Research On Control Of Rainwater Runoff Pollution Based On Water Quality Target

With the global warming and the intensification of my country's urbanization process,the frequency of rainfall,precipitation and the runoff coefficient of the underlying surface of the city have increased.As a result,the problem of water pollution caused by precipitation leaching and erosion has become increasingly prominent.In this paper,the Banguiyan River small watershed in the Hefei is taken as the research object.Through sampling and analysis of the rainwater runoff and river and lake water bodies in the watershed,the characteristics of rainwater runoff and river and lake water quality of different underlying surfaces arc obtained,and then the city is constructed according to the MIKE series model.Based on the water quality model of rainwater and runoff in river basins,the relationship between rainwater runoff and river and lake water quality was explored.Based on the water quality objectives of river and lake sections in the study area,the optimal non-point source LID measure combination plan was formulated and compared,and the point source control measures were combined to achieve The water quality target requirements of the study area provide reference for the construction of sponge city and water environment treatment in the study area.The main work and important conclusions of this article arc as follows:(1)Analysis of current water quality in the study area.The sampling and testing of the rainwater runoff on the typical underlying surface of the study area and the outflow of water from the outlets on both sides of the river and lake showed that the rainwater runoff and outflow exceeded the surface water class V water standards,causing pollution to rivers and lakes.According to the water quality monitoring data of the river section control section,the water quality of the section was analyzed over the years,and it was found that the water body of Qiaowan Road section belonged to inferior V water for most of the year,and the maximum non-compliance rate was as high as 89%in 2015.The water environment needs to be improved urgently(2)Construction of rainwater and runoff water quality model in the study area.First,MIKE URBAN was used to calculate the discharge process and discharge of rainwater runoff in the study area,and then the calculation results were used as the initial conditions of the corresponding point sources of rivers and lakes to simulate the water quality of rivers and lakes.According to the run-through sequence of runoff space and time,the city-basin storm-water runoff water quality model was constructed,and the model was verified by using rainfall data and cross-section water quality monitoring data in 2017 and 2018.The results show that the model parameters are set reasonably,and the calculation results meet certain accuracy requirements,indicating that the model has good reliability and applicability.(3)Simulation of stormwater runoff pollution under different LID measures Add different LID measures for rain garden,green roof,permeable pavement and storage tanks in the study area,calculate the load of rainwater runoff pollution under different design storms and different measure conditions through the model,and compare and analyze the reduction control effects of different measures.The results show that:After adding rain garden,green roof,permeable pavement and storage tank respectively.Under 1a operating conditions,the control rate of COD reduction is 7.48%,16.63%,11.71%and 38.16%respectively;NH3-N reduction control rates were 4.99%,16.24%,5.87%and 38.09%;the TP reduction control rates were 7.16%,16.07%,8.32%and 38.83%,respectively.Under 5a operating conditions,the control rate of COD reduction is 6.10%,15.20%,9.96%and 35.24%respectively;NH3-N reduction control rates were3.88%,14.85%,4.66%and 36.36%;the TP reduction control rates were 4.77%,14.12%,5.75%and 36.24%,respectively.Under 10a operating conditions,the control rate of COD reduction is 4.61%,11.01%,7.88%and 28.75%respectively;NH3-N reduction control rates were1.95%,12.25%,2.62%and 31.18%;the TP reduction control rates were 1.74%,11.55%,2.68%and 32.34%,respectively.It shows that the reduction control effect of the same LID measure decreases with the increase of the recurrence period,and the reduction control ability of the LID measure is limited Among the four different LID measures,the best reduction control is the storage tank,followed by the green roof.(4)Water quality simulation with different gray-green measures.Based on the green roof and typical gray-green measures of the storage tank,the annual scale precipitation is used to simulate the change process of the control section water quality,and the relationship between runoff pollution and river and lake water quality is explored.The results show that:the monthly average concentration of pollutants at the cross-section changes with the monthly inflow of the river;after adding green roofs and storage tanks,the monthly average COD concentration at the cross-section of Fushan Road decreased,and NH3-N and TP The average monthly concentration value rises.It shows that rainwater runoff has an impact on the water quality of rivers and lakes,and interception control is conducive to improving the water quality of rivers and lakes,but the water quality of rivers and lakes still exceeds the surface water quality standards for some periods,indicating that the pollution situation of rivers and lakes is still serious.(5)Research on the control of stormwater runoff pollution based on the water quality objectives in the study area.According to the reduction effect of different non-point source LID measures,formulate different LID measure combination plans,and evaluate and analyze them based on the simulation results and cost of each plan,and compare and select the best plan.The results show that Option 2 has better reduction control and the highest cost-effectiveness Pa value,indicating that this runoff control scheme is the most economical and reasonable,and has the highest cost performance.According to the optimal scheme combined with point source control measures,the water quality change process of river and lake control section is simulated and analyzed.The results show that the monthly average concentrations of COD,NH3-N and TP at the control section of the river and lake in different hydrological conditions have been significantly reduced,and the concentration values are below the surface ? water standard,indicating that the added control measures can effectively improve the water quality of the lake water meets the requirements of Class ? water in the study area.