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Combined sewer systems (CSS) are under regulatory mandate to reduce or treat combined sewer overflow (CSO) discharges in order to protect receiving waters. Under the requirements of the Clean Water Act, municipalities are responsible for developing comprehensive long-term control plans (LTCPs). These plans must identify a selected alternative, a level of control and a schedule for reducing discharges. Historically, CSO control methods included various approaches to manage the excess flows, including storage, remote treatment and conveyance to a centralized treatment plant or sewer separation. Many of the plans developed subsequent to 2007 include an approach which relies on green infrastructure and similar stormwater source controls. Green infrastructure includes practices and sitedesign techniques that store, infiltrate, evaporate, or detain stormwater runoff and in so doing, control the timing and volume of stormwater discharges from impervious surfaces (e.g., streets, building roofs, and parking lots) to the sewer system. In order to determine the most effective use of green infrastructure, municipalities are evaluating a number of strategies and approaches to its application. Implementation must consider site-specific issues in each community and the opportunities for cost effective implementation. An evaluation of 12 municipal programs that incorporate green infrastructure into their LTCP was performed in 2011. This paper summarizes the various approaches that municipalities used for evaluating green infrastructure. Those approaches included GIS evaluations, modeling and cost / benefit assessments.

Advanced design concepts such as Low Impact Development (LID) and Green Solutions (or upland runoff control techniques) are currently being encouraged by the U.S.EPA (EPA) as a management practice to contain and control stormwater at the lot or upland residential parcel level. These controls have shown that when implemented and maintained properly, they can increase retention at the runoff source — decreasing the runoff volume entering the drainage system and the demand on a drainage system. Both developed storm and combined sewersheds can benefit from the added storage from areas retrofitted with bioretention cells or rain gardens and other management, e.g., catchbasin retrofits or curb-cuts with tree planting. This paper documents an effort by the U.S. EPA to demonstrate the efficacy of implementing integrated, green infrastructure-based solutions to wet- weather flow pollution problems in and urban core neighborhood within a combined sewer system. The project involves local and regional efforts to provide the basis for success of the implementation of green infrastructure and stormwater management at the neighborhood, watershed, and regional levels. Specifically, the project will demonstrate the strategy and methodology for where and how attainment of Green Solutions will be implemented, including model support, within Kansas City, Missouri.

The United States Environmental Protection Agency (USEPA) has identified a need to use proven methodologies to develop computer tools that help communities properly characterize rainfall-derived infiltration and inflow (RDII) into sanitary sewer systems and develop sanitary sewer overflow (SSO) control plans. To accomplish this goal, the USEPA entered into a cooperative research and development agreement (CRADA) in 2003 with a technology partner Camp Dresser & McKee (CDM) Inc. to develop a public-domain Sanitary Sewer Overflow Analysis and Planning (SSOAP) Toolbox. The CRADA also prepared a technical guide for analyzing RDII, performing capacity analyses of sanitary sewer systems, and developing SSO control plans using the toolbox. This paper describes the CRADA outcomes and individual tools in the SSOAP Toolbox to perform capacity analyses of sanitary sewer systems and develop SSO control plans.

This paper describes early results and directions arising from ongoing research into factors that affect the preferred balance between primary treatment and disinfection in a conventional wastewater treatment plant during periods of wet weather overflow. Despite the fact that national policy and regional regulations have required or implied use of these elements of treatment for decades, there remain some basic issues that are unresolved. In the context of a wet weather overflow event, the selection of an optimum point and manner for disinfection as it relates to the degree solids removal is one such issue. The factors that affect the choice of this point, particularly as reflected by the current state of microbiological understanding of quantification methods and of the influences of water chemistry on disinfectant behavior and indicator bacteria partitioning between solid and liquid phase components of the flow stream, are examined. Potential avenues for improved treatment practices are noted, and research directions are discussed.

Development in sensitive watersheds continues to pose environmental problems for receiving waters. One contributor to the long-term pollution of sensitive waterways is building and construction materials. However, the long-term effect of many building materials on the environment has not been quantified. Prior testing of these materials in the laboratory has indicated that the potential for release (primarily nutrients, lighter hydrocarbons, pesticides, and metals) is significant. Additional testing for metals’ release from aged roofing panels also has shown that the potential for pollutant release still exists after 60 years of exposure to the environment. The data that is missing from a complete evaluation of specific building materials is behavior over the lifespan of the material, including the critical period of initial exposure. This paper provides an overview of the limited literature available on the subject, results from laboratory testing of common building materials and aged roofing panels, and an overview of the next phase of needed research.

While many types of inlet devices may capture some stormwater debris, care must be taken in their design. Catchbasins with sumps may remove up to about 30% of suspended loads that enter the intet, but much of this material is relatively coarse and in many cases would not have moved to the outfall. The sumps do minimize sediment accumulation in the sewerage and reduce maintenance. These should probably be considered as grit traps, more than pollutant trapping devices. Some devices can also trap floatables. H owever, if not frequently maintained, clogging and ponding may occur. In addition, if water is forced through the trapped debris (especially leaves), degradation of the organic material may occur, actually causing the production of some pollutants. Some new inlet devices have been recently designed and are undergoing testing that promise more effective control of stormwater pollutants, along with better retention of bed load material and floatables. Bellevue Catchbasin Monitoring Study Catchbasins, simple inlets, man -holes, and sewerage sediment accumulations were monitored at more than 200 locations in Bellevue, Washington, in two mixed residential and commercial study areas as part of the Bellevue research conducted for the Nationwide Urban Runoff Progra m (Pitt 1985). These locations were studied over three years to monitor accumulation of sediment and sediment quality. The sediment in the catchbasins and the sewerage was found to be the largest particles that were washed from the streets. The sewerage an d catchbasin sediments had a much smaller median particle size than the street dirt and were therefore more potentially polluting than the particulates that can be removed by street cleaning. Cleaning catchbasins twice a year was found to allow the catchbasins to capture particulates most effectively. This cleaning schedule was found to reduce the total residue and lead urban runoff yields by between 10 and 25 percent, and COD, total Kjeldahl nitrogen, total phosphorus, and zinc by between 5 and 10 percent. The first simple step is the preparation of grouped box and whisker plots to see how the observations in each of these 8 data groupings compare

Wet-weather flow (WWF), including combined-sewer overflow (CSO), sanitary-sewer overflow, and stormwater (SW), is a significant contributor of microbial contamination to surface water and ground water. By using effective wastewater or SW disinfection, introduction of pathogen contamination into receiving waters can be greatly minimized. CSO flowrates and volumes are significantly greater than those of dry-weather flow. The characteristics of CSO (e.g., flowrates, high suspended solids and pollutant content, variable temperature, and microorganisms) make it difficult to disinfect. Disinfection techniques need to be high-rate with strong microbe-killing capabilities. They must be adaptable (effective under varying conditions) and be able to achieve at least a three log (99.9%) reduction of target microorganisms. The most commonly used disinfecting agent is chlorine (Cl 2 ). Because of the high flowrates and volumes of CSO, its effective disinfection requires high Cl 2 dosing that results in a high level of toxic byproducts. Due to its effect on aquatic ecosystems, alternative disinfection processes are being investigated. The introduction of new disinfecting agents for lower-quality wastewater such as CSO has proven to be very difficult. Disinfection processes for such applications should be adaptable to use under dry and WWF conditions. Alternative disinfection technologies for CSO discussed in this paper are: ultraviolet irradiation, chlorine dioxide, and ozonation.

Many municipalities throughout the United States have sewerage systems (separate and combined) that may experience exfiltration of untreated wastewater. This study was conducted to focus on the magnitude of the exfiltration problem from sewer pipes on a national basis. The method for estimating exfiltration amounts utilized groundwater table information to identify areas of the country where the hydraulic gradients of the wastewater are typically positive, i.e., the wastewater flow surface (within pipelines) is above the groundwater table. An examination of groundwater table elevations on a national basis reveals that the contiguous United States comprises groundwater regions (established by the U.S. Geological Survey) which are markedly different. Much of the northeastern, southeastern, and midwestern United States has relatively high groundwater tables that are higher than the wastewater flow surface, resulting in inflow or infiltration. Conversely, a combination of relatively low groundwater table and shallow sewer creates the potential for widespread exfiltration in communities located in the western United States.

This paper presents an overview of the transport of toxic pollutants through multiple media and drainage systems in the urban watershed during wet-weather periods. It includes the origin of the toxic substances; their transport via atmospheric deposition, overland washoff, and urban sewer systems; and, their impacts on both surface and ground waters. During dry-weather periods, incompletely combusted hydrocarbons from automobiles combine with atmospheric particulates from a host of other sources and deposit on urban streets and other urban surfaces. During a storm event, these solids, in addition to solids from industrial and commercial parking lots, material storage areas, and vehicular service stations are washed off by surface runoff and drained into either separate storm sewer or combined sewer systems. Field studies have identified that a major portion of hazardous waste priority pollutants including benzene, polynuclear aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), pesticides, and heavy metals (e.g., arsenic, cadmium, chromium, copper, lead, mercury, and zinc) contained in urban stormwater runoff are in particulate form or sorbed onto particles. These stormwater particulate pollutants contribute significant toxicity to receiving waters. Mortality, epidermal lesions, or fin erosion can occur in fish and other aquatic life forms that are exposed to these toxic suspended solids and sediments. Methods for intercepting the cross-media transport of toxic constituents in the urban environment include best management practices to control surface runoff pollution; steeper sewer slopeage and improved pipe bottom shapes to maintain high velocity solids-carrying capacity during low-flow periods; and upstream sewer flushing and sediment trapping to reduce clogging and sediment in sewers.

The objective of this study was to evaluate the feasibility of using low-cost, natural filter materials for stormwater (SW) treatment. Generic mulch, pine bark mulch, and processed jute were evaluated for metal and organic pollutant removal from actual SW samples collected from a "hot-spot" site (commercial parking lot) in New Jersey. The retention and release behavior of pollutants in different filter materials was evaluated using a specially constructed bench-scale filtration apparatus which allowed for the simultaneous testing of up to 10 different media conditions. SW flowrates (fluxes) through the individual columns and the sorption capacity of each filter medium were studied under a variety of conditions. The benefits of combining mulch or jute with sand (in ratios of 0.25, 0.50, and 0.75) to improve the hydraulic properties (filter flux), removal ability, and cumulative capacity of the filter for a specific pollutant were evaluated. Initial tests were performed to evaluate the basic performance of the mulch and jute materials ("as received"). This performance was compared with the performance of the materials whose particle size was altered. This alteration of the particle size within the filter material was done by separating the mulch materials into "coarse" and "fine" fractions and cutting the jute fiber into significantly smaller pieces. The effectiveness of the filtration process was found to be dependent upon the physical characteristics of the filter media. Both the sand content and particle size of the filter media affected flowrates of SW and their pollutant removal capacities. Copper (Cu) and benzo(a) pyrene [B(a)P] were used a surrogates for heavy metals and organics, respectively. Removals as high as 100% of Cu were observed for all of the combinations of sand with mulch or jute. The removal of B(a)P was found to be dependent upon the media-to-sand ratios, and ranged from 68 to 94%. No significant amount of either pollutant was released from any of the

This paper illustrates how a state-of-the-art systemwide collection system modeling approach employed by the County of Henrico, Virginia enhanced the planning and design of its sanitary sewer overflow control facilities. The paper discusses the following planning components: (1) development of dry-weather wastewater flow projections using a geographical information system equivalent data of existing and projected land uses, existing and projected population density and distribution, existing base wastewater flows from water consumption records, and flow monitoring data from their supervisory control and data acquisition system; (2) prediction of wet-weather rainfall dependent infiltration/inflow using a predictive model with model parameters calibrated and verified with recorded wet-weather flow data; (3) analysis of the capacity of the existing sewer system under present and future conditions using the SWMM EXTRAN model; (4) analysis of the wastewater treatment facility to assess hydraulic and process capacity of unit processes and determine expansion requirements for treating increased flows; and (5) development of a capital improvement program for phased implementation of additional facilities (sewers, storage tanks, pump stations, force mains, and wastewater treatment plant expansion or process retrofitting) to meet the available projected capital investment budget and provide flexibility in the future for constructing improvements when they are needed. This paper also presents the steps that the County has taken to actually implement the capital improvement plan.

The nation's sanitary sewer infrastructure is aging with some sewers dating back over 100 years. There are more than 19,500 municipal sanitary sewer collection systems nationwide serving an estimated 149 million people and comprising about 500,000 sewer miles. Potential health and environmental risks associated with poor performance of many of these systems highlight the need to increase federal regulatory oversight of the management, operation, and maintenance of these systems. As a result, EPA is in the final stage of preparing and issuing a SSO Rule that will add control of SSO to the NPDES permit requirements. This paper provides a preview of the Rule and describes the advantages of employing a collection system modeling approach for capacity assurance of various components of a collection system and development of SSO mitigation plan. A case study at Henrico County, VA is provided to illustrate the application of a collection system modeling approach to plan for sanitary sewer system improvements.

This paper presents an historical overview of the sewer-sediment control projects conducted by the WWF Research Program of the U. S. Environmental Protection Agency (EPA). Research includes studies of the causes of sewer solids deposition and development/evaluation of control methods that can prevent sewer-sediment accumulation. Discussions focus on the relationship of wastewater characteristics to flow carrying velocity, abatement of solids deposition and solids resuspension in sewers, and sewerline-flushing systems for removal of sewer sediment.

As population and industry grow, water demand increases, and water supply becomes more of a problem. While reclamation of municipal wastewater for industry, subpotable domestic usage, and groundwater recharge has been practiced in the United States over the past several decades on a limited basis, similar studies need to be taken for urban storm runoff. Rainfall runoff becomes contaminated as it passes over urban land; billions of gallons of water can be recovered for beneficial uses if urban stormwater is properly controlled and treated. The water quality of the treated storm runoff can meet the required standards for subpotable usage. Accordingly, this will enable stormwater reclamation to become a more significant means of augmenting water supply. This paper discusses current urban stormwater control and treatment technologies leading to the feasibility of reclaiming urban stormwater for various purposes. A hypothetical-case study illustrating the cost-effectiveness of reclaiming urban stormwater for complete industrial supply is presented.

This paper presents information on the cost of stormwater pollution control facilities in urban areas, including collection, control, and treatment systems. Information on prior cost studies of control technologies and cost estimating models used in these studies was collected, reviewed, and evaluated. The collection phase involved identifying, screening, and consolidating publications associated with capital costs of stormwater conveyance systems and control technologies. The resulting data were evaluated to develop a critical review of costs for urban stormwater control technologies, including identification of cost information gaps and research needs.

The paper presents results of two case studies of Real-Time Control (RTC) alternatives evaluations that were conducted on portions of sewerage systems near Paris, France and in Quebec City, Canada, respectively. The studies were performed at real-scale demonstration sites. RTC alternatives use dynamic mathematical modeling and simulations to develop a program for a specific sewerage system to guide operation of automatic regulators when wet-weather flow is approaching. Advanced RTC alternatives also use a radar-based rainfall measurement and forecasting tool. Thus, the function of RTC-based combined sewer management is to assure efficient operation of the system and to maximize storage capacity of the existing sewerage facilities to contain combined sewer overflow (CSO) and there is cost saving aspect of this function. The first case study was conducted on a site, located northeast of Paris, France, that was a portion of the Seine-Saint-Denis combined sewer network with independent capture from other parts of the network. This site, controlled by six regulators, includes a primary settling and storage facility of 200,000 m 3 capacity, which can be operated either to increase settling efficiency of the retention pond or to increase the sewer relief capacity to decrease flood risk. This case study compared two RTC alternatives: the presently used Supervisory Predictive Control, aided by a radar-based CALAMAR system, and, a simulated, Local Reactive Control, without CALAMAR. The Supervisory Predictive Control was shown to be superior.

This paper presents an overview of the Environmental Protection Agency's (EPA's) wet-weather flow (WWF) research program, which was expanded in October 1995 with the establishment of the Urban Watershed Management Branch at Edison, New Jersey. Research priorities for 1999 are presented as well as efforts to collaborate with other government organizations and professional societies. The branch is in the Water Supply and Water Resources Division (WSWRD) of EPA-ORD's National Risk Management Research Laboratory. In November 1996, it issued the Risk Management Research Plan for Wet Weather Flows (EPA/600/R-96/140), a peer-reviewed plan which emphasizes the risk management aspects of urban WWF problems and anticipated research directions for the next five years. EPA divided the research plan into five major areas, each discussing a specific WWF problem and the anticipated research approach to solve the problem. The five research areas are: characterization and problem assessment, watershed management, toxic substances characterization and control, control technologies, and infrastructure improvement. Within each area, the state-of-the-art knowledge is presented and the unknowns cited; research questions to address the unknown are also posed. An update of the 1996 research plan will be issued in 1999. In the time since November 1996, other organizations, notably the Water Environment Research Foundation (WERF), have reviewed WWF research programs and developed associated research needs reports. EPA endorses these efforts and views collaboration as essential in times of limited resources.

This paper presents an overview of causes of sewer deterioration concurrently with a discussion of control methods that can prevent or arrest this deterioration. In particular, discussed are inline- and combined sewer overflow- (CSO) storage-tank-flushing systems for removal of sediments and minimizing hydrogen sulfide production and associated corrosion. During low-flow dry-weather periods, sanitary wastewater organics and solids deposited in combined sewer (CS) systems can generate hydrogen sulfide and methane gases due to anaerobic conditions. Sulfates are reduced to hydrogen sulfide gas which can then be oxidized to sulfuric acid on pipes and structure walls by further biochemical transformation. Furthermore, these solids deposits or sediments are discharged to the urban streams during storm events which can cause degradation of receiving-water quality. Thus, dry-weather sewer sedimentation not only creates hazardous conditions and sewer degradation but contributes significant pollutant loads to the urban receiving waters during wet-weather high-flow periods. Performance of two technologies, i.e., the tipping flusher and the flushing gate was evaluated by a detailed examination of 18 facilities in Germany, Canada, and United States. As a result, both the tipping flusher and flushing gate technology appear to be the most costeffective means for flushing solids and debris from CSO-storage tanks, while the flushing gate is considered to be the most efficient method for flushing large diameter, flat sewers. In addition, cost-effectiveness analysis was conducted for an actual project under construction, comparing flushing gate technology versus conventional large pipe cleaning operations using bucketing methods.

This paper presents an overview of high-rate disinfection technologies for combined sewer overflow (CSO). The presented high-rate disinfection technologies depend on: ultraviolet light irradiation (UV), ozone (O 3 ), chlorination/dechlorination (Cl 2 ), chlorine dioxide (ClO 2 ), peracetic acid (PAA or CH 3 COOOH), and high-voltage electron beam irradiation (E-Beam), respectively. Discussions of the technologies include: commercial availability and extent of use, state-of-development when not commercial, and where available, performance data and cost of either full-scale or pilot-scale installation. Also discussed is utility of increased mixing in concert with any disinfection technology. Disinfection of CSO is generally practiced to control the discharge of pathogens into receiving waters. Therefore, the disinfectant used at a facility for treatment of CSO should be adaptable to intermittent (dry and wet weather flow) use. Other considerations include effectiveness, oxidation rate, safety, and cost. Commonly used disinfection by chlorination forms toxic residual byproducts. Newer disinfectants such as UV, ClO 2 , O 3 , CH 3 COOOH, and E-Beam have a far lesser potential to generate toxic byproducts. Since CSO flowrates and volumes are significantly greater than dry weather flows, use of high-rate processes requiring less tankage and space is more cost-effective than use of conventional processes. High-rate disinfection can be accomplished by: (1) applying mixing energy, (2) increasing disinfectant concentration, (3) using faster acting oxidants, (4) using high-energy irradiation, or (5) using combinations of these. Use of increased mixing with any disinfection technology provides better dispersion of the disinfectant and forces disinfectant contact with a greater number of microorganisms per unit time. The increased rate of collisions decreases the required contact time, which enables a high-rate disinfection.