Characterization of Urban Runoff from Combined Sewer and Storm Sewer Catchments in Beijing, China

In order to investigate the characterization of runoff from combined sewer and storm sewer, two monitoring systems have been installed separately in separated and combined catchments, which have been held since July 2010 in urban area in Beijing (China). The results revealed that COD, TSS, TN, TP, and NH₃-N concentration values exceed the Class V surface water quality standard developed by Ministry of Environmental Protection of the People's Republic of China (MEP). A strong correlation is observed between COD and TSS concentrations, meanwhile, stronger correlation is observed between TSS and any other pollutant according to cumulative load of pollutants. First flush was seldom observed in storm sewer runoff and CSO due to the influence of sewer sediments, sewer system characteristics, catchment characteristics, etc. An EMC approach was used to quantify the pollution of runoff and CSOs. The Event Mean Concentration (EMC) of various pollutants in storm sewer runoff between rainfall events is comparable to the typical values observed in similar areas, according to other studies reported in literatures. Based on quantitative analysis, urban nonpoint pollution resulting from surface runoff and CSO emissions is recognized as one of the major causes of quality deterioration in the receiving water bodies in Beijing. An integrated system, which combines runoff source control and sewer control, will be an effective and economic approach to urban runoff pollution control.