Discharge Characteristics of Sewer Overflows from Small Urban Watersheds

Despites of efforts made for water quality conservation, water quality of the surface waters have not improved significantly due to diffuse pollution from urban and agricultural area. Especially sewer overflows impact on surface water as it show high contaminant concentrations. In this research, sewer overflows of six rainfall events at an urban watershed were monitored for their discharge rate and concentrations. For the chemical analysis, suspended solid, , , nitrogen, phosphorus, Total coliform, and E. coli were measured. Pollutographs of water quality constituent showed similar trend with hydrograph. Suspended solid concentration showed high correlation with flow rate. First flush effects were clearly shown in most cases. It can be seen that rainfall intensity affects on the magnitude of first flush. Relationship between discharge rate per unit area and loading were calculated for constituents to estimate annual loading and monthly loading based on precipitation data for last five years.