Managing Wastewater in Coastal Urban Areas (1993) / Chapter Skim
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D ENGINEERING AND MANAGEMENT OPTIONS FOR CONTROLLING COASTAL ENVIRONMENTAL...
D ENGINEERING AND MANAGEMENT OPTIONS FOR CONTROLLING COASTAL ENVIRONMENTAL...
Pages 295-393
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From page 295... ...
; water, energy, and other natural resource conservation; recycle and reuse; and nonpoint source control. SOURCE CONTROL The three basic source control alternatives, which may be practiced independently or concurrently in any municipality, are pollution prevention, pretreatment, and recycle and reuse.
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From page 296... ...
Elimination or minimization of water pollutants at the source is becoming more important as wastewater treatment plant effluent criteria become more strict. Once a pollutant is discharged into a sewer system, it is diluted by several orders of magnitude and usually much more difficult to remove.
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Pollution prevention options include product changes, technology modifications, raw materials and process changes, and operational changes. In the context of municipal wastewater management, some of the chief pollution prevention activities include source reduction, water conservation, energy conservation, and some approaches to nonpoint source control.
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The subject of nonpoint source control options is addressed later in this appendix. Pollution Prevention Programs Implementation At present there is no federal mandate to implement pollution prevention programs in municipalities and/or municipal wastewater management districts.
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While the pretreatment program at the 67 million gallons per day (MOD) Springfield Regional Wastewater Treatment Plant has effectively controlled the industrial discharge of cadmium, nonindustrial sources and/or nonpoint sources interfere with a Type I classification for the comporting and marketing of its sludge.
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In this study, the total annual cost of the zero sludge production alternative is 9 percent higher than the conventional sludge system. However,
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Conventional Sludge System Zero Sludge Production System Total Capital Cost $ 450,000$ 1,250,000 Capital Recovery $67,000$186,000 Operation and Maintenance2 $43,000$75,000 Labor $75,000$50,000 Chemicals and Power $75,000$54,000 Water- In/Out $22,000$2,000 Sludge Disposal & Fees $48,0000 Miscellaneous $ 10,000$5,000 Total Annual Cost $340,000$370,000 1Assuming an 8 percent opportunity cost. 2Assuming 12 percent of the original capital cost per annum.
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In 1976, the Sanitation Districts adopted a new industrial source reduction ordinance which included numerical limitations on all industrial discharges. The influent heavy metals reductions at the two regional wastewater treatment plants in the 15 years of record are shown in Figure D.1.
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The Robbins Company management realized that a pollution prevention approach, through the use of a closed-loop system, although risky, was its best choice. Figures D.2a, D.2b, and D.2c show the Robbins Company's success for the years 1985 through 1990 in water conservation, chemical use, and sludge production after implementing a pollution prevention program.
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As shown in Table D.4, the cost of the system with counter-current rinses and recovery units provided an annual cost savings of over 50 per cent in comparison to the other systems evaluated.
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Consequently, small businesses are often reluctant, and frequently find it impossible. to engage in advantageous pollution prevention or pretreatment programs without federal, state or local financial assistance, such as grants.
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No Pollution Prevention Pollution Prevention Pollution Prevention Standard Single Stage Rinses Captial Costs1 Annual Costs2 Counter-Current Rinses $ 192,000 $90,000 $ 1 86,000 $87,000 Counter-Current Rinses + Plating Recovery Systems $162,000 $40,000 1 The capital costs include equipment for treatment of wastewater and sludge. 2The annual costs include annualized capital (10 year life)
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From page 307... ...
Then businesses are faced with the problem of replacing the entire pollution control system or paying heavy fines with no redress. In order to provide small business with the necessary resources and confidence to acquire new technologies, a strict quality certification program of technology and vendors could certify the vendors and technology.
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From page 308... ...
Recognizing that more research and data collection are essential to a sound analysis of environmental and economic costs and benefits, the following preliminary conclusion can be reached: · A break-even cost situation between the pollution prevention approach and the pretreatment approach to source control has nearly been reached across a broad spectrum of industries. If higher discharge limitations and/or higher off-site waste disposal costs are applied in the future, businesses with pollution prevention programs in place will have an economic advantage.
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The first three of these technologies are discussed here; chemically-enhanced primary treatment is covered in the section on Municipal Wastewater Treatment Systems.
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High-rate settlers have significantly smaller land-area and basin-size requirements than conventional settlers. They have been operated at increased overflow rates compared with conventional primary treatment facilities, often with chemicals for increased removal efficiency.
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These technologies are discussed here. Nutrient removal systems are addressed in the section on Municipal Wastewater Treatment Systems.
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The majority of natural land-based wastewater treatment systems are preceded by a minimum of primary treatment. Slow-rate, rapid infiltration, and overland flow processes are the predominant municipal natural treatment systems in use today.
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Under an integrated coastal management plan, natural wastewater treatment systems could be used as a complement to conventional in regions where the required land area is available. Table D.6 presents a range of the land-area requirements for all of the systems described here.
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Water polishing and final nutrient removal is completed by flowers, shrubs, and trees. Retention times vary from 4 days for sewage up to 11 days for septage lagoon supernatant, each at constant flow.
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~ ~ _-AL. by:" '[ Rangeinmgd it_ 0-200 200 - 400 400- 1000 1000 - 2000 2000 - 3500 ~ - Y _ ~ ~''~ ~ 375 FIGURE D.3a Total treated wastewater design flows by state.
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Costs associated with secondary treatment of municipal wastewater are normally considered as water pollution control costs and are not included in wastewater reclamation and reuse costs (Asano 1991~. To aid in determining cost-effectiveness of water reclamation and reuse programs, the EPA has formulated "Cost Effectiveness Analysis Guidelines"
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From page 317... ...
These efforts have resulted in decreases in wastewater flows of between 10 percent and 40 percent at various municipal wastewater treatment plants (Bruskin and Lindstrom 1992~. Reduced wastewater flows can lower operating costs at existing facilities and lower costs, postpone, and reduce the capacity of future wastewater treatment facilities where inflow and filtration are minimized.
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starches, bark resins, and other biodegradable, renewable, and/or nonpetrochemical-based substances capable of removing constituents from wastewater, either selectively or comprehensively. Seeds from two moringa species native to the sub-Himalayan region of India have out-performed metal salts in municipal wastewater and water treatment tests (Folkard 1986~.
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Municipal Wastewater Treatment Systems A large number of technically feasible wastewater treatment technologies are currently available. Ten representative systems, arranged roughly from the simplest to the most complex, have been selected to demonstrate the wide range of treatment capabilities and costs.
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Description of Ten Wastewater Treatment Systems 1. Primary Treatment Primary treatment is a physical process that involves gravity separation of settleable and floatable solids from the influent wastewater stream.
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3. Conventional Primary + Biological Treatment Conventional biological treatment systems, often classified as either suspended (e.g., activated sludge)
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5. Nutrient Removal Wastewater treatment systems can be configured to remove the nutrients nitrogen and/or phosphorus.
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8. Nutrient Removal and Granular Activated Carbon This alternative adds the granular activated carbon (GAC)
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Matrix of Performance and Cost Summary Tables Data for the ten systems are summarized in the Matrix of Performance and Cost Summary Tables D.8a, D.8b, D.8c, and D.8d.2 Performance comparisons are made on the basis of conventional parameters. Performance and Costs The performance of each of the 10 wastewater treatment systems was assessed based on two surveys of over 100 U.S.
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Costs are expressed as capital cost, operation and maintenance cost, and total cost. Capital cost is expressed in two sets of units: dollars per gallon per day of installed capacity, and dollars per mission gallons.4 Operation and maintenance costs, and total costs are expressed in dollars per million 3Information on the two nationwide surveys conducted to obtain data on these ten candidate systems and the screening criteria used to select them has been published as a separate document: Performance and Innovation in Wastewater Treatment Technical Note #36, January, 1992, by Murcott, S., and Harleman, D., Parsons Laboratory, Massachusetts Institute of Technology, Cambridge, Massachusetts.
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81 88 99 94 99 100 TN (%) 91 94 94 96 96 97 NOTE: TSS = total suspended solids, BOD5 = 5-day biochemical oxygen demand, TP = total phosphorus, TN = total nitrogen, NH4 = ammonia nitrogen, = data insufficient or unavailable.
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. Here, the cost for conventional primary + biological treatment (System 3)
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Data were collected on 34 primary and 19 low-dose chemically-enhanced primary treatment plants through the two above-mentioned national surveys. These data are used to compare low-dose chemically-enhanced primary treatment performance with conventional primary and conventional primary plus biological treatment.
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FIGURE D.5a Total phosphorus performance and cost relationship. TABLE D.9 Comparison of Low-Dose Chemically-Enhanced Primary Treatment with Conventional Primary Treatment Plus Activated Sludge Constituent Low-Dose Chemically- Conventional Enhanced Primary Primary + Biological TSS Effluent (mg/l)
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Conventional primary + biological treatment uses approximately 2.5 times as much total energy. Total cost of chemicallyenhanced primary treatment is approximately half that of conventional primary + biological treatment.
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Comparing the performance at these well-operated plants with the average performance treatment as shown in the Matrix of Performance and Cost Summary Tables, a 48 percent increase in TSS performance and an 77 percent increase in BODs performance over conventional primary treatment is observed. Toxic Organics and Metals The ten representative wastewater treatment systems provide different capabilities in terms of their ability to remove toxic organics and heavy metals.
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FIGURE D.6a TSS removal efficiency for average primary and chemically-enhanced primary treatment.
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FIGURE D.7a State-of-the-art chemically-enhanced primary TSS removal efficiency at San Diego (Point Loma) and Los Angeles (Hyperion)
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wastewater treatment plants is termed oil and grease. Data on oil and grease removal efficiency for Systems 1-3, based on the two above-mentioned POTW surveys is presented in Table D.ll.
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From page 336... ...
336 APPENDIX D TABLE D.10 Typical Effluent Concentrations of Organics and Metals for Selected Treatment Trains Treatment Train Effluent Concentration (micrograms/liter) Constituent Influent 1 2 3 4 Chloroform 7-60 7-60 5.6-48 1.0-9.0 1.0-9.0 Bromodichloromethane 0.3-1.7 0.3-1.7 0.3-1.7 0.1-.05 0.1-0.5 Dibromochloromethane 1.0-6.0 1.0-6.0 1.0-6.0 0.1 -0.7 0.1-0.7 Bromoform 0.3-1.2 0.2-1.0 0.2-1.0 0.1-0.4 0.1-0.4 Carbon Tetrachloride 1.0-8.0 1.0-8.0 1.0-8.0 0.2-2.0 0.2-2.0 1,2-Dichloroethane 5.0-15.0 5.0-15.0 3.9-11.7 0.8-2.4 0.8-2.4 1,1,1 -Trichloroethane 7.5- 12.5 7.5- 12.5 7.5- 12.5 3.0-5.0 3.0-5.0 Tetrachloroethylene 1.0-4.0 1.0-4.0 1.0-4.0 0.5-2.0 0.5-2.0 Trichlorothylene 1.0-2.0 1.0-2.0 1.0-2.0 0.5- 1.0 0.5- 1.0 Xylene 0.06-0.2 0.06-0.2 0.06-0.2 0.03-0.1 0.03-0.1 Chlorobenzene 1.0-25.0 0.8-20.0 0.7-18.0 0.1-2.5 0.1-2.5 1,2-Dichlorobenzene 1.0-8.0 0.8-6.4 0.7-5.6 0.1 -0.8 0.1-0.8 1,3-Dichlorobenzene 1.0-8.0 0.8-6.4 0.7-5.6 0.1-0.8 0.1-0.8 1,4-Dichlorobenzene 15.0-25.0 12.0-20.0 10.0- 17.5 1.5-2.5 1.5-2.5 1,2,4-Trichlorobenzene 1.0-5.0 0.8-4.0 0.7-3.5 0.1-05 0.1-0.5 Ethylbenzene 0.4- 15.0 0.3- 13.0 0.3-9.0 0.04- 1.5 0.04- 1.5 Naphthalene 1.0-20.0 0.2-17.4 0.2-15.4 0.03-0.6 0.03-0.6 1-Methylnaphthalene 0.33-30.0 0.29-26.1 0.25-23.1 0.01-0.9 0.01-0.9 2-Methylnaphthalene 033-30.0 0.29-26.1 0.25-23.1 0.01-0.9 0.01-0.9 Dimethylphthalate 33-106 21-67 5.0-16.0 5.0-16.0 3.2-10.4 Diisobutylphthalate 20-33 12-21 3.0-5.0 3.0-5.0 1.9-3.2 Bis-[2-ethylhexyl]
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Sludge Treatment Costs The cost of sludge treatment is calculated as the cost following sludge stabilization and dewatering.7 In this analysis, four alternative sludge management options were considered: 1) land disposal in a dedicated landfill or a refuse landfill, 2)
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This is assumed to be not very different from the disposal of sludge in a refuse landfill, where the cost of sludge disposal would be prorated. Liquid sludge disposal is not considered because of the high cost of truck haul for large treatment plants and the inability of most to pass the paint filter test required for such sludges to be permitted at a landfill.
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From page 341... ...
Total Annual Cost ($ million) Dewatered sludge of 20 percent solids 20 0.7 1.8 2.5 60 1.5 4.0 6.4 120 3.0 9.1 12.1 180 4.2 13.3 17.5 Dewatered sludge of 30 percent solids 30 0.7 1.8 2.5 90 1.5 4.0 6.4 180 3.0 9.1 12.1 270 4.2 13.3 17.5 TABLE D.14 Cost of Composting Dry Tons of Sludge Annual Cost of Annual Cost of Total Annual Cost Composted & Composting Transport ($ million)
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From page 342... ...
are limited to sludge quantities less than 30 dry tons per day, and the higher values are therefore extrapolated. If chemically-enhanced primary treatment is used in a wastewater treatment facility, the quantity of sludge is increased relative to primary treatment and the unit heating value of the sludge incinerated is decreased.
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From page 343... ...
Note that the quantity of sludge to be incinerated is greater for chemically-enhanced primary treatment plants than for conventional primary treatment. Direct Land Application In direct land application, treated sludge is hauled to a site in a liquid or dewatered state and injected into, or spread and incorporated into the soil.
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Sludge volatile solids serve as an energy source in incineration and in anaerobic digestion. DISINFECTION Sources of pathogens include discharges from sewage treatment plants, combined sewer overflows (CSOs)
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They can also be used for treating combined sewer overflow discharges. A variety of the present and future disinfection methods, the major advantages and disadvantages of each method, and selected costs are given below.
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has been used in the past for wastewater treatment disinfection where phenolic wastes are present. It is used as an alternative disinfectant of raw water supplies.
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From page 347... ...
Ozonation produces fewer toxic by-products than chlorination and, because it reduces the need to store large quantities of chlorine in urban areas, it is safer to operate than a chlorine system. Because ozone is the strongest oxidizing agent and disinfectant used in wastewater treatment, only small doses and short contact times are needed.
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From page 348... ...
The efficacy of different disinfection methods is a function of the concentration of the chemical agent or intensity and nature of the physical agent, the contact time, the temperature, and the number or types of pathogenic organisms present. It also depends on water quality factors (e.g., the amount of solids, dissolved organic material, inorganic compounds, and pH)
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From page 349... ...
. TABLE D.l9 Logic Reduction of Microorganisms in Chlorinated Activated Sludge Effluents (Source: Nieuwstad et al.
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From page 350... ...
During dry weather, an interceptor sewer accepts wastewater from the combined sewer and conveys it to a treatment plant. During rain events, the limited capacity of the interceptor sewer allows only a portion of the wastewater/stormwater mixture to be carried to a treatment plant.
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From page 351... ...
351 ~ lo'= ·E ~ ° ~ o o ~ ~ ~ ·= blat .= ~ ~ in .~ A ..
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On September 8, 1989, the U.S. EPA published its National Combined Sewer Overflow Strategy (Federal Register 1989~.
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From page 353... ...
during the EPA's National Urban Runoff Project indicated that no significant reductions in pollutant concentrations are realized, although they could occur in certain site-specific cases (EPA 1983~. The EPA concludes that street sweeping in most of the United States is appropriate for aesthetic purposes but has limited water-quality benefits.
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From page 354... ...
. Sewer flushing involves scouring and transport of deposited pollutants to the wastewater treatment plant during dry weather when there is sufficient interceptor capacity to convey these flows.
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From page 355... ...
of Wastewater Treatment, Department of Public Utilities, City Saginaw, Michigan, personal communication, 1988~. The Marigot project in Laval, Quebec includes 13 new regulators controlling combined sewer flow to a new tunnel more than three miles long with pumpage to a new POTW located on the southerly side of the island of Laval, adjacent to Montreal, Canada.
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From page 356... ...
Separation is still practiced to solve pollution problems within small portions of combined sewer areas connected to separated systems or to solve flooding problems within combined systems where there is inadequate flow capacity. Conventional Full and Partial Separation.
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From page 357... ...
Flow slipping involves the use of inlet control in urbanized areas to manage the stormwater entering existing combined sewer systems. It has its roots in Scandinavia and the United Kingdom where the concept has been used on undersized combined sewers to relieve basement flooding and to mitigate the volume and frequency of overflows.
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From page 358... ...
For an investment of roughly $2,000 to $4,000 per acre, the storage and vortex treatment concept consumes very little land space. During peak design flow conditions, this system can achieve solids removals at levels between those obtained in preliminary and primary treatment.
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From page 359... ...
Presently, the $90 million construction program is under way. Average cost per million gallons treated per day for the 5 facilities is estimated at $10,000, which is approximately one-half of one percent of the cost of conventional wastewater treatment.
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From page 360... ...
Storage allows the maximum use of existing dry weather treatment facilities and is often the best low-cost solution to CSO problems. Combined sewage flow is stored until the treatment facilities can treat the excess flows.
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From page 361... ...
New York City is currently designing several near-surface storage tanks with storage volumes on the order of 10 to 40 million gallons. One negative feature of large near-surface storage tanks is the large amount of land required.
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From page 362... ...
Annual overflow reductions on the order of 80 percent to 90 percent are possible, but maintenance is costly because of the need to remove heavy solids regularly from the storage facilities. Integrating CSO Control Techniques A $4 million full-scale demonstration project in Metro Toronto, begun in May 1991 is exploring alternative CSO control strategies including a vortex solids separator, detention tanks, chemical addition, and alternative disinfection schemes (i.e., conventional chlorination and dechlorination versus ultraviolet treatment)
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From page 363... ...
If the requirement is to obtain fewer overflows per year, then adding more retention storage is about the only option available. Summary of Comparative Performance of CSO Control Technologies The efficacy and cost of the various CSO control technologies is summarized in Tables D.23, D.24, and D.25.
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From page 364... ...
Major community disruption Excellent reliability Easy to maintain High skill level needed Large area requirements High capital costs
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From page 365... ...
B: TSS (suspended solids) F: Nitrogen C: Organics (PAHs)
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From page 366... ...
366 TABLE D.25 Comparative Capital Costs for CSO Control Options APPENDIX D CSO Control Options Capital Costs ($ per acre) Source Controls Catchbasin Cleaning Street Sweeping Sewer Flushing Flow Svstem Optimization Enhanced Flow Regulation and Static In-Line Control Dynamic In-Line Storage Real Time Control Svstem Flow Reduction Conventional Full Separation Conventional Partial Separation Flow Slipping High Rate Satellite Treatment Screening Vortex Solids Separators Vortex Separators and Storage Combination Off-Line Storage Upstream Stormwater Hybrid Near-Surface Contaminated Upstream Storage Near-Surface Contaminated Downstream Storage Decentralized Deep Storage Consolidated Deep Storage Not Applicable Not Applicable $100 - $500 $ 1 00 - $500 $500 - $1,000 $500 - $1,000 $50,000 - $100,000 $ 1 0,000 - $50,000 $5,000 - $10,000 $2,000- $5,000 $2,000 - $5,000 $5,000 - $10,000 $ 1 o,ooo - $so,ooo $s,ooo - $10,000 $s,ooo - $10,000 $10,000 - $so,ooo $10,000 - $s0,000 NONPOINT SOURCE MANAGEMENT OPTIONS Introduction According the joint EPA/National Oceanic and Atmospheric Administration document Proposed Development and Approved Guidance-State Coastal Nonpoint Pollution Control Programs, nonpoint source pollution has become the largest single factor preventing the attainment of water quality standards nationwide (EPA 1991b)
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From page 367... ...
The Problem of Characterizing and Controlling Nonpoint Sources Unlike sewage treatment plants and other point sources which discharge at relatively constant rates, nonpoint sources deliver pollutants in pulses linked to storm events. The quantity and type of pollutant contained in nonpoint sources depends on the human activity, the intensity and duration of precipitation, and the time between storms.
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From page 368... ...
This increases the difficulty of implementing control measures. The Composition of Urban Runoff Tables D.26 and D.27 show ranges of contaminant levels found in urban runoff for several contaminants of concern, plus lead and suspended solids, as reported in the technical literature.
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From page 369... ...
1977 pipes, tire wear, solids carried on tires and vehicle bodies, and lubrication fluid loss. Litter Litter deposits contain items such as cans, broken glass, bottles, pull tabs, papers, building materials, plastic, vegetation, dead animals and insects, and animal waste that eventually wash into storm sewers.
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From page 370... ...
370 Ct au 1 Ct o Ct o s~ U)
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From page 371... ...
371 oo ~oo oo ~oo _~ ~C~ _ _ ~_ U=,-~ ~ ~ ~ U U O O ~ ~-~ ~ ~ o ~ ~ ~ o t4 Ct ~ o =4 m~ ~ c~ ~ ~Q ~ ~m ~ ~ ~ 00 Zz z O _ ¢Z Z ~Z ¢ ~ ~ ~ O ~ CM _c~ z z z z ~ ~ Z o O ~t 1 1 t 00 ~ ~ 0 ~ _ ~- - O ~ - - C~ - Z Z C~ _ ~ ~G~ ¢ ¢ ~ ~ - oo ~ r- ~ ~ ~ Z ~ ~ Z ~ Z ~ ~ ¢ ~ 00 ~ 0 1 ~ z z z z ~ U~ z ~ ~ ~ z ~ 0 .
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From page 372... ...
Combined sewerlsanitary systems Without special control measures, overflows from combined systems occur on average between 40 to 80 times per year. CSOs harbor all the pollutants found in municipal wastewater, including pathogenic microorganisms, trash, and unpleasant odors, and may carry objectionable debris such as the medical waste found on east coast beaches in recent years.
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From page 373... ...
Having determined that land-use category appears to be of little utility in explaining overall site-to-site, storm-to-storm variability of urban runoff, NURP researchers concluded that for estimating pollutant concentrations at unmonitored sites, the best general characterization may be obtained by pooling data for all land uses (other than the open, nonurban ones)
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From page 374... ...
19771. Suspended Solids: Pollutant Transporters The NURP study found that urban runoff carries high quantities of sediment.
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From page 375... ...
Consequently, systems designed to remove only larger solids will be ineffective for removing most solids-borne pollutants. Management Options Introduction In comparison to wastewater treatment technology, urban runoff treatment technology is in its infancy.
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From page 376... ...
They address structural and nonstructural types of control, design hydrology and pollutant removal efficiencies for structural controls, cost for implementation, and next steps required in applications and research. Types of Controls and Control Philosophy There are two basic controls of pollution in urban runoff: source reduction and structural control.
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From page 377... ...
Control of chemical application rates in areas exposed to rainfall and runoff is another source reduction measure. This control applies to fertilizer, pesticide, and herbicide application in private and public properties for gardening and pest control.
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From page 378... ...
These devices include swales, filter strips, infiltration basins and trenches, detention facilities, and artificial wetlands. Treatment facilities used for municipal wastewater and industrial wastes are not generally considered viable for stormwater treatment because 1)
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From page 379... ...
Thus 80 percent or 90 percent capture of annual runoff would appear to be a good technology-based standard for urban runoff quality control. Figure D.9b shows how many times per year each basin is expected to fill and overflow.
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From page 380... ...
1991. Reprinted, by permission, from American Society of Civil Engineers, 1991 .)
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From page 381... ...
Minimum length of a filter strip should be 20 feet, and its slope should be such that erosion does not occur, except infrequently during large storms. Swales and filter strips are widely used for urban runoff treatment in Florida and metropolitan Seattle.
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From page 382... ...
Because these basins are designed for peak shaving of runoff from large storms, the small storms of interest for urban runoff quality control pass through them with little or no detention or pollutant removal. (Peak runoff rates for small storms are much less than the outlet capacity of these detention basins.)
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From page 383... ...
A wet pond is the best detention facility for use in locations where nutrients are of concern because they remove two to three times as much phosphorus as extended detention ponds and 1.3 to two times as much total nitrogen, if the plants are harvested. Artificial Wetlands for Stormwater Quality Enhancement.
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From page 384... ...
It is noteworthy that, in contrast to wastewater treatment processes, most of the practices are not operationally difficult. Costs for Stormwater Quality Controls Cost data for source controls are not available.
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From page 385... ...
385 a BMP/design /~'l/~0~ / / // Extended Detention Pond Design 1 ~Moderate Design 2 0 ~Moderate Design 3 ~High Wet Pond Design 4 ~Moderate Design 5 ~Moderate Design 6 0 ~High Infiltration Trench Design 7 ~Moderate Design 8 0 ~O ~High Design 9 0 ~O O O High Infiltration Basin Design 7 ~Moderate Design 8 0 ~O ~High Design 9 0 ~O O O High Porous Pavement Design 7 ~Moderate Design 8 ~O ~High Design 9 0 ~O O O High Water Quality Inlet Design 10 0 ~Loo Filter Strip Design 11 ~O O O ~Low Design 12 0 ~i. O ~Moderate Grassed Swale Design 13 Design 14 O O O O O ~Low O ~low continued structural controls other than that collected by the Metronolitan W~chi^~^ Council of Governments (MWCOG)
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From page 386... ...
O - 0% to 20% removal Hi- 20% to 40% removal Hi- 40% to 60~o removal in- 60~o to 80% removal · - 80% to 100% removal O- Insufficient knowledge TABLE D.30 Comparative Removal of Pollutants of Concern by Runoff Treatment Practices / / / / /~; / 7§ i" Treatment Practice / ~ / C Grassed Swale (mild slope) Filter Strip (20 feet)
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From page 387... ...
1984. Evaluation of Urban Nonpoint Source Pollution Management in Milwaukee County, Wisconsin.
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From page 388... ...
1992. Experience with Vortex Separators for Combined Sewer Overflow Control.
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From page 389... ...
Pp. 323-337 in Urban Runoff Quality Impact of Quality Enhancement Technology.
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From page 390... ...
Pp. 421-433 in Design of Urban Runoff Quality Controls, L
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From page 391... ...
Pp. 378-387 in Design of Urban Runoff Quality Controls, L
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From page 392... ...
1989. Design of Urban Runoff Quality Controls.
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From page 393... ...
Pp. 268-279 in Design of Urban Runoff Quality Controls, L.A.
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