Analysis on Pollution Source

Abstract

In recent almost 20 years, the Tai Lake watershed area has developed its economy rapidly and the township enterprises have been flourishing, but the wastewater treatment and governance level has been far behind than the increase of pollution discharge; plenty of wastewater were discharged into rivers, lakes and sea directly without treatment to cause all of them get serious pollution. Currently the industrial and domestic wastewater and sewage of 5,000,000,000 m³ are directly discharged into rivers and lakes in the Tai Lake watershed every year. Among which, the percentage of the wastewater treated is only 20 % or less. According to the monitoring on the cross-section of main rivers and lakes in the Tai Lake watershed in 2000, including the main lakes, for instance, Tai Lake, Dianshan Lake; the main water supply courses in the watershed, for instance, Taipu River, Wangyu River; the main watercourses connecting the Tai Lake, for instance, the East and West Shao River, Nan River, Zhihu Port, Liangxi River, Xujiang River; and the provincial boundary watercourses, for instance, Hongqi Pond, Shanghai Pond, etc., the water quality at the monitoring cross-sections of 19.4 % can reach the surface water standard of Grade II or III (evaluation standard: GB3838—88); the water quality at the rest monitoring cross-sections of 80.6 % is found polluted seriously; among which the water quality at the monitoring cross-section of 48 % is Grade IV, 14 % Grade V, but 23 % is inferior to Grade V (such water has no any use value). The pollution type of the rivers in Tai Lake watershed is the organic pollution, and the nonconforming index of water quality is the permanganate index (COD_Mn), ammonia–nitrogen (NH₃-N), etc. Since plenty of nutritive salts (nitrogen, phosphor and other pollutants) go into lakes, the lakes are entrophicated seriously. Currently the Tai Lake, the maximum water supply source area in the watershed, is entrophicated seriously. In view of the monitoring data 2000, 71 % water area was entrophicated, and 29 % was in the middle of eutrophication.