Research on water environmental capacity of water quality standard in water function zone of Jiaxing

Jiaxing urban region belongs to plain water network witch has a complicated water system with rectilinear current as well as a large amount of discharged pollutants,which has resulted in water quality being degenerated. According to an investigation of pollution source in Jiaxing urban district,diffused pollution is rather critical; animal sources of fecal pollution is the major source in water environment pollution. Weight analysis of influence of pollution source show that endogenous and point sources have great impact inside the research area. Based on this,generalization of major pollution sources is performed; simultaneously,one-dimensional unsteady water quantity and quality model were established to achieve corresponding relationship between water quality in water function zones and generalized pollution sources. Through mathematical modle,based on water quality reaching standard for water function zones and reducing pollution source of sewage outlet in the same proportion,it calculated permissible pollution emission of sewage outlets and environmental capacity of water function zones as well as their reducing scheme. Results indicate as follows: ①Permissible pollution bearing capacity of COD,NH3-N and TP were 8642 t / a,794 t / a and 227 t / a; ②Pollutants in urban areas have exceeded the standard severely, NH3-N and TP have become the main pollution factors; ③Regarding pollutants discharged into the river in 2011,COD,NH3-N and TP needs to be cut 49%,57%,56% respectively. The result can provide decision-making foundation for water function zone to reach water quality standard and to reduce discharge of pollutants.