Drainage System Overflow Pollutant Reduction of Stormwater Detention Tanks in Central Shanghai

In order to control drainage system overflow pollutant during wet and dry seasons, five stormwater detention tanks (SDTs) were built along the Suzhou Creek in central Shanghai, China. The effect of SDTs on pollutant reduction was investigated based on the precipitation, storm runoff, pumping station discharge, SDT detention volume and drainage system overflow pollutant concentrations measured in 2012. The results show that: (1) The SDTs could reduce drainage system overflow pollutants effectively. The annual overflow water reduction rate was from 3.6% to 45.1%, respectively, and the annual overflow chemical oxygen demand (COD) reduction rate was from 7.2% to 62.9%, respectively. (2) In the local physiographic conditions of precipitation characteristic, drainage system area and land use type, volume design standard of SDT was the most important factor to the overflow water and pollutant reduction rates of drainage system. (3) In order to make full use of the overflow water and pollutant reduction effects of SDT, the proper volume design standard was suggested in physiographic conditions mentioned above in central Shanghai, China.