Pollution Characteristic Of Stormwater Runoff And Controy Effect Of Pollutants By LID Retrofitted In Xiushan

Accelerated urbanization and increased the proportion of impermeable surface area,the city pollutant erosion exacerbated the large city runoff pollutants into the water,causing water pollution.In the current,point source pollution control has been quite effective,non-point source pollution caused by surface runoff has become an important source of the water environment pollution.In order to control the non-point source pollution from the source,LID(low impact development)has become the main measures of non-point source pollution control at home and abroad.In the paper,as taking Chongqing C ity Xiushan Tujia and Miao Autonomous County as the study area,The runoff water quality and pollution characteristics are analysed.Secondly,the effect of LID retrofit measures on the reduction of pollutants is analyzed.Finally,the SWMM model is used to simulate the control effect of the current LID transformation and LID optimization scheme on pollutants under different recurrence periods.The main results are as follows:(1)From the analysis of variation of pollutant concentration with rainfall duration in Rain Water runoff on different underlying surfaces in Xiushan County,it can be seen tha tthe range of water quality and the time of peak formation are different among different underlying surfaces and different rainfall events,but the general trend is that,with rainfall duration increasing,the concentration of pollutants gradually decreased and stabilized after reaching the peak in a short period of time.The most serious pollution is Yu Xiu Road West rainfall runoff,and the lowest pollution is roof runoff.And the correlation between COD and TSS,TP and TSS is better.The correlation between NH3-N and TSS is poor.(2)In the 5 kinds of different underlying surfaces,the average EMC value in Yu Xiu Road West is the largest,and far greater than other kinds of surface.the average EMC of TSS,COD,NH3-N and TP is: 810.73mg/L,189.63mg/L,0.56mg/L,0.20mg/L.Roof runoff reached the surface water class III the water quality standard,Yu Xiu Road West,Yu Xiu Road East,residential area and the square did not reach grade V standard of surface water,and the main pollutant is COD.the first flush effect in all underlying surfaces is occurred,but not significant.The rainfall intensity,the antecedent dry days and the type of surface all have influence on the pollutants in surface runoff,among which the intensity of rainfall and the type of underlying surface have great influence,and the antecedent dry days have little influence on the surface of surface that is cleaned regularly.(3)The average removal rates of TSS,COD,NH3-N,TP in Bio-retenton cell were 83.81%,77.99%,53.80%,46.65%,and the effluent water concentration of NH3-N and TP was higher than that of influent during rainfall.The rain garden on TSS,COD,NH3-N,the average removal rate was 63.52% 37.55%.,57.98%,46.35%,the pollutant removal rate fluctuated greatly,and the instantaneous removal rate of TP reached 81.08%,but the lowest reached-11.31%.(4)the SWMM model results show that adding LID measures of 9.49% bioretention,0.26% rain garden,9.33% permeable pavement and grass ditch length of 612 m,in which the different pollutants are cut.And effect on the TSS reduction effect was the best,in the five year return period,reduction rate reached 56.17%.To optimize the current LID,add more LID measures of,the optimized LID layout were simulated,the results indicated that adding more LID measures of 12.38% bioretention,0.26% rain garden,26.59% green roof,18.66% permeable pavement and grass ditch length of 612 m,the pollutants and runoff reduction capacity increased,TSS reduction rate reached 67.41%,but the increase effect is limited,It is necessary to to consider the actual project economy and other problems to select the scheme.