Pollution and Management on Urban Rainfall Runoff

The urban rainfall runoff pollution originates from the precipitation,the urban surface and the drainage system.According to the sampling experiment on non-water leakage area,water leakage area and forest covering area in Wuhan,besides the air quality,rainfall runoff pollution is affected by the intensity and volume of rainfall,the time of rainfall,the interval of rainfall events,and the quality of collection area.The source of roof runoff pollution has variety,complexity and indefiniteness.Besides different kinds of pollution brought by the air subsidence,roof runoff pollution is affected by roof material,the using time of roof,material corrosion,pipeline corrosion and pollution residuum.In general,the first contaminant concentration of rainfall runoff is high and the contaminant concentration is decreasing,with the time of rainfall prolonging.In the combined sewer networks,the erosion of the in-sewer pollutant stocks can provide 20%~60% of total SS,COD,BOD5.Therefore,In order to maintain ecologic balance and protect water environment in cities,it is necessary to rebuild the drainage system and control runoff pollution.