Study On The Water Quality Analysis And Comprehensive Improvement Project In Lianhuadang, Yixing

Lianhuadang, located in the Dingshu Town of Yixing City in Jiangsu Province, flows into Taihu Lake via the Wuxi river. The water quality of Lianhuadang has deteriorated sharply in recent years and it fails to meet the requirement of the Function Area-dividing Project in the Surface Water (Environment) of Jiangsu Province. Therefore, there is an urgent need to identify the major pollution problems and establish a comprehensive strategy to improve the water quality of Lianhuadang, which is also essential for the pollution load reduction of Taihu Lake.In this study, a continuous monitoring of Lianhuadang water quality from December 2014 to December 2015 was carried out. The results showed the excessive pollution factors contained COD, NH4+-N, TN and TP, and the TN pollution was most serious which is valued as inferior Level V. Comprehensive water quality index assessment results showed the comprehensive water quality identification index of the normal seasons was 5.16, which showed the water quality of normal seasons was the worst. Based on the evaluation results of the water quality index method, the primary pollution factor was TN in the normal seasons and the dry seasons, while it was TP in the wet seasons.The export coefficient model was used to estimate the input load of COD, TN and TP of various pollution source into Lianhuadang. The results showed that input amount of COD, TN and TP were 167.34t/a,34.96t/a and 2.42t/a, respectively. The equivalent pollution load method was used to estimated the the effect of different pollution source to Lianhuadang. The results showed that the rural sewage was the main polluted source with the apportionment 74.16%, and followed by the large-scale livestock farms (22.09%), amospheric nitrogen deposition (2.2%) and farming source (1.55%). While the main pollutant was TN, followed by TP and COD.Based on the water quality monitor and pollution analysis results, a comprehensive strategy to improve the water quality of Lianhuadang was established, including:(1) the collection and treatment of rural sewage; (2) the relocate of livestock and poultry; (3) the ecological treatment of irrigation return flow; (4) Ecological dredging and (5) Ecological restoration of degraded lakeside.Through the above project, the reductions of TN and TP in Lianhuadang can be reduced to 961.61t/a and 26.03t/a respectively, and the water quality will be improved and finaly meet the standard of Level â…¢ of the Environmental Quality Standards for Surface Water (GB3838-2002).