Load and Control of Pollution from Combined Sewer Overflows in Cities

For the pollution from combined sewer overflows,the relationship between the overflow of pollutants from combined sewer and the rainwater flow at different interception ratios was studied.The results show that in the absence of intercepting,the overflows of COD,SS and BOD5 from combined sewer are directly proportional to the rainwater flow.In case of storm and heavy rain,the pollutant concentrations in rainwater runoff vary with rainwater flow.The total COD overflow of a combined sewer containing dry-weather flow of 0.5 m3/s is 33.66 t when the interception ratio(n0)is zero during 65 mm storm.When n0 is equal to 1,3 and 5,the total COD overflows are 93.14%,79.86% and 67.05% respectively.In China,wetland,low-lying land,pond,tunnel,cellar,pump station system,storage tank,landscape water body and so on can be used for detention of combined sewer overflows during storm to abate water pollution.