Abstract

The City of Piqua, Ohio, initiated a study to develop an alternative for meeting regulatory requirements regarding an active sanitary sewer overflow (SSO) in its wastewater collection system. Continuous hydraulic model simulations were used to study how to reduce the frequency of the city’s SSO. The U.S. Environmental Protection Agency’s Storm Water Management Model (SWMM) version 5 built upon the city’s existing model and validated the model based on reported annual SSO activity using continuous simulations. The city’s collection system includes 120 mi sanitary sewers. The city’s wastewater treatment plant (WWTP) accepts an average flow of 4 MGD. Five-year continuous simulations were used to assess performance of an alternative that included an equalization (EQ) basin to store excess wet weather flows (WWFs) to greatly reduce SSO. The modeling identified existing system hydraulic capacity limitations and helped to optimize the EQ basin alternative. Optimization included using the model to identify an EQ basin location that uses gravity-in/gravity-out operation, minimizing infrastructure modifications. The continuous simulation approach resulted in a phased alternative and corresponding conceptual design that will provide the city with flexibility in controlling SSO.

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