requirement is dry handling or a closed-loop system. Bottom ash
transport water is one of the three largest sources for discharges of the pollutants of concern from
steam electric power plants and these discharges occur at many power plants across the nation.
Based on data collected by the industry survey, approximately 30 percent of coal-fired and
petroleum coke-fired power plants handle bottom ash using technologies that do not generate any
transport water. In addition, another 12 percent of coal- and petroleum coke-fired power plants
manage the wet-sluicing bottom ash handling system as a closed-loop system that recirculates all
bottom ash transport water so that it is not discharged. In addition, 83 percent of coal-fired
generating units built in the last 20 years installed dry bottom ash handling systems.
EPA recognizes that the potential costs associated with compliance with a zero discharge
standard for discharges of bottom ash transport water would be substantial if applied to all
53 Physical/chemical treatment systems can be effective at removing mercury and certain other metals; however, to
achieve effective removal of selenium this technology must be coupled with additional treatment technology such as
anoxic/anaerobic biological treatment.
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Section 8 - Technology Options Considered as Basis for Regulation
facilities (for example, approximately half of Option 4 costs and approximately a third of Option
5 costs), and, therefore, EPA looked carefully at this wastestream with a particular focus on
generating unit size. EPA's review demonstrated that, in the case of bottom ash transport water,
units less than or equal to 400 MW are more likely to incur compliance costs that are
disproportionately higher per MW than those incurred by larger units. For example, the average
annualized cost of achieving zero discharge limits for bottom ash discharges (i.e. dry handling or
closed loop) per MW for a 200 MW unit is more than three times higher than the average cost
for a 400 MW unit. Based on the data from the industry survey, EPA estimates that 25 percent of
coal-fired power plants would incur costs to comply with a BAT zero discharge requirement for
bottom ash transport water from units greater than 400 MW.
Furthermore, while all plants, regardless of size, are capable of installing and operating
dry handling or closed-loop systems for bottom ash transport water, and the costs would be
affordable for most plants, EPA believes that companies may choose to shut down 400 MW and
smaller units instead of making new investments to comply with proposed zero discharge bottom
ash requirements. EPA is basing this belief on its review of units that facilities have announced
will be retired or converted to non-coal based fuel sources. Of those units that plants have
announced for retirement, and that also generate bottom ash transport water, over 90 percent are
400 MW or less [ERG, 2013d]. Therefore, for the reasons specified above, for units less than or
equal to 400 MW, Option 4a proposes to set the BAT effluent limits equal to the current BPT
effluent limits based on surface impoundments.
The two IGCC plants currently operating in the United States use the technology that is
the basis for all four preferred options for gasification wastewater. A third IGCC plant that will
soon begin commercial operation will also use the technology and, in addition to that, will also
operate a cyanide destruction step as part of the treatment system.
For all four preferred options, the proposed BAT limits for copper and iron in discharges
of nonchemical metal cleaning waste are equal to the current BPT effluent limits for these
pollutants in metal cleaning waste. These effluent limits are based on the same technology that
was used as the basis for the current ELG BPT requirements for metal cleaning waste (i.e.,
chemical precipitation).
Discharges of metal cleaning wastes that are generated from cleaning metal process
equipment without chemical cleaning compounds (i.e., nonchemical metal cleaning waste) are
already subject to BPT effluent limits for copper and iron equal to the BAT effluent limits in the
proposed rule. Based on responses to the industry survey, facilities typically treat both chemical
and nonchemical metal cleaning waste in similar fashion.
Since, as described above, nonchemical metal cleaning waste is included within the
definition of metal cleaning waste, and copper and iron are already regulated under metal
cleaning wastes, EPA would be establishing BAT limits equal to the BPT limits (for copper and
iron) that already apply to these wastes. As a result, facilities should incur no cost to comply with
the proposed BAT for these wastes. However, EPA recognizes that previous guidance provided
after the final 1974 regulation stated that wastes from metal cleaning with water are considered
"low volume" wastes. The extent to which this statement was relied upon is unclear, and EPA
rejected the guidance in the 1982 rulemaking for the steam electric ELGs (47 FR 52297).
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However, because permitting authorities and others may have relied on this guidance and the
potential costs to those facilities are not known, EPA is proposing to exempt from any new
copper and iron BAT requirements those discharges of nonchemical metal cleaning waste to
which this guidance was applied in the past. In other words, EPA is proposing to exempt from
proposed new copper and iron BAT limitations those discharges of nonchemical metal cleaning
wastes from generating units that are currently authorized to discharge nonchemical metal
cleaning wastes without copper and iron limits pursuant to existing BPT requirements for metal
cleaning waste. For such discharges, EPA is proposing to set BAT limitations equal to BPT
limitations for low volume waste.
To get a better understanding of how discharges of nonchemical metal cleaning wastes
are currently permitted, EPA's regional offices recently reviewed 45 permits for plants that EPA
had reason to believe generated nonchemical metal cleaning waste based on responses to the
industry survey. For these permits, EPA determined the following based on the review:
• 64 percent of the plants are either zero discharge of metal cleaning wastes or have to
comply with copper and iron limits;
• 27 percent of plants do not have to comply with copper and iron limits; and
• 9 percent of plant permits do not include enough information to determine whether
the plant would be in compliance with the proposed BAT limitations.
While not exhaustive, this review provides some information to suggest that many, but
not all, plants are either zero discharge or have iron and copper limits and thus are already
meeting the proposed BAT limitations. For additional information on the permit review
conducted, see Section 7.7.
In order to implement the exemption proposed for certain discharges of nonchemical
metal cleaning waste that have historically been treated as low volume wastes and not subject to
copper and iron limits under metal cleaning waste BPT requirements, EPA's current thinking is
to develop a specific list of generating units eligible for the exemption. Therefore, EPA is
seeking to identify those generating units that should be eligible for the exemption through the
public comment process on this rulemaking. To qualify for the proposed exemption, the
generating unit must meet all three of the following criteria:
• The generating unit must currently generate nonchemical metal cleaning wastes;
• The generating unit must discharge the nonchemical metal cleaning waste; and
• The generating unit must be located at a plant that is authorized to discharge the
nonchemical metal cleaning waste without limitations for copper and iron.
If the nonchemical metal cleaning wastes generated and discharged by a generating unit
do not meet all of these three criteria, then EPA proposes that the generating unit will not be
eligible for the exemption. For example, if the plant currently hauls the nonchemical metal
cleaning wastes off site for disposal, the generating units associated with the nonchemical metal
cleaning waste generation would not be exempt. Another approach EPA is considering would be
to define the conditions of the exemption, and then make it available to any facility that
qualified, regardless of whether the facility was identified to EPA during the comment period.
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This would give EPA less information on the potential effects of including this exemption in the
final rule, but would also allow qualified facilities to make use of the exemption even if they
were unaware of the need to file comments during the comment period in order to make use of it.
EPA is also considering setting BAT limitations equal to BPT limitations applicable to
metal cleaning waste for all discharges of nonchemical metal cleaning wastes (i.e., not creating
an exemption from copper and iron limits for discharges of nonchemical metal cleaning wastes
from generating units currently authorized to discharge those wastes without copper and iron
limits). As part of this approach, EPA is evaluating whether plants would incur costs to comply
with the current BPT requirements applicable to discharges of metal cleaning wastes.
EPA's analysis to date suggests that all four preferred options, Option 3a, Option 3b,
Option 3, and Option 4a, are economically achievable. EPA performed cost and economic
impact assessments using the Integrated Planning Model (IPM) for Option 3 and Option 4.54
Option 4 is more costly than any of the four preferred options including Option 4a; therefore by
performing the assessments with these two options, EPA can evaluate the potential effects of
each of the preferred options. Because the costs and the facilities affected by Option 3a and 3b
are a subset of Option 3, EPA can use the results of Option 3 to inform the potential impacts of
Option 3a and Option 3b. In a similar way, because the costs and the facilities affected by Option
4a are a subset of Option 4, EPA can use the results of Option 4 to inform the potential impacts
of Option 4a.
For the options analyzed overall, the model showed very small effects on the electricity
market, on both a national and regional sub-market basis. Based on the results of these analyses,
EPA estimates that the proposed requirements associated with Option 3a, Option 3b, and Option
3 would not lead to the premature retirement of any steam electric generating units (i.e., no
partial or full plant closures).
The results for Option 4 show fourteen unit (partial) closures and zero plant (full)
closures projected as of the model year 2030, reflecting full compliance of all facilities. 5'56 The
14 generating units are located at six plants. The IPM results also show that five steam electric
units that are projected to close under the base case (i.e., in the absence of the proposed revisions
to the ELG) would remain operating under proposed Option 4 (i.e., avoiding closure). As a
result, for Option 4, the IPM analysis projects total net closure of nine generating units, with total
combined generating capacity of 317 MW. These results support EPA's conclusion that Option 4
is economically achievable. As explained above, because the costs and facilities affected by
Option 4a are only a subset of Option 4 (i.e., are less than those for Option 4), the model would
project similar or smaller effects for Option 4a. These IPM estimates for closures and avoided
54 IPM is a comprehensive electricity market optimization model that can evaluate such impacts within the context
of regional and national electricity markets. See the Regulatory Impact Analysis for Proposed Effluent Limitations
Guidelines and Standards for the Steam Electric Power Generating Point Source Category for additional details.
55 As used here for the purpose of this rulemaking, the term partial closure refers to a plant where the closure of a
generating unit is projected, but one or more generating units at the plant will continue operating. A full closure
refers to a situation where all generating units at a plant are projected to shut down.
56 Given the design of IPM, unit-level and thereby plant-level projections are presented as an indicator of overall
regulatory impact rather than a prediction of future unit-level or plant-specific compliance actions.
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Section 8 - Technology Options Considered as Basis for Regulation
closures also support EPA's conclusion that Option 4a is economically achievable for the steam
electric industry.
As part of its consideration of technological availability and economic achievability, EPA
also considered the magnitude and complexity of process changes and new equipment
installations that would be required at facilities to meet the requirements of the rule. As described
in greater detail in Section 14, EPA is proposing that, where the limitations and standards being
proposed for existing direct and indirect dischargers are more stringent than existing BPT
requirements, those limitations and standards do not begin to apply until July 1, 2017
(approximately three years following promulgation of the final rule). EPA is proposing this
approach to provide the time that many facilities will need to raise capital, plan and design
systems, procure equipment, and construct and then test systems. Moreover, this approach will
enable facilities to take advantage of planned shutdown or maintenance periods to install new
pollution control technologies. EPA's proposal is designed to minimize any potential impacts on
electricity availability caused by forced outages.
Options 3a, 3b, 3 and 4a have acceptable non-water quality environmental impacts, as
discussed in Section 12. EPA estimates that Options 3a, 3b, 3, and 4a would increase energy
consumption by less than 0.003 percent, less than 0.004 percent, less than 0.008 percent, and less
than 0.012 percent, respectively, of the total electricity generated by power plants. EPA also
estimates that Options 3a, 3b, 3, and 4a would increase the amount of fuel consumed by
increased operation of motor vehicles (e.g., for transporting fly ash) by less than 0.009 percent,
less than 0.009 percent, less than 0.009 percent, and less than 0.014 percent, respectively, of total
fuel consumption by all motor vehicles.
As discussed in Section 12.2, EPA also evaluated the effect of the proposed rule on air
emissions generated by power plants (NOX, sulfur oxides (SOX), and CO2). For Options 3a, 3b,
and 3, the NOX emissions are estimated to increase by no more than 0.12 percent, and for Option
4a, by no more than 0.13 percent. EPA projects no significant increase in emissions of SOX or
CO2 under the four preferred options.
EPA also evaluated the effect of the proposed rule on solid waste generation and water
usage. There would be no increase in solid waste generation under Option 3a, and EPA estimates
that solid waste generation at power plants will increase by less than 0.001 percent under the
other three preferred options. EPA estimates the power plants would reduce water use by 50
billion gallons per year (136 million gallons per day) under Option 3a, 52 billion gallons per year
(143 million gallons per day) under Option 3b, 53 billion gallons per year (144 million gallons
per day) under Option 3, and 103 billion gallons per year (282 million gallons per day) under
Option 4a.
EPA also examined the effects of the preferred options on consumers as an "other factor"
that might be appropriate when considering what level of control represents BAT. If all
compliance costs were passed on to residential consumers of electricity instead of being borne by
the operators and owners of power plants, the monthly increase in electricity bill would be no
more than $0.04, $0.06, $0.13, and $0.22, respectively under Options 3a, 3b, 3, and 4a.
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EPA is not proposing either Option 1 or Option 2 as its preferred option for BAT because
neither option would represent the best available technology level of control for steam electric
power plant discharges. For example, Options 1 and 2 would allow plants to continue to
discharge fly ash transport wastewater without treating the wastes to remove dissolved metals
and many of the other pollutants present in the wastewater. However, 66 percent of all coal- and
petroleum coke-fired generating units that produce fly ash as a residue of the combustion process
already use dry fly ash technologies to manage all of their fly ash without any associated creation
or discharge of fly ash transport water. And another 15 percent of the coal- and petroleum coke-
fired generating units that produce fly ash also already operate dry fly ash handling systems in
addition to a wet ash handling system (either as a completely redundant system, or to manage a
fraction of the fly ash that is produced during combustion). Similarly, every generating unit
operating a FGMC system does so in a manner that avoids creating any FGMC wastewater (92
percent of units with FGMC), or manages the FGMC wastewater in a closed cycle process that
does not result in a discharge to surface water (8 percent of units with FGMC). The technology
serving as the basis for FGD effluent limits under Option 1 is not effective at removing many of
the pollutants of concern in FGD wastewater, including selenium, nitrogen compounds, and
certain metals that contribute to high concentrations of total dissolved solids in FGD wastewater
(e.g., bromides, boron). Furthermore, the information in the record for this proposed rule
demonstrates that the amount of mercury, selenium, and other pollutants removed by the
biological treatment stage of the treatment system, above and beyond the amount of pollutants
removed in the chemical precipitation treatment stage preceding the bioreactor, can be
substantial. Options 1 and 2 would remove fewer or similar levels of pollutants to the preferred
options, all of which EPA believes, based on its analysis to date, to be technologically available,
economically achievable, and have acceptable non-water quality environmental impacts. Options
1 and 2 would establish new effluent limits for three of the seven key wastestreams addressed in
this rulemaking. For the remaining four wastestreams, BAT effluent limits would be set equal to
the current BPT effluent limits.
EPA did not select Option 4 as its preferred regulatory option because of concerns
expressed above associated with the projected compliance costs associated with zero discharge
requirements for bottom ash for units equal to or below 400 MW. The bottom ash requirements
for Option 4 and the preferred Option 4a are the same with the exception that Option 4a proposes
to set the BAT effluent limits for bottom ash transport water equal to the current BPT effluent
limits for units less than or equal to 400 MW, while Option 4 would set the BAT effluent limits
for bottom ash transport water equal to the BPT effluent limits for units less than or equal to 50
MW. All other units would be subject to "zero discharge" effluent limits for all pollutants in
bottom ash transport water.
Moreover, Option 4 proposes to establish BAT discharge limitations for toxic discharges
for leachate. The record demonstrates that the amount of pollutants collectively discharged in
leachate by steam electric plants is a very small portion of the pollutants discharged collectively
for all steam electric power plants (i.e., less than /^ a percent). The technology basis for
limitations on discharges of combustion residual leachate proposed under Option 4 is chemical
precipitation. Because of the relatively low level of pollutants in this wastestream, and because
EPA believes this is an area ripe for innovation and improved cost effectiveness, EPA is not
putting forward this option as a preferred option. On balance, EPA would like to collect
additional information on costs and effectiveness of chemical precipitation and other possible
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technologies for reducing pollutants discharged in leachate before making a finding with respect
to what technologies represent the best available technology economically achievable for
controlling discharges of pollutants found in combustion residual leachate.
EPA did not select Option 5 as its preferred option for BAT because of the high total
industry cost for the option ($2.3 billion/year annualized social cost) and because of preliminary
indications that Option 5 may not be economically achievable. While EPA has traditionally
looked at affordability of the rule to the regulated industry, EPA has in some limited instances
over the past three decades rejected an option primarily on the basis of total industry costs. See
48 FR 32462, 32468 (July 15, 1983) (Final Rule establishing ELGs for the Electroplating and
Metal Finishing Point Source Categories); 74 FR 62996, 63026 (Dec. 1, 2009) (Final Rule
establishing ELGs for the Construction and Development Point Source Category); BP
Exploration & Oil, Inc. v. EPA, 66 F.3d 784, 796-97 (6th Cir. 1996) (upholding EPA's decision
not to require zero discharge of produced waters based on reinjection for the Offshore
subcategory of the Oil and Gas Extraction Point Source Category based in part on total industry
cost). EPA similarly finds this appropriate here. In addition, certain screening-level economic
impact analyses indicated that compliance costs may result in financial stress to some entities
owning steam electric plants. Although EPA did not select Option 5 as the preferred BAT option,
without question, Option 5 would remove the most pollutants from steam electric power plant
discharges. Also, the technologies are all potentially available and may be appropriate
(individually or in totality) as the basis for water quality-based effluent limits in NPDES permits,
depending on site-specific conditions. For example, any of the requirements that would be
established under Option 5, including at a minimum the vapor-compression evaporation
technology serving as the Option 5 technology basis for FGD wastewater, may be appropriate for
those power plants that discharge upstream of drinking water treatment plants and that have
bromide releases in wastewaters that impact treatment of source waters at the drinking water
treatment plants. See the Environmental Assessment for the Proposed Effluent Limitations
Guidelines and Standards for the Steam Electric Power Generating Point Source Category for
additional discussion about discharges of bromides.
For the reasons described in Section 8.2, EPA is proposing that, where the limitations and
standards in the proposed rule are more stringent than existing BPT requirements, those
limitations and standards do not begin to apply until July 1, 2017 (approximately three years
from the effective date of this rule).
For all eight of the main BAT options under consideration, EPA is proposing to establish
effluent limits for oil-fired generating units and small generating units (i.e., 50 MW or less) that
differ from the effluent limits for all other generating units.57 For oil-fired generating units and
small generating units, EPA is proposing to set the BAT effluent limits equal to the current BPT
effluent limits for all seven of the key wastestreams addressed by this proposed rule. For six of
these wastestreams, BAT would be set equal to current BPT numeric limits for TSS and oil and
grease, with these pollutants regulated as indicator pollutants for the control of toxic and
nonconventional pollutants. For nonchemical metal cleaning wastes, EPA is proposing to set
BAT equal to the current BPT effluent limits for copper and iron in metal cleaning wastes, but
57 For Option 4a, for discharges of pollutants found in bottom ash transport water only, as explained previously,
EPA is proposing to raise the value from less than or equal to 50 MW to less than or equal to 400 MW.
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Section 8 - Technology Options Considered as Basis for Regulation
would not establish BAT effluent limits for TSS and oil and grease (which are also currently
regulated by BPT for metal cleaning wastes).58 EPA's proposal and reasoning is detailed in
subsections 8.1.3.1 and 8.1.3.2.
In addition, EPA has identified some differences among the options in terms of cost
effectiveness. The Regulatory Impact Analysis for Proposed Effluent Limitations Guidelines and
Standards for the Steam Electric Power Generating Point Source Category describes EPA's
cost-effectiveness analysis for the preferred regulatory options. EPA's analysis to date shows
that the average cost effectiveness ($1981/TWPE) under Option 3a, 3b, 3, and 4a for existing
direct dischargers is $27, $31, $44, and $57, respectively. This demonstrates that Option 3a is the
most cost effective of the preferred options, Option 4a is the least cost effective of the preferred
options, and Option 3 and Option 3b are between the two.
EPA also calculated the cost-effectiveness of particular controls for the wastestreams that
would be controlled under the preferred options for existing direct dischargers.59 The cost-
effectiveness for zero discharge of fly ash transport and FGMC wastewater, as in Option 3a, is
$27 per TWPE removed. The cost effectiveness of chemical precipitation alone is $70 per TWPE
removed, while the cost effectiveness of chemical precipitation plus anaerobic biological
treatment, which is included in all options except Option 3a, is $60 per TWPE removed. The cost
effectiveness of zero discharge of bottom ash transport water for all units more than 50 MW is
$107 per TWPE. In comparison, when this requirement is applied only to units more than 400
MW, as in Option 4a, the cost effectiveness value is $99 per TWPE removed.
Thus, the cost effectiveness for control of the various wastestreams included within the
preferred options ranges from $27-$ 107 per TWPE in $1981; with zero discharge controls on fly
ash transport wastewater being the most cost-effective, zero discharge controls on bottom ash
transport wastewater being the least cost effective, and controls for FGD wastewater based on
chemical precipitation in combination with anaerobic biological treatment between the two.
8.1.3.1 Effluent Limits for Oil-Fired Generating Units
EPA is proposing to establish BAT limits equal to BPT for existing oil-fired units. For
the purpose of the proposed BAT effluent limits, oil-fired generating units would be those that
use oil as either the primary or secondary fuel and do not burn coal or petroleum coke. Units that
use oil only during startup or for flame stabilization would not be considered oil-fired generating
units. EPA is proposing to set BAT limits equal to BPT for existing oil-fired units because, in
comparison to coal- and petroleum coke-fired units, oil-fired units generate substantially fewer
pollutants, are generally older and operate less frequently, and in many cases are more
susceptible to early retirement when faced with compliance costs attributable to the proposed
ELGs.
As described earlier in this section, EPA is proposing to exempt from new BAT copper and iron limitations
existing discharges of nonchemical metal cleaning wastes that are currently authorized under their existing NPDES
permit without iron and copper limits. For these discharges, BAT limits would be set equal to BPT limits for low
volume waste.
59 While it is not included in the preferred options as a wastestream with additional controls, EPA also looked at the
cost effectiveness of controlling leachate using chemical precipitation and this value would exceed $1,000 per
TWPE removed.
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Section 8 - Technology Options Considered as Basis for Regulation
The amount of ash generated at oil-fired units is a small fraction of the amount produced
by coal-fired units. Coal-fired units generate hundreds or thousands of tons of ash each day, with
some plants generating more than 1,500 tons per day of ash. In contrast, oil-fired units generate
less than one ton of ash per day. This disparity is also apparent when comparing the ash tonnage
to the amount of power generated, with coal-fired units producing nearly 300 times more ash
than oil-fired units (0.04 tons per MW-hour on average for coal units; 0.000145 tons per MW-
hour on average for oil units). The amount of pollutants discharged to surface waters is roughly
correlated to the amount of ash wastewater discharged, thus oil-fired units discharge
substantially less pollutants to surface waters than a coal-fired unit even when generating the
same amount of electricity. EPA estimates that if BAT effluent limits for oil-fired units were set
equal to either the proposed Option 3 or Option 4a limits for coal-fired units (>50 MW), the total
industry pollutant reductions attributable to the proposed rule would increase by less than one
percent.
Oil-fired units are generally among the oldest steam electric units in the industry. Eighty-
seven percent of the units are more than 25 years old. In fact, more than a quarter of the units
began operation more than 50 years ago. Based on responses to the industry survey, only 20
percent of oil-fired units operate as baseload units; the rest are either cycling/intermediate units
(45 percent) or peaking units (35 percent). These units also have notably low capacity utilization.
While a quarter of the baseload units report capacity utilization greater than 75 percent, most
baseload units (60 percent) report a capacity utilization of less than 25 percent. Eighty percent of
the cycling/intermediate units and all peaking units also report capacity utilization less than 25
percent. Thirty-five percent of oil-fired units operated for more than six months in 2009; nearly
half of the units operated for less than 30 days.
As shown above, oil-fired units are generally older and operate intermittently (i.e., they
are peaking, cycling, or intermediate units). While these oil-fired units are capable of installing
and operating the treatment technologies evaluated as part of this rulemaking, and the costs
would be affordable for most of the plants, EPA believes that, due to the factors described here,
companies may choose to shut down these oil-fired units instead of making new investments to
comply with the rule. If these units shut down, it could reduce the flexibility that grid operators
have during peak demand because there would be less reserve generating capacity to draw upon.
But more importantly, maintaining a diverse fleet of generating units that includes a variety of
fuel sources is vital to the nation's energy security. Because the supply/delivery network for oil
is different from other fuel sources, maintaining the existence of oil-fired generating units helps
ensure reliable electric power generation. Thus, the oil-fired generating units add substantially to
electric grid reliability and the nation's energy security.
Based on responses to the industry survey, EPA estimates that less than 20 oil-fired units
discharged fly ash or bottom ash transport water in 2009. At the same time, EPA notes that many
oil-fired units operate infrequently, which could contribute to the relatively low numbers of units
discharging ash-related wastewater. Should more widespread operation of oil units be required to
meet demands of the electric grid, additional plants may find it necessary to discharge ash
transport water. Because of the operating conditions unique to the existing fleet of oil-fired units
and potential effects on the nation's electric power grid, a non-water quality environmental
impact that EPA considers under Section 304(b) of the CWA, EPA believes it is appropriate to
set BAT effluent limits for oil-fired equal to the current BPT limits.
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8.1.3.2 Effluent Limits for Small Generating Units
EPA is proposing to establish BAT effluent limits equal to BPT for existing small
generating units, which would be defined as those units with a total nameplate generating
capacity of 50 MW or less.60 Small units are more likely to incur compliance costs that are
disproportionately higher per amount of energy produced than those incurred by large units
because they are not as able to take advantage of economies of scale. For example, the unit-level
annualized cost for the proposed FGD wastewater treatment technology under Option 3
(chemical precipitation plus biological treatment) is approximately seven times more expensive
on a dollar-per-megawatt basis for small generating units, relative to units larger than 50 MW.
Similarly, the unit-level annualized cost to convert the fly ash handling system to dry technology
(conveyance equipment and intermediate storage silos) is more than four times more expensive
on a dollar-per-megawatt basis for small generating units, relative to units larger than 50 MW.
For Option 4, bottom ash conversions are more than six times more expensive for small units, on
a dollar-per-megawatt basis.
Moreover, the record demonstrates that the amount of pollutants collectively discharged
by small generating units is a very small portion of the pollutants discharged collectively for all
steam electric power plants (e.g., less than 1 percent under Option 3). As a result, setting BAT
limits equal to BPT for existing steam electric generating units with a capacity of 50 MW or less
will have little impact on the pollutant removals for the overall rule.
EPA considered establishing the size thresholds for small generating units at 25 MW
because that threshold is already used for this industry sector in some regulatory contexts. For
example, the Clean Air act defines an "electric utility generating unit" as "any fossil fuel fired
combustion unit of more than 25 megawatts that serves a generator that produces electricity for
sale." CAA Section 112(a)(8), 42 U.S.C. 7412(a)(8). The existing ELGs for the steam electric
power generating point source category also include different effluent limitations for plants with
total rated generating capacity of less than 25 MW. See 40 CFR 423.13(c)(l) and 423.15(i)(l).
EPA currently proposes a threshold of 50 MW rather than 25 MW because the proposed
50 MW threshold would do more to alleviate potential impacts. 61'62 EPA recognizes that any
attempt to establish a size threshold for generating units will be imperfect due to individual
differences across units and firms. However, EPA believes that a threshold of 50 MW or less
reasonably and effectively targets those generating units that should receive different treatment
based on the considerations described above.
60 Preferred Option 4a would increase this threshold for purposes of discharges of pollutants in bottom ash transport
water only, to 400 MW or less.
61 For Option 4a, for bottom ash transport water only, as explained previously, EPA is proposing to raise the value
from less than or equal to 50 MW to less than or equal to 400 MW.
62
As discussed in Section XVII. C, the proposed 50 MW threshold also alleviates potential impacts which may be
borne by small entities or municipalities.
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8.1.4 Rationale for the Proposed Best Available Demonstrated Control/NSPS Technology
Section 306 of the CWA directs EPA to promulgate New Source Performance Standards,
or NSPS, "for the control of the discharge of pollutants which reflects the greatest degree of
effluent reduction which the Administrator determines to be achievable through application of
the best available demonstrated control technology, processes, operating methods, or other
alternatives, including, where practicable, a standard permitting no discharge of pollutants."
Congress envisioned that new sources could meet tighter controls than existing sources because
of the opportunity to incorporate the most efficient processes and treatment systems into the
facility design. As a result, NSPS should represent the most stringent controls attainable through
the application of the best available demonstrated control technology, or BADCT, for all
pollutants (that is, conventional, nonconventional, and priority pollutants).
After considering all of the technology options described in Section 7, EPA is proposing
to establish NSPS based on the suite of technologies identified for Option 4 in Table 8-1. Thus,
the proposed NSPS would do the following:
• Establish numeric effluent limits for mercury, arsenic, selenium, and nitrate-nitrite in
discharges of FGD wastewater;
• Maintain the current "zero discharge" effluent limit for all pollutants in fly ash
transport water, and establish new "zero discharge" effluent limits for all pollutants in
bottom ash transport water and FGMC wastewater;
• Establish numeric effluent limits for mercury, arsenic, selenium, and TDS in
discharges of gasification wastewater;
• Establish numeric effluent limits for TSS, oil and grease, copper, and iron in
discharges of nonchemical metal cleaning wastes; and
• Establish numeric effluent limits for mercury and arsenic in discharges of leachate.
The record indicates that the proposed NSPS is technologically available and
demonstrated. The technologies that serve as the basis for Option 4 are all available based on the
performance of plants using components of the suite of technologies within the past decade. For
example, approximately a third of plants that discharge FGD wastewater utilize chemical
precipitation (in some cases, also using additional treatment steps). Five plants operate fixed-film
anoxic/anaerobic biological treatment systems for the treatment of FGD wastewater and another
operates a suspended growth biological treatment system that targets removal of selenium.63
EPA is aware of industry concerns with the feasibility of biological treatment at some power
plants. Specifically, industry has asserted that the efficacy of these systems is unpredictable, and
is subject to temperature changes, high chloride concentrations, and high oxidation reduction
potential in the absorber (that may kill the treatment bacteria). EPA's record to date does not
support these assertions, but is interested in additional information that addresses these concerns.
Moreover, approximately 50 coal-fired generating units were built within the last 20 years and
most (83 percent) manage their bottom ash without using water to transport the ash and, as a
63 Four of the six operate the biological treatment systems in combination with chemical precipitation. Other power
plants are considering installing the biological treatment technology to remove selenium, and at least one plant is
moving forward with construction.
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Section 8 - Technology Options Considered as Basis for Regulation
result, do not discharge bottom ash transport water. The Option 4 technologies in the proposed
rule represent current industry practice for gasification wastewater. Every IGCC power plant
currently in operation uses vapor-compression evaporation to treat the gasification wastewater,
even when the wastewater is not discharged and is instead reused at the plant. In the case of
FGMC wastewater, every plant currently using post-combustion sorbent injection (e.g., activated
carbon injection) either handles the captured spent sorbent with a dry process or manages the
FGMC wastewater so that it is not discharged to surface waters (or has the capability to do so).
For leachate, as discussed in Section 7, chemical precipitation is a well-demonstrated technology
for removing metals and other pollutants from a variety of industrial wastewater, including
leachate from other landfills not located at power plants. It therefore represents the "greatest
degree of effluent reduction.. .achievable" as that phrase is used in section 306 of the Clean
Water Act.
The proposed NSPS for discharges of nonchemical metal cleaning waste are equal to the
current BPT effluent limits that apply to discharges of these wastes from existing sources. As
such, the proposed NSPS would be consistent with current industry practice for treating
nonchemical metal cleaning waste and is based on the same technology that was used as the
basis for the current NSPS for chemical metal cleaning waste. Based on responses to the industry
survey, facilities typically treat both chemical and nonchemical metal cleaning waste in similar
fashion.
The NSPS being proposed also poses no barrier to entry. The cost to install technologies
at new units are typically less than the cost to retrofit existing units. For example, the cost
differential between BAT Options 3 and 4 for existing sources is mostly associated with
retrofitting controls for bottom ash handling systems. For existing generating units, the effluent
requirements considered under Option 4a for BAT would cause those plants with units greater
than 400 MW that discharge bottom ash wastewater to either modify their processes to become a
closed-loop wet sluicing system, or retrofit modifications such as replacing the bottom of boilers
to accommodate mechanical drag chain systems. For new sources, however, Option 4 would not
present plants with the same choice of retrofit versus modification of existing processes. This is
because every new generating unit already has to install some type of bottom ash handling
system as the unit is constructed. Establishing a zero discharge standard for pollutants in bottom
ash transport water as part of the NSPS means that power plants will install a dry bottom ash
handling system during construction instead of installing a wet-sluicing system. EPA estimates
that over the past 20 years, more than 50 new coal-fired generating units were built and that most
of these units (83 percent) installed dry bottom ash handling systems.
Moreover, as described in the Regulatory Impact Analysis for Proposed Effluent
Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source
Category, EPA assessed the possible impacts of Option 4 to new units by comparing the costs of
the Option 4 technologies to the costs of a new generating unit as part of its Integrated Planning
Model analyses. In both cases, the results show that the incremental costs that would be imposed
by Option 4 do not present a barrier to entry. EPA estimated that the compliance costs for a new
unit (capital and O&M) represent at most 1.5 percent of the annualized cost of building and
operating a new 1,300 MW coal-fired plant, with capital costs representing less than 1 percent of
the overnight construction costs, and annual O&M costs representing less than 5 percent of the
cost of operating a new plant. IPM results show no barrier to new generation capacity during the
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Section 8 - Technology Options Considered as Basis for Regulation
model years in which all existing plants must be in compliance as a result of the BAT/NSPS
compliance scenario.
Finally, EPA has analyzed non-water quality environmental impacts associated with
Option 4 for existing sources, and its analysis is relevant to the consideration of non-water
quality environmental impacts associated with Option 4 for new sources. EPA's analysis
demonstrates that the non-water quality environmental impacts associated with Option 4 for
existing sources are acceptable. Given that there is nothing inherent about a new unit that would
alter the analysis for such sources, EPA believes that the non-water quality environmental
impacts associated with the proposed NSPS regulatory option are, likewise, acceptable.
In contrast to the best available technology economically achievable, or BAT, that EPA is
proposing for existing sources, the proposed NSPS would establish the same limits for oil-fired
generating units and small generating units that are being proposed for all other new sources.64 A
key factor that affects compliance costs for existing sources is the need to retrofit new pollution
controls to replace existing pollution controls. New sources do not trigger retrofit costs because
the pollution controls (process operations or treatment technology) are installed at the time the
new source is constructed. Thus, new sources are less likely than an existing source to
experience financial stress by the cost of installing pollution controls, even if the pollution
controls are identical.
EPA is not proposing regulatory Options 1 or 2, which would establish new effluent
limits for only two of the seven key wastestreams addressed by this proposed rule, as its
preferred option for NSPS. As explained above, neither of these two options represents the
greatest degree of effluent reduction which the Administrator determines to be achievable
through the best available demonstrated control technology.
EPA also did not select any of the preferred BAT regulatory Options (i.e., Options 3a, 3b,
3, or 4a) as its preferred option for NSPS because they would not control FGD wastewater
(Option 3a and Option 3b for plants with a total wet-scrubbed capacity of less than 2,000 MW),
bottom ash transport water (Option 3a, Option 3b, Option 3, and Option 4a for units less than or
equal to 400 MW) or leachate discharges (Options 3a, 3b, 3, and 4a) and other, more effective,
available technologies exist that do not present a barrier to entry and have acceptable non-water
quality environmental impacts. EPA did not select preferred Option 3a for the same reasons it
rejected Options 1 and 2. EPA did not select Options 3b, 3, or 4a because, under these regulatory
options, NSPS effluent limits for bottom ash transport water for all or some portion of units and
leachate would be set equal to the current BAT effluent limits on TSS and oil and grease, which
are based on using surface impoundments.65 The record demonstrates that zero discharge
technologies are effective and available for managing bottom ash at new sources. Since these
zero discharge technologies have been installed at 83 percent of coal-fired units built in the last
20 years, effluent standards based on surface impoundments do not represent Best Available
Demonstrated Control Technology to control the discharge of pollutants in the bottom ash
wastestream from new sources regardless of the unit size. In addition, the record demonstrates
that chemical precipitation is a more effective technology than surface impoundments for
64 As a point of clarification, this similarly holds true for bottom ash limitations.
65 This rationale similarly applies to Option 3a.
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Section 8 - Technology Options Considered as Basis for Regulation
controlling the pollutants present in leachate. For these reasons, Options 3b, 3 and 4a do not
represent the best available demonstrated control technology to control the discharge of
pollutants of concern from new sources.
EPA did not select Option 5 as its preferred option for NSPS because of its high costs,
which are substantially higher than the costs for Option 4 and the other options evaluated for
NSPS. See Section 9.10 for more information about the estimated compliance costs for the NSPS
options. The cost differential between Options 4 and 5 is primarily due to the evaporation
technology basis for controlling pollutants in FGD wastewater under Option 5.
Finally, EPA notes that Option 5 is comparable to Option 4 with respect to much of the
anticipated pollutant removals, particularly the expected removals of arsenic, mercury, selenium
and nitrogen. At the same time, Option 5 would control other pollutants in FGD wastewater that
Options 1 through 4 do not effectively control, namely boron, bromides, and TDS. EPA is aware
that bromide in wastewater discharges from steam electric power plants located upstream from a
drinking water intake has been associated with the formation of trihalomethanes, also known as
THMs, when it is exposed to disinfectant processes in water treatment plants. EPA recommends
that permitting authorities consider the potential for bromide discharges to adversely impact
drinking water intakes when determining whether additional water quality-based effluent limits
may be warranted. Although EPA did not select Option 5 as the preferred NSPS option, the
technologies forming the basis for Option 5 are all technologically available and may be
appropriate (individually or in totality) as the basis for water quality-based effluent limits in
individual or general permits depending on site-specific conditions.
8.1.5 Rationale for the Proposed PSES Technology
Section 307(b), 33 U.S.C. 1317(b), of the Clean Water Act requires EPA to promulgate
pretreatment standards for pollutants that are not susceptible to treatment by POTWs or which
would interfere with the operation of POTWs. EPA looks at a number of factors in selecting the
technology basis for pretreatment standards. For existing sources, these factors are generally the
same as those considered in establishing BAT. However, unlike direct dischargers whose
wastewater will receive no further treatment once it leaves the facility, indirect dischargers send
their wastewater to POTWs for further treatment. As such, EPA must also determine that a
pollutant is not susceptible to treatment at a POTW or would interfere with POTW operations.
Table 8-2 summarizes the pass through analysis results for the BAT/NSPS pollutants for
the various wastestreams and regulatory options. As shown in the table, all of the pollutants
proposed for regulation under BAT/NSPS pass through.
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Section 8 - Technology Options Considered as Basis for Regulation
Table 8-2. Summary of Pass Through Analysis
Technology Option
Chemical Precipitation for FGD Wastewater
and/or Combustion Residual Leachate
Pollutant
Arsenic
Mercury
Pass Through?
(Yes or No)
Yes
Yes
Biological (one-stage chemical precipitation
followed by anoxic/anaerobic biological) for FGD
wastewater and/or Combustion Residual Leachate
Arsenic
Mercury
Nitrate Nitrite as N
Selenium
Yes
Yes
Yes
Yes
Mechanical Vapor-Compression Evaporation for
FGD Wastewater
Arsenic
Mercury
Selenium
TDS
Yes
Yes
Yes
Yes
Mechanical Vapor-Compression Evaporation for
IGCC Wastewater
Arsenic
Mercury
Selenium
TDS
Yes
Yes
Yes
Yes
Nonchemical Metal Cleaning Wastes
Copper
Yes
EPA evaluated the same model technologies and regulatory options for PSES that it
evaluated for BAT (described in Section 8.1.2). These standards would apply to existing
generating units that discharge wastewater to POTWs.
As explained in Section 1.2.5, in selecting the PSES technology basis, the Agency
generally considers the same factors as it considers when setting BAT, including economic
achievability. Typically, the result is that the PSES technology basis is the same as the BAT
technology basis. After considering all of the technology options described in Section 8.1.2, as is
the case for BAT, EPA is proposing four preferred alternatives for PSES (i.e., Options 3a, 3b, 3,
and 4a).
With the exception of oil-fired generating units and small generating units (i.e., 50 MW
or smaller), the proposed rule under Option 3a would:
• Establish a "zero discharge" effluent limit for all pollutants in fly ash transport water
and FGMC wastewater;
• Establish numeric effluent limits for mercury, arsenic, selenium, and TDS in
discharges of gasification wastewater;
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Section 8 - Technology Options Considered as Basis for Regulation
• Establish numeric effluent limits for copper in discharges of nonchemical metal
cleaning wastes;66 and
• Establish BAT effluent limits for bottom ash transport water and leachate that are
equal to the current BPT effluent limits for these discharges (i.e., numeric effluent
limits for TSS and oil and grease)
With the exception of oil-fired generating units and small generating units (i.e., 50 MW
or smaller), the proposed PSES under Option 3b would:
• Establish standards for mercury, arsenic, selenium, and nitrate-nitrite in discharges of
FGD wastewater for units located at plants with a total wet-scrubbed capacity of
2,000 MW;67
• Establish a "zero discharge" standard for all pollutants in fly ash transport water and
FGMC wastewater;
/-Q
• Establish standards for copper in discharges of nonchemical metal cleaning wastes;
and
• Establish standards for mercury, arsenic, selenium, and TDS in discharges of
gasification wastewater.
Under the third preferred alternative for PSES (Option 3), in addition to the requirements
described for Option 3b, the proposed rule would establish the same standards for mercury,
arsenic, selenium, and nitrate-nitrite in discharges of FGD wastewater as for Option 3b from
units at all steam electric facilities, with the exception of oil-fired generating units and small
generating units (i.e., 50 MW or smaller).
Under the fourth preferred alternative for PSES (Option 4a), the proposed rule would
establish "zero discharge" effluent limits for all pollutants in bottom ash transport water for units
greater than 400 MW. All other proposed Option 4a requirements are identical to the proposed
Option 3 requirements.
EPA is putting forth Options 3a, 3b, 3, and 4a as the Agency's preferred PSES regulatory
options in order to confirm its understanding of the pros and cons of these options through the
66 As described in Section VIII.A.3, EPA is proposing to exempt from new BAT copper and iron effluent limits
existing discharges of nonchemical metal cleaning wastes that are currently authorized by an NPDES permit without
iron and copper limits. This exemption also applies to any indirect discharges of nonchemical metal cleaning waste
that are authorized without copper pretreatment standards. For such indirect discharges, the regulation would not
specify PSES.
67 Under Option 3b (for units located at plants with a total wet-scrubbed capacity of less than 2,000 MW), the
regulations would not specify PSES for FGD wastewater, and POTWs would need to develop local limits to address
the introduction of pollutants by steam electric power plants to the POTWs that cause pass through or interference,
as specified in 40 C.F.R.403.5(c)(2).
68As described in Section VIII.A.3, EPA is proposing to exempt from new BAT copper and iron effluent limits
existing discharges of nonchemical metal cleaning wastes that are currently authorized by an NPDES permit without
iron and copper limits. This exemption also applies to any indirect discharges of nonchemical metal cleaning waste
that are authorized without copper pretreatment standards. For such indirect discharges, the regulation would not
specify PSES.
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Section 8 - Technology Options Considered as Basis for Regulation
public comment process and intends to evaluate this information and how it relates to the factors
specified in the CWA. For the same reasons identified in Section 8.1.3 for BAT, EPA's analysis
to date suggests that for indirect dischargers as well as direct dischargers, the Option 3a, Option
3b, Option 3, and Option 4a technologies are available and economically achievable, and that the
other regulatory options (Options 1, 2, 4, and 5) do not reflect the criteria for PSES. In addition,
EPA has determined that these standards will prevent pass-through of pollutants from POTWs
into receiving streams and also help control contamination of POTW sludge. EPA also
considered the non-water quality environmental impacts and found them to be acceptable, as
described in Section 12. Furthermore, for the same reasons that apply to EPA's preferred BAT
options and described in Section 8.1.3, with the exception of numeric standards for copper in
discharges of nonchemical metal cleaning wastes, EPA is proposing not to subject discharges
from oil-fired generating units and small generating units (i.e., 50 MW or smaller) to POTWs to
requirements based on Options 3a, 3b, 3, or Option 4a.69'70
Finally, similar to EPA's preferred BAT options and for the reasons supporting those
options, for certain wastestreams, EPA is proposing that any new PSES discharge standards
would apply to discharges of the regulated wastewater generated after July 1, 2017. See
discussion in Section 14.
8.1.6 Rationale for the Proposed PSNS Technology
Section 307(c) of the CWA, 33 U.S.C. 1317(c), authorizes EPA to promulgate
pretreatment standards for new sources (PSNS) at the same time it promulgates new source
performance standards (NSPS). As is the case for PSES, PSNS are designed to prevent the
discharge of any pollutant into a POTW that may interfere with, pass through, or may otherwise
be incompatible with POTWs. In selecting the PSNS technology basis, the Agency generally
considers the same factors it considers in establishing NSPS along with the results of a pass
through analysis. As a result, EPA typically promulgates pretreatment standards for new sources
based on best available demonstrated technology for new sources See National Ass'n of Metal
Finishers v. EPA, 719 F.2d 624, 634 (3rd Cir. 1983). The legislative history explains that
Congress required simultaneous establishment of new source standards and pretreatment
standards for new sources for two reasons. First, Congress wanted to ensure that any new source
industrial user achieve the highest degree of internal effluent controls necessary to ensure that
such user's contribution to the POTW would not cause a violation of the POTWs permit.
Second, Congress wished to eliminate from the new user's discharge any pollutant that would
pass through, interfere, or was otherwise incompatible with POTW operations.
For the proposed ELGs, EPA evaluated the same model technologies and regulatory
options for PSNS that it evaluated for NSPS (described in Section 8.1.4). These standards would
apply to new generating units or new facilities that discharge wastewater to POTWs. After
considering all of the technology options described in Section 8.1.2, as is the case for NSPS,
69 EPA is proposing to exempt from new PSES copper standards for existing discharges of nonchemical metal
cleaning wastes that are currently authorized. For these discharges, the regulation would not specify PSES.
70 Preferred Option 4a would increase this threshold for purposes of discharges of pollutants in bottom ash transport
water only, to 400 MW or less.
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Section 8 - Technology Options Considered as Basis for Regulation
EPA is proposing to establish PSNS based on the technologies specified in Option 4. The
proposed PSNS would:
• Establish standards for mercury, arsenic, selenium, and nitrate-nitrite in discharges of
FGD wastewater;
• Maintain a "zero discharge" standard for all pollutants in fly ash transport water, and
establish a zero discharge standard for bottom ash transport water and FGMC
wastewater;
• Establish standards for mercury, arsenic, selenium, and TDS in discharges of
gasification wastewater;
• Establish standards for copper in discharges of nonchemical metal cleaning wastes;
and
• Establish standards for mercury and arsenic in discharges of leachate.
For the same reasons identified forNSPS in Section 8.1.4, EPA is proposing Option 4 as
its preferred option because the technologies forming the basis for that option are available and
demonstrated and will not pose a barrier to entry.71 In addition, EPA has determined that these
standards will prevent pass-through of pollutants from POTWs into receiving streams and also
help control contamination of POTW sludge. EPA also considered the non-water quality
environmental impacts associated with the preferred option and found them to be acceptable, as
described in Section 14.
8.1.7 Consideration of Future FGD Installations on the Analyses for the ELG
Rulemaking
As explained earlier, implementation of air pollution controls may create new wastewater
streams at power plants. The analyses and the findings on economic achievability presented in
this preamble reflect consideration of wastestreams generated by air pollution controls that will
likely be in operation at plants at the time EPA takes final action on this rulemaking. However,
EPA recognizes that some recently promulgated Clean Air Act requirements, along with state
requirements or enforcement actions, may lead to additional air pollution controls (and resulting
wastestreams) at existing plants beyond this date. In an effort to assess the economic
achievability of the proposed rule in such cases, EPA also conducted a sensitivity analysis that
forecasts future installations of air controls through 2020 and the associated costs of complying
with the proposed regulatory requirements for the wastewater that may result from the forecasted
air control installations.72 The sensitivity analysis and results are described in more detail in the
memorandum entitled, "Flue Gas Desulfurization Future Profile Sensitivity Analysis" [ERG,
2013a].
71 For the same reasons discussed above in Section VIII for NSPS, EPA similarly determined the other regulatory
options do not reflect PSNS.
72 EPA considers that by forecasting future installations of controls out to the year 2020, the sensitivity analyses for
this rulemaking reasonably reflect full implementation of air pollution controls to comply with existing federal and
state requirements.
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EPA has two primary data sources upon which to make its projections of future air
control installations: 1) Integrated Planning Model estimates for the final MATS rule;73 and 2)
responses to EPA's steam electric industry survey. At the time EPA promulgated the MATS rule
in 2011, it projected air pollution control retrofits using IPM (which also included projected
retrofits for CSAPR). To support this rulemaking, EPA surveyed the industry about its plans for
installing certain new air pollution controls at facilities through 2020. EPA has no reason to
conclude that either the IPM FGD projections or the survey projections are more accurate than
the other. In fact, both of these sources may overstate actual installations. Prior to MATS
becoming final, many plant owners and operators assumed that wet scrubbers would be the only
technology available to meet emissions limits for acid gases. As EPA gathered and published
additional data on facility emission rates (which informed how the Agency set the standards),
and as stakeholders researched and published additional information on the performance of less
capital-intensive control technologies such as dry sorbent injection, it has become clear that
many facilities will find it more cost-effective to forgo wet scrubbers in favor of other emission-
reduction strategies. Furthermore, major economic variables such as electricity demand and
natural gas prices have changed substantially since the prevailing market conditions in 2010,
when respondents were answering the survey. For example, a facility originally indicating an
expectation in the industry survey to install a wet scrubber by 2020 may now find itself no longer
competitive in the updated marketplace with substantially lower natural gas prices and lower
electricity demand growth than previously expected. Consequently, the facility may elect to
retire and thereby neutralize the previously reported intent to scrub. Nevertheless, these two
sources remain the best available information EPA has with which to estimate future conditions.
As a first step in conducting a sensitivity analysis, EPA compared the projections from
the two sources described above. This comparison demonstrates that the IPM results for the
MATS Policy Case and the ELG industry survey responses are consistent at the aggregate level.
Furthermore, in very large part, both the survey and IPM identify the same generating units as
being wet-scrubbed, either currently or in the future (the two sources are in agreement for
approximately 94 percent of the wet-scrubbed units). The two sources also project similar wet-
scrubbed capacities. In the very few cases where there are differences between the two sources,
the differences are primarily due to the expected variation at a unit-level (e.g., IPM projects wet
FGD at unit A and dry FGD at unit B, but instead the survey responses report wet FGD at unit B
and dry FGD at unit A). Another difference between the MATS IPM estimates and the industry
survey estimates is that, in a very few cases, the IPM results estimate that certain plants would
retire (and therefore would not install wet scrubbers). In conducting the analyses for the ELG,
EPA made the conservative assumption (i.e., one that would tend to overestimate cost, if
anything) that a plant would still be in operation in 2020 unless the plant has formally announced
its closure by 2014.
Because its goal in conducting this sensitivity analysis was to assess the economic
achievability of the proposed ELG, even in light of possible future air controls, EPA developed a
conservative upper bound estimate of future installations by combining the results of the two
sources to develop its "future steam profile." In other words, EPA combined any source that
reported or projected a wet FGD into one "future steam profile." This "future steam profile" is
73 EPA IPM v.4.10 projections for units based on compliance with CSAPR, MATS, state rules, and enforcement
actions including consent decrees.
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conservative because it reflects more wet FGDs than are anticipated to actually be installed; that
is, by aggregating the survey and IPM forecast estimates it results in a total number of wet FGD
systems and wet-scrubbed capacity that is greater than either of those individual sources. EPA
then added costs associated with projected wastewater discharges from this future steam profile
to comply with the proposed ELGs to the total costs it previously calculated for the existing
universe. Based on the results of this conservative analysis, EPA finds that discharges from these
additional air controls (which, if actually installed, would be due to various requirements
including state rules, consent decrees, CSAPR/CAIR, and MATS) may increase the costs of the
proposed rule by no more than 10 to 15 percent. Even if all of these additional costs were to
come to fruition, which is unlikely since the "future steam profile" overestimates the number of
new wet FGD systems that are anticipated, EPA finds that these additional costs are
economically achievable.
EPA notes that subsequent to its analysis, the D.C. Circuit Court of Appeals vacated the
CSAPR. EPA will continue to assess the potential impacts that changes to air pollution
regulations may have on future installations of wet FGD systems. For the purpose of FGD
wastewater analyses for this rulemaking, EPA has made a conservative assumption that all of the
previously projected wet scrubber additions in the CSAPR-inclusive baseline (which also
included MATS, state rules, consent decrees, etc.) would continue to be built, and that discharges
from those additional wet scrubbers would therefore be subject to the proposed revisions to the
ELGs.
8.2 TIMING OF NEW REQUIREMENTS
As part of its consideration of technological availability and economic achievability, EPA
considered the magnitude and complexity of process changes and new equipment installations
that would be required at many existing facilities to meet the requirements of the rule. As
discussed in Section 8.1.2, EPA proposes that certain BAT limitations for existing sources (those
that would establish requirements more stringent than existing BPT requirements) would apply
on a date determined by the permitting authority that is as soon as possible when the next permit
is issued beginning July 1, 2017 (approximately three years from the effective date of this rule).
This is true of the proposed limitations and standards based on any of the eight main regulatory
options, including the preferred options, Option 3a, Option 3b, Option 3, or Option 4a.
EPA is proposing this approach for several practical reasons. While some facilities
already have the necessary equipment and processes in place, or could do so relatively quickly,
and may need little time before they are able to comply with the revised ELG requirements, not
all will be able to do so. Some facilities will need time to raise the capital, plan and design the
system, procure equipment, construct and then test the system. Moreover, providing a window of
time will better enable facilities to install the pollution control technology during an otherwise
planned shutdown or maintenance period. In some cases, a facility must apply for permission to
enter into such a period where they are producing no or less power.
During site visits, EPA found that most facilities need several years to plan, design,
contract, and install major system modifications, especially if they are to be accomplished during
planned maintenance periods to avoid causing forced outages. EPA recognizes that the proposed
rule would require a significant amount of system design by engineering firms, equipment
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Section 8 - Technology Options Considered as Basis for Regulation
procurement from vendors, and installation by trained labor forces. EPA anticipates that changes
to FGD wastewater treatment systems, fly ash systems, bottom ash systems, and/or leachate
treatment systems would constitute major system modifications requiring several years to
accomplish for many plants. EPA identified certain technical and logistical issues at some
facilities that may warrant additional time, such as coordinating ash system conversions for
multiple generating units. In order to avoid any impacts on the consistency and reliability of
power generation, outages at multiple facilities in one geographic area would need to be
coordinated, which could also result in the need for more time.
EPA recognizes that permitting authorities have discretion with respect to when to reissue
permits and can take into consideration the need to provide additional time to include BAT limits
to prevent or minimize forced outages. Thus, in some cases, the new BAT requirements may as a
practical matter be applied to a facility sometime after July 1, 2017. However, EPA judges that,
under the proposed approach, all steam electric facilities will have the proposed BAT limitations
applied to their permits no later than July 1, 2022, approximately 8 years from the date of
promulgation of any final ELGs. For indirect discharges, except with respect to discharges of
nonchemical metal cleaning waste, the proposed PSES requirements would apply by the date
determined by the control authority that is as soon as possible beginning July 1, 2017, or
approximately three years after promulgation of any final ELGs. EPA's record indicates it may
not take that long for all facilities to meet the limitations and standards. Some plants may not
require a major modification for one or more systems to be able to comply with new effluent
limits and therefore would need less time. For example, some plants have installed dry fly ash
handling systems that have capacity to handle all generated ash dry, yet they also maintain a wet
ash handling system as a backup. The backup wet system is typically operated only a few days
per year. According to the industry survey, plants such as these could quickly cease operation of
the wet system, complying with a zero discharge requirement with relative ease.
EPA envisions that each facility subject to the proposed ELGs would study available
technologies and operational measures, and subsequently install, incorporate and optimize the
technology most appropriate for each site. EPA believes the proposed rule affords flexibility for
a reasonable amount of time to conduct engineering studies, assess and select appropriate
technologies, apply for necessary permits, complete construction, and optimize the technologies'
performance. The permitting authority could establish any additional interim milestones, as
appropriate, within these timelines.
8.3 REFERENCES
1. Eastern Research Group (ERG). 2013a. Memorandum to the Record: Flue Gas
Desulfurization Future Profile Sensitivity Analysis. (29 January). DCN SE01989.
2. Eastern Research Group (ERG). 2013b. Memorandum to the Steam Electric Rulemaking
Record: Evaluation of Chemical Precipitation Costs for Ash Transport Water. (19 April).
DCN SE03869.
3. Eastern Research Group (ERG). 2013c. Memorandum to the Steam Electric Rulemaking
Record: Status of Biological Treatment Systems to Remove Selenium. (19 April). DCN
SE03874.
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Eastern Research Group (ERG). 2013d. Memorandum to the Rulemaking Record:
Methodologies for Estimating Costs and Pollutant Removals for Steam Electric ELG
Regulatory Option 4a. (19 April). DCN SE03834.
Electric Power Research Institute (EPRI). 2006. EPRI Technical Manual: Guidance for
Assessing Wastewater Impacts ofFGD Scrubbers. 1013313. Palo Alto, CA. (December).
Available online at: http://www.epriweb.com/public/000000000001013313.pdf. Date
accessed: 16 May 2008. DCN SE01817.
U.S. EPA. 2002. Development Document for Final Effluent Limitations Guidelines and
Standards for the Iron and Steel Manufacturing Point Source Category. EPA-821-R-02-
004. Washington, DC. (April).
U.S. EPA. 2003. Development Document for the Final Effluent Limitations Guidelines
and Standards for the Metal Products & Machinery Point Source Category. EPA-821-B-
03-001. Washington, DC. (February).
U.S. EPA. 1983. Development Document for Effluent Limitations Guidelines and
Standards for the Metal Finishing Point Source Category. EPA-440/1-83/091.
Washington, DC. (June).
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Section 9 - Engineering Costs
SECTION 9
ENGINEERING COSTS
This section presents EPA's methodology to determine incremental capital and operating
and maintenance (O&M) costs for the steam electric industry to comply with each regulatory
option considered for the proposed rule.
Section 9 describes EPA's general approach for estimating incremental compliance costs
for effluent limitations guidelines and standards (ELGs) for industrial categories. Section 9.2
provides a brief description of the basis for the compliance costs for each wastestream and
technology option. Section 9.3 describes the methodology EPA used to estimate costs for the
steam electric industry to achieve the limitations and standards based on each technology option
considered (described in Section 8 of this report). Section 9.3 presents information on the
specific cost elements included in EPA's methodology and the criteria EPA used to identify
plants that would likely incur compliance costs. Section 9.4 describes the development of the
data inputs, outputs, and model used to estimate the compliance costs. Section 9.5 presents
EPA's methodologies for estimating those components of compliance costs that are applicable to
more than one of the treatment technologies evaluated. Sections 9.6, 9.7, and 9.8 summarize the
technology options costed and the results of the costs analyses for flue gas desulfurization (FGD)
wastewater, fly ash and bottom ash transport water, and combustion residual landfill leachate,
respectively.
9.1 INTRODUCTION
Effluent limitations guidelines and standards establish numerical limits on the discharge
of pollutants to waters of the United States. These limits are based upon the performance of
specific technologies that comprise the regulatory options. While implementation of the specific
technologies that form the basis for the proposed regulatory options would not be required, EPA
calculates the cost for plants to implement these technologies to estimate the compliance costs
for the industry to meet the numerical limitations and standards, including any identified best
management practices (BMPs). For existing sources, compliance costs are incremental, meaning
they represent the costs expected to be incurred as a result of plants revising exiting operations to
match those that form the bases of the regulatory options. For new sources, EPA estimates the
costs to install such technologies compared to what a typical source would do in the absence of
the rule.
EPA often estimates costs on a per plant basis and then sums or otherwise escalates the
plant-specific values to represent industry-wide compliance costs. Calculating costs on a per
plant basis allows EPA to account for differences in plant characteristics such as types of
processes used, wastewaters generated and their flows/volumes and characteristics, and
wastewater controls in place (e.g., best management practices and end-of-pipe treatment). EPA
took this approach in estimating the compliance costs associated with the proposed rule.
EPA estimated the costs to steam electric power plants - whose primary business is
electric power generation or related electric power services - of complying with the proposed
ELGs. EPA evaluated the costs of the proposed ELGs on all plants currently subject to the
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Section 9 - Engineering Costs
existing ELGs.74 Some aspects of the proposed ELGs (e.g., applicability changes) would likely
not lead to increased costs to complying plants. Other aspects of the proposed ELGs would likely
lead to increased costs to a subset of complying plants. These plants are generally those that
generate the wastestreams for which EPA is proposing new limitations or standards. This section
describes the detailed costing evaluation EPA performed for these plants that may incur
compliance costs associated with the proposed rule.
As discussed earlier in Section 5, EPA proposes to establish a separate set of
requirements for existing oil-fired generating units and units with a capacity of 50 MW or less.
For these units, BAT limits would be set equal to BPT limits. As the proposed rule would not
establish additional control on discharges associated with these operations, EPA accordingly did
not include incremental costs for these units as a result of this proposed rule.75
EPA estimated compliance costs associated with each of the regulatory options from data
collected through survey responses, site visits, sampling episodes, and from individual power
plants and equipment vendors. EPA used this information to develop computerized cost models
for each of the technologies that form the basis of the regulatory options. EPA used these models
to calculate plant-specific compliance costs for all power plants that the information suggests
would incur costs to comply with one or more proposed requirements associated with the
regulatory options.76 Therefore, EPA's plant-specific cost estimates represent the incremental
costs for a plant when its existing practices would not lead to compliance with the option being
evaluated. While implementation of the specific technologies that form the basis for the proposed
regulatory options would not be required, EPA calculated the cost and for the plant to implement
these technologies to estimate of the compliance costs associated with EPA's proposal.
EPA's cost estimates include the following key cost components: capital costs (one-time
costs); annual operating and maintenance costs (which are incurred every year); and other one-
time or recurring costs. Capital costs comprise the direct and indirect costs associated with the
purchase, delivery, and installation of pollution control technologies. Capital cost elements are
specific to the industry and commonly include purchased equipment and freight, equipment
installation, buildings, site preparation, engineering costs, construction expenses, contractor's
fees, and contingency. Annual operating and maintenance costs comprise all costs related to
operating and maintaining the pollution control technologies or performing BMPs for a period of
one year. Operating and maintenance costs are also specific to the industry and commonly
include costs associated with operating labor, maintenance labor, maintenance materials (routine
replacement of equipment due to wear and tear), chemical purchase, energy requirements,
residual disposal, and compliance monitoring. In some cases, the technology options may also
74 Based on the Steam Electric Survey responses, Internet searches, articles, and data provided by the industry, EPA
removed the following types of plants, or steam electric generating units, from the analysis as they were considered
outside the applicability of the rule or would be by the time the final rule is promulgated: plants, or steam electric
generating units, expected to be retired by 2014; and plants, or steam electric generating units, converting to non-
fossil fuel sources (e.g., natural gas, municipal solid waste) by 2014.
75 EPA did estimate costs for these operations to comply with the BAT limits applicable to the rest of the units and
has included those estimates in the docket for the proposed rule. [U.S. EPA, 2012].
76 Because the rule is scheduled for promulgation in May 2014, EPA did not include compliance costs or pollutant
removals for plants that are expected to retire by 2014 and plants that do not discharge any of the applicable
wastestreams.
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Section 9 - Engineering Costs
result in recurring costs that are incurred less frequently than annually (e.g., 3-year recurring
costs for equipment replacement) or one-time costs other than capital investment (e.g., one-time
engineering costs).
9.2 STEAM ELECTRIC TECHNOLOGY OPTION COST BASES
The following subsections provide a brief description of the basis for the estimation of
the compliance costs for each wastestream and technology option. The technology options
considered as the bases of the regulatory options are identified in Section 8 and described in
detail in Section 7.
9.2.1 FGD Wastewater
EPA estimated compliance costs for plants to treat FGD wastewater using one of the
following three technology options:
• One-stage chemical precipitation;
• One-stage chemical precipitation followed by biological treatment; and
• One-stage chemical precipitation followed by softening and vapor-compression
evaporation.
For the one-stage chemical precipitation system, EPA included costs for the plants to
install and operate the following:
• Equalization tank to hold and store the wastewater;
• Reaction tanks for the addition of lime, organosulfide, ferric chloride, and polymers;
• Solids-contact clarifier to remove suspended solids;
• Gravity sand filter to reduce solids; and
• Effluent storage tank.
Additionally, EPA included costs for a sludge holding tank and filter presses to dewater
the solids collected in the clarifier. EPA also included costs for the transport and disposal of the
resulting solids in a landfill. The costs also include all ancillary equipment and the associated
operating and maintenance costs associated with the system.
For the one-stage chemical precipitation followed by biological treatment system, EPA
included all the costs described above for the chemical precipitation system, but it also included
costs for the following:
• Anoxic/anaerobic biological treatment system (two stages); and
• Heat exchanger (for plants in certain geographic locations).
EPA also included costs for the transport and disposal of additional solids collected in the
biological system. The costs include all ancillary equipment and the associated operating and
maintenance costs associated with the system.
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Section 9 - Engineering Costs
For the one-stage chemical precipitation followed by softening and vapor-compression
evaporation, EPA included all the costs described above for the chemical precipitation system,
but it also included costs for the following:
• Softening step, including clarification and solids dewatering;
• Reaction tank for acid addition;
• Heat exchanger to increase the temperature of the wastewater;
• Deaerator to remove noncondensibles;
• Mechanical vapor compression brine concentrator;
• Distillate tank; and
• Forced-circulation crystallizer.
EPA also included costs for the transport and disposal of additional solids collected in the
softener and the forced-circulation crystallizer. The costs include all ancillary equipment and the
associated operating and maintenance costs associated with the system.
9.2.2 Fly Ash Transport Water
EPA estimated compliance costs for plants operating wet sluicing systems to convert to
dry vacuum fly ash handling systems. For each generating unit with a wet sluicing system, EPA
determined that the plants would likely continue to use the existing valves and branch lines
underneath the fly ash collection hoppers, but the plant would require new valves and piping to
convey the ash to the silo(s). Additionally, EPA included costs for a mechanical exhauster to
create the vacuum. EPA also included costs for the plant to install a new silo, including pugmills
and wet unloading equipment. Finally, EPA included costs for the transport and disposal of all
the additional ash that the plant is now handling with the dry vacuum system.
9.2.3 Bottom Ash Transport Water
EPA estimated compliance costs for plants operating wet sluicing systems to convert to
bottom ash handling systems that eliminate the discharge of bottom ash transport water. For each
generating unit with a wet sluicing system, EPA estimated the costs for converting to one of the
following two systems:
• Mechanical drag system; and
• Remote mechanical drag system.
For the mechanical drag system, EPA included the costs for the demolition of the bottom
of the boiler and installation of a mechanical drag system at the bottom of the boiler. The MDS
design does not include operation as a closed-loop system (i.e., the water leaving the system with
the bottom ash does not need to be collected, cooled, and returned to the system), thereby
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Section 9 - Engineering Costs
eliminating the need for a heat exchanger.77 For the remote mechanical drag system, EPA
included the costs for the construction of a remote mechanical drag system away from the boiler,
as well as a sump, recycle pumps, and a chemical feed system to return the water to the boiler for
reuse as bottom ash transport water.78 EPA also included the costs for a semi-dry silo for both
systems. Additionally, EPA included the costs for the transport and disposal of all bottom ash to
a landfill.
For certain plants that recycle most of the bottom ash transport water within the system
and only discharge a small amount of wastewater, EPA estimated costs for these plants to hire a
consultant to help them cease discharging bottom ash transport water and operate a completely
closed-loop system.
9.2.4 Combustion Residual Leachate
EPA estimated compliance costs for plants generating combustion residual leachate from
landfills or surface impoundments to comply with requirements based on one of the following
two technology options:
• One-stage chemical precipitation; and
• One-stage chemical precipitation followed by biolo;
>gical treatment.
To estimate the compliance costs for plants that generate landfill leachate, EPA used the
same general methodology described in Section 9.2.1.
Plants that generate surface impoundment leachate will likely use a different approach
than installing the technology basis to comply with limitations or standards based on either of the
technology options. As described in Section 7.4, 36 percent of plants generating leachate from
combustion residual impoundments recycle the leachate back to the ash/FGD impoundment from
which it was collected. Additionally, some plants use the impoundment leachate for dust control
at a landfill or to moisture condition ash transported to a landfill. Based on these data, EPA
believes that when faced with the proposed effluent limitations for discharges of combustion
residual leachate, plants would comply with the limit by recycling the leachate back to the
ash/FGD impoundment from which it was generated (or use the leachate for dust
control/moisture conditioning) instead of installing the technology option to treat and discharge
the wastewater because it is a less expensive alternative. There would be no (or negligible) costs
associated with recycling the leachate back to the ash/FGD impoundment because the plant will
either: 1) use the existing pump that transfers the leachate to a separate location to pump it back
to the impoundment; or 2) install a pump to transfer the leachate to the impoundment, but the
costs would be offset because the plant no longer needs to operate a separate impoundment (or
other treatment system) that is currently used to treat the leachate to meet the existing BPT
77 Because the MDS system does not use water as the transport mechanism, the water removed from the system with
the bottom ash is not bottom ash transport water, and therefore, is not subject to the bottom ash transport water
effluent limitations.
78 Because the remote MDS system does use water as the transport mechanism, all water removed from the system
must be reused without discharge to meet the proposed zero discharge effluent limitations for bottom ash transport
water.
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Section 9 - Engineering Costs
effluent limitations prior to its discharge. Therefore, there are no compliance costs for
combustion residual leachate from surface impoundments. Therefore, where this section further
addresses the costing methodology for combustion residual leachate, it refers to the costs
associated with the treatment of combustion residual leachate from landfills.
9.2.5 Gasification Wastewater
As described in Section 4.2.3, there are two currently operating and one planned
integrated gasification combined-cycle (IGCC) units in the United States. Each of these three
plants is operating or will operate the vapor-compression evaporation system that is the
technology basis for the proposed ELGs for gasification wastewater. Therefore, because all the
plants are currently operating the BAT system, there are no compliance costs for gasification
wastewater.
9.2.6 Flue Gas Mercury Control Wastewater
As described in Section 6.4, there are approximately 73 plants with at least one activated
carbon injection (ACT) system. Of these, only six (three with current systems and three with
planned systems) reported handling the flue gas mercury control (FGMC) waste using a wet
sluicing system. However, of these six plants, only one discharges FGMC wastewater, and that
one plant collects the FGMC waste with the fly ash in the primary particulate control system and
already has the capability to handle both the FGMC and fly ash dry. Therefore, there are no
compliance costs for flue gas mercury control wastewater.
9.2.7 Nonchemical Metal Cleaning Wastes
As described in Section 8.1.3, EPA is proposing to set BAT limitations for nonchemical
metal cleaning wastes that are equivalent to the BPT standards that are already in place for this
wastestream. Because nonchemical metal cleaning wastes are already subject to the proposed
BAT limitations, based on the current BPT standard, the plants generating and discharging
nonchemical metal cleaning wastes should already be meeting these standards. Additionally, as
described in Section 8.1.3, EPA is proposing to exempt from new limitations and standards any
nonchemical metal cleaning wastes generated and authorized for discharge without copper and
iron limits. As a result, all facilities are either already in compliance or will be exempt from the
requirements and, therefore, EPA finds there are no compliance costs for nonchemical metal
cleaning wastes.
9.3 STEAM ELECTRIC COMPLIANCE COST METHODOLOGY
EPA developed a cost methodology to estimate plant-level compliance costs for existing
and new sources using data collected from the Questionnaire for the Steam Electric Power
Generating Effluent Guidelines (Steam Electric Survey), site visits, and sampling episodes. EPA
also solicited data from vendors of various wastewater treatment technologies and ash handling
operations to estimate plant-level compliance costs. The estimated costs are incremental costs to
account for only the additional costs beyond those the plant already incurs, or would incur as a
new source, in order to comply with the proposed regulations.
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Section 9 - Engineering Costs
As a first step in estimating costs associated with new or additional limitations or
standards for discharges from a particular generating unit at an existing steam electric plant (i.e.,
existing sources), EPA used the plant's survey response to determine if the wastestreams it
discharges may be subject to new requirements under a regulatory option. Then, for each of the
wastestreams that may be subject to new requirements for a regulatory option, EPA reviewed the
survey response, available sampling data, and industry long-term self-monitoring data for the
plant to determine if its existing practices would lead to compliance with the new or revised
limitations or standards (e.g. plant currently employs the technology option). In this case, EPA
finds the plant will incur no compliance cost associated with the discharge of that particular
wastestream other than compliance monitoring costs. For all other applicable wastestreams, EPA
assessed the operations and treatment system components in place at the plant, identified
necessary components that the plant would need to come into compliance, and estimated the cost
to install and operate those components. As appropriate, EPA also accounted for expected
reductions in the plant's costs associated with their current operations or treatment systems that
would no longer be needed as a result of installing and operating the technology bases (e.g.,
avoided costs to manage surface impoundments). For plants that may already have certain
components installed, EPA compared certain key operating characteristics, such as chemical
addition rates, to determine if additional costs (e.g., chemical costs) were warranted.
For example, to comply with Option 3, EPA estimated compliance costs for a plant that
currently sluices fly ash to an ash impoundment and subsequently discharges that fly ash
transport water. In this case, EPA estimated the cost for the plant to convert its fly ash handling
system to a dry vacuum system and determined that certain components of its existing system
would continue to be used following the conversion.79 EPA also included costs for additional
equipment, such as vacuum systems and silos, to handle and store the dry fly ash. EPA also
included additional transportation and landfill disposal costs, and cost savings for managing less
waste through the ash impoundment(s).
As another example, to comply with Option 3, EPA estimated compliance costs for a
plant that currently treats its FGD wastewater through a chemical precipitation system prior to
discharge. In this case, EPA evaluated 1) whether the chemical precipitation system design basis
includes equalization with 24-hour residence time, 2) if the plant had an equivalent number
and/or type of reaction tanks, and 3) if the plant already had components such as chemical feed
systems, solids contact clarifier, sand filter, effluent and sludge holding tanks, sludge filter
presses, and pumps in place. If the plant had any of these components in place, EPA did not
include that cost in its compliance cost estimate. EPA also evaluated whether chemical addition
costs would be required based on the plant's reported chemical addition and dosages, and
estimated the costs for installing and operating the biological treatment stage.
EPA also evaluated the additional transportation and landfill operations required to
dispose of the additional solid waste generated (FGD sludge, fly ash, bottom ash) from the
implementation of the technology options. EPA estimated disposal costs based on whether the
plant reported an on-site combustion residual landfill.
79 The conversion from wet to dry fly ash handling for a unit requires new equipment to pneumatically convey the
ash; however, ash handling vendors stated that for dry vacuum retrofits, the existing hopper equipment and branch
lines can be retained and reused.
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Section 9 - Engineering Costs
For each plant, EPA calculated compliance costs for all applicable technology options
and then calculated the total costs for the eight regulatory options, presented in Section 8.1 of
this report. For more information on the compliance cost methodology, see EPA's Incremental
Costs and Pollutant Removals for Proposed Effluent Limitation Guidelines and Standards for the
Steam Electric Power Generating Point Source Category [U.S. EPA, 2013].
9.4 STEAM ELECTRIC COST MODEL
EPA calculated the industry incremental compliance cost estimates by developing a
computer-based cost model containing the following main components:
• Input Data
• Industry Assumptions/Factors
• Technology Cost Modules
• Model Outputs
Input data include relevant plant-specific information, such as identification of which
wastewaters are discharged from each plant, together with plant characteristics such as plant
processes, wastewater flow rates, production data, and existing pollution control technologies.
Industry assumptions and factors are general values and factors that are not plant-specific and are
applicable to the entire industry. These include constants and coefficients used in the cost
calculations such as equipment design basis (used for equipment sizing, for example hydraulic
residence time), materials of construction, equipment capacity (accounts for maximum design
capacity as compared to typical operating conditions), equipment redundancy, transport distance
for equipment and supplies, transport mode and capacity, and cost indices (used to adjust cost
data from different years to a common base year). Technology cost modules use the plant-
specific input data and industry assumptions/factors to calculate and output costs for a specific
cost component (technology or technology component) for each applicable wastestream for each
plant and each regulatory option. Finally, reporting programs combine the applicable cost
components to calculate plant-level capital and operating and maintenance costs (and any
necessary one-time and/or recurring costs) for each regulatory option, and to sum or otherwise
escalate these plant-level costs to calculate total industry capital and operating costs by
regulatory option.
EPA used this computer-based cost model approach, including all four main components
described above, to generate plant-specific compliance costs. The steam electric cost model
calculates compliance costs by referencing several input tables and running the applicable
technology cost modules specific to each plant's input characteristics. The compliance costs for
each technology option are calculated using a combination of the technology cost modules, some
that calculate option costs specific to each technology option (e.g., biological treatment, dry fly
ash handling) and some that calculate common cost elements for each technology option,
although the inputs may differ based on specific wastestreams (e.g., transport and disposal costs).
Table 9-1 presents the different technology cost modules that compose the technology options.
Each technology option incorporates technology-specific and global assumptions and factors to
calculate the compliance costs (e.g., the model outputs).
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Section 9 - Engineering Costs
Table 9-1. Technology Costs Modules Used to Estimate Compliance Costs
Technology Option
FGD Wastewater Treatment: Chemical Precipitation
FGD Wastewater Treatment: Chemical Precipitation + Biological Treatment
FGD Wastewater Treatment: Chemical Precipitation + Evaporation
Fly Ash: Zero discharge
Bottom Ash: Zero discharge
Leachate Wastewater Treatment: Chemical Precipitation
Leachate Wastewater Treatment: Chemical Precipitation + Biological Treatment
Technology Cost Module
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metal cleaning wastes.
a - The technology cost module is called the "Dry Bottom Ash Handling" module, but it includes a technology option that is a closed-loop recycle system.
-------
Section 9 - Engineering Costs
9.4.1 Input Data to Technology Cost Modules
EPA developed a set of input tables based on information from the Steam Electric
Survey, site visits, and sampling episodes. The cost model references the input tables to estimate
the appropriate compliance cost for each plant for each technology option. The cost model
estimates compliance costs at a plant basis for each technology option and then sums the various
technology option to estimate the plant-level compliance costs for each regulatory option. The
cost model first references a plant-level input table, which indicates the technology options
specific to each plant. The plant-level cost input table was developed using data from the Steam
Electric Technical Questionnaire Database (survey technical database), which was developed
using the plant responses to the Steam Electric Survey to identify the population of plants that
discharge wastestreams that may be subject to new or additional limitations or standards [ERG,
2013d]. For all plants that generate at least one of these wastestreams, EPA determined if the
plant discharges (or may discharge by 2014) one or more of the applicable wastestreams (e.g.,
FGD wastewater, fly ash transport water) controlled by a regulatory option. If the plant does not
discharge an applicable wastestream, then EPA set the compliance costs for that wastestream to
be zero. If the plant does discharge an applicable wastestream, then EPA gathered the plant-
specific data appropriate for the applicable technology cost modules. Table 9-2 identifies the
number of plants that EPA finds will likely incur costs to comply with new or additional
limitations or standards for a wastestream under at least one of the evaluated regulatory options.
Table 9-2. Number of Plants Expected to Incur Compliance Costs by Wastestream and
Regulatory Option
Regulatory
Option
1
3a
2
3b
3
4a
4
5
FGD
Wastewater
116
0
116
17
116
116
116
116
Fly Ash
Transport
Water
0
66
0
66
66
66
66
66
Bottom Ash
Transport
Water
0
0
0
0
0
115
240
240
Combustion
Residual
Leachate
0
0
0
0
0
0
101
101
Gasification
Wastewater
0
0
0
0
0
0
0
0
Flue Gas
Mercury
Control
Wastewater
0
0
0
0
0
0
0
0
Nonchemical
Metal
Cleaning
Wastes
0
0
0
0
0
0
0
0
Total3
116
66
116
80
155
200
277
277
a - The number of plants incurring costs is not additive for each regulatory option because some plants may incur
costs for multiple wastestreams.
Each technology cost module includes a set of input tables. These input tables include
indicators specifying the level of costs required for each technology option and the plant-specific
data used in the cost equations. The following subsections describe each of the input tables used
in the technology cost modules. See the appendix of EPA's Incremental Costs and Pollutant
Removals for Proposed Effluent Limitation Guidelines and Standards for the Steam Electric
Power Generating Point Source Category report for the specific input tables described below
[U.S. EPA, 2013].
9-10
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Section 9 - Engineering Costs
FGD Wastewater Flow
For each applicable plant, EPA identified a plant-level FGD wastewater flow rate in
gallons per day. EPA used the purge rate reported in the Steam Electric Survey as the input value
for the FGD technology cost modules. For plants operating more than one FGD system, the input
value was the sum of the purge rates for the individual systems. For current FGD systems that
did not provide an FGD purge flow value, EPA estimated the purge rate based on the amount of
coal burned and the median FGD purge rate per ton of coal burned based on coal type. See
Section 4.1.1 of EPA's Incremental Costs and Pollutant Removals for Proposed Effluent
Limitation Guidelines and Standards for the Steam Electric Power Generating Point Source
Category report for more details on the FGD wastewater flow rate estimation methodology [U.S.
EPA, 2013].
FGD Treatment-In-Place Data
This input table includes data on each plant's current level of treatment for its FGD
wastewater. For plants currently treating the FGD wastewater using one-stage chemical
precipitation, anoxic/anaerobic biological treatment, or vapor-compression evaporation systems,
EPA did not estimate compliance costs for the specific pieces of equipment that are already
operating at the plant. For example, under Option 1, if a plant operates a one-stage chemical
precipitation system for the treatment of FGD wastewater that includes all the steps included as
the basis for the technology option other than sulfide precipitation, then EPA would include
capital costs for the plant to install a reaction tank and sulfide chemical feed system and
operating and maintenance costs for the amount of sulfide added to the system on a yearly basis.
The compliance costs for all other pieces of equipment for the system would be set to zero.
Fly Ash Production Data
For each applicable generating unit, EPA identified generating unit-level wet fly ash
production in tons per day and operating days per year. EPA used these values reported in the
Steam Electric Survey as input values for the fly ash technology cost module. Because the cost
model estimates fly ash compliance cost at the generating unit level, EPA used unit-level input
values.
EPA also identified generating units with existing dry fly ash handling equipment. Steam
electric generating units equipped with only wet fly ash handling systems would incur the costs
for complete conversion of the ash handling system. Those generating units equipped with both
wet and dry fly ash handling capabilities may need only certain additional equipment in order for
them to handle all fly ash dry (i.e., additional vacuum capacity, additional silo capacity,
additional unloading equipment). EPA evaluated each plant and unit to identify the additional
equipment that would be needed and included costs for only those pieces of equipment.
Bottom Ash Production Data
For each applicable generating unit, EPA identified generating unit-level wet bottom ash
production in tons per day, operating days per year, and capacity in megawatt (MW). EPA used
these values reported in the Steam Electric Survey as input values for the bottom ash technology
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Section 9 - Engineering Costs
cost module. Because the cost model estimates bottom ash compliance cost at the generating unit
level, EPA used unit-level input values.
Impoundment Data
EPA used data from the Steam Electric Survey and plant contacts to identify which plants
operate one or more impoundments containing combustion residuals including FGD solids, fly
ash, and/or bottom ash.
On-Site Landfill Data
EPA used data from the Steam Electric Survey to identify which plants operate on-site
active/inactive landfills containing combustion residuals including FGD solids, fly ash, and/or
bottom ash.
Landfill andLeachate Data
For each landfill identified as generating landfill leachate, EPA identified the landfill
leachate volume discharged each year in gallons per day. For those plants that did not report a
leachate volume in the Steam Electric Survey, EPA estimated a flow using data from other plants
that reported a leachate volume in the survey. EPA first determined a median leachate discharge
rate per acre of landfill containing combustion residuals, based on the plant responses to the
Steam Electric Survey, and multiplied this value by a plant's reported combustion residual
landfill acreage collecting leachate to estimate a flow. For those plants that didn't report a
leachate volume or a landfill acreage collecting leachate, EPA estimated the landfill acreage
collecting leachate based on the plant's reported total active/inactive landfill acreage and the
median ratio of landfill acreage collecting leachate to total active/inactive landfill acreage for
those plants that provided both values. Finally, for those plants EPA could not estimate a value
using the other two approaches, EPA estimated the leachate volume using the median leachate
volume for all plants reporting a volume.
See Section 4.1.3 of EPA's Incremental Costs and Pollutant Removals for Proposed
Effluent Limitation Guidelines and Standards for the Steam Electric Power Generating Point
Source Category report for more details on the landfill leachate flow rate estimation
methodology [U.S. EPA, 2013].
9.4.2 Industry Assumptions/Factors
The steam electric cost model includes several data tables containing values for industry
assumptions and factors. These assumptions and factors are used in the cost equations for the
specific technology options for all plants incurring costs for the specific technology option.
Each technology cost module contains a set of tables including the specific factors for
that technology option. These factors include the coefficients for the technology option equations
and other input constants applicable to all plants incurring the specific technology option costs.
For example, for the fly ash cost methodology, EPA used a dry fly ash density of 45 Ibs./ft3,
which is used to estimate the size of the silo(s) required to store the ash. EPA used this density
for all generating units for which the fly ash compliance costs are applicable. For more
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Section 9 - Engineering Costs
information on the specific technology cost module factors, see EPA's Incremental Costs and
Pollutant Removals for Proposed Effluent Limitation Guidelines and Standards for the Steam
Electric Power Generating Point Source Category report. [U.S. EPA, 2013]
Although each technology cost module contains its own set of factor tables, there are two
sets of industry factors referenced by all technology option modules. These coefficients and
constants do not change based on the different elements of the technology cost modules. These
industry factors include:
• Cost Indices. Because EPA presents all compliance costs in 2010 dollars, EPA had to
index several cost components. EPA adjusted all costs to 2010 dollars using the RS
Means Historical Cost Index values for all technology cost modules [RSMeans, 2011]
• Freight Cost Factors. For all technology options, EPA estimates several freight costs
for shipping equipment or materials to the plant. The factors used to estimate these
shipping costs are universal for all technology options. These values were estimated
using data from FreightCenter.com and vendor contacts. [U.S. EPA, 2013].
9.4.3 Technology Cost Modules
To estimate the plant-level technology option compliance costs, EPA developed nine
different technology cost modules that use the various input data, industry assumptions and
factors, and costing methodologies to generate plant-specific compliance cost outputs. Each
technology cost module calculates specific cost components for each plant incurring compliance
costs. The technology cost modules and a brief description of the cost components calculated are
included in the following listing. See Sections 9.4 and 9.5 for more specific information on the
technology cost modules.
• Biological Treatment - calculates capital and O&M costs associated with an
anoxic/anaerobic biological treatment system;
• One-Stage Chemical Precipitation - calculates capital and O&M costs associated with
the one-stage chemical precipitation system used as the basis for the technology
option;
• Vapor-Compression Evaporation - calculates capital and O&M costs associated with
the vapor-compression evaporation system used as the basis for the technology
option;
• Dry Fly Ash Handling - calculates capital, O&M, and recurring costs associated with
the dry fly ash handling system used as the basis for the technology option;
• Dry Bottom Ash Handling - calculates capital, O&M, one-time, and recurring costs
associated with a dry or closed-loop recycle bottom ash handling systems used as the
basis for the technology option;
• Transportation - calculates O&M costs associated with transporting FGD solid waste,
ash, and/or landfill leachate solid waste to an on- or off-site landfill;
• Disposal - calculates capital and O&M costs associated with disposing of FGD, ash,
and/or landfill leachate solid waste in an on- or off-site landfill;
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Section 9 - Engineering Costs
• Impoundment Operation - calculates O&M and recurring costs associated with
operating and maintaining an on-site impoundment; and
• Impoundment BMP Costs - calculates the annualized costs associated with BMP for
combustion residual impoundments.
EPA calculates each technology option cost by summing the costs estimated by the
applicable individual technology cost module (e.g., biological treatment or bottom ash handling)
and the technology cost modules that calculate transportation, disposal, and impoundment costs.
For each technology option, the cost model sums the costs associated with the technology cost
modules that compose each option, as shown in Table 9-1. The cost model combines the cost
components and calculates total capital, total O&M, one-time and recurring costs for each
technology option.
As explained in Section 8.1.2, EPA is also considering BMPs as part of all of the
regulatory options evaluated for the proposed ELGs. In order to better inform this consideration,
EPA also calculated costs associated with BMPs. EPA only calculated BMP costs for
impoundments that are expected to continue receiving combustion residual wastewater after the
implementation of the ELGs. Therefore, the determination of which impoundments will incur
BMP costs must be based on the entire regulatory option (e.g., Option 3), and not just at the
technology option (e.g., fly ash transport water) because EPA can only determine if an
impoundment will stay open or stop receiving combustion residual waste when assessing all the
wastes. For example, if an impoundment receives FGD wastewater and fly ash transport water,
the impoundment would stay open (i.e., continue to operate) under Option 1 because fly ash
transport water would still be sent to the impoundment, but the impoundment would stop
receiving combustion residual wastewater under Option 3. As shown in this example, the
impoundment BMP costs cannot be determined only based on the technology options, but must
be determined based on the regulatory option. Therefore, EPA did not include the impoundment
BMP cost module in Table 9-1. See Section 9.5.5 for additional information on EPA's approach
for estimating costs associated with BMPs.
9.4.4 Model Outputs
The cost model output is a plant-level summary of the incremental technology option
costs. The output reflects each plant incurring a cost for an evaluated wastestream. EPA presents
the incremental costs on two levels: at the cost-component level and at the total plant level. The
total plant costs include total capital, total O&M, total three-year recurring costs, total five-year
recurring costs, total 6-year recurring costs, total 10-year recurring costs, and total one-time costs
incurred by the plant. The cost-component level shows a breakdown of the individual cost
components for each of the technology costs. The cost-component level includes individual
capital costs (e.g. equipment, installation, land, and engineering) and individual O&M costs (e.g.
labor, materials, energy, effluent monitoring, and chemicals). See Sections 9.6.4, 9.7.3, and 9.8
for the cost model outputs for each technology.
9.5 COSTS APPLICABLE TO ALL WASTESTREAMS
EPA developed several methodologies to calculate compliance costs applicable to more
than one technology option. Using this approach, EPA could use the same methodology for each
9-14
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Section 9 - Engineering Costs
technology option without duplicating the calculations in the cost model. For example, the cost
methodology for disposing combustion residual solid waste to a landfill is the same for each type
of waste; however, the input values and factors (i.e., type, amount, and density of waste) vary
depending on the technology option (FGD, fly ash, or bottom ash). The following subsections
present the methodology used to estimate costs for compliance monitoring, transportation,
disposal, impoundment operations, and impoundment BMPs.
9.5.1 Compliance Monitoring Costs
Where a regulatory option would establish requirements for pollutants not currently
regulated in the existing ELGs, EPA calculated plant-level compliance monitoring costs for
plants to sample and analyze their discharges to assess their compliance with the proposed
effluent limitations. Compliance monitoring costs are annual O&M costs calculated by summing
the components shown in the equation below.
Compliance Monitoring Costs = Sampling Labor Costs + Sampling Materials Costs
+ Sample Shipping Costs + Sample Analysis Costs
Sampling labor costs are the costs associated with plant personnel collecting and
analyzing wastewater samples. EPA calculated sample labor costs using a labor rate and the total
number of labor hours required per year. EPA assumed samples would be collected and analyzed
weekly for NPDES compliance monitoring. EPA used data from the Steam Electric Survey and
the U.S. Bureau of Labor Statistics to estimate the labor rate for the sampling team and
environmental engineer required to collect and analyze the samples.
Sampling material and supply costs are the costs associated with the materials and
supplies, such as personal protective equipment, sampling containers, and other supplies,
required to collect and analyze samples. EPA calculated material and supply costs using the cost
of the materials and supplies per sampling events and the number of sampling events per year.
EPA based the sampling material costs on the costs the Agency incurred for individual items
during its field sampling program. EPA multiplied the item costs by the number of items that
would be required over the course of a year and then summed the costs for all the individual
items.
EPA estimated the costs for shipping the samples to laboratories using the cost of a
sample shipment and the total number of sample shipments per year. EPA assumed that samples
would be sent to two different laboratories, one for analysis of low-level mercury and one for
analysis of other metals. EPA assumed that one of the laboratories would be able to analyze the
samples for total dissolved solids and nitrate/nitrite.
EPA calculated sample analysis costs using the cost of analyzing each sample that would
be collected per sampling event and the number of sampling events per year. EPA based the
sample analysis costs on the costs the Agency incurred during its field sampling program. See
Section 5.2 of EPA's Incremental Costs and Pollutant Removals for Proposed Effluent
Limitation Guidelines and Standards for the Steam Electric Power Generating Point Source
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Section 9 - Engineering Costs
Category report for more details on the compliance monitoring cost methodology [U.S. EPA,
2013].
9.5.2 Transportation Costs
Steam electric power plants can reuse, market/sell, or give away combustion residuals.
Alternatively, plants can transport combustion residuals to a disposal site (e.g., landfill). For the
proposed ELGs, EPA conservatively included costs for plants to transport all solid waste to a
landfill because not all plants have the means to market/sell or give away the combustion
residuals.
All combustion residuals can be transported to on-site or off-site landfills in an open
dump truck. For plants with existing on-site landfills already containing combustion residuals,
EPA included costs for these plants to dispose of any additional combustion residuals resulting
from compliance with the ELGs in an on-site landfill, by either expanding the existing landfill or
building a new landfill to accommodate the additional waste. For plants that do not have existing
on-site landfills (or have only on-site landfills that do not contain combustion residuals), EPA
included costs for these plants to dispose of the additional combustion residuals in an off-site
non-hazardous landfill.
As described in Section 9.4.1, EPA used data from the Steam Electric Survey to identify
which plants have existing landfills containing combustion residuals. EPA estimated costs for
on-site transportation of ash and FGD solids for all plants with at least one open landfill
containing combustion residuals. EPA estimated off-site trasnportation costs for ash and FGD
solids for all other plants (i.e., those without an open landfill containing fuel combustion
residuals).
EPA based plant-level costs for transportation of combustion residuals on the total
amount of waste generated at each plant. For each wastestream, EPA calculated the amount of
solid waste generated using methodologies presented, by technology option, in Sections 9.6, 9.7,
and 9.8.
EPA estimated transportation costs for plants with an on-site landfill using the estimated
amount of solid waste and an on-site specific unitized cost value, in dollar per ton, based on
information provided by ORCR for the coal combustion residuals (CCR) rule, developed using
the Remedial Action Cost Engineering Requirements (RACER 2010) software version 10.4.
EPA estimated transportation costs for plants with an off-site landfill using the estimated amount
of solid waste and an off-site specific unitized cost value, in dollar per ton, provided by ORCR
based on the RACER 2010 model. For each plant and wastestream, EPA summed the total
tonnage of combustion residuals and multiplied it by the appropriate transportation cost to
estimate a plant-specific transportation cost. See Section 5.3 of EPA's Incremental Costs and
Pollutant Removals for Proposed Effluent Limitation Guidelines and Standards for the Steam
Electric Power Generating Point Source Category report for more details on the on- and off-site
transportation cost methodologies [U.S. EPA, 2013].
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Section 9 - Engineering Costs
9.5.3 Disposal Costs
EPA conservatively determined costs for plants to dispose of all combustion residual
landfills to on-site or off-site landfills. To the extent plants are able to market/sell these residuals,
EPA has over costed disposal and has not accounted for revenue associated with other options.
As previously discussed in Section 9.5.2, EPA used data from the Steam Electric Survey to
identify which plants have existing landfills containing combustion residuals. EPA estimated
costs for on-site disposal of ash and FGD solids for all plants with at least one open landfill
containing combustion residuals. EPA compliance costs estimate the costs for the plant to
expand the landfill to handle the additional combustion residuals that will need to be stored in the
landfill to comply with the ELGs. EPA estimated off-site diposal costs for ash and FGD solids
for all other plants (i.e., those without an open landfill containing combustion residuals).
EPA based plant-level costs for disposal of combustion residuals on the total amount of
waste generated at each plant. For each wastestream, EPA calculated the amount of solid waste
generated using methodologies presented, by technology option, in Sections 9.6, 9.7, and 9.8.
EPA estimated capital and O&M disposal costs for an on-site landfill. Capital costs
include the construction of the landfill, liner, additional groundwater monitoring, leachate
collection system, and closures associated with the expansion of an existing landfill. EPA used a
unitized cost value (in dollar per ton), that represents that capital cost components for an onsite
landfill, and the estimated amount of solid waste produced from the implementation of
technology options. EPA used a similar unitized cost approach to estimate the O&M costs based
on the estimated amount of additional solid waste produced and a unitized cost value (in dollar
per ton), that represents the costs associated with operating the landfill.
EPA estimated off-site disposal costs using a unitized cost (in dollar per ton) and the
estimated amount of additional solid waste transported off-site. The unitized cost value
represents the fee off-site landfills generally charge prior to accepting waste, known as the
tipping fee. EPA estimated the tipping fees using state-level tipping fees and data provided in the
Steam Electric Survey. See Section 5.4 of EPA's Incremental Costs and Pollutant Removals for
Proposed Effluent Limitation Guidelines and Standards for the Steam Electric Power Generating
Point Source Category report for more details on the on- and off-site disposal cost
methodologies [U.S. EPA, 2013].
9.5.4 Impoundment Operation Costs
Implementation of the technology options will reduce, and in some cases eliminate, FGD
wastewater, ash transport water, and combustion residuals managed in on-site impoundments.
EPA therefore expects plants will experience cost savings in operating these impoundments. To
calculate the incremental compliance cost of the technology option, EPA estimated the annual
O&M and recurring costs associated with managing these wastewaters and combustion residuals
in on-site impoundments. For each technology option evaluated, EPA estimated the amount of
wastewater or combustion residual no longer expected to be managed in on-site impoundments
and the associated cost savings. EPA estimated O&M and 10-year recurring costs associated
with impoundment operations using the equations provided below. See Section 5.5 of EPA's
Incremental Costs and Pollutant Removals for Proposed Effluent Limitation Guidelines and
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Section 9 - Engineering Costs
Standards for the Steam Electric Power Generating Point Source Category report for more
details on the impoundment operation cost methodology [U.S. EPA, 2013].
Total O&M Costs = (-1) x (Impoundment O&M Costs + Earthmoving O&M Costs)
x (Capacity Factor)
Impoundment O&M costs are the costs associated with the operation of the transportation
system (i.e., pipelines, vacuum source), impoundment site, wastewater treatment system, and
water recycle system at the impoundment. EPA calculated impoundment O&M costs using a
unitized cost value ($7.35/ton), representing the impoundment O&M costs only, and the
estimated amount of wet combustion residual waste generated (FGD solids, fly ash, and bottom
ash).
Earthmoving O&M costs are the costs associated with the operation of earthmoving
equipment (i.e., backhoe) required for sorting/stacking fuel combustion residual materials at the
impoundment site. EPA calculated the impoundment O&M costs using a unitized cost value
($2.49/ton), representing the O&M only associated with the operation of the earthmoving
equipment, and the estimated amount of wet combustion residual waste generated.
Additionally, EPA applied a capacity factor to adjust both unitized cost values for
impoundment and earthmoving O&M costs based on the size of plant (in MW). EPA applied this
factor to account for the economics of scale, the concept that larger plants, which will generally
operate larger impoundments, incur smaller costs per ton of wet combustion residual [U.S. EPA,
1985].
Total 10-Year Recurring Costs = (-1) x (Cost of Earth Moving Vehicle)
EPA calculated 10-year recurring costs associated with operating the earthmoving
equipment (i.e., backhoe). EPA calculated the total 10-year recurring costs by determining the
cost and average expected life of a backhoe. EPA determined that the expected life of a backhoe
is 10 years and that each plant will operate one backhoe.
9.5.5 Impoundment BMP Costs
Although implementation of the technology options will reduce, and in some cases
eliminate, FGD wastewater, ash transport water, and combustion residuals managed in on-site
impoundments, some impoundments may remain open. As explained in Section 8.1.2, EPA is
considering BMPs as part of all of the regulatory options evaluated for the proposed ELGs. In
order to better inform this consideration, EPA calculated costs associated with BMPs. EPA
estimated BMP costs for the impoundments that are expected to continue operating after
complying with the ELGs. See Section 5.6 of EPA's Incremental Costs and Pollutant Removals
for Proposed Effluent Limitation Guidelines and Standards for the Steam Electric Power
Generating Point Source Category report for more details on the impoundment BMP cost
methodology [U.S. EPA, 2013]. The BMPs include remedial actions (e.g., slope repairs, drawing
down water levels, controlling vegetation) and increases in inspection frequency from 17 times
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Section 9 - Engineering Costs
annually to 52 times annually. These management practices will help prevent future
impoundment failures that have the potential to devastate the surrounding communities.
In order to estimate costs associated with these BMPs, which may be beyond the current
state requirements, EPA reviewed the combustion residual impoundments at plants incurring
compliance costs for FGD wastewater, fly ash transport wastewater, and/or bottom ash transport
wastewater. For purposes of estimating BMP costs, EPA made some assumptions regarding the
continued use of existing impoundments. Because these impoundments can contain multiple
combustion residual waste, the probability that the impoundment will remain open depends on
the regulatory option. For example, if an impoundment contains FGD waste and bottom ash, the
impoundment would remain open based on the proposed Regulatory Option 3, which only
affects FGD and fly ash transport wastewaters. EPA would expect the probability that a plant
may elect to close the impoundment to be high based on the proposed Regulatory Option 4,
which affects all wastestreams of interest. Therefore, EPA estimated impoundment BMP costs
for this impoundment based on Regulatory Option 3; however, EPA estimated zero costs based
on Regulatory Option 4.
EPA estimated an annualized cost for each impoundment determined to remain open,
based on regulatory option. For each of these impoundments, EPA estimated that the remedial
actions will require $10,000 annually per impoundment. EPA estimated the costs for the
additional inspections based on information contained in Exhibit 3K of the Regulatory Impact
Analysis for EPA 's Proposed RCRA Regulation of Coal Combustion Residues (CCR) Generated
by the Electric Utility Industry [ORCR, 2010]. EPA used the information regarding the labor
hours and labor rate for recording keeping and weekly inspections to estimate the costs of the
additional inspections. Based on this information, EPA estimated that the additional inspections
will cost approximately $3,000 annually. Therefore, the total annual cost per impoundment is
approximately $13,000.
9.6 FGD WASTEWATER
EPA estimated capital, O&M, 6-, and 10-year recurring costs associated with installing
three technology options for FGD wastewater:
• One-Stage Chemical Precipitation;
• One-Stage Chemical Precipitation followed by Biological Treatment; and
• One-Stage Chemical Precipitation followed by Vapor-Compression Evaporation.
EPA estimated the chemical precipitation, biological treatment, and vapor-compression
evaporation system costs separately, and then summed the costs generated by the appropriate
technology cost modules to achieve the total technology option costs (i.e., the chemical
precipitation costs were added to the biological treatment and vapor-compression evaporation
costs to calculate the total costs for the technology option.
9.6.1 Chemical Precipitation
Section 7.1.2 describes the one-stage chemical precipitation system that forms the basis
for this technology option. Additionally, Section 9.2.1 provides a brief summary of the
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Section 9 - Engineering Costs
technology basis for the chemical precipitation system. EPA estimated the costs to install and
operate a one-stage chemical precipitation technology to treat FGD wastewater, specifically
developed to remove mercury and arsenic (and other heavy metals). See Section 6.1 of the
Incremental Costs and Pollutant Removals for Proposed Effluent Limitations Guidelines and
Standards for the Steam Electric Power Generating Point Source Category for more details on
the FGD chemical precipitation cost methodology [U.S. EPA, 2013].Based on site visits,
untreated FGD wastewater can contain elevated mercury concentrations based on a variety of
different plant operating characteristics. To ensure that the mercury concentrations in the effluent
discharged from the chemical precipitation system meet the proposed ELGs, EPA included costs
for a mercury analyzer and extra equipment to analyze mercury in the discharge and recycle the
chemical precipitation discharge for further treatment if necessary. The use of this equipment
will allow plants to test the mercury in the effluent daily to ensure compliance with the ELGs. If
the wastewater is not in compliance, the plant can recycle the treated water back to the
equalization tank and adjust the system (i.e., add additional chemicals) to further treat the
wastewater to meet the proposed ELGs. See Section 7 of this document for additional details.
As noted in Section 9.4.1, EPA evaluated plant responses to the Steam Electric Survey to
determine whether chemical precipitation technologies are currently in place to treat FGD
wastewater. As appropriate, plants operating these technologies were given credit for having
treatment in place. EPA gave plants credit only for the associated cost components that are
already in place at the plant. For example, for Regulatory Option 1, if a plant operates a one-
stage chemical precipitation system for the treatment of FGD wastewater that includes all the
steps included as the basis for the technology option other than sulfide precipitation, then EPA
would include capital costs for the plant to install a reaction tank and sulfide chemical feed
system and operating and maintenance costs for the amount of sulfide added to the system on a
yearly basis. The compliance costs for all other pieces of equipment for the system would be set
to zero.
EPA estimated capital, O&M, and 6-year recurring costs for a chemical precipitation
system using the equations provided below.
Total Capital Costs = Purchased Equipment Costs + Purchased Equipment
Installation Costs + Building Costs + Land Costs + Site Preparation Costs +
Engineering Costs + Construction Expenses + Other Contractor Fees + Contingency
Fees + Sludge Disposal Costs
Purchased equipment costs are the costs associated with purchasing the pieces of
equipment required to construct a chemical precipitation system, in addition to ancillary
equipment and freight costs. EPA included the following pieces of equipment in the calculation
of the chemical precipitation system purchased equipment costs:
• Pumps;
• Tanks (e.g., equalization tanks, reaction tanks, holding tanks);
• Chemical feed systems;
• Mixers;
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Section 9 - Engineering Costs
• Clarifiers;
• Filter presses; and
• Sand filters.
For each piece of equipment, EPA obtained cost information from vendors for various
sizes of the equipment (e.g., flow, volume). EPA then related all of these to an associated flow
rate using information based on the technology design basis (e.g., tank volume related to flow by
design residence time). EPA then used the cost and flow information to generate an equation that
could estimate the costs for any FGD wastewater flow rate.
Purchased equipment installation costs are the cost associated with installing those pieces
of purchased equipment, including piping, instrumentation, calibration, and structural supports.
Building, land, site preparation, engineering, construction, other contractor fee costs are the costs
associated with preparing a specific site for the installation of the chemical precipitation
equipment and the costs required for supervision and inspection of the installation. For each of
these costs components, EPA estimated the capital costs by developing cost factors from data in
the Steam Electric Survey. To develop these cost factors, EPA created ratios of the specific cost
component to the total reported purchased equipment cost for each plant that reported cost data
for an FGD chemical precipitation system. EPA then used the median or average ratio based on
the plants in the analysis as the cost factor for calculating the costs. Therefore, once EPA
calculated the total purchased equipment costs, EPA then multiplied the costs by each of the cost
factors to estimate the costs for each of these components.
To calculate the sludge disposal costs, associated with on-site landfill disposal described
in Section 9.5.3, EPA needed to estimate the quantity of sludge that would be generated
annually. EPA used data from the Steam Electric Survey to compare the quantity of FGD
wastewater treatment sludge generated to the FGD wastewater treatment system flow rate. EPA
calculated a ratio of these values for each plant and used the median as a flow-normalized
dewatered sludge generation rate in tons per gallon. Then based on the plant-specific FGD
wastewater flow rate, EPA estimated the quantity of sludge generated by the system.
Total O&M Costs = Operating Labor Costs + Maintenance Labor Costs +
Maintenance Materials Costs + Chemical Purchase Costs + Energy Costs + Sludge
Transportation Costs + Sludge Disposal Costs + Compliance Monitoring Costs +
Impoundment Operation Costs
Operating labor, maintenance labor, and maintenance material costs are the costs
associated with the manual labor and materials required to operate and maintain the chemical
precipitation system 24 hours per day, 365 days per year. To estimate these labor costs, EPA
used data from the Steam Electric Survey to compare the labor costs to the flow rate of the
system. From the costs reported in response to the survey and the associated FGD wastewater
treatment flow rate, EPA developed equations to estimate the cost based on the flow rate. EPA
then used these equations and each plant's FGD wastewater flow rate to determine the operating
labor and maintenance labor costs. EPA performed a similar analysis to estimate the maintenance
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Section 9 - Engineering Costs
material costs by using data from the Steam Electric Survey to develop an equation relating FGD
wastewater treatment flow to the total yearly maintenance material costs.
Chemical purchase costs are the costs associated with purchasing the chemicals required
to operate the chemical precipitation system. EPA estimated chemical purchase costs using a
chemical dosage rate (expressed in grams of chemical per liter of wastewater flow), the plant
FGD wastewater flow rate, and chemical costs (expressed in dollars per ton). EPA determined
the appropriate dosage rates based on the average chemical dosage rates used by the best
available technology economically achievable (BAT) plants included in EPA's sampling
program. EPA obtained chemical costs directly from chemical suppliers in dollars per ton.
Energy costs are the costs associated with the power requirement to run the chemical
precipitation system. EPA obtained the power requirements for each piece of equipment used in
the system from equipment vendors and used these power requirements to develop energy cost
equations and estimate total energy consumption (in kWh/yr). EPA used the national 2010
energy cost of 4.05 cents per kilowatt hour to calculate the energy cost [U.S. DOE, 2011].
EPA estimated the O&M costs associated with compliance monitoring, transportation,
disposal, and impoundment operations according to the methodologies described in Section 9.5.
EPA used the same estimated tonnage described for the capital cost equation above to estimate
sludge transportation, disposal, and impoundment operation costs.
Total Recurring 6-Year Costs = Cost of Mercury Analyzer
EPA calculated 6-year recurring costs associated with operating a mercury analyzer,
which is included in the system to allow plants to monitor the effluent quality on a daily basis to
ensure the treatment system is effectively treating mercury to the proposed limitations. EPA
estimated the total 6-year recurring costs by determining the cost and average expected life of a
mercury analyzer, based on vendor information. EPA assumed that the expected life of a
mercury analyzer is six years and that each plant will operate one analyzer for FGD wastewater.
9.6.2 Biological Treatment
Section 7.1.3 describes the anoxic/anaerobic biological treatment system that forms the
basis for this technology option. For Regulatory Options 3 and 4, EPA estimated compliance
costs to install and operate the anoxic/anaerobic system to treat FGD wastewater following the
BAT chemical precipitation system. The anoxic/anaerobic system is specifically designed and
operated to target removals of selenium (and other heavy metals). See Section 6.2 of the
Incremental Costs and Pollutant Removals for Proposed Effluent Limitations Guidelines and
Standards for the Steam Electric Power Generating Point Source Category for more details on
the FGD biological treatment cost methodology [U.S. EPA, 2013].
The system uses up-flow, fixed-film granular activated carbon (GAC) bed bioreactors,
inoculated with a proprietary, site-specific mixture of bacterial cultures, through which the FGD
wastewater passes.
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Section 9 - Engineering Costs
EPA developed untreated FGD wastewater characteristics to use as the basis for cost
or\
development for the biological treatment system. EPA developed these FGD wastewater
characteristics from industry site visits, its sampling program, and the Clean Water Act (CWA)
308 monitoring program. A treatment vendor developed the specific anoxic/anaerobic biological
treatment system design and system-level costs based on its evaluation of these untreated FGD
wastewater characteristics. The anoxic/anaerobic biological system design consists of a series of
two bioreactors operating in parallel trains. The number of trains and the size of the bioreactors
are dependent on a plant's FGD wastewater flow rate. For flow rates greater than 40 gallons per
minute (gpm), the vendor provided costs for customized field-erected biological treatment
systems. For flow rates less than 40 gpm, the vendor provided costs for a low-flow, prefabricated
modular reactor, which is more cost-effective for this flow range.
Based on site visits, EPA's sampling program, and the CWA 308 monitoring program,
FGD wastewater temperatures can exceed the maximum operating temperature for the biological
system, especially during the warmer seasons, and may require cooling prior to entering
biological treatment. Therefore, the design basis includes a heat exchanger for certain southern
plants determined to require cooling of FGD wastewater for biological treatment, based on set
latitudinal and longitudinal coordinates where the average July temperature is 90°F or greater.
As noted in Section 9.4.1, EPA evaluated plant responses to the Steam Electric Survey to
determine whether a biological treatment system for selenium removal is currently in place to
treat FGD wastewater. As appropriate, plants operating this technology were given credit for
having treatment in place, to ensure that incremental costs associated with compliance with the
technology options are accurately assessed. EPA gave plants credit only for the associated cost
components that are already in place at the plant.
EPA estimated capital and O&M costs for the anoxic/anaerobic system using the
equations provided below.
Total Capital Costs = Purchased Equipment Costs + Purchased Equipment Installation
Costs + Plant Overhead Engineering Costs + Sludge Disposal Costs
Purchased equipment costs are the costs associated with purchasing the pieces of
equipment required to construct the anoxic/anaerobic biological system. EPA calculated
purchased equipment costs by summing the costs of the anoxic/anaerobic biological system, the
heat exchanger (for applicable plants), and a backwash recycle pump. The vendor provided EPA
with cost equations based on FGD wastewater flow rate and backwash flow rate for the
anoxic/anaerobic system and backwash recycle pump, respectively. The costs provided by the
vendor include the following cost components:
The untreated FGD wastewater characteristics developed for this analysis are similar to the characteristics
identified in Section 6.1; however, they are slightly different because EPA had less data at the time this analysis was
completed. The wastewater characteristics are included in Incremental Costs and Pollutant Removals for Proposed
Effluent Limitations Guidelines and Standards for the Steam Electric Generating Point Source Category report
[U.S. EPA, 2012].
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Section 9 - Engineering Costs
• Two-stage bioreactor system (i.e., 2 reactors in series per train) with a 10-hour
residence time for the system, operating 24 hours per day and 365 days per year.
System-level costs include the following purchased equipment and associated
ancillary equipment:
- All process pumps, valves, and instruments;
- Process and instrument compressed air system, valves, and lines;
- Nutrient system, storage tank, and pumping;
- Process piping and supports;
- Concrete bioreactor tank walls and floor with epoxy-coated rebar and epoxy
flake-glass coating;
Concrete backwash supply and backwash wastewater tank walls and floor with
epoxy-coated rebar and epoxy flake-glass coating;
Concrete process and utility sump with pumps;
Support steel, access stairs, walkways, grating, handrails;
• Process equipment building with HVAC (concrete floor, block structure with steel
roof);
• Engineering, commissioning, and project management labor (the project structure is
executed by a consortium between the vendor and contractor with a balance of plant
engineering as a sub-contractor); and
• Construction equipment, materials, and labor.
EPA used information obtained from vendors to develop cost equations for the heat
exchanger, as well as the cooling water pumped needed for the system. Based on the chlorides
level in the FGD wastewater and vendor recommendations, EPA developed heat exchanger costs
for a carbon steel frame heat exchanger consisting of titanium plates. EPA estimated the size,
and cost, of the cooling water pumps based on the flow for the FGD wastewater treatment
system, accounting for the estimated heat transfer required to reduce the temperature of the
wastewater to 95°F prior to entering the bioreactors.
Installation equipment costs are the costs associated with installing the purchased
equipment, including any additional piping or instrumentation for the system. EPA estimated
installation capital costs for the biological treatment system for each plant using two different
installation cost factors. The first factor was provided by the vendor and is specific to installation
of the anoxic/anaerobic biological system. The second factor was determined based on responses
to the Steam Electric Survey and applies to installation of the heat exchanger and system pumps.
This second factor is the same installation equipment cost factor used for the FGD chemical
precipitation system.
Overhead engineering costs are costs associated with general process design and general
engineering fees for the plant. EPA calculated the ratio of the overhead engineering costs to the
total reported purchased equipment cost for each plant that reported cost data for an FGD
chemical precipitation and/or biological treatment system. EPA then used the median ratio based
on the plants in the analysis as the cost factor for calculating the costs.
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Section 9 - Engineering Costs
The sludge generated by the biological treatment system is associated with the backwash
from the system. The backwash water is recycled to the equalization tank prior to the FGD
wastewater chemical precipitation system and is ultimately removed with the chemical
precipitation sludge. The vendor provided an equation to calculate the estimated annual amount
of dry solids generated during the backwash based on plant-specific FGD wastewater flow. EPA
used the sludge generation rate to estimate the disposal costs, described in Section 9.5.3.
Total O&M Costs = Operating Labor Costs + Maintenance Labor Costs +
Maintenance Materials Costs + Chemical Purchase Costs + Energy Costs + Compliance
Monitoring Costs + Sludge Transportation Costs + Sludge Disposal Costs +
Impoundment Operation Costs
Operating labor, maintenance labor, and maintenance material costs are the costs
associated with the manual labor and materials required to operate and maintain the
anoxic/anaerobic system 24 hours per day, 365 days per year. EPA estimated these labor costs
using vendor data and industry responses to the Steam Electric Survey to estimate the number of
full time equivalent (FTE) workers required to operate the system. EPA used this estimation and
the median operating and maintenance labor rates from the Steam Electric Survey to calculate
the labor costs. To calculate the maintenance material costs, EPA used Steam Electric Survey to
compare the reported maintenance material costs to the sum of the energy, chemical, and
operating and maintenance labor O&M costs plants operate FGD chemical precipitation and/or
biological treatment systems. EPA used then used the calculated value and multiplied it by the
sum of the energy, chemical, and operating and maintenance labor O&M costs to estimate the
maintenance material costs for each plant.
Chemical purchase costs are the costs associated with purchasing the chemicals required
to operate the anoxic/anaerobic biological system. EPA estimated the chemical purchase costs
using nutrient dosages provided by the vendor, based on an assumed nitrate/nitrite (as nitrogen)
concentration in the FGD wastewater, a nutrient cost provided by the vendor, and the plant-
specific FGD wastewater flow rate.
Energy costs are the costs associated with the power requirement to run the
anoxic/anaerobic biological system. The vendor provided an equation to calculate power
requirements per gallon of FGD wastewater. EPA calculated the annual anoxic/anaerobic
biological system energy consumption (in kWh/yr) by multiplying the anoxic/anaerobic
biological system energy requirement by the plant-specific FGD wastewater flow and backwash
flow. For the pumps, EPA developed energy cost equations based on the power requirements
provided by equipment vendors (in kWh/yr). EPA used the national 2010 energy cost of 4.05
cents per kilowatt hour to calculate the energy cost [U.S. DOE, 2011].
EPA estimated the O&M costs associated with compliance monitoring, transportation,
disposal, and impoundment operations according to the methodologies described in Section 9.5.
EPA used the same estimated tonnage described for the capital cost equation above to estimate
sludge transportation, disposal, and impoundment operation costs.
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Section 9 - Engineering Costs
9.6.3 Vapor-Compression Evaporation
Section 7.1.3 describes the vapor-compression evaporation system that forms the basis
for this technology option. The purpose of the vapor-compression evaporation system is to
evaporate and condense the water from the FGD wastewater to produce a clean distillate stream
and a concentrated brine solution. The concentrated brine solution is then further treated to
generate a solid by-product. See Section 6.3 of the Incremental Costs and Pollutant Removals for
Proposed Effluent Limitations Guidelines and Standards for the Steam Electric Power
Generating Point Source Category for more details on the FGD vapor-compression evaporation
cost methodology [U.S. EPA, 2013].
As noted in Section 9.4.1, EPA evaluated plant responses to the Steam Electric Survey to
determine whether a vapor-compression evaporation system is currently in place to treat FGD
wastewater. As appropriate, plants operating this technology were given credit for having
"treatment in place" to ensure that incremental costs associated with compliance with the
technology options are accurately assessed. EPA gave plants credit only for the associated cost
components that are already in place at the plant.
EPA estimated capital and O&M for a vapor-compression evaporation system using the
equations provided below.
Total Capital Costs = Purchased Equipment Costs + Purchased Equipment
Installation Costs + Sludge Disposal Costs
Purchased and installation equipment costs are the costs associated with purchasing and
installing the pieces of equipment, including extra piping, instrumentation, and support
structures, required to construct a vapor-compression evaporation system. EPA estimated
purchased and installation costs using data from vendors. The vendors provided total system
costs for two different FGD wastewater treatment system flow rates. The system costs include
the following pieces of equipment:
• Water softener;
• Mechanical vapor compression brine concentrator; and
• Forced-circulation crystallizer.
Using the information provided by the vendors, EPA developed costs equations to
estimate the plant-specific compliance costs to install the system. For the brine concentrator and
crystallizer, EPA developed the equation to relate the costs to the FGD wastewater treatment
system flow rate. The cost for the softener is based on a percentage of the brine concentrator and
the crystallizer costs. EPA estimated installation costs using a factor provided by the vendors and
the calculated total purchased equipment costs.
Sludges generated by the vapor-compression evaporation system include softening sludge
and crystallizer sludge. Vendors provided an equation to calculate the estimated sludge based on
the plant-specific FGD wastewater flow. EPA used the sludge generation rate to estimate the
disposal costs, described in Section 9.5.3.
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Section 9 - Engineering Costs
Total O&M Costs = Operating Labor Costs + Maintenance Labor Costs +
Maintenance Materials Costs + Chemical Purchase Costs + Energy Costs +
Compliance Monitoring Costs + Sludge Transportation Costs + Sludge Disposal Costs
+ Impoundment Operation Costs
Operating labor, maintenance labor, and maintenance material costs are the costs
associated with the manual labor and materials required to operate and maintain a vapor-
compression evaporation system 24 hours per day, 365 days per year. To calculate labor rates,
EPA used industry responses to Steam Electric Survey for chemical precipitation systems with
and without subsequent vapor-compression evaporation treatment. EPA determined one
operator, 24 hours per day, is required to operate the system based on observations during a site
visit to a plant operating a vapor-compression evaporation system to treat FGD wastewater. The
median operating labor rate was multiplied by the expected labor hours to determine the
operating labor costs.
Vapor-compression evaporation system vendor information was insufficient for use in
estimating maintenance labor and maintenance material costs; therefore, EPA used the chemical
precipitation factors, described in Section 9.6.1, to calculate these cost elements.
Chemical purchase costs are the costs associated with purchasing the chemicals required
to operate the vapor-compression evaporation system. The softening portion of the system
requires soda ash to soften the wastewater. The vendor provided the cost to purchase soda ash for
one flow rate [HPD, 2009]. EPA used this cost and associated flow rate to generate a dollar per
gallon per minute value to estimate costs based on the plant-specific FGD wastewater flow rate.
Energy costs are the costs associated with the power requirement to run the vapor-
compression evaporation system. EPA obtained the power requirements for each piece of
equipment used in the system from equipment vendors and used these power requirements to
develop energy cost equations and estimate total energy consumption (in kWh/yr). EPA used the
national 2010 energy cost of 4.05 cents per kilowatt hour to calculate the energy cost [U.S. DOE,
2011].
EPA estimated the O&M costs associated with compliance monitoring, transportation,
disposal, and impoundment operations according to the methodologies described in Section 9.5.
EPA used the same estimated tonnage described for the capital cost equation above to estimate
sludge transportation, disposal, and impoundment operation costs.
9.6.4 Estimated Industry-Level Costs for FGD Wastewater by Treatment Option
Table 9-3 presents the estimated capital and O&M costs on an industry level for each
FGD wastewater treatment technology discussed in the sections above, including transport,
disposal, and impoundment costs. The table also includes the number of plants incurring costs
for each treatment technology. The costs presented in the table represent the compliance costs for
those generating units expected to be subject to the proposed ELGs; therefore, oil-fired units and
units with a capacity of 50 MW or less are not included because they do not need to install the
technology basis to meet the new BAT limitations (which are based on the current BPT
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Section 9 - Engineering Costs
requirements for these units). See EPA's Incremental Costs and Pollutant Removals for
Proposed Effluent Limitation Guidelines and Standards for the Steam Electric Power Generating
Point Source Category report for the costs for all generating units [U.S. EPA, 2013].
Table 9-3. Estimated Industry-Level Costs for FGD Wastewater Based on Oil-Fired Units
and Units 50 MW or Less Not Installing Technology Basis
Technology Option
Chemical Precipitation
Chemical Precipitation
followed by Biological
Treatment
Chemical Precipitation
followed by Vapor-
Compression Evaporation
Number
of Plants
116
116
116
Total Capital
Cost
($)
$1,450,000,000
$2,500,000,000
$6,240,000,000
Total O&M
Cost
($/year)
$194,000,000
$257,000,000
$1,030,000,000
6-Year
Recurring
Cost
($/6-year)
$9,900,000
$9,900,000
$9,900,000
10-Year
Recurring Cost
($/10-year)a
($33,000,000)
($33,000,000)
($33,000,000)
a - The values in this column are negative because they represent cost savings.
Note: Costs are rounded to three significant figures.
Note: All costs are indexed to 2010 dollars using RSMeans Historical Cost Indices [RSMeans, 2011].
EPA also estimated the industry-level costs for only those plants with a total plant-level
wet scrubbed capacity of 2,000 MW or greater to install the chemical precipitation followed by
biological treatment technology. To estimate these industry-level costs, EPA zeroed the costs
from its FGD biological treatment cost outputs and for those plants with a total plant-level wet
scrubbed capacity of less than 2,000 MW. For all plants with a total plant-level wet scrubbed
capacity of 2,000 MW or greater, EPA used the costs from its FGD biological treatment cost
outputs. For more details on how EPA estimated these plant-level FGD biological treatment
costs, see the memorandum entitled "Memorandum to the Rulemaking Record: Methodologies
for Estimating Costs and Pollutant Removals for Steam Electric ELG Regulatory Options 3a and
3b" [ERG, 2013c].
Table 9-4 presents the estimated capital, O&M, and recurring costs on an industry-level
associated with dry or closed-loop recycle bottom ash handling conversions for this analysis. The
table also includes the number of plants incurring compliance costs. The costs presented in the
table represent the compliance costs for those generating units expected to be subject to the
proposed ELGs for Regulatory Option 4a; therefore, oil-fired units and units with a capacity of
400 MW or less are not included because they do not need to install the technology basis to meet
the new BAT limitations (which are based on the current BPT requirements for these units).
Table 9-4 presents the estimated capital and O&M costs on an industry level for the FGD
chemical precipitation followed by biological treatment wastewater treatment technology
discussed in the sections above, including transport, disposal, and impoundment costs. The table
also includes the number of plants incurring costs for each treatment technology. The costs
presented in the table represent the compliance costs for those generating units expected to be
subject to the proposed ELGs; therefore, oil-fired units and units at plants with a total plant-level
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Section 9 - Engineering Costs
wet scrubbed capacity of less than 2,000 MW are not included because they do not need to install
the technology basis to meet the new BAT limitations (which are based on the current BPT
requirements for these units).
Table 9-4. Estimated Industry-Level Costs for FGD Wastewater Based on Oil-Fired Units
and Units at Plants with a Total Plant-Level Wet Scrubbed Capacity of Less Than 2,000
MW Not Installing Technology Basis
Technology Option
Chemical Precipitation
followed by Biological
Treatment
Number
of Plants
17
Total Capital
Cost
($)
$600,000,000
Total O&M
Cost
($/year)
$67,600,000
6-Year
Recurring
Cost
($/6-year)
$1,450,000
10-Year
Recurring Cost
($/10-year)a
($5,640,000)
a - The values in this column are negative because they represent cost savings.
Note: Costs are rounded to three significant figures.
Note: All costs are indexed to 2010 dollars using RSMeans Historical Cost Indices [RSMeans, 2011].
9.6.5 Compliance Costs Associated with Planned FGD Systems
In addition to existing sources, EPA also evaluated costs of compliance associated with
planned installations of FGD systems. Implementation of air pollution controls may create new
wastewater streams at power plants. The compliance costs and pollutant removal estimates
included in this document reflect consideration of wastestreams generated by air pollution
controls that will likely be in operation at plants at the time of ELG promulgation. However,
EPA recognizes that some recently promulgated Clean Air Act requirements may lead to
additional air pollution controls (and resulting wastestreams) at existing plants beyond the date
of ELG promulgation. In an effort to confirm that the proposed ELGs would be economically
achievable in such cases, EPA also conducted a sensitivity analysis that forecasts future
installations of air controls through 2020 and the associated costs of complying with the
proposed ELGs for the wastewater that may result from the forecasted air control installations.81
These sensitivity analyses are described in more detail in the memorandum entitled "Flue Gas
Desulfurization Future Profile Sensitivity Analysis" [ERG, 2013a].
9.7 ASH TRANSPORT WATER
As discussed in Section 4.2.1, combusting coal and oil in steam electric boilers produces
a residue of noncombustible fuel constituents, referred to as ash. The ash that is light enough to
be carried out of the boiler is referred to as fly ash and the heavier ash that falls to the bottom of
the boiler is referred to as bottom ash.
Based on survey responses, plants usually collect and handle fly ash and bottom ash
separately. Fly ash is either handled dry and pneumatically transferred dry to silos for temporary
EPA expects that plants will be in compliance with new federal and state air pollution control requirements by
2020.
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Section 9 - Engineering Costs
storage or sluiced with water to an impoundment. Bottom ash is either collected in a water-filled
hopper positioned below the hopper and sluiced with water to an impoundment, collected under
the boiler using a mechanical drag system and stored in an outdoor pile for temporary storage, or
pneumatically transferred to silos for temporary storage.
Because of the development of ash handling systems that require little to no water and the
ability to market dry fly and/or bottom ash, plants have been converting handling operations on
existing steam electric generating units from wet sluicing operations to systems that do not
transport the ash with water. The following sections describe the technology bases used to
estimate the compliance costs associated with converting from wet to dry fly ash handling and
wet to dry or closed-loop recycle bottom ash handling.
9.7.1 Fly Ash Transport Water
EPA estimated capital, O&M, and 10-year recurring costs associated with converting wet
fly ash handling systems (specifically wet fly ash sluicing systems) to dry vacuum fly ash
handling systems for steam electric generating units generating fly ash. Section 7.2.3 provides
more details on the dry vacuum fly ash handling system.
In addition to the dry vacuum system, EPA evaluated a different technology for
generating units with significantly less fly ash production. These generating units are usually oil-
fired. Based on Steam Electric Survey data, EPA evaluated costs for oil-fired units operating less
than 100 days per year to use a vactor truck to collect and handle the fly ash to comply with a
zero discharge requirement. See Chapter 7 of the Incremental Costs and Pollutant Removals for
Proposed Effluent Limitations Guidelines and Standards for the Steam Electric Power
Generating Point Source Category for more details on the fly ash cost methodology [U.S. EPA,
2013].
EPA's approach for estimating costs associated with converting to dry vacuum systems
and for using vactor trucks is described in more detail below.
Dry Vacuum Conversion
Based on data from the Steam Electric Survey and site visits, EPA determined that a
single steam electric generating unit can be equipped with both wet and dry handling
capabilities. Therefore, not all steam electric generating units require complete conversion costs
depending on the equipment, and the capacity of that equipment, already operating at the plant.
As appropriate, plants with wet and dry handling systems were given credit for having this
equipment at the plant. Therefore, to estimate compliance costs for a fly ash handling conversion
to a dry vacuum system, EPA developed a costing approach for three separate portions of the
system:
• Conveyance. The portion of the fly ash handling system from the bottom of the
collection hopper to the intermediate storage destination that includes the mechanical
exhauster, piping, valves, and filter-separators necessary to pull and convey ash from
the bottom of the hopper. EPA calculated conveyance costs at the steam electric
generating unit level.
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Section 9 - Engineering Costs
• Intermediate Storage. The destination to which the dry fly ash is conveyed from the
bottom of the hopper. The intermediate storage includes the structure itself (e.g., the
silo), including the vacuum equipment necessary to receive the ash from the
conveyance lines, and the unloading equipment necessary for moisture conditioning
oa
prior to transportation and disposal. EPA calculated intermediate storage costs at the
plant level.
• Transportation/Disposal. The trucking equipment and operation to move the dry fly
ash to its final destination (e.g., on-site or off-site landfill). EPA calculated
transport/disposal costs at the plant level.
For example, the vacuum lines for a generating unit may have the capacity to handle all
of the dry fly ash generated, but the silo may not be large enough to store all of the dry fly ash.
There EPA would only estimate compliance costs associated with the additional intermediate
storage (silo capacity) required.
EPA estimated capital, O&M, and 10-year recurring costs for the conversion to dry fly
ash handling using a dry vacuum system using the equations provided below. EPA calculated the
capital, O&M, and 10-year recurring costs by summing the estimated costs for the conveyance,
intermediate storage, and transport/disposal portions of the system.
Total Capital Costs = Purchased Equipment Costs + Purchased Equipment Installation
Costs + Plant Overhead Engineering Costs + Fly Ash Disposal Costs
Purchased equipment costs are the costs associated with purchasing all equipment to
retrofit all generating units, collecting fly ash with a wet sluicing system, with a dry vacuum
conveyance system. EPA calculated purchased equipment costs by summing the costs of dry
vacuum conveyance system(s), the concrete or steel silo(s), silo aeration equipment, and
pugmill(s). EPA calculated equipment costs for conveyance on a generating unit level, and
calculated silo and pugmill equipment costs at a plant level. EPA estimated conveyance, silo, and
pugmill equipment costs using a relationship between capital costs and wet fly ash generation
rate obtained from industry vendors.
EPA estimated installation capital costs for the fly ash handling conversion, including all
system elements, for each plant using an installation factor determined from Steam Electric
Survey data. EPA supplemented this information with cost data from industry vendors to
determine an installation factor for the conveyance and intermediate storage system elements.
EPA estimated the installation costs by applying the calculated factor by the purchased
equipment cost.
Plant overhead engineering costs were determined from Steam Electric Survey data.
Based on survey responses, EPA calculated a median installation factor for the conveyance and
Plants may have a silo; however, they may need to install the equipment for moisture conditioning ash prior to
unloading. Therefore, the intermediate storage costs are based on two cost indicators, one of the silo and one for the
pugmill.
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Section 9 - Engineering Costs
intermediate storage system elements. EPA estimated the overhead costs by applying the
calculated factor to the purchased equipment and installation costs.
Total O&M Costs = Operating Labor Costs + Maintenance Labor Costs + Maintenance
Materials Costs + Energy Costs + Fly Ash Transport Costs + Fly Ash Disposal Costs +
Impoundment Operation Costs
EPA calculated the amount of moisture-conditioned fly ash generated from the handling
conversion using wet fly ash generation rate at the plant-level and an average moisture content of
fly ash from the Steam Electric Survey, supplemented with vendor data. EPA used the moisture-
conditioned fly ash tonnage to estimate the disposal costs, described in Section 9.5.
Operating and maintenance labor costs are the costs associated with operating and
maintaining the conveyance, intermediate storage, and transport/disposal portions of the dry
vacuum system. EPA calculated operating labor costs using the labor rate, the estimated number
of required operator hours per day, and the total number of days the generating units operated.
EPA calculated the maintenance labor costs using the labor rate and the estimated maintenance
hours per year. EPA used the Steam Electric Survey data, supplemented with U.S. Bureau of
Labor Statistics data, to calculate the labor rate for fly ash conversion costs [U.S. Bureau of
Labor Statistics, 2010]. EPA estimated the number of required operator hours per day and
maintenance hours per year using data provided in the Steam Electric Survey. Additionally, EPA
used the number of unit operating days in 2009 reported the Steam Electric Survey.
In addition to the intermediate storage system operating labor costs, EPA also estimated
O&M costs for operating dust suppression water trucks around the fly ash unloading area,
including operating labor and fuel costs, if appropriate.83 EPA estimated the water truck
operating labor cost using a water truck labor rate, number of required operator hours per day,
the number of operating days per year, and the number of silos. To determine the water truck
labor rate, EPA selected the national average loaded labor rate for industrial truck/tractor
operators as reported by the U.S. Bureau of Labor Statistics [U.S. Bureau of Labor Statistics,
2010]. EPA estimated the number of required operator hours per day and the number of
operating days using data from the Steam Electric Survey. EPA calculated the number of silos as
part of the compliance cost methodology. EPA estimated the fuel costs associated with the water
trucks by multiplying the number of hours each water truck operates by the number of water
trucks, the distance the water truck travels every hour, and the gas mileage and fuel cost. The
number of water trucks required at a plant was determined using data from the Regulatory
Impact Analysis For EPA 's Proposed RCRA Regulation Of Coal Combustion Residues (CCR)
Generated by the Electric Utility Industry [ORCR, 2010], based on the dry fly ash tonnage
produced at the plant after the handling conversion. The fuel consumption of the water truck was
83 For plants that already have some portion of dry fly ash handling, EPA only included additional costs for water
trucks if the additional tonnage that would now be handled dry would require the plant to purchase and operate
additional water trucks. See Section 7.1.9 of the Incremental Costs and Pollutant Removals for Proposed Effluent
Limitations Guidelines and Standards for the Steam Electric Generating Point Source Category for additional
details on the water truck methodology [U.S. EPA, 2012].
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Section 9 - Engineering Costs
determined from vendor contacts. EPA assumed the same trip distance and fuel cost from the
disposal technology cost methodology.
Similarly, EPA used data from the Steam Electric Survey to determine a maintenance
materials factor with respect to the total O&M costs for conveyance and intermediate storage
system elements, respectively. EPA calculated a median maintenance material factor for each
system element (e.g., conveyance, intermediate storage) and applied it to the calculated O&M.
Energy costs are the costs associated with the power requirement to run the dry vacuum
system. EPA obtained the power requirements for each piece of equipment (pumps and pugmills)
used in the system from the vendors and used these power requirements to develop energy cost
equations for the system pumps and pugmill(s) and estimate total energy consumption (in
kWh/yr). EPA used the national 2010 energy cost of 4.05 cents per kilowatt hour to calculate the
energy cost [U.S. DOE, 2011].
EPA estimated the O&M costs associated with compliance monitoring, transportation,
disposal, and impoundment operations according to the methodologies described in Section 9.5.
EPA used the same estimated tonnage described for the capital cost equation above to estimate
fly ash transportation, disposal, and impoundment operation costs.
Total 10-Year Recurring Costs = Cost of Water Truck
EPA calculated 10-year recurring costs associated with intermediate storage water trucks
by determining the cost, expected life, and number of water trucks required (from ORCR
regulatory impact analysis information). EPA determined that the expected life of a water truck
is ten years.
Vactor Truck Conversion
For oil-fired units that operate less than 100 days, EPA used a different approach for
estimating capital and O&M costs because of the small amount of fly ash generated from these
units. This approach includes piping the fly ash away from the primary particulate collection
system using a vactor truck operated by a third-party contractor. The fly ash is drawn to a 10-
yard roll-off vacuum container stored at the end of the fly ash lines. To remove the fly ash from
the vacuum container, the plant would contract a vendor, on a yearly basis, to vacuum fly ash
from the vacuum container using a vactor truck.
The capital costs associated with this system include installing the piping from the
primary particulate collection system to the location were the roll-off vacuum container will be
stored. Capital costs for the vactor truck system were determined using a direct relationship
between capital cost and the fly ash generation rate, similar to the dry vacuum system. EPA used
Steam Electric Survey data to determine the capital cost estimates. Similarly, EPA used Steam
Electric Survey data and plant contact information to develop a relationship between the O&M
costs for conveyance and storage and the fly ash generation rate.
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Section 9 - Engineering Costs
9.7.2 Bottom Ash Transport Water
EPA estimated capital, O&M, three-year recurring, five-year recurring, and 10-year
recurring costs associated with converting bottom ash handling systems from wet sluicing to
mechanical drag or remote mechanical drag systems for generating units generating bottom ash.
EPA selected two systems, the mechanical drag system (MDS) and the remote MDS, as the basis
for the dry and closed-loop recycle systems, respectively, based on system operation data from
vendors and operation data from the Steam Electric Survey. The compliance costs estimated by
EPA include the conveyance system conversion, the additional required bottom ash storage, the
transport and disposal of the bottom ash, and impoundment costs associated with the change in
bottom ash handling. See Chapter 8 of the Incremental Costs and Pollutant Removals for
Proposed Effluent Limitations Guidelines and Standards for the Steam Electric Power
Generating Point Source Category for more details on the bottom ash cost methodology [U.S.
EPA, 2013].
EPA estimated costs for both MDS and remote MDS systems. The cost estimates reflect
fully erected and commissioned systems, including equipment, controls, foundations, and field
labor. For more detail on the MDS and remote MDS equipment, see Sections 7.3.2 and 7.3.3 of
this report.
Because EPA evaluated two technologies for bottom ash handling conversions, EPA
estimated compliance costs for both technologies for each plant. EPA selected the technology
associated with the lowest estimated annualized cost for the combined system conversion,
transport and disposal, and impoundment costs, at a plant level, as the cost basis for the plant.
EPA estimated capital, O&M, three-, five-, and 10-year recurring costs for MDS and
remote MDS conversions using the equations provided below. Because the MDS and remote
MDS share similar system elements, EPA calculated the O&M in four components. The
components include the following:
• Shared O&M Costs - Conveyance, transport, disposal, and impoundment O&M costs
applicable to both MDS and remote MDS;
• Additional Remote MDS O&M Costs - Additional O&M costs, primarily chemical
costs associated with the remote MDS;
• Intermediate Storage O&M Costs - Storage O&M costs applicable to both MDS and
remote MDS; and
Wet Sluicing O&M Costs - Costs associated with the currently operating wet sluicing
system.
Total MDS Capital Costs = Conveyance & Intermediate Storage Equipment Costs
Plant Overhead Engineering Costs + Bottom Ash Disposal Costs
Conveyance and intermediate storage equipment costs are the costs associated with the
purchase and installation for a fully erected and commissioned MDS, including equipment,
controls, foundations, and field labor. EPA estimated equipment costs on a generating unit basis
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Section 9 - Engineering Costs
using a relationship between capital cost and unit capacity (in MW). EPA obtained unit capacity
information from the Steam Electric Survey. Vendors provided the relationship between the cost
and the generating capacity. The conveyance and intermediate storage costs provided for the
MDS system include the costs for a semi-dry silo. After calculating the capital costs at the unit
level, EPA summed the capital costs to a plant level.
Plant overhead engineering costs were determined from Steam Electric Survey. Based on
survey responses, EPA calculated a median installation factor for the conveyance and
intermediate storage system elements. EPA estimated the overhead costs by applying the
calculated factor to the conveyance and intermediate storage equipment costs.
EPA calculated the amount of moisture-conditioned bottom ash generated from the
handling conversion using the wet bottom ash generation rate at the plant-level and an average
moisture content of bottom ash from the Steam Electric Survey, supplemented with vendor data.
EPA used the moisture-conditioned bottom ash tonnage to estimate the disposal costs, described
in Section 9.5.
Conveyance and intermediate storage equipment costs are the costs associated with the
purchase and installation for a fully erected and commissioned remote MDS, including
equipment, controls, foundations, and field labor. EPA estimated equipment costs on a
generating unit basis using a relationship between capital cost and unit capacity (in MW). EPA
obtained unit capacity from the Steam Electric Survey. Vendors provided the relationship
between the cost and the capacity. The conveyance and intermediate storage costs provided for
the remote MDS system include the costs for a semi-dry silo. After calculating the capital costs
at the unit level, EPA summed the capital costs to a plant level.
Recycle pump costs are the costs associated with the purchase of a pump used to recycle
the sluice water from the remote MDS back to the steam electric generating unit. The chemical
feed system costs are the costs associated with the purchase of a chemical feed system to adjust
the pH of the sluice water as required to completely recycle the bottom ash sluice. To estimate
the costs of the recycle pump and the chemical feed system for the remote MDS, EPA used the
same type of recycle pump type and chemical feed system used in the FGD chemical
precipitation cost methodology. See Section 6.1.6.1 of EPA's Incremental Costs and Pollutant
Removals for Proposed Effluent Limitation Guidelines and Standards for the Steam Electric
Power Generating Point Source Category report [U.S. EPA, 2013]. The recycle pump and
chemical feed system costs include the freight costs associated with each piece of equipment. To
estimate these costs, EPA used the bottom ash sluice rate, in gallons per day, from the Steam
Electric Survey at a generating unit level and summed them to the plant level. EPA obtained
recycle pump and chemical feed system cost relationships and estimated freight costs from
vendors.
Installation equipment costs are the costs associated with the installation of the recycle
pump and chemical feed system. EPA estimated capital installation costs associated with the
recycle pump and chemical feed system using an installation factor calculated based on Steam
Electric Survey data and vendor data used in the fly ash conveyance and intermediate storage
cost methodology.
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Section 9 - Engineering Costs
Plant overhead engineering costs and disposal costs are calculated using the same
methodology described for the total MDS capital costs.
Total Shared O&M Costs = Conveyance Operating Labor Costs + Conveyance
Maintenance Labor Costs + Conveyance Maintenance Materials Costs + Conveyance
Energy Costs + Bottom Ash Transportation Costs + Bottom Ash Disposal Costs +
Impoundment Operation Costs
Conveyance operating and maintenance labor costs are the costs associated with
operating and maintaining the conveyance portion of the bottom ash handling system. EPA
calculated the conveyance O&M labor costs using the labor rate and the number of required
operator or maintenance hours per year for operating or maintenance labor, respectively. EPA
used the Steam Electric Survey data supplemented with U.S. Bureau of Labor Statistics data to
calculate the labor rate for all system elements for the bottom ash conversion costs. Operating
and maintenance hours per year were calculated using data in the Steam Electric Survey.
Similarly, EPA used data from the Steam Electric Survey to determine a maintenance
materials factor with respect to the total O&M costs for the conveyance portion of the bottom ash
handling system. EPA applied the median maintenance material factor to the total conveyance
O&M costs to estimate the maintenance material costs.
Energy costs are the costs associated with the costs required to power the conveyance
portion of the bottom ash handling system. Vendors supplied the size and horsepower
specifications for pumps for the MDS and remote MDS systems based on generating unit
capacity (in MW). EPA used the vendor data to create equations for estimating the energy
consumption at the plant (in kWh/yr). EPA used the national 2010 energy cost of 4.05 cents per
kilowatt hour to calculate the energy cost [U.S. DOE, 2011].
EPA estimated the O&M costs associated with transportation, disposal, and
impoundment operations according to the methodologies described in Section 9.5. EPA used the
same estimated tonnage described for the capital cost equation above to estimate bottom ash
transportation, disposal, and impoundment operation costs.
Total Additional Remote O&M Costs = Chemical Purchase Costs + Chemical Pump
Energy Costs
Chemical purchase costs are the costs associated with purchasing chemicals to control pH
levels for bottom ash sluice recirculation. To calculate chemical purchase costs, EPA estimated
the hydrogen chloride (HC1) consumption, chemical purchase, and freight costs. EPA calculated
the HC1 consumption using wet sluicing data and operating days in the Steam Electric Survey.
For more explanation regarding estimating chemical consumption, see Section 6.1.7.4 in EPA's
Incremental Costs and Pollutant Removals for Proposed Effluent Limitation Guidelines and
Standards for the Steam Electric Power Generating Point Source Category report [U.S. EPA,
2013].
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Section 9 - Engineering Costs
Energy requirements unique to the remote MDS consist of the energy required to operate
the pump that returns sluice water from the sump pit back to the boiler area and the HC1 feed
pump. EPA determined this additional energy consumption (in kWh/yr) by calculating and
summing the annual power consumption for these two pumps for each unit, and then summing
these unit-level consumptions to calculate plant-level energy consumption. Pump energy
consumption (in kWh/yr) is a function of pump horsepower. EPA used the national 2010 energy
cost of 4.05 cents per kilowatt hour to calculate the energy cost [U.S. EPA, 2013].
Total Intermediate Storage O&M Costs = Storage Operating Labor Costs + Storage
Maintenance Labor Costs + Storage Maintenance Materials Costs + Storage Energy
Costs
Intermediate storage labor costs are the costs associated with operating and maintaining
the intermediate storage area where bottom ash is conveyed prior to disposal. EPA calculated
intermediate storage O&M labor costs using an estimated labor rate and the number of required
operator or maintenance hours per year for operating or maintenance labor, respectively. EPA
used the Steam Electric Survey data supplemented with U.S. Bureau of Labor Statistics data to
calculate the labor rate for all system elements for the intermediate storage costs. EPA calculated
O&M hours per year using data in the Steam Electric Survey.
Similarly, EPA used data from the Steam Electric Survey to determine a maintenance
materials cost factor with respect to the total O&M costs for the intermediate storage of the
bottom ash. EPA applied the median maintenance material cost factor to the total intermediate
storage O&M costs to estimate the maintenance material costs.
Intermediate storage energy costs are the costs associated with power requirements for
the pugmill unloader at the silo. EPA used vendor supplied size and horsepower specifications
for pugmill unloaders to calculate the intermediate storage energy consumption (in kWh/yr).
EPA used the national 2010 energy cost of 4.05 cents per kilowatt hour to calculate the energy
cost [U.S. EPA, 2013].
Total Wet Sluicing O&M Costs = Sluicing Operating Labor Costs + Sluicing
Maintenance Labor Costs + Sluicing Maintenance Materials Costs+ Sluicing Energy
Costs
The sluicing operating and maintenance labor costs are the costs associated with
operating and maintaining the sluicing portion of the bottom ash handling system. EPA
calculated wet sluicing O&M labor costs using an estimated labor rate and the number of
required operator or maintenance hours per year for operating or maintenance labor, respectively.
EPA used the Steam Electric Survey data supplemented with U.S. Bureau of Labor Statistics
data to calculate the labor rate for all system elements for the wet sluicing costs. EPA estimated
operating hours using median worker hours per day and the total number of days the unit
operated in 2009, obtained from the Steam Electric Survey. EPA used industry responses from
the Steam Electric Survey for wet sluicing systems to calculate median operating worker hours
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Section 9 - Engineering Costs
per day for the conveyance portion of the system. EPA used the number of unit operating days in
2009, reported in the Steam Electric Survey, to calculate the total O&M days per year. EPA
estimated maintenance hours per year using the maintenance labor median worker hours per year
obtained from industry responses to the Steam Electric Survey.
EPA estimated maintenance material costs based on an evaluation of O&M costs reported
in the Steam Electric Survey for generating units with wet sluicing bottom ash handling systems.
EPA calculated the ratio of reported maintenance material costs to the total sum of operating
labor, maintenance labor, energy, and other O&M costs. EPA applied the median maintenance
material cost factor to the total conveyance O&M costs to estimate the maintenance material
costs.
Wet bottom ash conveyance energy consumption (in kWh/yr) is a function of pump
horsepower. EPA estimated sluice pump horsepower using the same horsepower equation as that
developed for sump pumps for the FGD wastewater chemical precipitation costing methodology;
see Section 6.1.6.1 of EPA's Incremental Costs and Pollutant Removals for Proposed Effluent
Limitation Guidelines and Standards for the Steam Electric Power Generating Point Source
Category report [U.S. EPA, 2013]. The pump horsepower was estimated as a function of sluice
flow rate, obtained from the Steam Electric Survey. EPA estimated the hours of operation for the
system using the operating days of the generating unit and an estimated value for the number of
hours the system conveys bottom ash supplied by vendors. EPA used the national 2010 energy
cost of 4.05 cents per kilowatt hour to calculate the energy cost [U.S. DOE, 2011].
Total MDS O&M Costs = Shared O&M Costs + Intermediate Storage O&M Costs -
Wet Sluicing O&M Costs
As previously described, EPA estimated four different cost components to calculate total
O&M costs for each system because different components apply to the two different systems.
EPA estimated MDS costs using the shared, intermediate storage, and wet sluicing costs. EPA
subtracted wet sluicing cost components from the calculated costs to represent the incremental
cost achieved by the MDS system.
Total Remote MDS O&M Costs = Shared O&M Costs + Additional Remote MDS
O&M Costs + Intermediate Storage O&M Costs
Total O&M costs for the remote MDS system include the shared and intermediate storage
costs; however, EPA also included additional costs for operating the recycle pump and chemical
feed system to allow for complete recycle. EPA did not subtract wet sluicing O&M costs from
the remote MDS costs because the system still includes the operation of the existing sluicing
operations.
Total 3-Year Recurring Costs = Cost of Mechanical Drag Chain for MDS
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Section 9 - Engineering Costs
EPA calculated three-year recurring costs associated with the drag chain for the MDS.
The drag chain is the component of the system that drags the bottom ash from the water bath, up
the incline to intermediate storage. EPA calculated the three-year recurring cost by determining
the cost and expected life of a drag chain for the MDS. Because the drag chain of the MDS
system is located underneath the boiler, and more susceptible to large chunks of falling bottom
ash, EPA determined that the expected life of a MDS drag chain is three years.
Total 5-Year Recurring Costs = Cost of Mechanical Drag Chain for Remote MDS
EPA calculated five-year recurring costs associated with the drag chain for the remote
MDS. The drag chain is the component for the remote MDS is the same described for the MDS.
EPA calculated the five-year recurring cost by determining the cost and expected life of a drag
chain for the remote MDS. Because the drag chain of the remote MDS system is not located
directly underneath boiler, and less likely to be damaged by falling bottom ash, EPA determined
that the expected life of a remote MDS drag chain is five years.
One Time Costs = Engineering Consulting Cost
EPA reviewed plants operating bottom ash handling systems that recycled the majority of
their bottom ash sluice from wet handling operations. Instead of estimating compliance costs for
a full conversion to a MDS or remote MDS system, EPA estimated a one-time cost associated
with consulting an engineer to completely close the bottom ash recycle system, eliminating all
discharges of bottom ash transport water. See Section 8.5 of EPA's Incremental Costs and
Pollutant Removals for Proposed Effluent Limitation Guidelines and Standards for the Steam
Electric Power Generating Point Source Category report [U.S. EPA, 2013].
9.7.3 Estimated Industry-Level Costs for Ash Handling Conversions
Table 9-5 presents the estimated capital, O&M, and recurring costs on an industry level
associated with dry fly ash handling conversions, while Table 9-6 presents the estimated capital,
O&M, and recurring costs on an industry-level associated with dry or closed-loop recycle bottom
ash handling conversions. Both tables also include the number of plants incurring compliance
costs. The costs presented in the table represent the compliance costs for those generating units
expected to be subject to the proposed ELGs; therefore, oil-fired units and units with a capacity
of 50 MW or less are not included because they do not need to install the technology basis to
meet the new BAT limitations (which are based on the current BPT requirements for these units).
See EPA's Incremental Costs and Pollutant Removals for Proposed Effluent Limitation
Guidelines and Standards for the Steam Electric Power Generating Point Source Category
report for the costs for all generating units [U.S. EPA, 2013].
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Table 9-5. Estimated Industry-Level Costs for Fly Ash Handling Conversions Based on
Oil-Fired Units and Units 50 MW or Less Not Installing Technology Basis
Number of Plants
66
Total Capital Cost
($)
$398,000,000
Total O&M Cost
($/year)
$177,000,000
10-Year Recurring Cost
($/10-year)a
($20,700,000)
a - The values in this column are negative because they represent cost savings.
Note: Costs are rounded to three significant figures.
Note: All costs are indexed to 2010 dollars using RSMeans Historical Cost Indices [RSMeans, 2011].
Table 9-6. Estimated Industry-Level Costs for Bottom Ash Handling Conversions Based on
Oil-Fired Units and Units 50 MW or Less Not Installing Technology Basis
Number of
Plants
240
Total Capital
Cost
($)
$4,470,000,000
Total O&M
Cost
($/year)
$494,000,000
One Time
Cost
($)
$583,000
3-Year
Recurring
Cost
($/3-year)
$28,200,000
5-Year
Recurring
Cost
($/5-year)
$64,800,000
10-Year
Recurring
Cost
($/10-year)a
($83,800,000)
a - The values in this column are negative because they represent cost savings.
Note: Costs are rounded to three significant figures.
Note: All costs are indexed to 2010 dollars using RSMeans Historical Cost Indices [RSMeans, 2011].
EPA also estimated the industry-level costs for plants to convert only the generating units
that are greater than 400 MW to dry or closed-loop recycle bottom ash handling systems.
However, EPA used a different approach to estimate the plant-level costs for this analysis. For
those plants with all generating units with a nameplate capacity of 400 MW or less, EPA zeroed
the costs from its bottom ash cost outputs and for those plants with all generating units with a
nameplate capacity greater than 400 MW, EPA used the costs from its bottom ash cost outputs.
For those plants that have at least one generating unit with a nameplate capacity of 400 MW or
less and at least one other generating unit with a nameplate capacity of greater than 400 MW,
EPA approximated the plant-level bottom ash costs. To perform this approximation, EPA
calculated a plant-level bottom ash adjustment factor based on the amount of bottom ash
generated by the generating units expected to incur compliance costs with a nameplate capacity
greater than 400 MW compared to the total amount of bottom ash generated at the plant for those
generating units expected to incur compliance costs (excluding the generating units with a
nameplate capacity of 50 MW or less). EPA then multiplied the bottom ash adjustment factors by
the plant-level bottom ash compliance costs to estimate the bottom ash compliance costs for this
analysis. For more details on how EPA estimated these plant-level bottom ash costs, see the
memorandum entitled "Memorandum to the Rulemaking Record: Methodologies for Estimating
Costs and Pollutant Removals for Steam Electric ELG Regulatory Option 4a" (DCN SE03834).
Table 9-7 presents the estimated capital, O&M, and recurring costs on an industry-level
associated with dry or closed-loop recycle bottom ash handling conversions for this analysis. The
table also includes the number of plants incurring compliance costs. The costs presented in the
table represent the compliance costs for those generating units expected to be subject to the
proposed ELGs for Regulatory Option 4a; therefore, oil-fired units and units with a capacity of
9-40
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Section 9 - Engineering Costs
400 MW or less are not included because they do not need to install the technology basis to meet
the new BAT limitations (which are based on the current BPT requirements for these units).
Table 9-7. Estimated Industry-Level Costs for Bottom Ash Handling Conversions Based on
Oil-Fired Units and Units 400 MW or Less Not Installing Technology Basis
Number of
Plants
115
Total Capital
Cost
($)
$2,580,000,000
Total O&M
Cost
($/year)
$255,000,000
One Time
Cost
($)
$314,000
3-Year
Recurring
Cost
($/3-year)
$1,120,000
5-Year
Recurring
Cost
($/5-year)
$37,800,000
10-Year
Recurring
Cost
($/10-year)a
($35,600,000)
a - The values in this column are negative because they represent cost savings.
Note: Costs are rounded to three significant figures.
Note: All costs are indexed to 2010 dollars using RSMeans Historical Cost Indices [RSMeans, 2011].
9.8 COMBUSTION RESIDUAL LANDFILL LEACHATE
EPA estimated capital and O&M costs associated with installing and operating a one-
stage chemical precipitation wastewater treatment system to treat combustion residual landfill
leachate. Note that as described in Section 9.2.4, EPA finds that plants with combustion residual
surface impoundment leachate will not incur costs associated with any proposed leachate
requirements. Where a plant generates both landfill leachate and FGD wastewater, EPA
evaluated the leachate compliance costs in conjunction with FGD wastewater treatment (i.e.,
those plants discharging leachate and FGD wastewater would use only one wastewater treatment
system to treat the combined leachate and FGD wastewater flow.84 However, for plants that do
not have FGD wastewater, EPA calculated the cost for a chemical precipitation to handle just the
landfill leachate using the equations in Sections 9.6.1 associated with one-stage chemical
precipitation. [ERG, 2013d]
Of the plants identified as having some level of treatment in place for FGD chemical
precipitation, 29 plants also discharge landfill leachate. EPA conducted an analysis to determine
if the existing FGD wastewater treatment systems at these plants would be sufficient to treat the
amount of combustion residual landfill leachate produced at the plants in addition to the FGD
wastewater that is currently being treated. EPA compared the design flow rate (reported in Part D
Section 5.1 of the Steam Electric Survey) for each treatment system to the plant-specific
wastewater flow (i.e., FGD wastewater plus combustion residual landfill leachate). If this new
flow (FGD wastewater plus combustion residual landfill leachate) was less than the specified
design flow rate for the existing chemical precipitation system, EPA determined that the existing
system could support the additional flow. EPA identified 10 of these plants had sufficient
capacity to handle the additional combustion residual landfill leachate flow; however, 19 of the
plants did not have the capacity to treat the additional combustion residual landfill leachate flow.
The technology option for combustion residual landfill leachate is one-stage chemical precipitation while the
technology option for FGD wastewater is one-stage chemical precipitation followed by biological treatment. While
the plant could technically meet the proposed leachate limitations and standards with only a one-stage chemical
precipitation system, installing two separate treatment systems for the leachate and FGD wastewater would be more
expensive than a single system which subjects leachate to both chemical precipitation and biological treatment.
9-41
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Section 9 - Engineering Costs
For these 19 plants, EPA estimated costs for an additional one-stage chemical precipitation
wastewater treatment system sized to treat only the combustion residual landfill leachate.
Additionally, for leachate treatment, EPA developed cost equations and calculated costs,
including equipment and energy, to transport leachate from the landfill site back to the main
plant for treatment. The additional pieces of equipment needed to transport the leachate back to
the main plant area include leachate transport pumps and stainless steel piping.
Table 9-8 presents the estimated capital and O&M costs on an industry level associated
with the treatment of combustion residual landfill leachate. The table also includes the number of
plants incurring compliance costs. For plants where EPA calculated costs for the treatment of
FGD wastewater and combustion residual landfill leachate in the same system, EPA is presenting
the incremental increase in the cost of the treatment system compared to the treatment of only
FGD wastewater (i.e., the cost of treating FGD wastewater alone was subtracted from the cost of
treating the combined wastestreams). EPA estimated industry-level costs excluding units that are
50 MW or less and oil-fired units. The costs presented in the table represent the compliance costs
for those plants expected to be subject to the proposed ELGs; therefore, oil-fired units and units
with a capacity of 50 MW or less are not included because they do not need to install the
technology basis to meet the new BAT limitations (which are based on the current BPT
requirements for these units). See EPA's Incremental Costs and Pollutant Removals for
Proposed Effluent Limitation Guidelines and Standards for the Steam Electric Power Generating
Point Source Category report for the costs for all generating units. [U.S. EPA, 2013]
Table 9-8. Estimated Industry-Level Costs for Combustion Residual Leachate Based on
Oil-Fired Units and Units 50 MW or Less Not Installing Technology Basis
Technology Option
Chemical Precipitation
Chemical Precipitation
followed by Biological
Treatment
Number of
Plants
101
101
Total Capital
Cost
($)
$615,000,000
$931,000,000
Total O&M
Cost
($/year)
$58,600,000
$79,100,000
6-Year
Recurring Cost
($/6-year)
$5,630,000
$5,630,000
10-Year
Recurring Cost
($/10-year)
$0
$0
Note: Costs are rounded to three significant figures.
Note: All costs are indexed to 2010 dollars using RSMeans Historical Cost Indices [RSMeans, 2011].
Note: For plants where EPA calculated costs for the treatment of FGD wastewater and combustion residual landfill
leachate in the same system, EPA is presenting the incremental increase in the cost of the treatment system
compared to the treatment of only FGD wastewater (i.e., the cost of treating FGD wastewater alone was subtracted
from the cost of treating the combined wastestreams).
9.9 SUMMARY OF NATIONAL ENGINEERING COSTS
As described in Section 8, EPA evaluated eight regulatory options comprised of various
combinations of the technology options considered for each wastestream, as shown in Table 9-9.
The Agency estimated the costs associated with steam electric power plants to achieve
compliance for each regulatory option under consideration. This section summarizes the total
estimated compliance costs associated with each option (see Table 9-10). For each regulatory
9-42
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Section 9 - Engineering Costs
option, the capital cost, annual operating and maintenance costs, one-time costs, and recurring
costs are presented. See the Regulatory Impact Analysis for Proposed Effluent Limitations
Guidelines and Standards for the Steam Electric Power Generating Point Source Category for a
listing of total annualized costs by regulatory option. All cost estimates in this section are
expressed in terms of pre-tax 2010 dollars. The costs presented in the table represent the
compliance costs for those plants expected to be subject to the proposed ELGs; therefore, oil-
fired units and units with a capacity of 50 MW or less are not included because they do not need
to install the technology bases to meet the new BAT limitations (which are based on the current
BPT requirements for these units). See EPA's Incremental Costs and Pollutant Removals for
Proposed Effluent Limitation Guidelines and Standards for the Steam Electric Power Generating
Point Source Category report for the costs for all generating units. [U.S. EPA, 2013]
Table 9-9. Technology Options and Other Costs Included in the Estimated Compliance
Costs for Each Regulatory Option
Wastestream
FGD Wastewater
Fly Ash Transport Water
Bottom Ash Transport Water
Leachate
Gasification Wastewater
Flue Gas Mercury Control
Wastes
Nonchemical Metal
Cleaning Wastes
Technology Option
Chemical Precipitation
Biological Treatment
Vapor-Compression Evaporation
Dry Fly Ash Handling
Dry or Closed-loop recycle Bottom
Ash Handling
Chemical Precipitation
Vapor-Compression Evaporation
Dry Handling
Chemical Precipitation
Regulatory Option
1
X
X
X
2
X
X
X
X
3a 3b 3
X X
X X
XXX
XXX
XXX
XXX
4a 4
X X
X X
X X
X X
X
X X
X X
X X
5
X
X
X
X
X
X
X
X
Other Costs Not Specific to Wastestream
Solids Transportation
Solids Disposal
Impoundment Operation
Compliance Monitoring
X
X
X
X
X
X
X
X
XXX
XXX
XXX
X X
X X
X X
X X
X X
X
X
X
X
Table 9-10. Cost of Implementation by Regulatory Option [In millions of pre-tax
2010 dollars]
Regulatory
Option
1
3a
2
Number of
Plants
116
66
116
Capital Cost
$1,450
$398
$2,499
Annual
O&M Cost
$194
$177
$257
One Time
Costs
$0
$0
$0
Recurring Costs
3-year
$0
$0
$0
5-year
$0
$0
$0
6-year
$10
$0
$10
10-year
($33)
($21)
($33)
9-43
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Section 9 - Engineering Costs
Table 9-10. Cost of Implementation by Regulatory Option [In millions of pre-tax
2010 dollars]
Regulatory
Option
3b
o
5
4a
4
5
Number of
Plants
80
155
200
277
277
Capital Cost
$998
$2,897
$5,478
$8,011
$11,755
Annual
O&M Cost
$244
$434
$689
$988
$1,753
One Time
Costs
$0
$0
$0.3
$0.6
$0.6
Recurring Costs
3-year
$0
$0
$1
$28
$28
5-year
$0
$0
$38
$65
$65
6-year
$1
$10
$10
$16
$19
10-year
($26)
($54)
($90)
($137)
($137)
The compliance costs above account for unit retirements, repowerings and conversions
that have been announced by companies and are scheduled to occur by 2014, based on
information obtained by EPA as of August 2012. But they do not reflect additional planned unit
retirements, repowerings, and conversions that have been announced since August 2012, nor do
they reflect announced retirements, repowerings, and conversions that are scheduled to occur by
2022. (See DCN SE02033, "Changes to Industry Profile for Steam Electric Generating Units
Updates"). EPA estimates that accounting for these additional changes would reduce the total
annualized compliance costs for the rule, which are presented in the Regulatory Impact Analysis
for Proposed Effluent Limitations Guidelines and Standards for the Steam Electric Power
Generating Point Source Category. For example, EPA estimated that total pre-tax annualized
compliance costs for Option 3 would go from $561.3 million to $532.8 million (5 percent
reduction), whereas costs for Option 4 would go from $1,373.2 million to $1,252.9 million (9
percent reduction). EPA expects that similar levels of reductions would be seen in the capital and
O&M engineering compliance costs based on these changes.
9.10 COMPLIANCE COSTS FOR NEW SOURCES
EPA evaluated the expected costs of compliance for new sources. The construction of
new generating units may occur at an existing power plant or at a new plant construction site.
The incremental cost associated with complying with the proposed NSPS and PSNS
options will vary depending on the types of processes, wastestreams, and waste management
systems that would have been installed in the absence of the proposed new source requirements.
EPA estimated capital and O&M costs for eight different scenarios that represent the different
types of operations that are present at existing power plants or are typically included at new
power plants. These scenarios captured differences in the following characteristics:
• Plant status (i.e., Greenfield versus existing plant);
• Presence/capacity of on-site impoundments;
• Presence/capacity of on-site landfills;
• Type of FGD system in service;
• Bottom ash handling; and
• Combustion residual leachate collection and handling.
9-44
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Section 9 - Engineering Costs
While EPA evaluated eight different scenarios, EPA determined that two of the scenarios
best represent the conditions that will be present at new sources. One scenario reflects conditions
for a Greenfield plant and the other scenario reflects conditions for a new source constructed at
an existing plant. EPA selected the scenarios that most resembled current industry practices,
based on an evaluation of the industry profile, for use in the NSPS analysis. Table 9-11 identifies
the characteristics that were used for these two scenarios.
Table 9-11. NSPS Compliance Cost Scenarios Evaluated for the Proposed Rule
Plant Characteristics
Plant Status
Presence of On-Site Impoundments
Presence of On-Site Landfill
Type of FGD System
Bottom Ash Handling
Combustion Residual Leachate1
Existing Plant Scenario
Existing
On-site impoundment with no
additional capacity.
On-site landfill with available
capacity.
Wet FGD system.
Mechanical drag system already
planned.
No leachate collection in the landfill.
Greenfield Plant Scenario
Greenfield
No on-site impoundment.
On-site landfill to be installed.
Wet FGD system.
Mechanical drag system already
planned.
Landfill leachate collected and treated
with FGD wastewater.
a - Because the Greenfield plant includes leachate collection while the existing plant does not (because leachate at
the existing plant would likely be subject to BAT), the costs presented in Table 9-12 are more expensive for the
Greenfield plant than for the existing plant.
EPA evaluated new source costs for FGD wastewater, bottom ash transport wastewater,
and combustion residual leachate. Because the current Steam Electric NSPS ELGs already
require zero discharge for fly ash transport wastewater, EPA did not calculate new source costs
for fly ash. Additionally, because the technology bases for gasification wastewater, flue gas
mercury control wastewater, and nonchemical metal cleaning wastes are already standard
industry practices, EPA did not calculate new source costs for these wastestreams.
Additionally, EPA determined that the majority of plants installing bottom ash handling
systems in the last 10-25 years are installing dry handling systems (approximately 80 percent).
Therefore, EPA determined new source incremental compliance costs for dry bottom ash
handling would be zero.
In addition to calculating the compliance costs for these two different scenarios, EPA also
evaluated the costs for three different model-sized generating units (i.e., small, medium, and
large generating units). Table 9-12 presents the estimated capital and O&M costs for each
scenario and each model plant size. The estimated incremental compliance costs for each of
scenarios evaluated by EPA is included in the memorandum entitled "New Source Performance
Standards (NSPS) Costing Methodology."
9-45
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Section 9 - Engineering Costs
Table 9-12. Estimated Industry-Level NSPS Costs
Regulatory
Option3
Small Unit (350 MW)
Total Capital Cost
($)
Total O&M Cost
($/year)
Medium Unit (600 MW)
Total Capital Cost
($)
Total O&M Cost
($/year)
Large Unit (1,300 MW)
Total Capital Cost
($)
Total O&M Cost
($/year)
Greenfield Plant
1
2
3
4
5
b
12,900,000
12,900,000
13,500,000
38,200,000
b
1,110,000
1,110,000
1,379,281
3,850,000
b
15,400,000
15,400,000
19,400,000
43,500,000
b
1,550,000
1,550,000
2,010,000
5,840,000
b
24,600,000
24,600,000
26,900,000
61,500,000
b
2,860,000
2,860,000
3,820,000
11,700,000
Existing Plant
1
2
3
4
5
b
12,900,000
12,900,000
12,900,000
33,800,000
b
1,110,000
1,110,000
1,110,000
2,850,000
b
15,400,000
15,400,000
15,400,000
39,000,000
b
1,550,000
1,550,000
1,550,000
4,280,000
b
24,600,000
24,600,000
24,600,000
56,300,000
b
2,860,000
2,860,000
2,860,000
8,530,000
VO
Source: [ERG, 2013b]
Note: Costs are rounded to three significant figures.
Note: All costs are indexed to 2010 dollars using RSMeans Historical Cost Indices [RSMeans, 2011].
a - EPA did not evaluate Regulatory Option 3a for NSPS because the current ELGs already have a zero discharge standard for NSPS. EPA did not evaluate
Regulatory Option 3b for NSPS because EPA does not have data regarding future new source plant-level wet scrubbed capacity at existing plants. EPA also did
not evaluate Regulatory Option 4a for NSPS because, as is the case for Options 4 and 5, there are no incremental NSPS costs for bottom ash. Therefore, the costs
associated with Option 4a would be equal to Option 3.
b - The NSPS costs for Regulatory Option 1 have been withheld to protect confidential business information.
-------
Section 9 - Engineering Costs
9.11 REFERENCES
1. HPD. 2009. Communications between Name, HPD and Sarah Holman, Eastern Research
Group, Inc. RE: MVC Costs." (17 February). DCN SE01025.
2. Eastern Research Group (ERG). 2013a. Memorandum to the Record. "Flue Gas
Desulfurization Future Profile Sensitivity Analysis." (29 January). DCN SE01989.
3. Eastern Research Group (ERG). 2013b. Memorandum to the Steam Electric Rulemaking
Record: New Source Performance Standards (NSPS) Costing Memorandum. (19 April).
DCN SE02130.
4. Eastern Research Group (ERG). 2013c. Memorandum to the Rulemaking Record:
Methodologies for Estimating Costs and Pollutant Removals for Steam Electric ELG
Regulatory Options 3a and 3b. (19 April). DCN SE03881.
5. Eastern Research Group (ERG). 2013d. Steam Electric Technical Questionnaire Database
("Steam Electric Survey"). (19 April). DCN SE01958.
6. RSMeans. 2011. Building Construction Cost Data, 69th Edition.
7. U.S. DOE. 2011. U.S. Department of Energy, Energy Information Administration (EIA).
Electric Power Annual 2009. Washington, D.C. (January). DCN SE02023.
8. U.S. Department of Labor, Bureau of Labor Statistics. 2010. Occupational Employment
Statistics: May 2009 National Occupational Employment and Waste Estimates, United
States. Washington, D.C. (May). DCN SE02024.
9. U.S. EPA, Office of Resource Conservation and Recovery (ORCR). 2010. Regulatory
Impact Analysis for EPA's Proposed RCRA Regulation of Coal Combustion Residues
(CCR) Generated by the Electric Utility Industry. Washington, D.C. (April). DCN
SE03168.
10. U.S. EPA. 2013. Incremental Costs and Pollutant Removals for Proposed Effluent
Limitation Guidelines and Standards for the Steam Electric Power Generating Point
Source Category Report. (19 April). DCN SE01957.
9-47
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Section 10 - Pollutant Loadings and Removals
SECTION 10
POLLUTANT LOADINGS AND REMOVALS
This section discusses annual pollutant loadings and removal estimates for the steam
electric industry for each proposed regulatory option. EPA estimated the pollutant loadings and
removals from existing steam electric power plants to evaluate the effectiveness of the treatment
technologies, estimate benefits gained from removing pollutants discharged from plants, and
evaluate the cost-effectiveness of the regulatory options in reducing the pollutant loadings. EPA
defined baseline and post-compliance pollutant loadings as follows:
• Baseline Loadings. Pollutant loadings, in pounds per year, in steam electric
wastewater being discharged to surface water or through publicly owned treatment
works (POTWs) to surface water.
• Post-Compliance Loadings. Estimated pollutant loadings, in pounds per year, in
steam electric wastewater after implementation of the proposed rule; these are also
referred to as treated loadings. EPA calculated these loadings assuming that all steam
electric power plants would operate wastewater treatment and pollution prevention
technologies equivalent to the technology bases for the regulatory option.
• Pollutant Removals. The difference between the baseline loadings and post-
compliance loadings for each regulatory option.
Some aspects of the proposed ELGs (e.g., applicability changes) would likely not lead to
a change in pollutant loadings to complying plants. Other aspects of the proposed ELGs would
likely lead to a change in pollutant loadings for a subset of complying plants. These plants
generally generate the wastestreams for which EPA is proposing new limitations or standards.
This section describes the detailed pollutant loadings evaluation EPA performed for these plants
that are likely to achieve a reduction in pollutant loadings associated with the regulatory options
evaluated for the proposed ELGs. Specifically, EPA determined baseline and post-compliance
pollutant loadings for the following wastestreams: FGD wastewater, fly ash transport water,
bottom ash transport water, combustion residual landfill leachate, gasification wastewater, and
flue gas mercury control wastewater.
The currently operating gasification generating units operate vapor-compression
evaporation systems (i.e., the technology basis for the preferred options); therefore, EPA
determined that the baseline loadings are equal to the post-compliance loadings. Similarly, plants
currently manage their flue gas mercury control wastes so there is no pollutant discharge to
surface waters; therefore, the baseline loadings for these wastewaters are also equal to the post-
compliance loadings. Additionally, because nonchemical metal cleaning wastes are already
subject to the proposed BAT limitations, based on the current BPT standard (as described in
Section 8.1.3, and because EPA is proposing to exempt from limitations and standards any
nonchemical metal cleaning wastes currently generated and authorized for discharge without
copper and iron limits, EPA finds that the baseline loadings are equal to the post-compliance
loadings. Therefore, the remainder of this section applies to FGD wastewater, fly ash transport
water, bottom ash transport water, and combustion residual landfill leachate.
10-1
-------
Section 10 - Pollutant Loadings and Removals
10.1 GENERAL METHODOLOGY FOR ESTIMATING POLLUTANT REMOVALS
For each plant discharging an evaluated wastestream (i.e., FGD wastewater, ash transport
water, and combustion residual leachate), EPA calculated plant-level pollutant removals for each
of the technology options presented in Section 8. For example, for any plant discharging FGD
wastewater, EPA calculated both a baseline loading and post-compliance loadings associated
with each technology basis (i.e., one-stage chemical precipitation, one-stage chemical
precipitation with biological treatment, and one-stage chemical precipitation with vapor-
compression evaporation). On a plant-level basis, EPA calculates baseline loadings by
multiplying the average pollutant concentration in the discharge by the plant-specific wastewater
discharge flow rate to generate the mass of pollutant discharged per year, in pounds/year.
EPA used sampling data gathered through its sampling program described in Section 3,
as well as publicly available sources, to characterize the baseline loading and post-compliance
loading concentrations for each evaluated wastestream. Section 10.2 presents the data sources
and average discharge pollutant concentrations for baseline and each of the technology options
associated with the evaluated wastestreams.
Next, for each evaluated wastestream discharged by a specific plant, EPA used data from
the Questionnaire for the Steam Electric Power Generating Effluent Guidelines (Steam Electric
Survey) to determine the plant's discharge flow rate. In cases where survey data were
insufficient, EPA developed a methodology for estimating flow rates. Section 10.3 provides
details on these wastewater flow rates.
EPA calculated baseline pollutant loadings and post compliance treatment loadings for
each plant discharging an evaluated wastestream using the plant-specific wastewater flow for the
wastestream and average pollutant concentration of the specific wastestream in the following
equation:
/lbs\ /gallons\ /mgx /2.20462 lb\ / 1000 L \
L°adingpollutant (-) = FlowRate (-^-) x Concpollutant (-) x (^T^J >< (264.17 gallonj
Where:
T ,. The loadings from a specific pollutant discharged directly to surface
Loadmgpoiiutant . • j
op water, in pounds per year.
. = The flow rate of the wastestream being discharged, in gallons per
year.
„ = The average concentration of a specific pollutant present in the
pollutant wastestream, in milligrams per liter.
EPA identified several plants that report transferring wastewater to a POTW rather than
discharging directly to surface water. For these plants, EPA adjusted the baseline loadings to
account for pollutant removals expected from POTWs for each analyte. For each POC, Table
10-1 provides the percent removals expected from well-operated POTWs as reported in the
Memo to the 2006 Effluent Guidelines Program Plan Docket [ERG, 2005]. For any plant
10-2
-------
Section 10 - Pollutant Loadings and Removals
identified as discharging a wastestream to a POTW, EPA used the calculated baseline loadings
and the values shown in Table 10-1 to calculate the amount of pollutant discharged from the
POTW to surface water according to the following equation:
/lbs\ /lbs\
Loadingpollutant indirect ^—J =Loadingpollutant ^—J x(l-POTWRemoval)
Where:
Loadingp0nutant indirect ~~
Loadingpoiiutant
POTWRemoval
The loadings from a specific pollutant that is transferred to a POTW
prior to discharge, in pounds/year.
The loadings from a specific pollutant if it were discharged directly,
in pounds/year.
The estimated percentage of the pollutant loading that will be
removed by a POTW.
In addition to expressing pollutant loadings in pounds of pollutant discharged per year,
EPA uses toxic weighting factors (TWFs) to account for differences in toxicity across
pollutants.85 EPA calculated a toxic-weighted pound equivalent (TWPE) value for each pollutant
discharged to compare mass loadings of different pollutants based on their toxicity. To perform
this comparison, EPA multiplied the mass loadings of pollutant in pounds/year by the pollutant-
specific TWF to derive a "toxic-equivalent" loading (Ib-equivalent/yr), or TWPE.86 Section 10.4
discusses the wastestream mass loading (i.e., unweighted loadings) and TWPE loadings in more
detail.
Table 10-1. POTW Removals
Analyte
Aluminum
Ammonia
Antimony
Arsenic
Barium
Beryllium
Biochemical Oxygen Demand
Boron
Cadmium
Calcium
Median POTW Removal Percentage
91.0%
39.0%
66.8%
65.8%
55.2%
61.2%
NA
NA
90.1%
NA
85 A list of pollutant-specific TWF values is located in the Toxic Weighting Factor Development in Support ofCWA
304(m) Planning Process [U.S. EPA, 2004]. EPA has developed TWFs for more than 1,900 pollutants based on
aquatic life and human health toxicity data, as well as physical/chemical property data.
86 If discharged to a POTW, EPA adjusted the TWPE to account for POTW removals, as described above.
10-3
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Section 10 - Pollutant Loadings and Removals
Table 10-1. POTW Removals
Analyte
Chemical Oxygen Demand
Chloride
Chromium
Chromium (VI)
Cobalt
Copper
Cyanide, Total
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Nitrate Nitrite as N
Nitrogen, Kjeldahl
Phosphorus, Total
Selenium
Silver
Sodium
Sulfate
Thallium
Tin
Titanium
Total Dissolved Solids
Total Suspended Solids
Vanadium
Zinc
Median POTW Removal Percentage
NA
NA
80.3%
NA
10.2%
84.2%
NA
NA
77.5%
NA
40.6%
90.2%
NA
51.4%
90.0%
NA
NA
34.3%
88.3%
NA
NA
53.8%
NA
NA
NA
NA
8.3%
79.1%
Source: Memo to 2006 Effluent Guidelines Program Plan Docket [ERG,
NA - Not applicable.
2005].
10.2 WASTESTREAM POLLUTANT CHARACTERIZATION AND DATA SOURCES
As discussed earlier, loadings calculations require pollutant concentrations to determine
the mass pollutant loadings. EPA used a variety of data sources to generate characterization data
for each evaluated wastestream. For each wastestream, EPA excluded all pollutants that were not
measured above the quantitation limit in all of the samples representing the baseline effluent
discharges for that specific wastestream. Therefore, if a pollutant was measured above the
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Section 10 - Pollutant Loadings and Removals
quantitation limit at least once in the baseline effluent concentration dataset, that pollutant was
included in the loadings analysis. EPA generated a separate set of characterization data for
baseline and each post-compliance technology basis. Section 10.2.1, Section 10.2.2, and Section
10.2.3 present the data sources and characterization for FGD wastewater, ash transport water,
and combustion residual leachate, respectively.
10.2.1 FGD Wastewater Characterization
As described in Section 8, EPA is considering three technologies as the basis of proposed
discharge requirements for FGD wastewater: one-stage chemical precipitation, one-stage
chemical precipitation with biological treatment, and one-stage chemical precipitation with
vapor-compression evaporation. Table 10-2 summarizes the concentration data sets that were
included in the baseline and post-compliance FGD loadings analysis and their sources. EPA
performed the following review, made substitutions, as appropriate, and performed the following
analyses with the sampling data results, where appropriate, prior to using them in the technology
option loadings calculations:87
• J-Values and Nondetects: The laboratories performing the metals analyses provided
all the analytical results that were measured above the sample-specific method
detection limit (MDL). Therefore, the laboratory results include values flagged with a
"J" indicator (i.e., results measured above the method detection limit, but below the
quantitation limit). EPA did not use the "J-values" in the loadings calculations. EPA
treated all results that were less than the quantitation limit (i.e., J-values and
nondetects below the method detection limit) as half the sample-specific quantitation
limit for all analytes.
• Field Blank Analysis: EPA compared the sample results from a specific sampling
point to the field blank results for the same sampling point, on the specific day of
sample collection. For the purpose of the loadings calculations, EPA made the
following assumptions based on the results of this field blank analysis:
- If the sample result was less than five times the field blank result, then the sample
result was treated as a nondetect;
If the sample result was between five and 10 times the field blank result, then the
sample result was flagged and handled as a qualified value; and
If the sample result was greater than 10 times the field blank result, then the
sample result was unchanged.
Note: EPA used field blank results measured above the quantitation limit for this
analysis. J-values associated with field blanks samples were not used.
• Duplicate Sample Results: EPA averaged the results from each duplicate sample with
the results of its original sample. EPA made the following assumptions when
averaging the duplicate results:
87 Only EPA sampling activities collected and analyzed field blank and duplicate samples. EPA CWA 308 sampling
program did not include duplicate sample analysis therefore, only the field blank analysis was conducted on this data
set. The plant provided self-monitoring data included no field blank or duplicate samples.
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Section 10 - Pollutant Loadings and Removals
If one value was quantified and the other value was not quantified above the
quantitation limit, then EPA used one-half the sample-specific quantitation limit
for the non-quantified result in calculating the average;
If both values were not quantified above the sample-specific quantitation limit,
then EPA used one-half the quantitation limit for both non-quantified results in
calculating the average; and
Both qualified and unqualified data were used in the calculation.
Table 10-2. Data Sets Used in the FGD Loadings Calculation
Plant Name
Progress Energy Carolinas' Roxboro
Steam Electric Plant (Roxboro)
Duke Energy's Miami Fort Station
(Miami Fort)
RRI Energy's Keystone Generating
Station (Keystone)
Allegheny Energy's Hatfield's Ferry
Electric Plant (Hatfield's Ferry)
Duke Energy Carolinas' Belews Creek
Steam Station (Belews Creek)
Duke Energy Carolinas' Allen Steam
Station (Allen)
Enel Brindisi
Source of Data Set
Monitoring data provided by plant
EPA Sampling
EPA CWA 308 Sampling
EPA Sampling
EPA CWA 308 Sampling
EPA Sampling
EPA CWA 308 Sampling
EPA Sampling
EPA CWA 308 Sampling
Monitoring data provided by plant
EPA Sampling
EPA CWA 308 Sampling
Monitoring data provided by plant
EPA Sampling
Wastestreams Represented
in Data Set a
Settling impoundment effluent
Chemical precipitation effluent
Chemical precipitation effluent
Chemical precipitation effluent
Chemical precipitation effluent
Chemical precipitation effluent
Chemical precipitation effluent
Biological treatment effluent
Biological treatment effluent
Biological treatment effluent
Biological treatment effluent
Biological treatment effluent
Biological treatment effluent
Vapor-Compression Evaporation
Effluent
a -The three plants with data used for chemical precipitation effluent characterization operate one-stage chemical
precipitation systems.
Note: EPA excluded data from the We Energies' Pleasant Prairie Power Plant (Pleasant Prairie) in the loadings
calculation because the Pleasant Prairie FGD wastewater treatment system consists of a two-stage chemical
precipitation system, which is more advanced than the one-stage chemical precipitation system used as the bases for
the chemical precipitation technology option. In addition, EPA excluded data from the Mirant Mid-Atlantic, LLC's
Dickerson Generating Station (Dickerson) in the loadings calculation because the Dickerson plant was not adding
organosulfide chemicals to the wastewater treatment system at the time of sampling. The plant also experienced
frequent shutdowns, wastewater treatment upsets, and the treatment system is not designed to remove selenium.
Each of the following sections presents the characterization data set used to calculate
mass and TWPE loadings for each option, starting with the baseline characterization.
10.2.1.1 Baseline FGD Wastewater Loading Characterization
As discussed in Section 9, EPA identified 117 plants that operate wet FGD systems and
discharge FGD wastewater. For the FGD dischargers, EPA calculated baseline loadings by
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Section 10 - Pollutant Loadings and Removals
assigning pollutant concentrations based on the type of treatment system currently in place at the
plant. EPA assigned treatment in place for this wastewater to one of four classes of treatment:
surface impoundment, chemical precipitation, biological treatment, and vapor-compression
evaporation. As discussed in Section 9, EPA used survey data to determine the baseline FGD
wastewater treatment in place. Based on survey responses, EPA categorized 46 plants as
operating a treatment system more advanced than a surface impoundment:
• Forty plants operate a one-stage chemical precipitation system;
• Five plants operate a biological treatment system;88 and
• One plant operates a vapor-compression evaporation system.89
EPA categorized all plants not operating one of these three types of treatment systems as
impoundment systems in the baseline loadings calculations. While some of these plants may
operate a system that is not an impoundment, EPA determined that these other systems are
typically only solids removal systems that do not include hydroxide or sulfide precipitation (e.g.,
clarifier with polymer addition). The operation of these types of system are effective at removing
solids and metals in the particulate phase, but do not achieve removals of dissolved solids,
similar to the operation of an impoundment.
As discussed in Section 7.1.1, surface impoundments use gravity to remove particulates
from wastewater, reducing the amount of total suspended solids (TSS) and particulate forms of
other specific pollutants in the wastewater. EPA's sampling program collected and analyzed the
untreated FGD wastewater of seven steam electric power plants operating wet FGD systems that
use either chemical precipitation or chemical precipitation followed by biological treatment to
treat the FGD wastewater (see Section 3.4 for a description of these sampling activities and
plants). Based on analytical data for the untreated FGD wastewater at these sampled plants, EPA
estimated the effluent concentration from a surface impoundment by assuming that a surface
impoundment will remove most of the particulate phase metals, but will not remove dissolved
metals from the wastewater.90 EPA calculated proxy values representing impoundment effluent
concentrations for each analyte using the data for each of these seven EPA sampled plants. EPA
also obtained surface impoundment effluent data from a steam electric power plant that treats
only FGD wastewater in the impoundment. EPA averaged the surface impoundment data along
with the estimated impoundment effluent concentrations from the seven sampled plants for each
analyte to generate an average effluent concentration data set for FGD surface impoundments
based on the eight plants. Table 10-3 presents the average characterization data used to calculate
88 There are six plants currently operating biological treatment system, but at the time the costs and loadings were
developed, EPA had only identified five plants with biological treatment systems. Therefore, only five of the six
plants were identified as having biological treatment in place for these analyses.
89 There are two plants currently operating vapor-compression evaporation systems, but at the time the costs and
loadings were developed, EPA had only identified one plant with a vapor-compression evaporation system.
Therefore, only one of the two plants were identified as having vapor-compression treatment in place for these
analyses.
90 The methodology used to estimate settling impoundment effluent concentrations is presented in detail in the
Incremental Costs and Pollutant Removals for Proposed Effluent Limitation Guidelines and Standards for the Steam
Electric Generating Point Source Category Report [U.S. EPA, 2013].
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Section 10 - Pollutant Loadings and Removals
baseline loadings for plants currently treating FGD wastewater in a surface impoundment prior
to discharge.
Approximately 40 percent of plants discharging FGD wastewater use a more advanced
treatment system. For those plants currently operating a one-stage chemical precipitation system,
biological treatment system, or vapor-compression evaporation system, EPA used the
concentration data sets associated with the post-compliance technology options to calculate
baseline loadings. Section 10.2.1.2 discusses the characterization of one-stage chemical
precipitation systems. Sections 10.2.1.3 and 10.2.1.4 discuss the characterization of one-stage
chemical precipitation systems with biological treatment or with vapor-compression evaporation
systems, respectively.
Table 10-3. Average Effluent Pollutant Concentrations for FGD
Surface Impoundments
Analyte
Unit
Average Concentration
Classical*
Ammonia
Nitrate Nitrite as N
Nitrogen, Kjeldahl
Biochemical Oxygen Demand
Chemical Oxygen Demand
Chloride
Sulfate
Cyanide, Total
Total Dissolved Solids
Total Suspended Solids
Phosphorus, Total
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
NA
67,300
NA
NA
418,000
7,320,000
1,240,000
1,190
28,600,000
27,900
404
Total Metals
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Chromium (VI)
Cobalt
Copper
Iron
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
2,080
13
6.8
303
1.9
243,000
112
2,050,000
18
NA
183
21
1,510
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Section 10 - Pollutant Loadings and Removals
Table 10-3. Average Effluent Pollutant Concentrations for FGD
Surface Impoundments
Analyte
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Silver
Sodium
Thallium
Tin
Titanium
Vanadium
Zinc
Unit
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
Average Concentration
4.7
3,370,000
93,100
5.6
125
878
1,110
0.93
276,000
13
100
27
16
1,390
Source: [ERG, 2012a-20121]; [NCDENR, 2011].
Note: Concentrations are rounded to three significant figures.
NA - Not applicable.
10.2.1.2 Baseline and Post Compliance One-Stage Chemical Precipitation Pollutant
Characterization
As part of the sampling activities described in Section 3, EPA identified and collected
data from seven plants operating chemical precipitation systems, sometimes in conjunction with
other technologies, such as biological treatment. The specific operating characteristics of the
chemical precipitation treatment systems varied. EPA conducted an engineering review of the
data and identified three systems operating consistently with the one-stage chemical precipitation
technology basis. These three plants operate one-stage chemical precipitation systems that
include the addition of organosulfide.
The treatment systems at these plants have similar operations; however, the plants do
have varying configurations and operating characteristics, such as thickeners, filter presses, sand
filters, and retention time. Each of these systems were designed and are operated to remove
suspended solids and dissolved metals from the FGD wastewater to achieve a similar level of
pollutant discharge. The systems are sized to handle a specific flow rate of FGD wastewater,
which means that the sizes of the tanks were designed to allow for the residence time required
for settling and/or reactions to occur to achieve effluent concentrations meeting the plant's
permit limits.
To calculate the pollutant concentrations for the one-stage chemical precipitation
technology option, EPA first calculated an average concentration for each analyte using only the
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Section 10 - Pollutant Loadings and Removals
four-day EPA sampling data for each plant for which data were available. EPA included only
total concentrations except for hexavalent chromium, which is analyzed only as a dissolved
constituent. EPA then calculated an average concentration for each analyte at each plant by using
the four CWA 308 monitoring data results along with the average of the four-day EPA sampling
data (i.e., treating these as five results and calculating the average).
Using the average concentrations from the three plants, as calculated above, EPA then
calculated an overall average concentration for each of the analytes shown in Table 10-4. EPA
used this average concentration to calculate the post-compliance loadings that would be
discharged by plants that currently operate surface impoundments if they were to install the
chemical precipitation technology. EPA also used the average concentrations presented in Table
10-4 to calculate the baseline loadings for any plant currently operating a chemical precipitation
treatment system as FGD wastewater treatment.
As explained above, the values presented in Table 10-4 reflect three plants identified as
operating consistently with the technology basis and EPA has applied these values to all plants
that operate chemical precipitation systems as their baseline concentrations. As discussed in
Section 10.2.1.1, EPA classified 38 other plants as operating chemical precipitations systems.
However, these 38 plants do not operate their chemical precipitation system in the same manner
as the technology basis (or have all the components included in the technology basis) and would
likely discharge greater pollutant concentrations than the systems reflecting the technology basis.
Further, for these 38 plants that operate chemical precipitation systems that are not equivalent to
the technology basis, the baseline and post-compliance loadings are identical and EPA calculates
no removals for these plants, even though these plants are being assessed compliance costs to
upgrade the system to operate similarly to the technology basis.
Table 10-4. Average Effluent Pollutant Concentrations for One-Stage
Chemical Precipitation System
Analyte
Unit
Average Concentration
Classical*
Ammonia
Nitrate Nitrite as N
Nitrogen, Kjeldahl
Biochemical Oxygen Demand
Chemical Oxygen Demand
Chloride
Sulfate
Cyanide, Total
Total Dissolved Solids
Total Suspended Solids
Phosphorus, Total
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
8,120
67,300
27,000
3,130
418,000
8,940,000
5,980,000
1,190
23,100,000
6,560
404
Total Metals
Aluminum
ug/L
155
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Section 10 - Pollutant Loadings and Removals
Table 10-4. Average Effluent Pollutant Concentrations for One-Stage
Chemical Precipitation System
Analyte
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Chromium (VI)
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Silver
Sodium
Thallium
Tin
Titanium
Vanadium
Zinc
Unit
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
Average Concentration
5.0
4.5
163
1.00
279,000
3.8
2,330,000
9.1
5.3
10
2.0
127
1.00
3,340,000
13,600
0.17
215
5.6
455
1.00
420,000
8.6
100
10
15
18
Source: [ERG, 2012c]; [ERG, 2012f]; [ERG,
Note: Concentrations are rounded to three su
2012g]; [ERG, 20121].
;nificant figures.
10.2.1.3 Baseline and Post-Compliance One-Stage Chemical Precipitation with
Biological Treatment Characterization
EPA identified and collected data from two plants operating chemical precipitation
systems in conjunction with biological treatment systems that represent the biological treatment
technology option for the proposed rule. After conducting an engineering review of the data,
EPA determined that both plants operate systems consistent with the one-stage chemical
precipitation with biological treatment technology option. Both of the plants sampled operate
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Section 10 - Pollutant Loadings and Removals
chemical precipitation systems followed by anoxic/anaerobic biological treatment systems
specifically designed for selenium removal. EPA used the data from both plants to represent
treatment performance of a one-stage chemical precipitation system with biological treatment
system; however, these two plants do not fully represent the technology option because neither
plant currently uses sulfide precipitation in the chemical precipitation system. Therefore, these
two plants likely do not demonstrate mercury (and other metals) effluent concentrations as low
as could be achieved by the one-stage chemical precipitation (with sulfide precipitation)
followed by a biological treatment system that forms the basis of the option (see Section 7 for
complete description).
EPA has multiple sets of data for these two plants including EPA sampling data, CWA
308 sampling data, and self-monitoring data to calculate pollutant loadings associated with this
technology option. To calculate the average pollutant concentrations for the biological treatment
system technology option, EPA first compared long-term self-monitoring data provided by the
plants to EPA sampling data and CWA 308 monitoring data to determine which analytes were
represented in different sets of data. In cases where an analyte was not represented in the long-
term self-monitoring data, but was represented in the EPA sampling and CWA 308 monitoring
data, EPA averaged the four-day EPA sampling results and then combined that average with the
four CWA 308 monitoring data results (i.e., treated them as five results) for each plant. EPA then
averaged these five results to calculate an overall plant-level average concentration for each of
those analytes. In cases where an analyte was represented in the long-term self-monitoring data
provided by the plant, the EPA sampling, and the CWA 308 monitoring data, EPA averaged all
sample results to calculate a plant-level average concentration for each analyte. When combining
the industry self-monitoring data with EPA's sampling results (both four-day EPA sampling and
CWA 308 monitoring), there were some instances of overlap with two sample results occurring
on the same day. In these cases, the two results were averaged together to calculate one average
concentration for each day of sampling before calculating an average concentration for each
analyte.
Using the average concentrations from the two BAT plants, EPA calculated an overall
average concentration for each analyte, which is presented in Table 10-5. EPA used this average
concentration to calculate the post-compliance loadings that would be discharged by plants
currently operating surface impoundments or chemical precipitation systems if they were to
install all components of the biological technology option. EPA also used the average
concentrations presented in Table 10-5 to calculate the baseline loadings for any plant currently
operating chemical precipitation and a biological treatment system as FGD wastewater treatment.
The average concentration used to calculate baseline and post-compliance loadings for
the chemical precipitation and a biological treatment system technology basis, presented in Table
10-5, is based on two plants identified as operating consistently with the technology basis. As
discussed in Section 10.2.1.1, EPA classified five plants as operating biological treatment
systems.91 For each plant classified as a baseline biological treatment system EPA calculated the
baseline loadings using the average concentration presented in Table 10-5. Two of these plants
91 There are six plants currently operating biological treatment system, but at the time the costs and loadings were
developed, EPA had only identified five plants with biological treatment systems. Therefore, only five of the six
plants were identified as having biological treatment in place for these analyses.
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Section 10 - Pollutant Loadings and Removals
do not operate consistently with the technology basis and likely discharge greater pollutant
concentrations than the system reflecting the technology basis.92 Further, for these two plants,
the baseline and post-compliance loadings are identical and show no additional removals even
though these plants are being assessed compliance costs to upgrade the system to achieve the
technology basis.
Table 10-5. Average Effluent
Precipitation
Pollutant Concentrations for One-Stage Chemical
System with Biological Treatment
Analyte
Unit
Average Concentration
Classical*
Ammonia
Nitrate Nitrite as N
Nitrogen, Kjeldahl
Biochemical Oxygen Demand
Chemical Oxygen Demand
Chloride
Sulfate
Cyanide, Total
Total Dissolved Solids
Total Suspended Solids
Phosphorus, Total
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
8,750
79
12,100
1,740
156,000
6,720,000
1,380,000
74
14,100,000
8,210
115
Total Metals
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Chromium (VI)
Cobalt
Copper
Iron
Lead
Magnesium
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
155
2.0
4.6
323
0.97
125,000
2.5
2,970,000
2.2
3.0
10
2.7
302
1.00
741,000
Of the total five baseline biological treatment plants, only three are classified as operating consistently with the
technology basis.
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Section 10 - Pollutant Loadings and Removals
Table 10-5. Average Effluent Pollutant Concentrations for One-Stage Chemical
Precipitation System with Biological Treatment
Analyte
Manganese
Mercury
Molybdenum
Nickel
Selenium
Silver
Sodium
Thallium
Tin
Titanium
Vanadium
Zinc
Unit
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
Average Concentration
1,960
0.067
20
2.6
5.0
2.3
46,100
1.9
100
10
5.0
4.8
Source: [ERG, 2012a]; [ERG, 2012d]; [ERG, 2012i]; [Duke Energy, 201 la- 201 lb].
Note: Concentrations are rounded to three significant figures.
10.2.1.4 Baseline and Post-Compliance One-Stage Chemical Precipitation with Vapor-
Compression Evaporation Characterization
EPA conducted an engineering review of the data for the two plants operating vapor-
compression evaporation system. Because only one plant matches the technology basis and
operates a hydroxide-sulfide chemical precipitation system followed by softening, a brine
concentrator, and crystallization system, EPA used data from this plant to represent the
technology option.
To calculate the average pollutant concentrations for the vapor-compression evaporation
treatment system technology option, EPA first calculated an average concentration by analyte for
each of the two wastestreams at the plant (i.e., brine concentrator distillate and crystallizer
condensate) using available sampling data (i.e., three-day EPA sampling data). For this plant
EPA collected and analyzed only total concentrations; therefore, EPA did not have dissolved
concentrations or hexavalent chromium data to use in the analysis.
Using the average concentrations from the two streams (i.e., brine concentrator distillate
and crystallizer condensate), EPA calculated an overall average concentration for each analyte,
shown in Table 10-6.93 EPA used this average concentration to calculate the post-compliance
loadings that would be discharged by plants currently operating surface impoundments, chemical
EPA used both the brine concentrator distillate and crystallizer condensate streams to calculate the loadings
because both wastestreams could be discharged. The vapor-compression system at Brindisi is operated as a zero-
discharge system with no wastewater being discharge to surface water or POTW. The plant could choose to
discharge both the brine concentrator and the crystallizer condensate streams, together or separately.
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Section 10 - Pollutant Loadings and Removals
precipitation systems, or biological treatment systems if they were to install all components of
the vapor-compression evaporation technology option. EPA also used the average concentrations
presented in Table 10-6 to calculate the baseline loadings for any plant currently operating
chemical precipitation and a vapor-compression evaporation treatment system as FGD
wastewater treatment.
Table 10-6. Average Effluent Pollutant Concentrations for One-Stage Chemical
Precipitation System with Vapor-Compression Evaporation
Analyte
Unit
Average Concentration
Classical*
Ammonia
Nitrate Nitrite as N
Nitrogen, Kjeldahl
Chemical Oxygen Demand
Chloride
Sulfate
Total Dissolved Solids
Total Suspended Solids
Phosphorus, Total
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
24,300
100
23,500
10,000
1,500
2,500
10,800
2,000
25
Total Metals
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Silver
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
100
1.00
2.0
10
1.00
3,750
2.0
200
4.0
10
2.0
100
1.00
200
10
0.0103
20
2.0
2.0
1.0
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Section 10 - Pollutant Loadings and Removals
Table 10-6. Average Effluent Pollutant Concentrations for One-Stage Chemical
Precipitation System with Vapor-Compression Evaporation
Analyte
Sodium
Thallium
Tin
Titanium
Vanadium
Zinc
Unit
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
Average Concentration
5,000
1.0
100
10
5.0
28.5
Source: [ERG, 2012h].
Note: Concentrations are rounded to three significant figures.
NA - Not applicable.
10.2.2 Ash Transport Water Characterization
During this rulemaking effort, EPA relied on publicly available data sources to
characterize the effluent stream from ash impoundments at steam electric power plants; these
sources are listed below:
• EPA ash impoundment sampling data from the detailed study [U.S. EPA, 2009];
• Electric Power Research Institute (EPRI) Power Plant Integrated Systems-Chemical
Emissions Study (PISCES) Reports [EPRI, 1997-2001];
• Permit application data, as provided by member companies of the Utility Water Act
Group (UWAG) [UWAG, 2008]; and
• Development Document for Final Effluent Limitations Guidelines, New Source
Performance Standards, and Pretreatment Standards for the Steam Electric Point
Source Category, EPA 440-1-82-029, November 1982 (1982 TDD) [U.S. EPA,
1982].
Section 3 provides details regarding each of the four data sources used in the ash
impoundment loadings. EPA used information available from each data source to characterize
the impoundment/outfall as either a fly ash impoundment, bottom ash impoundment, or
combined ash impoundment. For the purposes of this analysis, EPA used the following criteria to
make those determinations:
• Fly ash impoundment: An impoundment/outfall that receives fly ash transport water
and does not receive bottom ash transport water or any other combustion residual
wastes. The impoundment may also receive other types of wastewater (e.g., low
volume wastewaters, cooling water).
• Bottom ash impoundment: An impoundment/outfall that receives bottom ash
transport water and does not receive fly ash transport water or any other combustion
residual wastes. The impoundment may also receive other types of wastewater (e.g.,
low volume wastewaters, cooling water).
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Section 10 - Pollutant Loadings and Removals
• Combined ash impoundment: An impoundment/outfall that receives both fly ash
transport and bottom ash transport water. The impoundment may also receive other
types of wastewater (e.g., low volume wastewaters, cooling water).
EPA used the concentration data obtained from these data sources to calculate the
average pollutant concentration in fly ash transport water, bottom ash transport water, and
combined ash transport water. EPA notes that because the data associated with these
impoundments may include other wastestream (e.g., cooling water), the concentrations may be
diluted and therefore, may underestimate the pollutant loadings. First, EPA reviewed the data
and, as appropriate, made some substitutions to the data sets. EPA set nondetects equal to one-
half the quantitation limit for the detailed study sampling data because EPA knew the
quantitation limit.94 For the other (i.e., EPRI, 1982 TDD, and Form 2C) data sets, EPA could not
confirm whether the nondetect results were presented as less than the quantitation limit or the
method detection limit (or some other value); therefore, EPA set the nondetects equal to the
value provided. For each data point, EPA first identified the type of impoundment system the
data represents (i.e., fly ash impoundment, bottom ash impoundment, combined ash
impoundment). EPA then calculated an average pollutant concentration for each impoundment
for which it had data. For example, if a plant had pollutant concentration data for its fly ash
impoundment for more than one day, EPA averaged all these data for that specific pollutant to
get a single representative value of average concentration of that pollutant in the effluent from
the fly ash impoundment. EPA used the same methodology to calculate the average
concentration of a pollutant in the effluents from bottom ash impoundments and combined ash
impoundments. Some data sources provided only one data point, and therefore, the average is the
same as that data point.
After calculating an average concentration for each type of impoundment at the plant-
specific level, EPA then calculated an industry-level average pollutant concentration for each
type of impoundment for which EPA had data by averaging the plant-level average
concentrations for each type of impoundment.95 Table 10-7 presents the average pollutant
concentration for all three types of ash impoundment. EPA used these average concentration data
sets to calculate the baseline loadings for discharges from ash impoundments.
The technology option under consideration for both fly ash and bottom ash is dry or
closed-loop recycle ash handling. As discussed in Section 7, these systems do not discharge ash
transport water; therefore, the average effluent concentration associated with dry or closed-loop
recycle ash handling is zero. Because no ash transport water is discharged, the post-compliance
discharge loading is zero.
94 To simplify the discussion, for the purpose of Section 10.2.2 the term "nondetect" is used to refer to both values
measured below the quantitation limit and those values measured below the detection limit.
95 The methodology used to calculate the average concentrations for ash impoundment effluent is presented in the
Incremental Costs and Pollutant Removals for Proposed Effluent Limitation Guidelines and Standards for the Steam
Electric Generating Point Source Category Report [U.S. EPA, 2013].
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Section 10 - Pollutant Loadings and Removals
Table 10-7. Average Effluent Pollutant Concentration for Ash Impoundment Systems
Analyte
Unit
Average
Fly Ash
Concentration
Average
Bottom Ash
Concentration
Average Combined
Ash Concentration
Classical*
Ammonia (as N)
Nitrate-Nitrite (as N)
Total Kjeldahl Nitrogen
Biochemical Oxygen Demand
Chloride
Sulfate
Sulfide (as S)
Sulfite (as SOS)
Cyanide
Total Dissolved Solids
Total Suspended Solids
Fluoride
Hexane Extractable Material
Nitrogen, Total Organic (as N)
Oil and Grease
Silica-Gel Treated Hexane
Extractable Material
Phosphorus (as P)
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
0.62
2.51
0.41
1.5
107
709
1.01
2
NA
1,362
8.06
NA
6.25
0.65
2.13
2
0.12
0.24
9.65
1.36
1
53.5
1,170
0.51
26.7
NA
1,260
8.36
NA
2.5
3.28
3.67
NA
0.36
0.27
2.53
3.39
4
16.4
203
0.52
1.63
0.01
262.4
13.8
0.15
6
0.51
2.83
2.5
0.28
Total Metals
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Hexavalent Chromium
Cobalt
Copper
Iron
Lead
Magnesium
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
0.46
0.028
0.042
0.13
0.003
4.67
0.006
102
0.017
0.005
0.014
0.042
1.81
0.03
18.8
0.59
0.093
0.018
0.078
0.004
2.24
0.008
186
0.014
0.001
0.048
0.027
2.44
0.037
97.3
1.11
0.024
0.064
0.2
0.005
1.97
0.008
70.7
0.02
0.012
0.012
0.04
0.58
0.027
15.3
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Section 10 - Pollutant Loadings and Removals
Table 10-7. Average Effluent Pollutant Concentration for Ash Impoundment Systems
Analyte
Manganese
Mercury
Molybdenum
Nickel
Selenium
Silica
Silver
Sodium
Thallium
Tin
Titanium
Vanadium
Yttrium
Zinc
Unit
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
Average
Fly Ash
Concentration
0.041
0.001
0.43
0.035
0.035
NA
0.003
298
0.011
0.025
0.008
0.11
0.003
0.17
Average
Bottom Ash
Concentration
0.13
0.001
0.065
0.13
0.013
NA
0.004
106
0.12
0.34
0.11
0.01
0.003
0.094
Average Combined
Ash Concentration
0.62
0.002
0.14
0.035
0.03
5.93
0.008
21.3
0.049
0.15
0.029
0.044
0.003
0.085
Source: [U.S. EPA, 2009]; [U.S. EPA, 1982]; [EPRI,
Note: Concentrations are rounded to three significant
NA - Not applicable.
1997 - 2001]; [UWAG, 2008].
figures.
10.2.3 Baseline and Post-Compliance Combustion Residual Leachate Characterization
As described in Section 6, EPA determined that combustion residual impoundments will
recycle the leachate back to the impoundment from which it was collected rather than install the
technology basis for the discharge requirements. EPA does not expect this recycled
impoundment leachate to alter the discharge loadings of the impoundment in anyway. By
recycling leachate generated by the impoundment back into the same impoundment no additional
pollutants are added to the system (i.e., the surface impoundment). The pollutants contained in
the impoundment leachate were previously in the system; adding these pollutants back to the
system at the concentrations found in the leachate will not alter the system as a whole. The
concentrations of pollutants in the discharge stream will remain at equilibrium. Therefore, EPA
finds that baseline and post-compliance pollutant loadings will be the same at baseline and at
post-compliance for combustion residual impoundment leachate. Therefore, the remainder of this
section only discusses the pollutant concentrations associated with combustion residual landfill
leachate.
As described in Section 8, EPA evaluated two technology options for treating combustion
residual landfill leachate: one-stage chemical precipitation and one-stage chemical precipitation
with biological treatment. EPA used data collected through the Steam Electric Survey to
calculate average effluent concentrations for untreated combustion residual landfill leachate.
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Section 10 - Pollutant Loadings and Removals
EPA's Steam Electric Survey required certain plants to collect and analyze samples of
landfill leachate and report the results of these analyses. EPA requested these plants to sample
any untreated landfill leachate collected from an on-site landfill containing combustion residuals.
EPA used all data as provided by the plants in the survey, except for the following:
• For values reported as less than the quantitation limit, EPA assumed the concentration
was equal to one-half the quantitation limit provided; and
• If the plant did not provide a quantitation limit, EPA assumed the concentration was
equal to the method detection limit.
EPA compiled all untreated landfill leachate sampling data reported in the Steam Electric
Survey from 26 landfills and split them into groups based on the landfill type (i.e., active or
inactive). The responses to the survey included data from 22 active combustion residual landfills
and four inactive combustion residual landfills. To determine the industry average concentrations
for a pollutant, EPA first averaged all concentration data provided for each individual landfill
providing sampling data to calculate a landfill-specific average concentration. EPA then
averaged the landfill-specific average concentrations at each plant based on the landfill type (i.e.,
active or inactive) to get a plant-level average pollutant leachate concentration for each landfill
type. EPA then used the average plant-level combustion residual landfill to calculate the average
concentrations across all plants. Table 6-10 presents the average concentration for leachate from
active and inactive landfills. EPA used these average concentrations to calculate baseline
loadings for all plants discharging combustion residual landfill leachate.
As explained in Section 7.4, based on a review of the Steam Electric Survey data
regarding the treatment of the combustion residual landfill leachate, EPA did not identify any
plants currently operating a chemical precipitation system to treat landfill leachate. Therefore,
EPA transferred the limitations and standards from the FGD chemical precipitation system,
Because EPA does not have analytical data that represent treated landfill leachate for the
technology options being considered, EPA also transferred the FGD chemical precipitation
effluent concentrations, identified in Section 10.2.1, to the landfill leachate for the purposes of
calculating post-compliance loadings. In cases where the average concentration of the untreated
active or inactive combustion residual landfill leachate is less than the FGD treated concentration
for the technology option, EPA assumed that the treated concentration was equal to the influent
(untreated leachate) average concentration. In this case, EPA did not calculate additional
removals of these particular pollutants by the wastewater treatment system.
Table 10-8. Average Pollutant Concentrations Untreated Landfill Leachate
Analyte
Unit
Untreated Active Landfill
Concentration
Untreated Inactive
Landfill Concentration
Classical*
Chloride
Sulfate
Total Dissolved Solids
Total Suspended Solids
ug/L
ug/L
ug/L
ug/L
542,000
1,910,000
3,860,000
41,400
11,100
1,070,000
1,670,000
4,210
Total Metals
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Section 10 - Pollutant Loadings and Removals
Table 10-8. Average Pollutant Concentrations Untreated Landfill Leachate
Analyte
Aluminum
Antimony
Arsenic
Barium
Beryllium
Boron
Cadmium
Calcium
Chromium
Cobalt
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Molybdenum
Nickel
Selenium
Silver
Sodium
Thallium
Tin
Titanium
Vanadium
Zinc
Unit
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
ug/L
Untreated Active Landfill
Concentration
5,030
4.6
46
57
1.9
20,500
2.7
481,000
4.9
84
10
59,000
1.4
115,000
4,360
1.4
1,880
69
74
0.68
327,000
1.3
11
17
3,240
154
Untreated Inactive
Landfill Concentration
100
4.9
10
50
0.47
3,640
1.9
386,000
1.6
3.8
1.7
95
0.47
33,700
355
0.01
995
43
84
0.42
16,700
0.96
13
15
6.2
58
Source: Steam Electric Survey [ERG, 2013].
Note: Concentrations are rounded to three significant figures.
10.3 WASTEWATER FLOW RATES FOR BASELINE AND POST-COMPLIANCE POLLUTANT
LOADINGS
As discussed earlier, EPA used plant-specific wastewater flow rates in the loadings
calculations. EPA used information from the Steam Electric Survey to determine which plants
discharge each specific wastestream of concern and the amount of wastewater each plant
reported discharging. This section provides more detail on EPA's methodology for calculating
the specific wastewater flow rates used in the loadings calculations.
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Section 10 - Pollutant Loadings and Removals
10.3.1 FGD Wastewater Flow Rates for Pollutant Loadings
As described in Section 9, EPA used plant-level FGD wastewater flow rates to calculate
compliance costs. EPA used the same FGD wastewater flow rates in both the FGD wastewater
technology cost modules and the FGD wastewater loadings to ensure consistency between the
two estimates.
10.3.2 Ash Transport Water Flow Rates for Pollutant Loadings
EPA used data from the Steam Electric Survey to identify those plants that discharge or
have the potential to discharge fly ash or bottom ash transport water. Based on the amount of ash
transport water discharged, EPA calculated ash impoundment discharge loadings for each of
these plants. EPA first identified all impoundments with ash transport water as an influent stream
and an effluent stream that discharges to a surface water or POTW.96 For each impoundment
included in its analysis, EPA identified the flow rate associated with the fly ash transport water,
bottom ash transport water, or combined ash transport water. EPA used the following hierarchy
to determine the ash transport water flow rates:97
• Influent flow rates to the impoundments reported in the pond/impoundment systems
section of the Steam Electric Survey;
• Ash transport water flow rates reported in the ash handling section of the survey; or
• Percent contributions of ash transport water to a plant outfall multiplied by the total
outfall flow rate reported in the general power plant operations section of the survey.
Because most generating units/ash handling systems do not operate 365 days per year,
EPA normalized the ash impoundment discharge flow rates. To do this, EPA calculated the
amount of ash transport water transferred to each ash impoundment per year by multiplying the
flow rate by the number of days the ash transport water is generated or transferred to the
impoundment, depending on which source is being used. EPA divided this yearly ash transport
water flow by 365 days per year to calculate a flow rate in gallons per day (gpd) for use in
loadings calculations. Using these normalized ash impoundment discharge flow rates, EPA
calculated plant-level ash impoundment discharge flow rates for each of the three possible types
(fly, bottom, and combined) of ash transport waters.
The ash transport water flow rates used for the loadings analysis is not the same data used
to estimate compliance costs for plants to eliminate fly ash or bottom ash transport water.
Compliance costs are based on the amount of fly ash or bottom ash generated by specific
generating units while baseline and post-compliance loadings are based on the flow rate of ash
transport water.
96 As defined in the Steam Electric Survey, impoundments refer to a system of one or more surface impoundments.
97 The Incremental Costs and Pollutant Removals for Proposed Effluent Limitation Guidelines and Standards for the
Steam Electric Generating Point Source Category Report provides more specific detail on the specifics of this
hierarchy and EPA's methodology for generating impoundment-specific ash impoundment discharge flow rates
[U.S. EPA, 2013].
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Section 10 - Pollutant Loadings and Removals
10.3.3 Combustion Residual Landfill Leachate Flow Rates for Pollutant Loadings
As described in Section 9, EPA used plant-level landfill leachate flow rates to calculate
compliance costs. EPA used the same landfill leachate flow rates in both the leachate technology
cost modules and the leachate loadings to ensure consistency between the two estimates.
10.4 BASELINE AND POST-COMPLIANCE POLLUTANT LOADINGS AND TWPE RESULTS
As discussed in Section 10.1, as applicable, EPA multiplied the average pollutant
concentrations for each wastestream presented in Section 10.2 with the plant-specific wastewater
flow rates presented in Section 10.3 to calculate the amount of pollutant discharged to surface
waters for each plant and wastestream. For those plants transferring the wastewater to a POTW,
EPA adjusted the loadings to account for additional removals that would take place at the
POTW. After calculating these loadings for each plant and wastestream, EPA then calculated the
TWPE associated with the pollutant discharges. These calculations were completed for the
baseline and post-compliance pollutant loadings for each plant associated with each technology
option. Using the plant-level loadings by wastestream, EPA was then able to calculate the
baseline and post-compliance loading at the industry level for each wastestream and regulatory
option. The following section discusses the specific loadings and TWPE calculations for each
wastestream, each of the technology options being considered, and each of the regulatory options
evaluated by EPA. The section also presents the industry-level loadings for each wastestream
and regulatory option.
10.4.1 FGD Wastewater Loadings and TWPE
EPA calculated plant-specific loadings for each of the technology options considered for
FGD wastewater. For baseline loadings, EPA multiplied the plant-specific FGD wastewater
discharge flow rate with the average pollutant concentrations that represent the current level of
treatment at the plant (i.e., surface impoundment, chemical precipitation, biological treatment, or
vapor-compression evaporation). EPA identified two plants transferring FGD wastewater to a
POTW. For these two plants, EPA adjusted the baseline loadings to account for pollutant
removals associated with POTW treatment.
For the post-compliance loadings associated with the one-stage chemical precipitation
technology option, EPA assumed the discharge loadings calculated for plants currently treating
their FGD wastewater with a one-stage chemical precipitation system, a biological treatment
system, or a vapor-compression evaporation system remain unchanged from baseline. EPA
assumed plants with a baseline surface impoundment would install a one-stage chemical
precipitation treatment system to meet the effluent requirements associated with this option. EPA
calculated post-compliance loadings for these plants using the average concentration data set
associated with one-stage chemical precipitation systems, presented in Table 10-4, and plant-
specific FGD wastewater flow rates. As described in Section 10.2.1.2, for each plant classified as
a baseline chemical precipitation system, EPA used the same chemical precipitation effluent
concentrations to calculate the baseline and post-compliance loadings, even if the system is not
equivalent to the technology basis. This underestimates the pollutant removals being achieved by
the treatment system because EPA calculates no removals for these plants, even though some of
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Section 10 - Pollutant Loadings and Removals
these plants are being assessed compliance costs to upgrade the system to operate similarly to the
technology basis.
For the post-compliance pollutant loadings associated with the one-stage chemical
precipitation treatment system followed by biological treatment technology option, EPA
assumed the post-compliance loadings calculated for plants currently treating their FGD
wastewater with a biological treatment system or a vapor-compression evaporation system
remain unchanged from baseline. EPA assumed plants with a surface impoundment would install
a one-stage chemical precipitation system with biological treatment and plants with a one-stage
chemical precipitation system (but no biological treatment for selenium removal) would install a
biological treatment system to meet the effluent requirements associated with this technology
option. EPA calculated the post-compliance loadings for these plants using the average
concentration data set associated with one-stage chemical precipitation systems followed by
biological treatment, presented in Table 10-5, and plant-specific FGD wastewater flow rates.
For the post-compliance pollutant loadings associated with the one-stage chemical
precipitation treatment system followed by vapor-compression evaporation option, EPA assumed
the post-compliance loadings calculated for plants currently treating their FGD wastewater with
this type of system remain unchanged from baseline. EPA assumed plants with any other current
treatment method (i.e., surface impoundment, chemical precipitation, or biological treatment)
would install a one-stage chemical precipitation treatment system with vapor-compression
evaporation to meet the effluent requirements associated with this technology option. EPA
calculated the post-compliance loadings for these plants using the average concentration data set
associated with one-stage chemical precipitation systems with vapor-compression evaporation,
presented in Table 10-6, and plant-specific FGD wastewater flow rates.
Table 10-9 presents the FGD wastewater loadings at an industry level for baseline and
each post-compliance technology basis. The loadings presented in Table 10-9 are based on the
oil-fired units and those units with a generating capacity of 50 MW or less not needing to install
the technology basis because they already meet the new BAT limitations (which are based on the
current BPT requirements for these units). The loadings also exclude the pollutant parameters
biochemical oxygen demand (BOD), chemical oxygen demand (COD), total dissolved solids
(TDS), and TSS to avoid double counting the loadings for other specific pollutants. The table
includes the number of plants identified as discharging FGD wastewater, the total industry
discharge flow rate associated with each technology option, and the total industry loading in
pounds per year and TWPE per year. Table 10-10 presents the pollutant removals, in both
pounds per year and TWPE per year, for the various technology options. EPA calculates the
pollutant removals by subtracting the post-compliance loadings from the baseline loadings. The
loadings for all units installing the technology basis, including the oil-fired units and small units
(i.e., 50 MW or less generating capacity), are presented in EPA''s Incremental Costs and
Pollutant Removals for Proposed Effluent Limitation Guidelines and Standards for the Steam
Electric Power Generating Point Source Category Report [U.S. EPA, 2013].
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Section 10 - Pollutant Loadings and Removals
Table 10-9. Industry-Level FGD Wastewater Loadings Excluding BOD, COD, TDS, and
TSS and Based on Oil-Fired Units and Units 50 MW or Less Not Installing Technology
Basis
Technology Option
Baseline
One-Stage Chemical Precipitation
One-Stage Chemical Precipitation
with Biological Treatment
One-Stage Chemical Precipitation
with Evaporation/Crystallization
Number of
Plants
117
117
117
117
Total Industry
Discharge Flow
(MGD)
65.4
56.8
56.8
56.8
Total Industry Loading
Pounds/Year
3,240,000,000
3,650,000,000
2,080,000,000
13,500,000
TWPE/Year
3,030,000
1,490,000
411,000
36,400
Note: Excludes loadings for BOD, COD, TSS and TDS.
Note: Loadings are rounded to three significant figures.
Table 10-10. FGD Wastewater Pollutant Removals Based on Oil-Fired Units and Units 50
MW or Less Not Installing Technology Basis
Technology Option
Reduction (Baseline -> One-Stage Chemical Precipitation)
Reduction (Baseline -> One-Stage Chemical Precipitation with
Biological Treatment)
Reduction (Baseline -> One-Stage Chemical Precipitation with
Evaporation/Crystallization)
Total Industry Pollutant Removals
Pounds/Year
-417,000,000a
1,160,000,000
3,220,000,000
TWPE/Year
1,530,000
2,620,000
2,990,000
Note: Excludes loadings for BOD, COD, TSS and TDS.
Note: Removals are rounded to three significant figures. The removals may not equal the subtraction of the
technology option from the baseline using the values in Table 10-9 due to rounding.
a - Characterization data used to estimate pollutant concentrations for baseline FGD surface impoundments does not
include concentration data for ammonia, hexavalent chromium, and TKN. These pollutants are included in the post-
compliance loadings and as a result appear to increase in concentration from baseline to technology option.
EPA also estimated the industry-level post-compliance loadings for the one-stage
chemical precipitation with biological treatment option for the scenario based on oil-fired units
and plants with a total plant-level wet scrubbed capacity of less than 2,000 MW not installing the
technology basis, which is associated with Regulatory Option 3b. Based on this scenario, there
are only 17 plants would be expected to install the technology basis; therefore, EPA calculated
the post-compliance loadings for each plant by applying the FGD biological treatment effluent
concentrations to those 17 plants and the FGD baseline concentrations to the remaining 100
plants. Table 10-11 presents the FGD wastewater loadings at an industry level for this post-
compliance scenario. The loadings presented in Table 10-11 exclude the pollutant parameters
BOD, COD, TDS, and TSS to avoid double counting the loadings for other specific pollutants.
The table includes the number of plants identified as discharging FGD wastewater, the total
industry discharge flow rate associated with the scenario, and the total industry loading in
pounds per year and TWPE per year. Table 10-12 presents the pollutant removals, in both
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Section 10 - Pollutant Loadings and Removals
pounds per year and TWPE per year, for the scenario. EPA calculates the pollutant removals by
subtracting the post-compliance loadings from the baseline loadings.
Table 10-11. Industry-Level FGD Wastewater Loadings Excluding BOD, COD, TDS, and
TSS and Based on Oil-Fired Units and Plants with a Total Wet Scrubbed Capacity of Less
Than 2,000 MW Not Installing Technology Basis
Technology Option
One-Stage Chemical Precipitation
with Biological Treatment
Number of
Plants
117
Total Industry
Discharge Flow
(MGD)
59.1
Total Industry Loading
Pounds/Year
2,790,000,000
TWPE/Year
2,120,000
Note: Excludes loadings for BOD, COD, TSS and TDS.
Note: Loadings are rounded to three significant figures.
Table 10-12. FGD Wastewater Pollutant Removals Based on Oil-Fired Units and Plants
with a Total Wet Scrubbed Capacity of Less Than 2,000 MW Not Installing Technology
Basis
Technology Option
Reduction (Baseline -> One-Stage Chemical Precipitation with
Biological Treatment)
Total Industry Pollutant Removals
Pounds/Year
446,000,000
TWPE/Year
908,000
Note: Excludes loadings for BOD, COD, TSS and TDS.
Note: Removals are rounded to three significant figures. The removals may not equal the subtraction of the
technology option from the baseline using the values in Table 10-9 and Table 10-11 due to rounding.
10.4.2 Ash Transport Water Loadings and TWPE
EPA calculated plant-specific loadings for the baseline discharges and technology option
considered for ash transport water. For baseline loadings, EPA multiplied the plant-specific ash
transport water discharge flow rate for each type of ash transport water (i.e., fly ash, bottom ash,
or combined ash transport water) by the appropriate average concentration data set for the type
of discharge. For example, for each fly ash impoundment, EPA multiplied the normalized
discharge flow rate described in Section 10.3.2 for the plant's fly ash impoundment by the
average concentration data set associated with fly ash impoundments presented in Section 10.2.2.
EPA identified two plants transferring bottom ash transport water to a POTW. For these two
plants, EPA adjusted the baseline loadings to account for pollutant removals associated with
POTW treatment, as described in Section 10.1.
As described in Section 10.2.2, EPA collected ash transport water characterization data
for fly ash impoundments, bottom ash impoundments, and combined ash impoundments. As
such, EPA calculated loadings for each of these different types of ponds at a plant-level. Because
EPA considered regulatory options that would establish different effluent requirements for fly
ash and bottom ash, EPA analyzed the pollutant loadings and removals for these two
wastestreams separately; therefore, EPA separated the loadings for combined ash impoundments
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Section 10 - Pollutant Loadings and Removals
into fly ash loadings and bottom ash loadings. To do this, EPA used data from the EPRI PISCES
reports to estimate the breakout of the loadings among fly ash and bottom ash contributions. The
PISCES reports include information from several plants operating impoundments receiving
either fly ash or bottom ash transport water. The reports include a table presenting loadings
associated with each stream entering the impoundment for several metal pollutants. EPA used
the fly ash and bottom ash loadings presented in the reports to calculate a site-specific percent
loading for fly ash and bottom ash for each pollutant. EPA then calculated an average percent
loading for fly ash and bottom ash using data from all available pollutants. EPA determined that,
on average, pollutant contributions from fly ash account for 86 percent of combined ash
loadings, with bottom ash contributing only 14 percent. Therefore, EPA assumed fly ash and
bottom ash account for 86 and 14 percent, respectively, of all combined ash loadings for those
pollutants for which a specific value could not be calculated using the EPRI data, EPA then used
these percentages to break out the combined ash loadings into associated fly ash and bottom ash
loadings. After separating the loadings into fly ash and bottom ash components, EPA calculated
total fly ash and bottom ash transport water baseline loadings for each plant.
For both fly ash and bottom ash transport water, EPA is considering only one technology
option: conversion to dry or closed-loop recycle ash handling. EPA assumes that all plants
currently discharging ash transport water will install dry handling systems for fly ash and will
operate wet-sluicing bottom ash handling systems as a closed loop system (i.e., zero discharge)
or will convert to dry bottom ash handling, resulting in post-compliance loadings of zero for fly
ash and bottom ash transport water pollutants for those plants subject to the proposed
requirements.
Table 10-13 presents the results of the baseline and post-compliance ash impoundment
loadings on an industry level. The table includes the number of impoundments discharging each
type of ash transport water, the total industry discharge flow rate, and the total industry loadings
in pounds per year and TWPE per year associated with each type of impoundment. The industry
loadings presented in Table 10-13 exclude the pollutant parameters BOD, COD, TDS, and TSS
to avoid double counting the loadings for other specific pollutants. Table 10-14 presents the
pollutant removals, in both pounds per year and TWPE per year, between the baseline and the
dry or closed-loop recycle handling technology option. The pollutant removals are based on the
oil-fired units and those units with a generating capacity of 50 MW or less not needing to install
the technology basis because they already meet the new BAT limitations (which are based on the
current BPT requirements for these units). EPA calculates the pollutant removals by subtracting
the post-compliance loadings from the baseline loadings. The pollutant removals for all units
installing the technology basis, including the oil-fired units and small units (i.e., 50 MW or less
generating capacity), are presented in EPA''s Incremental Costs and Pollutant Removals for
Proposed Effluent Limitation Guidelines and Standards for the Steam Electric Power Generating
Point Source Category Report [U.S. EPA, 2013].
10-27
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Section 10 - Pollutant Loadings and Removals
Table 10-13. Industry-Level Ash Impoundment Loadings by Type of Impoundment
Excluding BOD, COD, TDS, and TSS
Type of Ash
Impoundment
Number of
Impoundments
Total Baseline
Industry
Discharge Flow
(MGD)
Total Industry Baseline
Loading
Pounds/Year
TWPE/Year
Total Industry Post-
Compliance Loading
Pounds/Year
TWPE/Year
Fly Ash
Fly Ash Pond
Combined Ash
Pondb
16
80
61.7
262a
237,000,000
241,000,000
688,000
1,830,000
3,800,000
2,950,000
11,000
22,500
Bottom Ash
Bottom Ash
Pond
Combined Ash
Pondb
TOTAL
174
80
272
327
262a
651
1,660,000,000
44,900,000
2,180,000,000
2,420,000
295,000
5,240,000
5,100,000
550,000
12,400,000
7,290
3,610
44,400
Note: Excludes loadings for BOD, COD, TSS, and TDS.
Note: Loadings are rounded to three significant figures.
a - The total discharge flow from all combined impoundments is 262 MGD. The fly ash contribution and bottom ash
contribution cannot be determined with the data provided in the Steam Electric Survey.
b - The combined ash pond loadings were calculated based on the data used in the loadings calculation, but then the
total combined ash pond loadings were split between fly ash and bottom ash based the EPRI data, described in this
section.
Table 10-14. Fly Ash and Bottom Ash Pollutant Removals Based on Oil-Fired Units and
Units 50 MW or Less Not Installing Technology Basis
Type of Ash
Impoundment
Fly Ash
Bottom Ash
Technology Option
Reduction (Baseline -> Technology Option)
Reduction (Baseline -> Technology Option)
Total Industry Pollutant Removals
Pounds/Year
471,000,000
1,700,000,000
TWPE/Year
2,490,000
2,710,000
Note: Excludes loadings for BOD, COD, TSS, and TDS.
Note: Removals are rounded to three significant figures. The removals may not equal the subtraction of the
technology option from the baseline using the values in Table 10-13 due to rounding.
EPA also estimated the industry-level pollutant loadings for plants to convert only the
generating units that are greater than 400 MW to dry or closed-loop recycle bottom ash handling
systems. However, EPA used a different approach to estimate the plant-level loadings for this
analysis. For those plants with all generating units with a nameplate capacity of 400 MW or less,
EPA assumed that the post-compliance loadings would be equal to the baseline loadings and for
those plants with all generating units with a nameplate capacity greater than 400 MW, EPA
assumed that the post-compliance loadings would be zero (as was done for Options 4 and 5). For
those plants that have at least one generating unit with a nameplate capacity of 400 MW or less
and at least one other generating unit with a nameplate capacity of greater than 400 MW, EPA
approximated the plant-level bottom ash pollutant removals. To perform this approximation,
10-28
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Section 10 - Pollutant Loadings and Removals
EPA calculated a plant-level bottom ash adjustment factor based on the amount of bottom ash
generated by the generating units expected to incur compliance costs with a nameplate capacity
greater than 400 MW compared to the total amount of bottom ash generated at the plant for those
generating units expected to incur compliance costs (excluding the generating units with a
nameplate capacity of 50 MW or less). This is the same adjustment factor that was calculated for
the bottom ash compliance costs for Option 4a, described in Section 9.7.3. EPA then multiplied
the bottom ash adjustment factors by the plant-level bottom ash pollutant removals calculated
based on all generating units (other than oil-fired units) with a nameplate capacity greater than
50 MW to estimate the bottom ash pollutant removals for this analysis. For more details on how
EPA estimated these plant-level bottom ash pollutant removals, see the memorandum entitled
"Memorandum to the Rulemaking Record: Methodologies for Estimating Costs and Pollutant
Removals for Steam Electric ELG Regulatory Option 4a" (DCN SE03834).
Table 10-15 presents the pollutant removals, in both pounds per year and TWPE per year,
between the baseline and the dry or closed-loop recycle handling technology option associated
with Regulatory Option 4a. The pollutant removals are based on the oil-fired units and those
units with a generating capacity of 400 MW or less not needing to install the technology basis
because they already meet the new BAT limitations (which are based on the current BPT
requirements for these units). EPA calculates the pollutant removals by subtracting the post-
compliance loadings from the baseline loadings.
Table 10-15. Bottom Ash Pollutant Removals Based on Oil-Fired Units and Units 400
MW or Less Not Installing Technology Basis
Type of Ash
Impoundment
Bottom Ash
Technology Option
Reduction (Baseline -> Technology Option)
Total Industry Pollutant Removals
Pounds/Year
991,000,000
TWPE/Year
1,570,000
Note: Excludes loadings for BOD, COD, TSS, and TDS.
Note: Removals are rounded to three significant figures.
10.4.3 Combustion Residual Landfill Leachate Loadings and TWPE
EPA calculated plant-specific loadings for each of the technology options considered for
combustion residual landfill leachate. For baseline loadings, EPA multiplied the plant-specific
leachate discharge flow rate with the average pollutant concentrations that represent untreated
combustion residual landfill leachate. EPA identified seven plants transferring landfill leachate to
a POTW. For these seven plants, EPA adjusted the baseline loadings to account for pollutant
removals associated with POTW treatment.
For the one-stage chemical precipitation technology option, EPA assumed that all plants
would install that type of treatment system. No plants currently treat leachate with a one-stage
chemical precipitation system so all plants would need to install treatment to meet the effluent
requirements associated with this option. EPA calculated discharge loadings for these plants
using the average concentration data set associated with one-stage chemical precipitation
systems, presented in Section 10.2.3, and plant-specific leachate flow rates.
10-29
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Section 10 - Pollutant Loadings and Removals
For the one-stage chemical precipitation treatment system with biological treatment
technology option, EPA assumed that all plants would install that type of treatment to meet the
effluent requirements associated with this technology option. EPA calculated the discharge
loadings for these plants using the average concentration data set associated with one-stage
chemical precipitation systems followed by biological treatment, presented in Section 10.2.3, and
plant-specific leachate flow rates.
Table 10-16 presents the combustion residual landfill leachate loadings at an industry
level for baseline and each post-compliance technology basis. The loadings presented in Table
10-16 are based on the oil-fired units and those units with a generating capacity of 50 MW or
less not needing to install the technology basis because they already meet the new BAT
limitations (which are based on the current BPT requirements for these units). The loadings also
exclude the pollutant parameters BOD, COD, TDS, and TSS to avoid double counting the
loadings for other specific pollutants. Included in the table is the number of plants discharging
combustion residual landfill leachate, the total industry flow rate associated with each
technology option, and the total industry loading in pounds per year and TWPE per year. Table
10-17 presents the pollutant removals, in both pounds per year and TWPE per year, for the
various technology options. EPA calculated the pollutant removals by subtracting the post-
compliance loadings from the baseline loadings. The loadings for all units installing the
technology basis, including the oil-fired units and small units (i.e., 50 MW or less generating
capacity), are presented in EPA's Incremental Costs and Pollutant Removals for Proposed
Effluent Limitation Guidelines and Standards for the Steam Electric Power Generating Point
Source Category Report [U.S. EPA, 2013].
Table 10-16. Industry-Level Combustion Residual Landfill Leachate Loadings Excluding
BOD, COD, TDS, and TSS and Based on Oil-Fired Units and Units 50 MW or Less Not
Installing Technology Basis
Technology Option
Baseline
One-Stage Chemical Precipitation
One-Stage Chemical Precipitation with
biological treatment
Number of
Plants
102
102
102
Total Industry
Discharge Flow
(MGD)
7.90
7.90
7.90
Total Industry Loading
Pounds/Year
89,800,000
80,900,000
61,800,000
TWPE/Year
56,500
20,900
13,600
Note: Excludes loadings for BOD, COD, TSS and TDS.
Note: Loadings are rounded to three significant figures.
10-30
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Section 10 - Pollutant Loadings and Removals
Table 10-17. Combustion Residual Landfill Leachate Pollutant Removals Based on
Oil-Fired Units and Units 50 MW or Less Not Installing Technology Basis
Technology Option
Reduction (Baseline -> One-Stage Chemical Precipitation)
Reduction (Baseline -> One-Stage Chemical Precipitation with
Biological Treatment)
Total Industry Pollutant Removals
Pounds/Year
8,900,000
28,000,000
TWPE/Year
35,600
42,900
Note: Excludes loadings for BOD, COD, TSS and TDS.
Note: Removals are rounded to three significant figures. The removals may not equal the subtraction of the
technology option from the baseline using the values in Table 10-16 due to rounding.
10.4.4 Pollutant Loadings and Removals for Regulatory Options
As described in Section 8, EPA evaluated eight regulatory options comprised of various
combinations of the technology options considered for each wastestream. EPA estimated the
pollutant removals associated with steam electric power plants to achieve compliance for each
regulatory option under consideration. Table 10-18 presents the total industry loadings and
pollutant removals at baseline and for each of the eight regulatory options. The loadings and
TWPE values presented in these tables exclude pollutant parameters BOD, COD, TDS, and TSS.
The table presents the estimated loadings and pollutant removals based on the oil-fired units and
units with a capacity of 50 MW or less not needing to install the appropriate technology bases.98
The loadings and pollutant removals for all units installing the technology basis, including the
oil-fired units and small units (i.e., 50 MW or less generating capacity), are presented in EPA's
Incremental Costs and Pollutant Removals for Proposed Effluent Limitation Guidelines and
Standards for the Steam Electric Power Generating Point Source Category Report [U.S. EPA,
2013]. The pollutant-level baseline loadings and pollutant-level removals for each regulatory
option by wastestream are presented in the memorandum entitled, "Steam Electric Pollutant-
Level Loadings and Removals for Each Wastestream and Regulatory Option" (DCN SE03970).
Table 10-18. Estimated Pollutant Removals by Regulatory Option Based on Oil-Fired Units
and Units 50 MW or Less Not Installing Technology Basis
Regulatory
Option
Baseline
1
3a
2
3b
Total Industry Loading
Pounds/Year
5,500,000,000
5,920,000,000
5,030,000,000
4,350,000,000
4,590,000,000
TWPE/Year
8,320,000
6,790,000
5,830,000
5,710,000
4,920,000
Total Industry Pollutant Removals a
Pounds/Year
0
-417,000,000b
471,000,000
1,160,000,000
916,000,000
TWPE/Year
0
1,530,000
2,490,000
2,620,000
3,400,000
98 Except for Regulatory Options 4a and 3b. For Regulatory Option 4a, the bottom ash estimated loadings and
pollutant removals are based on the oil-fired units and units with a capacity of 400 MW or less not needing to install
the appropriate technology bases. For Regulatory Option 3b, the FGD wastewater estimated loadings and pollutant
removals are based on the oil-fired units and plants with a total wet scrubbed capacity of less than 2,000 MW not
needing to install the appropriate technology bases.
10-31
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Section 10 - Pollutant Loadings and Removals
Table 10-18. Estimated Pollutant Removals by Regulatory Option Based on Oil-Fired Units
and Units 50 MW or Less Not Installing Technology Basis
Regulatory
Option
o
6
4a
4
5
Total Industry Loading
Pounds/Year
3,880,000,000
2,870,000,000
2,160,000,000
107,000,000
TWPE/Year
3,220,000
1,640,000
474,000
102,000
Total Industry Pollutant Removals a
Pounds/Year
1,630,000,000
2,620,000,000
3,340,000,000
5,400,000,000
TWPE/Year
5,100,000
6,680,000
7,850,000
8,220,000
Note: Excludes loadings for BOD, COD, TDS, and TSS.
Note: Removals are rounded to three significant figures. The removals may not equal the sum of the removals
presented in the tables in this section from the various wastestreams due to rounding.
a - Compared to baseline.
b - Characterization data used to estimate pollutant concentrations for baseline FGD surface impoundments does not
include concentration data for ammonia, hexavalent chromium, and TKN. These pollutants are included in the post-
compliance loadings and as a result appear to increase in concentration from baseline to technology option.
10.5 REFERENCES
1. Duke Energy. 201 la. Industry Provided Sampling Data from Duke Energy's Belews
Creek Steam Station. (17 August). DCN SE01808.
2. Duke Energy. 201 Ib. Industry Provided Sampling Data from Duke Energy's Allen Steam
Station. (17 August). DCN SE01809.
3. Eastern Research Group (ERG). 2005. Memorandum to 2006 Effluent Guidelines
Program Plan Docket, From Ellie Codding and Deb Bartram, ERG, re: Publicly Owned
Treatment Works (POTW) Percent Removals Used for the TRI Releases2002 Database.
(12 August). DCN SE02932.
4. Eastern Research Group (ERG). 2006. Toxic Weighting Factor Development in Support
of CWA 304(m) Planning Process. (June). DCN SE02931.
5. Eastern Research Group, Inc. (ERG). 2008. Final Sampling Episode Report, Buckeye
Power Company's Cardinal Power Plant. (26 August). DCN SE02107.
6. Eastern Research Group (ERG). 2012a. Final Sampling Episode Report, Duke Energy
Carolinas' Belews Creek Steam Station. (13 March). DCN SE01305.
7. Eastern Research Group (ERG). 2012b. Final Sampling Episode Report, We Energies'
Pleasant Prairie Power Plant. (13 March). DCN SE01306.
8. Eastern Research Group (ERG). 2012c. Final Sampling Episode Report, Duke Energy
Miami Fort Station. (13 March). DCN SE01304.
9. Eastern Research Group (ERG). 2012d. Final Sampling Episode Report, Duke Energy
Carolinas' Allen Steam Station. (13 March). DCN SE01307.
10. Eastern Research Group (ERG). 2012e. Final Sampling Episode Report, Mirant Mid-
Atlantic, LLC's Dickerson Generating Station. (13 March). DCN SE01308.
10-32
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Section 10 - Pollutant Loadings and Removals
11. Eastern Research Group (ERG). 2012f. Final Sampling Episode Report, Allegheny
Energy's Hatfield's Ferry Power Station. (13 March). DCN SE01310.
12. Eastern Research Group (ERG). 2012g. Final Sampling Episode Report, RRI Energy's
Keystone Generating Station. (13 March). DCN SE01309.
13. Eastern Research Group (ERG). 2012h. Final Sampling Episode Report and Site Visit
Notes, Enel's Federico II Power Plant (Brindisi). (8 August). DCN SE02013.
14. Eastern Research Group (ERG). 2012L Final Power Plant Monitoring Data Collected
Under Clean Water Act Section 308 Authority ("CWA 308 Monitoring Data"). (30 May).
DCN SE01326.
15. Eastern Research Group (ERG). 2013. Steam Electric Technical Questionnaire Database
("Steam Electric Survey"). (19 April). DCN SE01958.
16. Electric Power Research Institute (EPRI). 1997 - 2001. PISCES Water Characterization
Field Study, Sites A-G Palo Alto, CA. DCN SE01818 through SE01823.
17. NCDENR. 2011. North Carolina Department of Environment and Natural Resources
(NCDENR). State Provided Sampling Data from North Carolina's Progress Energy
Roxboro Plant. (26 June). DCN SE01812.
18. Utility Water Act Group (UWAG). 2008. Form 2C Effluent Guidelines Database. (30
June). DCNs SE02918 and SE02918A1.
19. U.S. EPA. 1982. Development Document for Effluent Limitations Guidelines and
Standards and Pretreatment Standards for the Steam Electric Point Source Category.
EPA-440-1-82-029. Washington, DC. (November). DCN SE02933.
20. U.S. EPA. 2013. Incremental Costs and Pollutant Removals for Proposed Effluent
Limitation Guidelines and Standards for the Steam Electric Power Generating Point
Source Category Report. (19 April). DCN SE01957.
10-33
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Section 11 - Pollutants Selected for Regulation
SECTION 11
POLLUTANTS SELECTED FOR REGULATION
This section describes the selection of regulated pollutants for each wastestream for
which EPA evaluated new or revised discharge requirements in the Steam Electric ELGs.
Regulated pollutants are pollutants for which EPA proposes to establish numerical effluent
limitations and standards. This section describes the methodology and rationale EPA used to
select the subset of regulated pollutant parameters from the list of pollutants of concern (POC)
for each wastestream.
11.1 SELECTION OF REGULATED POLLUTANT FOR DIRECT DISCHARGERS
The list of POCs for each wastestream represents those pollutants that are present at
treatable concentrations in a significant percentage of untreated wastewater samples from that
wastestream; the selection of POCs for each wastestream is presented in Section 6.7 of this
document. Effluent monitoring for all POCs is not necessary to ensure that steam electric
wastewater pollution is adequately controlled because many of the pollutants originate from
similar sources, have similar treatabilities, are removed by similar mechanisms, and are treated to
similar concentrations. Therefore, it may be sufficient to monitor for one pollutant as a surrogate
or indicator of several others.
From the POC list for each wastestream, EPA selected a subset of pollutants for
establishing numerical effluent limitations. EPA considered the following factors in selecting
regulated pollutants from the list of POCs for each subcategory:
• The pollutant was detected in the untreated wastewater at the BAT plant(s) at
treatable levels in a significant number of samples. This was the same methodology
used to identify the POCs, as described in Section 6.7.
• The pollutant is not used as a treatment chemical in the treatment technology that
serves as a basis for the proposed regulatory option. EPA excluded pollutants that
may serve as treatment system additives: aluminum, calcium, iron, sodium, and
phosphorus. EPA eliminated these pollutants because regulating these pollutants
could interfere with efforts to optimize treatment system operation.
• The pollutant is effectively treated by the treatment technology that serves as the
basis for the proposed regulatory option. EPA excluded pollutants for which the
treatment technology was ineffective (i.e., pollutant concentrations remained
approximately unchanged or increased across the treatment system).
• The pollutant is not adequately controlled through the regulation of another pollutant.
• The following subsections describe EPA's pollutant selection analysis for each
wastestream.
11.1.1 FGD Wastewater
EPA proposes establishing BAT and NSPS limitations and standards for FGD wastewater
for four pollutants: arsenic, mercury, nitrate/nitrite, and selenium. These limitations and
11-1
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Section 11 - Pollutants Selected for Regulation
standards are based on a one-stage chemical precipitation system followed by anoxic/anaerobic
biological treatment, as described in Section 13.8. The regulated pollutant selection criteria
matrix for the 35 POCs considered for regulation for FGD wastewater is illustrated in Table
11-1. The following discussion explains the rationale used to select which of the 35 POCs to
regulate at BAT/NSPS for the preferred options.
• Conventional Pollutants: EPA identified oil and grease (O&G) and total suspended
solids (TSS) as POCs. TSS and O&G are adequately controlled by existing BPT
limitations.
• Treatment Chemicals: EPA identified and eliminated five POCs that are also used as
treatment chemicals: aluminum, calcium, iron, sodium, and phosphorus.
• Pollutants Not Effectively Treated by the Proposed BAT/NSPS Technology: EPA
eliminated eight pollutants, ammonia, boron, chloride, COD, cyanide, sulfate, TDS,
and TKN, because the technology option associated with the preferred options is not
designed to achieve consistent effluent concentrations of these pollutants.
• Pollutants Directly Regulated or Controlled by Regulation of Other Pollutants: The
remaining pollutants are metals and nitrate/nitrite. As described in Section 7,
chemical precipitation systems use chemicals to alter the physical state of dissolved
and suspended solids to help settle and remove solids from the wastewater. The
metals present in the wastewater form insoluble hydroxides and/or sulfide complexes.
The solubilities of these complexes vary by pH, therefore, specific pHs can be
targeted to remove specific metals. But in this process, most metals are precipitated to
at least some degree, thereby resulting in the removal of a wide range of metals.
EPA's design basis for the BAT system uses both hydroxide and sulfide precipitation,
as well as iron coprecipitation. EPA selected arsenic and mercury as regulated
pollutants and as indicators of effective removals of many other metal pollutants of
concern present in FGD wastewater, such as cadmium and chromium. While most
metals can be removed to low levels using chemical precipitation alone, selenium
requires additional treatment to achieve consistent removals. Therefore, EPA also
selected selenium and nitrate/nitrite for regulation.
11-2
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Section 11 - Pollutants Selected for Regulation
Table 11-1. Pollutants Considered for Regulation for Direct Dischargers (BAT/NSPS): FGD Wastewater
Pollutant Group
Conventional
Priority Pollutants
Nonconventional
Pollutant of Concern
Oil and Grease
Total Suspended Solids
Antimony
Arsenic
Beryllium
Cadmium
Chromium
Copper
Cyanide
Lead
Mercury
Nickel
Selenium
Thallium
Zinc
Aluminum
Ammonia
Barium
Boron
Calcium
Chemical Oxygen Demand
Chloride
Cobalt
Iron
Magnesium
Treatment Chemical
v'
v'
•/
Not Effectively Treated by
the Proposed BAT/NSPS
Technology
v'
v'
v'
v'
s
Directly Regulated or
Controlled by Regulation of
Another Parameter
•/
•/
•/
•/
•/
•/
•/
•/
^
S
s
s
s
s
s
•/
•/
-------
Section 11 - Pollutants Selected for Regulation
Table 11-1. Pollutants Considered for Regulation for Direct Dischargers (BAT/NSPS): FGD Wastewater
Pollutant Group
Nonconventional
Pollutant of Concern
Manganese
Molybdenum
Nitrate/Nitrite
Nitrogen, Kjeldahl
Phosphorus
Sodium
Sulfate
Titanium
Total Dissolved Solids
Vanadium
Treatment Chemical
•/
•/
Not Effectively Treated by
the Proposed BAT/NSPS
Technology
^
^
v'
Directly Regulated or
Controlled by Regulation of
Another Parameter
•/
•/
•/
•/
v'
-------
Section 11 - Pollutants Selected for Regulation
11.1.2 Fly Ash Transport Water
EPA proposes establishing BAT limitations requiring no discharge of wastewater
pollutants from fly ash transport water for each of the preferred regulatory options (i.e., Option
3a, 3b, 3, and 4a). Additionally, the same standard was already set for NSPS as part of the 1982
revisions to the ELGs. Therefore, the Agency did not apply its pollutant selection methodology
to this wastestream. All pollutants of concern would be regulated and removed by the preferred
options.
11.1.3 Bottom Ash Transport Water
EPA proposes establishing BAT limitations equal to the current BPT limitations for
bottom ash transport water under Regulatory Options 3a, 3b, and 3. Under Regulatory Option 4a,
EPA proposes establishing BAT limitations requiring no discharge of wastewater pollutants from
bottom ash transport water for generating units with a nameplate capacity greater than 400 MW,
while EPA is proposing to establish BAT limitations equal to the current BPT limitations for
bottom ash transport water for all generating units with a nameplate capacity of 400 MW or less.
EPA also proposes establishing NSPS standards requiring no discharge of wastewater pollutants
from bottom ash transport water. Therefore, because either all pollutants are regulated
(Regulatory Option 4a for generating units with a nameplate capacity of greater than 400 MW)
or the pollutants selected are the same as those regulated under BPT (Regulatory Options 3a, 3b,
3, and 4a for generating units with a nameplate capacity of 400 MW or less), the Agency did not
apply its pollutant selection methodology to this wastestream.
11.1.4 Combustion Residual Leachate
EPA proposes establishing BAT limitations for combustion residual leachate equal to the
current BPT limitations for low volume waste sources under a preferred regulatory options. EPA
is proposing to establish NSPS limitations for arsenic and mercury. These NSPS limitations are
based on a one-stage chemical precipitation system. The regulated pollutant selection criteria
matrix for the 16 POCs considered for regulation for combustion residual leachate is illustrated
in Table 11-2. The following discussion explains the rationale used to select which of the 16
POCs to regulate at NSPS (based on Regulatory Option 4)."
• Conventional Pollutants: EPA identified O&G and TSS as POCs. TSS and O&G are
adequately controlled by existing BPT limitations.
• Treatment Chemicals: EPA identified and eliminated four POCs that are also used as
treatment chemicals: aluminum, calcium, iron, and sodium.
• Pollutants Not Effectively Treated by the Proposed NSPS Technology: EPA
eliminated five pollutants, boron, chloride, selenium, sulfate, and total dissolved
solids, because the technology option associated with Regulatory Option 4 is not
designed to achieve consistent effluent concentrations of these pollutants.
• Pollutants Directly Regulated or Controlled by Regulation of Other Pollutants: The
remaining pollutants of concern are all metals. As explained above for FGD
99 These are also the 16 POCs that would be considered for regulation under BAT Options 4 and 5.
11-5
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Section 11 - Pollutants Selected for Regulation
wastewater, chemical precipitation is effective at removing metals present in
wastewater, especially when both hydroxide and sulfide precipitation mechanisms are
employed, which is part of the basis for the technology option. EPA selected arsenic
and mercury as regulated pollutants and as indicators of effective removals of many
other metal pollutants of concern present in combustion residual leachate, such as
magnesium and manganese.
11.1.5 Gasification Wastewater
For gasification wastewater, EPA is proposing to establish BAT and NSPS limitations
and standards for four pollutants: arsenic, mercury, selenium, and TDS. These limitations and
standards are based on a vapor-compression evaporation system for direct dischargers. The
regulated pollutant selection criteria matrix for the 20 POCs considered for regulation for
gasification wastewater is illustrated in Table 11-3. The following discussion explains the
rationale used to select which of the 20 POCs to regulate at BAT/NSPS.
• Conventional Pollutants: EPA identified BOD5 as a POC. BOD is not subject to BAT
limitations.
• Pollutants Not Effectively Treated by the Proposed BAT/NSPS Technology: EPA
eliminated five pollutants, ammonia, COD, cyanide, nitrate/nitrite, and TKN, because
the technology option associated with the preferred options is not designed to achieve
consistent effluent concentrations of these pollutants.
• Pollutants Directly Regulated or Controlled by Regulation of Other Pollutants: The
remaining pollutants are metals and salt ions (i.e., chloride and sulfate). As described
in Section 7, the vapor-compression evaporation system uses steam to evaporate the
water from the wastewater, producing a distillate stream and a solid residual
byproduct (i.e., crystallized salts). The removal of metals from this system will
depend on the volatility of the metals because the more volatile the metal, the greater
amount that will be carried over into the distillate stream. Therefore, EPA selected
three metals, arsenic, mercury, and selenium to represent different volatilities of
metals and act as indicator pollutants for other metals. EPA also selected TDS for
regulation as an indicator of pollutants (e.g., sodium, chloride) present in the
wastewater.
11.1.6 Flue Gas Mercury Control Wastewater
EPA proposes establishing BAT limitations requiring no discharge of wastewater
pollutants from FGMC wastewater. EPA also proposes establishing NSPS standards requiring no
discharge of wastewater pollutants from FGMC wastewater for NSPS. Therefore, the Agency did
not apply its pollutant selection methodology to this wastestream. All pollutants of concern
would be regulated and removed by the preferred options.
11.1.7 Nonchemical Metal Cleaning Wastes
EPA proposes establishing BAT limitations for nonchemical metal cleaning wastes for
two pollutants, copper and iron. EPA is also proposing to establish NSPS limitations for
nonchemical metal cleaning wastes for TSS, O&G, copper, and iron. These limitations and
11-6
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Section 11 - Pollutants Selected for Regulation
standards are based on the current BPT limitations for metal cleaning wastes. Because the
limitations and standards are based on the existing BPT limitations, the pollutants for regulation
are already identified, and therefore, EPA did not apply its pollutant selection methodology to
this wastestream.
11-7
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Section 11 - Pollutants Selected for Regulation
Table 11-2. Pollutants Considered for Regulation for Direct Dischargers (BAT/NSPS): Combustion Residual Leachate
Pollutant Group
Conventional Pollutants
Priority Pollutants
Nonconventional Pollutants
Pollutant of Concern
Oil and Grease
Total Suspended Solids
Arsenic
Mercury
Selenium
Aluminum
Boron
Calcium
Chloride
Iron
Magnesium
Manganese
Molybdenum
Sodium
Sulfate
Total Dissolved Solids
Treatment Chemical
^
^
v'
v'
Not Effectively Treated by
the Proposed BAT/NSPS
Technology
•/
•/
v'
v'
S
Directly Regulated or
Controlled by Regulation of
Another Parameter
v'
S
S
S
s
s
s
oo
-------
Section 11 - Pollutants Selected for Regulation
Table 11-3. Pollutants Considered for Regulation for Direct Dischargers (BAT/NSPS): Gasification Wastewater
Pollutant Group
Priority Pollutants
Conventional Pollutants
Nonconventional Pollutants
Pollutant of Concern
Antimony
Arsenic
Cyanide
Mercury
Nickel
Selenium
Thallium
Biochemical Oxygen Demand
Aluminum
Ammonia
Boron
Chemical Oxygen Demand
Chloride
Iron
Manganese
Nitrate/Nitrite
Nitrogen, Kjeldahl
Sodium
Sulfate
Total Dissolved Solids
Treatment Chemical
Not Effectively Treated
by the Proposed
BAT/NSPS Technology
v'
v'
^
v'
v'
Directly Regulated or
Controlled by Regulation
of Another Parameter
•/
v'
v'
•/
•/
•/
v'
s
v'
•/
•/
^
s
•/
•/
-------
Section 11 - Pollutants Selected for Regulation
11.2 REGULATED POLLUTANT SELECTION METHODOLOGY FOR INDIRECT DISCHARGERS
Unlike direct dischargers whose wastewater will receive no further treatment once it
leaves the plant, indirect dischargers send their wastewater to publicly-owned treatment works
(POTWs) for further treatment. However, POTWs typically install secondary biological
treatment systems that are designed to control conventional pollutants (i.e., BOD, TSS, oil &
grease (O&G), pH, and fecal coliform), the principal parameters in domestic sewage. Except for
nutrient control for nitrogen compounds and phosphorus, POTWs usually do not install advanced
or tertiary treatment technology to control priority and nonconventional pollutants, although
secondary biological treatment systems may achieve significant removals for some priority
pollutants. Instead, the Clean Water Act envisions that implementation of pretreatment programs
and industrial compliance with categorical pretreatment standards will adequately control toxic
and nonconventional pollutants in municipal effluents.
Section 307(b) and (c) of the CWA requires EPA to promulgate pretreatment standards
for pollutants that are not susceptible to treatment by POTWs or which would interfere with the
operation of POTWs. EPA looks at a number of factors in selecting the technology basis for
pretreatment standards for existing and new sources. These factors are generally the same as
those considered in establishing BAT and NSPS, respectively. However, unlike direct
dischargers whose wastewater will receive no further treatment once it leaves the plant, indirect
dischargers send their wastewater to POTWs for further treatment. As such, EPA must also
determine that a pollutant is not susceptible to treatment at a POTW or would interfere with
POTW operations.
Therefore, for indirect dischargers, before establishing PSES/PSNS for a pollutant, EPA
examines whether the pollutant "passes through" a POTW to waters of the U.S. or interferes with
the POTW operation or sludge disposal practices. In determining whether a pollutant would pass
though POTWs for PSES/PSNS, EPA generally compares the percentage of a pollutant removed
by well-operated POTWs performing secondary treatment to the percentage removed by
BAT/NSPS treatment systems. A pollutant is determined to pass through POTWs when the
median percentage removed nationwide by well-operated POTWs is less than the median
percentage removed by direct dischargers complying with BAT/NSPS effluent limitations and
standards. Pretreatment standards are established for those pollutants regulated under BAT/NSPS
that pass through POTWs to waters of the U.S. or interfere with POTW operations or sludge
disposal practices. This approach to the definition of pass-through satisfies two competing
objectives set by Congress: (1) that standards for indirect dischargers be equivalent to standards
for direct dischargers, and (2) that the treatment capability and performance of POTWs be
recognized and taken into account in regulating the discharge of pollutants from indirect
dischargers.
The POTW pass-through analysis was performed for pollutants selected for regulation for
direct dischargers for each wastestream of concern. Those pollutants that EPA determines pass
through POTWs are the pollutants EPA proposes to regulate. The following pollutants were not
analyzed for pass through even if selected for regulation under BAT/NSPS: biochemical oxygen
demand (BODs), TSS, and O&G. POTWs are designed to treat these pollutants; therefore, they
were not considered to pass through.
11-10
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Section 11 - Pollutants Selected for Regulation
For the proposed Steam Electric ELGs, EPA is setting limitations for the following
wastestreams:
• FGD wastewater;
• Fly ash transport water;
• Bottom ash transport water;
• Combustion residual leachate;
• Gasification wastewater;
• Flue gas mercury control wastewater; and
• Nonchemical metal cleaning wastes.
EPA conducted the pass-through analysis for all regulated pollutants for FGD
wastewater, combustion residual leachate, and gasification wastewater. EPA did not conduct its
traditional POTW pass-through analysis for fly ash transport water, bottom ash transport water,
and flue gas mercury control wastewater because limitations for these wastestreams for direct
dischargers consist of no discharge of process wastewater pollutants to waters of the U.S.100
Because the BAT/NSPS technology options for fly ash transport water, bottom ash transport
water, and flue gas mercury control wastewater achieve 100 percent removal of all pollutants,
which is greater than the percent removals by POTWs, EPA determined the pollutants would
pass through the POTW for these wastestreams.
During the 1976 development of pretreatment standards for chemical metal cleaning
wastes, EPA selected pollutants for regulation based on two criteria:
• The pollutant has the potential to harm the POTW (e.g., impair the activity of the
biological treatment system); or
• The pollutant has the potential to harm the receiving water (i.e., if the pollutant is not
removed or is removed inadequately by the POTW).
Using these criteria, the Agency determined it was appropriate to establish pretreatment
standards for the discharge of copper in chemical metal cleaning wastes. EPA believes that, as is
the case for copper in chemical metal cleaning wastes, the copper present in nonchemical metal
cleaning wastes would pass through the POTW.
The following subsections present the POTW pass-through analysis:
• Methodology for determining BAT percent removals;
• Methodology for determining POTW percent removals; and
• Results of the POTW pass-through analysis.
100 To ensure standards for indirect dischargers be equivalent to limitations for direct dischargers, EPA similarly
designates standards for these wastestreams as zero discharge.
11-11
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Section 11 - Pollutants Selected for Regulation
11.2.1 Methodology for Determining BAT Percent Removals
EPA calculated percent removals for each selected technology option using the data used
to determine the long-term averages (LTAs) and limitations/standards for the selected BAT or
NSPS technology option. Therefore, the data used to calculate the treatment option percent
removals was subjected to the same date editing criteria as the data used to establish the
limitations/standards. See Section 13.
1. For each pollutant and each model plant for which EPA had influent and effluent
data, EPA averaged the influent data and effluent data to obtain a plant-specific
average influent and effluent concentration, respectively.
2. EPA calculated percent removals for each pollutant for each model plant from the
site-specific average influent and effluent concentrations using the following
equation:
AveragelnfluentConcentration - AverageEffluentConcentration
PercentRemoval = : x 100
AveragelnfluentConcentration
3. If EPA calculated percent removals for multiple model plants for a pollutant, EPA
used the median percent removal for that pollutant from the plant-specific percent
removals as the BAT option percent removal.
11.2.2 Methodology for Determining POTW Percent Removals
EPA generally calculated pollutant percent removals at POTWs nationwide from two
available data sources:
• Fate of Priority Pollutants in Publicly Owned Treatment Works, September 1982,
EPA 440/1-82/303 (50 POTW Study); and
• National Risk Management Research Laboratory (NRMRL) Treatability Database,
Version 5.0, February 2004 (formerly called the Risk Reduction Engineering
Laboratory (RREL) database).
When available for a pollutant, EPA used data from the 50-POTW Study. For those
pollutants not covered in the 50 POTW Study, EPA used NRMRL data. The 50 POTW Study
presents data on the performance of 50 well-operated POTWs that employ secondary treatment
to remove toxic pollutants. EPA edited the data to minimize the possibility that low POTW
removals might simply reflect low influent concentrations instead of treatment effectiveness. The
criteria used in editing the 50-POTW study data for this rule are listed below:
1. Substitute the standardized pollutant-specific analytical ML for values reported as
"not detected," "trace," "less than (followed by a number)," or a number less than the
standardized minimum analytical detection limit (ML); and
11-12
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Section 11 - Pollutants Selected for Regulation
2. Retain pollutant influent and corresponding effluent values if the average pollutant
influent level is greater than or equal to 10 times the pollutant ML.
For each POTW that had data pairs that passed the editing criteria, EPA calculated its
percent removal for each pollutant using the equation provided above. EPA then used the median
value of all the POTW pollutant-specific percent removals as the nationwide percent removal in
its pass-through analysis. For this pass-through analysis, EPA used the 50-POTW study data for
arsenic and mercury.
The NRMRL database, used to augment the POTW database for the pollutants that the 50
POTW Study did not cover, is a computerized database that provides information, by pollutant,
on removals obtained by various treatment technologies. The database provides the user with the
specific data source and the industry from which the wastewater was generated. For each of the
pollutants regulated at BAT that were not found in the 50-POTW database (e.g., selenium), EPA
used data from portions of the NRMRL database. EPA applied the following editing criteria:
1. Only treatment technologies representative of typical POTW secondary treatment
operations (activated sludge, activated sludge with filtration, aerated lagoons) were
used;
2. Only information pertaining to domestic or industrial wastewater were used;
3. Pilot-scale and full-scale data were used, while bench-scale data were eliminated; and
4. Only data from peer-reviewed journals or government reports were used.
Using the NRMRL pollutant removal data that passed the above criteria, EPA calculated
the average percent removal for each pollutant. For this pass-through analysis, EPA used the
NRMRL database for selenium.
Neither source includes pollutant removal data for TDS. Secondary treatment
technologies are generally understood to be ineffective at removing TDS and as such TDS
removals at POTWs are likely to be close to zero. For purposes of this pass through analysis,
EPA assumes the percent removal to be zero [Metcalf & Eddy, 2003].
11.2.3 Results of POTW Pass-Through Analysis
The following subsections provide the results of EPA's pass through analyses for FGD
wastewater, combustion residual leachate, and gasification wastewater using the methodology
described above. EPA did not conduct its traditional pass-through analysis for fly ash transport
water, bottom ash transport water, and flue gas mercury control wastewater because limitations
for these wastestreams for direct dischargers consist of no discharge of process wastewater
pollutants to waters of the U.S., and therefore, all pollutants "pass through" the POTW for these
wastestreams.
11-13
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Section 11 - Pollutants Selected for Regulation
FGD Wastewater
The technology basis for PSES and PSNS for FGD discharges is one-stage chemical
precipitation followed by biological treatment. Table 11-4 presents the treatment technology
percent removals and POTW removals for FGD wastewater. Because the proposed FGD
wastewater BAT and NSPS limitations/standards for arsenic and mercury were transferred from
the one-stage chemical precipitation system, EPA performed the pass-through analysis for
arsenic and mercury based on the pollutant removals achieved by the one-stage chemical
precipitation system. All five regulated pollutants were determined to pass through POTW
secondary treatment and EPA selected them as regulated pollutants for PSES/PSNS.
Table 11-4. POTW Pass-Through Analysis (FGD Wastewater) - PSES/PSNS
Pollutant
Arsenic
Mercury
Nitrate, Nitrite as N
Selenium
Median BAT %
Removal
99.5%a
99.9%a
99.6%
99.9%
POTW % Removal
65.8%
90.2%
90.0%
34.3%
BAT % Removal >
POTW % Removal?
Yes
Yes
Yes
Yes
Does Pollutant Pass
Through?
Yes
Yes
Yes
Yes
a - The arsenic and mercury BAT percent removals are based on the one-stage chemical precipitation treatment,
because the proposed BAT effluent limitations were transferred from the one-stage chemical precipitation system.
Combustion Residual Leachate
The technology basis for PSES and PSNS for combustion residual leachate, under
Regulatory Options 4 and 5, is chemical precipitation. As explained further in Section 13, EPA is
transferring the limitations/standards for leachate from the one-stage chemical precipitation
technology option for FGD wastewater. Therefore, for arsenic and mercury, the technology basis
percent removals for leachate are based on the removals achieved by the one-stage chemical
precipitation system for FGD wastewater. Table 11-5 presents the treatment option percent
removals and POTW removals for combustion residual leachate using the methodology
described above. Both mercury and arsenic pass through and EPA is proposing them for
regulation under PSES and PSNS.
Table 11-5. POTW Pass-Through Analysis (Combustion Residual Leachate) - PSES/PSNS
Pollutant
Arsenic
Mercury
Median BAT %
Removal
99.5 %a
99.9% a
POTW % Removal
65.8%
90.2%
BAT % Removal >
POTW % Removal?
Yes
Yes
Does Pollutant Pass
Through?
Yes
Yes
a - The arsenic and mercury BAT percent removals are based on FGD wastewater one-stage chemical precipitation
treatment, because the proposed BAT effluent limitations were transferred from the FGD wastewater one-stage
chemical precipitation system.
11-14
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Section 11 - Pollutants Selected for Regulation
Gasification Wastewater
The technology option for gasification is vapor-compression evaporation. Table 11-6
presents the technology option percent removals and POTW removals for gasification
wastewater. All four regulated pollutants were determined to pass through POTW secondary
treatment and EPA is proposing them for PSES and PSNS.
Table 11-6. POTW Pass-Through Analysis (Gasification Wastewater) - PSES/PSNS
Pollutant
Arsenic
Mercury
Selenium
TDS
Median BAT %
Removal
99.4%
98.5%
88.9%
99.7%
POTW % Removal
65.8%
90.2%
34.3%
0%
BAT % Removal >
POTW % Removal?
Yes
Yes
Yes
Yes
Does Pollutant Pass
Through?
Yes
Yes
Yes
Yes
11.3 REFERENCES
1. Metcalf & Eddy, Inc. 2003. Wastewater Engineering, Treatment and Reuse, Fourth
Edition. McGraw-Hill. New York. DCN SE02936.
2. U.S. EPA. 1976. Supplement for Pretreatment to the Development Document for the
Steam Electric Power Generating Point Source Category. EPA 440/1-76/084.
Washington, D.C. (November). DCN SE02935.
11-15
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Section 12 -Non-Water Quality Environmental Impacts
SECTION 12
NON-WATER QUALITY ENVIRONMENTAL IMPACTS
The elimination or reduction of one form of pollution has the potential to aggravate other
environmental problems, an effect frequently referred to as cross-media impacts. Sections 304(b)
and 306 of the Clean Water Act require EPA to consider non-water quality environmental
impacts (NWQIs), including energy requirements, associated with effluent limitations guidelines
and standards (ELGs). Accordingly, EPA has considered the potential impacts of the proposed
regulation on energy consumption, air emissions, and solid waste generation and management.101
EPA determined that the proposed ELGs have non-water quality environmental impacts
associated with operations for treating and managing FGD wastewater, combustion residual
landfill leachate, and ash transport water. However, because all plants generating flue gas
mercury control wastewater and gasification wastewater currently operate the technologies
identified as the basis for BAT, EPA does not predict any net increase of energy or fuel usage,
sludge generation, or air emissions for these wastestreams for the proposed ELGs. Additionally,
because all plants generating and discharging nonchemical metal cleaning wastes are either
already meeting the proposed BAT limitations (based on the current BPT standard) or will be
exempt from the proposed BAT limitations, EPA does not predict any net increase of energy or
fuel usage, sludge generation, or air emissions for nonchemical metal cleaning wastes for the
proposed ELGs. As described throughout this section, although the regulatory options will result
in increases of energy and fuel usage, sludge generation, and air emissions, the increases are
small compared to national levels of energy/fuel usage, current air emissions from power plants,
1 09
and sludge production from municipal wastewater treatment plants.
12.1 ENERGY REQUIREMENTS
Steam electric power plants use energy when transporting ash and other solids on or off
site, operating wastewater treatment systems (e.g., chemical precipitation, biological treatment),
operating ash handling systems, or operating water trucks for dust suppression. For those plants
that EPA projected would incur costs to comply with the regulatory options, EPA considered
whether or not there would be an associated incremental energy need. That need varies
depending on the regulatory option evaluated and the current operations of the plant. Therefore,
as applicable, EPA estimated the additional energy usage in megawatt hours (MWh) for
equipment added to the plant systems or in consumed fuel (gallons) for transportation/operating
equipment. Similarly, as applicable, EPA also estimated the decrease in energy requirements
resulting from the reduction in wet sluicing operations and use of earth-moving equipment. EPA
scaled the plant-specific estimate to calculate the net change in energy requirements for the
regulatory options for this proposed rulemaking.
To determine potential increases in electrical energy use, EPA estimated the amount of
energy needed to operate wastewater treatment systems and ash handling systems. To determine
101 EPA also evaluated the increases of energy and fuel usage, sludge generation, and air emissions for the future
profile population and new sources. For more information on the NWQI EPA evaluated for future profile and new
sources, see EPA's memorandum "Evaluation of NWQI for the Future Profile Population and New Sources" [U.S.
EPA, 2012b].
102 The proposed regulatory options will also result in decreases of air emissions for certain pollutants.
12-1
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Section 12 -Non-Water Quality Environmental Impacts
potential decreases in electrical energy use, EPA estimated the amount of energy saved from
reducing wet sluice pumping operations based on the horsepower rating of the pumps. Similarly,
EPA estimated the amount of energy saved by reducing the number of backhoes needed to
dredge solids from ash impoundments, resulting from the reduction of wet sluice operations.
EPA estimated these energy savings using the horsepower rating of the backhoe engine. EPA
only estimated energy savings associated with earthmoving equipment for plants operating
surface impoundments. See EPA's Incremental Costs and Pollutant Removals for Proposed
Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point
Source Category for more information on the specific calculations used to estimate energy. [U.S.
EPA, 2013] Table 12-1 presents the net change in annual electrical energy usage associated with
the proposed regulation.
Table 12-1. Industry-Level Energy Requirements by Regulatory Option
Regulatory Option
1
3a
2
3b
3
4a
4
5
Electrical Energy Usage
(MWh/year)
84,333
112,004
191,327
160,753
303,332
472,369
673,780
2,835,389
Fuel
(GPY)
172,205
2,867,770
173,421
2,903,656
3,041,191
4,617,848
6,027,266
7,548,543
Energy usage also includes the fuel consumption associated with transportation. EPA
estimated the need for increased transportation of ash and other solid waste, including wastes
from the treatment of FGD wastewater and landfill leachate, at steam electric power plants to on-
site or off-site landfills, based on plant-specific data, using open dump trucks. In general, the fuel
usage was calculated as shown:
Fuel (gallons) piant = [((Loading Time (hr/trip) idling + Unloading Time (hr/trip) idiing) x
(Fuel Consumption (gal/hr) idling)) + (Transport Distance (mile/round trip) x
Fuel consumption (gal/mile))] x (Number of Trips (trips/yr))
Where:
Loading Time (hr/trip)
Unloading Time (hr/trip)
Fuel Consumption (gal/hr)
idling
The estimated time to load an open dump truck
with sludge and/or ash per trip, estimated to be
0.1667 hours (10 minutes) per trip.
The estimated time to unload an open dump truck
with sludge and/or ash per trip, estimated to be
0.1667 hours (10 minutes) per trip.
The estimated fuel consumption while the truck is
idling. The MOBILE6.2 vehicle emission
12-2
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Section 12 -Non-Water Quality Environmental Impacts
modeling software assumes that dump trucks
average 2.5 miles per hour and 6.6 miles per gallon
at idle. Therefore, EPA estimated the idle fuel
consumption to be 0.38 gal/hr.
Transport Distance = The estimated round trip distance to/from the
(mile/round trip) landfill. Distance varies based on plants with
onsite versus offsite landfills. For onsite landfills,
EPA estimated a round trip to be 2.6 miles. For
offsite landfills, EPA estimated a round trip to be
40 miles.
Fuel consumption (gal/mile) = The estimated fuel consumption while the truck is
in drive, estimated to be 20.24 gal/100 miles.
Number of Trips (trips/yr) = The calculated number of trips for one year in the
transportation methodology to truck all ash to the
onsite or offsite landfill.
The frequency and distance of transport depends on a plant's operation and configuration.
For example, the volume of waste generated per day determines the frequency with which trucks
will be travelling to and from the storage sites. The availability of either an on-site or off-site
non-hazardous landfill and its distance from the plant determines the length of travel time.
EPA also estimated fuel consumption associated with the dust suppression water trucks
based on the total distance (in miles) traveled and the total number of hours estimated for water
truck operations. See EPA's Incremental Costs and Pollutant Removals for Proposed Effluent
Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source
Category for more information on the specific calculations used to estimate transportation fuel
usage. [U.S. EPA, 2012c] Table 12-1 shows the net change in national annual fuel consumption
associated with the proposed regulation.
To provide some perspective on the potential net increase in annual electric energy
consumption associated with the preferred options, EPA compared the estimated increase in
energy usage (MWh), as shown in Table 12-1, to the net amount of electricity generated in a year
by all electric power plants throughout the United States. According to EPA's Emissions &
Generation Resource Integrated Database (eGRTD), the electric power industry generated
approximately 3,951 million MWh of electricity in 2009. EPA estimates that energy increases
associated with the preferred BAT and PSES regulatory options range from less than 0.003
percent (Option 3a) to 0.012 percent (Option 4a) of the total electricity generated by all electric
power plants.
Similarly, EPA compared the additional net fuel consumption (gallons) estimated for the
preferred options, as shown in Table 12-1, to national fuel consumption estimates for motor
vehicles. According to the U.S. Energy Information Administration (EIA), on-highway vehicles,
which include automobiles, trucks, and buses, consumed approximately 34 billion gallons of
distillate fuel oil in 2009. EPA estimates that the fuel consumption increase associated with the
proposed Option 3a for BAT and PSES will be 0.008 percent of total fuel consumption by all
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Section 12 -Non-Water Quality Environmental Impacts
motor vehicles. Fuel consumption is estimated to increase by less than 0.009 percent under
Options 3b and Option 3, and less than 0.014 percent under Option 4a.
12.2 AIR EMISSIONS POLLUTION
The proposed ELGs are expected to affect air pollution through three main mechanisms:
Additional auxiliary electricity use by steam electric plants to operate wastewater
treatment, ash handling, and other systems needed to comply with the new effluent limitations
and standards;
Additional transportation-related emissions due to the increased trucking of combustion
residual waste to landfills; and
The change in the profile of electricity generation due to relatively higher costs to
generate electricity at plants incurring compliance costs for the proposed rule.
This section provides greater detail on air emission changes associated with the first two
mechanisms and presents the estimated net change in air emissions that take all three
mechanisms into account. See EPA's Benefit and Cost Analysis for the Proposed Effluent
Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source
Category report for additional discussion of the third mechanism.
Air pollution is generated when fossil fuels are combusted. In addition, steam electric
power plants generate air emissions from the operating transport vehicles, such as dump trucks
and vacuum trucks, dust suppression water trucks, and earth-moving equipment, which release
criteria air pollutants and greenhouse gases when operated. Criteria air pollutants are those
pollutants for which a national ambient air quality standard (NAAQS) has been set and include
sulfur dioxide (802) and nitrogen oxides (NOx). Greenhouse gases are gases such as carbon
dioxide (CO2), methane (CH/i), and nitrous oxide (N2O) that absorb radiation, thereby trapping
heat in the atmosphere, and contributing to global warming.103 Similarly, a decrease in energy
use or vehicle operation will result in decreased air pollution.
EPA estimated the energy usage associated with the operation of wastewater treatment
systems and ash handling systems in megawatt hours (MWh). Additionally, EPA also estimated
the decrease in energy requirements associated with terminating wet sluicing operations and
reduced use of earth-moving equipment associated with the new technology options. EPA used
these estimates to calculate the net change in energy requirements for all regulatory options
considered for this proposed rulemaking.
EPA calculated air emissions resulting from increased auxiliary electricity using year-
explicit emission factors projected in IPM for CO2, NOX, and SO2. EPA obtained emission
factors for years 2017 through 2024 based on IPM outputs for Run Year 2020 and emission
103 EPA did not specifically evaluate nitrous oxide emissions as part of the NWQI analysis. To avoid double
counting air emission estimates, EPA only calculated nitrogen oxide emissions, which would include nitrous oxide
emissions.
12-4
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Section 12 -Non-Water Quality Environmental Impacts
factors for years 2025 through 2040 based on IPM output for Run Year 2030. EPA used the
values associated with Run Year 2030 because these values represent full implementation of the
proposed rule. Table 12-2 presents the IPM emission factors for Regulatory Options 3 and 4 for
CC>2, NOX, and SC>2 by NERC region, as well as the average for the United States.
12-5
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Section 12 - Non-Water Quality Environmental Impacts
Table 12-2. Summary of IPM Emissions Factors by NERC Region and Across Steam Electric Plants
Run
Year
2020
2030
NERC Region / Plants
US
ERCOT
FRCC
MRO
NPCC
RFC
SERC
SPP
WECC
US
ERCOT
FRCC
MRO
NPCC
RFC
SERC
SPP
WECC
Option 3
CO2
Metric Tonnes /
MWh
0.5324
0.5599
0.5031
0.6892
0.2694
0.5904
0.5674
0.7290
0.3772
0.5210
0.5411
0.4782
0.6555
0.2980
0.5764
0.5604
0.7130
0.3645
NOx
Tons / MWh
0.0004
0.0003
0.0003
0.0008
0.0002
0.0005
0.0004
0.0006
0.0005
0.0004
0.0003
0.0003
0.0007
0.0002
0.0005
0.0004
0.0006
0.0004
SO2
Tons / MWh
0.0005
0.0003
0.0003
0.0008
0.0002
0.0007
0.0006
0.0007
0.0002
0.0005
0.0002
0.0002
0.0008
0.0002
0.0006
0.0006
0.0007
0.0001
Option 4
CO2
Metric Tonnes /
MWh
0.5322
0.5610
0.5051
0.6902
0.2694
0.5904
0.5674
0.7290
0.3772
0.5204
0.5408
0.4781
0.6555
0.2979
0.5764
0.5604
0.7130
0.3645
NOx
Tons / MWh
0.0004
0.0003
0.0003
0.0008
0.0002
0.0005
0.0004
0.0006
0.0005
0.0004
0.0003
0.0003
0.0007
0.0002
0.0005
0.0004
0.0006
0.0004
SO2
Tons / MWh
0.0005
0.0003
0.0003
0.0008
0.0002
0.0007
0.0006
0.0007
0.0002
0.0005
0.0002
0.0002
0.0008
0.0002
0.0006
0.0006
0.0007
0.0001
to
-------
Section 12 -Non-Water Quality Environmental Impacts
For plants with capacity utilization rates (CUR) of 90.4 percent or less, EPA estimated
emissions using plant-specific and year-explicit emission factors obtained from IPM outputs.104
These plants are assumed to be able to generate the additional auxiliary electricity on site.
For plants with CUR greater than 90.4 percent, EPA used NERC-average emission
factors for each year instead of plant-specific emissions factors. EPA used these NERC-average
factors based on the assumption that additional electricity consumption for auxiliary power will
displace grid power within the region instead of coming from additional generation at the plant
(i.e., the plant will be using part of its existing generation to power equipment, requiring other
plants within the same NERC region to generate additional electricity to meet demand).
EPA calculated NOx emissions as follows:
733
t = Y £p x EF_NOXp:t x Tpit x Wp
Where:
NOX
P=i
NOXt = Total NOX emissions in year t.
Ep = Incremental auxiliary power electricity consumption at plant/?,
in MWh per year.
EF_NOXpj = NOX emission factor at plant/? in year t, in tons NOX per MWh.
If CURP > 90.4 percent, EF_NOXp:t is based on average
EF_NOXt for the NERC region where plant/? is located. For t =
2017 to 2024, the calculations use IPM EF_NOXpi2o20- For t =
2025 to 2040, the calculations use IPM EF_NOXP,2030.
Tp:t = Timing adjustment to reflect year when plants are assumed to
install the compliance technology between 2017 and 2021 and
start incurring additional electricity consumption (Tpit =0 if t <
Year when plant/? installs technology; Tpit =1 if t > Year when
plant/? installs technology).
Wi = Sample weight for plant/?.
Emissions of CO2 and SO2 are calculated similarly but using the CO2 and SO2 emission
factors, respectively.
Since IPM was run for Regulatory Options 3 and 4 only, EPA used IPM emission factors
for Option 3 to estimate changes in auxiliary power air emissions for Options 1 and 2, and IPM
emissions factors for Option 4 to estimate changes in auxiliary power air emissions for Option 5.
EPA used the auxiliary power air emissions calculated for Option 1 through 5 to estimate the
auxiliary power air emissions for Options 3a, 3b, and 4a. For additional details on these
estimation methodologies, see the memoranda entitled "Memorandum to the Rulemaking
104 Emission factors are calculated as plant-level emissions divided by plant-level generation.
12-7
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Section 12 -Non-Water Quality Environmental Impacts
Record: Methodologies for Estimating Costs and Pollutant Removals for Steam Electric ELG
Regulatory Options 3a and 3b" and "Memorandum to the Rulemaking Record: Methodologies
for Estimating Costs and Pollutant Removals for Steam Electric ELG Regulatory Option 4a"
[ERG, 2013a; ERG, 2013b].
To estimate air emissions associated with increased operation of transport vehicles, EPA
used the MOBILE6.2 model to generate air emission factors (grams per mile) for hydrocarbons
(HC), carbon monoxide (CO), NOx, CO2, and particulate matter (PM). EPA assumed the general
input parameters such as the year of the vehicle and the annual mileage accumulation by vehicle
class to develop these factors. See EPA's report entitled Incremental Costs and Pollutant
Removals for Proposed Effluent Limitations Guidelines and Standards for the Steam Electric
Power Generating Point Source Category for more specific information on the assumptions
made by EPA for year of the vehicle and annual mileage accumulation. [U.S. EPA, 2012c]
Because MOBILE6.2 does not estimate emission factors for CFLj, EPA used the emission factors
from the California Climate Action Registry, General Reporting Protocol, Version 2.2. Table
12-3 provides a table of the transportation emission factors for each air pollutant considered in
the NWQI analysis.
Table 12-3. MOBILE6.2 and California Climate Action Registry
Transportation Emission Rates
Nitrogen Oxides
Highway (ton/mi)
6.76 x 10"7
Nitrogen Oxides
Local (ton/mi)
6.52 x 10"7
Sulfur Oxides
(ton/mi)
1.58 xlO"8
Carbon Dioxide
(ton/mi)
0.0017
Methane
(ton/mi)
6.61 x 10"8
Source: MOBILE6.2 [U.S. EPA, 2004] and California Climate Action Registry, General Reporting Protocol, V2.2
[California Climate Action Registry, 2007]
Note: The MOBILE6.2 highway and local emission rates are the same for all pollutant except nitrogen oxides.
Using the transportation emission rates per mile, EPA calculated the air emissions
associated with the additional energy estimated for the regulatory options, as shown:
Emission (tons) poiiutantx, plant = (Air Emission Factor (ton/mile) pollutant x, vehicle) x
(Transport Distance (mile/round trip)) x (Number of Trips (trips/yr)).
Where:
Air Emission Factor
(ton/mile) poiiutantx, vehicle
Transport Distance
(mile/round trip)
The transportation emission factor for each pollutant
presented in Table 12-3.
The estimated round trip distance to/from the landfill.
Distance varies based on plants with on-site versus
off-site landfills. For on-site landfills, EPA estimated a
round trip to be 2.6 miles. For off-site landfills, EPA
estimated a round trip to be 40 miles.
12-8
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Section 12 -Non-Water Quality Environmental Impacts
Number of Trips (trips/yr)
The calculated number of trips for one year in the
transportation methodology to truck all ash to the on-
site or off-site landfill.
EPA estimated the annual number of miles that would be traveled by dump trucks or
vacuum trucks moving ash or wastewater treatment solids to on- or off-site landfills related to
the regulatory options. In addition to the trucks associated with transporting the additional solid
waste, EPA also estimated the annual number of miles that would be traveled by water trucks
spraying water around landfills and ash unloading areas to control dust. EPA used these
estimates to calculate the net increase in air emissions for this rulemaking. See EPA's report
entitled Incremental Costs and Pollutant Removals for Proposed Effluent Limitations Guidelines
and Standards for the Steam Electric Power Generating Point Source Category for more
information. [U.S. EPA, 2012c] The increases in national annual air emissions associated with
auxiliary electricity and transportation for each of the regulatory options are shown in Table 12-4
[ERG, 2013c].
Table 12-4. Industry-Level Air Emissions Associated with Auxiliary Electricity and
Transportation by Regulatory Option
Regulatory Option
1
3a
2
3b
o
5
4a
4
5
Air Emissions
NOX
(tons/year)
54
88
119
113
207
321
547
1,772
SOX
(tons/year)
90
84
190
126
274
418
709
2,708
C02
(metric tons/year)
79,753
117,863
181,366
164,318
299,229
459,074
663,957
2,674,207
CH4
(tons/year)
1.2
2.4
2.7
3.1
5.1
7.9
11
41
EPA estimated the change in the profile of electricity generation due to relatively higher
costs to generate electricity at plants incurring compliance costs for the proposed rule using data
from IPM. IPM predicts changes in electricity generation due to compliance costs attributable to
the proposed ELG options. Therefore, EPA predicts that these changes, either increases or
decreases, in electricity generation affect the air emissions from steam electric power plants.
EPA only estimated the changes associated with the IPM predications, one of the three air
emission mechanisms, for Option 3 and 4. The net changes in national annual air emissions
associated with the preferred options are shown in Table 12-5.
12-9
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Section 12 -Non-Water Quality Environmental Impacts
Table 12-5. Industry-Level Net Air Emissions For the Preferred Regulatory Options
Regulatory
Option
3a
3b
3
4a
4
Air Emissions
NOX
(tons/year)
88-l,090a
110-1, 110a
1,207
1,320C
1,547
sox
(tons/year)
<84b
<130b
-2,726
<-2,580c
-3,291
CO2
(metric tons/year)
<117,863b
<164,318b
-1,162,771
<-l,002,926c
-3,749,043
CH4
(tons/year)
2.4
3.1
5.1
7.9
11
a - EPA quantified the air emissions associated with additional electricity and additional transportation for Options
3a and 3b. Based on the values quantified for Option 3 for the changes to air emissions projected by IPM, EPA
calculated the range of emissions for NOx. The lower end of the range represents the emissions only associated with
additional electricity and transportation. The upper end of the range also includes the changes to air emissions
projected by IPM (based on Option 3), which are large than would be expected for Option 3a and 3b.
b - EPA quantified the air emissions associated with additional electricity and additional transportation for Options
3a and 3b. Based on the values quantified for Option 3 for the changes to air emissions projected by IPM, which
were negative, EPA decided not to include these IPM air emission changes in the calculated SOx and CO2 emissions
for Options 3a and 3b. These SOx and CO2 emissions are considered maximum values because EPA expects that the
air emission changes projected by IPM for Options 3a and 3b will also be negative (as they are for Options 3 and 4).
c - EPA quantified the air emissions associated with additional electricity and additional transportation for Option
4a. To estimate the total emissions for Option 4a, EPA added the changes to air emissions projected by IPM for
Option 3 because they are more conservative (i.e., they overestimate the emissions). The contribution of NOx is
unchanged compared to Option 3 and 4; therefore, EPA assumed this would also be the contribution for Option 4a.
For SOx and CO2, the contribution associated with Option 4 are lower (i.e., more negative); therefore, because EPA
used the Option 3 values, the values presented in the table are maximum values.
To provide some perspective on the potential increase in annual air emissions associated
with the preferred options, EPA compared the estimated increase in air emissions associated with
Regulatory Options 3a, 3b, 3, 4a, and 4 to the net amount of air emissions generated in a year by
all electric power plants throughout the United States. Table 12-6 presents the 2009 emissions
generated by the electric power industry, based on eGRID, and the percent of increased
emissions associated with the proposed rule. [U.S. EPA, 2012a]
12-10
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Section 12 -Non-Water Quality Environmental Impacts
Table 12-6. Electric Power Industry Air Emissions
Non-Water
Quality Impact
Value Associated with
Preferred Regulatory Option
(Million Tons)
2009 Emissions by Electric
Power Industry
(Million Tons)
Increase In Emissions
(%)
Regulatory Option 3a
NOX
sox
C02
CH4
0.000088-0.00109
O.000084
0.130
0.0000024
1
6
2,403
95
0.008-0.109
O.0014
0.0054
0.0000025
Regulatory Option 3b
NOX
sox
C02
CH4
0.00011-0.00111
0.00013
O.181
0.0000031
1
6
2,403
95
0.011-0.111
0.0021
O.0075
0.0000033
Regulatory Option 3
NOX
sox
C02
CH4
0.00121
-0.00273
-1.282
0.000001
1
6
2,403
95
0.121
-0.045
-0.053
0.000001
Regulatory Option 4a
NOX
SOX
C02
CH4
0.00132
<-0.00258
<-1.106
0.0000079
1
6
2,403
95
0.132
<-0.043
<-0.046
0.0000083
Regulatory Option 4
NOX
SOX
CO2
CH4
0.00154
-0.00329
-4.133
0.000001
1
6
2,403
95
0.154
-0.055
-0.172
0.000001
12.3 SOLID WASTE GENERATION
Steam electric power plants generate solid waste associated with sludge from wastewater
treatment systems (e.g., chemical precipitation, biological treatment). The regulatory options
evaluated would increase the amount of solid waste generated from FGD wastewater treatment,
including sludge from chemical precipitation, biological treatment, and vapor-compression
evaporation technologies. EPA estimated the amount of solid waste generated from each
technology for each plant and estimates that the preferred BAT/PSES regulatory options
(Options 3a, 3b, 3, and 4a) would increase solids generated annually from treatment. Fly ash and
bottom ash are also solid wastes generated at steam electric power plants. The preferred
regulatory options for BAT and PSES are, however, not expected to alter the amount of fly ash,
bottom ash, or other combustion residuals generated.
12-11
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Section 12 -Non-Water Quality Environmental Impacts
EPA determined dewatered sludge generation rates for chemical precipitation treatment
by multiplying a flow-normalized dewatered sludge generation rate (expressed in tons per day of
sludge per gallon per minute FGD flow) by the plant flow rate. The flow-normalized dewatered
sludge generation rate was determined based on responses in the questionnaire for FGD
wastewater chemical precipitation treatment. EPA selected the median flow-normalized
dewatered sludge generation rate based on an assessment of the characteristics of the dataset.
EPA then calculated the annual sludge generation as follows:
Annual Sludge Generation, tons/yr = Sludge Generation Rate x FGD Wastewater Flow,
gpm x60 min/hr x 24 hr/day x 365 day/year
Where:
Sludge = The median flow normalized rate of sludge generation based on
Generation Rate the questionnaire. EPA estimated this rate to be 0.24 tons per
day per gallon per minute of FGD wastewater flow.
FGD Wastewater = The FGD wastewater for the plant in units of gallons per
Flow minute. This value was calculated from the gallons per day
value reported in the survey and divided by 24 x 60 to convert
to gallons per minute.
Sludge generated by the biological treatment system is contained within the backwash
wastewater which is recycled to the FGD wastewater chemical precipitation system and is
ultimately removed with the chemical precipitation sludge. Sludge generated by the vapor-
compression evaporation system includes softening sludge and crystallizer sludge. EPA obtained
sludge generation rates for the softening sludge and crystallizer sludge based on FGD wastewater
flow rates from equipment vendors. [HPD, 2009] Based on this information, EPA calculated
sludge generation rates using the equations provided below.
Softening Sludge, tons/yr = Softening Sludge Factor, Ib/hr-gpm x FGD Wastewater Flow,
gpm x (1 ton/2,000 Ib) x 24 hpd x 365 dpy
Crystallizer Sludge, tons/yr = Crystallizer Sludge Factor, Ib/hr-gpm x FGD Wastewater Flow,
gpm x (1 ton/2,000 Ib) x 24 hpd x 365 dpy
Where:
A factor that relates the amount of sludge generated in the
Softening Sludge Factor = softening process to the scrubber purge flow based on data
provided by HPD, 51.43 Ib/hr-gpm.
A factor that relates the amount of sludge generated in the
Crystallizer Sludge Factor = crystallizer process to the scrubber purge flow based on data
provided by HPD, 17.14 Ib/hr-gpm.
12-12
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Section 12 -Non-Water Quality Environmental Impacts
See EPA's report entitled Incremental Costs and Pollutant Removals for Proposed
Effluent Limitations Guidelines and Standards for the Steam Electric Power Generating Point
Source Category for more information [U.S. EPA, 2012c]. The net change in national annual
sludge production associated with the regulatory options is shown in Table 12-7.
To provide some perspective on the potential increase in annual solid waste generation
associated with Regulatory Options 3a, 3, and 4a, EPA compared the estimated increase in solid
waste generation to the amount of solids generated in a year by electric power plants throughout
the United States. According to the EIA, power plants generated approximately 134 billion tons
of solids in 2009. EPA estimates that solid waste generation increases associated with the
preferred regulatory options will be less than 0.001 percent of the total solid waste generated by
all electric power plants.
Table 12-7. Industry-Level Solid Waste Increases by Regulatory Option
Regulatory Option
1
3a
2
3b
3
4a
4
5
Sludge (Tons/Year)
1,209,859
0
1,218,691
365,960
1,218,691
1,218,691
1,459,011
13,281,443
12.4 REDUCTIONS IN WATER USE
Steam electric power plants generally use water for handling solid waste, including ash,
and for operating wet FGD scrubbers. The technology options for fly ash and bottom ash will
eliminate or reduce water use associated with current wet sluicing operating systems. EPA
estimated the reductions in water use by calculating the amount of ash sluice water, specifically
that amount of water identified as intake process water, that will no longer be discharged as part
of the proposed rulemaking. In order to calculate this reduction, EPA used data from Part C of
the Steam Electric Survey to calculate an average percentage of ash sluice water identified as
intake water. EPA multiplied this percentage by the amount of sluice water discharged by each
plant to calculate the estimated process water reduction. See the memorandum entitled "Steam
Electric Effluent Guidelines Non-Water Quality Impacts" for more information [ERG, 2013c].
The technology basis for the preferred regulatory option with respect to FGD wastewater
discharges (e.g., chemical precipitation, biological treatment) would not be expected to reduce
the amount of water used unless plants recycle FGD wastewater as part of their treatment system.
EPA estimated that five plants would be able to incorporate recycle within their FGD systems
based on the maximum operating chlorides concentration compared to the design maximum
chlorides concentration (other plants may also be able to do so). In order to estimate the water
reductions associated with the recycled FGD wastewater, EPA used data from Part B of the
Steam Electric Survey to calculate an average percentage of FGD wastewater identified as intake
12-13
-------
Section 12 -Non-Water Quality Environmental Impacts
water. EPA multiplied this percentage by the amount of water that could be recycled by the FGD
system to calculate the estimated water reduction. EPA also used the adjusted FGD scrubber
purge flows to estimate compliance cost and pollutant loadings associated with these plants. See
EPA's report entitled Incremental Costs and Pollutant Removals for Proposed Effluent
Limitations Guidelines and Standards for the Steam Electric Power Generating Point Source
Category for more information [U.S. EPA, 2012c].
EPA estimates that power plants would reduce the use of water associated with the
regulatory options. Table 12-8 presents the expected reduction in process water use for each
regulatory option evaluated for the proposed rule. For comparison, EPA compared the expected
levels of process water reductions to the current amount of wastewater discharged from the
wastestreams expected to have associated non-water quality environmental impacts for this
proposed rulemaking, presented in Table 12-9.
Table 12-8. Industry-Level Process Water Reduction by Regulatory Option
Regulatory Option
1
3a
2
3b
3
4a
4
5
Water Reduction
(Million Gallons/Year)
2,820
49,900
2,820
52,100
52,700
103,000
153,000
153,000
Table 12-9. Wastewater Discharge at Steam Electric Power Plants
Type of Wastewater
FGD Wastewater
Fly Ash Transport Water
Bottom Ash Transport Water
Landfill Leachate
Number of Plants
Discharging Wastewater
117
95
245
100-115
Total Wastewater Discharged
(2009, Million Gallons/Year)
23,700
81,100
157,000
2,200
12.5 REFERENCES
1. California Climate Action Registry. 2007. General Reporting Protocol: Reporting Entity-
Wide Greenhouse Gas Emission, Version 2.2. (March). DCN SE02035.
2. Eastern Research Group (ERG). 2013a. Memorandum to the Rulemaking Record:
Methodologies for Estimating Costs and Pollutant Removals for Steam Electric ELG
Regulatory Options 3a and 3b. (19 April). DCN SE03881.
12-14
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Section 12 -Non-Water Quality Environmental Impacts
Eastern Research Group (ERG). 2013b. Memorandum to the Rulemaking Record:
Methodologies for Estimating Costs and Pollutant Removals for Steam Electric ELG
Regulatory Option 4a. (19 April). DCN SE03834.
Eastern Research Group (ERG). 2013c. Memorandum to the Steam Electric Rulemaking
Record. "Steam Electric Effluent Guidelines Non-Water Quality Impacts." (19 April).
DCN SE02025.
U.S. EPA. 2004. MOBILE6.2 Vehicle Emission Modeling Software, available online at:
http://www.epa.gov/oms/m6.htm.
U.S. EPA. 2012a. The Emissions & Generation Resource Integrated Database for 2012
(eGRID 2012) Technical Support Document. Available online at:
http ://www. epa.gov/cleanenergy/documents/egridzips/eGRID2012_year09_Technical Sup
portDocument.pdf. DCN SE02112.
U.S. EPA. 2012b. eGRID2012 Version 1.0 2009 Data. Available online at:
http://www.epa.gov/cleanenergy/energy-resources/egrid/index.html. DCN SE02111.
U.S. EPA. 2013. Incremental Costs and Pollutant Removals for Proposed Effluent
Limitation Guidelines and Standards for the Steam Electric Power Generating Point
Source Category Report. (19 April). DCN SE01957.
12-15
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Section 13- Limitations and Standards: Data Selection and Calculation
SECTION 13
LIMITATIONS AND STANDARDS: DATA SELECTION AND
CALCULATION
This section describes the data sources, data selection, and statistical methodology EPA
used to calculate the long-term average, variability factors, and limitations and standards for
existing and new sources. The effluent limitations guidelines and standards are based on long-
term average effluent values and variability factors that account for variation in treatment
performance within a particular treatment technology over time. For simplicity, in the remainder
of this section, the proposed effluent limitations and/or standards are referred to as "limitations."
Also, the term "option long-term average" and "option variability factor" are used to refer to the
long-term averages and variability factors for the treatment technology options for an individual
wastestream rather than the regulatory options described in Section 8.1.
Section 13.1 provides a brief overview of the criteria EPA used to evaluate and select
model plants (and the associated datasets) that are the basis of the proposed limitations. Section
13.2 describes the data exclusions and substitutions. Section 13.3 presents the procedures for
data aggregation. Section 13.4 describes data editing criteria used to select plant datasets in
developing the limitations. Sections 13.5 and 13.6 provide an overview and the procedure for
estimation of the long-term averages, variability factors, and limitations. Section 13.7 describes
the rationale for the transfer of limitations. Sections 13.8 and 13.9 provide the summary of the
limitations and engineering review of the limitations.
13.1 DATA SELECTION
In developing the long-term averages, variability factors, and limitations for a particular
wastestream and a particular technology option, EPA used wastewater data from plants operating
the model technology as the basis for the technology option. The data sources evaluated
include: (i) Sampling performed by EPA (hereafter referred to as "EPA sampling") during which
EPA collected samples; (ii) Sampling directed by EPA (hereafter referred to as "CWA 308
sampling") during which EPA directed plants to collect samples; and (iii) Plants self-monitoring
data (hereafter referred to as "plant self-monitoring") collected by Duke Energy for two plants
over a period of several years.
13.1.1 Data Selection Criteria
This section describes the criteria that EPA applied in selecting plants and data to use as
the basis for the limitations for FGD, leachate, and gasification wastestreams. EPA has used
these, or similar criteria, in developing limitations and standards for other industries. EPA uses
these criteria to select data that reflect consistently good performance of the model technology in
treating the industrial wastes under normal operating conditions. Generally, for each technology
option, EPA has defined a treatment system (or management practices) comprised of specific
components (e.g., equipment, chemical additives, etc.) that is carefully designed to operate under
the expected wastestream characteristics (e.g., pollutant concentrations, flow rates, etc.) and that
is diligently operated to achieve stable, optimized pollutant removal performance. Indicators of
diligent operation include adequate staffing by trained personnel, frequent monitoring of
treatment system operating conditions, and practice response to changes in operating conditions
13-1
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Section 13- Limitations and Standards: Data Selection and Calculation
or indicators of system performance. The following paragraphs describe the criteria specific to
the steam electric category.
The first criterion requires that the plant must have the model technology and
demonstrate consistently diligent and optimal operation. Application of this criterion typically
eliminates any plant with treatment other than the model technology. EPA generally determines
whether a plant meets this criterion based upon site visits, discussions with plant management,
and/or comparison to the characteristics, operation, and performance of treatment systems at
other plants. EPA often contacts plants to determine whether data submitted were representative
of normal operating conditions for the plant and equipment. EPA typically excludes the data in
developing the limitations when the plant has not optimized the performance of its treatment
system to the degree that represents the appropriate level of control (BAT or BADCT).
The second criterion generally requires that the influents and effluents from the treatment
components represent typical wastewater from the industry, without incompatible wastewater
from other sources. Application of this criterion results in EPA selecting only those plants where
the commingled wastewaters were not characterized by substantial dilution, unequalized slug
loads that resulted in frequent upsets and/or overloads, more concentrated wastewaters, or
wastewaters with different types of pollutants than those generated by the wastestream for which
EPA is establishing effluent limitations.
The third criterion typically ensures that the pollutants were present in the influent at
sufficient concentrations to evaluate treatment effectiveness. To evaluate whether the data meet
this criterion for the proposed rule, EPA often uses a long-term average test (or LTA test) for
plants where EPA possesses paired influent and effluent data. EPA has used this test in
developing regulations for other industries, e.g., the Iron and Steel Category (EPA 2002). The
test measures the influent concentrations to ensure a pollutant is present at sufficient
concentration to evaluate treatment effectiveness. If a dataset for a pollutant fails the test (i.e.,
not present at a treatable concentration), EPA excludes the data for that pollutant at that plant
when calculating the limitations. See Section 13.4 for a detailed discussion of the LTA test.
The fourth criterion typically requires that the data are valid and appropriate for their
intended use (e.g., the data must be analyzed with a sufficiently-sensitive method). Also, EPA
does not use data associated with periods of treatment upsets because these data would not
reflect the performance from well-designed and well-operated treatment systems. In applying the
fourth criterion, EPA may evaluate the pollutant concentrations, analytical methods and the
associated quality control/quality assurance data, flow values, mass loadings, plant logs, and
other available information. As part of this evaluation, EPA reviews the process or treatment
conditions that may have resulted in extreme values (high and low). As a consequence of this
review, EPA may exclude data associated with certain time periods or other data outliers that
reflect poor performance or analytical anomalies by an otherwise well-operated site.
The fourth criterion also is applied in EPA's review of data corresponding to the start-up
or initial commissioning period for treatment systems. Most industries incur commissioning
periods associated with installing new treatment systems to acclimate and optimize the system.
During this acclimation and optimization process, the effluent concentration values tend to be
highly variable with occasional extreme values (high and low). This occurs because the treatment
13-2
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Section 13- Limitations and Standards: Data Selection and Calculation
system typically requires some "tuning" as the plant staff and equipment and chemical vendors
work to determine the optimum chemical addition locations and dosages, vessel hydraulic
residence times, internal treatment system recycle flows (e.g., filter backwash frequency,
duration and flow rate; return flows between treatment system components), and other
operational conditions including clarifier sludge wasting protocols. It may also take several
weeks or months for treatment system operators to gain expertise on operating the new treatment
system, which also contributes to treatment system variability during the commissioning period.
After this initial adjustment period, the systems should operate at steady state with relatively low
variability around a long-term average over many years. Because commissioning periods
typically reflect one-time operating conditions unique to the first time the treatment system
begins operation, EPA generally excludes such data in developing the limitations.105
13.1.2 Data Selection for Each Technology Option
This section discusses the data selected for use in developing the limitations for each
pollutant for each technology option. This section includes an abbreviated description of the
technology options. See Section 8.1.2 for a more complete discussion of the technology basis of
the options considered.
For fly ash transport water and flue gas mercury control (FGMC) wastewater, all of the
preferred regulatory options propose zero discharge of pollutants based on dry handling
technologies; therefore, no effluent concentration data were used to set the limitations for these
wastestreams.106 This is also true for the regulatory options that include zero discharge of
pollutants for any set of dischargers for bottom ash. For nonchemical metal cleaning wastes,
EPA is proposing to establish limitations that are equal to the current BPT limitations that apply
to discharges of nonchemical metal cleaning wastes from existing sources that are direct
dischargers. No new effluent concentration data were used to set the effluent limitations for
nonchemical metal cleaning wastes in this rulemaking, therefore, the limitations for this
wastestream are not discussed in this section. For combustion residual leachate (hereafter
referred to in this section as leachate) limitations based on the chemical precipitation technology
option, EPA is proposing to transfer the limitations calculated based on the chemical
precipitation technology option for FGD wastewater because EPA does not have available
effluent data for leachate from plants employing the chemical precipitation technology. For the
limitations based on the biological treatment technology option for FGD wastewater, EPA is
105 Examples of conditions that are typically unique to the initial commissioning period include operator
unfamiliarity or inexperience with the system and how to optimize its performance; wastewater flow rates that differ
significantly from engineering design, altering hydraulic residence times, chemical contact times, and/or clarifier
overflow rates, and potentially causing large changes in planned chemical dosage rates or the need to substitute
alternative chemical additives; equipment malfunctions; fluctuating wastewater flow rates or other dynamic
conditions (i.e., not steady state operation); and initial purging of contaminants associated with installation of the
treatment system, such as initial leaching from coatings, adhesives, and susceptible metal components. These
conditions differ from those associated with the restart of an already-commissioned treatment system, such as may
occur from a treatment system that has undergone either short or extended duration shutdown.
1 °6 EPA also considered a technology option that would require zero discharge of pollutants in bottom ash transport
water. This technology option would be based on bottom ash handling practices that do not use water to carry the
ash away from the boiler or that operate wet sluicing systems as closed-loop systems that do not discharge
wastewater; therefore, no effluent concentration data would be used to set a zero discharge limitation for bottom ash
transport water.
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proposing to transfer the limitations for two pollutants (arsenic and mercury) calculated based on
the chemical precipitation technology option for the FGD wastewater for the reasons described
in Section 13.7.2. See Section 13.7 for a detailed discussion of the transfer of limitations.
Under some regulatory options being proposed, EPA would establish limitations for
certain wastewater discharges that are equal to current BPT limitations for those dischargers. No
new effluent concentration data would be used to establish BAT/NSPS limitations that are set
equal to BPT, therefore, such limitations are not discussed in this section. See Section 8 for a
more complete discussion of the basis for the proposed regulatory options.EPA used specific
data sources to set the limitations for the different FGD wastewater treatment technologies and
for gasification wastewater treatment. The data sources used to calculate effluent limitations for
each technology option are described below.
FGD Wastewater
As part of the EPA sampling program and additional plant self-monitoring data EPA
obtained during the rulemaking, EPA evaluated the performance of 10 FGD wastewater
treatment systems. For seven of the 10 systems, EPA collected data representing the influent and
effluent for chemical precipitation treatment system. EPA evaluated these seven systems and
determined that the systems operating the chemical precipitation system with both hydroxide and
sulfide precipitation achieved better removals of mercury compared to the plants that used only
hydroxide precipitation. Therefore, EPA did not use data from the three plants that use only
hydroxide precipitation. Four of the seven plants use hydroxide and sulfide precipitation;
however, one of the plants operates a two-stage chemical precipitation system. Because EPA's
basis for the technology option is a one-stage system, EPA did not use the data from the two-
stage system in developing the limitations.10? Therefore, EPA used data from the following three
plants to develop the limitations based on treatment of FGD wastewater using the chemical
precipitation technology option (i.e., one-stage chemical precipitation system employing both
hydroxide and sulfide precipitation and iron coprecipitation, as well as flow reduction at plants
with large FGD wastewater flow rates, hereafter referred to in this section as "chemical
precipitation"- see Section 8.1.2.1 above for a more detailed description):
• Duke Energy's Miami Fort Station (hereafter referred to as Miami Fort);
• RRI Energy's Keystone Generating Station (hereafter referred to as Keystone); and
• Allegheny Energy's Hatfield's Ferry Power Station (hereafter referred to as Hatfield's
Ferry).
For the treatment of FGD wastewater using a system that also includes a biological
treatment system (chemical precipitation system followed by anoxic/anaerobic biological
treatment to remove selenium, hereafter referred to as "biological treatment"), EPA evaluated the
107 Based on data EPA has evaluated for the steam electric industry and other industry sectors, two-stage chemical
precipitation systems generally achieve better pollutant removals than one-stage systems. Since the technology basis
for chemical precipitation treatment of FGD wastewater in the proposed rule is a one-stage system and that is the
configuration used to estimate compliance costs, EPA concluded that effluent data for the two-stage system
(Pleasant Prairie) should not be used when calculating effluent limits for the technology option.
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treatment systems that include biological treatment at three power plants as part of the EPA
sampling program.108 EPA determined that one of the biological treatment systems was not
designed for effective removal of selenium and does not represent the model technology.
Because EPA's basis for the technology option includes anoxic/ anaerobic biological treatment
to remove selenium, EPA did not use data from this system in developing the limitations.
Therefore, EPA used data from the following two plants to develop the limitations and
standards for the treatment of FGD wastewater using a one-stage chemical precipitation system
followed by biological treatment:109
• Duke Energy Carolina's Belews Creek Steam Station (hereafter referred to as Belews
Creek); and
• Duke Energy Carolina's Allen Steam Station (hereafter referred to as Allen).
For the treatment of FGD wastewater using chemical precipitation followed by a vapor-
compression evaporation system, hereafter referred to as a "vapor-compression evaporation"
system (which is the technology serving as the basis for Regulatory Option 5), EPA evaluated
three systems as part of the EPA sampling program. One plant operates a system that is similar to
the technology basis for the FGD wastewater limitations in the proposed rule: a one-stage
chemical precipitation system followed by softening and a vapor-compression evaporation
system. EPA used the data from this plant to develop the limitations based on the vapor-
compression evaporation technology for the treatment of the FGD wastewater. That plant is
Enel's Federico II Power Plant, located in Brindisi, Italy (hereafter referred to as Brindisi). EPA
used data from a second plant for characterization purposes and not for limitations development
because it only collected effluent data for one day from the plant. The third system does not
represent the technology serving as the basis for the vapor-compression evaporation option, and
was not used for the limitations development. This plant operates a solids removal process prior
to the vapor-compression evaporation system but includes neither a full chemical precipitation
system nor a softening step. Furthermore, this plant also operates a one-stage evaporation system
and instead of employing a second stage of evaporation to crystallize and remove salts and other
pollutants from the concentration brine, mixes the brine with fly ash and sends it to the landfill
for disposal.
Gasification Wastewater
For the treatment of gasification wastewater using a vapor-compression evaporation
system EPA evaluated systems from the following two plants as part of the EPA sampling
program:
• Tampa Electric Company's Polk Station (hereafter referred to as Polk); and
108 In the remainder of this section, the term "biological treatment" refers to chemical precipitation/iron
coprecipitation (with both hydroxide and sulfide precipitation) followed by anoxic/anaerobic biological treatment.
109 The limitations for arsenic and mercury for the biological (chemical precipitation followed by anoxic/anaerobic
biological treatment) technology option were transferred from chemical precipitation technology option. See Section
13.7.2 for a detailed discussion of the transfer of the limitations.
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• Wabash Valley Power Association's Wabash River Station (hereafter referred to as
Wabash River).
Both systems are representative of the system used as the basis for the technology option
and were used in calculating the limitations.
13.1.3 Combining Data from Multiple Sources within a Plant
Typically, if sampling data from a plant were collected over two or more distinct time
periods, EPA analyzes the data from each time period separately. In past ELG rulemakings,
where appropriate, EPA has analyzed the data as if each time period represents a different plant
since these data can represent different operating conditions due to changes in management,
personnel, and procedures. On the other hand, when EPA obtains the data (such as EPA
sampling and plant self-monitoring data) from a plant during the same time period, EPA
typically combines the data from these sources into a single dataset for the plant for the statistical
analyses.
For this rulemaking, data for most of the plants came from multiple sources such as EPA
sampling, CWA 308, or plant self-monitoring. For three plants (Allen, Belews Creek, and
Hatfi eld's Ferry), the multiple sources of the data were collected during overlapping time
periods, thus, EPA combined these data into a single dataset for the plant. For two plants
(Keystone and Miami Fort), the multiple sources of the data were collected during non-
overlapping time periods. However, in these instances the time period between the non-
overlapping data collection periods was relatively small (two months). Furthermore, EPA has no
information to indicate that the data represent different operating conditions. Thus, EPA also
combined the multiple sources of data for each of these plants into a single dataset for the plant.
This approach is consistent with EPA's traditional approach for other effluent guidelines
rulemakings. Three plants (Brindisi, Polk, and Wabash River) had data from a single source, and
for these plants it was not necessary to combine data. For a listing of all the data and their
sampling sources for each of the plants, see the document entitled, "Sampling Data Used as the
Basis for Effluent Limitations for the Steam Electric Rulemaking." [U.S. EPA, 2012c].
13.2 DATA EXCLUSIONS AND SUBSTITUTIONS
The sections below describe the data exclusions and substitutions. Other than the data
exclusions described in this section and the data excluded due to failing the data editing criteria
(described in Section 13.4), EPA used all the data from the plants presented in Section 13.1.2.
13.2.1 Data Exclusions
Following EPA's selection of the model plant(s), EPA applied the criteria described
above in Section 13.1.1 by thoroughly evaluating all available data for each model plant. EPA
identified certain data that warranted exclusion from calculating the limitations because: (i)
samples were analyzed using an insufficiently-sensitive analytical method (i.e., use of EPA
Method 245.1 instead of Method 163 IE for mercury); (ii) the samples were collected during
initial commissioning period for the treatment system; or (iii) the analytical results were
identified as questionable due to quality control issues, abnormal conditions or treatment upsets,
or were analytical anomalies. See the memorandum entitled "Effluent Limitations for FGD
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Wastewater, Gasification Wastewater, and Combustion Residual Leachate for the Proposed
Effluent Limitations Guidelines and Standards for the Steam Electric Rulemaking" for a detailed
discussion of the data that were excluded and a listing of the data excluded [U.S. EPA, 2012a].
13.2.2 Data Substitutions
In general, EPA used detected values or sample-specific detection limits (for non-
detected values) in calculating the limitations.110 However, there were some instances where
EPA substituted a baseline value for a detected value or a sample-specific detection limit. The
baseline value was used in the calculations to account for the possibility that certain a detected
result may be at a lower concentration than can be reliably achieved by well-operated
laboratories. This approach is consistent with the way EPA has calculated limitations in previous
effluent guidelines rulemakings. After excluding all the necessary data as described in Section
13.2.1, EPA compared each reported result to a baseline value. When a detected value or sample-
specific detection limit (i.e., sample specific quantitation limit) was lower than the baseline
value, EPA used the baseline value instead and classified the value as non-detected (even if the
actual reported result was a detected value). For example, if the baseline value was 10 ug/L and
the laboratory reported a detected value of 5 ug/L, EPA's calculations would treat the sample
result as being non-detected with a sample-specific detection limit of 10 ug/L.
EPA used the following baseline values for each pollutant in the development of the
effluent limitations for the steam electric rulemaking:
• Arsenic: 2 ug/L;
• Mercury: 0.5 ng/L;
• Nitrate-nitrite as N: 0.05 mg/L;
• Selenium: 5 ug/L; and
• TDS: 10 mg/L.
EPA determined the baseline values for mercury, nitrate-nitrite as N, and TDS using the
minimum levels (MLs) established by the analytical methods used to obtain the reported values
or a comparable analytical method where an ML was not specified by the method.111 The
baseline values for arsenic and selenium are based on the results of method detection limit
(MDL) studies conducted by well-operated commercial laboratories using EPA Method 200.8 to
analyze samples of synthetic FGD wastewater. [CSC, 2013]
110 For the purpose of the discussion of the calculation of the long-term averages, variability factors, and effluent
limitations, the term "detected" refers to analytical results measured and reported above the sample-specific
quantitation limit (QL). The term "non-detected" refers to values that are below the method detection limit (MDL)
and also those measured by the laboratory as being between the MDL and the quantitation limit in the original data
(before adjusting for baseline).
111 The baseline values for mercury and nitrate-nitrite as N are equal to the MLs specified in EPA Methods 163 IE
and 353.2, respectively. The method EPA used to analyze for TDS (Standard Method 2540C) does not explicitly
state a MDL or ML. However, EPA Method 160.1 is similar to Standard Method 2540C and the lower limit of its
measurement range is 10 mg/L (i.e., the nominal quantitation limit). Thus, EPA used 10 mg/L as the baseline value
for TDS.
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In addition to calculating the limitations for each pollutant for each technology option
adjusting for the baseline values, as described above, EPA also performed additional calculations
to determine what the limitations would be using all valid reported results (i.e., without
substituting baseline values and/or changing the classification of the result). The purpose of
calculating the limitations using the data as reported is to allow a comparison between the
limitations using baseline substitution and the limitations that would be obtained without the use
of baseline substitution. For a detailed discussion of these calculations and the results, see the
memorandum entitled, "Assessment of Effluent Limitations and Standards with No Baseline
Substitution for the Steam Electric Rulemaking" [U.S. EPA, 2012b].
13.3 DATA AGGREGATION
EPA used daily values in developing the limitations. In cases with at least two samples
per day, EPA mathematically aggregated these samples to obtain a single value for that day (the
procedure to aggregate the samples is described in subsections below). For the sampling data
used in this rulemaking, there are instances when there are multiple sample results available for a
given day. This occurred with field duplicates, overlaps between plant self-monitoring and EPA
sampling, or overlaps between plant self-monitoring and CWA 308 sampling.
When aggregating the data, EPA took into account whether each value was detected (D)
or non-detected (ND). Measurements reported as being less than the sample-specific detection
limit (or baseline values, as appropriate) are designated as non-detected (ND) for the purpose of
statistical analyses to calculate the limitations. In the tables and data listings in this document and
in the rulemaking record, EPA uses the indicators D and ND denote the censoring type for
detected and non-detected values, respectively.
The subsections below describe each of the different aggregation procedures. They are
presented in the order that the aggregation was performed; i.e., field duplicates were aggregated
first and then any overlaps between plant self-monitoring and EPA sampling data or CWA 308
sampling were aggregated.
13.3.1 Aggregation of Field Duplicates
During the EPA sampling episodes, EPA collected field duplicate samples as part of the
quality assurance/quality control activities undertaken to ensure that the quality of the data
collected is appropriate for their intended use. Field duplicates are two samples collected for the
same sampling point at approximately the same time. The duplicates are assigned different
sample numbers, and they are flagged as duplicates for a single sampling point at a plant.
Because the analytical data from a duplicate pair are intended to characterize the same conditions
at a given time at a single sampling point, EPA averaged the data to obtain one value for each
duplicate pair.
In most cases, both duplicates in a pair had the same censoring type, so the censoring
type of the aggregated value was the same as that of the duplicates. In some instances, one
duplicate was a detected (D) value and the other duplicate was a non-detected (ND) value. When
this occurred, EPA determined that the aggregated value should be treated as detected (D)
because the pollutant is confirmed to be present at a level above the sample-specified detection
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limit in one of the duplicates. The document entitled "Sampling Data Used as the Basis for
Effluent Limitations for the Steam Electric Rulemaking" lists the data before the aggregation as
well as after the aggregation [U.S. EPA, 2012c].
Table 13-1 below summarizes the procedure for aggregating the sample measurements
from the field duplicates. The aggregation of the duplicate pairs was the first step in the
aggregation procedures for both influent and effluent measurements.
Table 13-1. Aggregation of Field Duplicates
If the Field
Duplicates Are:
Both Detected
Both Non-Detected
One Detected and
One Non-Detected
Censoring Type
of Average Is:
D
ND
D
Value of the Aggregate Is:
Arithmetic average of measured values.
Arithmetic average of sample -specific
detected limits (or baseline).
Arithmetic average of measured value and
sample -specific detection limit (or baseline).
Formulas for Aggregate
Values of Duplicates
(Dj + D2)/2
(DLj + DL2)/2
(D + DL)/2
D - detected.
ND - non-detected.
DL - sample-specific detection limit.
13.3.2 Aggregation of Overlapping Samples
At the Allen and Belews Creek plants, sampling data were available from EPA sampling,
CWA 308 sampling, and plant self-monitoring. As explained in Section 13.1.3 above, there was
some overlap between the data from these sources. On some days at a given plant, samples were
available from two sources, specifically, plant self-monitoring and either EPA sampling or CWA
308 sampling. When these overlaps occurred, EPA aggregated the measurements from the
available samples to obtain one value for that day. The document entitled "Sampling Data Used
as the Basis for Effluent Limitations for the Steam Electric Rulemaking" lists the data before the
aggregation as well as after the aggregations [U.S. EPA, 2012c].
The procedure averaged the measurements to obtain a single value for that day. When
both measurements had the same censoring type, then the censoring type of the aggregate was
the same as that of the overlapping values. When one or more measurements were detected (D),
EPA determined that the appropriate censoring type of the aggregate was detected because the
pollutant is confirmed to be present at a level above the sample-specific detection limit in one of
the samples. The procedure for obtaining the aggregated value and censoring type is similar to
the procedure shown in Table 13-1.
13.4 DATA EDITING CRITERIA
After excluding and aggregating the data, EPA applied data editing criteria on a
pollutant-by-pollutant basis to select the datasets to be used for developing the limitations for
each technology option. These criteria are referred to as the long-term average test (or LTA test).
EPA established the LTA test to ensure that the pollutants were present in the influent at
sufficient concentrations to evaluate treatment effectiveness at the plant. The influent first had to
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pass a basic requirement that 50% of the influent measurements for the pollutants had to be
detected at any concentration. If the dataset at a plant passed the basic requirement, then the data
had to pass one of the following two criteria to pass the LTA test:
• Criterion 1. At least 50% of the influent measurements in a dataset at a plant were
detected at levels equal to or greater than 10 times the baseline value (described in
Section 13.2.2).
• Criterion 2. At least 50% of the influent measurements in a dataset at a plant were
detected at any concentration and the influent arithmetic average was equal to or
greater than 10 times the baseline value (described in Section 13.2.2).
If the dataset at a plant failed the basic requirement, then EPA automatically set both
Criteria 1 and 2 to "fail". If the dataset for a plant failed the basic requirement, or passed the
basic requirement but failed both criteria, EPA would exclude the plant's effluent data for that
pollutant when calculating limitations. Through the application of the LTA test, EPA ensures
that the limitations result from treatment of the wastewater and not simply the absence or
substantial dilution of that pollutant in the wastestream.
After performing the LTA test for all the pollutants at each plant that was selected as the
basis for the limitations for this rulemaking, it was found that all the datasets passed the LTA test
except for arsenic and mercury data at Wabash River. Thus, data for arsenic and mercury at
Wabash River were excluded from the calculation of the long-term average, variability factors,
and limitations. See the memorandum entitled, "Effluent Limitations for FGD Wastewater,
Gasification Wastewater, and Combustion Residual Leachate for the Proposed Effluent
Limitations Guidelines and Standards for the Steam Electric Rulemaking" for the results of the
LTA test for each pollutant at each plant [U.S. EPA, 2012a].
13.5 OVERVIEW OF LIMITATIONS
The preceding sections discussed the data selection, data exclusions and substitutions,
data aggregation as well as the data editing procedures that EPA used to obtain the daily values
for its calculations. This section describes EPA's objectives for the daily maximum and monthly
average effluent limitations, the selection of percentiles for those limitations, and compliance
with the limitations.
13.5.1 Objectives
EPA's objective in establishing daily maximum limitations is to restrict the discharges on
a daily basis at a level that is achievable for a plant that targets its treatment at the long-term
average. EPA acknowledges that variability around the long-term average occurs during normal
operations. This variability means that plants may discharge at a level that is higher (or lower)
than the long-term average. To allow for these possibly higher daily discharges, EPA has
established the daily maximum limitation. A plant that consistently discharges at a level near the
daily maximum limitation would not be operating its treatment to achieve the long-term average.
Targeting treatment to achieve the daily maximum limitations, rather than the long-term average,
may result in values that frequently exceed the limitations due to routine variability in treated
effluent.
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EPA's objective in establishing monthly average limitations is to provide an additional
restriction to help ensure that plants target their average discharges to achieve the long-term
average. The monthly average limitation requires dischargers to provide on-going control, on a
monthly basis, that supplements controls imposed by the daily maximum limitation. In order to
meet the monthly average limitation, a plant must counterbalance a value near the daily
maximum limitation with one or more values well below the daily maximum limitation. To
achieve compliance, these values must result in a monthly average value at or below the monthly
average limitation.
13.5.2 Selection of Percentiles
EPA calculates effluent limitations based upon percentiles that should be both high
enough to accommodate reasonably anticipated variability within control of the plant, and low
enough to reflect a level of performance consistent with the Clean Water Act requirement that
these effluent limitations be based on the "best" available technologies. The daily maximum
limitation is an estimate of the 99th percentile of the distribution of the daily measurements. The
monthly average limitation is an estimate of the 95th percentile of the distribution of the monthly
averages of the daily measurements. The percentiles for both types of effluent limitations are
estimated using the products of long-term averages and variability factors.
EPA uses the 99th and 95th percentiles to draw a line at a definite point in the statistical
distributions that would ensure that operators work to establish and maintain the appropriate
level of control. These percentiles reflect a longstanding Agency policy judgment about where to
draw the line. The development of the limitations takes into account the reasonable anticipated
variability in discharges that may occur at a well-operated plant. By targeting its treatment at the
long-term average, a well-operated plant should be capable of complying with the effluent
limitations at all times because EPA has incorporated an appropriate allowance for variability in
the limitations.
In conjunction with setting the limitations as described above, EPA performs an
engineering review to verify that the limitations are reasonable based upon the design and
expected operation of the control technologies and the plant process conditions. As part of the
review, for each plant EPA compared the influent and effluent measurements with the
limitations. See Section 13.8 below for details of these comparisons for each pollutant at each
plant, as well as a discussion of the findings of the engineering review.
13.5.3 Compliance with Limitations
EPA promulgates limitations with which plants are capable of complying at all times by
properly operating and maintaining their processes and treatment technologies. Commenters
often raise the issue of exceedances or excursions (i.e., values that exceed the limitations) on
limitations.
This issue was, in fact, raised in other rulemakings, including EPA's Organic Chemicals,
Plastics, and Synthetic Fibers (OCPSF) rulemaking. EPA's general approach there for
developing limitations based on percentiles is the same in this rule, and was upheld in the court
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ruling of Chemical Manufacturers Association v. U.S. Environmental Protection Agency, 870
F.2d 177, 230 (5th Cir. 1989). The Court determined that:
EPA reasonably concluded that the data points exceeding the 99th and 95th percentiles
represent either quality-control problems or upsets because there can be no other
explanation for these isolated and extremely high discharges. If these data points
result from quality-control problems, the exceedances they represent are within the
control of the plant. If, however, the data points represent exceedances beyond the
control of the industry, the upset defense is available.
Id at 230.
This issue was raised also in EPA's Phase I rule for the pulp and paper industry. In that
rulemaking, EPA used the same general approach for developing limitations based on percentiles
that it had used for the OCPSF rulemaking and for this proposed rule. This approach for the
monthly average limitation was upheld in National Wildlife Federation, et al v. Environmental
Protection Agency, No. 99-1452, Slip Op. at Section HID (D.C. Cir.) (April 19, 2002). The
Court determined that:
EPA's approach to developing monthly limitations was reasonable. It established
limitations based on percentiles achieved by plants using well-operated and controlled
processes and treatment systems. It is therefore reasonable for EPA to conclude that
measurements above the limitations are due to either upset conditions or deficiencies
in process and treatment system maintenance and operation. EPA has included an
affirmative defense that is available to mills that exceed limitations due to an
unforeseen event. EPA reasonably concluded that other exceedances would be the
result of design or operational deficiencies. EPA rejected Industry Petitioners' claim
that facilities are expected to operate processes and treatment systems so as to violate
the limitations at some pre-set rate. EPA explained that the statistical methodology
was used as a framework to establish the limitations based on percentiles. These
limitations were never intended to have the rigid probabilistic interpretation that
Industry Petitioners have adopted. Therefore, we reject Industry Petitioners' challenge
to the effluent limitations.
As the Court recognized, EPA's allowance for reasonably anticipated variability in its
effluent limitations, coupled with the availability of the upset defense, reasonably accommodates
acceptable excursions. Any further excursion allowances would go beyond the reasonable
accommodation of variability and would jeopardize the effective control of pollutant discharges
on a consistent basis. Further excursion allowances also could bog down administrative and
enforcement proceedings in detailed fact finding exercises, contrary to Congressional intent. See,
e.g., Rep. No. 92-414, 92d Congress, 2d Sess. 64, reprinted in_A Legislative History of the Water
Pollution Control Act Amendments of 1972 at 1482; Legislative History of the Clean Water Act
of 1977 at 464-65.
More recently, for EPA's rule for the iron and steel industry, EPA's selection of
percentiles was upheld in American Coke and Coal Chemicals Institute v. Environmental
Protection Agency, 452 F.3d 930, 945 (D.C. Cir. 2006).
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EPA expects that plants will comply with promulgated limitations at all times. If an
exceedance is caused by an upset condition, the plant would have an affirmative defense to an
enforcement action if the requirements of 40 CFR 122.41(n) are met. If the exceedance is caused
by a design or operational deficiency, then EPA has determined that the plant's performance
does not represent the appropriate level of control. For promulgated limitations and standards,
EPA has determined that such exceedances can be controlled by diligent process and wastewater
treatment system operational practices such as frequent inspection and repair of equipment, use
of back-up systems, and operator training and performance evaluations.
13.6 CALCULATION OF THE LIMITATIONS
EPA calculated the limitations by multiplying the long-term average by the appropriate
variability factors. In estimating the limitations for a pollutant, EPA first calculates an average
performance level (the option long-term average discussed below) that a plant with well-
designed and well-operated model technologies is capable of achieving. This long-term average
is calculated using data from the plant or plants with the model technologies for the option.
In the second step of developing a limitation for a pollutant, EPA determines an
allowance for the variation (the option variability factor discussed below) in pollutant
concentrations for wastewater that has been processed through well-designed and well-operated
treatment systems. This allowance for variation incorporates all components of variability
including shipping, sampling, storage, and analytical variability. This allowance is incorporated
into the limitations through the use of the variability factors which are calculated from the data
from the plants using the model technologies. If a plant operates its treatment system to meet the
relevant long-term average, EPA expects the plant will be able to meet the limitations.
Variability factors ensure that normal fluctuations in a plant's treatment are accounted for in the
limitations. By accounting for these reasonable excursions above the long-term average, EPA's
use of variability factors results in effluent limitations that are generally well above the long-term
averages.
The following sections describe the calculation of the option long-term averages, option
variability factors and limitations, and the adjustment made for autocorrelation in the calculation
of the limitations for each pollutant proposed for regulation.
13.6.1 Calculation of Option Long-Term Average
EPA calculated the option long-term average for a pollutant using two steps. First, EPA
calculated the plant-specific long-term average for each pollutant that had enough distinct
detected values by fitting a statistical model to the daily concentration values. In cases when a
dataset for a specific pollutant did not have enough distinct detected values, then the statistical
model was not used to obtain the long-term average. In these cases, the plant-specific long-term
average for each pollutant was the arithmetic mean of the available daily concentration values.
Appendix B contains the required minimum number of distinct detected observations and an
overview of the statistical model and a description of the procedures EPA used to estimate the
plant-specific long-term average.
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Second, EPA calculated the option long-term average for a pollutant as the median of the
plant-specific long-term averages for that pollutant. The median is the midpoint of the values
when ordered (i.e., ranked) from smallest to largest. If there is an odd number of values, then the
value of the m' ordered observation is the median (where m=(n+l)/2 and n=number of values).
If there are an even number of values, then the median is the average of the two values in the
n/2th and [(n/2)+l]//2 positions among the ordered observations.
13.6.2 Calculation of Option Variability Factors and Limitations
The following describes the calculations performed to obtain the option variability factors
and limitations. First, EPA calculated the plant-specific variability factors for each pollutant that
had enough distinct detected values by fitting a statistical model to the daily concentration
values. Each plant-specific daily variability factor for each pollutant is the estimated 99th
percentile of the distribution of the daily concentration values divided by the plant-specific long-
term average. Each plant-specific monthly variability factor for each pollutant is the estimated
95th percentile of the distribution of the 4-day average concentration values divided by the plant-
specific long-term average. The calculation of the plant-specific monthly variability factor
assumes that the monthly averages are based on the pollutant being monitored weekly
(approximately four times each month). In cases when there were not enough distinct detected
values for a specific pollutant, then the statistical model was not used to obtain the variability
factors. In these cases, the data for the pollutant at the plant was excluded from the calculation of
the option variability factors. Appendix B contains the required minimum number of distinct
detected observations and a description of the procedures used to estimate the plant-specific
daily and monthly variability factors.
Second, EPA calculated the option daily variability factor for a pollutant as the mean of
the plant-specific daily variability factors for that pollutant. Similarly, the option monthly
variability factor was the mean of the plant-specific monthly variability factors for that pollutant.
Finally, the daily maximum limitations for each pollutant for each technology option are
the product of the option long-term average and option daily variability factors. The monthly
average limitations for each pollutant for each technology option are the product of the option
long-term average and option monthly variability factors.
13.6.3 Adjustment for Autocorrelation Factors
Effluent concentrations that are collected over time may be autocorrelated. The data are
positively autocorrelated when measurements taken at specific time intervals, such as one or two
days apart, are similar. For example, positive autocorrelation would occur if the effluent
concentration were relatively high one day and were likely to remain high on the next and
possibly succeeding days. Because the autocorrelated data affect the true variability of treatment
performance, EPA typically adjusts the variance estimates for the autocorrelated data, when
appropriate.
For this rulemaking, whenever there was sufficient data for a pollutant at a plant to
evaluate the autocorrelation reliably, EPA estimated the autocorrelation and incorporated it into
the calculation of the limitations. For a plant without enough data to reliably evaluate and obtain
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Section 13- Limitations and Standards: Data Selection and Calculation
an estimate of the autocorrelation, EPA set the autocorrelation to zero in calculation of the
limitations. EPA did so because there were not sufficient data to reliably evaluate the
autocorrelation, nor did EPA have a valid correlation estimate available that could be transferred
from a similar technology and wastestream. See the memorandum entitled, "Serial Correlations
for Steam Electric With and Without Adjustment for Baseline Values" for details of the
statistical methods and procedures EPA used to determine the autocorrelation values, as well as a
detailed discussion of the minimum number of observations needed to obtain a reliable estimate
of the autocorrelation [Westat, 2013]. The following paragraphs describe the instances where
EPA was able to obtain an estimated autocorrelation and the assumptions made about the
autocorrelation when there were too few observations to estimate the autocorrelation.
For the biological treatment technology for FGD wastewater (represented by Allen and
Belews Creek plants), EPA was able to perform a statistical evaluation of the autocorrelation and
obtain a reliable estimate of the autocorrelation because several years of data were available for
these plants. As a result of the evaluation, EPA determined that adjustments for autocorrelation
should be incorporated into the limitations for the biological treatment technology option. Table
13-2 below lists the autocorrelation values EPA used in the calculation of the limitations for
nitrate-nitrite as N and selenium. No autocorrelation values are presented here for arsenic and
mercury since EPA transferred the limitations from chemical precipitation technology option for
FGD for these pollutants (see Section 13.7.2 for a detailed discussion of the transfer of these
limitations).
Table 13-2. Summary of Autocorrelation Values Used in Calculating the
Limitations for Biological Treatment Technology Option for FGD Wastewater
Pollutant
Selenium
Nitrate-nitrite as N a
Correlation Value Used for Limit Calculations
0.291
a - There were only eight observations available for nitrate-nitrite as N (only EPA sampling and CWA 308 sampling
data available) at Allen and Belews Creek, so EPA was not able to evaluate the autocorrelation. EPA transferred the
autocorrelation from selenium since these two chemicals behave similarly in the biological treatment system.
For the chemical precipitation treatment option for FGD wastewater (represented by
Hatfield's Ferry, Keystone, and Miami Fort plants), for the vapor-compression evaporation
treatment technology option for FGD wastewater (represented by Brindisi), and for the vapor-
compression evaporation treatment technology option for gasification wastewater (represented
by Polk and Wabash River), EPA was unable to perform an evaluation and obtain a reliable
estimate of the autocorrelation because there were too few observations available at the plants.
Thus, for these plants, EPA set the autocorrelation to zero in the calculation of the limits. EPA
did so because there were not sufficient data to reliably evaluate the autocorrelation, nor did EPA
have a valid correlation estimate available that could be transferred from a similar technology
and wastestream.
13.7 TRANSFERS OF THE LIMITATIONS
In some cases, EPA was either unable to calculate the limitations since there was no data
available for the treatment technology option or determined that the treatment provided by plants
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Section 13- Limitations and Standards: Data Selection and Calculation
employing the technology option did not fully represent the performance achievable by proper
operation of all components of the model technologies. In these cases, EPA transferred
limitations from another technology option. The following sections describe each case in which
the limitations were transferred.
13.7.1 Transfer of Arsenic and Mercury Limitations from Chemical Precipitation to
Leachate
The effluent limitations for leachate based on the chemical precipitation technology
option are transferred from the chemical precipitation technology option for FGD wastewater
because EPA does not have the available effluent data for leachate from the plants that employ
the chemical precipitation technology. This transfer of limitations for arsenic and mercury is
appropriate because the pollutants in leachate are similar to those in FGD wastewater except at
lower concentrations. The use of chemical precipitation technology to remove arsenic and
mercury has been extensively demonstrated for a wide variety of industrial wastewaters
including leachate from other industrial landfills. Because of the similarities between leachate
and FGD wastewater, plants employing chemical precipitation treatment technology for leachate
wastewater should be able to comply with the proposed limitations.
13.7.2 Transfer of Arsenic and Mercury Limitations from Chemical Precipitation to
Biological Treatment for FGD Wastewater
EPA is transferring the FGD wastewater effluent limitations for arsenic and mercury
calculated for the chemical precipitation technology option to the biological treatment
technology option. This transfer of limitations for arsenic and mercury is appropriate because the
plants represented by the chemical precipitation technology option better reflect the effluent
concentrations that would be attained by the biological technology when it employs all features
in the technology option that work to remove arsenic, mercury and many other metals from the
wastewater. The technology upon which biological treatment is based includes the following:
equalization of the influent wastewater; chemical precipitation/coprecipitation to precipitate and
remove both dissolved and particulate forms of the targeted pollutants (including pH adjustment,
hydroxide precipitation, iron coprecipitation, sulfide precipitation, and clarification/filtration);
and anoxic/anaerobic biological treatment to remove nitrogen (i.e., nitrate-nitrite as N) and both
soluble and insoluble forms of selenium. All of these treatment steps contribute to the mercury
removals achieved by the biological treatment technology although in different ways.
Equalization of the treatment system influent stream acts to reduce the variability of the
untreated wastewater, reducing extreme variations in flow rates and pollutant concentrations. In
doing so, chemical dosage rates in chemical reaction tanks and clarifiers are more closely tuned
to the characteristics of the untreated wastewater and provide the necessary chemistry
adjustments. In addition, physical mixing or settling conditions are not subjected to sudden
extreme fluctuations. The data for the biological treatment technology demonstrates that it is also
effective at removing mercury from FGD wastewater, on the order of as much as 90 percent of
the mercury entering the bioreactor.
EPA evaluated what the limitations for arsenic and mercury would be based on data from
the two plants employing biological treatment: Allen and Belews Creek. Both of these plants
have installed all equipment associated with the model technology; however, while both plants
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Section 13- Limitations and Standards: Data Selection and Calculation
have installed the capability to add organosulfide chemicals to achieve sulfide precipitation of
dissolved mercury in the chemical precipitation stage preceding the bioreactors, neither plant
was dosing the organosulfide chemical during the periods covered by the effluent performance
data. Although hydroxide precipitation may be sufficient for meeting NPDES permit limits for
some plants, plants striving to maximize removals of mercury and other metals will also include
sulfide addition (e.g., organosulfide) as part of the process. Adding sulfide chemicals in addition
to the alkali provides even greater removals of heavy metals due to the very low solubility of
metal sulfide compounds, relative to metal hydroxides. It is for this reason that the technology
basis, for both the chemical precipitation technology option and the biological treatment
technology option, includes the use of hydroxide precipitation, sulfide precipitation, and iron
coprecipitation. Thus, although both Allen and Belews Creek have the technology in place, since
neither was actually adding organosulfide they were not optimizing the pollutant removal
efficacy of the treatment systems. Because of this, the treatment systems are susceptible to
fluctuations in concentrations of dissolved metals, especially mercury, in the FGD wastewater.
When the technology is operated without adding the chemicals for sulfide precipitation, it can be
overwhelmed by high concentrations of dissolved mercury. To the extent these high
concentrations of dissolved mercury pass though the chemical precipitation treatment stage
(which is only partially effective at removing dissolved mercury when sulfide precipitation is not
employed), they can also pass through the biological treatment stage at higher than normal
concentrations even if approximately 90 percent of the mercury entering the bioreactors is
removed. EPA's analysis of the performance data for Allen and Belews Creek shows that
dissolved mercury is not being adequately treated at these plants, which is attributable to the
plants not adding organosulfide. In contrast, the plants used as the basis for the chemical
precipitation technology are all adding organosulfide chemicals and operating the other key
components for the chemical treatment stage for the biological treatment technology. EPA
determined that the data used for chemical precipitation limitations better reflect the treatment
efficacy for mercury and arsenic (and many other metals for which limitations are not being
established) for treatment systems employing chemical precipitation/coprecipitation with both
hydroxide and sulfide precipitation.
As a result, EPA is proposing to establish the biological treatment technology limitations
for arsenic and mercury based on transferring the limitations calculated for chemical
precipitation treatment technology. EPA notes that it is reasonable to expect plants employing
the biological treatment technology to actually achieve even better effluent performance, since
the biological treatment stage will remove additional mercury following the chemical
precipitation upon which the mercury and arsenic limits are now based.
13.8 SUMMARY OF THE LIMITATIONS
Section 13.8.1 provides a summary of the plant-specific long-term averages, plant-
specific daily variability factors, and plant-specific monthly variability factors for each pollutant
in each treatment technology option. Section 13.8.2 provides a summary of the proposed
limitations together with the option long-term average and variability factors for each pollutant
in each treatment technology option.
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Section 13- Limitations and Standards: Data Selection and Calculation
13.8.1 Summary of the Plant-Specific Long-Term Average and Variability Factors
for Each Treatment Technology Option for FGD and Gasification Wastewaters
The plant-specific long-term average and variability factors for each pollutant for each
treatment technology option for FGD and gasification wastewaters are presented below. The
document entitled, "Sampling Data Used as the Basis for Effluent Limitations for the Steam
Electric Rulemaking" contains a listing of the data that were used to calculate the plant-specific
results for each of the technology options [U.S. EPA, 2012c].
Chemical Precipitation Treatment Technology Option for FGD
Table 13-3 presents the plant-specific results (i.e., long-term averages and variability
factors) for chemical precipitation as the technology basis for FGD wastewater. The pollutants
proposed to be regulated under this technology option are arsenic and mercury.
Table 13-3. Plant-Specific Results for Chemical Precipitation as the
Technology Basis for FGD Wastewater
Pollutant
Arsenic (ug/L)
Mercury (ng/L)
Plant Name
Hatfield's Ferry
Keystone
Miami Fort
Hatfield's Ferry
Keystone
Miami Fort
Autocorrelation
Value
0
0
0
0
0
0
Plant-Specific
Long-Term
Average
6.682
4.006 a
4.483
75.404
64.260
168.569
Plant-Specific
Daily Variability
Factor
2.285
b
1.197
4.083
3.257
2.286
Plant-Specific
Monthly Variability
Factor
1.373
b
1.072
1.766
1.584
1.361
a - Long-term average is the arithmetic mean since there were too few detected observations.
b - Nearly all observations were non-detected, so variability factors could not be calculated.
Biological Treatment Technology Option for FGD
Table 13-4 presents the plant-specific results (i.e., long-term averages and variability
factors) for biological treatment for nitrate-nitrite as N and selenium as the technology basis for
FGD wastewater. The pollutants proposed to be regulated under this technology option are
arsenic, mercury, nitrate-nitrite as N, and selenium. As explained in detailed in Section 13.7.2
above, EPA is transferring the limitations for arsenic and mercury from the chemical
precipitation treatment technology for FGD wastewater, thus, the table does not present the
results for arsenic and mercury.
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Section 13- Limitations and Standards: Data Selection and Calculation
Table 13-4. Plant-Specific Results for Biological Treatment as the Technology
Basis for FGD Wastewater
Pollutant
Arsenic (ug/L) a
Mercury (ng/L) a
Nitrate-nitrite as N (mg/L)
Selenium (ug/L)
Plant Name
-
-
Allen
Belews Creek
Allen
Belews Creek
Autocorrelation
Factor
-
-
0.291
0.291
0.291
0.291
Plant-Specific
Long-Term
Average
-
-
0.104b
0.115
5.551
9.359
Plant-Specific
Daily Variability
Factor
~
~
C
1.499
1.627
2.663
Plant-Specific
Monthly
Variability
Factor
~
~
C
1.157
1.192
1.450
a - Option LTA, option variability factors, and effluent limitations were transferred from chemical precipitation
technology option for FGD wastewater.
b - Long-term average is the arithmetic mean since there were too few detected observations.
c - Nearly all observations were non-detected, so variability factors could not be calculated.
Vapor-Compression Evaporation Treatment Technology Option for FGD
EPA based the limitations for the vapor-compression evaporation technology option on
the effluent data at Brindisi. The treatment system for the Brindisi power plant actually produces
two effluent streams: (1) brine concentrator distillate; and (2) crystallizer condensate. Both of
these streams are essentially the condensed steam from different stages of the evaporation
process. At Brindisi, these streams are ultimately recombined in a distillate tank and then reused
at the plant. However, it is possible that a plant may choose to reuse both streams, discharge both
streams, or reuse one stream while discharging the other to surface water. The effluent quality
for the brine concentrator distillate and the crystallizer condensate are not identical. EPA
anticipates that plants employing this treatment technology will often combine the two effluent
streams from the evaporator. EPA considered establishing a single set of effluent limitations
based on the two effluent streams being combined prior to discharge or reuse; however, there is
sufficient uncertainty about the flow rates for each of the streams that preclude establishing a
combined limitation. EPA also considered establishing two sets of effluent limitations, with a
separate set of limitations for each effluent stream. Although this approach is technically
feasible, it would require plants to collect and analyze separate samples for each effluent stream.
EPA does not believe that establishing limitations for both effluent streams is necessary to ensure
the FGD wastewater is being treated to the effluent quality achievable by operation of the
evaporation technology, and that establishing separate limitations for each wastestream is
unnecessarily burdensome. EPA believes a single set of effluent limitations will be sufficient to
ensure the level of control would be achieved, should vapor-compression evaporation be selected
as the technology basis for FGD wastewater. Because the effluent quality of the two effluent
streams is not identical, EPA would establish the limitations based on the stream with the higher
pollutant concentrations: crystallizer condensate. Setting the limitations on the higher
concentration stream is necessary to ensure plants operating a well-designed and well-operated
evaporation system can meet the limitations, regardless of whether they sample the effluent
streams separately or as a combined stream. See the memorandum entitled, "Effluent Limitations
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Section 13- Limitations and Standards: Data Selection and Calculation
for FGD Wastewater, Gasification Wastewater, and Combustion Residual Leachate for the
Proposed Effluent Limitations Guidelines and Standards for the Steam Electric Rulemaking for
the limitations that were calculated for each of the effluent streams discussed above [U.S. EPA,
2012a].
Table 13-5 presents the plant-specific results (i.e., long-term averages and variability
factors) for vapor-compression evaporation treatment as the technology basis for FGD
wastewater. The pollutants proposed to be regulated under this technology option are arsenic,
mercury, selenium, and total dissolved solids (TDS).
Table 13-5. Plant-Specific Results for Vapor-Compression Evaporation
(Crystallizer Condensate) as the Technology Basis for FGD Wastewater
Pollutant
Arsenic (ug/L)
Mercury (ng/L)
Selenium (ug/L)
TDS (mg/L)
Plant Name
Brindisi
Brindisi
Brindisi
Brindisi
Autocorrelation
Value
0
0
0
0
Plant -Specific
Long-Term
Average
4.0 a
17.788
5.0 a
14.884
Plant -Specific
Daily Variability
Factor
b
2.192
b
3.341
Plant - Specific
Monthly Variability
Factor
b
1.338
b
1.572
a - Long-term average is the arithmetic mean since all observations were detected observations.
b - All observations were non-detected, so variability factors could not be calculated.
Vapor-Compression Evaporation Treatment Technology Option for Gasification
Wastewater
In developing the limitations for this technology option, EPA calculated the limitations
using the data from Wabash River and Polk. The treatment system at Wabash River produces
one effluent stream: condensate from vapor compression evaporator. The treatment system for
Polk Power Station actually produces two effluent streams: (1) condensate from the vapor
compression evaporator; and (2) condensate from the forced circulation evaporator. Both of
these streams at Polk are essentially the condensed steam from different stages of the evaporation
process. Because it is possible that a plant may choose to reuse both streams, discharge both
streams, or reuse one stream while discharging the other to surface water. EPA considered data
from the following effluent streams when developing the limitations for this technology option:
(i) forced circulation evaporator condensate effluent (based only on Polk); and (ii) vapor
compression evaporator effluent (based on Polk and Wabash River). EPA is proposing the
limitations for this technology option based on vapor compression evaporator effluent data. EPA
decided to propose the limitations based on vapor compression evaporator effluent data since
EPA determined that the data collected at forced circulation evaporator condensate did not
demonstrate typical removal rates for pollutants generally well treated by evaporation and
therefore were not adequate to form the basis of the limitations. Based on its review of the
treatment system, EPA believes that the evaporator (or at a minimum the forced circulation
evaporation stage) was operating abnormally and allowing carryover of pollutant to the
condensate effluent stream. For this reason, EPA based the limitations for this technology option
on the limitations calculated from the vapor compression evaporator effluent data. Table 13-6
presents the plant-specific results (i.e., long-term averages and variability factors) for vapor-
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Section 13- Limitations and Standards: Data Selection and Calculation
compression evaporation treatment as the technology basis for gasification wastewater. The
pollutants proposed to be regulated under this technology option are arsenic, mercury, selenium,
and total dissolved solids (IDS). As explained in Section 13.4, the data for arsenic and mercury
at Wabash River failed the data editing criteria, thus, EPA excluded the arsenic and mercury
datasets from Wabash River when calculating the limitations for this technology option.
Table 13-6. Plant-Specific Results for Vapor-Compression Evaporation
(Vapor-Compression Evaporator Condensate) as the Technology Basis
for Gasification Wastewater
Pollutant
Arsenic (ug/L)
Mercury (ng/L)
Selenium (ug/L)
TDS (mg/L)
Plant Name
Polk
Polk
Polk
Wabash River
Polk
Wabash River
Autocorrelation
Factor
0
0
0
0
0
0
Plant -Specific
Long-Term
Average
4.00 a
1.075
288.430
5.130
16.512
13.906
Plant -Specific Daily
Variability Factor
b
1.632
3.083
b
2.149
2.818
Plant - Specific
Monthly Variability
Factor
b
1.194
1.545
b
1.327
1.450
a - Long-term average is the arithmetic mean since there are too few detected observations.
b - Nearly all observations were non-detected, so variability factors could not be calculated.
13.8.2 Summary of the Option Long-Term Averages, Option Variability Factors,
and Limitations for Each Treatment Technology Option for FGD, Gasification,
and Leachate Wastewaters
This section presents the proposed daily maximum and monthly average limitations, as
well as the option long-term average and variability factors for each pollutant in each of the
treatment technology options for FGD, gasification, and leachate wastewaters. These results
were obtained by combining the plant-specific results in each technology option presented in
Section 13.8.1 (except for leachate wastewater because the limitations for leachate were
transferred). As mentioned above, the option long-term average for each pollutant is the median
of the plant-specific long-term averages. The option variability factor for each pollutant is the
mean of the plant-specific variability factors. The daily limitation for each pollutant is the
product of the option long-term average and option daily variability factor. The monthly average
limitation for each pollutant is the product of the option long-term average and option monthly
variability factor.
The limitations for FGD wastewater based on chemical precipitation followed by vapor-
compression evaporation and the limitations for gasification wastewater based on vapor-
compression are each based on data from one plant. As such, the option long-term averages and
variability factors for these options are the same as the plant-specific long-term averages and
variability factors. Also, in special cases where there are too few detected results, the statistical
models are not appropriate for calculating limitations since reliable estimates could not be
obtained from the models. In such instances, EPA has established the daily maximum limitations
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Section 13- Limitations and Standards: Data Selection and Calculation
119
based on the detection limit (i.e., "minimum level"). Also, monthly average limitations are not
established when the daily maximum limitation is based on the detection limit.
In developing the long-term average and variability factors, EPA used five digit decimal
points for accuracy (but only three digit decimal points are presented in for simplification of the
presentation); however, EPA rounded the limitations upward to allow for more variability during
actual monitoring. In most instances, limitations greater than 1.0 were rounded upward to the
next highest integer, while limitations less than 1.0 were rounded up to the next highest
hundredths decimal place. For gasification wastewater, however, if EPA were to round both
limitations up to the next highest integer, the daily and monthly average limitations for mercury
for gasification wastewater would be the same (i.e., both limits would be 2 ng/L since the pre-
rounded daily and monthly average limitations were calculated to be 1.754 and 1.284,
respectively). Thus, in order to avoid having the same value for the daily and monthly average
limitation, the proposed daily and monthly average limitations for mercury for gasification
wastewater were rounded to next highest hundredths decimal place.
Table 13-7 provides the preferred option long-term average, option variability factors,
and limitations for each of the FGD, gasification, and leachate technology options.
Table 13-7. Proposed Option Long-Term Averages, Option Variability Factors,
and Limitations for Each of the FGD, Gasification, and Leachate Technology Options
Treatment
Technology Option
Chemical Precipitation
for FGD Wastewater
Pollutant
Arsenic (ug/L)
Mercury (ng/L)
Option
Long-
Term
Average
4.483
75.404
Option Daily
Variability
Factor
1.741
3.209
Option
Monthly
Variability
Factor
1.223
1.570
Daily
Maximum
Limitation11
8
242
Monthly
Average
Limitation11
6
119
Chemical Precipitation
and Biological
Treatment
for FGD Wastewater
Arsenic (ug/L) a
Mercury (ng/L) a
Nitrate-nitrite as N
(mg/L)
Selenium (ug/L)
4.483
75.404
0.110
7.455
1.741
3.209
1.499
2.145
1.223
1.570
1.157
1.321
8
242
0.17
16
6
119
0.13
10
Chemical Precipitation
and Evaporation for
FGD Wastewater
Arsenic (ug/L)
Mercury (ng/L)
Selenium (ug/L)
TDS (mg/L)
4.0 b
17.788
5.0 b
14.884
C
2.192
C
3.341
C
1.338
C
1.572
4e
39
5e
50
f
24
f
24
As used in this chapter of this document, "detection limit" refers to the quantitation limit (QL) and not the
method detection limit (MDL). Thus, effluent limitations in those instances would be established as a daily
maximum limit at the quantitation limit.
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Section 13- Limitations and Standards: Data Selection and Calculation
Table 13-7. Proposed Option Long-Term Averages, Option Variability Factors,
and Limitations for Each of the FGD, Gasification, and Leachate Technology Options
Treatment
Technology Option
Vapor-Compression
Evaporation for
Gasification
Wastewater
Pollutant
Arsenic (ug/L)
Mercury (ng/L)
Selenium (ug/L)
TDS (mg/L)
Option
Long-
Term
Average
4.0 b
1.075
146.780
15.209
Option Daily
Variability
Factor
c
1.632
3.083
2.483
Option
Monthly
Variability
Factor
C
1.194
1.545
1.389
Daily
Maximum
Limitation"1
»4e
1.76
453
38
Monthly
Average
Limitation"1
f
1.29
227
22
Chemical Precipitation
for Leachate
Wastewater
Arsenic (ug/L)a
Mercury (ng/L)a
4.483
75.404
1.741
3.209
1.223
1.570
8
242
6
119
a - Option LTA, option variability factors, and limitations were transferred from chemical precipitation technology
option for FGD wastewater.
b - Long-term average is the arithmetic mean since all observations were non-detected.
c - All observations were non-detected, so variability factors could not be calculated.
d - Limitations less than 1.0 are rounded up to the next highest hundredths decimal place. Limitations greater than
1.0 have been rounded upward to the next highest integer, except for limitations for mercury based on the vapor-
compression evaporation treatment technology option for gasification wastewater which have been rounded up to
the next highest hundredths decimal place.
e - Limitation is set equal to the detection limit.
f - Monthly average limitations are not proposed when the daily maximum limitation is based on the detection limit.
13.9 ENGINEERING REVIEW OF THE LIMITATIONS
In conjunction with the statistical methods, EPA performed an engineering review to
verify that the proposed limitations are reasonable based upon the design and expected operation
of the control technologies. The following sections describe two types of comparisons that EPA
performed. First, EPA compared the limitations to the effluent data used to develop the
limitations. Second, EPA compared the limitations to the influent data. For the detailed results of
these comparisons, see the memorandum entitled, "Effluent Limitations for FGD Wastewater,
Gasification Wastewater, and Combustion Residual Leachate for the Proposed Effluent
Limitations Guidelines and Standards for the Steam Electric Rulemaking" [U.S. EPA, 2012a].
13.9.1 Comparison of Limitations to Effluent Data Used As Basis for the Limitations
As part of its data evaluations, EPA compared the value of the limitations to the effluent
values used to calculate the limitations. This type of comparison helps to evaluate how
reasonable the proposed limitations may be from an engineering perspective. Since EPA is
proposing both daily and monthly average limitations, EPA has performed two comparisons for
each pollutant in each technology option. EPA first compared the daily limitations to the daily
effluent values. Second, EPA compared the monthly average limitations to all the effluent daily
values, and identified those months where at least one value within a month exceeded the
monthly average limitations.
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Section 13- Limitations and Standards: Data Selection and Calculation
After thoroughly evaluating the results of the comparison between the limitations and the
effluent values used to calculate the limitations for each treatment technology option for FGD
and gasification wastewaters, EPA determined that the statistical distributional assumptions used
to develop the limitations are appropriate for the data, and thus the limitations for each
technology option are reasonable. (This conclusion is also true for the leachate limitations based
on the chemical precipitation technology since the leachate limitations were transferred from the
FGD wastewater technology option.) If a plant properly designs and operates its wastewater
treatment system to achieve the option long-term average for the model technology (rather than
targeting performance at the effluent limitations themselves), it will be able to comply with the
limitations. The sections below discuss the results of the comparisons for each of the technology
options. See the memorandum entitled, "Effluent Limitations for FGD Wastewater, Gasification
Wastewater, and Combustion Residual Leachate for the Proposed Effluent Limitations
Guidelines and Standards for the Steam Electric Rulemaking" for a listing of all daily effluent
values that exceeded the daily and monthly average limitations for each pollutant in each
treatment technology option [U.S. EPA, 2012a].
Chemical Precipitation Treatment Technology Option for FGD Wastewater
For the chemical precipitation treatment technology option for FGD wastewater, EPA is
proposing limitations for arsenic and mercury. The limitations were calculated using data from
three plants: Hatfield's Ferry, Keystone, and Miami Fort.
For both arsenic and mercury, there are some daily effluent concentration values that are
above both the daily and monthly average limitations. After thoroughly examining the data, EPA
determined that the concentration values that are above both the daily and monthly limitations
for arsenic came from the plant with relatively higher effluent concentration values (i.e., with a
higher long-term average than the other two plants). EPA observed that the same was true for the
mercury concentration values that are above both the daily and monthly limitations calculated for
the chemical precipitation technology option. Since the limitations are developed using the data
from all three plants, it is reasonable to expect that the plant with relatively higher concentrations
is more likely to have values above the daily and monthly limitations. As EPA explains below in
this section, it is reasonable for this situation to arise in the datasets used to calculate the
limitations and there are specific steps plants can take that enable them to improve treatment
system performance so that effluent concentrations would be in compliance with the proposed
limitations at all times.
EPA also identified an instance where two (of four) daily concentration values in a month
are higher than the monthly limitation, and the resulting monthly average is equal to the monthly
average limitation. Instances such as this (i.e., where one or more individual results are higher
than the monthly limitation, but the average of all results in a month are equal to or below the
monthly limitation) are normal and consistent with the way effluent limitations are calculated
and implemented in NPDES permits. This is illustrated, in fact, by the selenium data for the
biological treatment technology option, as described in the next section. EPA also identified
some cases where only one sample was taken during a month and the resulting concentration
value for that lone sample is above the average monthly limitation. In such cases, additional
monitoring of the effluent (e.g., at weekly intervals) would likely result in a monthly average that
would fall below the monthly limitation.
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Section 13- Limitations and Standards: Data Selection and Calculation
In addition, EPA identified one month where two (out of four) daily concentration values
from the month are above the monthly average limitation, and the resulting monthly average for
all four values is above the monthly limitation. Based on its engineering judgment developed
over years of evaluating wastewater treatment processes for power plants and other industrial
sectors, EPA determined that the combination of additional monitoring, closer operator attention,
and optimizing treatment system performance to target the effluent concentrations at the
technology option long-term average will result in lower effluent concentrations that would be in
compliance with the proposed effluent limitations.
EPA noted that while these plants were selected as representing the "best available"
technology, it does not mean that the plants have the systems fully optimized, especially since
most of the plants do not have specific limits on the FGD wastewater for the pollutants of
concern or because their existing limits are well above what the system is achieving.
Specifically, none of these three plants have specific limits for arsenic. Also, only Keystone and
Hatfield's Ferry have NPDES permit limits on mercury; however, their current permit limits are
more than 30 times higher than the proposed BAT effluent limitations. For this reason, these
plants currently do not need to closely monitor the treatment system to confirm performance
below their permit limitation. If these plants were required to meet the proposed limitations, EPA
believes that these plants would be capable of meeting the limitations without significant
expense. For example, EPA's review of chemical precipitation systems for this industry noted
that plants could benefit from using an in-house mercury analyzer to monitor the performance of
the system on a daily basis. Mercury analyzers have been effectively used at a power plant to
alert operators when mercury concentrations begin trending upward so that they may take steps
to adjust treatment system performance and remain in compliance with their NPDES permit
limits. Furthermore, some plants that rely solely on hydroxide precipitation could add sulfide
precipitation to improve removals of arsenic and mercury. Organosulfide addition, particularly
using long-chain organosulfide polymers, has been demonstrated to be particularly effective at
improving mercury removals in chemical precipitation treatment systems. Finally, EPA has also
evaluated the results of testing at a power plant that, although its FGD wastewater treatment
system had been in operation for more than a year and was operating at a steady state condition,
the plant significantly improved the pollutant removal performance merely by altering the dosage
rates for the wastewater treatment chemical additives. As a result, EPA identified various
approaches plants can use to improve their performance and achieve the limitations. EPA notes
that its compliance cost estimates for the proposed rule includes costs for mercury analyzers,
sulfide precipitation, and proper dosing of treatment system chemical additives.
Based on the results of the comparisons described above, EPA determined that the
statistical distributional assumptions are appropriate for the effluent data and that the proposed
limitations are reasonable.
Biological Treatment Technology Option for FGD Wastewater
For the biological treatment technology option for FGD wastewater, EPA is proposing
limitations for arsenic, mercury, nitrate-nitrite as N, and selenium. For arsenic and mercury, EPA
transferred the limitations from the chemical precipitation treatment system for FGD wastewater
(as explained in Section 13.7.2 above). Because the limitations for arsenic and mercury were
transferred and since this technology option includes chemical precipitation as a first step, the
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Section 13- Limitations and Standards: Data Selection and Calculation
comparison described above for the chemical precipitation technology option is relevant for
arsenic and mercury. Because of this, EPA expects that the plants employing this technology
option would be able to comply with the proposed arsenic and mercury limitations. Furthermore,
EPA's data demonstrate that the biological treatment stage provides pollutant removals for
arsenic and mercury (and other pollutants of concern with similar removal mechanisms) in
addition to the pollutant removals that occur in the chemical precipitation stage of the biological
treatment technology option (see, for example, Section 10.4.1). Thus, plants employing and
optimally operating all components of the biological treatment technology option (including
adding organosulfide to achieve sulfide precipitation) should achieve pollutant removals for
arsenic and mercury (and other pollutants with similar removal mechanisms) that are equal to or
even greater than the removals based on chemical precipitation technology.
For nitrate-nitrite as N at Allen, all daily effluent concentration values are below both the
daily and monthly limitations. For nitrate-nitrite as N at Belews Creek, all daily effluent values
are below the daily limitation. However, there are two nitrate-nitrite as N daily effluent values in
different months that are above the monthly limitation. In each case only one sample was
collected during the month. As explained above for the chemical precipitation technology option
and demonstrated in the following paragraph, additional effluent monitoring (e.g., at weekly
intervals) would likely result in a monthly average that would fall below the monthly limitation.
For selenium at Allen, all daily effluent concentration values are below the daily
limitation. Only one daily effluent value (out of two collected in the same month) for Allen is
above the monthly limitation. However, after averaging these two observations, the average for
the month is below the monthly limitation. All other daily concentration values for Allen,
spanning the period from September 2009 through May 2011, are below the average monthly
limitation.
For selenium at Belews Creek, there are some daily effluent observations that are above
both the daily and monthly limitations. After thoroughly examining the data, EPA determined
that the effluent concentration values at Belews Creek are relatively higher (i.e., with a higher
long-term average) than the effluent concentration values at Allen. As discussed above, since the
limitations are developed using the data from both plants, it is reasonable to expect that the plant
with relatively higher concentrations is more likely to have values above the daily and monthly
limitations. Furthermore, as EPA explained above there are steps plants can take to achieve
better treatment system performance to ensure compliance with the effluent limitations. EPA
identified instances in which some daily effluent values at Belews Creek are above the average
monthly limitations. However, these are the only concentration values that were collected within
each of those months. As described above, additional effluent monitoring (e.g., at weekly
intervals) would likely result in a monthly average that would fall below the monthly limitation.
EPA also identified four instances where some (or all) daily concentration values from a month
are above the monthly limitation, but the daily values for other samples collected within the
month are below the monthly limitation. In these instances, the average for all samples collected
within the month is above the monthly limitation. Three of these four instances occur in the first
three months of operation (August-October 2008) following the end of the initial commissioning
period for the treatment system. The Belews Creek FGD wastewater treatment system was the
first FGD bioreactor system operated by Duke Energy, and one of the first two systems to begin
operating in the U.S. After evaluating all selenium data for the biological treatment technology
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Section 13- Limitations and Standards: Data Selection and Calculation
option (nearly three years of data for Belews Creek and nearly two years for Allen, excluding the
initial commissioning periods), EPA concluded that the selenium results for August-October
2008 reflect less than optimum performance of the treatment system due either to the
inexperience of operators with this type of treatment system, or to continued variability
associated with the initial commissioning of the treatment system, or a combination thereof.113
Based on the results of this comparison for the biological treatment technology option based on
Allen and Belews Creek, EPA determined that the statistical distributional assumptions are
appropriate for the effluent data and that the proposed limits are reasonable.
Vapor-Compression Evaporator Treatment Technology Option for FGD Wastewater
For the chemical precipitation followed by vapor-compression evaporation treatment
technology option for FGD wastewater, EPA developed limitations for arsenic, mercury,
selenium, and TDS. The limitations were calculated using data from Brindisi plant. All daily
effluent concentration values are below the daily and monthly limitations. After thoroughly
reviewing the data, EPA determined that the statistical distributional assumptions are appropriate
for the effluent data and that the proposed limitations are reasonable.
Vapor-Compression Evaporator Treatment Technology Option for Gasification
Wastewater
For the vapor-compression evaporation treatment technology option for gasification
wastewater, EPA is proposing limitations for arsenic, mercury, selenium, and TDS. The
limitations were calculated using data from both the Polk and Wabash River plants, except for
the arsenic and mercury limitations, which were based only on data from Polk (since data from
Wabash River failed the LTA test).
For arsenic and mercury, daily concentration values are below both the daily and monthly
limitations. For total dissolved solids, there is one (out of four collected in the same month) daily
effluent concentration value at Polk above the monthly limitation. However, after averaging
these four observations, the average for the month is below the monthly limitation.
For selenium at Polk, there is one daily effluent concentration value above the daily
limitation. Also, there are two (out of four collected in the same month) daily effluent values
above the monthly average limitation. After averaging these four observations, the average for
the month is above the monthly limitation. After thoroughly examining the data, EPA
determined that the effluent concentration values for selenium at Polk are relatively higher (i.e.,
with a higher long-term average) than the effluent concentration values at Wabash River. As
discussed above, since the limitations are developed using the data from both plants, it is
113 Note that although the Belews Creek selenium data (and other pollutants as well) from August-October 2008 may
be influenced by the initial commissioning period for the treatment system, EPA used these data when calculating
the proposed effluent limitations for the biological treatment technology option for FGD wastewater. EPA has used
the August-October 2008 data because although EPA believes that, as a general rule, the initial commissioning
period duration will be on the order of 3-4 months, and certainly no more than 6 months except in unique
circumstances, EPA has not confirmed that the initial commissioning for Belews Creek was of such exceptional
duration. Without the information to confirm the commissioning period was still in progress, EPA concluded that
the sampling data should be used when calculating effluent limitations.
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Section 13- Limitations and Standards: Data Selection and Calculation
reasonable to expect that the plant with relatively higher concentrations is more likely to have
values above the daily and monthly limitations. Additionally, as discussed above in Section
13.8.1, the data for the Polk treatment system indicates that the evaporator (or at a minimum the
forced circulation evaporation stage) was operating abnormally and allowing carryover of
pollutants to the condensate effluent stream. Based upon its review of the data, EPA concluded if
the plant designed and operated its treatment system to achieve the option long-term average for
the model technology, then the plant will be able to comply with the proposed limitation.
Further, EPA notes that the Polk reuses all treatment gasification wastewater (i.e., condensate) in
the gasification process and does not discharge any gasification wastewater. As such, the plant's
treatment objective is to ensure the wastewater is of sufficient quality for reuse in the process
rather than to comply with a NPDES permit limit. Thus, EPA concluded that the statistical
distributional assumptions are appropriate for the effluent data and that the proposed limitations
are reasonable.
13.9.2 Comparison of Proposed Limitations to Influent Data
In addition to comparing the proposed limitations to the data used to develop the
limitations, EPA also compared the proposed limitations to the influent concentration values.
This comparison helps evaluate whether the proposed limitations are set at a level that ensures
that treatment of the wastewater would be necessary to meet the limitations and that the influent
concentrations were generally well-controlled by the treatment system. In doing so, EPA
confirms that treatment to remove the regulated pollutants will take place. See the memorandum
entitled, "Effluent Limitations for FGD Wastewater, Gasification Wastewater, and Combustion
Residual Leachate for the Proposed Effluent Limitations Guidelines and Standards for the Steam
Electric Rulemaking" for a detailed listing of the summary statistics for the influent data for each
pollutant in each treatment technology option [U.S. EPA, 2012a]
For all treatment technology options for both FGD and gasification wastewater, the
minimum, average, and maximum influent concentration values were much higher than the long-
term average and proposed limitations. Thus, EPA determined that plants would need to treat the
wastewater to ensure compliance with the proposed limitations and that the proposed rule would
result in removing the regulated pollutants and other pollutants of concern. Furthermore, in
evaluating influent concentrations, EPA found that influent concentrations were generally well-
controlled by the treatment plant for all plants with model technology. In general, the treatment
systems adequately treated even the extreme influent values, and the high effluent values did not
appear to be the result of high influent discharges.
13.10 REFERENCES
1. Computer Sciences Corporation (CSC). 2013. Results of the ICP/MS Collision Cell
Method Detection Limit Studies in the Synthetic Flue Gas Desulfurization Matrix. (16
January). DCN SE03872.
2. U.S. EPA. 2012a. Memorandum to Ronald Jordan: Effluent Limitations for FGD
Wastewater, Gasification Wastewater, and Combustion Residual Leachate for the
Proposed Effluent Limitations Guidelines and Standards for the Steam Electric
Rulemaking. (20 October). DCN SE01999.
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U.S. EPA. 2012b. Memorandum to Steam Electric Rulemaking Record: Assessment of
Effluent Limitations and Standards with No Baseline Substitution for the Steam Electric
Rulemaking. (18 November). DCN SE02000.
U.S. EPA. 2012c. Sampling Data Used as the Basis for Effluent Limitations for the
Steam Electric Rulemaking. (31 October). DCN SE02002.
Westat. 2013. Memorandum to Cue Schroeder: Serial Correlations for Steam Electric
With and Without Adjustment for Baseline Values. (15 April). DCN SE02001.
Results of the ICP/MS Collision Cell Method Detection Limit Studies in the Synthetic
Flue Gas Desulfurization Matrix - DCN SE03872
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Section 14- Regulatory Implementation
SECTION 14
REGULATORY IMPLEMENTATION
This section provides guidance to permit writers and control authorities (e.g., publicly
owned treatment works (POTWs)) in implementing the revisions to the steam electric effluent
limitations guidelines and standards (ELGs).
14.1 IMPLEMENTATION OF THE LIMITATIONS AND STANDARDS
Effluent guidelines limitations and standards act as a primary mechanism to control the
discharge of pollutants to waters of the United States. The BAT and NSPS limitations and
standards in the proposed rule would be applied to steam electric wastewater discharges through
incorporation into NPDES permits issued by the EPA or states under Section 402 of the Act. The
PSES and PSNS standards are implemented through pretreatment programs under Section 307 of
the Act.
The Agency has developed the limitations and standards for this proposed rule to control
the discharge of pollutants from the steam electric power generating point source category. Once
promulgated, those permits or control mechanisms issued after this rule's effective date would be
required to incorporate the effluent limitations guidelines and standards, as applicable. Also,
under section 510 of the CWA, states may require effluent limitations under state law as long as
they are no less stringent than the requirements of this rule. Finally, in addition to requiring
application of the technology-based effluent limitations guidelines and standards in this rule,
section 301(b)(l)(C) of CWA requires the permitting authority to impose more stringent effluent
limitations on discharges as necessary to meet applicable water quality standards.
14.1.1 Timing
For the reasons explained in Section 8.2, EPA proposes that certain limitations and
standards based on any of the eight main regulatory options being proposed for existing direct
and indirect dischargers do not apply until July 1, 2017 (approximately three years from the
effective date of this rule). EPA finds this is appropriate for any proposed BAT and PSES for
FGD wastewater, gasification wastewater, fly ash transport water, flue gas mercury control
wastewater, bottom ash transport water, or combustion residual leachate where EPA is not
proposing to establish BAT limitations that are equal to BPT limitations. For those plants and
wastestreams where EPA is proposing to establish BAT equal to the current BPT effluent
limitations, the revised BAT requirements would be applicable on the effective date of the final
rule.
The proposed requirements for new direct and indirect dischargers (NSPS and PSNS) and
the proposed requirements for existing sources where BAT is set equal to BPT would be
applicable as of the effective date of the final rule.
14.1.2 Applicability of NSPS/PSNS
In 1982, EPA promulgated NSPS/PSNS for certain discharges from new units.
Regardless of the outcome of the current rulemaking, those units that are currently subject to the
14-1
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Section 14- Regulatory Implementation
1982 NSPS/PSNS will continue to be subject to such standards. In addition, EPA is proposing to
clarify in the text of the regulation that, assuming the Agency promulgates BAT/PSES
requirements as part of the current rulemaking, units to which the 1982 NSPS/PSNS apply will
also be subject to any newly promulgated BAT/PSES requirements because they will be existing
sources with respect to such new requirements.
14.1.3 Legacy Wastes
For the reasons explained in Section 8.1.2, EPA is proposing that BAT and PSES
requirements for existing sources based on any of the eight main regulatory options would apply
to discharges of FGD wastewater, fly ash transport water, bottom ash transport water, FGMC
wastewater, combustion residual leachate, and gasification wastewater generated on or after the
date established by the permitting authority that is as soon as possible after July 1, 2017.114 Such
wastewater generated prior to that date (i.e., "legacy" wastewater), in the case of direct
dischargers, would remain subject to the existing BPT effluent limits. EPA is also considering
establishing BAT effluent limitations for legacy wastewater (except gasification wastewater) that
would be equal to the existing BPT effluent limits.
EPA also considered subjecting the legacy wastewater (except gasification wastewater) to
the proposed BAT and PSES requirements. However, EPA found that these legacy wastewaters
are typically transferred to surface impoundments that often commingle these legacy
wastewaters and also contain other plant wastewaters, such as cooling water, coal pile runoff,
and/or other low volume wastes. For each of the wastestreams for which EPA is proposing new
BAT/PSES requirements, EPA does not have data to demonstrate that the technologies identified
as representing BAT for newly generated wastewater from the various sources considered (e.g.,
FGD wastewater, fly ash transport wastewater) would also represent BAT for the legacy
wastewaters. For example, for fly ash transport water, the technology basis identified for the
proposed zero discharge requirement (i.e., conversion to dry ash handling) would eliminate
generating new volumes of fly ash transport water but does not eliminate fly ash transport water
that has already been generated and transferred to an impoundment prior to the conversion. EPA
also evaluated whether other technologies would be available that might represent BAT for these
legacy wastewaters. However, EPA determined these alternatives are either impracticable or
insufficient data are available for establishing effluent limitations. For example, for a surface
impoundment that receives both fly ash transport water and cooling tower blowdown, if the plant
converts to a dry ash handling system, the surface impoundment would cease to receive
additional fly ash transport water, but it would continue to receive the cooling tower blowdown.
In this example, the surface impoundment would now contain a mixture of cooling tower
blowdown and legacy fly ash transport water. As the plant continues to discharge from the
impoundment, the concentration of pollutants in the impoundment that are associated with the
legacy fly ash transport water would decrease over time but theoretically would never become
zero (i.e., "zero discharge") because the remaining legacy wastewater is diluted over time but is
never completely flushed from the impoundment. As pollutant concentrations associated with the
legacy wastewater decrease over time, the treatability of the legacy wastewater remaining in the
impoundment may be affected and, similarly, the resulting concentrations in the treated effluent
may be affected. For this reason, EPA has found that the technologies considered for legacy
114 Except where BAT is equivalent to BPT.
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wastewater in surface impoundments are either impracticable or insufficient data are available
for establishing effluent limitations.
The remainder of this subsection presents examples of how the proposed BAT effluent
limitations and the existing BPT limitations should be applied to these wastewaters after the date
established by the permitting authority that is as soon as possible after July 1 2017. Wastewater
generated prior to the date established by the permitting authority is referred to as "legacy"
wastewater and wastewater generated after the date established by the permitting authority is
referred to as "newly generated" wastewater.
Figure 14-1 presents an example treatment scenario for a plant operating an
impoundment receiving only FGD wastewater prior to the implementation of the ELGs. Under
Regulatory Options 3 and 4a, the plant will need to meet the new BAT effluent limitations for
the FGD wastewater, in which case, EPA envisions that the plant will have installed a tank-based
treatment system to meet the limits. However, the plant has several options for the configuration
of the treatment system in association with the existing impoundment, which are included in the
post rule scenarios in Figure 14-1. Under post rule scenario A, the plant transfers the newly
generated FGD wastewater to the tank-based system and discharges directly from the tank-based
system to the receiving water. In this case, the plant would be required to demonstrate
compliance with the new BAT and the existing BPT effluent limitations for the newly generated
FGD wastewater at the effluent from the tank-based treatment system. Additionally, any legacy
FGD wastewater that remains in the existing impoundment could still be discharged (e.g., after a
rainfall event, when dewatering the impoundment for closure) and would only be subject to the
existing BPT effluent limitations.115
Under post rule scenario B, the plant transfers the newly generated FGD wastewater to
the tank-based system and then transfers the effluent from the system to the existing
impoundment, containing legacy FGD wastewater, for additional polishing prior to discharge. As
stated in the proposed rule, and described further in Section 14.1.4.3, EPA is proposing to require
monitoring for compliance with the proposed BAT effluent limitations for newly generated FGD
wastewater prior to use of the FGD wastewater in any other non-FGD plant process or
commingling of the FGD wastewater with any water or other process wastewater, except for
combustion residual leachate (including legacy leachate) or legacy FGD wastewater that is
treated to achieve pollutant removals equivalent to or greater than achieved by the BAT
technology that serves as the basis for the proposed effluent limitations. In this case, because the
existing FGD wastewater impoundment does not achieve equivalent removals compared to the
tank-based system, the plant would be required to demonstrate compliance with the new BAT
limitations for the newly generated FGD wastewater at the effluent from the tank-based FGD
wastewater treatment system, and compliance with the BPT requirements for the commingled
new/legacy FGD wastewater at the point of discharge from the existing FGD wastewater
impoundment.
Under post rule scenario C, the plant transfers the newly generated FGD wastewater to
the existing FGD wastewater impoundment, containing legacy FGD wastewater. The
115 All examples presented in this section focus on the implementation of the ELGs. All NPDES discharge outfalls
may also be required to comply with additional water quality-based effluent limitations.
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Section 14- Regulatory Implementation
impoundment effluent is then transferred to the tank-based treatment system. In this case, both
the newly generated FGD wastewater and the legacy FGD wastewater would be treated by the
tank-based FGD wastewater treatment system . In this case, the plant would be required to
demonstrate compliance with the new BAT and existing BPT effluent limitations for FGD
wastewater at the effluent from the tank-based treatment system (i.e., prior to discharge or
commingling with other wastestreams).
FGD Treatment Scenarios
FGD
Wastewater
FGD Wastewater
Impoundment
BPT
Pre Rule
Receiving Water
Legacy
FGD Wastewater
Impoundment
BPT
Newly Generated
FGD Wastewater
Tank Based
Treatment
System
BAT
BPT
Post Rule
Receiving Water
Newly Generated
FGD Wastewater
Tank Based
Treatment
System
B
Receiving Water
Newly Generated
FGD Wastewater
BAT
BPT
Receiving Water
Figure 14-1. Legacy FGD Wastewater Treatment Scenario
(Regulatory Options 3 and 4a)
Figure 14-2 presents an example treatment scenario for an impoundment receiving only
fly ash transport water prior to the implementation of the ELGs. Under Regulatory Options 3a,
3b, 3, and 4a, the plant will need to meet the zero discharge BAT standard for fly ash transport
14-4
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Section 14- Regulatory Implementation
water, in which case, EPA envisions that the plant will have installed a dry fly ash handling
system to meet the new BAT limitation. In this case, the plant will no longer be transferring fly
ash transport water to the impoundment. However, legacy fly ash transport water could still be
discharged from the impoundment (e.g., after a rainfall event, when dewatering the
impoundment for closure) and would only be subject to the existing BPT effluent limitations.
Fly Ash Only Scenarios
Fly Ash
Transport Water
Fly Ash
Transport Water
Impoundment
BPT
Pre Rule
Receiving Water
Note: Fly ash converted to dry handling system
No newly generated fly ash transport water
Legacy Fly Ash
Transport Water
Impoundment
BPT
Post Rule
Receiving Water
Figure 14-2. Legacy Fly Ash Transport Water Treatment Scenario
(Regulatory Options 3a, 3b, 3, and 4a)
Figure 14-3 presents an example of the treatment scenario for a plant that operates a
complete recycle fly ash sluicing system in which the plant does not discharge any fly ash
transport water to a receiving water. Because the plant does not discharge fly ash transport water
prior to the implementation of the rule, the plant can continue to operate using the same system
(i.e., no system modifications required) and still be in compliance with the new zero discharge
BAT limitation.
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Section 14- Regulatory Implementation
Fly Ash
Transport Water
Fly Ash
Transport Water
Impoundment
X
No
Discharge
Pre Rule
Note: No changes/modifications are necessary for the system because the
configuration already meets the proposed zero discharge BAT limitation.
Post Rule
Fly Ash
Transport Water*
Legacy and Newly
Generated Fly
Ash Transport
Water
Impoundment
X
No
Discharge
*Consists of both newly generated fly ash transport
water and legacy fly ash transport water because
recycled impoundment wastewater is used as the
source of the transport water.
Figure 14-3. Complete Recycle Fly Ash Transport Water Treatment Scenario
(Regulatory Options 3a, 3b, 3, and 4a)
Figure 14-4 presents an example treatment scenario for a plant that operates a partial
recycle bottom ash sluicing system in which the plant recycles a majority of the bottom ash
transport water for reuse in the system, but some of the bottom ash transport water is discharged
to a receiving water. Under Regulatory Options 3 a, 3b, and 3, the plant could continue to operate
the system without any changes/modifications because Options 3a, 3b, and 3 would establish
BAT limitations for bottom ash transport water equal to the current BPT limitations. However,
under Regulatory Option 4, the plant will need to meet the new zero discharge BAT limitation, in
which case, EPA envisions that the plant has two options for complying with the new limitation,
which are included in the post rule scenarios in Figure 14-4. Under post rule scenario A, the
plant would convert to a dry bottom ash handling system, and would not transfer any newly
generated bottom ash transport water to the existing impoundment. However, legacy bottom ash
transport water could still be discharged from the impoundment (e.g., after a rainfall event, when
dewatering the impoundment for closure) and would only be subject to the existing BPT effluent
limitations.
Under post rule scenario B, the plant would evaluate the water balance for the bottom ash
system and determine whether the system could operate without discharging to a receiving
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Section 14- Regulatory Implementation
stream. If the plant determines that the system can achieve complete recycle, then the plant can
continue to operate the existing bottom ash handling system, but can no longer discharge the
wastewater from the impoundment to the receiving water in order to meet the new zero discharge
BAT limitation.
Bottom Ash
Transport Water
Bottom Ash
Transport Water
Impoundment
BPT
Pre Rule
Receiving Water
Post Rule
Note for Scenario A: Bottom ash converted to dry handling system.
No newly generated bottom ash transport water.
Legacy Bottom Ash
Transport Water
Impoundment
BPT
Receiving Water
Bottom Ash
Transport Water*
Legacy and Newly
Generated Bottom
Ash Transport Water
Impoundment
X
No
Discharge
B
"Consists of both newly generated bottom ash
transport water and legacy bottom ash transport
water because recycled impoundment wastewater is
used as the source of the transport water.
Figure 14-4. Partial Recycle Bottom Ash Transport Water Treatment Scenario
(Regulatory Option 4)
Figure 14-5 and Figure 14-6 present example treatment scenarios for an impoundment
receiving both fly ash and bottom ash transport water prior to the implementation of the ELGs.
Figure 14-5 presents the treatment scenario under Regulatory Options 3a, 3b, and 3 and Figure
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Section 14- Regulatory Implementation
14-6 presents the treatment scenario under Regulatory Option 4. Under Regulatory Options 3a,
3b, and 3, the plant will need to meet the zero discharge BAT limitation for fly ash transport
water, in which case, EPA envisions that the plant will have installed a dry fly ash handling
system to meet the limitation. In this case, the plant will no longer be transferring fly ash
transport water to the impoundment. However, the impoundment still contains legacy fly ash
transport water and legacy bottom ash transport water and the impoundment will continue to
discharge because of the newly generated bottom ash transport water that will continue to be
transferred to the impoundment. In this case, the plant would be required to demonstrate
compliance with the existing BPT effluent limitations for the legacy fly ash transport water and
legacy bottom ash transport water and the new BAT effluent limitations for the newly generated
bottom ash transport water.
Under Regulatory Option 4, the plant will need to meet the zero discharge BAT
limitation for both fly ash transport water and bottom ash transport water, in which case, EPA
envisions that the plant has two options for complying with the BAT limitations, which are
included in the post rule scenarios in Figure 14-6. Under post rule scenario A, the plant would
convert to a dry fly ash handling system and a dry bottom ash handling system, and would not
transfer any newly generated fly ash transport water or newly generated bottom ash transport
water to the existing impoundment. However, legacy fly ash transport water and legacy bottom
ash transport water could still be discharged from the impoundment (e.g., after a rainfall event,
when dewatering the impoundment for closure) and would only be subject to the existing BPT
effluent limitations.
Under post rule scenario B, the plant would evaluate the water balance for the fly ash and
bottom ash systems and determine whether the systems could operate without discharging to a
receiving stream. If the plant determines that the systems can achieve complete recycle, then the
plant can continue to operate the existing wet fly ash and bottom ash handling systems, but can
no longer discharge the wastewater from the impoundment to the receiving water in order to
meet the new zero discharge BAT limitations.
14-8
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Section 14- Regulatory Implementation
Fly Ash
Transport Water
Bottom Ash _
Transport Water
Fly Ash and Bottom Ash
Transport Water
Impoundment
BPT
Pre Rule
Receiving Water
Note: Fly ash converted to dry handling system.
No newly generated fly ash transport water.
Or, if fly ash transport water continues to be
handled wet, cannot discharge from impoundment.
Newly Generated
Bottom Ash —
Transport Water
Legacy Fly Ash and
Bottom Ash and Newly
Generated Bottom Ash
Transport Water
Impoundment
BPT \
BAT (for bottom J
ash only) /
Post Rule
Receiving Water
Figure 14-5. Legacy Fly Ash Transport Water Combined with Bottom Ash
Transport Water Treatment Scenario (Regulatory Options 3a, 3b, and 3)
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Section 14- Regulatory Implementation
Fly Ash _
Transport Water
Bottom Ash _
Transport Water
Fly Ash and Bottom Ash
Transport Water
Impoundment
Pre Rule
BPT
Receiving Water
Note: Fly ash and bottom ash converted to dry handling systems.
No newly generated fly ash or bottom ash transport water.
Post Rule
Legacy
Fly Ash and Bottom Ash
Transport Water
Impoundment
~® >
BPT
Receiving Water
Fly Ash and Bottom Ash
Transport Water*
Legacy and Newly
Generated Fly Ash and
Bottom Ash Transport
Water Impoundment
B
"Consists of both legacy fly ash transport water and
legacy bottom ash transport water because recycled
impoundment water is used as the source of the
transport water. Also includes newly generated fly
ash transport water and/or newly generated bottom
ash transport water based on which ash handling
system(s) continues wet sluicing operations (i.e., not
converted to dry handling.)
Figure 14-6. Legacy Fly Ash Transport Water Combined with Bottom Ash
Transport Water Treatment Scenario (Regulatory Option 4)
Figure 14-7 and Figure 14-8 present example treatment scenarios for a system where
FGD wastewater is treated in an impoundment receiving only FGD wastewater with the effluent
from the impoundment being transferred to an impoundment that receives both fly ash and
bottom ash transport water prior to the implementation of the ELGs. Figure 14-7 presents the
treatment scenario under Regulatory Option 3 and Figure 14-8 presents the treatment scenario
under Regulatory Option 4. Under Regulatory Option 3, the plant will need to meet the new BAT
effluent limitations for FGD wastewater, in which case, EPA envisions that the plant will have
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Section 14- Regulatory Implementation
installed a tank-based treatment system to meet the limitations. Additionally, the plant will need
to meet the zero discharge BAT limitation for fly ash transport water, in which case, EPA
envisions that the plant will have installed a dry fly ash handling system to meet the limitations.
The plant has a couple options for the handling of the FGD wastewater in association with the
existing impoundments, which are included in the post rule scenarios in Figure 14-7. Under the
post rule scenario, the plant can either transfer the FGD wastewater from the tank-based system
to the existing FGD impoundment, or the plant can bypass the FGD impoundment and transfer
the effluent from the tank-based FGD wastewater treatment system directly to the existing ash
impoundment. In either case, the plant would be required to demonstrate compliance with the
new FGD wastewater BAT limitations at the effluent from the tank-based system, prior to
entering either of the impoundments. The plant would also be required to demonstrate
compliance with the existing BPT limitations for legacy and newly generated FGD wastewater,
legacy fly ash transport water, and legacy bottom ash transport water, as well as the BAT
limitation for newly generated bottom ash transport water, at the effluent from the ash
impoundment.
Under Regulatory Option 4, the plant will need to meet the new BAT effluent limitations
for FGD wastewater and the zero discharge BAT limitations for fly ash transport water and
bottom ash transport water. In this case, EPA envisions that the plant will have installed a tank-
based treatment system to treat the FGD wastewater and dry fly ash and dry bottom ash handling
systems. As described for Regulatory Option 3, the plant has a couple options for the handling of
the FGD wastewater, which are included in the post rule scenarios in Figure 14-8. Under the post
rule scenario, the plant can either transfer the FGD wastewater from the tank-based system to the
existing FGD impoundment, or the plant can bypass the FGD impoundment and transfer the
effluent from the tank-based FGD wastewater treatment system directly to the existing ash
impoundment. In either case, the plant would be required to demonstrate compliance with the
new FGD wastewater BAT limitations at the effluent from the tank-based system, prior to
entering either of the impoundment. The plant would also be required to demonstrate compliance
with the existing BPT limitations for legacy and newly generated FGD wastewater, legacy fly
ash transport water, and legacy bottom ash transport water at the effluent from the ash
impoundment. The plant would not be able to discharge wastewater from the impoundments if
newly generated fly ash transport water or bottom ash transport water was sent to the
impoundment.
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Section 14- Regulatory Implementation
FGD
Wastewater
FGD Wastewater
Impoundment
Pre Rule
Fly Ash
Transport Water
Bottom Ash
Transport Wate~
FGD Wastewater, Fly Ash
and Bottom Ash Transport
Water Impoundment
BPT
Receiving Water
Note: Fly ash converted to dry handling system.
No newly generated fly ash transport water.
Or, if fly ash transport water continues to be
handled wet, cannot discharge from impoundment.
Post Rule
Newly Generated.
FGD Wastewater
Tank Based
Treatment
System
BAT
Legacy (and Newly
Generated)
FGD Wastewater
Impoundment
BAT\
Newly Generated Bottom_
Ash Transport Water
Legacy and Newly
Generated FGD Wastewater,
Legacy Fly Ash Transport
Water, and Legacy and
Newly Generated Bottom
Ash Transport Water
Impoundment
BPT
BAT (for bottom,
ash only) Receiving
Water
Figure 14-7. Legacy FGD Wastewater and Fly Ash Transport Water Combined with
Bottom Ash Transport Water Treatment Scenario (Regulatory Option 3)
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Section 14- Regulatory Implementation
Pre Rule
FGD
Wastewater
FGD Wastewater
Impoundment
Fly Ash
Transport Water
Bottom Ash
Transport Water
FGD Wastewater, Fly Ash
and Bottom Ash Transport
Water Impoundment
BPT
Receiving Water
Note: Fly ash and bottom ash converted to dry handling systems.
No newly generated fly ash transport water or bottom ash transport water.
Post Rule
Newly Generated.
FGD Wastewater
Tank Based
Treatment
System
BAT
Legacy (and Newly
Generated)
FGD Wastewater
Impoundment
BAT\
Legacy and Newly
Generated FGD Wastewater,
Legacy Fly Ash and Legacy
Bottom Ash Transport Water
Impoundment
Receiving Water
Figure 14-8. Legacy FGD Wastewater and Fly Ash Transport Water Combined with
Bottom Ash Transport Water Treatment Scenario (Regulatory Option 4)
14.1.4 Monitoring Requirements
The NPDES permit regulations at §122.41(j)(4) and the pretreatment regulations at
§403.12(b)(5)(vi) require that facilities conduct sampling and analyses to monitor compliance
according to the techniques set out at 40 CFR 136, as amended. The Agency is proposing several
specific monitoring requirements in the steam electric proposed rule. Sections 14.1.4.1 through
14.1.4.4 provide guidance on establishing these requirements.
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Section 14- Regulatory Implementation
14.1.4.1 Sample Types
EPA recommends flow-proportioned, 24-hour composite samples for the following
regulated pollutants:
• Total dissolved solids;
• Total arsenic;
• Total selenium; and
• Nitrate/nitrite as N.
Part 136 recommends that plants use the clean sampling techniques described in EPA's
draft method 1669: Sampling Ambient Water for Trace Metals at EPA Water Quality Criteria
Levels (EPA-821-R-96-011) for mercury collection for EPA Methods 245.7 and 163 IE to
prevent contamination at low-level, trace metal determinations.116 EPA Methods 245.7 and
163 IE are the only Part 136-approved methods that have a detection limit low enough to be used
for the mercury analysis for the FGD wastewater limit in the proposed rule. While EPA Methods
245.7, 163 IE, and 1669 do not specifically require plants to collect mercury samples as grab
samples, EPA recommends that mercury be collected as grab samples because there is less
potential for contamination compared to composite sampling. EPA also recommends that
mercury samples be collected as four grab samples in a 24-hour monitoring day, and that the
results should be averaged to represent a daily sample.
14.1.4.2 Monitoring Frequency
The monitoring frequencies specified in steam electric NPDES permits vary depending
upon the size of the plant, potential impacts on receiving waters, compliance history, and other
factors, including monitoring policies or regulations required by permit authorities. The Agency
is not proposing any specific monitoring frequencies; therefore, permit authorities may establish
monitoring frequencies at their discretion, consistent with the requirements in 40 CFR 122.
When developing the proposed rule, EPA assumed a monitoring frequency of once per
week for regulated pollutants. Facilities may monitor effluent more frequently than specified in
their permits. During site visits, EPA observed that many plants often collect samples for key
pollutants on a more frequent basis than required in their permits to help them stay attuned to
treatment system performance and facilitate improved performance.
14.1.4.3 Compliance Monitoring Locations
Working in conjunction with the effluent limitations guidelines and standards are the
monitoring conditions set out in a NPDES discharge permit or POTW control mechanism. An
integral part of the monitoring conditions is the monitoring point. The point at which a sample is
collected can have a dramatic effect on the monitoring results for that plant. Therefore, it may be
116 EPA also recommends that plants use the clean sampling techniques for the collection of arsenic and selenium. If
clean sampling techniques are not used, EPA recommends that field blanks be collected to evaluate whether
contamination may be affecting the sampling results.
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Section 14- Regulatory Implementation
necessary to require internal monitoring points in order to assure compliance. Authority to
address internal wastestreams is provided in 40 CFR 122.44(i)(l)(iii) and 122.45(h).
EPA is proposing that dischargers demonstrate compliance with the new effluent
limitations and standards applicable to a particular wastestream prior to mixing the treated
wastestream with other wastestreams, as described below. Therefore, with the exception of the
cases where BAT limitations are equivalent to BPT limitations, any final limitations or standards
(except pH) based on any of the eight main regulatory options in the proposed rule could require
internal monitoring points. The following provides more detailed information for each
wastestream:
• FGD Wastewater. Where an option proposes BAT/NSPS limitations for FGD
wastewater that are not equal to existing BPT limitations, EPA is also proposing to
require monitoring for compliance with the proposed effluent limitations and
standards prior to use of the FGD wastewater in any other non-FGD plant process or
commingling of the FGD wastewater with any water or other process wastewater.11?
This monitoring requirement would not, however, apply prior to commingling of
FGD wastewater with combustion residual leachate (including legacy leachate) or
legacy FGD wastewater that is treated to achieve pollutant removals equivalent to or
greater than achieved by the BAT/NSPS technology that serves as the basis for the
effluent limitations and standards in the proposed rule.
For example, many plants currently treat their FGD wastewater and leachate in onsite
surface impoundments. EPA envisions that, under the Option 3 requirements, some of
these plants may choose to install tank-based FGD wastewater treatment systems for
their newly generated FGD wastewater. Such a plant may choose to discharge the
effluent from its new treatment system directly or may wish to discharge it to the
existing surface impoundment containing legacy wastewaters. In this case, the plant
would be required to demonstrate compliance with the proposed effluent limitations
and standards for the newly generated FGD wastewater at the effluent from the tank-
based FGD wastewater treatment system, and compliance with the BPT requirements
for the commingled new/legacy FGD wastewater at the point of discharge from the
FGD wastewater impoundment. The same plant may also configure its system so that
the impoundment (which also contains legacy FGD wastewater) is used for
equalization, with the impoundment effluent sent to the tank-based treatment system.
In this case, both the newly generated FGD wastewater and the legacy FGD
wastewater would be treated by the tank-based treatment system and an appropriate
compliance monitoring point would be the treatment system effluent. Under such a
scenario, commingling of FGD wastewater generated at any date may occur as long
as such combined wastewater meets the effluent limitations or standards prior to use
of the treated commingled new/legacy FGD wastewater in any other plant process, or
combining the FGD wastewater with any water or other process wastewater. See
Figure 14-1 for illustrations of these examples of the compliance monitoring points.
117 Similarly applies to PSES and PSNS.
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Section 14- Regulatory Implementation
Ash Transport Water andFGMC Wastewater: EPA is proposing to specify that
whenever ash transport water or flue gas mercury control wastewater generated from
a generating unit that must comply with the "zero discharge" standard is used in any
other plant process or is sent to a treatment system at the plant, the resulting effluent
must comply with the proposed discharge prohibition for the pollutants in such
wastewater.
For example, many plants currently treat their fly ash transport water in an onsite fly
ash impoundment. In this case, under any proposed "no discharge" requirements,
EPA envisions that such plants may convert their fly ash handling to a dry system,
and no longer generate fly ash transport water. In such cases, the plant could
demonstrate compliance with the proposed zero discharge requirement by showing
that no fly ash transport water is generated after the date on which the new, proposed
standards apply and by monitoring for compliance with the BPT requirements at the
discharge from the legacy fly ash impoundment. See Figure 14-2 for an illustration of
the example compliance monitoring points. Under EPA's proposal, the plant could
not demonstrate compliance with the applicable discharge prohibition by simply
using the fly ash transport water or FGMC wastewater in another plant process that
ultimately discharges because the prohibition on the discharge of pollutants in ash
transport water and FGMC wastewater is also applicable to the discharge of
wastewater from plant processes that use these wastewaters.
Gasification Wastewater: EPA is proposing to require monitoring for compliance
prior to use of the gasification wastewater in any other plant process or commingling
of the gasification wastewater with water or any other process wastewater. For
example, EPA envisions gasification plants would show compliance with the
proposed BAT or PSES requirements directly following gasification wastewater
treatment (however, there would be no need to demonstrate compliance if the
gasification wastewater is completely reused within the gasification process).
Combustion ResidualLeachate: Under Options 4 and 5, EPA is proposing to require
monitoring for compliance prior to use of leachate in any other plant process or
commingling of the leachate with water or any other process wastewater. This
monitoring requirement would not, however, apply prior to commingling of
combustion residual leachate with FGD wastewater (including legacy FGD
wastewater) or legacy combustion residual leachate that is treated to achieve pollutant
removals equivalent to or greater than that achieved by the BAT/NSPS technology
that serves as the basis for the effluent limitations and standards in the proposed rule.
For example, many plants currently treat their leachate in onsite surface
impoundments. EPA envisions that some plants may choose to install a tank-based
leachate treatment system so that the impoundment (which also contains legacy
combustion residual leachate) is used for equalization, with the impoundment effluent
ultimately sent to the tank-based treatment system. In this case, both the newly
generated leachate and the legacy leachate would be treated by the tank-based
treatment system and an appropriate compliance monitoring point would be the
treatment system effluent. Under such a scenario, commingling of combustion
residual leachate generated at any date may occur as long as such combined
wastewater meets the effluent limitations or standards prior to use of the treated
14-16
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Section 14- Regulatory Implementation
commingled new/legacy leachate in any other plant process, or combining the
leachate with any water or other process wastewater. (If the combustion residual
leachate is commingled with FGD wastewater, the plant will also have to demonstrate
compliance with the applicable FGD wastewater effluent limitations and standards.)
14.1.4.4 Size Threshold Implementation
Under the BAT/PSES regulatory options, EPA is proposing to set size thresholds which
would subject discharges from certain generating units to a different set of controls. The
following provides examples of how these size thresholds should be evaluated for the purposes
of setting permit requirements.
Fly Ash 50 MW Threshold (Options 3a, 3b, 3, 4a, 4, 5)
Under the proposed regulatory options, there is the potential that some generating units at
a plant would need to comply with the proposed "zero discharge" requirement, while other units
at the plant would only need to comply with the current BPT standards. For example, consider a
plant that has a generating unit with a nameplate capacity of 50 MW or less and another
generating unit with a nameplate capacity of greater than 50 MW that both discharge fly ash
transport water. In this case, if the plant continues to wet sluice the fly ash from the unit with a
nameplate capacity greater than 50 MW, the fly ash transport water for that unit must be
completely reused in a process that does not ultimately discharge to surface waters, including
indirect discharges to POTWs, (or the unit converted to dry handling) to be in compliance with
the proposed "zero discharge" requirement. The fly ash transport water from the unit with a
nameplate capacity greater than 50 MW cannot be reused to wet sluice the fly ash for the
generating unit with a nameplate capacity of 50 MW or less if it is ultimately discharged.
Therefore, the plant has three potential options to comply with the proposed "zero discharge"
requirement for the generating unit with a nameplate capacity of greater than 50 MW:
• Convert the generating unit to dry fly ash handling;
• Commingle the fly ash transport water for all generating units and completely recycle
the fly ash transport water with no discharge from any of the generating units; or
• Segregate the fly ash transport water for the generating unit with a nameplate capacity
greater than 50 MW and completely recycle that within that specific unit, but still
discharge the fly ash transport water from the generating unit with a nameplate
capacity of 50 MW or less.
This example would also apply to the 400 MW threshold for bottom ash transport water
under Option 4a.
FGD Wastewater 2.000 MW Plant-Level Wet-Scrubbed Capacity Threshold (Option 3b)
EPA is not proposing to establish BAT/PSES for discharges of FGD wastewater under
Option 3b, for those plants that have a total plant-level wet scrubbed capacity of less than 2,000
MW. Therefore, if a plant has a total wet scrubbed capacity of 1,800 MW, no new effluent limits
would be established under BAT or PSES for discharges of FGD wastewater. However, if the
plant were to install a new wet FGD system with a nameplate capacity of 200 MW or greater at a
14-17
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Section 14- Regulatory Implementation
later time, which would put the plant at or above the 2,000 MW threshold, the plant would then
be required to comply with the proposed effluent limits for all FGD wastewater generated at the
plant, not just the wastewater associated with the new FGD system. Therefore, at the time the
plant begins operation of the new FGD system, the plant would be required to meet the proposed
arsenic, mercury, selenium, and nitrate-nitrite limitations for all FGD wastewater discharges at
the plant.
14.2 ANALYTICAL METHODS
Section 304(h) of the CWA directs the EPA to promulgate guidelines establishing test
procedures (methods) for the analysis of pollutants. These methods are used to determine the
presence and concentration of pollutants in wastewater and for compliance monitoring. They are
also used for filing applications for the National Pollutant Discharge Elimination System
(NPDES) permit program under 40 CFR 122.41(j)(4) and 122.21(g)(7), and under 40 CFR
403.7(d) for the pretreatment program. The EPA has promulgated analytical methods for
monitoring discharges to surface water at 40 CFR part 136 for the pollutants proposed for
regulation in the proposed rule. As part of this proposed rule, EPA is providing notice of
standard operating procedures (SOPs) for the analysis of FGD wastewater using collision cell
technology in conjunction with EPA Method 200.8. EPA Method 200.8 has been promulgated
under 40 CFR part 136 and is an approved method for use in NPDES compliance monitoring.
Also, the use of collision cell technology is an approved modification allowed under 40 CFR part
136.6. The SOPs developed by EPA are titled, "Draft Procedure for Trace Element Analysis of
Flue Gas Desulfurization Wastewaters Using Perkin Elmer NexION 300D ICP-MS
Collision/Reaction Cell Procedure" and "Draft FGD ICP/MS Collision Cell Procedure for Trace
Element Analysis in Flue Gas Desulfurization Wastewaters" [U.S. EPA, 2012a; U.S. EPA,
2012b].
In addition, as explained in Section 8.1.2.8, with the exception of the cases where BAT
limitations are equivalent to BPT limitations, EPA is proposing that compliance with any final
limitations or standards (except pH) based on any of the eight main regulatory options in the
proposed rule reflects results obtained from sufficiently sensitive analytical methods. Where
EPA has approved more than one analytical method for a pollutant, the Agency expects that
permittees would select methods that are able to quantify the presence of pollutants in a given
discharge at concentrations that are low enough to determine compliance with effluent limits. For
purposes of the proposed anti-circumvention provisions, a method is "sufficiently sensitive"
when the sample-specific quantitation level for the wastewater matrix being analyzed is at or
below the level of the effluent limit.118
14.3 UPSET AND BYPASS PROVISIONS
The CWA, the NPDES permit regulations at §122.41(m) and (n), and the pretreatment
regulations at §403.16 and §403.17 allow effluent discharges above permit limits under certain
exceptional and limited circumstances. A bypass is an intentional diversion of a wastestream
from any portion of a treatment facility to prevent unavoidable loss of life, personal injury, or
118 For the purposes of the discussion in this rulemaking, the following terms related to analytical method sensitivity
are synonymous: "quantitation limit," "reporting limit," "level of quantitation," and "minimum level."
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Section 14- Regulatory Implementation
severe property damage. Economic loss caused by delays in production does not constitute
severe property damage for the purposes of this regulation. The key requirements for the bypass
provisions of a permit are: (1) the bypass must be intentional; (2) prior notice (10 days, if
possible) must be provided; and (3) there must be no feasible alternatives to the bypass. A plant
does not meet these requirements if it lacks adequate back-up equipment that it should have
installed to prevent a bypass during periods of normal operation or maintenance using reasonable
engineering judgment. In other cases, intentional bypasses are allowed if required for essential
maintenance to ensure efficient operation, as long as these bypasses do not cause the plant to
exceed its effluent limitations.
An upset is an exceptional incident in which a facility unintentionally and temporarily
cannot comply with its technology-based permit effluent limitations due to factors beyond its
reasonable control. An upset does not include noncompliance due to operational error,
improperly designed treatment facilities, inadequate treatment facilities, lack of preventative
maintenance, or careless or improper operation. A plant can defend a case in which it exceeds its
effluent limitations if the permit holder can demonstrate the following: the cause of the upset can
be identified, the permitted facility was being properly operated at the time of the upset, and the
permit holder made the required 24-hour notification. In any enforcement proceeding, the burden
of proof is on the permit holder, through properly signed operating logs or other relevant
evidence, to demonstrate an upset has occurred.
Because Section 510 of the CWA authorizes permit authorities to include more stringent
controls than those contained in the federal regulations, any bypass and upset provisions must be
included in permits issued by permit authorities to become available to permit holders. Permit
authorities should anticipate that permit holders with properly designed and operated wastewater
treatment systems would have very few, if any, bypasses or upsets in the course of a five-year
NPDES permit that meet the above criteria.
14.4 VARIANCES AND MODIFICATIONS
The CWA requires application of effluent limitations established pursuant to Section 301
or the pretreatment standards of Section 307 to all direct and indirect dischargers. However, the
statute provides for the modification of these national requirements in a limited number of
circumstances. The Agency has established administrative mechanisms to provide an opportunity
for relief from the application of the national effluent limitations guidelines for categories of
existing sources for toxic, conventional, and nonconventional pollutants.
As opposed to the bypass and upset provisions that are applicable within the term of a
permit, the permit writer develops the variance and alternative limitations at the time of draft
permit renewal so that the variance and alternative limitations are subject to public review and
comment at the same time the entire permit is put on public notice. The variance and alternative
limitations remain in effect for the term of a permit, unless the permit writer modifies it prior to
expiration.
A permit applicant must meet specific data requirements before a variance is granted. As
the term implies, a variance is an unusual situation, and the permit writer should not expect to
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Section 14- Regulatory Implementation
routinely receive variance requests. The permit writer should consult 40 CFR §124.62 for
procedures on making decisions on the different types of variances, which are discussed below.
14.4.1 Fundamentally Different Factors Variances
As explained above, the CWA requires application of the effluent limitations established
pursuant to Section 301 or the pretreatment standards of Section 307 to all direct and indirect
dischargers. However, the statute provides for the modification of these national requirements in
a limited number of circumstances. Moreover, the Agency has established administrative
mechanisms to provide an opportunity for relief from the application of national effluent
limitations guidelines and pretreatment standards for categories of existing sources for priority,
conventional, and nonconventional pollutants.
EPA may develop, with the concurrence of the state, effluent limitations or standards
different from the otherwise applicable requirements for an individual existing discharger if it is
fundamentally different with respect to factors considered in establishing the effluent limitations
or standards applicable to the individual discharger. Such a modification is known as an PDF
variance.
EPA, in its initial implementation of the effluent guidelines program, provided for the
PDF modifications in regulations, which were variances from the BPT effluent limitations, BAT
limitations for toxic and nonconventional pollutants, and BCT limitations for conventional
pollutants for direct dischargers. PDF variances for toxic pollutants were challenged judicially
and ultimately sustained by the Supreme Court Chemical Manufacturers Association v. Natural
Resources Defense Council, 470 U.S. 116, 124 (1985).
Subsequently, in the Water Quality Act of 1987, Congress added new CWA Section
301(n). This provision explicitly authorizes modifications of the otherwise applicable BAT
effluent limitations, if a discharger is fundamentally different with respect to the factors specified
in CWA Section 304 (other than costs) from those considered by EPA in establishing the effluent
limitations. CWA Section 301(n) also defined the conditions under which EPA may establish
alternative requirements. Under Section 301(n), an application for approval of a FDF variance
must be based solely on (1) information submitted during rulemaking raising the factors that are
fundamentally different or (2) information the applicant did not have an opportunity to submit.
The alternate limitation must be no less stringent than justified by the difference and must not
result in markedly more adverse non-water quality environmental impacts than the national
limitation.
EPA regulations at 40 CFR Part 125, subpart D, authorizing the regional administrators
to establish alternative limitations, further detail the substantive criteria used to evaluate FDF
variance requests for direct dischargers. Thus, 40 CFR 125.31(d) identifies six factors (e.g.,
volume of process wastewater, age and size of a discharger's facility) that may be considered in
determining if a discharger is fundamentally different. The Agency must determine whether,
based on one or more of these factors, the discharger in question is fundamentally different from
the dischargers and factors considered by EPA in developing the nationally applicable effluent
guidelines. The regulation also lists four other factors (e.g., inability to install equipment within
the time allowed or a discharger's ability to pay) that may not provide a basis for an FDF
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Section 14- Regulatory Implementation
variance. In addition, under 40 CFR 125.3 l(b) (3), a request for limitations less stringent than the
national limitation may be approved only if compliance with the national limitations would result
in either (a) a removal cost wholly out of proportion to the removal cost considered during
development of the national limitations, or (b) a non-water quality environmental impact
(including energy requirements) fundamentally more adverse than the impact considered during
development of the national limits. The legislative history of Section 301(n) underscores the
necessity for the PDF variance applicant to establish eligibility for the variance. EPA's
regulations at 40 CFR 125.32(b)(l) impose this burden upon the applicant. The applicant must
show that the factors relating to the discharge controlled by the applicant's permit that are
claimed to be fundamentally different are, in fact, fundamentally different from those factors
considered by EPA in establishing the applicable guidelines. In practice, very few FDF variances
have been granted for past ELGs. An FDF variance is not available to a new source subject to
NSPS. DuPontv. Train, 430 U.S. 112 (1977).
14.4.2 Economic Variances
Section 301(c) of the CWA allows a plant to request a variance for nonconventional
pollutants from technology-based BAT effluent limitations due to economic factors, at the
request of the plant and on a case-by-case basis. There are no implementing regulations for
§301(c); rather, variance requests must be made and reviewed based on the statutory language in
CWA §301(c). The economic variance may also apply to nonguideline limits in accordance with
40 CFR §122.21(m)(2)(ii). The applicant normally files the request for a variance during the
public notice period for the draft permit. Other filing time periods may apply, as specified in 40
CFR §122.21(m)(2). Specific guidance for this type of variance is provided in Draft Guidance
for Application and Review of Section 301(c) Variance Requests, dated August 21, 1984,
available on EPA's Web site at http://www.epa.gov/npdes/pubs/OWM0469.pdf
The variance application must show that the modified requirements:
• Represent the maximum use of technology within the economic capability of the
owner or operator; and
• Result in further progress toward the goal of discharging no process wastewater.
Facilities in industrial categories other than utilities must conduct three financial tests to
determine if they are eligible for a 301(c) variance. Generally, EPA will grant a variance only if
all three tests indicate that the required pollution control is not economically achievable and the
applicant makes the requisite demonstration regarding "reasonable further progress."
To meet the second requirement for a 301(c) modification, the applicant must at a
minimum demonstrate compliance with all applicable BPT limitations and pertinent water
quality standards. In addition, the proposed alternative requirements must reasonably improve
the applicant's discharge.
14.4.3 Water Quality Variances
Section 301(g) of the CWA authorizes a variance from BAT effluent guidelines for
certain nonconventional pollutants due to localized environmental factors. These pollutants
14-21
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Section 14- Regulatory Implementation
include ammonia, chlorine, color, iron, and total phenols. As this proposed rule would not
establish limitations or standards for any of these pollutants, this variance would not be
applicable to this particular rule.
14.4.4 Thermal Discharge Variances
Section 316(a) of the CWA allows variances from effluent limitations for the thermal
component of a discharge. See 40 CFR 125, Subpart H for regulations for submitting and
reviewing thermal discharge variance requests. Permits may include less stringent alternative
thermal effluent limits if the discharger demonstrates that the promulgated limits are more
stringent than necessary to ensure the protection and propagation of a balanced, indigenous
community of shellfish, fish, and wildlife in and on the water body into which the discharge is
made. The applicant must take into account the cumulative impact of its thermal discharge
together with all other significant impacts on the species affected.
14.4.5 Net Credits
In some cases, solely because of the level of pollutants in the intake water, plants find it
difficult or impossible to meet technology-based limits with BAT/BCT technology. Under
certain circumstances, the NPDES regulations allow credit for pollutants in intake water. 40 CFR
§122.45(g) establishes the following requirements for net limitations:
• Credit for generic pollutants, such as BOD or TSS, are authorized only where the
constituents resulting in the effluent BOD and TSS are similar between the intake
water and the discharge;
• Credit is authorized only up to the extent necessary to meet the applicable limitation
or standard, with a maximum value equal to the influent concentration;
• Intake water must be taken from the same body of water into which the discharge is
made; and
• Net credits do not apply to the discharge of raw water clarifier sludge generated
during intake water treatment.
Permit writers are authorized to grant net credits for the quantity of pollutants in the
intake water where the applicable ELGs specify that the guidelines are to be applied on a net
basis or where the pollution control technology would, if properly installed and operated, meet
applicable ELGs in the absence of the pollutants in the intake waters. The proposed ELGs are to
be applied on a gross basis.
14.4.6 Removal Credits
Section 307(b)(l) of the CWA establishes a discretionary program for POTWs to grant
"removal credits" to their indirect dischargers. Removal credits are a regulatory mechanism by
which industrial users may discharge a pollutant in quantities that exceed what would otherwise
be allowed under an applicable categorical pretreatment standard because it has been determined
that the POTW to which the industrial user discharges consistently treats the pollutant. EPA has
promulgated removal credit regulations as part of its pretreatment regulations. See 40 CFR
14-22
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Section 14- Regulatory Implementation
403.7. These regulations provide that a POTW may give removal credits if prescribed
requirements are met. The POTW must apply to and receive authorization from the Approval
Authority. To obtain authorization, the POTW must demonstrate consistent removal of the
pollutant for which approval authority is sought. Further, the POTW must have an approved
pretreatment program. Finally, the POTW must demonstrate that granting removal credits will
not cause the POTW to violate applicable Federal, State and local sewage sludge requirements.
40CFR403.7(a)(3).
The United States Court of Appeals for the Third Circuit interpreted the Clean Water Act
as requiring EPA to promulgate the comprehensive sewage sludge regulations required by CWA
§405(d)(2)(A)(ii) before any removal credits could be authorized. See NRDC v. EPA, 790 F.2d
289, 292 (3d Cir., 1986); cert, denied., 479 U.S. 1084 (1987). Congress made this explicit in the
Water Quality Act of 1987, which provided that EPA could not authorize any removal credits
until it issued the sewage sludge use and disposal regulations. On February 19, 1993, EPA
promulgated Standards for the Use or Disposal of Sewage Sludge, which are codified at 40 CFR
Part 503 (58 FR 9248). EPA interprets the Court's decision in NRDC v. EPA as only allowing
removal credits for a pollutant if EPA has either regulated the pollutant in part 503 or established
a concentration of the pollutant in sewage sludge below which public health and the environment
are protected when sewage sludge is used or disposed.
The Part 503 sewage sludge regulations allow four options for sewage sludge disposal:
(1) land application for beneficial use, (2) placement on a surface disposal unit, (3) firing in a
sewage sludge incinerator, and (4) disposal in a landfill which complies with the municipal solid
waste landfill criteria in 40 CFR Part 258. Because pollutants in sewage sludge are regulated
differently depending upon the use or disposal method selected, under EPA's pretreatment
regulations the availability of a removal credit for a particular pollutant is linked to the POTW's
method of using or disposing of its sewage sludge. The regulations provide that removal credits
may be potentially available for the following pollutants:
1. If POTW applies its sewage sludge to the land for beneficial uses, disposes of it in a
surface disposal unit, or incinerates it in a sewage sludge incinerator, removal credits
may be available for the pollutants for which EPA has established limits in 40 CFR
Part 503. EPA has set ceiling limitations for nine metals in sludge that is land applied,
three metals in sludge that is placed on a surface disposal unit, and seven metals and
57 organic pollutants in sludge that is incinerated in a sewage sludge incinerator. 40
CFR403.7(a)(3)(iv)(A).
2. Additional removal credits may be available for sewage sludge that is land applied,
placed in a surface disposal unit, or incinerated in a sewage sludge incinerator, so
long as the concentration of these pollutants in sludge do not exceed concentration
levels established in Part 403, Appendix G, Table II. sewage sludge that is land
applied, removal credits may be available for an additional two metals and 14 organic
pollutants, sewage sludge that is placed on a surface disposal unit, removal credits
may be available for an additional seven metals and 13 organic pollutants, sewage
sludge that is incinerated in a sewage sludge incinerator, removal credits may be
available for three other metals 40 CFR 403.7(a)(3)(iv)(B).
14-23
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Section 14- Regulatory Implementation
3. When a POTW disposes of its sewage sludge in a municipal solid waste landfill that
meets the criteria of 40 CFR Part 258, removal credits may be available for any
pollutant in the POTW's sewage sludge. 40 CFR 403.7(a)(3)(iv)(C).
14.5 REFERENCES
1. U.S. EPA. 2010. NPDES Permit Writer's Manual. EPA-833-K-10-001. Washington, DC.
(September).
2. U.S. EPA. 1989. Industrial User Permitting Guidance Manual. EPA 833/R-89-001.
Washington, DC. (29 September).
3. U.S. EPA. 2005. Method 245.7, Mercury in Water by Cold Vapor Atomic Fluorescence
Spectrometry, Revision 2.0. EPA-821-R-05-001. Washington, DC. (February).
4. U.S. EPA. 2002. Method 163 IE, Revision E: Mercury in Water by Oxidation, Purge and
Trap, and Cold Vapor Atomic Fluorescence Spectrometry. EPA-821-R-02-019.
Washington, DC. (August).
5. U.S. EPA. 2009. Steam Electric Power Generating Point Source Category: Final Detailed
Study. EPA 821-R-09-008. Washington, DC. (October). DCN SE00003.
6. U.S. EPA. 2012a. Draft Procedure for Trace Element Analysis of Flue Gas
Desulfurization Wastewaters Using Perkin Elmer NexION 300D ICP-MS
Collision/Reaction Cell Procedure. (1 December). DCN SE03868.
7. U.S. EPA. 2012b. Draft FGD ICP/MS Collision Cell Procedure for Trace Element
Analysis in Flue Gas Desulfurization Wastewaters. (June). DCN SE03835.
8. U.S. EPA. 1984. Technical Guidance Manual for the Regulations Promulgated Pursuant
to Section 301(g) of the Clean Water Act of 1977, 40 CFR Part 125 (Subpart F).
Washington, D.C.
14-24
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Appendix A - Survey Design and Calculation of National Estimates
APPENDIX A
SURVEY DESIGN AND CALCULATION OF NATIONAL ESTIMATES
-------
Appendix A - Survey Design and Calculation of National Estimates
Survey Design and Calculation of National Estimates
In June 2010, EPA distributed a survey, entitled The Questionnaire for the Steam Electric
Power Generating Effluent Guidelines, to 733 steam electric power plants. The survey was
designed to collect technical information related to wastewater generation and treatment, and
economic information such as costs of wastewater treatment technologies and financial
characteristics of affected companies.
Section 1 of this appendix describes the survey design, and Section 2 provides a summary
of the survey responses. Section 3 discusses the weighting procedures, while Section 4 discusses
the calculation of national estimates and variance estimation.
A.1 SURVEY DESIGN
This section describes the development of the sample frame, stratification factors, sample
design and selection, and the targeted level of precision.
A.1.1 Sample Frame
The sample frame for the Steam Electric Survey is a list of steam electric power
generating plants subject to the steam electric power generating effluent guidelines. In addition
to listing population elements in terms of contact information (address, phone number, etc.),
other information in a sample frame was also used to design the survey.
For this survey, EPA considered the target population to be all fossil- and nuclear-fueled
steam electric power plants in the U.S. that report as operating under North American Industry
Classification System (NAICS) code 22. EPA constructed the sampling frame using databases
that are maintained by the Energy Information Administration (EIA), a statistical agency of the
U.S. Department of Energy (DOE), and supplemented it with additional information compiled by
EPA. The primary source of information was the 2007 Electric Generator Report (Form EIA-
860). Supplemental information was found in Form EIA-923 and in a survey conducted by
EPA's Office of Resource Conservation and Recovery. In addition, EPA identified several
facilities that started operations after 2007 and obtained necessary information for them.
Using these sources of information, EPA compiled a sample frame containing
information on 1,197 steam electric power plants with a total of 2,571 generating units that were
within the scope of the survey.
A.1.2 Plant Fuel Classification: the Main Stratification Variable
For this survey, the plant is the sampling unit. EPA stratified the sample frame based on
the plant fuel classification, which was determined by the type of fuel used by each of the
generating units in operation at the plant. EPA classified each plant's fuel type in the sample
frame using the following hierarchical structure:
First, plants were identified as coal plants if the plant had one or more generating units
that used coal as its primary or secondary fuel. Since the integrated gasification combined cycle
(IGCC) units used coal as the fuel source, they were classified as coal plants.
-------
Appendix A - Survey Design and Calculation of National Estimates
Second, plants were identified as petroleum coke plants if the plant had one or more
generating units that used petroleum coke as its primary or secondary fuel (and the plant was not
already classified as a coal plant);
Third, among the remaining plants, those plants for which all units used the same primary
fuel type were classified as follows:
• Gas: all units used gas as the primary fuel type, but did not use combined cycle steam
turbines;
• Gas-Combined Cycle (CC): all units used gas as the primary fuel type and each used
combined cycle steam turbines;
• Oil: all units used oil as the primary fuel type;
• Nuclear: all units were nuclear-fueled;
Finally, all remaining plants with generating units having different fuel types were
classified as combination plants as follows:
• Combination - Gas and Gas-CC;
• Combination - Gas and Oil;
• Combination - Gas-CC and Oil;
• Combination - Gas, Gas-CC, and Oil;
• Combination - Gas-CC, Nuclear, and Oil.
A. 1.3 Sample Design
The basic sample design of the survey was a stratified design of the plants. The first
stratification variable was the plant fuel classification as defined in subsection A. 1.2. The second
stratification variable was regulatory status, by which each plant was classified as regulated or
unregulated. The questionnaire included questions about generating units, and each selected
plant was required to complete the questionnaire for every generating unit at the plant.
Another candidate variable for stratification was North American Electric Reliability
Corporation (NERC) region but it was not used as a stratification variable. Instead it was used as
a sorting variable in systematic sampling to ensure the sample be spread evenly by NERC
region; stratum members were sorted by NERC region and every k' member was selected
(where k is the ratio of the stratum population size to the stratum sample size). As a result of this
systematic sampling, the percentage representation of each NERC region in the sample was
expected to be proportional to the size of the region in the population.
All coal and petroleum coke plants were taken with certainty (i.e., all plants in the
stratum were selected), whereas for other strata, the sampling rate was 30 percent with a
minimum sample size constraint of 10. Therefore, if a stratum population size was less than 34,
10 plants were selected systematically or all plants if there were not more than 10 plants. Due to
this constraint, most combination strata were taken with certainty. Table A-l presents the
A-2
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Appendix A - Survey Design and Calculation of National Estimates
distribution of the sample frame (plants and generating units) and sample allocation of the plants
by design stratum.
Table A-l. Population Distribution of Plants and Generating Units, and Plant
Sample Size by Design Stratum
Plant Fuel Classification
Coal
Gas
Gas-Combined Cycle (CC)
Nuclear
Oil
Petroleum Coke
Combination: Gas-CC and Nuclear
and Oil
Combination: Gas-CC and Oil
Combination: Gas and Gas-CC
Combination: Gas and Gas-CC and
Oil
Combination: Gas and Oil
Total
Regulatory Status
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Sample Frame
Plant
344
151
129
54
96
276
31
32
23
20
0
9
1
0
2
0
20
6
1
0
1
1
1,197
Generating Unit
963
340
310
137
129
375
52
48
55
38
0
9
5
0
6
0
69
23
4
0
4
4
2,571
Sample
Plant
344
151
39
16
29
83
10
10
10
10
0
9
1
0
2
0
10
6
1
0
1
1
733
The exact number of generating units from these 733 plants to be selected was not known
prior to the sample draw because the number of generating units varies by plant and thus would
depend on the specific set of plants selected. EPA estimated that about 1,722 generating units
would be included in the survey from these 733 plants. This estimated number of generating
units was arrived at in the following manner. Generating units within plants that are selected with
certainty will automatically be included in the sample. For each non-certainty stratum, EPA
estimated the corresponding number of generating units by assuming that the rate of generating
units per plant in the sample will be the same as the rate among plants in the sampling frame.
A.1.4 Subsample of Coal and Petroleum Coke Plants for Questionnaire Parts E, F, and G
A subsample of coal and petroleum coke plants was selected to receive additional
questions in Parts E, F, and G of the questionnaire. To minimize the burden on small entities,
A-3
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Appendix A - Survey Design and Calculation of National Estimates
EPA did not collect this additional information from plants that were operated by small entities.
Of the 495 coal plants, 55 of these were identified as small entities. The remaining 440 non-small
(i.e., not owned by small entities) coal plants were further stratified by whether the plant had a
pond or a landfill for waste management as EPA intended to collect information from plants that
had ponds and/or landfills containing coal combustion residues (i.e., coal ash or flue gas
desulfurization (FGD) wastes). Thus, plants that were classified as "No ponds or landfills" were
excluded from sub sampling for Parts E, F, and G.
Strata defined by pond-landfill status are as follows:
• Pond Only - FGD: Contained all coal plants identified in the sample frame as having
a pond with FGD waste as one of its contents, but not a landfill;
• Pond Only - No FGD: Contained all coal plants with an ash pond that does not
receive FGD waste, but without landfill;
• Landfill Only - FGD: Contained all coal plants that had a landfill with FGD waste as
one of its contents, but no pond containing coal combustion residues (CCR);
• Landfill Only - No FGD: Contained all coal plants that had a landfill containing ash
but without FGD wastes, and did not operate a CCR pond;
• Ponds and Landfills: Contained all coal plants that had both ponds and landfills
containing CCR (either ash or FGD wastes). To minimize the number of strata, no
distinction in plants was made by FGD status; and
• No Ponds or Landfills: Contained all coal plants that did not store or dispose ash or
FGD wastes in a pond or landfill.
Seven plants known to operate leachate collection systems were selected with certainty
because EPA wanted to capture this information fully. EPA excluded two coal plants (containing
a total of six generating units) from subsampling to avoid the potential burden imposed on these
plants. Other plants were subsampled with a sampling rate of 30 percent or 10 plants, whichever
was larger for each stratum listed above.
Table A-2 displays the population counts of coal and petroleum coke plants and the
corresponding number of generating units, and the sample size for each stratum defined by
business size and pond-landfill status. The total sample size for Parts E, F, and G for the coal
plants is 94, of which seven were plants with leachate system selected with certainty (shown in
parentheses in table A-2). All three non-small petroleum coke plants were included in the
subsample that received Parts E, F, and G. These plants were not classified by pond-landfill
status. Therefore, the total sample size for Parts E, F, and G was 97, which consisted of 94 coal
plants and 3 petroleum coke plants.
A-4
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Appendix A - Survey Design and Calculation of National Estimates
Table A-2. Population Counts of Coal/Pet Coke Plants and Generating Units,
and Parts EFG Subsample Size by Substratum
Plant Fuel
Classification
Coal
Pet Coke
Total
Business
Size
Small
Non-Small
Small
Non-Small
Pond/Landfill
All
Pond Only - FGD
Pond Only - No FGD
Landfill Only - FGD
Landfill Only - No FGD
Both Pond and Landfill
No Pond or Landfill
Avoid Burden3
~
~
Population
Count of Plants
55
39
99
18
55
84
143
2
6
3
504
Population
Count of
Generating
Units
121
122
315
34
142
256
307
6
6
o
5
1,312
Sample Size
(Certainty
Selection)11
0
12(1)
30(0)
10(1)
17(3)
25(2)
0
0
0
3
97(7)
a - EPA excluded two coal plants from receiving parts E, F, and G to avoid overburdening these plants.
b - In parentheses, the number of plants with the leachate system selected with certainty is shown. The sample size
includes this number.
The exact number of generating units at the 94 coal plants to be selected was not known
prior to the sample draw because the number of generating units varies by plant and thus would
depend on the specific set of coal plants selected. Prior to selecting the sample of coal plants,
EPA estimated that about 272 generating units at these 94 coal plants would be included in the
survey. In addition, there were three petroleum coke generating units (from three plants)
that were selected with certainty. Thus, it was expected that there would be about 275 generating
units from these 97 plants that would be included in the subsample.
A.1.5 Sample Selection
The regular sample that received the questionnaire without Parts E, F, and G was selected
according to the sample design described in subsection A. 1.3, resulting in 733 sample plants. The
majority of the strata were sampled with certainty by design or the constraint of minimum
sample size of 10 if possible. Because of this minimum sample size constraint, almost all
combination fuel type strata were certainty strata.
The coal and petroleum coke plants were selected with certainty in the regular sample by
design but only a subsample of 97 was selected by a stratified design to receive Parts E, F, and G
of the questionnaire. This subsample is called the Parts EFG subsample. The sample results are
summarized in Table A-3. The table also presents the base weights, which are the inverse of the
sampling probability.
A-5
-------
Appendix A - Survey Design and Calculation of National Estimates
Table A-3. Summary of Sample Selection of Plants
Stratum/Coal Substratum
Coal - Small Entity
Coal - Pond Only -FGD
Coal - Pond Only -no FGD
Coal - Landfill Only - FGD
Coal - Landfill Only - No FGD
Coal - Both Pond and Landfill
Coal - No Pond and Landfill
Coal Subtotal
Gas-Regulated
Gas-Unregulated
Gas-CC-Regulated
Gas-CC-Unregulated
Nuclear-Regulated
Nuclear-Unregulated
Oil-Regulated
Oil-Unregulated
Petroleum Coke -Unregulated/Small Entity
Petroleum Coke-Unregulated/Non-small
Combination: Gas-CC, Nuclear, and Oil-
Regulated
Combination: Gas-CC and Oil-Regulated
Combination: Gas and Gas-CC-Regulated
Combination: Gas and Gas-CC-Unregulated
Combination: Gas, Gas-CC and Oil-
Regulated
Combination: Gas and Oil-Regulated
Combination: Gas and Oil-Unregulated
Non-Coal Subtotal
Grand Total
Population
Size
55
39
101b
18
55
84
143
495
129
54
96
276
31
32
23
20
6
3
1
2
20
6
1
1
1
702
1,197
Regular Sample
Size
55
39
101
18
55
84
143
495
39
16
29
83
10
10
10
10
6
o
J
1
2
10
6
1
1
1
238
733
Base Weight
-
3.31
3.38
O O 1
3.31
o o o
J.JJ
3.1
3.2
2.3
2
1
1
1
1
2
1
1
1
1
-
-
Subsample
Size
-
12
30
10
17
25
-
94
-
-
-
-
-
-
-
-
-
3
-
-
-
-
-
-
-
3
97
Base Weight"
3.45
3.37
1.89
3.71
3.57
-
-
-
-
-
-
-
-
-
-
1
-
-
-
-
-
-
-
-
-
a - The subsample base weights are for non-certainty coal plants or for certainty petroleum coke plants.
b - This count includes two plants that were not subsampled due to burden consideration.
A.1.6 Expected Precision
An expected precision is usually calculated for a population proportion of 50 percent.
Assuming a response rate of 90 percent, the final sample size for the regular sample was
expected to be 660 (i.e., 90 percent of the 733 sampled plants). To calculate an expected
precision, a design effect of one was assumed, and the finite population correction was ignored
to be conservative. The stratification would decrease the design effect but weighting adjustment
for nonresponse would increase the design effect. So we assumed that these two effects would
A-6
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Appendix A - Survey Design and Calculation of National Estimates
cancel each other to make the design effect close to one. Under this scenario, the 95 percent
confidence interval for a point estimate of a population proportion of 50 percent was expected to
be within ±3.8 percentage points of the point estimate. If we project the precision for a
population proportion of 30 percent, the 95 percent confidence interval would be within ±3.5
percentage points.
For the subsample of the coal plants for the Parts E, F, and G questionnaire, under the
same assumption, it was estimated to have an expected sample size of 85 from the subsample of
94 coal plants. The 95 percent confidence interval for a point estimate of a population proportion
of 30 percent was expected to be within +/- 9.2 percentage points of the point estimate.
For generating unit level estimates, under the same assumption made above and further
ignoring the clustering effect, the final sample size was expected to be 1,550 (i.e., 90 percent of
the expected number of generating units of 1,722 in the sample), and the 95 percent confidence
interval for a point estimate of a population proportion of 50 percent was expected to be within
+/- 2.5 percentage points of the point estimate.
EPA determined that these precisions were sufficient to meet the objectives of the survey,
both for overall plant-level and generating unit level estimates. Moreover, the actual precision is
expected to be better than the projected precision when the finite population correlation is
incorporation. Furthermore, the plant level response rate was 100 percent, which further adds
more precision than projected.
A.2 SURVEY RESPONSES
Of the 733 survey questionnaires sent out, all were returned, so the plant level response
rate was 100 percent. However, the survey responses indicate that the frame information on plant
eligibility, plant fuel classification, and pond-landfill status for coal and petroleum coke plants
was imperfect. The following subsections provide updated information on the eligibility
assessment, plant classifications, and pond-landfill classification.
A.2.1 Survey Result of the Eligibility Assessment
Out of 733 respondent plants, a total of 53 plants were found to be ineligible (i.e., out of
scope). The reasons for the ineligibility include the following: plant did not have the capability to
engage in steam electric power production; plant would be retired by December 31, 2011; or
plant did not generate electricity in 2009 using any fossil or nuclear fuels. Of these 53 plants that
were deemed ineligible, the distribution over the plants fuel types is as follows: 26 coal plants,
17 gas plants, 6 gas-combined cycle plants, 2 oil plants, 1 petroleum coke plant, and 1
combination plant. To see the distribution of these ineligible plants further classified by
regulatory status, see Table A-6 in Section A.3.1, where the number of eligible plants is shown
and the number of ineligible plants can be obtained by the balance between the original sample
size and the number of eligible plants.
A-7
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Appendix A - Survey Design and Calculation of National Estimates
A.2.2 Update of Plant Fuel Type Classification
At the survey design stage, plant fuel type was classified based on the EIA data and other
information available to the EPA. After receiving the survey responses, EPA reclassified the
sampled plant fuel types using the information from the questionnaire. EPA found that 17 of 680
eligible plants had a fuel type that was different from the original plant fuel type determined at
the design stage. The table below provides the final plant fuel classification for all 680 eligible
sampled plants based on the survey data.
Table A-4. Final Eligible Sampled Plant Fuel Types
Final Plant Fuel Type
(Classified Based on the Survey Data)
Coal
Gas
Gas - Combined Cycle
Nuclear
Oil
Petroleum Coke
Combination: Gas-CC and Nuclear and Oil
Combination: Gas-CC and Oil
Combination: Gas and Gas-CC
Combination: Gas and Gas-CC and Oil
Combination: Gas and Oil
Total
Number of Plants
463
44
109
20
13
9
1
o
5
14
1
3
680
A.2.3 Survey Results for the Coal and Petroleum Coke Plants and the Subsample for
Parts E, F, and G
The 504 coal and petroleum coke plants identified at the survey design stage were
selected with certainty, but only a subsample of 97 of these plants was selected to receive Parts
E, F, and G of the questionnaire using the sample design described in Section A. 1.4.
Of the 94 coal plants that were selected to receive Parts E, F, and G, 92 plants remained
eligible after receiving the survey responses. Of the 3 petroleum coke plants selected to receive
Parts E, F, and G, two plants remained eligible after receiving the survey responses.
Further, the updated pond-landfill status for each plant was obtained from Part A, which
was completed by every regular sample plant, including those that were not subject to
subsampling. Based on the survey information, EPA found that some of the pond-landfill for
coal and petroleum coke plants were incorrectly classified in the frame. The table below provides
the final summary of how these coal and petroleum coke plants were classified based on the
updated survey data.
A-8
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Appendix A - Survey Design and Calculation of National Estimates
Table A-5. Frequency Summary by the Updated Pond-Landfill Status for
Eligible Coal Plants and by Petroleum Coke Status in the Population and in
the Parts EFG Subsample
Updated Pond/Landfill Stratum
(Based on the Survey Data)
Coal - Both Pond and Landfill
Coal - Landfill Only - FGD
Coal - Landfill Only - No FGD
Coal - Pond Only - FGD
Coal - Pond Only - No FGD
Coal -No Pond or Landfill
Petroleum Coke
Total
Eligible Plants in the
Population
192a
12
22
37
112a
88
9
472
Eligible Plants in
Subsample
56
1
1
7
27
0
2
94
a - The count includes coal plants, which were excluded from subsampling due to concerns of burden.
A.3 WEIGHTING OF THE SURVEY DATA
This section describes the weighting procedure for the regular sample and the subsample
at the pi ant level.
A.3.1 Plant-Level Weighting
Weighting the survey data starts with calculating the base weight, which is the inverse of
the sampling probability, and then nonresponse adjustment is usually applied. Nonresponse
adjustment entails adjusting the base weight for both non-response and unknown eligibility.
However for the Steam Electric Survey, there was neither non-response nor sample plants with
unknown eligibility. Thus, there was no need for EPA to apply this type of weighting adjustment.
Consequently, the final weight for this survey is defined as the base weight for all sample plants
in the regular sample (note that the Parts EFG subsample is also included in the regular sample).
The ineligible plants in the sample represent the ineligible population and are given the same
base weights as well.
Reclassification of stratification variables does not affect the weighting because the
weight is the inverse of the selection probability, which is determined at the time of sample
selection. However, a reclassified stratum now consists of plants from other design strata that
may have different weights, and this would affect analyses that would be done using the updated
classification. Table A-6 shows the original population and sample sizes, the number of sample
plants that were eligible among the original regular sample, the final weight, the reclassified
number of eligible plants that includes plants from other strata due to reclassification, and the
estimated population size based on updated classification, which was calculated as the sum of
final weights of the reclassified plants.
A-9
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Appendix A - Survey Design and Calculation of National Estimates
Table A-6. Estimated Eligible Population Size for Survey-Based Fuel Type Classification
Fuel
Classification
Coal
Gas
Gas-CC
Nuclear
Oil
Petroleum Coke a
Comb: Gas-CC,
Nuclear & Oil
Comb: Gas-CC
and Oil
Comb: Gas and
Gas-CC
Comb: Gas and
Gas-CC and Oil
Comb: Gas and
Oil
Total
Regulatory
Status
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Regulated
Unregulated
Population
Size in
Frame
344
151
129
54
96
276
31
32
23
20
0
9
1
0
2
0
20
6
1
0
1
1
1,197
Original
Sample
Size
344
151
39
16
29
83
10
10
10
10
0
9
1
0
2
0
10
6
1
0
1
1
733
Number
of
Eligible
Plants
328
141
29
9
28
78
10
10
9
9
0
8
1
0
2
0
10
5
1
0
1
1
680
Final
Weight
1.0
1.0
3.308
3.375
3.310
3.325
3.1
3.2
2.3
2.0
-
1.0
1.0
-
1.0
-
2.0
1.0
1.0
-
1.0
1.0
-
Reclassified
No. of
Eligible
Plants"
323
140
31
13
30
79
10
10
8
5
1
8
1
-
2
1
12
2
1
0
0
3
680
Estimated
Population
Sizeb
323
140
98
39
92
258
31
32
18
10
1
8
1
-
2
1
26
2
1
-
-
5
1,088
a - The count includes reclassified plants initially belonging to a different design stratum.
b - This column shows the sum of the final weights of reclassified plants that was rounded to the nearest integer.
While the column "Number of Eligible Plants" provides the number of eligible plants
based on the original fuel type classification (regardless of their reclassified fuel type), the
column named "Reclassified Number of Eligible Plants" gives the number of eligible plants
based on the reclassification of their fuel type. For example, there were 29 eligible plants among
those plants originally classified as gas - regulated but 31 plants fell in the class after
reclassification based on the survey response. Therefore, it should be noted that the estimated
population size in the last column is the (rounded) sum of the final weights of the reclassified
eligible plants as each plant carries its own final weight wherever it is reclassified. It is not the
A-10
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Appendix A - Survey Design and Calculation of National Estimates
same in general as the product of the reclassified number of eligible plants (which may have
different final weights due to reclassification) and the final weight for the original stratum.119
In general, the estimated population size is smaller than the frame population size for due
to reclassification and loss of ineligible plants. However, it could be larger if more plants were
reclassified into that stratum. The overall estimated population size for this survey is 9.9 percent
less than the frame population size due to loss of ineligible plants.
The same weighting principle applies to the subsample of 97 coal or petroleum coke
plants that received Parts E, F, and G because this subsample was selected from the census of the
coal/petroleum coke population. However, there is an important departure from the weighting
method used for the full (regular) sample because the subsample was made also to cover plants,
which were not subject to subsampling. Moreover, it was necessary to do more because almost
half of the plants in the subsample changed their stratification. So, post-stratification weight
adjustment was used to address these issues, which is further explained in Section A.3.2 below.
A.3.2 Plant-Level Weighting for the Parts EFG Subsample
The subsample of 97 plants was selected from the 504 coal or petroleum coke plants
identified in the sample frame to receive Parts E, F, and G of the questionnaire. However, 206
plants were not subject to subsampling (including plants operated by small entities (61), plants
with no CCR pond or landfill (143), and plants excluded to avoid overburdening (2)).
Nevertheless, EPA wanted to use the subsample to represent the whole population. Therefore,
non-coverage weighting adjustment was performed for the subsample.
One subsample was selected for Parts E, F, and G but Part E items do not have as much
bearing with the Pond-Landfill status as do Parts F and G items. Part E of the questionnaire
collected information about metal cleaning wastes, which is relevant to all plants, including
plants with or without CCR ponds or landfills. On the other hand, since Parts F and G are
applicable only to coal or petroleum coke plants with CCR ponds or landfills, the weighting had
to account for the Pond-Landfill status. To address the difference in the characteristics of Part E
items and Parts F and G items, two different sets of weights were developed as explained below:
one set for Part E and another set for Parts F and G.
A.3.2.1 Development of the Final Weight for Part E
As explained in the previous section, the relevant Part E items do not have much bearing
with the stratification by the Pond-Landfill status. Therefore, non-coverage weight adjustment
was done so that the sum of the adjusted weights of the subsample of 94 eligible plants is equal
to the eligible population size of 472 (504 frame size minus 32 plants that were ineligible or were
reclassified as non-coal or non-petroleum coke plants) regardless of their Pond-Landfill status.
This amounts to using a single weighting adjustment factor that is given by 472 divided by the
total sum of the base weights of 94 eligible subsample plants, which is 290.4, so the factor is
119 In the Gas - Regulated stratum, there are 31 reclassified eligible plants, which consist of 29 original plants and 2
reclassified from the Coal stratum (see Table A-6). Therefore, the estimated eligible population size for the Gas -
Regulated stratum is obtained by 29*3.308+2*1 = 97.932, which is rounded to 98.
A-ll
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Appendix A - Survey Design and Calculation of National Estimates
472/290.4 = 1.6253. This factor is multiplied by the subsampling base weights to obtain the Part
E final weights.
A.3.2.2 Development of the Final Weight for Parts F and G
Since Parts F and G are only applicable to coal or petroleum coke plants with a CCR
pond or landfill, the relevant population for Parts F and G consists of all eligible coal plants with
either a CCR pond or a CCR landfill or petroleum coke plants. Therefore, the subsample of 94
coal or petroleum coke plants was weighted so that the final weights sum to the eligible
population size of 384 coal plants with a pond or landfill and petroleum coke plants (i.e., 384 =
472 eligible coal and petroleum coke plants - 88 plants without pond/landfill).
As shown in Table A-5 above, after the reclassification process, it was found that the
numbers of sampled plants in some updated substrata are very small (i.e., in the updated "Coal -
Landfill Only - FGD" and "Coal - Landfill Only - No FGD" strata, there was only 1 plant in
each received Parts E, F, and G of the questionnaire). Moreover, the ratios between the
population sizes and sample sizes vary widely. This indicates that if updated substrata are used as
post-strata for weight adjustment, the resulting weights will be very unstable, and it will cause
instability of the variance estimate. Therefore, small substrata were collapsed to form the post-
strata. With this goal in mind, the updated substrata "Coal - Landfill Only - FGD" and "Coal -
Landfill Only - No FGD" were collapsed into the updated substratum "Coal - Both Pond and
Landfill" resulting in four post-strata as follows:
• Post-stratum 1: Coal - Both Pond and Landfill, Coal - Landfill Only - FGD, and
Coal - Landfill Only - No FGD;
• Post-stratum 2: Coal - Pond Only - FGD;
• Post-stratum 3: Coal - Pond Only - No FGD;
• Post-stratum 4: Petroleum Coke.
Note that all post-strata above were defined using the updated strata.
The weight adjustment factors presented below were used to obtain the final survey
weights, which are the product of the adjustment factor and the initial base weight in each post-
stratum. The weight adjustment factor is defined as the ratio of the population size to the sum of
base weights of eligible subsample plants in the post-stratum.
A-12
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Appendix A - Survey Design and Calculation of National Estimates
Table A-7. Weight Adjustment Factors for the Four Post-Strata
Post Stratum
Number
1
2
o
J
4
Total
Updated Substratum
Coal - Both Pond and Landfill
Coal - Landfill Only - FGD
Coal - Landfill Only - No FGD
Coal - Pond Only - FGD
Coal - Pond Only - No FGD
Pet-Coke - Selected for EFG
Population
Size
226
37
112
9
384
Eligible
Sample Size
58
7
27
2
94
Weight
Adjustment
Factor
1.27
1.86
1.24
4.5
A.4 ESTIMATION METHOD
This section presents the general methodology and equations for calculating estimates
from the survey.
A.4.1 National Estimates
The survey collected many sub-items below the plant level. For example, some
characteristics of generating units were collected. However, sub-units (e.g., generating unit)
below the plant were all selected, therefore the weight appropriate for weighted analysis is the
same as the plant level weight. Some of the missing data were filled in using data from the 2009
EIA database, which is the same year basis as the data provided in response to the questionnaire.
A small amount of missing data remains, primarily among the sub-plant level variables.
Nevertheless, in the discussion below, no adjustments are made for missing data. For most
variables, the consequence of this is negligible due to the small amount of missing data.
There are three levels of analytical unit (plant, generating unit, sub-generating-unit
element) with item characteristics at each of these levels. Let whi be the sampling weight for
plant / within variance stratum h. 12° The variance stratum is defined in the following section,
where variance estimation is explained.
Different formulas are used for point estimation depending on the type of estimate. Since
estimation of the population total is the most basic, and many estimates can be defined using the
total estimates, we first discuss estimation of the population total.
Suppose that the parameter of interest is the population total (7) of a variable denoted by
y. Then the plant-level weighted total of the_y-values for plant /' in variance stratum h,yhi, is
defined as:
We could use the design stratum to give the estimation formula but to tie point estimation with variance
estimation, it is more convenient to use the variance stratum.
A-13
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Appendix A - Survey Design and Calculation of National Estimates
wuyu if the ^-variable is at the plant level
m if the ^-variable is at the generating-unit level (1)
yh,=\
— j
] yHjk if the ^-variable is at the sub-generating-unit level
Using this, the total 7 is estimated by:
where H is the total number of variance strata, and nh is the number of sample plants in variance
stratum h for the analysis. Note that the strata involved in analysis depend on the analysis
variables (items). If the variable is one of the Part E, F, or G items, then the strata are those for
the Parts EFG subsample. The "hat" over the population parameter indicates an estimate of the
parameter. When a weighted frequency (e.g., the total number of generating units with a fly wet
handling system) is calculated, the same formula is used, but the analysis variable y has a value
of one if the case has the attribute (e.g., having a fly wet handling system), and a value of zero
otherwise.
To estimate the population mean, we need an estimate of the eligible population size (TV),
and it is estimated by the sum of the weights as follows:
where chj is the count of the analysis units for plant / in variance stratum h - it is one if the
analysis unit is the plant, otherwise the count of sub-plant level units.
An estimate of the population mean (7 ) for ^-variable is given by:
± Y
Y=^. (4)
N
Population proportions are estimated by (4) if the ^-variable is dichotomous. The estimate
given by (4) is defined as the ratio of two total estimates, so it is called the ratio estimate. When
the population parameter of interest is a ratio (R) of two analysis variables^ and x, then it is
defined as the ratio of two estimated totals:
(5)
X
A-14
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Appendix A - Survey Design and Calculation of National Estimates
A.4.2 Variance Estimation
The original regular sample was selected by a stratified equal probability sample of
plants, and some strata are very small in size. For variance estimation, small design strata with
one or two plants selected in Combination strata were collapsed into one stratum. This redefined
stratum and other original design strata were used as strata for variance estimation, and for this
reason, they are called variance strata.
For the Parts EFG subsample, a stratified equal probability sampling method was also
used except for those coal plants with a leachate collection system, which were selected with
certainty. These original substrata were also the variance strata for variance estimation for the
variables from Parts E, F, and G.
Any elements below the plant level such as the generating unit were selected with
certainty. Therefore, the sample design can be regarded as a single stage cluster sample for items
at the sub-plant level, where the plants are the primary sampling unit (PSU) and sub-plant level
elements are the secondary sample unit (SSU). Furthermore, the sub-generating-unit element
under the generating unit can be considered as the tertiary sampling unit (TSU). The PSUs are
usually used as variance units for variance estimation, where the variance of an estimate (e.g.,
total) is calculated as the variability of PSU estimates, as is the case for the Steam Electric
Survey. The variance estimate for the total estimate given in (2) is given by:
where -^ ~Hh' h , which is the variance stratum sampling fraction, Hfi is the plant sample size of
the variance stratum for the analysis, Nh is the variance stratum population size, and
factor ^ in (6) is called the finite population correction (FPC). The
variance estimate for a non-linear statistic such as the ratio estimate given by equation (4) or (5)
needs a different formula or technique.
There are two main approaches for estimating the variance of a non-linear point estimate:
the Taylor linearization method and resampling methods. For the analyses in all parts (except for
Parts F and G), the Taylor method was used. Since complex post-stratification weighting was
used for Parts F and G items, a resampling method known as the jackknife was chosen for the
analysis, for which the jackknife replicate weights were developed for the Parts F and G. For
analysis of Parts F and G variables the Taylor method could have been used as well, but the
jackknife variance estimates were used since they are less biased. The jackknife and FPC factors
for analysis of variables from Parts F and G are provided in the following table.
A-15
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Appendix A - Survey Design and Calculation of National Estimates
Table A-8. The Jackknife and Finite Population Correction (FPC) Factors
for Parts F and G
Variance
Stratum
1
2
o
3
4
5
6
7
Description of Variance Stratum
Coal - Both Pond and Landfill
Coal - Landfill Only - FGD
Coal - Landfill Only - No FGD
Coal - Pond Only - FGD
Coal - Pond Only - No FGD
Coal - All other types
Petroleum coke - Selected for EFG
Number of
Replicates
23
9
14
11
28
7
2
Jackknife
Factor
0.95652
0.88889
0.92857
0.90909
0.96429
0.85714
0.5
FPC Factor
0.77841
0.59805
0.78810
0.78898
0.76230
0.24871
0.77778
A-16
-------
Appendix B -Modified Delta-Log Normal Distribution
APPENDIX B
MODIFIED DELTA-LOGNORMAL DISTRIBUTION
-------
Appendix B -Modified Delta-Log Normal Distribution
APPENDIX B
Contents
B.I Basic Overview of the Modified Delta-Lognormal Distribution
B.2 Continuous and Discrete Portion of the Modified Delta-Lognormal Distribution
B.3 Combining the Continuous and Discrete Portion
B.4 Autocorrelation
B.5 Plant-Specific Estimates Under the Modified Delta-Lognormal Distribution
B. 5.1 Dataset Requirement
B.5.2 Estimation of Plant-Specific Long-Term Averages and Variability Factors
B.5.2.1 Estimation of Plant-Specific Long-Term Averages (LTA)
B.5.2.2 Estimation of Plant-Specific Daily Variability Factors (VF1)
B.5.2.3 Estimation of Plant-Specific Monthly Variability Factors (VF4)
B.6 Estimation of Plant-Specific Long-Term Averages and Variability Factors
Assuming Autocorrelation
B.6.1 Estimation of Plant-Specific Long-Term Averages (LTA)
B.6.2 Estimation of Plant-Specific Daily Variability Factors (VF1)
B.6.3 Estimation of Plant-Specific Monthly Variability Factors (VF4)
B.7 Evaluation of Plant-Specific Variability Factors
B.8 References
B-l
-------
Appendix B -Modified Delta-Log Normal Distribution
This appendix describes the modified delta-lognormal distribution and the estimation of
the plant-specific long-term averages and plant-specific variability factors used to calculate the
limitations and standards. This appendix provides the statistical methodology that was used to
obtain the results presented in Section 13 of the Technical Development Document. For
simplicity, in the remainder of this appendix, references to "limitations" include "standards".
The term "detected" in this document refers to analytical results measured and reported
above the sample-specific quantitation limit. Thus, the term "non-detected" refers to values that
are below the method detection limit (MDL) and those measured by the laboratory as being
between the MDL and the quantitation limit (QL) in the original data (before adjusting for
baseline).
B.I Basic Overview of the Modified Delta-Lognormal Distribution
EPA selected the modified delta-lognormal distribution to model pollutant effluent
concentrations from the steam electric industry in developing the long-term averages and
variability factors. A typical effluent dataset from EPA sampling, CWA 308 sampling, or from a
plant's self-monitoring consists of a mixture of measured (detected) and non-detected values.
The modified delta-lognormal distribution is appropriate for such datasets because it models the
data as a mixture of detected measurements that follow a lognormal distribution and non-detect
measurements that occur with a certain probability. The model also allows for the possibility that
non-detected measurements occur at multiple sample-specific detection limits. Because the data
appeared to fit the modified delta-lognormal model reasonably well, EPA has determined that
this model is appropriate for these data.
The modified delta-lognormal distribution is a modification of the 'delta distribution'
171
originally developed by Aitchison and Brown. While this distribution was originally
developed to model economic data, other researchers have shown the application to
environmental data.122 The resulting mixed distributional model, that combines a continuous
density portion with a discrete-valued spike at zero, is also known as the delta-lognormal
distribution. The delta in the name refers to the proportion of the overall distribution contained in
the discrete distributional spike at zero, that is, the proportion of zero amounts. The remaining
non-zero amounts are grouped together and fit to a lognormal distribution.
EPA modified this delta-lognormal distribution to incorporate multiple detection limits.
In the modification of the delta portion, the single spike located at zero is replaced by a discrete
distribution made up of multiple spikes. Each spike in this modification is associated with a
distinct sample-specific detection limit associated with non-detected (ND) measurements in the
database. A lognormal density is used to represent the set of detected values. This modification
of the delta-lognormal distribution is illustrated in the figure below.
121 Aitchison, J. and J.A.C. Brown. 1963. The Lognormal Distribution Cambridge University Press, pages 87-99.
122 Owen, WJ. and T.A. DeRouen. 1980. "Estimation of the Mean for Lognormal Data Containing Zeroes and Left-
Censored Values, with Applications to the Measurement of Worker Exposure to Air Contaminants." Biometrics,
36:707-719.
B-2
-------
Appendix B -Modified Delta-Log Normal Distribution
Modified Delta-Lognormal Distribution
Censoring Type D
•ND
Figure B-l. Modification of the Delta-Lognormal Distribution
The following two sections describe the delta and lognormal portions of the modified
delta-lognormal distribution in further detail.
B.2 Continuous and Discrete Portions of the Modified Delta-Lognormal Distribution
In the discrete portion of the modified delta-lognormal distribution, the non-detected
values correspond to the k reported sample-specific detection limits. In the model, S represents
the proportion of non-detected values and is the sum ofSt, i=l,...,k, which represents the
proportion of non-detected values associated with the ith distinct detection limit. By letting A
equal the value of the ith smallest distinct detection limit in the dataset and letting the random
variable^) represent a randomly chosen non-detected measurement, the cumulative distribution
function of the discrete portion of the modified delta-lognormal model can be mathematically
expressed as:
,00
(1)
B-3
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Appendix B -Modified Delta-Log Normal Distribution
The mean and variance of this discrete distribution can be calculated using the following
formulas:
(2)
k
Var(XD} = - 8t(Dt - E(XD}}2 (3)
The continuous, lognormal portion of the modified delta-lognormal distribution was used
to model the detected measurements. The cumulative probability distribution of the continuous
portion of the modified delta-lognormal distribution can be mathematically expressed as:
/Zn(c) - u\
Pr(Xc < c) =
-------
Appendix B -Modified Delta-Log Normal Distribution
U = IuXD + (1 - lu}Xc (7)
where XE> represents a random non-detect from the discrete portion of the distribution, Xc
represents a random detected measurement from the continuous lognormal portion, and Iv is a
variable indicating whether any particular random measurement, U, is non-detected or detected
(that is, Iu=\ if u is non-detected, and 7^=0 if u is detected). Using a weighted sum, the
cumulative distribution function from the discrete portion of the distribution (equation 1) can be
combined with the function from the continuous portion (equation 4) to obtain the overall
cumulative probability distribution of the modified delta-lognormal distribution:
Pr(U < c) = V St + (1 - <5) (———- )
Z_i \ a I
j. n .**f ^ '
(8)
The expected value of the random variable f/can be derived as a weighted sum of the
expected values of the discrete and continuous portions of the distribution (equations 2 and 5,
respectively) as follows:
£({/) = 8E(XD} + (1 - 8}E(XC} (9)
In a similar manner, the expected value of U2 can be written as a weighted sum of the
expected values of the squares of the discrete and continuous portions of the distribution:
E(U2} = 8E(X2} + (1 - 8}E(X2C} (10)
Although written in terms of U, the following relationship holds for all random variables:
E(U2} = Var(U} + (E(U}}2 (11)
Now using equation 1 1 to solve for Var(U), and applying the relationships in equations 9 and 10,
the variance of f/is given by
7or(f/) = 8 var(XD} + (E(XD + (1 - 5) var(Xc} + (E(Xc - (E(u (12)
Thus the modified delta-lognormal distribution can be described by the following parameters: the
k distinct detection limits, A, and their corresponding probabilities, St,i = l,...,k, and the
parameters // and a of the lognormal distribution for detected values.
B.4 Autocorrelation
Effluent data from wastewater treatment technologies may be autocorrelated. For
example, positive autocorrelation is present in the data if the effluent concentration was
relatively high one day and was likely to remain high on the next and possibly succeeding days.
B-5
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Appendix B -Modified Delta-Log Normal Distribution
For data with autocorrelation, statistical time series are appropriate for modeling the data. There
are many time series models that might be considered for modeling wastewater measurements.
One method of modeling autocorrelation is by using an autoregressive lag-1 model, designated
as an AR(1) model. The AR(1) model is a reasonable model for many series of wastewater
measurements. The AR(1) model has one parameter, pi, the correlation between log-transformed
measurements from successive sampling events equally spaced over time, otherwise referred to
as the lag-1 correlation. Unless specified otherwise, pi is assumed to be zero, i.e., no
autocorrelation.
The autocorrelation affects the mean and variance estimates. Specifically, when the data
are deemed to be positively autocorr elated, the variance estimate from samples collected on
successive days will be less than the variance of the long-term concentration series, and thus the
variance estimates from the sampled days should be adjusted for the correlation in order to
obtain an accurate estimate of the variance for the long-term series. Adjustments for
autocorrelation have been made whenever appropriate. See Section 13 of the Technical
Development Document for a discussion of the use of autocorrelation in calculating the limits.
The equations in Section B.5 were used when the autocorrelation was assumed to be
zero; otherwise the equations in Section B.6 were used.
B.5 Plant-Specific Estimates Under the Modified Delta-Lognormal Distribution
In order to use the modified delta-lognormal model, the parameters of the distribution
must be estimated from the data. These estimates are then used to calculate the limitations. The
following assumes that the parameter estimates are calculated from n observed daily values.
The parameters dt and S are estimated from the data using the following formulas:
S=^L 03)
n
where n is the number of measurements (both detected and non-detected), /() is an indicator
function equal to one if the argument is true (and zero otherwise), djj = 1,. . ., w^, is the detection
limit for the/72 non-detected measurement, and Tid is the total number of non-detected
measurements. The "hat" over the parameters indicates that these values are estimated from the
data.
The expected value and the variance of the discrete portion of the modified delta-
lognormal distribution can be estimated from the data as:
(14)
B-6
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Appendix B -Modified Delta-Log Normal Distribution
k
Var(XD} = - 8t ot - E(XD (15)
The parameters ju and a of the continuous portion of the modified delta-lognormal
distribution are estimated from
11 =
nc
v v IJ—— (17)
<=i Uc ~ l
where xt is the ith detected measurement and nc is the number of detected measurements (note
that n = rid + nc).
The expected value and the variance of the lognormal portion of the modified delta-
lognormal distribution can be calculated from the data as:
ft + ^] 08)
2} - 1) (19)
Finally, the expected value and variance of the modified delta-lognormal distribution can
be estimated using the following formulas:
£({/) = 8E(XD) + (1 - S)E(XC-) (20)
Var(U} = 6 (var(XD} + (E(XD^ + (l -
-------
Appendix B -Modified Delta-Log Normal Distribution
observations with at least two distinct detected concentration values. If the plant dataset for a
pollutant did not meet these requirements, EPA used an arithmetic average to calculate the plant-
specific long-term average and excluded the dataset from the variability factor calculations (since
the variability could not be calculated in this situation).
B.5.2 Estimation of Plant-Specific Long-Term Averages and Variability Factors
If a dataset for a pollutant at a plant meets the requirement described in Section B.5. 1
above, then the plant-specific long-term averages and variability factors are estimated as
described in the subsections below. Furthermore, another assumption made in the estimating
procedures described below is that no autocorrelation exists in the data (i.e., daily measurements
are independent).
B.5.2.1 Estimation of Plant-Specific Long-Term Averages (LTA)
The plant specific long-term average (LTA) is calculated as follows:
fc
LTA = £({/) = 8E(XD) + (1 - <£)£(*c) = Y 8^ + (l - §)exp(p. + 0.5a2) (22)
i=l
Section B.5 contains all the formulas used for each of the expressions above. In the case
where there are less than two distinct detected values, the variance in the above formula cannot
be calculated. In this case, the long-term average is calculated as the arithmetic mean of the
available data (consisting of detected values and detection limits).
B.5.2.2 Estimation of Plant-Specific Daily Variability Factors (VF1)
The plant-specific daily variability factor is the ratio of the 99th percentile to the long-
term average and is calculated as follows:
iqq r qq
VFl = -^- = —2- (23}
£({/) LTA ( '
Below a description is given of how the 99th percentile of the modified delta-lognormal
distribution is estimated, including how multiple detection limits are accounted for when
estimating the 99* percentile.
Under the modified delta-lognormal distribution, if DI < D2 < ... < Dk are the k observed
detection limits expressed in increasing order, then let
Z , , „ fln^Dm) - p\
8t + (l- 5)0 ( T Im = I ..... k (24)
where (•) is the cumulative distribution function of the standard normal distribution. If all k of
the Rvalues are below 0.99, then
B-8
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Appendix B -Modified Delta-Log Normal Distribution
0.99 - S\ .
V M-*-- (25)
where 3}~l(p) is the// percentile of the standard normal distribution. Otherwise, findy such that
/v ^ ft.
Z)7 is the smallest detection limit for which qj > 0.99, and letg* = q. - 8.. Then the 99 percentile
is found by the following:
if q* < 0.99
P99 =
B.5.2.3 Estimation of Plant-Specific Monthly Variability Factors (VF4)
Plant-specific monthly variability factors were based on 4-day monthly averages because
EPA assumed the monitoring frequency to be weekly (approximately four times a month). The
plant-specific monthly variability factor for each plant is the ratio of a 95th percentile to the long
term average. In this case, the percentile we seek is the 95 percentile of the distribution of[/4,
which represents the average of four samples for a given plant. The monthly variability factor is
calculated as follows:
p P
i qq i qq
VF4 = ^- = —^ (27)
£({/) LTA v '
Below a description is given of how the 95th percentile is estimated under the assumption
that [74 has a modified delta-lognormal distribution. The following steps also show how multiple
detection limits (for non
of the monthly average.
detection limits (for non-detected values) were accounted for when estimating the 95* percentile
In order to calculate the 4-day variability factor (VF4), the assumption was made that the
approximating distribution of U4 , the sample mean for a random sample of four independent
concentrations, was also derived from the modified delta-lognormal distribution. To obtain the
expected value of the mean of the four daily values, equation 20 is modified to indicate that it
applies to the average:
E(U4~) = 84(E(X4~)D] + (1 - 84}E(X4~)C (28)
where (x\ denotes the mean of the discrete portion of the distribution of the average of four
independent concentrations, (i.e., when all observations are non-detected) and (jf4) denotes the
mean of the continuous lognormal portion (i.e., for averages involving detected observations).
B-9
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Appendix B -Modified Delta-Log Normal Distribution
First, it was assumed that the detection of each measurement is independent (the
measurements were also assumed to be independent). Therefore, the probability of the detection
of the measurements can be written as 64 = d4. Because the measurements are assumed to be
independent, the following relationships hold:
E(U4~) = £({/)
. _ Var(U}
Var(U4} = —^
D) = E(XD} (29)
Var(XD}
Substituting into equation 28 and solving for the expected value of the continuous portion
of the distribution gives:
(30)
Using the relationship in equation 21 for the averages of 4 daily values, substituting terms
from equation 29, and solving for the variance of the continuous portion of f/4 gives:
1 —
Using equations 18 and 19 and solving for the parameters of the lognormal distribution
describing the distribution of (X4)c gives:
fVar(X4-)c
(£(*4)c)2 ^
- °4 (32)
~2 T I v^^^c .
°4 =ln( _ _ ,2 + l
The non-detects can generate an average that is not necessarily equal to any of the Dj,
D2,...,Dk. Consequently, more than k discrete points exist in the distribution of the 4-day
averages. For example, the average of four non-detects when there are k=2 distinct detection
limits are at the following discrete k* points with the associated probabilities denoted by£.*,
/=!,...,**:
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Appendix B -Modified Delta-Log Normal Distribution
I
1
2
O
4
5 (=**)
Value of U4 (£>*)
D!
(3£>7+£>2)/4
(2D; + 2£>2)/4
(D; + 3£>2)/4
D2
Probability of Occurrence ( 8* )
c4
<>1
4<^2
6S^S22
^8\
^
When all four observations are non-detected values, and when k distinct non-detected
values exist, the multinomial distribution can be used to determine associated probabilities. That
is,
4!
Iti \U2\ ---Uifl 1 1 l
12 k =1
(33)
where ut is the number of non-detected measurements at the detection limit A. The number k* of
possible discrete averages for k=\,...,5, are as follows:
K
k*
1
2
3
4
5
1
5
15
35
70
The remaining approach to estimating P$5 is similar to the approach used to estimate Pg9
in the calculation of one-day variability factors, as described above. For m= 1, ...,&*, let
(34)
where O( ) is the cumulative distribution function of the standard normal distribution.
Now, if all lvalues of qm defined above are less than 0.95, then the 95* percentile is
defined as:
B-ll
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Appendix B -Modified Delta-Log Normal Distribution
I 1/0.95-<£4
P95 = exp U4 + a4 • O-1 ^ t_^4 (35)
where O"1^) is the//h percentile of the standard normal distribution. Otherwise, let D* denote
the smallest of the k* values of D* for which qj > 0.95, and let q * = qj - 8*. Then, the 95th
percentile is defined by the following:
.36)
^4 + 04'V-l , f4- ] | ijqzux*
< \
B.6 Estimation of Plant-Specific Long-Term Averages and Variability Factors
Assuming Autocorrelation
Section B.5 above described the procedure used to estimate the long-term averages and
variability factors assuming no autocorrelation existed in the data. The subsections below
describe how the plant specific long-term averages and variability factors are estimated assuming
the autocorrelation exists in the data. Autocorrelation in the successive measurements affects the
variance of the observed data. Therefore, if autocorrelation is deemed present in the data, then it
should be accounted for when calculating the long term average and variability factors.
When the concentrations have autocorrelation, EPA substitutes the detection limit for the
non-detects and assumes that all resulting values are detected and have a lognormal distribution.
Since all measurements are treated as detects, S=0 and the equations for the continuous portion
of the delta-lognormal distribution can be adapted to describe all the data.
B.6.1 Estimation of Plant-Specific Long-Term Averages (LTA)
If a dataset for a pollutant at a plant meets the requirements described in Section B.5.1,
then the plant specific long-term average (LTA) is calculated as follows:
LTA = exp(ftall + 0.53!) (37)
The parameter estimates fa^ and a2A are obtained using all n measurements as follows:
Zfri(*i)
—^- (38)
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Appendix B -Modified Delta-Log Normal Distribution
n
2 = _J_ y (.ln(.xi)- ,^
g(R)L-i n-1
where xt is the / measurement value, n is the total number of measurements (including both
detected and non-detected values), and g(R} is the adjustment for autocorrelation. For an AR(1)
model with a 1-day lag correlation of pl and n daily values, the correlation (in the log scale)
between xt and Xj (i i^j} is Corr(ln(x^ ln(x)) = p^J\. Then the adjustment for the autocorrelation
is
(40)
where T = {!,...,«} is the set of days with observed daily values. For an AR(1) model with n
sequential daily values, this reduces to
since
where /?7 is the correlation of the log-transformed measurements from successive sampling events.
Note that if the daily values are independent (i.e., autocorrelation is not present in the data), then
B.6.2 Estimation of Plant-Specific Daily Variability Factors (VF1)
The plant-specific daily variability factor is the ratio of the 99th percentile to the long-
term average and is calculated by
VF1 = -^ = - (42)
IT A ^ }
The 99th percentile P99 in equation 42 is calculated as
P99 = exp(£flU + 2.326 aA] (43)
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Appendix B -Modified Delta-Log Normal Distribution
where 2.326 is the 99th percentile of the standard normal distribution.
B.6.3 Estimation of Plant-Specific Monthly Variability Factors (VF4)
Plant-specific monthly variability factors were based on 4-day monthly averages because
EPA assumed the monitoring frequency to be weekly (approximately four times a month). The
plant-specific monthly variability factor for each plant is the ratio of a 95* percentile to the long-
term average. In this case, the percentile we seek is the 95* percentile of the distribution of£/4 ,
which represents the average of four samples for a given plant.
Assuming the data follow a lognormal distribution, the monthly variability factor is
calculated as:
VFA = (44)
LTA
where
'Var(U4-)c
. -i
+ 1
The variance of the average represented by Var(U4} is
(46)
where the factor f4(R) is used to adjust for the autocorrelation among the four values in the
average. This adjustment factor is found by
(47)
B.7 Evaluation of Plant-Specific Variability Factors
The parameter estimates for the lognormal portion of the distribution can be calculated
with as few as two distinct measured values in a dataset (in order to calculate the variance);
however, these estimates can be imprecise (as can estimates from larger datasets). As stated in
Section B.5. 1 above, EPA developed plant-specific variability factors for datasets that had three
or more observations with two or more distinct measured concentration values.
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Appendix B -Modified Delta-Log Normal Distribution
To identify situations producing unexpected results, EPA reviewed all of the variability
factors and compared daily to monthly variability factors. EPA used several criteria to determine
if the plant-specific daily and monthly variability factors should be included in calculating the
option variability factors (the option variability factors refer to the technology option variability
factor for a pollutant rather than regulatory option). One criterion that EPA used was that the
daily and monthly variability factors should be greater than 1.0. A variability factor less than 1.0
would result in an unexpected result where the estimated 99th percentile would be less than the
long-term average. This would be an indication that the estimate of o (the standard deviation in
log scale) was particularly large and most likely imprecise. A second criterion was that not all of
the sample-specific detection limits could exceed the detected values. All plant-specific
variability factors used for the limitations and standards met both the first and second criteria. A
third criterion was that the daily variability factor had to be greater than the monthly variability
factor. When this criterion was not met, the daily and monthly variability factors were excluded.
B.8 References
1. Aitchison, J. and J.A.C. Brown. 1963. The LognormalDistribution. Cambridge
University Press, New York.
2. Barakat, R. 1976. "Sums of Independent Lognormally Distributed Random Variables."
Journal Optical Society of America, 66: 211-216.
3. Cohen, A. C. 1976. "Progressively Censored Sampling in the Three Parameter Log-
Normal Distribution." Technometrics, 18:99-103.
4. Crow, E.L. andK. Shimizu. 1988. Lognormal Distributions: Theory and Applications.
Marcel Dekker, Inc., New York.
5. Kahn, H.D., and M.B. Rubin. 1989. "Use of Statistical Methods in Industrial Water
Pollution Control Regulations in the United States." Environmental Monitoring and
Assessment. Vol. 12:129-148.
6. Owen, WJ. and T.A. DeRouen. 1980. "Estimation of the Mean for Lognormal Data
Containing Zeroes and Left-Censored Values, with Applications to the Measurement of
Worker Exposure to Air Contaminants." Biometrics, 36:707-719.
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