State Water Resources Research Institute Program

Project ID: 2008DC92B
Title: Modeling of Integrated Urban Wastewater System in the District of Columbia (Pase II)
Project Type: Research
Start Date: 3/01/2008
End Date: 2/28/2009
Congressional District: District of Columbia
Focus Categories: Surface Water, Models, Toxic Substances
Keywords: Modeling, water quality, urban wastewater management
Principal Investigators: Deksissa, Tolessa (None); Behera, Pradeep K.
Federal Funds: $ 25,682
Non-Federal Matching Funds: $ 61,528
Abstract: The ultimate objective of this study is to develop a conceptual mathematical model that can assist water quality regulators as a tool for urban wastewater management. Scheme of the proposed integrated model for urban wastewater system includes three components: sewer, wastewater treatment plant and the river. Despite their interaction in various ways, these three components are considered separately in the traditional urban wastewater modeling, and therefore their mutual interaction among the three components is missing. Urban wastewater system must be considered as one system, and all component need to be included in one model that simulate the three components simultaneously, which allows evaluation and optimization of system performance in terms of environmentally and economically sound planning and management.

This study is the continuation of the ongoing project towards developing an integrated mathematical model that comprises sewer, wastewater treatment plant and the receiving water or river. Attempt was made to develop a conceptual mathematical model for wastewater treatment plant and river on the basis of Activated Sludge Model No. 1 (ASM1) and River Water Quality Model No. 1 (RWQM1). These two models are not only complex, but also there are differences in state variables, biochemical processes and parameters used in the different sub-models. To link these two models, a model interface or connectors have been developed. The sewer model however is more complex and requires further investigation to select an appropriate model that is suitable for the District of Columbia where a problem of Combined Sewer Overflows (CSO) is impacting the surface water quality of the District.

Approximately, one third of the District of Columbia is served by combined sewer system, which was designed to convey sewage from homes, businesses and runoff from streets, parking lots, and rooftops to the wastewater treatment plant during dry weather flow. The capacity of the combined sewer system is limited and when it is exceeded during storms, the excess flow, which is a mixture of raw sewage and storm water runoff, is discharged to the receiving waters: Anacostia and Potomac Rivers, Rock Creek and tributary waters. Thus, Combined Sewer Overflows (CSOs) allows discharging of a mixture of untreated sewage and storm water runoff to the receiving waters during high flow periods due to storms. Discharging such untreated wastewater may cause acute toxicity to the aquatic life, and if not controlled, it results in continuous deterioration of water quality of the receiving waters.

The proposed integrated model helps to identify the core elements of the problem by conducting different scenario analysis. It also provides better understanding of how to control and monitor this entire urban wastewater system to overcome the water quality problem in the District of Columbia and other states where the receiving water quality is being adversely affected by Combined Sewer Overflows (CSOs). The proposed study is therefore helpful for a researcher, planner and regulator to detect weak points in the system and to evaluate the efficiency of alternative actions such as construction of storm tank, sewer tunnel and low impact development projects.

In this study, appropriate sub model selection, and implementation of the sewer model including rainfall runoff will be carried out. Also, selected water quantity and quality parameters will be collected in the Rock Creek and the Potomac and Anacostia Rivers.

Progress/Completion Report, PDF

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