Study on the Sewage Control Amount of Main Into-lake Rivers around Taihu Lake

Water environmental problems of main into-lake rivers were analyzed in the present study according to the monitoring data from 2006 to 2008.Through the investigation on the distribution and sewage amount of the industry pollution source,agriculture pollution source and the urban sewage source in studied region,total amount of pollutant drainage into the rivers was calculated.According to the water quality target,the water environment capacity of main into-lake rivers and the studied region,as well as the sewage control amount were calculated.Results showed 15 rivers significantly exceeded the water quality standards,and pollution level of the rivers erratically changed in the recent 3 years and the serious pollution factor was NH4-N.Pollutants load into rivers were very large.Domestic pollution source not takeover had the largest pollution load contribution with the proportion between 50% and 60% and Zhang jia-gang got the largest proportion between 18%~20% compared with the other cities.There are many rivers in the studied region and the distribution of the water environment capacity is not homogenous.Wangyu river,Zhihu river,Wujin river and other 4 rivers have relatively large water environment capacity,and Zhang jia-gang has relatively large region water environment capacity.About 66554.38 t/a COD,8105.71 t/a NH4-N and 1324.42 t/a TP should be cut down recently and 96719.08t/a COD,11541.45t/a NH4-N and 1788.71t/a TP should be cut down in forward future to ensure the water quality reach the standard.