Numerical simulation on pollutant tracking released from the sewerage outfalls in Shanghai

The authors undertook 2D numerical simulations of the pollutant drogues tracking released form the existing and proposed sewerage outfalls in Shanghai by using Delft 3D model.The results showed the drogues released from 4 outfalls would not move to the shore though they would drift downstream near the shoreline and the drift materials would not pollute the shore.The drogues eventually left the model boundary towards the Hongzhou Bay.The drogues released from 3 outfalls moved out of the computational domain in 2 or 3 days in wet season,while the drogue released from the 4shidongkou outfall in wet season and from all 4 outfalls in dry season took 5-10days or more to leave the computational domain.It was suggested that in the sewerage building planning of Shanghai the selfpurification capacity of the Hangzhou Bay and the Yangtze Estuary should be considered.The sewage should be treated properly before discharging.The treatment degree should be regulated according to the outfall positions and seasons in order to protect the water environment in Yangtze Estuary and Hangzhou Bay.