Novel design of volume of detention tanks assisted by a multi-source pollution overflow model towards pollution control in urban drainage basins.

The commonly employed design of detention tanks cannot effectively control overflow pollution because of non-stormwater entry and sewer sediments in the urban drainage system. Herein, a multi-source overflow model considering both overflow water quality and quantity has been developed for simulating real overflow events. Subcatchment and drainage information is extracted through geographic information system (ArcGIS) and a multi-source overflow model is developed in Stormwater Management Model (SWMM) by coupling runoff mode, non-stormwater mode, and sediment mode. This model is successfully calibrated and validated with the reasonable root-mean-square error (RMSE) of 8.2 and 5.8% for water quality and quantity, respectively. The simulated results suggest that the misconnected non-stormwater entry can affect overflow contaminant concentrations over the period of overflow due to its continuous pollution, while sewer sediments mainly exert effects on the peak pollution period of overflow. Based on model prediction, an approach called overflow peak pollution interception (OPPI) is proposed for model application and design optimization. The OPPI designed detention tank is suitable for high non-stormwater entries and long antecedent dry days (large amount of sediment). A case study is conducted in a high-density urban area of Shanghai, and compared with two commonly employed design methods in Germany and China, which have the similar design principle of volume, relying on amount of precipitation multiplying area of region, the combination of overflow model and OPPI approach enables to offer more accurate and effective design of detention tanks for pollution control in urban areas. Graphical abstract .