Numerical Study on the Impact of the Sewage Drainage on Water Quality of Shanghai Water Sources

Abstract

A 2D current and water quality model was set up with Delft3D-FLOW in this research, which was well calibrated and verified with the observed tidal levels and velocities. Considered with the project of the Qingcaosha Water Source, Pollution concentration distribution caused by sewage outfalls in the south bank of the Yangtze River during a neap tide of dry season is simulated and the computed results show: a high pollution zone appears near the south shore, and moves upward with flood flow and downward with ebb flow, however, it is bounded a limit region around the outfalls. During the tidal period, the water quality of the Qingcaosha water source can be classified as the second class water, which can ensure the normal water supply as the Shanghai water source. It is suggested that the regular monitoring water quality in this high pollution zone should be put into practice to ensure the water quality of water sourecs. The Yangtze River is adjacent to the East Sea and it’s the largest river in China, with obvious seasonal variant runoff and tidal flow. The Yangtze River was bifurcated by Chongming Island to south and north branch from Xuliujing, most of the flow go down through the south branch. The south branch was divided into south and north channel by Changxing Island and Hengsha Island. The south channel was bifurcated by Jiuduansha Shoal to south and north passage, three bifurcation areas and four estuarine outlets were formed (see Fig 1.)