Sewage discharge from land-based sewage outlets to sea in Shanghai City and effects on adjacent marine areas

The sewage discharge from 29 land-based sewage outlets to the sea monitored in Shanghai City during the period from 2005 to 2010 was investigated and analyzed. Meanwhile,the environment of the marine area adjacent to the sewage outlet of the Shidongkou Sewage Treatment Plant was assessed. The results show that,over the six years,municipal sewage outlets accounted for 45% of the total outlets monitored,while the sewage quantity discharged by municipal sewage outlets accounted for 80% of the total sewage quantity. Thus,municipal sewage outlets were the largest source of pollution to the sea in Shanghai City. COD,suspended sediment,and NH3-N were the top three pollutants discharged into the sea,accounting for 98. 80% of the total pollutants. The five main standard-exceeding pollutants included COD,NH3-N,total organic carbon,phosphate,and suspended sediment. Within a monitoring range of 19. 33 km2in the marine area adjacent to the sewage outlet of the Shidongkou Sewage Treatment Plant,the nutrient content exceeded the grade IV standard of the Sea Water Quality Standard of China, while the quality of the sediment met the Marine Sediment Quality Standard of China. The state of macro-benthonic organisms was generally steady. This verifies that land-based pollutant discharge has a certain impact on the water quality of adjacent marine areas.