Research On Water Pollution Prevention And Control In Xianghe River Basin Based On Water Environment Control Unit

The Xianghe River belongs to the Chu River system in the Yangtze River Basin and runs through Quanjiao County,Chuzhou City,Anhui Province.It is the river with the longest length of reach and the largest drainage area in the county.The Xianghe River assumes the function of drinking water sources in Quanjiao County and some urban areas of Chuzhou City,and also includes industrial consumption,agricultural water and corresponding sewage receiving water functions.According to water function zoning in Anhui Province,the Xianghe River Basin is from the Huanglishu Reservoir area to the bottom of the Huanglishu Reservoir dam,which is the source protection area of the Huangjiaoshu Reservoir Quanjiao River.This shows that the quality of the Xianghe River water quality directly affects the drinking water safety of people in Quanjiao County and Chuzhou City.In order to effectively carry out the prevention and control work in the Xianghe River Basin,this study uses a combination of township administrative division and watershed management,using GIS platforms and DEM data to divide the control units of the Xianghe River Basin.Based on the monitoring and analysis of the current status of water quality in 2017 and the monitoring data over the years,the natural social and economic survey of the river basin,we understand the discharge of pollutants from various pollution sources in the corresponding control unit into the river,systematically analyzed the water quality of the river basin,and identified the major pollutant types and their Causes of pollution.Based on the water quality objectives of the control section,the water environment capacity at the average flow rate of the driest month in each control area in the past 10 years were calculated,and the pollutant reduction task volume and specific emission reduction measures of the pollution sources of each control unit were determined.The following conclusions are drawn from this:(1)The main pollutants in the Xianghe River Basin are COD,ammonia nitrogen and total phosphorus,and the maximum excess multiples are 0.59,4.37 and 0.73,respectively.The pollution types are mainly ammonia-nitrogen-based pollution and industrial pollution as a supplement.(2)Based on the GIS platform and DEM data,the Hydrology Modeling module in Arc Gis software is used to divide the corresponding hydrological units and determine the catchment area.Combined with the key control nodes of the Xianghe River and the catchment characteristics of the catchment area,the administrativearea-hydrological response unit was organically integrated to establish the "key control node-control river section-corresponding land area" water-land response relationship to divide the control units and divide them.It is a 5-segment water area control unit(denoted by AE respectively).The land area control unit includes Zhangguang Town,Shiji Town,Yaopu Town of Chuzhou City and Shipei Town,Machang Town,Liuzhen Town,Shijiao Town,Quanjiao County,Related catchment areas of Xianghe Town and Wugang Town.(3)The total inflow of COD into the Xiang River Basin is 3942.41t/a,the inflow of non-point source pollution accounts for 47.73% of the total inflow,and the inflow of point source pollution accounts for 52.27% of the total inflow;ammonia nitrogen enters the river The total amount is 603.51t/a,the amount of non-point source pollution entering the river accounts for 65.94% of the total amount,the point source pollution entering the river accounts for 34.06% of the total amount;the total amount of phosphorus entering the river is 96.28t/a,Non-point source pollution into the river account for 58.75% of the total,and point source pollution into the river accounts for41.25% of the total.From the control area,79.30% of the inflow of COD comes from the DE section,16.24% comes from the BC section,and 4.46% comes from the section A;74.30% of the ammonia nitrogen inflow comes from the DE section,and20.48% comes from the BC section.5.22% comes from section A;74.43% of the total phosphorus inflow comes from section DE,19.15% comes from section BC,and6.42% comes from section A.The main source of pollutants in the Xianghe River Basin is section D-E.(4)The amount of pollutants entering the Xiang River Basin in 2017 is far greater than its water environment capacity.After considering the safety margin,the COD reduction was 2012.963t/a,and the ammonia nitrogen reduction was 488.229t/a.The reduction of total phosphorus is 78.325t/a.Based on the divided control unit,the calculated reductions will be distributed to each pollution source gradually according to the three-tier distribution system,and appropriate pollution reduction programs and prevention measures will be proposed from point sources and non-point sources.