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
liability. Anyone using this information assumes all liability arising from such use, including but not
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per page. Requests for special permission or bulk copying should be addressed to Permissions &
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)
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                 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)

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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

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                                        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

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                                      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

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                                        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

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                                 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

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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

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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

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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.

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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

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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,

-------
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.

-------
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

-------
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

-------
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

-------
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

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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

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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

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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

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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

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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

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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

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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

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                                                                 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

-------
      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





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       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

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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

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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

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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

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                                           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

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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

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            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

-------
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

-------
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

-------
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
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1
T3
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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

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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

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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

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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

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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

-------
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
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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
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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
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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.
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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-
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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
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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
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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.
                                                  117

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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.
                                                  120

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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-
                                                  121

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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.
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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.
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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

-------
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

-------
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

-------
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

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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

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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

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                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

-------
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.
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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
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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.
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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
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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
                                                 146

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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
                                                   153

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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
                                                  154

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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.
                                                   157

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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
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End

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Time































Length of
Operating Period
(DaysHours)































2. Injection Rate (gpm)


Maximum

































Minimum

































Average































3. Well Head Injection Pressure (pd)


Maximum

































Minimum

































Estimated
Average































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Fluid Injected


Dally

































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Injection Rage (gpm)


Total Pressure (pslg) 1
1
SPECIFIC INJECnVTTY
Shut-In Pressure (pslg)

Date:
I Specific Pressure (pslg)

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                                 MONTHLY OPERATIONAL REPORT - Page 3



                                            INJECTION WELL



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                                                                              State:
                                       2.   Permit Number:

                                           Signed:	
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Date:
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i .
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Starting Ending

Starting Ending
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Solids
(mg/L)










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Lower
Upper
Lower
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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

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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

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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

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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

-------
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

-------
                                                         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

-------
                              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
                                                   183

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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

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                        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

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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

-------
                       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.
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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

-------
      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
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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

-------
                                     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

-------
          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

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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

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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

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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

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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

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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

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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

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                                     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.
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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

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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

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                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

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                     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

-------
                                    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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