Research On Green Space Reduction Technology Of Rainfall Runoff Pollution Load

Urban rainwater runoff carries a large number of pollutants including grease,heavy metals,nutrients,suspended particulate matter and various organic matter.Therefore,it has become the main non-point source pollution source in the city.It is particularly important to carry out the control and prevention of rainwater runoff pollution to build a livable environment and improve urban ecology.As an important urban infrastructure,green space can not only improve the environment and reduce soil erosion,but also reduce rainfall runoff and reduce the concentration of pollutants in runoff,which plays a key role in controlling urban non-point source pollution.However,at present,there are not many studies on runoff pollution control based on the urban green space system.In this paper,through the monitoring of roof and pavement rainwater quality,it is proposed that rooftop rainwater treatment relies on the technical idea of"adding coagulant in the downpipe+greenfield precipitation interception",and built an improved greenland test system,using biochar to improve the grassland soil in the greenland.By improving the soil's water holding capacity and infiltration performance,collecting and infiltrating the roof runoff rainwater and road path rainwater,the in-situ control of high pollution runoff in the initial roof rain can be achieved.The research results include:?1?Lzs16?44?coagulation and sedimentation orthogonal test results show that,according to the pollutant concentration from high to low,the rainwater pollutant concentration is divided into high,medium and low loads.For rainwater with low pollutant load concentration,PAC The optimal dosage is 20-25mg/L;for rainwater with medium pollutant load concentration,the optimal dosage for PAC is 25-30mg/L;for rainwater with high pollutant load concentration,the optimal dosage for PAC The dosage is 30-35mg/L.?2?For roof rain runoff,the initial concentration of pollutants in rainfall is higher.When the dosage of PAC is 35-45mg/L,the length of grassland is 2m,the slope is 5°,and the coverage rate is 100%,the removal rate of NH3-N,TP,turbidity,TN,COD_Crr pollutants is 54-62%,respectively,71-74%,90-95%,34-51%,54-73%.The water quality index conforms to the urban miscellaneous water quality standard and basically meets the Class V water standard of the"Surface Water Environmental Quality Standard"?GB3838-2002?.?3?For the rainwater runoff on the roof and pavement,improve the grassroots soil through the mixing and mixing of biochar.The green structure simulation device of the improved structure has improved water storage capacity and greatly reduced the concentration of pollutants in the effluent.After the roof rainwater runoff is purified by biochar modified green space,the removal rates of NH3-N,TP,turbidity,TN,COD_Crr are respectively 73.10?84.84%,68.47?81.23%,56.27?71.36%,70.57?84.05%,54.66?67.68%;after the road runoff rainwater is purified by biochar modified green space,the removal rates of NH3-N,TP,turbidity,TN,COD_Cr are respectively 51.08-74.09%,64.99-82.54%,49.02-65.92%,51.35-70.59%,47.76-64.21%.