Calculation of environmental capacity and pollutant discharge in Changxing county based on sustainable development

Due to the improvement of the understanding of the natural environment and social service function of rivers, many countries in the world have started the research and practice of water environment protection. Lots of Chinese cities also paid most of their attentions to the water environment especially in the river network area. Systematic calculation and analysis of the water environment status becomes famous in most of the Chinese cities, which not only shows the current status of water environment but also indicates the methods to reduce the domestic pollution. In this study, Changxing county is selected as a typical Chinese city, COD (Chemical Oxygen Demand) and TN (Total Nitrogen) are considered as two typical pollutants, both water environmental capacity and current pollution are calculated. From the comparison between the present pollution load and the discharge limit into the river, it can be seen that TN is the key influencing factor of the water environment carrying capacity in Changxing County, and its overload ratio is up to 5.0. A series of measures to reduce the pollution load into the river are put forward in order to provide an auxiliary decision-making basis for further protecting "clear water and green mountains".