Author(s): Joonghyun Yur; Kim Geonha; Jeongkon Kim
Linked Author(s):
Keywords: Non-point source; CSOs; First flush; Urban rivers
Abstract: Enormous amounts of efforts have been made for the abatement of pollutant sources to meet the strengthened water quality standards for urban rivers last decades. But the efforts for non-point sources have not been enough to significantly improve water-quality. The combined sewer overflows (CSOs) in urban areas are well-known for a heavy pollution load discharged directly into the receiving water such as rivers during wet weather periods. However, monitoring data for CSOs are not available enough to make a viable decision. In this research, the CSOs from urban watershed located in Taejeon city, Korea, were monitored for their discharge rate and pollutant concentrations. Recently, Taejeon city started the restoration project of major urban rivers to improve water quality, eco-system, and other amenity functions. From the five rainfall events observed in the study area, the minimum total rainfall for CSOs to take place was found to be about 10mm. The event mean concentrations (EMCs) ranged from 45~812mg/L for SS, 199~671mg/L for TCODcr, 60~198mg/L for BOD, 13. 8~20. 3mg/L for TN and 7. 1~19. 4mg/L for TP, which were much higher than the background levels. The relative strengths of first flush from the first flush phenomenon analysis employing the M (V) curve were in the order of SS > TCODcr > TP > BOD > TN. The first flush coefficients were found to have very close relationship with rainfall intensity, with the person coefficients ranging from 0. 759 to 0. 851, and suspended solid showed the closest relationships with discharge and other pollutants. The optimum storage volumes estimated using the point of inflection in the cumulative runoff mass and volume curves ranged from 15~30% of total discharged volume, corresponding cumulative volumes of 1600~3900m3.
Year: 2005