Study On Runoff Reduction And Pollution Purification Technology Of Urban High Level Parterre

With the acceleration of urbanization,the degree of urban underlying surface hardening has increased year by year.This makes the city surface into an impermeable layer,bring about waterlogging,water shortage and runoff pollution.If the urban rainwater runoff flows directly into the urban water body or into the urban pipe network,it will pollute the receiving water body and increase the city pipe network load.The important method to solve the urban waterlogging,water shortage and runoff pollution is to effectively collect,purify and utilize urban runoff rainwater before the urban rainwater runoff enters the receiving water body and drainage pipe network.In order to solve the problems of urban water resources,the Ministry of housing and construction put forward the"technical guidelines for the construction of sponge city-low impact development rainwater system construction"?Trial?in 2014.According to the construction requirements of sponge City,aiming at urban rainwater runoff,a high level parterre was constructed on the basis of soil infiltration system.Through the structure design,introducing new matrix and layering filling,high level parterre with large water holding capacity,high permeation rate and strong pollutant removal performance were constructed.Through the laboratory device with artificial urban rainwater runoff to determine operation range,optimize the operation parameters.And the contents of total nitrogen?TN?,total phosphorus?TP?,suspended solids?SS?and chemical oxygen demand?COD?in water were monitored.According to the formula to calculate the rainfall related parameters in Shenyang City,provide technical support for the construction of sponge city.The main conclusions are as follows.?1?In this experiment,vermiculite,zeolite,cinder,ceramsite,volcanic stone,matrix A?vermiculite:zeolite:cinder=3:3:4?and matrix B?vermiculite:zeolite:ceramsite=3:3:4?were selected as the seven substrates.The results showed that the matrix adsorption performance of nitrogen and phosphorus in runoff rainwater was better than that of the single matrix,and the matrix B had the best performance.?2?By filling column experiment,it was concluded that the adsorption layer was the best in layered filling with zeolite+vermiculite+ceramsite.After stable operation,the filling column holds about 40%water,and the average permeability can theoretically withstand more than 6 times of heavy rainstorm flow.The concentration of NH₃-N,TP and COD_Cr in water is consistent with urban rainwater recycling standard.And the result show that this kind of filling method can adapt to the continuous heavy downpour of 72h in the city and meet the performance requirement of the high flowerbed.?3?The high flower-bed model is used to conclude that it can run more than 288h under heavy rainfall.According to the infiltration rate,in theory,the high altars can absorb the water infiltration of the area within 6 times of their own area.According to the maximum amount of water,the high flower beds per square meter can restore the rainfall of 16m² area.According to the pollutant treatment effect,high flower bed best rainfall intensity in the range of 224-448 mm,odorless,no significant water color,NH⁴⁺-N concentration is less than 5 mg/L,TP concentration is less than 0.2 mg/L,COD_Cr concentrations less than 30 mg/L,pH between 6-9.The high-level flower bed can control the total runoff volume,reduce runoff peak and runoff pollutant,and meet the requirements of sponge city construction,which can be applied to practical engineering.?4?According to the actual operation simulation effect of the high bed,the high-order flower-bed has a remarkable effect on the water purification effect of the actual urban runoff.The removal rate of SS,COD,NH₃-N and TP in actual rainwater runoff was 95%,90%,83%and 95%respectively.The water quality of the effluent meets the water quality index of urban waste water and recreational landscape.The high-level flowerbed has good stability,can achieve the expected effect in the actual application,can provide technical support for the sponge city construction.