Chi-Yuan Fan

Costs of Urban Stormwater Control

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.

Toxic Pollutants in Urban Wet-Weather Flows: An Overview of the Multi-Media Transport, Impacts, and Control Measures

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.

Sewer-Sediment Control: Overview of an EPA Wet-Weather Flow (WWF) Research Program

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.

Sewer and Tank Flushing for Corrosion and Pollution Control

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.

Collection System Modeling for Planning/Design of Sanitary Sewer Overflow (SSO) Control

The nations 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.

Industrial Use of Stormwater: A Hypothetical-Case Study

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.