Characterization of storm-water pollutant sources in a combined sewer network

The flux and quality of wet weather flows from the entry to the exit of the typical combined sewer network in Kunming was measured,aiming to follow up the quality of the runoff in the sewer network and the contribution of different sources to the pollution in the runoff. Rain events were measured on roads,roofs and yards of the catchment,as well as in dry and wet weather flows at the catchment outlet. The results showed that artificial disturbance is the main factor which influences the concentration of the urban runoff. Among the main urban ground surface types,the order of runoff pollutant concentration is: roadyardroof. Roads are the key source of the pollution in urban runoff. In the study area,road runoff,which generates about 25% of the total runoff volume,represents more than 40%~80% of the total runoff pollution mass. Roof runoff,which generates about 50% of the total runoff volume,represents only 4%~30% of the total runoff pollution mass. The erosion of in-sewer sediment is an important source of pollution during wet weather flows through the combined sewers. For the four rains measured,more than 30% of the total TN,TP,SS,COD and BOD5 loads originated from the in-sewer sediments. Maximum rain intensity is an important factor which influences the erosion of the in-sewer sediment. For the high rain intensity,the contribution of the in-sewer sediment to the total pollution mass is more than 50%. For rainfalls of different character,the dominant source contributing to the wet weather flows differs.