Analysis Of Urban Non-point Source Pollution In Tanchong River Basin And Study Of Treatment Options

In recent years,China’s urbanisation level is getting higher and higher,and the high concentration of population also brings great pressure on the urban water environment,and urban non-point source pollution,which is closely linked to people’s production and life,is becoming more and more prominent.The Tanchong River Basin is located in Feixi County,Hefei,and is a major tributary of the Pai River,which in turn is a major river entering Chaohu Lake.To alleviate the pressure on the urban water environment in the Tanchong River Basin and as part of the management of the Chaohu Lake Basin,it is necessary and urgent to study the urban non-point source pollution problem in the Tanchong River Basin and propose corresponding solutions.The main research elements of this paper are as follows:（1）In order to diagnose the problem of pollution in the Tan Chong River basin,a preliminary survey was conducted on the current status of the stormwater network and initial stormwater collection in the basin.（2）Pollution in the Tan Chong River Basin:Combining the actual monitoring data with the research data,the amount of pollutants entering the river in the whole section of the Tanchong River Basin is 491.51t/a of COD_Cr,44.93t/a of NH₃-N and7.07t/a of TP.The contribution of each pollutant from urban non-point source sources is 467.11t/a for COD_Cr,41.13t/a for NH₃-N and 6.67t/a for TP,accounting for 95.03%,93.77%and 94.34%of the overall pollutants entering the river in the basin respectively.（3）Structural characteristics of urban non-point source pollution in the Tanchong River Basin:Urban non-point source pollution in the Tanchong River Basin mainly comes from surface runoff pollution,direct river pollution,and pipeline scouring pollution.COD_Crin urban non-point source pollution is mainly from annual runoff pollution,accounting for 73.32%,NH₃-N is mainly from annual runoff pollution,accounting for 98.08%,TN is mainly from annual runoff pollution,accounting for 63.96%,TSS is mainly from annual runoff pollution,accounting for65.43%,TP is mainly from pipeline scouring pollution,accounting for 67.77%.（4）From the analysis of the equivalence pollution load method,the equivalence pollution load ratios of annual direct river pollution,annual surface runoff pollution and pipeline scouring pollution are 1.19%,67.19%and 31.62%respectively for the urban non-point source pollution in the Tan Chong River basin.The order of magnitude of the impact of different sources of pollution from urban non-point source in the basin on the environmental quality of the Tan Chong River water is:annual runoff pollution>pipeline scouring pollution>annual direct river pollution.The equivalence pollution load ratios of the pollution factors COD_Cr,NH₃-N,TN and TP for urban non-point source pollution in the basin are 13.08%,23.59%,44.67%and 18.67%respectively.That is,the order of the impact of different pollutants in urban non-point source pollution on the environmental quality of watershed water is TN>NH₃-N>TP>COD_Cr.It can be seen that the main sources of urban non-point source pollution in the Tanchong River Basin are annual runoff pollution and pipeline scouring pollution,and the main pollution factors are nitrogen pollution and phosphorus pollution.（5）Based on the high proportion of urban non-point source pollution in the Tanchong River Basin and its pollution structure,and according to the relevant planning,the overall framework strategy of source control,process collection and end treatment,a low impact development model is proposed to control urban non-point source pollution in the Tanchong River Basin.And by the fact that annual runoff pollution in the basin is the largest contributor to urban non-point source of pollution,a scheme for the collection and treatment of initial stormwater is proposed,taking into account the actual situation in the Tanchong River basin.