xvEPA
United States
Environmental Protection
Agency
Office of Research and
Development
Cincinnati, OH 45268
EPA/625/R-95/008
April 1996
AMERICAN SOCIETY OF
CIVIL ENGINEERS
AMERICAN WATER WORKS ASSOCIATION
6666 W. QUINCf AVE., DENVER CO 80235
Technology Transfer
Handbook
Management of Water
Treatment Plant Residuals
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EPA/625/R-95/008
April 1996
Technology Transfer Handbook
Management of Water Treatment Plant Residuals
U.S. Environmental Protection Agency
Office of Research and Development
National Risk Management Research Laboratory
Cincinnati, Ohio
American Society of Civil Engineers
New York, New York
American Water Works Association
Denver, Colorado
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Notice
The U.S. Environmental Protection Agency (EPA) through its Office of Research and Development
partially funded and collaborated in the research described here under EPA Contract 68-C3-0315
to Eastern Research Group, Inc. It has been subjected to the Agency's peer and administrative
review and has been approved for publication as an EPA document.
The material presented in this publication has been prepared in accordance with generally recog-
nized engineering principles and practices and is for general information only. This information
should not be used without first securing competent advice with respect to its suitability for any
general or specific application.
The contents of this publication are not intended to be a standard of the American Water Works
Association (AWWA) or the American Society of Civil Engineers (ASCE) and are not intended for
use as a reference in purchase specifications, contracts, regulations, statutes, or any other legal
document.
No reference made in this publication to any specific method, product, process, or service consti-
tutes or implies an endorsement, recommendation, or warranty thereof by AWWA, ASCE, or EPA.
AWWA, ASCE, and EPA make no representation or warranty of any kind, whether expressed or
implied, concerning the accuracy, product, or process discussed in this publication and assume no
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Copyright Dept., ASCE.
Copyright © 1996 by the American Society of Civil Engineers and the American Water Works
Association. All rights reserved.
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Contents
Page
Chapter 1 Introduction 1
1.1 Overview of Differences in Water Treatment Processes 1
1.2 Overview of Residuals Categories 2
1.3 Overview of Residual Solids Treatment Processes 2
1.4 Selection of Residuals Management Plan Options 4
1.5 Handbook User's Guide 5
Chapter 2 Regulatory Issues Concerning Management of
Water Treatment Plant Residuals 6
2.1 Discharge to Waters of the United States 6
2.1.1 Technology-Based Effluent Limitations 6
2.1.2 Water Quality Standards 7
2.1.3 Special Concerns Regarding Aluminum 7
2.2 Discharge to Wastewater Treatment Plants 7
2.3 Landfilling 8
2.3.1 Municipal Nonhazardous Solid Wastes 8
2.3.2 Summary 9
2.4 Land Application 9
2.4.1 Federal Regulations 9
2.4.2 State Regulations 10
2.5 Underground Injection 10
2.5.1 Underground Injection Control Program 10
2.5.2 Underground Injection Requirements Under RCRA 11
2.6 Disposal of Radioactive Waste 12
2.7 Hazardous Waste 12
2.8 Air Emissions 13
2.8.1 Federal Regulations 13
2.8.2 State Regulations 14
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Contents (continued)
Page
Chapter 3 Characterization of Water Treatment Plant Residuals 17
3.1 Types and Quantities of Residuals 17
3.1.1 Sludges 17
3.1.2 Liquid Wastes 18
3.1.3 Radioactive Wastes 25
3.2 Physical Characteristics of Residuals 30
3.2.1 Solids Content 31
3.2.2 Specific Resistance 33
3.2.3 Compressibility 34
3.2.4 Shear Stress 35
3.2.5 Density 36
3.2.6 Particle Size Distribution 37
3.3 Chemical Characteristics of Residuals 39
3.3.1 Solids Content 39
3.3.2 Metals Content 39
3.3.3 Toxicity 40
Chapter 4 Water Treatment Residuals Processing 41
4.1 Residuals Handling Process Types 41
4.2 Process Descriptions 42
4.2.1 Collection Processes 42
4.2.2 Thickening 43
4.2.3 Conditioning 45
4.2.4 Dewatering 46
4.2.5 Drying 52
4.2.6 Additional Residuals Handling Processes 53
4.3 Residuals Handling Process Performance 53
4.3.1 Process Performance 53
4.3.2 Comparison of Thickening Processes 54
4.3.3 Comparison of Dewatering Processes 54
4.4 Developing Preliminary Residuals Processing Alternatives 54
4.4.1 Residuals Processing Requirements 54
4.4.2 Preliminary Selection of Residuals Processing Alternatives 56
4.5 Specific Residuals Unit Process Selection Criteria 60
4.5.1 Operating Experience 60
4.5.2 Bench-Scale and Pilot-Scale Tests 61
IV
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Contents (continued)
Page
4.5.3 Environmental Impacts 62
4.6 Final Screening of Residuals Handling Processes 62
4.6.1 Additional Selection Criteria 62
4.6.2 Process Alternative Selection Matrix 63
4.7 Residuals Handling Process Design Issues 63
4.7.1 Mass Balance Diagrams 63
4.7.2 Equipment Sizing 63
4.7.3 Contingency Planning 64
4.7.4 Specific Design Elements of Mechanical Dewatering Systems 65
4.8 Air Emissions Control 68
4.8.1 Gaseous Residual Byproducts 68
4.8.2 Accidental Release of a Gaseous Treatment Chemical 71
Chapter 5 Direct Discharge of Water Treatment Plant Residuals to Surface Waters 73
5.1 Theory 73
5.1.1 Chemical Interactions 73
5.1.2 Toxicity 74
5.2 Applications 77
5.2.1 Stream Hydraulics 77
5.2.2 Available Transport and Chemical Models and Their Application 79
5.3 Examples 80
5.3.1 California Plant, Cincinnati Water Works, Cincinnati, Ohio 80
5.3.2 Ralph D. Bollman Water Treatment Plant, Contra Costa Water
District, California 83
5.3.3 Mobile Water Treatment Plant, Mobile, Alabama 86
5.3.4 City of Phoenix Utility, Phoenix, Arizona 88
5.4 Recommended Practices 100
Chapter 6 Discharge to Wastewater Treatment Plants 102
6.1 Background 102
6.2 Survey of Operating Systems 102
6.3 Design Considerations and Conveyance Systems 102
6.3.1 Regulatory Considerations 104
6.3.2 Conveyance System Design Considerations 105
6.4 Design Considerations for Wastewater Treatment Plants 109
6.4.1 Hydraulic Loading 110
6.4.2 Organic Loading 110
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Contents (continued)
Page
6.4.3 Solids Loading 110
6.4.4 Toxics Loading 111
6.4.5 Liquid/Solids Separation 111
6.4.6 In-Plant Solids Handling 113
6.5 Ultimate Disposal of Wastewater Treatment Plant Biosolids 116
6.5.1 Direct Discharge 117
6.5.2 Land Application 117
6.5.3 Incineration 117
6.5.4 Composting 118
Chapter 7 Landfill Options 119
7.1 Landfill Siting 119
7.1.1 Airports 120
7.1.2 Floodplains 120
7.1.3 Wetlands 120
7.1.4 Fault Areas 120
7.1.5 Seismic Impact Zones 121
7.1.6 Unstable Areas 121
7.2 Landfill Design 121
7.2.1 Performance-Based Design Under 40 CFR Part 258 121
7.2.2 Minimum Technology-Based Design Under 40 CFR Part 258 122
7.3 Landfill Operations 125
7.4 Metal Content Considerations 125
7.4.1 Classification as Hazardous or Nonhazardous Waste 126
7.4.2 Mobility of Trace Metals 127
7.5 Dewatering 129
7.5.1 Mechanical Dewatering 130
7.5.2 Nonmechanical Methods 130
7.6 Physical Characteristics of Water Sludges 130
7.6.1 Plasticity 130
7.6.2 Compaction Behavior 131
7.6.3 Compressibility 131
7.6.4 Shear Strength 132
Chapter 8 Land Application 136
8.1 Regulatory Requirements 136
8.2 Environmental Considerations 136
VI
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Contents (continued)
Page
8.2.1 Major Components of Water Treatment Residuals and Their Impact on
Soil Parameters 137
8.2.2 Effects of Trace Metals Concentrations on Soil Properties 139
8.2.3 Impact of Water Treatment Residuals on the Availability of
Phosphorus in Agricultural Soils 139
8.2.4 Effects of WTP Residuals on Soil Physical Properties 140
8.3 Land Application Options 141
8.3.1 Agricultural Land 141
8.3.2 Silviculture 143
8.3.3 Land Reclamation 143
8.3.4 Dedicated Land Disposal 143
8.3.5 Other Use Options for WTP Residuals 144
8.4 Operational Considerations in Land Application 144
8.4.1 Application Procedures 144
8.4.2 Public Participation 144
8.4.3 Transportation 144
8.4.4 Monitoring 145
Chapter 9 Brine Waste Disposal 146
9.1 Background Information 146
9.1.1 Amount of Concentrate Generated and Disposal Methods 146
9.1.2 Constraints and Concerns 146
9.1.3 Early Disposal Regulations 147
9.1.4 Current Regulations and Their Trends 147
9.2 Conventional Disposal Methods 148
9.2.1 Surface Water Discharge 148
9.2.2 Disposal to Sanitary Sewers 149
9.2.3 Deep Well Injection 150
9.2.4 Boreholes 166
9.2.5 Spray Irrigation 167
9.3 Nonconventional Methods of Concentrate Disposal 168
9.3.1 Evaporation and Crystallization of Brines for Zero Discharge 168
9.3.2 Evaporation Ponds 175
9.3.3 Emerging Technologies 176
9.4 Costs Associated With Brine Waste Disposal 176
9.5 Conclusion 176
VII
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Contents (continued)
Page
Chapter 10 Radioactive Waste Disposal 177
10.1 Background 177
10.2 Waste Disposal Practices 178
10.3 Waste Disposal Guidelines 178
10.3.1 Liquid Disposal 178
10.3.2 Solids and Sludge Disposal 180
10.4 Recordkeeping 181
Chapter 11 Economics 182
11.1 Cost Assumptions 182
11.1.1 Capital Cost Assumptions 182
11.1.2 Operation and Maintenance Assumptions 183
11.1.3 Total Annual Cost Assumptions 183
11.1.4 Cost Components Excluded 183
11.1.5 Cost Equations 184
11.1.6 Cost Curves 184
11.1.7 Calculating Residuals Management Costs 184
11.2 Gravity Thickening 185
11.2.1 Design Assumptions 185
11.2.2 Capital Components 185
11.2.3 Operation and Maintenance Components 185
11.2.4 Cost Components Excluded 185
11.2.5 Gravity Thickening Cost Equations and Cost Curves 185
11.3 Chemical Thickening 186
11.3.1 Design Assumptions 186
11.3.2 Capital Components 186
11.3.3 Operation and Maintenance Components 187
11.3.4 Cost Components Excluded 187
11.3.5 Chemical Precipitation Cost Equations and Cost Curves 187
11.4 Mechanical Sludge Dewatering 188
11.4.1 Pressure Filter Press Cost Components 188
11.4.2 Scroll Centrifuge Cost Components 190
11.5 Nonmechanical Sludge Dewatering 191
11.5.1 Storage Lagoons Cost Components 191
11.5.2 Evaporation Ponds Cost Components 194
11.6 Discharge to Publicly Owned Treatment Works 196
VIII
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Contents (continued)
Page
11.6.1 Design Assumptions 196
11.6.2 Capital Components 196
11.6.3 Operation and Maintenance Components 196
11.6.4 Cost Components Excluded 196
11.6.5 Cost Equations and Cost Curves for Discharge to Publicly Owned
Treatment Works 197
11.7 Direct Discharge 200
11.7.1 Design Assumptions 200
11.7.2 Capital Components 201
11.7.3 Operation and Maintenance Components 201
11.7.4 Cost Components Excluded 201
11.7.5 Cost Equations for Direct Discharge 201
11.8 Land Application 203
11.8.1 Liquid Sludge Land Application Cost Components 203
11.8.2 Dewatered Residuals Land Application Cost Components 204
11.9 Nonhazardous Waste Landfill 206
11.9.1 Off-Site Nonhazardous Waste Landfill Cost Components 206
11.9.2 Onsite Nonhazardous Waste Landfill Cost Components 207
11.10 Hazardous Waste Landfill 209
11.10.1 Design Assumptions 209
11.10.2 Cost Components 209
11.10.3 Cost Components Excluded 209
11.10.4 Total Annual Cost Equation and Cost Curves 209
11.11 Radioactive Waste Disposal 210
11.11.1 Low-Level Radioactive Waste Disposal 210
11.11.2 Cost Information for Radioactive Waste Disposal 210
Chapter 12 Case Studies 211
12.1 Case Study 1: Disposal of Water Treatment Residuals From Pine Valley Water
Treatment Plant, Colorado Springs, Colorado 211
12.1.1 Facility Information 211
12.1.2 Residuals Management 211
12.1.3 Residuals Handling Facilities and Operations 212
12.1.4 Residuals Disposal 215
12.1.5 Handling and Disposal Costs 215
12.2 Case Study 2: Disposal of Water Treatment Residuals From Mesa Treatment Plant,
Colorado Springs, Colorado 219
IX
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Contents (continued)
Page
12.2.1 Facility Information 219
12.2.2 Residuals Management 220
12.2.3 Residuals Handling Facilities and Operations 220
12.2.4 Residuals Disposal 223
12.3 Case Study 3: Land Application of Water Treatment Plant Residuals at
Cobb County-Marietta Water Authority, Marietta, Georgia 224
12.3.1 Facility Information 225
12.3.2 Residuals Handling Facilities 230
12.3.3 Ultimate Disposal—Land Application 232
12.3.4 Disposal Costs 234
12.4 Case Study 4: Treatment of Residuals at the Lake Gaillard Water Treatment Plant,
North Branford, Connecticut 235
12.4.1 Facility Information 235
12.4.2 Lessons Learned 236
12.5 Case Study 5: Disposal of Water Treatment Plant Residuals From the San Benito
Water Plant, Brownsville, Texas 236
12.5.1 Residuals Handling Facilities 237
12.5.2 Final Disposal 237
12.5.3 Disposal Costs 237
12.6 Case Study 6: Management of Water Treatment Plant Residuals in the Chicago Area,
Chicago, Illinois 237
12.6.1 Description of the Jardine Water Purification Plant 237
12.6.2 Residuals Handling and Disposal 238
12.6.3 Disposal Costs 239
Chapter 13 Waste Minimization and Reuse 242
13.1 Waste Minimization 242
13.1.1 Process Modifications 242
13.1.2 Dewatering 243
13.1.3 Drying 243
13.2 Chemical Recovery 244
13.2.1 Coagulant Recovery 244
13.2.2 Lime Recovery 244
13.3 Innovative Use and Disposal Options 244
13.3.1 Beneficial Use 244
13.3.2 Disposal Options 245
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Contents (continued)
Page
Chapter 14 References 246
Appendix A Survey of State Regulatory Requirements: Summary of Results 254
Appendix B 1992 Survey of Water Treatment Plants Discharging to Wastewater Treatment Plants... 261
Appendix C Charges From Publicly Owned Treatment Works 268
Appendix D Chemical Monthly Average Doses, Pine Valley Water Treatment Plant,
Colorado Springs, CO, 1987-1992 (Pine Valley, 1994) 270
Appendix E Chemical Monthly Average Doses, Mesa Water Treatment Plant,
Colorado Springs, CO, 1987-1992 (Mesa, 1994) 276
XI
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Figures
Figure Page
1-1 The primary target of a residuals management plan 4
1-2 Handbook user's guide 5
2-1 Areas exceeding the ozone NAAQs 15
3-1 Generation of wastewater volumes with ion exchange 21
3-2 Change in sludge settled solids concentration throughout a treatment plant 32
3-3 Effect of Ca-to-Mg ratio on the solids concentration of softening sludge 32
3-4 Water distribution and removal in a softening (CaCO3) slurry and coagulant (AI(OH)3) slurry 33
3-5 Use of specific resistance to determine optimum chemical dosage 34
3-6 Variation in shear strength with sludge moisture content 35
3-7 Comparison of sludge settled solids concentration with the solids concentration where a sludge
becomes "handleable" 36
3-8 Compaction curves of test sludges 36
3-9 Variation of floe density with floe size 37
3-10 Variations in dewatered cake solids concentration of aluminum hydroxide sludges as a function of
organic content 37
3-11 Effect of incorporation of organic carbon on the relative size distribution of aluminum hydroxide
sludge floe formed at pH 6.5 37
3-12 Variations in measured floe density as a function of both coagulation pH and presence or absence of
TOC from sludge floe matrix 37
3-13 Floe size and resistance of metal hydroxide sludges to dewatering by vacuum filtration 38
3-14 Effect of specific surface area on the specific resistance of alum sludges 38
3-15 Representative results from metal hydroxide sludge conditioning studies 39
3-16 Effect of Gt on optimum polymer dose for alum sludge conditioning 39
4-1 Residuals sources in water treatment plants 42
4-2 Residuals handling process categories 42
4-3A Residuals handling process schematic: sedimentation basin used water flow 43
4-3B Residuals handling process schematic: solids dewatering 43
4-4 Gravity thickener cross-section 44
4-5 Gravity belt thickener cross section 46
4-6 Sand drying bed section 47
4-7 Wedgewire drying bed cross section 48
4-8 Dewatering lagoon cross section 48
4-9 Belt filter press 50
4-10 Solid-bowl-type centrifuge schematic 50
4-11 Solid-bowl-type centrifuge 52
4-12 Vacuum filter 53
XII
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Figures (continued)
Figure Page
4-13 Residuals handling process selection flow chart 60
4-14 Bench/pilot testing decision flow 61
4-15A Mass balance schematic 64
4-15B Mass balance calculation 65
4-16 Preliminary residuals handling process schematic 66
4-17 Aerial view of residuals handling process system, Val Vista WTP, Cities of Phoenix/Mesa, AZ 67
4-18 Belt filter press—example of system layout 68
4-19 Centrifuge—example of system layout 68
4-20 Filter press—example of system layout 69
4-21 Vacuum filter—example of system layout 70
4-22 Packed tower 71
5-1 Flow frequency analysis of the Schuylkill River, Philadelphia, PA; minimum 7-day average flow
values, 1932-1964 78
5-2 Scenarios for mass balance calculations 78
5-3 Decay of a nonconservative pollutant 79
5-4 Control techniques for improving downstream water quality 80
5-5 Flow schematic of California Plant, Cincinnati Water Works, Cincinnati, OH 81
5-6 Sediment aluminum concentration (dry weight) from Ohio River, Cincinnati, OH 82
5-7 Flow schematic of Ralph D. Bollman WTP, Contra Costa Water District, CA 84
5-8 Sediment aluminum concentration from Mallard Reservoir, Concord, CA 85
5-9 Flow schematic of Mobile WTP, Mobile, AL 86
5-10 Sediment aluminum concentration from Three Mile Creek, Mobile, AL 87
5-11 Location of City of Phoenix WTPs, Phoenix, AZ 88
5-12 Recommended practices for direct discharge of WTP residuals to surface waters 100
6-1 Effect of WTP sludge on the combined volume of wastewater sludge after 30 minutes of settling 112
7-1 Considerations for sludge monofill design 123
7-2A Compaction curve, Ferric Sludge 3 128
7-2B Compaction curve, Alum Sludge 1 128
7-2C Compaction curve, Alum Sludge 2 128
7-3 Consolidation curves of Alum Sludges 1 and 2 and Ferric Sludge 3 131
7-4 Void ratio versus consolidation pressure of treated and untreated Alum Sludge 1 132
7-5 Strength versus solids content for Alum Sludges 1 and 2 132
7-6 Strength versus curing time at various solids contents for ferric sludge 133
7-7 Shear strength versus additive level, Alum Sludge 2 (nonaged) 134
7-8 Undrained sheer strength versus curing time for untreated and treated Alum Sludge 1 134
7-9 Landfill height versus shear strength/unit weight for different slope angles 135
8-1 Simplified planning procedure for land application of WTP residuals 137
8-2 Partitioning of trace metals in WTP residuals 139
8-3 Average (of three cuttings) phosphorus concentration in sorghum-sudangrass grown in Colby soil .... 140
9-1 Monthly operational report, page 1 158
9-2 Monthly operational report, page 2 159
XIII
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Figures (continued)
Figure Page
9-3 Monthly operational report, page 3 160
9-4 Monthly operational report, page 4 161
9-5 Monthly operational report, page 5 162
9-6 Well drilling cost 167
9-7 Zero discharge 168
9-8 Brine concentrator system 169
9-9 Brine concentrator capital and operating costs 171
9-10 Brine concentrator cost components 173
9-11 Waste crystallizer system 173
9-12 Steam driven circulation crystallizer 174
9-13 Steam power crystallizer capital and operating costs 175
9-14 Steam power crystallizer cost components 175
9-15 MVR crystallizer capital and operating costs 175
9-16 MVR crystallizer cost components 176
11-1 Capital costs for gravity thickening 186
11-2 O&M costs for gravity thickening 186
11-3 Capital costs for chemical precipitation 187
11-4 O&M costs for chemical precipitation 187
11-5 Capital costs for pressure filter press 189
11-6 O&M costs for pressure filter press 189
11-7 Capital costs for scroll centrifuge 191
11-8 O&M costs for scroll centrifuge 191
11-9 Capital costs for lime softening storage lagoon 193
11-10 O&M costs for lime softening storage lagoon 193
11-11 Capital costs for alum sludge storage lagoon 194
11-12 O&M costs for alum sludge storage lagoon 194
11-13 Capital costs for evaporation ponds 195
11-14 O&M costs for evaporation ponds 195
11-15 Capital costs for 500 feet of discharge pipe 197
11-16 O&M costs for 500 feet of discharge pipe 197
11-17 Capital costs for 1,000 feet of discharge pipe 198
11-18 O&M costs for 1,000 feet of discharge pipe 198
11-19 Capital costs for 500 feet of discharge pipe with storage lagoon 199
11-20 O&M costs for 500 feet of discharge pipe with storage lagoon 199
11-21 Capital costs for 1,000 feet of discharge pipe with storage lagoon 200
11-22 O&M costs for 1,000 feet of discharge pipe with storage lagoon 200
11-23 Capital costs for liquid sludge land application 204
11-24 O&M costs for liquid sludge land application 204
11-25 Capital costs for trucking system 205
11-26 O&M costs for trucking system 205
11-27 Capital costs for dewatered sludge land application 206
XIV
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Figures (continued)
Figure Page
11-28 O&M costs for dewatered sludge land application 206
11-29 O&M costs for off-site nonhazardous waste landfill 207
11-30 Capital costs for onsite nonhazardous waste landfill 208
11-31 O&M costs for onsite nonhazardous waste landfill 208
11-32 Closure costs for onsite nonhazardous waste landfill 208
11-33 Postclosure costs for onsite nonhazardous waste landfill 208
11-34 O&M costs for hazardous waste disposal 210
11-35 O&M costs for stabilization and hazardous waste disposal 210
12-1 Locus map of Pine Valley WTP, Colorado Springs, CO 212
12-2 Schematic of Pine Valley WTP, Colorado Springs, CO 213
12-3 Flow chart of Pine Valley WTP, Colorado Springs, CO 214
12-4 Sediment and decant piping schematic, Pine Valley WTP, Colorado Springs, CO 215
12-5 Letter regarding new sludge handling facility at Pine Valley WTP, Colorado Springs, CO 216
12-6 Mesa WTP, Colorado Springs, CO 221
12-7 Letter from Colorado Springs Department of Utilities, CO 228
12-8 Schematic process diagram of Quarles WTP, Marietta, GA 230
12-9 Schematic process diagram of Wyckoff WTP, Marietta, GA 230
12-10 Schematic flow diagram of Jardine Water Purification Plant, Chicago, IL 238
12-11 Schematic diagram of residuals management system, Jardine Water Purification Plant, Chicago, IL . . . 239
xv
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Tables
Table Page
1-1 Treatment Processes and Waste Streams 3
1-2 Representative Solids Concentration Treatment Processes 4
2-1 Required Management Practices for Nonhazardous Industrial Waste Only and Co-Disposal Landfills,
and Land Application Sites 8
2-2 TCLP Constituents and Regulatory Limits 13
2-3 National Ambient Air Quality Standards 14
3-1 Alum/Iron Coagulant Sludge Characteristics 17
3-2 Chemical Softening Sludge Characteristics 17
3-3 Typical Chemical Constituents of Ion Exchange Wastewater 20
3-4 Regeneration of Cation Exchange Resins 21
3-5 Membrane Process Operations Summary 22
3-6 Membrane Process Applications for RO, NF, and ED-EDR 23
3-7 Concentration Factors for Different Membrane System Recoveries 23
3-8 Tabulation of Concentration Factors 25
3-9 Summary of Treatment Processes and the Types of Wastes Produced From the Removal of
Radionuclides From Drinking Water 26
3-10 Water Treatment Process Materials Containing Radionuclides 26
3-11 Summary of Radium Concentration in Lime Softening Sludges and Backwash Water 27
3-12 Summary of Radium-226 Concentrations in Brine Waste From Ion Exchange Treatment 28
3-13 Summary of Uranium Concentrations in Ion Exchange Treatment Plant Wastewater 28
3-14 Summary of Radium-226 Concentrations in Waste Stream From Iron Removal Filters 28
3-15 Summary of Radium-226 Concentrations in Reject Water of Reverse Osmosis Treatment 29
3-16 Summary of Uranium Concentration in Reject Water of Reverse Osmosis Treatment 29
3-17 Concentration of Radionuclides on Water Treatment Process Media and Materials 30
3-18 Settled Solids Concentration of Residuals From Water Treatment Plants in Missouri 31
3-19 Effect of Coagulation Mechanism on Alum Sludge Properties 31
3-20 Specific Gravity of Sludge Particles and Cake Solids Concentrations Obtainable From Various
Laboratory Dewatering Methods 33
3-21 Specific Resistance for Various Chemical Sludges 34
3-22 Summary of Floe Density and Dewatered Solids Concentration Data for Several Chemical Sludges .... 35
4-1 Typical Ranges of Conditioner Use for Hydroxide Sludges in Various Mechanical
Dewatering Systems 46
4-2 Comparison of Thickening Processes 54
4-3 Comparison of Dewatering Processes 54
4-4 Preliminary Residuals Processing Selection Matrix 57
4-5 Survey of Thickening Methods at Water Treatment Plants in the United States 60
XVI
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Tables (continued)
Table Page
4-6 Survey of Dewatering Methods at Water Treatment Plants in the United States 60
4-7 Example of Weighting System for Alternative Analysis 64
4-8 Residual Handling Facility Contingency Planning Issues 67
5-1 Possible In-Stream Water Quality Guidelines and Standards 76
5-2 Average Daily Chemical Use at California Plant, Cincinnati Water Works, Cincinnati, OH 81
5-3 Chemical Composition of Sludge and Ohio River Water Sampled at California Plant, Cincinnati Water
Works, Cincinnati, OH, September 21,1988, December 18, 1988, and January 10, 1989 82
5-4 S. CapricomutumTest Results on Alum Sludge Extracts From California Plant, Cincinnati Water
Works, Cincinnati, OH 82
5-5 Benthic Macroinvertebrates Collected From Site CO on the Ohio River, Cincinnati, OH, 1989 83
5-6 S. CapricomutumTest Results on Alum Sludge Extracts From Ralph D. Bollman Water Treatment
Plant, Contra Costa, CA 84
5-7 Benthic Macroinvertebrates Collected From Mallard Reservoir at Site CC, Contra Costa Water
District, Concord, CA, February 21, 1989 85
5-8 S. CapricomutumTest Results on Alum Sludge Extracts From the Mobile, AL, Water
Treatment Plant 87
5-9 Benthic Macroinvertebrates Collected From Three Mile Creek, Mobile, AL, 1989 87
5-10 Typical Canal Source Water Characteristics 89
5-11 Summary of Plant Flows and Turbidity Data 90
5-12 Val Vista WTP Discharge Stream Characteristics 90
5-13 Squaw Peak WTP Discharge Stream Characteristics 90
5-14 Deer Valley WTP Discharge Stream Characteristics 90
5-15 Existing Discharge Quantities 91
5-16 Grain Size Distribution for WTP Residuals 91
5-17 Estimated Amount of Solids Deposited in the Canal System, Phoenix, AZ 91
5-18 Total Number of Fish Caught by Electrofishing, Arizona Canal, Phoenix, AZ, October 15, 1992, to
April 30, 1993 92
5-19 Estimated WTP Discharge Stream Pollutant Concentrations 93
5-20 Daily Resultant Pollutant Concentration Contribution to Canal at Typical Flow, Phoenix, AZ 94
5-21 Daily Resultant Pollutant Concentration Contribution to Canal at 25% of Typical Flow, Phoenix, AZ 94
5-22 Toxicity of Arsenic to Freshwater Organisms 95
5-23 Toxicity of Cadmium to Freshwater Organisms 96
5-24 Toxicity of Chromium to Freshwater Organisms 97
5-25 Toxicity of Selenium to Freshwater Organisms 98
5-26 Toxicity of Mercury to Freshwater Organisms 99
5-27 Maximum Contaminant Levels (u,g/L) Cold Water Fishery 99
6-1 Survey of Water Treatment Plants Discharging to WWTPs 103
6-2 Treatment Chemical Analysis Range of Detected Contaminant Levels 108
6-3 Comparison of Digester 11 With Background Digesters 114
6-4 Alum Treatment Plant Sludge Dewatering Test Results 116
7-1 Solid Waste Landfill Criteria: Monofill for WTP Residuals and Co-disposal of Residuals With
Nonhousehold Solid Waste 119
XVII
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Tables (continued)
Table Page
7-2 Solid Waste Landfill Criteria: Co-disposal of WTP Residuals With Municipal Solid Wastes 119
7-3 Field Investigations for New Information, Landfill Design 122
7-4 Maximum Contaminant Levels in Uppermost Aquifer at Relevant Point of Compliance 124
7-5 Comparison of Metals Concentrations in WTP Residuals, Natural Soils, and Sewage Sludge 126
7-6 Worst Case TCLP Results Using Maximum Metals Concentrations in Table 7-5, Compared With
TCLP Regulatory Limits 127
7-7 EP Toxicity Test Results for Alum Residuals 127
7-8 TCLP Results for Five Water Treatment Plant Coagulant Residuals 127
7-9 Chemical Constituents of Synthetic Rainwater 128
7-10 Total Metals Analysis for Sludges Used in Leaching Research 129
7-11 Leaching of Metals in Lysimeter Test 129
7-12 Maximum Metals Concentrations in Lysimeter Leachate Compared With MCLs 129
7-13 Liquid Limit, Plastic Limit, and Plasticity Index of Water Sludges 131
7-14 Shear Strength Parameters of Test Sludges 133
7-15 Remolded and Cured Undrained Strengths and Strength Gain Ratio 133
7-16 Undrained Shear Strength of Alum Sludge, Untreated and Treated 134
7-17 Required Shear Strength and Solids Concentration for Hypothetical Monofill Supporting Various
Types of Heavy Equipment 135
8-1 Composition of WTP Residuals Compared With Sewage Sludge and Agronomic Soils 138
8-2 Agronomic Components in WTP Residuals 138
8-3 Phosphorus Recommendations for Several Agronomic Crops 143
9-1 Membrane Concentrate Generation 146
9-2 Concerns and Requirements Associated With Conventional Disposal Methods 147
9-3 Concentrate Disposal Costs 166
9-4 Typical Brine Concentrator Process Conditions in Zero Discharge Applications 169
9-5 Effect of Concentration Factor (CF) on Calcium Sulfate Seed Concentrations 169
9-6 Typical Brine Crystallizer Process Conditions 173
10-1 Summary of Residuals Produced From Water Treatment Processes 178
10-2 Water Treatment Methods for Residuals Containing Radionuclides 178
11-1 Capital Cost Factors and Selected Unit Costs for WTP Facility Planning 182
11-2 Operation and Maintenance Cost Factors and Unit Costs for WTP Facility Planning 183
11-3 Flow Rate Use in Calculating Facility Costs 184
11-4 Holding Tank Capacities, Gravity Thickening 185
11-5 Capital Cost Equation Determinants, Chemical Precipitation 187
11-6 Capital Cost Equation Determinants, Pressure Filter Presses 189
11-7 Capital Cost Equation Determinants, Scroll Centrifuge 190
11-8 Capital Cost Equation Determinants, Lime Softening Storage Lagoons 192
11-9 Capital Cost Equation Determinants, Alum Storage Lagoons 192
11-10 Capital Cost Equation Determinants, Evaporation Ponds 195
11-11 Capital Cost Equation Determinants, Discharge to POTW 196
11-12 Capital Cost Equation Determinants, Direct Discharge 201
XVIII
-------
Tables (continued)
Table Page
11-13 Capital Cost Equation Determinants, Liquid Residuals Land Application 203
11-14 Capital Cost Equation Determinants, Dewatered Residuals Land Application 205
12-1 Water Treated and Used, Pine Valley WTP, Colorado Springs, CO 215
12-2 Sediment Disposal, Pine Valley WTP, Colorado Springs, CO 219
12-3 Characteristics of Residuals Generated in 1982, Pine Valley WTP, Colorado Springs, CO 220
12-4 Characteristics of Residuals Generated in 1992, Pine Valley WTP, Colorado Springs, CO 221
12-5 Laboratory Samples: April 1992, Fountain Creek, Colorado Springs, CO 222
12-6 Laboratory Samples: August 1992, Mesa WTP, Colorado Springs, CO 223
12-7 Raw Water Source for Mesa WTP, Colorado Springs, CO 224
12-8 Water Treated and Used, Mesa WTP, Colorado Springs, CO, in Million Gallons 224
12-9A Chemical Characteristics of Residuals (Sludge) From Mesa WTP, Colorado Springs, CO, 1978 225
12-9B Chemical Characteristics of Residuals (Supernatant) From Mesa WTP, Colorado Springs, CO, 1978 . . . 226
12-10 Chemical Characteristics of Residuals Generated in 1992, Mesa WTP, Colorado Springs, CO 227
12-11 Sediment Disposal, Mesa WTP, Colorado Springs, CO 227
12-12 TCLP Data, Cobb County-Marietta Water Authority, Marietta, GA 231
12-13 Total Metals Data, Cobb County-Marietta Water Authority, Marietta, GA 231
12-14 Other Analyses, Cobb County-Marietta Water Authority, Marietta, GA 232
12-15 Pesticides and PCBs (Solids), Cobb County-Marietta Water Authority, Marietta, GA 232
12-16 Triazine Herbicides, Cobb County-Marietta Water Authority, Marietta, GA 233
12-17 Reactivity, Solids, Cobb County-Marietta Water Authority, Marietta, GA 233
12-18 Pilot Study, Soil Data, Cobb County-Marietta Water Authority, Marietta, GA 234
12-19 Pilot Study, Plant Tissue Data, Cobb County-Marietta Water Authority, Marietta, GA 234
12-20 Water Treatment Sludges Discharged by the City of Chicago WTPs to the District, Chicago, IL,
1984-1992 239
12-21 Water Treatment Sludges Discharged by Various Suburban WTPs to the District, Chicago, IL,
1984-1992 240
12-22 Local Limits on Dischargers Into District Sewarage Systems, Chicago, IL 240
12-23 Concentrations of Metals Found in WTP Sludges Discharged Into the District, Chicago, IL 240
12-24 User Charge Costs for Disposal of Water Treatment Residuals to the Metropolitan Water
Reclamation District, Chicago, IL, 1984-1992 241
12-25 Water Treatment Sludges Discharged From Various Water Treatment Plants to the District From
1984 Through 1992 241
C-1 Sewer Rates—Large Cities 268
C-2 Sewer Rates—Minnesota Cities 269
D-1 Raw Water, Pine Valley, 1987 270
D-2 Raw Water, Pine Valley, 1988 271
D-3 Raw Water, Pine Valley, 1989 272
D-4 Raw Water, Pine Valley, 1990 273
D-5 Raw Water, Pine Valley, 1991 274
D-6 Raw Water, Pine Valley, 1992 275
E-1 Raw Water, Mesa, 1992 276
XIX
-------
Tables (continued)
Table Page
E-2 Raw Water, Mesa, 1991 277
E-3 Raw Water, Mesa, 1990 278
E-4 Raw Water, Mesa, 1989 279
E-5 Raw Water, Mesa, 1988 280
E-6 Raw Water, Mesa, 1987 281
xx
-------
Conversion Factors
To convert.. .
to...
multiply by ...
acres
cubic feet
degrees Fahrenheit
feet
inches
miles
ounces
pounds
pounds per 1,000 gallons
pounds per square inch
square inches
tons
U.S. gallons
hectares
cubic meters
degrees Celsius
meters
centimeters
kilometers
grams
kilograms
grams per liter
kiloPascals
square centimeters
metric tons
liters
0.4046944
0.02831685
t-c = (t.F-32)71.8
0.3048
2.54
1.609344
28.3495
0.45354237
0.1198322
6.895
6.4516
0.90718474
3.785
XXI
-------
A cknowledgments
The organizations responsible for the development of this handbook are the U.S. Environmental
Protection Agency's (EPA's) National Risk Management Research Laboratory (NRMRL), Technol-
ogy Transfer and Support Division, the American Society of Civil Engineers (ASCE), and the
American Waterworks Association (AWWA). EPA's Office of Research and Development partially
funded this effort under Contracts 68-CO-0068 and 68-C3-0315 with Eastern Research Group, Inc.
(ERG). Funding was also provided by ASCE.
Many individuals participated in the preparation and review of this handbook. Below is a partial list
of the major contributors.
Chapter 1: Introduction
Primary author: Jerry Russell, John Carollo Engineers, Phoenix, AZ. Contributing authors: Carl P.
Houck, Camp Dresser & McKee Inc., Denver, CO; Janine B. Witko, Malcolm Pirnie, Inc., Mahwah,
NJ; Brian Peck, John Carollo Engineers, Phoenix, AZ; and James E. Smith, Jr., EPA NRMRL,
Cincinnati, OH.
Chapter 2: Regulatory Issues Concerning Management of Water Treatment
Plant Residuals
Primary author: Scott Carr, Black & Veatch, Charlotte, NC. Contributing authors: James E. Smith,
Jr., EPA NRMRL, Cincinnati, OH; Suzanna I. McMillan, Black & Veatch, Charlotte, NC; and Nancy
E. McTigue, Environmental Engineering & Technology, Inc., Newport News, VA. Key reviewers:Man
Rubin and Robert Southworth, EPA Office of Water, Washington, DC.
Chapter 3: Characterization of Water Treatment Plant Residuals
Primary author: Timothy A. Wolfe, Montgomery Watson, Inc., Cleveland, OH. Contributing authors:
Mike Mickley, Mickley and Associates, Boulder, CO; John Novak, Virginia Polytechnic Institute and
State University, Blacksburg, VA; Leland Harms, Black & Veatch, Kansas City, MO; and Thomas J.
Sorg, EPA NRMRL, Cincinnati, OH.
Chapter 4: Water Treatment Residuals Processing
Primary author: Jerry Russell, John Carollo Engineers, Phoenix, AZ. Contributing authors: Brian
Peck, John Carollo Engineers, Phoenix, AZ; Tim Stephens, HDR Engineering, Inc., Phoenix, AZ;
Duncan Browne, WRC Engineers and Scientists, Huntingdon Valley, PA; Jeannette Semon, City of
Stamford WPCF, Stamford, CT; Betsy Shepherd, John Carollo Engineers, Phoenix, AZ; and Dale
D. Newkirk, EBMUD-Water Treatment, Oakland, CA.
Chapter 5: Direct Discharge of Water Treatment Plant Residuals to Surface Waters
Primary author: Dennis George, Tennessee Technological University, Cookeville, TN. Contributing
author: Christina Behr-Andres, University of Alaska, Fairbanks, AK.
XXII
-------
Chapter 6: Discharge to Wastewater Treatment Plants
Primary author: Carl P. Houck, Camp Dresser & McKee Inc., Denver, CO. Contributing authors:
Janine B. Witko, Malcolm Pirnie, Inc., Mahwah, NJ; Timothy A. Wolfe, Montgomery Watson, Inc.,
Cleveland, OH; Richard Tsang, Camp Dresser & McKee Inc., Raleigh, NC; and Paula Murphy, ERG,
Lexington, MA.
Chapter 7: Landfill Options
Primary author: Nancy E. McTigue, Environmental Engineering & Technology, Inc., Newport News,
VA. Contributing authors: Daniel Murray, EPA NRMRL, Cincinnati, OH; and Mark Wang, The
Pennsylvania State University, University Park, PA.
Chapter 8: Land Application
Primary author: Bob Brobst, EPA Region 8, Denver, CO. Contributing authors: David R. Zenz and
Thomas C. Granato, Metropolitan Water Reclamation District of Greater Chicago, Chicago, IL. Key
re vie wers: Robert Southworth and Alan Rubin, EPA Office of Water, Washington, DC; and Herschel
A. Elliott, The Pennsylvania State University, University Park, PA.
Chapter 9: Brine Waste Disposal
Primary author: William J. Conlon, Rust Environment and Infrastructure, Sheboygan, Wl. Contrib-
uting authors: Thomas D. Wolfe, The Palmyra Group, Rough & Ready, CA; and William Pitt, Camp
Dresser & McKee Inc., Miami, FL.
Chapter 10: Radioactive Waste Disposal
Primary author: Thomas J. Sorg, EPA NRMRL, Cincinnati, OH. Key reviewers: Marc Parrotta, EPA
Office of Water, Washington, DC; Nancy E. McTigue, Environmental Engineering & Technology, Inc.,
Newport News, VA; and Darren Lytle, EPA NRMRL, Cincinnati, OH.
Chapter 11: Economics
Primary author: Bruce Bums, HDR Engineering, Inc., Irvine, CA. Contributing author: Christopher
Lough, DPRA, St. Paul, MN. Key re viewer: Janine B. Witko, Malcolm Pirnie, Inc., Mahwah, NJ.
Chapter 12: Case Studies
Primary author: Balu P. Bhayani, Colorado Springs Utilities, Colorado Springs, CO. Contributing
authors: James M. Parsons, Cobb County-Marietta Water, Marietta, GA; Cecil Lue-Hing, Metropoli-
tan Water Reclamation District of Greater Chicago, Chicago, IL; and Jerry Russell, John Carollo
Engineers, Phoenix, AZ.
Chapter 13: Waste Minimization and Reuse
Primary author: Janine B. Witko, Malcolm Pirnie, Inc., Mahwah, NJ. Contributing author: James E.
Smith, Jr., EPA NRMRL, Cincinnati, OH.
Peer Reviewers
James H. Borchardt, Montgomery Watson, Inc., Walnut Creek, CA; C. Michael Elliott, Stearns &
Wheeler, Cazenovia, NY; Terry L. Gloriod, Continental Water Company, St. Louis, MO; Paul E.
Malmrose, Montgomery Watson, Inc., Saddle Brook, NJ; Howard M. Neukrug, Philadelphia Water
Department, Philadelphia, PA; S. James Ryckman, University of Dayton, Dayton, OH; James K.
Schaefer, Metcalf & Eddy, Inc., Somerville, NJ; J. Edward Singley, Montgomery Watson, Inc.,
XXIII
-------
Gainesville, FL; Kevin L. Wattier, Metropolitan Water District, Los Angeles, CA; and Thomas L. Yohe,
Philadelphia Suburban Water, Bryn Mawr, PA.
Handbook Development Team
Project directors: James E. Smith, Jr., EPA NRMRL, Cincinnati, OH; and Maria Berman, ASCE,
Washington, DC. Additional coordinators: Jon DeBoer, AWWA, Denver, CO; Nancy E. McTigue,
Environmental Engineering & Technology, Inc., Newport News, VA; and Janine B. Witko, Malcolm
Pirnie Inc., Mahwah, NJ. Technical and copy editing and production support were provided by
Eastern Research Group, Inc., of Lexington, Massachusetts.
XXIV
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Chapter 1
Introduction
Potable water treatment processes produce safe drink-
ing water and generate a wide variety of waste products
known as residuals, including organic and inorganic
compounds in liquid, solid, and gaseous forms. In the
current regulatory climate, a complete management pro-
gram for a water treatment facility should include the
development of a plan to remove and dispose of these
residuals in a manner that meets the crucial goals of
cost effectiveness and regulatory compliance. The de-
velopment of a comprehensive water treatment residu-
als management plan typically involves each of the
following steps:
• Characterize the form, quantity, and quality of the
residuals.
• Determine the appropriate regulatory requirements.
• Identify feasible disposal options.
• Select appropriate residuals processing/treatment
technologies.
• Develop a residuals management strategy that meets
both the economic and noneconomic goals estab-
lished for a water treatment facility.
This handbook provides general information and insight
into each of the above-mentioned steps that a potable
water treatment facility should follow in developing a
residuals management plan. For additional information
on some of the processes described in this handbook,
see the Handbook of Practice: Water Treatment Plant
Waste Management (Cornwell et al., 1987) or Slib,
Schlamm, Sludge (Cornwell and Koppers, 1990).
1.1 Overview of Differences in Water
Treatment Processes
The form taken by water treatment plant (WTP) residu-
als can vary greatly, depending on the source of un-
treated water and the type of unit processes
incorporated in a water treatment facility. Although many
different forms of residuals are generated in the potable
water treatment industry, this handbook primarily ad-
dresses those residuals produced by the following gen-
eral categories of WTPs, which are identified by the
names of their most common unit processes:
• Coagulation/Filtration plant: This traditional form of
WTP is typically used to remove turbidity and patho-
genic organisms. These facilities may also be used
to remove color, taste, and odor-causing compounds
from the water supply. A variation of the process may
use aeration and oxidation processes for the removal
of iron and manganese. Unit processes may include
screening, chemical pretreatment, presedimentation,
microstraining, aeration, oxidation, coagulation/floc-
culation, sedimentation/precipitation, filtration, disin-
fection, and dissolved air flotation treatment. Other
nonchemical variations include direct filtration, diato-
maceous earth filtration, and slow sand filtration.
• Precipitative softening plant: This variation of a co-
agulation/filtration facility uses additional processes
to reduce water hardness. Unit processes may in-
clude screening, chemical pretreatment, presedimen-
tation, microstraining, aeration, oxidation, coagulation/
flocculation, lime softening, sedimentation/precipita-
tion, filtration, and disinfection.
• Membrane separation: This process is typically used
to remove turbidity, total dissolved solids, hardness,
nitrates, and radionuclides from a water supply. More
recent applications address removal of microbiologi-
cal contaminants. Membrane separation generally
involves the use of microfiltration, ultrafiltration, nanofil-
tration, reverse osmosis, or electrodialysis, often times
in combination with pretreatment practices.
• Ion exchange (IX): These facilities are used to re-
move inorganic constituents, including hardness, ni-
trates, arsenic, and radionuclides from water. The
process involves the use of IX reactors in combina-
tion with pretreatment processes.
• Granular activated carbon (GAC) adsorption: GAG is
used in many processes for the removal of naturally
occurring and synthetic organic matter from water.
The fundamental differences between the unit proc-
esses of these five plant types characterize the type of
residuals generated at a given facility. WTPs con-
structed to meet the ever-widening scope of future regu-
lations may require a combination of these unit
processes—a coagulation/filtration treatment plant using
-------
GAG as a filter medium, for example. Consequently, this
handbook's discussion of different water treatment
methods is purposely broad to include existing types of
residuals as well as those from future potable water
treatment facilities. The treatment of off-gas from an air
stripping process and the residuals from diatomaceous
earth filtration are some of the residual streams not
extensively addressed in this handbook.
1.2 Overview of Residuals Categories
WTP residuals are typically derived from suspended
solids in the source water, chemicals (e.g., coagulants)
added in the treatment processes, and associated proc-
ess control chemicals (e.g., lime). Some potable water
treatment processes produce residuals that are rela-
tively straightforward to process and dispose of. For
example, the leaves, limbs, logs, plastic bottles, and
other large floating debris separated from water during
the screening process are simply disposed of at conven-
tional solid waste landfills. Most other treatment proc-
esses generate more complex residual waste streams
that require more sophisticated processing methods and
final disposal methods to protect human health and the
environment. The four major categories of residuals
produced from water treatment processes are:
• Sludges (i.e., water that contains suspended solids
from the source water and the reaction products of
chemicals added in the treatment process). Presedi-
mentation, coagulation, filter backwashing opera-
tions, lime softening, iron and manganese removal,
and slow sand and diatomaceous earth filtration all
generate sludge.
• Concentrate (brines) from IX regeneration and salt
water conversion, membrane reject water and spent
backwash, and activated alumina waste regenerant.
• IX resins, spent GAG, and spent filter media (includ-
ing sand, coal, or diatomaceous earth from filtration
plants).
• Air emissions (off-gases from air stripping, odor con-
trol units, ozone destruction on units).
The chemical characteristics and contaminant concen-
tration levels in these residual waste streams often dic-
tate the ultimate disposal options. Furthermore, it is
reasonable to expect that as drinking water quality is
increasingly regulated, higher removal efficiencies of
more contaminants will be required. To achieve these
higher efficiencies, WTPs will need to use more ad-
vanced treatment technologies. Of potential concern is
the case where the residuals are characterized as either
hazardous or radioactive waste. Depending on the raw
water quality and treatment process removal efficiency,
hazardous or radioactive characteristics could be exhib-
ited in potentially any residual waste stream mentioned
above. Classification of WTP residuals as hazardous or
radioactive material, however, is unlikely at this time or
in the near future; no water treatment residuals have yet
been classified as either.
Some other typical residual waste streams associated
with a WTP are considered beyond the scope of this
handbook. These waste streams include storm drain-
age, sanitary sewage flows, laboratory and building floor
drainage, and waste from spill containment areas, all of
which generate residuals processing and disposal con-
cerns for the drinking water industry. Each of these
residual waste streams has specific regulatory require-
ments typically associated with point and nonpoint
source pollution control as defined under the Clean
Water Act (CWA). As with all residual treatment and
disposal issues, consult with the appropriate state and
local regulators to determine specific requirements.
Table 1-1 lists some typical residuals generated from
drinking water treatment processes, possible contami-
nants normally found in each waste stream, available
residual disposal methods, and a quick reference to the
applicable federal regulations. In all cases, specific state
and local regulations must also be considered.
1.3 Overview of Residual Solids
Treatment Processes
In many instances, regulatory requirements or the need
for cost effectiveness dictate that a residual receive
further treatment to make it acceptable for disposal. The
three classic treatment processes for residuals solids
are thickening, dewatering, and drying. Application of a
particular process depends on the solids concentration
of the residual. This handbook describes applications of
several types of solids concentrating processes.
Table 1-2 indicates which common residual treatment
processes are usually applied to residuals with low,
medium, or high solids concentrations, respectively.
Wthin the water treatment industry, the definitions of
low, medium, and high solids concentrations vary, de-
pending on whether a sludge is produced by a coagula-
tion/filtration plant or a precipitative softening plant. The
processes presented in Table 1-2 are often configured
in series to create combination systems that can provide
a low level of operational complexity with a high degree
of operational flexibility.
This handbook gives background information about
each of the most common treatment processes. This
information can then be used in the preliminary selection
and sizing of appropriate unit processes during the de-
velopment of a residuals management plan. This hand-
book also briefly discusses available treatment
technologies for gaseous residuals. These technologies
include stripping, odor control, gaseous chemical leak
treatment, and ozonation.
-------
Table 1-1. Treatment Processes and Waste Streams (Robinson and Witko, 1991)
Major
Treatment
Process
Type
Coagulation/
Filtration
Precipitative
softening
Typical Residual Waste
Streams Generated
Aluminum hydroxide,
ferric hydroxide, or
polyaluminum chloride,
sludge with raw water
suspended solids,
polymer and natural
organic matter
(sedimentation basin
residuals)
Spent backwash
filter-to-waste
Calcium carbonate and
magnesium hydroxide
sludge with raw water
suspended solids and
natural organic matter
Typical Contaminant
Categories
Metals, suspended
solids, organics,
biological, radionuclides,
inorganics
Metals, organics,
suspended solids,
biological, radionuclides,
inorganics
Metals, suspended
solids, organics,
unreacted lime,
radionuclides
Typical Disposal Methods
Landfilling
Disposal to sanitary
sewer/WWTP
Land application
Surface discharge
Recycle
Surface discharge
(pumping, disinfection,
dechlorination)
Disposal to sanitary
sewer/WWTP
Landfilling
Relevant
Chapter in
Handbook
Chapter 7
Chapter 6
Chapter 8
Chapter 5
Chapter 5
Chapter 6
Chapter 7
Regulation Covering
Disposal Method
RCRA/CERCLA
State and local
regulations
RCRA, DOT
NPDES (CWA), state
and local DOH
State and local DOH
NPDES (CWA), state
and local regulations
State and local
regulations
RCRA/CERCLA, state
and local regulations
Spent backwash
filter-to-waste
Metals, organics,
suspended solids,
biological, radionuclides,
inorganics
Membrane
separation
Reject streams
containing raw water
suspended solids
(microfiltration), raw
water natural organics
(nanofiltration), and
brine (hyperfiltration, RO)
Metals, radionuclides,
TDS, high molecular
weight contaminants,
nitrates
Ion exchange Brine stream
Metals, TDS, hardness,
nitrates
Disposal to sanitary
sewer/WWTP
Land application
Recycle
Surface discharge
(pumping, disinfection,
dechlorination)
Disposal to sanitary
sewer/WWTP
Surface discharge
(pumping, etc.)
Deep well injection
(pumping)
Discharge to sanitary
sewer/WWTP
Radioactive storage
Surface discharge
Evaporation ponds
Discharge to sanitary
sewer/WWTP
Chapter 6
Chapter 8
Chapter 5
Chapter 6
Chapter 9
Chapter 9
Chapter 9
Chapter 10
Chapter 9
Chapter 9
Chapter 9
Granular Spent GAC requiring
activated disposal and/or
carbon3 reactivation, spent
backwash, and
gas-phase emissions in
reactivation systems
VOCs, SOCs
(nonvolatile pesticides),
radionuclides, heavy
metals
Landfill Chapter 7
Regeneration—on/off site Chapter 14
Incineration
Radioactive storage
Return spent GAC to
supplier
Chapter 10
State and local
regulations
RCRA, state and
local regulations, DOT
State and local DOH
NPDES (CWA), state
and local regulations
State and local
regulations
RCRA, NPDES, state
and local regulations
RCRA, NPDES, state
and local regulations
State and local
regulations
RCRA, DOT, DOE
RCRA, NPDES, state
and local regulations
RCRA, NPDES, state
and local regulations
State and local
regulations
RCRA, CERCLA, DOT
State and local air
quality regulations
(CAA)
State and local air
quality regulations
(CAA)
DOT, DOE
-------
Table 1-1. Treatment Processes and Waste Streams (Robinson and Witko, 1991) (Continued)
Major
Treatment
Process
Type
Stripping
process
(mechanical
or packed
Typical Residual Waste
Streams Generated
Gas phase emissions
Typical Contaminant
Categories
VOCs, SOCs, radon
Typical Disposal Methods
Discharge to atmosphere
GAC adsorption of off-gas
(contaminant type and
concentration dependent)
Relevant
Chapter in
Handbook
Not addressed
Regulation Covering
Disposal Method
State and local air
quality regulations
(CAA)
tower)
Spent GAC if used for
gas-phase control
VOCs, SOCs,
radionuclides
GAC adsorption of off-gas
(contaminant type and
concentration dependent)
Return spent GAC to
supplier
Not addressed
State and local air
quality regulations
(CAA)
aThe discussion on disposal methods for GAC residuals is generic in nature. For more specific information on disposal options for GAC, see
McTigue and Cornwell (1994).
Key
CAA = Clean Air Act
CERCLA = Comprehensive Environmental Response, Compensation and Liability Act
DOE = Department of Energy
DOH = Department of Health
DOT = Department of Transportation
NPDES = National Pollutant Discharge Elimination System
RCRA = Resource Conservation and Recovery Act
RO = Reverse osmosis
SOC = Synthetic organic chemical
IDS = Total dissolved solids
VOC = Volatile organic compound
Table 1-2. Representative Solids Concentration Treatment Processes3
Process
Thickening
Dewatering
Drying
Solids
Concentration
Low
Medium
High
Gravity
Equalization Settling
X X
Dissolved Air
Flotation
X
Lagoon
X
X
X
Mechanical
X
X
X
Open Air
X
X
Thermal
Drying
X
1 Chapter 4 of this handbook provides a more complete discussion of processing alternatives.
1.4 Selection of Residuals Management
Plan Options
Before selecting the treatment and disposal actions nec-
essary to develop a residuals management plan, the
manager of a WTP may start with a large array of
residuals processing and disposal options. These op-
tions are narrowed through consideration of specific
residuals characteristics and associated regulatory re-
quirements. A focus on the available disposal options
further narrows the array to a finite set of residuals
management alternatives.
Figure 1-1 illustrates that the primary target during the
development of a residuals management plan should be
practical disposal options and treatment processes that
will take into account economic and noneconomic fac-
tors of concern to the community. The technical criteria
used in the selection of the final management plan differ
from user to user; economic, cultural, social, and envi-
ronmental factors are also site-specific, and are typically
included in any final selection. The technical information
Type of Water
Treatment Plant
Disposal
Options
Social/Cultural
Environmental
Economic
Figure 1 -1. The primary target of a residuals management plan.
-------
in this handbook can be used to screen out inappropri-
ate residuals processing and disposal options. Cost
curves for various treatment processes and a matrix of
commonly encountered social, cultural, and environ-
mental factors are included.
1.5 Handbook User's Guide
This hand book offers background information about the
components of, and the development process for, a
comprehensive residuals management plan. Develop-
ing a successful residuals management plan requires an
understanding of the value of residuals characterization
and the regulatory requirements, tailoring the treatment
options to the requirements of the available disposal
alternatives, and then developing rational evaluation cri-
teria. This handbook is organized to logically guide the
user through each of these steps.
Figure 1-2 illustrates a generic decision process for
developing a residuals management plan. Each step in
the process is keyed to a chapter in this handbook.
Figure 1-2 can also be used as a quick reference to find
specific information throughout the book.
Emerging Technologies
^
See Chapter 13
Water Treatment Plant Residuals
Addressed in This Handbook
1
No
Identify Disposal Options
Landfill Land Application
1
r
Develop Residuals Processing
Treatment Alternatives
Select Cost-Effective
Residuals Handling Strategy
CASE
(STUDIES I
Figure 1-2. Handbook user's guide.
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Chapter 2
Regulatory Issues Concerning Management of
Water Treatment Plant Residuals
Water treatment utility managers who are beginning to
explore alternative methods for disposal of water plant
wastes may encounter difficulty identifying the regula-
tions that affect the various management practices. The
difficulty is compounded by the many different types of
wastes produced by water treatment plants (WTPs).
This chapter provides an overview of the regulatory
requirements governing the following disposal methods
for WTP residuals: direct discharge, discharge to waste-
water treatment plants, disposal in landfills, land appli-
cation, underground injection, disposal of radioactive
waste, and treatment of air emissions. Applicable fed-
eral regulations and typical state requirements are both
discussed. In addition, the results of two surveys of state
regulatory requirements conducted by the American
Waterworks Association (AWWA) Water Treatment Re-
siduals Management Committee and the American So-
ciety of Civil Engineers (ASCE), are summarized in
Appendix A. The surveys also identify commonly used
residuals management practices in each state.
At the federal level, EPA has not established any regu-
lations that are specifically directed at WTP residuals.
Applicable regulations are those associated with the
Clean Water Act (CWA); Criteria for Classification of
Solid Waste Disposal Facilities and Practices (40 CFR
Part 257); the Resource Conservation and Recovery Act
(RCRA); the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA); and the
Clean Air Act (CAA). The CWA limits direct discharges
into a water course, while the other legislation governs
other methods of use and/or disposal of wastes. Most
states are responsible for establishing and administer-
ing regulations that will meet the requirements of these
acts. The regulation of wastes, therefore, is primarily the
responsibility of the states.
2.1 Discharge to Waters of the
United States
The federal program to protect the quality of the nation's
water bodies is authorized under the Federal Water
Pollution Control Act (FWPCA) of 1972. Since its pas-
sage, the statute has been amended in 1977, 1978,
1980, 1981, and 1987, and renamed the Clean Water
Act (CWA). The act and associated regulations attempt
to ensure that water bodies maintain the appropriate
quality for their intended uses, such as swimming, fish-
ing, navigation, agriculture, and public water supplies.
The National Pollutant Discharge Elimination System
(NPDES) applies to WTPs that discharge wastes di-
rectly to a receiving water. Under Section 402 of the
CWA, any direct discharge to waters of the United
States must have an NPDES permit. The permit speci-
fies the permissible concentration or level of contami-
nants in a facility's effluent. EPA authorizes states to act
as the primary agent for the NPDES program, provided
that the state program meets all EPA requirements.
State regulations and guidelines controlling the dis-
charge of residuals, however, vary throughout the
United States. Certain states permit direct discharge of
residuals with or without pretreatment requirements. In
other states, direct discharge has been restricted
through limitations on suspended solids and pH (WE.
Gates and Associates, 1981; Cornwell and Koppers,
1990). Generally, direct discharge into streams has
been permitted for clarified water such as settled back-
wash water or overflow from solids separation proc-
esses.
For states not granted primacy, EPA regional offices
issue NPDES permits. An NPDES permit is issued to a
discharger based on technology-based effluent limita-
tions, water quality standards, or both.
2.1.1 Technology-Based Effluent Limitations
Under Sections 301 and 304 of the CWA, EPA is re-
quired to establish national effluent limitations for the
major categories of industrial dischargers. These limita-
tions reflect the capabilities of the best available tech-
nology that is economically feasible for use in treating
industrial discharges to surface waters. Federal effluent
limitations have not yet been issued for WTP residuals;
therefore, the delegated states or the regional EPA of-
fices are responsible for establishing the limits for WTP
discharges. Federal guidelines for controlling WTP dis-
charges were drafted but never fully implemented. The
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draft guidance document divides WTPs into three cate-
gories (WE. Gates and Associates, 1981; Cornwell and
Koppers, 1990):
• Plants that use coagulation, oxidation for iron and
manganese removal, or direct filtration.
• Plants that use chemical softening procedures.
• Plants that use a combination of the procedures in
the above categories.
The draft document defines the best practical control
technology for each category and establishes discharge
limits on pH and total suspended solids (TSS). Based
on plant capacity, WTP discharge limits varied in the
document from 0.6 to 1.3 g TSS per cubic meter of water
treated, which corresponds to a TSS of approximately
30 to 60 mg/L in the discharge, assuming a 2 percent
waste discharge of the main stream. Because secon-
dary treatment or the equivalent is required for treating
drinking water, 85 percent removal and/or a TSS level
of 30 mg/L are typically required for WTP discharges.
2.1.2 Water Quality Standards
Under Section 303 of the CWA, each state is required
to establish ambient water quality standards for its water
bodies. These standards define the type of use and the
maximum permissible concentrations of pollutants for
specific types of water bodies. The states use water
quality criteria documents published by EPA, as well as
other advisory information, as guidance in setting maxi-
mum pollutant limits. EPA reviews and approves the
state standards.
According to EPA, certain in-stream water quality stand-
ards at the edge of the mixing zone must be met to allow
direct discharge of WTP residuals. A controlled release
of water clarifier residuals and filter backwash that
meets water quality standards may be considered tech-
nology-based controls in appropriate circumstances
(Cornwell and Lee, 1993).
Some states have established maximum allowable con-
centrations for pollutants in discharges to water bodies.
These limits generally apply if they are more stringent
than the allowable discharge that will meet the in-stream
water quality criteria. For example, Illinois does not allow
a discharge of greater than 15 mg/L fluoride, and barium
discharge must be lower than 2 mg/L, even if the 1 mg/L
in-stream standard could be met through dilution in the
mixing zone (Cornwell et al., 1987). An overflow from a
solids separation process such as a lagoon, thickener,
or, sometimes, backwash water, requires a discharge
permit.
2.1.3 Special Concerns Regarding Aluminum
EPA has developed an ambient water quality standard
for aluminum, requiring that the in-stream soluble alumi-
num level not exceed 87 u,g/L on a 4-day average. The
1-hour average must not exceed 750 u,g/L. This stand-
ard may be of concern for WTPs that use aluminum
sulfate or other aluminum coagulants and rely on an
NPDES-permitted discharge to dispose of settled back-
wash wastewater, supernatant from dewatering process
units, or coagulation/flocculation residuals. The stand-
ard is focused on dissolved aluminum; most aluminum
in WTP discharges is in solid form.
Because aluminum is abundant in some geologic forma-
tions, it is not unusual to find it in concentrations higher
than 1 mg/L in receiving streams for NPDES discharges.
Consequently, some states may mandate complete
elimination of any NPDES discharges that contribute to
the aluminum load of the receiving stream.
2.2 Discharge to Wastewater Treatment
Plants
Three general categories of regulations affect the deci-
sion of whetherto discharge WTP residuals to a sanitary
sewer or directly to a wastewater treatment plant
(WWTP): 1) federal and state hazardous waste regula-
tions; 2) federal and state radioactive waste regulations;
and 3) local receiving wastewater utility regulations,
driven generally by the need for a utility to comply with
the provisions of the CWA.
The first two categories of regulation usually are not a
problem. WTP residuals are rarely, if ever, classified as
hazardous waste. While water treatment facilities often
generate a radioactive component in residuals, it is at a
very low level. The radioactive component results from
removing normally occurring radioactive material
(NORM) from the process water by the addition of a
coagulant. The resulting low-level radioactive WTP re-
siduals are generally acceptable for disposal to a waste-
water utility. The third category of regulations, local
receiving wastewater utility discharge permit regula-
tions, incorporates any provisions concerning hazard-
ous or radioactive wastes that may be germane.
Provisions are sometimes included that reduce the risk
of operational problems at the receiving WWTP or of
violation to its discharge permit. In small utility situ-
ations, often no formal local receiving wastewater utility
regulations exist, and compliance with any regulatory
guidance is of little concern.
All WWTPs must comply with EPA's general pretreat-
ment requirements, under which WTP residuals are
clearly identified as industrial wastes. In addition, EPA
requires all WWTPs with wastewater inflow greater than
5 million gallons per day (mgd) to establish formal pre-
treatment enforcement programs. Under these pro-
grams, the WWTPs regulate discharges into municipal
sewers by industries, including water treatment facilities,
and other entities. The WWTPs must, at a minimum,
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enforce national pretreatment standards. They also may
implement additional controls or limits based on local
conditions for any of the following reasons:
• A WWTP's NPDES permit may require removal of
pollutants that the plant itself cannot remove.
• Pollutants in residuals discharged into the sewer sys-
tem may adversely affect the performance of the col-
lection system or removal systems in the WWTP.
• Pollutants in residuals discharged into the sewer sys-
tem may contaminate WWTP wastes, making dewa-
tering and disposal more difficult and expensive.
EPA authorizes the states to review and approve indi-
vidual WWTP pretreatment programs. In addition to the
individual plant's pretreatment requirements, state
agencies may provide specific guidelines.
2.3 Landfilling
Under RCRA Subtitle D regulations (40 CFR Parts 257
and 258), criteria have been established for the design
and operation of nonhazardous, solid waste landfills.
Landfills that receive only drinking water treatment re-
siduals are subject to the requirements of 40 CFR Part
257. These requirements are also applicable to landfills
that accept solid waste other than household waste,
such as industrial waste. These criteria apply to all
nonhazardous, nonhousehold solid waste disposal fa-
cilities and practices. They address seven areas of en-
vironmental concern pertaining to landfill design and
operation (see Table 2-1). It should be noted that these
criteria are performance based and do not include any
specific design criteria.
2.3.1 Municipal Nonhazardous Solid Wastes
Municipal solid waste landfills (MSWLFs) are subject to
the criteria of 40 CFR Part 258. Unlike Part 257, Part
258 includes specific design criteria in addition to per-
formance-based criteria. If a utility disposes of its WTP
residuals in a monofill, then, under federal regulations,
Part 258 does not apply; Part 257 (discussed above)
does instead. If, however, the WTP residuals are co-dis-
posed of with municipal solid waste, the requirements
established for MSWLFs apply. These landfill criteria
(40 CFR Part 258) address six major areas as listed in
Table 7-2.
Six location restrictions apply to MSWLFs. Landfills can-
not be located in floodplains, wetlands, seismic impact
zones, and unstable areas. Additionally, specific set-
backs are required for landfills near airports and fault
areas.
The minimum design criteria for new landfills are in-
tended to give owners/operators two basic design op-
tions—a composite liner design, or a site-specific design
Table 2-1. Required Management Practices for Nonhazardous
Industrial Waste Only and Co-Disposal Landfills,
and Land Application Sites (40 CFR Part 257)
Environmental
Concern Management Practice
Floodplains Facilities in floodplains shall not restrict the flow of
the 100-year flood, reduce the temporary water
storage capacity of the floodplain, or result in
washout of solid waste, so as to pose a hazard to
human life, wildlife, or land or water resources.
Endangered Facilities shall not cause or contribute to the taking
species of any endangered or threatened species of plants,
fish, or wildlife, and shall not result in the
destruction or adverse modification of the critical
habitat of endangered or threatened species.
Questions about the potential for adversely
affecting endangered or threatened species at a
particular site should be directed to the nearest
Regional office of the U.S. Fish and Wildlife
Service. (Note: Notices of draft NPDES permits
also are routinely sent to the U.S. Fish and Wildlife
Services. See 40 CFR 124.10(c).)
Surface water Facilities shall not cause a discharge of pollutants
into waters of the United States in violation of
Section 402 of the Clean Water Act, shall not
cause a discharge of dredged or fill material in
violation of Section 404 of the Act, and shall not
cause nonpoint source pollution that violates an
approved Section 208 water quality management
plan.
Ground water Facilities shall not contaminate an underground
drinking water source beyond the solid waster
boundary, or beyond an alternative boundary.
Consult the regulation for procedures necessary to
set alternative boundaries (see Appendix D). To
determine contamination, Appendix I of 40 CFR
Part 257 provides a list of contaminant
concentrations. Release of a contaminant to
ground water which would cause the
concentrations of that substance to exceed the
level listed in Appendix I constitutes contamination.
Disease Disease vectors shall be minimized through the
periodic application of cover material or other
techniques as appropriate to protect public health.
Air Facilities shall not engage in open burning of
residential, commercial, institutional, or industrial
sold waste. Infrequent burning of agricultural
wastes in the field, silvicultural wastes for forest
management purposes, land-clearing debris,
diseased trees, debris from emergency cleanup
operations and ordinance is allowed.
Safety 1. Explosive gases generated by the facility shall
not exceed 25 percent of the lower explosive
limit for the gases in facility structures and 100
percent of the lower explosive limit at the
property line.
2. Facilities shall not pose a hazard to the safety of
persons or property from fires.
3. Facilities within 10,000 feet of any airport
runway used by turbojet aircraft, or within 5,000
feet of any airport runway used by piston-type
aircraft shall not pose a bird hazard to aircraft.
4. Facilities shall not allow uncontrolled public
access so as to expose the public to potential
health and safety hazards at the disposal site.
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that meets the performance standard of RCRA Subtitle
D and has been approved by the permit writer.
Subtitle D establishes specific criteria for the following
landfill operational factors: regulated hazardous waste
detection program, cover material, disease vector con-
trol, explosive gases control, air criteria, access require-
ments, storm water run-on and runoff management,
surface water, liquids restrictions, recordkeeping.
The most extensive portion of Subtitle D pertains to
ground-water monitoring and corrective action. The rule
mandates that all landfills must have a monitoring sys-
tem that yields sufficient ground-water samples from
around the site. Both upgradient and downgradient wells
and sampling are required. Tests to detect 15 heavy
metals and 47 volatile organic compounds must be
conducted, but approved states can modify the list to
reflect site-specific conditions.
The financial assurance requirements of RCRA are de-
signed to guarantee that funds will be available for
closure and postclosure care of landfills and, if needed,
corrective action. All landfills are required to install a final
cover system with at least two components, an infiltra-
tion layer and an erosion layer. The minimum final cover
requirements mandate an infiltration layer at least 18
inches thick with a very low permeability limit, and an
erosion layer at least 6 inches thick that can sustain
native plant growth. A written closure plan must be
submitted to the state solid waste director. Postclosure
care must be provided for 30 years; it includes maintain-
ing the final cover, the leachate collection and disposal
system, the ground-water monitoring program, and the
landfill gas monitoring system.
WTP residuals that are co-disposed of with municipal
solid waste in a sanitary landfill do not have to meet
numerical pollutant limits. The residuals, however, can-
not be hazardous and must not contain free liquids.
Mechanical and natural dewatering of residuals is often
adequate for removing the free liquid from the water
treatment solids. Because EPA requires landfill opera-
tors to make random inspections of incoming waste or
take other steps to ensure that incoming loads do not
contain regulated hazardous wastes, landfill operators
may require residuals disposers to prove their solids are
not hazardous. Hazardous wastes (as defined in 40
CFR Part 261) are waste materials that exhibit ignitabil-
ity, corrosivity, reactivity, ortoxicity (see Section 2.7).
EPA now prohibits the disposal of noncontainerized or
bulk liquid wastes in landfills. Subtitle D requires that the
landfill owner or operator determine if the wastes (in-
cluding municipal water treatment solids) are liquid
wastes according to the Paint Filter Liquids Method
9095. This simple test is performed by placing a repre-
sentative sample of the solids in a mesh Number 60
paint filter (available at paint stores) and allowing it to
drain for 5 minutes. The solids are considered a liquid
waste if any liquid passes through the filter during the
5-minute period.
2.3.2 Summary
In summary, neither 40 CFR Part 257 nor Part 258
requires that WTP plant residuals be stabilized or have
a certain percent solids concentration. 40 CFR Part 258
does require that the residuals pass a paint filter test
prior to co-disposal with solid wastes in a landfill. Both
regulations require that the filled areas be periodically
covered to protect public health. Both regulations re-
quire attention to protection of ground and surface water
sources and control of gas migration.
Some states may impose further restrictions on bulk or
special wastes such as those produced during water
treatment. Besides the paint filter test, states also re-
quire a minimum total solids content. Nebraska, one of
the most restrictive states, requires a minimum total
solids content of 70 percent. Some states also have a
maximum allowable ratio of residuals-to-municipal solid
waste.
2.4 Land Application
2.4.1 Federal Regulations
Land application of WTP residuals is typically regulated
at the state level. The recently developed federal stand-
ards for the use or disposal of sewage residuals (40
CFR Part 503) specifically exclude WTP residuals. Cri-
teria for classification of solid waste disposal facilities
and practices (40 CFR Part 257), however, could affect
land application of WTP residuals (see Table 2-1). This
rule regulates the disposal of nonhazardous wastes,
which include residuals generated from a WTP. The
objective of this rule is to prevent construction or opera-
tion of a residuals processing or disposal facility from
adversely affecting surface water, ground water, endan-
gered or threatened wildlife, or public health. Criteria
were established under 40 CFR Part 257 regulating
application of residuals containing cadmium and poly-
chlorinated biphenyls (PCBs). As discussed in Chapter
3 on residuals characterization, concentrations of cad-
mium and PCBs in WTP residuals are usually below
detection levels, making these criteria inapplicable.
Specific requirements for controlling disease vectors are
also included under Part 257 to prevent adverse public
health impacts resulting from application of solid
wastes/residuals. Criteria are also established to protect
ground-water quality beyond the application site bound-
ary. Land application activities must not cause specific
organic and inorganic chemicals to exceed maximum
contaminant levels in the area. These criteria generally
should not affect the ability to land-apply WTP residuals.
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2.4.2 State Regulations
Most state agencies are waiting for EPA to establish land
application criteria for WTP residuals. Despite the differ-
ences in their characteristics, many states apply WWTP
biosolids criteria, such as metals loading limits, to the
land application of WTP residuals.
Some states have taken it on themselves to establish
specific criteria for land application of WTP residuals.
For example, the Colorado Department of Health regu-
lates beneficial land application of WTP residuals under
domestic sewage sludge regulations (Colorado, 1986).
The department has established specific regulations
pertaining to the beneficial use of WTP residuals on
land. These regulations require development of an ap-
proved beneficial use plan that:
• Identifies where the material will be used.
• Contains approval from the land owner and the ap-
propriate county health department.
• Contains residuals analyses.
• Identifies the types of crops to be grown and the
application rates.
Parameters to be analyzed include aluminum, arsenic,
cadmium, pH, total solids, and nutrients. If WTP residu-
als are used with biosolids, then the practice must com-
ply with the biosolids regulations. Application to land
where root crops or low-growing crops are to be grown
is prohibited if the crops are intended for human con-
sumption.
The Colorado Department of Health does not allow
beneficial use of WTP residuals with radioactivity levels
exceeding 40 picocuries total alpha activity per gram
(pCi/g) of dry residuals.
The Missouri Department of Natural Resources has also
established guidelines for land application of alum re-
siduals. These guidelines recommend that soil pH be
maintained near 7.0 for alum residuals application and
that total aluminum loading to the soil not exceed 4,000
Ib/acre without site-specific investigations. No restric-
tions apply to land application of lime softening residuals
(Missouri, 1985).
2.5 Underground Injection
The federal government has promulgated regulations
for injecting wastes into the ground. Most states have
fully adopted these regulations and have been granted
primacy for enforcing the program. These regulations
alone, however, will probably not prevent underground
injection of WTP residuals. Some states, such as Flor-
ida, have chosen to promulgate and/or issue stricter
regulations and/or policies, making it very difficult to
dispose of WTP residuals such as brines via under-
ground injection.
2.5.1 Underground Injection Control Program
Underground injection may be a disposal option for
concentrates and brines from drinking water treatment
processes. This option is subject to regulatory approval
under the underground injection control (DIG) program,
authorized by the Safe Drinking Water Act (SDWA). The
DIG program regulates the subsurface placement of
fluid in wells or dug-holes with a depth greater than their
width. The program covers the disposal of hazardous
waste and various other substances in wells.
After the 1980 amendments to the SDWA, EPA devel-
oped a mechanism to grant individual states primary
enforcement responsibility for underground injection.
The DIG regulations are enforced through a permitting
system. Each state is required to develop a DIG permit
program that enforces EPA standards, prevents under-
ground injection unless authorized by a permit or rule,
authorizes underground injection only where the proc-
ess will not endanger drinking water sources, and main-
tains thorough records and inspection reports. Currently,
all 50 states have established DIG programs, some of
which are managed by EPA regional offices.
2.5.1.1 Classification of Underground Injection
Wells
To prevent contamination of drinking watersources, EPA
established regulatory controls and a classification sys-
tem based on the type of waste injected and the location
of the injection well (40 CFR 146.5):
• Class I includes wells used to inject hazardous waste,
or industrial and municipal waste beneath the lower-
most formation containing an underground source of
drinking water within 1/4 mile of the well bore.
• Class II includes wells used to inject fluids generated
from oil and natural gas production and refining.
• Class III includes wells that are injected with liquid
(such as water) for extraction of minerals including
sulfur, uranium, and other metals in situ.
• Class IV includes wells that are used to inject haz-
ardous or radioactive wastes into or above a forma-
tion containing an underground source of drinking
water within 1/4 mile of the well. This class of wells
also includes wells used to dispose of hazardous
waste into or above a formation containing an aquifer
that has been exempted pursuant to 40 CFR 146.04.
• Class V includes the injection wells that are not cov-
ered in Classes I through IV.
Wells used for underground injection of WTP residuals
fall into Classes I, IV, and V
10
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2.5.1.2 Permit Application
Underground injection wells are authorized by rule un-
der RCRA and permitted at the state level under the
SDWA.
Authorization by Rule
Authorization of underground injection by rule gives
owners and operators an opportunity to operate under-
ground injection facilities before their permit applications
are approved. To be authorized by rule, owners or op-
erators must comply with the applicable requirements.
For Class I and III wells, the owners or operators must
meet the requirements listed in 40 CFR 144.28 and
individual state requirements. The authorization is void
if a permit application has not been filed in a timely
manner as specified in 40 CFR 144.31(c)(1); otherwise,
it can be extended until the permit is issued or revoked
by a DIG program administrator. For Class IV wells, the
operation period can be as long as 6 months on the
condition that requirements specified in 40 CFR 144.13,
144.14(c) are met. Currently, the operation of Class V
wells is not authorized by rule.
Authorization by Permit
Except for owners or operators who are authorized by
rule to run underground injection facilities, all other fa-
cilities must be authorized by permits. Facilities author-
ized by rule are also required to apply for a permit to
continue operating their facilities on a long-term basis.
All applicants for underground injection permits must
complete the application forms provided by a state DIG
program, and submit necessary supporting documents.
This paperwork should include the following information:
• Facility name, address, and ownership.
• Activities that are conducted in the facility and which
require a permit under RCRA, CWA, or CAA.
• A list of principal products or services provided by the
facility.
• Lists of the relevant permits and construction approv-
als issued to the facility.
• Geographic and topographic characteristics of the fa-
cility.
2.5.1.3 Underground Injection Control Criteria
and Standards
The DIG program administrator reviews the permit ap-
plications based on DIG criteria and standards (40 CFR
146). Different criteria and standards apply to different
classes of injection wells. The major criteria and stand-
ards are:
• Construction requirements: Configuration of the injec-
tion wells (hole size, depth of injection zone), injection
pressure, type of cement, and type of injected fluids
must be specified and meet the requirements. Both
new and existing wells must be cased and cemented
to protect sources of drinking water.
• Operating requirements: Certain operating conditions
must be met. For example, the injection pressure
must not exceed a maximum, and injection between
the outermost well casing and the well bore must be
avoided to protect underground sources of drinking
water.
• Monitoring requirements: The nature of the injected
fluids, injection pressure, flow rate, cumulative vol-
ume, and mechanical integrity must be monitored.
Monitoring should take place at regular intervals and
is based on class of well and operation type.
• Reporting requirements: Quarterly or yearly reports
should include the operating conditions for the period,
the results of the monitoring, and the results of any
other required tests.
2.5.1.4 Actions Against Violations
Under the SDWA, no operator or owner of an under-
ground injection facility is allowed to construct, operate,
maintain, convert, plug, or abandon that facility, or con-
duct any other injection activity in a way that might
contaminate a ground-water source of drinking water.
For Class I, II, and III wells, if ground-water quality
monitoring shows the intrusion of contaminants to a
ground-water source, then corrective action may be re-
quired. Corrective actions may be taken in the areas of
operation, monitoring, or reporting, or might include
closing the well, if required. If the operation of the well
is authorized by a permit, modification of the permit with
additional requirements might occur (40 CFR 144.39). If
the permit is violated, appropriate enforcement action
might be taken (40 CFR 144.55).
Under the SDWA, new construction of most Class IV
wells is strictly prohibited. Increasing the amount or
changing the type of waste injected in these wells is also
forbidden.
If a Class V well causes a violation of primary drinking
water regulations under 40 CFR Part 142, the operator
of the well must take any action (including closing the
injection well) to prevent contaminating drinking water
sources.
2.5.2 Underground Injection Requirements
Under RCRA
Section 3004(f) of RCRA requires EPA to determine
whether underground injection of hazardous wastes will
endanger human health and the environment. In re-
sponse, EPA has banned the underground injection of
hazardous wastes that do not meet the applicable treat-
11
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ment standards of the land disposal restrictions (see 40
CFR Part 148). The 1986 Hazardous and Solid Waste
Amendments (HSWA) to RCRA enhanced the restric-
tion of underground injection of hazardous waste. These
amendments prohibit the disposal of hazardous waste
through underground injection into or above a formation
within 1/4 mile of an underground source of drinking
water.
2.6 Disposal of Radioactive Waste
When radium isotopes and other radioactive materials
are removed from a drinking water supply, they are
usually concentrated in residuals that must be disposed
of in ways that are cost-effective, practical, and protec-
tive of human health and the environment. The U.S.
Nuclear Regulatory Commission (NRC) has the author-
ity to regulate the handling and disposal of all licensed
synthetic radioactive material. Certain materials, such
as water and WWTP wastes containing naturally occur-
ring radioactive material (NORM), are not licensed or
regulated by NRC because they are not included under
its authority as source, special nuclear, or byproduct
material. Regulation of NORM is left to individual states
(Hahn, 1989). Limitations on radioactive residuals are
established case-by-case, using best professional judg-
ment (Koorse, 1993a). Recognizing that water treatment
could concentrate radionuclides, EPA has issued guide-
lines for managing radionuclide waste from water treat-
ment containing up to 2,000 pCi/g (dry weight) of NORM
(U.S. EPA, 1994b). The guidelines addressing disposal
of residuals, brines, and solid wastes containing radium
or uranium are discussed in detail in Chapter 10.
Several states regulate disposal of WTP residuals con-
taining radionuclides. For example, in certain states,
water quality standards include specific criteria for ra-
dionuclides. Some states also limit the discharge of
wastes containing naturally occurring radionuclides into
sanitary sewers. Illinois limits the use of residuals for soil
conditioning on agricultural lands. Illinois and Wisconsin
have developed criteria for landfilling residuals contain-
ing radium. In Wisconsin, the discharge of WTP residu-
als to a sanitary sewer collection and treatment system
that is otherwise acceptable is governed by radium dis-
charge limits as follows:
CRa-226 CRa-228 .
-+ < 1
400
800
where
CRa_226 = the concentration in picocuries per liter
(pCi/L) of soluble Ra-226 in the wastewater
CRa_228 = the concentration of soluble Ra-228 in
pCi/L in the wastewater
The average monthly combined radium concentrations
discharge, measured in pCi/L, must not exceed the
limits of the preceding equation, and the total amount of
radiation released to the sanitary sewer system in any
1-year period cannot exceed 1.0 Ci (Hahn, 1989).
In Colorado, if the total alpha activity of the WTP residu-
als exceeds 40 pCi/g (dry weight), the WTP is required
to contact the Colorado Department of Health, Radiation
Control Division, for further disposal guidance (Colo-
rado, 1990). In addition, North Dakota has regulations
requiring the water plant to be licensed as a generator
of radioactive material (Cornwell et al., 1987). Other
states have adopted similar regulations that may affect
whether WTP residuals containing radioactivity may be
discharged to sanitary sewers.
2.7 Hazardous Waste
WTP residuals are generally not considered hazardous
wastes. Even spent granular activated carbon (GAG)
residuals are usually not hazardous wastes (McTigue
and Cornwell, 1994; Dixon, 1993). Some disposal or use
measures for WTP residuals, however, require demon-
stration that the material is not hazardous according to
governing hazardous waste regulations.
Subtitle C, Section 3001 of RCRA addresses treatment,
storage, and disposal of hazardous waste. These regu-
lations are designed to ensure proper management of
hazardous waste from "cradle to grave"—i.e., from the
moment the waste is generated until it is ultimately
disposed of. This approach has three elements:
• A tracking system requiring that a uniform manifest
document accompany any transported hazardous
waste from the point of generation to the point of final
disposal.
• An identification and permitting system that enables
EPA and the states to ensure safe operation of all
facilities involved in treatment, storage, and disposal
of hazardous waste.
• A system of restrictions and controls on the place-
ment of hazardous waste on or into the land.
EPA employs two separate mechanisms for identifying
hazardous wastes (as defined in 40 CFR Part 261).
Wastes may be defined as hazardous based on their
characteristics (ignitability, corrosivity, reactivity, or tox-
icity), or they may be specifically designated as hazard-
ous in lists published by the agency. Since WTP
residuals are not specifically designated as hazardous
wastes, they can be classified as hazardous only if they
exhibit any of the four hazardous characteristics.
A waste is classified as ignitable if it is capable of
causing a fire that burns vigorously and persistently
under standard pressure and temperature, causing a
hazard. An aqueous waste stream is corrosive if it has
a pH lower than 2.0 or higher than 12.5. A waste is
reactive if it has any of these characteristics:
12
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• Is unstable.
• Reacts violently or forms potentially explosive mix-
tures with water.
• Generates toxic gases or fumes when mixed with water.
• Contains cyanides or sulfides that can generate toxic
gases or fumes.
• Can detonate if exposed to heat.
• Is already defined as an explosive material.
Although domestic WTP residuals are rarely ignitable,
corrosive, or reactive, the greatest concern for water
treatment wastes is toxicity, as determined by the Tox-
icity Characteristic Leaching Procedure (TCLP) (U.S.
EPA, 1992c). The TCLP applies to certain metals, her-
bicides, pesticides, and volatile organic compounds
(VOCs). A water treatment residual failing the TCLP test
can be classified as a hazardous material. Many landfills
require the disposer to document TCLP analysis results
as proof that the material is not toxic before solids
disposal is allowed.
The TCLP uses a vacuum-sealed extraction vessel to
capture VOCs in the sample. Table 2-2 lists the contami-
nants analyzed in the TCLP, along with maximum allow-
able pollutant concentrations at which the waste is
considered nonhazardous. WTP solids generally do not
fail the TCLP and are not classified as hazardous mate-
rials. If WTP wastes are classified as hazardous wastes,
they are subject to the handling, treatment, and disposal
requirements specified in RCRA Subtitle C.
CERCLAalso affects landfilling of WTP wastes. Through
CERCLA, cleanup costs at hazardous waste sites can
be assessed against the user of the site on a volume-
use basis; the waste itself need not have directly caused
the problems. Co-disposal of water treatment residuals,
then, with potentially hazardous wastes significantly in-
creases the potential for a utility to be held responsible
for landfill remediation costs.
2.8 Air Emissions
The federal government has promulgated regulations to
control air emissions from industrial sources. Most
states have fully adopted these regulations and have
been granted primacy for enforcing them. Some states
such as New Jersey, Michigan, and California, have
promulgated stricter regulations and/or policies govern-
ing air emissions. These states may require treatment
of air stripper emissions using activated carbon treat-
ment or combustion.
2.8.1 Federal Regulations
Federal regulations do not specifically regulate air emis-
sions from drinking water treatment plants. Instead, they
Table 2-2. TCLP Constituents and Regulatory Limits (40 CFR
Part 261.24)
Constituents
Reg. Level (mg/L)
Arsenic
Barium
Benzene
Cadmium
Carbon tetrachloride
Chlordane
Chlorobenzene
Chloroform
Chromium
o-Cresol
m-Cresol
p-Cresol
Cresol3
2,4-D
1,4-Dichlorobenzene
1,2-Dichloroethylene
1,1-Dichloroethylene
2,4-Dinitrotoluene
Endrin
Heptachlor (and its hydroxide)
Hexachlorobenzene
Hexachloro-1,3-butadiene
Hexachloroethane
Lead
Lindane
Mercury
Methoxychlor
Methyl ethyl ketone
Nitrobenzene
Pentachlorophenol
Pyridine
Selenium
Silver
Tetrachloroethylene
Toxaphene
Trichloroethylene
2,4,5-Trichlorophenol
2,4,6-Trichlorophenol
2,4,5-TP (Silvex)
Vinyl chloride
5.0
100.0
0.5
1.0
0.5
0.03
100.0
6.0
5.0
200.0
200.0
200.0
200.0
10.0
7.5
0.5
0.7
0.13
0.02
0.008
0.13
0.5
3.0
5.0
0.4
0.2
10.0
200.0
2.0
100.0
5.0
1.0
5.0
0.7
0.5
0.5
400.0
2.0
1.0
0.2
' If o-, m-, and p-cresol concentrations cannot be differentiated, the
total cresol concentration is used.
13
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set national standards for the quality of ambient air and
the states must ensure that these standards are met.
States generally regulate sources of air contaminants on
a case-by-case basis. WTPs that use aeration technolo-
gies, for example, might be subject to state air quality
regulations because of concerns about human exposure
to air emissions.
The CAA, initially passed in 1970 and amended in 1977,
1988, and 1990, gives EPA authority to set national
standards for the quality of ambient air and to regulate
sources of pollution that may affect air quality. The cor-
nerstone of the CAA is a set of National Ambient Air
Quality Standards (NAAQS) for six pollutants: ozone,
total suspended particulates, sulfur oxides, lead, nitro-
gen dioxide, and carbon monoxide. The NAAQS estab-
lish the maximum allowable concentration for each
pollutant in all areas of the United States (see Table 2-3).
Table 2-3. National Ambient Air Quality Standards (40 CFR
Part 50)a
Carbon monoxide Primary: 35.0 parts per million (ppm)
averaged over 1 hour and 9.0 ppm
averaged over 8 hours; neither level to be
exceeded more than once per year.
Secondary: Same as primary.
Primary: 150 |ig/m3 averaged over 24
hours, with no more than one exceedance
per year averaged over a 3-year period;
also, 50 |ig/m3 expected annual arithmetic
mean.
Secondary: Same as primary.
Primary: 1.5 |ig/m3 arithmetic average over
a quarter of a calendar year.
Secondary: Same as primary.
Primary: 100 |ig/m3 (or 0.053 ppm) as
annual arithmetic mean concentration.
Secondary: Same as primary.
Primary: 235 |ig/m3 (0.12 ppm) averaged
over 1 hour, not to be exceeded more than
once per year. (The standard is satisfied if
the number of calendar days on which the
standard is exceeded is 1 or less. Multiple
violations in a day count as one violation).
Secondary: Same as primary.
Primary: 365 |ig/m3 (0.14 ppm) averaged
over a 24-hour period, not to be exceeded
on average more than once per year over
a 3-year period; 80 |ig/m3 (0.03 ppm)
annual arithmetic mean.
Secondary: 1,300 |ig/m3 average over a
3-hour period, not to be exceeded more
than once per year.
a National Primary and Secondary Ambient Air Quality Standards,
July 1, 1987.
b Standard applies only to particulate matter that is <10|im in
diameter.
Fine particulate
matte rb
Lead
Nitrogen dioxide
Ozone
Sulfur oxides
The federal NAAQS do not specify the means by which
the emission levels are to be met. States must ensure
that NAAQS are achieved by enforcing all national emis-
sion standards and implementing any additional controls
necessary for their particular region. States must pub-
lish, and EPA must approve, State Implementation Plans
(SIPs) that describe the measures to be taken to ensure
that NAAQS are achieved and maintained.
Parts of the U.S. that fail to meet one or more of the
NAAQS are designated as nonattainment areas. Figure
2-1, for example, shows the location of nonattainment
areas for ozone. NAAQS have been established for
ozone, and VOCs are regulated by the states as ozone
precursors on a source-by-source basis.
In addition to setting NAAQS and limiting emissions to
achieve these standards, EPA has implemented other
programs for controlling airborne contaminants. Under
Section 111 of the CAA, EPA has the authority to estab-
lish New Source Performance Standards (NSPS) for
restricting emissions from new industrial facilities or fa-
cilities undergoing major modifications. Under the CAA,
EPA must set the NSPS control levels that reflect the
"degree of emission reduction achievable" through use
of the best available control technology (BACT) that has
been "adequately demonstrated."
For toxic air pollutants not covered by the NAAQS or
NSPS, EPA promulgates National Emission Standards
for Hazardous Air Pollutants (NESHAPs). NESHAPs
address pollutants with more limited exposure but more
extreme health effects than pollutants controlled under
the other standards. Most NESHAPs are defined in
terms of the rate of emission from a source. Thus far,
NESHAPs have been promulgated for eight com-
pounds: arsenic, asbestos, benzene, beryllium, mer-
cury, polycyclic organic matter (POM), radionuclides,
and vinyl chloride. For example, NESHAPs governing
radionuclide emissions require that the maximum radia-
tion dose to an individual be no more than 10 mrem/yr.
Facilities must monitor their emissions at doses of 1
percent of the limit or 0.1 mrem/yr.
2.8.2 State Regulations
As indicated earlier, NAAQS are established by EPA for
specific pollutants and the states then set standards to
attain and maintain them. Each state's approach and
timetable for ensuring compliance with NAAQS are
summarized in its SIP. The SIP can incorporate many
regulatory measures that go beyond federal emissions
limitations to achieve compliance with the NAAQS. Each
SIP is reviewed and approved by EPA.
Individual states differ considerably in their approaches
and timetables for regulating air emissions. In general,
states do not have specific requirements for WTPs;
instead, they evaluate emissions of air contaminants on
14
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Figure 2-1. Areas exceeding the ozone NAAQs (U.S. EPA, 1992a).
a source-by-source basis. For example, some state
requirements, along with local air quality regulations,
limit gas phase emissions from stripping processes
(mechanical or packed tower) and from reactivation sys-
tems using GAG because of the possibility of generating
contaminants such as VOCs or radon. Some states do
not permit radionuclide air emissions, thereby prevent-
ing the use of the packed tower aeration process. Other
states require radon off-gas treatment. Some states only
require permit applications from source operations
where emissions exceed the maximum allowable rate
set by the state.
Michigan has an extensive air quality program that en-
compasses emissions from WTPs. The Michigan Air
Pollution Act authorizes the Michigan Air Pollution Con-
trol Commission (MAPCC) and the Michigan Depart-
ment of Natural Resource's Air Quality Division to issue
permits for the installation and operation of equipment
or processes that may emit air contaminants. Based on
this authority, MAPCC has promulgated a set of General
Rules (amended April 17, 1992) concerning air use ap-
proval. These regulations require the issuance of an air
use permit from MAPCC for the installation or modifica-
tion of any process or equipment that may emit an air
contaminant.
After installing the equipment, MAPCC must issue an
operating permit before the equipment can go into op-
eration full time. Rule 285 of MAPCC General Rules
outlines permit system exemptions. Subsection (j) of this
rule exempts lagoons and sewage treatment equipment
from permitting requirements except for lagoons and
equipment primarily designed to treat VOCs in waste-
water or ground water, unless the emissions from these
lagoons and equipment are only released into the gen-
eral in-plant environment.
Air use permit applications submitted to MAPCC must
include descriptions of the equipment; the site; the ex-
haust system configuration; data on the exhaust gas
flow rate; an operating schedule; and information on any
air pollutants to be discharged. Application review con-
sists of a technical evaluation by the Permit Section
engineers and a site evaluation by the Compliance Sec-
tion district staff. After internal processing is completed,
the Air Quality Division develops the necessary permit
conditions and stipulations to ensure that the proposed
15
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process or plant operates in an environmentally safe
and acceptable manner. Under Michigan law, failure to
obtain or comply with a permit can result in fines of up
to $10,000 and additional fines of up to $2,000 per day
for as long as the violation continues.
In California, local districts develop their own regulations
and permitting requirements for stationary sources of air
emissions. These districts regulate operations that re-
sult in air emissions on a source-by-source basis. The
Bay Area Air Quality Management District, for instance,
has no specific regulation governing air emissions from
WTPs but it does have permitting requirements for air
stripping processes. California's South Coast Air Quality
Management District has a nuisance regulation (Rule
402) that prohibits discharging, from any source, air
contaminants that can cause injury, nuisance, or annoy-
ance to the public. WTPs generating air emissions in this
district would be evaluated on a case-by-case basis.
Applications for air use must be submitted to the district.
The State of New Jersey has not promulgated regula-
tions that specifically address air emissions from WTPs.
Subchapter 16 of New Jersey's Air Pollution Control Act,
however, outlines requirements for the control and pro-
hibition of air pollution by VOCs. Section 16.6(a) of the
law prohibits emitting VOCs into the atmosphere from
any source, in excess of the maximum allowable emis-
sion rate as set in the regulation. In New Jersey, WTPs
generating VOCs would be evaluated on a case-by-
case basis.
16
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Chapter 3
Characterization of Water Treatment Plant Residuals
The majority of residuals from water treatment plants
(WTPs) fall into one of four categories:
• Naturally occurring, colloidal/particulate matter (e.g.,
clay, silt, algae) removed from raw water by sedimen-
tation, filtration, membranes, or other processes; and,
inert material in treatment chemicals (e.g., grit in lime).
• Naturally occurring, soluble substances (e.g., iron,
manganese, calcium, and magnesium) converted to
their insoluble precipitate forms by oxidation or pH
adjustment.
• Precipitates formed (e.g., AI(OH)3, Fe(OH)3) when
chemicals are added to water.
• Spent materials (e.g., granular activated carbon [GAG],
powdered activated carbon [PAC], filter media, res-
ins) that must periodically be removed from unit treat-
ment processes after exceeding their useful lives.
These residuals are addressed in this chapter, which
includes a discussion of sludges, liquid wastes, radioac-
tive wastes, and physical and chemical characteristics.
3.1 Types and Quantities of Residuals
3.1.1 Sludges
Semi-solid residuals produced from mechanical water
clarification processes (e.g., screenings, presedimenta-
tion), as well as those produced from the clarification of
waterthat has been chemically preconditioned, are gen-
erally referred to as sludges. The three most common
types of sludges are coagulant/polymeric, chemical sof-
tening, and oxidized iron/manganese.
If a raw water source has a high concentration of total
suspended solids (TSS) the alum/iron coagulant
sludges will contain a high percentage of gelatinous,
hydroxide precipitates (e.g., AI(OH)3, Fe(OH)3), and will
exhibit the overall characteristics indicated in Table 3-1.
Iron/manganese sludges also tend to be composed of
gelatinous hydroxide solids (e.g., Fe(OH)3, Mn(OH)2).
Chemical softening sludges primarily consist of crystal-
line calcium carbonate (CaCO3), with the magnesium
hydroxide (Mg(OH)2) portion of the solids increasing as
the magnesium content of the raw water increases.
Because of the structured, crystalline nature of the
CaCO3 precipitate, the relationship between solids con-
tent and the overall sludge characteristics of chemical
softening sludges is different from that for coagulant and
iron/manganese sludges (see Table 3-2).
Table 3-1. Alum/Iron Coagulant Sludge Characteristics
(ASCE/AWWA, 1990)
Solids Content
Sludge Characteristic
0-5%
8-12%
18-25%
40-50%
Liquid
Spongy, semi-solid
Soft clay
Stiff clay
Table 3-2. Chemical Softening Sludge Characteristics
(ASCE/AWWA, 1990)
Solids Content
Sludge Characteristic
0-10%
25-35%
40-50%
60-70%
Liquid
Viscous liquid
Semi-solid
Crumbly cake
Several equations can be used to predict the quantity of
alum/iron coagulant sludge to be generated, based on
the raw water characteristics and amount of coagulant
dose. The principal factors used in the estimation of
coagulant sludge quantities are: 1) the suspended solids
(SS)-to-turbidity ratio for the raw water (Cornwell et al.,
1987); and 2) the waters of hydration assumed for the
coagulant. Perhaps the most commonly used equations
for predicting the quantity of alum or iron coagulant
sludge are (Cornwell et al., 1987):
S = (8.34Q)(0.44AI + SS + A) (Eq. 3-1)
where
S = sludge produced (Ibs/day)
Q = plant flow, million gallons per day (mgd)
Al = liquid alum dose (mg/L, as 17.1% AI2O3)
SS = raw water suspended solids (mg/L)
A = net solids from additional chemicals added
such as polymer or PAC (mg/L)
17
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and
S = (8.34Q)(2.9Fe + SS + A) (Eq. 3-2)
where
Fe = iron dose (mg/L, as Fe)
Similar equations can be used to predict the quantity of
sludge produced when calcium and magnesium, car-
bonate and noncarbonate hardness is chemically pre-
cipitated. The quantity of sludge produced depends on
whether lime/soda ash or caustic soda is used as the
softening chemical(s) and on the total amount of hard-
ness that is removed. Obviously, much more sludge is
produced when lime, rather than caustic soda, is used
to precipitate carbonate hardness, since the calcium
associated with the lime must also be precipitated in the
chemical softening process.
The quantity of sludge produced when soluble iron (II)
and manganese (II) are oxidized to their insoluble
precipitate forms (i.e., Fe(lll) and Mn(IV)) depends on
several factors. The factor that most affects the sludge
quantities is the oxidant used (e.g., oxygen, permanga-
nate, chlorine dioxide, ozone). Similar to using lime to
precipitate calcium from hard water, using permanga-
nate to oxidize iron or manganese results in more
sludge. The manganese associated with the permanga-
nate is reduced from a (VII) to (IV), and is precipitated
along with the iron and/or manganese being oxidized.
3.1.2 Liquid Wastes
Perhaps the most common liquid waste generated at
WTPs in the past has been spent filter backwash water.
The spent filter water associated with filter-to-waste (re-
wash) has become more common as WTPs prepare for
compliance with the Surface Water Treatment Rule.
Slow sand filter wastes are also becoming more preva-
lent as some smaller communities return to the com-
bined physical/biological benefits of slow sand filtration
as described in Section 3.1.2.2. Regenerate wastes (i.e.,
brine and rinse water wastes) associated with ion ex-
change (IX) facilities continue to be produced by some
softening plants. Reject waters from various membrane
processes (e.g., reverse osmosis, nanofiltration, ultrafil-
tration, microfiltration) are gaining prominence as maxi-
mum contaminant levels for finished water are set at lower
levels for more organic and inorganic contaminants.
3.1.2.1 Spent Filter Backwash Waters
Spent filter backwash water generally represents a vol-
ume of 2 to 5 percent of the total water processed at a
WTP. The suspended solids concentration of spent filter
backwash varies throughout the 10- to 15-minute dura-
tion of the backwash, with the water gradually becoming
cleaner as the backwash proceeds. The average sus-
pended solids concentration of spent backwash typically
falls within the range of 50 to 400 mg/L.
Filter backwash water historically has been returned to
the head of a WTP to be processed again. An equaliza-
tion basin is usually used so that the spent backwash
water can be returned to the head of the WTP at a rate
less than 10 percent of the raw water flow into the WTP.
Concerns over the recycling of microorganisms, aggra-
vation of taste and odor problems, increase in disinfec-
tion byproducts, and other issues have drastically
reduced the number of WTPs that directly recycle spent
filter backwash. Thus, in recent years interest has been
generated in better understanding the characteristics of
backwash wastes, since these must be processed along
with other WTP residual streams.
Another form of waste from filters that is becoming
popular again is filter-to-waste, or rewash, which refers
to the wasting of filtered water during the ripening stage
of a clean filter. Concern over the passage of certain
microorganisms (e.g., Giardia, Cryptosporidium, and vi-
ruses) through the filter media of a freshly backwashed
filter has renewed interest in filter-to-waste.
The filter-to-waste period for ripening a freshly back-
washed filter at most WTPs ranges from 15 minutes to
an hour in length. Some WTPs are finding that the length
of this filter ripening period can be shortened by intro-
ducing a coagulant aid or by allowing a filter to sit idle
for a time between when it has been backwashed and
is returned to service. The filtration rate used to ripen a
filter varies from one WTP to another. While many WTPs
filter-to-waste at the normal filtration rate, some plants
filter at only a fraction of the normal rate. Often, this
variation is due to the fact that a smaller pipe is available
to convey the filter-to-waste flow. The filter-to-waste
flow, while not considered to be of a quality that it can
be sent directly into the distribution system, is generally
a fairly clean waste stream. Therefore, at most WTPs
this flow is equalized and returned to the head end of
the plant. Other options being used to handle the filter-
to-waste flow include discharging it to a local storm
sewer with an appropriate National Pollutant Discharge
Elimination System (NPDES) permit; discharging it to a
sanitary sewer for processing at a local wastewater
treatment plant (WWTP); introducing it to the solids
handling stream of the WTP; or, treating it with a mem-
brane process prior to returning the flow to the head end
of the plant.
3.1.2.2 Slow Sand Filter Wastes
Slow sand filtration is a simple, economical, and gener-
ally reliable method of treating low turbidity waters for
potable uses. Since application rates for slow sand fil-
tration are low, on the order of 40 to 150 gallons per day
per square feet (gpd/ft2), the process is mostly used by
smaller treatment facilities. Organics, silt, and other par-
ticles are trapped in the upper portions of the filter, which
is periodically removed for cleaning. This process is called
18
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scraping and is normally performed by hand, but small
mechanical equipment is sometimes used. The filter is
resanded after several scrapings when the filter depth
reaches a predetermined minimum design thickness.
Material for resanding can be either new sand or old
filter sand that has been removed and washed. A unique
feature of the slow sand filter is the schmutzdecke, a
biologically active layer in the top of the filter. Viruses,
cysts, and other organisms are almost entirely removed
during slow sand filtration. Thus, the sand removed
during scraping can contain a fairly active biological
population.
Sources of Liquid Residuals
• Scraping: Normal scraping removes the top 0.5 to 1
inch of sand (Tanner and Ongerth, 1990), although
scraping to a depth of 4 inches has been reported
(U.S. EPA, 1985a). Scraping generally is conducted
at a given headless or reduction in flow, but may be
initiated on a regular cycle without regard for head-
loss. Consequently, scraping may occur from three
to forty times annually. Some facilities dispose of the
removed material by stockpiling it for other uses such
as road sanding during the winter or as soil additives.
More commonly, the material is washed and then
stored for later addition back to the filter. In this case,
the wash water constitutes a residuals stream that
may require treatment. Current common disposal
methods include discharging to a sewer or a receiv-
ing watercourse without treatment. Discharge to a
receiving watercourse may require a state or EPA
regional NPDES permit.
• Raking: Slow sand filters are sometimes raked, usu-
ally by hand with a garden rake, to loosen the top
layer of material and improve the hydraulic rate with-
out removing sand. This process normally does not
produce any waste residuals. Wet-harrow cleaning is
sometimes used; this procedure uses a flow of water
to flush the raked deposits from the filter, and these
deposits may require treatment (Logsdon, 1991).
Facilities that practice raking normally need to re-
move more sand during scraping than facilities that
do not rake.
• Backwash water: One facility reportedly reverses the
flow through the slow sand filter without expanding
the bed. The filter is raked prior to backwashing,
which promotes removal of the schmutzdecke (Tan-
ner and Ongerth, 1990). The backwash water is nor-
mally discharged directly to the receiving water, but
may require treatment at some locations.
• Filter-to-waste: A fairly large volume of wastewater
can be generated during filter-to-waste cycles as
some WTPs waste the filtered water for 24 to 48
hours before slow sand filters are placed back on line
after cleaning. A filter-to-waste procedure is specified
under the current edition of "Ten State Standards"
(Great Lakes, 1992). The high quality of this water
normally allows disposal without treatment.
Quantities of Residuals
• Scraping: Scraping can remove sand to depths of 0.5
to 4 inches. Removing 1 inch of sand will generate
2 to 6 ft3 of material per 1,000 gpd of filter design
capacity, based on design rates of 45 to 150 gpd/ft2.
• Spent backwash water: Because slow sand filters are
seldom subjected to any type of backwashing, the
majority of WTPs do not generate this particular re-
siduals stream. A slow sand filter in northern Idaho
was periodically cleaned by backwashing and scrap-
ing, and frequently exhibited higher-than-desired fil-
tered water turbidities (Tanner and Ongerth, 1990).
The extent, if any, to which backwashing contributed
to this problem is not known, but backwashing is not
normally a recommended practice.
• Filter-to-waste: Filtering to waste after cleaning is a
recommended operating practice, and is required by
some states. High quality filtered water is normally
discharged to waste without treatment. At some lo-
cations, however, this residuals stream may be sub-
ject to provisions of an NPDES permit. Waste
volumes are generally in the range of 200 to 600
gal/hr/100 ft2 of slow sand filter area. Filtering-to-
waste periods are normally of 24- to 48-hour duration
but vary from site to site.
3.1.2.3 Ion Exchange Brine
IX offers the possibility of removing one or more ionic
species from one liquid phase and transferring them to
another liquid phase via an intermediate solid. In many
cases the transfer can be made on a selective basis and
with good chemical efficiency. The IX process is primar-
ily used to remove hardness from water, particularly in
small water systems and for residential use. IX also has
been shown to be effective in removing nitrates and
other contaminant ions, including barium, radium, arse-
nate, selenate, fluoride, lead, and chromate (Pontius,
1990).
In the application of IX to remove hardness, the hard-
ness in the water (most often Ca2+ and Mg2+) exchanges
with an ion from the resin (generally sodium, Na+) be-
cause the resin prefers the contaminant ions. The reac-
tions are as follows (where X represents the solid IX
material):
Carbonate Hardness
Ca(HC03)2 + Na2X -» CaX + 2NaHCO3
Mg(HC03)2 + Na2X -» MgX + 2NaHCO3
19
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Noncarbonate Hardness
CaSO4 + Na2X -» CaX + Na2SO4
CaCI2 + Na2X -» CaX + 2NaCI
MgSO4 + Na2X -» MgX + Na2SO4
MgCI2 + Na2X -» MgX + 2NaCI
Regeneration
CaX + 2NaCI -» CaCI2 + Na2X
MgX + 2NaCI -» MgCI2 + Na2X
Through these reactions, calcium, magnesium, and
other materials are removed from the water and re-
placed by an equivalent amount of sodium (i.e., two
sodium ions for each divalent cation removed).
The exchange results in nearly 100 percent removal of
hardness from the water; in the process, the resin be-
comes saturated and reaches its exchange capacity. At
this point, breakthrough occurs and hardness can no
longer be completely removed from the water. In prac-
tice, there is competition for the IX sites by elements
other than calcium or magnesium; these other constitu-
ents may also limit the effectiveness of the resin at
removing hardness. When this situation occurs or the
resin is saturated, the IX material is regenerated. Re-
generant water containing a large excess of Na+ (such
as a concentrated NaCI solution) is passed through the
column to remove the hardness. The mass action of
having a large excess of Na+ in the water causes ions
on the resin to be replaced by Na+ and then enter the
water phase. This constitutes a reversal of the initial IX
reactions. The regenerated IX material can then be used
to remove more hardness (Cornwell et al., 1987).
In addition to this regenerant waste—consisting of so-
dium, chloride, and hardness ions—wastes produced by
IX processes include the backwash water and rinse
water used, respectively, before and after the formal
regeneration of the resin. The term regenerant waste, or
brine, is frequently applied to the combination of the
used regenerant and the slow rinse, the initial portion of
the rinse. When comparing data, it is important to know
whether concentrations are reported as only concentra-
tion in the regenerant waste itself, or as diluted with rinse
water and/or backwash water.
Solids Content
Spent brine often has a very high concentration of total
solids and total dissolved solids (TDS). Brine wastes
usually contain very few suspended solids. Gradually,
resins lose their capacity to be regenerated and upon
being replaced, become a solid waste.
pH
IX brine from the water softening process is generally of
neutral range pH. More generally, the pH of the brine
depends on the nature of the regenerant. Other cation
exchange resins may be regenerated using concen-
trated sulfuric or hydrochloric acid. The resulting regen-
erant waste will need to be neutralized from its low pH,
which is primarily determined by how much excess acid
was present in the regenerant solution. Anion exchang-
ers are usually regenerated with a basic material or
sodium chloride. Weak basic resins (which will remove
strong anions such as chloride, sulfate, and nitrate) are
typically regenerated using sodium carbonate. Strong
basic resins (which will remove most anions such as
chlorides, sulfate, nitrate, bicarbonate, and silica) are
regenerated using sodium hydroxide. In this case, the
high pH of the resultant regenerant waste will need to
be neutralized before being discharged.
Ion Content
Regenerant waste contains the hardness removed from
the resin, chloride from the regenerant solution, sodium
present as excess regenerant, and smaller amounts of
other ions removed from the IX resins. Table 3-3 shows
the typical ranges of ion concentrations in the wastewater.
Table 3-3. Typical Chemical Constituents of Ion Exchange
Wastewater (AWWARF, 1969)
Constituents
Range of Averages (mg/L)
TDS
Ca++
Mg++
Hardness (as CaCO3)
Na+
cr
15,000-35,000
3,000-6,000
1,000-2,000
11,600-23,000
2,000-5,000
9,000-22,000
The chemical concentration of brines varies widely from
plant to plant, depending on raw water hardness (con-
centration of the cations to be removed), regenerant
dose and concentration, rinsing procedures, and cation
exchange capacity of the resin.
Because the exchange of hardness for sodium ions is
stoichiometric—that is, one equivalent for one equiva-
lent—the total equivalents of ions in the wastewater will
equal the original number of equivalents in the regener-
ant. The distribution of these equivalents between the
various chemical species depends on the IX capacity of
the resin and its regeneration efficiency, or taken to-
gether, the operating capacity of the resins. The operat-
ing capacity is always less than advertised exchange
capacity because of incomplete regeneration and con-
taminant leakage (breakthrough of the least binding
counter-ion prior to saturation of the resin).
20
-------
Toxicity
IX brine typically has a high IDS content, with the
predominant ion being the co-ion in the regenerant
(chloride, sulfate, carbonate, or sodium, depending on
the type of resin and, consequently, the type of regen-
erant used). The other ions present are those removed
by the resin and reclaimed by the regenerant. With
chlorides present, brine is corrosive to materials it con-
tacts. Brine possesses varying levels of toxicity to the
environment, depending on its IDS level and specific
chemical makeup.
Quantity
The total amount of wastewater (spent brine) usually
ranges from 1.5 to 10 percent of the amount of water
softened, depending on the raw water hardness and the
operation of the IX unit (AWWARF, 1969; O'Connor and
Novak, 1978).
Figure 3-1 shows the expected wastewater volume as a
function of raw water hardness for the case where all
other variables are held constant. Table 3-4 reflects how
the parameters mentioned above influence the quantity
of brine wastewater produced.
3.1.2.4 Reverse Osmosis, Nanofiltration, and
Electrodialysis-Electrodialysis Reversal
Process Description
Reverse osmosis (RO), nanofiltration (NF) (or mem-
brane softening), ultrafiltration (UF), and microfiltration
(MF) membrane processes use semipermeable mem-
branes to remove contaminants from a feedwater. Typi-
cally pretreated to minimize scaling and fouling of the
membrane, feedwater flows across the membrane sur-
face. Increase in pressure on the feedside of the mem-
brane transports some of the water from the feedside,
through the membrane, to the permeate side. Other
constituents may be rejected by the membrane, to an
extent that depends on the properties of the particular
750
650
^ 550
D)
$ 450
c
T3
TO
I 350
$
o
250
150
50
10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000
Total Wastewater Volume, gal/MG Treated
Figure 3-1. Generation of wastewater volumes with ion ex-
change (U.S. EPA, 1984a).
membrane used and the operating conditions. Water
and other constituents not permeating the membrane
flow out of the membrane system as the concentrate
stream. Table 3-5 provides a system operation summary
for these membrane processes. Each process has dif-
ferent operating conditions and ranges of feedwater TDS.
At one extreme of high rejection RO membranes, typi-
cally used for seawater or brackish water applications,
ions may be almost completely rejected (rejections
greater than 99 percent). The larger, more effective
pore-sized NF membranes reject ions to a lesser de-
gree. Here, the monovalent ions may be rejected to
perhaps 50 to 70 percent and multivalent ions (hard-
ness) to perhaps 90 percent levels. Other membrane
processes have lower rejection rates of dissolved ions.
Species other than dissolved ions, such as dissolved
organics, dissolved gases, biological contaminants, and
suspended solids, not removed in pretreatment steps,
Table 3-4. Regeneration of Cation Exchange Resins (AWWARF, 1969)
Gal
Wastewater/
1,000 Gal
Water
Plant Processed
Crystal Lake Plant #6
Crystal Lake Plant #8
Eldon
Grinnell
Holstein
Estherville
21.9
17.2
71.9
49.5
53.5
82.8
Raw Water
Total
Hardness
(mg/L as
CaC03)
233
244
375
388
885
915
Gal Gal Concentration
Regenerant/ft3 Rinse/ft3 of Brine
Resin Resin (Ib/gal)
7.3
5.1
3.9
14.5
5.7
4.4
19.4
19.0
61.7
35.0
19.7
24.7
0
1
1
.90
.26
.43
0.50
1
1
.16
.25
Gal
Processed/ft3
Resin-Cycle
1,220
1,400
750
1,000
475
350
Dosage
(Ib salt/ft3
resin) Reference
6.6
6.5
5.6
7.2
6.6
5.5
U.S.
U.S.
U.S.
U.S.
U.S.
U.S.
EPA,
EPA,
EPA,
EPA,
EPA,
EPA,
1984a
1984a
1976a
1976b
1976b
1976b
Note: The chemical characteristics of the backwash water did not show a large variation from the raw water; therefore, they were not included
in this analysis.
21
-------
Table 3-5. Membrane Process Operations Summary (Mickley et al., 1993)
Membrane Process
Seawater RO
Brackish RO
Nanofiltration
Ultrafilt ration,
microfi It ration
Electrodialysis (ED)
Feedwater IDS (mg/L)
10,000-45,000 (high P)
500-3,500 (low P)
3,500-10,000 (medium P)
Up to 500
Not used to remove IDS
Up to 7,500 (not economical
at high IDS)
Typical
Operating
Pressure (psi)
800-1 ,200
1 00-600
50-1 50
Below 100
Not applicable
Typical System
Recovery (%)
20-50
60-85
75-90
90 and above
70-90+
System Rejection (%)
99+ (IDS)
85-96 (IDS)
95-98 (hardness)
80-90 (hardness)
Zero rejection of IDS; rejection
of other species dependent on
specific membrane
(Effective monovalent removal
can be >95 for ED and >99+ for
EDR)
Key
P = phosphorus.
IDS = total dissolved solids.
are similarly rejected according to their size and interac-
tions with the membrane.
In the electrodialysis (ED) process there is no pressure
used and, thus, no significant bulk flow of water through
the membrane. The process employs sets of anion- and
cation-selective membranes, electrodes placed outside
of the sets of membrane pairs, and an impressed elec-
trical potential across the entire membrane stack. Sev-
eral flow channels are created between the membrane
pairs and between the outer membranes and the elec-
trodes. Water is fed to all channels. The electrical force
causes movement of the cations and anions in different
directions and out of certain channels into other chan-
nels. Some channels become relatively depleted in ions
and others become more concentrated. All product
streams are combined and all concentrate streams are
combined upon exit from the membrane stack. Elec-
trodialysis reversal (EDR) is an ED process in which the
polarity of the electrodes is reversed on a prescribed
time cycle, thus reversing the direction of ion movement
in a membrane stack. The effective rejection of dis-
solved ions in the ED-EDR process can be quite high
(above 90 percent). The EDR process has several ad-
vantages over the straight ED system, including lower
membrane fouling, less need for pretreatment, and
higher reliability. Virtually all new ED plants are of the
EDR type. ED-EDR processes do not remove nonpolar
contaminants.
UF and MF membrane systems are receiving increased
attention because of their potential to remove particu-
lates, microorganisms, and larger organics—constitu-
ents addressed in the Safe Drinking Water Act (SDWA)
amendments. This discussion, however, is restricted to
the RO, NF, and ED-EDR membrane processes.
The recovery rate of these membrane systems refers to
the percent of feedwater that is converted into product
water. Thus, a 60 percent recovery process would have
a concentrate stream of 40 percent of the feedwater flow.
Table 3-6 shows the applications for the RO, NF, and
ED-EDR processes and the removal characteristics of
the membrane processes. For producing drinking water,
NF is limited to freshwater (lower TDS) applications and
ED-EDR to applications calling for removal of polar
constituents in a nonselective manner.
As of September 1992, 137 drinking water membrane
plants sized 25,000 gpd or greater, of the various types
mentioned, existed in the continental United States
(Mickley et al., 1993). Of these plants, 101 (74 percent)
were brackish water RO plants, 16 (12 percent) were NF
plants, 13 (9 percent) were ED-EDR plants, and the
remaining 7 (5 percent) were seawater RO plants.
Nature of the Concentrate
Most residuals, or more generally, industrial wastes, are
characterized by the chemicals added during the proc-
essing of the waste. Membrane concentrate, on the
other hand, has very few process-added chemicals and
thus reflects the character of the raw water used. Mem-
brane processes do not produce more pollutant material
or mass—they redistribute, or concentrate, those con-
stituents present in the raw water that are rejected by
the membrane.
Generally, posttreatment concentrate contains all the
species in the raw water that are not removed in pre-
treatment. Pretreatment typically consists of acid addi-
tion, antiscalant addition, and a 5-u.m filtration step.
Species that are not rejected by the membrane are
present in both the product and concentrate at the same
concentration as in the original feedwater. Species that
are rejected by the membrane are concentrated to an
extent depending on the membrane rejection of the
particular species and the membrane system recovery
(defined as the percentage of the feed flow recovered
as permeate product). The nature of the concentrate
may be affected by posttreatment.
22
-------
Table 3-6. Membrane Process Applications for RO, NF, and ED-EDR (Mickley et al., 1993)
Applications
Reverse Osmosis (RO)
Nanofiltration (NF)
Electrodialysis-Electrodialysis
Reversal (ED-EDR)
TDS reduction
Seawater desalting
Brackish water desalting
Very effective
Very effective
Key
TDS = total dissolved solids.
THM = trihalomethane.
Not effective
Dependent on feedwater
makeup
No (not economical at high TDS)
Very effective
Freshwater treatment
Hardness ions removal (softening)
Dissolved organics removal
Color removal
THM precursor reduction
Specific inorganic and radionuclide
removal
Very effective
Very effective
Very effective
Very effective
Very effective
Very effective
Very effective
Very effective
Very effective
Dependent on feedwater
makeup
No
No
No
No
Dependent on
makeup
feedwater
Because membrane concentrate is defined by the raw
water characteristics and raw water characteristics are
site specific, the specific nature of the concentrate is
also site specific.
Solids
Due to the need to prevent plugging of membrane sys-
tem flow channels, allowable feedwater levels of sus-
pended solids are fairly low for the RO, NF, and ED-EDR
systems. Depending on the specific flow channel dimen-
sions, the feedwater limits may range from 1 to 5 SDI
units. In general, therefore, the levels of suspended
solids are low in the feedwater, and these levels are
concentrated to a degree that depends on the system
recovery.
The TDS level can vary over a wide range, depending
on the TDS level of the feedwater and the membrane
system rejection and recovery. Table 3-7 provides
ranges for feedwater TDS for the various membrane
processes. The amount of TDS in the concentrate de-
pends on the rejection level of the particular membrane
system and the process recovery.
pH
The pH of the concentrate depends on the pretreatment
pH adjustments and possible posttreatment pH adjust-
ments. The pretreatment adjustments are dictated by
Table 3-7. Concentration Factors for Different Membrane
System Recoveries (Mickley et al., 1993)
Recovery (%)
Concentration Factor
50
60
70
80
90
2.0
2.5
3.33
5.0
10.0
the need to control the scaling potential from solubility-
limited species, such as calcium carbonate, and by the
pH limits of the particular membrane. Typically, the feed-
water is acidified to a range of about 5.5 to 7.0. The pH
of the concentrate is generally higherthan the feedwater
pH, due to distribution of the carbonate species between
the concentrate and the product streams. Posttreatment
pH adjustment may be used to render the concentrate
compatible with the receiving water, in the case of dis-
posal to surface waters. Adjustment may be used to en-
sure the noncorrosive nature of the concentrate in cases
where the discharge will be exposed to piping or confin-
ing vessels prior to, or as part of, the disposal method.
Quantity
The quantity of concentrate is directly related to the
recovery, R, of the membrane system. Equation 3-3 can
be used to calculate the quantity of concentrate that is
generated by the membrane system.
Qc = Qf(1 - R) (Eq 3.3)
where
Qc = quantity of concentrate flow
Qf = quantity of feedwater flow
R = recovery rate of the membrane system
Qc may also be expressed in relation to the product
volume flow (Equation 3-4).
Qc = Qp(1 - R)/R (Eq 3.4)
where
Qp = quantity of product volume flow
R = recovery rate of the membrane system
For example, if the feed flow is 2 million gallons per day
(mgd) and the recovery is 70 percent (R = 0.70), then
Qp equals 1.4 mgd and Qc equals 0.6 mgd from either
of the above expressions.
23
-------
The recovery of a membrane process is generally limited
by the potential for sparingly soluble salts, as they become
concentrated, to precipitate and scale membranes.
Toxicity
The potential toxicity concerns for concentrate have to
do with aquatic species, in the case of surface dis-
charge, and with vegetation, in the case of land applica-
tions such as spray irrigation. Potential sources of
toxicity include individual components in the raw water
that are concentrated in the membrane process to an
extent that they are toxic to the life form in question. In
general, drinking water membrane concentrate is not
toxic as long as the affected life forms are matched to
the general TDS level of the concentrate. In the inci-
dences where concentrate is potentially toxic, dilution of
the concentrate is generally a means of rendering the
concentrate nontoxic.
Ionic Content and Prediction of Concentrate
Concentrations
For species that are completely rejected by the mem-
brane and thus totally retained in the concentrate, the
degree of concentration, orthe concentration factor (CF)
may be defined as:
CF =
- R)
(Eq. 3-5)
where
R = the fractional system recovery
The CFs for different recoveries are shown in Table 3-7.
For example, if the feedwaterhas a TDS level of 10,000
parts per million (ppm), the rejection of the membrane
is assumed to be complete, and the recovery is 60
percent, then the concentrate would have a TDS level
of 25,000 ppm (from 10,000 multiplied by a concentra-
tion factor of 2.5). Each constituent of the TDS would
similarly be present in the concentrate at 2.5 times the
feedwater concentration.
As suggested by Table 3-5, complete rejection of con-
stituents is not always the case. For species that are not
completely rejected, concentration still takes place, but
to a lesser extent. A theoretical expression for this situ-
ation (Saltonstall and Lawrence, 1982) is
CF =
- R)r
(Eq. 3-6)
where
r = the fractional rejection for the species in question
Note that for the case where r= 1, Equation 3-6 reduces
to Equation 3-5.
Table 3-8 shows concentration factors calculated from
Equation 3-6.
Each constituent has its own characteristic rejection,
which is a function of the particular membrane, the
particular species, and the operating conditions. The
data in Table 3-8 provide some insight into the complex-
ity of estimating concentrate concentrations, but do not
provide a simple means for doing this.
Estimates for concentrate concentrations require the
specification of raw water characteristics, the particular
membrane used, the membrane system configuration,
and the operating conditions. Membrane manufacturers
have computer programs that can provide design quality
estimates for this. These programs, however, do not
provide 1) a rapid and simple means of estimating, or 2)
a means for estimating the concentrations of constitu-
ents present in minor amounts—constituents that may
influence the permitting of concentrate disposal.
Analysis has shown that assumption of 100 percent
rejection is quite accurate for seawater and brackish RO
membranes (Mickley et al., 1993). Use of the 100 per-
cent rejection assumption will be conservative in the
sense of overestimating the concentration of the con-
centrate, a worst-case scenario. This approach may
also be used for EDR systems. The errors should be in
the range of 15 percent and under. For NF membrane
systems, assumption of complete rejection of all species
leads to more significant errors. Consequently, it is rec-
ommended that rejections of 70 and 90 percent be used,
respectively, for monovalent and multivalent ions.
Other guidelines to be used in estimating concentrate
concentrations are:
• Heavy metals should be considered to be rejected as
multivalent ions.
• Organics cover a wide range of molecular weights,
from less than 100 to greater than 100,000. Most are
rejected to a high degree in RO systems, somewhat
less so for NF systems, and to a low degree in EDR
systems (unless the organics in question are polar in
nature). For RO and NF systems, organics of mo-
lecular weight of approximately 1,000 may be con-
sidered to be completely rejected.
• Non-ionized gases have a rejection of zero in these
systems. Thus, the product and concentrate concen-
trations are the same as for the feed concentration.
• In RO and NF systems, the pH of the permeate will
be lower than that of the feedwater, and the pH of
the concentrate will be greater than that of the feed-
water. The changes are caused by the redistribution
of carbonate species across the membrane. The
amount of the pH change in permeate and concen-
trate depends on the feed pH, the recovery, and the
amount of carbonate species present. Typical feed
pH values are in the range of 5 to 7, depending on
the type of membrane. Concentrate pH values may
be up to 1 or 1.5 pH units higher than the feed pH,
24
-------
Table 3-8. Tabulation of Concentration
Recovery Values
0.90
0.88
0.86
0.84
0.82
0.80
0.78
0.76
0.74
0.72
0.70
0.68
0.66
0.64
0.62
0.60
1.0
10.0
8.33
7.14
6.25
5.56
5.00
4.55
4.17
3.85
3.57
3.33
3.13
2.94
2.78
2.63
2.50
Factors3 (Mickley et al., 1993)
Rejection Values
0.99
9.77
8.16
7.00
6.13
5.46
4.92
4.48
4.11
3.79
3.53
3.29
3.09
2.91
2.75
2.61
2.48
0.98
9.55
7.99
6.87
6.03
5.37
4.84
4.41
4.05
3.74
3.48
3.25
3.05
2.88
2.72
2.58
2.45
0.95
8.91
7.50
6.47
5.70
5.10
4.61
4.21
3.88
3.60
3.35
3.14
2.95
2.79
2.64
2.51
2.39
0.90
7.94
6.74
5.87
5.20
4.68
4.26
3.91
3.61
3.36
3.14
2.96
2.79
2.64
2.51
2.39
2.28
0.80
6.31
5.45
4.82
4.33
3.94
3.62
3.36
3.13
2.94
2.77
2.62
2.49
2.37
2.26
2.17
2.08
0.70
5.61
4.41
3.96
3.61
3.32
3.09
2.89
2.72
2.57
2.44
2.32
2.22
3.13
2.04
1.97
1.90
3 Calculated using the equation CF = 1 •*• (1 - R)r.
prior to any pH adjustment that may be done in post-
treatment.
• Although dependent on pH, any chlorine present as
essentially non-ionized HCIO may be considered as
not rejected by membranes.
• Radionuclides should be treated as multivalent ions.
• Fluorine and bicarbonate have pH-dependent rejec-
tions that range from values of zero at pH of 5 to
typical monovalent rejections at pH of 7.
• Silica rejections are dependent on the type of membrane;
the rejections can range from 75 to 98 percent for RO
membranes to 20 to 70 percent for NF membranes.
3.1.3 Radioactive Wastes
The types and quantities of radionuclides in residuals
depend on the ability of the WTP to remove specific
radionuclides from the drinking water. For example, un-
der normal operation, cation exchange treatment will
remove radium, but not uranium or radon. Conse-
quently, the regenerant brine waste from a cation ex-
change system will contain only radium, even though
the raw water may contain uranium and radon. Table 3-9
lists drinking water treatment processes, the radioactive
contaminant that they remove, and the types of residu-
als. This list is based upon the known ability of the water
treatment processes to remove the specific radionu-
clides either currently regulated or proposed for regula-
tion for drinking water by EPA (U.S. EPA, 1991b). The
radionuclides radium-226, radium-228, uranium, and ra-
don-222, are all naturally occurring.
Radon is a gas than can be removed from drinking water
by air stripping and GAG, neither of which produces a
residual for routine disposal. Furthermore, radon has a
very short half-life of approximately 3.5 days and decays
to essentially zero in roughly 28 days. Therefore, radon
should not be found in any waste stream from a conven-
tional water treatment process, except in the air from an
air stripper. Lead-210, the next long-lived daughter prod-
uct following radon-222 in the decay series, will be found
on any material that adsorbs radon, however.
Some materials used in drinking water treatment proc-
esses, either for direct removal of a contaminant such
as GAG and IX resins, or indirect removal of a contami-
nant such as filter sand in conventional treatment, will
adsorb radionuclides. When the time arrives for these
materials to be replaced, they will contain the radionu-
clides adsorbed but not removed from the material dur-
ing the treatment process. A list of drinking water
treatment process materials and the potential radio-
nuclides contained on these materials is provided in
Table 3-10.
The concentration of radionuclides in waste streams
produced by any water treatment process depends on
a number of factors: concentration of the radionuclide in
the source water, the percent removal of the contami-
nant, the volume of the waste streams, and the mode of
operation of the treatment process. These factors will
25
-------
Table 3-9. Summary of Treatment Processes and the Types
of Wastes Produced From the Removal of
Radionuclides From Drinking Water
Treatment Process
Radionuclide
Removed
Types of
Residual/Waste
Coagulation/Filtration
Lime softening
Cation exchange
Anion exchange
Iron removal processes
• Oxidation/Filtration
• Greensand adsorption
Reverse osmosis
Electrodialysis
Air stripping
Uranium
Sludge (alum/iron)
Filter backwash water
Radium, uranium Lime sludge
Filter backwash water
Radium Brine waste
Backwash water
Uranium Brine waste
Backwash water
Radium Filter backwash water
Radium, uranium Reject water
Radium, uranium Reject water
Radon Airborne radon
Table 3-10. Water Treatment Process Materials Containing
Radionuclides
Treatment Process
Radionuclide
Removed
Process Materials
Coagulation/Filtration Radium, uranium
Lime softening
Cation exchange
Anion exchange
Iron removal processes
• Oxidation/Filtration
• Greensand adsorption
Radium, uranium
Radium
Uranium
Radium
Filter medium (sand)
Filter medium (coal)
Filter medium (sand)
Filter medium (coal)
Resin
Resin
Filter medium (sand)
Filter medium (coal)
Greensand
Reverse osmosis
Electrodialysis
GAC adsorption
Selective sorbents
Radium, uranium
Radium, uranium
Radon, uranium,
radium
Radium, uranium
Membrane
Membrane
GAC
Selective sorbent media
Key
GAC = granular activated carbon.
not be identical for any two plants and, consequently,
the concentration of radionuclides in the waste streams
will be site specific.
A limited amount of information has been reported on
the concentration of radionuclides in the waste streams
of several water treatment processes. Although these
data are site specific, these field measurements can be
used for approximating ranges, or levels, of radionuclide
concentrations that may be expected in these waste
streams.
3.1.3.1 Coagulation/Filtration Wastes
Laboratory, pilot plant, and full-scale system studies
have shown that uranium can be removed from source
water by conventional coagulation/filtration treatment,
and that removals are pH dependent (White and Bon-
dietti, 1983; Lee and Bondietti, 1983; U.S. EPA, 1987).
Removals can range from 50 to 85 percent. The techni-
cal literature does not reveal any information on the
concentration of uranium in the waste streams of the
full-scale plants reported upon.
3.1.3.2 Lime Softening Wastes
Lime softening has been found to be very effective in
removing both radium and uranium, achieving removals
of up to 99 percent of both radionuclides (Lee and
Bondietti, 1983; Clifford, 1990; Bennett, 1978; Brink et
al., 1978; U.S. EPA, 1976a,b; Meyers et al., 1985; Sorg
and Logsdon, 1980; Jelinek and Sorg, 1988; Sorg,
1988). Removals are pH-dependentwith highest remov-
als achieved at pH levels of 10.0 to 10.5.
The lime softening process generates a lime sludge that
is precipitated during the process and which will contain
most of the uranium and radium removed during the
treatment cycle. A liquid waste is also produced by the
backwashing of the filter media. The backwash water
may be recycled to the front of the treatment plant, or
disposed of separately or with the lime sludge.
Field data showing specific measurements of radium-
226 and 228 in grab samples from full-scale WTP waste
streams are listed in Table 3-11. These data show a wide
range of radium concentrations in the waste streams.
For example, wet sludge from clarifier systems has
radium concentrations ranging from 980 to 4,577 pCi/L.
Dry weight concentrations vary from 2.8 to 21.6 pCi/g
for the same source of sludge. As expected, concentra-
tions of radium-226 in lagoon sludges are higher with
volumes ranging from 5,159 to 11,686 pCi/L. Radium-
226 in filter backwash water ranges from 6 to 92 pCi/L.
No information was found in the literature on the con-
centration of uranium in lime softening treatment wastes.
3.1.3.3 Cation Exchange Wastes
The chemistry of radium is similar to that of calcium and
magnesium (hardness ions). Thus, cation exchange
resins in the sodium form used to soften water are very
capable of removing radium-226 and radium-228 from
drinking water (Clifford, 1990; Bennett, 1978; Brink et
al., 1978; U.S. EPA 1976a,b; Meyers et al., 1985; Sorg
and Logsdon, 1980). The cation IX regeneration process
produces three waste streams: backwash water, regen-
erant brine, and final rinse water. Although the regener-
ant brine contains most of the radium released from the
resin during the regeneration process, both the initial
backwash water and final rinse water will contain some
quantity of radium.
The concentration of radium in the waste streams is site
specific and depends on the method of plant operation
26
-------
Table 3-11. Summary of Radium Concentration in
Source Water3
Location/Waste (pCi/L) Ra-226
W. Des Moines, IA 9.3
Sludge (clarifier drawoff)
Backwash water
Lagoon sludge
Webster City, IA 6.1
Sludge
Backwash water
Elgin, IL 3.5-7.5
Sludge (clarifier)
Sludge (clarifier)
Sludge (blanket)
Sludge (lagoon-active)
Sludge (lagoon-inactive)
Sludge (lagoon-entrance)
Backwash water
Sludge (filtrate)
Bushnell, IL 12.6
Sludge (clarifier)
Peru, IL 3.1-6.1
Backwash water
Sludge (pit)
Colchester, IL 12.1
Sludge (clarifier)
Backwash water
Beaver Dam, Wl 2.7-7.1
Sludge (clarifier)
Wapum, Wl 3.3-4.1
Sludge (clarifier)
Lime Softening Sludges and Backwash
Ra-228 Ra-226 pCi/L
76.0
6.3b
5,159
980-1,114
50-92
—
948
—
9,642
11,686
—
11.5-21.9°
0.5-0.48
4,577C
9.6, 13.8, 87.7b
—
2,038
<20
1 .0-2.4
—
1 .9-1 .4
—
Water
Ra-228
pCi/L
—
596
—
—
—
873
—
9,939
12,167
—
—
—
—
—
—
236
<39
—
—
—
Ra-226
pCi/g (dry)
—
10.8b
—
—
2.8-10.7
8.6
1.3-12.5
11.3
10.9
6-30
—
—
21 .6C
—
9.2
15.0
—
1.4
1.9
1.9
Ra-228
pCi/g (dry)
—
1.3
—
—
—
8.0
—
11.7
11.3
—
—
—
—
—
—
1.7
—
1.4
0.9
0.9
aCornwell et al., 1987; AWWARF, 1969; U.S. EPA, 1987; U.S. EPA, 1976a; Myers et a I., 1985; Sorg and Logsdon, 1980.
b Composite samples.
c Grab samples.
and regeneration employed. Examples of radium-226
concentrations in waste streams from several IX plants
are shown in Table 3-12. The average concentration of
radium-226 in backwash water, brine, and rinse water
together ranged from 22 to 82 pCi/L. The peak concen-
trations of radium-226 that occur during the brine cycle
ranged from 158 to 3,500 pCi/L.
3.1.3.4 An ion Exchange Wastes
Laboratory, pilot plant, and full-scale system studies have
shown that anion exchange treatment (chloride form) is
very effective for removing uranium from drinking water
(U.S. EPA, 1987; Jelinek and Sorg, 1988; Sorg, 1988).
This treatment process is similar to cation exchange for
radium and hardness removal. Anion resins are used in
the chloride form and are regenerated with sodium chlo-
ride (salt). Similar to cation exchange, the anion ex-
change process produces three waste streams during
regeneration: backwash water, regenerant brine, and
rinse water. Although the waste is a continuous stream,
each portion contains significantly different concentra-
tions of uranium. The highest concentrations occur dur-
ing brine regeneration; lower concentrations occur during
the initial backwash and rinse cycles.
The quantity and concentration of uranium in the waste
stream are site specific and depend upon the method of
plant operation and regeneration used. Most conven-
tional anion resins have such high uranium removal
capacities that treatment runs could last as long as a
year or more. Current practice shows, however, that
regeneration generally is conducted once every month
or two to produce waste streams with lower uranium
concentrations. The concentration of uranium in the
waste streams depends to a great extent on the raw
water concentration and the length of the treatment run
(i.e., the volume of water treated).
Field data from a uranium removal plant treating waterwith
a uranium concentration of approximately 130 u,g/L for two
months show peak uranium concentrations during brine
regeneration as high as 9.1 mg/L (see Table 3-13) (Sorg
et al., 1991). When the backwash water, brine waste, and
rinse water are combined, the average uranium concen-
tration was in the range of 2 to 10 x 105 u,g/L.
3.1.3.5 Iron Removal Processes Wastes
Oxidation/filtration and greensand filtration are basic
water treatment methods for iron and manganese re-
moval, but field data have shown that these processes
27
-------
Table 3-12. Summary of Radium-226 Concentrations in Brine Waste From Ion Exchange Treatment (Clifford, 1990; Bennett, 1978;
Brink et al., 1978; Clifford et al., 1988)
Location
Eldon, IA
Estherville, IA
Grinnell, IA
Holstein, IA
Dwight Correctional
Center, IL (Greensand)
Hersher, IL
Lynwood, IL
Elkhorn, Wl
Redhill Forest, CO
Raw Water
Concentration
(pCi/L)
49
5.7
6.7
13
3.3
14.3
14.7
7.2
11-35
Backwash Water
(pCi/L)
9-30a
94b
6-1 9a
12b
7.8a
—
—
—
5.2-7.8a
10-30
Brine
(pCi/L)
400-3,500a
5-320a
21 0-320a
70-1, 100a
—
—
—
27-158
11-2,000
Avg. of Backwash
+ Brine + Rinse
(pCi/L)
—
—
—
—
22, 27, 29b
65-94b
64b, 70b, 82b
23.1
—
Peak
Concentration in
Wastewater (pCi/L)
3,500
320
320
1,100
—
315
—
158
2,000
a Grab samples.
b Composite samples.
Table 3-13. Summary of Uranium Concentrations in Ion Exchange Treatment Plant Wastewater (Jelinek and Sorg, 1988; Sorg et
al., 1991)
Location
Arrowbear County
Water Distribution, CA
Coal Creek, CO
Raw Water
Concentration Backwash3
135 2.4-1,040
39-110 —
Brine3
(ng/L)
53 2—
6,780,000
—
Rinse3
36-
9,140,000
—
Avg. ofb
Backwash +
Brine + Rinse
(iJtg/L x 105)
2.0-9.9
16.5
Peak
Concentration
in Wastewater
(9/L)
9.1
—
aGrab samples during regeneration cycle.
b Samples collected from storage tank.
frequently remove some fraction of radium in the source
water as well (Bennett, 1978; Brink et al., 1978; U.S.
EPA, 1976a,b). These data show a wide range of radium
removal efficiencies, from almost 0 percent to as high
as 70 percent. These filtration processes produce a
backwash water waste stream from the filters; the con-
centration of radium in this stream will vary widely be-
cause of the wide range of removal. Table 3-14 shows
data from several filtration systems in Iowa, Illinois, and
Wisconsin. The concentration of radium in grab samples
of backwash water from these plants ranges from 120
to 1,980 pCi/L, while composite samples range from 34
to 165 pCi/L.
3.1.3.6 Reverse Osmosis and Electrodialysis
Wastes
RO and ED are capable of removing anions and cations
and, therefore, are effective for the removal of both
radium and uranium from backwash waste (Clifford,
1990; U.S. EPA, 1976a; Sorg and Logsdon, 1980; Sorg
et al., 1991). The quantity and concentrations of radio-
active contaminants in reject water depend on the con-
centration of contaminants in the source water, the
Table 3-14. Summary of Radium-226 Concentrations in
Waste Stream From Iron Removal Filters
(Clifford, 1990; Bennett, 1978; Brink et al., 1978;
Clifford et al., 1988; U.S. EPA, 1992b; Wisconsin,
1984)
Location
Eldon, IA (anthracite filter)
Esterville, IA (anthracite filter)
Holstein, IA (anthracite filter)
Adair, IA (greensand filter)
Stuart (anthracite filter)
Redhills Forest, CO
(conventional treatment package
plant)
Kaukauna, Wl (greensand filter)
(anthracite filter)
Elkhorn, Wl (sand filter)
Herscher, IL (150 avg.)
(anthracite filter)
Raw Water
Ra-226
(pCi/L)
49
5.7
13
6.6
16
31.5
—
7.2
14.3
Backwash
Water Ra-226
(pCi/L)
254-1 ,027a
165-1,980a
165b
80b
190a
120-2303
60 pCi/L (filter
backwash)
52.5b
33.5b
11. 9 (avg.)
144b, 159b, 149b
3 Grab samples.
b Composite sample.
28
-------
removal rate, and the fraction of water rejected. Assum-
ing a high contaminant removal rate of 95 percent or
greater, a good approximation of the concentration of
radionuclides in reject water can be easily calculated by
the following:
Concentration in
reject water
Concentration of radionuclide
in raw water
Fraction of water rejected
(Eq. 3-7)
Table 3-16. Summary of Uranium Concentration in Reject
Water of Reverse Osmosis Treatment (U.S. EPA,
1988c)
System Raw Percent
Capacity System Water Water Reject3
(1,000 TDS Uranium Rejected Water
Location gpd) (mg/L) (|Jtg/L) (|Jtg/L) Uranium
Table 3-15 presents radium-226 concentrations in reject
waters from several RO plants in Iowa and Florida. The
data show a radium-226 concentration range of 7.8 to
43 pCi/L in the reject water.
Uranium levels in reject waters from a pilot plant study
conducted by Charlotte Harbour Water Association are
shown in Table 3-16. Reject water concentrations range
from 301 to 1,125 u,g/L for three different RO mem-
branes. This broad range is a result of the wide-ranging
feedwater uranium concentrations, 154 to 682 u,g/L, and
the recovery rates of the individual membranes tested.
Although no field data on the concentration of radium or
uranium were found in the literature for ED, the concen-
tration of these contaminants in the reject waste stream
from ED systems should be in the same range as RO
wastes because of the similarity in the treatment proc-
esses used for each method.
Charlotte Harbour, FLb
Membrane 1
Membrane 2
Membrane 3
5
5
5
450
760
575
682
154
277
40
50
90
1,125
301
304
3 Calculated based on 99 percent rejection.
b Single membrane.
Key
TDS = total dissolved solids.
3.1.3.7 Waste Materials
Solid waste materials from drinking water treatment
processes can be grouped into two categories: 1) selec-
tive/specific sorbants that are not regenerated or
reused, and 2) materials used in treatment processes
that will retain some level of contamination and are
replaced periodically (e.g., filter sand). These materials
are listed in Table 3-10. Of the two categories, selec-
tive/specific sorbants will contain the highest concentra-
tion of contaminant by a very large factor because, by
design, they are used to remove specific contaminants
from source water. Two of the more widely known sor-
bants are the radium selective complexes (RSC), used
for radium removal, and GAG, used for radon removal.
The amount of radioactive contaminant retained on
Table 3-15. Summary of Radium-226 Concentrations in Reject Water of Reverse Osmosis Treatment
Location
Bay Lakes Estates MHP, FLa
Venice, FLa
Sorrento Shores, FLa
Spanish Lakes MHP, FLa
Nokomis School, FLa
Bayfront TP, FLa
Kings Gate TP, FLa
Sarasota Bay, FLa
Greenfield, IAb
Lament, ILc'd
• Pilot system-1
• Pilot system-2
• Pilot system-3
System Capacity
(1,000 gpd)
40
1,000
200
70
0.8
1.6
30
5
150
—
—
—
Raw Water TDS
(mg/L)
2,532
2,412
3,373
1,327
1,442
895
1,620
2,430
2,200
510
681
451
Raw Water
Ra-226 (pCi/L)
3.2
3.4
4.6
10.4
11.1
12.1
15.7
20.5
7.6
11.6
13.9
13.0
Percent Water
Rejected (%)
—
46
61
69
—
72
—
50
31
50
85
75
Reject Water
Ra-226
(pCi/L)
—
7.8
7.9
20.5
11.9
19.4
—
37.9
43
19.2
14.2
14.1
aSorg et al., 1980.
bU.S. EPA, 1976b.
c Clifford etal., 1988.
d Single membranes.
29
-------
these materials depends on the concentration of the
contaminant in the source water, the percent removal of
contaminants, and the length of operation (usually de-
termined by the capacity of the sorbant).
RSC material has been used to remove radium directly
from source water and from the brine waste of IX proc-
esses (Clifford etal., 1988; U.S. EPA, 1988b; U.S. EPA,
1985a). Samples of RSC material from several WTPs in
Illinois, Wisconsin, and New Hampshire, show radium
concentrations ranging from 3.6 to 9.1 pCi/g (Redhill
Forest, CO) (see Table 3-17). The low value of 3.6 nCi/g
was the average of three RSC samples from an ex-
hausted bed treating a water source with a total radium
concentration of 18.1 pCi/L. The higher concentration of
9.1 nCi/g was the calculated concentration of radium-
226 on an RSC system at 1 year, removing radium
(1,200 pCi/L) from a spent brine solution of an IX plant.
This system was not run to exhaustion at that point in time.
GAG is used to remove radon from source water, but
because of the short half-life of radon, the longer-lived
decay product, lead-210, is actually contained on the
GAG (U.S. EPA, 1990b; Lowry and Brandow, 1985;
Watson and Crawford-Brown, 1991). The amount of
lead-210 retained on GAG can be calculated from data
on the source water radon concentration and the per-
cent removal.
Core GAG samples from two GAG radon removal plants
in New Hampshire were analyzed for lead-210 after 293
days of operation (Mont Vernon), and after approxi-
mately 4 months (Amherst). As expected, the concen-
tration of lead-210 decreased with bed depth. The
maximum level at the top for the Mont Vernon system
was 757 pCi/g, and 297 pCi/g for Amherst. The Mont
Vernon system had a higher influent radon concentra-
tion (210,500 pCi/L) as compared with the Amherst sys-
tem (41,800 pCi/L), and had been operating for
approximately 3 months longer. Thus, a higher level of
lead-210 would be anticipated at the Mont Vernon site.
Neither system was considered to be close to radon
exhaustion, each having an expected bed life of 5 to 10 years.
3.2 Physical Characteristics of Residuals
The increasing need to process WTP residuals in prepa-
ration for their final disposal/beneficial reuse has inten-
sified investigations into their physical characteristics.
These characteristics significantly affect the ability to
handle, thicken, dewater, and convey WTP residuals
prior to the disposal/beneficial reuse. The following sec-
tions discuss solids content, specific resistance, corn-
Table 3-17. Concentration of Radionuclides on Water Treatment Process Media and Materials (Bennett, 1978; Brink et al., 1978)
Location
Lament, IL (Pilot Study)
Redhill Forest, CO
Herscher, IL
Lynwood, IL
Dwight Correctional Institute, IL
Peru, IL
Elgin, IL
Elkhorn, Wl
Mt. Vernon, NH
Amherst, NH
Treatment Process
Radium selective complexer
Radium selective complexer
(brine treatment)
Iron removal
Cation exchange
Cation exchange
Natural greensand
(cation exchange)
Lime softening
Lime softening
Iron removal
Cation exchange
GAC
Radon removal
GAC
Radon removal
Process
Media/Material
Resin
Resin
Filter media
Resin
Resin
Greensand
Filter media
Filter media
Filter media (sand)
Resin
GAC
GAC
Radionuclide
Ra-226
Ra-226
Ra-226
Ra-226
Ra-226
Ra-228
Ra-226
Ra-226
Ra-228
Ra-226
Ra-226
Ra-228
Ra-226
Ra-228
Ra-226
Ra-228
Ra-226
Ra-228
U-235/238
Pb210
Pb-210
Concentration
3.6 nCi/g (exhaustion)
(total radium)
770x1 88 pCi/ft3
111.6 pCi/g
38.9 pCi/g
43 pCi/g
9.6 pCi/g
6.6 pCi/g
29-46 pCi/g
4.6 pCi/g
3.6 pCi/g
16.0 pCi/g
8.3 pCi/g
1 .47 pCi/g
0.48 pCi/g
6.04 pCi/g
2.7 pCi/g
549-9,050 pCi/g (top
of bed)
757 pCi/g (max)
297 pCi/g (max)
Key
GAC = granular activated carbon.
30
-------
pressibility, shear stress, density, and particle size—
physical characteristics that can affect the solids dewa-
tering process.
3.2.1 Solids Content
The solids content of residuals varies widely, depending
on factors such as the raw water characteristics, coagu-
lant type and dose, and whether lime is used. The data
Table 3-18. Settled Solids Concentration of Residuals From
Water Treatment Plants in Missouri (Calkins and
Novak, 1973)
Location
Higginsville
Macon
Boonville3
Jefferson City3
St. Louis County3
Moberly
Kirksville
Kansas City3
Boonville3
St. Louis3
Boonville
St. Joseph3
St. Louis County3
Kansas City3
Jefferson City3
St. Louis3
St. Louis County3
Kansas City3
Jefferson City3
Columbia
St. Louis3
St. Joseph3
Mexico
Sludge
Alum
Alum
Lime and alum backwash
Lime and iron backwash
Iron backwash
Alum
Alum
High magnesium softening sludge
Lime and alum
Iron backwash
Lime and alum
Catfloc backwash
Iron (secondary basin)
Lime and magnesium
Lime and iron
Iron (secondary basin)
Iron (primary basin)
Softening sludge
Lime and iron
Lime
Lime and iron (primary basin)
Catfloc
Lime
Settled
Solids (%)
3.1
3.4
3.96
4.1
4.62
6.3
7.8
8.0
8.17
8.95
10.1
11.3
12.2
15.2
19.1
19.3
21.1
25.3
26.8
33.0
35.6
35.8
54.0
shown in Table 3-18 indicate the range of solids found
for a variety of water treatment sludges in Missouri. The
alum sludges have the lowest solids content, while the
lime sludges and sludges from Missouri River plants
have the highest. In general, the greater the amount of
incorporated suspended solids and calcium carbonate
in the sludge, the higher the solids content. Therefore,
when low-turbidity water is treated, the solids content of
the residuals will be low, while the solids content of
residuals from turbid waters will be much higher.
In Table 3-19, the data show that the solids content
following gravity settling and vacuum dewatering de-
pends on the raw water turbidity, coagulant dose, and
coagulation mechanisms. Because the pH at which
coagulation occurs will determine the coagulation
mechanism, pH will also influence the residuals solids
content.
For example, in Table 3-19, the data show that the
thickened and dewatered solids content are lower when
coagulation is conducted at pH 8.1 than when it occurs
at pH 6.5. At a coagulation pH of 6.5, the predominant
means of incorporating the natural turbidity-causing par-
ticles into the sludge was adsorption-charge neutraliza-
tion (i.e., the positive hydrolysis species formed by
adding alum to the water were able to adsorb on the
surface of the natural turbidity particle, neutralizing the
negative charge of these particles and allowing them to
be incorporated into the sludge). This process results in
a lower alum dose and, consequently, in a sludge that
is easier to thicken/dewater due to a higher percentage
of natural turbidity-causing particles and a lower per-
centage of gelatinous aluminum hydroxide.
At a pH of 8.1, the predominant means of incorporating
the natural turbidity into the sludge was enmeshment in
a precipitate, or sweep-floe (i.e., the alum added reacted
with the alkalinity of the water to form large amounts of
gelatinous aluminum hydroxide precipitate, in which the
natural turbidity particles were entrapped). This type of
sludge is more difficult to thicken/dewater because of
the high percentage of aluminum hydroxide present.
Also, alum sludge has been shown to have a lower
solids content than iron or lime sludge.
Table 3-19. Effect of Coagulation Mechanism on Alum Sludge Properties (Knocke et al., 1987)
Coagulation Conditions
Influent Turbidity Coagulant
NTU Dose mg/L
40
40
7
7
7
10
15
40
75
75
Ultimate Thickened Specific Vacuum
Coagulation Solids Cone. Resistance r Dewatered Solids
pH Mechanism Percent m/kg x 1011 Cone. Percent
6.2
6.3
6.5
7.1
8.1
Adsorption-charge neutralization
Adsorption-charge neutralization
Mixed
Enmeshment
Enmeshment
6.0
5.5
1.0
1.0
0.5
55
60
95
150
310
42
22
15
11
9
31
-------
Ltme
Iron
Iron
Raw 1 — »
SETTLED
SOLIDS (%)
PRE- \
SETTLING
I
63.8
Ca/Fe 52 5
WEIGHT RATIO
^ PRIMARY j
1
21.1
8.15
^ SECONDARY
1
12.2
6.37
^ FILTERS
I
4.6
1.38
Figure 3-2. Change in sludge settled solids concentration throughout a treatment plant (Calkins and Novak, 1973).
The solids content of residuals varies through a plant
and depends on the chemicals added and the addition
sequence. In Figure 3-2, the change in solids throughout
a Missouri River surface water treatment plant is shown.
The settling sludge, consisting of settled clay and cal-
cium carbonate residues, settles to greater than 60 per-
cent solids. At the other end of the plant, the settled filter
backwash is 4.6 percent solids. Filter backwash solids
generally will consist of the lighter solids that fail to settle
in sedimentation basins, so they are usually lower in
solids than is material from the clarifiers. As shown in
Figure 3-2, the decrease in settled solids corresponds
to a decrease in calcium carbonate as reflected by the
calcium-to-iron weight ratio of the sludge solids.
With regard to softening residues, calcium carbonate
solids form dense slurries with a high solids content.
Settled solids in excess of 60 percent have been found
for relatively pure calcium carbonate. When Mg(OH)2 is
incorporated into softening residues, however, the solids
content decreases, usually in direct proportion to the
magnesium fraction. Figure 3-3 shows that the settled
solids content of softening residues can vary from less
than 10 percent to more than 60 percent as the magne-
sium fraction in the sludge decreases.
An operational definition for water in sludges divides the
water into three simple fractions—nonremovable water,
capillary water, and removable floe water. While there is
considerable debate about the types and distribution of
water in sludges, this operational definition is useful in
estimating the potential solids content that can be
achieved by dewatering. Nonremovable water is the
water associated with surfaces and has been described
as "vicinal" water. This water is thought to form a hydra-
tion shell around surfaces. The large crystalline surfaces
of calcium carbonate residues will have relatively little
nonremovable or visual water because the surface area
of this material is relatively small.
Capillary water is that which is trapped between parti-
cles and retained by capillary action. Capillary water is
removed by application of pressure, which results in
70-
60-
50-
i
O 40
cr
H
30-
u
o
8 20
CO
o
CO
IO--
Figure 3-3.
Co/M.g MOLAR RATIO
Effect of Ca-to-Mg ratio on the solids concentration
of softening sludge (Calkins and Novak, 1973).
floes moving closer together and squeezing out water
between floes. Removable floe water is water retained
within floes in a manner similar to that of a sponge; it is
removed as the floes are squeezed or compressed by
the application of pressure. In effect, both capillary water
and removable floe water are expelled simultaneously
by the application of pressure. As the pressure in-
creases, more water is removed; at the highest pres-
sure, any remaining water is primarily nonremovable
water. This process is depicted in Figure 3-4.
Applied pressure is the major operational variable in
dewatering. As the applied pressure of a dewatering
process is increased, the cake solids concentration
increases, but the lower-solids alum sludge is always
well below lime sludge levels, no matter what process
32
-------
CAPILLARY WATER
NON-REMOVABLE
(VICINAL) WATER
REMOVABLE FLOC WATER
NON-REMOVABLE
WATER
APPLIED PRESSURE
Figure 3-4. Water distribution and removal in a softening
(CaCOs) slurry and coagulant (AI(OH)s) slurry
(adapted from Novak, 1986).
is used (see Table 3-20). Lime sludge particles contain
almost no floe water. Water retained after settling is fixed
to surfaces and between particles (capillary water).
Alum sludge, in addition to a having higher nonremov-
able water fraction, contains a large amount of internal
floe water.
Because polymer conditioning agents interact only with
the outer surface of floes and do not alter their internal
floe structure, polymer conditioning neither affects inter-
nal floe water or vicinal water, nor significantly affects
dewatered cake solids. Therefore, the solids content of
any water treatment residue is determined by the inher-
ent composition of the solids as they form and by the
applied pressure of the dewatering device. Once
formed, only processes that affect the internal floe struc-
ture (such as freeze-thaw conditioning) will substantially
influence the solids content that can be achieved by
dewatering.
3.2.2 Specific Resistance
Specific resistance is a measure of the rate at which a
sludge can be dewatered, and it reflects the size of
particles in the filter cake as water passes through the
sludge. While initially developed to assess vacuum filter
performance, specific resistance also indicates the de-
watering rate by a variety of filtration processes, includ-
ing gravity settling and sand bed dewatering.
A residue's specific resistance to filtration is usually
measured using a vacuum filter device. The test is de-
scribed in detail in Cornwell et al. (1987). Resistance to
filtration depends on the porosity or permeability of the
sludge cake. Permeability is a function of particle size
and particle deformation (compressibility) when pres-
sure is applied. Specific resistance may be calculated
from filtration data using the following formula:
r = -
2PA2b
uc
(Eq. 3-8)
where
r = specific resistance to filtration
P = pressure drop across sludge cake
A = surface area of filter
u, = filtrate viscosity
c = weight of dry solids deposited per volume of
filtration
b = slope of a plot of t/V versus V
t = time of filtrate
V = filtrate volume
Specific resistance data are useful for comparing
sludges and for evaluating the effect of polymers on
dewatering (See Figure 3-5). Because the specific re-
sistance of a sludge often depends on the pressure
applied during filtration (see Section 3.2.3) and on the
mixing applied during chemical addition, resistance val-
ues are used primarily as an index of dewaterability
rather than as well-defined sludge properties. Sludge
Table 3-20. Specific Gravity of Sludge Particles and Cake Solids Concentrations Obtainable From Various Laboratory Dewatering
Methods (Novak, 1989)
Cake Solids Concentration (%)
Type of Slurry
Lime sludge (low Mg)
Iron sludge
Ferric hydroxide
Lime sludge (high Mg)
Aluminum hydroxide
Specific Gravity
of Particles
1.19
1.16
1.07
1.05
1.03
Settled Solids
Concentration (%)
28.5
26.0
7.2
5.6
3.6
Vacuum
Filtration
56.1
50.1
22.7
21.0
17.2
Centrifugation
60.6
55.6
28.2
24.8
19.0
Pressure
Filtration
69.5
64.6
36.2
34.6
23.2
33
-------
UJ
o
I
a:
o
OPTIMUM CONDITIONING
CHEMICAL DOSAGE
CONDITIONING CHEMICAL DOSAGE V. BY WEIGHT
Figure 3-5. Use of specific resistance to determine optimum
chemical dosage (Cornwell et al., 1987).
Table 3-21. Specific Resistance for Various Chemical
Sludges (Calkins and Novak, 1973)
Location
Jefferson City
Jefferson City
Kansas City
Boonville
Boonville
Jefferson City
Jefferson City
Jefferson City
Kansas City
Boonville
St. Joseph
St. Louis
Kansas City
St. Louis
Boonville
St. Louis County
St. Louis County
St. Joseph
St. Louis
St. Louis County
Moberly
Specific
Resistance 1010
Sludge (m/Kg)
Lime and iron
Lime and iron
High magnesium softening
sludge
Lime and alum
Excess lime and alum
backwash
Lime and iron
Lime and iron
Lime and iron
Softening
Excess lime and alum
backwash
Cationic flocculent
Lime and iron
High magnesium softening
sludge
Iron
Lime and alum
Iron backwash
Iron
Cationic-flocculent
backwash
Iron backwash
Iron
Alum
2.11
4.3
5.49
5.83
5.98
6.12
6.79
7.0
11.57
13.2
14.1
21.2
25.1
40.8
53.4
76.8
77.6
80.1
121.8
148.5
164.3
resistances change during storage as a result of chemi-
cal aging and biological activity. Specific resistance val-
ues are most useful in comparing treatment options,
conditioning chemicals, or mixing conditions.
Specific resistance of sludges varies widely, as shown
in Table 3-21. In general, residuals with specific resis-
tance of 10 x 10 m/kg or less are considered to dewater
readily, while those with a specific resistance of 100 x
1011 m/kg have poor dewaterability. As indicated by the
data in Table 3-22, lime softening sludges dewater rap-
idly and alum sludges from relatively clean surface wa-
ters dewater slowly.
Specific resistance for coagulant sludges increases as
the pH rises and as the raw water turbidity decreases.
The factors in coagulation that lead to high moisture
content in the sludge cakes also cause sludge to dewa-
ter slowly. Alum sludges from low turbidity raw waters
have both a low rate of dewatering and a low solids
content.
Chemical conditioners, usually anionic polymers, may
be added to sludges to decrease the specific resistance.
The selection of polymers and the appropriate dose for
conditioning is usually determined by laboratory testing.
Factors influencing the polymer dose include the solids
content, pH, and mixing intensity.
3.2.3 Compressibility
Most coagulant residues are highly compressible. Com-
pressibility is thought to occur as a result of floe defor-
mation during dewatering. The major consequence of
compression is that dewatering rates decrease as the
pressure applied during the process increases.
The compressibility of residues is often represented by
the following equation:
r2 = r^APs (Eq. 3-9)
where
T! = specific resistance at pressure, P-i
r2 = specific resistance at pressure, P2
AP = P2 - P!
S = coefficient of compressibility
The coefficient of compressibility, S, is usually deter-
mined from a log-log plot of specific resistance (R)
versus pressure (P). For coagulant residues, values of
S vary from approximately 0.8 to 1.5, while values for
softening residues may be as low as 0.4 for materials
comprised primarily of calcium carbonate.
Similar relationships have been described, where com-
pressibility relates to empirical constants that are deter-
mined experimentally. A somewhat different approach
describes the formation of a skin at the surface of the
filtering medium that resists the transport of water
through a filter cake. These approaches all recognize
34
-------
Table 3-22. Summary of Floe Density and Dewatered Solids Concentration Data for Several Chemical Sludges (Knocke et al., 1993)
Maximum Dewatered Solids Concentration (% by wt)
Sludge Type
Polymer WTP
Polymer WTPa
Iron I
Iron I
Alum I
Alum III
Lime
Floe Density
(g/mL)
1 .06-1 .08
>1.30
1 .26-1 .28
>1.30
1 .22-1 .25
1.14-1.16
>1.30
Dry Solids
Density (g/mL)
1.58
1.60
2.86
2.86
2.55
2.45
2.47
Grav. Thick.
2.7
25
8.9
16
3.0
3.0
13
Vacuum Filter
17
45
27
54
17
14
41
Centrifuge
11
33
31
44
15
10
42
Pres. Fill.
21
40
30
53
25
—
—
a Freeze-thaw conditioning provided.
that residuals tend to deform under pressure, resulting
in an increased resistance to filtration.
Some of the changes in filtration resistance are attribut-
able to particle shear, which results from the movement
of water through the cake. The particles in sludge cakes
undergoing filtration have been shown to desegregate,
an effect that was especially troublesome for alum
sludges. In contrast, calcium carbonate slurries were
resistant to shear. Because the breakup or disaggrega-
tion of floes led to increased polymer conditioning re-
quirements, high pressure dewatering systems may be
appropriate for alum sludges.
Generally, solids that consist primarily of coagulant ma-
terials from clean raw water sources dewater poorly
when pressure is applied. In contrast, solids with a large
fraction of rigid particles, such as softening sludges, will
not deteriorate as dramatically when pressure is ap-
plied. Whether this effect is caused by particle deforma-
tion, skin formation, or particle breakup may be less
important than the effect high compressibility has on
dewatering and on the selection of dewatering equipment.
3.2.4 Shear Stress
Shear stress is an important characteristic in determin-
ing the handleability of a sludge. The undrained shear
strength of various water treatment residues, shown in
Figure 3-6, varies markedly with the solids content.
Figure 3-6 also shows that the sludge settled solids
concentration provides a reasonable estimate of the
range of solids concentrations where a sludge makes
the transition from a liquid to a handleable solid. This
condition is clearly presented in Figure 3-7, where the
solids concentration needed to produce a handleable
sludge occurs in a range of 0.02 to 0.05 tons/ft2. The
data in Figures 3-6 and 3-7 also show that alum sludges
0.125+
o.io •
cT 0.075-
i-
ti.
—
CO
o
K.
<
UJ
0.05--
0.025.
SLUDGE TYPE
ALUM
IRON
LIME AND IRON
UME AND IRON
LIME
SETTLED SOLIDS
CONCENTRATION
SETTLED SOLIDS
6.7
13.1
22.3
26.1
37.2
37,2%
Range of shear
values where sludge
becomes handleable
10 20 30 40
SOLID CONCENTRATION (%!
50
70
Figure 3-6. Variation in shear strength with sludge moisture content (Novak and Calkins, 1973).
35
-------
30--
o
z
o
20--
Q
_J
O
10--
SLUDGE BECOMES
HANOLEABLE
O.O5 Tons/Ft2
10 20 30 40
SOLIDS CONCENTRATION {%)
50
60
Figure 3-7.
Comparison of sludge settled solids concentration
with the solids concentration where a sludge be-
comes "handleable" (Novak and Calkins, 1973).
generally fall in the settled solids range of 7 percent and
below. Therefore, solids concentrations of 15 to 20 per-
cent may be sufficient to produce a handleable sludge.
In contrast, some softening sludges may require con-
centrations above 50 percent before they can be handled.
In a study of the dry weight density-moisture relationship
for an iron coagulant and two alum coagulant sludges,
the iron sludge showed the typical humped curve, where
maximum density occurs at an optimum moisture con-
tent. The alum sludge reached a maximum density at
the lowest moisture content (Figure 3-8). The coagulant
residuals were extremely plastic and compressible and
greatly exceeded these values for high clay soils.
When landfilling these materials, the solids content
should be as high as possible to minimize the amount
of landfill space required. In addition, because the cost
of landfilling is most often determined on a weight basis,
increasing the solids content and reducing the water
content of residuals prevents having to pay for the cost
of landfilling water.
3.2.5 Density
Floe density varies with floe size, with density decreas-
ing as floe size increases (see Figure 3-9). The major
impact of mixing shear is to make floes smaller. For
similar floe sizes, mixing has no effect on floe density, a
finding supported by others.
As the volume of suspended solids (Kaolinite clay) in the
floe increases, the floe density also increases. Settled
and dewatered cake solids increase as the suspended
solids in the cake increase. The effect of the solids-to-
coagulant ratio on floe density and cake solids suggests
that these two factors are related. The apparent density
or specific gravity of floes is a useful predictor of the
dewatered cake solids produced by a variety of proc-
16 r-
14
12
10
SLUDGE 1
IRON
20
40
12
D)
'CD
4 .
60
SLUDGE 2
ALUM
100
11
200
SLUDGE 3
ALUM
300
0 80 160 240
Water Content (%)
Figure 3-8. Compaction curves of test sludges (Cornwell et al.,
1992).
esses (Table 3-20), with floe density measurements
varying from 1.03 to 1.19 for various water treatment
residuals. In a study of the effects of organic matter on
floe density, when floes contained more organic matter,
36
-------
O
-C-f
• =
A == 4
D =.
0 — i
,
"~" — 9
o o •— •
3S/ft
LI
12
30
10
-Q^_ «a
~*~O
t
M
i "
?~^.
^
"
"^^^A *A
»* •
-•D
100 r
0.15 0.2 0.3 0.4 0.6 0.8 1.0
Floe Size-area sq mm
1.5
Figure 3-9. Variation of floe density with floe size (Lagvankar
and Gemmell, 1968).
30
25
20
15
10
O pH 5.8
£ pH 6.2
O PH 7.2
JL
JL
0.2 0.4 0.6 0.8
mg TOC R«mov«d/mg Aluminum Addod
1.0
Figure 3-10.
Variations in dewatered cake solids concentration
of aluminum hydroxide sludges as a function of
organic content (Dulin and Knocke, 1989).
their density declined, dewatering rates decreased and
dewatered cake solids decreased (see Figures 3-10,
3-11, and 3-12). Floe densities for alum sludges have
been reported in the range of 1.14 to 1.22, depending
on the amount of total organic content (TOC) incorpo-
rated in the floes.
A recent study comparing various methods of floe den-
sity measurement showed that the use of a low osmotic
pressure gradient medium to measure floe density is
more sound than other commonly used methods such
as the sucrose method. High osmotic pressure media
are likely to produce densities higher than actual be-
cause the high osmotic pressures cause the flow of
water out of the floe during measurement. The data
presented in Table 3-22 show floe densities ranging from
1 .06 to greater than 1 .3 g/mL for various water treatment
residues. The solids content obtained by various dewa-
a
V
E
"5
3
-3
u
40 -
20
10
20 30 40 50 60
Parllcl» Dlamoler—^m
70 BO
Figure 3-11. Effect of incorporation of organic carbon on the
relative size distribution of aluminum hydroxide
sludge floe formed at pH 6.5 (Dulin and Knocke,
1989).
1.22 r
1.20
Q
8.
1.16
1.14
1.12
Figure 3-12.
I
O With TOC
6 Wllhout TOC
I
6.0
7.0
Coagulation pH
8.0
Variations in measured floe density as a function
of both coagulation pH and presence or absence
of TOC from sludge floe matrix (Dulin and Knocke,
1989).
tering methods suggests that floe density may be an
important determinant in the cake solids obtained by
dewatering.
3.2.6 Particle Size Distribution
According to the theory of filtration, the resistance of
sludges to filtration is a function of particle size of the
floes in the sludge cake. While several factors such as
compressibility and filter media blinding may cause vari-
ation from a precise relationship between particle size
37
-------
200
= 150
100
= 50
0
o
0
O0O
Co
00
ooo
o oo
°°pOO
o60o°o
§ °
00 o
0 0
°00
o ° P
f °o Jig0
° 8 oo
o
0
o
On OO
00 0
3
OQ
0
o o
o
0 0
yacuucn=l5 in. Hg
o
o
s
o
0
40 60
Sludge mean floe size, in microns
IQO
120
Figure 3-13. Floe size and resistance of metal hydroxide sludges to dewatering by vacuum filtration (Knocke et al., 1980).
and cake resistance, measurements of particle size
generally support this theory.
Data presented in Figure 3-13 for various metal hydrox-
ide sludges show the relationship between mean floe
size and specific resistance. Additional data shown in
Figure 3-14 for alum sludges show a similar trend.
These data were measured using a HIAC particle
counter and indicate that unconditioned alum sludge
has a mean floe size of 20 u, or less.
Conditioning chemicals can also be seen to influence
particle size. Data presented in Figure 3-15 show the
increase in particle size resulting from addition of poly-
mer and the associated decrease in the specific resis-
tance to filtration.
Although the mean particle size is the primary factor in
determining sludge filtration behavior, two other factors
are important. If the particle distribution is bimodal, the
sludge is susceptible to "blinding," which is defined as
the migration of fines through the cake, resulting in much
lower cake permeability near the filtering surface. This
phenomenon has been documented for certain sewage
sludges but does not appear to be common for WTP
residuals.
A more likely problem, especially with alum sludges, is
the formation of small particles from the breakup or
disaggregation of alum floe due to shear. Alum sludge is
very sensitive to shear (Figure 3-16), and shear, G,
equal to 500/sec can be attained in filter cakes from the
passage of water during vacuum dewatering. Therefore,
much of the demand for conditioning chemicals results
from the shear associated with the dewatering process
and not because alum sludge is comprised of small
,cco
Q Ref. 22
0 Kef. 23
I Z 3456 789D 2 345 S789102 2 345
(l/De) X I04, (
Figure 3-14. Effect of specific surface area on the specific re-
sistance of alum sludges (Knocke et al., 1980).
particles. An important role of conditioning chemicals is
to make the sludge resistant to shear.
Particle size, as measured by conventional commercial
particle counters, generally verifies that particle counting
is a useful means to evaluate sludge dewatering prop-
erties. Using microscopic examination and considering
the particles to be elliptical, the relationship between
38
-------
10 20 30 «
Anionic polymer dose, in
milligrams pet liter
20 n 60 80 100 120 140 160
Figure 3-15. Representative results from metal hydroxide sludge conditioning studies (Knocke et al., 1980).
Alum Sludge
Belz II20
Figure 3-16. Effect of Gf on optimum polymer dose for alum
sludge conditioning (Werle et al., 1984).
particle surface area and specific resistance has been
described.
3.3 Chemical Characteristics of
Residuals
The chemical characteristics of WTP residuals tend to
affect the options for disposal/beneficial reuses more
than they affect the ability to handle, thicken, or dewater
residuals.
3.3.1 Solids Content
The solids content of WTP residuals varies widely,
based on whether the residual is a liquid waste, sludge
(i.e., semi-solid waste), or solid waste. Furthermore, the
solids content of sludges varies significantly depending
on the solids handling processes to which the sludge is
subjected (e.g., thickening, dewatering).
The type and concentration of solids affect the distribu-
tion of water within a sludge (Cornwell et al., 1987).
Because floe water is trapped within the floes, capillary
water is held to sludge floes by surface tension and
attractive forces, and bound water is chemically bound
to individual floe particles. Equally important to the solids
content is the residual's volatile solids-to-total solids
ratio (i.e., VS/TS). Fortunately the majority of the solids
in WTP residuals tend to be inert, and the VS-to-TS ratio
is typically less than 30 percent. In coagulant sludges,
the inert SS tend to be aluminum or iron hydroxide
precipitates that can be difficult to dewater because of
their gelatinous nature. In softening sludges the inert SS
are associated with crystalline calcium carbonate, which
drastically reduces the flow water trapped within the floe.
3.3.2 Metals Content
The metals content of WTP residuals is important for a
number of reasons: 1) potential impacts on the disposal
of the residual in a sanitary landfill; 2) possible inhibitory
effects if the residuals are discharged to a WWTP for
processing; 3) potential adverse contributions to the
residuals from the WWTP based on Part 503 sewage
sludge regulations; and 4) possible effects on the whole
effluent toxicity of the effluent from the WWTP.
The mean total levels of cadmium, copper, chromium,
nickel, lead, and zinc in coagulant sludges from WTPs
are generally 10 to 35 percent of the corresponding
values for sewage sludges. Except for cadmium, 76 to
39
-------
87 percent of these were found to be within the oxide or
silicate matrix of the alum and iron sludges. Although
cadmium could become mobilized under acidic condi-
tions, the levels were measured at levels too low to
promote significant leaching of the cadmium. Another
investigation into the mobilization of several heavy met-
als from ground-water and surface water sludges sug-
gests extreme decreases in pH (i.e., less than 2.5) and
alternating aerobic/anaerobic conditions are necessary
for significant mobilization.
Fortunately, it is known that much of the heavy metals
content of WTP sludges is often contributed by impuri-
ties in the coagulant. Consequently, heavy metal con-
centrations in the residuals can be limited by carefully
specifying the coagulants and other chemicals added to
the water.
3.3.3 Toxicity
Before 1990, the potential toxicity of WTP residuals was
determined based on the EP toxicity test. The Toxicity
Characteristic Leaching Procedure (TCLP) has now re-
placed the EP toxicity test. Coagulant sludges from
WTPs have been shown to easily meet the TCLP crite-
ria. The metals content of WTP residuals is not antici-
pated to be a problem under the criteria for the TCLP.
40
-------
Chapter 4
Water Treatment Residuals Processing
Residuals handling at water treatment plants (WTPs)
has traditionally dealt with the handling of waste streams
from sedimentation, precipitation, and filtration from
conventional coagulation type plants or lime softening
facilities. Historically, residuals from these types of facili-
ties have been most commonly disposed of through
discharge to sanitary sewers, streams, or similar bodies
of water. The changing regulatory environment is lead-
ing to an increase in the number of plants incorporating
solids handling facilities. This chapter provides informa-
tion concerning the selection of residuals handling proc-
esses for a WTP, including:
• Basic descriptions of standard residuals handling
processes.
• Definition of preliminary residuals processing require-
ments.
• Criteria for the preliminary selection of unit process
combinations.
• Discussion of sizing procedures for select unit proc-
esses.
This chapter identifies unit processes for treating tradi-
tional types of residuals. Changes in the regulatory en-
vironment, however, are also requiring an additional
form of residuals handling—that of air emissions control.
This form of control may be applied to the discharge of
gaseous residual byproducts from processes such as
ozonation or air stripping.
4.1 Residuals Handling Process Types
Some water treatment processes that may produce sol-
ids are grit collection, sedimentation, and filtration (Fig-
ure 4-1). These processes can include mechanisms for
collection and concentration of solids before convey-
ance to disposal or to another unit process. These re-
siduals can be handled through a variety of process
types. A residuals handling flow schematic with each of
the process types is shown in Figure 4-2.
The process types are:
• Thickening: A process of concentrating the solids
content of a residual stream to reduce the volume
before disposal or further treatment.
• Coagulant recovery: A treatment technique for im-
proving solids dewatering characteristics and lower-
ing the concentration of metallic ions in the residuals.
Recalcination is a related process associated with
lime softening sludges (see Chapter 13).
• Conditioning: Adding a chemical to a residual or
physically altering its nature. Conditioning is tradition-
ally used as a method to optimize the dewatering
process.
• Dewatering: Similar to thickening in that both proc-
esses involve a liquid-solids separation approach
with a goal of minimizing the amount of residuals for
disposal. Dewatering is defined as a process to in-
crease the solids concentration of residuals (by
weight) to greater than 8 percent, typically in the 10
to 20 percent range.
• Drying: An extension of the liquid-solids separation
approach of thickening and dewatering. Drying is de-
fined as a process to increase the solids concentra-
tion of residuals (by weight) to greater than 35
percent.
• Disposal and reuse: Removal of residuals from the
WTP site or permanent storage of residuals at the
WTP site. This category includes hauling to landfill,
discharging to sanitary sewer or natural waterway,
land application, and various reuse options (e.g., soil
supplement, brick manufacture).
• Recovered and nonrecovered water handling: Thick-
ening, dewatering, and drying processes produce
both liquid and solids components. The solids com-
ponent may be further treated and disposed of. The
liquid component is returned to the main WTP proc-
esses if it is recoverable, which means it has little
impact on the main treatment process and no harmful
effect on the finished water quality. Quality parame-
ters that can affect the recoverable status of the water
include the following:
- Residuals metal concentrations.
- Disinfectant byproduct formation potential.
- Use of unapproved polymers in the residuals han-
dling processes.
41
-------
Raw
Water ->
Finished
Water
Pre-
Grit Sedimentation
Waste
Coagulant Filter
Sludge Backwash
Waste
Pre-
Sedimentation
Basin
Flocculation
Rapid
Mix
Figure 4-1. Residuals sources in water treatment plants.
Filters
Final Sedimentation
Basin
it
-I *" ' *^\
Main 'i
", Water
* Treatment •
. Process
> Stream »
1 i
>V *;«\
Liquid portion
• • • • Solids portion
4 Further Liquid Heturn
" Treatment ' i
i i
i i
Recoverable Recoverable"
Wafer'"," '"Water '
•^- • . ^^-
•••.••; -Futltiet -, - """" "•" •"•'• Fur
_^ Nonrecoverable t TreMrttent -k Norirecoverable w -]-rea
r Water' " ' -or • , r ;_ water " c
ther.
tment
>r •
Disposal. Disposal
tfc
%
1 • • • "^^ Thickening • ^ Recoverv ' ™ r Disposal i >p Dewatering
<»*
' '
Underflow
1 Conditioning
• Equalization
• Transport
Figure 4-2. Residuals handling process categories.
Nonrecoverable water must either be disposed of or
subjected to further treatment.
• Other processes: Those that do not readily fit into a
category listed above, including equalization, chemi-
cal conditioning, and residuals conveyance.
Actual residuals handling facilities may use any or all of
these processes in different combinations. Figures 4-3A
and 4-3B depict a facility that uses collection, thickening,
and dewatering processes. An example of a facility with
only one process in operation would be a plant with a
sedimentation basin and no sludge collection system.
The basin is taken out of operation periodically to manu-
ally remove the solids.
4.2 Process Descriptions
4.2.1 Collection Processes
Collection processes are the means by which WTP
residuals are collected from the process unit in which
they were removed from the water. In the water treat-
ment process, residuals are removed from the process
stream by several different mechanisms. Inlet screens
remove larger pieces of debris (greaterthan 1 inch) from
the raw water source. Grit basins collect the coarsest,
densest material from the raw water source prior to
presedimentation. Presedimentation basins collect the
denser solids that do not require coagulation and floc-
culation for solids separation. Sedimentation basins pro-
mote gravity settling of solids particles to the bottom of
42
-------
Grit
OO
Grit Classifier
Grit Flow
To
Presedimentation
Basin
To Dewatering Process
Sedimentation Basin Used Water Flow
Figure 4-3A. Residuals handling process schematic: sedimentation basin used water flow (Peck et al., 1993).
Gravity
Thickeners
j
1
i
t
Thickened
Sludge
— 1£7
/
Decant
1
E(
fhickened
Sludge
qualization
Basins
_ Dewaterinq
Centrate _ . .
— Centrate
(Recoverable Water) I . "
^
p
C
Inte
ewa
entr
rim
fuges
Evaporation
Lagoons
Centrate (Non-recoverable
Water) |
Solids \ ^
Solar Drying
-^ Beds/Extendec
Drying Area
1
1
^ Partially Dewatered l^
Solids (If Necessary) |
Solids t^ ^
Decant I T
(Recoverable Water) (Non-recoverable Water)
Figure 4-3B. Residuals handling process schematic: solids dewatering (Peck et al., 1993).
Disposal
(Off Site)
a water column where accumulated solids are then
removed. Several different types of processes can be
used in the sedimentation mode, such as chain and
flight, suction, and circular collector units.
In the conventional treatment plant, filtration is generally
the last step in the removal of suspended solids. Solids
are removed by a bed of granular media (sand, anthra-
cite, and/or garnet) via straining, impingement, gravita-
tional settling, or adsorption. Solids are removed from
the bed through a backwash procedure.
4.2.2 Thickening
Residuals concentration, or thickening, processes begin
after clarification, sedimentation, filtration, or water sof-
tening processes. Concentration processes are critical
to the economical removal of solids from the treatment
process. Thickening has a direct effect on downstream
processes such as conditioning and dewatering, and
can make the difference between an efficient, economi-
cal operation and an inefficient, high-cost one. WTP
residuals are most commonly concentrated using grav-
43
-------
ity thickeners, but they can also be concentrated in
flotation thickeners or by gravity belt thickeners.
4.2.2.1 Gravity Thickening
Thickening of WTP residuals is most commonly per-
formed in gravity thickeners, which work only when the
specific gravity of the solids is greater than 1. In this
process, both carbonate and metallic hydroxide residu-
als are conveyed to gravity settling tanks at a flow rate that
allows the residuals sufficient retention time to settle.
Gravity thickeners can be either batch feed or continu-
ous flow. Residuals thickened in gravity thickeners may
require conditioning.
Thickener tanks (Figure 4-4) are generally circular and
are usually concrete, although small tanks can be made
from steel. They are typically equipped with rake mecha-
nisms to remove solids. The floors are conical in shape
with a slope of between 10 and 20 percent. This slope
enables the mechanism to more efficiently move solids
to the discharge hopper.
Metallic hydroxide residuals, which come from either
clarifier operations or backwashing of filters, thicken to
only approximately 1 to 3 percent solids at loadings of
4.0 Ib/day/ft2. The degree of thickening is generally de-
pendent on the hydroxide-to-total suspended solids
(TSS) ratio; high TSS solids can thicken to 5 to 30
percent solid. Carbonate residuals produced from water
softening processes settle readily and will thicken to
concentrations ranging from 15 to 30 percent solids at
loadings of 20 to 40 Ib/day/ft2 (Cornwell et al., 1987).
In a continuous feed thickening operation, the solids
slurry enters the thickener through ports in a column
located in the center of the tank. In theory, the solids are
distributed equally, both horizontally and vertically. The
solids settle to the bottom of the unit and the clarified
supernatant flows over discharge weirs located on the
periphery of the tank. These units are equipped with a
bottom scraper mechanism that rotates slowly, directing
the sludge to the drawoff pipe or sump near the bottom.
The thickener bottom is sloped to the center to help
collect the sludge. The slow rotation of the scraper also
prevents bridging of the solids.
Batch fill thickening tanks are often equipped with bot-
tom hoppers. Sludge flows into these tanks, usually from
a batch removal of solids from the sedimentation basin,
until the thickening tank is full. The slurry is allowed to
settle in a telescoping decant pipe, which may be con-
tinuously used to remove supernatant. The decant pipe
may be lowered as the solids settle, until the desired
solids concentration is reached, or until the slurry will not
thicken further. The solids are then pumped out of the
bottom hoppers for further treatment or disposal.
4.2.2.2 Flotation Thickening
Flotation thickening is a solids handling option for re-
siduals concentrates consisting of low-density particles.
Potential benefits include lower sensitivities to changes
in influent feed solids concentration and solids feed rate.
The process may also have more applicability for
sludges with high hydroxide components (greater than
40 percent by weight). While flotation has been used in
the European water industry, it has not been used for
long-term, large-scale thickening in the United States
(Cornwell and Koppers, 1990). The process is attracting
HANDRAILING
1" GROUT
INFLUENT
PIPE
BAFFLE
SUPPORTS
TURNTABLE
EFFLUENT
WEIR
"r"
BRIDGE
— L-
— r
t
/
<-
/
**.
r
n
-P
7-
/
1 i"
MAX. WATER SURFACE
/ 1'3-MIN.
LL
EFFLUENT
LAUNDER
TOP OF TANK
1%" BLADE
CLEARANCE
1 ft = 0.305 m
1 in = 2.54 cm
Figure 4-4. Gravity thickener cross-section (U.S. EPA, 1979b).
ADJUSTABLE
'SCRAPER SQUEEGEES
BLADES
SLUDGE
HOPPER
44
-------
interest currently as both a concentration process and
as a thickening process in the water treatment industry.
Flotation thickening can be performed through any of
three techniques.
• Dissolved air flotation (DAF): Small air bubbles (50
to 100 urn in diameter) are generated in a basin as
the gas returns to the vapor phase in solution after
having been supersaturated in the solution.
• Dispersed air flotation: Large gas bubbles (500 to
1,000 urn in diameter) are dispersed in solution
through a mixer or through a porous media.
• Vacuum flotation: Operates on a similar principle to
the DAF with the condition of supersaturation being
generated through a vacuum.
Each of these techniques uses air bubbles to absorb
particles which may then be floated to the water surface
for separation from the liquid stream. DAF is the most
typically used flotation system in the municipal waste-
water industry (U.S. EPA, 1979b).
In the DAF thickening process, air is added at pressures
in excess of atmospheric pressure eitherto the incoming
residual stream or to a separate liquid stream. When
pressure is reduced and turbulence is created, air in
excess of that required for saturation at atmospheric
pressure leaves the solution as the 50 to 100 um-sized
bubbles. The bubbles adhere to the suspended particles
or become enmeshed in the solids matrix. Because the
average density of the solids-air aggregate is less than
that of water, the agglomerate floats to the surface.
Water drains from the float and affects solids concentra-
tion. Float is continuously removed by skimmers.
Usually a recycle flotation system is used for concentrat-
ing metallic hydroxide residuals. In this type of system,
a portion of the clarified liquor (subnate) or an alternate
source containing only minimal suspended matter is
pressurized. Once saturated with air, it is combined and
mixed with the unthickened residual stream before it is
released to the flotation chamber. This system mini-
mizes high shear conditions, an extremely important
advantage when dealing with flocculent-type residuals
such as metallic hydroxides.
Several sources indicate that European facilities have
had success in concentrating hydroxide sludge to levels
between 3 to 4 percent solids (ASCE/AWWA, 1990;
Brown and Caldwell, 1990). These results appear to
include facilities that use flotation both as a concentra-
tion process (as an alternative to sedimentation) and as
a thickening process. Loading rates for hydroxide
sludges vary from 0.4 Ib/ft2/hr to 1.0 Ib/ft2/hr for facilities
achieving from 2 to 4 percent float solids concentration.
Hydraulic loading of DAF units is reported at less than
2 gpm/ft2 (Cornwell and Koppers, 1990).
The lack of historic operating data for this process indi-
cates the need for bench- and pilot-scale testing prior to
selection of the process.
4.2.2.3 Gravity Belt Thickeners
Although the thickening of hydroxide slurries can be
accomplished using gravity belt thickeners, this technol-
ogy is just beginning to be used. In this process, metallic
hydroxide sludge is discharged directly onto a horizon-
tal, porous screen (Figure 4-5). As the sludge moves
along the length of the screen, water is removed by
gravity. Solids concentrations of 2.5 to 4.5 percent can
be achieved using these thickeners. The gravity belt
thickening units are made up of a sludge inlet port,
drainage screen, scraper blades, discharge outlet for
water, and a discharge outlet for the thickened residuals.
4.2.2.4 Other Mechanical Thickening Processes
Although gravity belt thickening is the most common
thickening process, some mechanical devices used for
dewatering may also be applied to this process. Exam-
ples include the continuous-feed polymer thickener,
drum thickener, and centrifuges. Solid-bowl-type centri-
fuges have been used in several pilot-scale studies
evaluating residuals thickening. Full-scale operating
data on mechanical processes for water treatment sol-
ids thickening are not currently available.
4.2.3 Conditioning
Conditioning is a process incorporated into many residu-
als handling systems to optimize the effectiveness of the
dewatering process. Conditioning of WTP residuals is
generally done by either chemical conditioning or physi-
cal conditioning.
4.2.3.1 Chemical Conditioning
Chemical conditioning is included in most mechanical
thickening or dewatering processes. This conditioning
involves the addition of ferric chloride, lime, or polymer.
The type and dosage of chemical conditioner vary
widely with raw water quality, chemical coagulants, pre-
treatment, desired solids concentration, and thicken-
ing/dewatering process used. A recent publication
(Malmrose and Wolfe, 1994) identified typical ranges of
conditioner use for hydroxide sludges in various me-
chanical dewatering systems (see Table 4-1). Condition-
ing agents used for lime sludges are typically lower in
volume if used at all. Recorded use of conditioning
agents for solids dewatered in open air processes is also
minimal.
A wide variety of polymers are available for use in the
dewatering processes. The most successful polymers
used are anionicwith a high molecular weight. Polymers
can be obtained in a variety of dry and liquid emulsion
45
-------
Pressure Belt Hydraulic Cylinder
Support Rollers
_ _
Compressed Air^.. ........ ^
Woven Synthetic Fiber Belt
Flocculator
Air Actuated Pinch Rollers
Bottom Drain Pan
S!Z'5e|tWash spray Nozzies:
Conveyor
..•Filtration and Washwater Discharge
Figure 4-5. Gravity belt thickener cross section (Infilco Degremont, 1994).
Table 4-1. Typical Ranges of Conditioner Use for Hydroxide
Sludges in Various Mechanical Dewatering
Systems (after Malmrose and Wolfe, 1994)
Pyash precoat
Diatomaceous
earth precoat
Lime
Ferric chloride
Polymer
Filter Press Centrifuge
10lb/100ft2 —
6lb/100ft2 —
10-30% —
4-6 —
3-6 2-4
Belt Filter
Press
—
—
1-3
2-8
Note: All values are in units of Ib/ton dry solids unless noted otherwise.
forms. A system should be equipped to feed either form
(Malmrose and Wolfe, 1994). Chemical suppliers should
be asked for a chemical's NSF rating if process bypro-
duct water is to be returned to the treatment plant
stream.
4.2.3.2 Physical Conditioning
The following physical processes may also be used to
optimize thickening/dewatering effectiveness (Cornwell
and Koppers, 1990):
• Precoat or nonreactive additives: Some dewatering
systems, primarily vacuum filtration and pressure fil-
ters, use a precoat additive in the process, typically
diatomaceous earth.
• Freeze-thaw conditioning: This process may be ac-
complished through either an open-air process in cold
weather climates or through mechanical equipment.
• Thermal conditioning at high temperatures (350°F to
400°F) under high pressure (250 to 400 psig): This
conditioning process is typically effective when there
is a high organic content present in the solids.
4.2.4 Dewatering
4.2.4.1 Air Drying Processes
Air drying refers to those methods of sludge dewatering
that remove moisture either by natural evaporation,
gravity, or induced drainage. Most air drying systems
were developed for dewatering residuals produced from
wastewater treatment plants (WWTPs) but have since
been used for the dewatering of WTP residuals. Air
drying processes are less complex, easier to operate,
and require less operational energy than mechanical
systems. They are used less often, however, because
they require a great deal of land area, are dependent on
climatic conditions, and are labor intensive. The effec-
tiveness of air drying processes is directly related to
weather conditions, type of sludge, conditioning chemi-
cals used, and materials used to construct the drying bed.
Sand Drying Beds
Sand beds are commonly used to dewaterWTP residu-
als and have been used successfully for many years.
Dewatering on the sand bed occurs through gravity
drainage of free water (interstitial water in the residuals
slurry), followed by evaporation to the desired solids
concentration level. Figure 4-6 illustrates details of a
typical sand bed. In areas of high precipitation, covered
sand beds have been used.
Residuals on sand beds dewater primarily by drainage
and evaporation. Initially, water is drained through the
material, into the sand and removed through under-
drains. This step, normally a few days in duration, lasts
46
-------
GATE
Figure 4-6. Sand drying bed section (U.S. EPA, 1979b).
until the sand is clogged with fine particles or until all the
free water has drained away. A decanting process re-
moves any surface water. This decanting step can be
especially important for removing rain which, if allowed
to accumulate on the surface, can slow the drying proc-
ess. Water remaining after initial drainage and decanting
is removed by evaporation.
Sand beds are more effective for dewatering lime re-
siduals than residuals produced by coagulation with
alum. In both cases, however, conditioning the residual
slurry before discharging it into the sand bed helps the
dewatering process.
When designing a sand bed, the following factors should
be considered:
• Required solids concentration of the dewatered re-
siduals.
• Solids concentration of the residual slurry applied to
the bed.
• Type of residuals supplied (lime or alum).
• Drainage and evaporation rates.
The required solids concentration depends on the tech-
nical or regulatory requirements for final residuals
disposal.
The amount of water that can be removed by drainage
is strongly influenced by the type of residuals applied to
the bed. The rate of evaporation varies with local cli-
matic conditions and the solids surface characteristics.
Seasonal evaporation rates can be obtained from local
pan values. These values are tested and recorded by
the National Weather Service as measures of the local
evaporation rate. Because the crust that forms on the
surface of the sand bed inhibits evaporation, the pan
values must be adjusted when designing the sand bed.
An adjustment factor of 0.6 was experimentally derived.
Once cracking of the surface occurs, the evaporation
rate should again approach the pan value.
Thin layers of solids dry faster than a thick layer, but the
annual solids loading is of the depth of the individual
layers applied. Using too thin a layer has several disad-
vantages, including more frequent operation and main-
tenance, greater sand loss from the bed, and increased
costs.
To keep operation and maintenance costs as low as
possible, the design goal is to achieve the maximum
solids loading with the minimum number of application
and removal cycles.
Freeze-Assisted Sand Beds
Alum residuals have a gelatinous consistency that
makes them extremely difficult to dewater. By freezing
and then thawing alum residuals, the bound water is
released from the cells, changing the consistency to a
more granular type of material that is much easier to
dewater.
Freezing alum residuals changes the structure of the
residuals slurry and the characteristics of the solids
themselves. In effect, the solids matter is compressed
into large discrete conglomerates surrounded by frozen
water. When thawing commences, drainage occurs in-
stantaneously through the large pores and channels
created by the frozen water. Cracks in the frozen mass
also act as conduits to carry off the melt water.
Freezing can be done mechanically or naturally. Be-
cause of the high cost associated with mechanical sys-
tems, natural systems are used most frequently.
The maximum potential response during both the freez-
ing and thawing portions of the cycle can be obtained
by exposing the solids on uncovered beds. The drainage
water during thawing may move at a faster rate, and will
produce a greater volume than if applying the same
unconditioned solids to a conventional sand bed.
The critical operational requirement is that the solids
layer be completely frozen before the next layer is ap-
plied. Hand probing with a small pick or axe is the
easiest way to determine if this has been accomplished.
Solar Drying Beds
Until recently, paved beds used an asphalt or concrete
pavement on top of a porous gravel subbase. Unpaved
areas constructed as sand drains were placed around
the perimeter or along the center of the bed to collect
and convey drainage water. The main advantage of this
approach was the ability to use relatively heavy equip-
ment for solids removal. Experience showed that the
47
-------
pavement inhibited drainage, so the total bed area had
to be greater than that of conventional sand beds to
achieve the same results in the same period.
Recent improvements to the paved bed process include
a tractor-mounted horizontal auger, or other device, to
regularly mix and aerate the sludge. The mixing and
aeration break up surface crust that inhibits evaporation,
allowing more rapid dewatering than conventional sand
beds.
Vacuum-Assisted Drying Beds
This dewatering technology applies a vacuum to the
underside of rigid, porous media plates on which
chemically conditioned residuals have been placed. The
vacuum draws free water through the plates, retaining
sludge solids on top and forming a cake of fairly uniform
thickness.
Cake solids concentrations of 11 to 17 percent can be
obtained on a vacuum-assisted drying bed, depending
on the type of solids being dewatered and the kind and
amount of conditioning agents used.
Problems with this method stem from two sources: im-
proper conditioning and plate cleaning. The wrong types
of polymer, ineffective mixing of polymer and solids
slurry, and incorrect dosage result in poor performance
of the bed. Overdosing of polymer may lead to progres-
sive plate clogging and the need for special cleaning
procedures to regain plate permeability. Plate cleaning
is critical. If not performed regularly and properly, the
media plates are certain to clog and the beds will not
perform as expected. Costly, time-consuming cleaning
measures are then required. Removal of dewatered
solids tends to be a constant, time-consuming operation.
Wedgewire Beds
The wedgewire, or wedgewater, process is physically
similarto the vacuum-assisted drying beds. The medium
consists of a septum with wedge-shaped slots approxi-
mately 0.01 inches (0.25 mm) wide. This septum serves
to support the sludge cake and allow drainage through
the slots (Figure 4-7). Through a controlled drainage
CONTROLLED DIFFERENTIAL HEAD IN VENT
BY RESTRICTING RATE OF DRAINAGE
- PARTITION TO FORM VENT
SLUDGE
sis
cO-J " ~ '
^Cv^i^riOQ SLUDGE a°rtrtV ^J^M^.6^
^yo^oT^fel^
WEDGEWIRE SEPTUM-
OUTLET VALVE TO CONTROL TO CONTROL .
RATE OF DRAINAGE
process, a small amount of hydrostatic suction is ex-
erted on the bed, thus removing water from the sludge.
4.2.4.2 Lagoons
Lagoons are one of the oldest processes used to handle
water treatment residuals. Lagoons can be used for
storage, thickening, dewatering, or drying. In some in-
stances, lagoons have also been used for final disposal
of residuals.
The lagoon process involves discharging residuals into
a large body of water. Solids settle to the bottom and are
retained in the lagoon for a long period. Sedimentation
and compression are two mechanisms used to separate
the solids from the liquid. Liquid can be decanted from
various points and levels in the lagoon. Evaporation may
also be used in the separation process if the residuals
are to be retained in the lagoon for an extended period.
The traditional lagoon consists either of earthen berms
built on the ground surface, or of a large basin exca-
vated from the ground. Various types of systems are
installed in lagoons to decant the supernatant and, ulti-
mately, drain the lagoon. State and local regulations
have become more stringent about preventing ground
pollution, and in some areas, laws affect the design of
WTP residual lagoons. Liners made of high-density
polyethylene (HOPE), leachate collection systems, and
monitoring wells are becoming common features of la-
goon designs (see Figure 4-8). Lagoon depth typically
varies from 4 to 20 feet and the surface area ranges from
0.5 to 15 acres (Cornwell et al., 1987).
The effectiveness of lagoons in concentrating solids
typically depends on the method of operation. For metal
hydroxide solids retained in a lagoon for 1 to Z months,
operating the lagoon at full water depth without further
air drying of the solids typically results in a solids con-
centration of 6 to 10 percent. Solids concentrations of
20 to 30 percent may be achieved for lime sludge under
the same conditions. Some facilities have achieved sol-
ids concentrations above 50 percent by stopping the
influent into the lagoon and allowing drying through
WATER SURFACE
SYNTHETIC LINER
Figure 4-7. Wedgewire drying bed cross section (U.S. EPA,
1979b).
COMPACTED SAND
GUNITE
Figure 4-8. Dewatering lagoon cross section.
48
-------
evaporation. This process may require well over a year
of holding the solids in the dewatering lagoon.
The lagoon process may incorporate certain modifica-
tions similar to sand and/or solar drying bed systems.
Adaptation of a freeze-thaw process to lagoons is com-
mon in northern climates.
4.2.4.3 Mechanical Dewatering Equipment
Belt Filter Presses
Belt filter press design is based on a very simple con-
cept. Sludge sandwiched between two porous belts is
passed over and under rollers of various diameters. As
the roller diameter decreases, pressure is exerted on the
sludge, squeezing out water. Although many different
belt filter press designs are used, they all incorporate the
same basic features—a polymer conditioning zone, a
gravity drainage zone, a low pressure zone, and a high
pressure zone.
The polymer conditioning zone can be either a small
tank with a variable speed mixer (approximately 70 to
100 gallons) located 2 to 3 feet from the press, a rotating
drum attached to the top of the press, or an in-line
injector. Press manufacturers usually supply the poly-
mer conditioning unit with the belt filter press.
The gravity drainage zone is a flat or slightly inclined belt
that is unique to each press model. In this zone, solids
are dewatered by the gravity drainage of the free water.
If the solids do not drain well in this zone, problems such
as solids extruding from between the belts and binding
the belt mesh can occur.
The low pressure zone, also called the wedge zone by
some manufacturers, is the area where the upper and
lower belts come together with the solids in between,
thus forming the solids "sandwich." The low pressure
zone prepares the solids by forming a firm cake able to
withstand the forces within the high pressure zone.
In the high pressure zone, forces are exerted on the
solids by the movement of the upper and lower belts as
they go over and under a series of rollers of decreasing
diameters. Some manufacturers have an independent
high pressure zone that uses belts or hydraulic rams to
further increase the pressure on the solids, thus produc-
ing a drier cake.
Belt filter presses can be used to dewaterthe residuals
produced from either lime softening processes or alum
coagulation. Performance, however, can be affected by
many variables, including solids type and charac-
teristics, conditioning requirements, pressure require-
ments, and belt speed, tension, type, and mesh.
The type and characteristics of the solids to be dewa-
tered are very important in determining the effectiveness
of belt press dewatering. Lime softening residuals de-
water very readily and are efficiently dewatered on belt
filter presses. Since these residuals are more granular
in nature, they can withstand high pressures and easily
dewater to 50 to 60 percent solids.
Conversely, alum residuals are more difficult to dewater
because of the gelatinous nature of the solids. The
dewatering results are variable, depending on the
source of the water coagulated with alum. An almost
pure alum residual is the most difficult to dewater and
must be dewatered at low pressures. The pure alum
residual will dewater to 15 to 20 percent solids. If the
source of the water is a river, and silt and sand are mixed
in with the aluminum hydroxide, the slurry will be more
easily dewatered, with the resulting cake solids between
40 and 50 percent. Even this type of alum residual,
though, must be dewatered at low pressure.
To ensure optimum performance on a belt filter press,
lime and alum solids must first be conditioned with
polymer. Polymer produces a large, strong floe that
allows free water to drain easily from the solids in the
gravity drainage zone of the belt filter press. A typical
belt filter press is shown in Figure 4-9.
Centrifuges
Centrifugal dewatering of solids is a process that uses
the force developed by fast rotation of a cylindrical bowl
to separate solids from liquids. When a mixture of solids
and water enters the centrifuge, it is forced against the
bowl's interior walls, forming a pool of liquid that sepa-
rates into two distinct layers. The solid cake and the
liquid centrate are then separately discharged from the
unit. Both types of centrifuges used to dewater WTP
residuals—basket and solid-bowl—use these basic
principles. They are differentiated by method of solids
feed, magnitude of applied centrifugal force, cost, and
performance.
Although commonly used in the past, basket centrifuges
are now rarely used to dewater WTP residuals because
they are a batch process, are more difficult to operate,
and do not perform as well as solid-bowl centrifuges.
The solid-bowl centrifuge, also known as the decanter,
conveyor, or scroll centrifuge, is characterized by a ro-
tating cylindrical conical bowl (Figure 4-10). A helical
screw conveyor fits inside the bowl with a small clear-
ance between its outer edge and the inner surface of the
bowl. The conveyor rotates at a lower or higher speed
than that at which the bowl is rotating. This difference in
revolutions per minute (rpm) between the bowl and
scroll is known as the differential speed and causes the
solids to be conveyed from the zone of the stationary
feed pipe, where the sludge enters, to the dewatering
beach, where the sludge is discharged. The scroll
pushes the collected solids along the bowl wall and up
49
-------
Figure 4-9. Belt filter press (Andritz Ruthner, 1994).
Cover
Differential Speed
Gear Box
Main Drive Sheave
I
Rotating
Conveyor
I
Centrate
Discharge
*
Feed Pipes
(Sludge and
Chemical
Bearing
Base Not Shown
Sludge Cake
Discharge
I '
Figure 4-10. Solid-bowl-type centrifuge schematic (Cornwell et al., 1987).
the dewatering beach at the tapered end of the bowl for
final dewatering and discharge.
The differential speed between the bowl and conveyor
is maintained by several methods. Earlier designs used
a double output gear box that imparted different speeds
as a function of the gear ratio. It was possible to vary
the output ratio by driving two separate input shafts.
Eddy current brakes are also used to control the differ-
ential. The latest designs can maximize solids concen-
tration through automatic speed control as a function of
conveyor torque.
The solid-bowl centrifuge operates in one of two modes:
counter-current or continuous concurrent. The major
differences in design are the location of the sludge feed
ports, the removal of centrate, and the internal flow
patterns of the liquid and solid phases.
For the most part, solid-bowl centrifuges use organic
polyelectrolytes for flocculating purposes. Polymer use
50
-------
improves centrate clarity, increases capacity, often im-
proves the conveying characteristics of the solids being
discharged, and often increases cake dryness. Cake
solids concentrations vary considerably, depending on
the type of alum residuals being dewatered and the
source of the water. High turbidity water yields much
higher cake solids concentrations than does low turbid-
ity water. Lime residuals with high cake solids concen-
trations dewatervery easily. Polymer dosages also vary,
depending on the source of water and the magnesium
and calcium concentrations.
The machine variables that affect performance include:
• Bowl diameter
• Scroll rotational speed
• Bowl length
• Scroll pitch
• Bowl flotational speed
• Feed point of sludge
• Beach angle
• Feed point of chemicals
• Pool depth
• Condition of scroll blades
Many of these variables are preset by the manufacturer,
although some can be adjusted by the operator. Atypical
solid-bowl centrifuge is pictured in Figure 4-11.
Pressure Filters
Filter presses for dewatering were first developed for
industrial applications and, until development of dia-
phragm presses, were only slightly modified for munici-
pal applications. The original models of the press were
sometimes called plate and frame filters because they
consisted of alternating frames and plates on which filter
media rested or were secured. There are currently 20
U.S. installations of filter presses being used to dewater
residuals.
The equipment commonly used to dewater WTP residu-
als is either the fixed-volume recessed plate filter or the
diaphragm filter press. The diaphragm filter press was
introduced within the last 10 years.
A recessed plate filter press consists of a series of
plates, each with a recessed section that forms the void
into which the solids are pumped for dewatering. Filter
media are placed against each wall and retain the solids
while allowing passage of the filtrate.
The surface under the filter media is specifically de-
signed to ease the passage of the filtrate while holding
the filter cloth. Solids are pumped with high-pressure
pumps into the space between the two plates and indi-
vidual pieces of filter media. The filtrate passes through
the cake and filter media and out of the press through
special ports on the filtrate side of the media.
The pumping of solids into the press continues up to a
given pressure. When solids and water fill the space
between the filter cloths and no further filtrate flow oc-
curs, pumping is stopped. The press is then opened
mechanically and the cake is removed.
The diaphragm filter press is a machine that combines
the high pressure pumping of the recessed plate filter
press with the capability of varying the volume of the
press chamber. A flexible diaphragm is used to com-
press the cake held within the chamber. A two-step
process is used, with the compression of the diaphragm
taking place after the initial pumping stage. The release
of water at low pressures helps maintain the integrity of
the floe. After water release appears complete following
the initial filling period, pumping is stopped and the
diaphragm cycle is initiated. The diaphragm pressure is
applied, using either air or water on the reverse side of
the diaphragm. Pressures of up to 200 to 250 psi (1,380
to 1,730 kPa) are applied at this stage for additional
dewatering.
When dewatering alum residuals, lime is added as a
conditioning agent. Cake solids ranging from 30 to 60
percent can be achieved, depending on the source of
the alum residual. Lime softening residuals do not need
any conditioning and can be dewatered to 50 to 70
percent solids.
Precoat is generally not needed when inorganic condi-
tioning chemicals, particularly lime, are used. Precoat is
normally used in cases where particle size is extremely
small, or when considerable variability in filterability and
substantial loss of fine solids to and through the filter
media are anticipated. When substantial quantities of
lime are used, cloth washing may require both an acid
and a water wash. A medium is needed, therefore, that
is resistant to both acid and alkaline environments.
Vacuum Filters
Vacuum filtration was the most common means of me-
chanically dewatering WTP residuals until the mid-
1970s. It has been used to some extent in the water
treatment industry to dewater lime residuals. Alum solids
have not been successfully dewatered on vacuum filters.
A vacuum filter consists of a horizontal cylindrical drum
(Figure 4-12) which rotates while partially submerged in
a vat of solids slurry. The filter drum is partitioned into
several compartments or sections. Each compartment
is connected to a rotary valve by a pipe. Bridge blocks
in the valve divide the drum compartments into three
zones, which are referred to as the cake formation zone,
the cake drying zone, and the cake discharge zone. The
filter drum is submerged to roughly 20 to 35 percent of
51
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Figure 4-11. Solid-bowl-type centrifuge (Alfa-Laval Sharpies, 1994).
its depth in a vat of solids; this submerged zone is the
cake formation zone. Vacuum applied to this submerged
zone causes the filtrate to pass through the media,
retaining solids particles on the media. As the drum
rotates, each section is successively carried through the
cake formation zone to the cake drying zone. This latter
zone begins when the filter drum emerges from the
sludge vat. It represents from 40 to 60 percent of the
drum surface and ends at the point where the internal
vacuum is shut off. At this point, the sludge cake and
drum section enter the cake discharge zone, where the
sludge cake is removed from the media. Figure 4-12
illustrates the various operating zones encountered dur-
ing a complete revolution of the drum.
No conditioning is required when dewatering lime re-
siduals. As with all types of mechanical dewatering
equipment, optimum performance depends on the
type of solids and how the filter is operated. Selection
of vacuum level, degree of drum submergence, types
of media, and cycle times are all critical to optimum
performance.
4.2.5 Drying
The drying of dewatered WTP residuals has historically
revolved around the economics of reducing transporta-
tion and disposal costs by reducing solids volume and
water content. Drying to solids concentrations greater
than 35 percent is becoming a regulatory issue in many
areas. For instance, the State of California requires that
the solids concentration of a WTP waste be at least 50
percent before disposal in a landfill. Similar to the dewa-
tering process, the drying process may be carried out
through either open air means or through mechanical
devices.
4.2.5.1 Open Air Drying
Any of the solar drying or lagoon procedures may be
applied to the drying process. Drying depends on the
evaporation mechanism. An extended drying process
may require years to achieve the desired solids concen-
trations, although various innovations have been used
with extended drying to accelerate the drying process.
One such device uses specially mounted tractors to
furrow and mix the solids to increase their exposure to
sun and air.
4.2.5.2 Mechanical Drying
Of the mechanical drying techniques presented in the
discussion of dewatering only, the filter press has shown
the ability to consistently produce solids concentrations
52
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4.2.6 A dditional Residuals Handling
Processes
CLOTH CAULKING
STRIPS-
AUTOMATIC VALVE
DRUM
FILTRATE PIPING
.CAKE SCRAPER
SLURRY AGITATOR
VAT
AIR BLOW-BACK LINE
SLURRY FEED
CUTAWAY VIEW OF A DRUM OR SCRAPER-TYPE
ROTARY VACUUM FILTER
Figure 4-12. Vacuum filter (U.S. EPA, 1979b).
greater than 35 percent. The ability of this process to
achieve solids concentrations greater than 50 percent,
as would be necessary in California, is not proven.
Thermal drying of solids from WTPs has not been prac-
ticed on a full-scale operation basis in the United States.
Cornwell and Koppers (1990) identify the potential for
using steam-operated dryers to raise the solids concen-
tration of a dewatered metal hydroxide sludge to the 65
to 75 percent range, but this process is untried in full-
scale operation. Although many thermal processes have
been used with wastewater solids, including the Best
Process, the Carver Greenfield Process, and various
forms of incineration, they are more applicable to a solid
with a high organic content. No conclusive information
is available to evaluate the effectiveness of mixing
wastewater and water solids together before feeding
into a thermal process.
4.2.6.1 Conveyance
Movement of a solids stream from one process to either
another process or to a disposal point may be accom-
plished by gravity through a pipeline, pumping through
a pipeline, transporting along a mechanical conveyor, or
transporting by vehicle. The type of conveyance used
depends on the form and concentration of the solids
stream and on the transport distance.
4.2.6.2 Equalization Basins
Equalization basins even out the flow of waste streams.
Equalization takes place to prevent surges of water from
being reintroduced at the head of the treatment plant or
at inlets to other residuals handling processes. Equali-
zation basins can also be used to equalize peak daily,
weekly, or monthly loads.
4.3 Residuals Handling Process
Performance
4.3.1 Process Performance
A preliminary screening of processes may be based on
the percent concentrations that the processes can
achieve. This section provides typical ranges of values
for percent solids that each thickening and dewatering
process may generate; insufficient information exists for
drying processes. Many factors can influence the per-
formance of the process: the type of solids, charac-
teristic of solids, solids concentration of the influent,
climatological conditions for open air processes, vari-
ations in influent flow rates, and type and dosage of
chemical conditioner. The values presented here should
only be used for screening purposes. The following
value ranges are used to suggest whether thickening,
dewatering, or drying processes should be used to proc-
ess metal hydroxide solids:
Desired Residual
Metal Hydroxide
Solids Concentration
Suggested Process
8-35%
>35%
Thickening
Dewatering
Drying
These processes will generally yield a higher percent
solids concentration for a lime sludge than for a metal
hydroxide sludge. For example, a centrifuge may only
dewater a metal hydroxide sludge to a 15 percent solids
concentration, while the lime sludge is dewatered to 50
percent. When selecting a handling process for a lime
softening WTP, the following concentrations apply:
53
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Desired Residual
Lime Solids
Concentration
Suggested Process
<30%
30-60%
>60%
Thickening
Dewatering
Drying
4.3.2 Comparison of Thickening Processes
A comparison of the various thickening processes, in-
cluding solids loading on the units and the solids con-
centration of various types of residuals, is shown in
Table 4-2.
4.3.3 Comparison of Dewatering Processes
A comparison of dewatering process performance is
shown in Table 4-3.
4.4 Developing Preliminary Residuals
Processing Alternatives
Many unit process combinations are capable of meeting
any set of residuals processing requirements. Most
facilities need to consider the addition of residuals proc-
Table 4-2. Comparison of Thickening Processes (Cornwell et
al., 1987; Cornwell and Koppers, 1990; Brown and
Caldwell. 1990)
Solids
Solids Concentration
Process Residual Loading (%)
Gravity
Gravity
Flotation
Gravity belt
Carbonate
Hydroxide
Hydroxide
Hydroxide
30 Ib/day/ft2
4.0 Ib/day/ft2
20 Ib/day/ft2
N/Aa
15-30
1-3
2-4
2.5-4.5
a No solids loading rate is shown for the gravity belt thickener as it is
not comparable to the values for the gravity thickener and the DAF
unit. Care must be taken in the use of solids loading and percent
solids values for both the flotation and gravity belt thickening, due
to the absence of operating experience for those processes.
Table 4-3. Comparison of Dewatering Processes (Cornwell et
al., 1987)
Solids Concentration (%)
Process
Gravity thickening
Scroll centrifuge
Belt filter press
Vacuum filter
Pressure filter
Diaphragm filter press
Sand drying beds
Storage lagoons
Lime Sludge
15-30
55-65
10-15
45-65
55-70
N/A
50
50-60
Coagulant
Sludge
3-4
20-30
20-25
25-35
35-45
30-40
20-25
7-15
essing, however, because of increased regulatory re-
quirements, changes in finished water-quality goals, in-
creased external disposal costs, and community
relations issues. Two technical factors are used to de-
termine the residuals processing requirements fora util-
ity. The most definitive is the solids concentration of the
residual flow stream. The second factor is the solids
concentration required for different types of residuals
disposal strategies.
A water utility must identify preliminary combinations of
unit processes that can achieve generic residual proc-
essing requirements according to a limited set of selec-
tion parameters. The approach needed to achieve the
goal includes these steps:
1. Define the fundamental information needed, attempt-
ing to identify a preliminary residual processing al-
ternative.
2. Define a methodology of using the fundamental in-
formation to make a preliminary selection of a residu-
als processing alternative that has the potential of
achieving the desired needs.
3. Present a Preliminary Residuals Processing Selec-
tion Matrix that can be used with other fundamental
information to make a preliminary selection.
4.4.1 Residuals Processing Requirements
To identify the ideal combination of unit processes for a
preliminary residuals processing alternative, the specific
requirements of the residuals processing system must
first be defined. To do this, information must be obtained
on residuals disposal limitations, quantity and quality of
residuals sources, resource recovery potential, and re-
siduals mass balance.
4.4.1.1 Residuals Disposal Limitations
Often, the ultimate method of residuals disposal deter-
mines the limitations, which in turn define the process
design requirements. The percent solids content of a
residual is the primary criterion used to define the ac-
ceptable limits of a disposal option. Of course, landfill
and land application disposal options can be accom-
plished over a wide range of solids content, but both
disposal options have different equipment requirements
at the low and high solids limits of their ranges. The
following tasks will help establish the disposal limitations
that a water utility must consider for further evaluation
of residual process alternatives:
• Identify available residuals disposal alternatives: The
six most common methods of WTP residuals disposal
used in the water industry are:
- Land application
- Landfilling (monofill)
54
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- Direct stream discharge
- Landfilling (co-disposal)
- Discharge to sewer
- Residual reuse
• Identify disposal limitations for each alternative: The
normal range of acceptable residual solids content
for the six common methods of disposal are:
- Land application, <1% to 15% solids
- Landfilling (co-disposal), <15 to 25% solids
- Landfilling (monofill), >25% solids
- Discharge to sewer, <1 % to 8% solids
- Direct stream discharge, <1% to 8% solids (Note:
Allowable solids concentration for this disposal
method may be lower than 8 percent due to regu-
latory requirements or sewerage concerns such as
deposition.)
- Residual reuse, <1% to >25% solids
• Identify external disposal costs, if they apply: Dis-
posal in a co-disposal municipal landfill may involve
a per unit weight tipping fee levied by an agency
external to the water utility. A user charge can be
assessed for discharges to a sewer, based on flow
rate units and/or the combination flow rate and sus-
pended solids concentrations. In some instances of
residuals reuse, the water utility pays a fee to the
user to cover the additional costs of special handling
or the difference in production costs associated with
accommodating sludge over a more traditional mate-
rial.
4.4.1.2 Quantity and Quality of Residuals
Sources
For many water utilities, monitoring the quantity and
quality of residuals sources either has not been done,
or has not achieved the same level of accuracy or
frequency as has monitoring of the finished water. This
deficiency may require that additional effort and time be
spent to collect the following information:
• Residuals sources: The typical residuals sources as-
sociated with conventional WTPs are:
- Headworks/bar screens
- Presedimentation basins
- Filter backwash
- Grit basins
- Sedimentation basins
- Filter-to-waste
• Flow rates and quantities of residuals sources: Flow
rate data collected for each residuals source should
include the following:
- Maximum flow rate
- Average flow rate
- Maximum volume per release event
- Frequency of events
- Maximum number of events per day
- Potential for concurrent events
- Minimum flow rate
- Average volume of release
- Minimum volume per event
- Average event duration
• Quality of each residuals source: The primary quality
parameter to monitor is percent solids which, in ana-
lytical terms, represents total suspended solids. Other
parameters that should be analyzed on a limited ba-
sis are:
- Aluminum and/or iron
- Total dissolved solids
- Trihalomethane formation potential
- Trace metals
- Toxicity Characteristic Leachate Procedure (TCLP)
- pH
- Total organic carbon
4.4.1.3 Resource Recovery Potential
Although standard water conservation strategies sup-
port the recovery of reusable residuals, the value of
recycle water is being challenged by the potential risks
of recycling infectious organisms, heavy metals, manga-
nese, and DBPs. Typical recycling of untreated residu-
als streams (e.g., backwash and filter-to-waste
residuals) to the plant influent may result in the accumu-
lation of these contaminants in the treatment processes.
Little documentation as to the extent of this is currently
available. Because of these concerns, the value of water
continues to increase with time. The recovery potential
for reusable residuals streams should be evaluated us-
ing the following procedure:
• /Assess the value of recovered water: Essentially, the
value of recovered water depends on the value of
raw water and the relative abundance of supply. Es-
tablish whether the cost of recovery is justified.
• Identify residuals sources easily recovered: The
backwash and filter-to-waste residuals streams gen-
erally comprise the largest volume of residuals gen-
erated with the lowest percent solids concentration.
Treatment of these residual streams is usually justi-
fied for the value of the water recovered. Other re-
siduals streams need to be evaluated closely for their
potential effect on finished water quality.
• Identify residuals sources unsuitable for recovery:
The most difficult residuals streams to justify are the
55
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sidestreams of the mechanical dewatering proc-
esses, which usually contain many components that
are not desirable to return to the plant.
4.4.1.4 Residuals Mass Balance
The most valuable exercise in evaluating the residuals
generated at a WTP is the development of a mass
balance. A mass balance is a theoretical accounting of
the water and solids content that come into a plant;
solids added to the water; and the water and solids
content that come out of the plant in the finished water
and residuals streams. This assessment must include
the effects that normal variations in raw water quality
and associated chemical feed rates have on residuals
production rates. The objective of the mass balance is
to specifically define the following parameters, which
become more useful in further evaluations:
• Maximum, minimum, and average solids production
rates for the raw water and each residuals side
stream in terms of percent solids, flow rates, and total
solids produced per million gallons of water treated.
• Allowable return residuals stream limits in terms of
hydraulic and percent solids limit (e.g., maximum
backwash return to plant influent should not exceed
5 percent of operating production capacity).
• Allowable solids content in the finished water.
• Allowable flow rate and solids content for available
residuals disposal options.
• Required residuals processing efficiency for each re-
sidual stream (based on the allowable return limits,
effluent limits, and disposal limits for each residual
stream).
The product of this exercise is the identification of po-
tential solids content objectives for each residual stream
process.
4.4.2 Preliminary Selection of Residuals
Processing Alternatives
The next step in developing a preliminary residuals
processing alternative is to select a unit process or
combination of unit processes that can fulfill the defined
processing requirements. There are four general types
of criteria on which the selection process is based.
These are:
• Specific problem-based criteria
• Residuals disposal-based criteria
• Solids concentration-based criteria
• Other selection criteria
In the event that the problem-specific approach does not
apply, the secondary level of selective review addressed
the available disposal methodology. The third selective
review focuses on the residuals solids concentration
categories.
The Preliminary Residuals Processing Selection Matrix
shown in Table 4-4 provides a finite set of unit process
combinations categorized according to three ranges of
residual solids concentrations that they would be used
to treat.
The rules of selection generally follow the basic premise
that most water utilities will want to minimize the capital
and labor costs of residuals processing. The preliminary
selection should attempt to find the lowest solids con-
tent, operationally simple, single-unit process that can
fulfill the requirements. The preferred alternatives, from
best to worst, are:
• Low solids; simple operations; single unit process.
• Low solids; simple operations; combined unit process.
• Low solids; complex operations; single unit process.
• Low solids; complex operations; combined unit process.
• Medium solids; simple operations; single unit process.
• Medium solids; simple operations; combined unit
process.
• Medium solids; complex operations; single unit process.
• Medium solids; complex operations; combined unit
process.
• High solids; simple operations; single unit process.
• High solids; simple operations; combined unit process.
• High solids; complex operations; single unit process.
• High solids; complex operations; combined unit
process.
The following approach can be used to select a pre-
liminary residuals processing alternative that can be
evaluated in detail. Site-specific factors such as land
availability, climate, community, and environmental con-
cerns will play a significant role in the selection process.
4.4.2.1 Specific Problem-Based Selection
At the first level of selective review a WTP operation
must consider the following residuals processing issues:
• Regulatory related issues: These issues result from
the ever-changing regulatory environment. Typical
concerns are land application and landfill disposal
regulations.
• Finished water-quality issues: With the recent publi-
cation of the draft Disinfection/Disinfection Byproduct
Rule (D/DBP), the most prevalent concern facing the
water industry is how to deal with the residuals bypro-
ducts of enhanced coagulation and the increased
56
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Table 4-4. Preliminary Residuals Processing Selection Matrix
en
Problem-Specific Alternative Categories
Residual Solids
Concentration
Categories
Low solids content
(<1 to 8%) by dry
weight
Medium solids
content (<8 to 25%)
Residuals Disposal
Alternative
Categories
Direct discharge
• To source water
• To water of USA
• Intermittent stream
Sewer disposal
Land application
• Agricultural
• Forest land
• Disposal site
Residual reuse
• Landscape tree
nursery
• Irrigation of turf grass
Land application
• Disposal
• Agricultural
• Forest
Residual reuse
• Sod amendment for
turf farms
• Landscape tree
nursery
• Coagulant recovery
Landfill
• Co-disposal with
municipal solid waste
(low moisture content
refuse)
Regulatory Related
Issues
NPDES permit for direct
discharge
Water supplier policy
change on return water
quality (i.e., "zero
discharge")
Residual disposal
regulations (if applicable)
Aquifer protection
requirements
Residual disposal
regulation (if applicable)
Residual reuse
regulations on
agricultural land
Landfill operation
requirements
Disposal of hazardous
waste byproducts from
coagulant recovery
Finished Water
Quality Issues
Increased sludge
production due to
enhanced
coagulation (EC)
Increased volume of
residuals due to
implementation of
"filer-to-waste"
Concern for
increased arsenic
concentrations
associated with EC
arsenic removal
Increased concern
with recycling of
infectious organisms
in the recovered
water
Increased sludge
production due to
EC
Potential for
hazardous waste
classification with
arsenic
Organics, color,
and heavy metal
concentrations in
recovered coagulant
Concern with
recycling of
infectious organisms
in recovered water
Disposal
Economic Issues
Change in sewer
service charges for
sludge disposal
Restrictions on
solids content in
sludge for sewer
disposal
Land application
disposal requires
nutrient content
augmentation
Loss of market for
reuse product
Limit on minimum
solids content
Increase in tipping
Community
Relation Issues
"Not in my back
yard" syndrome
(NIMBY)
Potential odors
Concern with traffic
of transport vehicles
Concern for risk of
incidental exposure
Concern for aerial
dispersion of
biological
contaminants
General
environmental
concerns of public
NIMBY
Potential odors
Noise pollution with
fee per ton at landfill sludge handling
Loss of reuse
product market
Future refusal to
accept sludge at
landfill
Land application
may require nutrient
augmentation
equipment
Traffic concerns
Incident exposure
risk
Environmental
concerns
Single Unit Process
Alternatives"
Simple
Operations
Direct discharge
from process
basin (DDPB)
Lagoon (LAG)
Sand drying bed
(SDB)
Solar drying basin
Complex
Operations
Gravity thickener
(GT)h
Dissolved air
flotation thickener
(DAF)h
Mechanical
thickening (MT)d'h
with decant (DB/D) Vacuum assisted
Wedge wire filter
bed (WFB)
LAG
SDB
DB/D
WFB
plate filter bed
(VAFB)ah
Backwash water
sedimentation
basin (BWSB)C
MTd
VAFB9
Mechanical
Dewatering (MDf
Combined Unit Process Alternatives3
Simple Operations
DDPB + residuals pump
station (PS)
Complex Operations
PS + GTh
PS + DAFh
PS + LAG + decant pump PS + MI*"
station (DPS)
PS + DB/D + DPS
PS + WFB + DPS
PS + SDB + DPS
Backwash recovery pump
station (BRPS)C
Equalization basin and
pump station (EB/PS)0
PS + LAG + DPS
PS + SDB + DPS
PS + DB/D + DPS
PS + WFB + DPS
BRPS + LAG + DPSc
PS + VAFBah
BRPS + BWSBC
EB/PS + GTc'h
PS GT + MTd'h
PS DAF + MTd'h
PS VAFBah
PS GT + MDe'h
PS DAF + MDe'h
PS MTd
PS MDe
PS LAG + DPS + MTd
PS LAG + DPS + MDe
EB/PS + GT + MDc'e'h
BRPS + LAG + DPS + MTc'd
-------
Table 4-4. Preliminary Residuals Processing Selection Matrix (Continued)
en
oo
Problem-Specific Alternative Categories
Residual Solids
Concentration
Categories
High solids content
(>25%)
Residuals Disposal
Alternative
Categories
Landfill
• Monofill
• Use as landfill cover
extender
Residual reuse
• Coagulant recovery
• Integrated into
masonry products
• Filler in Portland
cement
Regulatory Related
Issues
Landfill design
requirements
Landfill operation
requirements
Disposal of hazardous
waste byproduct from
coagulant recovery
Residual reuse
requirements (if any)
Finished Water Disposal
Quality Issues Economic Issues
Increased sludge Future refusal to
production due to EC accept sludge at
Need to segregate landfill as cover
unrecoverable extender
sidestreams of high Refusal to accept
solids unit processes future sludge in
Potential hazardous landfill
classification of Loss of reuse
sludge due to product market
arsenic and other
metal concentrations
Community
Relation Issues
NIMBY
Traffic concerns
Noise pollution from
dewatering
equipment
Long-term
environmental
concerns
Single Unit Process
Alternatives'1
Simple Complex
Operations Operations
LAG + extended VAFP + EDh
drying activities MDe
(ED)
SDB + ED
DB/D + ED
WFB + ED
Combined Unit Process Alternatives3
Simple Operations Complex Operations
PS + LAG + DPS + ED PS LAG + DPS + MT + EDAd
PS + SDB + DPS + ED PS
PS + DB/D + DPS + ED PS
PS + WFB + DPS + ED PS
PS + LAG + DPS + PS
extended drying area PS
(EDA) PS
PS + SDB + DPS + EDA PS
LAG + DPS + MDe
GT + DPS + MT + EDAd
GT + DPS + MDe
DAF + DPS + MT + EDAd
DAF + DPS + MDe
MT + MDd'e
MD + EDA"
PS + DB/D + DPS + EDA EB/PS + GT + MDc'e'h
PS + WFB + DPS + EDA EB/PS + DAF + MDc'e'h
BRPS + LAG + DPS + BRPS + LAG + DPS + MDc'e
EDA BRPS + LAG + DPS + MT + EDAc'd
a Assumes residuals collection systems exist in process basins with gravity flow to residual processing and excludes sludge storage, transport, and disposal related equipment.
b Assumes residuals collection systems exist in process basins with gravity flow to residuals pump station and excludes sludge storage, transport, and disposal equipment.
0 These alternatives are additional unit processes necessary to accommodate backwash flow rates.
d Mechanical thickening includes gravity belt thickeners, centrifuges, etc.
e Mechanical dewatering includes belt filter presses, centrifuges, filter presses, etc., plus cake handling equipment.
f This combination offers good potential for optimum recovery of used water.
9 This combination is commonly used for coagulant recovery.
h These unit processes include thickened sludge pump stations.
Key
BRPS = Backwash recovery pump station
BWSB = Backwash water sedimentation basin
DAF = Dissolved air flotation
DB/D = Solar drying basin with decant
DDPB = Direct discharge from process basin
DPS = Decant pump station
EB/PS = Equalization basin and pump station
EC = Enhanced coagulation
Extended drying
Extended drying area
Gravity thickening
Lagoon
Mechanical dewatering
Mechanical thickening
Residuals pump station
Sand drying bed
ED
EDA
GT
LAG
MD
MT
PS
SDB
VAFB = Vacuum-assisted plate filter bed
WFB = Wedge wire filter bed
-------
volume of residuals that will be processed and dis-
posed of. This category also addresses concerns as-
sociated with returning untreated residuals to the
treatment process.
• Disposal economics issues:These issues require ex-
isting residuals processing practices to be revisited
in response to cost increases for disposal activities
that are interutility and external to the water utility.
• Community relations issues.
Table 4-4 provides a brief description of these issues
and identifies residuals disposal alternatives associated
with low-, medium-, and high-solids content residuals.
To use the matrix for the selective review process, a
utility should first identify the Residuals Solids Concen-
tration category (low, medium, high) that applies to its
current capabilities. Next, the utility should identify,
within its concentration category, a specific problem that
is similar to one currently facing the utility. After these
two steps, a preliminary selection can be made from the
four right-hand columns, using the priority protocol listed
in the previous section. Ideally, the selection made will
use the maximum number of existing unit processes.
This approach can be rationalized by the obvious eco-
nomic benefit of reusing existing facilities in a process
group to meet the processing requirements.
4.4.2.2 Residuals Disposal-Based Selection
If a relevant problem cannot be identified on Table 4-4,
the utility should select a preliminary alternative based
on the available solids disposal option with the highest
probability of being implemented. Selection of the pre-
liminary alternative follows the same procedure de-
scribed in the previous section, using the Residuals
Disposal Alternatives column instead of the Problem-
Specific one. The scope of each disposal alternative is
outlined below:
• Landfilling: The four most common landfill disposal
techniques for WTP residuals are:
- Co-disposal with municipal solid waste (refuse)
- Use as daily landfill cover extender
- Monofill of WTP residuals only
- Co-disposal with WWTP biosolids
• Land application: The three most common land ap-
plication techniques for WTP residuals are:
- Land application on agricultural land
- Land application on forest land
- Land application on a designated disposal site
• Sewer disposal: This alternative assumes that the
sewer ends at an existing WWTP.
• Direct discharge to source stream: Several configu-
rations of direct discharge are possible:
- Discharge to waters of the United States.
- Discharge to a water district supply canal.
- Discharge to an intermittent stream bed.
- Discharge to a dry arroyo (a watercourse in the
arid southwest that only typically flows during, or
directly after, a storm event).
• Residuals reuse: Although WTP residuals do not
have the inherent fertilizer value of WWTP residuals,
these reuse alternatives are being practiced:
- Recovery of coagulants
- Recovery of lime at softening plants
- Use in landscape tree nursery (low solids)
- Use in making bricks (high solids)
- Use in Portland cement (high solids)
- Use in turf farming
4.4.2.3 Solids Concentration-Based Selection
The most basic level of review is to identify preliminary
processes that can produce a specific range of solids
concentrations. Three possible categories of solids con-
centration are:
• Low: Low processes can produce solids concentra-
tions ranging from less than 1 percent to 8 percent
solids, by weight. This group represents the general
limits of the thickening processes, specifically the
common gravity thickener.
• Medium: Medium processes can produce solids con-
centrations ranging from greater than 8 percent to 25
percent solids, by weight. This group represents the
general limits of the simple dewatering processes,
such as sand drying beds, and general mechanical
dewatering with belt filter presses and general serv-
ice centrifuges.
• High: High processes can produce solids concentra-
tions of greater than 25 percent solids, by weight.
These are the general limits of the high solids dewa-
tering processes, such as filter presses and high-sol-
ids centrifuges. These limits are also associated with
the minimum solids content for a monofill, although
50 percent solids is preferable.
4.4.2.4 Other Selection Criteria
The matrix also identifies unit processes and combined
unit processes used to accomplish optimal water re-
source recovery alternatives and coagulant recovery
alternatives.
59
-------
4.5 Specific Residuals Unit Process
Selection Criteria
Selection of residuals handling processes is a more
complicated task than selection of traditional drinking
water treatment processes for the following reasons:
• Little operating experience with residuals handling
processes exists for use as a basis of comparison.
• Residuals handling processes are more difficult to
test with a procedure such as a jar test or a pilot filter
because of the interdependence of solids handling
on other unit processes (e.g., coagulation, sedimen-
tation, and thickening).
Five selection criteria may be used in screening and
selecting residuals handling processes:
• Discharge limitations and the effective operating
range of the residuals handling process.
• Similar operating experience with unit process.
• Bench- and pilot-scale testing of unit process.
• Construction, operation, and maintenance costs.
• Environmental impact of unit process.
Each of these selection criteria is described in more
detail in this chapter. The flowchart in Figure 4-13 shows
how the five selection criteria (in boxes) are used to
identify a desired process alternative. No attempt is
made to weigh the relative impacts of these criteria,
which vary from facility to facility.
-f What are the discharge limits? )
What combination of unit processes
can operate effectively in this range?
Develop preliminary process alternatives. t
What is the similar operating experience
with each alternative?
Screen alternatives
c
What are the relative environmental
impacts of each alternative?
f Is it feasible to perform ^
I bench- and/or pilot- I
I scale testing? j
1 NO
Size alternative residuals
handling processes.
YI-;-;
d>
Develop and
perform bench/
pilot testing.
Develop and compare
I alternative costs. j
Select residuals handling process.
4.5.1 Operating Experience
The effectiveness of residuals handling processes are
very specific to the characteristics of the raw and proc-
essed water and, in some cases, to environmental con-
ditions. Bench-, pilot-, and full-scale tests provide
information needed to select processes. Circumstances
may dictate that no testing or very little testing can be
performed by a utility; in this case, the experience of
other utilities with various residuals handling processes
may be the best source of information. The Water Indus-
try Data Base (WIDE), developed by the American
Waterworks Research Foundation (AWWARF) and the
American Water Works Association (AWWA), makes
this information available (Kawczyinski and Achterrman,
1991).
This survey covered 438 utilities and 347 WTPs. Treat-
ment methods and disposal practices were categorized
for each facility. The different thickening and watering
categories are summarized in Tables 4-5 and 4-6. Note
that, since the database was published in 1991, a series
of new facilities have started operation using processes
such as vacuum-assisted drying beds. Consult with
equipment manufacturers for more recent operating
histories.
Table 4-5. Survey of Thickening Methods at Water Treatment
Plants in the United States (Kawczyinski and
Achterrman, 1991)
Treatment Methods
Existing Number of Facilities
Lagoons
Gravity thickening
Dissolved air flotation
Gravity belt thickeners
180
48
0
0
Table 4-6. Survey of Dewatering Methods at Water Treatment
Plants in the United States (Kawczyinski and
Achterrman, 1991)
Treatment Methods
Existing Number of
Facilities
Figure 4-13. Residuals handling process selection flow chart.
Lagoons
Sand drying beds
Freeze assisted drying beds
Solar drying beds
Belt filter press
Centrifuges
Filter presses
Vacuum filters
Screw press
180
26
33
Number included with sand
drying beds
Number included with filter
presses
10
20
4
0
60
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4.5.2 Bench-Scale and Pilot-Scale Tests
4.5.2.1 General
Bench- and pilot-scale tests serve two functions in the
selection of residuals handling processes. First, they
provide additional data for the sizing of the full-scale
equipment. Second, they provide an indication of the
process performance (i.e., the solids concentration that
can be achieved).
Figure 4-14 is a guide to the use of bench- and pilot-
scale tests for this application. Bench- and/or pilot-scale
testing should be considered after the alternative resid-
ual handling schemes have been screened and nar-
rowed down to a few options. Pilot- and bench-scale
testing may not be needed if there is similar experience
with the process at a comparable facility, defined as one
of similar size with approximately the same raw water
quality and unit processes. Short implementation sched-
ules and limited study budgets may curtail bench- and
pilot-scale testing, but the lack of related experience can
make bench- and pilot-scale testing desirable.
4.5.2.2 Bench-Scale Testing
These bench-scale tests are generally used for thicken-
ing and dewatering processes (Dentel et al., 1993):
Screen Residuals Handling Alternatives
Enough Similar Experience Available
to Estimate Sizing and Performance?
I
No
Time and Budget Allow
BenclWPilot-Scale Testing?
Yes
I
Yes
Data Available to
Correlate Bench Testing and
Full-Scale Performance?
Identify Availability of
Manufacturer Pilot Equipment
Select Bench Tests
C
Identify Elements
of Program
Perform Pilot Testing
Perform Testing and Analyze Results
Figure 4-14. Bench/pilot testing decision flow (Dentel et al.,
1993).
• For thickening: settling tests, flotation test, and cap-
illary suction time test.
• For dewatering: time-to-filter test, filter leaf test, cap-
illary suction time test, and settling tests.
Detailed lists of equipment and test procedures for each
of these tests are available (Cornwell et al., 1987; Dentel
et al., 1993). The performance of a bench-scale test
does not have any direct correlation to the performance
of a given process. Bench-scale tests typically simulate
full-scale operations. Thus, a correlation may be devel-
oped, for instance, between the results of capillary suc-
tion time tests and the performance of centrifuges. The
application of the bench-scale test is then to analyze the
effect of different sludge conditioners. Bench-scale tests
may have application to the selection of a residuals
handling process if the bench-scale tests can be corre-
lated to process performance based on previous testing.
Equipment suppliers should be asked about the avail-
ability of past bench-test comparisons. Suppliers, often
times, can bench test units at their own facilities.
4.5.2.3 Pilot-Scale Testing
Pilot-scale testing involves the use of test equipment
similar enough in size to full-scale operating equipment
that the test results can be directly compared between
pilot-scale test and full-scale operation. This testing may
involve the construction of a scaled-down version of a
process basin such as a gravity thickener or a sand
drying bed. Suppliers of mechanical thickening and de-
watering equipment typically have test units available for
rent or loan, and can test either on site or at the sup-
plier's facilities.
4.5.2.4 Test Procedures and Analysis
The use of bench- and pilot-scale tests has many pit-
falls. The test must be as representative as possible of
the real world conditions, and must simulate all of the
processes involved with the alternative in question. This
is particularly a concern with thickening and dewatering,
where the incoming solids must represent the solids that
will actually be concentrated and transported from the
previous process. Even when the bench- or pilot-scale
testing successfully models the performance of a proc-
ess, the results may not reveal operational problems
that are part of the full-scale process.
The duration of testing is a particular concern. Year-
round operation may involve significant changes in raw
water quality that can affect the operation of the residual
handling process. One week of pilot-scale testing may
not reflect this impact, and year-round pilot-scale testing
is usually not feasible. The use of short-term pilot-scale
testing to correlate the results with bench-scale tests
may come close to approximating the results of long-
term testing, though on a lesser scale.
61
-------
When analyzing the results, the limitations of the test
setup and test protocol should be considered. If limited
testing is done, less emphasis should be placed on the
results.
4.5.3 Environmental Impacts
Environmental impacts have become a standard consid-
eration for public facilities, and are typically part of this
selection process. Environmental criteria, however, are
subjective, making them difficult to use as a basis for
comparison. The environmental impacts of a WTP re-
siduals handling process can vary greatly, depending on
whether one's viewpoint is that of an operator, a neigh-
bor, or even a migrating bird! Some relevant environ-
mental considerations for this selection process are:
• Effectiveness in meeting discharge requirements:
The ultimate criterion for the selection of a process
or a combination of processes is whether the process
will reliably and consistently meet the regulatory dis-
charge requirements. This depends on many factors,
including the size of the application and process load-
ing conditions.
• Ground-water quality: My process that might release
contaminants that could migrate to the ground water
should be approached with caution. Unlined lagoons
and drying beds are typically of greatest concern.
• Noise: Of concern to both plant employees and site
neighbors, noise is typically associated with thicken-
ing and dewatering processes that use mechanical
equipment. Open-air processes may also involve
noise from front-end loaders or other devices used
to move and remove solids. Offsite transport of solids
is another solids concern. Mitigation techniques in-
clude hearing safety equipment for workers, acousti-
cally sealed buildings for mechanical devices, and
specified operating hours for front-end loaders and
other vehicles.
• Odors: Many operators emphatically say that no
odors are associated with WTP residuals and, fre-
quently, they are correct. With open-air processes
(and sometimes even mechanical systems), how-
ever, odors are a possible consequence. The tradi-
tional technique used to mitigate odors is an
operational change in the loading and removal of
solids from process units. Chemicals such as caustic
and chlorine may be needed to stabilize and destroy
odor causing organisms in the sludge. Odor control
units may also be required for systems installed in-
doors.
• Energy use: Energy use varies with both equipment
usage and the cost of removing solids from the site.
Mechanical dewatering techniques require the high-
est energy consumption, although consumption var-
ies widely between the different processes. Different
applications of processes can also affect the percent
solids concentration of the residual before disposal.
A higher concentration translates to a lower volume
for disposal. This lower volume then results in the
use of less transport energy.
• Insects and other pests: Insects are a potential con-
cern with open-air processes. Submerged lagoons or
gravity thickeners may serve as breeding grounds for
mosquitoes and other flying insects. Flies and gnats
may be a concern when drying residuals in the open
air.
• Impact on the neighborhood: This broad category
encompasses many environmental concerns that can
result in the lowering of local property values.
• Air pollution: A typical concern when evaluating
wastewater processes, air pollution (stripping volatile
contaminants into the air) is a small concern with
water treatment systems. Some concerns may arise
from the potential use of mechanical equipment hav-
ing gas or diesel engines.
• Space requirement: Many plant sites do not have a
large property area or the ability to expand onto ad-
jacent vacant land. Limited space typically drives
process selection away from open-air processes and
toward mechanical processes.
• Employee and public safety: Mechanical handling
processes typically involve the highest safety con-
cerns because they use heavy equipment with the
potential to cause serious accidents. All processes
involve some potential hazard, however, ranging from
suffering heat stroke while working in a solar drying
bed to drowning in a thickener.
In comparing environmental criteria, the interrelation-
ship of these criteria with both construction and opera-
tion and maintenance costs is noteworthy. For example,
the ground-water quality concerns associated with la-
goons can be resolved by the installation of a relatively
impermeable liner beneath the lagoons; the liner miti-
gates the environmental concern at a significant in-
crease in construction cost. The relationship between
environmental controls and operation and maintenance
costs should be considered in the analysis of different
residuals handling approaches.
4.6 Final Screening of Residuals
Handling Processes
4.6.1 A dditional Selection Criteria
Previous operating experience, environmental impacts,
and bench- and pilot-scale testing are criteria common
to most residual handling process selections. Additional
criteria applicable to both wastewater processes and
water treatment process are (U.S. EPA, 1979b):
62
-------
• Compatibility: Compatibility with existing land-use
plans; areawide, solid waste, water, and air pollution
controls; and with existing treatment facilities.
• Implementability: Available sites; available personnel
(including specially skilled labor); sufficient or ex-
pandable existing utilities; meets regulatory review
requirements; can be achieved within the required
schedule; whether existing processes can be inter-
rupted for construction connection.
• Flexibility: Ability to respond to new technology,
changing regulations; changing loads; incremental
expansion.
• Reliability: Vulnerability to disasters; probable failure
rate; backup requirements; operator attention re-
quired.
• Impact of residual handling process sidestreams on
existing process.
4.6.2 Process Alternative Selection Matrix
Process combinations that achieve different degrees of
residuals solids concentrations are shown in Table 4-4.
The final selection of the process combination depends
on the relative importance of the selection criteria. One
approach uses a weighting table to aid a decision-maker
in analyzing different process combinations in terms of
weighted criteria (U.S. EPA, 1979b). An example of this
approach is presented in Table 4-7. The weights pre-
sented in this table are examples only; each facility must
assign the appropriate relative weights according to its
own priorities.
4.7 Residuals Handling Process Design
Issues
4.7.1 Mass Balance Diagrams
4.7.1.1 Estimating Solids Production
Solids mass balances are used to develop estimates of
hydraulic and solids loading on residuals handling unit
processes. Solids production from a WTP may be esti-
mated based on the raw water suspended solids re-
moval and the quantity of process chemical added.
Refer to Chapter 3 for equations used to estimate solids
product.
When estimating solids production for the preliminary
design of a facility, the following should be considered:
• Historical trends of raw water suspended solids load-
ing must be analyzed to determine the average day,
maximum day, and peak hour loadings. These values
are typically used in evaluating the following design
issues:
- Average day: Used to analyze annual solids dis-
posal fees and land availability for open-air dewa-
tering and drying processes.
- Maximum day: Used to size thickening, dewater-
ing, and drying processes.
- Peak hour: Used to size piping and pumping. If
equipment such as centrifuges or belt filter presses
are sized based on maximum day loadings, then
the residual handling systems must be designed
with the capacity to absorb the difference between
the peak hour and the maximum day loadings. This
may be done by incorporating equalization basins
into the design. Sedimentation basins and thicken-
ers can also equalize peak hourly, daily, and
weekly flows. An alternate approach is to consider
the ability of a given process to handle short-term
spikes in the solids loading rate.
• Most water treatment facilities record solids loadings
in terms of turbidity (NTU) rather than suspended
solids. Methods of converting turbidity values to sus-
pended solids values are available (Cornwell et al.,
1987). Generally, the ratio of suspended solids to
NTU is 1 to 2.
• Estimating raw water suspended solids loadings is
inherently more difficult for new WTPs than is adding
residuals handling facilities to existing WTPs. The
options are:
- To use the historical records of a WTP that uses
similar processes with a comparable water source.
- To develop a water-quality database through a pro-
gram of sampling, jar testing, filtration, and analy-
sis. Because a short-term program will represent
conditions only for one period in time, such a pro-
gram may not reflect long-term water quality at
the site.
4.7.1.2 Developing the Diagram
Examples of a mass balance diagram and calculation
are shown in Figures 4-15A and 4-15B, respectively.
The percent of solids captured for the gravity thickeners
and the filter presses are based on the typical values in
Tables 4-2 and 4-3. These values should be verified in
a bench- or pilot-scale testing program. The diagram
can also provide valuable data regarding the quantity of
chemical conditioner—polymer, in this case—which is
required in the process.
4.7.2 Equipment Sizing
WTP residuals handling systems can vary from simple
sewer/stream disposal systems to elaborate thicken-
ing/dewatering/drying complexes. The mass balance
examples in Figures 4-15A and 4-15B are only the
starting point; the next step is the generation of a sche-
matic such as that shown in Figure 4-16, which is based
63
-------
Table 4-7. Example of Weighting System for Alternative Analysis (U.S. EPA, 1979b)
Alternative 1 Alternative 2
Economic impacts:
Construction cost
O&M cost
Total weighted
alternative ratingd
28
8
1,576
32
9
1,430
Alternative n
Categories and
Criteria
Effectiveness:
Flexibility
Reliability
Sidestream effects
Compatibility:
With existing land
use plans
With areawide
wastewater, solid
waste, and air
pollution programs
With existing
treatment facilities
Relative
Weight3
3
5
3
2
3
4
ARb
4
3
10
8
3
5
WRC
12
15
30
16
9
20
AR
6
5
9
8
6
5
WR
18
25
27
16
18
20
AR
6
2
7
4
7
3
WR
18
10
21
8
21
12
28
1,317
3 Relative importance of criteria as perceived by reviewer; scale, 0 to 5; no importance rated zero, most important rated 5.
b Alternative rating. Rates the alternative according to their anticipated performance with respect to the various criteria; scale 1 to 10; least
favorable rated 10.
c Weighted rating. Relative weight for each criteria multiplied by alternative rating.
d Sum of weighted ratings for each alternative.
Q = 50
SS = 10 Fe Polymer
Q = 0.268 3 = 1117560
Q = 0.017 5 = 27980
5 = 12417
rcrc
Figure 4-15A. Mass balance schematic.
on refined flow rates and individual equipment loadings.
Issues that must be identified at this preliminary design
stage are the number of anticipated shifts, coordination
with main plant operations, and provision for redundant
process trains. Equipment size can also be reduced by
providing adequate equalization facilities. Projected
equipment suppliers also play a key role in this phase
as the specific equipment capabilities and requirements
are identified.
Open air dewatering/drying systems are the most com-
mon form of residual handling process. While the proc-
ess approach and the system equipment are relatively
simple, the actual design is dependent on local clima-
tological conditions, regulatory requirements, and pro-
jected use. Detailed information on design details for
these systems exists in the literature (Cornwell et al.,
1987; Cornwell and Koppers, 1990).
4.7.3 Contingency Planning
The Process Design Manual for Sludge Treatment and
Disposal (U.S. EPA, 1979b) presents the contingency
planning design issues that should be incorporated into
a WWTP solids handling facility. These issues are
equally applicable to a water treatment facility.
Contingency planning concerns and possible design
resolutions are listed in Table 4-8.
64
-------
MASS BALANCE EXAMPLE
Assumptions:
2.
3.
For purpose of preliminary calculation do not include impact of dewatering polymer or
filter press washdown water.
Note givens and assumptions as listed below.
For purpose of preliminary calculation assume % capture = 100%.
Main plant flow (mgd)
Suspended solids (mg/L)
Ferric chloride dosage (mg/L
asF)
Coagulant and filter aid
polymer (mg/L)
50
10
1
0.5
Given
Given
Given
Given
Solids removed from main
treatment process (Ibs/day)
5,587.8
S = [Q (2.9 Fe + SS + P)](834)
To Gravity Thickening
Solids (@ %)
Flow (mgd)
Dry solids (Ibs/day)
Total mass (Ibs/day)
To Filter Press
Solids (@ %)
Flow (mgd)
Dry solids (Ibs/day)
Total mass (Ibs/day)
Overflow Back to Main Plant
Flow (mgd)
To Hauling Trucks
Solids (@ %)
Dry solids (Ibs/day)
Total mass (Ibs/day)
0.5 -
0.268 .
5,587.8
1,117,560
2
0.01675
5,587.8
279^90
0.25125
45
5,587.8
279,390
Assumed
Total mass [(10,000)(% solids)(8.34)]
As calculated above
Dry solids •*• % solids
Assumed
Total mass [(10,000)(% solids) (8.34)]
As calculated above
Dry solids •*• % solids
Q to thickener - Q to filter press
Assumed
As calculated above
Dry solids -H % solids
Figure 4-15B. Mass balance calculation.
Backup systems and storage spaces are key contin-
gency planning items that are often incorporated into
residuals handling facility designs. An aerial view of a
residuals handling facility is shown in Figure 4-17. This
facility uses centrifuges as the primary mode of dewa-
tering along with solar drying beds. The drying beds
serve the following purposes:
• Handle peak solids loadings that the centrifuges may
not be able to effectively treat.
• Serve as a dewatering process in case of centrifuge
failure.
Provide a dewatered solids storage area in the event
that offsite solids hauling is disrupted.
4.7.4 Specific Design Elements of
Mechanical Dewatering Systems
Mechanical dewatering systems are generally the most
complex of the residuals handling systems. Layout ex-
amples for belt filter presses, centrifuges, filter presses,
and vacuum filters are shown in Figures 4-18, 4-19,
4-20, and 4-21.
65
-------
O)
O)
ffOK COHTIHUAnOM »-
KE VLUDK THtCKENDN I
AND EEMMEKim POLYUEH u
PIPMO MMMH, TW* «HECT)
ORMNAOE SYSTEM
Figure 4-16. Preliminary residuals handling process schematic (Bratby et al., 1993).
-------
Table 4-8. Residual Handling Facility Contingency Planning
Issues (U.S. EPA, 1979b)
Potential
Problems
Potential Resolutions
Equipment
breakdowns
Solids disposal
disruption
Solids production
greater than
expected
Provide redundant units and piping.
Allow for solids storage during repair.
Base design on single shift; second or third
shift can be utilized on an emergency basis.
Plan for a secondary disposal approach.
Allow for solids storage during disruption.
Provide for safety factors in process design.
Allow for solids storage during peak periods.
Base design on single shift; second or third
shift can be used on emergency basis.
These schematics identify common elements of me-
chanical dewatering system design:
• Redundant dewatering units.
• Chemical conditioner (polymer) feed system.
• Simplified approach for removing dewatered solids
from the unit.
• Byproduct water removal system.
• Mechanism for removing dewatering unit from build-
ing for repair.
Additional design items that should be considered are:
• Local control of sludge feed into the units.
• Provisions for equipment washdown and drainage.
• Acoustic paneling in room to dampen noise.
• Odor control system (rarely implemented in water
production facilities).
• Local shower facilities for staff.
Figure 4-17. Aerial view of residuals handling process system, Val Vista WTP, Cities of Phoenix/Mesa, AZ (John Carollo Engineers, 1994).
67
-------
Hand Railing
Discharge
Upper Level Plan
Sludge met
sub-system
Polymer met
i sub-system
Elevation
Figure 4-18. Belt filter press—example of system layout (U.S.
EPA, 1979a).
4.8 Air Emissions Control
Along with traditional residuals generated by the physi-
cal/chemical treatment of water, some treatment proc-
esses can generate gaseous residuals that can be
released to the atmosphere. Gaseous residuals form
two groups: emissions intentionally generated as a
byproduct of a treatment process, and emissions gen-
erated by the accidental release of a gaseous chemical
used in water treatment.
4.8.1 Gaseous Residual Byproducts
The treatment of potable water can generate various
types of gaseous residuals, from the simple release of
hydrogen sulfide caused by aerating sulfur water, to the
exhaust of various volatile and synthetic organic com-
pounds from a stripping tower treating contaminated
ground water. Other gaseous byproducts include the
ozone-tainted air exhausting from an ozone contactor at
a modern WTP, and radon released from contaminated
source water.
Sludge Feed Line
/~v
•f*
*• Feed
Polymer pump
Tank
Electrical Controls
Ce'ntrifuge
Plan View
Centrate
Return
Sludge
Section View
Figure 4-19. Centrifuge—example of system layout (U.S. EPA,
1979a).
4.8.1.1 Treatment of Inorganic Gaseous
Emissions
The release of naturally occurring inorganic gases found
in ground water (i.e., hydrogen sulfide) to the atmos-
phere is not an environmental concern unless it exceeds
a 1 part per million (ppm) concentration. As urban de-
velopment continues to encroach upon existing water
treatment facilities, the concentration of gases in the
exhaust from aeration and stripping processes may ul-
timately need to be reduced for aesthetic reasons,
namely odor control. Aeration is a process that mixes air
and water, normally by injecting air into the bottom of a
tank of water; spraying water into the air; or allowing
water to aerate by cascading over an irregular surface
like an artificial stream bed. Stripping is a highly control-
led form of aeration engineered for the optimum removal
of a specific gas at a maximum concentration by spray-
ing water into a variable counter-current flow of air
through a stripping chamber.
68
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Sludge Feed Lines siudge to Filter Presses
Plan View
Filter Press __.
/
11 L
(gj Future
y^- Press
[r -i
I I
!L j|
~a
Sludge
Conditioner
AFeed Pumps ;
Elevation View
Figure 4-20. Filter press—example of system layout (U.S. EPA, 1979a).
In cases where aeration is used, concentrations of hy-
drogen sulfide gas in the exhaust are below the 1 ppm
threshold and are expelled directly into the atmosphere.
If the gas concentrations in exhaust from an aeration
process need to be controlled, the exhaust must be
collected and delivered to a scrubber. Collection is nor-
mally achieved by installing a cover over the aeration
process and using an exhaust fan to deliver the air to a
scrubber system. When stripping is used, the exhaust
gas is likely to exceed the 1 ppm concentration and
would probably be directed to a scrubber system.
In air pollution control, a scrubber is an air cleaning
process in which a contaminant gas is absorbed into a
scrubbing liquid. The most common method of scrub-
bing is accomplished with a packed tower, a vertical
chamber filled with various types of packing materials
(see Figure 4-22). Process exhaust air is discharged into
the bottom of the chamber and flows upward around the
packing materials while scrubbing liquid trickles down
through the packing in a counter-current flow pattern.
The resultant sinuous pathway for the air and liquid
provides an extended exposure of the air to the liquid
and allows the gas to transfer from a gaseous state into
a solution state and react with the scrubber liquid.
In the scrubbing of hydrogen sulfide, the scrubbing liquid
is typically sodium hydroxide (caustic soda), which ulti-
mately is converted to sodium sulfate through the reac-
tion with hydrogen sulfide. To maintain scrubber
efficiency, the scrubbing liquid is periodically replaced
when it can no longer absorb the target gas. The sodium
sulfate liquid is typically discharged directly into a sewer,
as it is a nonhazardous residual. Other disposal alterna-
tives must be evaluated in the event that a sewer is not
available.
4.8.1.2 Treatment of Volatile Organic Gaseous
Emissions
In many industrialized areas of the world, ground water
has been contaminated by the careless disposal of vari-
ous manmade organic chemicals. Most of these organic
chemicals are very toxic and must be removed from the
water before it is suitable for potable use. A group of
these chemicals is called volatile organic chemicals or
69
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Vacuum
Filter
I I
I I
r-
1 1
1 1
Vacuum | |
Filter | |
1 i
I i
Control
Panel
Vaccum and
Filtrate Assembly
D
Sludge
Conveyor
Preccat
Assembly
Plan View
Vacuum
Filter
Vacuum and ||
Filtrate A
Assembly
Sludge
/^ Conveyor
Sludge Pumps
and Mechanical
Equipment
Elevation View
Figure 4-21. Vacuum filter—example of system layout (U.S. EPA, 1979a).
VOCs (e.g., trichloroethylene, known as TCE) because
they can be easily removed from the water by violent
agitation using a stripping chamber similar to that de-
scribed above for removing inorganic gases.
Stripping chambers are similar to packed scrubbing tow-
ers except they have large blowers that can be regulated
to vary the amount of air being forced into the chamber.
Controlling the air flow rate relative to water flow rate
regulates the stripping of the VOC from the water, which
flows counter-current to the air flow. Depending on the
concentration of the VOC being stripped and the local
air quality standards, the stripper exhaust may be dis-
charged directly into the atmosphere. Under these con-
ditions, the volume of air forced through the stripper can
effectively diffuse the concentration of the organic to
trace levels.
In cases where the stripper has unacceptable concen-
trations of VOCs in the exhaust, it is discharged into an
afterburner that incinerates the organic constituents. An
afterburner is essentially a combustion chamber with an
external fuel source that heats the air flowing through
the chamber to a temperature sufficient to ignite the
volatile organic gases. The size and temperature re-
quirements of an afterburner depend on the specific
organic chemical and the volume of air into which it is
being vented.
70
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Off Gases
Liquid Distributor
Packing
Liquid Redistributor
Influent Pipe
MM
^*
MV
-*
--<
Blower — _
/^»H $
PJ
llsiiuusii
ilHIUI!!<|
Jisnisinu
ninnimi
ii>!:ir,i['
-rflniunr
i'.inii;i:i
"ftjnnj!J<
imninn
(llilUJill
isusuun
uiinjnu-
liuiiinu
UIUSIIKI
iiiiiindi
isiiuimi
KltlllitVI,
Kiiuiurr
iHHinin
Treated Water
^
(Q «** -J-^J fL.*TJ
a
"a
" ^rP
- - Dl
Figure 4-22. Packed tower (ASCE/AWWA, 1990).
4.8.1.3 Treatment of Nonvolatile Organic
Gaseous Emission
A counterpart to the VOCs found in contaminated
ground water is the nonvolatile organics group. These
organic compounds are more difficult to strip, and their
acceptable concentration in the exhaust is so limited
that stripping with an afterburner is not a viable removal
method. In these cases, the chemicals are removed
using liquid-phase adsorption with granular activated
carbon (GAG). Depending on the organic compound
and the acceptable atmospheric discharge limits, the
GAG can be regenerated or must be disposed of as a
hazardous solid waste, as is the case with GAG contain-
ing dibromochloropropane (DBCP). Regeneration of
GAG can be used for some nonvolatile compounds, but
the regeneration exhaust is usually cycled through an
afterburner for neutralization by incineration.
4.8.1.4 Treatment of Ozone-Contaminated Air
The use of ozone in potable water treatment has be-
come more common within the water industry and may
become even more popular as an alternative disinfec-
tant. Although ozone is not the panacea to the pending
Disinfectant/Disinfection Byproduct (D/DBP) Rule, it
may be the only method that can truly deactivate infec-
tious organisms like Cryptosporidium. When used in
potable water treatment, its discharge into the atmos-
phere must be prevented.
Ozone is typically generated in an air flowstream or a
pure oxygen flowstream discharged at least 22 feet
below the water surface in a completely enclosed ozone
contact chamber. Although the half-life of ozone is very
short, trace concentrations in the basin exhaust are
common. Two of the processes that are commonly used
to eliminate the potential release of ozone into the at-
mosphere are thermal and catalytic destruction.
Thermal ozone destruction systems rely on the rapid
decay of ozone at elevated temperatures. By heating the
contactor off-gas to approximately 300 to 350 degrees
Celsius for 5 seconds, the ozone is converted back to
oxygen. The air is heated by a heat exchanger supplied
with heat from electrically powered heating coils. As
thermal pollution is also a concern in many places, the
heated exhaust can be passed through an air-to-air heat
exchanger, where heat is transferred to incoming air and
thereby kept out of the atmosphere.
Catalytic ozone destruction units have only been in use
since 1990. Although the true composition of the cata-
lysts is considered proprietary by their manufacturers, in
all designs the ozone is destroyed by electron-level
exchanges and manipulations. Because the catalysts
are subject to severe damage if exposed to moisture,
they are usually combined with an air heater, which can
also be used to regenerate the catalyst. The key advan-
tage of the catalytic process is that it has the lowest
energy costs of the two processes.
4.8.2 Accidental Release of a Gaseous
Treatment Chemical
The oldest and most common water treatment process
is chlorination, which, until recently, had been exclu-
sively accomplished using compressed chlorine gas de-
livered and stored in cylindrical pressure vessels. The
water industry has learned to handle the toxic chlorine
gas with great care, but accidents do occur, usually
resulting in the release of chlorine gas into the atmos-
phere.
The potentially deadly impact of the release of large
amounts of chlorine has prompted many changes during
the past 6 years in the applicable codes and laws regu-
lating its use. In response to the increased regulatory
constraints, some water utilities have modified their
treatment process to reduce or eliminate the use of
chlorine, and have implemented systems to provide
neutralization of the chlorine in case of a leak. In some
communities, public awareness and fear have forced
the utilities to use a liquid form of chlorine (sodium
hypochlorite/bleach). The liquid form is safer and essen-
tially has the same disinfection capacity as the gas, but
71
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the liquid chlorine is much more expensive to transport
and adds sodium to the finished water.
Since the use of chlorine is expected to continue into the
future, it is reasonable to expect existing water utilities
to construct chlorine containment and neutralization
systems as required by the current building codes. The
code requires that the accidental release of chlorine
must be contained and neutralized using a treatment
system such that the chlorine gas exiting the treatment
exhaust does not exceed 15 ppm. The neutralization of
chlorine requires the use of a scrubber system that
employs caustic soda as the scrubber liquid. A chlorine
scrubber operates essentially the same way as that
used for inorganic gas emissions control, with one ex-
ception—the motive force for the extraction of the chlo-
rine from the containment structure commonly uses a
venturi with a caustic soda spray nozzle discharging into
the throat of the venturi. The exhausted caustic soda
becomes sodium hypochlorite (bleach), which can be
disposed of through beneficial reuse as a disinfectant.
Coincidentally, the gaseous chemicals ammonia and
sulfur dioxide are also commonly used in potable water
treatment and can be neutralized by the same system
as is used for chlorine.
72
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Chapter 5
Direct Discharge of Water Treatment Plant Residuals to Surface Waters
Water treatment residuals are primarily produced
through the coagulation, filtration, and oxidation of sur-
face waters to remove turbidity, color, bacteria, algae,
organic compounds and, frequently, iron and/or manga-
nese. One type of residual is generated by the aluminum
and iron salts that are commonly used for coagulation.
A second type of residual results from the lime, sodium
hydroxide, and/or soda ash added to reduce calcium
and magnesium and soften the water.
Historically, direct discharge of water treatment effluent
to surface waters has been the most commonly prac-
ticed disposal method. A 1984 water utility survey indi-
cated that approximately 50 percent of the total
residuals generated by 429 utilities (at least 548,820
metric tons) were pumped directly to surface waters
(AWWA, 1986). Most of these residuals were alum
sludges. Recently, this disposal method has been ques-
tioned because of concerns about possible risk to public
health and aquatic life.
5.1 Theory
The chemistry of aluminum and iron in water are similar
to one another; however, iron species are less soluble
than aluminum species are over a wider pH range.
Because of the potentially adverse effects of aluminum
in the environment, more information is available on the
discharge of alum residuals to surface waters than is
information on residuals produced from the addition of
iron salts. Consequently, this section will focus on alum
residuals.
In the United States, aluminum in surface waters is
primarily in solid form, with approximately 31 percent of
the aluminum being dissolved (Andelman, 1973). Alumi-
num is abundant in the environment, yet in surface
waters above pH 4.0, its concentration is normally less
than 0.1 mg/L. Understanding the chemistry of alumi-
num is important to understanding the impact of alumi-
num on aquatic organisms.
5.1.1 Chemical Interactions
Aluminum is amphoteric—soluble in acidic and basic
solutions, but quite insoluble at neutrality. The trivalent
state, Al+3, is the only naturally occurring oxidation state
found in solutions and solids. The aqueous chemistry of
aluminum is extremely complex; the molecular form, or
species and concentration of each species depend upon
pH, complexes with ligands, and, to a lesser extent, on
temperature and reaction time (Campbell et al., 1983).
Aluminum sulfate, used as the primary coagulant in
most water treatment systems, dissociates in aqueous
solutions, and Al+3 bonds with water molecules, hydrox-
ide ions, other inorganic ions, and organic ions or mole-
cules. When mixed thoroughly with turbid waters at pH
levels from 4.0 to 8.5, new compounds form, especially
with phosphates and organics, which are very insoluble
and which, therefore, precipitate (U.S. EPA, 1988a; Dris-
coll and Schecher, 1988). Other aluminum coordination
compounds are very soluble and only precipitate upon
oversatu ration.
While temperature and inorganic and organic ligand
concentration are important factors affecting aluminum
solubility, aluminum solubility is largely controlled by pH
(Baker, 1982; Driscoll, 1985). The optimum pH for co-
agulation using aluminum salts generally ranges from
4.6 to 8.0. The presence of anions such as sulfate
affects the solubility of aluminum salts and can move the
optimum pH for coagulation to 4.0 (Hundt, 1986). Fur-
thermore, the use of other chemicals in the water treat-
ment scheme will affect the solubility and speciation of
aluminum. Fluoride addition after alum coagulation
causes increased aluminum solubility and an increase
in inorganic Al+3 species concentration (Driscoll et al.,
1987).
The source of aluminum ions in an aqueous environ-
ment is important. An additive can affect parameters
important to solubility, such as pH and temperature. For
example, if a loosely bound aluminum ion enters natural
water from a sludge or desorbs from an organic clay
particle, the resulting solubility of aluminum in that water
will change as an indirect effect of the additive (Driscoll,
1985). Speciation is also dependent on the aluminum
source, as it is influenced by the binding capability of
ligands with aluminum ions. Tightly bound crystals of
aluminum hydroxides will solubilize slowly over a period
of months (Smith and Hem, 1972). Aluminum also may
be held tightly within an organic complex and not solu-
bilize readily.
73
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The hydrated trivalent ion is the predominant form of
aluminum at pH levels below 4.0. Between pH 5 and 6,
the predominant hydrolysis products are AI(OH)2+ and
AI(OH)2+, while the solid AI(OH)3 is most prevalent be-
tween pH 5.2 and 8.8 (Martell and Motekaitis, 1989).
The soluble species AI(OH)4- is the predominant spe-
cies above pH 9, and is the only species present above
pH 10 (Martell and Motekaitis, 1989). Polymeric alumi-
num hydroxides appear between pH 4.7 and 10.5, and
increase in size until they are transformed into colloidal
particles of amorphous AI(OH)3, which crystallizes to
gibbsite in acidic waters (Brusewitz, 1984). Within the
pH range of 5 to 6, aluminum bonds with phosphate and
the resulting compound is removed from solution. Be-
cause phosphate is a necessary nutrient in ecological
systems, this immobilization of both aluminum and
phosphate may result in depleted nutrient states in sur-
face waters (Brusewitz, 1984). The concentrations of
aluminum in water vary with pH levels and the humic-
derived acid content of the water. Even at neutral pH
levels, higher aluminum levels have been found in lakes
with a high humicacid content (Brusewitz, 1984; DHHS,
1990).
5.1.2 Toxicity
A key concern regarding the direct discharge of alumi-
num residuals to waterways is aluminum toxicity in the
aquatic environment. When aluminum is mobilized in
lakes and streams, it may be toxic to aquatic life. It is
difficult to generalize about the environmental impacts
of water treatment residuals discharges on receiving
waterways, because such impacts are inherently de-
pendent on an array of physical, chemical, and biologi-
cal stream parameters. The characteristics of each case
must be individually assessed to evaluate the potential
threat of water treatment plant (WTP) residuals on the
water and sediment qualities of receiving streams.
The aluminum species concentration causing toxicity
depends on water chemistry, the organism being af-
fected, and the effect monitored. The aqueous chemistry
of aluminum has been difficult to study for several rea-
sons. First, its form and, therefore, its effects vary with
pH. Second, aluminum ions tend to undergo complex
hydrolytic reactions with many ligands of differing chem-
istries, forming salts of differing solubilities. Additionally,
aluminum is abundant in the environment, making it
difficult to isolate the effects of residuals aluminum from
those of ambient aluminum. Lastly, aluminum has vary-
ing solubility rates (i.e., weak complexes dissolve
quickly and strongly bound complexes dissolve slowly)
(George et al., 1991).
5.1.2.1 Aquatic Biota
Burrows (1977) presents toxicity data for several fresh-
water species offish, invertebrates, bacteria, and algae.
Studies have shown that under low pH conditions (pH
less than 6), inorganic aluminum can be toxic to aquatic
organisms. Major fish kills in southern Norway were
attributed to the release of aluminum from soil by acid
precipitation (Muniz and Leivestad, 1980). Furthermore,
inorganic aluminum concentrations less than 400 u,g/L
had significant inhibitory effects on brook trout (Driscoll
et al., 1980) and white suckers (Baker and Schofield,
1982).
Mobilization of aluminum in Adirondack lakes (pH of 4.3
to 5) may be the primary factor limiting trout survival
there (Schofield and Trojnar, 1980). Freeman and Ever-
hart (1971, 1973) studied the effects of aluminum hy-
droxide and aluminate (pH greater than 7.5) on rainbow
trout and discovered that the aluminate ion is acutely
toxic to trout at or above levels of 0.5 mg/L. In addition,
freshly precipitated aluminum hydroxide can cause
chronic injury in fish. Hall et al. (1985) conducted in-
stream studies on the episodic effect of aluminum addi-
tion. They discovered that episodic additions of
aluminum can have significant biological, physical, and
chemical consequences in dilute, acidic surface waters.
An increase in aluminum under acidic conditions causes
the disruption of the ion regulatory mechanism and,
thus, the subsequent loss of tissue ions in various
aquatic biota. Species of fish (Buckler etal., 1987; Muniz
and Leivestad, 1980; Wood and McDonald, 1987),
daphnids (Havas, 1985), and immature aquatic insects
(Havas and Hutchinson, 1983; Witters et al., 1984) have
experienced net losses of sodium (Na+) and chloride
ions (Cl") under certain conditions in the presence of
aluminum. Ionic imbalances in fish resulting from alumi-
num exposure are usually accompanied by low pH and
alkalinity levels in surrounding waters (Muniz and
Leivestad, 1980).
Aluminum may also cause antagonistic effects to fish
whenpH is less than 5 (Brown, 1983; Evans etal., 1988;
Havas, 1985; Hunn et al., 1987; Wood and McDonald,
1987). Baker and Schofield (1982) concluded that the
initial step toward aluminum toxicity involved the binding
of aluminum hydroxide to the gill surfaces.
Respiratory blockage in fish is another effect of in-
creased aluminum concentrations. Fish may experience
symptoms such as elevated ventilation frequency, in-
creased standard oxygen uptake rate, and a fall in dor-
sal aortic oxygen tension (Baker, 1982; Muniz and
Leivestad, 1980). This effect is normally observed at
circumneutral pH where aluminum exists as a colloidal
species (Malate, 1986; Ramamoorthy, 1988), or in the
presence of high calcium concentrations, where the ef-
fect on the ion regulatory mechanism is masked
(McDonald et al., 1983; Muniz and Leivestad, 1980;
Wood and McDonald, 1987).
74
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Aluminum may exert indirect effects on aquatic organ-
isms as well. The release of copper (Cu2+) from an
organic chelator due to competitive replacement by
aluminum was toxic to Scenedesmus (Rueter et al.,
1987). In addition, aluminum's high affinity for phos-
phate and other compounds could remove nutrients
from the environment and thereby inhibit productivity
(Zarini etal., 1983; Sanvilleetal., 1976; Funketal., 1977).
George et al. (1991) evaluated the toxicity of water
extracts from the discharged alum residuals often North
American WTPs. The receiving water samples from
each plant were adjusted to three pH levels for testing
purposes. Extracts from these samples were subjected
to a battery of toxicity tests, including the Selenastrum
capricornutum growth test, Ceriodaphnia dubia survival
and reproduction test, the fathead minnow survival and
growth test, a protozoan mortality test, and the Microtox
test. S. capricornutum was more sensitive than any
other test organism to the sludge extracts. Algal growth
inhibition was observed at pH 5 and generally not at
circumneutral pH. Dissolution of aluminum was ob-
served in acidic and basic solutions; aluminum was only
slightly soluble in circumneutral solutions. Alum sludge
extracts were toxic to S. capricornutum at all receiving
water pH levels when the receiving water hardness was
less than 35 mg CaCOyL.
5A.2.2 Benthic Macroinvertebrates
Potential threats to benthic communities are magnified
when direct discharge occurs in quiescent bodies of
water. When discharging WTP residuals to a low-veloc-
ity languid stream or lake, mass balance equations (see
Section 5.2.1.3) do not apply. In this instance, a sludge
deposit made up of discharge effluent will accumulate in
the locus of the point of discharge. This poses a potential
threat to any benthic communities at, or in close prox-
imity to, the discharge point. A major concern with direct
discharge is that residuals solids will cover the bottom
sediments, damaging the periphyton community. Sludge
deposits on sediments in receiving waters may limit
carbon sources on which macroinvertebrates feed, and
limit the available oxygen required for respiration. Areas
of lesser flow with more clay substrate provide a more
suitable benthic habitat than a sandy river channel does.
Historically, studies on the impacts of WTP effluent on
benthic communities in large- to mid-sized rivers have
found little evidence of related environmental degrada-
tion. A study by Evans et al. (1979) on the impact of
waste discharges on the Vermillion River from a water
works employing alum coagulation/filtration treatment
techniques, concluded that the influence of the waste
discharges on macroinvertebrates was imperceptible. A
later study by Evans et al. (1982) on waste discharges
from an alum coagulation/rapid sand filter plant on the
Mississippi River, found no marked environmental deg-
radation to the river, as measured by sediment size
distribution and benthic macroinvertebrate abundance
and diversity.
A study on the influence of residuals discharge on
Crooked Creek in Illinois (Lin and Green, 1987) con-
cluded that stream sediments immediately downstream
of the discharge outfall showed an increase in chemical
concentrations, a change in particle size distribution,
and a shift in the diversity and abundance of macroin-
vertebrates. The macroinvertebrate biotic index (MBI),
used by Illinois to indicate water quality on the basis of
the type of benthic life present, showed no change at
the sample stations immediately upstream and down-
stream of the water plant's discharge (Illinois, 1987).
Studies on the effects of alum sludge on benthic com-
munities provide additional information on aluminum
toxicity. Aluminum hydroxide has been shown to be toxic
to Tanytarsus dissimilis (a representative of the chiro-
comidae), at concentrations of 80, 240, and 480 mg/L
(Lamb and Bailey, 1981). A heavy floe layer on a lake
bottom could inhibit deposited eggs from reaching the
sediment and the surface.
An assessment of the effects of alum sludge discharges
into coastal streams (Roberts and Diaz, 1985) shows a
depression in the productivity of phytoplankton during
an alum discharge event. This was attributed to the high
level of suspended solids associated with the sludge
discharge. The researchers concluded that "this turbidity
effect in itself would argue for the cessation of sludge
discharge even in the absence of toxic effects" (Cornwell
et al., 1987). At plants where coagulation sludge is
allowed to accumulate in settling basins for several
months and is then discharged over short periods of
time, a substantial increase in total suspended solids
(TSS) and turbidity has been observed in the plant's
receiving waters. Continuous withdrawal may minimize
this problem (Illinois, 1987).
5.1.2.3 Nonaluminum Substances
Residuals discharged from lime softening WTPs may
not adversely affect aquatic organisms due to the pro-
tection provided by high calcium and alkalinity levels.
Toxicity testing, however, of residuals extract obtained
at pH 8.3 from the Florence Water Treatment Plant (a
lime softening facility), Omaha, Nebraska, indicated
growth inhibition of S. capricornutum only in 50 and 100
percent extract solutions (George et al., 1995). Residu-
als extracts obtained at pH 6.0 also inhibited S. capri-
cornutum growth in 12.5 percent extract solution plus
87.5 percent Missouri River water.
Most substances discharged into surface waters from
WTPs have established toxicity levels and are state
regulated. In-stream guidelines and standards are pre-
sented in Table 5-1. After characterizing the waste
75
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Table 5-1. Possible In-Stream Water Quality Guidelines and Standards (Cornwell et al., 1987)
Guidelines
Example Standards
Arsenic (dissolved)
Barium
Beryllium
Cadmium
Chloride
Chromium
hexavalent, dissolved
trivalent, active
total
Copper
Cyanide, free
Fluoride
Hydrogen sulfide
Iron
total
soluble
Lead
Manganese
total
soluble
Mercury
Nickel (total)
Nitrate (as N)
Phenol
Selenium
Silver
Sulfate
IDS
Zinc
Aldrin
Chloride
Endrin
Heptachlor
Lindane
Methoxychlor
Toxaphene
DDT
Chloroform
Radioactivity (Ra226+228)
Gross alpha particle activity (excluding
radon and uranium)
Aquatic Life Chronic
Fresh ng/L
72
130
1.16 (ln(hardness))-3.841
7.2
0.819 (ln(hardness))+.537
2.0
4.2
2.0
1,000
1.34 (ln(hardness))-5.245
0.00057
0.76 (ln(hardness))+1.06
1.0
35
0 01 e172 (|n(hardness))-6-52
47
0.03
0.0043
0.0023
0.0038
0.08
0.03
0.013
0.001
1,240
Criteria
Salt ng/L
63
12
54
4(2y)
23(A)
0.57
2.0
8.6
100
0.1
7.1
1.0
54
0.023
58
0.003
0.004
0.0023
0.0036
0.0016
0.03
0.0007
0.001
Human
Health3
2.2 ng/L
3.7 ng/L
10.0 |ig/L
1 70 |ig/L
20.0 |ig/L
50 |ig/L
1 46 ng/L
13.4|ig/L
3,500 |ig/L
10|ig/L
50 |ig/L
5,000 |ig/L
0.074 ng/L
0.46 ng/L
1 .0 |ig/L
0.28 ng/L
0.71 ng/L
0.024 ng/L
0.19|ig/L
Stream Used for
Potable Water
0.05 mg/L
1 .0 mg/L
0.01 mg/L
250 mg/L
0.05 mg/L
1.0 mg/L
1 .4 mg/L
0.3 mg/L
0.05 mg/L
0.05 mg/L
0.002 mg/L
10 mg/L
0.001 mg/L
0.01 mg/L
0.05 mg/L
250 mg/L
500 mg/L
5.0 mg/L
0.0002 mg/L
0.004 mg/L
0.10 mg/L
0.005 mg/L
0.1 mg/L
5 pCi/L
15 pCi/L
a Values given are the ambient water quality criteria for protection of human health for noncarcinogens, and for carcinogens the value is the
risk of one additional case of cancer in 1,000,000 persons.
76
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stream quality and flow rate, a mass balance calculation
(see Section 5.2.1.3) should be conducted to determine
possible toxicity of certain substances.
5.1.2.4 Summary
Based on the findings of research on aluminum toxicity,
the following recommendations should be followed
when disposal to surface waters is being considered for
WTP residuals:
• Toxicity tests should be conducted on a variety of
representative aquatic organisms from the intended
receiving waters to fully determine potential toxic ef-
fects to the ecosystem.
• Alum sludges should not be discharged to acid
streams (pH less than 6); discharge into water with
circumneutral pH levels, however, should have mini-
mal effects on primary production, and is acceptable.
• Caution should be taken in discharging alum sludges
to soft receiving waters (i.e., hardness less than 50
mg CaCO3/L).
• An environmental assessment should be undertaken
for any sludge disposal to surface waters. Factors
such as receiving water use, sediment structure,
water chemistry, system hydrology, and receiving
water biology need to be assessed to ascertain if
discharge of alum sludges into a specific surface
water will have a detrimental effect on the ecosystem.
5.2 Applications
5.2.1 Stream Hydraulics
The primary sources for residuals discharged to streams
typically include clarifier underflow sludge, filter back-
wash wastes, and sedimentation basin sludge. These
residuals are generated at varying rates. For example,
filter backwash wastes are generated at high flow rates
over short periods of time and may require equalization
before discharge; sedimentation basin sludge is dis-
charged more frequently according to periodic basin
cleaning, unless the basins are equipped with mechani-
cal sludge removal.
The impact that discharge of drinking water treatment
residuals has on a stream depends upon the frequency
of the discharge (ranging from daily to annually), the
variability of the stream flow, and the load discharged.
Under conditions of high velocity flow, more frequent
controlled discharge is possible because the residuals
will be suspended in the flow and dispersed down-
stream, diluting and minimizing the potential toxicity of
the residuals. As previously described, under conditions
of low velocity flow, high frequencies of discharge can
significantly affect the aquatic ecology of the stream
because the residuals will deposit in the vicinity of the
outfall. This type of deposit can be subject to scouring
during periods of high flow velocities.
5.2.1.1 Stream Characteristics and Flow Analysis
When considering the effects of a point source dis-
charge on a stream, the principal stream characteristics
of interest include geometry (width and depth relations),
velocity, and flow. Stream flow, Q, is a function of the
average stream velocity, U, and cross-sectional area, A,
as:
Q = U(A)
(Eq. 5-1)
Stream flow rates can be determined by several meth-
ods (Thomann and Mueller, 1987):
• Directly measuring cross-sectional area and average
flow velocity (as with a current meter).
• Tracking of markers or dyes over time.
• Obtaining stage-discharge relations from gauging
stations (operated by the U.S. Geological Survey along
most major rivers).
Given the concept of dilution, it is intuitive that the effects
of residuals discharges are most critical during low
stream flow periods. Consideration of minimum flow
involves an analysis of a stream's flow frequency. Gen-
erally, most design work uses the minimum average
7-day flow expected to occur once every 10 years.
Minimum design flow is calculated using the following
equation:
minimum design flow = a Q b
(Eq. 5-2)
where
a = number of days used in the average
Q = stream flow (see Eq. 5-1)
b = interval in years over which the flow is expected
to occur
The minimum design flow, therefore, is expressed as:
minimum design flow = 7(Q)(10) (Eq. 5-3)
Determinations of flow frequency can be made from
plotting a stream's flow data and the percent of the time
that the stream will have a flow less than or equal to a
specific flow rate (Figure 5-1). From a flow frequency
analysis of the Schuylkill River in Philadelphia, Pennsyl-
vania, for instance, the discharge of a periodic effluent
could be timed to coincide with the river's high flow
periods to minimize effects of the discharge on the
receiving stream.
5.2.1.2 Length to Mixing
The concentration and flow of a pollutant into a stream
whose flow and other hydraulic properties are defined,
can be approximated (Thomann and Mueller, 1987).
This requires the assumption that water quality variables
77
-------
10050 20 10
Recurrence interval, yr
5 2 1.25
1.05
2000
1000
800
600
500
400
300
200
I I
I
7Q10
-II 1 1 1 1 1 1 1 1 1
1 1
II
12 5 10 20 30 405060 70 80 90 95 98 99
Percent of time flow is equal to or less than
Figure 5-1. Flow frequency analysis of the Schuylkill River,
Philadelphia, PA; minimum 7-day average flow val-
ues, 1932-1964 (after Thomann and Mueller, 1987).
are homogeneous laterally, across the stream, and ver-
tically, with depth. In addition, it must be assumed that
the stream flow involves only advective flow — i.e., there
is no mixing in the longitudinal, or downstream, direc-
tion. True plug flow in streams is never attained, but
these assumptions are valid for a simple steady-state
analysis. Effluent discharge from a point source will
result in a plume that will gradually spread across the
stream and extend over the entire depth. The estimated
distance from point of discharge to the point of complete
mixing of effluent in the stream depends on whether the
discharge enters the stream from the side bank or from
midstream. For a side bank discharge, the length from
the source to the zone where the discharge is laterally
well mixed, Lm (in feet), is approximated by:
Lm = 2.6 U B2/H
(Eq. 5-4)
where
U = average stream velocity in feet per second
B = average stream width in feet
H = average stream depth in feet
Fora midstream discharge, the mixing length is approxi-
mated by:
Lm = 1.3 U B2/H
(Eq. 5-5)
Qu = upstream flow
QI = influent plant flow
Qe = effluent plant flow
Qd = downstream flow
Cu = upstream pollutant concentration
Ce = effluent pollutant concentration
Cd = downstream pollutant concentration
The flow variables are in units of volume per time and
the concentration measurements are in units of mass
per volume. This results in units of mass per time, or
mass flux, in the mass balance calculations.
In the first scenario (common supply/discharge source)
depicted in Figure 5-2, the flow balance equation is:
Qd = Qu -
i + Qe
(Eq. 5-6)
The mass balance equation is:
QdCd = QUCU -
QeCe (Eq. 5-7)
Typically, the upstream concentration of the pollutant is
omitted because it is much less than that of the effluent
or downstream concentration. The mass balance equa-
tion is then reduced to:
or
QdCd = QeCe
Cd = (QeCe)/Qd
(Eq. 5-8)
(Eq. 5-9)
Q,Q.
QJX
Common Supply/Discharge Source
5.2.1.3 Flow and Mass Balance Calculations
Flow and mass balance calculations can be used to
estimate pollutant concentrations downstream from an
effluent discharge. To simplify mass balance calcula-
tions for point source effluent discharge to a stream,
assume that effluent mixing in the stream occurs instan-
taneously and that flow occurs only through advective
processes—i.e., there are no dead zones downstream
to cause flow dispersion, for example.
Figure 5-2 shows two scenarios for water supply and
effluent discharge sources for a WTP, where
Different Supply/Discharge Sources
Figure 5-2. Scenarios for mass balance calculations.
78
-------
In the second scenario for water supply and effluent
discharge sources, the flow balance equation is:
Qd = Qu + Qe (Eq. 5-10)
The mass balance equation is:
QdCd = QUCU + QeCe
(Eq. 5-11)
Again, assuming the upstream concentration is insignifi-
cant, the mass balance equation is reduced to the same
form as for the first scenario:
Cd = (QeCe)/Qd
(Eq. 5-12)
If the effluent stream is continuous, the pollutant is con-
servative (its concentration does not degrade with time
or flow), and the river is assumed to flow as an ideal plug
flow reactor, then the downstream concentration, Cd, will
be constant for all downstream distances. Pollutant con-
centrations from WTP effluents, however, will decrease
downstream from the discharge point through advective
flow processes in the river, and chemical reactions,
bacterial degradations, or particulate settling of the pol-
lutant in the water column. Typically, the concentration
decreases occur according to first order reaction kinet-
ics. The concentration of a substance downstream is
then calculated as:
Cd = Cm[(-kX)/U] (Eq. 5-13)
where
Cd = downstream pollutant concentration
Cm = mixed effluent and upstream pollutant
concentration
k = first order reaction constant
X = distance downstream from the discharge point
U = river velocity
The change in pollutant concentration with downstream
flow is shown in Figure 5-3.
5.2.1.4 Water Quality Controls
Three factors influence the downstream fate of a pollut-
ant: effluent flow rate, stream flow rate, and the decay
rate of the pollutant (Thomann and Mueller, 1987). By
modifying one of these variables, the downstream water
quality can be improved. Figure 5-4 shows the effects of
three techniques for controlling downstream water qual-
ity: decreasing effluent flow rate (a), making use of
increased upstream flow rate (b), and increasing decay
rate, k (c). With the first technique, if the effluent flow
rate is decreased and the effluent concentration remains
constant, the mixed pollutant concentration at the dis-
charge point and the downstream concentration will be
reduced.
The second technique involves discharging during in-
creased upstream flow rates, as from a storm event. In
this case, the discharged effluent will mix with a greater
C (mg/L)
Distance (X)
Figure 5-3. Decay of a nonconservative pollutant.
flow of water in the stream and pollutant concentrations
near the discharge point will decrease. The disadvan-
tage of this technique is that high stream flow rates will
carry pollutant concentrations farther downstream than
usual.
The third technique requires more sophisticated meth-
ods to modify the pollutant properties so that its decay
rate increases in the stream. The pollutant concentra-
tions at the discharge point are unaffected by this tech-
nique, but the increased decay rate results in rapid
decreases in downstream pollutant concentrations.
5.2.2 Available Transport and Chemical
Models and Their Application
Numerous computer models are used to predict the
transport and fate of pollutants in natural systems. The
EPA Center for Exposure Assessment Modeling in Ath-
ens, Georgia, provides and supports public domain soft-
ware that simulates air, water, and soil processes,
enabling the user to make risk-based decisions con-
cerning environmental protection (Ambrose and Barn-
well, 1989). The software is available to the user at no
cost, but considerable technical expertise is needed to
successfully use this software for problem-solving.
MINTEQ, for example, is one of six geochemical-
equilibrium computer models routinely used to quantita-
tively evaluate the equilibrium behavior of inorganic and
organic constituents in various chemical environments
(U.S. EPA, 1991 a; Bassett and Melchoir, 1990; U.S.
79
-------
a)
C (mg/L)
Distance (X)
b)
C (mg/L)
Distance (X)
c)
C (mg/L)
Distance (X)
a) decreased effluent flow rate;
b) increased upstream flow rate;
c) increased decay rate
Note: dashed lines represent initial conditions and
solid lines represent improved conditions.
Figure 5-4. Control techniques for improving downstream
water quality.
EPA, 1984a). MINTEQ describes the chemical condi-
tions and reactions that control leaching. It then calcu-
lates the fate (or mass distribution) of dissolved and
solid phases of a pollutant under equilibrium conditions
in dilute aqueous systems. The model considers ion
speciation, adsorption, redox, gas-phase equilibria, and
precipitation and dissolution reactions in its calculations.
To obtain accurate information from the model, users
must be familiar with these processes and techniques
and be able to quantify them for a specific pollutant and
river system. There are currently no user-friendly aque-
ous chemical equilibrium models that are sophisticated
enough to make the necessary accurate downstream
water quality predictions.
5.3 Examples
An investigation of the adverse effects of alum sludge
on benthic invertebrates was conducted in 1991 by
Tennessee Technological University (TTU) for the
AWWA Research Foundation (George et al., 1991).
Three of the four following examples were summarized
from this research report. The fourth example was ob-
tained from a report to the City of Phoenix, Arizona,
evaluating the discharge of three WTPs to the Salt River
Project canal system (HDR, 1995).
5.3.1 California Plant, Cincinnati Water
Works, Cincinnati, Ohio
5.3.1.1 Description
The California Plant in Cincinnati, Ohio, treats drinking
water at a rate of 618 m3/min. The WTP consists of
primary coagulation-sedimentation, offstream storage
reservoirs, secondary coagulation-sedimentation, sand
filtration, and disinfection facilities (Figure 5-5). Primary
sedimentation is achieved using a 460 m3/min facility
equipped with plate settlers to separate solids that are
continuously returned to the Ohio River. This process is
responsible forthe bulk of the solids removal conducted
at the facility. The water from the storage ponds is
pumped to the secondary sedimentation facility, which
delivers a low turbidity water to the sand filters. The
storage reservoirs provide emergency capacity during
hazardous spill conditions that might occur in the Ohio
River system.
Aluminum sulfate and polymer are added to the raw
water. Ferric sulfate, powdered activated carbon (PAC),
and polymer are used intermittently. When needed, PAC
can be applied to the raw water; after the primary sedi-
mentation basins and before pumping the water to the
storage reservoirs; and at the rapid-mix basin before the
secondary sedimentation basins. The plant can pre-
chlorinate the raw water; add chlorine at the rapid-mix
basin between the reservoirs and the secondary sedi-
mentation facility; chlorinate between the secondary
sedimentation basins and the sand filters; and
postchlorinate between the filters and the clean/veil. Fer-
ric sulfate, lime, and soda ash also can be added at the
rapid-mix basin prior to the secondary sedimentation
basins. The quantities of chemicals used at the Califor-
nia Plant from July 1988 through June 1989 are pre-
sented in Table 5-2.
Waste solids from the secondary sedimentation facility
and the backwash water are transported to the primary
sedimentation facility, which has plate settlers. An aver-
age of 5 m3/min of the wasted sludge (0 to 4 percent
solids) from the primary sedimentation basins is dis-
charged continuously to the Ohio River.
Data on the chemical composition of the Cincinnati
sludge and of the Ohio River at the point of discharge
are presented in Table 5-3. The Ohio River samples
tested by George et al. (1991) were moderately hard
(123 to 155 mg CaCO3/L); alkalinity ranged from 53 to
67 mg CaCO3/L; and total aluminum concentrations
80
-------
Ferrle Sulfftte
Um« . nuorldv *
CKIorln«
Storage Ponds
Rapid
Mix
Floe
Cells &
Settlers "~El
Filters
Clearwell
n i i
Distribution System
Presettling
Figure 5-5. Flow schematic of California Plant, Cincinnati Water Works, Cincinnati, OH (George et al., 1991).
Table 5-2. Average Daily Chemical Use at California Plant, Cincinnati Water Works, Cincinnati, OH (George et al., 1991)
Month
1988
July
August
September
October
November
December
1989
January
February
March
April
May
June
Meanb
Alum
(kg/d)
6,882
6,313
4,948
4,886
4,895
6,648
8,849
7,470
6,346
6,864
7,555
4,886
6,379
Polymer
(kg/d)
0
0
0
0
207
142
0
986
625
405
574
531
496
PAC
(kg/d)
970
6,628
2,302/27a
0
0
0
0
0
1,404
3,103
1,986
0
2,731
Ferric Sulfate
(kg/d)
0
877/1 5a
766/1 3a
742/1 8a
646/5a
656/1 6a
662/1 9a
965/1 3a
638/1 8a
0
618/163
757/25a
733
Lime
(kg/d)
6,729
8,133
5,938
4,695
3,895
4,501
4,751
4,695
4,171
4,156
4,540
4,702
5,076
Fluoride
(kg/d)
652
666
445
425
363
398
405
452
429
465
466
554
477
Chlorine
(kg/d)
2,970
3,453
2,585
1,876
1,688
1,546
1,426
1,223
1,110
1,132
1,134
1,806
1,829
were less than 0.02 to 0.56 mg/L. The waste stream
from the WTP contained little aluminum (1.69 to 24.1
mg/L), and suspended solids varied from 170 to 4,272
mg/L. The Ohio River provided tremendous dilution of
the waste stream from the plant (2 x 10"5 m3 sludge/m3
of river flow).
5.3.1.2 Toxicity
Samples of discharged sludge and receiving waterwere
taken for three different pH levels. Toxicity tests indi-
cated that none of the sludge extracts produced a toxic
response in a protozoan (Tetrahymena) mortality test,
Microtox toxicity test, Ceriodaphnia toxicity test, or fat-
head minnow (Pimephales) toxicity test. At pH 5, how-
ever, the sludge extract was toxic to S. capricornutum
(Table 5-4) at a 50 percent and 100 percent extract
exposure. No adverse response was observed at pH 7.4
and 8.
5.3.1.3 Benthic Organisms
At the time it was studied, the California Plant dis-
charged alum sludge to the Ohio River at a point just
above the confluence with the Little Miami River. PAC
was added as needed for taste and odor problems.
81
-------
Table 5-3. Chemical Composition of Sludge and Ohio River Water Sampled at California Plant, Cincinnati Water Works,
Cincinnati, OH, September 21, 1988, December 18, 1988, and January 10, 1989 (George et al., 1991)
Parameter
Aluminum (mg/L)
Iron (mg/L)
Manganese (mg/L)
Calcium (mg/L)
Magnesium (mg/L)
Total organic carbon (mg/L)
Alkalinity (mg CaCOs/L)
Total suspended solids (mg/L)
PH
9/21/88
24.1
12.0
3.59
124.0
20.3
84
1,122
4,272
7.8
Sludge
12/18/88
23.6
13.4
<0.005
43
12.5
2.3
56
170
7.0
1/10/89
1.69
0.84
0.056
34
9.4
21
53
3,656
9/21/88
<0.02
0.16
0.048
35
13.5
2.5
54
10.2
7.4
Ohio River
12/18/88
<0.02
<0.005
<0.005
40
10.0
2.1
53
5.4
7.6
1/10/89
0.56
0.56
0.22
34
9.2
6.4
67
92
Table 5-4. S. Capricornutum Test Results on Alum Sludge
Extracts From California Plant, Cincinnati Water
Works, Cincinnati, OH (George et al., 1991)
Monomeric
Aluminum
Sample Percent Concentration Percent Percent
Site pH Filtrate (mg M-AI/L) Inhibition Stimulation ECso
pH 5
pH 7.4
pH 8
12.5
25
50
100
12.5
25
50
100
12.5
25
50
100
<0.04
0.05
0.10
0.20
<0.04
<0.04
0.07
0.14
0.05
0.10
0.19
0.38
NE
NE
35
70
NE
NE
NE
NE
NE
NE
NE
a
—
—
—
—
—
—
—
—
—
50 —
—
3 Insufficient data to compute
Key
NE = No statistically determined effect.
ECso = Effective concentration producing a 50 percent reduction in
growth rate compared with the growth rate of control populations.
In January, March, and May 1989, water and sediment
samples were collected from the Ohio River to deter-
mine the impact of the sludge discharge on the benthic
communities. During January, aluminum concentrations
in the water column immediately above the sediments
ranged from 1.63 to 4.67 mg/L, with the highest concen-
tration occurring at the point of discharge. Sediment
aluminum concentration (Figure 5-6) was also greatly
elevated at the point of discharge (23,560 mg/kg) and
gradually decreased to 1,882 mg/kg of dry sediment as
the sludge was dispersed downstream.
24000
22000
20000
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
"3
CD
|
i
u
g
o
£
e
E
_3
-
0
E
•D
10
24000
22000
20000
18000
16000
14000
12000
10000
8000
5000
4000
2000
0
-
i
1
1
1
|
XX,
\v
§\
1
• fc^N
fcxN
,
Mid-River Sampling Stations
•• Approximately 1 .7 km Downstream
to&xx Aprroxlmately 1 2 km Downstream
IQ.WI Point of Discharge
SSSS3 Approximately 200 m Upstream
™ HUSSUl ^^3r\xffi
^ ^Kxtvv^^ ^BSJxx^^
January 24,1989 March 12,1989 May 2,1989
Monitoring Period
Shallow Water Near Ohio Shore
Approximately 1.2 km Downstream
Point of Discharge
Approximately 200m Upstream
March 12,1989
May 2,1 989
Monitoring Period
Figure 5-6. Sediment aluminum concentration (dry weight) from
Ohio River, Cincinnati, OH (George et al., 1991).
Aluminum concentrations in the water column immedi-
ately above the sediment collected in March ranged
from 3.92 to 8.96 mg/L. The two highest concentrations
of aluminum were found at 1,700 meters downstream
(8.69 mg/L) and 1,158 meters downstream (8.96 mg/L),
82
-------
and were approximately twice the aluminum concentra-
tions measured at the upstream stations. Discharged
alum sludge floe may have been entrained in the water
currents. The greatest sediment concentrations of alu-
minum observed in March were collected near the point
of discharge. Concentrations of aluminum in the sedi-
ment ranged from 2,100 to 20,000 mg/kg dry weight.
Increased concentrations of aluminum at the point of
discharge (20,000 mg/L) were expected, due to settling
of suspended solids as the stream velocity decreases
toward the bank of the river. Aluminum concentrations
in the Ohio River during May remained fairly constant,
ranging from 0.94 to 1.27 mg/L. In May, aluminum con-
centrations in the sediment were highest near the shore
with less than 2,500 mg/kg measured in the deeper
channel.
The California Plant commonly added ferric sulfate,
along with increased amounts of aluminum sulfate, to
the raw water because of high turbidity following rain
events. The mean iron concentration in January was
1.79 mg/L (range 0.79 to 4.14 mg/L); it increased to 6.52
mg/L (range 2.55 to 7.90 mg/L) in March. By May (sam-
pling period #3), the mean iron concentration dropped
to 1.92 mg/L (range 1.56 to 2.49 mg/L). Aluminum con-
centrations were also higher in March, increasing to a
mean of 5.69 mg/L (range 3.92 to 8.69 mg/L) from a
mean of 2.57 mg/L (range 1.63 to 4.67 mg/L) observed
on the previous sampling trip in January. The alum
sludge discharge, more dense with the addition of PAC,
apparently settled out quickly nearthe point of discharge
in January. Greater flow throughout the remainder of the
study period transported sediment deposits downstream
from the point of discharge.
Benthic macroinvertebrate data from the same sampling
location are presented in Table 5-5. Benthic samples
Table 5-5. Benthic Macroinvertebrates Collected From Site
CO on the Ohio River, Cincinnati, OH, 1989
(George et al., 1991)
Distance From Point of Number
Discharge of Taxa
Organism
Density (No.
Organisms/m2)
Sampling Period 1, January 24-25, 1989
1,661 m downstream 3
1,158 m downstream 7
0 (point of discharge) —a
200 m upstream 4
Sampling Period 2, March 12-13, 1989
1,661 m downstream —a
1,158 m downstream 5
0 (point of discharge) 5
200 m upstream 7
Sampling Period 3, no sample
113
646
a
1,227
330
174
322
aZero macroinvertebrates found.
were not collected in May because of high flow veloci-
ties. Heavy scouring of the sandy bottom during high
flow was observed by Chisholm and Downs (1978), who
found damage to benthic communities resulting from the
relatively high flow velocities. All composited benthic
macroinvertebrate samples collected contained fewer
than 100 organisms. As the accuracy of the species
diversity indices is diminished when the samples contain
fewerthan 100 organisms (U.S. EPA, 1983), no diversity
indices were calculated. Dipterans (Chironomidae) and
oligochaetes were the dominant taxa collected in these
samples.
No organisms were collected at the point of discharge
in January; this phenomenon was probably due to
sludge accumulations over the substrates. The tempo-
rary nature of these sludge deposits was evidenced by
the presence of a benthic community sampled at the
point of discharge in March. At the same time, no organ-
isms were found in the sample taken 1,661 m down-
stream from the point of discharge. The lack of
organisms at this site immediately below the confluence
of the Little Miami and the Ohio Rivers was probably due
to high flow conditions in both water bodies and appar-
ent scouring of the sandy bottom. Low numbers of taxa
and organisms at all stations indicate stress to the ben-
thos in the study area. Lack of suitable substrate is
believed to be a major contributing factor to the low
species richness numbers of organisms in this reach of
the river.
In summary, the effects of alum sludge discharged from
the California Plant into the Ohio River could not be
separated from ambient impacts within the system. High
concentrations of sludge components in the study area
appear to be transitory in both the water column and
sediment. Benthic macroinvertebrate communities ap-
pearto exhibit transient impacts at the point of discharge
that were overshadowed by high-flow scouring from
storm events and lack of suitable habitat.
5.3.2 Ralph D. Bollman Water Treatment
Plant, Contra Costa Water District,
California
5.3.2.1 Description
The Ralph D. Bollman Water Treatment Plant, Contra
Costa Water District, California, treats water from the
Sacramento-San Joaquin River delta in northern Cali-
fornia. Flow from the river delta is pumped into Mallard
Reservoir (capacity 13.8 million m3), where it is held until
it is treated. The design capacity of the WTP is approxi-
mately 237 m3/min, and the average production is 81
m3/min. Water treatment consists of prechlorination;
alum coagulation; flocculation; sedimentation; chlorina-
tion prior to filtration; high-rate, dual-media filtration;
ammoniation; and pH control (Figure 5-7). At the time of
83
-------
Coagulant Aid
Powdered Activated C&rboi
Intake
Pumps
Rapid Flocculatic
Mix Basins
Coagulan
A
n
Clarifiers
Mallard
Reservoir
Storage
Filler Aid
Chlorine
Lime
Fluoride
Powdered Aclivoled Carbon
Distribution
Figure 5-7. Flow schematic of Ralph D. Bollman WTP, Contra Costa Water District, CA (George et at, 1991).
this study, PAC was used to control taste and odor
problems. From November 1986 to December 1988, the
average dosage of PAC was 3.5 mg/L. The 1988 dosage
totaled approximately 146 metric tons. Also in 1988, an
average of 1,816 metric tons of alum and 182 to 227
metric tons of lime were added to the water.
Solids residuals from the sedimentation basins were
discharged daily to an embayment of Mallard Reservoir
fora 15-month period (October 1987 through December
1988). Filters were backwashed approximately once
every 50 hours and the water was wasted to the reser-
voir. During 1988, the backwash water was approxi-
mately 1 percent of the water treated. Approximately
1,504 metric tons of solids were discharged into Mallard
Reservoir. The water district did not waste solids from
the sedimentation basins to Mallard Reservoir after De-
cember 1988.
Sludge samples were collected from Mallard Reservoir
in October 1988 and February 1989 and contained from
803 to 1,450 mg/L aluminum and 196 to 319 mg/L iron.
Total suspended solids concentration in the sludge was
13,733 mg/L. Mallard Reservoir water contained 0.36 to
0.81 mg/L aluminum and was moderately hard (approxi-
mately 126 to 143 mg CaCO3/L). Chloride concentra-
tions were high (159 to 217 mg/L) due to salt water
intrusion into the Sacramento-San Joaquin River delta.
5.3.2.2 Toxicity
Sludge extracts obtained with Mallard Reservoir water,
which was pH adjusted, were not toxic to bacteria (Mi-
crotox assay), the protozoan Tetrahymena ceriodaph-
nia, or fathead minnow. Sludge extracts obtained with
pH 5 reservoir water, however, were toxic to S. capricor-
nutum (Table 5-6). An EC50 (the effective concentration
producing 50 percent reduction in growth rate compared
with the growth rate of control populations) of 22.5 per-
Table 5-6. 5. Capricornutum Test Results on Alum Sludge
Extracts From Ralph D. Bollman Water Treatment
Plant, Contra Costa, CA (George et at, 1991)
Sample
Site pH
pH 5
pH 7.5
pH 8.5
Monomeric
Aluminum
Percent Concentration
Filtrate (mg M-AI/L)
12.5
25
50
100
12.5
25
50
100
12.5
25
50
100
<0.04
0.05
0.10
0.20
<0.04
<0.04
0.05
0.09
0.07
0.14
0.27
0.54
Percent
Inhibition
37
54
60
100
NE
NE
NE
NE
NE
NE
Percent
Stimulation ECso
22.5%
a
a
a
29 — a
a
43 — a
a
a
a
a
a
a Insufficient data to compute ECso.
Key
NE = No statistically determined effect.
ECso = Effective concentration producing a 50 percent reduction in
growth rate compared with the growth rate of control populations.
cent was computed. Although the alum sludge extract
obtained at pH 7.5 stimulated algal growth at the lower
extract concentrations (i.e., 12.5 percent and 50 per-
cent), no effect occurred at any concentration at pH 8.5.
5.3.2.3 Benthic Organisms
The Ralph D. Bollman WTP discharged wasted solids
daily into Mallard Reservoir from October 1987 through
December 1988. Taste and odor problems with the fin-
ished product water were controlled by the addition of
PAC, and the waste carbon was discharged to the
84
-------
reservoir with the alum sludge. Sludge discharge to
Mallard Reservoir ended in December 1988.
Water and sediment samples were collected from Mal-
lard Reservoir at three stations during February 1989.
Station 1 was located at the point of discharge, and
Stations 2 and 3 were located in the opposite corners of
the reservoir, outside the mixing zone. At the point of
discharge, aluminum concentration in the water column
above the sediments was 9.40 mg/L and averaged 0.36
mg/L within the bulk of the reservoir. The iron concen-
tration was 2.80 mg/L at the point of discharge while an
average iron concentration of 0.15 mg/L existed in the
water column above the sediments in most of the im-
poundment.
Aluminum concentrations in the sediment (Figure 5-8)
were much higher at discharge point (102,000 mg/kg dry
weight) than at other locations within the reservoir (av-
eraging 42,640 mg/kg). A thick layer of alum sludge
containing PAC appeared to be distributed over much of
the bottom surface of Mallard Reservoir.
Oligochaetes and amphipods dominated the benthic
macroinvertebrate communities at all stations. The point
of discharge had the highest number of taxa and also
the highest species diversity (Table 5-7). At the point of
discharge, eight taxa were identified and a Shannon
species diversity of 1.90 was computed. The other moni-
1?
75)
c
_o
"cfl
um Concentr
|
<
"c
01
0)
1 1 0000
100000
90000
80000
70000
60000
50000
40000
30000
20000
10000
0
February 21,1989
Monitoring Period
Figure 5-8. Sediment aluminum concentration from Mallard
Reservoir, Concord, CA (George et al., 1991).
toring stations within the reservoir had five taxa with a
diversity of 1.16, and four taxa and a diversity of 0.62.
Species diversity and evenness values were lower at
Station 2 (500 organisms/m2) and Station 3 (1,049 or-
ganisms/m2), while the estimated number of organisms
per square meter, i.e., the density at these stations was
greater than at the sludge discharge location (113 or-
ganisms/m2).
Impacted communities and stations usually exhibit a
reduced Shannon diversity value (Washington, 1984),
and values less than 3 indicate moderate to heavy
pollution (Goodnight, 1973). Margalef species richness
values were also highest at the discharge point (1.03)
and lowest at Station 3 (0.030). The major difference
between the benthic communities of the three sites was
the number of Oligochaetes collected. Oligochaetes
composed 15 percent of the sample collected at Station
1, the point of discharge; 57 percent at Station 2; and
13 percent at Station 3. Fine particle, consolidated sedi-
ments apparently favored oligochaete assemblages at
the expense of aquatic insects (Pennak, 1989).
The low density of organisms at the point of discharge
(113 organisms/m2) was indicative of moderate stress
on the benthic macroinvertebrate community and was
characteristic of a system subjected to toxic metal
wastes (Cairns et al., 1971; Young et al., 1975). Rela-
tively high numbers of Oligochaetes in the sample from
Station 2, along with a relatively low species diversity
and evenness value, also indicate a probable negative
impact on the ecological integrity of the benthic commu-
nity (Washington, 1984; Cairns, 1977; Brinkhurst et al.,
1968). The Simpson heterogeneity index indicated
greatest species heterogeneity at the point of discharge
(0.84), where the highest number of taxa (eight) were
collected. Lowest heterogeneity (0.32) and lowest num-
ber of taxa (four) were found at Station 3.
In summary, data from the water and sediment field
samples taken at three stations at Mallard Reservoir
indicate moderate stress on benthic community struc-
ture, possibly resulting from alum sludge discharge and
habitat constraints. High concentrations of alum were
present in the water column and sediment of all stations,
with the highest concentration found at the point of
discharge. Assessment of benthic macroinvertebrate
Table 5-7. Benthic Macroinvertebrates Collected From Mallard Reservoir at Site CC, Contra Costa Water District, Concord, CA,
February 21, 1989 (George et al., 1991)
Station
1
2
3
Number
of Taxa
8
5
4
Organism
Density (No.
Organisms/m2)
113
500
1,049
Shannon
Diversity Index
1.90
1.16
0.62
Pielou
Evenness
Index
0.91
0.72
0.45
Margalef
Richness
Index
1.03
0.45
0.30
Simpson
Heterogeneity
Index
0.84
0.63
0.32
85
-------
data supports the observation of a stressed community
at all stations sampled.
5.3.3 Mobile Water Treatment Plant, Mobile,
Alabama
5.3.3.1 Description
The Mobile Water Treatment Plant has a capacity of 158
m3/min and an average daily drinking water production
of 105 m3/min. The raw water treated by the plant is
taken from the Big Creek Lake, which is a 1,457 hectare
(ha) reservoir. The water from the reservoir is very ag-
gressive (Aggressive Index less than 10), with an aver-
age calcium concentration of only 2.9 mg CaCO^/L, a
bicarbonate concentration of 4 mg CaCO3/L, and a pH
of 6.2. Water is pumped from Big Creek Lake to a
ground-level storage basin from which water is pumped
to the plant. As water is transported from the storage
basin to the plant, it is disinfected by chlorine dioxide. At
the plant the water pH is raised by lime addition. Water
treatment includes coagulation by alum (average dose
24.8 mg/L), flocculation, sedimentation, rapid sand filtra-
tion and postchlorination (Figure 5-9). Zinc orthophos-
phate is added for corrosion control. The average mass
loading of aluminum to the system has been about 3.8
metric tons/day, and the average daily lime addition has
been 2.4 metric tons.
Settled solids from the sedimentation basins are wasted
daily for approximately 2.5 hours each morning at a rate
of 13 m3/min. The filters are backwashed over a 3-hour
period every afternoon at a rate of approximately 2.1
m3/min. The waste discharge goes into a small drainage
ditch that enters Three Mile Creek, which flows through
the city of Mobile, Alabama. At the time of the study,
Three Mile Creek water was soft (approximately 15 mg
CaCO3/L hardness) and had low alkalinity, ranging from
12 to 20 mg CaCO3/L. Aluminum in the Three Mile Creek
water samples ranged from less than 0.02 to 0.19 mg/L.
5.3.3.2 Toxicity
The protozoan mortality test using Tetrahymena indi-
cated no toxic response of the organism to extracts from
the Mobile Water Treatment Plant waste sludge. Using
the Microtox assay, however, sludge extracts had a
15-minute EC50 equal to 85 percent of the filtered sludge
extract at pH 9. The predominant aluminum species at
pH 9 was most likely the aluminate ion. The Microtox
test showed no toxic effects to any of the remaining alum
sludge extracts. Mobile's sludge extracts were signifi-
cantly inhibitory to S. capricornutum at all concentra-
tions of each pH level (Table 5-8).
5.3.3.3 Benthic Organisms
The brownish alum sludge discharge was clearly visible
for approximately 400 meters downstream of the point
of entry before mixing with the receiving water. During
water and sediment monitoring in January 1989, sulfate
concentrations in Three Mile Creek ranged from 2.7
mg/L upstream from the point of discharge to 18.7 mg/L
at the point of discharge. TSS also followed this trend in
January when concentrations ranged from 3.2 mg/L
upstream (Station 4) to 185 mg/L at point of discharge
(Station 3). Likewise, aluminum concentrations ranged
from 1.21 mg/L at Station 4 to 5.26 mg/L at Station 3 in
January.
While the aluminum concentration upstream from the
point of discharge ranged from 1.21 (January) to 0.02
Chlorine Dioxide
Lime
Polymer
Chlorine Dioxide
Floe
Cells
Clarifiers
Low
Head
Pumps
Clear
Well
Gravity
Filters
Flow
^f \
Lime
Distribution Syste
High
Service
Pumps
Figure 5-9. Flow schematic of Mobile WTP, Mobile, AL (George et al., 1991).
86
-------
Table 5-8. 5. Capricornutum Test Results on Alum Sludge
Extracts From the Mobile, AL, Water Treatment
Plant (George et al., 1991)
Sample
Site pH
pH 6.7
pH 8
pH 9
Percent
Filtrate
12.5
25
50
100
12.5
25
50
100
12.5
25
50
100
Monomeric
Aluminum
Concentration
(mg M-AI/L)
0.04
0.08
0.17
0.34
0.04
0.08
0.17
0.34
1.34
2.69
5.38
10.76
Percent
Inhibition
18
27
62
92
30
63
95
99
99.6
100
100
100
ECso
37%
a
—
—
19%
—
—
—
—
—
—
—
a Insufficient data to compute ECso.
Key
EC50 = Effective concentration producing a 50 percent reduction in
growth rate compared with the growth rate of control populations.
mg/L (February), the downstream mean aluminum con-
centration in January was 12.6 mg/L, decreasing to 0.05
mg/L in February, and increasing to 1.09 mg/L in March.
Downstream mean TSS concentrations were also high-
est in January 78.2 mg/L, dropping to 5.2 mg/L in Feb-
ruary. Iron exhibited a similar trend, as downstream
mean concentration was 2.59 mg/L in January, 0.30
mg/L in February, and 0.96 mg/L in March.
The data gathered suggest the possibility that deposi-
tion of aluminum from the plant's alum sludge occurred
in sediment downstream from the point of discharge
(Figure 5-10). Aluminum concentrations in the sediment
at the downstream Station 2 (2,208 mg/kg) were higher
•» 2400 r
OJ
_f
0
£;
C
d)
0
o
O
E
c
|
1
"c
1
T3
a
CO
2200
2000
1800
1600
1400
1200
1000
800
600
400
200
0
Upstream Site
Point of Discharge
K\\\N Approximately 400 m Downstream
Approximately 3 km Downstream
February 14,1989 March 21,1989
Monitoring Period
Figure 5-10. Sediment aluminum concentration from Three Mile
Creek, Mobile, AL (George et al.. 1991).
than the concentrations found at the point of discharge
(1,236 mg/kg).
Benthic macroinvertebrate data are presented in Table
5-9. Oligochaetes and dipterans (Chironomidae) were
the dominant taxa collected in Three Mile Creek, in
addition to trichopterans (Cheumatopsyche sp.). The
upstream monitoring station had the greatest number of
taxa and the greatest number of organisms for two of
the three sampling events. In February, the density of
organisms ranged from 4 organisms/m2 to 3,606 organ-
isms/m2 at Station 4. By March, the number of organ-
isms per square meter ranged from 41 at the point of
discharge to 3,641 at the upstream reference station. In
January, the lowest number of organisms was recorded
at the point of discharge. The alum sludge discharged
by the Mobile Water Treatment Plant apparently had an
adverse effect on the benthic macroinvertebrate density
of Three Mile Creek at and below the point of discharge.
A study by Lin (1989) also found an impact to benthic
macroinvertebrates from alum sludge discharge.
In summary, the alum sludge discharged by the Mobile
Water Treatment Plant appeared to have an adverse
effect on the benthic macroinvertebrate community of
the receiving stream at and below the point of discharge.
Moderate recovery of the macroinvertebrate community
appeared to have occurred approximately 1,200 meters
below the point of discharge.
Table 5-9.
Station
Benthic Macroinvertebrates Collected From Three
Mile Creek, Mobile, AL, 1989 (George et al., 1991)
Number
of Taxa
Organism
Density (no.
organisms/m2)
Sampling Period #1 - January 19, 1989
1 - ~3 km downstream location 6 1,570
from point of discharge
2 - ~0.5 km downstream from 6 54
point of discharge
3 - point of discharge 6 14
4 - upstream monitoring station 11 517
Sampling Period #2 - February 14, 1989
1
2
3
4
Sampling Period #3 - March 21, 1989
1
2
3
4
9
8
22
21
12
3
5
15
529
57
4
3,606
335
167
41
3,641
Note: Samples were collected using a Surber sampler and consisted
of five replicates per station. The numbers of taxa and organisms are
the summations of the numbers found in each replicate sample for
each site.
87
-------
5.3.4 City of Phoenix Utility, Phoenix, A rizona
5.3.4.1 Description
The Val Vista, Deer Valley, and Squaw Peak WTPs,
which are owned and operated by the City of Phoenix,
Arizona, directly discharge their waste residual solids
into the Salt River Project (SRP) canal system (Figure
5-11). The SRP also serves as the raw water source for
these WTPs. EPA has determined that discharges to the
SRP canals, considered waters of the United States, are
subject to NPDES permitting requirements (HDR, 1995).
Water in the SRP is a combination of the Salt and Verde
Rivers. Furthermore, the SRP canal system is intercon-
nected with water from the Central Arizona Project
(CAP). The quality of raw water treated by the WTP
varies according to the proportion of water received from
each of the aforementioned sources. Table 5-10 pre-
sents the average raw water quality for each of these
three sources.
Table 5-11 shows the flow rates and average turbidity
data for each facility. Even though Deer Valley and
Squaw Peak WTPs obtain raw water from the same
source (the Arizona Canal), the average raw water tur-
bidities at the Deer Valley WTP were higher than turbid-
ity levels treated by the Squaw Peak plant. The higher
raw water turbidity at the Deer Valley WTP has been
attributed to the residuals solids discharged into the
canal by the Squaw Peak WTP.
The three WTPs each use conventional treatment, em-
ploying grit removal, presedimentation, chemical addi-
tion, rapid mixing, flocculation, final sedimentation,
filtration, and disinfection. Direct discharge of residuals
solids into SRP was an acceptable practice at the time
the facilities were constructed and, therefore, no solids
handling facilities were constructed at any of the WTPs.
The following residuals solids were in waste streams
discharged to the canal system from the following water
treatment processes:
• Raw water solids (usually without chemical addition)
from grit and presedimentation basins.
• Alum residual solids from final sedimentation basins.
• Wasted washwater from filter backwashing and filter-
to-waste flows (i.e., filtered water immediately after a
filter is backwashed when turbidities exceed drinking
water standards).
• Miscellaneous waste streams from leaking valves,
basin and reservoir overflows, surface drainage, and
sample sink return flows (no chemical addition except
for chlorine residuals).
Currently, residuals solids from the three WTPs are
being discharged directly into the canals without equali-
N
\
r
Figure 5-11. Location of City of Phoenix WTPs, Phoenix, AZ (HDR, 1995).
88
-------
Table 5-10. Typical Canal Source Water Characteristics
(HDR, 1995)
Salt River
Verde River Below Stewart Colorado
Parameter Below Bartlett Mountain River Below
(mg/L unless Dam, SRP Dam, SRP Parker Dam,
noted otherwise) Canal3 Canal3 CAP Canal3
Arsenic 0.013 0.004 0.003
Barium 0.1 0.1 0.7b
Bicarbonate 235 160 155
Boron 0.19 0.19 0.19b
Cadmium 0.006 0.007 0.001
Calcium 43 50 82
Carbonate 2 00
Chloride 19 235 91
Chromium 0.004 0.002 0.006b
Copper 0.009 0.009 0.006b
Fecal coliform 13 7 4
(rf\ i/ml ^
^uiu/i i ii_y
Fluoride 0.3 0.4 0.4
Hardness 212 180 330
(as CaCOs)
Hardness 19 49 203
Iron 0.19 0.19 0.13
Lead 0.07 0.07 0.01
Magnesium 26 14 30
Manganese 0.09 0.06 0.02
Mercury 0.00026 0.00004 0.00003
Nitrate (as N) 0.4 0.1 0.1C
pH (units) 8.0 7.7 8.0
Phosphorus 0.21 0.22 0.02
Potassium 3.4 5.8 5.1
Selenium 0.00006 0.00003 0.00003
Specific 472 1,138 1,083
conductance
Silver 0.00001 0.0017 0.0001 b
Sodium 30 161 104
Sulfate 53 51 294
Total dissolved 280 5,007 721
solids
Total organic 3.5d 3.5d 5.2e
carbon
Turbidity (NTU)g 58 11 4C
7inr D D4 D m? D D9
£—\\ IU VJ.VJf VJ.VJOO VJ.VJ^
a National Stream Quality Accounting Network (NASQAN) Period of
Record, March 1975 to September 1979. Information on this water
source is provided because CAP water can be released to the Salt
River and be carried in the SRP canal.
b Period of Record, Water Year 1979 only.
c Combined nitrate-nitrite
d Water Quality Master Plan.
e Tucson Water, Period of Record: October 1986 to August 1987.
f cfu/mL: colony forming units per milliliter.
g Turbidities can range from as low as 1 NTU to as high as 500+
NTUs.
zation or treatment. Characteristics of the waste
streams from each of the WTPs are presented in Tables
5-12, 5-13, and 5-14. The solids mass loading dis-
charged from each treatment process was computed
based on the flows and total suspended solids data
(Table 5-15). The Phoenix Water Service Department
funded a study to determine the effects of these residu-
als solids on the hydraulics, water quality, and biological
communities of the SRP canal system (HDR, 1995).
5.3.4.2 Effects of Discharged Residuals Solids
on Canal Hydraulics and Sediment Load
Solids discharged by the Val Vista WTP to the South
Canal are permitted through an agreement between the
City and SRP. The City pays SRP's costs for dredging
sediment from a specific length of canal downstream
from each discharge point. These portions of the canal
are drained and dried annually. During this time, the
sediments are removed and placed on the canal banks
to dry. In 1995, the annual cost to the City ranged from
$15,000 to $50,000. If the discharged solids settle and
are retained in the canal, the resulting sediments may
affect the canal hydraulics.
The U.S. Army Corps of Engineers' HEC-2 computer
models of canal physical and hydraulic characteristics
were used to determine the impact of residuals solids
on the SRP canal system. Computer simulations were
compared with information from the SRP on water level
profiles corresponding to specific flow rates in the canal.
The SRP also included water surface elevations corre-
sponding to design capacities within the Arizona Canal
(19.8 m3/sec at Station 38+862 to Station 73+963) and
South Canal (41.1 m3/sec at Station 0+000 to Station
25+700). The velocities in the canal system varied
slightly but were generally about 94 cm/sec. The HEC-2
hydraulic analysis compared favorably with inde-
pendently measured flow and cross-section data.
HDR (1995) evaluated the settling characteristics of the
discharged solids to determine if they would settle and
be retained in the canal system. According to Table 5-16,
81 .4 percent of the solids measured were finer than a
#200 sieve. Using the U.S. Army Corps of Engineers'
HEC-6 computer program, transport of solids in the
canals was assessed. HEC-6 uses the same input
scheme as HEC-2 to describe the hydraulic and geo-
metric characteristics of the canals. In addition, grain
size distribution data (Table 5-16) and total volume of
solids entering the canal are entered into the program.
The model calculates the volume of each grain size that
will settle out at each canal cross section. The canals
being evaluated are divided into reaches and the model
predicts the solids mass load for each of the reaches
(Table 5-17).
Computer results indicate that the material finer than a
#200 sieve (approximately 81 percent of the particles)
would be transported through the canal system. These
results were based on the assumption of maintaining a
water velocity of 58 cm/sec or greater. Localized areas
exist — eddies caused by intakes, delivery and disper-
sion structures, control structures, bridge piers, and
89
-------
Table 5-11. Summary of Plant Flows and Turbidity Data (HDR, 1995)
Average
Maximum
Peak
WTP
Val Vista
Squaw Peak
Deer Valley
Flow
(m3/min)
315
184
210
Turbidity
(NTU)
11
10
20
Flow
(m3/min)
368
368
315
Turbidity
(NTU)
20
20
40
Flow
(m3/min)
368
368
315
Turbidity
(NTU)
40
40
40
Table 5-12. Val Vista WTP Discharge Stream Characteristics (HDR, 1995)
Discharge Stream
Parameter
Operational frequency
Flow (m3/min)
Turibidity (NTU)
Total suspended solids (mg/L)
Total aluminum (mg/L)
Raw Water
Continuous
315
11
20
<0.05
Grit Basin
Discharge
Intermittent
0.68
N/A
16
N/A
Presed.
Basin
Slowdown
1 hr/day
0.63
N/A
1,600
19
Final Sed.
Basin
Slowdown
1-4 hr/day
3.4
N/A
1,400
1,800
Filter Waste
Wash water
4 times/day
7.9
N/A
55
165
Leakage and
Drains
Continuous
5.0
N/A
3
0.010
Note:
1. To be reduced under current plant modifications.
2. Storm drainage not included.
Table 5-13. Squaw Peak WTP Discharge Stream Characteristics (HDR, 1995)
Discharge Stream
Parameter
Operational frequency
Flow (m3/min)
Turbidity (NTU)
Total suspended solids (mg/L)
PH
Dissolved aluminum (mg/L)
Raw Water
Continuous
184
10
30
7.8
0.2
Presed. Basin
Slowdown
3 times/day
1.6
N/A
130
N/A
0.2
Final Sed. Basin
Slowdown
0.5 hr/day
1.3
N/A
3,900
N/A
0.2
Filter Waste
Washwater
3 times/day
1.3
N/A
360
N/A
0.6
Leakage
Continuous
1.3
N/A
N/A
N/A
N/A
Table 5-14. Deer Valley WTP Discharge Stream Characteristics (HDR, 1995)
Discharge Stream
Parameter
Operational frequency
Flow
Turbidity (NTU)
Total suspended solids (mg/L)
Settleable solids (mg/L)
PH
Temperature (°C)
Total dissolved solids (mg/L)
Total aluminum (mg/L)
Raw Water
Continuous
210 m3/min
20
39
0.16
8.4
24
732
1.27
Grit Basin
Discharge
3 times/year
757 m3/
discharge
>1 ,000
4,900
18
760
240
Presed. Basin
Slowdown
3 times/week
2,200 m3/
discharge
>1 ,000
21 ,000
290
7.65
24
801
769
Final Sed. Basin
Slowdown
2 times/week
1 ,500 m3/
discharge
>1 ,000
9,400
310
7.83
26
813
704
Filter Waste
Washwater
6 times/day
2.4 m3/min
71.25
264
35
7.45
28
731
45.3
Leakage
Continuous
5.3 m3/min
4.4
14.5
0.27
N/A
N/A
740
0.91
90
-------
Table 5-15. Existing Discharge Quantities (HDR, 1995)
Val Vista WTP
Squaw Peak WTP
Deer Valley WTP
Discharge
Stream
Grit basin drain
Presediment
basin blowdown
Final sediment
basin blowdown
Filter waste
washwater
Leakage and
drains
Totals
Plant
Flow
Cond
Ave.
Max.
Peak
Ave.
Max.
Peak
Ave.
Max.
Peak
Ave.
Max.
Peak
Ave.
Max.
Peak
Ave.
Max.
Peak
Flow
(m3/min)
0.68
0.68
0.68
0.68
0.63
7.6
3.4
3.4
6.6
12.6
12.6
19.7
0.18
0.18
0.18
17.6
17.6
33.9
Dur.
(min)
Cont.
Cont.
Cont.
120
120
120
120
120
120
8
30b
30b
Cont.
Cont.
Cont.
Solids
(kg/day)
27
50
100
24,500
4,500
9,100
12,700
24,500
48,100
1,700
3,300
6,400
1.4
2.3
5.4
17,200
32,200
63,500
Flow Dur.
(m3/min) (min)
No grit
1.6
1.6
1.6
1.3
1.3
2.6
1.3
5.3
10.0
Included in
basin
4.2
8.1
14.2
Solids
(kg/day)
basin drain
60
60
60
60
60
60
10b
15b
15b
181
726
1,450
1 0,400
31,000
62,000
1,000
4,400
8,600
final sediment
blowdown
5.3
5.3
Cont.
Cont.
12,000
36,000
73,000
Flow
(m3/min)
Dur.
(min)
Solids
(kg/day)
Intermittent discharge3
0.37
0.37
0.37
0.47
0.68
0.68
2.4
5.8
5.8
5.3
8.5
12.1
12.1
19
20
30
31
35
35
20b
20b
20b
cont.
13,000
44,000
44,000
3,900
14,000
14,000
900
3,200
3,200
15
15
15
18,000
61,000
61 ,000
a Grit basin discharges are estimated to be 760 m3 per event with a solids content of 3,600 kg. This discharge will be eliminated in upcoming
modifications.
b Data obtained through telephone conversations with plant managers.
Table 5-16. Grain Size Distribution for WTP Residuals
(HDR, 1995)
Sieve Size
Retained (%)
Passing (%)
#4
#8
#10
#16
#30
#40
#50
#100
#200
Pass #200
0
2
1
4
5
2
1
2
1
100
98
97
93
88
86
85
83
82
81.4
mossy areas—where the stream velocity may fall below
58 cm/sec and increased deposition might occur.
The City of Phoenix investigated the concentration of
suspended solids in the Southern Canal following dis-
charge of waste residuals solids from the Val Vista WTP.
The sample collected upstream from the point of dis-
Table 5-17. Estimated Amount of Solids Deposited in the
Canal System, Phoenix, AZ (HDR, 1995)
Suspended Solids
Load
WTP
Squaw Peak
Deer Valley
Val Vista
Entering
Reach
(mt/day)
24.5
17.7
17.0
Existing
Reach
(mt/day)
22.4
17.3
12.2
Solids
Deposited
in Reach
(mt/year)
762
132
73
Length of
Canal
Reach (m)
10,700
3,500
7,800
charge was a grab sample, whereas the remaining sam-
ples were time-weighted composite samples. The City
discovered that the TSS concentration at the point of
discharge in the canal ranged from 200 mg/L (presedi-
mentation blowdown) to 1,600 mg/L (final sedimentation
blowdown). At 25 m downstream from the discharge
point, 50 percent of the solids had been removed, and
at 100 m downstream at least 70 percent of the solids
had been removed from the water column. Analysis of
suspended solids in water samples collected 500 m
downstream indicated a TSS reduction of 78 to 98
91
-------
percent and TSS levels 3 to 45 times the concentration
measured upstream of the point of discharge.
5.3.4.3 Impact on Aquatic Organisms
The Arizona Game and Fish Department electrofished
the Arizona Canal between October 1992 and April
1993. The results of the electrofishing are presented in
Table 5-18. Ctenopharyngodon idellus (white amur or
grass carp) has been used for the control of aquatic
vegetation and, therefore, is probably the most eco-
nomically important species.
Indigenous planktonic invertebrates were assumed to
have originated from the Salt River reservoir system.
Analysis of zooplankton in Canyon Lake by McNatt
(1977) revealed that at least 15 cladoceran, 5 copepod,
and 1 rotifer species may inhabit the rivers and canals.
Among the cladocera identified were Bosmina longiros-
tris, Daphnia parvula, Daphnia pulex, Daphnia galeata,
Daphnia ambigua, Diaphanosoma leuchtenbergianum,
Ceriodaphnia lacustris, Chydorus sphaericus, and
llyocryptus sp. Copepod species found include Paracy-
clops fimbriatus, Acanthocyclops vernalis, Diacyclops
bicuspidatus, and Diaptomis siciliodes. Asplanchna pri-
odonta was the identified rotifier. In the Salt River sys-
tem benthic communities, several species have been
identified: Chironomus, Cryptochironomus, Polypedium,
Procladius, Tanypus, two tubificid worms (Branchiura
and Limnodrilus), the Asiatic clam (Corbicula malinen-
sis), a crayfish (Oroconectes virilus) and two sponge
species. HDR (1995) did not conduct a study of the
phytoplankton present in the canal system. Based on
another analysis of water in the SRP reservoirs (Olsen,
1975), however, HDR inferred that a reasonable repre-
sentation of flora in the canals would include Cyclotella,
Stephanodiscus, Synedra, Spirulina, Anabaenopsis, Di-
nobryon, Glenodinium, Phacotus, Closteriopsis, Tetras-
trum, Tetraedron, and Ankistrodesmus.
The primary pollutants found in the WTP wastestreams
that may adversely affect aquatic organisms were arse-
nic, barium, cadmium, chromium, mercury, selenium,
and trihalomethanes. Barium is only toxic to freshwater
aquatic life at levels greater than 50 mg/L (U.S. EPA,
1986c) and was not viewed as a problem by the consult-
ants. Concentrations of the remaining pollutants in the
discharged waste streams are presented in Table 5-19.
An evaluation of the pollutants in the City of Phoenix's
waste streams revealed that 85 to 98 percent of the
metals discharged were in particulate form and would
ultimately settle once the turbulence was reduced down-
stream (HDR, 1995). HDR (1995) used a simple mathe-
matical model to estimate the concentration of pollutants
in the water column downstream from the discharge
points. The assumptions were: 1) complete mixing of the
pollutants occurred in the volume of water passing the
Table 5-18. Total Number of Fish Caught by Electrofishing, Arizona Canal, Phoenix, AZ, October 15, 1992, to April 30, 1993
(HDR, 1995)
Common
Site #1
Site #2
Site #3
Site #5
Site #7
Total
Bluegill
Carp
Channel
Desert sucker
Goldfish
Largemouth
Mosquitofish
Rainbow trout
Red shiner
Roundtail
Smallmouth
Sonora sucker
Threadfin
White amur
Yellow bass
Yellow
10
1
5
35
1
20
0
0
225
0
1
82
579
97
11
2
0
1
35
98
0
7
0
1
223
2
0
157
97
4
4
14
0
1
1
474
0
3
0
0
48
15
0
467
29
15
0
3
0
1
2
300
0
7
0
1
40
1
0
571
62
12
3
0
0
1
20
91
0
0
7
0
33
5
0
518
33
5
2
0
10
5
63
998
1
37
7
2
599
23
1
1,795
800
133
20
19
Site 1: From 67th Ave. downstream to the Skunk Creek drain gates.
Site 2: From the corner of 43rd Ave. and Peoria, downstream to the corner of 51st Ave. and Cactus.
Site 3: From the 19th Ave. bridge downstream to the Black Canyon freeway bridge, which lies between Peoria and Dunlap.
Site 5: From the 68th Street bridge downstream to the water control structure located near the 56th Street bridge.
Site 7: From Pima Road bridge downstream to Hayden Road, which lies between Indian Bend Road and McDonald Drive.
92
-------
discharge point by the end of a 24-hour period; and 2)
no volume reduction was made to compensate for sedi-
mentation. Using data in Table 5-19 to compute daily
pollutant mass loadings, average and maximum daily
pollutant contributions to the receiving stream were
computed for typical flows in the Arizona Canal (213
m3/sec) and Southern Canal (442 m3/sec). HDR (1995)
also computed the pollutant concentration at a low flow
condition of 25 percent of the typical flow. The results
of these computations are presented in Tables 5-20
and 5-21.
Under maximum mass discharge conditions and typical
canal flow, the computed aluminum concentration in the
receiving water ranged from 1 mg/L (Val Vista WTP) to
45 mg/L (Deer Valley WTP). Estimated aluminum con-
centration during low flow would be 179 mg/L below the
Deer Valley point of discharge. Deer Valley's residuals
solids would produce the highest concentration of met-
als in the canal water column (see Tables 5-20 and
5-21). The estimated increase in arsenic, cadmium,
chromium, and selenium in the water downstream from
Squaw Peak WTP would be less than 1 u,g/L.
Metal Toxicity
Environmental factors may affect aluminum toxicity to
aquatic organisms. High calcium concentrations protect
against the effect of aluminum on the ion regulatory
mechanism of rainbow trout (McDonald et al., 1983;
Muniz and Leivestad, 1980), brown trout (Wood and
McDonald, 1987) and Daphnia magna (Havas, 1985).
Furthermore, natural organic compounds can complex
with aluminum and protect aquatic organisms (Birchall
etal., 1989; Driscoll etal., 1980; Karlson-Norrgren etal.,
1986). Increases in hardness and alkalinity reduce the
Table 5-19. Estimated WTP Discharge Stream Pollutant Concentrations (HDR, 1995)
WTP
Squaw Peak
Presedimentation
Average
Maximum
Final sedimentation
Average
Maximum
Filter back wash
Average
Maximum
Deer Valley
Presedimentation
Average
Maximum
Final sedimentation
Average
Maximum
Filter back wash
Average
Maximum
Val Vista
Presedimentation
Average
Maximum
Final sedimentation
Average
Maximum
Filter back wash
Average
Maximum
Total
Discharge
(m3/min)
0.05
0.18
2.79
10.75
4.73
18.92
0.03
0.16
2.37
9.12
4.21
15.77
0.05
0.16
2.68
9.59
8.67
23.13
TSS
(mg/L)
8,400
9,400
5,000
5,000
190
280
1 4,400
9,400
4,700
4,700
170
280
7,800
7,800
4,800
5,000
100
150
Al
(mg/L)
0.2
0.2
840
406
8
11
0.2
0.2
560
560
14
14
0.2
0.2
214
300
5
16
As
(mg/L)
0.015
0.015
0.005
0.005
0.010
0.010
0.428
0.428
0.478
0.478
0.056
0.056
0.005
0.005
1.170
1.600
0.005
0.005
Cd
(mg/L)
0.005
0.005
0.005
0.005
0.005
0.005
0.036
0.036
0.028
0.028
0.005
0.005
0.005
0.005
0.005
0.005
0.005
0.005
Cr
(mg/L)
0.01
0.01
0.01
0.01
0.01
0.01
0.30
0.30
0.34
0.34
0.01
0.01
0.01
0.01
0.07
0.10
0.01
0.01
Hg
(mg/L)
0.0002
0.0002
0.0002
0.0002
0.0002
0.0002
0.0045
0.0045
0.0012
0.0012
0.0002
0.0002
0.0002
0.0002
0.0002
0.0002
0.0002
0.0002
Se
(mg/L)
0.005
0.005
0.005
0.005
0.005
0.005
0.005
0.005
0.029
0.029
0.005
0.005
0.005
0.005
0.005
0.005
0.005
0.005
THM
(mg/L)
0.100
0.100
0.136
0.136
0.100
0.100
0.026
0.026
0.126
0.126
0.061
0.061
0.100
0.100
0.220
0.300
0.100
0.100
93
-------
Table 5-20. Daily Resultant Pollutant Concentration Contribution to Canal at Typical Flow, Phoenix, AZ (HDR, 1995)
Resultant Concentration Contribution (ng/L)
Squaw Peak
Average
Maximum
Deer Valley
Average
Maximum
Val Vista
Average
Maximum
Canal Flow
(m3/s)
213
213
Canal Flow
(m3/s)
213
213
Canal Flow
(m3/s)
442
442
TSS
(mg/L)
13
51
TSS
(mg/L)
10
41
TSS
(mg/L)
6
21
Al
(mg/L)
2
4
Al
(mg/L)
1
45
Al
(mg/L)
0
1
As
0.05
0.20
Resultant
As
1.20
46
Resultant
As
2
6.3
Cd
0.03
0.12
Concentration
Cd
0.1
2.9
Concentration
Cd
0.0
0.1
Cr
0.06
0.25
Contribution I
Cr
7.2
28
Contribution I
Cr
0.1
0.4
Hg
0.001
0.005
li^g/L)
Hg
0.03
0.13
li^g/L)
Hg
0.001
0.003
Se
0.03
0.12
Se
0.8
2.9
Se
0.0
0.1
THM
0.75
2.83
THM
4.7
18
THM
0.6
2.1
Table 5-21. Daily Resultant Pollutant Concentration Contribution to Canal at 25% of Typical Flow, Phoenix, AZ (HDR, 1995)
Resultant Concentration Contribution (|Jtg/L)
Squaw Peak
Average
Maximum
Deer Valley
Average
Maximum
Val Vista
Average
Maximum
Canal Flow
(m3/s)
53
53
Canal Flow
(m3/s)
53
53
Canal Flow
(m3/s)
110
110
TSS
(mg/L)
51
204
TSS
(mg/L)
41
164
TSS
(mg/L)
23
86
Al
(mg/L)
8
16
Al
(mg/L)
5.0
179
Al
(mg/L)
1.0
5.3
As
0.20
0.80
Resultant
As
4.6
186
Resultant
As
7.1
25.3
Cd
0.12
0.50
Concentration
Cd
0.3
12
Concentration
Cd
0.09
0.27
Cr
0.26
1.00
Contribution (|j
Cr
29
111
Contribution (|j
Cr
0.38
1.76
Hg
0.005
0.020
ig/L)
Hg
0.11
0.5
ig/L)
Hg
0.004
0.011
Se
0.12
0.50
Se
3.1
12
Se
0.09
0.26
THM
3
11
THM
18
72
THM
2.4
8.5
degree of toxicity of alum sludge in water (George et al.,
1991). HDR (1995) concluded that with the neutral pH
levels, high alkalinity (130 to 185 mg CaCO^/L) and
hardness (180 to 212 mg CaCO3/L) of the receiving
water, aluminum toxicity to aquatic organism in canal
water should be minimized or eliminated.
Table 5-22 presents acute arsenic toxicity data for several
aquatic organisms. Estimated arsenic levels in the canal
water column downstream from a WTP discharge were
less than 0.2 mg/L. Arsenic does not appear to bioaccu-
mulate in fish (U.S. EPA, 1986c). Based on the low bioac-
cumulation potential, short half-life of arsenic, and the
toxicity data, HDR (1995) concluded that arsenic toxicity
should not be a problem with aquatic organisms.
Cadmium can bioaccumulate and cause damage to fish
vital organs (Kay, 1986). Acute exposure to cadmium
can result in respiratory failure caused by damage to the
gills. Data on toxicity of cadmium to aquatic organisms
are presented in Table 5-23. As water hardness, alkalin-
ity, salinity, temperature, and organic matter increase,
the toxicity of cadmium to aquatic organisms decreases
(Sorensen, 1991).
Hardness has a similar effect on chromium toxicity to
aquatic organisms (Mance, 1987; U.S. EPA, 1986c).
94
-------
Table 5-22. Toxicity of Arsenic to Freshwater Organisms (HDR, 1995)
Species
Oncorhyncus mykiss
Ictalurus lacustris
Lepomis macrochirus
Micropterus dolomieu
Pimephales promelas
Crustacea
Bosmina longirostris
Cyclops (mixed spp)
Daphnia magna
Daphnia pulex
Gammarus
pseudolimnaeus
Mollusca
Aplexa hyorumpn
Helisoma companulata
Insecta
Pieronarcys dorsata
Tenytarsus dissimilis
Rotifera
Philodina roseola
Benthic fauna (mixed)
Life
Stage
Eggs
Adult
2 months
Parr
Adult
Adult
Immature
Adult
Fingerling
Fry
Egg
Egg
4 cm
1 day
Nauplii
1 day
1 day
1 day
Adult
Adult
Adult
Adult
Larva
Larva
Hardness
(mg/L)
—
—
13.2
385
45
—
310
310
—
47
47
47
48
120
139
—
47
47
120
47
44
49.5
44
44
47
—
—
pH (SU)
—
—
8.3
8
7.3
—
7.6
7.6
—
7.2
7.8
7.8
7.2
6.8
7.6-8.8
—
7.2-8.1
7.2-8.1
6.1-7.8
7.2-8.1
6.9-7.3
7.4-7.7
6.9-7.3
6.9-7.3
7.2-7.7
—
0.5-3.0
Concentration
(mg/L)
0.1
13.3
1
13.2-19.4
<0.09
3,050
0.2-0.7
0.02-2.3
900
5-19
<16.5
<2.13
135
0.85
1 .6-1 0
0.8-31
1.32
0.6-1 .8
49.6
0.8-2.0
0.09-0.96
24.5
0.85-0.97
0.85-0.97
97
5.0-18
112
Duration
(days)
180
6
21
6
28
4
112
112
4
1-4
29
29
4
4
14
1-4
28
1-4
2
2-4
14
4
28
28
2
4
Effect
No effect migration
LCso
Reduced growth
LCso
No mortality
LCso
Growth unaffected
Growth/survival unaffected
LCso
No mortality
No effect hatching
No effect survival/growth
LCso
ECso
<20% mortality
LCso
50% mortality, no young,
growth reduced 10%
LCso
ECso
LCso
10-100% mortality
LCso
No mortality
No mortality
LCso
LCso
50-90% reduction in
numbers
Key
= Lethal concentration of substance causing mortality in 50 percent of the population exposed to the substance.
Chromium is more toxic in soft water. Chronic chromium
toxicity to D. magna was reported at 66 u,g/L in soft
water, whereas 44 u,g/L inhibited reproduction in hard
water. Fish are more susceptible to inhibitory effects of
chromium at low pH. Table 5-24 presents data on toxicity
of chromium to freshwater organisms.
Sorensen (1991) states that maximum selenium levels
for fish should not exceed 3to8u,g/L. Inorganic selenate
has been shown to be acutely toxic to aquatic organisms
at levels as low as 760 ug/L (U.S. EPA, 1986c). HDR
(1995) indicated that no chronic toxicity data were avail-
able on selenium effects on freshwater organisms. Tox-
icity effects of selenium vary according to environmental
conditions such as differences in oxygen tension, habi-
tat, food availability, trophic level offish, chemical form,
fish age, dietary consumption, population composition
and competition, presence of other metals, and thermal
gradient (Sorensen, 1991). A summary of selenium tox-
icity data is presented in Table 5-25.
95
-------
Table 5-23. Toxicity of Cadmium to Freshwater Organisms (HDR, 1995)
Life Hardness
Species Stage (mg/L) pH (SU)
Oncorhyncus mykiss
Castostomus commersoni
Cyprinus carpio
Lepomis macrochirus
Pimephales promelas
Crustacea
Cyclops abyssorum
Daphnia magna
Daphnia pulex
Eudiaptomus padanus
Gammarus pulex
Cyclops (mixed sp.)
Annelida
Tubifex tubifex
Limnodrilus hoffmeisteri
Mollusca
Physa Integra
Lymnaea stagnalis
Insecta
Ephemerella subvaria
Ephemerella spp.
Hydropsyche betteni
Chironomus tendipes
Eggs
Alevins
Fry
Juvenile
Adult
Adult
Embryo
Adult
Yearling
Yearling
Egg/Larvae
Adult
Larvae
Larvae
Immature
Immature
Fry
Eggs
Eggs
Adult
1 day
Mature
Female
1 day
Adult
Adult
Nauplii
Adult
Adult
Adult
Adult
Larva
Larva
Larva
Larva
80
80
80
125
82
18
—
55
200
200
200
200
200
200
201
201
204
204
204
50
130
—
—
106
50
40
139
224
224
224
46
soft
54
46
46
220
7.9
7.9
7.2
7.8
7.8
6.3
—
8
7.2
7.2
7.2
7.2
7.2
7.2
7.2
7.2
7.6
7.6
7.6
7.2
6.95
7.8-8.6
7.8-8.6
8.5-8.6
7.2
—
7.6-8.8
8.5
7
7
7.1-7.7
—
7
7.1-7.7
7.1-7.7
7
Concentration
(mg/L)
>0.124
>0.124
0.091-0.677
0.01-0.03
0.006-0.40
0.95-6.7
>0.012
0.24-0.45
>0.08
0.757-2.14
0.031-0.80
>0.757
0.031
0.08
<0.057
0.068-0.150
<0.057
<0.027
<0.037
3.8
0.005-0.008
>0.5
<0.025
0.115
0.015
0.005
0.55
0.12-0.68
0.04
0.016
0.4
450
320
0.2-0.55
0.02-0.114
0.11-0.33
2
0.085
0.238
25
Duration
(days)
13
27
2
7-10
4-14
1-4
1-4
330
270
330
6
60
30
30
270
30
180
180
2
2-4
1-3
1-3
1
70
58
2
2-4
14
14
14
1
2
4
7-21
7-14
4
21
28
2
Effect
No effect migration
LCso
Reduced growth
LCso
No mortality
LCso
Reduced growth
LCso
90% survival
100% mortality
No effect
No spawning
18% mortality
70% mortality
No effect survival/growth
LCso
No effect survival/growth
Hatchability
Spawning unaffected
LCso
LCso
1 00% mortality, <25°C
No mortality, @ 30°C
LCso
Brood size reduced
Survival reduced
LCso
LCso
100% survival
54% mortality
73% mortality
LCso, 28°C
LCso, 10°C
LCso
LCso
LCso
LCso
No mortality
No mortality
LCso
Key
LC50 = Lethal concentration of substance causing mortality in 50 percent of the population exposed to the substance.
96
-------
Table 5-24. Toxicity of Chromium to Freshwater Organisms (HDR, 1995)
Life Hardness Concentration
Species Stage (mg/L) pH (SU) (mg/L)
Oncorhyncus mykiss
Castostomus commersoni
Cyprinus carpio
Lepomis macrochirus
Pimephales promelas
Crustacea
Cyclops abyssorum
Daphnia magna
Eudiaptomus padanus
Gammarus pseudolimnaeus
Gammarus sp.
Annelida
Nais sp.
Mollusca
Lymnaea emarginata
Physa Integra
Insecta
Ephemerella subvaria
Hydropsyche betteni
Tanytarsus dissimilis
Rotifera
Philodina acuticornis
Eggs
Juvenile
Alevins
Alevins
Fry
Fry
Adult
Adult
4-9
months
Fingerling
Egg/Fry
Adult
Egg/Fry
Adult
Immature
11 weeks
Juvenile
Adult
Adult
1 day
Adult
Adult
Adult
Adult
—
Adult
Adult
Larva
Larva
—
—
—
80
80
80
80
70
70
70
—
70
80
35
55
35
35
209
209
209
270
50
50
50
50
45
50
50
154
154
50
42
44
25
81
7.8 0.02-2.0
7.8 2
7.8 0.02-2.0
7.8 0.2-2.0
7.8 0.013
— 0.017
— 0.077-0.170
— 8.88-32
— 7.0-180
7.8 2.0-50
— >0.29
8 14.3-21.2
— 1.122
— <0.522
7.5 27-58
7.5 18.0-140
7.5 1-3
7.6 38-61
7.2 10
7.8 1.8
7.2 10.1
7.2 0.55
— 0.067
— 3.2
— 9.3
— 34.8
— 0.66
6 2
— 64
— 59.9
— 3
— 15
Duration
(days)
9
224
224
224
60
60
60
4
4
4
60
1-4
60
60
25
1-11
400
2-7
2
1
2
2
4
4
4
2
2
4
4
4
4
4
Effect
Unaffected
50-100% mortality
Unaffected growth/survival
50-100% mortality
Reduced growth
94% mortality
Unaffected growth/survival
LCso
LCso
30-70% mortality
Reduced growth
LCso
Reduced growth
No effect
No effect survival/growth
LCso
No effect spawning/hatching
LCso
LCso
LCso
LCso
LCso
LCso
LCso
LCso
LCso
LCso
LCso
LCso
LCso
LCso
LCso
Key
LC50 = Lethal concentration of substance causing mortality in 50 percent of the population exposed to the substance.
Mercury (Hg) can accumulate in tissue; concentrations
as high as 27.8 mg/L have been measured in fish mus-
cle (Sorensen, 1991). In general, mercury levels greater
than 1 u,g/L have been toxic to freshwater organisms
(Table 5-26). Chronic mercury toxicity to fathead min-
nows in their early life stage has occurred at 0.26 u,g/L.
The estimated mercury levels in the canal water column
were less than 1 u,g/L and were generally less than 0.2
u,g/L, except for Deer Valley during minimum flow con-
ditions (0.5 u,g Hg/L) (see Table 5-21).
97
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Table 5-25. Toxicity of Selenium to Freshwater Organisms (HDR, 1995)
Species
Oncorhyncus mykiss
Carassius auratus
Cyprinus carpio
Ictalurus punctatus
Lepomis macrochirus
Micropterus salmoides
Pimephales promelas
Life
Stage
Juvenile
Uneyed eggs
Fingerlings
Adult
Juvenile
3-26 g
Juvenile
Juvenile
Juvenile
Juvenile
Hardness
(mg/L)
135
36
148
—
140
150
25 & 200
151
pH (SU)
7.9
7.6
7.2-8.2
7.9
7.75
6.0 or 8.7
7.8
Concentration
(mg/L)
5.41
0.47 and less
0.47 and less
12.5
36.6
8.8
35
19.1
30.7
17.6
0.01
7.3
2.9
Duration
(days)
4
42
42
4
4
14
4
4
7
14
120
4
7
Effect
LCso daily feed
No mortality
No effect
Mortality/growth
LCso
LCso
LCso
LCso
LCso
LCso
LCso
No mortality
LCso
LCso
Crustacea
Daphnia magna
Daphnia pulex
1 day
1 day
Adult
140
46
46
8.2
7.4
7.4
1.87
1.5
1
0.6
1.374
7
32
32
28
2
LCso
Reproduction unaffected
Growth unaffected
No effect
LCso
Key
LCso = Lethal concentration of substance causing mortality in 50 percent of the population exposed to the substance.
Combinations of dissolved metals in the aquatic envi-
ronment may have antagonistic, synergistic, and addi-
tive effects on organisms (Esernick et al., 1991; Goss
and Wood, 1988; Speharand Fiandt, 1986; Mukhopad-
hayay and Konar, 1985; Kaverkamp et al., 1983; Kaviraj
and Konar, 1983; Suffern, 1981; Westerman and Birge,
1978). These effects will vary with respect to environ-
mental conditions and exposed indigenous organisms.
The State of Arizona and EPA acute and chronic water
quality standards for heavy metals to protect aquatic life
are presented in Table 5-27. Based on these standards
and the source water quality data presented in Table 5-10,
cadmium (6 to 7 u,g/L) and mercury (0.04 to 0.26 u,g/L)
levels in the Verde and Salt Rivers exceed chronic
standards. Contribution of cadmium (12 u,g/L) from the
Deer Valley WTP may cause the levels in the canal to
exceed state and federal acute toxicity standards, 5.6
u,g/L and 3.9 u,g/L, respectively.
Suspended Solids
HDR (1995) states that sedimentation of residuals solids
may affect benthic communities, algae, aquatic macro-
phytes, and suitability of fish spawning habitat. The
European Fisheries Advisory Commission states that
salmonids will not spawn in areas of high solids deposi-
tion (EIFAC, 1969). Siltation shortly after spawning may
affect the proper transfer of oxygen and carbon dioxide
between the egg and adjacent water and, thus, result in
mortality (EIFAC, 1969; U.S. EPA, 1986c).
Deposition of solids can also smother benthic organisms
(Gammon, 1970; Tebo, 1965; George et al., 1991). Fur-
thermore, alum sludge sediments may adversely affect
benthic macroinvertebrates by limiting the availability of
carbon (George et al., 1991). Deposition of solids can
also reduce species diversity of the benthic organisms
(Mackenthun, 1973; George et al., 1991). As previously
mentioned, the deposition of residuals solids depends
on stream velocity. George et al. (1991) found that
deposition rates could be reduced and, therefore, the
detrimental effects of alum sludge deposits to benthic
communities could be minimized by discharging residu-
als solids during periods of high stream velocities.
HDR (1995) concludes that any effects of WTP residuals
deposition on fish spawning would be considered negli-
gible to the City, since the white amur, the most eco-
nomically valuable species, is sterile and will not spawn
anyway. Arizona's surface waters must comply with the
state Water Quality Standards for Navigable Waters,
which states that "navigable waters shall be free from
pollutants in amounts or combinations that settle to form
deposits that adversely affect aquatic life, impair recrea-
tional uses, or are unsightly." Discharge of residuals
98
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Table 5-26. Toxicity of Mercury to Freshwater Organisms (HDR, 1995)
Species
Oncorhyncus mykiss
Carassius auratus
Channa punctatus
Cyprinus carpio
Lepomis gibbosus
Lepomis macrochirus
Pimephales promelas
Tilapia mossambica
Annelida
Limnodrilus hoffmeisteri
Tubifex tubifex
Planaria
Dugesia dorotocephala
Crustacea
Cyclops (mixed sp.)
Cyclops abyssorum
Eudiaptomus padanus
Mollusca
Aplexa hypnorum
Insecta
Chironomus tendipes
Ephemerella subvaria
Hydropsyche betteni
Life
Stage
2 month
Adult
55-g
Adult
Adult
0.6 g
3.2-4.2 cm
Adult
Adult
Adult
Adult
Nauplii
Adult
Adult
Adult
Larva
Larva
Larva
Hardness
(mg/L)
82-132
100
160
55
55
46
40-48
115
5
5
—
139
50
50
50
220
42
42
pH (SU)
6.4-8.3
—
7.4
8
8
7.1-7.3
7.2-7.9
8.5
7
7
—
7.6-8.8
7.2
7.2
7.2-7.4
7
7.6
7.6
Concentration
(mg/L)
0.33
0.35
1.8
0.18
0.3
0.16
1-Jan
1
0.15-0.50
0.14-0.27
0.2
<0.032
2.2
0.85
0.37
64
2
2
Duration
(days)
4
2
4
4
4
4
4
14
4
4
10
14
2
2
4
1
4
4
Effect
LCso
LCso
LCso
LCso
LCso
LCso
LCso
LCso
LCso
LCso
no mortality
1 00% survival
LCso
LCso
LCso
LCso
LCso
LCso
Key
LC50 = Lethal concentration of substance causing mortality in 50 percent of the population exposed to the substance.
Table 5-27. Maximum Contaminant Levels (ug/L) Cold Water
Fishery (HDR, 1995)
Acute Standard
Chronic Standard
Contaminant
Arsenic (total)
Cadmium (total)
Chromium III (total)
Mercury (dissolved)
Selenium (dissolved)
TTHM
State
360
5.6a
2,261
2.4
20.0
NNS
EPA
360
3.9
1,700
2.4
260
11,000
State
190
1.5
269
0.01
2.0
NNS
EPA
190
1.1
210
0.012
35
NNS
a Value for warm water fishery is 34.6.
Key
NNS = No numerical standard.
solids may violate state surface water quality standards
by reducing benthic community populations and diver-
sity, and destroying suitable spawning beds (HDR, 1995).
5.3.4.4 Conclusions
After evaluating the available data, HDR (1995) con-
cludes that no adverse effects to aquatic organisms are
anticipated from metals (aluminum, arsenic, cadmium,
chromium, selenium, and mercury) contained in WTP
waste stream discharges. If low flow conditions (25
percent of typical flow) are maintained, cadmium con-
centrations in the canal downstream from the Deer Val-
ley WTP may exceed state and EPA water quality
standards. The hardness, circumneutral pH, and high
alkalinity of the waters in the SRP canal system would
help reduce any potential inhibitory effects from metals
on aquatic life. Solids deposition may affect benthic
communities and eliminate spawning areas and the suc-
cessful development of fish eggs. HDR (1995) further
states that the impacts may not be important unless the
Arizona Game and Fish Department attempt to create a
sustainable urban fishery in the canals.
99
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Determirie.Stats Regulatory Requirements
<.<• ^A-S^V* --Vr •- *
I Avoid Direct Discharge of Water PlantStudge '••
to Languid Streams or Lakes -; • H1
I Inififis EnvironmentalAssessment to Ascertain
the Impact of Sludge Deposits on the Aquatic
^Ecosystemsof ihe Hecehnng Waters. Determine
, Bedewing Water Use^Sedlment'Structure,', /
"'Water Chemstry,'System Hydrology and-^-'
"^ocet&JQWaterBiofogy -', '* '-'C' ' 'x
DevetoppischarQeAjiocations^or Water '^f^T
' Treattnert Residuals Based on Natural -^ "^ '
Sediment toati in Streams, Sofids Addition at'
the "Treatment Facility, Stream How and ,
Stream Depth - -
• Avoid Discharging Coagutent Sludge That Has "
Been Allowed to Accumulate in Settling Basins
' for Several Months to Surface V75ters Over
" Short Periods of Time ^V, ' t "'""' ' '
"'
Closely Scrutinize Discharges of Alurn Sludge;tp's
Determine Detrimental Effects to Primary -%'ff *
Production and Benthic Mactbinvertebrates"'''^ '
• Less Detrimental to Benthic Macroinvertebrate
Communities to Dsscbarge Sludges During Periods
"! of Fast Water Movement where Deposifion
'' " ' ' '
Conduct Toxkaty Tests on a Variety of AqoaficV,
;*7 fully Determine the PotenfiaJ Tb»c Effects IB '
5 \i; .1 ' ""?? '/•• ••
-anf
[ Do f-flt Discharge Alum Sludge to Ac% Streams
"'" '
i,Exercise Caut'on'tn Discfiarging Alum Sludge
' ts Soft Surface- Waters, Le., - -~ ='- •'-" •,
'Hardness<50mgCaCOyL ^1; $%<
Figure 5-12. Recommended practices for direct discharge of WTP residuals to surface waters.
5.4 Recommended Practices
Limited information exists regarding the impact of direct
discharge of WTP residuals solids on aquatic environ-
ments. Regulatory agencies have permitted the direct
discharge of residuals to streams and impoundments
because of the absence of information showing any ad-
verse effects. Some states have taken a more conserva-
tive approach recently and have discontinued allowing
discharge of residuals solids to freshwater. The first step,
therefore, by a utility considering direct discharge of WTP
residuals into a receiving stream is to determine its state
regulatory requirements (see Figure 5-12).
The scientific literature and examples discussed in this
chapter show that deposition of residuals solids can
adversely affect benthic community populations and di-
versity. These direct consequences on benthic organ-
isms may limit a food source for certain fish species. In
addition, solids deposition may affect fish egg survival.
Discharge of WTP residuals in sluggish streams or lakes
should be avoided. A utility can use hydrologic models
such as the U.S. Army Corps of Engineers' HEC-2 or
HEC-6 models to estimate possible deposition within a
receiving stream. More frequent, reduced solids mass
loading from the WTP during high stream flow will pos-
sibly reduce deposition and adverse effects to down-
stream benthic organisms.
The receiving water chemistry can minimize toxic effects
of metals in the discharged waste stream. Hardness,
alkalinity, pH, dissolved oxygen, sulfate, and other water
quality parameters minimize the inhibitory effects of
heavy metals. Because of the potential toxicity to
aquatic organisms, utilities that are evaluating discharge
to soft waters (hardness less than 50 mg CaCO3/L)
should consider an alternate residuals disposal method.
Furthermore, receiving waters with a pH less than 6
100
-------
should be avoided. Discharge to these waters could
result in increased solubility of metals and increased
toxic effects. The chemical characteristics of the waste
streams must be determined as well as the contaminant
mass loadings to the receiving stream. Using informa-
tion on stream hydrology and stream and waste quality,
a mass balance should be conducted to estimate poten-
tial concentrations of contaminants downstream from a
prospective point of discharge. Consideration of mixing
zone should be included in modeling the system.
When considering the future use of a receiving water, a
utility should consider whether direct discharge of its
residuals will negatively affect the downstream aquatic
life or quality. As part of this consideration, the utility
should evaluate upstream and downstream water qual-
ity, sediments, and aquatic life to determine if the water
has already been negatively affected by some previous
use. To fully evaluate the toxicity of the WTPs dis-
charged residuals, a series of toxicity tests should be
conducted on a variety of aquatic organisms that are
indicative of the organisms inhabiting the aquatic eco-
system. As shown in the case studies, one toxicity test
may not adequately describe toxic effects.
Residuals from WTPs using aluminum salts have
been the focus of research on the impacts of direct
discharge of wastestreams to freshwater aquatic eco-
systems. The recommended protocol presented in
Figure 5-12, however, can be followed for any type of
discharge. Aluminum may not be inhibiting organism
growth or survival; other metals or contaminants con-
tained in wasted residuals may be the primary toxi-
cant. Detrimental effects of solids deposition on
benthic organisms can be caused by limiting oxygen
transfer to chemical toxicity. In any case, sedimenta-
tion of solids must be evaluated and anticipated.
Other chemical residuals can affect benthic communi-
ties and fish spawning areas. In addition, chemical
characteristics and quantities of the receiving water
and the wastestreams must be determined to antici-
pate chemical changes to the water downstream
from the points of discharge. Toxicity testing must
be conducted to determine potential toxic effects on
the ecosystem.
101
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Chapter 6
Discharge to Wastewater Treatment Plants
Discharge of water treatment plant (WTP) residuals to a
wastewater treatment plant (WWTP) is an attractive
disposal option for water utilities. This chapter provides
information on the experience of utilities using this prac-
tice, factors that should be considered, regulatory limi-
tations, and design considerations for conveyance
facilities (both gravity and pumped systems) and for the
receiving WWTPs. The impacts on options for ultimate
disposal of residuals from WWTPs are also considered.
6.1 Background
Many water utilities across the country discharge WTP
residuals to a sewer and/or to a WWTP. These options
are often economically attractive, and transfer disposal
liability to the WWTP. The American Water Works Asso-
ciation (AWWA) Water Industry Database (AWWA/
AWWARF, 1992), a survey of WTPs currently discharg-
ing to a WWTP, reveals that such plants are variable in
size, and typically treat surface water supplies as op-
posed to ground waters. Table 6-1 summarizes the fa-
cilities surveyed.
Conventional WTPs (coagulation, sedimentation, filtra-
tion) commonly discharge filter backwash solids and/or
clarification basin residuals to a sanitary sewer system
for eventual treatment at a WWTP.
Several factors must be considered when evaluating the
feasibility of discharging residuals to a WWTP. The in-
terests and concerns of WWTP managers and operators
are different from those of similar personnel in water
utilities. Factors for a WWTP to consider are available
capacity (conveyance system and treatment plant),
treatment process compatibility, and final disposal re-
quirements. Introducing water treatment residuals to a
WWTP may offer some benefits in terms of process
performance. On the water treatment facility side, pre-
treatment requirements, storage facilities, and convey-
ance systems must be considered. Costs and service
agreement terms must also be evaluated.
Regulatory requirements, especially those related to ul-
timate disposal, must also be addressed. Essentially, all
states allow for discharge of WTP residuals (sludge and
brines, or reject waters) to a WWTP, but the specific
requirements and limitations vary. Regulatory require-
ments imposed on WWTPs will be directly or indirectly
imposed on the WTP discharging to the WWTP. Quality
issues, especially levels of metals and other inorganics,
are likely to be a concern.
6.2 Survey of Operating Systems
The results of a nationwide survey of WTPs currently
discharging to WWTPs are shown in Appendix B.
6.3 Design Considerations and
Conveyance Systems
For WTP managers and operators, disposal of WTP
residuals into a sewer system or to a wastewater treat-
ment facility is usually very attractive, cost effective, and
offers significant benefits from a regulatory and opera-
tional standpoint (Weaver, 1985; Price et al., 1989;
Robertson and Lin, 1981; Reh, 1978). This disposal
method, however, has not been universally accepted by
the wastewater community (Novak, 1989). Provided that
the water treatment facility complies with the receiving
wastewater utility's pretreatment and discharge require-
ments, the liability for proper disposal of the water treat-
ment residuals is transferred from the water utility to the
wastewater utility. Operationally, a WTP has no further
responsibility for its waste residuals once they have
been transferred to a wastewater utility; routine mainte-
nance of the sewer system and/or operation of the
wastewater treatment facility is the responsibility of the
wastewater utility.
Costs associated with this option include the capital
expenditures necessary to intercept, tie in, or transport
residuals; user fees imposed by the receiving wastewa-
ter utility to recover conveyance; treatment and ultimate
disposal operation and maintenance (O&M) costs; and
other costs. These costs are often less than other op-
tions for directly handling WTP residuals. In some
cases, the receiving WWTP benefits from increased
removal of suspended solids and/or biochemical/chemi-
cal oxygen demand (BOD/COD), additional phospho-
rus, and H2S conversion at the treatment plant (van
Nieuwenhuyze et al., 1990).
WWTP operators, however, may be increasingly
reluctant to accept WTP residuals because of
102
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Table 6-1. Survey of Water Treatment Plants Discharging to WWTPs (AWWA/AWWARF, 1992)
Facility
Dunkirk Water Treatment Plant
Dunkirk, NY
City of Boulder WTP
Boulder, CO
Chesterfield County WTP
Conestoga WTP
Lancaster, PA
T.W. Moses WTP
Indianapolis, IN
Texarkana WTP
Texarkana, TX
Franklin WTP, Charlotte-
Mecklenburg Utility District
Vest WTP, Charlotte-Mecklenburg Utility
District
City of Myrtle Beach WTP
Myrtle Beach, NC
City of Greensboro WTP
Greensboro, NC
Knoxville WTP
Knoxville, TN
Erie City Water Authority
Erie, PA
Chattanooga WTP
Chattanooga, TN
Belmont WTP
Philadelphia, PA
Queens Lane WTP
Philadelphia, PA
Nottingham WTP
Cleveland, OH
Morgan WTP
Cleveland, OH
Baldwin WTP
Cleveland, OH
Nashville WTP
Nashville, TN
City of Milwaukee Waterworks
Milwaukee, Wl
RE. Weymouth Filtration Plant
LaVerne, CA
Robert A. Skinner Filtration Plant
Temecula, CA
Joseph Jensen Filtration Plant
Granada Hills, CA
Size
Avg. Daily
(mgd)
4
5.3
10.5
7
10
11
47.6
18.9
14
31
30-33
35-40
38
60
100
87.1
80
85
120
60 Winter, 120
Summer
330
300
333
Design
(mgd)
8
12
12
16
16
18
96
24
29.5
44
60
60-80
72
80
100
100
150
165
180
250
520
520
550
Major Processes
Coagulation, lime softening, filtration
Coagulation, sedimentation, filtration
Fe/Mn removal, coagulation, lime softening, filtration
Coagulation, sedimentation, filtration
Coagulation, sedimentation, filtration
Sedimentation, filtration
Coagulation, sedimentation, filtration
Coagulation, sedimentation, filtration
Coagulation, sedimentation, filtration, ozone
Coagulation, sedimentation, filtration
Coagulation, sedimentation, filtration
Coagulation, sedimentation, filtration
Coagulation, sedimentation, filtration, GAC
Coagulation, sedimentation, filtration
Coagulation, sedimentation, filtration
Coagulation, sedimentation, filtration
Coagulation, sedimentation, filtration
Coagulation, sedimentation, filtration
Coagulation, softening, filtration
Coagulation, sedimentation, filtration
Coagulation, sedimentation, filtration
Coagulation, sedimentation, filtration
Coagulation, sedimentation, filtration
concerns regarding National Pollutant Discharge
Elimination System (NPDES) compliance and toxicity.
For example, the Charlotte-Mecklenburg Utility Depart-
ment will limit future sewer disposal of residuals from
its Franklin WTP because this practice violates pre-
treatment ordinances (Appendix B). Potential limiting
concerns for a WWTP when it accepts WTP residuals
include increased final suspended solids, decreased
effective digester capacity, overloading of primary
clarifier and sludge removal systems, and overloading
of dewatering operations (van Nieuwenhuyze et al.,
1990).
103
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Discharge to a sewer is possible only when water treat-
ment and wastewater treatment facilities work together
cooperatively. Information sharing is imperative to es-
tablish such a relationship. A water utility should provide
information concerning residuals quality and quantity,
dry solids content, pH, nutrients, heavy metals, and
other relevant parameters. In addition, a wastewater
utility and water utility must cooperate to determine
whether positive or negative effects can be expected at
the wastewater facility with respect to hydraulic condi-
tions in the sewer lines, hydraulic and process capacity
at the WWTP, sludge treatment, and ultimate disposal
of VWVTP biosolids.
6.3.1 Regulatory Considerations
Regulations governing discharge to WWTPs are dis-
cussed in Chapter 2. Hazardous waste regulations (fed-
eral and state) are usually not a problem, since WTP
residuals are rarely, if ever, classified as hazardous
waste. Radioactive waste regulations are also not a
problem, since the radioactive component of WTP re-
siduals usually is very low and results from the removal
of normally occurring radioactive material (NORM) from
the raw water supply. Local receiving wastewater regu-
lations are usually driven by the need for a utility to
comply with provisions of the Clean Water Act. These
local regulations are imposed to reduce the risk of op-
erational problems at the receiving plant or of violation
of its discharge permits.
Discharges to sanitary sewers are subject to the U.S.
Environmental Protection Agency's (EPAs) National
Pretreatment Standards and possibly to more stringent
pretreatment requirements imposed by the state or
WWTP. The requirements imposed by a wastewater
treatment facility are necessary to enable the facility to
achieve compliance with its NPDES permit (including
provision for sludge disposal). Pretreatment standards
are typically industry or site specific. The local discharge
requirements imposed by a wastewater utility may be
governed by:
• Impact of residuals on the waste conveyance system
(sewer, pump station, force mains, abrasion, and cor-
rosion).
• Impact of residuals on either the liquid or solids proc-
ess treatment system at the wastewater treatment
facility (e.g., rate of discharge, solids concentrations,
need for flow equalization).
• Concerns about biotoxicity (within the WWTP or in
the plant's effluent).
The wastewater facility may refuse to accept the waste,
or it may impose extremely strict local limits on the
supplier's discharge (Koorse, 1993b).
Limitations often placed on WTP residuals discharged
to sanitary sewers and/or to WWTPs are the result of
problems perceived or experienced by the receiving
wastewater treatment facilities. The data in Appendix B
indicate that discharge of residuals through a force main
from a WTP in Knoxville, TN, caused a high degree of
solids accumulation in flocculation basins and consider-
able yearly maintenance. In a study of 13 WTPs oper-
ated by the American Water Works Service Company in
West Virginia (EET, 1992), five of the plants discharged
directly to sanitary sewers, and three plants hauled their
residuals to a WWTP. Sewer systems at two locations
experienced blockages that resulted in backwash water
and WTP residual overflows to surface water. Only one
plant is operating under a local industrial user permit,
stipulating maximum heavy metal concentrations, pH
and flow limitations, and monitoring requirements.
As greater concern is paid to WWTP effluent toxicity,
municipalities are adopting pretreatment regulations to
limit the strength or quality of discharge to sanitary
sewers. Aquatic toxicity caused by aluminum in waste-
water plant effluent has been widely studied. Hall and
Hall (1989) report that a substantial increase in the
mortality rate of Ceriodaphnia dubia is not observed in
100 percent alum effluent, but delayed brood release
and significant reduction in reproduction are observed.
Reductions in pH and dissolved oxygen concentrations,
high levels of suspended solids, and, possibly, aqueous
aluminum were implicated as likely causes of toxicity. In
Norfolk, Virginia, WWTP effluent toxicity was tested
(Tsang and Hurdle, 1991). When the greatest quantities
of alum sludge were fed into the wastewater plant influ-
ent, no acute but some chronic toxicity results were
measured. At lower feed rates of alum residuals to the
plant, no toxic effects were noted.
Larger WTPs that discharge their residuals to a sanitary
sewer or WWTP are usually regulated by local industrial
user permits. Examples of this are Indianapolis, Milwau-
kee, and several large WTPs at the Metropolitan Water
District in southern California, where a surcharge is
required if heavy metal limits are exceeded (see Appen-
dix B).
The City of Philadelphia's Queens Lane and Belmont
WTPs discharge all of their residuals to sanitary sewers
and operate under combined effluent discharge permits
required in-house between the water and wastewater
plants. The permits are administered by the Industrial
Waste Unit of the Philadelphia Water Department. Limi-
tations were placed on the discharge from these plants
because of NPDES permit violations by the WWTPs.
The City of Philadelphia's permits limit the discharges
resulting from periodic raw water basin cleaning, routine
flocculation/sedimentation tank discharges, and peri-
odic flocculation/sedimentation tank cleaning. The user
permit requires notification of discharges, sampling and
104
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monitoring, onsite detention for equalization and solids
relocation, prohibition of accidental or slug discharges,
and maximum 3-day discharge levels (Ib/day dry weight)
of residuals solids that may be discharged (AVWVA/
AWWARF, 1992).1
Municipal discharge permit ordinances are written to
protect the receiving WWTPs and are industry oriented.
The limitations specified are often too stringent for the
discharge of WTP residuals. When the discharge of
WTP residuals is allowed, discharge permit limitations
may include:
• Limitations on maximum discharge rates, often during
stated periods of the day.
• Maximum BOD concentration limits.
• Maximum total suspended solids (TSS) concentration
limits.
• Total dry solids limits—tons/day maximum.
• Cessation of discharge upon notification during high
storm flow periods.
• Prenotification of discharge occurrences.
6.3.2 Con veyance System Design
Considerations
6.3.2.1 Selection of Type
Three types of conveyance systems generally are used
to transport WTP residuals to a wastewater treatment
facility: 1) gravity sanitary sewers, 2) pumping/force
main systems, and 3) truck transport. Factors that affect
the choice of system include the receiving wastewater
system's availability and capacity, impacts of the residu-
als on the treatment plant, cost, corrosion considera-
tions, and ultimate disposal considerations. Discharge
to sanitary sewers, where available, is often the least
expensive and preferred choice for a WTP. This option,
however, provides the receiving wastewater utility with
the least treatment flexibility—all of the WTP residuals
must be processed through the wastewater liquid
stream processes. If a WWTP has excess design ca-
pacity beyond its normal wastewater loading, WTP re-
siduals received through the sanitary sewer generally
can be also processed.
When problems develop because of WTP residuals,
they usually occur in the liquid stream processes. Alter-
natives to the sanitary sewer are generally more costly:
discharge by pumping/force main or truck haul directly
to the wastewater treatment facility. With either of these
alternatives, the discharge is controllable and can be
1 Wankoff, W. 1992. Personal communication between C.P. Houck
and W. Wankoff, Water Treatment Plant Manager, City of Philadel-
phia Water Department. December 14.
directed to the desired liquids or solids stream process
at the WWTP. The WTP residuals do not have to go
through the liquid stream treatment process at all. They
can either be directed through the solids processing
facilities, in a combined facility or separately, or they can
be combined with the wastewater treatment biosolids
after the solids processing facilities for ultimate disposal.
There are other reasons for considering alternatives to
the sanitary sewer for conveying WTP residuals to a
wastewater plant. Koplish and Watson (1991), for exam-
ple, described a situation in Allentown, Pennsylvania,
where one entity is responsible for all water and waste-
water functions. There the preferred, most cost-effective
option for dewatering residuals (water and wastewater)
is to have all equipment at a single location. This, in turn,
necessitates direct transport (versus gravity sewer
transport) of the alum residuals to the wastewater treat-
ment facilities, where they are fed into a thickener prior
to belt filter press dewatering.
6.3.2.2 Pretreatment Requirements
Wastewater utilities often impose requirements on a
water treatment facility that govern the release of residu-
als to a sanitary sewer. The most common of these
requirements is equalization of discharge flow. Other
pretreatment requirements can include regulating the
quality of the discharge, which may include pH neutrali-
zation; homogenization of the waste stream to ensure
uniform concentration versus slug concentration dis-
charges; limits on the total solids allowed to be dis-
charged; and limitations on quality parameters such as
heavy metals or components that may cause corrosion,
odors, or other undesirable conditions.
Equalization
Directly discharging WTP residuals to a sewer system
in a fairly continuous and uniform way may be possible
if the sedimentation basins at a WTP are equipped with
residuals removal mechanisms. Generally, flow equali-
zation is required to ensure a uniform sludge flow to the
sewer. Equalization facilities provide storage for quanti-
ties of waste discharge that exceed the allowable dis-
charge to a sewer system. The storage requirements
depend on the designated waste discharge schedule.
Flow equalization is almost always required when sedi-
mentation basins are being cleaned, to control wastes
from ion exchange processes that are only produced
during media regeneration, and before discharging filter
backwash water to a sewer.
The need to control the rate of water treatment waste
discharge into a sewer system was shown in the 1989
Durham study by McTigue et al. (1989). The water treat-
ment facility examined had sedimentation basins in two
groups of four basins each. Each basin had six conical
hoppers in the inlet end; each hopperwas approximately
105
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10 feet deep and had a drain in the bottom for the
removal of residuals. Normal operation of the plant con-
sisted of flushing the residuals from each hopper daily.
Half of the basin hoppers were discharged to a sanitary
sewer for 2 weeks, with no significant effect on the
receiving WWTP effluent quality.
Based on these results, the remaining hoppers were
connected so that all hopper-flushing residuals could be
sent to the wastewater plant. Only slight increases in
effluent suspended solids, turbidity, and color were ob-
served from the additional hopper flushings. Problems
did occur, however, when a complete basin was cleaned
and the residuals were discharged over 6 hours. A slug
discharge caused severe deterioration of the wastewa-
ter utility's effluent quality in terms of turbidity, color, and
suspended solids. It took approximately 6 days for the
wastewater treatment facility to recover from the shock
load. In addition, the inert WTP solids captured by the
WWTP began to accumulate in the digester when the
operators failed to compensate by increasing the
amount of digested biosolids removed for ultimate dis-
posal. The result was a deterioration in digester super-
natant quality.
The need for equalization capabilities is often realized
during an unanticipated experience such as a situation
that developed in Philadelphia in 1988.2 Philadelphia
has three WTPs, two of which—Queens Lane WTP (100
mgd) and Belmont WTP (60 mgd)—discharge their re-
siduals to sanitary sewers. In 1988, the Queens Lane
WTP cleaned flocculation/sedimentation basins that are
stacked, with chain and flight residuals collectors on the
top, and no residuals collection on the bottom. A signifi-
cant time had elapsed since the last basin cleaning. A
slug of approximately 400 tons (dry weight) of solids was
discharged into the sanitary sewer that then completely
overloaded the 210 mgd Southwest Water Pollution
Control Plant (then loaded at 120 mgd). Residuals from
the Southwest Plant were discharged via a 5-mile force
main to the Sludge Recycling Center, and so the addi-
tional 400 tons of WTP residuals were pumped as
quickly as possible into the Sludge Recycling Center,
overloading it as well.
The result of the poor coordination between the water
and wastewater treatment plants was that two WWTPs
fell out of compliance with their discharge permits. When
the permits were renewed, EPA required that an internal
city permit be issued by the Wastewater Department to
the Water Department, regulating the WTP residual dis-
charges. Extensive monitoring was also required.
In Philadelphia, effluent limits have been established for
WTP discharges from cleaning of raw water basins,
routine flocculation/sedimentation tank discharges, and
periodic flocculation/sedimentation tank cleaning. Be-
2 See footnote 1.
cause their solids content is low, routine filter backwash
discharges are not regulated by permit, even though a
high volume of water is discharged. Flow, total sus-
pended solids (TSS), aluminum, iron, and arsenic are
monitored on a daily maximum and monthly average
basis. TSS limitations of 132,000 Ib/day (daily max) and
53,000 Ib/day (monthly average) have been placed on
the Queens Lane plant discharges.
Similar limits are placed on Philadelphia's Belmont plant
discharges. Total discharge to the city sewers must be
at a controlled rate such that no more than 10 percent
of the total solids in the basin is removed per day. TSS
concentrations must be below 100 ppm. Total allowed
maximum flow from either plant is 18 mgd, and it must
occur during the first shift only. Cleaning and discharge
from both plants cannot occur simultaneously. Addition-
ally, the Queens Lane plant is required to maintain, in
good working order, an onsite lagoon to receive diver-
sional flow streams. The need for the installation and
operation of equalization facilities forwaste WTP residu-
als in Philadelphia is obvious, given its 1988 experience.
Equalization restrictions may include limitations on the
time of day of discharge, the maximum flow over a
certain period, or the maximum solids discharge that is
allowed. Cornwell et al. (1987) present a mass storage
diagram approach that analyzes storage volume re-
quired for a given solids concentrations. The resulting
equalization basin is usually sized to be capable of
decanting and thickening. Either a continuous flow or
batch fill and draw thickener may be designed. The
capability to mix the contents of the equalization/thick-
ener tank also may be desirable. Cornwell et al. (1987)
also discuss design considerations for equalization fa-
cilities to handle backwash water or similar high-flow,
short-duration discharges before their release to sani-
tary sewers. Sometimes, discharges of peak flows dur-
ing otherwise low flow periods in the sanitary sewer may
be desirable.
Quality Discharge Limitations
Limitations may be imposed on TSS or total dissolved
solids (TDS), pH range, heavy metal constituents (either
from a receiving water quality or residuals standpoint, or
from a biotoxicity standpoint), and on corrosion causing
constituents. These limitations may be in a permit that
regulates discharge directly to the WWTP through a
force main or truck discharge, or in a permit for dis-
charge to a sanitary sewer. Most municipal permit limi-
tations imposed on industrial discharge to sanitary
sewer systems contain a provision that the water dis-
charged must be in a pH range of 6 to 9. This could
cause problems for lime softening WTPs that either
have continuous discharge of softening residuals, or
periodic cleaning and discharge of sedimentation ba-
106
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sins. Neutralization facilities for pH adjustment before
discharge at the water treatment facility may be re-
quired.
Heavy metals in the water environment are increasingly
regulated to ensure against toxicity to humans, plants,
and aquatic organisms. Heavy metals are generally con-
centrated in the residual solids of water treatment and
wastewater treatment wastes, and limitations on the
ultimate disposal of those residuals, as well as on the
dissolved fraction of heavy metals in the effluent, are
becoming more stringent.
Under the final City of Norfolk, Virginia/Hampton Roads
Sanitation District (HRSD) implementation plan to treat
WTP residuals at a district wastewater plant, WTP re-
siduals were to be pumped directly to the wastewater
solids processing facility to circumvent problems both
with sludge settling and effluent toxicity (Tsang and Hur-
dle, 1991). The heavy metal content of the water plant
residuals, compared with HRSD's Industrial Waste Dis-
charge Regulations, indicated that the concentrations of
copper, chromium, lead, and zinc were close to the
HRSD limits (COM, 1989).
In Philadelphia, the occurrence and level of arsenic in
the city's WTP residuals discharged to the sanitary
sewer may be of concern.3 The city's Sludge Recycling
Center biosolids (received from the city's WWTPs) have
an arsenic concentration of 11 to 12 mg/kg. The city's
WTP residuals contribute less than 30 percent of the
total arsenic in the biosolids and are responsible for no
more than 2 to 3 mg/kg of the total. EPA's 40 CFR Part
503 biosolids regulations establish a maximum allow-
able concentration of 41 mg/kg of arsenic in bulk sew-
age sludge, applied to a lawn or home garden, or in
sludge that is sold or given away. For land application
of biosolids, the State of New Jersey has set a maximum
limit of 10 mg/kg (New Jersey, 1993). The concentration
of arsenic in Philadelphia's biosolids is not a problem
under the EPA regulation, but under New Jersey state
regulations, it may be. The city permit requires monitor-
ing of the arsenic concentration discharged by the
WTPs to the city's sanitary sewer system.
A similar situation exists in Massachusetts, where the
Type 1 cadmium and nickel standards of the Massachu-
setts Department of Environmental Protection are sub-
stantially more stringent than the federal 503 regulations
for "exceptional quality" biosolids (Donovan and Toffey,
1993). Should the arsenic levels become problematic, a
higher grade aluminum sulfate could be used which
generally contains lower levels of contaminants such as
arsenic.
Additional quality concerns that a WTP and a WWTP
receiving industrial discharge must consider are the po-
! See footnote 1.
tential corrosive nature of the WTP residuals and the
potential for hydrogen sulfide (H2S) generation. Aside
from the potential odor problem, the presence of H2S
can lead to corrosion of certain construction materials in
the sewer system. If the waste residuals to be dis-
charged are septic (e.g., a lagoon cleaning operation) or
contain a high sulfate content, the sanitary sewergrades
are especially flat, or the sewers are constructed with
concrete pipe, the potential for H2S generation and cor-
rosion attack should be investigated.
The discharge of WTP ferric residuals can counteract
the problems of H2S formation in sewers. Iron residuals
promote H2S binding. Iron residuals can also benefit the
wastewater treatment process through partial promotion
of presedimentation and partial phosphorus removal.
They can also minimize problems with sulfide or H2S
formation by keeping the H2S content in anaerobic di-
gester gas at an acceptable level (van Nieuwenhuyze et
al., 1990).
The corrosive nature of brines resulting from ion ex-
change (IX), reverse osmosis (RO), or activated alumina
treatment of ground water is well known. Brines dis-
charged to WWTP could be corrosive to piping systems
(Snoeyinketal., 1989) and may also upset the biological
balance in biological wastewater treatment systems.
A final quality concern is the amount of heavy metal
impurities in the water treatment chemicals used at the
WTP. The effect of contaminants on the chemical char-
acter of treated residuals can be significant (Lee et al.,
1990). The data in Table 6-2 analyze sludge from a
water treatment facility in Pennsylvania. Theoretical cal-
culations show that the treatment chemicals could be
responsible for 100 percent of the levels of chromium,
copper, and lead detected in the residuals. A large frac-
tion (78 percent) of the zinc concentration could also be
attributed to chemical addition. At the plant represented
in Table 6-2, the levels of zinc in the residuals prohibit
use for agricultural land application.
6.3.2.3 Gravity Sewers
Although WTP residuals will settle in the sanitary sewer,
their deposition should not occur more rapidly than sani-
tary solids (except residuals from lime softening and
diatomaceous earth WTPs). Sanitary sewers designed
with adequate slopes for conveying sanitary solids
should also convey WTP residuals. Generally, a velocity
of approximately 2.5 ft/sec (0.8 m/sec) or a residuals dry
solids content of less than 3 percent should be main-
tained to prevent sedimentation of hydroxide residuals
solids (van Nieuwenhuyze et al., 1990; Cornwell et al.,
1987). While not reporting the percent solids of its re-
siduals, the Indianapolis Water Company did report that
its residuals were too thick for gravity flow (Appendix B).
Lime residuals may have settling velocities much higher
than those of metal coagulant residuals, and deposition
107
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Table 6-2. Treatment Chemical Analysis Range of Detected Contaminant Levels (Dixon et al., 1988)
Cat Hydrofluo-
Cat Floe- Hydrated Pebble silicic Caustic
Chloride Alum Alum Percol Floc-T TL Lime Lime Carbon Acid Soda C-9 C-39
Contaminant (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/kg) (mg/L) (mg/L) (mg/L) (mg/kg)
Ferric3 Liquidb Granular
Arsenic (As)
Barium (Ba)
Cadmium (Cd)
Chromium (Cr)
Copper (Cu)
Lead (Pb)
Nickel (Ni)
Selenium (Se)
Zinc (Zn)
No. of Samples
108-122
<5.0-7.4
<0.5-59
148-568
32-840
<0.5-332
1.5-114
129-150
69-7,990
8
214-270
<5.0
<0.5-7.5
16-24
<0.2-5.3
<0.5
<5.0
84-1 04
<0.5-2.3
6
555-621
<50
<5.0
<5.0
<2.0
<5.0
<50
<5.0-204
<5.0-12
3
<5.0
<50
<5.0
<5.0
<2.0
<5.0
<50
<5.0
<5.0
1
13
1.3
<0.5
<0.5
<0.2
<0.5
<5.0
<0.5
<0.5
1
14
<5.0
<0.5
<0.5
1.3
2.8
2.2
10.7
1.6
1
<5.0-15.5
24-83
<5.0
<5.0-24
<2. 0-6.1
<5.0-21
<50
<5.0-50
<5.0-9.5
4
<5.0
<50
<5.0
<5.0
<2.0
<5.0
<50
<5.0
<5.0
1
<5.0
45-78
<5.0
<5.0
5.9-13.5
<5.0
<50
<5.0
<5.0-8.0
3
3.4-18
0.8-8.7
1 .8-2.9
<0.50-2.9
<0.2-0.5
44-55
<5.0
14.7-13.5
<0.5-1,418
4
<0.50
<5.0
<0.50
<0.50
<0.20
<0.50
<5.0
<0.50
<0.50
2
27
1.7
4.6
27.5
1.4
52
21
39
203,400
1
25
<50
<5.0
26
<2.0
44
<50
35
114,600
1
a Solution 30 percent w/w; specific gravity = 1.346 g/mL Contaminant concentration expressed in milligrams per kilogram (mg/kg) ferric chloride
solution.
b Solution 8 percent w/w AI2O3; specific gravity = 1.33 g/mL. Contaminant concentration expressed in mg/kg liquid alum.
in sewer lines can be difficult to prevent. Robertson and
Lin (1981) recommend against the disposal of softening
basin residuals by direct discharge to a wastewater
utility because of the adverse effects on the sewer sys-
tem conveying the wastes and on the equipment and
unit processes of the pollution control plant.
The capacity of the sanitary sewer system into which
WTP residuals are to be discharged should be checked
against the planned rate of residuals discharge and the
background flow in the sanitary sewer. Tsang and Hurdle
(1991) identify other considerations regarding convey-
ance that should also be checked:
• Ensure that there are adequate upstream dischargers
to flush the water plant residuals through the sewer
system.
• If there are no dischargers or too few dischargers
upstream, consider a discharge of "clean" filter back-
wash water after the residuals are discharged.
• If dilution flows are inadequate, plan on increased
maintenance at intermediate raw sewage pump sta-
tions to guard against damage from abrasive material
in the water plant residuals (especially if the raw
water source is a river) and from the low pH of the
residuals.
6.3.2.4 Pumping/Force Mains
Considerable data are published on the pumping of
water treatment residuals (e.g., Gandhi, 1992), as well
as on wastewater sludges (U.S. EPA, 1979b; Metcalf &
Eddy, 1991; Mulbarger et al., 1981). Relatively little
information is available, however, about the differences
in pumping dilute water treatment coagulant residuals
(less than 3 percent solids, dry weight) versus pumping
water. Dilute concentrations of coagulant residuals may
be pumped using centrifugal pumps with nonclog impel-
lers (ASCE/AWWA, 1990). An operating point should be
selected to the right of the pump curve so that when the
pipe begins to clog, adequate head is available to unclog
it. A pump with a steep pump curve should be selected
to give a large reserve head. Precautions are required
to protect pumps and pipeline materials from corrosion
and abrasion, especially the abrasion of pump impellers.
If impeller abrasion is a serious concern, it may be
possible to use pneumatic ejectors to transport WTP
residuals (Foster, 1975).
In the design of a force main, the pipeline should be laid
out like a sewer—with constant slope—so pockets of
residuals do not solidify in the dips during periods when
pumping does not occur. Air release valves should be
provided at high points, but without using small orifices
that can clog. The pipeline should be provided with
flushing ports and cleanouts, and a drain facility at either
end so that the line can be flushed without creating a
problem. Pigging has been used for long reaches where
cleanouts are impractical, but rodding and jetting facili-
ties are the most cost-effective cleaning alternatives for
shorter runs. The pipeline should be designed with a
minimum velocity of 2 ft/sec. If valving in the pipeline is
required, eccentric plug valves are best, but ball valves,
butterfly valves, pinch valves, and knife gate valves also
108
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work. Using a valve that will not obstruct solids or rod-
ding equipment is best.
EPA's Process Design Manual for Sludge Treatment and
Disposal (U.S. EPA, 1979b) discusses the differences
between pumping water and wastewater residuals. In
water piping, flow is usually turbulent. Formulas for fric-
tion loss with clean water (Hazen-Williams, Darcy-Weis-
bach) are based on turbulent flow. Residuals flow may
also be turbulent, in which case the friction loss may be
roughly that of water. Residuals flow, however, is unlike
clean water in that laminar flow is also common. When
laminar flow occurs, the friction loss may be much
greater than that for water. Residuals up to 3 percent
solids concentration may have friction loss charac-
teristics up to twice that of water under laminar flow
conditions when velocities are between 2.5 and 8 ft/sec.
The thixotropic behavior of residuals flow may signifi-
cantly increase friction losses in residuals pumping, es-
pecially when restarting a pipeline that has been shut
down over a period of time. Head loss calculations must
consider the residuals viscosity and density, or alterna-
tively, allow some safety factor of two to three times the
head loss with clean water. One rule of thumb for residu-
als thicker than 5 percent is to multiply the water head
loss by the percent total solids. In Pipeline Friction
Losses for Wastewater Sludges, Mulbarger et al. (1981)
prepared an extensive review of the literature on waste-
water residuals pumping and rheology, resulting in a
methodology for predicting head loss relationships with
appropriate use of safety factors. Their document pro-
vides a series of predictive head loss curves for cast or
ductile iron pipelines, 4 through 20 inches in diameter.
Curves are presented for routine operation and worst
case (50 percent greater head loss than associated with
water) scenarios.
If the range of solids to be pumped is over 3 percent (dry
weight), the solids tend not to separate (especially over
6 percent) unless a super polymer or chemical (H2O2 or
acid) is added. In this event, pumping velocity is not so
important, since keeping solids in suspension is not a
serious concern. Also, head loss may preclude high
velocities. Positive displacement pumps are recom-
mended (and are mandatory for solids greater than 4
percent). Cleanouts and flushing ports are mandatory.
Keeping the suction line short into the pump is also
important.
Communities in which WTP residuals are currently
pumped include Norfolk, Virginia (37th St. WTP) (COM,
1989), Wichita, Kansas (lime sludge), North Marin County
Water District, and Novato, California (U.S. EPA,
1978a).
6.3.2.5 Truck Hauling
A primary consideration in determining whether to use
truck hauling to transport liquid WTP residuals is the
potential impact, perceived or real, of residuals on the
WWTP liquid stream processes. When a significant im-
pact is anticipated, the use of truck transport allows the
separate introduction of WTP residuals into a process
or receiving vessel at the WWTP, where negative im-
pacts can be minimized. Distance to the WWTP and
quantity of residuals, as well as the congestion of land
use, often determine whether to use a pumping/force
main system or truck haul. If residuals quantities are
small or if distance to the WWTP exceeds 10 miles,
truck haul is preferred over pumping through a force
main. Additionally, if the WTP residuals have already
been thickened or dewatered, truck transportation is
often the only feasible method of delivering the residuals
to the WWTP.
Trucking partially dewatered WTP residuals often re-
sults in solids compression because of vibration and
release of free water (ASCE/AWWA, 1990). As a result,
the truck bed should be sealed and watertight. Waste-
water treatment facilities are well aware of the require-
ments for truck transport of sludges from their facilities,
and the same precautions and limitations should be
applied to truck transport of WTP residuals, whether
dewatered, thickened, or unthickened.
6.4 Design Considerations for
Wastewater Treatment Plants
Anything discharged to a WTP, including WTP residuals,
has an impact on the design and operation of the facility.
Careful consideration of the design and/or operation of
the WWTP, however, can mitigate the effects of dis-
charging WTP residuals to the facility.
The first issues to consider are the types and charac-
teristics of WTP residuals to be discharged to the
WWTP. These include not only the physical and chemi-
cal characteristics of the residuals, but the form in which
they are to be conveyed to the WWTP (i.e., as a liquid,
semi-solid, solid.
The next important factor to consider is the manner in
which the residuals are to be conveyed to the WWTP.
Typical conveyance systems include gravity sewers,
pumping/force mains, and truck hauling. The type of
conveyance system used is important because it deter-
mines where the WTP residuals can be introduced into
the WWTP's processes (i.e., to the liquid and/or solids
handling processes), as well as the rate at which the
residuals are to be introduced (i.e., gradually over a long
period of time, or as a slug dose).
The points at which WTP residuals are introduced to the
WWTP for processing must be carefully considered. In
109
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certain cases, introducing residuals to the liquid treat-
ment processes may have an adverse effect on those
processes while, in other situations, it may improve the
performance of the processes. Sometimes, it may be
more advantageous to introduce the residuals to the
WWTP's solids handling processes to prevent overload-
ing the liquid treatment processes. Introducing WTP
residuals to the solids handling processes does not
necessarily eliminate all impacts on the liquid treatment
processes because this option can still affect the recy-
cled flows to the liquid treatment processes.
Obviously, the final and most important consideration in
accepting WTP residuals at a WWTP is the impact on
the performance of the WWTP. The performance of the
unit treatment processes at the WWTP must be main-
tained to ensure that discharge of the final effluent to the
receiving body is not adversely affected, and that dis-
posal or beneficial reuse of the residuals from the
WWTP does not become a problem.
As noted in Chapter 2, the NPDES permit governs any
direct discharges to waters of the United States. The
introduction of WTP residuals to a WWTP may affect two
areas of the WWTP's NPDES permit: the parameters for
which specific effluent limits are described, and the
Whole Effluent Toxicity (WET).
Equally important to meeting effluent NPDES permit
requirements is the fact that the disposal and/or reuse
of residuals from a WWTP has taken on new meaning
as a result of the promulgation of the 40 CFR Part 503
sewage sludge regulations (U.S. EPA, 1993c). These
regulations address the disposal and beneficial reuse of
sewage sludge in three general categories—land appli-
cation, surface disposal, and incineration.
Constituents in WTP residuals discharged to a WWTP
may affect the quality of the WWTP residuals as gov-
erned by 40 CFR Part 503, especially the concentra-
tions of 10 heavy metals. If aluminum is included in
round 2 of the 40 CFR Part 503 regulations, it definitely
will present a problem for discharge of WTP residuals to
WWTPs. The remaining sections of this chapter discuss
design issues that must be carefully considered when
evaluating whether to accept WTP residuals in the liquid
or solids handling processes at a WWTP.
6.4.1 Hydraulic Loading
Hydraulic loading is generally not a factor in the accep-
tance of WTP residuals conveyed by gravity sewers to
a WWTP. Large volumes of liquid wastes generated by
WTP processes in a short period (e.g., filter backwash
waters, IX regenerate waste, reject water from mem-
brane processes), are usually equalized at the WTP
prior to being discharged to a sewer. This is done to
prevent overloading of the gravity sewer itself. If large
volumes of liquid WTP residuals are not equalized be-
fore discharge, attenuation that takes place in the sewer
generally prevents a hydraulic loading problem at the
WWTP.
It is generally more important to check the hydraulic
loading of WTP residuals conveyed to a WWTP through
a dedicated pump/force main or by truck. The hydraulic
loading on unit treatment processes at the WWTP is
usually not the controlling parameter when WTP residu-
als are introduced to the liquid treatment process train,
unless the WWTP is a small one.
The condition that most warrants concern about hydrau-
lic loadings is when WTP residuals are discharged to the
solids handling processes at a WWTP. In this case,
equalization at either the WTP or WWTP is generally
required.
6.4.2 Organic Loading
The organic content of WTP residuals varies widely,
depending heavily on the quality of the raw water proc-
essed at the WTP (Albrecht, 1972; Calkins and Novak,
1973; Cornwell et al., 1987). The concentration of or-
ganic matter in WTP residuals, as measured by BOD or
COD, is not typically in the range of that found in waste-
water. Although organics loading is typically the control-
ling parameter for the biological unit treatment processes
in both the liquid and solids handling process trains at a
WWTP, the additional organics loading encountered by
introducing WTP residuals generally does not have a
significant impact.
6.4.3 Solids Loading
The impact of solids in WTP residuals on the WWTP is
limited to two general areas:
• The performance of primary, intermediate, and final
clarifiers.
• The constituents in the WWTP biosolids as related
to the requirements of the 40 CFR Part 503 sewage
sludge regulations.
The introduction of additional solids from WTP residuals
generally does not significantly affect the ability of the
WWTP to comply with its NPDES permit requirements
for the final effluent (McTigue et al., 1989; Tsang and
Hurdle, 1991). In several cases, alum and iron residuals
from WTPs have actually improved the efficiency of
primary clarification in WWTPs; in another case, these
residuals increased the amount of phosphorus chemi-
cally precipitated from a WWTP (McTigue et al., 1989;
Tsang and Hurdle, 1991). A common factor related to the
discharge of WTP residuals to a WWTP is an increase
in biosolids from the WWTP, with a corresponding de-
crease in the volatility of the biosolids.
In certain instances, metals present in WTP residuals
can affect NPDES permit effluent limits. This situation is
110
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becoming more of a problem since most of the specific
effluent requirements for metals in NPDES permits have
daily limits. If a significant portion of the precipitates in
the WTP residuals is in colloidal form, the solids pass
through primary and/or secondary clarification at the
WWTP.
Another cause of increased metals concentrations in a
WWTP effluent can be the resolubilization of metals that
occurs when WTP residuals are processed in a WWTP's
solids handling processes, and recycled flows from sol-
ids handling are returned to the liquid process train.
Precipitates and other solids in WTP residuals are fairly
inert. Concern has been expressed that additional solids
from WTP residuals could impair fixed film biological
treatment processes, but definitive information to sub-
stantiate this concern is unavailable.
6.4.4 Toxics Loading
The potential toxicity of WTP residuals is a concern
because of 1) the potential inhibitory impact on biologi-
cal unit treatment processes at the WWTP, and 2) the
possibility of failing a bioassay with Ceriodaphnia dubia
or fathead minnows, resulting in noncompliance with the
WET requirements.
A discussion of the potential for hazardous waste clas-
sification of WTP residuals is presented in Chapter 2.
Passing the TCLP test allows a WTP residual to be
classified as nonhazardous; however, it does not pre-
clude the possibility of toxic effects on a WWTP if the
WTP residual is discharged to the facility. Although or-
ganics and inorganics can be the cause of toxic effects
from WTP residuals, heavy metals are most often re-
sponsible for toxicity problems at WWTPs.
Nearly all heavy metals can exert toxic effects at ele-
vated concentrations. Heavy metals can be grouped into
"essential" and "nonessential" metals, according to their
importance in biological systems. The vast majority of
heavy metals fall into the "essential" category. Cad-
mium, mercury, and lead are the most commonly found
nonessential heavy metals. In assessing the potential
toxicity of individual heavy metals, two important issues
should be considered:
• For metals essential to biological processes, an in-
crease in concentration can often improve biological
conditions if a deficiency of metals existed initially.
• When they are present in excess, the essential met-
als can sometimes exert greater toxicity than the non-
essential heavy metals.
Metal speciation plays a major role in the potential tox-
icity of a particular heavy metal. The dissolved portion,
available as the free metal ion, is generally the most
toxic to biological systems. This simple differentiation
between the dissolved and particulate forms, however,
is generally not adequate to determine toxicity effects.
Heavy metals in the dissolved phase can be free metal
ions, or can be tied up with inorganic or organic com-
pounds to form complexes. Heavy metals in the particu-
late phase are capable of being bound to the surface of
other solids, or tied up in the bulk phase of a precipitate.
6.4.5 Liquid/Solids Separation
A key impact of WTP residuals on WWTP unit processes
is that additional residuals handling will be necessary.
The effects of the additional residuals on clarification,
digestion, dewatering, and final disposal must be con-
sidered. Generally, final biosolids volume increases as
the amount of influent WTP residuals increases. An
increase in the primary clarifier sludge volume is to be
expected with the addition of WTP residuals to raw
wastewater.
Liquid/solid separation is an important unit operation in
water and wastewater treatment. The success of the
overall treatment process depends greatly on a facility's
ability to separate solids from the liquid stream. Liquid/
solid separation can be accomplished by several unit
operations. This section discusses the primary and sec-
ondary sedimentation operations, while other liquids/
solids operations are discussed in Section 6.4.6.3.
When WTP residuals are discharged into a sanitary
sewer system, one of the first unit processes that they
encounter is primary sedimentation at a WWTP. Several
studies conducted on the impact of WTP residuals on
the sedimentation process have reported fairly consis-
tent results.
Full-scale testing at the Hookers Point Sewage Treat-
ment Plant in Tampa, Florida (Wilson et al., 1975)
showed that when WTP residuals were discharged to a
sanitary sewer system, a fluffy blanket layer of sludge
formed at a level somewhat above the normal blanket
level in WWTP primary sedimentation tanks. At times,
the sludge collectors in the primary sedimentation tanks
seemed incapable of collecting this fluffy material even
when the sludge pumps were run at their maximum rate.
Data show that at a WTP residuals dosage of up to 50
mg/L, removal of suspended solids from the primary
sedimentation tanks improved. At dosages above 50
mg/L, the percentage removals may be expected to
drop. Wilson et al. (1975) note that when WTP residuals
were accepted on a regular basis at the plant, the pri-
mary sludge solids content dropped from 5.8 to 4.7
percent. The addition of high concentrations of alum
residuals tended to produce a primary sludge that was
difficult to handle. Dosages of fresh alum less than 100
mg/L or WTP residuals of 40 mg/L were reported to
produce a more manageable product.
Rolan and Brown (1973) report that combined alum
residuals and sewage sludge did not settle as well as
111
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each would separately. Sludge volume tests were con-
ducted for different dosages of WTP alum residuals to a
WWTP (see Figure 6-1). The addition of 200 mg/L of
alum residuals approximately doubled the volume of
primary clarifier sludge. It was concluded that WTP re-
siduals in concentrations of 200 mg/L or less would have
no significant adverse effects on a WWTP.
Rindt (1973) studied the effects of alum on primary
sedimentation in a series of laboratory tests using labo-
ratory-prepared alum and WTP alum residuals. He re-
ports that WTP alum residuals caused nearly a four-fold
increase in the sludge volume index (SVI) when added
to wastewater samples. Turbidity and total suspended
solids in the supernatant also increased in proportion to
the amount of residuals disposed of and the suspended
solids concentration of the residuals.
Hsu and Pipes (1973) investigated the effect of alumi-
num hydroxide floe on the settling characteristics of
primary and secondary effluent. Settleability of bulking
sludge, as measured by the SVI, may be improved
significantly with the addition of aluminum hydroxide, but
there will be no effect on the SVI of normal sludge. The
authors attribute the decrease in the SVI of bulking
sludge to the inorganic aluminum hydroxide enmesh-
ment, which increased the density and the compatibility
of the sludge.
Nelson et al. (U.S. EPA, 1978a) conducted a full-scale
evaluation of alum residuals discharged via sanitary
sewer to an activated sludge WWTP and found that the
25 -
5 20
in
115 +
m
Q10--
< 5-
SLOPE =1.2
(BASED ON VOLUME)
10
15-
(ML/l)
50
100
150
200
250
r MG/L DRY
SOLIDS
WTPS ADDED
Figure 6-1. Effect of WTP sludge on the combined volume of
wastewater sludge after 30 minutes of settling
(Rolan and Brown, 1973).
efficiency of primary settling decreased by approxi-
mately 10 percent. Phosphorus removal improved by
approximately 12 percent, and scum removal and set-
tling improved in secondary clarification.
Camp Dresser & McKee, Inc. (COM, 1989), conducted
a study of Norfolk, Virginia's, 37th Street Water Treat-
ment Plant residuals and their subsequent treatment at
the Hampton Roads Sanitation District (HRSD) Virginia
Initiative Plant (VIP). To verify the potential effect that
WTP residuals might have on the VIP, representative
quantities of the residuals were hauled by truck to two
of HRSD's smaller plants at a rate comparable to VIP
receiving all of the residuals. The sludge was processed
through liquids and solids processing facilities at one
plant, and through liquid stream facilities at the other.
The study showed the following:
• The addition of WTP residuals to the WWTP influent
caused the primary sludge concentration at the
WWTP to drop from 3.5 to 2.5 percent, increasing
the volume of liquid primary sludge to be pumped by
approximately 60 percent.
• The addition of WTP residuals to the WWTP influent
decreased the efficiency of solids settling in the sec-
ondary clarifiers, resulting in the need for additional
clarifier capacity or the addition of a polymer to en-
hance settling.
• Discharging of WTP residuals directly to the WWTP
solids handling facilities resulted in minimal adverse
impacts on solids processing facilities other than in-
creased flows.
The study concluded that sanitary sewer discharge of
WTP residuals to the VIP was not feasible because of
the adverse effect on settling at VIP and the need to
obtain an exception to the HRSD Industrial Discharge
Regulations as a result. The processing of WTP residu-
als, transported by force main to the VIP and introduced
directly to the solids processing facilities (i.e., centri-
fuges), appears technically feasible. The residuals will
be dewatered separately by the centrifuges and then
combined with the WWTP biosolids before being fed to
the incinerators.
6.4.5.1 Summary
All the above studies involved WTP coagulation residu-
als, which constitute most of the WTP residuals pro-
duced in the United States. The findings from these
studies confirm that 1) the WWTP sludge volume will
generally increase, 2) phosphorus removal from the
wastewater will be improved, and 3) sludge concentra-
tion in the underflow may decrease when coagulation
sludge is discharged to a WWTP. Lime softening residu-
als settle very well and should not affect the wastewater
treatment primary settled sludge volume as much as
coagulation residuals do.
112
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When evaluating the option of discharging WTP residu-
als to a WWTP via a sanitary sewer system, sedimen-
tation tank capacities must be checked to ensure that
they will not be overloaded by the additional solids. This
precaution is especially critical for primary sedimenta-
tion, since the majority of the residuals solids will be
removed here. The capacity of sludge pumps, pipes,
and subsequent conveyance systems must also be ex-
amined; the removal of a larger volume of sludge at a
lower solids concentration would require a larger pump-
ing capacity and/or a higher pumping frequency.
6.4.6 In-Plant Solids Handling
The introduction of WTP residuals to a WWTP will inevi-
tably increase the solids loading to the whole treatment
train. This is especially critical for the solids handling
operations and treatment processes such as sludge
digestion, thickening, and dewatering.
6.4.6.1 Aerobic Digestion
Aerobic digestion is a sludge stabilization process used
primarily in small treatment facilities. The process is
similar to the activated sludge process. Sludge in the
digester is aerated to oxidize the organic substrate, and
as the available substrate is depleted, the microorgan-
isms begin to consume their own protoplasm through
endogenous respiration.
Important design criteria for aerobic digesters include
hydraulic detention time, solids loading, oxygen require-
ment, and energy requirements for mixing. Both volatile
solids loading together with total solids loading should
be considered. Because aerobic digestion is similar to
the activated sludge process, the effect of WTP residu-
als on aerobic digestion should be somewhat similar to
the impacts of the residuals on activated sludge sys-
tems. More data are available on the impact of WTP
residuals on activated sludge, than on aerobic digestion.
Consequently, some of the following discussion will be
on activated sludge systems.
To accommodate WTP residuals, an aerobic digestion
system must have the physical capacity to accept the
additional solids loading that residuals bring. Although
the volatile solids contribution from the residuals is ex-
pected to be low and should not significantly affect the
overall volatile solids loading to the digester, the impact
of the residuals on hydraulic and solids retention time,
as well as the overall reduction in volatile solids concen-
tration, must be considered.
Toxic compounds present in WTP residuals can ad-
versely affect the biological processes of wastewater
treatment facilities. Dissolved solids present in a liquid
phase waste may thwart the biological process, depend-
ing on their form and/or concentration. Predischarge
equalization techniques may alleviate toxicity problems,
as a continuous discharge of suitable dilution will en-
hance the ability of the microorganisms present in the
biological process to adapt and adjust to the presence
of any inorganic ion. If the dosing of WTP residuals is
equalized so that surges do not occur, and the dose is
kept below 150 to 200 mg/L, no direct effect on the
activated sludge process is likely to take place, although
downstream process effects or solids handling process
effects are possible (van Nieuwenhuyze et al., 1990).
Several investigations have found no evidence that
alum hinders the substrate removal properties of the
activated sludge process. Nelson et al. (U.S. EPA,
1978a) reported no change in the efficiencies of COD
and BOD removals when alum sludge was discharged
into a wastewater treatment plant. In a series of labora-
tory-scale studies, Voorhees (1974) studied the effects
of alum sludge on the activated sludge process and
reported that no significant effects on either COD or
TOC removal were observed at alum dosage of up to
100 mg/L. Voorhees observed that aluminum hydroxide
sludge did not decrease SVI, and that the settling char-
acteristics were not adversely affected in the secondary
clarifier. When a shock load of alum sludge was intro-
duced to the system, the COD and TOC removals were
decreased. The system was able, however, to recover
to the same COD and TOC removal efficiencies before
the shock load.
Despite several findings reporting the apparent lack of
impact of WTP residuals on biological treatment proc-
esses, the metal contents of these residuals do pose
some concerns. Reid et al. (1968) presented data to
show that metallic ions such as hexavalent chromium,
cadmium, copper, nickel, aluminum, and silver can hin-
der biological processes.
Hsu and Pipes (1973) reported that doses of aluminum
hydroxide in the range of 10 to 300 mg/L as aluminum
to an aeration tank caused a significant increase in total
phosphorus removal, no change on the nitrification, and
a slight increase in COD removal. Hsu and Pipes stated
that the most significant adverse effect on the biological
treatment process was the increased volume of sludge
produced. As a result, the sludge withdrawal rate and
sludge return rate would have to be controlled very
carefully to ensure adequate supply of active biological
sludge mass to the aeration tank.
Anderson and Hammer (1973) studied the effects of
alum addition on activated sludge biota and found that
the bacteria were able to synthesize soluble organics in
a chemical-biological sludge process and that BOD re-
moval was not affected. Higher life forms such as pro-
tozoa, however, found the environment under high alum
additions too adverse for normal existence.
The level of salt concentration in WTP residuals is ex-
tremely important to the proper performance of the bio-
113
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logical processes at a WWTP. Introducing WTP residu-
als with high sodium chloride concentrations, such as
may occur from the undiluted discharge of IX waste,
could cause considerable stress to biological organ-
isms. As a result, COD of the biological reactor effluent
could increase afterthe salt addition. Threshold concen-
trations of toxic ions in the biological process are the
level above which a decrease in the COD removal effi-
ciency of the biological process occurs. If precautions
for equalization and dilution of WTP residuals prior to
discharge are adhered to, then brine discharges are
unlikely to affect the receiving wastewater plant detri-
mentally (Cornwell et al., 1987).
6.4.6.2 Anaerobic Digestion
Anaerobic digestion is one of the oldest processes used
to stabilize sludges. It involves the decomposition of
organic and inorganic matter in the absence of oxygen.
Important design criteria for anaerobic digestion include
hydraulic and solids retention times, volatile solids load-
ing, mixing energy, gas production, and volatile solids
reduction.
The additional volume and dry weight of sludge and the
decrease in percent of volatile matter must be consid-
ered when determining the sizing and performance pa-
rameters of digesters. A 1989 study (Foley et al., 1989)
of the East Bay Municipal Utility District (EBMUD) in San
Francisco, California, examined the effects of alum re-
siduals on a digester by placing the alum residuals
directly into the digester. The performance of digester 11
receiving alum residuals directly was compared with
digesters operating under "normal" procedures (i.e.,
Table 6-3. Comparison of Digester 11 With Background
Digesters (Foley et al., 1989)
Parameter
Aluminum
Cadmium
Chromium
Copper
Iron
Lead
Nickel
Silver
Zinc
PH
TS
VS
TS/VS
Digester 11
(mg/L)
15,000
16
140
390
16,000
180
41
16
900
7.7
2.3
1.4
58
Background
Digesters
(mg/L)
7,200
18
140
400
17,000
160
41
23
960
7.6
2.5
1.6
61
treating a mixture of primary and WTP residuals intro-
duced into the influent).
The results of this part of the study are presented in
Table 6-3. The alum residuals that were fed directly to
digester 11 had an average total solids (TS) percent of
2.5 and an average volatile solids of 1 percent TS. No
data were presented on the rate of gas production ver-
sus volatile solids reduction. There was a significant
increase in aluminum concentration in the digester re-
ceiving the alum residuals compared with the digesters
operating under "normal" procedures. This needs to be
considered relative to ultimate disposal options. All other
parameters were essentially equal.
Because softening residuals can cause lime deposition,
discharging softening residuals to a WWTP may ad-
versely affect the performance of the anaerobic digester.
If softening residuals are added directly into the anaero-
bic digester, the temperature can fall because of the
additional volume of inert material. Additional heating
may be required in this event.
A study in Durham, North Carolina (McTigueetal., 1989)
investigated the impact of controlled alum residuals dis-
charge to a sanitary sewer on the physical facilities at a
WWTP. The study showed an insignificant effect on flow
rate through the wastewater treatment system. The di-
gested solids, however, increased 46 percent with the
addition of WTP residuals. The loadings on the biosolids
drying beds increased by the same percentage, from 9.8
Ib/ft2/yrto 14.3 Ib/ft2/yr, with the addition of these residu-
als. The retention time and surface loading rate associ-
ated with other processes were not significantly
affected, with the exception of the volume of sludge
collected and handled in the primary clarifier, which was
estimated to increase by 59 percent, from approximately
3.91 to 6.2 tons per day (TPD). The retention time in the
aerobic digesters decreased from 34.7 to 26.7 days, a
23 percent reduction, when WTP residuals were intro-
duced. The impact on the wastewater treatment facility
was significant, particularly in the retention time of the
aerobic digesters, increased pumping needed for the
primary clarifier sludge, and the additional drying bed
capacity required.
Rindt (1973) used a laboratory-scale study to evaluate
the impact of alum residuals on anaerobic digestion. He
found that gas production and TOC remained largely
unaffected. Total solids in the digester increased be-
cause of the additional alum residuals load. The pH in
the digester was also depressed slightly by the alum
residuals. The percentage of volatile solids in the di-
gester decreased because of the increased inorganic
input. Inorganic phosphates in the digester were almost
entirely precipitated by the aluminum present.
These results were confirmed by Reed (1975), who
used laboratory-scale anaerobic digesters to study the
114
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effects of both reagent grade alum (aluminum sulfate)
and WTP residuals (aluminum hydroxide) on the diges-
tion process. Under comparable aluminum concentra-
tions, Reed found that digestion was adversely affected
in the digester where feed sludge contained aluminum
sulfate, but not in the digester where feed sludge con-
tained aluminum hydroxide residuals. Inhibition was at-
tributed to the high sulfide concentration associated with
the reagent grade alum.
Earth et al. (1965) studied the effect of metals on bio-
logical processes and found that for chromium, nickel,
and zinc, an influent metals concentration of 10 mg/L—
for any one or combination of the three—did not affect
digestion. Copper continuously present at 10 mg/L
caused failure of combined sludge digestion.
Wilson et al. (1975) did not observe any negative im-
pacts at the anaerobic digesters in Tampa, Florida, ex-
cept that the solids content of the biosolids discharged
to the drying beds was reduced by a factor of approxi-
mately two as a result of the WTP residuals addition.
Nelson et al. (U.S. EPA, 1978a) observed an increase
in digester gas production beyond that generated by the
increased load of volatile solids applied. Nelson et al.
speculated that this was due to easier mixing of the
digester contents as a result of WTP residuals being
added. Hsu and Pipes (1973) reported that aluminum
hydroxide retarded the digestion process.
Emig (1979) conducted a full-scale test employing alum
and polymer to treat phosphorus at a WWTP He re-
ported a drop in digester gas production, accompanied
by a drop in digester pH (from approximately 7.2 to 6.0)
after the addition of alum. This change led to a digester
upset at alum dosage of approximately 400 mg/L. Alum
addition had reduced the alkalinity of the digesting
sludge and increased the volatile acid levels. The upset
was caused by the depression of the alkaline wastewa-
ter pH.
These studies show that unless alum residuals are in-
troduced at a very high rate, anaerobic digesters are
unlikely to be significantly affected, provided the di-
gester has adequate capacity to accommodate the in-
creased solids loading. In assessing digester capacity,
the reduced volatile solids concentration of the residuals
stream must be taken into account.
6.4.6.3 Thickening/Dewatering
Thickening and dewatering are unit operations that
separate liquid from solids. In its unthickened condition
(e.g., underflow withdrawal from a clarifier), a WTP re-
siduals/WWTP sludge blend normally has a solids con-
centration in the range of 2 to 6 percent total solids.
Thickening can reduce the water content to the range of
9 to 15 percent total solids. In this range, the thickened
residual still behaves like a liquid but has the consis-
tency and physical properties of chocolate pudding. De-
watering of thickened residuals will result in a cake with
a solids content of 18 to 40 percent.
Thickening and dewatering can be accomplished by
natural or mechanical means. Examples of thickening
operations are gravity thickening, flotation thickening,
centrifuge thickening, and rotating drum thickening.
Common dewatering operations include sand or paved
drying beds, dewatering centrifuges, belt filter presses,
and recessed chamber filter presses. All thickening and
dewatering equipment is sized according to solids load-
ing. The introduction of WTP residuals may cause over-
loading of these facilities, depending on the quantity of
residuals introduced and the existing WWTP loadings
relative to the plant's design capacity.
Hsu and Pipes (1973) reported that the dewaterability of
wastewater biosolids, as measured by the specific re-
sistance to filtration, was improved by an increase in the
dosage of aluminum hydroxide. Nelson et al. (U.S. EPA,
1978a) found that the concentrate quality and cake sol-
ids content of the centrifuge were not significantly
changed by the introduction of WTP residuals. They
noted that the yield from the centrifuge increased from
600 to 800 Ib/hr for biosolids, to about 900 Ib/hr for the
alum residuals biosolids mixture. A study in Norfolk,
Virginia (COM, 1989), showed that the settling charac-
teristics of waste activated sludge as measured by the
sludge volume index was negatively affected by the
addition of alum residuals. No significant impacts on
centrifuge dewatering in terms of cake solids, polymer
dosage, and centrate recovery were reported.
In almost every case, the dewaterability of the wastewa-
ter biosolids, as measured by the specific filtration resis-
tance, was shown to improve with the addition of WTP
residuals (van Nieuwenhuyze et al., 1990). A study by
McTigue et al. (1989) investigated how the use of WTP
residuals changed sludge handling characteristics and
affected WWTP performance. A pilot column evaluation
was conducted to determine the effect of WTP residuals
on drainage characteristics of the WWTP biosolids.
These tests were necessary to determine the impact of
the WTP residuals on the WWTP's ultimate dewatering
process (i.e., sand drying beds). McTigue et al. (1989)
found that the addition of WTP residuals had little influ-
ence on the drainage characteristics of the aerobically
digested activated sludge. The addition, however, of
residuals to aerobically digested activated sludge
caused the biosolids to settle in the bed and produce a
clear water layer suitable for decant, thus improving the
dewatering process. The dewatering tests on the com-
bined anaerobically digested primary sludge and WTP
residuals were very similar. The major difference was
that the anaerobically digested primary sludge drained
faster than the aerobically digested activated sludge and
115
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also contained some clarified surface water available for
decant.
In Allentown, Pennsylvania, a pilot test was conducted
to determine the effects of dewatering alum residuals
either separately or combined with biosolids using a
recessed chamber filter press (Koplish and Watson,
1991). The dewatering results indicated that the highest
cake solids of 46.8 percent were achieved by dewater-
ing alum residuals alone, although a cycle time of 3
hours was required. In comparison, wastewater
biosolids were dewatered to 34.3 percent cake at a cycle
time of 1 hour. When they were mixed at different pro-
portions, the resultant cake solids were between 34.3 to
46.8 percent; the blend having higher portions of alum
residuals resulted in the higher cake solids.
With the success of the pilot tests, the City of Allentown
has proceeded to install full-scale facilities for accepting
and dewatering a combination of biosolids and WTP
residuals at its WWTP. The operation is termed the
"Centralized Dewatering and Co-Disposal (CDCD)" con-
cept, and is described by Koplish et al. (1995). Dewa-
tering of a 50-50 blend is accomplished at the WWTP
by high-solids belt filter presses, and the combined op-
eration is saving the city at least a quarter of a million
dollars annually. At a 50-50 blend, feed solids in January
and February 1995 were 2.6 percent; cake solids were
25.6 percent. The WTP residuals are tank-trucked to the
WWTP, where they are discharged to a blended residu-
als holding tank and mixed with biosolids. The operation
has been so successful that the city is now considering
accepting third party liquid residuals for processing,
which could represent a new revenue source for the city.
A pilot study was conducted in Wilmington, North Caro-
lina, employing a belt filter press.4 It was found that alum
residuals dewatered alone attained a maximum cake
solids content of 23 to 27 percent. Wastewater biosolids
were dewatered to 15 to 18 percent solids. When alum
residuals and wastewater biosolids were blended, the
dewatered cake had a solids concentration of 17 to 20
percent. The results were consistent with bench-scale
tests conducted earlier on the same sludges. The re-
ported test results followed a pattern similar to the Allen-
town study.
Vandermeyden and Potter (1991) reported on full-scale
sludge dewatering tests for alum WTP residuals using
both centrifuge and belt filter press equipment. The tests
yielded favorable results in terms of cake solids concen-
tration, polymer dose, and centrate/filtrate quality. The
dewatering test results are summarized in Table 6-4 and
indicate that cake solids concentrations typically ranged
from 20 to 27 percent, polymer dose from 5 to 70 Ib/ton
of solids, and overall solids capture around 98 percent.
Table 6-4. Alum Treatment Plant Sludge Dewatering Test
Results (Vandermeyden and Potter, 1991)
Parameter
Loading rate (Ib/hr)
Feed solids (%)
Polymer dose (Ib/hr)
Solids capture (%)
Belt Filter
Press
700-800
2.5
20-23
98
Centrifuge
560-750
2.5
25-27
98
1 City of Wilmington. 1991. Personal communication.
Although available information has generally shown that
WWTP biosolids dewaterability is not negatively im-
pacted by alum residuals, gravity settling of the waste-
water sludge may be affected. The ability to reduce the
water content of sludge depends on many factors, in-
cluding the physical, chemical, and biological charac-
teristics of the sludge, and the unit operations employed
to thicken ordewater it. To date, the science of dewater-
ing has not advanced to the point when sludge dewater-
ability can be predicted precisely without actual testing.
Data that are useful in determining sludge dewaterabil-
ity, such as particle size distribution and zeta potential,
are seldom available.
If the impacts of cake solids are critical to downstream
processing, the effect of WTP residuals on sludge thick-
ening and dewatering should be fully investigated
through pilot- or full-scale testing before the co-process-
ing of WTP residuals and WWTP biosolids is imple-
mented.
6.5 Ultimate Disposal of Wastewater
Treatment Plant Biosolids
Several different ultimate disposal options are available
to WWTPs. Before the advent of the Clean Water Act
(CWA), one common disposal option was direct dis-
charge to a nearby surface water body. Current regula-
tions limit this as a viable option for WWTPs. The
regulatory climate further requires WWTPs to develop,
evaluate, and implement alternative ultimate disposal
methods. Options include land application, incineration,
and composting, all of which could be considered bene-
ficial uses. The regulations governing beneficial reuse
options have only recently been established by some
primacy agencies; other primacy agencies are still de-
veloping regulations. The promulgation of 40 CFR Part
503 will further these options as guidelines and regula-
tions are established.
Quality, quantity, and cost are key factors in determining
which disposal options a WWTP employs. The regula-
tory requirements for WWTP biosolids, established by
the primary agencies responsible for monitoring ultimate
disposal, are applied to WTPs that discharge to
WWTPs. Regulatory requirements and technical issues
116
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relating to these disposal options are addressed in the
following sections.
6.5.1 Direct Discharge
In the past, direct discharge was commonly used to
dispose of WTP residuals. Protection of aquatic re-
sources and maintenance or improvement of water
quality conditions has resulted recently in more stringent
regulation. As a result of the CWA, regulation of this
option has increased the cost and concern over liability
to the WTP. The regulatory requirements are primarily
associated with the Federal Ambient Water Quality Cri-
teria, established through the CWA to protect aquatic life
in marine and freshwater environments. Regulations of
particular interest to the water treatment industry are
those that establish acceptable levels of metals, sus-
pended solids, and water treatment-related contami-
nants (see Chapters 2 and 5).
For a WWTP to consider receiving WTP residuals, an-
ticipated levels of metals and other contaminants would
have to be determined to ensure compliance with
NPDES permits limits.
6.5.2 Land Application
Land application, as it applies to disposal of WTP residu-
als, is discussed in Chapter 8. The same quality restric-
tions and load limitations that apply to land application
WTP residuals apply to wastewater biosolids; however,
biosolids have the added benefit of higher organic or
nutrient content. Higher organic content, nitrogen, and
phosphorus levels are beneficial if land application of
the biosolids is associated with agricultural uses.
The addition of alum WTP residuals to WWTP biosolids
could reduce the level of available phosphorus and
create concerns over aluminum toxicity. The addition of
residuals from a water softening WTP, or the addition of
alum residuals conditioned by lime for dewatering could
prove to be very beneficial to a joint land application
program with biosolids. Examples of each of these two
approaches are reported by Parsons and Waldrip (1995)
and by Assadian and Fenn (1995).
Ionic aluminum is toxic to many plants, including agri-
cultural crops (Elliot and Singer, 1988). This detrimental
effect could limit the land application process for
biosolids containing alum WTP residuals. A WWTP
manager currently land applying biosolids must there-
fore be watchful of additional aluminum in the biosolids
to ensure that regulatory limits are not exceeded. Re-
cent studies, however, performed by Grabarekand Krug
(1989) show that large doses of alum sludge do not
necessarily produce aluminum toxicity (Elliot et al., 1988).
As discussed previously, one benefit of land applying
WWTP biosolids is the contribution of organic matter
and nutrients. The addition of aluminum or iron hydrox-
ides could result in a strong fixation of available phos-
phorus (PO4"3), thus making it unavailable for vegetation.
This does not preclude the addition of WTP residuals,
but careful consideration must be given to relative quan-
tities and qualities of any additives, as well as beneficial
reuse objectives. If land spreading for nonagricultural
purposes is the ultimate disposal method, concerns over
aluminum toxicity and available phosphorus are mini-
mized. Pilot-scale testing and chemical analysis can be
conducted to assess viability.
The City of Boulder, Colorado, has undertaken an ex-
tensive evaluation of the benefits and risks of coappli-
cation of WTP residuals and WWTP biosolids (Harberg
and Heppler, 1993). They reported that the beneficial
effects of direct addition of WTP residuals to WWTP
biosolids depend on soil conditions, characteristics of
the residuals, and application rates. If not properly man-
aged, direct application of WTP residuals could cause
detrimental plant growth and other environmental ef-
fects. An evaluation of the literature on the effects of
WTP residuals on crop growth response suggested that
land coapplication of WTP residuals and WWTP
biosolids for beneficial use was a viable way to recycle
WTP residuals, and did not reduce the plant-available
phosphorus in soils. In fact, the WWTP biosolids would
help supplement the phosphorus available in the soil. A
proper combination of the two materials could also pro-
vide the nitrogen needed by the plants without reducing
the phosphorus availability in the soil. The City of Boul-
der study is specifically evaluating coapplication of an
aluminum-based WTP residual and a WWTP biosolid to
dry land winter wheat. Based on crop yield, the WTP
residuals did not significantly affect yields, and no differ-
ence between control and applied plots was found.
6.5.3 Incineration
Incineration provides an effective method for reducing
volume and creating a relatively inert material. Depend-
ing on the initial metals levels in the biosolids, leaching
of metals from the ash residue may be a concern.
The trend in biosolids disposal is increasingly in favor of
beneficial reuse options. Incineration is becoming a less
desirable option because of its relatively higher costs, as
well as recent concerns and regulations on air emissions.
The addition of a WTP residual into the processes of a
WWTP currently incinerating biosolids could create
some problems. Because the organic content of WTP
residuals is generally lower than that of WWTP
biosolids, the thermal destruction process may be hin-
dered. The presence and contribution of iron and alumi-
num, as well as other coagulant contaminants, must
also be considered relative to facility operations, air
emissions, and leaching from ash residue.
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6.5.4 Composting
Composting is a biological process that converts
biosolids into a stable humic material that could be land
applied (Tsang and Hurdle, 1991). Composting (includ-
ing co-composting) of WWTP biosolids, considered a
beneficial reuse option, has been increasing as a dis-
posal practice in the United States (Bowen et al., 1991).
The problems associated with composting WWTP
biosolids are generally related to the presence of patho-
gens and odors. The addition of WTP residuals to the
WWTP waste stream would not compound these prob-
lems, and could act to dilute them. The resulting lower
volatile solids content of the biosolids, however, could
inhibit the degradation process (Tsang and Hurdle,
1991) by reducing the level of biological activity.
Studies conducted in Greenwich, Connecticut, and Myr-
tle Beach, South Carolina, indicate that if managed prop-
erly, composting WTP residuals and WWTP biosolids
could be an attractive alternative.
Vandermeyden and Potter (1991) reported on full-scale
tests of joint composting of alum residuals and waste-
water biosolids. A 25-percent mix ratio (residuals/
biosolids) appeared to be the maximum ratio for attain-
ing proper composting temperatures for pathogen de-
struction and for maintaining levels of volatile solids. No
observable differences in color or physical charac-
teristics were noted between compost with mix ratios of
25 and 12.5 percent and virgin biosolids compost. The
introduction of metals from the alum residuals did not
produce a degradation in compost quality and actually
caused a higher allowable loading rate for the finished
compost, based on a lowering of the copper and zinc
concentrations in the final compost.
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Chapter 7
Landfill Options
As a drinking water utility evaluates its treatment plant
residuals management options, landfilling will most
likely be considered. In nearly every case, landfilling
falls into two categories: co-disposal and monofilling.
This discussion assumes that the water treatment plant
(WTP) residuals to be managed have not been classi-
fied as hazardous wastes. When the WTP residuals
exhibit hazardous characteristics, they must be handled
as RCRA Subtitle C wastes. In most instances, WTP
residuals will be classified as nonhazardous solid waste,
subject to the requirements of RCRA Subtitle D.
Under RCRA Subtitle D regulations (40 CFR Parts 257
and 258), criteria have been established for the design
and operation of nonhazardous solid waste landfills. The
requirements of 40 CFR Part 257 apply to landfills that
receive only WTP residuals (monofills), as well as land-
fills that accept solid waste other than household waste
(e.g., industrial waste). These criteria, which are per-
formance based and do not include any specific design
criteria, address seven landfill design and operation ar-
eas (see Table 7-1).
Municipal solid waste landfills (MSWLFs) are subject to
the criteria of Part 258. Like the provisions of Part 257,
Part 258 covers performance-based criteria, but it also
includes specific design criteria. If a utility disposes of
its drinking water residuals in a monofill, then Part 258
criteria do not apply. If, however, the WTP residuals are
co-disposed of with municipal solid waste, including
household waste, the requirements established for
MSWLFs apply. The landfill criteria in 40 CFR Part 258
address six major areas, as listed in Table 7-2.
RCRA Subtitle D establishes minimum criteria to be
applied in all states. In addition, each state may develop
its own landfill requirements provided that the criteria at
least meet the minimum federal standards. In many
states, landfill requirements are more restrictive than
federal criteria. Many states have developed unique
solid waste landfill programs that reflect specific state-
wide factors and concerns.
Any evaluation of landfilling options for the management
of WTP residuals should include a careful examination
of state landfill requirements. In many states, the flexi-
Table 7-1. Solid Waste Landfill Criteria: Monofill for WTP
Residuals and Co-disposal of Residuals With
Nonhousehold Solid Waste (40 CFR Part 257)
Section
Subpart
Floodplains
Endangered species
Surface water
Ground water
Disease
Air
Safety
3-1
3-2
3-3
3-4
3-6
3-7
3-8
Table 7-2. Solid Waste Landfill Criteria: Co-disposal of WTP
Residuals With Municipal Solid Wastes (40 CFR
Part 258)
Section
Location restrictions
Operating criteria
Design criteria
Ground-water monitoring and corrective
action
Closure and postclosure care
Financial assurance criteria
Subpart
B
C
D
E
F
G
bility exists to design and operate landfills according to
site-specific conditions and limitations.
7.1 Landfill Siting
Landfill siting criteria usually address two concerns—
landfill performance and protection of public health and
the environment. Restrictions on siting a landfill in or
near airports, floodplains, wetlands, fault areas, seismic
impact zones, and unstable areas are typically estab-
lished to protect the landfill's integrity, thus protecting the
public and minimizing environmental damage should the
landfill fail.
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7.1.1 Airports
Scavenger birds such as crows, gulls, and starlings are
the most common aircraft safety concern at landfills,
especially those that receive household solid waste.
Birds are attracted to landfills to nest, roost, and search
for food and water. Therefore, regulations restrict the
construction and operation of landfills in areas surround-
ing airports. For example, MSWLF criteria (40 CFR Part
258) require that owners/operators of landfills within
10,000 feet of the end of a runway used by turbojet
aircraft and within 5,000 feet of the end of a runway used
only by piston-type aircraft demonstrate that design and
operation of the landfill does not pose a bird hazard to
aircraft. In addition, landfills within a 5-mile radius of the
end of a runway must notify the Federal Aviation Admini-
stration of their existence.
For monofills, the issue of airport safety may only be a
concern if co-disposal with household solid waste is
used.
Reducing bird problems at MSWLFs is difficult because
of the tenacity of scavenger birds. Operational practices
that can minimize the attraction of birds to the landfill
include:
• Frequent covering of wastes that provide a source of
food.
• Baling, milling, or shredding food-containing wastes.
• Attempting to eliminate food-type wastes from the
landfill using waste management techniques such as
source separation and composting.
7.1.2 Floodplains
Floodplains are areas inundated by water during a 100-
year flood. These areas usually include lowland and
relatively flat areas next to inland and coastal waters,
including flood-prone offshore islands. Landfills located
in floodplains can restrict river flow during flood events,
reduce the temporary water storage capacity of the
floodplain, or fail, resulting in the washout of solid waste
which can pose a threat to human health and the envi-
ronment. Therefore, siting landfills in floodplains is usu-
ally restricted.
In most cases, these restrictions do not prohibit the
location of a landfill in a floodplain, but a technically
sound demonstration of the design and operational as-
pects of the landfill that address these concerns is
needed before the applicable regulatory approvals can
be secured. At a minimum, the technical demonstration
requires the landfill owner/operator to identify the
boundaries of the floodplain and its relation to the landfill
and future landfill expansions, and to address engineer-
ing considerations. The velocity during base flow and
flood flow conditions and the temporary water storage
capacity of the floodplain must be determined. Modeling
of the effects of the landfill on these velocity and storage
volume characteristics is usually required. The U.S.
Army Corps of Engineers has developed several com-
puter models to assist in the evaluation of these flow and
storage parameters.
Cost-effective methods to adequately protect a landfill
from flood damage have been developed. These meth-
ods include using rip-rap and geotextiles to prevent
erosion or other damage to the landfill.
7.13 Wetlands
With the concern over increasing loss of wetland re-
sources, the location of landfills in or near wetlands is
severely restricted. The concern relates to the effects of
construction and operation on surface water quality and
fish, wildlife, and other aquatic resources and their habi-
tat, especially endangered or threatened species.
Requirements for the protection of wetlands are found
in numerous federal statutes and orders including:
• Clean Water Act (Sections 401, 402, and 404)
• Rivers and Harbors Act of 1989
• Executive Order 11990, Protection of Wetlands
• Nation Environmental Policy Act (NEPA)
• Migratory Bird Conservation Act
• Fish and Wildlife Coordination Act
• Coastal Zone Management Act
• Wild and Scenic Rivers Act
• National Historic Preservation Act
Besides federal requirements, most states and many
local jurisdictions have requirements to safeguard the
integrity of wetlands. The use of wetlands for the con-
struction of a landfill requires a permit from the U.S.
Army Corps of Engineers, which oversees wetlands
under authority delegated by the U.S. Environmental
Protection Agency (EPA). Usually, owners/operators are
required to demonstrate that no other alternatives exist
to siting a landfill in a wetland, and only under very
limited conditions will landfill construction in wetlands be
approved. Owners/operators are required to develop
extensive plans for mitigating and offsetting wetland
impacts, including the creation of wetlands in other ar-
eas.
7.14 Fault Areas
Many landfill siting restrictions include a prohibition
against locating a landfill within a certain distance from
an earthquake fault. Seismologists generally believe
that the structural integrity of an engineered unit cannot
be unconditionally guaranteed when built within 200 feet
of a fault along which movement is highly likely to occur.
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MSWLF criteria (40 CFR Part 258) have established
200 feet as the minimum allowable distance between a
fault and a landfill. Fault areas affected by the 200-foot
limitation are those that have experienced movement in
Holocene time, which is approximately during the last
10,000 years.
The U.S. Geological Survey (USGS) has developed
maps that identify the location of Holocene faults in the
United States. Landfill owners/operators should use
these maps to determine the location of fault areas that
may affect the location of a proposed landfill. A state may
allow the construction of a landfill within a fault area if a
detailed engineering demonstration of the survivability
of the landfill has been developed. Any variance from
these criteria requires a demonstration that no other
practicable waste management alternative exists.
7.1.5 Seismic Impact Zones
In addition to fault areas, most landfill siting restrictions
include consideration of seismic impact zones. A seis-
mic impact zone (40 CFR 258.14) is an area in which a
greater than 10 percent chance exists that the maximum
horizontal acceleration in the bedrock, expressed as a
percentage of the earth's gravitational pull (g), will ex-
ceed 0.10 g in 250 years. Owners/operators can review
the seismic 250-year interval maps in the USGS report
entitled, Probabilistic Estimates of Maximum Accelera-
tion of Velocity in Rock in the Contiguous United States
(USGS, 1982). In addition, the National Earthquake In-
formation Center at the Colorado School of Mines in
Golden, Colorado, can provide seismicity maps of all 50
states.
For landfills to be located in seismic impact zones, an
evaluation of the seismic effects should consider both
foundation soil stability and waste stability under seismic
loading. The evaluation of waste stability for monofills
should be more reliable because of the homogeneous
nature of the waste compared with the heterogeneous
waste properties of municipal solid waste.
While no standard procedures exist for designing landfill
components to withstand seismic events, engineering
evaluations should be conducted on the influence of
local soil conditions on ground response and shaking
intensity, soil settlement, soil liquefaction, and slope
stability during earthquakes.
7.1.6 Unstable Areas
An unstable area is an area susceptible to natural or
manmade events or forces capable of reducing the in-
tegrity and performance of all or some of the landfill
components. Factors that contribute to inadequate sup-
port are poor foundation conditions; down-slope move-
ment of soil, rock, or debris caused by the influence of
gravity; and sinkholes resulting from Karst terraces un-
derlain by soluble bedrock that may contain extensive
subterranean drainage systems and relatively large sub-
surface voids.
The construction and operation of landfills in unstable
areas should be avoided. If built, the landfill should be
engineered and constructed to accommodate the con-
ditions that classify the area as unstable. A detailed
geotechnical and geological evaluation of a landfill site
should be conducted to assess the subsurface under
natural and manmade conditions. This evaluation
should analyze the potential for inadequate support for
the structural components of the landfill.
7.2 Landfill Design
As previously discussed, monofills are subject to the
performance-based criteria specified in 40 CFR Part
257. These criteria require that the owner of a monofill,
usually the drinking water utility, demonstrate that the
construction of such a landfill will not adversely affect
surrounding floodplains, endangered species, surface
water, ground water, or air quality, and will not create
disease or safety threats. The criteria do not specify
design considerations that must be followed. Table 7-3
provides some general guidance on the type of informa-
tion that is necessary before design begins.
The major sludge monofilling methods are trench filling
and area filling. Trench filling can be further subdivided
into narrow trench and wide trench monofilling tech-
niques. Area filling methods include area fill mound, area
fill layer, and diked containment. Sludge solids content,
sludge stability, site hydrogeology (location of ground
water and bedrock), ground slope, and land availability
determine the monofilling method that is selected. The
following sections describe specific aspects of the vari-
ous sludge monofilling methods. Figure 7-1 highlights
the design consideration for monofills.
A landfill that accepts municipal solid wastes is subject
to the criteria described in 40 CFR Part 258. Under
federal regulations, WTP residuals are subject to the
provisions of Part 258 only if they are co-disposed of in
a landfill that also accepts municipal solid waste. In that
case, the landfill is designated as an MSWLF.
Landfill design under Part 258 can be based on perform-
ance or minimum technology standards. These two ap-
proaches are described in detail below.
7.2.1 Performance-Based Design Under
40 CFR Part 258
Performance-based landfill designs are developed so
that the landfill system will result in compliance with
established performance standards. By allowing a de-
signer to use a performance-based approach, site-
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Table 7-3. Field Investigations for New Information, Landfill
Design (U.S. EPA, 1978b)
Information
Base Map
Soils
Bedrock
Ground
water
Climatology
Information
Property
boundaries
Topography and
slopes
Surface water
Utilities
Roads
Structures
Land use
Vegetation
Depth
Texture
Structure
Bulk density
Porosity
Permeability
Moisture
Ease of
excavation
Stability
PH
Cation
exchange
capacity
Depth
Type
Fractures
Surface outcrops
Depth
Seasonal
fluctuations
Hydraulic
gradient
Rate of flow
Quality
Uses
Precipitation
Evaporation
Temperature
No. of freezing
days
Wind direction
Method and Equipment
Field survey
Field survey
Field survey
Field survey
Field survey
Field survey
Field survey
Field survey
Soil boring and compilation of
boring log
Soil sampling and testing via
sedimentation methods (e.g.,
sieves)
Soil sampling and inspection
Soil sampling and testing via
gravimetric, gamma ray detection
Calculation using volume of voids
and total volume
Soil sampling and testing via
piezometers and lysimeters
Soil sampling and testing via oven
drying
Test excavation with heavy
equipment
Test excavation of trench and
loading of sidewall of Hueem
stabilimeter
Soil sampling and testing via pH
meter
Soil sampling and testing
Boring and compilation of boring
log
Sampling and inspection
Field survey
Field survey
Well installation and initial readings
Well installation and year-round
comparison of readings
Multiple well installation and
comparison of readings
Calculation based on permeability
and hydraulic gradient
Ground-water sampling and testing
Field survey via inspection
Rain gauge
Class A Evaporation Pan
Standard thermometer
Minimum-maximum temperature
thermometer
Wind arrow
specific factors can be considered in the design such as:
• Hydrogeologic characteristics of the landfill and the
surrounding land.
• Volume and physical and chemical characteristics of
the leachate.
• Quality, quantity, and direction of ground-water flow.
• Proximity and withdrawal rate of ground-water users.
• Existing quality of the ground water.
The MSWLF criteria require compliance with perform-
ance standards that set maximum contaminant levels
(MCLs) (Table 7-4) not to be exceeded in the ground
water at the relevant point of compliance. The MSWLF
criteria allow for a relevant point of compliance to be
established as far as 150 meters from the waste man-
agement unit boundary. In some cases, the relevant
point of compliance must be at the waste management
unit boundary.
Successful application of the performance-based ap-
proach, leading to a reliable landfill system design, de-
pends on the designer's ability to accurately model the
rate of pollutant movement through the landfill system
and the site stratigraphy. Contaminant transport at the
landfill site must be studied carefully to determine the
direction, speed, and concentration of contaminant flow.
Because contaminant transport in ground water can be
very complicated, accurate prediction of contaminant
movement significantly increases the cost of design and
site characterization for an MSWLF (U.S. EPA, 1994a).
7.2.2 Minimum Technology-Based Design
Under 40 CFR Part 258
The MSWLF criteria have established minimum technol-
ogy-based design standards for landfills that cannot
apply performance-based design standards. Technol-
ogy-based standards require a composite liner system
consisting of an upper geomembrane liner and a lower
compacted-soil liner. The geomembrane liner minimizes
the exposure of the compacted soil liner to leachate,
thus significantly reducing the volume of leachate reach-
ing the soil liner. Reducing membrane penetration is vital
to controlling the escape of leachate into ground water.
The geomembrane must be at least 30 millimeters thick;
high density polyethylene (HOPE) geomembranes must
be at least 60 millimeters thick. The compacted soil liner
must be at least 2 feet thick and have a hydraulic
conductivity of less than 1 x 10"7 centimeters per second.
Many state MSWLF programs have established alterna-
tive technology-based design requirements. Whenever
technology-based designs are being considered, the
state MSWLF program should be contacted to obtain
applicable design requirements.
122
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Project Solids
Production
t i
Physical Characterization
Shear Strength vs. % Solid
Wet Unit Weight vs. % Solic
s
Chemical Characterization
Total Metals
t
Area Fill
T
Slope Stability ^
Analysis
1
Equipment:
Bearing Capacity
Analysis
1
1 '
Size Based
Weight &% Solids
^
Bulking
Agents
~* r
Required Sludge
% Solids
Develop S te Layout
in Accordance With
Local Siting
Ordinances
j
Economic Analysis
*
Trench Fill
t
Wide Narrow
1 1 °r
1 1 Wide
T T
Equipment:
Bearing
Capacity Narrow
Analysis
t
1 '
Sludge
Requirements
-*
Figure 7-1. Considerations for sludge monofill design (Cornwell et al., 1992).
Many factors must be considered for a successful
geomembrane design and installation:
• Selection of proper geomembrane materials that con-
sider chemical resistance and biaxial stress-strain
properties.
• Proper subgrade preparation to ensure that the com-
pacted soil liner is smooth and strong enough to
provide continuous support for the geomembrane.
• Proper geomembrane transportation, storage, and
placement.
• Favorable installation conditions, including fair weather,
low winds, and proper temperature.
• Proper geomembrane seaming and seam testing.
• Development and implementation of a reliable and
reasonable construction quality assurance (CQA)
program.
Because of its low hydraulic conductivity characteristics,
clay is usually the soil of choice for compacted soil
liners. Unfortunately, clay is a difficult engineering
material to work with because of its highly moisture-
dependent physical properties. As a basic landfill liner,
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Table 7-4. Maximum Contaminant Levels in Uppermost
Aquifer at Relevant Point of Compliance (Fed.
Reg., October 9, 1991)
Parameter
MCL (mg/L)
Arsenic
Barium
Benzene
Cadmium
Carbon tetrachloride
Chromium (hexavalent)
2,4-Dichlorophenoxy acetic acid
1 ,4-Dichlorobenzene
1 ,2-Dichloroethane
1,1-Dichloroethylene
Endrin
Fluoride
Lindane
Lead
Mercury
Methoxychlor
Nitrate
Selenium
Silver
Toxaphene
1 ,1 ,1 -Trichloromethane
Trichloroethylene
2,4,5-Trichlorophenoxy acetic acid
Vinyl chloride
0.05
1.0
0.005
0.01
0.005
0.05
0.1
0.075
0.005
0.007
0.0002
4.0
0.004
0.05
0.002
0.1
10.0
0.01
0.05
0.005
0.2
0.005
0.01
0.002
clay must meet certain criteria to protect ground water
from leachate contamination. To meet the requirements
of the MSWLF criteria and to produce a reliable barrier
against leachate movement, the following steps should
be taken during construction of a compacted clay liner:
destroy soil clods, eliminate lift interfaces, conduct
proper compaction, meet moisture-density criteria, and
avoid desiccation.
To minimize holes in a geomembrane liner caused by
product defects, transportation, installation, and seam-
ing, and to produce a reliable soil liner that prevents the
movement of leachate into the ground water, a CQA
program should be developed and implemented (U.S.
EPA, 1993a). The CQA program is a planned system of
activities implemented by the landfill owners or their
representatives, to ensure that the components of the
landfill system are constructed as specified in the de-
sign. The CQA program should be developed along with
the landfill design. All involved state and federal regula-
tors should review the CQA program before approvals
and permits for construction are issued.
CQA is different and distinct from construction quality
control (CQC). CQC is a program that the construction
contractor develops and implements to ensure the qual-
ity of its work. In contrast, the CQA program is an
additional check of the construction contractor's work
conducted by the owners of the landfill. Several key
components to a successful CQA program are:
• Responsibility and authority: Landfill owners give
CQA personnel the responsibility and authority to rep-
resent their interest and to ensure that the landfill
components meet design specifications.
• Personnel qualifications: The CQA inspector must
have extensive experience and knowledge about the
work performed in the field. A program administered
by the National Institute of Certifying Engineering
Technicians (NICET) gives formal examinations and
certifies CQA inspectors.
• Inspection activities: The CQA program must clearly
define the testing program and acceptance criteria for
significant components of the landfill system. For the
liner system, the CQA program should specify the fre-
quency of testing to be done on the compacted soil and
geomembrane liner, outline the sampling strategy, and
define the specific tests to be performed.
• Sampling strategies: CQA testing is performed using
a combination of statistical and judgmental sampling
strategies. Typical statistical sampling strategies in-
clude defined interval testing, such as one destructive
seam test per 5,000 feet of geomembrane seam or
one moisture/density test per 5,000 cubic yards of
soil liner. Judgmental testing allows the CQA inspec-
tor to call for testing when the quality of workmanship
is suspect.
• Documentation: Before a permit to operate the landfill
is issued, most states now require documentation
that a CQA program was performed. All CQA activi-
ties must be clearly documented so that a third party
can understand and verify the testing and inspection
program.
Another requirement of technology-based systems in
the design and construction of a leachate collection
system is to collect leachate and convey it out of the
landfill. The MSWLF criteria require this system to en-
sure that less than 30 centimeters of leachate accumu-
lates over the composite liner system to minimize
hydraulic head and possible contamination of the
ground water. When a leachate collection system is
designed and constructed, the following components
should be included:
• Area collector: the drain that covers the liner and
collects the leachate.
124
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• Collection laterals: the pipe network that drains the
area collector.
• Sump: the low point where leachate exits the landfill.
• Stormwater/Leachate separation system: a system
for minimizing leachate generation and possible treat-
ment costs.
These components must be designed to handle larger
leachate flows associated with initial operations and to
resist problems such as biological clogging that can
destroy the long-term performance and flow capacity of
the system.
7.3 Landfill Operations
To meet the regulatory requirements for liners and
leachate collection systems, landfill design and con-
struction have become increasingly complex. Thus, the
integrity of landfill components can be threatened by
careless or inappropriate operations. Facility operators
should be fully aware of landfill operational requirements
and the reasons for these requirements to ensure that
the landfill performs as designed, especially in situations
where the reason for some operational procedures may
not be readily apparent. At the same time, landfill de-
signers and regulators should obtain feedback from
landfill operators on day-to-day operational require-
ments. A complex, sophisticated design that cannot
be operated in the field will not achieve its intended
purpose.
Operational requirements for landfills are designed to
ensure the safety of people on the landfill, including
landfill operators, waste haulers, and the public, and to
protect the environment. MSWLF criteria require the
following list of measures to be implemented at all
landfills:
• Exclude hazardous waste and polychlorinated
biphenyls (PCBs).
• Provide daily cover.
• Control onsite disease vectors.
• Provide routine methane monitoring.
• Eliminate most open burning.
• Control public access.
• Institute run-on and runoff controls.
• Control discharges to surface waters.
• Eliminate the disposal of most liquid wastes.
• Keep records that document implementation of
operational requirements.
7.4 Metal Content Considerations
The most prominent environmental consideration in the
siting, construction, and operation of a residuals monofill
under 40 CFR Part 257 is the potential for ground-water
contamination through the leaching of metal constitu-
ents in the residuals. Assessing the potential for con-
tamination involves determining the metals concentration
in the residuals and the degree to which these metals
can be expected to mobilize into ground water.
The major sources of metals are raw water and treat-
ment chemicals. Table 6-2 presents the findings of one
investigation into the metals content of water treatment
chemicals (Dixon et al., 1988). Aluminum is, of course,
a major constituent of alum coagulant, and iron is a
major constituent in ferric chloride coagulant; these met-
als predominate in WTP residuals as a result. The data
in Table 6-2 indicate that many heavy metal impurities
can exist in coagulants and in other treatment chemi-
cals. Raw water sources also can contain metals natu-
rally or because of source contamination. Raw water
metals largely wind up in WTP residuals.
Metals levels in both treatment chemicals or raw water
can vary, especially in the case of raw water. Because
metals concentrations in WTP residuals vary widely at
different water treatment facilities, a general charac-
terization of metals concentrations in WTP residuals is
difficult to make. Such a characterization is complicated
by the lack of comprehensive surveys of metals concen-
tration in WTP residuals.
Nonetheless, a rough characterization of typical WTP
residuals metals concentrations is presented in Table
7-5. The number of samples from which each range was
compiled should be noted when interpreting the ranges.
The American Water Works Service Co. survey of 19
water plants in Pennsylvania covered only seven met-
als—cadmium, chromium, copper, lead, mercury, nickel,
and zinc (Dixon et al., 1988)—which accounts for the
disparity in sample set sizes.
Typical metals concentration ranges in natural soils and
sewage sludge are provided in Table 7-5 for comparison
with WTP residuals (Dragun, 1988). Median concentra-
tions for sewage sludge are also presented (U.S. EPA,
1984b). The concentration data for both natural soils
and sewage sludge are based on more comprehensive
information than could be compiled for WTP residuals.
The three substances covered in Table 7-5 are roughly
comparable. WTP residuals usually contain much lower
metals levels than typical sewage sludge contains and
often levels are very similar to those found in natural
soils.
125
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Table 7-5. Comparison of Metals Concentrations in WTP Residuals, Natural Soils, and Sewage Sludge
Number of WTP Range of
Residuals Concentrations in
Samples Included WTP Residuals
Metals in Compilation (mg/kg, dry)3
Aluminum
Arsenic
Barium
Cadmium
Chromium
Copper
Iron
Lead
Manganese
Mercury
Nickel
Selenium
Silver
Zinc
7
6
6
24
26
25
4
26
5
24
23
5
4
25
10,000-170,000
5.7-36
30-333
0-16
6.7-200
7-1 ,300
15,200-79,500
1-100
68-4,800
0-9.8
12-1,319
0-36
0-2
6.2-3,325
Average
Concentration in
Compiled WTP Typical Range of
Residuals Concentrations
Samples in Natural Soils
(mg/kg, dry)3 (mg/kg, dry)b
72,729
20
131
3.3
59
176
51 ,400
50
1,453
0.9
209
8
1
598
10,000-300,000
1 .0-40
100-2,500
0.01-7.0
5.0-3,000
2.0-100
7,000-550,000
2.0-200
100-4,000
0.01-0.08
5.0-1 ,000
0.1-2.0
0.1-5.0
10-300
Typical Range of
Concentrations in
Sewage Sludge
(mg/kg, dry)
N/A
1.1-230
N/A
1-3,410
10-99,000
84-1 7,000
1 ,000-1 54,000
13-26,000
32-9,870
0.6-56
2-5,300
1.7-17.2
N/A
101-49,000
Median
Concentration in
Sewage Sludge
(mg/kg, dry)
N/A
10
N/A
10
500
800
17,000
500
260
6
80
5
N/A
1,700
a Cornwell et al., 1992; Dixon et al., 1988.
b Dragun, 1988.
CU.S. EPA, 1984b.
Key
N/A = not analyzed.
7.4.1 Classification as Hazardous or
Nonhazardous Waste
The total metals concentrations in a material do not, by
themselves, give a good indication of the potential fora
material to contaminate ground water with metals in a
landfill situation; the degree to which the metal constitu-
ents readily solubilize into ground water is an equally
important factor. Laboratory extraction testing is one
method to assess the extent to which a material's metals
will readily solubilize.
As part of the RCRA Subtitle C regulations, EPA has
defined four extrinsic characteristics, any one of which
can qualify a waste as hazardous. The four charac-
teristics are reactivity, corrosivity, ignitability, and toxicity.
Since the inception of the RCRA regulations, toxicity has
been defined in terms of extraction testing results. Prior
to May 1990, the extraction procedure (EP) toxicity test
was the standard test for determining toxicity. Since May
1990, the standard test has been the toxicity charac-
teristics leaching procedure (TCLP) test. Both tests in-
volve the preparation of an aqueous extract from a
waste sample, which is in turn analyzed for a number of
toxic parameters including metals (the same eight in
each test) and organic compounds.
Although extraction testing is the means by which a
substance is determined to be toxic, according to the
RCRA regulations, it is also a means for determining the
mobility of toxic analytes in a waste that is not toxic. For
WTP residuals, failure of the TCLP test is not likely
because the metals content of most residuals samples
is low enough that even if 100 percent of each metal
were extracted into the extraction fluid, the TCLP con-
centration limits would not be exceeded (Cornwell et al.,
1992).
Table 7-6 demonstrates this point by presenting the
TCLP concentrations that would result from 100 percent
extraction of the metals in a residuals sample having
metals concentrations equal to the maximums given in
Table 7-5. These TCLP concentrations are based on the
assumption of a 35 percent solids sample. As part of the
TCLP test, samples are subjected to pressure filtration
to remove excess water. Dewatered coagulant residuals
will not yield any water when subjected to pressure
filtration and will, therefore, be tested at their dewatered
solids concentration. Even 100 percent extraction of the
TCLP metals from a hypothetical dewatered residuals
sample that contained all the maximum metals concen-
trations given in Table 7-5 would not cause an ex-
ceedance of any of the TCLP regulatory limits. This
clearly indicates that WTP residuals should rarely, if
ever, qualify as toxic under RCRA regulations.
This conclusion is supported by actual extraction test
results for WTP residuals. Table 7-7 presents actual
126
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results for EP toxicity tests performed on several WTP
residuals samples and Table 7-8 presents TCLP results
for WTP residuals from five facilities. In all cases, no
TCLP regulatory limits were even approached (Cornwell
et al., 1992). In fact, TCLP metals often cannot be
detected in extraction fluid because concentrations are
so low.
Table 7-6. Worst Case TCLP Results Using Maximum Metals
Concentrations in Table 7-5, Compared With TCLP
Regulatory Limits (Cornwell et al., 1992)
Metal
Arsenic
Barium
Cadmium
Chromium
Lead
Mercury
Selenium
Silver
Maximum Possible
Concentration in
Extraction Fluid
(mg/L)
0.63
5.83
0.28
3.50
1.75
0.17
0.63
0.04
TCLP
Regulatory
Limit (mg/L)
5.0
100.0
1.0
5.0
5.0
0.2
1.0
5.0
Because the detection limits of metals are often encoun-
tered in such testing, it is difficult to measure the per-
centage of a metal's original amount. The results from
pilot lysimeter testing, however, often can be expressed
in terms of percentages of metals extracted.
7.4.2 Mobility of Trace Metals
Lysimeter testing can provide additional insight into the
mobility of metals from WTP residuals. A recent study
used the lysimeter setup shown in Figures 7-2Ato 7-2C
to test the leachability of metals from three residuals
samples (Cornwell et al., 1992). The residuals used in
this lysimeter test came from three WTPs. Two alum
residuals samples were used, one from the Williams
WTP in Durham, North Carolina, and one from the
Chesapeake WTP in Chesapeake, Virginia. The third
residuals sample was a ferric chloride sample from the
Aldrich WTP operated by the Pennsylvania-American
Water Co. TCLP test results are presented in Table 7-8.
The study lasted 24 weeks. Each week, 44.1 liters of
simulated rainwater were pumped over a 24-hour period
into each lysimeter column. The simulated rainwater
was made in the laboratory, having a pH of 4.5 and
containing the constituents listed in Table 7-9. A perfo-
rated plate was used to hold the rainwater and allow it
Table 7-7. EP Toxicity Test Results for Alum Residuals (Cornwell et al., 1992)
Contaminant
Arsenic
Barium
Cadmium
Chromium
Lead
Mercury
Selenium
Regulatory
Threshold
(mg/L)
5.0
100.0
1.0
5.0
5.0
0.2
1.0
Saltonstall, CT
(mg/L)
<0.01
0.21
<0.005
<0.01
<0.01
<0.001
0.09
West River,
CT (mg/L)
<0.01
0.1
<0.005
<0.01
<0.001
<0.001
<0.01
City of
Chesapeake,
VA (mg/L)
<0.003
<0.1
0.005
<0.05
<0.001
<0.001
<0.007
American Water Works
Service Co. 66-Plant
Survey (mg/L)
<0.2-0.4
<0.1-34.0
<0.005-0.06
<0. 1-3.8
<0.0004-0.003
<0.0004-0.003
<0.001— 0.08
Table 7-8. TCLP Results for Five Water Treatment Plant Coagulant Residuals (Cornwell et al., 1992)
Contaminant
Arsenic
Barium
Cadmium
Chromium
Lead
Mercury
Selenium
Silver
Regulatory
Threshold
Level (mg/L)
5.0
100.0
1.0
5.0
5.0
0.2
1.0
5.0
Contra Costa, CA,
Water District
Alum Sludge (mg/L)
0.04
1.1
<0.05
0.06
<0.2
<0.001
<0.02
<0.05
Phoenix, AZ,
Alum Sludge
(mg/L)
<0.3
1.1
<0.02
<0.04
<0.5
<0.01
<1
<0.01
Durham, NC,
Alum Sludge
(mg/L)
0.0088
1
<0.02
<0.1
<0.1
<0.002
<1
<0.1
Chesapeake,
VA, Alum
Sludge (mg/L)
0.0023
<1
<0.02
<0.1
<0.1
<0.002
<0.002
<0.1
Aldrich, PA,
WTP Ferric
Sludge (mg/L)
0.006
<2
0.02
<0.1
<0.1
<0.002
<0.002
<0.1
127
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85 90
SOLDS CONCENTRATION (?.}
Figure 7-2A. Compaction curve, Ferric Sludge 3 (Cornwell et
al., 1992).
<= 30
_J I I I L_
20 30 40 50 60 70 80 90 100
SOLIDS CONCENTRATION (7.)
Figure 7-2B. Compaction curve, Alum Sludge 1 (Cornwell et al.,
1992).
to drip to the surface of each lysimeter in a manner
similar to rainfall. Residuals were placed loosely in each
lysimeter column to allow the rainwater to percolate
through. Because residuals are a nearly impermeable
material, had they been compacted the water would
have formed a pond at the top of the columns and not
drained through. Rainwater was allowed to sit in the
columns for a week before being drained for sampling.
The total amount of rainwater applied to each lysimeter
was equivalent to 450 inches of rainfall, about 12 years
of rain in Virginia. The total metals concentrations for
these residuals are presented in Table 7-10.
Table 7-11 summarizes the results from the lysimeter
study in terms of the percentages of each metal leached.
Manganese was the only metal that leached at a rate of
40 50 60 70
SOUDS CONCENTRATION (7.)
Figure 7-2C. Compaction curve, Alum Sludge 2 (Cornwell et al.,
1992).
Table 7-9. Chemical Constituents of Synthetic Rainwater
(Cornwell et al., 1992)
Constituent
Concentration (mg/L)
NH3
CA2+
Mg2+
Na+
K+
cr
N3-5
S042-
PH
0.045
0.14
0.073
0.46
0.078
1.63
0.036
1.54
4.5
over 1 percent in all three residuals samples. This
lysimeter study clearly indicates that not only do WTP
residuals generally contain small concentrations of met-
als, but only small portions of these metals tend to leach.
In the test, aluminum, barium, chromium, lead, and sil-
ver did not leach measurably from any of the residuals
samples. Cadmium and nickel leached only from the
ferric chloride residuals. Arsenic, copper, iron, manga-
nese, and zinc leached from all the residuals samples.
Table 7-12 presents the maximum leachate concentra-
tions of each metal measured as part of the lysimeter
study. As indicated in the table, no primary MCLs were
exceeded in any of the leachate samples, although the
secondary MCLs (SMCLs) for iron and manganese
were exceeded. The iron SMCL was exceeded in the
leachate of one of the alum residuals samples and the
ferric residuals sample, while the manganese SMCL
128
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Table 7-10. Total Metals Analysis for Sludges Used in
Leaching Research (Cornwell et al., 1992)
Metal
Aluminum
Arsenic
Barium
Cadmium
Chromium
Copper
Iron
Lead
Manganese
Mercury
Nickel
Selenium
Silver
Zinc
Durham,
NC, Alum
Sludge 1
(mg/kg
dry weight)
107,000
25.0
30
1
120
168
48,500
11
1,180
0.1
24
<2
<2
91.7
Chesapeake,
VA, Alum
Sludge 2
(mg/kg dry
weight)
123,000
32.0
<30
1
130
16
15,200
9
233
<0.1
23
<2
<2
393
Aldrich, PA,
WTP Ferric
Sludge 3
(mg/kg dry
weight)
28,600
9.2
230
2
50
52
79,500
40
4,800
0.2
131
<2
<2
781
Table 7-12. Maximum Metals Concentrations in Lysimeter
Leachate Compared With MCLs (Cornwell et al.,
1992)
Table 7-11. Leaching of Metals in Lysimeter Test (Cornwell et
al., 1992)
Percentage of Total Metal Present That
Actually Leached
Metal
Aluminum3
Arsenic
Barium
Cadmium
Chromium
Copper3
Iron3
Lead
Manganese3
Nickel3
Seleniumb
Silver
Zinc3
Alum
Sludge 1
0.00
0.05
0.00
0.00
0.00
0.12
0.03
0.00
12.48
0.00
—
0.00
0.13
Alum
Sludge 2
0.00
0.05
0.00
0.00
0.00
0.42
0.05
0.00
3.38
0.00
0.00
0.00
0.05
Ferric
Sludge 3
0.00
2.77
0.00
2.03
0.00
0.08
0.01
0.00
2.45
0.03
—
0.00
0.08
3 These metals were not analyzed in a standard TCLP test.
b Selenium leaching could not be quantified.
was exceeded in the leachate from all three residuals
samples. These SMCLs are not a part of the list of
indicator parameters for ground-water protection moni-
toring given in federal municipal landfill regulations.
Metal
Arsenic
Cadmium
Copper
Iron
Manganese
Nickel
Zinc
Durham,
NC, Alum
Sludge 1
(mg/L)
0.0035
—
0.12
2.00
9.50
—
0.036
Chesapeake,
VA, Alum
Sludge 2
(mg/L)
0.0019
—
0.03
0.30
0.36
—
0.017
Aldrich,
PA, WTP
Ferric
Sludge 3
(mg/L)
0.0366
0.01
—
1.00
22.80
0.06
0.373
MCL
(mg/L)
0.05
0.01
1.0
0.3a
0.05a
N/A
5.0
a Secondary MCL.
Leachate pH was monitored in addition to metals con-
centrations as part of the lysimeter study. pH has a
crucial impact on the leaching of metals from wastes.
The simulated rainwater applied to each lysimeter had
a pH of 4.5; the pH of leachate samples was consider-
ably higher than this. The leachate from Durham's alum
residuals had a pH range of 5.5 to 6. The other two
residuals samples produced leachate in the pH range of
6.5 to 7. pH buffering was exhibited by all three residuals
samples. This quality was probably a key factor in keep-
ing the solubility of metals low and limiting metal
leaching.
The testing of metals concentrations and mobility in
WTP residuals indicates that leachate from WTP residu-
als should not, in most cases, cause ground water to
exceed drinking water MCLs for metals. The permeabil-
ity of the residuals was not accounted for, however, in
any of the extraction or lysimeter tests. As part of an
American Water Works Association Research Founda-
tion (AWWARF) landfill study, the Unified Soil Classifi-
cation System was used to determine that the residuals
samples tested exhibited the characteristics of a CH soil
group (i.e., inorganic clay of high plasticity). The perme-
ability of this class of soil is typically less than 2 x 10"8
inches per second. This is a lower permeability than that
of typical clay liners, which must be at least 4 x 10"8
inches per second.
7.5 Dewatering
Before landfilling, WTP residuals are often dewatered to
reduce the liquid content and increase the solids con-
centration. This is necessary so that the residuals will
have a high enough solids content to qualify for disposal
in a landfill. Sludge dewatering methods are both me-
chanical and nonmechanical. Mechanical dewatering
methods use vacuum or pressure to remove the liquid
129
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portion of the sludge, whereas nonmechanical methods
depend on gravity and evaporation to reduce the unde-
sired liquid in the sludge.
7.5.1 Mechanical Dewatering
The equipment used most frequently for mechanical
dewatering includes the vacuum filter, continuous belt
filter press, plate pressure filter, and centrifuge. An es-
sential element of the vacuum filter is the rotating cylin-
drical drum. Lying on its side, the drum rotates around
its lengthwise axis with its lower part submerged in a
tank of water sludge. Its periphery surface is covered
with a permeable fabric or other filter material. A vacuum
is applied to suck water through the fabric. Solids left on
the drum surface, called filter cake, are then removed
using a scraper blade.
The continuous belt filter press is equipped with two filter
belts, one on top of the other, which wind through a
series of rolls. The water sludge contained between the
two belts is subjected to bending and shearing action as
the belts continuously move around the rolls. This bend-
ing and shearing action causes the sludge to drain and
form a sludge cake.
A plate pressure filter contains a series of recessed
plates covered with a filter cloth. The water treatment
sludges are pumped between the plates, and the liquid
seeps through the filter cloth, leaving behind the sludge
cake. When the spaces between the plates are filled,
the sludge cakes are removed.
The centrifuge method of dewatering uses centrifugal
force to generate pore water pressure in the sludge.
When pore water pressure develops, water drains out
of the sludge, leaving the sludge cake in a machine. The
centrifuge rotating speed typically ranges between 800
and 2,000 rotations per minute. With other parameters
being equal, the faster the rotating speed, the greater
dewatering power.
7.5.2 Nonmechanical Methods
In nonmechanical dewatering, WTP residuals are
spread out in a lagoon or a sand drying bed, exposed to
the air, and allowed to dry by evaporation.
Lagoons are large basins that are either enclosed with
earthen embankments or excavated for WTP residuals
deposits. They can be used for either dewatering or
residuals storage. Dewatering lagoons have pervious
bottoms such as sand layers with underdrains to facili-
tate drainage; storage lagoons must have impermeable
bottoms to protect the ground water. Storage lagoons
generally are equipped with a decanting facility such as
pumps to remove the standing water.
Sand drying beds are shallow basins with sand bottoms
and underdrain systems. They are also equipped with
facilities for decanting the standing water. Sand drying
beds perform the same function as dewatering lagoons;
the main difference is the thickness of deposited sludge
and the frequency of deposition. Sand drying beds re-
ceive thinner layers and more frequent deposition of
sludges than dewatering lagoons receive.
The degree of dewatering depends on the effectiveness
of the dewatering method and the water-holding capac-
ity of the sludge. Because the water-holding capacity of
sludges can vary, the obtainable solids concentration of
sludge cakes also varies by both dewatering methods
and sludge types.
7.6 Physical Characteristics of Water
Sludges
The physical characteristics of water sludges that need
to be addressed in any effective landfill plan include
plasticity, compaction behavior, compressibility, and
shear strength. Of these, plasticity characteristics affect
sludge handleability. Compaction data, which provide
moisture-density curves, are needed for landfill con-
struction control. Compressibility data are necessary to
determine landfill settlement. Shear strength affects the
landfill stability, which controls the maximum height and
slope of a stable landfill and the ability of the landfill to
support heavy equipment.
7.6.1 Plasticity
The plasticity characteristics of water sludges can be
evaluated from the value of Atterberg limits, especially
liquid limit and plasticity index. The plasticity index
equals the difference between the liquid limit and the
plastic limit. Both liquid and plastic limits are expressed
as water content in percentage. The water content is
defined as the ratio between the weights of water and
solid phases, which can be related to the solids content
as shown in Equation 7-1, in which the solids content is
the ratio between the weights of solids and the sludge
mass expressed in percentage:
water
content
solidscontent(%)
-1 )(100)
(Eq. 7-1)
This equation can be reduced to:
solidscontent(%)
100
water m._, solids content (%)
content (/o)~1~ 100 (Eq. 7-2)
The Atterberg limits of WTP residuals vary greatly with
the type of sludge. The lime/alum/polyamine coagulant
water sludge of the Jersey City Water Treatment Plant
has only slight to little plasticity (Raghu et al., 1987). As
130
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Table 7-13. Liquid Limit, Plastic Limit, and Plasticity Index of
Water Sludges (Cornwell et al., 1992)
Water Sludge
Alum Sludge 1
Alum Sludge 2
Ferric Sludge 3
Liquid
Limit (%)
423
550
108
Plastic
Limit (%)
137
239
47
Plasticity
Index
286
311
61
shown in Table 7-13, however, the liquid limit, plastic
limit, and plasticity index of Alum Sludge 1, Alum Sludge
2, and Ferric Sludge 3 are very high (Cornwell et al.,
1992). Alum Sludge 1 was produced from treatment of
medium-color, medium-turbidity raw water, dewatered
using the sand drying bed method and obtained from
Williams Water Treatment Plant in Durham, North Caro-
lina. Alum Sludge 2 was generated from high-color,
low-turbidity raw water, dewatered using the sand drying
bed method and obtained from Chesapeake Water
Treatment Plant in Chesapeake, Virginia. The ferric
sludge was generated from medium-color, medium-tur-
bidity raw water, dewatered using the lagoon method
and obtained from Aldrich Water Treatment Plant in
Pittsburgh, Pennsylvania.
Materials with a high plasticity index are considered
highly plastic and difficult to handle. Thus, of these four
different sludges, the lime/alum/polyamine coagulant
sludge is the easiest to handle, and Alum Sludge 2 is
the most difficult.
7.6.2 Compaction Behavior
Compaction data are used to establish the degree of
sludge compaction necessary to increase stability, de-
crease permeability, and enhance resistance to erosion.
The shape of the moisture-density relation (compaction
curve) varies greatly with sludge type. For the lime/alum/
polyamine coagulant sludge (Raghu et al., 1987), the
moisture-density curve of the modified Proctor compac-
tion exhibits the typical one-hump shape; the optimal
water content and maximum dry unit weight equal 65
percent and 51 pounds per cubic foot (Ib/ft3), respec-
tively. The moisture-density curve of a coagulant sludge
under the Standard Proctor compaction also exhibits the
typical one-hump shape, with the optimal water content
and maximum dry unit weight of 17 percent and 105
Ib/ft3 (16.5 kN/m3), respectively. Of the three coagulant
sludges shown in Table 7-13, however, only the ferric
sludge exhibits the one-hump shape; the optimal water
content and maximum dry unit weight of the Standard
Proctor equal 45 percent and 72 Ib/ft3 (11.3 kN/m3),
respectively.
Both Alum Sludges 1 and 2 show a decrease in dry unit
weight with increasing water content without a peak
formation. Meanwhile, for Alum Sludge 2, admixing a
bulking agent—a slaked lime, a class C fly ash, or a
natural soil—insignificantly affects the moisture-density
relation. The amount of additive equals 60 percent by
dry weight of the sludge. The moisture-density relations
of these three sludges are plotted in terms of percent
solids concentration versus dry unit weight in Figure 7-3.
Each curve is accompanied by the zero-air-void curve
(ZAVC) that outlines the upper limit of the curve regard-
less of the compaction effort used. The ZAVC is ob-
tained from Equation 7-3:
dry
(specific gravity) (unit weight of water)
water content (%)
unit =
weight (1 + specific gravity)
100
(Eq. 7-3)
For landfill construction, the sludge should be com-
pacted to the highest possible density that can be ac-
complished only when the amount of water in the sludge
is at the optimal water content. For Alum Sludges 1 and
2, however, the compaction water content should be as
low as possible.
Alum Sludge 1
X-
o
>
Consolidation Pressure (kPa)
Figure 7-3. Consolidation curves of Alum Sludges 1 and 2 and
Ferric Sludge 3 (Wang et al., 1992b).
7.6.3 Compressibility
In the landfill, under the sustained weight of the over-
lying mass, sludge may undergo volume reduction from
the extrusion of water. As a result, the landfill may settle,
creating airspace for depositing additional sludge on top
of the landfill. To determine the amount of landfill settle-
ment, the compressibility property of the sludge is
required.
131
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Normally, the compressibility property is obtained from
the consolidation test. The test results can be analyzed
using the conventional small-strain theory or the finite-
strain theory of consolidation. Although the small-strain
theory is more widely used, the resulting analyses are
not as accurate as those that use the finite-strain theory.
Based on the traditional small-strain theory, Raghu et al.
(1987) reported a compression index (Cc) of approxi-
mately 0.3 for their lime/alum/polyamine coagulant
sludge. The compression index (Cc) is computed from
the slope of the field compression curve, which relates
the void ratio (e) with the logarithm-of-consolidation
pressure (p), namely, e versus log p curve. The void ratio
is the ratio between the volume of void and the volume
of solid phase of the sludge.
The e versus log p curves of Alum Sludges 1 and 2 and
Ferric Sludge 3 are shown in Figure 7-3 (Wang et al.,
1992b). From these curves, Cc equals 6.69, 5.29, and
1.99 for Alum Sludge 1, Alum Sludge 2, and Ferric
Sludge 3, respectively. Under the same sustained pres-
sure, the higher the Cc value is, the greater the landfill
settlement will be. Thus, of these four sludges, it can be
expected that the landfill of Alum Sludge 1 will settle
most, while the lime/alum/polyamine sludge will settle
least, other factors being equal.
From Figure 7-3, the swelling index (Cs) can also be
obtained. The value of Cs is computed from the slope of
the swelling (or rebound) portion of the graph and is
normally used to determine the amount of landfill re-
bound caused by reduction of the sustained weight. The
values of Cs are 0.17, 0.15, and 0.03 for Alum Sludge 1,
Alum Sludge 2, and Ferric Sludge 3, respectively. Thus,
of these three sludges, the amount of landfill rebound
will be greatest for Alum Sludge 1 and smallest for Ferric
Sludge 3.
The effect of a bulking agent on the e versus log p
relation of Alum Sludge 1 is illustrated in Figure 7-4
_ With Fly Ash
(Wang et al., 1992a). As shown, admixing of a bulking
agent results in a lower e versus log p curve. To consider
the effect of pozzolanic reaction in the lime and fly ash
treated sludge, these two treated sludges were curved
to two different durations: 2 weeks and 4 weeks. The
compression indexes of these treated sludges are 4.04
for the soil-treated, 3.56 for the lime-treated and 2-week
cured, 4.34 for the lime-treated and 4-week cured, 3.70
for the fly ash-treated and 2-week cured, and 3.93 for
the fly ash-treated and 4-week cured.
7.6.4 Shear Strength
Shear strength is essential for the design and analysis
of landfill stability with or without heavy equipment op-
erating on the landfill. Different testing methods are
available for the determinations of shear strength, in-
cluding cone penetration test, vane shear test, and
triaxial compression test. The first two methods normally
are used to measure undrainedshearstrength, while the
third method is used to determine both undrained and
drained strengths. The undrained shear strength is for
use when there is insufficient time forthe sludge to drain
during shearing. Underthe undrained loading condition,
excess pore water pressure develops, reducing the ca-
pacity of sludge particles to resist shear and resulting in
a lower shear strength. On the other hand, the drained
shear strength is for when, during shearing, the sludge
drains completely without developing excess pore water
pressure. The sludge particles more effectively resist
shear, resulting in a higher shear strength. The un-
drained shear strength is used for analysis of landfill
stability during or immediately after construction; the
drained shear strength is needed in the analysis of
long-term stability of the landfill.
Alum Sludge 1
1 20
"o)
0
CO 15
ro
CD
-C
CO
T5
| 10
'2
T5
C
=)
Consolidation Pressure (TSF)
30 40
Solids Content (%)
Figure 7-4. Void ratio versus consolidation pressure of treated
and untreated Alum Sludge 1 (Wang et al., 1992a).
Figure 7-5. Strength versus solids content for Alum Sludges 1
and 2 (Cornwell et al., 1992).
132
-------
The shear strength property of water treatment sludges
varies not only with the type and nature of the sludge
but with solids content as well. The rate and amount of
strength increase with increasing solids content also
differ for various sludge types. Figure 7-5 shows the
undrained shear strength versus solids content curves
for Alum Sludges 1 and 2 and Ferric Sludge 3. As
shown, the shear strength increases very slowly in the
beginning and should approach a constant value at very
high solids content for each sludge, although the later
portion of the curve is not seen within the range of
conditions investigated. The solids content required for
a given shear strength is highest for Alum Sludge 1 and
lowest for Ferric Sludge 3. Also, at a given solids con-
tent, the shear strength is greatest for Alum Sludge 1
and least for Ferric Sludge 3.
The shear strength parameters and pore water pressure
parameter at failure (Af) obtained from the triaxial com-
pression test are summarized in Table 7-14 (Wang etal.,
1992b). Also included is the range of initial solids content
of the test specimens. The initial solids content of each
sludge is near the value required for ease in test speci-
men preparation. The Af value of 0.75 to 0.79 falls within
the range for normally consolidated clays or sensitive
clays. The effective internal friction angle (0), however,
is unusually high when compared with highly plastic
clay soils.
Water treatment sludges exhibit rheotropic and thixo-
tropic behavior; namely, sludges undergo strength re-
duction from disturbance or remolding, and after
disturbance the strength increases with curing time with-
out a change in solids content. The reduction in sludge
strength from disturbance has been experienced by
workers who operated a hydraulic excavator on a trench
fill of Chesapeake sludge (Alum Sludge 1). According to
the machine operator, the sludge that initially was stable
enough to operate the machine on became weak and
unstable overtime (Cornwell et al., 1992).
The rate and amount of strength increase from curing
depends on sludge type and solids content. The in-
crease of undrained shear strength at different solids
contents for the ferric sludge is shown in Figure 7-6.
From these strength data, the strength-gain ratios are
computed for different sludges at different solids con-
tents and are shown in Table 7-15. The strength-gain
ratio is the ratio between cured strength and remolded
strength. The data in Table 7-15 indicate that the
strength-gain ratio appears first to increase, then to
decrease with decreasing solids content. Thus, there is
an optimal solids content for the strength-gain ratio to
reach the maximum.
The rheotropic and thixotropic behavior of sludge should
be properly considered in the analysis, design, and
construction of sludge landfills. Because construction
operation inevitably causes sludge remolding, it is ap-
Table 7-14. Shear Strength Parameters of Test Sludges
(Wang et al., 1992b)
Total Stress
Effective Stress
Alum
Sludge 1
Alum
Sludge 2
Ferric
Sludge 3
Pore
Pressure
Initial c 0 c' 0' Parameter
Content (kPa) (°) (kPa) (°) Af
13.4-15.5 4.14 19.3 6.89 42.3 0.75
24.3-26.3 4.83 19.0 8.27 44.0 0.77
36.2-40.4 8.27 17.5 8.27 42.8 0.79
Curing Time (Day)
Figure 7-6. Strength versus curing time at various solids con-
tents for ferric sludge (Wang et al., 1992b).
Table 7-15. Remolded and Cured Undrained Strengths and
Strength Gain Ratio (Wang et al., 1992b)
Solids Remolded Cured Strength
Content Strength Strength Gain
(%) (kPa) (kPa) Ratio
Alum Sludge 1
Alum Sludge 2
Ferric Sludge 3
16.3
13.6
11.9
11.1
19.3
18.6
41.2
36.8
35.4
33.5
2.21
1.10
0.48
0.34
2.76
2.07
2.34
1.03
0.83
0.62
12.96
7.65
3.86
1.93
17.93
115.17
7.24
3.45
1.86
1.24
5.9
7.0
8.0
5.7
6.5
7.3
3.1
3.4
2.2
2.0
propriate to use the remolded undrained shear strength
to design the landfill and also to analyze the stability of
the landfill during construction. After construction, the
shear strength of sludge increases with time from thixo-
133
-------
tropic hardening and consolidation. Consequently, the
landfill becomes more stable.
Admixing a bulking agent enhances the shear strength
of the sludge. Figure 7-7 shows that for Alum Sludge 2
without curing, the degree of strength improvement var-
ies with the type of bulking agent, being greatest for the
slaked lime, fly ash, and finally the soil. Furthermore, for
each bulking agent, strength increases with increasing
treatment level (Cornwell et al., 1992). The strength
increase from curing also differs for various bulking
agents, as illustrated in Figure 7-8 (Cornwell et al., 1992).
Although the ultimate cured strength is greatest for lime,
then fly ash, soil, and the untreated sludge, the strength-
gain ratio is in reverse order, as shown in Table 7-16.
The data in Table 7-16 indicate a drastic increase in the
remolded shear strength of Alum Sludge due to treat-
ment, by a factor of more than four times for lime, almost
three times for fly ash, and about one-and-a-half times
for soil. Such an improvement in shear strength makes
it possible to construct a higher landfill with a steeper
slope. Additionally, admixing stabilization makes the
sludges less plastic and therefore easier to handle.
Using the shear strength data in landfill analysis and
design has been demonstrated by Cornwell et al. (1992)
and Wang et al. (1992b). Specifically, the strength data
were used to make a hypothetical monofill design for the
three different sludges with varying solids concentration.
The maximum fill height for a desired slope angle or the
maximum slope angle for a desired fill height were
determined. The hypothetical monofill has a uniform
slope with a constant slope angle from the toe to the top
of the slope. The top of the landfill is level, extends very
far, and carries no surface loading. Meanwhile, the land-
fill is supported on very large, firm, level ground, which
allows it to be treated as a two-dimensional problem.
Figure 7-9 shows landfill height versus the ratio between
shear strength and wet unit weight of sludge for different
slope angles using a safety factor of 1.20. The minimum
solids content required for maintaining a stable slope
can be determined by:
1. Selecting the desired slope angle and landfill height.
2. Finding the required shear strength to wet unit weight
ratio from Figure 7-9.
3. Assuming a wet unit weight of the sludge and com-
puting the shear strength.
4. Finding the solids content for the computed shear
strength from Figure 7-5.
5. Checking the wet unit weight for the obtained solids
content using Equation 7-4:
APPITK/E
O UUE
A FLY ASH
D SOIL
ADDITIVE LEVEL {
Figure 7-7. Shear strength versus additive level, Alum Sludge
2 (nonaged) (Cornwell et al., 1992).
CO
0.
CO
Soil
1 Untreated
Curing Time (Days)
Figure 7-8. Undrained sheer strength versus curing time for
untreated and treated Alum Sludge 1 (Cornwell et
al., 1992).
Table 7-16. Undrained Shear Strength of Alum Sludge,
Untreated and Treated (Wang et al., 1992a)
Sludge
Untreated
Treated with soil
Treated with fly ash
Treated with lime
Remolded
(psi)
0.30
0.42
0.82
1.39
Cured
(psi)
1.70
2.10
2.50
3.25
Strength Gain
Ratio
5.7
5.0
3.0
2.3
y=.
Sc(%)
100
(Eq. 7-4)
where
y= wet unit weight of the sludge
jw = unit weight of water
Gs = specific gravity of the solid phase of sludge
134
-------
Shear Strength/Unit Weight (M)
Figure 7-9. Landfill height versus shear strength/unit weight for
different slope angles (Wang et al., 1992b).
Sc = solids content in percentage
6. Repeating the procedure from step 3 until satisfac-
tory results are achieved.
strength and solids content required to support the vari-
ous types of heavy equipment with a safety factor of 3.0
are summarized in Table 7-17. The minimum shear
strength required to support heavy equipment varies
greatly among the different types of equipment, and the
data were obtained for a safety factor of 3.0. When a
smaller safety factor is used, the required minimum
shear strength is reduced. For example, for a safety
factor of 1.5, the required minimum shear strength to
support the excavator decreases from 19.8 to 9.8
kiloPascals. This value is very close to 10 kiloPascals
of the European standard (Cornwell and Koppers,
1990). It is not known, however, whether the European
standard was developed for the conditions stated. The
minimum shear strength required to support heavy
equipment should be selected with consideration of the
factors that influence equipment stability: equipment
type (weight, dimension, wheel design, and nature of
loading), sludge layer thickness, sludge surface area
and condition (level or sloped), and safety factor, among
other factors.
According to Table 7-17, the minimum solids concentra-
tion required to support heavy equipment varies consid-
erably among the three sludges. Thus, the required
minimum solids concentration must be determined for
every sludge, precluding a single value of minimum
solids concentration for general use. The minimum sol-
ids concentration for Alum Sludge 1 in Table 7-17 report-
Table 7-17. Required Shear Strength and Solids Concentration for Hypothetical Monofill Supporting Various Types of Heavy
Equipment (Cornwell et al., 1992)
Ground Pressure
Type
Crawler dozer
Crawler dozer
Excavator
Dump truck (empty)
Dump truck (full)
(psi)
4.2
6.7
5.9
25
50
(kN/m2)
28.7
45.8
40.4
171.0
342.0
Minimum Shear
Strength
(psi)
2.0
3.3
2.9
12.2
24.4
(kN/m2)
13.7
22.6
19.8
83.5
166.9
Approximate Sludge Concentration (%)
Alum
Sludge 1
29
33
32
37
41
Alum
Sludge 2
22
25
23
28
33
Ferric
Sludge 3
52
54
53
58
62
The shear strength data were also used to analyze the
stability of heavy construction equipment operation on
the landfill. The types of equipment analyzed were
crawler dozer, dump truck, and excavator. The shear
edly correlates well with field conditions (Cornwell et al.,
1992). Therefore, the data should be useful in determin-
ing minimum solids concentration and other information
pertinent to landfilling of water treatment sludges.
135
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Chapters
Land Application
Land application is an increasingly popular disposal
option in the water supply industry due to the escalating
regulatory and environmental constraints associated
with other disposal options. Land application options for
water treatment plant (WTP) residuals include agricul-
tural use, silvicultural application, application for recla-
mation to disturbed and marginal lands, and disposal to
dedicated lands (U.S. EPA, 1995b). In addition to the
obvious advantages of waste disposal, this application
process may beneficially modify soil properties while
recycling residual components. Potential disadvantages
of land application of WTP residuals include an increase
in the concentration of metals in the soil and possibly in
ground water; adsorption of soil phosphorus by water
residuals, decreasing the productivity of the soil; exces-
sive application of nitrogen, resulting in the transport of
nitrate to ground water; and possible effects caused by
the application of poorly crystallized solids of aluminum
(Dempsey et al., 1990).
This chapter provides decision-makers with the basic
information they need to evaluate land application as a
disposal option for WTP residuals. A simplified planning
procedure for land application is presented in Figure 8-1.
8.1 Regulatory Requirements
The Water Pollution Control Act of 1972 defined WTP
residuals as industrial waste, and they are listed as a
solid waste under 40 CFR Part 257. If land application
is to be considered a viable option, the residuals cannot
be hazardous. Section 2.7 outlines a method for deter-
mining whether the residuals are hazardous. Other than
those listed in 40 CFR Part 257, specific federal regula-
tions do not exist for the water industry, and most state
regulatory agencies use the same criteria for WTP
wastes as they use for other industrial sludges. Accord-
ing to 40 CFR Part 257, criteria in the following areas
must be met: floodplains, endangered species, surface
water, ground water, disease vectors, air emission, and
safety. The regulations also contain application limits for
cadmium (Cd), and poly chlorinated biphenyls (PCBs).
The Clean Water Act (40 CFR Part 503), establishes
criteria for land application of sewage sludge solids
generated during the treatment of domestic sewage.
Although these criteria are only designed for sewage
sludge, or biosolids, they may provide general guide-
lines for use or disposal of WTP residuals. The guide-
lines contain numerical values for biosolids application
rates that are based on experiments with biosolids, and
risk assessment algorithms developed using the
biosolids data. The criteria should not be used for deter-
mining land application rates of WTP residuals.
The risk assessment algorithms that were used as a
technical basis for the Part 503 rule contain data that
were obtained from field studies using biosolids. There
is no way to determine, without similar field studies done
specifically on WTP residuals, whether residuals would
demonstrate the same behavior as that of biosolids.
Therefore, land application of WTP residuals should be
based on the criteria set forth in 40 CFR Part 257, and not
on the criteria developed under Part 503. If WTP residu-
als are field tested and their behavior relative to
biosolids is known, then it is possible that the risk as-
sessment methodology used in Part 503 could be used to
develop criteria for WTP residual use in land application.
Regulations vary from state to state but typically require
that residuals be tested for total metals concentrations,
nutrients, and pH. The application rate of WTP sludge
may be selected to limit hydraulic loading, nitrogen con-
tent, or metal content.
8.2 Environmental Considerations
When land application was originally investigated as a
potential disposal option for WTP residuals, it was
thought that the lack of organic components and the
high metals content in WTP residuals would inhibit the
water industry from accepting this option. Since then, a
number of studies have examined the potential limiting
effects of WTP residuals on soil parameters. Most stud-
ies to date have focused on identifying the effects of
WTP residuals on the physical characteristics of soil and
on determining the potential for these wastes to cause
phosphorus deficiency in plants. Current research has
yielded a better understanding of the chemical charac-
teristics of WTP residuals and has produced analytical
techniques to quantitatively predict these effects when
136
-------
Determine Physical and Chemical Sludge Characteristics
(Chapter 3 and Section 8.2.1)
Review Applicable Regulations and
Guidelines for Land Application
Federal, State, and Local (Chapter 2 and Section 8.1)
Begin Public Participation
(Section 8.4.2)
Compare Sludge Characteristics With
Regulatory Requirements and
Choose Land Application Option
Agricultural and
Silvicultural Application
(Sections 8.3.1 and 8.3.2)
T
Dedicated
Land Disposal
(Section 8.3.4)
Land Reclamation
(Section 8.3.3)
Select Application Site Based on Acreage Required for
Sludge Application, Costs, and Land Area Available
(Section 8.3)
Determine Sludge Transportation and Application Systems
Based on Operational Considerations and Costs
(Section 8.4.1 and Section 8.4.3)
I
Determine Storage Requirements and Rates of Application
(Section 8.4.1)
Develop Soil and Ground-water Monitoring Programs
(Section 8.4.4)
Figure 8-1. Simplified planning procedure for land application of WTP residuals.
applied to land. The conclusions of this research are
described below.
8.2.1 Major Components of Water Treatment
Residuals and Their Impact on Soil
Parameters
A 1990 American Water Works Association Research
Foundation study of land application of WTP residuals
was conducted to establish a scientific basis for land
application of WTP residuals. This study examined data
regarding the chemical composition and fractionation of
WTP residuals, the phytotoxicity of WTP residuals, and
the effects of these residuals on the physical and nutri-
ent status of soil. The study also investigated concen-
trations of residuals' major components, and the impact
these components might have on agricultural soil after
land application. Table 8-1 shows the composition of WTP
residuals compared with sewage sludge and agronomic
soils in the United States. The cadmium reading of 5.15
parts per million (ppm) is much higher than is typically
found in WTP residuals. This is particularly true now that
chemical suppliers are more conscious of heavy metals
contaminants in coagulants, the major source of metals
in residuals. Most cadmium levels in residuals are less
than 1 to 2 ppm and are often undetectable.
WTP residuals are predominantly inorganic and consist
of clays, humic substances, and other materials typically
suspended or dissolved in lakes and streams. Typical
WTP residuals contain 3 percent or less organic carbon
by weight and 0.5 percent or less organic nitrogen by
137
-------
Table 8-1. Composition of WTP Residuals Compared With
Sewage Sludge and Agronomic Soils3
Sewage
Table 8-2. Agronomic Components in WTP Residuals3
Parameter
Range of Values
Constituent WTP Residuals
Aluminum
Arsenic
Barium
Boron
Cadmium
Calcium
Chromium
Copper
Iron
Lead
Manganese
Mercury
Molybdenum
Nickel
Selenium
Strontium
Vanadium
Zinc
60,111.0(52,095)
14.7 (14.7)
122.5 (127.52)
40.7 (61.3)
5.15 (11.67)
20,815.0(33,108)
49.5 (56.5)
270.2 (326.1)
52,751 .0 (63,642)
79.9(100.2)
385.4 (398.5)
1 .5 (2.5)
9.1 (12.9)
37.8 (53.8)
2.8 (1.5)
84.3 (60.6)
35.4(17.4)
1,047.4(3,036.1)
Sludgec
9.93(18.84)
6.94(11.76)
118.6 (339.2)
741 .2 (961 .8)
134.4(197.8)
5.2 (15.5)
9.2(16.6)
42.7 (94.8)
5.2 (7.3)
1,201.9(1,554.4)
Agronomic Soil
72,000d
7.2d
580d
33d
0.265 (0.253)8
24,000d
54d
29.6 (40.6f
26,000d
12.3 (7.5f
9,000d
0.09d
0.97d
23.9 (28. 1f
0.39d
240d
80d
56.5 (37.2)e
a Data are arithmetic mean and standard deviation ( ) presented as
mg/kg dry weight.
b Survey of 12 land-applied WTP residuals, including 10 alum and 2
ferric (Brobst, 1994).
CU.S. EPA, 1990a.
dShacklette and Boerngen, 1984.
e Holmgren et al., 1993.
weight. Both values are representative of agricultural
soils but are much lower than those found in sewage
sludge. WTP residuals are similar to fine-textured soil.
Elliott et al. (1990a) reported no coliform organisms in
alum or ferric WTP residuals. This absence may be
attributed to clean raw water, disinfection processes
during treatment, and/or lagoon storage of residuals
over long periods. In a waste stream recycling study
(Cornwell and Lee, 1994), however, Giardia and Cryp-
tosporidium were found to concentrate in the sedimen-
tation basin residuals. The study did not examine the
issues of the viability and persistence of these patho-
gens, nor did it discuss the survival of pathogens in WTP
residuals over time.
WTP residuals largely consist of materials that are re-
moved from water before its distribution. Coagulant ad-
dition can enhance turbidity removal and contribute to
the quantity of residuals. Depending on the quality of the
intake water, the final residuals can be clay-like or sand-
like in texture, which may become important in choosing
the final use. WTP residuals by their nature are usually
low value fertilizer, as can be seen in Table 8-2. The
concentration of aluminum or iron in WTP residuals is
Total solids (%)
Volatile solids (%)
Conductivity (|imho/cm)
pH (S.U.)
Total Kjeldahl nitrogen (%)
Organic nitrogen (%)
Ammonia-nitrogen (%)
Nitrate-nitrite (%)
Total phosphorus (%)
Total potassium (%)
8.14-81
9.32-29.09
563.8 (530.2)
6.98-8.82
0.495 (0.256)
0.752 (0.399)
0.016 (0.016)
0.003 (0.003)
0.226 (0.248)
0.225 (0.317)
a Data are presented as a range or as arithmetic mean and standard
deviation ( ). These data should be used with caution. Individual
residuals may vary significantly from those used in this table.
b Survey of 12 land-applied WTP residuals, including 10 alum and 2
ferric (Brobst, 1994).
generally 5 to 15 percent of dry solids. These concen-
trations stem from the use of coagulants in the water
treatment process and may be higher when a specific
coagulant is overdosed. The aluminum content of WTP
residuals treated with alum is similar to aluminum con-
centrations in soils. The speciation of aluminum or iron
in WTP residuals, however, is different from that occur-
ring in native soils. While soils contain significant con-
centrations of aluminum in the form of aluminosilicates,
WTP residuals contain aluminum (or iron) in amorphous
hydrous oxide forms, which exhibit greater reactivity
than the corresponding soils materials. The various alu-
minum forms, however, quickly convert to the stable
aluminum oxides away from aluminum hydroxides, and
do not exhibit reactivity.
Moderate applications of WTP residuals may improve
the physical condition, or tilth, of soils by flocculating
colloidal particles, thereby promoting soil aggregation
via reactions that are analogous to those occurring dur-
ing water treatment. The hydrous metal oxides con-
tained in WTP residuals are strong adsorbents of trace
metals and phosphorus. In terms of trace metals, this is
beneficial to soils and results in a decreased and buff-
ered concentration of free trace metals. Elliott et al.
(1990b) concluded that in the case of soils treated with
WTP residuals, soluble aluminum usually decreases,
and the level of the dithionite-citrate-bicarbonate (DCB)1
extractable aluminum residuals is typically elevated over
original levels but remains within the range normally
observed for native soils (see Table 8-1). The amor-
phous hydrous oxides in alum-treated WTP residuals
may also benefit coarse soils by increasing the cation
exchange capacity, particularly at the neutral or slightly
1 DCB is an extracting solution that removes the more reactive fraction
of the total iron and aluminum present in a substance.
138
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alkaline soil pH that can increase the nutrient holding
capacity.
8.2.2 Effects of Trace Metals Concentrations
on Soil Properties
Trace metals in most WTP residuals originate from co-
agulant chemicals and or the water source. These met-
als are strongly adsorbed to the aluminum hydroxide or
ferric hydroxide precipitates formed during the coagula-
tion process. Concentrations of trace metals will likely
determine the lifetime application of water treatment
residuals (metric tons per hectare, dry weight) on agri-
cultural soils.
Elliott et al. (1990a) assessed potential metal mobility
under field conditions using a five-step fractionation pro-
cedure. Most heavy metals in WTP residuals are bound
in forms not readily released into solution due to their
strong adsorption and coprecipitation by aluminum (Al)
and iron (Fe) hydroxides freshly formed in the coagula-
tion treatment step. From 76 to 87 percent of the chro-
mium (Cr), copper (Cu), nickel (Ni), lead (Pb), and zinc
(Zn) examined were bound within an oxide or silicate
matrix. Less than 6 percent of the total concentration of
each of these metals was in the exchangeable fraction,
which is considered to represent the easily available
metal pool. If soil conditions should become acidic (pH
less than 5), approximately 25 percent of the residuals
cadmium could become mobile.
Greenhouse pot studies showed that with the more
acidic aluminum-based WTP residuals, application rates
of 20 and 25 g/kg increased the cadmium concentration
of plant tissue to greater than 2 mg/kg (Heil and Bar-
barick, 1989). Figure 8-2 illustrates the partitioning of
trace metals in WTP residuals. For example, most chro-
mium is released upon dissolution of AI(OH)3(s) and
Fe(OH)3(s) (i.e., the iron-manganese oxide-bound frac-
tion), whereas a very small portion of chromium is re-
leased in the acid-soluble fraction. Similar results can
be obtained for other trace metals. Soil pH conditions
are critical in preventing the dissolution of AI(OH)3(s) or
other hydrous metal oxides; if nonacidic soil conditions
exist, trace metals will be tightly bound, rendering them
immobile and unavailable for plant uptake. Therefore, in
the case of moderate WTP residuals application rates
(20 dry mt/ha) and properly managed soils (pH greater
than 6.0), movement of metals into ground water or into
plant tissues can be minimized.
8.2.3 Impact of Water Treatment Residuals
on the Availability of Phosphorus in
Agricultural Soils
Because phosphate deficiency greatly affects agricul-
tural soil fertility, much research has been conducted
into the decreased availability of phosphorus in soils
following the addition of WTP residuals. This decrease
100
90
80
70
60
>
50
40
? so
20
10
Cr
Pb
Zn
Nl
gggl Exchangable
V/A Organically Bound [S3 Fe-Mn Oxide Bound
[SSi Acid Soluable K3 Residual
Definitions:
1. Exchangeable: 16 ml 1M MgCI2 (pH 7.0); shake time, 1 hr.
2. Dilute acid extractable: 16 ml 1M NaOAc adjusted to pH 5.0
with HOAc; shake time, 5 hrs.
3. Fe-Mn oxide bound: 40 ml of 0.175M (NH4)2C2O4 and 0.1 M
H2C2O4; shake time, 4 hrs.
4. Organically bound: 40 ml of 0.1 M Na4P2O7; shake time, 24 hrs.
5. Residuals: Dry 0.1 g of material remaining after 41. Add 4 ml
HN03, 1 ml HCI04 and 6 ml of HF, heat at 140°C for 3.5 hrs.
Add 5.0 g Boric acid and dilute to 100 ml volume.
Figure 8-2. Partitioning of trace metals in WTP residuals (after
Elliott et al., 1990a).
in available phosphorus occurs because of the large
amounts of aluminum and iron hydroxide solids present
in WTP residuals. These hydroxides are strong adsor-
bents of inorganic phosphorus and contain only low
concentrations of phosphorus. This phosphorus-limiting
characteristic of WTP residuals is illustrated in Figure 8-3.
Greenhouse studies found phosphorus deficiencies in
sorghum-sudangrass were possible when application
rates of aluminum- or iron-based WTP residuals ex-
ceeded 10 g/kg soil or approximately 22.5 mt/ha (Heil,
1988; Heil and Barbarick, 1989). The study also found
that both alum- and iron-based WTP residuals decrease
the availability of phosphorus but can effectively in-
crease iron availability in iron-deficient soil. WTP residu-
als applied at a rate of 60 g/kg or approximately 135
mt/ha, produced phosphorus deficiencies in tomato
plants (Elliott and Singer, 1988).
This reduction in plant-available phosphorus is qualita-
tively different from the potential toxicity problem that
may be associated with land application of WTP residu-
als. The depletion of plant-available phosphorus neces-
sitates the addition of supplemental phosphorus
139
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D)
-S
Q-
0)
•E
JD
Q.
10
20
I
25
Figure 8-3.
I
5 15
WTP Residuals Application Rate (g/kg)
D Average Alum
0 Average Iron
Average (of three cuttings) phosphorus concentra-
tion in sorghum-sudangrass grown in Colby soil
(after Heil and Barbarick, 1989).
fertilizer to obtain optimal plant yields. This is a manage-
ment problem rather than a public health issue; there-
fore, the problem is easy to correct with either adjusted
management practices or additional phosphorus fertilizer.
Soluble phosphorus levels are commonly determined by
the equilibrium phosphorus concentration (EPC) test
(White, 1981). The EPC is the concentration of phos-
phorus at which no adsorption ordesorption of phospho-
rus occurs. The phosphate buffer capacity (PBC)
provides information about the response of a soil to
fertilization, specifically whether the added phosphorus
will be adsorbed by the soil or will remain in the soil
solution and be available for plant uptake. Elliott et al.
(1990b) used both EPC and PBC techniques to investi-
gate the incremental amount of phosphorus fertilizer
that should be applied to soils treated with WTP residu-
als to obtain good plant growth.
The typical range of EPC values for optimal production
is 50 to 200 u,g/L EPC. Between 50 and 100 of the triple
superphosphate (TSP) fertilizer used in this study is
conventionally added to agricultural soils to maintain
crop production (White, 1981). Farmers usually apply
nitrogen and potassium fertilizers to agricultural soils in
addition to various pesticides. Therefore, the cost of
restoring the EPC after residuals application should be a
fraction of the entire cost of preparing a soil for planting.
Application techniques may be used to mitigate the
impact of WTP residuals on the availability of phospho-
rus in agricultural soils. WTP residuals can be applied
to the top soil layers or injected below the surface,
depending on the growth stage of specific crops. Seed-
lings generally have higher phosphorus requirements
than mature plants do; therefore, deep injection (greater
than 18 cm) may be preferable at this growth stage.
When residuals are applied to the soil surface, the re-
sulting drying action decreases the surface area of the
aluminum and iron hydroxides, and organic matter in the
surface litter will localize the adsorption sites for phos-
phorus. This may in fact be beneficial in areas of high
naturally occurring phosphates, and WTP residuals may
be able to reduce phosphorus loadings to surface wa-
ters by adsorbing the phosphorus. In addition, in areas
in which stormwater runoff carries excess phosphorus
to lakes and streams, WTP residuals could be used to
bind excess phosphorus and improve the runoff water
quality.
Crops may be selected that tend to use labile phospho-
rus ratherthan just soluble phosphorus. Large quantities
of phosphorus fertilizer are applied in close proximity to
seeds to accommodate the phosphorus requirements of
seedlings. Sewage sludge contains significant amounts
of phosphorus that can add to total soil phosphorus.
Several Colorado facilities have studied the coapplica-
tion of both sewage sludge and WTP residuals to miti-
gate the effects of phosphorus adsorption by WTP
residuals. The experiments have met with varying de-
grees of success in the short evaluation periods, how-
ever, they have shown that the assumption of
phosphorus being bound on a one-to-one molar basis,
as required by state regulations, may be conservative.
In the case of excessively fertilized soils, phosphorus
adsorption by WTP residuals may be agriculturally ad-
vantageous. WTP residuals applied to high phosphorus
soils can produce a lower EPC for optimal crop growth.
8.2.4 Effects of WTP Residuals on Soil
Physical Properties
Research has been conducted to determine whether
application of WTP residuals conditions agricultural soils
by increasing the soil organic matter content. Soil con-
ditioning is treatment that modifies a soil's physical prop-
erties for the improvement of crop growth (Chang et al.,
1983). The organic matter content of dry WTP residuals
varies depending on the original raw water source and
the treatment methods employed at individual WTPs.
Estimates of percent organic matter in WTP residuals
range from 14.4 percent (Lin, 1988) to 25 to 35 percent
(Bugbee and Frink, 1985). These values seem high and
should be used with caution. Appropriate methods for
determining organic matter in WTP residuals should be
used. Current research in this field (Elliott et al., 1990a)
determined that the average organic matter content of
seven test residuals was 3 percent, with an average loss
on ignition (LOI) value of 33 percent. Thus, the soil
conditioning effects of organic matter in WTP residuals
are probably quite small and may not be measurable
under field conditions.
140
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At a land application site in Colorado with cumulative
application rates of up to 179 mt/ha (80 tons/acre) (by
1984) researchers theorized that the cumulative load-
ings of quartz and aluminum hydroxides exhibited some
potential to change soil texture in fields near an indus-
trial water treatment facility (King et al., 1988). The
annual application rate was approximately 45 mt/ha (20
tons/acre). Soils on the fields amended with alum re-
siduals have shown a potential for dusting and more
rapid drying than the nonamended fields. Application
rates were lowered to control this situation.
8.3 Land Application Options
8.3.1 Agricultural Land
Agricultural use of WTP residuals is the beneficial appli-
cation or disposal of residuals on agronomic lands. Suc-
cessful implementation of this disposal option requires
an understanding of the effects of WTP residuals on soil
fertility and physical properties (discussed in the pre-
vious section). The physical characteristics of soil that
determine whether it can support vegetative growth in-
clude cohesion, aggregation, strength, and texture.
These parameters directly affect the hydraulic proper-
ties of a soil, such as moisture-holding capacity, infiltra-
tion, permeability, and drainage. Any adverse impact on
these hydraulic soil characteristics from land-applied
WTP residuals can effect crop growth and ultimately
degrade ground water quality (Elliott et al., 1990b).
Concentrations of the WTP residuals listed in Table 8-1
tend to be elevated compared with the concentration of
trace metals described in Chapter 3. Many of the sam-
pled WTPs in Colorado treat surface waters affected by
past mining activities. The length of time a site may be
used depends on the quality of the WTP residuals ap-
plied. Two basic types of residuals are generated at a
WTP—lime softening residuals and coagulant (alum or
ferric) residuals. These residuals are discussed below.
8.3.1.1 Lime Softening Residuals
Addition of lime to agricultural soil is a common practice
in areas where the soil pH is too low for optimal plant
growth; lime modifies the balance between acidity and
alkalinity in the soil. Soil pH should be maintained at 6.5
or above to minimize crop uptake of metals (U.S. EPA,
1983). In addition to providing a desirable pH for plant
growth, lime residuals can be substituted for agricultural
limestone and offer calcium carbonate equivalence
(CCE) or neutralization effectiveness. Lime residuals
can be dewatered to higher solids content than alum
residuals can; therefore, the potential for unique dis-
posal or co-disposal opportunities is greater than for
other residuals. Studies show the neutralizing power of
lime residuals is equal or superior to that of agricultural
limestone (Che et al., 1988). Lime residuals increase the
porosity of tight soils, rendering the soils more workable
for agricultural purposes.
The best way to estimate the liming requirement of a soil
is to titrate individual samples of the soil with a standard
base. The result is the quantity of base required to raise
the pH of the soil to a specified pH. The theoretical
chemical process is illustrated below:
CaCCb + H2O = Ca2+ + HCO3 - + OhT
Ten mmoles of a base per kilogram consumed during
titration is equivalent to 4.5 metric tons of pure CaCO3
per hectare at a 30-cm plough layer (ha-30 cm) of the
sample soil.
Field liming results may differ considerably from these
experimental results, depending on the mixing of lime
residuals with the soil, the solubility of the liming agent,
and the soil sampling procedures. Use of a conversion
factor generally corrects this difference. The U.S. De-
partment of Agriculture's Extension Service may be con-
sulted for the appropriate conversion factor for a given area.
Lime residuals can be applied as a liquid or dewatered
and applied as a cake using an agricultural manure
spreader. The application rate for lime residuals must be
calculated on a dry weight basis, then converted to the
equivalent wet weight for application to the farm field.
8.3.1.2 Alum Residuals
Alum residuals when dry generally have the consistency
of very fine soils. Bugbee and Frink (1985) indicate that
alum residuals improve the physical characteristics of
soil media but inhibit plant growth by adsorbing phos-
phorus. As stated earlier, this reduction in phosphorus
available to plants is different from the toxicity problem
that may be associated with land application of WTP
residuals. To obtain optimal plant yields when land ap-
plying alum residuals, phosphorus fertilizer must be added.
As previously mentioned, soil conditioning effects from
organic matter in WTP residuals are probably quite
small and may not be measurable under field conditions.
Management practices such as lowering application
rates can control the dusting and rapid drying seen in
fields amended with alum residuals. Application of alum
residuals at rates that are not considered excessive (20
mt/ha) does not cause environmental degradation. Alum
residuals are applied as a liquid unless the WTP has
dewatering capabilities. Liquid alum residuals can be
applied with a liquid manure spreader, like lime residu-
als, or with conventional irrigation equipment.
Example 1: Co-disposal With Sewage Sludge
Colorado in the late 1980s developed a WTP residuals
land application policy based on research completed in
northeastern Colorado. This approach assumed that
aluminum and iron would bind with the phosphorus in
141
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the WTP residuals on a one-to-one basis. Because of
this potential phosphorus binding effect, Colorado de-
veloped a conservative method of estimating the frac-
tion of WTP residuals that can be coapplied with sewage
sludge. That method is described in Equation 8-1 .
P(SS)-1.15AI(SS)-
WTP residual = _ 0.55 Fe(SR) _
fraction " [1.15 AI(WTR)- 1.15 AI(SR)] +
[0.55 Fe(WTR) - 0.55 Fe(SR)]
(Eq. 8-1)
where
P(SS) = phosphorus content (mg/kg) in sewage
sludge
AI(SS) = aluminum content (mg/kg) in sewage
sludge
Fe(SS) = iron content (mg/kg) in sewage sludge
AI(WTR) = aluminum content (mg/kg) in WTP
residuals
Fe(WTR) = iron content (mg/kg) in WTP residuals
For example, if
P(SS) = 25,000 mg/kg (average value from U.S.
EPA, 1995)
AI(SS) = 8,000 mg/kg (typical value)
Fe(SS) = 15,000 mg/kg (typical value)
AI(WTR) = 60,111 mg/kg (average value from Table
8-1)
Fe(WTR) = 52,751 mg/kg (average value from Table
8-1)
then, the WTP residuals fraction =
25,000 m3/kg P - 1 .1 5 (8,000 m3/kg Al) -
0.55(1 5,000
_ _
[1.15 (60,111 m9/1
-------
Table 8-3. Phosphorus Recommendations for Several
Agronomic Crops3 (Foth and Ellis, 1988)
Phosphorus Applied kg/ha (Ibs/acre)
Soil P Test
mg/kg
15
30
50
80
175
Corn
1 5 (30)
6.5 (13)
0
0
0
Wheat
1 9.5 (39)
11 (22)
0
0
0
Soybeans
11 (22)
0
0
0
0
Potatoes
38 (76)
35 (70)
30.5 (61)
24 (48)
0
3 Yield goals assumed: corn, 140 bushels/acre; wheat, 70 bushels/
acre; soybeans, 50 bushels/acre; potatoes, 400 cwt/acre.
residuals applied at 1 mt/ha. Again, the assumptions
made here are for illustration purposes only; the WTP
must modify this information to reflect local conditions.
8.3.2 Silviculture
Silviculture, another agricultural practice, is the estab-
lishment, growth, reproduction, and care of forest trees
as a crop. Land application of both wastewater and WTP
residuals is relatively uncommon in silviculture com-
pared with application to agricultural lands. Bugbee and
Frink (1985) indicated the following effects of residuals
application to silvicultural use: no significant effects on
tree growth, nutrient levels, or the appearance of the
forest floor; slightly diminished uptake of phosphorus;
and increased soil pH for trees treated with WTP residu-
als. Grabarek and Krug (1987) concluded that limited
application of WTP residuals to a healthy forested area
does not upset the phosphate cycle to the point of
affecting forest growth patterns.
The effects of long-term (30 months) application of alum
residuals were evaluated by Geertsema et al. (1994).
Alum residuals were applied to experimental plots with
two to four replicates of each application rate: 0, 36, and
52 mt/ha (0, 16, and 23 dry tons per acre). The study
found no statistically significant differences in soil char-
acteristics, ground-water characteristics, or loblolly pine
growth analyses between the unamended and the re-
siduals-amended plots. Geertsema et al. also found no
significant metal migration through the soil profile. At the
application rate used in the study, no problems were
observed in available phosphorus as evidenced by the
similar pine tree growth in the treated and untreated
plots. The results of the study did not indicate any envi-
ronmental problems; therefore, the City of Newport
News has implemented a full-scale project.
8.3.3 Land Reclamation
Sewage sludge is more commonly used than WTP re-
siduals to reclaim surface-mined areas or other dis-
turbed lands and to establish vegetative growth and/or
restore or enhance soil productivity. Disturbed lands
include highway construction sites, overgrazed ran-
gelands, and other construction sites. In combination
with other fertilizers, however, WTP residuals may bene-
fit reclamation efforts. WTP residuals can be used to
treat a particular or site-specific concern. For example,
lime residuals can control soil pH just as they do in
agriculture, but in these cases the pH adjustment may
be more critical because mine soils can be very low in
pH. In addition, alum residuals can control runoff of
excess phosphate into surface waters. Care must be
taken to ensure that the site is suitable for use of WTP
residuals and that controls (best management practices)
are in place to protect public health and the environment.
Application rates may vary from 5 mt/ha on arid ran-
geland to 450 mt/ha or higher on a mineland reclamation
site. On a mineland reclamation site, WTP residuals
may actually be used as a topsoil replacement; thus, the
application rate may be as high as 450 mt/ha.
8.3.4 Dedicated Land Disposal
Dedicated land disposal (OLD) of WTP residuals is gen-
erally the alternative chosen by those operations that
either generate residuals continuously or have quantity
or quality concerns. DLDs are designed to treat and
dispose of large quantities of residuals through soil mi-
croorganisms, sunlight, and/or oxidation. In addition, the
soils are used to bind or fix the metals, thus making them
unavailable.
A distinct advantage to using a OLD is that, for the most
part, the WTP controls the application times, rather than
other factors (e.g., crop growth cycles). OLD application
rates are generally much higher than those of other land
application operations, ranging from 20 mt/ha to greater
than 200 mt/ha. This increased application rate can greatly
decrease the amount of land required for the WTP.
The tradeoff between DLDs and other land application
options is that stricter requirements generally apply to
the DLDs. Increased application rates require that the
site be carefully designed, managed, and monitored.
The site must be designed to contain any of the residual
constituents that might threaten public health or the
environment. The site must take more care with surface
runoff controls and the generation of contaminated
leachate or infiltration. Generally, surface water controls
include physical structures such as dikes, ditches, and
lagoons. Control of leachate that is generated may re-
quire collection and treatment prior to discharge or dis-
posal. Discharge of the treated leachate may require a
National Pollutant Discharge Elimination System (NPDES)
permit and/or additional state permits.
143
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8.3.5 Other Use Options for WTP Residuals
Other applications for WTP residuals include use at turf
farms, parks and recreational areas, highway rights of
way, airports, and construction sites. Most of these pro-
jects utilize WTP residuals as a soil replacement or soil
amendment. For example, in turf farming, each time a
crop is harvested, a significant amount of soil is re-
moved. WTP residuals can be used as a partial replace-
ment. The other options also typically require imported
soil, and in areas where topsoil is scarce residuals may
be used as a partial or total replacement. As with all land
application projects, however, the quality of the residu-
als must be matched with the needs of the user.
8.4 Operational Considerations in Land
Application
8.4.1 Application Procedures
Once land application is selected as the preferred dis-
posal option, the next step is to evaluate the land appli-
cation site, the costs associated with that site, and the
potential social and environmental impacts on the site.
In addition, the costs of dewatering and hauling must be
reviewed because the higher the percentage of solids,
the less volume of residual must be hauled.
The land area requirement depends on the application
rate. In general, application rates are determined using
agricultural methods, as with fertilizer. In the case of
WTP residuals, this fertilizer recommendation is at least
two fold; the nutrient requirements for the crop are
based on the expected yield and the available nutrients
in the soil. The first nutrient to consider is nitrogen. WTP
residuals tend to be very low in this nutrient. A WTP
should always check the nitrogen content of the residu-
als to be land applied. Basing the application rate on
nitrogen alone, however, may cause problems with the
crop yield because aluminum and/or iron hydroxide sol-
ids present in WTP residuals are strong adsorbents of
inorganic phosphorus. The low concentrations of phos-
phorus in WTP residuals may further diminish total
phosphorus in soils, restricting plant growth.
As previously noted, concentrations of trace metals will
likely determine the lifetime application amount of WTP
residuals (metric tons per hectare, dry weight) on agri-
cultural soils. Most metals in WTP residuals are bound
in forms not readily released into solution due to their
strong adsorption and co-precipitation by aluminum and
iron hydroxides freshly formed in the coagulation treat-
ment step.
Buffer zones between residuals applications, such as
surface water, drinking water wells, drainage ditches,
property lines, residences, schools, playgrounds, air-
ports, and public roadways, play an important role in a
successful WTP residual program. Identification of site-
specific buffer zones may be critical to the land applica-
tion program. In addition, many states have buffer zone
regulations that must be followed. Guidelines for buffer
zone delineation can be found in the following EPA
publications:
• Process Design Manual Land Application of Munici-
pal Sludge (U.S. EPA, 1995b).
• Biosolids Management Handbook for Small Municipal
Wastewater Treatment Plants, U.S. EPA Regions 7,
8, and 10 (U.S. EPA, 1995a).
Land application may be feasible only at certain times
of the year, depending on the moisture conditions of the
soil and weather conditions. Another, often overlooked
factor is the local cropping cycle. Farmers will want to
restrict application to certain times of the year, which will
require additional or supplemental storage of WTP re-
siduals. This timing and storage must be factored into
the land application program.
Land application of WTP residuals can be accomplished
through injection, incorporation, or surface application.
Surface application requires the least additional equip-
ment. Land application equipment is widely available,
often from farm implement dealers.
8.4.2 Public Participation
Involving area residents may seem an obvious step but
is often not considered. Those responsible for the use
or disposal of WTP residuals must involve the commu-
nity before starting the project. Holding public hearings
is only a small part of a broad-based participatory proc-
ess. Often the public can help make necessary deci-
sions. Given information and allowed to participate, the
public often becomes an advocate for the WTP. Target
community leaders, place information in libraries, and
talk to people. Community leaders include elected offi-
cials, church pastors, community activists, and others.
Consensus on the best solution is gained only through
the joint effort of all involved: regulators, contractors,
and the public.
8.4.3 Transportation
Transportation of WTP residuals represents a major
cost and should be carefully examined. The first consid-
eration is the type of WTP residuals being handled and
transported, liquid or cake. The lower the percentage of
solids, the more liquid the residuals, and the greater the
volume of residuals that must be handled and transported.
Liquid can be transported either by pipeline or by truck.
Pipeline offers the convenience of transporting residuals
regardless of weather or other external factors. The
distinct disadvantage, however, is that pipelines gener-
ally go to one location and limit the options for land
application. To overcome this disadvantage, the WTP
144
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can maintain a large tract of land, enough to handle the
residuals generated. Truck transportation offers WTPs
more options for land application; therefore, most land
application programs use this transportation method.
Before various residuals dewatering and disposal alter-
natives can be compared, the costs of loading, dewater-
ing, hauling, and disposal must be evaluated.
8.4.4 Monitoring
8.4.4.1 Residuals Sampling and Analysis
Either grab samples or composites can be used to
analyze WTP residuals. WTP residuals range in consis-
tency from liquid to solid; sampling techniques differ for
each residual consistency. The U.S. Environmental Pro-
tection Agency (EPA) has developed guidance for sam-
pling methods for sewage sludge that both explain (U.S.
EPA, 1989) and show (U.S. EPA, 1993c) residuals sam-
pling. The goal of all sampling is to obtain a repre-
sentative sample, which is easiest to accomplish with a
liquid being pumped.
One method to obtain a representative sample from a
residual pile was developed in the early 1900s (first
referenced in 1902) in the mining district of England.
Many samples are taken from different depths and at
different locations in the pile. A cone is built of the
subsamples, and the cone is then flattened and quar-
tered, thus the term "quartering." Opposite quarters are
re-coned and quartered again. This process continues
until the required sample volume is reached.
Analytical methods for metals are found in the latest
edition of Test Methods for Evaluating Solid Waste((J.S.
EPA, 1986b). A common analytical error is for labs to
conduct the metals analysis using a method developed
for water and wastewater. In addition, the sample prepa-
ration method is as important for metals as the correct
analytical method. All metals analysis samples should
be prepared using SW-846 method 3050. With this
preparation method, it is important to use equivalent to
1 gram dry weight of solids for the digestion. The results
should be reported as dry weight, which requires the
analysis of percent total solids so that dry weight can be
calculated.
8.4.4.2 Soil Sampling and Analysis
Soil sampling is essential for accurate fertilizer recom-
mendations. The recommendation may be used to cal-
culate the quantity of WTP residuals to apply. With alum
and ferric residuals, however, supplemental phosphorus
fertilizer may be needed.
Total metals in the soil should be analyzed using the
method described in Methods of Soil Sampling and
Analysis (Page et al., 1982). Total metals should be
analyzed rather than plant-available levels; methods
vary depending on locale, and the scientific community
still has concerns about the comparability of results.
Local land grant universities should be consulted for
more information. As a basic guideline, however, one set
of composite samples should represent no more than 16
hectares.
When sampling an area of a field, samples should be
taken from areas of similar soil characteristics, such as
color, slope, and texture. Areas with different charac-
teristics may require additional samples. A minimum of
20 subsamples for compositing should be taken from the
sampling area, regardless of size. The sample should
be taken to a depth approximately equal to the plow
depth, discarding the surface litter of each sample. Sam-
ples can then be air dried and sent to the laboratory for
analysis. Typically, the cost of metals analysis of WTP
residuals ranges from $100 to $250 per sample. Other
analysis, such as TCLP, may cost as much as $1,500.
Soil analyses are similar in cost. The local land grant
university may be contacted for both analysis and fertil-
izer recommendations.
8.4.4.3 Other Analyses
Other sampling techniques and chemical analyses may
be required to assess a specific site or residual, such as
plant tissue sampling and monitoring, ground-water
monitoring, or deep soil monitoring. Deep soil monitor-
ing samples soils to a specific depth; in EPA Region 8,
depth is 5 feet. Each 1-foot increment is analyzed to
assess migration of pollutants of concern, thus a facility
can use deep soil monitoring instead of ground-water
monitoring.
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Chapter 9
Brine Waste Disposal
Currently, reverse osmosis (RO), electrodialysis (ED) or
electrodialysis reversal (EDR), nanofiltration (NF), ul-
trafiltration (UF), and microfiltration (MF) are the only
membrane processes being used or considered for use
in treating public water supplies. All of these processes
produce residuals waste streams, but not all generate
waste streams that could be classified as brine—that is,
as having a concentration of dissolved salt higher than
that of ordinary seawater (Lapedes, 1978; Ingram,
1969). Only seawater RO, ED or EDR, and brackish
water RO can produce brine waste streams. All other
residuals waste streams from membrane processes are
concentrates rather than brine. In fact, the American
Society for Testing and Materials (ASTM) publishes a
standard for definitions of water-related terms (ASTM,
1982) that interprets the residuals portion of an aqueous
solution applied to a membrane as a concentrate. This
chapter focuses primarily on the disposal of brine waste,
with information and background on concentrates sup-
plied as appropriate.
9.1 Background Information
9.1.1 Amount of Concentrate Generated and
Disposal Methods
The U.S. Office of Technology Assessment (OTA) evalu-
ates waste concentrate generation from membrane
processes in terms of percent recovery of feed water
and percent disposal as waste concentrate (Table 9-1).
Conventional methods of concentrate disposal involve
disposal to surface bodies of water, spray irrigation com-
bined with another dilution stream, deep well injection,
Table 9-1. Membrane Concentrate Generation
Membrane Process
UF
NF
Brackish water RO
Seawater RO
ED
Percent
Recovery of
Feedwater
80-90
80-95
50-85
20-40
80-90
Percent
Disposal as
Concentrate
10-20
5-20
15-30
60-80
10-20
drainfields, boreholes, or wastewater collection sys-
tems. These methods are usually the most cost-effec-
tive. Nonconventional methods are generally considered
cost-prohibitive and are usually associated with a zero
discharge scenario. These include use of evaporation
and crystallization technologies and other ancillary
equipment to concentrate the waste stream into a cake.
Other nonconventional methods include evaporation by
solar ponds or solar distillation.
It should be noted that water treatment sometimes in-
volves ion exchange, a separation process in which
water is passed through a column containing an ion
exchange resin or medium, often a cationic or anionic
synthetic polymer. As the water passes through, the
resins exchange their ions with those in the water ac-
cording to the preference of the exchange sites for
specific ions and the concentrations of these ions. In this
way, ions from the water adsorb onto the resin. When
the resin approaches its capacity for taking up ions, the
ion exchange process is taken off line and the column
regenerated by exposing the resin to a regenerant solu-
tion that, through ion exchange, converts the resin back
to its initial form. The off-line steps include backwashing,
regeneration, and rinsing. After regeneration, the ion
exchange column is returned to service.
9.1.2 Constraints and Concerns
Concentrate disposal methods must be evaluated in
light of geographic, environmental, and regulatory im-
pacts. Geographic constraints generally have to do with
limitations in local geology, hydrology, weather, and land
availability. Environmental concerns such as impacts on
wetlands, flora and fauna, and surface or ground-water
pollution limit the use of some disposal methods in some
locations.
At least eight states have established regulations to
protect water resources from further degradation from
brine or concentrate disposal. Section 305(b) of the
Clean Water Act requires states to report to the U.S.
Environmental Protection Agency (EPA) the extent to
which their waters are meeting the goal of the Act and
to recommend how compliance may be accomplished.
According to the National Water Quality Inventory 1986
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Report to Congress (U.S. EPA, 1986a), 36 of 52 (69
percent) U.S. states and territories reported brine/salin-
ity as a major ground-water contaminant, indicating that
proper disposal of concentrate should be a concern to
all professionals engaged in the use of membrane proc-
esses. Table 9-2 summarizes concerns and requirements
associated with conventional concentrate disposal
methods.
9.1.3 Early Disposal Regulations
The State of Florida has by far the highest percentage
of membrane process plants in the United States. A case
study of permitting requirement, disposal option, and
regulatory trends in Florida indicates the direction that
concentrate disposal regulation is likely to take in the
rest of the country. In Florida, regulatory agencies began
governing concentrate disposal in the late 1960s. The
relatively simplistic mass balance or dilution approach
taken in that era evolved to a more complex approach
by the mid-1980s. The trend towards more stringent
Table 9-2. Concerns and Requirements Associated With
Conventional Disposal Methods
Disposal
Method
Regulatory
Concerns
Other Requirements
Disposal to
surface water
Deep well
injection
Receiving stream
limitations
Radionuclides
Odors (hydrogen
sulfide)
Low dissolved
oxygen levels
Sulfide toxicity
Low pH
Confining layer
Upconing to USDWs
Injection well integrity
Corrosivity
Spray irrigation
Drainfield or
borehole
Sanitary
sewer
collection
systems
Ground-water
protection
Ground-water
protection
Effect on local
wastewater
treatment plant
performance (toxicity
to biomass or
inhibited settleability
in clarifiers)
Mixing zone
Possible pretreatment
Multiple port diffusers
Modeling of receiving
stream
Well liner
Monitoring well
Periodic integrity test
Water quality of
concentrate must be
compatible with the
water quality in the
injection zone
Monitoring wells
Possible pretreatment
Backup disposal method
Need for irrigation water
Availability of blend
waters
Monitoring wells
Proper soil conditions
and/or rock permeability
None
regulations has continued into the 1990s. This trend is
likely to occur in other states, such as California, Texas,
and states along the east coast where use of membrane
process plants is increasing.
Movement towards increasingly stringent regulation of
concentrate disposal has been brought on by regula-
tions passed to preserve and protect surface water bod-
ies, bird sanctuaries, endangered flora and fauna,
ground-water resources, and other environmentally sen-
sitive areas. In particular, the permitting process has
become more difficult. In the late 1960s, no permit was
required to discharge concentrate to surface waters.
Later, the State of Florida required a permit, but did not
have a separate permit category for concentrate. Thus,
the State of Florida permitted its first concentrate dis-
charge in the early 1970s as an industrial waste. In
retrospect, placing concentrate disposal under a sepa-
rate waste permitting category would have been better
because EPA later issued a new permitting requirement,
the National Pollution Discharge Elimination System
(NPDES), that required discharges to surface waters to
be permitted. This resulted in dual permitting of concen-
trate discharges to surface waters.
As more recent membrane process technology began
being applied to potable water treatment, systems be-
gan being sited farther away from coastal surface bodies
of water and new disposal methods such as deep well
injection began being employed. The first spray irriga-
tion of diluted concentrate occurred in 1978, and the first
deep well injection of concentrate occurred in 1983.
Between 1978 and 1983, regulatory requirements had
changed so much that only monitoring requirements
were imposed on the spray irrigation project, while very
stringent well construction integrity and monitoring re-
quirements were required for the deep well injection
project.
9.1.4 Current Regulations and Their Trends
Regulations vary widely from state to state and, in some
cases, from county to county. In general, regulations are
designed to protect surface- and ground-water re-
sources; rarely do they specifically address the disposal
of concentrates or brine. One specific regulation con-
cerning the disposal of concentrate to ground waters
was passed in Florida on July 28, 1988. Passage of an
amendment to Chapter 17-28.700 of the Florida Admin-
istrative Code (FAC) allowed nonhazardous concen-
trates to be discharged through land application to
aquifers containing greater than 1,500 milligrams per
liter (mg/L) of total dissolved solids (TDS). More re-
cently, increased public awareness, the activities of en-
vironmental organizations, and public concern have
increased the difficulty of siting and permitting mem-
brane process plants in Florida. In recent years, bills
have been introduced in the Florida legislature to ban
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deep well injection. To date, these bills have failed, but
one might be successful in the future.
After his election in 1994, Governor Bush of Texas
banned the use of deep well injection. At the same time,
Safe Drinking Water Act (SDWA) regulations are caus-
ing membrane processes to be declared best available
technology (BAT) for the removal of many contaminants.
Yet, without a viable method of concentrate disposal,
membrane processes cannot be used. If pretreatment
requirements drive the cost of disposal too high, some
proposed membrane projects will not be cost-effective.
Already, some cities have been unable to obtain dis-
posal permits. At a recent meeting of the Florida Depart-
ment of Environmental Protection (FDEP) Fact Finding
Committee on Concentrate Disposal, it was recom-
mended that a permit application be made in advance
when alternative concentrate disposal methods will be
proposed; application before beginning the detailed de-
sign of a proposed membrane process plant is intended
to reduce losses if a plant cannot be permitted. It was
further recommended that the permit application be
made for the full plant nominal capacity required at
buildout. Given that regulations are a moving target, it
should be kept in mind that what is permittable now
might not be permittable in the future.
9.2 Conventional Disposal Methods
9.2.1 Surface Water Discharge
Disposal of brine is a critical issue facing WTPs through-
out the country. Because the majority of surface water
discharges occur in Florida, the discussion that follows
is based on Florida's experience.
The question of the environmental impact of brine dis-
posal to surface waters was first addressed by the State
of Florida in 1986. At that time, the state determined that
concentrate disposal posed a significant threat to sur-
face water quality and began requiring that any dis-
charge to surface waters be permitted.
9.2.1.1 Constituents in Water Treatment Brines
Several constituents of WTP brines have been identified
as potential threats to surface water quality. In Florida,
ground water is the principal source of raw water.
Ground waters are devoid of dissolved oxygen and
contain hydrogen sulfide. This is a concern in relation to
surface waters, because a lack of dissolved oxygen and
the presence of detectable quantities of hydrogen sul-
fide are toxic to aquatic organisms. Fortunately, both
conditions are easily remedied via a relatively simple
and inexpensive treatment: aeration, which simultane-
ously adds dissolved oxygen and removes hydrogen
sulfide. Some facilities have also removed hydrogen
sulfide through chemical treatment. Typical Florida "end-
of-pipe" permits require a minimum dissolved oxygen
concentration of 5.0 mg/L and a maximum hydrogen
sulfide concentration of 0.04 mg/L.
The presence of radionuclides in the brine can also pose
a major water quality problem. Florida water quality
criteria contain limits for combined radium (Ra-226 +
Ra-228) and gross alpha. RO brines can contain com-
bined radium at levels greater than 100 picoCuries per
liter (pCi/L)—much higher than the Florida surface water
standard of 5.0 pCi/L. Gross alpha levels are more
difficult to measure due to interference from the dis-
solved solids in brines. High gross alpha values, how-
ever, typically occur with high levels of combined radium
and should be handled similarly. The presence of radio-
activity in any waste, including brine, can become an
issue of great public concern, increasing the need
to deal with radionuclide exceedances promptly and ap-
propriately.
With brine, an additional disposal concern with surface
water discharge is the impact of the concentrated salts
(dissolved solids) on the receiving water. Water quality
criteria for fresh water surface waters greatly limit the
capacity of a fresh water body to receive brine. Unless
the water body is a stream or river with a flow many
times greater than the brine flow volume, discharge is
not likely to meet the surface water criteria, even after
mixing. Therefore, outfalls should be located to dis-
charge brine waste to brackish or marine waters with
adequate flushing.
Fluoride and several metals have been found in high
concentrations in the brines of some facilities. Differ-
ences in the concentrations of these substances in
brines from different facilities reflect differences in the
composition of the ground water that provides the raw
water to the facilities. In some cases, fluoride and metal
concentrations in ground water exceed surface water
criteria; in other cases, they do not exceed these criteria,
but they are higher than the fluoride and metal con-
centrations in the receiving waters. When brine concen-
trations exceed receiving water concentrations, antide-
gradation issues must be addressed. The new metals
criteria proposed by EPA and adopted in Florida are
hardness-dependent for many metals. The ultimate im-
pact of these changes has not been determined, but will
require careful examination.
Nutrients are a new area of concern in Florida. As
facilities have increased in size, their brine volumes
have also increased. Today, nitrogen and phosphorus
concentrations in large volume brines can provide a
significant nutrient load to receiving waters. Because
many Florida surface waters are already overenriched,
significant nutrient additions are not likely to be approved.
A permit to discharge brine to a surface water will require
establishing an effluent limitation—the brine quality nec-
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essary to ensure that the receiving water quality is not
degraded beyond what is allowed by state and federal
regulations. While effluent limitations are typically devel-
oped through application of sophisticated mathematical
computer models, this is not always necessary for brine
discharges.
9.2.1.2 Dilution, Mixing Zones, Modeling, and
Multiport Diffusers
The hydrologic characteristics of receiving waters are
important in considering surface water discharges of
brines. The receiving waters' flow is the first issue that
must be addressed. Most brine constituents are conser-
vative materials that can be assimilated only through
dilution. If the discharge dominates the receiving water,
little dilution will occur. Small streams, for example, have
little ability to dilute a discharge. Neither do lakes (even
large lakes), because mixing and transport away from
outfalls are slow, resulting in a localized buildup of brine
constituents.
With the exception of aeration and hydrogen sulfide
removal, treatment of brine has not been practical in
Florida. Therefore, dilution has been the only way to
meet receiving water quality criteria that are not met at
the end of the pipe. Dilution calculations do not usually
require sophisticated models. Often, desktop mass bal-
ance calculations are sufficient to determine the neces-
sary effluent limitations. This is especially true when the
surface water flow past the brine outfall is easily meas-
ured and an assumption of complete mixing is appropriate.
When an assumption of complete mixing is not appro-
priate, simple mixing models such as the EPA-supported
CORMIX1, CORMIX2, UPLUME, and UMERGE can be
used to establish effluent limits. The CORMIX models
are particularly attractive because they are compiled
from routines that the model chooses from based on
input specified by the user. EPA has identified methods
for determining tidal prisms, flushing times, and initial
dilution that can aid in the calculation of mixing areas
(U.S. EPA, 1985b). Many mixing models also permit
analysis of the use of a multiport diffuser, which is often
necessary to achieve adequate mixing in a reasonable
area. Models should be used that consider the number,
size, and orientation of multiple ports. Analysis is helpful
because multiple ports do not always provide better
mixing than a single port.
When concentrations in brine exceed surface water cri-
teria, regulatory agencies may require the development
of a mixing zone. In Florida, for example, a mixing zone
is required for any discharge with end-of-pipe constitu-
ent concentrations in excess of numeric surface water
criteria. No implied opportunity for mixing is given. In
these cases, it is necessary to use a mixing model that
establishes geographic boundaries as well as numeric
constituent limits.
Assumptions specified in modeling exercises should be
conservative. That is, they should examine worst case
situations to ensure that the effluent limits developed will
protect receiving water quality and comply with permit
conditions. Minimum and maximum flows should be
modeled to examine the dilution provided and estimate
variations in brine plume boundaries underdifferent con-
ditions. These analyses require data on constituent con-
centrations in the receiving water and in the brine. If the
facility is not yet constructed, analyzing brine from a pilot
test facility might be possible. Otherwise, analysis of the
raw water and calculation of expected brine concentra-
tions will be necessary.
9.2.1.3 Toxicity Relative to Surface Water
Discharges
Any discharge to surface waters must address the issue
of toxicity. Discharges are typically screened fortoxicity
using whole effluent toxicity bioassay. These bioassays
expose sensitive test organisms to 100 percent effluent
for 48 (EPA) or 96 (some states) hours, while control
organisms are exposed to "clean" water. At the end of
the test, the number of deaths in the effluent is com-
pared to that in the controls to determine if the effluent
is acutely toxic. If an effluent is found to be toxic in this
type of screening test, it is subjected to a definitive
bioassay in which the organisms are exposed to various
concentrations of effluent to determine the concentra-
tion lethal to 50 percent of the test organisms in the test
period.
For toxic effluents, the degree of toxicity determines
whether effluent limitations can be established, whether
a mixing zone will allow the establishment of effluent
limitations, or whether additional treatment to remove or
reduce the toxicity will be required. In some cases, the
facility may need to determine the cause of the toxicity
through a Toxic Identification Evaluation (TIE).
In Florida, bioassays are required for all permitted sur-
face water discharges. The frequency with which these
tests must be performed varies with the volume of the
discharge and the type of discharge. Because several
discharges have failed bioassays, more test require-
ments are likely. The cause of brine toxicity has not been
definitively determined and might vary among facilities.
9.2.2 Disposal to Sanitary Sewers
Discharge of concentrates to sanitary sewer systems is
sometimes feasible if the concentrate mixture is not
toxic and does not adversely affect the clarifier settle-
ability or restrict final effluent disposal. Generally, the
restrictions and requirements of sewer agency user or-
dinances must be followed. WTP agencies typically re-
quire detailed analytical screening before agreeing to
accept a proposed brine or concentrate discharge. Spe-
cial attention will be given to the discharge's effect on
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metal and hazardous constituent levels in WTP residu-
als, which must be disposed of safely.
In California and other western states, regional dedi-
cated brine interceptor lines have been in place for many
years. Originally installed to carry away waste brines
from the oil industry and other industrial sources, they
are now being used for residual brines from municipal
well head treatment, such as brines from nitrate reduc-
tion ion exchange systems and concentrates from inland
desalters used to reduce IDS in ground waters contami-
nated by years of agricultural operations. The cost of
using these regional brine interceptors is often high—in
some cases, higher than the cost of the proposed treat-
ment processes. Costs include contribution-in-aid to
construction of treatment facilities, other capacity
charges, construction of pipelines from the treatment
process to the interceptor lines, cost per acre or foot of
discharging to the interceptor sewer, and pretreatment
costs (if required).
9.2.3 Deep Well Injection
9.2.3.1 History of Deep Well Injection and
Injection Regulations
During the last two decades, intensifying awareness of
the problems associated with wastewater disposal into
the surface and near-surface portions of the earth (e.g.,
lakes, rivers, ponds, irrigation fields, and shallow aqui-
fers) has increased interest in deep well injection. As its
name implies, deep well injection is the pumping of
waste into deep geologic formations. The injection depth
depends on site-specific geologic conditions and the
quality of the receiving waters as set by minimum criteria
in federal and local regulations.
Regulatory criteria for deep well injection of non-oil drill-
ing waste waters was first formalized at the federal level
in a Federal Water Quality Administration order dated
October 15, 1970. That order only gave general guid-
ance; it was not until 1973 that true criteria were estab-
lished through the issuance of Administrative Decision
Statement No. 5 by the Administrator of EPA. After the
1980 amendments to the 1974 SDWA, EPA consoli-
dated the rules into the underground injection control
(DIG) regulations and compiled them in the Code of
Federal Regulations (40 CFR Parts 144 and 146), with
general program requirements located in 40 CFR Part 122.
In May 1981, EPA developed a mechanism for granting
individual states primary enforcement responsibility, or
primacy, on DIG and issued a corresponding guidance
paper. Many states have since developed their own DIG
regulations, which, by law, can be stricter but not more
lenient than the federal rules. Most states have opted to
allow full regulatory control by EPA on certain types of
injection wells by choosing not to develop and enforce
rules that would give them primacy over those types of
wells. Regulations in 40 CFR Part 147 describe how
individual states operate under EPA rules.
9.2.3.2 Classes of Injection Wells
In the federal DIG regulations, injection wells are defined
as wells into which fluids are injected. A well itself is
defined as a bored, drilled, or driven shaft, or a dug hole,
with a depth greater than the largest surface dimension.
By definition, well injection means the subsurface em-
placement of fluids through a bored, drilled, or driven
well, or through a dug well, where the depth of the dug
well is greater than the largest surface dimension (40
CFR Part 144.3). Specific inclusions covered by DIG
regulations are septic tanks and cesspools used for
hazardous waste disposal and those serving more than
20 persons per day.
Within this broad definition, EPA has classified injection
wells into five different groups as described in 40 CFR
Part 144.6 and 40 CFR Part 146.5. Paragraph 146.5
provides a detailed definition of Class V injection wells,
while paragraph 144.6 does not. Otherwise, the two
paragraphs are the same. The five classes of injection
wells are:
• Class I injection wells:
- Inject hazardous wastes beneath the lowermost
formation containing a source of drinking water at
least a quarter mile from the well.
- Inject nonhazardous industrial and/or municipal flu-
ids beneath the lowermost formation containing a
source of drinking water at least a quarter mile
from the well.
• Class II injection wells:
- Inject nonhazardous fluids associated with produc-
tion and storage of oil and natural gas.
• Class III injection wells:
- Inject fluids for the extraction of minerals by solu-
tion mining, leaching mining, etc.
• Class IV injection wells:
- Inject hazardous or radioactive water into or above
a formation that contains a source of drinking water
within a quarter mile of the well or that injects
hazardous or radioactive water into aquifers ex-
empted from DIG rules by the EPA Administrator.
• Class V injection wells:
- All injection wells not included in the other four
classifications, including air conditioning return
wells, cesspools, cooling water return wells, drain-
age wells, recharge wells, salt intrusion barrier
wells, thermal recovery return wells, experimental
wells, etc.
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Under these five classifications, injection wells used for
the disposal of WTP residuals, such as concentrated
salt water from desalination, are classified as Class I
injection wells; within that classification, they belong to
Group 2, which includes nonhazardous industrial wells.
This industrial classification is significant because it in-
vokes stricter requirements for well construction and
monitoring, even when the injection fluids are of better
quality than domestic injection fluids that can routinely
be disposed of into Group 1 Class I injection wells.
On the other hand, when WTPs are used to remove
hazardous waste from a source water, the residuals are
considered hazardous water and extra precautions must
be taken to ensure proper operation and monitoring of
the injection system. In some states, hazardous waste
injection wells are banned, and in several other states
with primacy rights, banning hazardous waste injection
wells is being considered at this time. In some cases,
chemicals used in the treatment process could be con-
sidered hazardous wastes. When these chemicals are
removed with the treatment residuals, they must be
neutralized or removed before they can be injected.
9.2.3.3 Water Treatment Plant Residuals
Two types of residuals are important: those derived from
the water being treated and those derived from the
chemicals being used to treat the water. Assuming a
noncontaminated source, residuals from water generally
consist of concentrated salt and minerals, the concen-
trations and types of which depend on the source water.
Added chemicals usually include antiscallants, acids,
flocculants, and pH adjusting chemicals; they may also
include nonhazardous cleaning solutions and other
chemicals.
Residuals can be suspended or dissolved. When deep
injection is considered, it is essential to evaluate the
effect of mixing these residuals with the receiving waters
in the injection zone. Mixing can cause the formation of
precipitates, flocculants, gases, and bacterial mats,
which can hinderthe injection process and can harm the
receiving aquifer by plugging it or by otherwise reducing
its permeability.
9.2.3.4 Requirements of Injection Sites
An important element in the Class I Injection Well defi-
nition is the reference to injection below the lowermost
formation containing an underground source of drinking
water. An underground source of drinking water (USDW)
is any nonexempted aquifer or portion of an aquifer that
supplies water to a public water system (or is large
enough to supply a public water system) and that does
indeed currently supply drinking water to someone, as
long as that water contains less than 10,000 mg/L of
TDS. Thus, a Class I injection well must be sited such
that injection occurs into an aquifer zone with water
having at least 10,000 mg/L TDS (i.e., into waters that
are not USDWs). In addition, the injection zone of the
aquifer must be separated from the USDW zones above
it by hydrologically impermeable formations that pre-
clude upward migration of the injected fluids into the
USDWs. These formations are referred to as confining
beds, although in reality they are never fully confining,
since, theoretically at least, every formation has some
measure of permeability.
A third requirement is that the injection zone be a good
receiving zone from both a water quality and hydrologic
point of view. From the water quality point of view, the
quality of the receiving water must not be aggressive to
the injection fluid. The two waters must be compatible
physically, chemically, and bacteriologically. From the
hydrologic point of view, the receiving zone must be of
high permeability and effective porosity such that the
volumes of water injected can be discharged into the
zone without excessively raising the pressure in the
receiving formation. Excessive injection pressure can
fracture the receiving zone and the confining layer
above it, causing upward migration of the injection fluids
into the USDWs. Similarly, fluid should not be injected
into areas where the confining zone has fissures or
fractures or is crossed by known faults, as these geo-
logic features will become routes of injected fluid migra-
tion into the USDWs. In addition, injection should not
occur in areas where seismic forces are active; in some
cases, injection fluids have been suspected of acting as
a lubricant to induce slippage in underground forma-
tions, resulting in seismic disturbance at the land sur-
face.
9.2.3.5 Environmental Concerns of Deep Well
Injection
The primary environmental concern with deep well in-
jection is the potential for the injected fluids to migrate
into potable water zones. This migration can occur via
two mechanisms:
• Natural migration across confining layers that are not
as confining as they should be, in which case the
injection fluid migrates laterally into other potable
zones through geologic faults or by simply flowing
into other areas where the water is less than 10,000
mg/L TDS.
• Artificial migration of injected fluids through improp-
erly constructed injection systems, such as defective
cement, construction induced fracturing near the
borehole, casing failures, etc.
Depending on the types of residuals being disposed, the
waste to be discharged will have a higher or lower
density than the receiving waters. Assuming a homoge-
neous aquifer, when the injection fluids are more dense,
they sink to the bottom of the injection zone, migrating
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first downward and then horizontally. When the injection
fluids are less dense than the receiving waters, they float
on top of the injection zone, forming a bubble of fresher
(less dense) fluids that produces an upward force across
the confining zone. Similar conditions, in reverse, occur
when the permeability of the injection zone is not homo-
geneous, (i.e., when the injection zone is more perme-
able in one direction than the other). For example, if the
permeability is higher in the vertical than in the horizon-
tal direction, vertical buoyant forces will induce a vertical
movement of the injection fluid.
When vertical forces across the confining layer are in-
duced by any of these injection pressures, vertical mi-
gration through the confining bed eventually occurs.
This may take years, hundreds of years, or longer, but
because no formation is totally impermeable, when the
data are entered into a formula, there will always be a
time when the fluid will move across the confining layer.
This environmental problem is often mentioned qualita-
tively, although quantitatively it may be of little or no
concern.
Two major concerns about confinement are uncertainty
about whether the confining layer extends over a suffi-
ciently large area and uncertainty about whether the
confinement might be broken by faults, geologic cav-
erns, or other geologic features. These issues are diffi-
cult to resolve because it is economically impossible to
drill enough test holes to show that the confining layer
exists everywhere over the area of concern. However, it
is logical to expect that a thick confining bed will not
suddenly thin out and disappear in a short distance.
Similarly, while it is possible to show the existence of
faults (typically identified through other sources in nearby
sites), it is not possible to affirm that no faults exist.
Environmental concerns related to well construction and
the problems associated with improper construction are
discussed in Section 9.2.3.7.
9.2.3.6 Regulatory Requirements
Because ground water is the primary source of water for
many communities, deep well injection is carefully regu-
lated and monitored. Design and permitting are strictly
regulated by EPA when not regulated by the state under
primacy rules. Florida is a primacy state with a growing
practice of using deep injection wells for desalination
residuals disposal; it is a good example to describe how
the permitting process works.
Permitting Requirements
In Florida, permitting and regulatory control of deep well
injection is exercised by FDEP with aid from a technical
advisory committee (TAG). This committee consists of
five voting members who represent environmentally ori-
ented government agencies. The voting members of the
TAG are representatives of the regional office of the U.S.
Geological Survey (USGS), EPAs Atlanta office,
FDEP's Tallahassee office, the appropriate local Water
Management District office, and the local FDEP district
office. Two nonvoting members representing the local
county pollution control office and the local county health
department are also part of the TAG. The representative
of the local FDEP district office serves as the TAG
chairperson.
The TAG reviews and approves every engineering de-
sign and exercises control of every aspect of construc-
tion and testing from beginning to end. The TAG also
reviews and approves specified construction materials
and methods, including the size and weight of the steel
casings, the cement and cement additives used in the
casing installation, the method of drilling, the frequency
and types of tests to be conducted, and other details.
The TAG meets regularly with injection well engineers
and owners to discuss project specifics, including review
and approval of the depth of installation of each casing
and the tests used to ensure mechanical integrity of the
well. A preliminary Plan of Study is usually submitted to
the TAG to inform the regulatory agencies about the
project and the proposed method of construction and
testing.
After extensive review, the TAG may suggest changes
that are incorporated into a final Plan of Study. A formal
permit application is then made for a test well which, if
successful, usually becomes the first injection well of the
system. In areas of Florida where the suitability of geo-
logic conditions for deep well injection is in doubt, the
test well may be preceded by an exploratory well, which
is usually converted into a monitor well.
Under the Florida Administrative Code, there is a 90-day
permitting clock for the permit application procedure.
However, a permit is rarely issued within 90 days of
application submission because the permitting clock
stops each time a TAG member requests additional
information. When the TAG chairperson is satisfied with
the application, FDEP issues a notice of receipt of a
complete application. This notice is published in the
local newspaper and a public hearing date is set and
advertised.
If there is no public opposition to the application at the
hearing and no one requests additional public hearings,
the TAG will begin reviewing of application and all asso-
ciated data, including design documents and specifica-
tions. At the next regularly scheduled meeting of the
TAG, voting members may give approval for the project
to proceed with the test well or they may again request
additional changes. After approval by the TAG, FDEP
issues a second notice of intent to permit, which is also
published in local newspapers, and another public hear-
ing is advertised. If there is no opposition, FDEP will
issue the permit to construct and test the test well. This
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permit usually lasts a year. At the end of the operational
test period, the inspection well operator must apply for
a final operating permit.
Design Requirements
Specifications and contract documents for permit appli-
cations must follow the design criteria required by regu-
latory agencies. These criteria require the use of:
• Well head vacuum release or air release valves to
prevent fluid column separation and air entrapment.
• Hydropneumatic tanks to prevent water hammer.
• Cushioned valves and pump systems designed to
maintain injection velocities below 8 feet/second
(ft/sec) to prevent erosion in the well bore.
• Instrumentation and controls to maintain injection
pressures below the fracturing limits of the formation
receiving the treated effluent.
Designs must include a sufficient margin of error to
ensure that the formation's ability to receive the effluent
is not exceeded and that the opportunity for aquifer
recovery is provided. The system must be designed to
minimize water quality changes of injected fluid to avoid
turbidity and air entrapment, to avoid formation of pre-
cipitates, and in general to ensure that nothing clogs the
formation.
Construction requirements may include use of:
• A drilling pad capable of retaining spilled fluids during
construction to avoid surface contamination.
• Multiple casings to protect each fresh water produc-
ing zone that is drilled.
• Casing and liner materials compatible with the in-
jected fluids.
• Heavy wall casing (e.g., a minimum of 0.375-inch
casing wall thickness).
• Su If ate-resistant cement only, a minimum of 2.5
inches of grout between exterior casings, and a mini-
mum of 5 inches of grout outside of the injection casing.
• Appropriate annular fluid between the injection casing
and the liner of the wells such that the packer in the
annular space is not subject to chemical attack by
that fluid.
• Backflow preventers and check valves.
• Well head designs that facilitate monitoring and log-
ging without major disturbance to system operation
and without requiring a drill rig on site.
Finally, monitoring, inspection, and testing—both during
construction and during operation of the injection sys-
tem—must be addressed in the design process. Princi-
pal elements include:
• Performing geophysical logging before and after each
casing installation.
• Conducting downhole television surveys before cas-
ing installation and after final casing is installed.
• Sampling water quality at every change of formation
or every 30 feet to detect the 10,000 mg/L TDS zone.
• Sampling and testing the quality of water in the in-
jection zone, monitor zones, injection fluid, and shal-
low monitor wells.
• Monitoring annular pressure and the quality of annu-
lar fluid (industrial wells only).
• Conducting aquifer performance tests, injectivity
tests, and mechanical integrity tests.
• Measuring and continuously monitoring and record-
ing injection pressure and injection volume.
• Conducting recertification testing every 5 years.
9.2.3.7 Well Construction
A well must be properly constructed so that it serves its
function without harming the environment. Proper con-
struction ensures that a well passes construction-related
and site condition-related mechanical integrity require-
ments. Of these, only construction-related mechanical
integrity requirements can be controlled through proper
construction, use of adequate materials, and proper
operation and maintenance. Site conditions must be
controlled by proper well siting, which usually occurs
after the first well in a given area has been drilled to
show that the site is adequate. Even in areas where
other injection wells are operating satisfactorily, any new
well should be nominated as a test injection well be-
cause of the possibility that the construction could turn
out to be faulty or the site inadequate.
Contractor Selection
Selecting a qualified well driller for a project is best
accomplished by prequalifying drillers based on their
experience and reputation and by inviting qualified firms
to bid on the specifications and drawings. Special atten-
tion must be given to ensuring that drillers have the
proper equipment to complete the contract on schedule.
The lowest responsible bidder is generally awarded the
contract. Private firms may choose to negotiate con-
tracts rather than select a driller through competitive
bidding. Bid price is influenced by a number of condi-
tions, especially the volume of work available at the time
of bidding.
Drilling Pad and Drilling Equipment
The first stage in drilling the deep injection well involves
drilling the shallow portion of the hole and setting the
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surface casing. By specifying a small drilling rig during
this stage, costs can be minimized.
Once the surface casing is installed, an impervious
drilling pad must be constructed to prevent contamina-
tion of the aquifer by salt water spills during construction.
The pad is constructed of 4- to 6-inch thick reinforced
concrete and is surrounded by a berm. All drilling equip-
ment, fluid circulation equipment, and settling tanks are
installed on top of this drilling pad. Shallow monitorwells
drilled around the pad serve as an early warning system
to detect salt water spills. As an additional precaution
against spillage, a temporary flow control device is in-
stalled before drilling through salt water zones.
After the surface casing is set and the pad and shallow
monitorwells are complete, a large drilling rig is brought
on site. The well size and depth will determine the type
of rig. Assembling a rig and installing all peripheral
equipment can take up to a month.
Fluid Circulation System and Other Equipment
During drilling, all drilling fluid is recirculated through a
series of settling tanks to allow collection of rock cuttings
from the hole. Provisions are sometimes made for tem-
porary storage of salt water overflow in polyvinyl chlo-
ride (PVC) lined ponds. This salt water can later be
reinjected into the well. Cement and cement additives
for grouting casings usually are brought to the site dry
and are stored until they are mixed and pumped by a
cement company specializing in well grouting.
Field offices of the engineer and drilling contractor are
generally located on site. Once drilling starts, it usually
continues 24 hours a day, 7 days a week. Construction
supervision should be provided around the clock by the
consulting engineer.
Geologic Sampling—Proper Well Siting
Formation samples are collected at preselected inter-
vals and at every change of geologic formation. Sam-
ples are catalogued according to their physical
characteristics and mineral composition to identify con-
fining layers and injection zones.
Several formation cores must be obtained from specific
depths in the well. The best core samples typically come
from the confining zones, since samples from the injec-
tion zones are usually broken and fractured. After field
inspection and cataloguing, the cores are shipped to a
laboratory where they are tested for physical and chemi-
cal characteristics, including permeability to water.
These tests determine if the confining beds are suffi-
ciently impermeable to meet regulatory standards.
Construction Procedures
All drilling is preceded by a pilot hole 8 inches or less in
diameter, which yields better formation samples and
facilitates more accurate geophysical logs. The pilot
hole is reamed to full size after it has reached total depth
for casing installation. Full size is usually about 6 inches
larger than the nominal diameter of the casing to be
installed. The one exception is the reamed hole for the
innermost (injection) casing. This hole is always 10
inches larger in diameter than the injection casing to
maintain the minimum requirement of 5 inches of ce-
ment grout in the annular space around the injection
casing
Casing Installation
Injection well construction requires several sizes of cas-
ings, with the largest diameter being used at the surface
and successively smaller casings being used deeper
into the ground. The smallest is the injection casing at
the bottom of the well.
A drilling rig elevator and an auxiliary elevator are used
to raise each casing to the top of the drilling platform and
then to lower it into the hole. Special care should be
exercised to prevent damage during installation. As sec-
tions of casings are lowered into the well bore, they are
welded into place. To ensure that there are no voids in
the welds, two full welding passes should be performed.
Inspectors should examine each weld and pressure
tests should be conducted to detect any imperfection. If
a defect is found, corrective action can be taken before
the well is put into operation. The welding operation
usually continues around the clock over a period of
several days. The pressure test on the final string of
casing must be conducted at 1.5 times the estimated
injection pressure when the well is completed and
placed into operation.
Cementing Operations
After the casing has been installed, cement must be
placed in the annular space between the walls of the
well hole (or inside a telescoping casing) and in the
casing itself. A sulfate-resistant cement (Type II, Class
H) is generally used because deep aquifers contain
unusually high levels of sulfate. Cementing is accom-
plished by pumping cement through a pumper truck into
a small diameter "tremie" pipe in the annular space at
the bottom of the well hole. As the annular space fills
with cement, the tremie is slowly pulled out of the hole.
The first cement installation (lift) usually contains no
additives. Subsequent cement lifts usually contain vari-
ous concentrations of additives to give the cement more
or less plasticity, faster or slower setting times, or
greater or lesser density to fill voids or cavities in the
formation. The cement mix and additives are selected
by the cement engineer and the consulting engineer
after a review of geologic samples and geophysical logs.
The local regulatory program is responsible for and must
review and approve the cement program. If no local
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program exists, EPA must review and approve the ce-
ment program prior to implementation.
Water Sampling
Throughout the drilling process, representative water
samples must be collected from discrete sections of a
formation to define water quality at specific depths in the
hole. Samples are collected using a packer consisting
of a perforated pipe with two inflatable rubber seals at
each end. When the seals are inflated and the packer
assembly is pumped, a water sample is obtained from
the formation section between the seals. These samples
are pretreated at the site and shipped to a laboratory for
analysis. Time-dependent parameters are measured in
the field.
Injection Test
The injection test is performed by injecting clean water
into the injection well and monitoring pressure changes
and water quality. Desalination reject water cannot be
used for injection tests because system failure could
result in ground-water or USDW contamination.
Performing an injection test requires that the monitor
well be completed and equipped with gauges to monitor
pressure changes—typically, a fluid-filled gauge backed
by a mercury manometer that measures pressure in
inches of mercury or 10-inch and 12-inch test grade
gauges. Electronic gauges are usually avoided because
they can be unreliable in injection test conditions. Use
of pressure transducers installed at the bottom of the
hole is ideal because they eliminate the need to correct
for pipe friction losses and water density differences. All
pressure readings are corrected to feet of water and are
referred to a fixed datum, usually the surface of the
drilling pad. This calculation facilitates monitoring of in-
jection pressure and well injectivity overtime.
Samples of the water being injected are collected at
various intervals during the test to determine the quality,
density, and temperature of the water.
After the well is constructed and the injection test is
performed, a downhole television survey of the well
should be conducted using a slim television camera
equipped with a fish-eye lens and a light source. The
videotape of the downhole survey is used to confirm that
there are no holes in the casing and no defective joints.
The videotape also provides a permanent visual record
of the injection zone before injection occurred so that a
comparative analysis of the casing and injection zone
can be performed in the future.
Other geophysical surveys are usually conducted at the
same time to complement those conducted during con-
struction.
Well Head Completion and Monitoring
Proper design of the well head will facilitate collection of
all future monitoring data. Easily readable gauges at the
injection and deep monitor wells should always be
specified and, if funding is sufficient, remote reading
transducers are highly recommended.
The most important design elements are the pressure
and vacuum release valves because they are the ulti-
mate line of protection against high pressure and vacu-
ums that can develop during electrical malfunctions or
scheduled and unscheduled shutdowns. A hydropneu-
matic tank system should also be added to all wells to
further increase protection.
Proper valve design also ensures safe access to the well
when geophysical logs and television surveys are con-
ducted in the future. For example, proper valve design
permits insertion of probes (including the television cam-
era) and avoids spills of injected residuals.
9.2.3.8 Operational Considerations
Any injection system operating program must reflect the
hydrogeological characteristics of the injection zone and
the volume and chemistry of the injection fluids. The
injection rate determines the injection pressure, which
may not exceed the maximum value for the injection
system. The maximum allowable injection pressure is
the highest pressure that:
• Preserves the integrity of the formations in the injec-
tion zone and the overlying confining zone.
• Prevents significant change in the fluid movement
capabilities of the overlying confining zone.
• Protects the mechanical integrity of the well structure.
Similarly, the permissible injection rate for a deep injec-
tion well is that which:
• Protects the mechanical integrity of the well structure.
• Preserves the integrity of the formations in the injec-
tion zone.
• Preserves the fluid movement capabilities of the in-
jection zone.
Injection Pressure and Preservation of Formation
Integrity
Safe operating pressures can be determined with cer-
tainty only by conducting fracture tests on the formations
in the injection zone. The maximum safe bottom-hole
injection pressure typically ranges from about 0.5 to 1.0
pounds per square inch (psi) per foot of well depth,
depending on the types of materials that make up the
formations and geological conditions in the open hole.
In Florida, for example, a value of 0.6 psi per foot of well
depth is typically used to calculate the maximum safe
155
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bottom-hole injection pressure for a 2,700-foot deep
injection well into a dolomitic formation. Multiplying 0.6
per foot of well depth by the well depth of 2,700 feet
yields a maximum safe bottom-hole injection pressure
of 1,620 psi.
The maximum safe well head injection pressure is the
difference between the maximum safe bottom-hole in-
jection pressure and the measured bottom-hole hydro-
static pressure. If the system in the example above
produced a bottom-hole hydrostatic pressure of 1,200
psi during pumping at a design capacity, the difference
between the maximum safe bottom-hole injection pres-
sure and the measured bottom-hole hydrostatic pres-
sure would be 420 psi (1,600 to 1,200 psi). Dividing 420
psi by a safety factor of 3.0 yields a maximum well head
injection pressure of 140 psi for the well. The safety
factor might differ from site to site because it is an
engineering designer's choice, not a regulatory require-
ment. Friction losses are then calculated for the design
flow and the diameter of the injection liner. High friction
losses are subtracted from the 140 psi to yield the
maximum safe well head injection pressure to be used
in monitoring reports.
Injection Pressure and Prevention of Fluid
Movement in the Confining Zone
Success in preventing significant change in the fluid
movement capabilities of the confining zone is some-
what difficult to evaluate due to different interpretations
of the word "significant." Analyses of cores and geo-
physical logs from the confining zone should show low
permeability values. Regardless of how small, however,
any permeability value entered into a leakage equation
will result in some leakage value. Determining what is
or is not significant leakage is subjective.
Injection into a well generates piezometric heads in all
radial directions. The amount of leakage should be cal-
culated within the area determined to be critical—usu-
ally the quarter-mile radius or area of review (AOR) from
the injection well. Beyond the 1/4-mile radius of the
AOR, the differential pressure across the confining zone
should also be calculated to determine when pressure
buildup will (at least in theory) produce leakage beyond
the AOR.
Injection Pressure and Protection of Well
Mechanical Integrity
The maximum well head injection pressure for a deep
injection well must also protect the mechanical integrity
of the well structure. In particular, it must be lower than
the bursting pressure of the steel pipe used for the inner
(injection) casing and the bursting pressure of the injec-
tion liner within the inner casing. The bursting pressure
of water filled, unsupported pipes of various diameters
and wall thicknesses is provided by the manufacturer.
Because the steel pipe is always encased in cement
grout the entire length of the well, the maximum permis-
sible pressure inside the casing, is much higherthan the
bursting pressure of the unsupported casing. As a result,
it is not usually a significant consideration in design,
construction, or operation. For the liner, the collapsible
pressure rather than the bursting pressure is more im-
portant, especially during construction. For example, an
unsupported fiberglass casing with a bursting pressure
of 600 psi might withstand only 100 psi in compression.
Thus, the use of a 600-psi injection pressure must be
weighed against the need to keep the annular pressure
below 100 psi.
The annular packer also influences mechanical integrity.
Packers should be tested to hold in tension and in
compression.
Injection Pressure Data Reporting
A data reporting program must be part of operation and
maintenance (O&M) procedures. The program should
include regular reporting of operational well head injec-
tion pressures. If at any time the injection pressures
show a rapid increase toward the maximum, measures
should be taken to alleviate an impending violation be-
fore it occurs.
If, under normal operating conditions, the well head
injection pressure suddenly starts to approach the per-
mitted maximum, the injection pumps and deep injection
well should be shut down until an emergency evaluation
can be conducted and other contingency plans put into
operation. On the other hand, if the well head injection
pressure rises result from excessive injection rates, the
injection should be throttled back immediately to a rate
that will reduce the well head injection pressure to below
the maximum.
Injection Rate and Protection of Well Structure
Due to the potential for damage, maximum injection
rates cannot be established through empirical injection
rate tests. Instead, standard practice has been to estab-
lish a maximum permissible injection velocity of 8 ft/sec,
the maximum velocity that can be expected to not create
erosion of the open hole in most formations. This rate
has been adopted as the ruling criterion for maximum
safe injection rate in some states.
The 8-ft/sec velocity limit protects the injection well from
large flow velocities that can lower fluid pressure close
to the saturated vapor pressure at the injection pump (or
at any other flow obstruction in the pipeline, such as a
sudden turn or constriction). Lowering fluid pressure
within the injection line can lead to cavitation within the
pump and the injection line, resulting in fluid flow inter-
ruptions that can damage the system. Because higher
injection rates within a well require larger injection velo-
156
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cities, maintaining lower rates minimizes the possibility
of damaging pressure reductions.
Injection Rate and Preservation of Formation
Integrity
Stable operating conditions also help protect the integ-
rity of the injection zone. Pressure fluctuations under
variable injection rates create variable stress-strain re-
lationships within formations, particularly the rock
shelves that separate the porous zones. These stresses
and strains in turn can induce rapid cyclical flexing of the
rock matrix, which can affect the rock matrix and fracture
the formations. To prevent fracturing, rapid cyclical injec-
tion should be kept to a minimum. This can be accom-
plished by using the hydropneumatic tank and pressure
and vacuum release valves discussed above.
Injection Rate and Protection of Injection Zone
Capabilities
The transmissivity of the injection zone and its ability to
receive injection fluid must also be considered. The
maximum rate of injection that can be received by the
injection zone is largely limitless as long as the well
structure and the rock matrix within the injection zone
are able to receive the fluid. Nevertheless, economic
considerations favor the use of the lowest possible in-
jection pressure, since the frictional head loss increases
exponentially with increasing flow rate.
In general, therefore, the limiting criterion for increasing
injection rate is a matter of economics and the need to
protect the well structure and injection zone. The maxi-
mum safe injection rate for a deep injection well is
determined by the most restrictive of those considera-
tions, usually the 8-ft/sec limitation on fluid velocity
within the injection pipe.
9.2.3.9 Monitoring Requirements
During the time that a deep injection well is operational,
some types of monitoring must be conducted on a regu-
lar basis and others must be carried out on an as-
needed basis.
Regular Monitoring
Regular Injection Well Monitoring. Regular monitoring of
a deep injection well consists of:
• Keeping continuous record of the variable nature of
the flow rate for each 24-hour period and recording
the daily flow volume. Data on the daily flow rate and
the total monthly flow, together with the average and
maximum daily flow and the maximum instantaneous
rate, must be reported monthly.
• Recording the variable nature of the well head injec-
tion pressures. Daily average and daily maximum
injection pressures must be recorded for each 24-
hour period and reported monthly.
• Recording the annular space pressure to show any
fluctuations with flow rate. The annular space volume
contracts and expands with injection pressure
changes as well as with the temperature changes of
the injection fluid.
• Running and reporting a specific injectivity test at
pre-approved intervals to ensure that the receiving
formations are not being affected by excessive plug-
ging or excessive dissolution.
• Monitoring the water quality of the WTP residuals in
accordance with required parameters in the regula-
tions. Water quality must be reported monthly, but is
usually reported by the plant rather than the well
operator.
A sample report format (adapted from forms used by
FDEP) is shown in Figures 9-1 through 9-5.
The injected fluid must also be tested weekly as part of
the operation of the well itself. These tests involve taking
a sufficient quantity of injection fluid from the pipeline
between the WTP and the deep injection well. For analy-
sis for TDS, total suspended solids (TSS), chloride,
sulfate, conductivity, pH, and temperature. The tempera-
ture reading and the pH must be taken immediately after
the sample has been collected. The remaining water
quality parameters may be determined later in the water
quality testing laboratory. An ongoing record of the vari-
ous parameters must be maintained.
All of the data must be kept on site and available for
inspection by regulatory authorities on request. The log
sheets must include any annotations and will constitute
the record of operation.
At the time of sample collection or sample analysis, the
following monitoring information must be provided:
• Date, exact place, and time of sampling or measure-
ments.
• Person responsible for performing the sampling or
measurements.
• Date(s) analyses were performed.
• Person responsible for performing the analyses.
• Analytical techniques or methods used.
• Results of the analyses.
Regular Monitor Well Monitoring. Monitor wells are usu-
ally used to monitor two water-producing zones above
the injection zone: one at the first permeable zone above
the injection zone and one at the first USDW above the
confining zone. As part of overall ground-water monitor-
ing, those zones must be tested on a monthly basis and
the results reported to regulatory agencies.
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MONTHLY OPERATIONAL REPORT
I. OPERATING PERIOD MONTH YEAR
II. INJECTION WELL OPERATOR
1. Name
2. Address
3. City State
5. Permit Number
III. SUMMARY OF OPERATIONAL DATA
A. Injection Volumes
1. Maximum daily volume specified in permit gal/day
2. Maximum daily volume during operating period gal/day
3. Present average daily volume gal/day
4. Total volume injected to date gal
B. Injection Rate
1. Maximum injection rate specified in permit gpm
2. Maximum injection rate during month gpm
3. Minimum operational injection rate during month gpm
4. Average injection rate during month gpm
C. Injection Pressure
1. Maximum well head injection pressure specified in permit psi
2. Maximum well head injection pressure during month psi
3. Minimum operation well head injection pressure during month psi
4. Estimated average well head injection pressure during month psi
IV. INSTRUCTIONS
A. The operator of the injection system shall furnish information on this form not later than
the 15th day of the month following the month reported.
B. Report any irregularities relative to dairy injection practices on reverse side of this page.
C. All data will be retained on site and made available upon request.
D. All operational problems and significant changes in injection systems or wastes are to be
reported when they occur.
Signed Date
Figure 9-1. Monthly operational report, page 1.
158
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MONTHLY OPERATIONAL REPORT - Page 2
1. Continuous Operating Period
Start
Date
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
lime
End
Date
Time
Length of
Operating Period
(DaysHours)
2. Injection Rate (gpm)
Maximum
Minimum
Average
3. Well Head Injection Pressure (pd)
Maximum
Minimum
Estimated
Average
4. Total Cumulative
Fluid Injected
Dally
Cumulative
Injection Rage (gpm)
Total Pressure (pslg) 1
1
SPECIFIC INJECnVTTY
Shut-In Pressure (pslg)
Date:
I Specific Pressure (pslg)
By:
Specific Injecdtdty Index
(gpm/Spedflc Pressure pslg)
gpm/pslg
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MONTHLY OPERATIONAL REPORT - Page 3
INJECTION WELL
,19
Sampled by:
1. Name.
City_
State:
2. Permit Number:
Signed:
Address:
Phone Number:.
Date:
Month
:
i .
Starting Ending
Starting Ending
Starting Ending
Starting Ending
Starting Ending
Date of
Sample
BOD
(mg/L)
Total
Dissolved
Solids
(mg/L)
Total
Suspended
Solids
(mg/L)
Chloride
(mg/L)
Sulfate
(mg/L)
Conductivity
(pmhos/cm)
Temperature
(°C)
Fecal
Coliform
(Colonies/
100 ml)
PH
(range)
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I. Operating Period:
MONTHLY OPERATIONAL REPORT - Page 4
MONITOR WELL
,19
II. Sampled by:
1.
2.
Name
Citv
Permit Number:
Signed:
Address:
State: Phone Number:
Date:
Month
:
j
Starting Ending
Starting Ending
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Starting Ending
Starting Ending
Starting Ending
Date of
Sample
Monitor
Zone
Upper
Lower
Upper
Lower
Upper
Lower
Upper
Lower
Upper
Lower
BOD
(mg/L)
Total
Dissolved
Solids
(mg/L)
Chloride
(mg/L)
Sulfate
(mg/L)
Conductivity
( |unhos/cm)
Temperature
CQ
Fecal
Colifonn
(Colonies/
100ml)
PH
(range)
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-------
Monthly monitoring of the monitor zones must include
the following steps:
• Recording the pressure or water level in each zone,
noting monthly daily highs and lows on the monthly
form.
• Collecting a monthly water quality sample from each
of the two monitor zones (every 2 weeks for the
shakedown test period).
The water quality samples collected monthly (or bi-
monthly at first) must be taken to a water quality testing
laboratory to measure IDS, chloride, sulfate, and spe-
cific conductances (conductivity). Temperature and pH
should be measured in the field immediately after sam-
ple collection. Records of monitoring information should
include:
• Date, exact place, and time of sampling or measure-
ments.
• Person responsible for performing the sampling or
measurements.
• Date(s) analyses were performed.
• Person responsible for performing the analyses.
• Analytical techniques or methods used.
• Results of the analyses.
The results from the water quality analyses must be
submitted on a monthly basis. Atypical report format is
shown in Figures 9-1 through 9-5.
Special As-Needed Monitoring
Special injection well monitoring may consist of the
following tests, either alone or in combination: mechani-
cal integrity test, pressure test, television survey, noise
and radioactive tracer test, and controlled injection test
(inject!vity test).
The mechanical integrity of a deep injection well must
be checked every 5 years via a 1-hour pressure test on
the injection casing. To perform this test, a temporary
packer must first be installed at the bottom of the injec-
tion liner. Within 3 months, the results of the pressure
test must be submitted to regulatory authorities with an
interpretative letter. Copies of the results must also be
retained at the plant office.
A television survey of the deep injection well must also
be made every 5 years. This involves running a televi-
sion camera down to the maximum depth possible
within the open hole. Within 3 months of the survey, a
copy of the videotape must be submitted with an inter-
pretative letter, and a copy of the videotape must be
retained on site. Similarly, a radioactive tracer test
and/or a noise log may also be required.
If regular monitoring records begin to indicate significant
increases in well head injection pressures over time, a
controlled injection test and/or television survey may be
required before 5 years to ascertain the probable cause.
If a sudden significant increase occurs in well head
injection pressures, regulatory agencies must be noti-
fied within 24 hours. A testing program could then be
required for the deep injection well, which would prob-
ably include a controlled injection test and a television
survey. After the results from these tests are analyzed,
an interpretative report must be submitted within 3
months. If the tests results require any work in the deep
injection well, the results of the work must also be
submitted within 3 months.
A routine injectivity test must be performed every month
during the shakedown period. Subsequently, a special
injectivity test must be performed quarterly or as
needed. For meaningful comparisons between tests,
standard test procedures must be followed exactly each
time the test is conducted. These procedures include:
• Once a month, allowing the final effluent storage tank
to fill sufficiently to allow the injection system to op-
erate at the maximum permissible injection rate.
• Measuring the shut-in pressure in the well (prior to
the start of the injectivity test).
• Connecting the injection pump directly to the injection
well (bypassing the hydropneumatic tank) and oper-
ating it at the predetermined number of revolutions
per minute that will result in the maximum permissible
injection rate.
• After 1 hour of injection at the maximum permissible
rate, recording the injection pressure at the well head.
This must be repeated again just prior to the end of
the test, at the end of the second hour.
• Arranging the two pressure readings together to de-
termine the specific injection pressure for the injec-
tion rate used.
• Reporting the specific injectivity index as the ratio of
the fixed volumetric rate to the specific pressure (the
average of the two readings). This result is the spe-
cific injectivity index (in gallons per minute/specific
pressure).
• Preparing a running chart by plotting the locations of
the monthly results. In the chart, the x and y coordi-
nates represent the volumetric rates and their pres-
sures, respectively.
Sampling Procedures
Water quality monitoring of desalination plant residuals
is discussed in Section 10.3.3.1. Sampling procedures
for the deep monitor well require samples to be collected
163
-------
after the system has been properly evacuated. The
methodology must be customized for each well.
Shutdown and Startup Procedures
Normal Operation. Once put into operation, injection
wells operate automatically without the need to open or
close any valves. The air release and vacuum release
valves on the well head are the only valves that open
and close with any regularity, and they do so automat-
ically. Moreover, the hydropneumatic tank acts as a
buffer and creates redundancy so that even the auto-
matically operated air and vacuum release valves need
not be controlled in any way. In fact, the control valves
to the air release and vacuum release valves should
always be in the open position whether or not the well
is in operation. The valve that connects the release
valves to the well should always be open as well.
Startup. Before the well is put into operation and when
it is shut down, all of the valves should be closed. Once
the injection pump is turned on, the master valve (a
slow-closing butterfly valve that connects the well to the
plant) should be opened within 30 seconds to prevent
buildup of pressure in case the hydropneumatic tank is
bypassed. If the hydropneumatic tank is not bypassed,
the capacity available in the tank reduces the need to
open the master valve immediately. Even then, however,
the master valve must be opened before the hydropneu-
matic tank fills (within 1 to 2 minutes).
Shutdown. Shutting down the well is a straightforward
operation, requiring only that the master valve be closed.
If the shutdown is temporary, other valves may be left
open. If the shutdown is long-term, all valves except the
vacuum and pressure valves should also be closed.
Attaching a lockable chain to all valves to prevent tam-
pering is strongly recommended. Alternatively, the valve
handles can be removed. The master valve should also
be specially protected by a chain lock or by removing its
handwheel. Valves used for water sampling should be
shut down at all times except while sampling. The han-
dles should be removed when not in use to prevent un-
authorized opening, which would waste the annular fluid.
Schedules and Procedures for Calibration and
Operation of Pumps and Monitoring Equipment
Calibration procedures depend primarily on the types of
equipment used and the manufacturers' recommenda-
tions. Each equipment manufacturer has specific proce-
dures that are documented in reference manuals; these
should be followed. Single copies of these manuals are
provided by the manufacturer through the contractor
and are to be retained on site at all times.
9.2.3.10 Data Reporting
Data reporting requirements for a deep injection well
include:
• Regular monthly operational reports
- Pressures and volumes (injection well)
- Water quality (injection well)
- Water quality (upper and lower monitor zones)
- Pressures (upper and lower monitor zones)
• Special interpretative reports
• Noncompliance reports
Regular Monthly Operational Reports
Operational reports for each calendar month should be
submitted no later than the 15th day of the following
month or according to permit requirements.
Pressures and volumes (Injection well). This part of the
monthly report (see Figures 9-1 and 9-2) follows the
EPA-suggested reporting format for injection wells.
Page 1 of the monthly operational report contains four
sections. Sections I and II are self-explanatory. Section
III details restrictions on the maximum daily injection
volume, maximum injection rate, and maximum well
head injection pressure. The maximum and average
daily injection volumes and the cumulative total volume
forthe month are recorded in Section III-A. Sections III-B
and III-C are used to record the maximum, average, and
minimum injection rates and the well head injection
pressures for the month. Section IV contains instruc-
tions for filling out the report.
The maximum daily injection volume during the operat-
ing period is the largest of the average daily injection
volumes calculated for each of the operating periods
during the month. The present average daily volume for
the month is the total volume injected for the month
divided by the sum of the lengths of the operating peri-
ods during that month. The total volume injected to date
is taken directly at the end of the month from the daily
volumes recorded.
The maximum injection rate during the month is the
largest of the daily maximum injection rates. The mini-
mum operational injection rate is the lowest of the daily
minima. The average injection rate during the month is
equivalent to the present average daily volume recorded
in Section lll-A-3, except for a time that includes only the
length of actual injection.
The maximum well head injection pressure during the
month is the largest of the daily maxima. The minimum
operational well head injection pressure is the lowest of
the daily minima. The estimated average well head in-
jection pressure during the month must be estimated for
each operating period from the daily values. The time-
164
-------
weighted average is calculated from the various esti-
mated average well head injection pressures for the
month.
Column 1 on page 2 is used to record the start, end, and
length of each operating period during the month. The
maximum and minimum injection rates must be read
each day and recorded in Column 2. The average injec-
tion rate is calculated from the daily total flow at the end
of each day, dividing the difference by the duration of
operation that day. Both the maximum and minimum
well head injection pressures are recorded each day in
Column 3. The average daily well head injection pres-
sure is also estimated each day and recorded in Column
3. The total volumes are recorded at the end of each day
whenever operating periods exceed 1 day. If the opera-
tional period is less than a day, the flow at the end of the
period is recorded.
Water quality (Injection well). Page 3 of the monthly
report (see Figure 9-3) is used to list the laboratory
results of tests performed on samples of the injection
fluid after it has passed through the desalination treat-
ment plant (just prior to injection). The report form pro-
vides space for recording the results of the tests
recommended for inclusion in the monitoring program.
The water quality samples should be sent to a certified
water quality testing laboratory, which will return the test
results to the operator for inclusion in the monthly op-
erational report.
Water quality (Upper and lower monitor zones). Page 4
of the monthly operational report (see Figure 9-4) in-
cludes data from both the upper and lower monitor
zones. It covers the range of parameters described
earlier in this chapter. Data analysis must be performed
by a certified laboratory.
Pressures (Upper and lower monitor zones). Page 5 of
the monthly operational report (see Figure 9-5) should
be filled in whenever water level measurements are
taken. Water level data for both monitor zones should
be recorded daily. The water level of the lower monitor
zone can be measured by taping down to the water
surface and recording the distance (as depth to water,
in feet) below the measuring point (MP). Alternatively, a
calibrated recording bubbler system installed on the well
can be used as long as the calibration holds true. The
water level for the upper monitor zone can be read
directly from the gauge or recorder.
Interpretative Reports
Interpretative reports are usually submitted following
any type of special monitoring. These reports typically
consist of letters; the specific format depends on the
nature of the special monitoring. Interpretive reports are
usually developed by the engineering consultants forthe
WTP and are submitted within 3 months of completion
of the special monitoring.
Noncompliance Reports
Noncompliance reports are required in the case of ab-
normal events (e.g., equipment breakdown, power fail-
ure, clogging of the well, etc.). In such cases, a verbal
report must be made within 24 hours, a preliminary
written report must be submitted within 3 days, and a
comprehensive written report must be submitted within
2 weeks. These reports must describe the nature and
cause of the event, the period of noncompliance (dates
and times), steps taken to correct the problem and to
prevent its recurrence, emergency procedures in use
pending correction of the problem, and the estimated
date by which the facility will again be functioning in
accordance with permit conditions.
If the deep injection well is abandoned, the owner and/or
operator must provide adequate documentation indicat-
ing that the well was properly abandoned. The docu-
mentation must describe the method of abandonment
and evaluate the results of the operation.
9.2.3.11 Stimulation Program
An injection zone intersected by the open hole of a
properly operating deep injection well derives its ability
to receive injection fluids from natural cavities in the rock
matrix and from larger interstices. These cavities are
relatively large and numerous and are not usually sus-
ceptible to clogging, unlike the smaller cavities within the
rock matrix itself. Therefore, an injection zone is not
considered to be susceptible to any serious clogging
effects, although it is possible that injectivity will de-
crease over time. Observing the restrictions that apply
to the quality and composition of the injection fluid will
reduce the chance of clogging and maintain the high
injectivity essential to successful operation of the well.
Federal regulations require that a stimulation program
be available in case it is needed. If the deep injection
well becomes clogged or plugged and thus becomes
less receptive to the injection fluid, it may be necessary
to enact a well stimulation program. Unless the cause
of the reduced intake is already known, the well operator
might also be asked to conduct a special monitoring
program. An interpretative report on the deep injection
well must then be submitted, discussing the problem
and reporting on the special monitoring program. The
report should recommend corrective actions (including
a stimulation program for the deep injection well) to
rehabilitate the well.
A well stimulation program may include surging, acidiz-
ing, or a combination of both. Other stimulation tech-
niques (shooting, hydraulic featuring, and vibratory
explosions) are used primarily within the petroleum in-
165
-------
dustry, are controversial, and are only recommended as
a last resort.
Surging to stimulate the deep injection well involves use
of a pump that can inject water into or discharge water
from the well at continuously fluctuating rates. This ac-
tion is designed to loosen any matter that might be
clogging the rock openings. Well acidization is designed
to chemically break down any matter clogging the rock
pores, thereby improving flow movement through the
injection zone. The acid used in this procedure should
be 18°Baume (27.92 percent) hydrochloric (muriatic)
acid. The acid should contain a nontoxic stabilizer to
prevent after-precipitation of dissolved minerals and a
nontoxic inhibitorto prevent corrosion of well head com-
ponents. Use of the stabilizing and inhibiting chemical
agents must first be discussed with the appropriate
regulatory agencies.
The procedure used for acid treatment is subject to
regulatory approval. The two most common methods are:
• Method 1: Full strength acid is introduced to the well
by means of a 3/4- or 1-inch diameter drop pipe. The
acid must not be introduced by pouring it from the
top of the well casing. The drop pipe must be black
iron or plastic pipe, not galvanized pipe. Overflows
and vents required for safety must be provided. The
acid is introduced to the well starting from the bottom
of the open hole. The drop pipe is gradually retracted
during filling operations to ensure that equal concen-
trations of acid are present in the entire length of
open hole. The quantity of acid used should be 1-1/2
to 2 times the volume of water in the open hole
section of the well. At no time during the acidizing
process should the pH of the well contents be allowed
to rise above 2.0. Additional acid is introduced to the
well as required to ensure that the pH remains below
2.0 for the duration of treatment. After introducing the
acid to the well, the acid should begin being agitated
as soon as possible. Agitation can be accomplished
by surge block bailers or by any other appropriate
means available. The acid should be agitated for 3
to 4 hours. Following acid treatment, the well should
be pumped clear of all sediment until the water is free
of discoloration and the pH level returns to normal
(between 6.0 and 8.0). Pumped out waste should be
discharged to the plant.
• Method 2: If pressure acidizing is used instead, pres-
sure control is provided by a sealing arrangement
between the well casing and the acid drop pipe. The
seal must be capable of maintaining a minimum op-
erating pressure of 100 psig in the well. The sealing
arrangement should include the pressure gauges and
valves needed to accurately determine the gauge
pressure in the well and to ensure that acid and air
can be introduced into or vented from the well. Pres-
sure should be maintained at 75 to 100 psig for a
minimum of 2 hours. Following pressure acidization,
the waste valve should be opened and the well
pumped at a rate to produce substantial drawdown
to clear the well of all sediment until the water is free
of discoloration and the pH level returns to normal
(between 6.0 and 8.0). Discharge should be to the
plant. Following the initial acid treatment, a second
acid treatment might be required to further increase
the well yield.
The second method is generally used only if the clog-
ging is so extensive that high pressures can be main-
tained in the injection zone during acid application.
The results of a stimulation program must be tested by
a special monitoring program. Both the stimulation pro-
gram and the special monitoring program should then
be fully described and analyzed in an interpretative
report submitted to regulatory agencies.
9.2.3.12 Costs for Concentrate Disposal
The estimated cost of deep well disposal (cost per gallon
of membrane treatment plant capacity) is shown in Table
9-3. The actual cost of well construction is shown in
Figure 9-6. Well construction costs depend primarily on
well depth and diameter. Nevertheless, the injection
liner material and the manner of liner installation can
cause the cost of a typical well to vary by as much as
$50,000.
Table 9-3. Concentrate Disposal Costs
Deep Well O&M
Disposal Capital Engineering Land Cost
Facility Cost Cost ($ per Requirements ($/1,000
(mgd) ($/gallon) gallon) (acre) gallons)
3
5
10
15
20
$0.58
$0.44
$0.40
$0.37
$0.30
$0.087
$0.066
$0.060
$0.056
$0.045
0.5
0.5
1.0
2.0
3.0
$0.032
$0.024
$0.022
$0.02
$0.016
In addition to the O&M costs shown in Table 9-3, a
recurring cost is associated with the mechanical integrity
test that must be conducted every 5 years. Contractor
costs for this test usually range between $70,000 and
$90,000; engineering fees add another $50,000 to
$60,000. Permit renewal fees can also be high. In Flor-
ida, the fee for renewal of a Class I well permit is
$10,000.
9.2.4 Boreholes
Drainfields and boreholes can be used with regulatory
approval when the concentrate water quality meets the
regulatory requirements for discharge into surficial
ground-water aquifers and when soil conditions and
166
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1,000
2,000
Depth, in feet
3,000
Figure 9-6. Well drilling cost.
permeability of rock strata permit. In Florida, this occurs
in coastal areas where ground-water quality exceeds
10,000 mg/LTDS and USDW regulatory parameters are
not exceeded. Surficial aquifer discharge of brine from
coastal seawater RO plants that use shallow boreholes
or seawells (where the ground water is very brackish)
can be more cost-effective and environmentally palat-
able than an ocean outfall.
9.2.5 Spray Irrigation
In general, spray irrigation is viable only if the following
conditions are met:
• The IDS, chloride content, or salinity of the concen-
trate or the mixture of concentrate and a blend liquid
do not exceed a level that will damage the grass or
crop being irrigated.
• There is a requirement for irrigation water in the vi-
cinity of the WTP to avoid a long conveyance system.
• A backup disposal system (e.g., storage for use dur-
ing sustained periods of rainfall, when irrigation is not
needed) is available.
• The water quality of the surficial ground water is pro-
tected from degradation.
• Local, state, and federal regulations are met.
• A system of monitoring wells is in place to check
overall irrigation system performance. A monitoring
plan is generally a prerequisite to obtaining an oper-
ating permit.
If these conditions can be satisfied, spray irrigation can
be an attractive option because it is economical, pro-
vides an appropriate source of irrigation water, and con-
serves natural resources.
Major variables affecting the cost of spray irrigation
include land, concentrate conveyance systems to the
disposal site, and site developments (e.g., relocation,
land preparation, surface runoff control, subsurface
drainage, distribution and irrigation, storage require-
ments, and pretreatment).
Spray irrigation of concentrates almost always requires
dilution prior to irrigation to prevent pollution or degra-
dation of ground-water resources while meeting regula-
tory requirements. Dilution also reduces the chloride
167
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content to acceptable levels to prevent damage to the
grass or crops being irrigated.
Disposal of concentrates by spray irrigation is being
proposed for several very large systems currently being
designed. Recently, a sprayfield demonstration program
in Boynton Beach, Florida, was funded jointly by the
South Florida Water Management District and the City
of Boynton Beach. The primary purpose of the demon-
stration program was to better manage water resources
by using a product ordinarily disposed of as waste.
Years after the permitting for the Boynton Beach con-
centrate disposal was finalized, deep well injection was
chosen as the disposal method.
9.3 Nonconventional Methods of
Concentrate Disposal
9.3.1 Evaporation and Crystallization of
Brines for Zero Discharge
9.3.1.1 Brine Characteristics
Achieving a zero liquid discharge at any desalination
facility almost always requires some type of evaporation
and crystallization process. Evaporation is differentiated
from crystallization only in that crystallization usually
involves the development and processing of slurries,
while evaporation refers mostly to liquid solutions. Tech-
niques for handling high-density slurries are quite differ-
ent from those for liquids, however, and are always more
expensive per gallon of water evaporated. Figure 9-7
shows a basic zero discharge flow sheet.
Brines from desalination operations generally become
wastewater because they cannot be concentrated fur-
ther in membrane systems due to a high TDS content
or the presence of scale-forming materials. Calcium
sulfate and silica are the usual scaling components,
ZERO D SCHARGE
BRINE CONCENTRATOR
CRYSTALL IZES
RECOVERED WATER
SOL I DS
Figure 9-7. Zero discharge.
although the barium and strontium sulfates can also
contribute to scaling. Fortunately, techniques for dealing
with scale-forming materials have been developed for
use with both evaporators and crystal I izers.
Control of scaling is generally accomplished through
"seeding." Both evaporators and crystallizers use the
same fundamental approach, but the concentrations of
solid particles differ greatly. In either case, sufficient
crystals, or "seed slurry," are maintained in suspension
to provide enough crystalline surface area to effectively
allow most or all of the precipitation to occur on existing
crystals ratherthan on the heat exchange surfaces. This
is a simplistic explanation, but it is correct in concept and
will help guide the process designer in developing work-
able zero discharge systems.
Just as TDS limit the operation of membrane systems,
they can limit the operation of evaporators and brine
concentrators. Crystallizers can process streams with
virtually any TDS level, even up to the point at which the
circulating stream is more a melt than a solution. As an
example, crystallizers are often used to concentrate
sodium hydroxide to 50 percent by weight or higher
(dissolved) while crystallizing sodium chloride from the
liquor.
9.3.1.2 The Brine Concentrator
The workhorse of the zero discharge plant, the brine
concentrator is most often designed as a vertical tube
or falling film evaporator, although horizontal spray film
and plate type evaporators are also used in this appli-
cation. Various manufacturers provide brine concentra-
tors; currently, most are used in the electric utility
industry. These units concentrate cooling tower blow-
down and other wastes to about 20 percent total solids,
which are then processed further to a solid waste in
either solar ponds or a crystallizer. The first brine con-
centrators entered commercial service at coal-fired utili-
ties in the mid-1970s, and some of these units are still
in service today.
The common characteristic of most brine concentrator
designs is the circulation of a slurry of calcium sulfate
crystals, which act as seeds. Calcium sulfate and other
scale-forming compounds preferentially precipitate on
the circulating seed crystals (ratherthan the heat trans-
fer surfaces), preventing scaling. The development of
the seeding technique for calcium sulfate and silica
allowed brine concentrators to process wastewaters at
or near saturation in calcium sulfate and silica to very
high concentrations. Up to 20 percent total solids by
weight is often achievable in the brine concentrator
discharge, while a distillate of more than 10 parts per
million (ppm) TDS can be returned to the power station
for use as boiler makeup. Figure 9-8 shows the typical
components of a brine concentrator. Because most
brine concentrators are powered using a mechanical
168
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VENT
BRINE
CONCENTRATOR
ACID
BRINE FEED FE5D
TANK PUMP
RECOVERED WATES
RECIRCULATION
PUMP
Figure 9-8. Brine concentrator system (HPD, 1994).
vapor recompression (MVR) cycle, the system shown in
Figure 9-8 includes a compressor. Direct steam power
could be used, but the cost of steam energy almost
always exceeds that of MVR, except in special situ-
ations.
MVR evaporators or, more simply, vapor compression
(VC), use a compressor to raise the condensing tem-
perature and pressure of the evaporated water suffi-
ciently to reuse the vapor as the primary heat source for
evaporation. In this manner, the heat of vaporization in
the evaporated water is recovered immediately in the
evaporation of more process water. In a typical steam
driven system, the heat of vaporization in the evapo-
rated water is simply lost to the final condenser. At best,
only a portion of the heat is recovered in a multiple-effect
evaporation system.
In MVR evaporators, the compressor draws suction
from the evaporating water in the vapor body of the
evaporator. The condensing temperature and pressure
are raised in the compressor 10° to 15°F above the
boiling temperature in the evaporator. The now higher
temperature vapor is then fed to the outside of the heat
transfer tubes, where it gives up heat and condenses.
More water evaporates inside the tubes, which is in turn
recompressed, and so on. The steam is reused without
first condensing it.
MVR systems can achieve very high thermal efficiencies
compared to steam driven systems. MVR brine concen-
trators require evaporation energy that, if converted to
steam, is equivalent to 1 pound of steam evaporating
over 28 pounds of water; for example, only 35 British
thermal units (BTUs) are required to evaporate 1 pound
of water.1 A single-effect evaporator, in contrast, requires
1 pound of steam per pound (or less) of water. In terms
of energy consumption, MVR is at least 28 times more
efficient than a single-effect steam driven evaporator.
Representative brine concentrator process conditions
for zero discharge applications are listed in Table 9-4.
These conditions are shown as ranges and should be
used as guidelines. Many factors affect the operating
limits of brine concentrators, but a few are important for
planners of zero discharge systems.
Crystallizers are much more expensive to build and
operate than evaporators or brine concentrators. Be-
cause of this great cost differential, operating a mem-
brane system at its limits of concentration might become
counterproductive in some instances. If the membrane
system waste brine is too highly concentrated, a brine
concentrator might be unusable (see Table 9-5), and a
much larger crystallizer will be required to reach zero
discharge. The upper limit for feed concentration into a
brine concentrator is determined by the need to keep
enough seed material in suspension to prevent scaling
as well as by the solubility of the more soluble salts. This
usually occurs with a feed TDS of somewhere between
Table 9-4. Typical Brine Concentrator Process Conditions in
Zero Discharge Applications
Feed TDS
Feed temperature
Preheater approach temperature
Concentration factor
Seed slurry concentration
Boiling point rise
Compression ratio
Recirculation pump rate
TDS of waste brine, weight %
Total solids waste brine
Overall power/1,000 ga
Distillate TDS
2,000-20,000 ppm
40-120°F
7-15°F
8-120
1-10%
1-10°F
1.20-2.0
20-40x feed
15-22%
15-30%
175-110 kWh
5-25 ppm
Table 9-5. Effect of Concentration Factor (CF) on Calcium
Sulfate Seed Concentrations3
1 During operation, 85 kilowatt-hours (kWh)/1,000 gallons (gal) evapo-
rated is routinely obtained; 85 x kWh 3,418 BTU/kWh/(1,000 gal x
8.3 Ib/gal) = 35 BTU/lb.
Ion/Species
Calcium
Sodium
Chloride
Sulfate
TDS
Total solids
Suspended solids
(calcium sulfate)
Feed
400
1,100
550
2,500
4,550
4,550
5 CF
2,000
5,500
2,750
12,500
17,510
22,750
5,240
10 CF
4,000
11,000
5,550
25,000
33,460
45,500
1 2,040
20 CF
8,000
22,000
11,000
50,000
65,360
91,000
25,640
50 CF
20,000
55,000
27,500
125,000
161,060
227,500
66,440
a All values in ppm.
169
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25,000 and 40,000 ppm, a range easily reached with
membranes.
Boiling point elevation (BPE), which increases with con-
centration, also limits the economical concentration fac-
tor. The BPE is the difference in boiling temperature at
constant pressure between pure water and a solution.
In an MVR system, the compressor must first overcome
the BPE before any evaporative energy can be recov-
ered. Typical commercial systems operate with BPEs
ranging from 1.0° to 4.0°F. Above about 5° to 7°F, energy
requirements begin to rise significantly.
Seeding
A brine concentrator cannot concentrate into the precipi-
tation region of soluble salts such as sodium sulfate,
sodium chloride, or the mixed salt glauberite,
CaNa2(SO4)2. This upper limit of concentration is typi-
cally reached with brackish waters at the 20- to 25-per-
cent TDS level. Because most brine concentrators must
be seeded to prevent scaling, however, sufficient seed
material must be maintained in suspension in the sys-
tem. The seed material most often used is calcium
sulfate because it is the primary scaling component of
most brackish wastewaters and is, therefore, usually
present.
If insufficient seed is maintained in suspension, scaling
of the heat transfer surfaces promptly results due to the
deposition of calcium sulfate, silica, or both. Scale re-
moval is expensive and time-consuming, and generally
cannot be tolerated on a regular basis. Operating expe-
rience has shown that calcium sulfate seed crystals can
effectively seed for themselves, for other sulfates such
as barium and strontium, and for silica. In most applica-
tions, the seed material is formed in situ from dissolved
calcium sulfate present in the feedwater.2
To precipitate most of the calcium sulfate and maintain
a useful seed concentration in the brine concentrator,
the feedwater must be concentrated many times. As a
practical minimum, the operating brine concentrator
must maintain a seed suspended solids concentration
of at least 1 to 1.5 percent by weight calcium sulfate or
10,000 to 15,000 ppm suspended solids. With a feed
completely saturated in calcium sulfate, the minimum
concentration factor that will result in enough seed ma-
terial, even with a seed recovery system, is about eight
concentrations, or 87.5 percent water recovery. Fifteen
or more concentrations are preferred, but operation at
eight concentration factors is possible if a seed recovery
system is used.
The seed recovery system recoups seed material in the
discharge from the brine concentrator and recycles the
naturally produced seed material. The apparatus gener-
2 At startup, of course, calcium sulfate is added directly to the brine
concentrator to form the initial charge of seed material.
ally consists of a hydrocyclone bank or settling tank that
recovers suspended solids from the waste brine blow-
down and recycles them back into the system. For
example, consider a feedwater with the characteristics
shown in Table 9-5, where calcium sulfate is close to
saturation. The data in Table 9-5 show the effect of
concentrating the feedwater to various degrees on sus-
pended solids and TDS. Even with a feedwater near
saturation with calcium sulfate, 20 concentration factors
(20 CF) are needed to reach 2.5 percent or 25,000 ppm
seed concentration in the evaporator if no seed recycle
is used.
This example illustrates why it is necessary to achieve
the maximum cycles of concentration in the brine con-
centrator. Because the brine concentrator is practically
limited to a maximum TDS of about 200,000 ppm and
needs at least ten concentration factors to reach mod-
erate seed concentrations, the upper feed TDS limit for
a brine concentrator is in the range of 25,000 to 40,000
ppm TDS. For example, concentrating a feedwater of
25,000 ppm for eight cycles will result in total solids of
200,000 ppm, near the maximum. With a 35,000-ppm
feedwater, eight cycles results in 280,000 ppm, beyond
the limit of most brine concentrators. Yet eight cycles are
required to develop sufficient seed material to prevent
scaling without an external supply of seed. Thus, a
feedwater with 35,000 ppm TDS may be a candidate for
a crystallizer rather than a brine concentrator.
When silica is the primary scaling component, or when
calcium sulfate is not near saturation, addition of exoge-
nous calcium sulfate might be required. This can be
accomplished by adding calcium chloride and sodium
sulfate orsulfuricacid and lime. Conceivably, anhydrous
calcium sulfate could be added directly to the evapora-
tor, although this has not been done commercially.
Another reason to design brine concentrators at the
maximum concentration factor obtainable is that sensi-
ble heat loss in the concentrated waste discharge
stream becomes a consideration as recovery de-
creases. Waste is hot and filled with slurry, making
conventional heat exchangers difficult to operate. The
additional cost required to recover the heat in the waste
is usually not worth the cost of providing a larger com-
pressor and accepting the energy loss penalty. At a high
discharge rate (e.g., a waste flow equal to 20 percent of
the feed flow), however, the compressor can have diffi-
culty making up the heat loss, and makeup steam might
be required.
In summary, brine concentrator designs with greater
than 87.5 percent recovery (8 concentration factors) can
usually be made to function in the normal operating
range. Below 87.5 percent recovery, special considera-
tions are required to maintain both proper seeding and
a balanced heat input.
170
-------
Design Considerations: Major Components
As shown in Figure 9-9, the main components of a brine
concentrator are:
• Distillate heat feed heat exchanger: Usually a tita-
nium plate type heat exchanger, this recovers heat
from the hot distillate into the feedwater. Typical ap-
proach temperature for the feedwater is 10°F below
the boiling point.
• Deaerator: Feedwater deaeration is required to pre-
vent calcium carbonate scaling, to eliminate noncon-
densible gases that would interfere with heat transfer,
and to remove dissolved oxygen for corrosion control.
Ordinarily, the deaerator is a packed column (316L
shell and internals, ceramic or 316L packing) with
steam supplied from a hot distillate flash tank or a
compressor bleed stream.
• Main heater: Wastewater is inside the tubes, and
steam is outside. A falling film vertical tube unit is
shown. Typically, 2-inch outside diameter tubes are
used. Vertical lengths range from 30 to 55 ft. Tube
material is usually titanium grade 2, with a 0.028- to
0.035-inch wall. Noncondensible venting occurs at
approximately 1 to 3 percent of steam flow. Design
heat transfer coefficients range from 400 to 600
BTU/hr/ft2/°F for vertical tubes. Horizontal tube units
are usually operated with the wastewater sprayed on
the outside of the tubes. Typical tube diameter is 1 inch.
• Vapor body: The main vessel holding the circulating
waste water also provides disengagement of steam
from the liquid. The vapor body can be integral with
the heater or a separate vessel. Typical volumes
based on feed retention time range from 30 to 60
minutes of feed flow. The vapor disengagement area
usually sets the minimum diameter of the vapor body.
Materials used depend on the equilibrium concentra-
tions of chloride and magnesium; 316L and 317L
have been used with success in relatively low chlo-
ride applications with very good deaeration. Inconel
625 and SMO 254 or equivalent alloys have seen
more use since the late 1980s.
• Demisters/Entrainment separators: Mesh pads or
chevron-style entrainment separators are used to
clean the vapor stream of entrained droplets of very
salty water. Correct design is very important in MVR
applications to prevent corrosion and buildup in the
compressor. Entrainment separators can be external
to the vapor body and used with vapor scrubbers if
very high purity distillate is required. Chevrons and
mesh pads are usually fabricated in the same mate-
rial as the vapor body.
• Recirculation pump: Circulation of the concentrated
waste stream through the tubes is required. Typical
circulation rates in brine concentrators are 20 to 40
times the evaporation rate.
• Compressors: With low BPEs (e.g., below 4° to 5°F),
single-stage centrifugal compressors are widely
used. Typical compression ratios for single-stage
units are 1.2 to 1.4. For higher BPEs, lobe-type com-
pressors or multiple-stage centrifugals are needed.
Compressors as large as 5,000 horsepower have
been used in MVR installations. Guidevanes or vari-
able speed motors are required to provide efficient
operation over a wide range of inlet flow rates. Com-
100
WASTE BRINE CONCENTRATOR
Capital & Operating Costs
150
200
250 300
FLOW - GPM
350
400
Operating Costs
Capital Costs
450
Power: JO.DAS/lowh
Operating Labor: S20.00/hr
Capita! Recovery: 10!t/yr
Walir Ricovvy: 98X
Powsr: 85 lcwh/1000 ;d
H2SO*: 75 ppm
V)
O
O
Q.
D
O
CO
_c
-------
pressor wheels are fabricated in stainless steel or
cast iron. Housings are typically cast iron. Good en-
trainment separation is critical to prevent corrosion
and/or wheel buildup.
• pH control: pH adjustment is usually needed to con-
vert carbonate and bicarbonate in the feedwater to
carbon dioxide before removal in the deaerator.
• Scale control: Scale control compounds are injected
just before the feedwater preheater. This delays the
precipitation of calcium sulfate at the higher tempera-
tures found in the preheater and the deaerator.
• Startup boiler: In an MVR system, it is necessary to
raise the circulating water temperature to near the
boiling point before engaging the compressor. The
required startup steam is furnished by the plant or by
a small electrically fired startup boiler. For example,
with a 200-gallon per minute system, a 200 kw
startup boiler could bring the system to operating
temperature in 10 to 15 hours.
Design Considerations: Process
For the desalting engineer, the most important process
consideration is a system design that delivers feedwater
within the known operating constraints of the brine con-
centrator system. This typically requires:
• A calcium sulfate concentration greater than 50 per-
cent of saturation in feedwater. This assures that
enough will be available to produce seed crystals.
With less than 50 percent of saturation (about 750
ppm calcium sulfate) and less than 15 concentration
factors, external seed supplies may be necessary.
• A TDS level low enough to permit high concentration
factors in the brine concentrator without precipitation
of soluble salts. Eight to 10 concentration factors are
the minimum required for normal operation.
Volatile components of the feedwater will distill over in
the brine concentrator and contaminate the recovered
water. Typical volatile components encountered include:
• Ammonia: Carryover is a function of pH, but even at
pH 6 to 7, ammonia can be found in the distillate.
• Boron/Boric acid: Boron carries over less than am-
monia and is less sensitive to pH conditions.
• Organic acids: These are highly sensitive to pH and
species. Higher pH results in less carryover as the
ionized forms dominate.
• Trihalomethanes, etc.: The degree of carryover must
be determined by laboratory or pilot testing.
• Hydrogen sulfide: Carryover is a function of pH. Oxi-
dation to sulfate might be necessary.
Capital and Operating Costs
The graphs shown in Figures 9-9 and 9-10 provide a
rough estimate of the capital and operating costs of
typical brine concentrator systems. For smaller systems
below 100-gallons per minute capacity, the equipment
is generally skidded. Larger systems require some field
fabrication of the vapor bodies and assembly of the
structural steel. The costs shown in the graphs are
based on installed outdoor systems with foundations.
Control rooms are assumed to be located within the
central plant facilities.
9.3.1.3 Waste Crystallizers
Crystallization technology for zero discharge grew out of
the chemical process industries. It was extended to the
nuclear power industry with the development of mixed
salt waste crystallizers for ion exchange regeneration
wastes. There it was necessary to produce a nearly dry
solid from the low-level wastes. The forced circulation
crystallizer has now become the primary tool for produc-
tion of dry or nearly dry waste salts for zero discharge.
A basic waste crystallizer flow scheme is shown in Fig-
ure 9-11. In this illustration, an MVR cycle is shown, but
steam can be used instead. Figure 9-12 shows a sim-
plified steam system with a barometric condenser. Be-
cause the crystallizer circulates a slurry, some method
of dewatering is required. The drawings show a centri-
fuge, but a filter press, rotary filter, or belt filter could also
be used.
Crystallizers do not have the same feed supply limita-
tions as brine concentrators; streams with widely vary-
ing composition can be effectively processed. Because
the crystallizer does not generate a liquid blowdown,
concentration factor is not the appropriate term to de-
scribe system operation. The crystallizer simply evapo-
rates water, leaving a circulating crystal slurry. The slurry
is dewatered at a rate that maintains a slurry concentra-
tion in the crystallizer of about 25 percent suspended
solids by weight. The TDS level eventually reaches an
equilibrium point, determined largely by the exact com-
position of the feed stream.
Residual water is entrained in the dewatered crystals,
but the amount is small compared to the inlet flow.
Centrifuges produce solids with 10 to 20 percent en-
trained liquid, while filters typically leave 40 to 50 per-
cent entrained liquid with the solids. The entrained liquid
can be as high as 50 percent TDS; thus, in many appli-
cations, the hot crystals can absorb all the residual water
into water of hydration, leaving a dry-to-the-touch solid
at room temperature. For example, sodium sulfate ex-
ists as the anhydrous form at typical atmospheric boiling
temperatures, yet forms the decahydrate (Na2SO4-
10H2O) at room temperature, absorbing more than its
weight in water.
172
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Table 9-6. Typical Brine Crystallizer Process Conditions
WASTE BRINE CONCENTRATOR
Operating Costs - 200 gpm feed rate
H2S04
CLEANING CHEMICALS, 1 TIME/YR
SCALE INHIBITOR ®5 PPM
PUMPING ENERGY © $0.0 4.5/KWH
OPERATING LABOR 9$20/HR
MAINTENANCE @3% OF CAPITAL/YR
COMPRESSOR ENERGY @ $0.045/KWH
CAPITAL RECOVERY @IO%/YR
TOTAL
2 4 z a
Operating Cost - $/1000 gallons
10
12
Figure 9-10. Brine concentrator cost components.
Design Considerations: Process
Typical operating conditions for a forced-circulation
waste crystallizer are shown in Table 9-6. With regard to
the feed stream, all of the dissolved and suspended
material will remain in the solids. The overall system
concentration factorforthe desalting process, brine con-
centrator, and crystallizer can be very high. In some
applications, it may be possible to concentrate relatively
low levels of metals or other components in the feed to
levels that create a concern. As in a brine concentrator,
volatile materials will transfer to the distillate.
Steam is generally required if the waste solution has a
high percentage of magnesium chloride or nitrates.
These compounds are highly soluble and exhibit high
BPEs. At equilibrium, the solution boiling point might
Feed IDS
Feed temperature
Concentration factor
Boiling point rise
Compression ratio (MVR)
Recirculation pumping rate
Solids, % free liquid hot
Solids, % free liquid cool
kWh/1,000 gal (MVR)
BTU/1,000 gal (steam)
kWh/1,000 gal (steam)
Cooling water (steam)
Distillate IDS
>20,000 ppm
40-220°F
N/A
1-50°F
2.0-3.0
>200x feed
15-50%
0-10%
150-200 kWh
10 mm BTU
2-4 kWh
50x feed
15-50 ppm
well exceed the compression ratio available in typical
MVR systems. Steam at 25 to 30 psig or higher will be
needed. A condensing water supply equal to about 40
to 50 times the crystallizer feed rate will also be required.
In many cases, it should be possible to use the brine
concentrator and the membrane system product water
to condense the crystallizer vapors in a direct contact or
barometric condenser.
By necessity, the MVR waste crystallizer will require a
high lift compressor. A multistage or positive displace-
ment compressor will also be required. Above a com-
pression ratio of about 2.0 to 3.0, steam begins to be
favored from an economic viewpoint in almost all cases.
HEATER
VAPOR BODY
SEPARATOR
COMPRESSOR
STEAM
FEED STORAGE
TANK
Figure 9-11. Waste crystallizer system (HPD, 1994).
173
-------
Cooling
Water
Steam Driven Forced Circulation Crystallizer
Entrainment
Separator
Barometric
Condenser
Main Heater
(Two Pass)
RecircJ
Pump'
Solids Recovery
Hot Well
Figure 9-12. Steam driven circulation crystallizer.
Because the waste crystallizer usually has a relatively
small capacity, steam might be preferred for simplicity of
control and maintenance, even in cases with low BPEs.
For large capacity systems (100 gallons per minute or
greater), the designer or specifier can consider the use
of multiple-effect systems to lower steam usage. Multi-
ple-effect systems use less steam than single-effect
units, but have higher capital costs.
Separating solids from the crystallizer circulating liquor
can be difficult. Centrifuges are almost always effective,
but they are expensive to buy and maintain. In order of
solids dewatering effectiveness and cost, options for
solids removal include:
• Centrifuge (highest cost, lowest residual water).
• Belt filter (automatic operation, 40 to 50 percent re-
tained liquid).
• Filter press (manual or semiautomatic, 40 to 60 per-
cent retained liquid).
• Hydrocyclone (lowest cost, no moving parts, 50 to 70
percent retained liquid).
If solids meeting the "no free water rule" are required,
testing of the filter options and hydrocyclone might be
needed to demonstrate sufficient absorption of the free
water.
Design Considerations: Major Components
Vapor release and entrainment separation determine
the minimum size of the vapor body. A minimum of 6 feet
of straight side above the liquid level is required for
proper disengagement. Maximum vapor release veloci-
ties can be estimated using the following equation:
Velocity (ft/sec) = k[(D, - DV)/DV]° 5
where
D| = density of the liquid in Ib/ft3
Dv = density of the vapor in Ib/ft3
k = constant ranging from 0.10 to 0.04
(dimensionless)
The minimum diameter can easily be calculated. For
example, a 50-gallon per minute crystallizer operating at
atmospheric pressure with a 20-degree BPE will require
a minimum diameter of 10.3 ft with k set at 0.05. Vapor
body materials must be suitable for harsh service. In-
conel 625 is used for rad waste units, while titanium,
Inconel 825, and SMO254 or FRP units have been used
in commercial service.
The recirculation pump must overcome the heater pres-
sure loss and the lift to the surface in the vapor body.
The vapor body must be located enough above the heat
exchanger to suppress boiling in the heat exchanger
and to provide sufficient NPSH. Pump heads, in net
TDH, typically run at about 15 to 25 feet. The circulating
liquor specific gravity is greater than 1.2. Axial flow
pumps are usually specified, but low (lower than 1,100)
revolutions-per-minute centrifugal pumps can also be
used.
Cooling water or air cooling can be used in the con-
denser (which is not required for MVR). The cooling
requirement, in BTUs/hr, is approximately equal to the
steam BTUs/hr. Direct contact condensation using the
174
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CRYSTALLIZER - STEAM POWER
Capital & Operating Costs
84
c
.2
<§
o.
o
o
20 25
Flow — gpm
Operating Costs
Capital Costs
Pow«-: $O.OtS/kwh
Opwotina Labor: $20.QO/hr
Figure 9-13. Steam power crystallizer capital and operating costs.
desalted product can be considered as well. Tubes are
usually 304 or 316 ss.
Tubes in shell units are typically used for the heat ex-
changer. Its orientation can be vertical or horizontal.
Boiling inside the tubes should be suppressed with suf-
ficient head above the exchanger and tube velocities
must be sufficient to avoid settling of the solids; 6 to 8
ft/sec is typical. Temperature rise per pass through the
heat exchanger is kept low to avoid violent flashing in
the vapor body. Titanium tubes are standard. Differential
temperatures (steam to liquor) of 20°F can be used.
Heat transfer coefficients are a function of temperature
and concentration. For preliminary sizing at atmospheric
boiling, an overall coefficient of 400 BTU/°F/ft2 can be
used.
Capital and Operating Costs
Figures 9-13 to 9-16 provide ways of estimating the
capital and operating costs of crystal I izers. The costs
are based on single unit systems at 100 percent of
design capacity. Single-effect steam driven systems are
assumed. The values provided range roughly an order
of magnitude for installed systems.
9.3.2 Evaporation Ponds
The suitability of evaporation ponds for concentrate dis-
posal depends on ideal climatological conditions. The
principal factors that affect the evaporation rate are
relative humidity, wind velocity, barometric pressure, air
and water temperature, and the salinity of the water.
The need for dry, arid conditions where evaporation
losses are much greater than the amount of rainfall limits
Stocm U»s«: 1 ISO btu/b
Slaom Cosh SS.OO/mmtatu
CRYSTALLIZER - STEAM POWER
Operating Costs — 15 gpm feed rate
PUMPING & MISC. ENERGY 9 S0.045/KWK
|^ OPERATING LABOR SS20/HR
1 MAINTENANCE @ 2% OF CAPITAL/YR
STEAM 9 $5.00/MMBTU
20 30 40 50 60 70
Operating Cost — $/1000 gallons
Figure 9-14. Steam power crystallizer cost components.
CRYSTALLIZER - MVR
Operating Costs - 1 5 gpm feed rate
PUMPING & MISC. ENERGY @ $O.CU5/KWH
OPERATING LABOR @$20/HR
MAINTENANCE @3% OF CAPITAL/YR
COMPRESSOR ENERGY (9 $O.G45/KWH
CAPITAL RECOVERY @10%/YR
TOTAL
0 5 10 15 20 25 30 35 40 45 50
Operating Cost - $/1000 gallons
Figure 9-15. MVR crystallizer capital and operating costs.
use of evaporation ponds to just a few areas in the
United States. In addition, the amount of land required
175
-------
is an economic consideration. Because evaporation
losses are directly proportional to area, large areas of
land must be available for this option to be viable. A
backup system is necessary, since an unusual weather
event could affect the evaporation rate. Some large
brackish water RO plants in the Middle East have em-
ployed this method of concentrate disposal successfully
or have used it in combination with percolation onto the
desert.
9.3.3 Emerging Technologies
Currently, no identifiable new technologies are predicted
to be used in disposing of brines. Refinements, increased
efficiencies, and combinations of existing disposal tech-
nologies might lower the cost of disposal, but no new
options are anticipated.
9.4 Costs Associated With Brine Waste
Disposal
Capital and O&M costs for concentrate disposal will be
specific to a given site. Cost variables include:
• Quality of concentrate water.
• Quantity of concentrate water.
• Disposal method.
• Distance from disposal point (and the length of the
conveyance system).
• Pretreatment required, if any.
• Regulatory requirements for method of disposal.
• Permitting.
• Use of energy recovery.
• Requirement for backup or redundant disposal method.
• Climatological conditions.
• Residual pressure of the concentrate stream exiting
the membrane process plant.
9.5 Conclusion
Concentrates from membrane process plants have
been disposed of for over two decades without incident.
Membrane processes are important treatment technolo-
gies that will assist the water treatment industry in meet-
ing present and future drinking water regulations.
Membrane technologies probably will be the best avail-
able technology in terms of the most organic and inor-
ganic contaminant removal for the amount of capital
invested. Safe methods of concentrate disposal as well
as fair and pragmatic regulations will be necessary for
membrane processes to continue. It is the responsibility
of all those involved in the membrane process industry
to work together to:
• Prevent damage to the environment that could occur
from improper disposal of concentrate wastes.
• Ensure that proper engineering judgment is used in
interpreting agency rules and regulations.
• Guarantee that future regulations do not unduly limit
the use of membrane process technology.
• Secure new methods for concentrate disposal through
research and development.
CRYSTALLIZER - MVR
Capital & Operating Costs
20 25
Flow — gpm
30
35
Operating Costs
Capital Costs
-2.5
-1.5
40
0.5
Pow«r: $0.0*S/kwh MVR Comprisson 150 lorh/1000 gol fwd
Optroting Lofaor: J20.00/hr Copitol R«cov«ry: 1 OS/yr
Figure 9-16. MVR crystallizer cost components.
o
o
8-
O
ID
176
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Chapter 10
Radioactive Waste Disposal
Nearly all of the radionuclides found in drinking water
supplies are naturally occurring and are members of one
of three natural radioactive decay series: the uranium
series, the thorium series, and the actinium series. In
1976, the U.S. Environmental Protection Agency (EPA)
promulgated interim drinking water regulations for ra-
dionuclides that established limits for gross alpha activ-
ity, gross beta and photon activity, and the specific
elements of radium-226 (Ra-226) and radium-228 (Ra-
228) (40 CFR Part 141).
On July 18,1991, the Agency proposed new regulations
that would increase radium maximum contaminant lev-
els (MCLs) and add limits for uranium and radon (40
CFR Parts 141 and 142). The final regulation was
scheduled to be promulgated April 30, 1995; as of this
printing, however, this promulgation date is postponed
until an undetermined time after December 1995. EPA
is considering separating the other radionuclides from
radon because regulation of radon is under a congres-
sional freeze.
10.1 Background
A variety of treatment processes exist to remove radio-
active contaminants from drinking water, such as con-
ventional coagulation/filtration, ion exchange, lime
softening, reverse osmosis, and granular activated carb-
on (GAG) adsorption (U.S. EPA, 1976b; Brinck et al.,
1978; U.S. EPA, 1977; Lassovszky and Hathaway, 1983;
Sorg etal., 1980; and Lowry and Brandow, 1985). These
processes separate the contaminants from drinking water
and concentrate them in the waste streams. Because
these processes are also commonly used to remove
other nonradioactive contaminants, they could poten-
tially concentrate significant levels of radioactivity in
waste treatment residuals even if the treatment was not
originally designed or intended to remove radioactivity.
In addition to the waste streams containing the concen-
trated contaminants, some materials used to treat
drinking water adsorb radioactive contaminants and per-
manently retain them. One good example is sand used
in filtration processes. Sand adsorbs and retains radium
on its surfaces. Although the radium does not interfere
with the treatment process, at the end of its useful life
the sand must be replaced and disposed of.
The handling and disposal of the water treatment plant
(WTP) residuals containing naturally occurring radionu-
clides pose significant concerns to water suppliers, local
and state governments, and the public. The unresolved
question is do these wastes require special handling
and disposal, or can they be disposed of by the same
methods used to dispose of conventional, nonradioac-
tive wastes? Presently, the federal government does not
regulate the disposal of naturally occurring radioactive
materials (NORM) waste from drinking water treatment
processes. The U.S. Nuclear Regulatory Commission
(NRC) has the authority to regulate the handling and
disposal of all licensed radioactive materials, but this
does not include NORM in drinking water. Licensed
materials include high-level radioactive wastes, such as
spent nuclear reactor fuel rods and wastes from nuclear
weapons processing centers and low-level radioactive
wastes such as those used in building materials, ma-
chinery, and clothing from nuclear power plants, as well
as spent nuclear medicines.
Although federal agencies do not classify NORM wastes
as radioactive wastes, policies could change, and defi-
nitions to characterize these wastes as radioactive could
be developed in the future. Because of current concern
for the proper disposal of these wastes, in July 1990
EPAs Office of Drinking Water published Suggested
Guidelines for the Disposal of Drinking Water Treatment
Wastes Containing Naturally Occurring Radionuclides
(U.S. EPA, 1990c; Parrotta, 1991). These guidelines
were intended to help WTPs and state and local regu-
lators achieve safe and responsible waste management
practices for water treatment residuals containing ra-
dionuclides at concentrations in excess of background
levels.
The EPA guidelines clearly state that no federal regula-
tions specifically address the disposal of wastes con-
centrated by water treatment processes on the basis of
their naturally occurring radioactive content. The docu-
ment further states that the guidelines developed were
taken from a review of the regulations and from guide-
lines originating in other industries and programs. For
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example, one source of information for the suggested
guidelines for radium wastes was disposal criteria for
WTP residuals that the states of Illinois and Wisconsin
(Illinois, 1984; Wisconsin, 1985) developed. Some states
have also established rules for the disposal of wastes
that contain radioactivity. EPA emphasizes in its guide-
lines, therefore, that where radioactivity in water treat-
ment residuals is anticipated, state agencies should
always be consulted.
A review of the current literature shows that almost all
information on the disposal of WTP residuals containing
radionuclides comes from the EPA guidance document.
The guidelines are being revised, but no major changes
are anticipated. Until formal regulations are developed,
states having no specific rules or regulations will likely
cite and use this document as general policy. Conse-
quently, the sections on waste disposal in this chapter
have been summarized from EPAs revised 1994 draft
guideline document (U.S. EPA, 1994b). The revised
guidelines will not be issued to the public until the regu-
lations are promulgated, some time after December 1995.
10.2 Waste Disposal Practices
A list of residuals generated from common water treat-
ment practices appears in Table 10-1. Except for dis-
posal at a radioactive waste disposal site, current
disposal methods are basically the same as those used
for nonradioactive wastes. These methods are shown in
Table 10-2.
Federal, state, and local regulations exist that govern
and limit the discharge of nonradioactive WTP residuals
into the environment. These regulations also apply to
residuals containing radionuclides. The radioactivity of
Table 10-1. Summary of Residuals Produced From Water
Treatment Processes
Water Treatment
Process
Waste Streams/Material
Conventional
coagulation/filtration
Lime softening
Ion exchange
Reverse
osmosis/electrodialysis
Greensand filtration
Selective sorbents
(GAC, resins activated
alumina)
Filter backwash water
Sludge (alum or iron)
Filter material
Filter backwash water
Sludge (lime)
Filter material
Reuse and backwash water
Regeneration liquid (brine, caustic, acid)
Resin
Reject water
Membrane/Material
Filter backwash water
Sludge
Greensand media
Sorbent media
Table 10-2. Water Treatment Methods for Residuals
Containing Radionuclides
Residuals
Type Disposal Method
Liquids Direct discharge to surface water
Direct discharge to sanitary sewer
Deep well injection
Irrigation
Lagooning/Evaporation ponds
Sludge Lagooning (temporary)
Landfill disposal
• No pretreatment
• With prior lagooning
• With mechanical dewatering
Land disposal
Licensed low-level radioactive waste disposal site
Solids Landfill disposal
Licensed low-level radioactive waste disposal facility
these residuals causes additional concern with dis-
posal and thus may narrow disposal options or place
additional requirements on the options. In selecting the
disposal option, the concentration of radioactive con-
taminants in the residuals is the governing factor. Unfor-
tunately, no current federally established levels of
radionuclides have been developed to define low or high
radioactive wastes or dictate the acceptable disposal
method.
10.3 Waste Disposal Guidelines
The following information on disposal of liquids, solids,
and sludges has been summarized from EPAs revised
1994 draft guideline document (U.S. EPA, 1994b).
10.3.1 Liquid Disposal
10.3.1.1 Discharge to Surface Waters
The Clean WaterAct requires that dischargers of pollutants
to navigable waters obtain National Pollutant Discharge
Elimination System (NPDES) permits containing, at a
minimum, technology-based effluent limitations that re-
flect various levels of wastewater treatment and, where
necessary, more stringent limitations necessary to en-
sure attainment and maintenance of state water quality
standards. EPA has not promulgated any rule estab-
lishing technology-based effluent limitations applicable
to WTPs nationwide.
In the absence of such a categorical standard, limita-
tions are established on a case-by-case basis, using the
best professional judgment. After determining minimum
technology-based requirements, the effect(s) of dis-
charge on the receiving water is also determined; if
necessary, more stringent limitations are established to
protect the receiving water quality (see Chapter 5). In
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certain states, water quality standards may include spe-
cific criteria for radionuclides. State water quality stand-
ards that require more stringent discharge limitations
must be reflected in any NPDES permit.
The NPDES permitting process should include study of
the flow and geometry of receiving storm sewers and
surface waters, as well as the potential uses of the
surface waters (e.g., drinking water, agriculture). Based
on site conditions, a state or other regulatory agency
may use its discretion in determining a limiting concen-
tration (e.g., a drinking water MCL) or a percentage of
the background concentration(s) of radionuclides (e.g.,
10 percent) that would limit the increase of radionuclides
in the water body and/or the sediments due to the
discharge of WTP residuals.
The NRC has established levels of radionuclides that its
licensees are allowed to release into unrestricted areas
of the environment (10 CFR Section 20.1302(b)(2)(i)
and Sections 20.1001-20.2401). The referenced NRC
limits are: 60 pCi/LforRa-226 and Ra-228 and 300 pCi/L
for natural uranium. If no state or local standards are in
place, the NRC standards may be used as guidelines
for surface water discharge. Some states and local
authorities have promulgated conservative limits of 10
percent of the NRC levels under 10 CFR 20 for release
of radionuclides into the environment.
If the conditions of flow and geometry are not adequate
to prevent a buildup of radionuclides in surface water or
sediments to within the limit set by the regulator, then
other solutions need to be studied. These may include
additional waste treatment, waste storage, and control-
led discharge measures to produce a waste stream that
can meet in-stream requirements. Otherwise, discharge
to surface waters should not be allowed, and other
options need to be considered.
10.3.1.2 Discharge Into Sanitary Sewers
Federal regulations prohibit discharges to sewers that
would cause a municipal waste water treatment plant
(WWTP) to violate an NPDES permit or that would
interfere with wastewater treatment operations or sludge
disposal. In addition, states or localities may establish
more stringent limitations on the discharge of wastes
from WTPs into a sanitary sewer, or may require pre-
treatment of the waste prior to its release into the sani-
tary sewer. State or local regulations limiting the
discharge of WTP residuals that contain naturally occur-
ring radionuclides into sanitary sewers would govern
those discharges.
The NRC limits the discharge by its licensees of wastes
containing radioactive materials into sanitary sewers.
For NRC licensees, the monthly quantity of soluble Ra-
226, Ra-228, and natural uranium, diluted by the aver-
age monthly quantity of total WTP residuals released
into a sewer, should not exceed 600 pCi/L, 600 pCi/L,
and 3,000 pCi/L, respectively. Also, the gross quantity of
all radioactive material (excluding tritium and carbon-14)
that a facility releases into sanitary sewer should not
exceed 1 curie per year, according to the same NRC
standards. EPA puts forth these standards for consid-
eration in this context.
The NRC standards correspond to an individual radia-
tion dose of 50 millirem per year. Although high, the
reasonable dilution that a receiving waterway provides
may reduce this dose to levels below any applicable
drinking water standards. This should be examined,
however, on a case-by-case basis.
If accumulation of radioactivity in the sanitary sewer
distribution system, sewage treatment facility or publicly
owned treatment works (POTW) is observed, discharg-
ing radioactive residuals into a sanitary sewer should be
discontinued until radiation exposures and possible haz-
ards to personnel repairing sewage pipelines are evalu-
ated. Discharge of residuals containing radionuclides
into a sanitary sewer results in the accumulation of
radionuclides in the sludge that the POTW produces.
Affected sewage sludge should be monitored for high
levels of radioactivity and disposed of properly.
10.3.1.3 Deep Well Injection
Under Part C of the Safe Drinking Water Act (SDWA),
EPA is required to promulgate minimum requirements
for effective underground injection control (DIG) pro-
grams to prevent endangering underground sources of
drinking water by subsurface emplacement of fluids
through wells. Regulations may be implemented by
states that have adopted requirements at least as strin-
gent as the federal requirements and have been given
primary enforcement responsibility for the DIG program.
For states that do not have primacy, EPA has promul-
gated state-specific regulations that EPA regional offices
implement.
A WTP interested in discharging residuals containing
radionuclides into an injection well in a primacy state
should first consult with the appropriate state agency.
State regulations may be more stringent than federal
requirements and may actually ban such a practice. The
WTPs in other states should consult with the appropriate
DIG regional branch office of EPA before deciding to
dispose of residuals containing radionuclides into an
injection well in accordance with a method recom-
mended below.
Under the federal requirements, regulation of WTP re-
siduals containing radionuclides depends on the con-
centrations of radionuclides present. Furthermore,
requirements are specified for shallow and for deep well
injection. Shallow wells are defined as those above or
in an underground source of drinking water (USDW).
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USDWs and injection wells are defined very broadly. A
USDW is an aquifer or its portion that 1) supplies any
public water system or that contains sufficient quantity
of water to supply a public water system and 2) supplies
drinking water for human consumption, or contains
fewerthan 10,000 mg/LTDS. Awell is any bored, drilled,
ordriven hole where the depth of the hole isgreaterthan
the largest surface dimension. This definition includes
septic systems and cesspools used for disposal of wastes.
Radioactive wastes are treated differently from nonra-
dioactive wastes under the DIG program. As defined in
40 CFR Section 144.3, radioactive waste means any
waste that contains radioactive concentrations that ex-
ceed those listed in 10 CFR 20, Appendix B, Table 11,
Column 2. The concentration for Ra-226 and Ra-228 is
currently listed as 60 pCi/L, while the radioactive con-
centration for natural uranium is 300 pCi/L.
Radioactive wastes as defined by the DIG program (i.e.,
wastes containing greater than 60 pCi/L Ra-226 or Ra-
228, and/or containing greater than 300 pCi/L uranium)
would not be disposed of in a shallow well, as defined
above. Shallow injection of radioactive wastes (e.g.,
injection above or into a USDW) is a banned practice
under the DIG program. The definitions of USDW and
shallow injection would virtually eliminate any shallow
disposal of radioactive waste.
Well disposal of radioactive waste below a USDW is
currently considered a Class V well injection and is
under study by EPA as part of the Class V regulatory
development effort. At this time, EPA is not prepared to
make any recommendations regarding these wells. The
following is suggested guidance for nonradioactive
wastes as defined by the UIC program (i.e., wastes
containing less than 60 pCi/L Ra-226 or Ra-228, or less
than less than 300 pCi/L uranium).
Well injection of nonradioactive WTP residuals beneath
the lowest USDW is classified as a Class I nonhazard-
ous practice, provided the waste contains no other haz-
ardous components. EPA recommends disposal of
nonradioactive waste through a Class I well because
these wells must be permitted, and current permitting
requirements for these wells ensure adequate protec-
tion of USDWs and human health.
10.3.1.4 Other Options
If, due to the properties of a residual, or local regulatory
restrictions, a residual containing NORM cannot be
processed using one of the above methods, then the
treatment operator may choose from another treatment
or disposal option such as evaporation of liquid wastes,
sand drying or lagooning, chemical precipitation of con-
taminants, or other solids separation techniques. Other
state regulations may apply to these practices. At a
minimum, no practice should be less environmentally
protective than the options mentioned above.
For instance, lagooning of radioactive wastes would be
analogous to shallow well injection, if practiced in an
unlined unit. Lagoons or other impoundments should, at
a minimum, be lined to prevent infiltration. If WTPs
intend to evaporate radioactive waste, the evaporation
unit should be designed and operated properly to ensure
isolation of the waste from the watertable.
10.3.2 Solids and Sludge Disposal
The following disposal guidance for radioactive WTP
residuals is summarized from the EPA guidelines. The
guidance is based solely on the radioactivity of these
wastes and does not address other potentially hazard-
ous substances.
10.3.2.1 Landfill Disposal
Wastes containing less than 3 pCi/g (dry weight) of
radium and less than 50 g/g of uranium may be disposed
of in a municipal landfill without the need for long-term
institutional controls if the wastes are first dewatered
and then spread and mixed with other materials when
they are emplaced. The total contribution of radioactive
wastes to the landfill should constitute only a small
fraction (less than 10 percent of the volume) of the
material in the landfill.
Wastes containing 3 to 50 pCi/g (dry weight) of radium
should be disposed of using a physical barrier (i.e., a
cover) that protects against radon release and isolates
the wastes. Institutional controls designed to avoid inap-
propriate uses of the disposal site should also be pro-
vided. A physical barrier consisting of 10 feet of cover
earth or nonradioactive waste, properly designed for
long-term stability of the waste, should suffice.
Sludge should be dewatered prior to disposal to mini-
mize migration of contaminants. Consideration should
be given to the hydrogeology of the site and other
factors affecting long-term stability of the wastes. Sites
that fully comply with EPAs Subtitle D regulations and
guidance under the Resource Conservation and Recov-
ery Act (RCRA) would be appropriate for disposal of
these wastes.
A jurisdiction may choose to ensure ground-water pro-
tection by specifying RCRA hazardous waste require-
ments (e.g., properly lined waste unit or sludge
stabilization), to prevent seepage of contaminants from
the landfill. The degree of additional protection a juris-
diction wants to provide against intrusion and misuse
may vary from site to site but should be determined
before waste disposal.
Disposal of solid wastes containing 50 to 2,000 pCi/g
(dry weight) of radium should be determined on a case-
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by-case basis. Methods that comply with EPA's stand-
ards for disposal of uranium mill tailings should be con-
sidered (40 CFR 192). A decision not to employ such
methods fully should be based on a demonstration of
significant differences between the quantity and poten-
tial for migration of uranium mill tailings versus water
treatment residuals. The disposal method should be
augmented by long-term institutional controls to avoid
future misuse of disposal sites; such controls are not
normally already in place at sanitary landfills.
At a minimum, disposal in RCRA-permitted hazardous
waste units should be considered. In states where dis-
posal is licensed or permitted, disposal at these sites
should be considered for radium-bearing solid wastes. At
concentrations approaching 2,000 pCi/g, waste disposal
within a licensed low-level radioactive waste disposal
facility or a facility that is permitted by EPA or a state to
dispose of discrete wastes, should be considered.
In states where lower concentration waste disposal is
licensed or permitted, that option should be considered
for disposal of solids containing 50 to 500 g/g (dry
weight). Recovery of the uranium resource (e.g., at a
uranium milling site) may be considered. NRC may
require licensing of the recovered material (greater than
0.05 percent), however, as a source material under the
provision of the Atomic Energy Act. Disposal at a li-
censed low-level radioactive waste facility should also
be considered.
Solid wastes containing more than 2,000 pCi/g (dry
weight) of radium or more than 500 %g/g (dry weight)
uranium should be disposed of in a low-level radioactive
waste disposal facility or at a facility that is permitted by
EPA or a state to dispose of NORM wastes. Recovery
of the uranium resource (e.g., at a uranium milling site)
may be considered. NRC may require licensing of the
material containing uranium (if greater than 0.05 percent
uranium) as a source material under the provisions of
the Atomic Energy Act. Also, when radium occurs with
uranium, it is regulated as part of that source material.
10.3.2.2 Land Disposal
EPAdoes not recommend applying, mixing, or otherwise
spreading NORM wastes onto open land (e.g., farm
land, pasture, orchard or forestry lands, construction
sites, roadbeds) for several reasons:
• Data relating to plant, animal, and human uptake and
the potential exposure that may result from land-ap-
plied NORM wastes need to be collected and ana-
lyzed. Preliminary assessments suggest that human
health risks from radon inhalation significantly in-
crease in buildings constructed on such areas.
• The long-term control of and monitoring at a site that
may contain higher than background levels of ra-
dionuclides (which sometimes are very long-lived)
cannot be assured.
• Diluting wastes runs counter to EPA's general policy
of concentrating wastes before safe disposal.
• EPA has not collected or reviewed any data on the
status of surface runoff from sites that host land ap-
plication of WTP residuals. Preliminary risk assess-
ments using conservative assumptions, however,
indicate that runoff and surface water contamination
may pose a significant risk to the general population.
• Although certain types of sludge have been found to
have beneficial properties as amendments to agricul-
tural soils, EPA has not decided that the beneficial
results outweigh the potential adverse results, such
as food-chain contamination, future misuse of sites
for building, and impacts on surface and ground-
water quality.
10.4 Recordkeeping
EPA guidelines recommend that water treatment facili-
ties keep records of the amount and composition of
radioactive wastes (solid and liquid) they generate and
the manner and location of their disposal. Repositories
of wastes containing more than 50 pCi/g (dry weight)
should be permanently marked to ensure long-term pro-
tection against future misuse of the site and/or its mate-
rials. This guideline is not meant to cause an increase
in the federal recording requirements for water treat-
ment facilities.
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Chapter 11
Economics
Any water utility manager considering a new residuals
management option for a water treatment plant (WTP)
will want to estimate as closely as possible the cost of
the residuals management option. This chapter provides
cost equations that can be used to estimate the total
annual costs associated with several different residuals
treatment and disposal options. The cost equations pro-
vided here were developed using computer cost mod-
els, published cost information, and quotes provided by
vendors. All costs presented in this chapter are in 1992
dollars.
These equations should be used for relative comparison
purposes only. Certainly, more accurate, site-specific
estimates should be developed for facility planning and
budgeting purposes. The specific factors and treatment
requirements will likely drive the costs up.
Final project costs have been found to be higher than
those costs presented herein. This is primarily due to
site-specific factors such as physical and chemical
characteristics of the residuals, site constraints, op-
erational costs, and differing state and local regulatory
requirements.
11.1 Cost Assumptions
11.1.1 Capital Cost Assumptions
Table 11-1 presents cost factors and unit costs used to
calculate the capital costs presented in this chapter. The
land, buildings, and piping components are discussed in
detail below. Other capital cost items (e.g., tanks, la-
goons, and pumps) are calculated individually.
11.1.1.1 Land
Land prices vary considerably across the country and
depend on proximity to metropolitan areas, the state of
land development (i.e., improved or unimproved), cur-
rent use, and scarcity of land. A cost of $10,000 per acre
is assumed for the cost estimates included in this chap-
ter. Costs for suburban or industrial unimproved land
average $10,000 per acre and range from approxi-
mately $4,000 to $350,000 per acre depending on loca-
tion. Costs for unimproved agricultural or rural land vary
from approximately $150 per acre in states with large
Table 11-1. Capital Cost Factors and Selected Unit Costs for
WTP Facility Planning (U.S. EPA, 1993c)
Component
Factor/Unit Cost
Land
Buildings
Piping
Pipe fittings
Electrical
Instrumentation
Engineering fee
Contingency, bonding, and
mobilization
Contractor's overhead and profit
$10,000/acre
$33.00/ft2
5% of installed equipment3
20% of piping costs'3
1% of installed equipment
1-2% of installed equipment
15% of direct capital
20% of direct capital
12% of direct capital
a Piping costs are calculated directly when piping is a significant cost
(e.g., for direct discharge).
b Factor is used when piping costs are calculated directly.
tracts of undeveloped land, to $2,200 per acre in states
with small tracts of undeveloped land. An average cost
for rural, unimproved land is $1,000 per acre.
Costs for purchasing land are included in the capital cost
equations provided here for all treatment and disposal
processes that use surface impoundments. For exam-
ple, assume an impoundment is used for liquid residuals
storage prior to land application. The land costs are
presented as a separate cost in the capital cost equation
to allow the user to delete the cost for land if no purchase
is required or to vary the cost of the land if the unit cost
of land for a given area is available. A minimum land
purchase of a 1/2 acre is used in developing land costs.
Land costs are not included for direct discharge and
discharge to a publicly owned treatment works (POTW).
It is assumed that the water treatment authority is able
to obtain an easement for placement of a sewer or
discharge line.
11.1.1.2 Buildings
Building costs also vary considerably based on geo-
graphic location. The building cost of $33.00 per square
foot, listed in Table 11-1, comes from 1992 Means Build-
ing Construction Cost Data (R.S. Means Co., Inc.,
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1991). This cost is for a basic warehouse or storage
building and includes electrical, foundations, heating,
ventilation, air conditioning, and plumbing costs. It in-
cludes a 10 percent surcharge for structures of less than
25,000 square feet. This cost is the median cost for
basic warehouse and storage buildings. The lower quar-
tile cost is $21.30 per square foot and the upper quartile
cost is $45.65 per square foot. Different warehouse or
building configurations will change this unit cost. An
aesthetically pleasing architecturally designed building
or a complex building with several levels may cost sub-
stantially more than the building costs included in this
chapter.
11.1.1.3 Piping and Pipe Fittings
Piping costs are calculated using two different method-
ologies that depend on the magnitude of the piping
costs. For management systems in which the piping
constitutes a significant portion of the capital cost (e.g.,
direct discharge and discharge to a POTW), piping costs
are calculated by sizing individual pipe lengths and de-
termining installation charges. For these management
systems, pipe fittings are assumed to be 20 percent of
the installed piping costs. For management systems
where piping is not a significant cost (e.g., chemical
precipitation and mechanical dewatering), piping and
pipe fittings are assumed to be 5 percent of the installed
equipment costs.
11.1.2 Operation and Maintenance
Assumptions
Table 11-2 presents cost factors and unit costs used to
calculate the operation and maintenance costs pre-
sented in this chapter.
11.1.2.1 Labor
The labor rate is based on a 20-city average for union
scale laborers. The hourly rate of $28.00 is based on an
average salary of $18.74 per hour including fringe bene-
fits and a 50 percent labor overhead cost. Average
Table 11-2. Operation and Maintenance Cost Factors and
Unit Costs for WTP Facility Planning (U.S. EPA,
1993c)
Component Factor/Unit Cost
Labor
Supervision
Supervision factor
Insurance and general and
administrative expenses
Maintenance
Electricity
$28.00/hour
$42.00/hour
10% of labor hours
2% of direct capital, excluding
land and buildings
2 to 3% of direct capital,
excluding land and buildings
$0.086/kilowatt-hour
salaries, including fringe benefits, by region range from
$11.17 per hour in the southeast to $26.23 in the west-
ern United States.
11.1.2.2 Supervision
The supervision rate is based on an estimated salary of
$45,000 per year for a water system treatment manager.
The $42.00 per hour assumes a 30 percent fringe bene-
fit and a 50 percent labor overhead cost. The supervi-
sor's salary is based on 1992 job postings in Public
Works magazine (Public Works, 1992).
11.1.3 Total Annual Cost Assumptions
Total annual costs are equal to the sum of the yearly
operation and maintenance costs plus the annualized
capital costs. Annualized capital costs are calculated
based on a 20-year operating life and an interest rate of
10 percent. The capital recovery factor for a 20-year
operating life at a 10 percent interest rate is 0.1175.
Alternate capital recovery factors can be calculated us-
ing the formula presented below.
Capital recovery factor = ..
(1 + i)N - 1
where
i = interest rate
N = number of years
11.1.4 Cost Components Excluded
The following cost components are not included in the
cost estimates presented in this chapter. Other excluded
costs, specific to each management option, are high-
lighted under their respective technology cost sections.
11.1.4.1 Sample Collection and Laboratory
Analysis
Costs for sample collection and analysis to determine
solids content, free liquids, toxicity characteristics, and
other parameters are not included in the costs presented in
this chapter. Sampling frequency is highly variable. De-
pending on the residuals management method selected,
sampling requirements could be minimal or extensive.
11.1.4.2 Permits and Other Regulatory
Requirements
Costs for permits and other regulatory requirements are
not included in this chapter. Requirements vary consid-
erably from state to state for a given management op-
tion. Permitting costs will vary based on the size and
complexity of a unit and the local governing jurisdiction.
Management methods that may require permits include
landfills, land application, evaporation ponds, and stor-
age lagoons. In addition, generators of hazardous waste
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are required to comply with RCRA generator require-
ments (40 CFR Part 262).
11.1.4.3 Mechanical Standby Equipment
Costs for standby equipment, or redundancy, are not
included in these cost estimates.
11.1.5 Cost Equations
The cost equations for the capital components and for
operation and maintenance were developed by estimat-
ing the costs for different residuals flow rates. Equip-
ment sizes, retention times, installed equipment costs,
operation and maintenance expenses, commercial dis-
posal fees, component cost factors, and unit costs were
developed based on published literature, (e.g., AWWA
reports, technical journal articles, EPAdocuments), ven-
dor contacts, and best engineering judgment. Capaci-
ties for major equipment components are presented in
each cost section. Each cost equation covers the range
of expected residuals flow rates unless a specific tech-
nology is not applicable to the entire range. For exam-
ple, some technologies are not feasible for very high
flow rates because of excessive land requirements or
equipment limitations.
The limits of the cost equations presented for each
residuals management method may be extended
slightly beyond the ranges presented in this chapter. The
upper or lower end for some equations, however, may
represent the largest or smallest practical limits of a
specific technology. Consequently, the design assump-
tions should be carefully reviewed before extending the
range of the equations. Best engineering judgment
should be used when extending the equations beyond
their specified limits.
The capital and operation and maintenance equations
encompass the residuals volumes generated by WTPs
ranging from a design flow rate of 1.8 million gallons per
day (mgd) (average operating flow rate, 0.7 mgd) to 430
mgd (average operating flow rate, 270 mgd). One option
is to size the equipment (i.e., determine the capital cost)
for the residuals produced from the water treatment
system design flow rate, while calculating the operating
cost using the average residuals flow rate. Thus, the
equipment is sized for peak flow periods, but the actual
operating costs may be more closely estimated using an
average daily flow rate.
Typically, the design flow rate for a WTP may be two to
three times the average flow rate for the facility. When
calculating the costs for capital intensive management
technologies such as chemical precipitation and me-
chanical dewatering, calculate both the capital and op-
eration and maintenance costs using the average flow
rate. Table 11-3 indicates whether the water treatment
design flow rate or average flow rate should be used to
Table 11-3. Flow Rate Use in Calculating Facility Costs (U.S.
EPA, 1993c)
Technology
Gravity thickening
Chemical precipitation
Mechanical dewatering
Nonmechanical dewatering
Evaporation ponds
POTW discharge
Direct discharge
French drain
Land application
Nonhazardous waste disposal
Hazardous waste disposal
Radioactive waste disposal
Capital
Cost
Average
Average
Average
Design
Design
Design
Design
Design
Design
Average
N/A
N/A
Operation &
Maintenance Cost
Average
Average
Average
Average
Average
Average
Average
Average
Average
Average
N/A
N/A
calculate the capital and operation and maintenance
costs. The design flow rate can be used to calculate
costs, but this calculation may result in substantial over-
estimation of the cost to treat WTP residuals generated
by an actual facility.
All costs presented in this chapter are in 1992 dollars.
To update cost results obtained from either the cost
equations or cost curves specified in the following sec-
tions, the Builders' Construction Cost Indexes are rec-
ommended and available in quarterly "cost report"
issues of Engineering News Record (ENR). The ENR
20-city construction cost index or the Means Construc-
tion Cost Indexare good general-purpose cost updating
indexes. Their January 1992 values are 455.08 and
97.90, respectively.
11.1.6 Cost Curves
The cost curves in this chapter are the direct graphical
representations of the cost equations. A break in the
curve indicates that two equations covered two different
ranges of the data. In these instances, the two curves
typically do not meet at the same point at the overlap.
11.1.7 Calculating Residuals Management
Costs
WTP residuals management costs are calculated using
the capital, operating and maintenance and total annual
cost equations presented in the following sections.
Known residual flow rates from an operating facility may
be used or residuals volumes can be estimated using
the information presented in Chapter 3. The annual
residuals management costs can be determined by cal-
culating a total annual cost for each required treatment
or disposal technology and then summing the costs
184
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associated with all WTP residuals management proc-
esses at the facility.
11.2 Gravity Thickening
The following section presents the design assumptions,
capital components, and the operation and maintenance
components used to estimate the costs for gravity thick-
ening of filter backwash streams from chemical coagu-
lation, or lime softening residuals streams and/or their
sludge waste streams.
11.2.1 Design Assumptions
• Gravity thickening is used to pretreat filter backwash
or sludges from chemical coagulation and lime sof-
tening.
• The waste streams flow by gravity from the treatment
plant to settling tank.
• The backwash volume ranges from 7,000 to 2,500,000
gallons per day.
• The total backwash volume is 0.5 to 2 percent of the
design flow rate.
• The initial solids concentration of the backwash is 0.1
percent and the discharge concentration is equal to
1 percent.
• The backwash is thickened in a tank.
• The volume of backwash is reduced by 90 percent.
• The supernatant is pumped to the head of the treat-
ment plant.
• The thickened sludges are discharged to another
treatment for further dewatering.
11.2.2 Capital Components
The capital components for each filter backwash system
consist of the following items: holding tank, piping and
fittings, pump, trenching, electrical, and instrumentation.
Table 11-4 indicates the holding tank capacities used to
develop the capital cost equation for gravity thickening.
11.2.3 Operation and Maintenance
Components
The operation and maintenance components for each
gravity thickening system include: electricity, labor and
supervision, maintenance labor and materials, insur-
ance, and general and administration.
11.2.4 Cost Components Excluded
The following cost components are not included in the
cost equations for gravity thickening systems:
Table 11-4. Holding Tank Capacities, Gravity Thickening (U.S.
EPA, 1993c)
Waste Stream
Volume (gpd)
7,000
13,300
36,000
96,000
165,000
270,000
510,000
1 ,050,000
2,150,000
Number of
Tanks
1
1
1
1
1
1
1
2
2
Waste Stream Settling
Tank Capacity (gal)
30,000
50,000
30,000
30,000
50,000
50,000
50,000
50,000
50,000
• Supernatant disposal, if the supernatant cannot be
pumped to the head of the treatment plant.
• Thickened sludge disposal.
• Costs for supernatant disposal, if the supernatant
cannot be pumped to the head of the treatment plant,
and treatment of the thickened sludge can be deter-
mined using other sections of this chapter.
11.2.5 Gravity Thickening Cost Equations
and Cost Curves
The cost equations for the capital components and the
operation and maintenance components for gravity
thickening were developed by estimating the costs for
nine different filter backwash flow rates. The filter back-
wash and sludge flow rates (X) used in the equations
below are the average daily volumes generated (e.g.,
for filter backwash, 2.5 percent of the daily treated water
flow rate). The capital cost equation calculates the total
capital cost (i.e., installed capital plus indirect capital
costs). The total annual cost is calculated based on the
capital and operation and maintenance costs obtained
using the equations presented below. Capital costs for
gravity thickening are presented graphically in Figure
11-1 and operation and maintenance costs are shown
in Figure 11-2.
Capital Costs
Y = 32,400 + [41.7(XU bu)]
where
Y= $
X = gallons of filter backwash/sludge per day
Range: 7,000 gpd < X < 270,000 gpd
Y = 21,700 + [66.5(X° 50)]
where
Y=$
X = gallons of filter backwash/sludge per day
185
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Figure 11-1. Capital costs for gravity thickening.
Range: 270,000 gpd < X < 2,500,000 gpd
Operation and Maintenance
Y = 5,800 + [8.04(X050)]
where
Y = $/year
X = gallons of filter backwash/sludge per day
Range: 7,000 gpd < X < 2,500,000 gpd
Total Annual Cost
Y = [CAP(CRF)] + O&M
where
Y = $/year
CAP = capital cost
CRF = capital recovery factor (e.g., 0.1175)
O&M = operation and maintenance cost
11.3 Chemical Thickening
This section presents the design assumptions, capital
components, and the operation and maintenance com-
ponents used to estimate the costs for chemical thick-
ening of residuals streams such as ion exchange
backwash and reverse osmosis brines.
11.3.1 Design Assumptions
• The chemical precipitation system consists of mixing
and holding tanks for the lime solution, a precipitation
tank, a clarifier, agitators, and pumps.
Figure 11-2. O&M costs for gravity thickening.
• The precipitation tank has a 1/2-hour retention time
and a 5 percent overdesign.
• The clarifier (settling tank) has a 1- to 2-hour retention
time.
• Waste brines flow to the treatment system under
pressure from the ion exchange or reverse osmosis
system.
• The chemical precipitation equipment is located in
the water treatment building.
• Sludge from the clarifier may require additional de-
watering prior to disposal.
• The sludge volumes generated by chemical precipi-
tation are 5 and 2 percent of the influent volumes for
reverse osmosis and ion exchange brines, respec-
tively.
11.3.2 Capital Components
The capital components for each chemical precipitation
system consist of: carbon steel mixing tank, carbon steel
holding tank, carbon steel precipitation tank, clarifier,
agitators, sludge pumps, building, piping, electrical and
instrumentation.
Table 11-5 indicates the brine volumes, tank capacities,
and clarifier capacities used to develop the capital cost
equation for chemical precipitation.
186
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Table 11-5. Capital Cost Equation Determinants, Chemical
Precipitation (U.S. EPA, 1993c)
Residuals
Flow Rate
(gpd)
27,400
67,500
274,000
500,000
1 ,000,000
2,740,000
Precipitation
Tank Size
(gai)
650
2,000
6,000
12,000
23,000
60,000
Mix Tank
Capacity
(gai)
50
75
200
600
1,200
1,500
Clarifier
Capacity
(gai)
2,500
8,000
24,000
40,000
50,000
40,000 x 2
A capital cost curve for chemical precipitation is shown
in Figure 11-3. Operation and maintenance costs for
chemical precipitation are shown in Figure 11-4.
11.3.3 Operation and Maintenance
Components
The operation and maintenance components for each
chemical precipitation system include: lime, electricity,
labor, maintenance labor and materials, insurance, gen-
eral and administration, and water.
11.3.4 Cost Components Excluded
The following cost components are not included in the
cost equations for chemical precipitation systems since
they are accounted for elsewhere:
• Sludge dewatering (if needed for the selected dis-
posal option).
• Sludge disposal.
• Clarifier overflow disposal, if the overflow cannot be
pumped to the head of the treatment works.
Costs for sludge dewatering and sludge disposal tech-
niques are included in other sections of this chapter.
Costs for clarifier overflow disposal, if the overflow can-
not be pumped to the head of the treatment works, can
be determined using other sections of this chapter.
11.3.5 Chemical Precipitation Cost
Equations and Cost Curves
The cost equations for the capital components and op-
eration and maintenance were developed by estimating
the costs for six different brine flow rates. The capital
cost equation calculates the total capital cost (i.e., in-
stalled capital plus indirect capital costs). Equipment
costs and building costs are separate components in the
capital cost equation to enable the user to exclude the
cost for a building addition if it is not necessary. The total
annual cost is calculated based on the capital and op-
eration and maintenance costs obtained using the equa-
tions presented below.
100, OOD 1. ODD, 000
Brine (gpd)
Figure 11-3. Capital costs for chemical precipitation.
i ii 11 ii 1—i—i i i 1111
1D,OGO 100,000 1,000,000
Brine (gpd)
Figure 11-4. O&M costs for chemical precipitation.
187
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Capital Costs
Y = [34,600 + 206(X050)] + [110(X055)]
Y = [equipment cost] + [building cost]
where
Y= $
X = gallons of brine per day
Range: 25,000 gpd < X < 500,000 gpd
Y = [34,600 + 206(X050)] + [65,000 + 160(X050)]
Y = [equipment cost] + [building cost]
where
Y= $
X = gallons of brine per day
Range: 500,000 gpd < X < 3,000,000 gpd
Operation and Maintenance
Y = 37,300 + 0.17(X)
where
Y = $/year
X = gallons of brine per day
Range: 25,000 gpd < X < 500,000 gpd
Y = 57,500 + 0.13(X)
where
Y = $/year
X = gallons of brine per day
Range: 500,000 gpd < X < 3,000,000 gpd
Total Annual Cost
Y = [CAP(CRF)] + O&M
where
Y = $/year
CAP = capital cost
CRF = capital recovery factor (e.g., 0.1175)
O&M = operation and maintenance cost
11.4 Mechanical Sludge Dewatering
11.4.1 Pressure Filter Press Cost
Components
This section presents the design assumptions, capital
components, and the operation and maintenance com-
ponents used to estimate the costs for a pressure filter, or
plate and frame, press for mechanical sludge dewatering.
11.4.1.1 Design Assumptions
• Pressure filter presses are effective for residuals flow
rates greater than 100 gallons per day.
• The polymer feed system consists of a polymer stor-
age tank, a polymer pump, a polymer/sludge contact
tank, and a 20- to 30-minute holding tank.
• A positive displacement pump delivers residuals to
the filter press.
• The filter press operates on a batch basis.
• Filtrate collects in a filtrate holding tank before being
pumped to the head of the treatment plant.
• In smaller systems, the filter cake collects in a small,
wheeled container, which is emptied into a larger
solids bin as necessary.
• In larger systems, the filter cake drops into rolloff bins
located beneath the filter press.
• Accumulated solids require disposal on a periodic
basis.
• The dewatered residuals volume is 0.03 and 10 per-
cent of the initial volume for alum and lime residuals,
respectively.
11.4.1.2 Capital Components
The capital components for each pressure filter press
system consist of the following items: Schedule 40 steel
piping, polymer feed system, positive displacement
pump(s), pressure filter press(es), steel filtrate tank and
pump, filter cake storage bin, building, piping, electrical,
and instrumentation.
Table 11-6 indicates the sludge volumes and filter press
capacities used to develop the capital cost equation for
pressure filter presses.
11.4.1.3 Operation and Maintenance
Components
The operation and maintenance components for each
pressure filter press system include: electricity, polymer,
labor, maintenance labor and materials, insurance, and
general and administration.
11.4.1.4 Cost Components Excluded
The following cost components are not included in the
cost equations for pressure filter press systems:
• Dewatered residuals disposal.
• Filtrate disposal, if the filtrate cannot be pumped to
the head of the treatment plant.
• Acid wash system, if required.
Costs for residuals disposal techniques are included in
other sections of this chapter. Costs for filtrate disposal,
if the overflow cannot be pumped to the head of the
treatment works, can be determined using other sec-
tions of this chapter.
188
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Table 11-6. Capital Cost Equation Determinants, Pressure
Filter Presses (U.S. EPA, 1993c)
Sludge Flow Rate
(gpd)
500
2,000
5,000
50,000
250,000
600,000
Filter Press Capacity
(ft3)
2.0
10
24
50
130x2
160 x 3
11.4.1.5 Pressure Filter Press Cost Equations
and Cost Curves
The cost equations for the capital components and op-
eration and maintenance were developed by estimating
the costs for six different residuals flow rates. The capital
cost equation calculates the total capital cost (i.e., in-
stalled capital plus indirect capital costs). Equipment
costs and building costs are separate components in the
capital cost equation to enable the user to exclude the
cost for a building addition if it is not necessary. The total
annual cost is calculated based on the capital and op-
eration and maintenance costs obtained using the equa-
tions presented below. A capital cost curve for pressure
filter press is shown in Figure 11-5. An operation and
maintenance cost curve is shown in Figure 11-6.
Capital Cost
Y = [15,600 + 1,520(X050)] + [4,600 + 3.0(X)]
Y = [equipment cost] + [building cost]
where
Y= $
X = gallons of sludge per day
Range: 500 gpd < X < 50,000 gpd
Y = [4,181 (X050) - 579,900] + [22,300 +
(9.8x1Q-2)(X)]
Y = [equipment cost] + [building cost]
where
Y= $
X = gallons of sludge per day
Range: 50,000 gpd < X < 600,000 gpd
Operation and Maintenance
Y= 13,400+ 0.92(X)
where
Y = $/year
X = gallons of sludge per day
Range: 500 gpd < X < 50,000 gpd
Figure 11-5. Capital costs for pressure filter press.
Figure 11-6. O&M costs for pressure filter press.
Y = 32,900 + 0.67(X)
where
Y = $/year
X = gallons of sludge per day
Range: 50,000 gpd < X < 600,000 gpd
189
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Total Annual Cost
Y = [CAP(CRF)] + O&M
where
Y = $/year
CAP = capital cost
CRF = capital recovery factor (e.g., 0.1175)
O& = operation and maintenance cost
11.4.2 Scroll Centrifuge Cost Components
This section presents the design assumptions, capital
components, and the operation and maintenance
components used to prepare the costs for the solid-
bowl, or scroll centrifuge, used for mechanical
sludge dewatering.
11.4.2.1 Design Assumptions
• The polymer feed system consists of polymer storage
tank, a polymer pump, and a polymer/sludge contact
tank, and a 20- to 30-minute holding tank.
• A positive displacement pump feeds conditioned
sludge to the scroll centrifuge.
• The scroll centrifuge operates 8 to 24 hours per day,
depending on the size of the water system.
• Centrate collects in a centrate holding tank before
being pumped to the head of the treatment works.
• Dewatered residuals collect in a small, wheeled con-
tainer that is emptied into a larger solids bin as nec-
essary.
• Large systems are located on the second floor and
the dewatered residuals drop into sludge containers
located below the centrifuge.
• Accumulated solids require disposal on a periodic
basis.
• The dewatered residuals volume is 0.04 of the initial
residuals volume.
11.4.2.2 Capital Components
The capital components for each scroll centrifuge sys-
tem are: Schedule 40 steel piping, polymer feed system,
positive displacement pump, scroll centrifuge with
backdrive, steel centrate tank and pump, dewatered
sludge storage bin, building, piping, electrical, and
instrumentation.
Table 11-7 indicates the sludge flow rates and centrifuge
motor sizes used to develop the capital cost equation for
the scroll centrifuge system.
Table 11-7. Capital Cost Equation Determinants, Scroll
Centrifuge (U.S. EPA, 1993c)
Sludge Flow Rate
(gpd)
2,000
5,000
50,000
250,000
600,000
2,500,000
5,200,000
Centrifuge Motor Size
7 1/2 hp
7 1/2 hp
10 hp
25 hp
40 hp
80 hp x 2
80 hp x 4
11.4.2.3 Operation and Maintenance
Components
The operation and maintenance components for each
scroll centrifuge system include: electricity, polymer, la-
bor, maintenance labor and materials, insurance, and
general and administration.
11.4.2.4 Cost Components Excluded
The following cost components are not included in the
cost equations for scroll centrifuge systems: scroll
cleaning apparatus, dewatered residuals disposal, and
centrifuge overflow disposal, if the overflow cannot be
pumped to the head of the treatment plant.
Costs for residuals disposal techniques are included in
other sections of this chapter. Costs for centrifuge over-
flow disposal, if the overflow cannot be pumped to the
head of the treatment works, can be determined using
other sections of this chapter.
11.4.2.5 Scroll Centrifuge Cost Equations and
Cost Curves
The cost equations for the capital components and op-
eration and maintenance were developed by estimating
the costs for seven different sludge flow rates. The
capital cost equation calculates the total capital cost
(i.e., installed capital plus indirect capital costs). Equip-
ment costs and building costs are separate components
in the capital cost equation to enable the user to exclude
the cost for a building addition if it is not necessary. The
total annual cost is calculated based on the capital and
operation and maintenance costs obtained using the
equations presented below. A capital cost curve for scroll
centrifuge is shown in Figure 11-7 and operation and
maintenance costs are shown in Figure 11-8.
190
-------
100. 000
Sludge (gpd)
Figure 11-7. Capital costs for scroll centrifuge.
Capital Cost
Y = [138,400 + 666(X050)] + [15,400 + 59(X050)]
Y = [equipment cost] + [building cost]
where
Y= $
X = gallons of sludge per day
Range: 2,000 gpd < X < 250,000 gpd
Y = [287,000 + 0.63(X)] + [40,400 + (2.26 x 1Q-2)(X)]
Y = [equipment cost] + [building cost]
where
Y= $
X = gallons of sludge per day
Range: 250,000 gpd < X < 5,500,000 gpd
Operation and Maintenance
Y= 17,500 +311(X050)
where
Y = $/year
X = gallons of sludge per day
Range: 2,000 gpd < X < 250,000 gpd
Y = 72,000 + 0.43(X)
where
Y = $/year
X = gallons of sludge per day
Range: 250,000 gpd < X < 5,500,000 gpd
Sludge (gpd)
Figure 11-8. O&M costs for scroll centrifuge.
Total Annual Cost
Y = [CAP(CRF)] + O&M
where
Y = $/year
CAP = capital cost
CRF = capital recovery factor (e.g., 0.1175)
O&M = operation and maintenance cost
11.5 Nonmechanical Sludge Dewatering
11.5.1 Storage Lagoons Cost Components
This section presents the design assumptions, capital
components, and the operation and maintenance com-
ponents used to estimate the costs for residuals dewa-
tering using storage lagoons.
11.5.1.1 Design Assumptions
• Storage lagoons are used to dewater alum residuals
and are periodically dredged.
• Permanent lagoons are used to dewater lime residu-
als; each storage lagoon has a 10-year capacity.
• The lagoons are earthen basins lined with a synthetic
membrane and a geotextile support fabric. They have
no underdrains, but have a variable height outlet
structure to discharge supernatant. Permanent la-
goons are 6- to 12-feet deep and storage lagoons
range from 3- to 5-feet deep.
191
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Decanted supernatant from the lagoon is collected
and pumped to the head of the treatment plant.
Residuals flow from the treatment plant to the lagoon
by gravity via 1,250 to 4,000 feet of 2- to 6-inch
diameter PVC piping. Pipes are laid 4 feet below
grade.
Alum treatment plants operate two lagoons. Each
lagoon has a 6-month storage capacity. After 6
months, the second lagoon is used while free liquid
from the idle lagoon is allowed to evaporate. The
remaining free liquid is decanted and returned to the
head of the treatment plant. Sludge is dredged from
the lagoon on an annual basis.
Lime treatment plants operate two or four lagoons to
provide a total of 20 years of permanent storage.
Each lagoon has a 6- or 12-month storage capacity
prior to drying and decanting. Free liquid is continu-
ously decanted from the lagoon while it is accepting
sludge and returned to the head of the treatment
plant. After the 6- or 12-month period, another lagoon
is used while free liquid from the idle lagoon is de-
canted and evaporated. The remaining sludge is al-
lowed to dry prior to the next sludge application.
Approximately 1.5 cubic feet of solids per 1,000 gal-
lons of initial alum residuals volume will require final
disposal from the storage lagoons.
11.5.1.2 Capital Components
The capital components for each storage lagoon consist
of: two or four lined earthen lagoons, piping and fittings,
trenching, decant collection pump, electrical, instrumen-
tation, and land clearing.
Tables 11-8 and 11-9 indicate the sludge volumes, num-
ber of ponds, and total lagoon surface area used to
develop the capital cost equation for lime softening and
alum storage lagoons, respectively.
Table 11-8. Capital Cost Equation Determinants, Lime
Softening Storage Lagoons (U.S. EPA, 1993c)
Table 11-9. Capital Cost Equation Determinants, Alum
Storage Lagoons (U.S. EPA, 1993c)
Lime Softening
Sludge Volume
(gpd)
7,000
20,000
50,000
100,000
500,000
1 ,000,000
Number
of Ponds
2
2
2
2
4
4
Total Lagoon
Surface Area
(acres)
5
7
18
37
112
224
Alum Sludge Volume
(gpd)
250
1,000
5,000
10,000
50,000
100,000
200,000
500,000
Number
of Ponds
2
2
2
2
2
2
2
2
Total Surface
Area (acres)
0.1
0.4
2
4
19
22
45
112
11.5.1.3 Operation and Maintenance
Components
The operation and maintenance components for each
storage lagoon include: labor and supervision, mainte-
nance labor and materials, electricity, insurance, gen-
eral and administration, and annual sludge removal
(alum sludge only).
11.5.1.4 Cost Components Excluded
The following cost components are not included in the
cost equations for storage lagoons: sludge dewatering
equipment, dewatered sludge disposal, and supernatant
disposal, if the supernatant cannot be pumped to the
head of the treatment plant.
Costs for sludge disposal techniques are included in
other sections of this chapter. Costs for supernatant
disposal, if the supernatant cannot be pumped to the
head of the treatment plant, can be determined using
other sections of this chapter.
11.5.1.5 Lime Softening Storage Lagoon Cost
Equations and Cost Curves
The cost equations for the capital components and op-
eration and maintenance were developed by estimating
the costs for six different sludge flow rates. The capital
cost equation calculates the total capital cost (i.e., in-
stalled capital plus indirect capital costs). Equipment
costs and land costs are separate components in the
capital cost equation to enable the user to exclude the
cost for purchasing land if it is not necessary. The total
annual cost is calculated from the capital and operation
and maintenance costs obtained using the equations
presented below. A capital cost curve for lime softening
storage lagoon is shown in Figure 11-9. An operation
and maintenance cost curve is shown in Figure 11-10.
192
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Sludge (gpd)
i. ooo. DGO
Lsad cost»«. 000/are
Figure 11-9. Capital costs for lime softening storage lagoon.
Capital Costs
Y = [144(X091)] + {[(1.57 x 10-3)(X087)](Z)}
Y = [equipment cost] + [land cost]
where
Y=$
X = gallons of sludge per day
Z = land cost in $/acre (e.g., $10,000/acre)
Range: 2,800 gpd < X < 1,000,000 gpd
Operation and Maintenance
Y = 7,700 + 1.69(X)
where
Y=$
X = gallons of sludge per day
Range: 2,800 gpd < X < 50,000 gpd
Y = 33,100 + 1.33(X)
where
Y = $/year
X = gallons of sludge per day
Range: 50,000 gpd < X < 1,000,000 gpd
Total Annual Cost
Y = [CAP(CRF)] + O&M
where
Y = $/year
CAP = capital cost
CRF = capital recovery factor (e.g., 0.1175)
O&M = operation and maintenance cost
Figure 11-10. O&M costs for lime softening storage lagoon.
11.5.1.6 Alum Sludge Storage Lagoons Cost
Equations and Cost Curves
The cost equations for the capital components and op-
eration and maintenance were developed by estimating
the costs for eight different sludge flow rates. The capital
cost equation calculates the total capital cost (i.e., in-
stalled capital plus indirect capital costs). Equipment
costs and land costs are separate components in the
capital cost equation to enable the user to exclude the
cost for purchasing land if it is not necessary. The total
annual cost is calculated from the capital and operation
and maintenance costs obtained using the equations
presented below. A capital cost curve for alum sludge
storage lagoons is shown in Figure 11-11. An operation
and maintenance cost curve is shown in Figure 11-12.
Capital Costs
Y = [13,700 + 60.8(X)] + {[0.5 + (3.44 x 1Q-4)(X)](Z)}
Y = [equipment cost] + [land cost]
where
Y= $
X = gallons of sludge per day
Z= land cost in $/acre (e.g., $10,000/acre)
Range: 250 gpd < X < 10,000 gpd
Y = [326,500 + 28.6(X)] + {[4.2 + (2.35 x 10'4)(X)](Z)}
Y = [equipment cost] + [land cost]
where
Y= $
193
-------
mil
mr
~/ -
1,000.000
SIMOO/acre
Figure 11-11. Capital costs for alum sludge storage lagoon.
X = gallons of sludge per day
Z = land cost in $/acre (e.g., $10,000/acre)
Range: 10,000 gpd < X < 500,000 gpd
Operation and Maintenance
Y = 6,100 + 2.56(X)
where
Y = $/year
X = gallons of sludge per day
Range: 250 gpd < X < 10,000 gpd
Y = 28,500 + 1.02(X)
where
Y = $/year
X = gallons of sludge per day
Range: 10,000 gpd < X < 500,000 gpd
Total Annual Cost
Y = [CAP(CRF)] + O&M
where
Y = $/year
CAP = capital cost
CRF = capital recovery factor (e.g., 0.1175)
O&M = operation and maintenance cost
11.5.2 Evaporation Ponds Cost Components
The following section presents the design assumptions,
capital components, and the operation and maintenance
Sludge (gpd)
Figure 11-12. O&M costs for alum sludge storage lagoon.
components used to prepare the costs for evaporation
ponds.
11.5.2.1 Design Assumptions
• The evaporation pond is used for treatment of IX or
RO brines. The influent solids concentration ranges
from 1.5 to 3.5 percent by weight.
• RO systems with flow rates of 4.8 mgd and greater,
and IX systems with flow rates of 51 mgd and greater
are not considered applicable for evaporation ponds
since over 150 acres is required to evaporate the
daily generation volumes.
• Waste brines flow from the treatment plant to the
evaporation pond by gravity or by the pressure from
the treatment system via 1,250 to 4,000 feet of 4- to
8-inch diameter PVC piping. Pipes are laid 4 feet
below grade.
• Waste brine flow rates range from 31,000 to 500,000
gallons per day.
• The pond is designed for a geographical region with
a net annual evaporation rate of at least 45 inches
per year.
• The pond has no outlet.
• The pond sides and earthen berm are engineered to
have 2.5 to 1 side slopes and 2 feet of free board.
• Soils cut from the excavation of the basin are used
to construct the berm.
194
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• The pond is constructed with a synthetic membrane
liner and a geotextile support fabric; 1 foot of sand is
placed on top of the liner.
• Piping from the treatment process is sized to dis-
charge the waste brines to the ponds as they are
generated. The treatment process is assumed to run
8 to 16 hours per day.
• The evaporation ponds are sized with sufficient sur-
face area to evaporate the average daily flow. The
pond depth is 2 feet, which provides solids storage
volume and accommodates peak flows.
11.5.2.2 Capital Components
The capital components for each evaporation pond are:
evaporation ponds, piping and fittings, pumps, land
clearing, and instrumentation.
Table 11-10 indicates the brine volumes, number of
ponds, and the total required surface area used to de-
velop the capital cost equation for evaporation ponds.
Table 11-10. Capital Cost Equation Determinants,
Evaporation Ponds (U.S. EPA, 1993c)
Brine Volume
(gpd)
31,000
50,000
100,000
200,000
400,000
500,000
Number of
Ponds
2
2
2
4
6
3
Total Surface
Area (acres)
10
15
30
60
120
150
11.5.2.3 Operation and Maintenance
Components
The operation and maintenance components for each
evaporation pond include: mowing, labor and supervi-
sion, maintenance labor and materials, insurance, and
general and administration.
11.5.2.4 Cost Components Excluded
The cost component not included in the cost equations
for evaporation ponds is dewatered sludge disposal.
Costs for sludge disposal are included in other sections
of this chapter.
11.5.2.5 Evaporation Ponds Cost Equations and
Cost Curves
The cost equations for the capital components and for
operation and maintenance were developed by estimat-
ing the costs for six different brine flow rates. The capital
cost equation calculates the total capital cost (i.e., in-
stalled capital plus indirect capital cost). The total annual
cost is calculated from the capital and operation and
maintenance costs obtained using the equations pre-
sented below. A capital cost curve for evaporation ponds
is shown in Figure 11-13. An operation and maintenance
cost curve is shown in Figure 11-14.
Figure 11-13. Capital costs for evaporation ponds.
Figure 11-14. O&M costs for evaporation ponds.
195
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Capital Cost
Y = [193,600 + 28.8(X)] + [4.08(X098)(Z)]
Y = [equipment cost] + [land cost]
where
Y=$
X = gallons of brine per day
Z = land cost in $/acre (e.g., $10,000/acre)
Range: 30,000 gpd < X < 150,000 gpd
Y = [44,820(X05) - (1.43 x 107)] + [4.08(X098)(Z)]
Y = [equipment cost] + [land cost]
where
Y=$
X = gallons of brine per day
Z = land cost in $/acre (e.g., $10,000/acre)
Range: 150,000 gpd < X < 500,000 gpd
Operation and Maintenance
Y= 11,600 + 0.96(X)
where
Y = $/year
X = gallons of brine per day
Range: 30,000 gpd < X < 150,000 gpd
Y= 1,500(X050)-476,000
where
Y = $/year
X = gallons of brine per day
Range: 150,000 gpd < X < 500,000 gpd
Total Annual Cost
Y = [CAP(CRF)] + O&M
where
Y = $/year
CAP = capital cost
CRF = capital recovery factor (e.g., 0.1175)
O&M = operation and maintenance cost
11.6 Discharge to Publicly Owned
Treatment Works
This section presents the design assumptions, capital
components, and the operation and maintenance com-
ponents used to estimate the costs for discharging to a
POTW.
11.6.1 Design Assumptions
• Residuals flow rates range from 2,000 to 25 million
gallons per day, depending on the water treatment
technology.
• The sewer line connection is 500 feet or 1,000 feet
from the water treatment system.
• The residuals stream flows by gravity or under pres-
sure from the treatment process to the sewer line.
• Two-inch minimum diameter pipe is used to prevent
clogging. Pipe diameter ranges from 2 to 24 inches.
• PVC or reinforced concrete piping is used.
• A 1- to 2-day storage lagoon is optional.
11.6.2 Capital Components
The capital components of system for discharge to a
POTW consist of piping and fittings, trenching, and land
clearing.
In addition, a pump, storage lagoon, electrical, and in-
strumentation are added for those facilities electing to
store residuals prior to discharge to a POTW.
Table 11-11 indicates the brine volumes, pipe diameters,
and lagoon capacities used to develop the capital cost
equation for discharge to POTW systems.
Table 11-11. Capital Cost Equation Determinants, Discharge
to POTW (U.S. EPA, 1993c)
Residuals Flow Rate
(gpd)
30,000
67,500
162,500
500,000
750,000
1 ,000,000
10,000,000
25,000,000
Pipe Diameter
(in.)
2
2
3
4
6
6
24
36
Lagoon
Capacity (gal)
50,000
115,000
330,000
750,000
1,125,000
1 ,500,000
15,000,000
37,500,000
11.6.3 Operation and Maintenance
Components
The operation and maintenance components of each
system for discharge to a POTW include: labor and
supervision, maintenance labor and materials, basic
POTW charges, total suspended solids (TSS) sur-
charges, electricity, insurance, and general and admini-
stration.
11.6.4 Cost Components Excluded
The cost components not included in the cost equations
for systems for discharge to a POTW are any fees
charged by the POTW for the initial connection and land
cost.
It is assumed the water treatment facility would be able
to gain access for piping via an easement.
196
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11.6.5 Cost Equations and Cost Curves for
Discharge to Publicly Owned
Treatment Works
The cost equations for the capital components and op-
eration and maintenance were developed by estimating
the costs for eight different brine flow rates. The capital
cost equation calculates the total capital cost (i.e., in-
stalled capital plus indirect capital costs). The total an-
nual cost is calculated from the capital and operation
and maintenance costs obtained using the equations
presented below.
11.6.5.1 500 Feet of Discharge Pipe
Capital costs for 500 feet of discharge pipe are shown
in Figure 11-15. Operation and maintenance costs are
shown in Figure 11-16.
Capital Costs
Y = 4,500
where
Y=$
X = gallons of brine per day
Range: 2,000 gpd < X < 150,000 gpd
Y = 4,600 + (1.9x1Q-3)(X)
where
Y=$
X = gallons of brine per day
Range: 150,000 gpd < X < 25,000,000 gpd
rm r
i, ooo. ooo 10, ODO, ODO 100, ooi
Operation and Maintenance
Y = 1,000 + [(1.83 x 10-3)(365)(X)] + [(0.12)(365)(Z)]
Y = [operating cost] + [POTW volume charge] +
[POTW strength charge]
where
Y = $/year
X = gallons of brine per day
Z = TSS pounds per day in excess of 300 ppm
(1.83 x 10'3 = POTW volume charge)
(0.12 = TSS surcharge)
Range: 2,000 gpd < X < 25,000,000 gpd
Total Annual Cost
Y = [CAP(CRF)] + O&M
where
Y = $/year
CAP = capital cost
CRF = capital recovery factor (e.g., 0.1175)
O&M = operation and maintenance cost
11.6.5.2 1,000 Feet of Discharge Pipe
Capital costs for 1,000 feet of discharge piping are
shown in Figure 11-17 and operation and maintenance
costs are shown in Figure 11-18.
-i—i i 11 mi :—i Mill
10, DDO 100, ODD 1, ODO, ODO 10, DDO. 000 103. DOD, OOC
Brine {gpd) TSS cut exceeding 300 ppm
Figure 11-15. Capital costs for 500 feet of discharge pipe.
Figure 11-16. O&M costs for 500 feet of discharge pipe.
197
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~1—I I i I I III 1—I I I I [III i—I I I Mill | I I I I
[.ODD 10,000 100,000 1,000,000 10,000,000 100,000,000
Brine (gpd)
Figure 11-17. Capital costs for 1,000 feet of discharge pipe.
Capital Costs
Y = 8,700
where
Y= $
X = gallons of brine per day
Range: 2,000 gpd < X < 150,000 gpd
Y= 9,000 + (3.9x1Q-3)(X)
where
Y=$
X = gallons of brine per day
Range: 150,000 gpd < X < 25,000,000 gpd
Operation and Maintenance
Y = 1,000 + [(1.83 x 10-3)(365)(X)] + [(0.12)(365)(Z)]
Y = [operating cost] + [POTW volume charge] +
[POTW strength charge]
where
Y = $/year
X = gallons of brine per day
Z = TSS pounds per day in excess of 300 ppm
(1.83 x 10'3 = POTW volume charge)
(0.12 = TSS surcharge)
Range: 2,000 gpd < X < 25,000,000 gpd
100.000 1.000, 000
Brine (gpd)
10.000, 000 10D, DOC, 000
1SS not erceeding 300 pp;n
Figure 11-18. O&M costs for 1,000 feet of discharge pipe.
Total Annual Costs
Y = [CAP(CRF)] + O&M
where
Y = $/year
CAP = capital cost
CRF = capital recovery factor (e.g., 0.1175)
O&M = operation and maintenance cost
11.6.5.3 500 Feet of Discharge Pipe With a
Storage Lagoon
Capital and operation and maintenance cost curves for
500 feet of discharge pipe with a storage lagoon are
shown in Figures 11-19 and 11-20.
Capital Costs
Y = [44.3(X056)] + [0.5(Z)]
Y = [equipment cost] + [land cost]
where
Y=$
X = gallons of brine per day
Z = land cost in dollars per acre (e.g., $10,000/acre)
Range: 25,000 gpd < X < 750,000 gpd
Y = [1.13(X084)] + [(2.47 x 10-5)(X074)(Z)]
Y = [equipment cost] + [land cost]
where
Y= $
X = gallons of brine per day
198
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Brine (gpd)
10. 000. 000 100. 000. 000
A cost $10. 000/ac
Figure 11-19. Capital costs for 500 feet of discharge pipe with
storage lagoon.
Z = land cost in dollars per acre (e.g., $10,000/acre)
Range: 750,000 gpd < X < 25,000,000 gpd
Operation and Maintenance
Y = [3,500 + (2.25 x 1Q-2)(X)] + [(1.83 x 1Q-3)(365)(X)]
+ [(0.12)(365)(Z)]
Y = [operating cost] + [POTW volume charge] +
[POTW strength charge]
where
Y = $/year
X = gallons of brine per day
Z = TSS pounds per day in excess of 300 ppm
(1.83 x 10'3 = POTW volume charge)
(0.12 = TSS surcharge)
Range: 25,000 gpd < X < 500,000 gpd
Y = [0.30(X081)] + [(1.83 x 1Q-3)(365)(X)] +
[(0.12)(365)(Z)]
Y = [operating cost] + [POTW volume charge] +
[POTW strength charge]
where
Y = $/year
X = gallons of brine per day
Z = TSS pounds per day in excess of 300 ppm
(1.83 x 10'3 = POTW volume charge)
(0.12 = TSS surcharge)
Range: 500,000 gpd < X < 25,000,000 gpd
ID, ODD, COD 130, 000,000
ISS not exceeding 300 ppm
Figure 11-20. O&M costs for 500 feet of discharge pipe with
storage lagoon.
Total Annual Cost
Y = [CAP(CRF)] + O&M
where
Y = $/year
CAP = capital cost
CRF = capital recovery factor (e.g., 0.1175)
O&M = operation and maintenance cost
11.6.5.4 1,000 Feet of Discharge Pipe With a
Storage Lagoon
Capital and operation and maintenance cost curves for
1,000 feet of discharge pipeline with a storage lagoon
are shown in Figures 11-21 and 11-22.
Capital Cost
Y = [19,500 + (0.11)(X)] + [0.5(Z)]
Y = [equipment cost] + [land cost]
where
Y=$
X = gallons of brine per day
Z = land cost in dollars per acre (e.g., $10,000/acre)
Range: 25,000 gpd < X < 750,000 gpd
199
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Ifiud cost 110, DDO/acte
Figure 11-21. Capital costs for 1,000 feet of discharge pipe with
storage lagoon.
Y = [60,200 + (6.97 x 10'2)(X)] + [(2.47 x 10'5)
(X074)(Z)]
Y = [equipment cost] + [land cost]
where
Y=$
X = gallons of brine per day
Z = land cost in dollars per acre (e.g., $10,000/acre)
Range: 750,000 gpd < X < 25,000,000 gpd
Operation and Maintenance
Y = [3,500 + (2.25 x 1Q-2)(X)] + [(1.83 x 1Q-3)(365)(X)]
+ [(0.12)(365)(Z)]
Y = [operating cost] + [POTW volume charge] +
[POTW strength charge]
where
Y = $/year
X = gallons of brine per day
Z = TSS pounds per day in excess of 300 ppm
(1.83 x 10'3 = POTW volume charge)
(0.12 = TSS surcharge)
Range: 25,000 gpd < X < 500,000 gpd
Y = [0.30(X081)] + [(1.83 x 1Q-3)(365)(X)] +
[(0.12)(365)(Z)]
Y = [operating cost] + [POTW volume charge] +
[POTW strength charge]
where
Y=$/year
1, 000, 000
Brine (gjd)
TSS not exceeding 300 ppm
Figure 11-22. O&M costs for 1,000 feet of discharge pipe with
storage lagoon.
X=gallons of brine per day
Z=TSS pounds per day in excess of 300 ppm
(1.83 x 10'3 = POTW volume charge)
(0.12 = TSS surcharge)
Range: 500,000 gpd < X < 25,000,000 gpd
Total Annual Cost
Y = [CAP(CRF)] + O&M
where
Y =
CAP =
CRF =
O&M =
$/year
capital cost
capital recovery factor (e.g., 0.1175)
operation and maintenance cost
11.7 Direct Discharge
This section presents the design assumptions, capital
components, and the operation and maintenance com-
ponents used to estimate the costs for direct discharge
into surface water.
11.7.1 Design Assumptions
• Residuals flow rates range from 2,000 to 25,000,000
gallons per day depending on the water treatment
technology.
• The discharge point is 500 or 1,000 feet from the
water treatment system.
200
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• The residuals stream flows by gravity or under pres-
sure from the treatment process to the discharge
point.
• Two-inch minimum diameter pipe is used to prevent
clogging. Pipe diameter ranges from 2 to 24 inches.
• PVC or reinforced concrete piping is used.
• A 1- to 2-day storage lagoon is optional.
11.7.2 Capital Components
The capital components for each direct discharge sys-
tem are piping and fittings, trenching, and land clearing.
In addition, a pump, storage lagoon, electrical, and in-
strumentation are added for those facilities electing to
store residuals prior to direct discharge.
Table 11-12 indicates the residuals flow rate, pipe di-
ameters, and storage lagoon capacities used to develop
the capital cost equation for direct discharge.
Table 11-12. Capital Cost Equation Determinants, Direct
Discharge (U.S. EPA, 1993c)
Residuals Flow
Rate (gpd)
30,000
67,500
162,500
500,000
750,000
1 ,000,000
10,000,000
25,000,000
Pipe Diameter
(in.)
2
2
3
4
6
6
24
36
Lagoon
Capacity (gal)
50,000
115,000
330,000
750,000
1,125,000
1 ,500,000
15,000,000
37,500,000
11.7.3 Operation and Maintenance
Components
The operation and maintenance components for each
direct discharge system include: labor and supervision,
maintenance labor and materials, electricity, insurance,
and general and administration.
11.7.4 Cost Components Excluded
The cost components not included in the cost equations
for direct discharge systems are: NPDES permit appli-
cation and monitoring costs, and land costs. It is as-
sumed that the water treatment facility would be able to
gain access for piping via an easement.
11.7.5 Cost Equations for Direct Discharge
The cost equations for the capital components and op-
eration and maintenance were developed by estimating
the costs for eight different residuals flow rates. The
capital cost equation calculates the total capital cost
(i.e., installed capital plus indirect capital costs). The
total annual cost is calculated from the capital and op-
eration and maintenance costs obtained using the equa-
tions presented below.
11.7.5.1 500 Feet of Discharge Pipe
Capital Costs
Y = 4,500
where
Y= $
X = gallons of brine per day
Range: 2,000 gpd < X < 150,000 gpd
Y = 4,600 + [(1.9x10-3)(X)]
where
Y= $
X = gallons of brine per day
Range: 150,000 gpd < X < 25,000,000 gpd
Operation and Maintenance
Y= 1,000
where
Y = $/year
X = gallons of brine per day
Range: 2,000 gpd < X < 25,000,000 gpd
Total Annual Cost
Y = [CAP(CRF)] + O&M
where
Y = $/year
CAP = capital cost
CRF = capital recovery factor (e.g., 0.1175)
O&M = operation and maintenance cost
11.7.5.2 1,000 Feet of Discharge Pipe
Capital Cost
Y = 8,700
where
Y= $
X = gallons of brine per day
Range: 2,000 gpd < X < 150,000 gpd
Y = 9,000 + [(3.9x1Q-3)(X)]
where
Y=$
X = gallons of brine per day
Range: 150,000 gpd < X < 25,000,000 gpd
201
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Operation and Maintenance
Y= 1,000
where
Y = $/year
X = gallons of brine per day
Range: 2,000 gpd < X < 25,000,000 gpd
Total Annual Cost
Y = [CAP(CRF)] + O&M
where
Y = $/year
CAP = capital cost
CRF = capital recovery factor (e.g., 0.1175)
O&M = operation and maintenance cost
11.7.5.3 500 Feet of Discharge Pipe With a
Storage Lagoon
Capital Costs
Y = [44.3(X056)] + [0.5(Z)]
Y = [equipment cost] + [land cost]
where
Y=$
X = gallons of brine per day
Z = land cost in dollars per acre (e.g., $10,000/acre)
Range: 25,000 gpd < X < 750,000 gpd
Y = [1.13(X084)] + [(2.47 x 10-5)(X074)(Z)]
Y = [equipment cost] + [land cost]
where
Y= $
X = gallons of brine per day
Z = land cost in dollars per acre (e.g., $10,000/acre)
Range: 750,000 gpd < X < 25,000,000 gpd
Operation and Maintenance
Y = 3,500 + [(2.25x10-2)(X)]
where
Y = $/year
X = gallons of brine per day
Range: 25,000 gpd < X < 500,000 gpd
Y = 0.30(X081)
where
Y = $/year
X = gallons of brine per day
Range: 500,000 gpd < X < 25,000,000 gpd
Total Annual Cost
Y = [CAP(CRF)] + O&M
where
Y = $/year
CAP = capital cost
CRF = capital recovery factor (e.g., 0.1175)
O&M = operation and maintenance cost
11.7.5.4 1,000 Feet of Discharge Pipe With a
Storage Lagoon
Capital Cost
Y = [19,500 + (0.11)(X)] + [0.5(Z)]
Y = [equipment cost] + [land cost]
where
Y= $
X = gallons of brine per day
Z = land cost in dollars per acre (e.g., $10,000/acre)
Range: 25,000 gpd < X < 750,000 gpd
Y = [60,200 + (6.97 x 10'2)(X)] + [(2.47 x 10'5)
(X074)(Z)]
Y = [equipment cost] + [land cost]
where
Y=$
X = gallons of brine per day
Z = land cost in dollars per acre (e.g., $10,000/acre)
Range: 750,000 gpd < X < 25,000,000 gpd
Operation and Maintenance
Y = 3,500 + [(2.25x10'2)(X)]
where
Y = $/year
X = gallons of brine per day
Range: 25,000 gpd < X < 500,000 gpd
Y = 0.30(X081)
where
Y = $/year
X = gallons of brine per day
Range: 500,000 gpd < X < 25,000,000 gpd
Total Annual Cost
Y = [CAP(CRF)] + O&M
where
Y = $/year
CAP = capital cost
CRF = capital recovery factor (e.g., 0.1175)
O&M = operation and maintenance cost
202
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11.8 Land Application
11.8.1 Liquid Sludge Land Application Cost
Components
This section presents the design assumptions, capital
components, and the operation and maintenance com-
ponents used to estimate the costs for the land applica-
tion of liquid residuals.
11.8.1.1 Design Assumptions
• The storage lagoon is constructed with a synthetic
membrane liner, overlaid by 12 inches of sand.
• The applied residuals consist of lime or alum residuals.
• The water treatment plant is 500 feet from the storage
lagoon; the residuals are gravity-fed to the lagoon.
• The lagoons are sized for 6-month storage.
• The application field is cultivated farmland. The
farmer uses a personally owned tractor and fuel to
till the land following the residuals application.
- Application by truck: The residuals are applied
twice a year, spring and fall, in a 1-inch layer.
- Application by sprinkler: The sprinkler system is a
portable system with aboveground piping and a
radius of 50 feet. The land application rate is 1/4
inch per day.
11.8.1.2 Capital Components
The capital components for land application consist of:
storage lagoon, piping, land, electrical, and sprinkler
system, when appropriate. Table 11-13 indicates the
residuals volume and pond surface areas used to de-
velop the capital cost equation for the land application
systems.
Table 11-13. Capital Cost Equation Determinants, Liquid
Residuals Land Application (U.S. EPA, 1993c)
Residuals Volume
(gpd)
2,000
10,000
20,000
60,000
100,000
500,000
Pond Surface Area
(acres)
0.27
0.92
1.26
2.64
3.72
10.97
11.8.1.3 Operation and Maintenance
Components
The operation and maintenance components for land
application include: electricity, labor and supervision,
sludge removal from storage pond, maintenance labor
and materials, insurance, general and administration,
and transportation and land application fees, when ap-
propriate.
11.8.1.4 Cost Components Excluded
Costs for incorporation of the liquid residuals into the
soil, if necessary, are not included in the cost equations
for liquid residuals.
11.8.1.5 Liquid Residuals Land Application Cost
Equations and Cost Curves
The cost equations for the capital components and op-
eration and maintenance were developed by estimating
the costs for six different residuals flow rates. The capital
cost equation calculates the total capital cost (i.e., in-
stalled capital plus indirect capital costs). Equipment
costs and land costs are separate components in the
capital cost equation to enable the user to exclude the
cost for purchasing land if it is not necessary. The total
annual cost is calculated based on the capital and op-
eration and maintenance costs obtained using the equa-
tions presented below.
Sprinkler System
A capital cost curve for liquid residuals land application
using a sprinkler system is shown in Figure 11-23. Op-
eration and maintenance costs are shown in Figure 11-24.
Capital Cost
Y = [120(X078)] + [(2.06 x 10-3)(X066)(Z)] +
[(2.87x10-4)(X)(Z)]
Y = [equipment cost] + [pond land cost] + [application
field cost]
where
Y= $
X = gallons of residuals per day
Z= land cost in $/acres (e.g., $10,000/acre)
Range: 2,000 gpd < X < 500,000 gpd
Operation and Maintenance
Y = 81.7(X° 56)
where
Y = $/year
X = gallons of residuals per day
Range: 2,000 gpd < X < 60,000 gpd
Y = 8.63(X°76)
where
Y = $/year
X = gallons of residuals per day
Range: 60,000 gpd < X < 500,000 gpd
203
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1,000, 000
laai rat (10, 000/am
Figure 11-23. Capital costs for liquid sludge land application.
Total Annual Cost
Y = [CAP(CRF)] + O&M
where
Y = $/year
CAP = capital cost
CRF = capital recovery factor (e.g., 0.1175)
O&M = operation and maintenance cost
Trucking System
Capital and operation and maintenance cost curves for
liquid residuals land application with a residuals applica-
tion truck are shown in Figures 11-25 and 11-26, respec-
tively.
Capital Cost
Y = [104(X078)] + [(2.06 x 10-3)(X066)(Z)]
Y = [equipment cost] + [land cost]
where
Y= $
X = gallons of residuals per day
Z = land cost in $/acre (e.g., $10,000/acre)
Range: 2,000 gpd < X < 100,000 gpd
Operation and Maintenance
Y= 18.9(X096)
where
Y = $/year
X = gallons of residuals per day
1C, ODD 100,000
Sludge (gpd)
Figure 11-24. O&M costs for liquid sludge land application.
Range: 2,000 gpd < X < 100,000 gpd
Total Annual Cost
Y = [CAP(CRF)] + O&M
where
Y = $/year
CAP = capital cost
CRF = capital recovery factor (e.g., 0.1175)
O&M = operation and maintenance cost
11.8.2 Dewatered Residuals Land
Application Cost Components
11.8.2.1 Design Assumptions
• The residuals are stockpiled on site.
• The residuals are transported off site for land appli-
cation.
• A front-end loader is used to load the residuals for
transport. The front-end loader is owned by the WTP.
• The application field is within 25 miles of the plant.
• The application field is agricultural. The farmer grow-
ing crops on the field uses a personally owned tractor
and fuel to till the residuals into the soil.
• The application rate is 2 dry tons of residuals per acre.
204
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Figure 11-25. Capital costs for trucking system.
11.8.2.2 Capital Components
The capital components for dewatered residuals land
application consist of: land for residuals stockpile, and
land clearing. Table 11-14 indicates the residuals vol-
ume and storage pile surface area used to develop the
cost equations for the land application of dewatered
residuals.
Table 11-14. Capital Cost Equation Determinants, Dewatered
Residuals Land Application (U.S. EPA, 1993c)
Residuals Volume
(gpd)
2,000
10,000
20,000
60,000
Storage Pile Surface
Area (acres)
0.34
2.2
4.5
9.2
Figure 11-26. O&M costs for trucking system.
11.8.2.5 Dewatered Residuals Land Application
Cost Equations and Cost Curves
The cost equations for the capital components and op-
eration and maintenance were developed by estimating
the costs for four different residuals flow rates. The
capital cost equation calculates the total capital cost
(i.e., installed capital plus indirect capital costs). Equip-
ment costs and land costs are separate components in
the capital cost equation to enable the user to exclude
the cost for purchasing land if it is not necessary. The
total annual cost is calculated based on the capital
and operation and maintenance costs obtained using
the equations presented below. Capital and operation
and maintenance cost curves for dewatered residuals
land application are shown in Figures 11-27 and 11-28,
respectively.
11.8.2.3 Operation and Maintenance
Components
The operation and maintenance components for each
dewatered residuals land application include: labor and
supervision, residuals loading, and transportation and
land application fees.
11.8.2.4 Cost Components Excluded
Costs for incorporation of the dewatered residuals into
the soil, if necessary, are not included in the cost equa-
tions for dewatered residuals.
Capital Cost
Y = [(111)(XUbU) - 4,700] + [0.5(Z)]
Y = [equipment cost] + [land cost]
where
Y=$
X = gallons of residuals per day
Z= land cost in $/acre (e.g., $10,000/acre)
Range: 2,000 gpd < X < 2,500 gpd
205
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land coat $10, 000/acte
Figure 11-27. Capital costs for dewatered sludge land
application.
Y = [(111)(X050) - 4,700] + {[(4.9 x 10'2)
(X° 50) -
Y = [equipment cost] + [land cost]
where
Y=$
X = gallons of residuals per day
Z = land cost in $/acre (e.g., $10,000/acre)
Range: 2,500 gpd < X < 60,000 gpd
Operation and Maintenance
Y = 800 + 28.2(X)
where
Y = $/year
X = gallons of residuals per day
Range: 2,000 gpd < X < 60,000 gpd
Total Annual Cost
Y = [CAP(CRF)] + O&M
where
Y = $/year
CAP = capital cost
CRF = capital recovery factor (e.g., 0.1175)
O&M = operation and maintenance cost
Figure 11-28. O&M costs for dewatered sludge land
application.
11.9 Nonhazardous Waste Landfill
11.9.1 Off-Site Nonhazardous Waste Landfill
Cost Components
This section presents the design assumptions used to
estimate the costs for offsite nonhazardous waste landfills.
11.9.1.1 Design Assumptions
• A commercial nonhazardous waste landfill is used for
residuals disposal.
• Transportation distance varies from 5 to 50 miles.
• There is no economy of scale for large waste volumes.
• All wastes pass the Paint Filter Liquids Test.
• The waste does not exhibit the characteristics of ig-
nitability, corrosivity, reactivity, or toxicity.
11.9.1.2 Cost Components
The cost components for nonhazardous waste landfill
consist of commercial nonhazardous waste landfill tip-
ping fee and transportation fees.
11.9.1.3 Offsite Nonhazardous Waste Landfill
Cost Equation and Cost Curve
The total operation and maintenance cost is based on
the disposal and transportation costs shown in the equa-
tion presented below. An operation and maintenance
cost curve for offsite nonhazardous waste landfill with
206
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transportation distances of 5 miles and 50 miles is
shown in Figure 11-29.
Total Annual Cost
Y = [35(X)] + [(2.48 + 0.16Z)(X)]
Y = [disposal] + [transportation]
where
Y = $/year
X = tons of residuals requiring disposal/year
Z = transportation distance from 5 to 50 miles
11.9.2 Onsite Nonhazardous Waste Landfill
Cost Components
This section presents the design assumptions used to
estimate the costs for onsite nonhazardous waste land-
fills, the capital cost components, and the operation and
maintenance components.
11.9.2.1 Design Assumptions
• The landfill has a 20-year operating life.
• The landfill is a combination fill (i.e., a design com-
bining below and above grade fills).
• The landfill containment system consists of 2 feet of
clay, a 30 mil HOPE liner, 1 foot of sand with a
leachate collection system, a geotextile filter fabric,
and 1 foot of native soil fill.
Sludge (toss/year)
Figure 11-29. O&M costs for off-site nonhazardous waste
landfill.
• The intermediate cover consists of slope and earthfill
soils.
• Aground-water monitoring system is installed and is
sampled biannually.
• The final cover consists of 1 foot of native soil fill, a
geotextile support fabric, a 30 mil PVC liner, 1 foot
of sand with drain tiles, a geotextile filter fabric, and
1.5 feet of topsoil.
• The postclosure care period is 30 years.
11.9.2.2 Capital Components
The capital components for each landfill consist of land,
land clearing, landfill excavation, composite (clay and
synthetic) liner, leachate collection system, ground-
water monitoring system, equipment storage and main-
tenance buildings, visual screening berm, bulldozer,
truck, and inspection, testing and quality assurance.
11.9.2.3 Operation and Maintenance Components
The operation and maintenance components for each
landfill include labor and supervision, maintenance labor
and materials, intermediate cover, ground-water moni-
toring, leachate collection and treatment, and utilities,
including electricity and water.
11.9.2.4 Closure Components
The closure components for each landfill include final
cover system (including drain tiles), revegetation, and
inspection, testing, and quality assurance.
11.9.2.5 Postclosure Components
The postclosure components for each landfill include
ground-water monitoring, leachate collection and treat-
ment, landscape maintenance, slope maintenance, and
annual inspection.
11.9.2.6 Cost Components Excluded
Siting and permitting costs are not included in the cost
estimates. Regulatory requirements for RCRA-regu-
lated Subtitle D landfills vary from state to state. Permit-
ting costs will vary based on the size of the landfill and
the local governing jurisdiction.
11.9.2.7 Onsite Nonhazardous Waste Landfill
Cost Equations and Cost Curves
The capital cost, operation and maintenance cost, clo-
sure cost, and postclosure cost equations for onsite
nonhazardous waste landfills are presented below. A
capital cost curve is shown in Figure 11-30. An operation
and maintenance cost curve is presented in Figure 11-
31. Figure 11-32 shows a closure cost curve, and Figure
11-33 an annual postclosure cost curve.
207
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Figure 11-30. Capital costs for onsite nonhazardous waste
landfill.
Figure 11-31. O&M costs for onsite nonhazardous waste
landfill.
Sludge (tons/year)
10. ooo
Sludge (tons/jear)
Figure 11-32. Closure costs for onsite nonhazardous waste Figure 11-33. Postclosure costs for onsite nonhazardous
landfill. waste landfill.
208
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Capital Costs
Y = [8,079(X° 67)] + {[20.4 + 0.33(X° 50)](Z)}
Y = [landfill cost] + [land cost]
where
Y=$
X = tons of residuals requiring disposal per year
Z = land cost in $/acre (e.g., $10,000/acre)
Range: 2,500 TRY < X < 100,000 TRY
Operation and Maintenance
Y= [2,411(X050)]-83,900
where
Y = $/year
X = tons of residuals requiring disposal per year
Range: 2,500 TRY < X < 30,000 TRY
Y = [246(X050)] + 300,900
where
Y = $/year
X = tons of residuals requiring disposal per year
Range: 30,000 < X < 100,000 TRY
Closure
Y = 506(X° 80)
where
Y= $
X = tons of residuals requiring disposal per year
Range: 2,500 TRY < X < 100,000 TRY
Postclosure
Y = 600 + 58.2(X
0.5\
where
Y = $/year
X = tons of residuals requiring disposal per year
Range: 2,500 TRY < X < 100,000 TRY
Total Annual Cost
Y = [8,483(X050) - 250,300] + {[2.4 + 0.04(X050)](Z)}
where
Y = $/year
X = tons of residuals requiring disposal per year
Z = land cost in $/acre (e.g., $10,000/acre)
Range: 2,500 TRY < X < 100,000 TRY
11.10 Hazardous Waste Landfill
This section presents the design assumptions, capital
components, and the operation and maintenance com-
ponents used to estimate the costs for hazardous waste
landfills.
11.10.1 Design Assumptions
• A commercial hazardous waste landfill is used for
residuals disposal.
• Transportation distance varies from 200 to 500 miles.
• There is no economy of scale for large waste vol-
umes.
• All wastes pass the Paint Filter Liquids Test or, if they
fail it, they are stabilized prior to disposal.
• The waste fails the TCLP test.
• Some wastes require stabilization prior to disposal to
meet the Land Disposal Restrictions Treatment
Standards for toxicity characteristic (TC) wastes.
11.10.2 Cost Components
The cost components for hazardous waste landfill con-
sist of: hazardous waste landfill charges, stabilization
charges, and transportation fees.
11.10.3 Cost Components Excluded
The cost components not included in the cost equations
for hazardous waste landfills are: generator notification
requirements, manifest requirements, and other RCRA
requirements, as applicable.
11.10.4 Total Annual Cost Equation and Cost
Curves
Operation and maintenance cost equations for hazard-
ous waste disposal and for stabilization and hazardous
waste disposal are presented below.
11.10.4.1 Hazardous Waste Disposal
An operation and maintenance cost curve for hazardous
waste disposal is shown in Figure 11-34, based on
transportation distances of 200 and 500 miles.
Y = [200 X] + {[7.9 + 0.22(Z)](X)}
Y = [disposal] + [transportation]
where
Y = $/year
X = tons of residuals requiring disposal per year
Z = transportation distance between 200 and 500
miles
11.10.4.2 Stabilization and Hazardous Waste
Disposal
An operation and maintenance cost curve for stabilization
and hazardous waste disposal is shown in Figure 11-35.
209
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Figure 11-34. O&M costs for hazardous waste disposal.
Figure 11-35. O&M costs for stabilization and hazardous waste
disposal.
Y = [400(X)] + {[7.9 + 0.22(Z)](X)}
Y = [stabilization/disposal] + [transportation]
where
Y = $/year
X = tons of residuals requiring disposal per year
Z = transportation distance between 200 and 500
miles
11.11 Radioactive Waste Disposal
11.11.1 Low-Level Radioactive Waste
Disposal
There are three low-level radioactive waste disposal
sites operating in Nevada, South Carolina, and Wash-
ington, and one naturally occurring radioactive material
(NORM) disposal site operating in Utah. Each low-level
site bases waste disposal costs on several factors in-
cluding state of origin of the waste, type of waste, and
measured radioactivity at the container surface. All dis-
posal facilities are part of a regional pricing compact.
The Low-Level Radioactive Waste Policy Amendments
Act (LLRWPAA) of 1985 authorized the formation of
regional compacts and a system of incentives and pen-
alties to ensure that states and compacts will be respon-
sible for their own waste after January 1, 1993. States
that are part of a compact with an operational waste
disposal facility pay the lowest disposal costs while
states located outside of the compacts with disposal
facilities pay a disposal surcharge of $40 or $120 per
cubic foot (approximately $300 to $900 per 55-gallon
drum). The NORM disposal site is not part of a pricing
compact and does not add surcharges.
11.11.2 Cost Information for Radioactive
Waste Disposal
Radioactive waste disposal costs are not included within
this chapter. These costs may be obtained from EPAs
guideline document, Suggested Guidelines for the Dis-
posal of Drinking Water Treatment Wastes Containing
Naturally Occurring Radionuclides (U.S. EPA, 1990c).
These guidelines provide cost-related information, rec-
ommendations, and a summary of existing regulations
and criteria used by EPA and other agencies in address-
ing the disposal of radionuclides.
210
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Chapter 12
Case Studies
12.1 Case Study 1: Disposal of Water
Treatment Residuals From Pine
Valley Water Treatment Plant,
Colorado Springs, Colorado
The Pine Valley Water Treatment Plant, located on the
southwest boundary of the U.S. Air Force Academy in
Colorado Springs, Colorado, was originally constructed
as a 42 million gallons per day (mgd) direct filtration
plant and placed into service in July 1969. The location
of the plant is shown in Figure 12-1. Expansion and
improvements over the years have increased design
and overload capacities to 56 and 84 mgd, respectively.
The addition of sedimentation basins in 1987 converted
the plant to a conventional treatment plant. Figure 12-2
illustrates the present site plan and facilities.
12.1.1 Facility Information
12.1.1.1 Treatment Processes
The Pine Valley Treatment Plant is a conventional facility
using the following processes: chemical addition with
in-line static mixing, coagulation-flocculation, sedimen-
tation, and dual-media filtration, using two parallel treat-
ment trains. An underground reservoir adjacent to the
plant provides 10 mgd of treated water storage. Two of
the eight filters are multimedia, i.e., containing coal, filter
sand, and garnet sand. The sedimentation basins con-
tain stainless steel lamella plates. The rapid mix and
slow mix units, numbers 6 and 10 on Figure 12-3, have
been taken out of service. Figure 12-3 is a schematic
showing the direction of flow through the facility.
The chemicals applied at the Pine Valley Plant include
chlorine, aluminum sulfate, sodium aluminate, coagu-
lant aid (Nalco 8100), filter aid (Nalco 8170), and soda
ash. Monthly average dosages for the chemicals used
from 1987 through 1992 are shown in Appendix D.
12.1.1.2 Raw Water Supply
The Pine Valley Plant was constructed primarily to treat
the Homestake Project water supply stored in Rampart
Reservoir. Subsequent acquisition of additional western
slope water supplies has provided other sources need-
ing storage in the Rampart Reservoir. A 3.5-mile pres-
surized pipeline supplies raw water from the reservoir to
the plant. Water quality data for the plant's influent raw
water for 1987 through 1992 are shown in Appendix D.
12.1.1.3 Plant Facility and Flow
Raw water is conveyed to the plant through a pipeline that
reduces from 42 to 36 to 30 inches (see Figure 12-2).
Modulating valves are in place to control the flow of water
to one of two parallel treatment trains designated as "A" or
"B." Water enters a static mixer, continues through the
flocculation and sedimentation basins, and then flows onto
the filters, as shown in this schematic. Treated water leav-
ing the plant is stored in an adjacent 10 million gallon (MG)
covered reservoir until needed in the system. Filter back-
wash water is discharged into the washwater recovery
basin. Sedimentation basin sludge and washdown water
are discharged to the sediment collection pond (see Figure
12-4) and/or washwater recovery basin. Water from the
recovery basin is systematically recycled to the plant head-
works. Annual figures for the quantities of waste streams
generated are presented in Table 12-1. Decant water from
the sedimentation/collection pond will not be recycled until
a pump station is constructed; one is currently scheduled
for installation in 1996.
12.1.2 Residuals Management
The original plan for residuals management at the Pine
Valley WTP included the use of sediment lagoons (sedi-
ment drying beds), decanting, and landfilling. Decanting
operations were discontinued when the 1973 Colorado
Water Quality Control Act was promulgated. Pine Valley,
in service since 1969, did experience labor intensive
operations and limited capacity to store their annual
sediment production. In 1980, additional sediment han-
dling facilities were installed to include sediment re-
moval and transfer equipment in the washwater
recovery basin and two sediment drying beds. The new
facilities did not perform as planned, resulting in residu-
als containing too much water and incapable of being
removed with loaders and dump trucks (see Figure 12-5).
Because the facilities did not produce the desired re-
sults, a long-range plan was developed for ultimate
disposal. The plan, considered the most suitable and
211
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USAIR FORCE
ACADEMY
MANITOU SPRINGS
BLACK FOREST:
NORTH
NO SCALE
COLORADO SPRINGS
Figure 12-1. Locus map of Pine Valley WTP, Colorado Springs, CO (Colorado Springs Utilities, 1994).
economical method of sediment disposal, was to obtain
a site just east of Pine Valley and construct new disposal
facilities. The new sediment disposal facilities would
receive sediment from the Pine Valley WTP and another
proposed 150-mgd WTP. The new facilities, including a
175 acre-foot (acre-ft) sediment collection pond and two
3.5-acre-ft sediment drying ponds, were constructed
and placed into service in 1991. The new 150-mgd WTP
is scheduled for completion in 1996.
12.1.3 Residuals Handling Facilities and
Operations
12.1.3.1 Facilities
Current residuals disposal facilities at Pine Valley con-
sist of a 1.5-MG washwater recovery basin with sedi-
ment collection and transfer equipment, four sediment
drying ponds (2 MG), and an offsite designated landfill
(Hanna Ranch). Additional facilities include sharing of
the 17 million-ft3 sediment collection/holding basin, and
the two 3.5-acre-ft sediment drying ponds. Equipment
used to transfer sediment from the sediment drying
ponds to the landfill area include a sludge pump, tractor,
and 9,000-gallon tank trailer. Additional equipment is
used at the landfill site for monitoring, landscaping, and
erosion, dust, weed, and pest control.
12.1.3.2 Operations
Filter backwash water is discharged into the 1.5-MG
washwater recovery basin. Water containing sediment,
generated by washing down the flocculation and sedi-
mentation basins, is transferred to the 128-MG sediment
collection basin (see Figures 12-2 and 12-4). Decant
from the recovery basin is pumped back to the plant
212
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WEST
MONUMENT CTEE1C
IMTAKE
\
. (-1-
2.
r^Xe
J* F*4 "
**' >**" *, ^
TO SEDMENTiTlC
DISPOSAL PONDS
SEDMENTATION BU1N
SLLOOE OOMTROL'
STRJCTURE
33* CVERFLO* » DRAIN
Figure 12-2. Schematic of Pine Valley WTP, Colorado Springs, CO (Colorado Springs Utilities, 1994).
213
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Pine Valley Purification Plant - Flow Chart
1. Diversion dam (raw water intake)
2. 980,000 Gallon Regulating Tank
3. 36-Inch Raw Water Supply Line
4. Plant Divides Into A (south) and B (north) Halves
5. Control Valves
6. Rapid Mixers
7. Alum Feeders
8. Soda Ash Feeders
9. Chlorinators
10. Slow Mix Basins
11. Filter Influent Headers and Valves
12. Central Control Console
13. Diagrammatic Section Rapid Sand Filter
14. Cutaway View of Filter Bed
15. 42-Inch Filtered Water Header
16. 10 Million Gallon Filtered Water Reservoir (underground)
17. 48-Inch Transmission Main to City
18. Washwater Tank Supply
19. 400,000 Gallon Washwater Storage Tank
20. 24-Inch Washwater Waste Pipe
21. Washwater Recovery Basin and Pump Station
22. 20-Inch Recovery Basin Discharge Pipe
(returns wastewater to raw water system)
23. Sludge Drying Beds
Stream
in
a>
£
V)
O)
O
•O
s
.0
o
o,
o
o
in
O)
Q.
v>
o
•o
re
.o
o
o
c
£
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•c
re
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o
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AIR RELEASE VALVE
I J
Figure 12-4. Sediment and decant piping schematic, Pine Val-
ley WTP, Colorado Springs, CO (Colorado Springs
Utilities, 1994).
Table 12-1. Water Treated and Used, Pine Valley WTP,
Colorado Springs, CO (Pine Valley WTP, 1994)
Percent Mainten- Percent
Water Wash- Wash- ance W/W & Recycled
Treated water water Water M/W Water
1987
1988
1989
1990
1991
1992
Averages
9,805.310
11,636.362
11,820.405
10,112.920
10,082.701
11,010.706
10,744.743
165.185
192.959
142.346
115.852
117.096
131.890
144.555
1.71
1.66
1.20
1.13
1.16
1.20
12.420
18.687
26.609
17.552
18.890
15.995
18.359
1.83
1.82
1.43
1.32
1.35
1.34
361 .0409
224.1929
227.6053
211.0325
234.9224
261 .4732
253.3778
Note: Figures in million gallons.
headworks and retreated. The supernatant from the
sediment collection basin will be pumped either to the
recovery basin at Pine Valley or to the new WTP, when
operational. The sediment that is retained in the recov-
ery basin is systematically pumped and sprayed onto
one of the four sediment drying ponds. Prior operations
and storage capacities required that the ponds be
cleaned annually. Present facilities will provide both
Pine Valley and the new WTP with sufficient capacity to
store their combined sediment production for a period of
15 to 20 years before removal is necessary.
12.1.4 Residuals Disposal
The first cleaning of the sediment drying ponds at Pine
Valley occurred in 1971. Data such as yardage, cost,
and disposal site for cleaning operations from 1971
through 1991 are presented in Table 12-2. (Note that in
1981, two more sediment drying ponds were added.)
Chemical characteristics of the residuals generated
from this process are represented in two water quality
laboratory reports from 1982 and 1992 (Tables 12-3 and
12-4). The 1982 analysis employed the Aqua Regea
total dissolving method, while the 1992 sample was
analyzed using the EP toxicity test.
From 1971 to 1976, cleaning and sediment disposal
operations were handled by the WTP's construction and
equipment divisions. A dragline, trackloader, and loading
dump trucks were used to haul the frozen sediment to
an area on the U.S. Air Force Academy (USAFA)
grounds, 1/4 mile away. In 1977, the sediment drying
ponds were full well ahead of freezing and had to be
cleaned. The water construction division did not have
the equipment necessary to handle the soupy residue.
As a result, that was the year the department began
contracting sediment disposal operations. The contrac-
tor pumped the diluted sediment (2 to 4 percent solids)
into a tanker and hauled it to a private landfill, with the
exception of the first contractor who hauled it to the area
on the USAFA.
Sediment, accumulating at the rate of 7,000 to 8,000
cubic yards per year, eventually became too expensive
to contract. The Water Department purchased the
needed equipment (sludge pump and tanker) and, in
1983, began hauling sediment (5 to 10 percent solids)
itself. The sediment was hauled to Hanna Ranch (city-
owned property), for which a certificate of designation
was obtained. With the new sediment disposal facilities
in operation and receiving most of the sediments, the
sediment drying ponds at Pine Valley did not require
cleaning in 1992.
12.1.5 Handling and Disposal Costs
Over the years, several thousands of dollars have been
spent in removing tons of sediment from Pine Valley.
Specifically, the costs associated with cleaning and
hauling sediment from Pine Valley have totaled almost
$363,000 since 1971 (see Table 12-2). The sludge pump
and tank trailer were purchased for $57,000. The 1981
additions to the disposal facilities cost over $475,000,
and the 1991 construction of the sediment disposal
facilities cost almost 5 million dollars (excluding engi-
neering fees). Additional expenses and time were spent
obtaining certificates of designation for the Hanna
Ranch and Pine Valley disposal sites. Annual engineering
215
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CITY OF COLORADO SPRINGS
COLORADO BO947
P.O. BOX 1JO3
UTILITIES SUI101NC DEPARTMENT OF PUBLIC UTIUTIES
I s. NEVADA AVE. WATER—ELECTRIC—GAS—WASTE WATER
October 23, 1981
Mr. Walley Mitsven
Black & Veatch
P.O. Box 8405
Kansas City, MO 64114
Re: Operation of Sludge Handling Facilities at Pine Valley Plant
Dear Walley:
Written and verbal correspondence regarding problems encountered with Pine Valley's
sludge removal and drying process can be traced back to early 1972. The basic
problems discussed then were as follows:
1. Difficulty in transferring sludge from the washwater recovery
basi-n to the sludge drying beds. The effect of this problem
created several others.
a. Sludge build-up requiring additional work in hosing and
pushing-out sludge.
b. Additional water on sludge bed prolonging dewatering.
c. Plugging of drain line which required installing an eductor
line.
d. Sludge accumulating at influent structure of sludge beds.
The possible causes suggested and outlined were: size of drain
line, {8") was too small, inadequate slope/gradient of drain line
(2.5') from basin to sludge bed, plus additional bends and smaller
size inlet pipe in the drain lineal! restricted the movement of
sludge.
2. Sludge drying beds are too small to handle the amount of water and sludge
which causes unsatisfactory dewatering. Also the decanting structure
proved virtually impossible to utilize. In addition, the appearance
of ground water in the east sludge bed kept the bed-continually
saturated with water.
In the April 1977, Black & Veatch Report on "Waste Disposal Facilities for
Pine Valley", the foregoing conditions were summarized on page three. Recopied
here for easy reference:
The unsatisfactory sludge handling operation at the Pine Valley Purification
Plant is the result of the characteristics of the sludge and of inadequate
facilities that do not permit frequent uniform distribution of sludge to the
beds. The low relative humidity in the summer and a combination of low
humidity and frequent freeze-thaw cycles in the winter should provide
conditions favorable for satisfactory dewatering, if the sludge could be
frequently applied to the beds to a proper uniform thickness.
Figure 12-5. Letter regarding new sludge handling facility at Pine Valley WTP, Colorado Springs, CO (Colorado Springs Utilities,
1994).
216
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Mr. Wai ley Mitsven 2 October 23, 1981
Improvements mentioned in that report were installed and placed in operation
February 17, 1981. Attached is Table 1, summarizing six months of operational
data pertaining to parameters affecting sludge accumulation and Table 2, refer-
ring to the operation of these facilities. Our experience thus far with the new
sludge handling facilities indicates the sludge pumps and sprinklers are sized
properly. An overspray initially occurred, but enlarging the sprinkler nozzle
size by 1/8-inch did correct the problem. Since then, we have satisfactorily
transferred sludge in a proper uniform thickness across the beds with optimum
moisture content. This was accomplished by utilizing the small pump to transfer
sludge to the two lower beds, and the large pump to the two upper beds. As
mentioned in the Black and Veatch report, sludge collection and transfer cycles
have varied with operations being closely monitored. Bed changing cycles, intended/
proposed operations, and assessed conditions found on page eight of the report
have closely coincided.
Several problems still exist which are similar in nature to those previously
described. Dewatering will not, nor does not occur in spite of frequent uniform
application of sludge, and with the equipment being operated in close accordance
with the design concept (see Table 2 for operational practice). The improvements
made, in our opinion, will never render the sludge removable with trucks and loaders.
Our experience has shown dewatering of the top four to six inches does occur, but
when additional sludge is sprayed on, this layer absorbs moisture leaving it
wet and mucky. In addition mother-nature inevitable interferes, disrupting
satisfactory dewatering with some form of precipitation.
The other problems eluded too, besides the unsatisfactory dewatering of the
sludge drying beds are:
1. Sludge build-up in the Washwater Recovery Basin - During high production
periods there is about a six to eight foot build-up of sludge in the
corners, one to two feet on the side's, and 1/8-inch to li-inches
in the sludge collector area. This sludge build-up necessitates cleaning
the basin on a monthly basis. The water sparger we installed in the
intake corner has kept this area fairly clear. Refer to Fig. 1,
structure sketch for area location.
2. Basin drain for pump suction lines are sized to small. The four and
six inch drain/suction lines besides being too small have additional
fittings and bends in the line causing an insufficient gradient to
handle the consistency of the sludge to be removed. The lines plug
with coal and residue and require back'flushing to unplug.
3. Air duffusers are too close to the basin floor. When operating they
stir up the sludge and increase turbidity. Plans are to raise the
diffusers to about three feet above the floor.
4. Sludge pumps require a minimum positive suction head - The water level
in the basin cannot be lowered below four or five feet without cavitating
the pumps. This hampers cleaning operations and reduces the pumping
level range/capacity.
Figure 12-5. Letter regarding new sludge handling facility at Pine Valley WTP, Colorado Springs, CO (Colorado Springs Utilities,
1994) (Continued).
217
-------
Mr. Walley Mitsven 3 October 23, 1981
5. Sprinklers cannot be drained - drains are below the sludge level in
the beds. A connection to the air compressor should allow us to blow
out the lines and prevent freezing.
6. Decanting structure has not been utilized - In pumping concentrated
sludge there is very little water on the sludge to decant. Also very
seldom is the water level in the range of the decanting valves.
7. Sludge Drying Bed Number 4 - Ground water is still entering the bed;
however, we feel more time should be allowed before other alternatives
are considered besides sludge sealing.
If additional information, monitoring, or data gathering is needed, please let
me know. I feel our operational procedures are within the guidelines established;
however, other operating conditions may occur, altering operating cycles and
procedures.
Sincerely,
'JERRY SOULEK
Supervisor
Treatment Plants
Regulation & Treatment
Water Division
JS:ras
Attachments
cc: E. Bailey
D. Mulligan
Figure 12-5. Letter regarding new sludge handling facility at Pine Valley WTP, Colorado Springs, CO (Colorado Springs Utilities,
1994) (Continued).
218
-------
Table 12-2.
Year
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1978
1979
1979
1980
1980
1981
1982
1983
1984
1985
1986
1987
1988
1988
1989
1990
1991
1991
1992
Sediment Disposal, Pine
Dates
02/17
01/17
01/05
02/26
02/28
04/20, 12/07
Nov.
Aug.
Sept.
Apr.
Sept.
May
Aug.
Mar.
Apr.
Sept.
Oct.
Sept.
Apr.
Mar.
July
Jan.
May
Valley WTP, Colorado Springs
Yardage
N/A
N/A
2,500-3,000
2,500-3,000
2,500-3,000
2,500-3,000
2,500-3,000
2,500-3,000
2,057
3,491
3,609
2,997
3,961
3,900
4,900
N/A
7,100
7,200
7,500
7,100
7,100
7,100
2,600
1,800
N/A
N/A
2,400
1,200
N/A
, CO (Pine Valley WTP, 1994)
Contractor
Water Const.
Water Const.
Water Const.
Water Const.
Water Const.
Water Const.
Waste Transport
JD Dye Landfill Costs
JD Dye Landfill Costs
JD Dye
Ready Mix
Ready Mix
Ready Mix
(added two new beds)
JD Dye
Water Const.
Water Const.
Water Const.
Water Const.
Water Const.
Water Const.
Water Const.
Water Const.
Water Const.
Cost
$3,600.00
$3,750.00
$3,900.00
$4,200.00
$4,350.00
$4,500.00
$4,155.00
$17,105.90
$2,820.80
$13,630.28
$2,915.57
$14,863.50
$19,370.17
$17,511.00
$19,355.00
$41,110.15
$35,000.00
$33,000.00
$27,000.00
$28,400.00
$28,500.00
$10,400.00
$7,200.00
$10,800.00
$5,400.00
Disposal Site
USA FA
USA FA
USA FA
USA FA
USA FA
USAFA
USAFA
Landfill
Landfill
Mesa
Private
Private
Private
Mesa
Hanna
Hanna
Hanna
Hanna
Hanna
Hanna
Hanna
Hanna
Mesa
costs for certification renewal since 1991 are unavail-
able. Additional operation and maintenance charges not
accounted for include pest and weed control, landscap-
ing, erosion control measures, and monitoring and col-
lection data requirements.
12.2 Case Study 2: Disposal of Water
Treatment Residuals From Mesa
Treatment Plant, Colorado Springs,
Colorado
The Mesa Water Treatment Plant, located near the Gar-
den of the Gods in the western part of Colorado Springs,
was built in 1942 with a design capacity of 4 mgd. It
treats waters from the Pikes Peak North and South
Slope watersheds. Several expansions and modifica-
tions since the plant's opening have increased its design
and overload capacities to 42 and 64 mgd, respectively.
Figure 12-6 shows the site plan and facilities.
12.2.1 Facility Information
12.2.1.1 Treatment Processes
The existing treatment plant is a conventional facility
using chemical addition with rapid mixing, coagulation,
flocculation, and sedimentation in three separate treat-
ment trains. Filtration of the combined discharge from
the three trains occurs in the filter building using eight
dual-media filters (see Figure 12-6). Chemical additions
219
-------
Table 12-3. Characteristics of Residuals Generated in 1982,
Pine Valley WTP, Colorado Springs, CO (Pine
Valley WTP, 1994)
Water Utility:
County:
Source of Supply:
Where Collected:
Collected By:
Date Sampled:
Date Analyzed:
Chemist:
MAIL TO:
Colorado Springs Water Dept.
El Paso
Pine Valley Sludge
Sludge Ponds
John Uhrich
9/16/82
9/20/82
Monte Fryt
% Dry Wt = 1.07
Results3
Parameters
Arsenic
Barium
Cadmium
Chromium
Fluoride
Lead
Mercury
Nitrate as N
Total Hardness as
CaC03
Sulfate
PH
Selenium
Silver
Calcium as CaC03
Magnesium
Iron
Manganese
Zinc
Molybdenum
PCB
Aluminum
a Factor converting
b As supernatant.
% Dry
Weight
0.0003
0.052
0.0007
0.003
0.15
0.007
0.00009
0.00003
0.0000003
0.65
0.075
2.01
1.81
0.66
0.0007
<0.0025
0.078
mg/L to ng/g = 43.48.
mg/L
0.064
10.4
0.14
0.5
30.5
1.50
0.0175
0.09b
60b
22.3b
6.62b
0.006
0.00054
130.0
15.0
400.0
360.0
132.0
0.158
<0.01
15.5
i*g/g
2.78
452.19
6.1
21.7
1,326
65.2
0.76
N/A
N/A
N/A
N/A
0.26
0.023
5,652
652.2
17,391
15,652
5,739
6.87
<0.5
674
at the Mesa Plant include chlorine, aluminum sulfate,
sodium aluminate, coagulant aid (Nalco 8100), filter aid
(Nalco 8170), and soda ash. Monthly average dosages
for the chemicals used from 1987 through 1992 can be
found in Appendix E.
12.2.1.2 Raw Water Supply
Presently, the plant treats a combination of waters from the
Pikes Peak watershed, as well as from western slope
waters diverted into the North Slope Reservoirs. Water is
conveyed to the plant through three pipelines—two gravity
flow pipelines from the Manitou Hydro Afterbay, and one
pumped pipeline from the Fountain Creek intake pump-
ing station. Water quality data for the plant influent raw
water from 1987 through 1992 are shown in Appendix
E. Results of influent laboratory analyses for April and
August of 1992 are listed in Tables 12-5 and 12-6. Data
from specific pipeline supplies are outlined in Table 12-7.
12.2.1.3 Plant Facility and Flow
Raw water enters the plant through three pipelines (see
Figure 12-6). Modulating valves control the flow of water
to one of three parallel treatment trains designated as
numbers 24, 30A, and SOB. Water enters one of the
rapid mix chambers, then travels through the floccula-
tion and sedimentation basins before moving on to the
filters. Treated water leaving the plant is stored in an
adjacent 20-MG covered reservoir. Filter backwash
water and other wastewater from the basins are dis-
charged into an 18-MG earthen collection basin and are
then recycled to the plant influent for retreatment. The
volumes of water recycled from 1987 through 1992 are
shown in Table 12-8.
12.2.2 Residuals Management
The management of water treatment plant residuals
commenced with the Federal Water Pollution Control
Act/Colorado Water Quality Control Act promulgated in
1973. This act prohibited the discharge of pollutants in
excess of prescribed limits into streams. Direct dis-
charges of residuals from the Mesa Plant did not meet
the established standards; therefore, the practice was
discontinued. Residuals management and disposal was
then a reality and had to be dealt with.
Over the years, several contingency plans were studied
to determine the most effective and efficient method of
residuals management. This meant considering ways to
minimize operating expenses, reduce handling costs,
and maximize water reuse. Sediment lagoons (sediment
drying beds) were determined to be the most effective
way to handle residuals. Until this option could be im-
plemented, certificates of designation were obtained or
amended, and alternate disposal sites were sought.
Other proposals that were occasionally considered in-
cluded various types of mechanical dewatering equip-
ment, chemical conditioning of the sediment, and
discharging wastes to a sanitary sewer. None of these
proposals ever materialized.
12.2.3 Residuals Handling Facilities and
Operations
12.2.3.1 Facilities
Current residuals disposal facilities at Mesa Plant con-
sist of a large collection and holding basin (18 MG-wash-
water recovery basin), a sediment drying pond (4 MG),
220
-------
Table 12-4. Characteristics of Residuals Generated in 1992, Pine Valley WTP, Colorado Springs, CO (Pine Valley WTP, 1994)
CITY OF COLORADO SPRINGS WATER QUALITY LABORATORY
SAMPLE REPORT
Sample Site:
Sample Number:
Comments:
PVSD Pine Valley
92120331
Sediment (PVSD) Date:
Water Type:
Sample Date
3/18/93 09:56 AM
M
: 12/30/92
Minimum
Analysis Description/Code
PH
Percent solid
PH
PS
Magnesium (dissolved) MGD
Silver (dissolved)
AGO
Aluminum (dissolved) ALD
Arsenic (dissolved)
Barium (dissolved)
ASD
BAD
Cadmium (dissolved) CDD
Chromium (dissolved) CRD
Copper (dissolved)
Mercury (dissolved)
Lead (dissolved)
CUD
HGD
PBD
Selenium (dissolved) SED
Key
ND = Not detected.
\\bt
Operation .
Control
Center L^
~^L/
/
Reported
Result Result Code Level Test Units Method Code
5.8
14.8
0.16
0 ND
S.U. E
mg/L GRAV
0.10 mg/L FAASA
0.5 ng/L GFAAS
3,200 400 ng/L FAASN
0 ND
4 ng/L GFAAS
150 100 ng/L FAASN
2.2
0.10 ng/L GFAAS
0 ND 50 ng/L FAASN
19 12 ng/L FAASA
0 ND
2
0 ND
To Sed ,
X X\ Dr^ln9 /
JT jS -^, BSCl /
0.2 ng/L CVAAS
1 .0 ng/L GFAAS
1 .0 ng/L VGAAS
Figure 12-6. Mesa WTP, Colorado Springs, CO (Colorado Springs Utilities, 1994).
221
-------
Table 12-5. Laboratory Samples: April 1992, Fountain Creek, Colorado Springs, CO (Mesa WTP, 1994)
CITY OF COLORADO SPRINGS WATER QUALITY LABORATORY
Sample Site:
Sample Number:
Comments:
FCR Fountain
92040281
Analysis Description/Code
PH
Conductivity
Turbidity
HCO3 alkalinity
CO3 alkalinity
Hardness as CaCO3
Fluoride
Total dissolved solids
Ammonia (total)
Chloride
Nitrate
Sulfate
Barium (dissolved)
Cadmium (dissolved)
Copper (total)
Iron (total)
Iron (dissolved)
Manganese (total)
Manganese (dissolved)
Selenium (dissolved)
Chlorine residual
Temperature centigrade
Threshold odor number
Total coliform
Fecal coliform
Fecal Streptococus
Key
ND = Not detected.
PH
CON
TUR
ALK
COS
HAR
F
TDS
NH3
CL
N03
SO4
BAD
CDD
CU
FE
FED
MN
MND
SED
CL2
TEC
TON
TC
FC
FS
Creek at 33rd
Result
8.07
245
23
81
0
94
2.56
161
0.06
13
0.66
13.2
67
0.26
1
980
120
120
30
0
0
8
3
24,000
5,000
70
SAMPLE REPORT
Street (FCR) Date:
Water Type:
Sample Date:
Minimum
Reported
Result Code Level
0.10
0.05
0.4
0.01
1.0
5
0.10
1
40
40
20
20
ND 1.0
31-Mar-1993 03:59 PM
R
28-APR-92
Test Units
S.U.
limhos
NTU
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
mg/L
Mfl/L
H9/L
H9/L
Mfl/L
Mfl/L
H9/L
H9/L
Mfl/L
mg/L
C
cfu/100mL
cfu/100mL
cfu/100mL
Method Code
E
E
N
T
T
T
E
GRAV
E
1C
1C
1C
GFAAS
GFAAS
GFAAS
FAASA
FAASA
FAASA
FAASA
VGAAS
DPD
THER
NO
MTF
MTF
MF
and an onsite designated landfill area. Equipment used
to transfer sediment from the holding basin to the landfill
area includes a Mudcat/dredge, trackloader, dump
trucks, and bulldozer.
12.2.3.2 Operations
Spent filter backwash water and water latent with sedi-
ment from the flocculation and sedimentation basins are
discharged into the recovery basin. Decant water is
periodically pumped back to the head of the plant and
retreated. The sediment that is retained in the waste-
water recovery basin accumulates at the rate of approxi-
mately 7,000 to 8,000 cubic yards per year and remains
there until removed. Mesa has sufficient capacity to
store approximately 40,000 to 50,000 cubic yards of
sediment in its recovery basin before storage becomes
a problem. This storage capacity is equivalent to roughly
4 to 5 years of residuals production. Analyses of the
chemical characteristics of the residuals generated in
1978 and 1992 are presented in Tables 12-9A, 12-9B,
and 12-10, respectively. Note that there a re two different
222
-------
Table 12-6. Laboratory Samples: August 1992, Mesa WTP, Colorado Springs, CO (Mesa WTP, 1994)
CITY OF COLORADO SPRINGS WATER QUALITY LABORATORY
SAMPLE REPORT
Sample Site: MPI Mesa Plant Influent (MPI)
Sample Number: 92080222
Comments: recov. pumps on; plant TUR=3.0
Analysis Description/Code
PH
Conductivity
Color
Turbidity
HCO3 alkalinity
CO3 alkalinity
Hardness as CaCO3
Fluoride
Chloride
Nitrate
Sulfate
Sodium (dissolved)
Potassium (dissolved)
Magnesium (dissolved)
Calcium (dissolved)
Silver (dissolved)
Arsenic (dissolved)
Chromium (dissolved)
Iron (total)
Iron (dissolved)
Manganese (total)
Manganese (dissolved)
Chlorine residual
Temperature centigrade
Threshold odor number
Total coliform
Fecal coliform
Fecal Streptococus
PH
CON
COL
TUR
ALK
COS
HAR
F
CL
NO3
S04
NAD
KD
MGD
CAD
AGO
ASD
CRD
FE
FED
MN
MND
CL2
TEC
TON
TC
FC
FS
Result Result Code
7.45
50
25
3.8
16
0
24
2.28
0.4
0.13
3.3
2.1
1.3
0.7
5.8
0 ND
0 ND
0 ND
240
120
20
0 ND
0
12
1
170
4
20
Date: 31-Mar-1993 04:01 PM
Water Type: R
Sample Date: 25-AUG-92
Minimum
Reported
Level Test Units
S.U.
limhos
NTU
mg/L
mg/L
mg/L
0.10 mg/L
0.4 mg/L
0.01 mg/L
1 .0 mg/L
0.5 mg/L
0.5 mg/L
0.5 mg/L
3 mg/L
0.5 ng/L
4 ng/L
0.4 ng/L
40 ng/L
40 ng/L
20 ng/L
20 ng/L
mg/L
C
Cfu/100mL
Cfu/100mL
Cfu/100mL
Method Code
E
E
COMP
N
T
T
T
E
1C
1C
1C
1C
1C
1C
1C
GFAAS
GFAAS
GFAAS
FAASA
FAASA
FAASA
FAASA
DPD
THER
NO
MF
MF
MF
Key
ND = Not detected.
test methods employed in these analyses—the Aqua
Regea total dissolving method used in 1978, and the EP
toxicity test used in 1992.
12.2.4 Residuals Disposal
Since the first cleaning of the recovery basin in 1974,
the basin has been cleaned every 5 years. Information
pertaining to these cleaning operations can be found in
Table 12-11. In late 1973, the plant was taken out of
service, recycling most of the water from the recovery
basin before shutting down. Over the winter, the recov-
ery basin was allowed to dry and freeze; in early spring,
a track loader, dragline, and dump trucks removed and
transferred the sediment to a city-owned landfill area.
In 1979, a different method of sediment disposal was
employed. Higher levels of water demand prevented the
223
-------
Table 12-7. Raw Water Source for Mesa WTP,
Colorado Springs, CO (Mesa WTP, 1994)
Fountain Creek
Sample
PH
Alkalinity (mg/L)
Hardness (mg/L)
Temperature (°F)
Turbidity (NTU)
Mean
7.58
27.30
29.8
47.2
4.70
Range
8.15-7.19
76.0-11.0
86.0-13.0
62.7-35.1
133.6-0.6
Manitou Afterbay
Sample
Mean
7.56
24.5
26.4
47.0
3.70
Range
8.05-7.17
62.0-12.0
64.0-14.0
62.7-35.6
36.0-0.6
plant and recovery basin from being taken out of service.
A floating dredge (Mudcat) was purchased to dredge and
pump the sediment to a small berm area isolated from one
end of the recovery basin. From here, a contractor pumped
the diluted sediment, which was mostly water, into a tanker
and hauled it to a private landfill.
Cleaning and sediment disposal operations in 1984 and
1989 were handled in the same manner—the Mudcat
was used to dredge and pump sediment from the recov-
ery basin into a large sediment drying pond built in 1984.
A floating outlet discharge line was used to decant clear
water from the drying pond back into the recovery basin.
Cleaning operations were discontinued when the recov-
ery basin was considered cleaned or when the drying
pond was full of sediment. The Mudcat was removed
from the recovery basin, and the sediment drying pond
was allowed to freeze, thaw, and dry over the winter and
into the next year.
In the spring of 1985, the underlying sediment was still
too soupy to load and haul. In autumn of 1985 and 1990,
after 1 year of the freeze-thaw drying cycle, the sedi-
ment had dewatered to a level conducive to hauling
(estimated between 10 to 15 percent solids). The depth
of sediment had been reduced from roughly 8 feet to 3
feet. Atrack loader, belly dump, and bulldozerwere used
to transfer and spread the sediment onto the adjacent
landfill in a layer approximately 1 foot thick.
When the top layer of sediment at the landfill dried, it
would turn into a fine granular powder, which created
quite a dust problem when the wind blew. A dust ban
polymer was applied to minimize the dust problem dur-
ing the dewatering process. In addition, newly placed
sediment at the landfill was seeded with native grasses
to control erosion and dust pollution. Ground-water
monitoring wells are not required at Mesa; however, they
are in place at Hanna Ranch where sediment from Mesa
has been taken. Results of a leachate sample collected
in April 1990 are shown in Figure 12-7.
12.3 Case Study 3: Land Application of
Water Treatment Plant Residuals at
Cobb County-Marietta Water
Authority, Marietta, Georgia
The Cobb County-Marietta Water Authority (CCMWA)
operates two WTPs in Cobb County, Georgia, which is
in the metropolitan Atlanta area. The James E. Quarles
Plant is permitted to treat 58 mgd of raw water from the
Chattahoochee River. The Chattahoochee River is the
primary source of drinking water for metropolitan Atlanta.
The Hugh A. Wyckoff Plant is permitted to treat 72 mgd
of raw water from Lake Allatoona, a U.S. Army Corps of
Engineers impoundment on the Etowah River in north-
west Georgia.
Both plants use the same method of residuals handling.
Sludge is removed daily from the settling basins and
sent to gravity sludge thickeners. Backwash water from
the filters is sent to a backwash recycle tank where the
sludge settles out and the clarified backwash water is
returned to the head of the plant. The settled sludge is
scraped to one end of the recycle tank and pumped to
the gravity sludge thickeners. The gravity thickened
sludge is then pumped to a conditioning tank where lime
slurry is mixed with the sludge on a 10 to 15 percent dry
weight basis. The conditioned sludge is then dewatered
in a pressure filter to obtain a sludge cake of approxi-
mately 35 percent total solids. The cake is then trans-
ported to a sludge storage yard where it is stockpiled for
several months. Two to three times each year, the
sludge is loaded into trucks and hauled to agricultural
land in or near Cobb County. The dewatered sludge is
applied to the fields with a manure spreader. The
Table 12-8. Water Treated and Used, Mesa WTP, Colorado Springs, CO, in Million Gallons (Mesa WTP, 1994)
1987
1988
1989
1990
1991
1992
Averages
Water
Treated
6,089.827
6,695.425
6,554.006
6,662.514
6,929.688
6,530.272
6,576.955
Washwater
149.977
196.539
269.520
215.598
201 .402
132.187
194.202
Percent
Washwater
2.46
2.94
4.11
3.24
2.91
2.02
Maintenance
Water
2.729
6.830
8.359
11.069
19.709
7.587
9.381
Percent
W/W& M/W
2.51
3.04
4.24
3.40
3.19
2.14
Recycled
Water
319.408
431.176
388.040
344.745
389.142
366.373
373.147
224
-------
Table 12-9A. Chemical Characteristics of Residuals (Sludge) From Mesa WTP, Colorado Springs, CO, 1978 (Mesa WTP, 1994)
Water Analysis3
Location: Mesa Plant Sludge (6.571% dry wt)
Date: 20 March, 1978
Analysis (Dry Wt)
Total coliform (per 100 ml)
Carbon dioxide (CC>2)
Residual CI2
Temperature (°F)
Color intensity
Taste and odor (Threshold
Odor Units)
Turbidity (NTU)
Specific conductance
(Micromhos -25°C)
Total dissolved solids
Hardness as CaCO3
Noncarbonate hardness as
CaCO3
Bicarbonate (HCO3)
Carbonate (CO3)
Chloride (Cl)
Silica (SiO2) 0.085
Sulfate (SO4) 0.28
Nitrate (NO3)
Total phosphate (PO4) 0.17
Fluoride (F) 0.22
Aluminum (Al) 3.08
Total chromium (Cr) 0.006
Limits Results
4 —
NL —
NLT —
0.1
78° —
15 —
3 —
1.0 —
NL —
NL —
NL —
NL —
NL —
NL —
250 —
NL 104.7
250 350
45 —
NL 205.4
62° 272
2.0
NL 3,800
0.05 7.8
Analysis (Dry Wt)
Iron (Fe) 1 .30
Manganese (Mn) 0.22
Nickel (Ni) 0.001
Copper (Cu) 0.012
Lead (Pb) 0.000002
Zinc (Zn) 0.014
Calcium (Ca) 0.23
Magnesium (Mg) 0.12
Cadmium (Cd) 0.0002
Barium (Ba) 0.003
Sodium (Na) 1.82
Potassium (K) 1 .30
PH
Acidity
Mercury (Hg) 0.002 (|ig/100 mL)
Molybdenum (Mo)
Arsenic (As) 0.0001
Cyanide (CN) 0.0001
Fecal coliform (per 100 ml)
Fecal Streptococcus (per 100 mL)
Plate count (org/mL)b
Limits
0.30
0.05
NL
1.0
0.05
5
NL
125
0.01
1.0
NL
NL
9.5
5.6
NL
0.2
0.05
0.2
4
Results
1,600
270.0
1.60
14.6
0.003
17.0
280.0
145
0.20
3.50
2,250
1,600
—
—
3.0
—
0.14
0.14
—
—
Backwash Sludge
H2O pond
700 39
Cobalt (Co) 0.0004
0.50
aAII chemical analyses in milligrams per liter except where otherwise indicated.
b Sample collected 3/22/78.
application rate depends on the lime requirements of the
soil and the lime content of the sludge.
As of 1995, there are no state or local regulations that
deal with the land application of WTP residuals. The
Georgia Environmental Protection Division has classi-
fied the residuals as "recovered materials" under the
Rules for Solid Waste Management, Chapter 391.3 to
4.04(7). Under this classification the residuals do not
require a solids waste handling permit.
12.3.1 Facility Information
The James E. Quarles Plant is presently permitted for a
total flow of 58 mgd. It consists of an older plant, Plant
No. 1, that is permitted to handle 36 mgd, and a newer
plant, Plant No. 2, that is permitted to handle 22 mgd.
Figure 12-8 is a schematic outline of the plant.
The raw water for both plants is drawn from the Chatta-
hoochee River and pumped 8,500 feet to a small raw
water reservoir with a capacity of 20 MG. From the
reservoir, the water flows through separate lines to
Plants No. 1 and 2.
Plant No. 1 adds alum, chlorine, and chlorine dioxide at
the rapid mix facility. The water then flows through eight
hydraulic flocculators with a detention time of 17 min-
utes at the rated flow of 36 mgd. There are eight rectan-
gular sedimentation basins with a theoretical detention
225
-------
Table 12-9B. Chemical Characteristics of Residuals (Supernatant) From Mesa WTP, Colorado Springs, CO, 1978 (Mesa WTP, 1994)
Water Analysis3
Location: Mesa Plant Sludge (Supernatant) (93.429%)
Date: 20 March, 1978
Analysis (Dry Wt)
Total coliform (per 100 ml)
Carbon dioxide (CO2)
Residual CI2
Temperature (°F)
Color intensity
Taste and odor (Threshold
Odor Units)
Turbidity (NTU)
Specific conductance
(Micromhos -25°C)
Total dissolved solids
Hardness as CaCO3
Noncarbonate hardness as
CaCO3
Bicarbonate (HCO3)
Carbonate (CO3)
Chloride (Cl)
Silica (SiC>2) 0.085
Sulfate (SO4) 0.28
Nitrate (NO3)
Total phosphate (PO4)
Fluoride (F)
Aluminum (Al)
Total chromium (Cr)
Limits
4
NL
NLT
0.1
78°
15
3
1.0
NL
NL
NL
NL
NL
NL
250
NL
250
45
NL
62°
2.0
NL
0.05
Results
Backwash
H2O
Sludge pond
20,000
2.7
0
—
—
—
—
260
174
109
40
69
0
8.5
1.55
30
0.25
0.55
2.40
0.17
0.01
Analysis (Dry Wt)
Iron (Fe)
Manganese (Mn)
Nickel (Ni)
Copper (Cu)
Lead (Pb)
Zinc (Zn)
Calcium (Ca)
Magnesium (Mg)
Cadmium (Cd)
Barium (Ba)
Sodium (Na)
Potassium (K)
PH
Acidity
Mercury (Hg) (|ig/100 mL)
Molybdenum (Mo)
Arsenic (As)
Cyanide (CN)
Fecal coliform (per 100 mL)
Fecal Streptococcus (per 100 mL)
Plate count (org/mL)b
Limits
0.30
0.05
NL
1.0
0.05
5
NL
125
0.01
1.0
NL
NL
9.5
5.6
NL
0.2
0.05
0.2
4
Results
1.5
20.0
0.014
0.009
0.001
0.025
41.6
3.5
0.001
0.002
11.2
4.0
7.70
3.5
0.062
—
0.004
0
—
—
Backwash Sludge
Cobalt (Co)
pond
700 39
0.0025
aAII chemical analyses in milligrams per liter except where otherwise indicated.
b Sample collected 3/22/78
time of 160 minutes. The sludge is removed with retrofit-
ted siphon-type sludge collectors located in the upper
one-third of each basin. Once or twice each year the
basins are drained to remove any buildup of sludge that
occurs.
The water is then filtered through eight double-bay grav-
ity dual media filters. The present permitted filter rate is
4.5 gallons per minute per square foot (gpm/ft2). The
filter backwash system consists of surface sweeps and
underdrain backwash.
The filtered water is then treated with lime, fluoride, and
additional chlorine before storage in the plant clean/veils.
The finished water is then pumped to customers.
Plant No. 2, which was built in 1980, has the same
process train as Plant No. 1. Alum, chlorine, and chlo-
rine dioxide are added at the rapid mix facility. The
water then flows through four hydraulic flocculators
with a detention time of 19 minutes at the rated flow
of 22 mgd. There are four rectangular sedimentation
basins with a theoretical detention time of 155
226
-------
Table 12-10. Chemical Characteristics of Residuals Generated in 1992, Mesa WTP, Colorado Springs, CO (Mesa WTP, 1994)
CITY OF COLORADO SPRINGS WATER QUALITY LABORATORY
SAMPLE REPORT
Sample Site:
Sample Number:
Comments:
MPSD Mesa
92120330
Analysis Description/Code
PH
Percent solid
Magnesium (dissolved)
Silver (dissolved)
Aluminum (dissolved)
Arsenic (dissolved)
Barium (dissolved)
Cadmium (dissolved)
Chromium (dissolved)
Copper (dissolved)
Mercury (dissolved)
Lead (dissolved)
Selenium (dissolved)
PH
PS
MGD
AGO
ALD
ASD
BAD
CDD
CRD
CUD
HGD
PBD
SED
Plant Sediment
Result
7.03
39.8
3.6
0
7,300
0
370
0.25
0
0
0
0
0
(MPSD)
Result Code
ND
ND
ND
ND
ND
ND
ND
Date: 03/18/93
Water Type: M
Sample Date: 12/30/92
Minimum
Reported
Level
0.10
0.5
400
4
100
0.10
50
12
0.2
1.0
1.0
Test Units
SU
mg/L
mg/L
Mfl/L
H9/L
H9/L
Mfl/L
Mfl/L
H9/L
H9/L
Mfl/L
Mfl/L
H9/L
09:56 AM
Method Code
E
GRAV
FAASA
GFAAS
FAASN
GFAAS
FAASN
GFAAS
FAASN
FAASA
CVAAS
GFAAS
VGAAS
Key
ND = Not detected.
Table 12-11. Sediment Disposal, Mesa WTP, Colorado Springs, CO (Mesa WTP, 1994)
Year Date Cubic Yards Contractor Cost Disposal Site
Method
1974
1979
1984
1989
Totals
Mar.
May
Oct.
Oct.
40,000
50,000
25,000
25,000
140,000
Water construction
Dye construction
Water construction
Water treatment
Water construction
Water treatment
$17,000
$150,000
$40,000
$45,000
$252,000
City landfill
Private landfill
On site
On site
Loader and dump trucks
Dredge and tanker
Dredge loader, dump
trucks, bulldozer
Dredge loader, dump
trucks, bulldozer
minutes. The sludge is removed with siphon-type
sludge collectors that traverse the entire length of
each basin. The sedimentation basins are drained
once or twice each year to remove any sludge buildup.
The water is then filtered through four double-bay gravity
dual media filters. The present permitted filter rate is 5.5
gpm/ft2. The filter backwash system consists of surface
sweeps and underdrain backwash. One filter is fitted
with an air backwash system.
The filtered water is then treated with lime, fluoride, and
additional chlorine before storage in the plant clean/veils.
The finished water is then pumped to customers.
The Hugh A. Wyckoff Plant is presently permitted for a
total flow of 72 mgd. The raw water forthis plant is drawn
from Lake Allatoona and pumped 4.5 miles to the plant.
Figure 12-9 is a schematic outline of the plant.
Alum, chlorine, and chlorine dioxide are added before
an in-line mechanical mixer. The water then goes
through six flocculator basins. Four basins have mech-
anical mixers with a detention time of 23 minutes. Two
basins have hydraulic mixing with a detention time of 32
minutes. Six rectangular sedimentation basins have a
detention time of 136 minutes. The sludge is removed
from four of the basins with circular mechanical sludge
collectors, located in the first two-thirds of each basin.
The two newer basins are equipped with floating siphon-
type sludge collectors for the entire length of the basins.
The sedimentation basins are drained each year to re-
move sludge buildup.
227
-------
CITY OF COLORADO SPRINGS
DEPARTMENT OF UTILITIES
WATER R EGULATION & TREATM ENT
wito. 2Z55 MESA ROAD
N COLORADO SPRINGS. CO 809CW
TABLE M-14
June 7, 1990
Maggie Bierbaum
Colorado Department of Health
Hazardous Materials and Waste
Management Division
4210 East llth Avenue
Denver, Colorado 80220
RE: City of Colorado Springs - Certificate of Designation -
Solid Waste Disposal Site (CD-86-1)
City of Colorado Springs - Special Use - Solid Waste
Disposal Site (AL-86-30)
In accordance with subject permits, groundvater monitoring veils have
been checked weekly throughout the quarter, February, 1990 through
April, 1990. No water was detected in the south well; however, water
continued to be present in the north well. A sample was collected
April 4, 1990, and analyzed according to "Standard Methods for the
Examination of Water and Wastewater," 16th Edition. Results, are
expressed below as milligrams per liter unless otherwise noted.
PARAMETER CONCENTRATION
pH (s.u.) 7.62
Manganese (Dissolved) <0.02
Sodium (Dissolved) 290
Potassium (Dissolved) 6.4
Alkalinity (CaC03) 304
Copper (Dissolved) 0.008
Magnesium (Dissolved) 36
Chloride 27
Iron (Dissolved) <0.04
Calcium 130
Sulfate 777
Nitrate (N) 0.12
Zinc (Dissolved) 0.009
Total Dissolved Solids 1470
Figure 12-7. Letter from Colorado Springs Department of Utilities, CO (Colorado Springs Utilities, 1994).
228
-------
Maggie Bierbaum 2 June 7, 1990
Radiochemical analysis of Mesa and Pine Valley Water Treatment sludges
by the Colorado Department of Health resulted in the following:
MESA PINE VALLEY
(pCi/gm) (pCi/gm)
Alpha 11-9 60
Beta 71 33
Radium 226 2.9 0.7
Uranium 16 18
Sincerely,
Pat McGlothlin
Laboratory Director
If
c: El Paso County Health Department
Edvard Bailey
Pete Eisele
Donald Mulligan
Figure 12-7. Letter from Colorado Springs Department of Utilities, CO (Colorado Springs Utilities, 1994) (Continued).
229
-------
Chlorine 2
Raw Water
Pumping
Stalion
2
Raw Yfaler
Storage
Reservoir
"" \
Mu
Ch
Ch
Lii
m 1
orine 1
orine Dioxide 1
le 2
Flocculation/
Rapid Sedimenlalioi
Mix Basins
— -•
-
F
P
ilter Aid
olymer 2
Fillers
Chlorine 1
Fluoride 3
Lirne 1
Clearwells
L
>
To
Distribution
Chattahoochee
River
™ Water Flow
Solids Flow
1 Added for typical operations
2 Added infrequently
Thickeners
Lime 1
lutris
V-
1 1
-*-
Filter Press
Backwash
Tanks
Stockpile
Area
Figure 12-8. Schematic process diagram of Quarles WTP, Marietta, GA (Cobb County, 1994).
Chlorine 2 . Alum 1
\
\
\
\ Raw Water
\ Pumping
\ Station
Lake
Allftl.oona
Chlorine 1
Chlorine
Chlorine Dioxide 1
Lime 2
Rapid
Mix
i
Flocculation/
Sedimentation Fillers
Basins
-> -
.. .?_
•••>
Fluoride
lime 1
1
1
Cleanrelte
• -—*>
To
I [ Distribution
1 1
Thickeners
Water Flow
Solids Flow
1 Added (or typical operations
2 Added infrequently
Figure 12-9. Schematic process diagram of Wyckoff WTP, Marietta, GA (Cobb County, 1994).
1
e 1
Fill
e —
er Press
Jj
Backwash
Tanks
Stockpile
Area
The water is then filtered through eight double-bay grav-
ity dual media filters. The present permitted filter rate is
6.0 gpm/ft2. The filters can be operated in the constant
rate or declining rate modes. The filter backwash system
consists of surface sweeps and underdrain backwash.
The filtered water is then treated with lime, fluoride, and
additional chlorine before storage in the plant clean/veils.
The finished water is then pumped to customers.
12.3.2 Residuals Handling Facilities
The physical and chemical characteristics of the residu-
als generated from the two plants differ slightly because
of the different raw water sources and the amount of lime
used by the plants in the dewatering process. The re-
siduals handling facilities for both treatment plants are
the same.
The residuals generated by the two plants each have a
solids content of approximately 35 percent following
pressure filtration. The lime content on a dry weight
basis is approximately 10 to 15 percent. The calcium
carbonate equivalency (CCE) for the material ranges
from 20 to 40 percent. The material is highly plastic until
it is dried further. It has the appearance of moist dirt and
has a slight but noticeable odor.
Extensive testing of the sludge has been conducted.
The Toxicity Characteristic Leaching Procedure (TCLP)
has been used to analyze the residuals from both
plants on several occasions. TCLP analyses for metals,
230
-------
Table 12-12. TCLP Data, Cobb County-Marietta Water
Authority, Marietta, GA (Cobb County, 1994)
Compound
Volatile Organics
Chloroform
Carbon tetrachloride
Tetrachloroethene
Clorobenzene
1 ,2-Dichloroethane
Benzene
Vinyl chloride
1,1-Dichloroethene
Trichloroethene
1 ,4-Dichlorobenzene
2-Butanone (MEK)
Metals
Arsenic
Barium
Cadmium
Chromium
Lead
Mercury
Selenium
Silver
Pesticides and
Herbicides
Chlordane
Endrin
Heptachlor
Heptachlor epoxide
Lindane
Methoxychlor
Toxaphene
2,4-D
2,4,5-TP (Silvex)
Semivolatile Organics
Cresol (total)
1,4-Dichlorobenzene
2,4-Ninitrotoluene
Hexachlorobenzene
Hexachloro-1 ,3-butadiene
Hexachloroethane
Nitrobenzene
Pentachlorophenol
Pyridine
2,4,5-Trichlorophenol
2,4,6-Trichlorophenol
pesticides, herbicides,
Regulatory
Level Laboratory Data
EPA Quarles Wyckoff
(mg/L) (mg/L) (mg/L)
6.0 0.013 <0.005
0.5 <0.005 <0.005
0.7 <0.005 <0.005
100.0 <0.005 <0.005
0.5 <0.005 <0.005
0.5 <0.005 <0.005
0.2 <0.005 <0.005
0.7 <0.005 <0.005
0.5 0.016 <0.005
7.5 <0.005 <0.005
200.0 <0.10 <0.10
5.0 <0.005 <0.005
100.0 1.03 1.22
1 .0 <0.005 <0.005
5.0 0.12 <0.05
5.0 <0.05 <0.05
0.2 <0.0002 <0.0002
1 .0 <0.005 <0.005
5.0 <0.01 <0.01
0.03 <0.01 <0.01
0.02 <0.001 <0.001
0.008 <0.001 <0.001
0.008 <0.001 <0.001
0.44 <0.001 <0.001
10.00 <0.002 <0.002
0.50 <0.01 <0.01
10.00 <0.005 <0.005
1 .00 <0.005 <0.005
200.0 <0.01 <0.01
7.5 <0.01 <0.01
0.13 <0.01 <0.01
0.13 <0.01 <0.01
0.5 <0.01 <0.01
3.0 <0.01 <0.01
2.0 <0.01 <0.01
100.0 <0.05 <0.05
5.0 <0.01 <0.01
400.0 <0.01 <0.01
2.0 <0.01 <0.01
volatile organics, and semivola-
tile organics have been conducted. Table 12-12 pre-
sents the most recent
TCLP data for the Quarles and
Table 12-13. Total Metals Data, Cobb County-Marietta Water
Authority, Marietta, GA (Cobb County, 1994)
Laboratory Data
Quarles Wyckoff
Compound (mg/kg) (mg/kg)
A ,,__„:_ Q Q-7 Q "~)R
Arsenic o.o/ o.zb
Cadmium 3.37 3.26
Chromium 25 20
Copper 29 35
Lead <5 <5
Mercury <0.01 <0.01
Molybdenum 5 9
Nickel 15 15
Selenium 0.75 0.44
Zinc 53 58
Wyckoff plant residuals. The toxics levels have been
extremely low for all samples.
The levels of heavy metals in the sludge have also been
determined and are shown in Table 12-13.
Additional analyses of nutrients and other metals, pes-
ticides and PCBs, triazine herbicides, and reactivity for
cyanide and sulfide were conducted. The data from
these analyses show that this material has a very low
nutrient content. Neither pesticides, PCBs, nor herbi-
cides were detected. The reactivity for cyanide and sul-
fide was below the EPA criteria limits stated in 40 CFR
Part 261 .23. The data for these analyses are reported
in Tables 12-14, 12-15, 12-16 and 12-17.
The Quarles Plant has two gravity thickeners, both 40
feet in diameter with a sidewater depth of 14 feet. The
sludge conditioning takes place in two tanks with
10,000-gallon capacities each. Pebble lime is slaked
and fed to the conditioning tank. Approximately 10 to 15
percent of the dry weight of the dewatered sludge is
lime. The plant controls conditioning by maintaining a
pH of 11.7 to 12.0 in the conditioned sludge. The plant
has two filter presses containing 50 chambers each. The
total volume per press is 60 cubic feet. The plates are
spray washed approximately every load and acid
washed every month.
The dewatered sludge is discharged into dump trucks
and hauled to a sludge storage site at the Wyckoff Plant.
The sludge storage site is an approximately 15-acre
fenced site with gravel roads and a washdown station.
The Wyckoff Plant has three gravity thickeners. Two
units are 40 feet in diameter with a 14-foot sidewater
depth. The third unit is 65 feet in diameter with a 14-foot
sidewater depth. The sludge conditioning tank capacity
is 7,000 gallons. Hydrated lime is mixed with water and
fed to the conditioning tank. Approximately 10 to 15
231
-------
Table 12-14. Other Analyses, Cobb County-Marietta Water
Authority, Marietta, GA (Cobb County, 1994)
Laboratory Data
Quarles Wyckoff
Compound (mg/L) (mg/L)
TKN nitrogen 2,000 5,600
Nitrate nitrogen 300 750
Ammonia nitrogen 100 300
Phosphorus 900 2,000
Potassium 700 500
Sulfur 3,400 2,300
Calcium 161,000 228,000
Magnesium 4,800 6,000
Sodium 100 200
Iron 14,600 18,600
Aluminum 46,000 67,300
Manganese 2,100 2,260
Calcium carbonate equivalency 250,600 338,500
Chloride 700 12,500
Boron 5 15
TOC 66,000 146,000
percent of the dry weight of the dewatered sludge is
lime. The plant controls conditioning by maintaining a
pH of 11.5 to 12.0 in the conditioned sludge. The plant
has two filter presses containing 61 chambers, with a
total volume per press of 74 cubic feet. The plates are
spray washed when necessary and acid washed once
per month.
The dewatered sludge is also discharged into dump
trucks and taken to the sludge storage site adjacent to
the Wyckoff Plant.
12. 3. 3 Ultimate Disposal — Land Application
Tha t\A/r\ r\lontc tr\nathar r\rr\Hi ir*a or\r\rr\vimatalw A HHH
Table 12-15. Pesticides and
PCBs (Solids), Cobb
County-Marietta Water Authority, Marietta, GA
(Cobb County,
Compound
Aldrin
alpha-BHC
beta-BHC
delta-BHC
gamma-BHC (Lindane)
Chlordane (Technical)
4,4'-DDD
4,4'-DDE
4,4'-DDT
Dieldrin
Endosulfan I
Endosulfan II
Endosulfan sulfate
Endrin
Endrin aldehyde
Heptachlor
Heptachlor epoxide
Mothoxychlor
Mi rex
Parathion
Toxaphene
PCB 1016
PCB 1221
PCB 1232
PCB 1242
PCB 1248
PCB 1254
PCB 1260
1994)
Laboratory
Quarles
(iJtg/kg)
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<50.0
<20.0
<20.0
<20.0
<20.0
<20.0
<20.0
<20.0
Data
Wyckoff
(iJtg/kg)
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<5.0
<50.0
<20.0
<20.0
<20.0
<20.0
<20.0
<20.0
<20.0
cubic yards of dewatered sludge per year. The solids
content varies from 25 to 40 percent solids but is usually
around 35 percent solids. Because of the size of the
storage site it is necessary to haul sludge to the appli-
cation sites two or three times per year.
The ultimate disposal is handled by a contractor for the
Water Authority. The contractor uses trailers with a
dumping capability and that haul 30 cubic yards per
load. Usually, approximately 3,000 to 5,000 cubic yards
of sludge are hauled during an application period, involv-
ing up to 170 truck loads.
The Authority has also contracted with a firm to obtain
the land necessary for the application program and to
coordinate the monitoring program. The firm has ac-
quired under contract approximately 1,560 acres to re-
ceive the WTP residuals, which are called lime bypro-
duct. As of this writing, approximately nine sites totaling
1,107 acres have received lime byproduct. The firm that
handles the land application program meets with farm-
ers who may be interested in receiving lime byproduct
and discusses the program with them. The farmers'
fields are sampled to determine their lime requirements.
Fields that are included in the program must be of a
certain size and slope to be acceptable. The farmers
must also practice good soil management techniques in
the operation of their farms.
232
-------
Table 12-16. Triazine Herbicides, Cobb County-Marietta Water
Authority, Marietta, GA (Cobb County, 1994)
Laboratory Data
Quarles
Compound
Wyckoff
Ametryn
Atraton
Atrazine
Cyanazine
Dipropetryn
Prometon
Prometryn
Propazine
Simazine
Simetryne
Terbuthylazine
Tertbutryn
Trietazine
Table 12-17. Reactivity, Solids, Cobb County-Marietta Water
Authority, Marietta, GA (Cobb County, 1994)
Laboratory Data
Quarles
Parameter
Wyckoff
Reactivity, cyanide
Reactivity, sulfide
<0.25
<5.0
<0.25
<5.0
Actual land application involves transporting the dewa-
tered sludge to a farmer's field and discharging it in a
location mutually agreeable to the farmer and the con-
tractor. The sludge is then placed into a manure
spreader using a front end loader. The manure spreader
is a side-discharging unit that evenly spreads the mate-
rial across the field.
The scheduling of the land application is determined by the
farmer involved. The farmer's planting and harvesting
periods, condition of his fields (particularly the soil dry-
ness), and the availability of the lime byproduct are
considerations. Because of the demand for the material,
some farmers have had to wait a year before they
receive any material.
Lime byproduct is applied to both pasture and cropland.
Approximately 88 percent of the land under contract is
pasture, with the remainder in crops. No restrictions
exist on the types of crops or pasture where the material
is applied, except for the agronomic pH requirements of
the plants involved. Because the land used in the pro-
gram is not a dedicated site, and because the metal and
nutrient content of the material is very low, there are no
concerns about heavy metal or nitrogen loadings.
The application rate for the material depends on the lime
requirements of the field and the lime content of the
plant residuals. The wet tons per acre value ranges from
approximately 34 to 100 metric tons per hectare (mt/ha)
(15 to 45 tons/acre) and dry tons per acre ranges from
11 to 34 mt/ha (5 to 15 tons/acre). The CCE application
rate ranges from approximately 2 to 5.6 mt/ha (1 to 2.5
tons/acre). As of this writing, it has not been determined
how frequently lime byproduct can be applied on the
same field, but it will probably be no sooner than every
three years. One farmer in the program had material
applied in the fall of 1990 and still had good pH levels
in his fields in the spring of 1993. The material is nor-
mally surface applied with no soil incorporation. On
some farms a drag has been run over the field after
application to further break up the material and speed
up its incorporation into the soil. Normally, the material
is washed by rain into the soil within a few weeks.
The monitoring program that the Authority uses for its
land application program includes sampling and analy-
sis of the residuals and the affected soil and vegetation.
Ground-water monitoring is not conducted because the
program does not use a dedicated site. Stream monitor-
ing is conducted on the stream in the drainage area
where the sludge storage yard is located.
The sludge is sampled quarterly for percent solids, per-
cent CCE, pH, and TCLP for certain metals. Semiannual
sampling is conducted for TCLP for a wider list of metals,
total metals, and nutrients. Annual sampling is con-
ducted for chlorotriazine herbicides. TCLP for organics
is presently sampled every other year pending the re-
sults of the analyses. PCBs, total organic carbon (TOC),
total Kjeldahl nitrogen (TKN), phosphorus, ammonia ni-
trogen, and nitrate nitrogen have all been sampled once.
Soil monitoring is conducted on ten fields per year in-
cluding one field on each farm in the program for that
year. Each field is sampled before and after application
of residuals. Among the analyses conducted are total
metals and standard soil fertility tests. The soil analysis
parameters for the metals tests are: aluminum, arsenic,
boron, cadmium, calcium, chromium, chloride, copper,
iron, lead, magnesium, manganese, mercury, molybde-
num, nickel, potassium, selenium, sodium, sulfur, and
zinc. The standard soil fertility test includes tests for:
percent organic matter, nitrate, phosphorus, potassium,
calcium, magnesium, cation exchange capacity (CEC),
pH, and percent base saturation. Soil monitoring was
conducted in a 1991 pilot study of three soil plots. One
plot had commercial lime applied, one had lime bypro-
duct applied, and one had no lime applied. Except for
the pH and calcium content of each plot, no significant
differences were noted between them. Table 12-18 pre-
sents the soil data from that study.
233
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Table 12-18. Pilot Study, Soil Data, Cobb County-Marietta
Water Authority, Marietta, GA (Cobb County,
1994)
Component (ppm)
PH
Nitrogen
Phosphorous
Potassium
Aluminum
Cadmium
Chromium
Copper
Nickel
Lead
Calcium
Magnesium
Boron
Iron
Manganese
Molybdenum
Sodium
Zinc
a
Soil
Without
Sludge
5.7
22,900
3,100
24,900
80
<0.5
<5
9
<5
<5
2,900
1,800
8
106
68
0.4
100
22
Soil With
Agricultural
Lime3
6.6
18,400
3,200
13,300
30
<0.5
<5
8
<5
<5
2,875
1,800
7
96
80
0.9
100
25
Soil With
Sludge
6.7
23,150
3,750
20,280
90
<0.5
<5
9
<5
<5
3,500
1,800
9
119
60
0.6
100
22
Table 12-19. Pilot Study, Plant Tissue Data, Cobb
County-Marietta Water Authority, Marietta, GA
(Cobb County, 1994)
Component (ppm)
Nitrogen
Phosphorous
Potassium
Aluminum
Cadmium
Chromium
Copper
Nickel
Lead
Calcium
Magnesium
Boron
Iron
Manganese
Molybdenum
Sodium
Zinc
Plant
Tissue
Without
Sludge
22,900
3,100
20,000
80
<0.5
<5
9
<5
<5
2,900
1,800
8
106
68
0.4
100
22
Plant
Tissue
With
Agricultural
Lime3
18,400
3,200
13,250
30
<0.5
<5
8
<5
<5
2,900
1,800
7
96
80
0.9
100
25
Plant
Tissue
With
Sludge
23,200
3,800
20,300
90
<0.5
<5
9
<5
<5
3,500
1,800
9
119
60
0.6
100
22
samples on the other plots. This sampling difference accounts for
lower levels for nitrogen, potassium, aluminum, and calcium.
Plant tissue analyses will be conducted on several
fields during the first year of the monitoring program. At
least one field on each farm in the program during that
year will be sampled. Row crops are sampled before
harvest, and pastures, or forages, are sampled prior to
grass dormancy. Standard plant analyses will be con-
ducted on the samples. The parameters for these analy-
ses are as follows: aluminum, boron, cadmium, calcium,
chloride, copper, iron, lead, magnesium, manganese,
molybdenum, nickel, nitrogen, phosphorus, potassium,
sodium, sulfur, and zinc.
Plant tissue analyses were conducted on corn grown on
the same three soil plots from the aforementioned 1991
pilot study. No significant differences were found in the
tissue analyses conducted or in the crop yields on the
plots. Table 12-19 presents the plant tissue data from
that study. The average yields for the plots ranged from
122.9 bushels/acre to 130.9 bushels/acre with the lime
byproduct-treated plot having the highest yield.
Stream monitoring is conducted quarterly on sampling
sites above and below the lime byproduct storage area
at the Wyckoff Plant. The analyses evaluate pH, cal-
cium, aluminum, and turbidity levels. The data at present
a Only four samples were taken on these plots compared with six
samples on the other plots. This sampling difference accounts for
lower levels for nitrogen, potassium, aluminum, and calcium.
show little variation between the upstream and down-
stream sites.
12.3.4 Disposal Costs
The costs for dewatering residuals include personnel,
equipment, chemical, and maintenance costs. The total
1992 costs for Quarles and Wyckoff plants were ap-
proximately $360,000. These costs do not include em-
ployee benefits or the costs for capital improvement
projects.
The costs for the land application program are on a
cost-per-ton basis, excluding laboratory costs. The ele-
ments of the program include land acquisition, transpor-
tation to the application site, spreading, monitoring
support, and annual reporting. During 1992, this pro-
gram cost both plants a total of approximately $170,000.
The laboratory monitoring costs for the first year of the
CCMWA's program will be about $10,000. In sub-
sequent years the Authority will do many of the analyses
themselves and eliminate others that have not been
detected in the testing. Based on this reduced program,
external laboratory costs should be reduced to about
$2,000 per year.
234
-------
The economic benefits gained from the land application
program are based on the avoided costs of tipping fees
that must be paid to the local landfill. These costs are
expected to increase in the years to come with the
increase in regulations and the difficulty in obtaining
landfill sites. Based on landfill tipping fees of $32.50/ton,
the annual cost would be about $220,000 per year.
Because the dewatering costs are incurred whether the
material is land applied or placed in a landfill, the sav-
ings per year are approximately $50,000. During the first
year of the present monitoring program the savings will
be less due to the higher monitoring costs.
12.4 Case Study 4: Treatment of
Residuals at the Lake Gaillard Water
Treatment Plant, North Branford,
Connecticut
12.4.1 Facility information
12.4.1.1 Major Plant Modifications
• Added four new rapid sand dual media filters to the
plant, thereby expanding the number of filters in the
plant to 16, and increasing plant capacity from 60
mgd to 80 mgd.
• Expanded flocculation basins by 20 percent by add-
ing a new flocculation basin system.
• New control valves and mag meters were added to
outflow of equalization basins to optimize the clarifier
loading rate.
• Doubled the number of clarifiers.
• Installed new sludge pumps-rotary lobe (variable fre-
quency drive).
• Installed new recycle pumps and controls (variable
frequency drive).
• Installed new sludge lagoon/freeze-thaw/sand drying
beds.
12.4.1.2 Sludge Lagoon/Freeze-Thaw/Sand
Drying Beds
Lagoon Construction
• Site constraints influenced lagoon construction, i.e.,
wetlands required lagoons to be constructed with
gabions (1 on 1 slopes).
• Site includes approximately 20,000 square feet of
lagoon bottom in each of the four lagoons.
• Lagoons were initially constructed with natural soil
bottoms and gravity decant chambers.
• Following unsatisfactory performance of the first la-
goon once placed into service, all lagoons were
retrofitted with a sand/filter fabric/gravel PVC piping
underdrain system.
12.4.1.3 Dewatering Method as Designed
Backwash Water From Equalization Basin to Gravity
Clarifiers
• Clarifiers Parkson (lamella) and EIMCO (stainless
"Flex-Klear") parallel units.
• Clean water recycled to head of the plant.
• Sludge thickened to approximately 2 percent solids.
Sludge Pumped by Rotary Lobe Pumps to Natural
Silt Bottom/Freeze-Thaw Lagoons
Evaporation
Decant Through Gravity Decant Chambers Back to
Equalization Basins
12.4.1.4 Retrofitted Dewatering Method
• Gravity clarifiers (same).
• Sludge pumped by hose pumps to sand drying
bed/freeze-thaw lagoons with piped underdrain sys-
tems. Rotary lobe pumps could not achieve 2 percent
solids based on our piping arrangement, and anthra-
cite particles caused the pumps to fail.
• Evaporation.
• Decant through gravity chambers (limited).
• Gravity drainage through underdrain system.
• Some initial short circuiting was noted at the interior
lagoon perimeter. Modifications were made to the
filter fabric/sand/gabion interface that solved this
problem. This type of short circuiting (at any vertical
interior lagoon boundary condition) is something that
needs to be considered very carefully during lagoon
design and construction.
• Installed vertical filter drains to enhance dewatering
from sludge column to sand underdrain system.
• Conducted summer furrowing of thin sludge layers to
increase evaporation by breaking up the top skim
layer, which greatly increased the effective surface
area of the sludge.
• Conducted mechanical (in-lagoon) winter mixing of
the sludge to enhance the freeze-thaw process. This
method allows freezing of three to inch-inch layers
each night.
• Following the freeze/thaw process, the sludge at ap-
proximately 40 percent solids is removed from the
lagoon by front end loader and trucked to a monofill
235
-------
owned and operated by the Lake Gaillard Water
Treatment Plant.
72.4.2 Lessons Learned
• Sludge will not dewater by evaporation and decanting
alone.
- Some means of drainage at the bottoms of lagoons
is required. At this plant a sand/gravel underdrain
system with PVC piping was installed.
- A skim layer forms on the surface of sludge caus-
ing a rapid decrease in the rate of evaporation.
- The skim layer should be broken up during the
summer months to enhance evaporation and si-
multaneously to increase the surface area. Surface
cracking down to the sand layer (while beneficial
to enhance dewatering and channel away rain) is
not in itself sufficient to dewater the sludge. In our
case, furrowing with a small tractor over thin (8 to
10 inches) layers in summer produced good re-
sults, i.e., 25 to 30 percent solids.
- Decanting a lagoon while it is being filled with new
sludge may result in short circuiting. This hap-
pened at this plant and is unacceptable because
decant water is directed back to the equalization
basins/recycle system, causing undesireable tur-
bidity to the head waters of the WTP.
• Sludge blinds the sand layer at the surface boundary
of the sand but not completely. Blinding does not
occur throughout the layer of sand depth.
- The rate of underdrain flow will decrease overtime
given a relatively constant head of sludge in the
lagoon. The headless is due to a blinding layer
immediately at the sand layer surface boundary.
- What appears to be an anaerobic (dark) layer of
sludge becomes evident at the sand layer surface
boundary. At this plant, the dark layer was approxi-
mately one to several inches thick after several
(summer) months of initial application.
- In the case of this plant, what appeared to be an
(orange) iron precipitate formed at the filter fabric
layer between the bottom of the sand layer and
the top of the gravel underdrain pipe layer. Over
time this may blind the filter fabric.
- Vertical filter drains, designed by the plant opera-
tor, were found to enhance the dewatering process
by automatically decanting surface water (and
some sludge column), and directing it to the sand
underdrain system.
• Sand layers should be approximately 12 to 18 inches
thick, to protect the filter fabric below the sand layer.
- Heavy equipment entering the lagoon digs into the
sand and tears the fabric if it is too close to the
sand surface. At this plant, the initial sand depth
was 6 inches and we experienced substantial tear-
ing of the filter fabric. After the initial cleaning of
the lagoons the sand layer was increased to 12
inches. Approximately two inches of sand was re-
moved during the lagoon cleaning process.
- Track equipment is superior to rubber tire equip-
ment for working on sand drying beds.
- Careful attention to the sand/filter fabric/gabion
connection at the lagoon interior perimeter needs
to be made during construction to avoid short cir-
cuiting of sludge into the underdrain system.
• Lagoons divided into several "compartments" or "sub
lagoons" are beneficial because sludge drying and
cracking do not proceed effectively until loading of
the lagoon is complete. This has not been imple-
mented at Lake Gaillard WTP at this time.
- Loading should be completed in thin layers (three
to four inches) to enhance summer drying or winter
freeze-thawing. Lagoon compartments will accom-
modate this.
- Sufficient area is the key to the successful opera-
tion of sand drying/freeze-thaw beds with under-
drains. This plant is seeking ways to expand its
workable lagoon area.
• Only the top three or four inches of sludge will freeze.
This frozen layer then insulates the sludge below and
stops the freezing process.
- Winter mixing by use of a track-mounted backhoe
or other similar equipment can expose fresh
sludge for freezing every night. A layer of approxi-
mately three inches can be frozen every night at
temperatures of 20°F or less.
- A thin layer of snow will insulate the sludge lagoon
and prevent the freezing process.
• The sludge lagoons produce a "musty," "low tide"
odor during the summer months.
• Elevated levels of chloroform were noted in the un-
derdrain water during the spring melt period (1992).
This may be due to prechlorination at the plant.
12.5 Case Study 5: Disposal of Water
Treatment Plant Residuals From the
San Benito Water Plant, Brownsville,
Texas
The San Benito Water Plant is located in the Rio Grande
Valley near Brownsville, Texas. The water plant is a
mixed media, rapid filtration, surface water plant. The
source of water for the San Benito plant is the Rio
Grande River. Water from this river is pumped into a
system of canal-type lakes called Resacas. The design
capacity of the plant is 6 mgd. The maximum daily
demand is approximately 2.7 mgd in the winter, and 4
236
-------
mgd in the summer. WTP residuals are removed from
the San Benito plant as follows:
1. Sludge is removed from two upflow clarifier units to
storage lagoons through a drain system at the bot-
tom of the clarifiers. Backwash water (205,000 gal-
lons per day) containing residuals is also directed to
the storage lagoon. The lagoon is equipped with a
pump to return excess water to the headworks, to be
treated again.
2. Settled sludge is retained in the storage lagoons for
approximately 3 months.
3. At the end of the 3-month period, the plant uses a
tractor loader and dump truck to remove the thick-
ened sludge to a local landfill.
12.5.1 Residuals Handling Facilities
The storage lagoons are lined with concrete below
ground level. Sludge is removed from the treatment
plant to the lagoons by gravity flow, thus saving pumping
costs.
The plant does not use any sludge thickening proc-
esses. The supernatant is removed after the sludge
settles, and the sludge is exposed to the sun. Approxi-
mately 2 weeks before removing the sludge from the
lagoons, a divider is used to separate the basin into two
halves. The portion not receiving flow dries in the hot
Texas sun. The sludge is then dry enough for a tractor
loader to remove it to a landfill.
12.5.2 Final Disposal
The sludge is disposed of in a local landfill that is clas-
sified to receive this type of waste. At the time of this
writing, the operation of the landfill had recently been
privatized. Instead of being run by the City of San Be-
nito, it is to be operated by a private company. The San
Benito WTP intends to continue disposing of its residu-
als at this landfill.
12.5.3 Disposal Costs
Labor costs form the greatest portion of the San Benito
plant's total disposal costs. Normally, sludge removal to
the landfill requires a week of two people working full-
time. In 1992, labor costs totaled an estimated $5,000.
Equipment costs were estimated at $1,000, including
fuel and maintenance costs. The plant's estimated total
annual disposal costs for 1992 were $6,000.
12.6 Case Study 6: Management of Water
Treatment Plant Residuals in the
Chicago Area, Chicago, Illinois
The major source of drinking water in the metropolitan
Chicago area is Lake Michigan. Seven water treatment
plants draw water from Lake Michigan to supply drinking
water to Chicago and various neighboring communities.
The largest water system is the City of Chicago system,
which serves a population of more than 4.6 million peo-
ple in Chicago and 118 suburban municipalities in both
Cook and DuPage counties. The Chicago water system
includes two of the largest water treatment plants in the
world (Jardine Water Purification Plant (WPP) and
South Water Filtration Plant (WFP)), three water intake
cribs located 2 to 2.5 miles offshore in Lake Michigan,
11 pumping stations, and thousands of miles of water
mains. The finished water from the Chicago water sys-
tem is supplied for drinking and industrial use.
Six other municipalities along the lakeshore (Evanston,
Glencoe, Kennilworth, Northbrook, Wilmette, and Wn-
netka) obtain water directly from Lake Michigan and
maintain their own treatment plants, which serve a com-
bined population of approximately 0.44 million people.
Twenty-five years ago, the residuals generated from all
of the abovementioned WTPs were disposed of by di-
rect discharge into Lake Michigan. In keeping with a
mandate to prevent pollution of Lake Michigan, the Met-
ropolitan Water Reclamation District of Greater Chicago
(the District) adopted an ordinance that contained a
provision prohibiting the discharge of waste of any kind
to Lake Michigan. In the early 1970s, the District took
action requiring WTPs to eliminate the practice of dis-
charging their residuals into Lake Michigan. By 1974, all
of these discharges were diverted into the sewerage
system of the District.
The District covers over 872 square miles within Cook
County, and serves 125 municipalities including the City
of Chicago. The population served by the District is 5.2
million people. In addition, a nondomestic equivalent of
4.5 million people is also served by the District, resulting
in a total sewage treatment load equivalent to almost 10
million. The wastewater collection system operated by
the District consists of more than 500 miles of intercept-
ing sewers and 23 pumps stations. The District owns
and operates seven water reclamation plants (WRPs)
with a combined maximum capacity of about 2,000 mil-
lion gallons. They include the world's largest activated
sludge plant, the Stickney WRP, which has a maximum
capacity of 1,440 mgd. All of the other District WRPs are
also activated sludge treatment plants. About 500 dry
tons of sludge solids are generated per day from these
plants.
This case study focuses on the Jardine WPP, which
discharges its residuals into the District's Stickney WRP.
12.6.1 Description of the Jardine Water
Purification Plant
The Jardine WPP is located in Chicago on Lake Michi-
gan, just north of the Chicago River. It has a design
237
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Schematic Flow Diagram
Jardine Water Purification Plant
Chlorinel
Polymer1
Fluoridei
1-Routine
2-As needed
Figure 12-10. Schematic flow diagram of Jardine Water Purification Plant, Chicago, IL (MWRDGC, 1994).
capacity of 960 mgd based on a sand filter design rate
of 2 gpm/ft2. A schematic flow diagram is shown in
Figure 12-10. The plant has 192 sand filters, each with
a nominal filter rate of 5 mgd. Water is drawn from Lake
Michigan either through a 20-foot diameter tunnel from
a crib located 2.5 miles out in the lake, or directly
through a shore intake at the plant.
The unit processes at the Chicago WTPs include trav-
eling screens to remove fish, aquatic weeds, and trash.
The water from Lake Michigan is then pumped upward
21 feet to permit gravity flow through the WFP. Chlorine,
fluoride, and polyelectrolyte are added after the screen
in the intake basin.
Alum is added ahead of flocculation basins where slow-
speed mixers enhance the flocculation process. The
flocculation water then passes into settling basins with
a detention time of 4 hours. The settled water is then
conveyed to sand filters. Hydrated lime is added ahead
of the filters to minimize corrosion in the water distribu-
tion system. After filtration, the water flows to filtered
water clean/veils where additional chlorine is added,
along with caustic soda. From the clearwells the water
is taken to a 10-acre filtered water reservoir prior to
being conveyed to the distribution system.
Sludge from the settling basins of the WFP is removed
and collected in a holding tank. The filter backwash is
returned to the settling basins. Organic material re-
moved from the intake screens is macerated and
pumped into the sludge holding tank. The collected
sludge in the holding tank is pumped at a controlled rate
into an interceptor sewer of the District. A schematic of
the sludge management system at the Jardine WPP is
presented in Figure 12-11.
12.6.2 Residuals Handling and Disposal
Table 12-20 shows the volume and strength of the water
treatment residuals discharged by Chicago's Jardine
and South WFP into the District's WRPs from 1984 to
1992. The Jardine WPP's residuals volume ranged from
192 to 378 million gallons per year, with suspended
solids ranging from 7,605 to 11,148 tons per year (20.1
to 30.6 dt/day). These quantities are roughly 5 to 6
percent of the residuals produced by the District's
WRPs. The biochemical oxygen demand (BOD) is rela-
tively low, less than 200,000 pounds per year, because
the majority of the sludge solids is inorganic. Similar
data for the other six WFPs, which treat Lake Michigan
water and discharge their sludges into the District sys-
tem, are summarized in Table 12-21.
The District has, under its Sewage and Industrial Waste
Ordinance, imposed local limits for several heavy metals
(see Table 12-22). A summary of the metals concentra-
tions observed in the WTP residuals is shown in Table
12-23. A comparison of the residual metals concentra-
tions with the limits imposed by the Ordinance indicates
238
-------
Schematic Diagram of Residuals
Management System
Jardine Water Purification Plant
Intake
Traveling
Screens
Pump
Rate of Flow
Control Valve
To +—t>
-------
Table 12-21.
Water Treatment Sludges Discharged by Various Suburban WTPs to the District, Chicago, IL, 1984-1992
(MWRDGC, 1994)
Evanston
Wilmette
Northbrook
Year
1984
1985
1986
1987
1988
1989
1990
1991
1992
Volume
(MG)
2.056
2.032
1.286
1.601
0.898
7.335
6.345
3.801
8.521
BOD
(Ib)
7,928
14,436
3,652
5,480
3,383
28,996
26,547
17,109
31,711
TSS
(Ib x 103)
528
456
364
851
466
2,447
2,238
2,350
2,641
Volume
(MG)
18.06
13.661
15.406
11.055
12.629
12.740
11.326
13.034
11.244
Winnetka
Year
1984
1985
1986
1987
1988
1989
1990
1991
1992
Volume
(MG)
0.683
0.631
1.694
1.361
1.096
1.111
1.423
1.075
BOD
(Ib)
1,563
1,761
2,057
1,879
3,678
1,712
4,161
5,444
TSS
(Ib x 103)
330
220
321
198
271
114
246
308
Volume
(MG)
0.44
0.44
0.44
0.44
0.44
0.44
0.44
0.44
Table 12-22. Local Limits on Dischargers Into District
Sewarage
Systems,
Chicago, ILa
BOD
(Ib)
4,497
4,494
11,716
3,436
5,918
6,418
5,671
6,957
3,881
Kennilworth
BOD
(Ib)
60
171
408
200
270
220
387
288
TSS
(Ib x 103)
679
705
755
788
685
597
565
820
644
TSS
(Ib x 103)
33
22
22
24
86
34
45
55
Volume
(MG)
3.77
3.77
2.407
1.414
0.777
0.976
1.709
1.889
Volume
(MG)
0.324
0.342
0.388
0.398
0.359
0.337
0.238
0.292
BOD
(Ib)
5,320
3,716
3,212
2,521
1,962
1,703
4,396
3,386
Glencoe
BOD
(Ib)
354
661
618
915
111
744
835
613
TSS
(Ib x 103)
353
340
363
334
176
183
481
512
TSS
(Ib x 103)
102
52
58
129
47
63
97
108
Table 12-23. Concentrations of Metals Found in WTP
Sludges Discharged
(MWRDGC, 1994)
IL (MWRDGC
Maximum
Concentration
Pollutant
Cadmium
Chromium
Chromium
Copper
(total)
(hexavalent)
Cyanide (total)
Fats, oils,
lronb
Lead
Nickel
Zinc
pH range:
and greases (FOG)
not lower than
(mg/L)
2.0
25.0
10.0
3.0
5.0
250.0
250.0
0.5
10.0
15.0
Water
Treatment
Jardine
Plant Cd Cu
0.01 0.02
South (Chicago) 0.02 0.08
Evanston
Wilmette
Winnetka
Northbrook
0.29 1.40
0.18 0.58
0.23 1.48
0.03 0.06
, 1994)
Into the District,
Chicago,
Concentration in mg/L
Cr
0.04
0.06
1.44
0.83
0.90
0.05
Total
Fe Ni Ph
7.1 0.0 0.03
11.1 0.1 0.07
866 1 .3 4.89
225 0.7 2.37
464 0.9 4.35
8.5 0.1 0.09
Hga
0.3
0.9
1.5
0.7
2.6
0.1
Zn
0.1
0.2
5.2
2.6
2.8
0.1
a Hg concentration in |ig/L.
5.0 or greater than 10.0
a Sewage and Waste Control Ordinance as amended September 5,
1991.
b Discharges from domestic WTPs that supply potable water to the
general public are exempt from this limitation for iron.
240
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the costs per dry ton is due to differences in the amount
of water discharged with the solids. The average annual
cost of discharging WTP residuals from the Chicago
facilities ranged from $159/dt in 1984 to $275/dt in 1992
(see Table 12-24). Similarly, the average annual cost for
discharging sludges from the other treatment plants
(see Table 12-25) ranged from $164/dt in 1984 to
$246/dtin 1991.
Table 12-24. User Charge Costs for Disposal of Water
Treatment Residuals to the Metropolitan Water
Reclamation District, Chicago, IL, 1984-1992
(MWRDGC, 1994)
Year
1984
1985
1986
1987
1988
1989
1990
1991
1992
Key
dt = dry
Jardine
WRP
$1 ,744,204
$1,617,996
$1,317,075
$1,511,031
$1,188,896
$1,762,091
$1,837,940
$2,335,947
$2,723,317
ton.
Cost/dt
$156
$153
$143
$169
$156
$200
$224
$253
$273
South WFP
$887,063
$944,780
$669,625
$1,135,339
$893,417
$1,167,141
$1 ,442,383
$1 ,464,025
$1 ,726,593
Cost/dt
$162
$157
$150
$174
$159
$202
$223
$255
$276
Average
Cost/dt
$159
$155
$147
$172
$158
$201
$224
$254
$275
Table 12-25. Water Treatment Sludges Discharged From Various Water Treatment Plants to the District From 1984 Through 1992
(MWRDGC, 1994)
Evanston
Wilmette
Northbrook
Winnetka
Kennilworth
Glencoe
Volume
Year (MG)
1984 2.056
1985 2.032
1986 1.286
1987 1.601
1988 0.898
1989 7.335
1990 6.345
1991 3.801
1992 8.521
BOD
(Ib)
7,928
14,436
3,652
5,480
3,383
28,996
26,547
17,109
31,711
TSS
(Ibx
103)
528
456
364
851
466
2,447
2,238
2,350
2,641
Volume
(MG)
18.06
13.661
15.406
11.055
12.629
12.740
11.326
13.034
11.244
BOD
(Ib)
4,497
4,494
11,716
3,436
5,918
6,418
5,671
6,957
3,881
TSS
(Ibx
103)
679
705
755
788
685
597
565
820
644
Volume
(MG)
3.77
3.77
2.407
1.414
0.777
0.976
1.709
1.889
BOD
(Ib)
5,120
3,716
3,212
2,521
1,962
1,703
4,396
3,386
TSS
(Ibx
103)
353
340
363
334
176
183
481
512
Volume
(MG)
0.683
0.631
1.694
1.361
1.096
1.111
1.423
1.075
BOD
(Ib)
1,563
1,761
2,057
1,879
3,678
1,712
4,161
5,444
TSS
(Ibx
103)
330
220
321
198
271
114
246
308
Volume
(MG)
0.44
0.44
0.44
0.44
0.44
0.44
0.44
0.44
BOD
(Ib)
60
171
408
200
270
220
387
288
TSS
(Ibx
103)
33
22
22
24
86
34
45
55
Volume
(MG)
0.324
0.342
0.388
0.398
0.359
0.337
0.238
0.292
BOD
(Ib)
354
661
618
915
777
744
835
613
TSS
(Ibx
103)
102
52
58
129
47
63
97
108
241
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Chapter 13
Waste Minimization and Reuse
In the process of treating a raw water supply for potable
water use, contaminants are removed from the raw
water typically in the form of residual solids, brines, and
concentrates. The treatment and disposal of these
waste streams have been discussed extensively in prior
chapters. Historically, these waste streams have been
stored, treated, and then disposed of.
Many years ago, the typical method of disposal was
direct discharge into a nearby receiving stream, or la-
goon storage. Often, solids would accumulate in an
onsite lagoon for years. Once capacity was reached, the
waste stream would simply flow directly into an overflow
structure, onto adjacent properties, or into receiving
streams, with little or no settling. This would typically
leave the water utility with an immediate problem, requir-
ing removal of solids and, often, onsite disposal with few
or no control measures. The potential for polluting the
environment, both aquatic and terrestrial, was high.
Over the years, there has been an increased emphasis
on minimizing negative impacts on the environment
through pollution prevention and reuse of materials. This
is most evident in the adoption of the National Pollutant
Discharge Elimination System (NPDES) program. The
implementation of the NPDES program has eliminated
direct discharge to a receiving stream as a viable option
for many water supply systems. Uncontrolled onsite
disposal is generally no longer permissible, requiring the
utility to construct a monofill, discharge to a sanitary
sewer system, or transport the material to a nearby sani-
tary landfill.
While all of these are viable options, implementation is
becoming more problematic. Construction of an onsite
monofill requires available land and is costly both to
construct and to monitor. Discharge to a sanitary sewer
is often limited by a wastewater treatment plant's capac-
ity to accept more flow and inert solids, both of which
might affect the wastewater treatment process.
The regulatory framework that controls the wastewater
industry has also become increasingly stringent, requir-
ing higher levels of wastewater treatment and increasing
costs. In addition, the impact of 40 CFR Part 503 on the
wastewater industry has caused increased concerns
over accepting new material into the waste stream that
may be perceived to limit disposal or reuse options.
Transport and disposal to a nearby landfill is also in-
creasingly difficult. Many landfills have reached capacity
or are nearing capacity, requiring utilities to look beyond
the immediate area for disposal options and significantly
increasing costs. Often, the associated costs of disposal
drive the utility to consider means of reducing quantities
of residuals generated and to give more consideration
to recovery or reuse options.
The net result of these changes is that utilities need to
develop long-term, flexible management plans. They
need to consider innovative techniques for reducing the
quantities of waste, and they need to implement reuse
options. Ultimately, this will result in more cost-effective
solutions for residuals handling and will improve public
acceptance. The dilemma, however, is that some of the
treatment techniques for reducing residual waste stream
volume or recovering chemical aids (i.e., coagulant or
lime recovery) have had limited application over the
years and, at present, may be costly. The markets for
beneficial reuse of residuals at this time are limited.
Some of the available waste minimization, recovery, and
reuse options that apply primarily to residuals generated
from the coagulation/filtration or lime softening proc-
esses are discussed below.
13.1 Waste Minimization
13.1.1 Process Modifications
Perhaps the best means of reducing waste is to mini-
mize or optimize the types and quantities of coagulants
and chemical aids used and to optimize associated
mixing conditions. Control at the source is the most
effective first step and should be evaluated in all facili-
ties. Process optimization allows facilities to achieve a
balance between water quality, chemical addition, and
physical parameters. Ultimately, the quality of the raw
water supply will dictate the type of treatment provided.
For example, EPA's proposed Disinfection/Disinfectant
Byproduct Rule may require utilities to increase coagu-
lant dosages to maximize water quality benefits and
reduce the potential for disinfectant byproduct formation.
242
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13.1.2 Dewatering
Dewatering—both mechanical and nonmechanical—is
a potential step in the process of minimizing waste.
Details of this process are provided in Chapter 4.
Several mechanical dewatering techniques are avail-
able and employed throughout the country. These typi-
cally include filter presses and centrifuges. Mechanical
dewatering significantly reduces the residuals volume
by removing some of the water, thereby increasing the
percent solids content. Several other mechanical dewa-
tering processes have the potential for increased use in
the future. As discussed by Malmrose and Wolfe (1994)
and presented in Slib, Schlamm, Sludge (Cornwell and
Koppers, 1990), these include:
• Mechanical freeze-thaw machine
• Centrifuge
• Diaphragm filter press
• Continuous high-pressure (CHP) filter press
• Tubular filter press
• Cross-flow microfiltration process
• Hi-Compact press
• Compactor
The applicability of these processes depends on raw
water quality, coagulant practices, and desired dewa-
tered cake characteristics. The need for chemical con-
ditioning or pretreatment is also site specific. Most of
these techniques were developed for application in the
wastewater industry. As a result, little information is
available relative to performance in the drinking water
industry. A brief description of these alternatives is pro-
vided below.
The mechanical freeze-thaw machine employs freezing
as the method of separating the solid and liquid phases.
This method is employed primarily in Europe; no oper-
ating facilities exist in the United States. Energy-
intensive and generally costly, the process is initiated
by freezing through refrigeration, followed by a thawing
process. This conditioning process, when followed by
other dewatering processes, can achieve a solids con-
tent of 30 to 50 percent (Malmrose and Wolfe, 1994).
Scroll and spinning centrifuges have been used in the
United States for many years; however, they typically
have been associated with wastewater operations.
Solid-liquid separation occurs through application of
centrifugal force. Application in the drinking water indus-
try has typically yielded a dewatered cake with a solids
content on the order of 15 percent. Recent improve-
ments in the equipment, as well as the availability of
more operational data, indicate that the dewatered cake
can achieve a solids content in excess of 20 percent,
depending on the solids characteristics, velocity gradi-
ent (g value), and feed concentrations. Thickening to 2
to 4 percent prior to centrifugation yields improved re-
sults. Centrifuges are usually lower in cost, smaller in
size, and easier to operate than many other types of
mechanical dewatering equipment.
The diaphragm filter press is similar to a basic filter
press, which comprises filter plates that are pressed
together to form a chamber. The plates are lined with a
porous cloth. Residuals are pumped into the chamber;
the solids are retained by the cloth liner, and the liquid
fraction is pushed through as the driving pressure in-
creases with continued pumping. In the diaphragm
press, the liner is replaced with a membrane which,
when pressurized, aids the dewatering process by
squeezing the solids retained in the chamber. This batch
process can achieve a dewatered cake with a solids
content in excess of 30 percent (Cornwell and Koppers,
1990).
The CHP filter press combines elements of both the belt
and pressure filters. An initial gravity thickening zone is
followed by wedging the residuals between two belts at
a low pressure (35 psi). High pressure, on the order of
300 psi, is then applied through cylinders that exert
pressure to a mobile armored belt (Malmrose and Wolfe,
1994).
The tubular filter press and cross-flow microfiltration
process feed residuals, under pressure, to a tubular
matrix. The tubes are composed of porous material, and
the solids are retained on the tubes. In the tubular filter
press, the solids are removed by rollers; the cross-flow
microfiltration unit employs a vortex cleaning system
(Malmrose and Wolfe, 1994). Conditioning prior to ap-
plication on the presses may not be required. Limited
experience indicates that a solids content in the 20 to
40 percent range can be achieved (Malmrose and
Wolfe, 1994; Cornwell and Koppers, 1990).
The remaining processes, specifically the Hi-Compact
press and the Compactor system, have limited full-scale
applications, even in the wastewater industry. The Hi-
Compact press requires prior thickening and dewatering
to greater than 20 percent solids content.
13.1.3 Drying
As discussed in Chapter 4, a drying step would serve to
further reduce the quantities of solids generated for
reuse or disposal. Two processes for drying are the
Carver-Greenfield and electroacoustical dewatering
(EAD) processes. They are difficult to operate and po-
tentially very costly because of elaborate equipment and
high energy requirements. The Carver-Greenfield proc-
ess, however, may be able to achieve a dewatered cake
with a greater than 90 percent solids content, thereby
reducing the volume of residuals significantly. Applica-
243
-------
bility to the drinking water industry is still somewhat
unclear, however. Continued investigations are war-
ranted.
13.2 Chemical Recovery
13.2.1 Coagulant Recovery
Coagulant recovery provides a method for recovering a
resource (i.e., coagulant) and for minimizing waste by
extracting aluminum or iron coagulants from the waste
stream. Extraction is achieved by acidification, which
puts the metals back into solution. Critical design and
operations factors include extraction pH and acid con-
tact time. Extraction pH is typically in the range of 1.8 to
3.0. Acid contact time of 10 to 20 minutes appears to be
reasonable based on full-scale operations data and
laboratory testing (Saunders and Roeder, 1991). An-
other critical component is the amount of metal coming
from the raw water compared with the coagulant. For
example, aluminum associated with raw water solids is
more difficult to dissolve than that associated with an
alum coagulant.
The quality of the recovered coagulant is an important
factor in determining the feasibility of coagulant recov-
ery. The impact of coagulant reuse on treatment plant
operation and resulting finished water quality must be
given serious consideration. While the acidification proc-
ess is beneficial for achieving dissolution of the coagu-
lant, concentrations of coagulant impurities and raw
water contaminants may also become dissolved and get
recycled to the head of the plant. While these contami-
nants may again be removed from the water supply by
the coagulant, settling, and filtration processes, the net
result is a concentration of contaminants. This impact
must be carefully considered as the regulatory climate
becomes increasingly stringent.
Concentration and recycling of contaminants may pre-
sent a problem in achieving compliance. Of particular
interest is the recycling of organic material, which may
increase disinfection byproduct formation potential. This
may be due in part to the demonstrated need for in-
creased chlorination when organic matter is recycled
(Saunders and Roeder, 1991). Full-scale operations ex-
perience at the Vernon S. Wade plant in Athens, Geor-
gia, also indicates an increased alkalinity demand as a
result of using the recovered coagulant.
Coagulant recovery has been investigated in the United
States over the last 30 to 40 years; however, few full-
scale facilities are currently active (Saunders and
Roeder, 1991). Saunders and Roeder (1991) have re-
viewed coagulant recovery extensively and present their
findings in the American Water Works Association Re-
search Foundation research report Coagulant Review:
A Critical Assessment. Pilot- or laboratory-scale opera-
tions should be performed when evaluating the feasibil-
ity of implementing this option.
13.2.2 Lime Recovery
Lime recovery is accomplished through the recalcination
process whereby the lime residual is dewatered and
then burned to produce quicklime (Cornwell et al.,
1987). As with other recovery processes, strong consid-
eration must be given to the expected quality of the
recovered product and to incorporating processes to
remove impurities. For example, as presented in Hand-
book of Practice: Water Treatment Plant Waste Man-
agement (Cornwell et al., 1987), the first step is
generally a purification process such as centrifugation.
After purification and dewatering of the calcium carbon-
ate, a drying process is generally employed. A variety of
furnaces are available, as well as other means of drying.
Certainly, power and fuel costs are a key factor in evalu-
ating the applicability of this process for a particular
utility. As mentioned previously, the required purity of the
quicklime must also be considered in the decision-mak-
ing process.
13.3 Innovative Use and Disposal Options
Several alternative uses and disposal methods for resid-
ual solids are presented in Slib, Schlamm, Sludge
(Cornwell and Koppers, 1990) and in recent articles by
Copeland et al. (1994,1995). These alternatives include
options such as land application and reclamation, sup-
plementation of a soil matrix, blending with compost
material, and brick and cement production. Implementa-
tion of these alternative methods may prove to be more
cost-effective than traditional disposal methods and will
likely achieve a high degree of public acceptance.
The regulatory framework for acceptance of these op-
tions varies among states. It appears that few states
have a well-defined program for approving these uses
as they apply to water treatment plant (WTP) residuals.
Disposal of wastewater treatment plant (WWTP)
biosolids is more clearly regulated than disposal of WTP
residuals, primarily because WWTP biosolids are cov-
ered under Part 503 regulations. While Part 503 specifi-
cally excludes WTP residuals, many states are applying
similar approaches and standards to the drinking water
industry. As the characteristics of water and wastewater
residuals are very different from one another, more de-
finitive guidance and regulations are needed to address
WTP residuals specifically. Key factors and considera-
tions associated with these innovative use and disposal
alternatives are discussed below.
13.3.1 Beneficial Use
Beneficial use options for WTP residuals include land
application and reclamation, supplementation of a soil
244
-------
matrix, and blending with compost material. Potential
concerns have been raised about aluminum levels in
alum coagulant residuals and their tendency to bind up
available phosphorus in the soil. Phosphorus is needed
as a nutrient for vegetation. To overcome this potential
deficiency, supplemental fertilization may be necessary.
This may be of particular relevance when using residu-
als for land application, soil matrix supplementation, or
blending with compost material. Some potential benefits
associated with using coagulant solids include improve-
ments in aeration and moisture retention (Copeland et
al., 1994, 1995).
Soil conditioning with lime softening residuals is also a
beneficial use. Farmers often add calcium carbonate to
soils to counteract the chemical reduction that results
from nitrogen application and to maintain an appropriate
soil pH. Any difficulty associated with this use is due
more to farmers' lack of familiarity with handling the
residual solids than to the residuals themselves.
Blending with compost requires further definition of mix
ratios and maintenance of temperature requirements.
As discussed in Copeland et al. (1994), different mix
ratios must be evaluated and the optimum defined, both
in terms of the existing regulatory framework as well as
the end-use requirements. Maintenance of appropriate
temperature during composting is essential to a suc-
cessful project.
13.3.2 Disposal Options
Some research and actual implementation has been
conducted in the development of co-products such as
bricks and cement. Again, limited application has oc-
curred in the United States. Willingness of all parties to
conduct preliminary research as well as bench- and
pilot-scale studies is essential.
One successful project involves the Santa Clara Valley
Water District, where bricks are constructed using co-
agulant residuals. The project took a great deal of effort
and time, however. Careful consideration of associated
costs, benefits, and other economic factors must also be
considered in the development of a co-product.
245
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Chapter 14
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253
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Appendix A
Survey of State Regulatory Requirements: Summary of Results
The American Water Works Association's (AWWAs)
Water Treatment Residuals Management Committee
and the American Society of Civil Engineers (ASCE)
conducted a survey of state regulations governing the
disposal of water treatment plant residuals. The results
of this survey were presented at the 1991 Annual AWWA
Conference and Exposition Preconference Seminar,
"Current Perspectives on Water Treatment Plant Sludge
Disposal: Practices and Regulations" on June 23,1991,
in Philadelphia, Pennsylvania (AWWA/ASCE, 1991).
Those results are summarized below.
ALABAMA
Department of Environmental Management
Municipal Waste Department
1751 Dickinson Drive
Montgomery, AL 36130
(205)271-7825
The state regulates water treatment plant (WTP) wastes
under the Division of Municipal Wastes in the Depart-
ment of Environmental Management. All discharges are
regulated and require a permit. The permits have limits
of waste constituents (liquid wastes) that must be moni-
tored and cannot be exceeded. Most liquid wastes, such
as backwash decant, are sent to settling basins, then
discharged to surface water bodies after settling. Mon-
ofilling on site is the most common disposal practice for
sludges.
ALASKA
Department of Environmental Conservation
Treatment Section
P.O. Box O
Juneau,AK 99811-1800
(907) 465-2656
No regulations exist specifically covering WTP waste
disposal. A state statute requires a waste disposal per-
mit to discharge solid or liquid waste to lands or waters
of the state. The statute also provides that a state-certi-
fied U.S. Environmental Protection Agency (EPA) Na-
tional Pollutant Discharge Elimination System (NPDES)
permit also serves as a state waste disposal permit.
ARIZONA
Department of Environmental Quality (ADEQ)
P.O. Box 600
Phoenix, AZ 85001-0600
(602) 392-4002
ADEQ is responsible for the regulation of water plant
wastes within the state. ADEQ is in the process of
implementing the NPDES program and obtaining pri-
macy from EPA. Currently, Arizona has specific regula-
tions governing land application of wastewater biosolids;
these regulations are expected to apply to WTP residu-
als as well. Landfilling, monofilling, and co-disposal
have no additional state requirements beyond those
given in the existing federal regulations. The Depart-
ment's current policy allows the disposal of WTP residu-
als provided that 1) sampling and analysis of the
residuals reveal that they are nonhazardous; and 2) the
residuals are dewatered prior to disposal. No permits
are required by ADEQ for disposal of nonhazardous
WTP residuals.
ARKANSAS
Department of Pollution Control and Ecology
P.O. Box8913
Little Rock, AR 72219-8913
(501) 570-2164
Arkansas has been granted the NPDES permit process
by EPA. They have a general permit that must be met
by all surface water treatment plants. Parameters regu-
lated in the permit include aluminum, manganese, iron,
pH, and total suspended solids (TSS). If land application
is practiced, a permit is required. Co-disposal is com-
monly practiced in standard municipal landfills.
CALIFORNIA
Regional Water Quality Control Board
Los Angeles Region
101 Center Plaza Drive
Monterey Park, CA 91754
(213)266-7512
California has regulations that classify wastes, including
water plant wastes, as hazardous, inert, and other cate-
254
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gories. The classification system is used to identify the
appropriate management plan. The Regional Board can
regulate waste streams that are discharged to surface
water. A broad range of management practices is used,
including monofilling, co-disposal, direct discharge, and
land application. For WTP residuals to be landfilled, the
landfill must be equipped with a leachate collection and
removal system. The solids content must be at least 15
percent and a minimum solids-to-liquid ratio of 5 to 1 by
weight must be maintained. The state also maintains
criteria regarding the burial or the release of radioactive
material into air, water, or sanitary sewer systems.
COLORADO
Department of Public Health and Environment (CDPHE)
Water Quality Control Division
4300 Cherry Creek Drive South
Denver, CO 80222-1530
(303) 692-3500
CDPHE classifies WTP residuals and wastewater treat-
ment plant (WWTP) biosolids according to heavy metal
and PCB concentrations. Classes 1 and 2 can be ap-
plied to agricultural land. Class 3 can be applied to
non-food chain land only. Class 4 is regulated by solid
waste rules. Monitoring requirements increase with the
higher classifications. Common disposal practices in-
clude monofilling, land application on site, lagooning,
and recycle/reuse. CDPHE permits the co-application of
WTP residuals and WWTP biosolids to land at a rate at
which the phosphorus fixing capability of the mixture
does not exceed the available phosphorus content of the
mixture.
CONNECTICUT
Not contacted.
DELAWARE
Delaware Pollution Control Branch
P.O. Box1401
Dover, DE 19903
(302) 739-5731
Only two surface water treatment plants exist in the
state. Each discharge is reviewed and permitted sepa-
rately according to NPDES guidelines.
FLORIDA
Department of Environmental Regulation (DER)
Drinking Water Section
2600 Blair Stone Road
Tallahassee, FL 32399-2400
(904)487-1762
DER regulates watertreatment plant wastes through the
Drinking Water Section. Florida is not a NPDES-dele-
gated state and therefore is unable to issue NPDES
permits. The majority of wastes are lime softening or
reverse osmosis (RO) concentrates. RO concentrates
can be disposed of through ocean outfalls. Recycling
other wastewaters to the head of the plant is the most
common practice. Most residuals are recycled or land-
applied, with some lime softening residuals used in road
bed mixtures. Monofills are also used. Radium content
in residuals is a major concern.
GEORGIA
Drinking Water Program
205 Butler Street Southeast
Floyd Tower East
Suite 1066
Atlanta, GA 30334
(404) 656-2750
Georgia regulates WTP wastes under the Drinking
Water Program with aid from the Wastewater Division of
NPDES. Georgia law requires all WTPs to have waste
disposal facilities and plans, and the Water Program
enforces all permits. No specific regulations address
WTP residuals. Most liquid wastes such as backwash
decant are sent to settling basins, then discharged to
surface water bodies after settling. Residuals are either
disposed of in municipal landfills (co-disposal) or by land
application.
HAWAII
Department of Health
Safe Drinking Water Branch
5 Waterfront Plaza, Suite 250-C
500 Ala Moana Boulevard
Honolulu, HI 96813
(808) 543-8258
Hawaii is aware of the concern about WTP residuals,
but because of staffing and budget constraints, it is
unable to actively pursue a waste treatment program.
Land application is the primary method of disposal. The
state is awaiting EPA guidance.
IDAHO
Division of Environmental Quality (DEQ)
Water Quality Bureau
1410 North Hilton
Boise, ID 83706
(208) 334-5865
DEQ does not administer the NPDES program, and
there are no plans for developing regulations for WTP
residuals at this time. The most common disposal prac-
tice is probably landfilling.
255
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ILLINOIS
Environmental Protection Agency
2200 Churchill Road
Springfield, IL 62794-9276
(217) 785-8653
Illinois EPA regulates WTPs that discharge any treat-
ment waste stream to waters of the state. The pollutants
regulated depend on the plant, but suspended solids,
pH, and iron are the primary concerns. The most com-
mon method of disposal is discharge to sanitary sewers.
Lagooning is also used, with effluent discharged to
streams (NPDES permit required) and solids disposed
of in a landfill. Another concern is the discharge of salt
backwash from zeolite softeners to sanitary sewers.
INDIANA
Department of Environmental Management
105 South Meridian Street
P.O. Box 6015
Indianapolis, IN 46206
(317)233-4222
WTP residuals have not been a major problem for the
state. Filter backwash is usually discharged to a sanitary
sewer or allowed to percolate through the ground.
Sludge solids from surface water plants are usually land
applied. The state is responsible for administering the
NPDES program.
IOWA
Department of Natural Resources (DNR)
Environmental Protection Division
Wastewater Permit Section
900 East Grand
Des Moines, IA50319
(515)281-8998
DNR is seeking authority from the state legislature to
develop a permit by rule process in which permit require-
ments would be identified by a DNR rule. Discharges to
surface waters require an NPDES permit. Land applica-
tion of WTP residuals may be regulated similarly for
industrial and sewage sludges with respect to metals.
WTP residuals have not been a primary concern be-
cause of limited resources.
KANSAS
Department of Health and Environment
Bureau of Water
Forbes Field
Topeka, KS 66620
(913)296-5503
The state regulates all types of waterwastes but has not
actively pursued permitting facilities. At this time, the
primary objective is to keep softening sludge solids out
of the streams and rivers. Rivers have been identified
as nonattainment areas for suspended solids by non-
point legislation. In the future, this may affect manage-
ment of presedimentation solids. The state administers
the NPDES program for discharges; lagoons are permit-
ted through a state water pollution control permit.
KENTUCKY
Division of Waste Management
Solid Waste Branch
18 Reilly Road
Frankfort, KY 40601
(502)564-3410
The state regulates WTP residuals under the Division of
Solid Waste. While specific regulations are being writ-
ten, disposal is presently handled on a case-by-case
basis. Some liquid wastes, such as backwash decant,
are sent to settling basins, then discharged to surface
water bodies after settling, while others are recycled to
the head of the plant. Roughly half of the plants land-ap-
ply sludges, and half send the solids to a landfill (co-dis-
posal). A few monofills exist.
LOUISIANA
Department of Environmental Quality
Water Pollution
P.O. Box82215
Baton Rouge, LA 70884-2215
(504) 765-0635
WTP residuals are regulated by the state's water pollu-
tion control programs. An NPDES permit, administered
jointly by the state and EPA, is required for surface water
discharges. Only liquid wastes may be discharged. Solid
wastes are commonly disposed of in permitted landfills.
MAINE
Department of Environmental Protection (DEP)
(207) 582-8740
The DEP requires that all WTP residuals be dewatered
to a minimum of 20 percent total solids and disposed of
in a secure landfill. The landfills must be equipped with
a system for leachate collection.
MARYLAND
Not contacted.
MASSACHUSETTS
(617)292-5529
The state is in the process of updating its existing regu-
lations. Sludge disposal is considered on a case-by-
case basis. The state is concerned about some gaps in
the existing regulations.
256
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MICHIGAN
MONTANA
Department of Public Health (DPH)
3423 North Logan
Lansing, Ml 48909
(517)335-9216
The DPH requires water utilities to develop a manage-
ment plan for WTP residuals. If the plan is acceptable,
no further regulation is necessary. If backwash water is
discharged to a surface water, an NPDES permit is
required from the Department of Natural Resources.
The most common methods of disposal include co-dis-
posal, direct discharge, and land application.
MINNESOTA
Not contacted.
MISSISSIPPI
Office of Pollution Control
P.O. Box 10385
Jackson, MS 39289-0385
(601)961-5171
Mississippi regulates WTP residuals under the Office of
Pollution Control. New regulations take their cue from
EPA and use federal effluent guidelines for wastes, par-
ticularly with regard to toxicity. Most liquid wastes, such
as backwash decant, are sent to settling basins, then
discharged to surface water bodies after settling. A few
plants discharge to a publicly owned treatment works
(POTW) or recycle washwaterto the head of the plant.
The majority of sludges go to municipal landfills, with
some land application of waste solids. No monofills exist
in the state.
MISSOURI
Department of Natural Resources
P.O. Box 176
Jefferson City, MO 65102
(314) 751-6624
WTP residuals are regulated as solid waste unless the
material is applied to agricultural land or is discharged
to a surface water. A solid waste permit may be required
for landfill disposal, which could include requirements
for TCLP testing, liners, and leachate collection sys-
tems. An NPDES permit is required for direct discharge.
Solids may be discharged only into large rivers; treated
filter backwash may be discharged to small rivers. No
restrictions are placed on land application of lime sof-
tening sludges. Guidelines for total aluminum loadings
to the soil are established for the application of alum
sludges. With some limitations, brine wastes may be
discharged to a sanitary sewer, abandoned quarries,
gravel pits, or evaporation lagoons.
Department of Health and Environmental Services
(MDHES)
Water Quality Building
Cogswell Building
Helena, MT 59620
(406) 444-2406
MDHES may regulate all types of WTP residuals on a
case-by-case basis. In the future, these residuals may
be addressed along with sewage sludges. NPDES regu-
lations apply to any discharges. The majority of the
sludges are from lime softening facilities and are land-
applied. The primary concern of this practice is checking
soil pH to ensure suitability for application.
NEBRASKA
Department of Environmental Control (NDEC)
P.O. Box 98922
Lincoln, NE 68509-8922
(402)471-2186
NDEC regulates disposal of WTP residuals on a case-
by-case basis. In the future, residuals may be addressed
along with sewage sludges. NPDES regulations apply
to any discharges. The majority of the sludges are from
lime softening facilities and are land-applied.
NEVADA
Division of Environmental Protection
123 West Nye Lane
Carson City, NV 89710
(702) 687-5872
In general, WTP residuals are not a major concern
because they are nonhazardous. No permits are re-
quired for landfilling solid waste; however, discharge of
treated washwaterto rivers requires a permit. The state
plans to update existing regulations in the near future
and to develop new regulations within 1 to 5 years.
NEW HAMPSHIRE
(603)271-3503
The state encourages landfilling and land application of
WTP residuals. The state plans to update existing regu-
lations within 1 year. Concerns include heavy metals
and nutrients.
NEW JERSEY
(609) 292-5550
The state regulates WTP residuals treatment and dis-
posal processes on a case-by-case basis and is respon-
sible for administering the NPDES program. Concerns
include heavy metals and organics.
257
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NEW MEXICO
OHIO
Environmental Department
P.O. Box 26110
Santa Fe, NM 87502
An NPDES permit is required for any discharges from
water treatment plants. The EPA has primacy for permit-
ting discharges. The state receives a 106 grant from the
Clean Water Act to assist EPA with compliance monitor-
ing. The most common methods of disposal include
co-disposal and direct discharge.
NEW YORK
Department of Environmental Conservation
(518)457-1067
Permits are issued based on the type of disposal prac-
tice proposed and the sludge quality characteristics. A
wide range of disposal practices, including monofilling,
co-disposal, direct discharge, land application, and re-
cycle/reuse, are commonly used. Concerns include
heavy metals, organics, and nutrients.
NORTH CAROLINA
Division of Environmental Management
P.O. Box 29535
Raleigh, NC 27626
(919) 733-5083
North Carolina regulates WTP residuals through the
Division of Environmental Management. Wastes are
classified by the treatment process, and a certified op-
erator is required to run the waste treatment aspects of
the plant. Most liquid wastes are discharged to a POTW
via a sanitary sewer. Some direct discharge, recycling
to the head of the plant, and subsurface disposal of
liquid wastes are practiced. Solids disposal is generally
through a municipal landfill, although there are a few
monofills and some land application of sludges.
NORTH DAKOTA
Department of Health
Solid Waste Division
P.O. Box 5520
Bismarck, ND 58502-5520
(701)221-5166
The state has no specific rules for WTP residuals. Tech-
nically, all types of water treatment plant residuals are
regulated; for the most part, only lime softening wastes
are regulated. Solids are disposed of primarily by land-
filling, which is regulated on a case-by-case basis. Land-
fills must have a plan established for managing the
waste.
Environmental Protection Agency
Division of Public Drinking Water
18 West Water Mark Drive
Columbus, OH 43266
(614)644-2752
The state is responsible for administering the NPDES
program. Discharge of backwash water is regulated by
water quality standards and limitations have been estab-
lished forTSS, pH, iron, manganese, and chlorides. The
state prefers that utilities discharge to a sanitary sewer.
No unregulated discharges exist, and wastes are not
recycled through the plant. The primary disposal method
for solids is agricultural land application of lime softening
sludge. Other acceptable methods of disposal include
landfilling and mixing with compost.
OKLAHOMA
State Department of Health
1000 Northeast 10th Street
Oklahoma City, OK 73152
(405)271-7370
Oklahoma jointly administers the WTP residuals pro-
gram with EPA. Permits for direct discharges require
analysis for pollutants listed in 40 CFR Part 122, Appen-
dix D, Tables II and III. The most common disposal
practices include co-disposal, direct discharge, and land
application. WTP residuals are being more closely con-
trolled.
OREGON
Department of Environmental Quality
811 S.W Sixth Avenue
Portland, OR 97204
(503) 229-5782
Disposal of WTP residuals in Oregon is regulated under
solid waste management rules. A solid waste permit is
required to construct and operate onsite waste handling
facilities. Offsite agricultural land application practices
are covered in the permit. For discharge to surface
water, an NPDES permit is required. The most common
methods of disposal include monofilling and co-disposal
with solid waste.
PENNSYLVANIA
Department of Environmental Resources
Room 518, Executive House, South 2nd Street
Harrisburg, PA 17105
(717)787-9035
The state has primacy for regulating WTP residuals. It
regulates backwash solids, alum, ferric chloride, poly-
mer, and activated carbon discharge. The primary con-
cern has been solids, alum, and ferric wastes. (No
258
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softening plants exist in the state.) The NPDES classifi-
cation system is used with organics, inorganics, TSS,
and pH monitored. Common sludge disposal includes
landfill and land application. Backwash water can be
recycled to the head of the plant or lagoon-treated. No
new regulations are planned.
RHODE ISLAND
Not contacted.
SOUTH CAROLINA
Department of Health and Environmental Control
2600 Bull Street
Columbia, SC 29201
(803) 734-5241
The state regulates WTP residuals under the Industrial
Wastewater Division of the Department of Health and
Environmental Control. Reverse osmosis concentrate
has recently become a concern. Most liquid wastes,
such as backwash decant, are sent to settling basins,
then discharged to surface water bodies after settling.
Few facilities discharge to POTWs. Future goals are to
encourage recycling of all washwaters to the head of the
plant. Most sludges are disposed of at municipal landfills
or transferred to a WWTP for mixing and disposal with
sewage sludge. Land application of sludges is not
practiced.
SOUTH DAKOTA
Department of Environment and Natural Resources
Office of Drinking Water
Joe Foss Building, Room 412
Pierre, SD 57501
(605) 773-3754
Landfilling and land application are the primary methods
of WTP residuals disposal. Therefore, the solid waste
program covers most of the monitoring requirements.
Landfills must be permitted. Radium removal is a con-
cern, with allowable limits set at the NRC's limits for
low-level radioactive wastes.
TENNESSEE
Water Quality Control Department
Industrial Facilities Section
150 Ninth Avenue North, 4th Floor
Nashville, TN 37247-3001
(615)741-7883
Tennessee regulates WTP residuals under the Industrial
Facilities Section of the Water Quality Control Depart-
ment. New regulations will be developed within the year
for filter backwash wastes. The most common disposal
practice for liquid wastes is to send them to a POTW,
while discharge to surface water bodies and recycling to
the head of the plant are lesser used options. Sludges
are most often disposed of in municipal landfills, yet a
few plants land-apply or monofill their solid wastes.
TEXAS
Department of Environmental Health
1100 West 49th Street
Austin, TX 78756
(512)458-7542
Permitting is performed jointly with EPA, but the Texas
Water Commission controls the permitting. Treated ef-
fluent from filter backwash and clarifier blowdown is
typically recycled to the plant. Waste solids are usually
not discharged to the watercourse. Sludge disposal is
regulated in two ways: 1) onsite disposal must be regis-
tered with the Municipal Waste Department, and 2) off-
site disposal requires a solid waste permit from the
Department.
UTAH
Bureau of Water Pollution Control
P.O. Box16690
Salt Lake City, UT84116
(801) 538-6146
The most common disposal practices for WTP residuals
are landfilling and land application. The state has no
specific regulations for WTP residuals. Best manage-
ment practices are required for disposal. These prac-
tices include containment (no runoff), dewatering, and
disposal in a way that does not create a nuisance. No
discharge is allowed to natural drainage.
VERMONT
(802) 244-7831
The most common options for disposal of WTP residuals
include landfilling and land application. All types of water
plant wastes are regulated. The constituents of concern
include heavy metals, organics, and nutrients.
VIRGINIA
Department of Health
State Water Control Board
(804)786-1766
The Department of Health regulates backwash water
reuse. Direct return of the backwash to the treatment
train is discouraged. The State Water Control Board
monitors and permits plants on a case-by-case basis.
Constituents of concern for discharges include alumi-
num, TSS, pH, and chlorine residual.
259
-------
WASHINGTON
Department of Ecology
Mail Stop PV-11
Olympia, WA 98504-8711
(206) 438-7037
The state has established guidelines for the disposal of
WTP residuals. The guidelines establish NPDES permit
requirements, including effluent limitations and monitor-
ing requirements, and guidelines for permitting mech-
anical dewatering and sewage disposal facilities. Astate
statute allows plants on specific rivers to discharge sedi-
ment to the originating river. EPA may prohibit this prac-
tice by not concurring with the draft NPDES permit.
WEST VIRGINIA
Department of Natural Resources (DNR)
Water Resources Division
1201 Greenbriar Street
Charleston, VW 25375
(304) 348-2107
DNR is responsible for administering the NPDES pro-
gram. Treated filter backwash liquid requires a permit for
discharge to rivers. Discharge criteria are established on
a case-by-case basis but typically include criteria for
aluminum and other metals. Solids are typically land
applied, but some sewer discharge is practiced. WTP
residuals have not been a primary concern for the state.
WISCONSIN
Department of Natural Resources
(608) 266-2290
Wisconsin is in the process of upgrading all regulations.
The state requires a complete analysis of the waste
stream, and an NPDES permit is required for discharge
to surface waters. For backwash water, the state prefers
pond percolation into the ground. This practice requires
a ground-water discharge permit. The primary method
of waste disposal is discharge to a sanitary sewer sys-
tem.
WYOMING
Department of Environmental Quality
Water Quality Division
Herscher Building, 4 West
Cheyenne, WY 82002
(307) 777-7781
WTP residuals have not been a major concern. No
discharges to natural drainage are allowed, and all filter
backwash effluent must be recycled to the plant. Land-
filling is the most common disposal practice and is regu-
lated by the solid waste criteria, which primarily require
dewatering.
260
-------
Appendix B
1992 Survey of Water Treatment Plants Discharging to
Wastewater Treatment Plants
All of the water treatment plants that appear in the following tables (AWWA/AWWARF, 1992) treat surface water.
Size of Plant
Chemicals Added at WTP
RE. Weymouth
Filtration Plant,
LaVerne, CA,
Metropolitan Water
District
Robert A. Skinner
Filtration Plant,
Temecula, CA,
Metropolitan Water
District
Joseph Jensen
Filtration Plant,
Granada Hills, CA,
Metropolitan Water
District
Dunkirk WTP,
Dunkirk, NY
Chesterfield County
WTP
City of Myrtle
Beach WTP, NC
Average Maximum Peak
Design Daily Daily Hourly
Capacity Demand Demand Demand
(MGD) (MGD) (MGD) (MGD)
520 330 — —
520 300 402 402
550 333 — —
8 4 — —
12 10.5 — —
29.5 14 20 1
Major Processes
at Water
Treatment Plant
Coagulation,
filtration
Coagulation,
filtration
Coagulation,
filtration
Coagulation, lime
softening, filtration,
carbon adsorption
(summer)
Fe/Mn removal,
coagulation, lime
softening, filtration
Coagulation,
filtration, ozone
Coagulant
(Ib/day)
Alum 7,930
Alum 15,290
Alum 5,510
Polyalumi-
num
chloride 100
Alum
13,000-2,000
Coagulant Filter
Aid Aid
(Ib/day) (Ib/day)
Cationic —
polymer
2,420
Cationic —
polydadmac
3,290
Cationic Poly-
polydad- acryla-
mac mide 28
2,770
— —
— 20-3
Oxidant/
PAC Disinfectant
(Ib/day) (Ib/day)
— Chlorine
8,120
— Chlorine
9,935
— Chlorine
8,720
500-1 ,000 Chlorine 65
(July-Aug)
— Ozone
2,800-400
Other
(Ib/day)
Ammonia
750
Ammonia
1,135
Ammonia
800
Lime 30
Chlorine
2,000-500
261
-------
Residuals Streams
at WTP
Monitored Characteristics
of Residuals Streams
Residuals Handling Facilities
Filter
Back-
wash
RE. Weymouth 31.7
Filtration Plant, MGD
LaVerne, CA,
Metropolitan
Water District
Clarifi-
cation Equali-
Basin COD/ zation Chemical
Sludge Other TSS BOD pH Metals Other Basins Recovery
1.4 — Yes COD Yes — Sulfides — —
MGD
Final %
Process Solids at
Streams Dewater- Thick- Treatment
Recycled ing
Yes Cationic —
polyacryla-
mide
ening Plant
Yes <3%
Robert A. 7.5 0.036 — Filter
Skinner Filtration MGD MGD back-
Plant, Temecula, wash
CA, Metropolitan 3%
Water District
Joseph Jensen 21 0.8 — Yes
Filtration Plant, MGD MGD
Granada Hills, (max) (max)
CA, Metropolitan
Water District
Yes
Yes
Yes, belt
press
Future Cationic
construe- polyacry-
tion to iamide
pump to
head of
plant
Yes
Yes
2-3%
Dunkirk WTP,
Dunkirk, NY
Chesterfield
County WTP
Yes
Yes — —
325,000 —
GPD
— 250
Yes, —
holding
tank
Yes —
— 0.5-1.0%
City of Myrtle 0.3 0.043
Beach WTP, NC MGD MGD
Backwash —
decant
Construe- —
ting mech-
anical
dewatering
processes
16%
1%
F.E. Weymouth Filtration Plant,
LaVerne, CA, Metropolitan
Water District
Conveyance to WWTP
Discharge to sewer
Where Residuals
Introduced
Front end
Problems
Encountered
—
Formal Agreement
With WWTP
Surcharge if exceed
levels
Alternate Disposal/Beneficial
Reuse Options
Yes
Robert A. Skinner Filtration
Plant, Temecula, CA,
Metropolitan Water District
Discharge to sewer
Joseph Jensen Filtration Plant, Discharge to sewer
Granada Hills, CA, Metropolitan
Water District
Front end
Front end
Dunkirk WTP, Dunkirk, NY
Chesterfield County WTP
Pumped through force main Front end
Pumped through force main Front end
Heavy metals not
accepted; surcharge
if exceed levels
City of Myrtle Beach WTP, NC Pumped through force main Front end decant —
from alum lagoons
This WTP has onsite
reclamation plant, full liquid
recovery system, and onsite
disposal approved site
Yes
Land application
Composting
262
-------
Size of Plant
Chemicals Added at WTP
Maxi-
Average mum Peak
Design Daily Daily Hourly Major Processes
Capacity Demand Demand Demand at Water
(MGD) (MGD) (MGD) (MGD) Treatment Plant
Coagulant Filter Oxidant/
Coagulant Aid Aid PAC Disinfectant Other
(Ib/day) (Ib/day) (Ib/day) (Ib/day) (Ib/day) (Ib/day)
City of Greensboro
WTP, NC
Texarkana WTP, TX
44
18
31
11
44
17
54 Coagulation, Alum 5,900 —
filtration
Sedimentation, — —
filtration
— — Chlorine
500
— — Chlorine
dioxide
chloramines
Potassium
perman-
ganate
Knoxville WTP, TN 60
Nashville WTP, TN 180
Queens Lane WTP, 100
Philadelphia, PA,
City of Philadelphia
Belmont WTP, 80
Philadelphia, PA,
City of Philadelphia
Franklin WTP, NC, 96
Charlotte-Mecklenburg
Utility District
Vest WTP, NC, 24
Charlotte-Mecklenburg
Utility District
City of Boulder 12
WTP, CO
T.W Moses WTP, 16
Indianapolis, IN,
Indianapolis Water
Company
30-33 40-42
120 140
100 120
60
47.6
18.9
5.3
10
75
71.4
24
12
20
34 Coagulation,
filtration
— Coagulation,
softening, filtration
130 Coagulation,
filtration
90 Coagulation,
filtration
— Coagulation,
filtration
— Coagulation,
filtration
12 Coagulation,
filtration
1 Coagulation,
filtration
Alum 600
Alum
Ferric
chloride;
alum as
needed
Ferric
chloride;
alum backup
Alum
9.0 mg/L
Alum
9.2 mg/L
Alum
Alum
20
Chlorine
1,200
PAC as —
required
Lime
Lime
Cationic
polymer
PAC as — Lime
required
Carbon — —
0.9 mg/L
Carbon — —
mg/L
Yes Prechlori- —
nation
— Chlorine
263
-------
Residuals Streams
at WTP
Monitored Characteristics of
Residuals Streams
Residuals Handling Facilities
City of Greensboro
WTP, NC
Texarkana WTP, TX
Filter
Back-
wash
0.5
MGD
Yes
Clarifi-
cation
Basin
Sludge Other
0.1 —
MGD
COD/
TSS BOD pH Metals Other
Not available
300-700— — — —
mg/L
Equali- Process De-
Final %
Solids
at Treat-
zation Chemical Streams water- Thick- ment
Basins Recovery Recycled Chemical ing
Yes
Filter backwash and
sedimentation basins
ening Plant
Yes —
Knoxville WTP, TN —
Nashville WTP, TN
Queens Lane WTP, Yes
Philadelphia, PA City
of Philadelphia
Belmont WTP, City of Yes
Philadelphia, PA
Franklin WTP, NC Yes
Charlotte-Mecklenburg
Utility District
Vest WTP, NC Yes
Charlotte-Mecklenburg
Utility District
City of Boulder WTP, Yes
CO
T.W. Moses WTP, Yes
Indianapolis, IN
Indianapolis Water
Company
Yes —
Yes —
Yes —
Yes — — —
30,000 — — —
mg/L
Not available
Not available
— Gravity 2%
thick- thickened
ener solids
Yes —
Not available —
— Yes Yes Yes
Yes — — — — Yes Yes — —
Yes — — — — — —
Yes — — — — — —
Yes —
Back- —
wash
water
Yes —
264
-------
City of Greensboro WTP, NC
Texarkana WTP, TX
Knoxville WTP, TN
Nashville WTP, TN
Conveyance to Where Residuals
WWTP Introduced Problems Encountered
Discharge to sewer Front end —
Discharge to sewer Front end —
Pumped through Front end Problems in flocculation
force main basin; a lot of sedimentation;
yearly maintenance
Pumped through Front end; influent Minor problems on small line
force main chamber
Formal Agreement
With WWTP
WTP and WWTP
operated by same
agency
WTP and WWTP
operated by same
agency
WTP and WWTP
operated by same
agency
—
Alternate
Disposal/Beneficial
Reuse Options
—
"
"
Composting
Queens Lane WTP,
Philadelphia, PA, City of
Philadelphia
Discharge to sewer Front end
Belmont WTP, Philadelphia, PA, Discharge to sewer Front end
City of Philadelphia
Franklin WTP, NC, Discharge to sewer Front end
Charlotte-Mecklenburg Utility
District
Vest WTP, NC, Discharge to sewer Front end
Charlotte-Mecklenburg Utility
District
City of Boulder WTP, CO
T.W Moses WTP, Indianapolis, Gravity main
IN, Indianapolis Water Company
Discharge to sewer Front end
Front end
WWTP can handle routine
discharges but seasonal
basin cleaning causes
problems
WWTP can handle but
seasonal basin cleaning at
WTP must be cleared first
Pretreatment and toxicity
concerns at WWTP; this
disposal method will not be
feasible in future due to
requirements of discharge
permits for WWTP
Pretreatment and toxicity
concerns at WWTP; this
disposal method will not be
feasible in future due to
requirements of discharge
permits for WWTP
Main problem encountered is
too thick a sludge for gravity
flow
Discharge restricted
by permit
Discharge restricted
by permit
WTP and WWTP
operated by same
utility
WTP and WWTP
operated by same
utility
Evaluating onsite
dewatering with disposal
to landfill/reclamation on
site
Evaluating onsite
dewatering with disposal
to landfill/reclamation on
site
Co-disposal with biosolids;
agronomic land
application; dedicated land
application; turf farming
Co-disposal with biosolids;
agronomic land
application; dedicated land
application; turf farming
Co-disposal with
wastewater sludge
Allowed a no-charge —
level for
ammonia-nitrogen,
TSS, and BOD. The
WTP always exceeds
the levels for TSS and
BOD and never
exceeds nitrogen
allowance. There are
no restrictions
265
-------
Size of Plant
Chemicals Added at WTP
Nottingham WTP,
Cleveland, OH
City of Cleveland
Morgan WTP,
Cleveland, OH
City of Cleveland
Baldwin WTP,
Cleveland, OH
City of Cleveland
Erie City Water
Authority, Erie, PA
Conestoga WTP,
Lancaster, PA
City of Lancaster
Average Maximum Peak
Design Daily Daily Hourly Major Processes at Coagulant Filter
Capacity Demand Demand Demand Water Treatment Coagulant Aid Aid PAC
(MGD) (MGD) (MGD) (MGD) Plant (Ib/day) (Ib/day) (Ib/day) (Ib/day)
100 87.1 131 152 Disinfection, Alum — — PAC
adsorption, oxidation,
coagulation,
flocculation,
sedimentation,
filtration, fluoridation
150 80 140 150 Disinfection, Alum — — PAC
adsorption, oxidation,
coagulation,
flocculation,
sedimentation,
filtration, fluoridation
165 85 155 162 Disinfection, Alum — — PAC
adsorption, oxidation,
coagulation,
flocculation,
sedimentation,
filtration, fluoridation
60-80 35-40 60 Coagulation, filtration Polyalum — — PAC
chloride
16 7 10.2 0.425 Coagulation, filtration Alum — — PAC
MGH
Oxidant/
Disinfectant Other
(Ib/day) (Ib/day)
Chlorine Sodium
silicofluoride,
potassium
permanganate
Chlorine Hydrofluosilicic
acid
Chlorine Sodium
hypochlorite,
sodium
silicofluoride,
potassium
permanganate
Potassium
permanganate
Chlorine Lime
(hyd rated),
liquid
hydrofluosilicic
acid,
potassium
permanganate
Residuals Streams
at WTP
Monitored Characteristics of
Residuals Streams
Residuals Handling Facilities
Filter
Back-
wash
Clarifi-
cation
Basin
Sludge Other
COD/
TSS BOD pH
Equali-
zation Chemical
Metals Other Basins Recovery
Process De-
Final %
Solids at
Streams water- Thick- Treatment
Recycled Chemical ing
ening Plant
Nottingham WTP,
Cleveland, OH,
City of Cleveland
Morgan WTP, Yes
Cleveland, OH,
City of Cleveland
Baldwin WTP, Yes
Cleveland, OH,
City of Cleveland
Erie City Water Yes
Authority, Erie, PA
Yes Yes —
Conestoga WTP,
Lancaster, PA,
City of Lancaster
Yes
Yes —
Yes —
Yes —
Yes —
2,500- BOD 7.0-7.4 —
4,000 210
mg/L mg/L
2,500- BOD 7.0-7.4 —
4,000 200
mg/L mg/L
2,500- BOD 7.0-7.4 —
4,000 210
mg/L mg/L
30-60 2-14 7.6-8.0 —
Attenu-
ation
tank
Alum,
75
mg/L
Yes —
Yes
Yes —
Yes —
Yes —
— Yes —
Sludge, -
partially
thickened
266
-------
Where Residuals Formal Agreement Alternate Disposal/Beneficial
Conveyance to WWTP Introduced Problems Encountered With WWTP Reuse Options
Nottingham WTP,
Cleveland, OH,
City of Cleveland
Solids diluted if necessary
and pumped through force
main
Morgan WTP, Cleveland, Force main
OH, City of Cleveland
Baldwin WTP, Cleveland, Diluted then discharged to
OH, City of Cleveland sewer
Erie City Water Authority, Discharge to sewer
Erie, PA
Conestoga WTP,
Lancaster, PA,
City of Lancaster
Discharge to sewer
Front end
Front end
Front end
Front end
Front end
Maintenance of optimal
discharge parameters for
cost-effectiveness requires
ongoing effort
Yes
Yes
Yes
Considering beneficial use via
private hauling to Susquehanna
WTP, Lancaster, PA
Size of Plant
Chemicals Added at WTP
City of Milwaukee
Waterworks,
Milwaukee, Wl
Chattanooga WTP,
TN
Design
Capacity
(MGD)
250
72
Average Maximum
Daily Daily
Demand Demand
(MGD) (MGD)
Winter- 171
60
Summer-
120
38 —
Peak
Hourly
Demand
(MGD)
240
48
Major Processes
at Water
Treatment Plant
Coagulation,
filtration
Coagulation,
filtration, GAC
Coagulant Filter
Coagulant Aid
(Ib/day) (Ib/day)
Poly-aluminum —
hydroxy chloride
Polymers —
Aid PAC
(Ib/day) (Ib/day)
— PAC
when
needed
— —
Oxidant/
Disinfectant
(Ib/day)
Chlorine
Chlorine
Other
(Ib/day)
Ammonia,
fluosilicic
acid
Fluorine
Residuals Streams
at WTP
Clarifi-
Filter cation
Back- Basin
wash Sludge Other
Monitored Characteristics of
Residuals Streams
COD/
TSS BOD pH Metals Other
Residuals Handling Facilities
Final %
Equaliza- Process De- Solids at
tion Chemical Streams water-Thick- Treatment
Basins Recovery Recycled Chemical ing ening Plant
City of
Milwaukee
Waterworks,
Milwaukee, Wl
Chattanooga
WTP, TN
Yes
Yes
Yes
Spent
PAC
4,257 310
mg/L mg/L
Yes —
Yes
Conveyance to
WWTP
Where Residuals
Introduced
Problems
Encountered
Formal Agreement
With WWTP
Alternate Disposal/Beneficial
Reuse Options
City of
Milwaukee
Waterworks,
Milwaukee, Wl
Chattanooga
WTP, TN
Discharge to sewer Front end
Sometimes exceed
solids limit;
sometimes need to
flush sewer
Industrial surcharge;
discharge restrictions;
cannot exceed 20,000 Ibs
solids per day:
Copper - 6.0 mg/L, Lead -
2.0 mg/L, Nickel - 4.0 mg/L,
Zinc - 8.0 mg/L
267
-------
Appendix C
Charges From Publicly Owned Treatment Works
The publicly owned treatment works (POTW) charges
presented in Chapter 11 were based on a limited sam-
pling of POTW rates conducted for this analysis and on
a survey published by the League of Minnesota Cities.
Table C-1 presents the results of the telephone sample,
and Table C-2 presents selected results from the
League of Minnesota Cities Survey. Ten of the cities
contacted during the telephone sample do not charge to
accept wastes from water treatment plants; three were
not certain. In addition, some of the POTWs contacted
during the telephone sample and by the League of
Minnesota Cities charge a flat rate per month with no
additional charges for higher flow rates.
Table C-1. Sewer Rates—Large Cities (DPRA, Inc., 1992)
City State Population Sewage Fee Charged
BOD
TSS
Misc.
Little Rock
Tucson
Arkansas
Arizona
175,818
405,390
$1.42/1,000 gallons +
monthly service charge
Varies per industry
>300 ppm:
$0.092/pound
>300 ppm:
$0.0883/pound
a
Oil and grease
>100 ppm:
$0.047/pound
CODa
Chula Vista
California
138,000
Denver
Colorado
467,610
Derby
Connecticut
Boca Raton Florida
Lewiston
Anderson
Ft. Scott
Idaho
Indiana
Kansas
Bloomington Minnesota
12,346
49,505
27,986
64,695
8,893
81,831
$16.70/month
$1.65/1,000 gallons
$0.82/gallon
(commercial)
$0.74/gallon (industrial)
$1.70/1,000 gallons
$1.47/1,000 gallons
$2.57/1,000 gallons
2,244 gallons:
$6.16/month
2,244+ gallons:
$1.18/1,000 gallons
$1.53/1,000 gallons
0-200 ppm:
$1.97/1,000 gallons
200-499 ppm:
$2.42/1,000 gallons
>500 ppm:
$3.26/1,000 gallons
No surcharge No surcharge
No surcharge No surcharge
$0.12/pound $0.11/pound
>300 ppm: >300 ppm:
$0.14/pound $0.12/pound
No surcharge No surcharge
No surcharge No surcharge
Pretreatment:
$450/million
gallons for
metal treating
facilities
$250/million
gallons for
other significant
industries
$0.25/gallon
surcharge
outside city
limits
Industry
surcharge:
$0.09/1,000
gallons
Billing charge:
$0.77/month
268
-------
Table C-1. Sewer Rates—Large Cities (Continued)
City State Population Sewage Fee Charged
BOD
TSS
Misc.
Duluth
Minneapolis
Minnesota
Minnesota
85,000
370,951
$4.25 + $2.32/1 ,000 c
gallons
$2.21/1,000 gallons
c
>250 ppm:
c
MPCA charge
$0.106/pound
for
non-residential:
$25/month
COD
>250 ppm:
$0.053/pound
Bozeman Montana 24,500
Fargo North Dakota 76,000
Salem Oregon 100,000
$3.95 + $0.87/1,000
gallons
$0.70/1,000 gallons
(Minimum: $7.70/month)
$0.41/1,000 gallons
No surcharge No surcharge
No surcharge No surcharge
$0.15/pound $0.117/pound
$1.55 billing
charge;
$108/diameter
inch mile
Richmond Virginia
Seattle Washington
219,214 $1 .79/1 ,000 gallons >250 ppm:
$12.827
hundred-
weight
493,846 $3.42/1 ,000 gallons >300 ppm:
$0.093/pound
>275 ppm:
$1 4.847
hundred-weight
>400 ppm:
$0.14/pound
Metals:
$0.000806/
gallon
Oils, grease,
fats:
$0.0001 24/gallon
3 If average TSS and COD are exceeded, a high strength factor ranging from $1.00 to $3.78 is assessed.
b(Vc) 8.34 [(0.142)(BOD-220)] + [(0.10)(TSS-250)].
c Surcharges unknown.
Key
BOD = Biological oxygen demand.
TSS = Total suspended solids.
COD = Chemical oxygen demand.
Table C-2. Sewer Rates—Minnesota Cities (League, 1991)
City State Population Sewage Fee Charged
Misc.
Benson
Wadena
Ely
Chisholm
Arden Hills
Andover
Bemidji
Owatonna
Albert Lea
Mankato
Burnsville
Duluth
Minnesota
Minnesota
Minnesota
Minnesota
Minnesota
Minnesota
Minnesota
Minnesota
Minnesota
Minnesota
Minnesota
Minnesota
3,656
4,699
4,820
5,930
8,012
9,387
10,949
18,632
19,200
28,651
35,674
92,811
$2.47/1 ,000 gallons
$1.55/1,000 gallons
$2.62/1 ,000 gallons
$0.90/1 ,000 gallons
$1 .64/1 ,000 gallons
Varies for "area"; ranges between $4.50
and $8.50/month
Flat rate ranges between $4.45 and
$44.00
$2.50/month + $1.78/1,000 gallons
$3.65/month
$0.86/unit
Commercial: 90% of winter water usage
or metered water
$3.75/month + $1 .72 to $2.99/1 ,000
gallons
Minimum: $6.23
Minimum: $7.84
Connection charge:
$75 digging fee
Minimum: $2.50
$14 connection charge
if turned off
Connection charge:
$168/unit
269
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Appendix D
Chemical Monthly Average Doses, Pine Valley Water Treatment Plant,
Colorado Springs, CO, 1987-1992 (Pine Valley, 1994)
Table D-1. Raw Water, Pine Valley, 1987
Water Analysis
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Alka.
29.60
38.00
23.00
28.33
33.00
24.00
28.70
38.00
14.00
29.72
34.00
16.00
26.02
30.00
22.00
25.78
30.00
20.00
26.00
34.00
24.00
25.69
34.00
24.00
26.30
30.00
24.00
25.71
30.00
22.00
26.23
32.00
21.00
25.46
42.00
22.00
CaC03
38.50
50.00
30.00
38.21
60.00
32.00
37.00
44.00
23.00
36.48
44.00
32.00
33.31
48.00
28.00
30.86
40.00
26.00
26.00
36.00
24.00
28.53
34.00
23.00
28.40
32.00
25.00
28.07
34.00
20.00
28.57
32.00
26.00
28.09
40.00
24.00
PH
7.65
8.04
6.25
7.58
7.97
7.21
7.60
8.16
7.13
7.53
8.16
6.99
7.59
8.49
7.10
7.44
8.40
6.65
7.36
8.80
6.20
6.93
7.80
6.70
6.97
7.70
6.70
7.23
7.70
6.60
7.51
7.99
6.89
7.62
7.89
7.19
Temp.
5.96
6.50
5.50
6.01
6.40
5.60
6.30
7.00
5.40
6.88
8.70
6.00
7.50
8.30
6.30
6.93
12.00
5.20
7.48
8.50
6.40
7.78
9.10
7.00
8.63
10.00
7.50
10.93
12.90
9.50
8.80
10.50
6.20
6.93
8.00
6.00
Turb.
1.24
5.60
0.78
1.47
9.60
0.81
1.41
4.50
0.90
1.79
8.90
0.88
2.66
10.40
0.89
2.26
21.00
0.83
1.72
9.20
0.95
2.18
3.00
1.06
1.66
4.40
1.15
1.61
5.30
0.73
1.09
3.00
0.73
1.07
5.30
0.75
Chemical Application
Soda Soda Polymer Polymer Polymer
Alum Alum Ash Chlorine 8170 8101 NP10
4.05 1.04 11.73 1.64 1.03 12.22
3.74 1.15 14.18 1.65 1.01 12.39
4.47 1.03 14.2 1.51 1.00 12.06
4.59 1.01 14.79 1.32 1.03 12.33
6.60 1.02 13.18 1.36 1.02 14.75
5.86 0.97 13.56 1.30 1.00 15.97
5.81 0.83 14.56 1.33 1.03 18.19
5.53 1.05 16.55 1.33 1.03 20.29
5.55 1.02 18.01 1.33 1.00 20.41
5.75 1.13 13.71 1.41 0.98 21.95
4.55 0.95 8.58 1.42 1.01 20.85
3.83 0.99 6.58 1.29 0.99 16.22
Note: Polymer 8170 dosage figures are in ppb. All other chemicals are expressed in mg/L.
270
-------
Table D-2. Raw Water, Pine Valley, 1988
Water Analysis
Chemical Application
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Alka.
24.48
28.00
20.00
24.40
28.00
20.00
24.89
31.00
22.00
24.77
32.00
19.00
23.47
30.00
20.00
24.53
30.00
22.00
24.11
32.00
22.00
24.42
28.00
22.00
23.80
28.00
18.00
23.85
26.00
21.00
23.19
28.00
20.00
23.19
26.00
20.00
CaC03
26.03
31.00
20.00
27.35
32.00
20.00
29.55
36.00
26.00
29.71
34.00
28.00
28.75
34.00
24.00
28.38
40.00
24.00
28.42
34.00
23.00
28.23
32.00
24.00
28.32
32.00
26.00
28.69
32.00
26.00
27.79
31.00
26.00
26.85
32.00
20.00
PH
7.61
8.16
7.16
7.44
7.97
7.09
7.25
7.54
6.92
7.34
7.65
6.94
7.52
8.29
7.09
7.43
7.83
7.06
7.41
7.70
7.14
7.36
7.62
7.11
7.34
7.65
7.06
7.51
7.92
7.06
7.85
8.33
7.32
7.90
8.25
7.51
Temp.
6.29
6.80
5.60
6.58
7.60
6.00
6.39
6.90
5.50
6.53
7.60
5.70
7.51
8.60
6.30
8.88
10.60
7.50
9.40
12.90
7.60
9.64
10.50
9.00
10.19
11.00
8.90
11.70
13.00
10.40
9.27
11.70
6.50
5.68
6.80
4.30
Turb.
1.15
4.90
0.74
1.30
5.60
0.92
1.27
4.70
0.79
1.43
12.30
0.62
1.40
3.70
0.55
1.29
8.00
0.66
1.40
4.40
0.84
1.16
5.20
0.74
1.51
5.70
0.80
1.74
4.60
0.63
1.09
3.37
0.59
0.93
2.20
0.59
Soda Soda Polymer Polymer
Alum Alum Ash Chlorine 8170 8101
3.92 8.96 0.89 1.36 1.02
3.62 9.80 1.00 1.24 1.02
3.49 10.23 1.03 1.22 1.00
5.42 11.25 0.63 1.20 0.80
4.19 9.58 0.96 1.26 0.99
3.59 10.33 0.96 1.26 1.01
3.54 10.36 0.96 1.25 1.01
3.55 12.17 0.91 1.28 1.01
3.44 12.72 1.00 1.16 0.99
3.52 11.23 0.99 1.12 0.99
3.96 7.32 1.01 1.30 0.96
3.91 6.75 1.04 1.17 14.23 0.99
Polymer
NP10
15.65
18.29
16.91
15.47
20.23
0.57
20.54
19.95
20.09
19.64
18.68
Note: Polymer 8170 dosage figures are in ppb. All other chemicals are expressed in mg/L.
271
-------
Table D-3. Raw Water, Pine Valley, 1989
Water Analysis
Chemical Application
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Alka.
22.35
26.00
17.00
22.34
28.00
16.00
21.05
24.00
16.00
21.90
25.00
17.00
21.48
26.00
17.00
21.00
73.00
7.00
20.00
24.00
12.00
21.00
28.00
15.00
23.00
27.00
20.00
23.00
27.00
19.00
23.00
28.00
18.00
23.00
28.00
19.00
CaC03
27.31
32.00
24.00
26.96
30.00
26.00
26.77
30.00
24.00
27.00
30.00
25.00
26.13
29.00
22.00
26.00
28.00
24.00
26.00
32.00
18.00
26.00
32.00
21.00
27.00
24.00
30.00
27.00
32.00
24.00
26.00
28.00
24.00
27.00
30.00
24.00
PH
7.88
8.63
7.49
7.89
8.13
7.46
7.97
8.41
7.32
7.89
8.34
7.45
7.87
8.44
7.40
7.84
8.45
7.00
7.80
8.53
7.31
111
8.38
7.28
7.71
8.21
7.25
7.76
8.35
7.24
7.84
8.25
7.48
7.94
8.23
7.62
Temp.
4.96
5.30
4.40
4.95
5.40
44.00
5.65
6.40
5.00
6.52
7.80
5.80
7.84
8.60
6.80
8.60
9.30
7.70
9.40
10.40
8.70
10.00
10.70
8.70
11.00
12.20
10.10
12.50
14.20
11.00
8.80
11.20
6.70
5.80
6.80
4.90
Turb.
0.62
1.88
0.47
0.70
2.50
0.54
0.73
6.00
0.43
0.65
4.30
0.44
0.85
3.90
0.49
1.11
4.50
0.04
1.20
4.90
0.86
1.17
4.70
0.71
1.22
5.70
0.81
1.29
12.40
0.62
1.49
15.00
0.66
1.08
2.90
0.45
Soda Soda Polymer Polymer
Alum Alum Ash Chlorine 8170 8101
3.93 7.53 1.02 1.15 13.78 0.97
4.00 7.92 1.02 1.12 12.73 1.00
4.33 8.18 0.92 1.16 0.28 0.97
4.69 8.45 0.96 1.15 1.09
3.88 8.65 0.76 1.18 18.34 1.18
3.81 9.68 0.61 1.15 17.32 1.03
3.66 11.41 0.98 1.11 19.78 1.06
3.69 12.66 0.93 1.13 18.28 1.01
3.90 13.72 1.00 1.19 18.42 1.01
5.03 12.50 1.01 1.20 16.42
6.03 8.53 0.95 1.16 15.97
6.38 8.64 1.05 1.11 16.35
Polymer
NP101P
13.67
10.79
0.24
16.33
13.16
17.53
17.71
(NP10P)
0.77
(Polymer
8100)
0.52
(Polymer
8100)
0.51
(Polymer
8100)
0.51
(Polymer
8100)
Note: Polymer 8170 dosage figures are in ppb. All other chemicals are expressed in mg/L.
272
-------
Table D-4. Raw Water, Pine Valley, 1990
Water Analysis
Chemical Application
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Alka.
23.00
28.00
14.00
21.00
26.00
14.00
22.00
28.00
16.00
22.00
28.00
19.00
21.00
26.00
17.00
20.00
26.00
18.00
20.00
26.00
16.00
21.00
25.00
18.00
21.00
25.00
18.00
21.00
26.00
18.00
21.00
26.00
18.00
21.00
26.00
19.00
CaC03
27.00
31.00
24.00
27.00
36.00
22.00
27.00
32.00
24.00
26.00
30.00
21.00
25.00
28.00
22.00
25.00
28.00
22.00
25.00
27.00
20.00
25.00
28.00
20.00
25.00
28.00
20.00
26.00
28.00
20.00
25.00
34.00
14.00
25.00
28.00
22.00
PH
7.96
8.30
7.36
7.71
8.04
7.41
7.47
9.99
7.18
7.50
7.90
7.30
7.72
7.91
7.11
7.55
8.54
7.21
7.43
7.61
7.18
7.35
7.51
7.21
7.29
7.90
7.15
7.26
7.45
7.04
7.95
8.55
7.14
8.06
8.75
7.54
Temp.
5.50
5.80
5.10
5.70
6.10
5.40
5.90
6.20
5.50
6.20
6.80
6.00
7.20
8.20
6.10
8.70
9.40
7.80
9.60
11.00
8.90
9.60
10.20
9.10
9.90
10.50
9.60
9.90
10.60
9.60
9.40
10.70
7.60
5.90
7.80
4.20
Turb.
1.02
1.98
0.74
0.91
3.40
0.54
0.88
2.30
0.62
0.75
3.00
0.48
0.97
3.80
0.66
1.16
4.40
0.71
1.58
10.20
0.96
1.31
4.90
0.92
1.03
4.30
0.68
1.07
9.60
0.77
0.85
1.81
0.58
0.76
1.06
10.50
Soda Soda Polymer
Alum Alum Ash Chlorine 8100
5.56 9.30 1.00 1.13 0.52
5.77 8.36 1.00 1.14 0.52
5.90 10.40 1.04 1.23 0.51
6.29 11.75 0.56 1.11 0.51
6.65 9.24 0.74 1.13 0.51
6.77 10.49 0.92 1.08 0.57
6.78 11.53 1.04 1.14 0.56
6.31 11.95 1.06 1.13 0.50
6.08 12.45 1.02 1.13 0.50
5.81 14.40 0.96 1.18 0.50
6.67 9.30 0.75 1.20 0.53
7.00 8.69 0.88 1.15 0.51
Polymer Polymer
8170 NP10
16.02
16.19
16.16
16.22
16.31
15.65
16.42
16.11
16.21
16.11
16.04
16.05
Note: Polymer 8170 dosage figures are in ppb. All other chemicals are expressed in mg/L.
273
-------
Table D-5. Raw Water, Pine Valley, 1991
Water Analysis
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Alka.
22.00
28.00
18.00
21.00
28.00
19.00
21.00
26.00
15.00
21.00
24.00
17.00
20.00
22.00
18.00
20.00
24.00
18.00
21.00
26.00
18.00
20.00
23.00
17.00
21.00
24.00
18.00
21.00
24.00
18.00
20.00
22.00
17.00
20.00
22.00
18.00
CaC03
25.00
28.00
22.00
26.00
30.00
24.00
26.00
30.00
22.00
25.00
28.00
20.00
24.00
26.00
22.00
24.00
26.00
22.00
24.00
28.00
22.00
24.00
30.00
20.00
24.00
30.00
20.00
24.00
28.00
20.00
24.00
28.00
20.00
24.00
28.00
20.00
PH
7.76
8.02
7.22
7.73
7.97
7.51
7.57
7.81
7.29
7.59
7.90
7.14
7.68
7.94
7.47
7.42
7.66
7.09
9.50
10.60
8.80
9.40
10.30
8.90
9.40
10.40
9.00
9.80
10.60
9.20
8.50
10.60
6.40
5.40
6.60
4.90
Temp.
5.20
5.50
4.80
5.50
6.20
5.10
5.90
6.30
5.40
6.20
6.70
6.00
7.70
8.90
6.00
8.80
9.60
8.00
7.34
7.68
7.04
7.14
7.30
7.04
7.10
7.25
6.99
7.00
7.63
6.88
7.71
7.99
7.29
7.78
7.95
7.56
Chemical Application
Soda Soda Polymer Polymer Polymer
Turb. Alum Alum Ash Chlorine 8100 8170 NP10
1.34 7.29 10.13 0.97 1.27 0.50 15.74
54.00
0.41
0.73 7.64 10.40 1.01 1.37 0.49 16.39
3.50
0.33
0.62 7.56 11.11 1.02 1.38 0.49 16.28
2.50
0.37
0.84 7.57 10.34 1.03 1.21 0.50 16.32
7.20
0.45
0.95 7.53 9.67 0.98 1.19 0.50 16.00
3.70
0.67
1.00 7.49 11.35 0.90 1.15 0.51 18.20
3.10
0.72
0.92 7.50 12.62 0.96 1.10 0.51 18.23
3.00
0.69
1.06 7.34 14.68 0.99 1.21 0.51 18.27
2.70
0.70
1.13 7.32 16.14 1.00 1.21 0.49 18.00
3.70
0.82
1.11 6.76 16.89 1.09 1.20 0.51 18.81
2.90
0.68
0.90 7.42 9.63 0.98 1.43 0.51 17.89
46.00
0.48
0.58 7.31 9.67 0.58 1.33 0.49 18.09
1.61
0.43
Note: Polymer 8170 dosage figures are in ppb. All other chemicals are expressed in mg/L.
274
-------
Table D-6. Raw Water, Pine Valley, 1992
Water Analysis
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Alka.
20.00
22.00
18.00
20.00
22.00
16.00
19.00
22.00
15.00
20.00
24.00
18.00
20.00
24.00
17.00
20.00
27.00
17.00
19.00
24.00
16.00
19.00
22.00
16.00
20.00
23.00
17.00
20.00
22.00
17.00
20.00
22.00
17.00
20.00
22.00
17.00
CaC03
24.00
26.00
20.00
24.00
32.00
20.00
24.00
30.00
22.00
24.00
30.00
16.00
23.00
26.00
19.00
23.00
24.00
20.00
23.00
28.00
19.00
24.00
30.00
20.00
24.00
30.00
20.00
24.00
26.00
18.00
23.00
26.00
18.00
24.00
26.00
20.00
PH
5.20
5.70
4.80
4.90
5.40
4.70
5.20
5.50
4.90
5.80
6.80
5.20
7.40
8.10
6.60
8.20
8.80
7.40
8.60
9.20
8.20
9.00
10.30
7.80
8.80
9.20
8.20
9.40
9.90
8.80
8.70
10.30
6.60
5.50
6.60
5.00
Temp.
7.60
7.79
7.37
7.39
7.56
7.21
7.37
7.82
7.13
7.41
8.31
7.04
7.46
7.72
7.29
7.30
7.51
7.15
7.18
7.80
7.02
7.08
7.51
6.90
7.07
7.23
6.87
7.03
7.25
6.90
7.74
8.06
6.97
7.97
8.37
7.51
Chemical Application
Soda Soda Polymer Polymer Polymer
Turb. Alum Alum Ash Chlorine 8100 8170 NP10
0.47 7.11 10.27 1.08 1.32 0.50 18.33
1.43
0.24
0.72 6.95 11.97 0.89 1.44 0.50 17.98
1.94
0.43
0.88 7.02 12.22 1.03 1.45 0.50 18.20
10.80
0.53
0.92 7.58 12.04 1.07 1.41 0.52 17.95
2.80
0.57
0.85 7.54 11.41 0.85 1.41 0.49 18.83
3.10
0.48
0.57 7.83 12.60 1.04 1.41 0.51 22.29
2.30
0.32
0.68 7.92 14.20 0.99 1.39 0.51 23.80
2.10
0.43
0.70 7.98 15.80 0.91 1.37 0.51 24.08
3.70
0.47
0.89 7.99 17.07 0.91 1.38 0.49 23.76
2.20
0.53
1.12 7.50 17.24 0.95 1.41 0.50 23.99
2.60
0.79
0.75 8.17 11.52 0.30 1.43 0.50 23.82
3.40
0.47
0.64 8.52 10.94 1.44 0.50 24.16
20.00
0.39
Note: Polymer 8170 dosage figures are in ppb. All other chemicals are expressed in mg/L.
275
-------
Appendix E
Chemical Monthly Average Doses, Mesa Water Treatment Plant,
Colorado Springs, CO, 1987-1992 (Mesa, 1994)
Table E-1. Raw Water, Mesa, 1992
Water Analysis
Chemical Application
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Alka.
40.14
52.00
22.00
22.71
28.00
19.00
21.75
26.00
18.00
20.14
24.00
16.00
18.89
24.00
16.00
18.05
22.00
16.00
17.82
24.00
14.00
18.75
24.00
14.00
18.47
24.00
14.00
23.42
60.00
16.00
43.20
60.00
22.00
49.37
62.00
34.00
CaC03
39.88
52.00
20.00
23.17
28.00
18.00
23.11
28.00
18.00
21.21
30.00
16.00
19.37
25.00
16.00
17.52
22.00
12.00
16.63
20.00
12.00
17.89
28.00
12.00
17.78
28.00
14.00
22.07
54.00
16.00
40.95
56.00
20.00
48.56
60.00
30.00
PH
7.65
7.86
7.26
7.35
7.50
7.20
7.35
8.09
7.11
7.42
7.69
7.04
7.49
7.74
7.17
7.15
7.69
6.43
7.29
7.73
7.05
7.15
7.52
6.83
7.02
7.35
6.73
7.35
7.87
7.07
7.90
8.73
7.56
7.92
8.82
7.40
Temp.
40.55
43.00
39.00
40.65
43.00
49.00
41.67
43.00
41.00
42.66
46.00
41.00
46.53
50.00
44.00
50.25
55.00
45.00
53.33
56.00
51.00
53.25
58.00
49.00
51.91
55.00
49.00
49.53
52.00
47.00
41.00
48.00
36.00
38.26
41.00
36.00
Turb.
2.26
6.10
1.40
2.85
79.50
1.60
2.20
7.00
1.40
2.88
32.00
1.40
1.63
15.50
0.60
2.22
58.10
0.60
1.74
20.70
0.80
3.42
75.50
1.00
1.65
19.50
0.90
3.45
100.00
0.70
3.99
76.00
0.70
2.27
15.50
0.80
Soda Soda Polymer
Alum Ash Alum Chlorine 8100
5.52 6.65 3.91 1.49 0.71
3.99 11.57 6.36 1.62 0.80
4.08 10.51 6.21 1.62 0.79
4.25 11.36 6.09 1.70 0.80
4.49 11.37 3.84 1.75 0.60
6.13 14.87 3.82 2.03 0.67
4.93 11.45 6.30 2.04 0.89
5.11 13.12 6.20 2.11 0.97
5.33 13.90 6.24 2.06 0.94
5.43 11.41 5.76 1.79 0.90
5.54 8.19 2.56 1.47 0.66
5.27 8.12 2.41 1.43 0.61
Polymer Polymer
8170 NP10
8.00
1.20
7.20
8.60
8.10
0.80
0.30
1.30
5.30
8.00
6.80
Note: Polymer 8170 dosage figures are in ppb. All other chemicals are expressed in mg/L.
276
-------
Table E-2. Raw Water, Mesa, 1991
Water Analysis
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Alka.
28.89
68.00
14.00
51.70
62.00
20.00
51.76
82.00
26.00
44.33
56.00
24.00
38.60
54.00
18.00
27.34
54.00
14.00
24.52
44.00
12.00
26.46
40.00
16.00
27.68
48.00
14.00
27.48
44.00
16.00
38.96
58.00
20.00
42.16
54.00
26.00
CaC03
28.89
66.00
18.00
53.34
64.00
24.00
52.68
78.00
28.00
45.68
58.00
24.00
39.40
54.00
18.00
28.15
54.00
14.00
24.19
40.00
12.00
25.92
40.00
16.00
26.98
46.00
16.00
26.03
40.00
14.00
38.60
56.00
22.00
41.96
58.00
30.00
PH
7.87
8.22
7.49
7.92
8.16
7.55
8.00
8.37
7.60
8.10
8.64
7.49
7.98
8.62
7.52
7.74
8.24
7.39
7.45
7.94
6.93
7.60
8.04
7.15
7.56
7.91
7.08
7.64
7.98
7.18
7.88
8.08
7.58
7.83
8.19
7.47
Temp.
38.39
39.00
37.00
39.19
41.00
37.00
41.14
44.00
39.00
43.17
46.00
40.00
47.71
55.00
41.00
52.41
58.00
47.00
56.43
60.00
53.00
55.96
61.00
50.00
54.28
59.00
50.00
50.07
54.00
42.00
41.78
45.00
39.00
40.23
42.00
38.00
Chemical Application
Soda Soda Polymer Polymer Polymer
Turb. Alum Ash Alum Chlorine 8100 8170 NP10
1.86 6.17 8.72 1.36 0.39 15.80
27.00
0.50
2.66 7.51 10.03 2.01 0.55 18.40
22.00
1.40
4.20 7.76 6.51 1.66 0.59 18.90
20.00
1.20
7.74 7.96 5.63 1.79 0.62 16.80
196.00
0.90
6.69 8.56 6.35 2.05 0.69 17.20
122.30
0.70
13.33 10.57 10.43 2.39 1.13 14.60
230.00
0.70
10.14 10.28 14.36 2.37 0.86 17.30
900.00
0.70
13.82 11.99 14.37 0.14 2.22 1.11 15.90
180.00
1.10
5.28 6.48 8.24 1.14 2.11 0.80 14.30
370.00
0.70
1.67 5.90 7.78 0.97 1.88 0.67 8.80
7.50
0.60
3.01 6.01 5.81 1.12 1.65 0.71 11.80
31.00
0.70
2.50 5.75 5.54 1.03 1.56 0.66 9.20
35.00
0.60
Note: Polymer 8170 dosage figures are in ppb. All other chemicals are expressed in mg/L.
277
-------
Water Analysis
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Alka.
43.70
58.00
40.00
47.60
70.00
24.00
40.90
60.00
24.00
42.50
62.00
20.00
31.30
46.00
15.00
30.10
44.00
14.00
26.00
46.00
12.00
24.50
42.00
14.00
33.10
54.00
12.00
30.90
61.00
14.00
41.10
96.00
16.00
54.50
72.00
20.00
CaC03
46.50
58.00
34.00
48.40
66.00
28.00
43.60
62.00
26.00
44.10
66.00
22.00
33.40
46.00
16.00
29.90
44.00
16.00
25.30
42.00
10.00
23.80
40.00
10.00
31.80
52.00
15.00
30.00
64.00
16.00
40.00
84.00
16.00
58.80
70.00
24.00
PH
111
8.10
7.46
7.81
8.16
7.49
7.66
8.01
7.32
7.78
8.09
7.29
7.77
8.04
7.34
7.39
7.92
6.91
7.31
8.87
6.82
7.56
8.05
6.80
7.52
7.94
7.18
7.73
8.13
7.34
8.05
8.25
7.83
8.01
8.25
7.54
Temp.
39.90
41.00
39.00
40.30
43.00
39.00
41.30
42.00
39.00
43.70
47.00
41.00
46.50
53.00
41.00
55.50
59.00
48.00
56.20
62.00
52.00
54.90
60.00
51.00
54.80
57.00
51.00
46.40
54.00
44.00
42.20
46.00
39.00
38.60
41.00
39.00
Chemical Application
Soda Soda Polymer Polymer Polymer
Turb. Alum Ash Alum Chlorine 8100 8170 NP10
1.73 5.75 10.32 1.42 0.38 14.24
6.20
1.10
2.19 5.27 8.81 1.30 0.33 12.60
34.30
0.50
5.47 6.61 12.00 1.56 0.47 16.70
107.80
1.20
15.49 9.40 13.92 1.72 0.76 14.92
180.00
1.70
7.11 9.72 14.66 1.90 0.79 14.61
91.70
0.60
7.91 5.61 14.55 2.38 1.57 16.88
615.00
0.80
47.50 7.79 19.61 2.71 2.00 14.59
2,700.00
1.00
11.60 6.84 14.48 2.39 1.55 18.31
1,200.00
0.70
3.62 5.19 12.74 2.09 1.41 18.59
48.00
0.70
3.04 5.16 11.92 1.95 1.42 16.54
63.60
0.60
1.59 3.21 10.97 1.61 1.22 15.95
51.00
0.50
1.16 6.65 9.38 1.27 0.62 16.58
6.40
0.60
Note: Polymer 8170 dosage figures are in ppb. All other chemicals are expressed in mg/L.
278
-------
Water Analysis
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Alka.
46.50
60.00
24.00
38.20
50.00
20.00
38.70
48.00
38.00
36.38
56.00
16.00
27.60
42.00
16.00
23.70
46.00
12.00
27.90
44.00
16.00
30.70
60.00
14.00
30.00
50.00
18.00
34.70
48.00
18.00
34.60
58.00
14.00
50.10
62.00
18.00
CaC03
42.30
62.00
26.00
39.80
65.00
18.00
41.50
52.00
24.00
38.90
52.00
16.00
30.50
44.00
18.00
25.90
50.00
14.00
29.70
46.00
18.00
30.10
50.00
14.00
30.80
46.00
20.00
36.60
54.00
22.00
35.60
67.00
20.00
52.40
64.00
20.00
PH
7.86
8.12
7.58
7.62
8.02
7.11
7.79
8.13
7.53
7.90
8.15
7.70
7.88
8.14
7.61
7.64
7.85
7.26
7.31
7.57
6.90
7.44
7.85
6.96
7.34
7.72
7.05
7.89
8.59
7.28
8.06
8.32
7.71
7.99
8.26
7.55
Temp.
48.40
50.00
47.00
48.80
50.00
47.00
49.30
55.00
43.00
46.70
51.00
43.00
51.10
56.00
47.00
55.10
58.00
52.00
58.00
60.00
56.00
56.70
62.00
53.00
54.00
58.00
50.00
51.00
55.00
44.00
42.60
45.00
40.00
39.60
42.00
39.00
Turb.
3.51
135.10
1.30
8.44
133.00
1.20
12.66
288.00
1.80
4.93
79.50
0.80
4.31
73.00
1.00
3.09
43.00
1.40
7.71
56.00
1.80
11.95
430.00
1.00
5.06
475.00
0.80
1.64
15.20
0.50
0.69
4.50
0.30
1.18
7.10
0.40
Chemical Application
Soda Soda Polymer Polymer Polymer
Alum Ash Alum Chlorine 8100 8170 NP10
6.07 8.06 0.97 1.26 0.90 14.19
7.99 16.92 0.97 1.84 5.90 1.33 8.56
9.13 15.95 9.13 1.75 7.45 1.17 8.89
7.78 10.52 1.63 12.82 0.79 0.82
(N101P)
7.37 11.35 1.53 0.73 11.30
(N101P)
8.50 14.83 1.81 0.90 14.28
(N101P)
9.57 18.69 2.05 11.24 1.10 12.80
(N101P)
9.62 17.63 1.93 12.54 1.09
8.47 18.46 1.73 11.64 0.90
7.25 11.30 1.71 12.39 0.75 0.48
(Polymer
8100)
6.07 9.11 1.59 16.53 0.39
(Polymer
8100)
6.09 7.89 1.50 16.78 0.42
(Polymer
8100)
Note: Polymer 8170 dosage figures are in ppb. All other chemicals are expressed in mg/L.
279
-------
Table E-5. Raw Water, Mesa, 1988
Water Analysis
Chemical Application
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Alka.
50.90
66.00
40.00
49.10
70.00
20.00
48.50
70.00
22.00
32.30
70.00
10.00
31.50
50.00
14.00
23.30
38.00
8.00
26.20
158.00
12.00
23.00
46.00
12.00
28.50
42.00
14.00
34.30
50.00
20.00
34.50
42.00
22.00
42.90
60.00
22.00
CaC03
47.40
62.00
38.00
46.60
68.00
22.00
44.60
60.00
20.00
30.00
68.00
12.00
28.20
44.00
8.00
21.00
35.00
8.00
23.70
126.00
10.00
20.90
40.00
12.00
23.30
34.00
12.00
31.90
48.00
17.00
32.00
41.00
22.00
38.70
52.00
18.00
PH
7.94
8.10
7.69
7.91
8.13
7.45
111
808.00
731 .00
111
8.33
6.67
7.87
8.34
7.59
7.71
8.15
6.80
7.53
8.35
7.19
7.54
8.70
7.19
7.58
8.07
7.21
7.67
8.17
7.15
7.97
8.25
7.37
7.86
8.13
7.44
Temp.
41.20
43.00
39.00
40.40
42.00
30.00
38.30
41.00
35.00
39.80
45.00
34.00
45.80
52.00
41.00
55.50
59.00
48.00
57.50
63.00
55.00
61.00
63.00
58.00
58.80
62.00
56.00
55.70
60.00
63.00
51.20
55.00
48.00
48.40
49.00
47.00
Turb.
4.71
200.00
1.00
6.19
77.00
1.10
16.21
340.00
1.00
7.26
1 ,480.00
1.00
2.99
25.00
1.00
10.64
492.00
1.10
6.51
567.00
0.80
9.92
1 ,330.00
0.80
3.70
100.00
0.80
1.57
16.10
0.70
1.30
525.00
0.70
6.14
168.00
0.60
Soda Soda Polymer Polymer
Alum Ash Alum Chlorine 8100 8170
6.38 7.14 0.19 1.22 0.70
6.13 6.97 1.02 1.43 0.72
6.33 8.60 1.00 1.70 0.96
8.48 10.96 1.01 1.59 1.01
7.84 11.29 0.37 1.69 1.06
9.89 14.58 1.95 1.27
9.49 15.40 1.87 1.15
9.70 15.96 2.02 1.32
8.09 13.66 1.72 0.88
7.20 12.84 1.53 0.85
7.34 10.52 1.42 0.73
7.30 10.30 0.34 1.35 0.82
Polymer
NP10
12.05
12.17
14.53
15.03
18.19
15.80
16.83
14.55
14.88
13.91
17.42
18.64
Note: Polymer 8170 dosage figures are in ppb. All other chemicals are expressed in mg/L.
280
-------
Table E-6. Raw Water, Mesa, 1987
Water Analysis
Chemical Application
Jan.
Feb.
Mar.
Apr.
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Avg.
Max.
Min.
Alka.
35.00
66.00
18.00
34.70
56.00
18.00
49.80
66.00
18.00
38.20
58.00
20.00
25.20
44.00
16.00
21.70
44.00
10.00
24.80
40.00
12.00
26.00
50.00
12.00
38.30
58.00
18.00
29.40
54.00
14.00
32.90
68.00
16.00
36.10
58.00
18.00
CaC03
35.50
68.00
18.00
36.50
64.00
18.00
53.90
72.00
20.00
43.50
64.00
24.00
29.40
44.00
20.00
24.30
46.00
16.00
26.90
46.00
16.00
28.20
46.00
14.00
40.40
58.00
20.00
30.20
50.00
15.00
32.10
54.00
15.00
35.20
56.00
20.00
PH
7.69
8.19
7.32
7.64
8.17
7.13
7.74
8.13
7.17
7.68
8.11
7.14
7.58
8.57
6.59
7.47
8.17
6.63
7.54
8.58
6.81
7.47
8.88
6.73
7.78
8.24
7.29
7.85
8.29
7.31
8.04
8.73
7.59
7.97
8.24
7.31
Temp.
36.90
39.00
34.00
38.80
41.00
37.00
38.70
46.00
35.00
43.40
54.00
37.00
50.10
57.00
42.00
59.40
66.00
51.00
63.50
67.00
59.00
64.30
68.00
61.00
61.00
65.00
57.00
53.90
58.00
50.00
50.60
56.00
46.00
44.70
48.00
42.00
Turb.
3.18
47.00
0.60
7.04
86.00
1.60
63.65
925.00
2.10
17.45
208.00
2.30
27.63
1 ,554.00
1.40
22.03
1,073.00
2.50
6.28
27.00
2.50
12.76
533.00
0.80
24.25
861.00
2.90
1.76
16.60
0.40
1.11
3.10
0.30
1.62
15.40
0.30
Soda Soda
Alum Ash Alum Chlorine
8.23 13.58 1.51
9.18 12.41 1.72
12.91 10.73 2.47
11.88 14.23 1.77
11.31 16.32 1.70
12.30 18.89 2.12
10.92 18.41 1.94
10.58 17.25 2.05
10.15 10.06 1.73
7.58 10.96 1.66
6.14 7.99 1.43
5.75 7.79 1 .24
Polymer Polymer
8100 8170
0.95
1.08
1.68
1.57
1.34
1.63
1.28
1.41
1.17
0.81
0.67
0.58
Polymer
NP10
21.31
20.12
18.89
13.91
17.37
16.89
17.78
16.75
15.95
17.92
13.73
12.56
Note: Polymer 8170 dosage figures are in ppb. All other chemicals are expressed in mg/L.
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