Spatial Distribution of Rural Domestic Sewage and Its Control in the Dianchi Lake Basin by PSR Model,China

Village domestic sewage discharge has become one of the major causes of the Dianchi Lake water pollution.Understanding distribution of village sewage pollution is the basic condition for pollution control.Based on the survey data of rural non-point source pollution,we analyzed the pollutant emission amount of village sewage and its spatial pattern in the Dianchi Lake Basin.Applied the Pressure-State-Response(PSR)Model,we identified the key control areas of rural sewage treatment in the Dianchi Lake Basin.Firstly,we took the amounts of the village wastewater discharge and its spatial distribution characteristics as thestateindicators,as well as the status of sewage treatments and proposed the measurements.The results showed that the village wastewater discharge amounts were as follows:Xishan DistrictGuandu DistrictJinning CountyChenggong CountyPanlong DistrictWuhua DistrictSongming County,and lakesides areasmountainous areas.Depended on the population and the discharge coefficient,the village wastewater discharge amount of the Dianchi Lake Basin was 1.02×106 t.a-1,the COD Cr in the wastewater was 2.18×104 t.a-1,the TN was 761.94 t.a-1,and the TP was 98.38 t.a-1.The weakness and shortage in rural wastewater control was revealed by Gap analysis.It was that theresponseby overlapping between rural wastewater discharge range and the scope of existing urban or township wastewater treatment plants to provide a spatial scheme for developing village-based scattered rural sewage treatment systems.At present,the capacity of urban wastewater treatment plants covered 20 499.7 t.d-1(73.26%)of rural domestic sewage discharge,and township wastewater treatment stations covered 934.8 t.d-1(3.34%).So,village-based scattered rural sewage treatment systems should be built to treat the rest 6 549.2 t.d-1,accounted for 23.40% of the village sewage discharge in the Dianchi Lake Basin.Facilities of village-based scattered rural sewage treatment systems were suggested to be established in 157 villages in the coming years in an optimized sequence by priority analysis.