| Environmental capacity is the limiting factor of regional social economic development. In the requirements of sustainable development and coordinated development, the impact of regional social economic development on the environment must be limited within the scope of environmental capacity or environmental carrying capacity, otherwise it will lead to environmental degradation or degradation of ecological environment quality. Accordingly, the water environmental capacity of the regional socio-economic development plan, especially water environmental protection is an important basis for planning and development work.Based on the improvement of water quality standards, this paper makes a comprehensive investigation and analysis on the current situation of water environment quality and pollution sources in Yizheng.The appropriate water quality model is selected and established to calculate the water environmental capacity of the main rivers in Yizheng, and the water environment total control and water pollution reduction measures are studied and analyzed.Considering the change of the water quality objectives, the new calculation of the water environmental capacity of Yizheng city is of positive significance to the total quantity control and environmental management.According to the hydrological characteristics of the river, the water quality model is selected to meet the applicable conditions of different rivers, and the reference of Yizheng section of the Yangtze River has been selected as one or two-dimension mathematical model of non-steady state water quality solutions.Depending on inland rivers exhibit different hydrological characteristics and differences outfall, each river derivation and solution of one-dimensional steady-state model.The Yizheng section of the Yangtze River is raised to the Ⅲ standard to Ⅱ standard,and the environmental capacity of the two sewage outlets is calculated;In addition to the main river water quality objectives in accordance with the current situation of environmental capacity is calculated, but also in accordance with the increase to Ⅲ water standards. In addition, the Shikang sewage treatment plant is considered to move up,the environmental capacity after Yangtze River two sewage outfall into a sewage outfall is calculated.The results shows,the water standards of Yangtze River improved from Ⅲ to Ⅱ, Yizheng section of the Yangtze River has two sewage outfall, pollution belt length is 1000m,800m and 500m.The environmental capacity of COD was 11344 t/a,10134 t/a and 7900 t/a, respectively, the environmental capacity of ammonia nitrogen was377.7 t/a,337.4t/a and263.1 t/a. After the Shikang sewage treatment plant is moved up, after two outfall into one outlet,the pollution belt is 2000m,1000m and 800m,The environmental capacity of COD was8504t/a,5970 t/a and 5334 t/a, respectively, the environmental capacity of ammonia nitrogen was 282.7t/a,198.8t/a and 177.6t/a.In this paper, the existing main pollution discharge port of Yizheng City is generalized.In this paper, the water environmental capacity of 10%,25%,50%,75% and 90% five different flow rates are calculated,The total environmental capacity of COD in Yizheng city is 124975.9t/a.69358.34t/a,23320.44t/a,6849.03t/a,3309.38t/a,respectively, the total environmental capacity of ammonia nitrogen is 8882.79t/a,4934.61 t/a,1665.77t/a,495.18t/a, 242.16t/a.After the improvement of water quality objectives into III water standards,and under 90% flow rate guarantee,the COD total environmental capacity respectively of YiYang River, Xupu River, long river, Yanshan River and YiCheng River is 2652.96t/a,341.53t/a,165.68t/a, 50.63t/a,98.58t/a;the Ammonia nitrogen total environmental capacity respectively of YiYang River, Xupu River, long river, Yanshan River and YiCheng River is 188.30t/a,32.57t/a,13.61 t/a, 6.52t/a,1.16t/a.In 2014, The COD remaining environmental capacity of YiYang River, Xupu River, long river, Yanshan River and YiCheng River is respectively 389.47t/a,-533.03t/a,-81.33t/a,-120.55t/a,89.26t/a; The ammonia nitrogen remaining environmental capacity is respectively-85.15t/a,-12.97t/a,2.63t/a,3.39t/a,-0.27t/a;In 2020, The COD remaining environmental capacity of YiYang River, Xupu River, long river, Yanshan River and YiCheng River is respectively 980.45t/a、-307.66t/a、-11.86t/a、-161.48t/a、90.96t/a; The ammonia nitrogen remaining environmental capacity is respectively-51.72t/a、-31.74t/a、-0.22t/a、3.09t/a、-0.75t/a.According to the results of the environmental capacity calculation, most of the remaining environmental capacity has been negative, indicating that the water quality of the river has been polluted, and more than the water quality standard of water environment function zoning.In order to make the water quality up to standard of the water environment function area of the negative environmental capacity, we need to cut down the discharge of pollutants.For comparison with Related literature,Considering the change of pollution sources and the change of water quality objectives,water pollution control units are divided and pollution sources are investigated and analysed. On this basis, the calculation of the water environment capacity is smaller, the COD environmental capacity has been reduced by 9421.92t/a,the environmental capacity of ammonia nitrogen was reduced by 267.48t/a,and the environmental capacity of the Yangtze River after the merger has been calculated of 75% before the merger,on environmental protection and pollution control have more stringent requirements.In this paper,using the results of calculation of water environmental capacity,we analyze the development of COD and ammonia nitrogen in Yizheng city from the perspective of environmental capacity. According to the difference between the water environmental capacity and the present situation, the amount of pollutants in inland river need to be cut down, and the measures to reduce the pollutant in the river are studied,and putting forward relevant pollution control measures and environmental management requirements.According to a study in yizheng city of project implementation of living water, can meet the requirements of river water quality after the living water engineering, improve the river environment, to do a better job of running water and engineering operations has the positive significance, and providing a scientific basis for effective measures to protect Yizheng river water environment. |
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