Experimental Results And Engineering Application Analysis Of "Sponge City" Rainwater Utilization System

"Sponge City" is a construction mode which is at the point of using city rainfall integratively and efficiently,the city is compared to a sponge,and it can cope well with variety of rainfall as the return period changes from low to high,the rainwater on the road or nearby could effectively be absorbed and stored,penetrate,recharge groundwater,regulate water cycle,the stored water can be used when the drought comes,the mode first greatly increases the efficiency of urban recycling water,second it reduces the probability of occurrence of floods,third it takes good advantage of rain properly and efficiently,forth it maintains good hydrological and ecological environment."Sponge City" includes some rainwater recycling systems,such as rain gardens,ecological ditches,green roofs,and so on.In this paper,experiments and engineering application analysis are done in rain gardens and ecological ditches in turn,which may find or solve problems in the development of Feng Xi New Town in XiXian new area in using rainwater at high level.(1)Rain gardens experiment rainwater pollutant removal effectiveness analysis showed that rain gardens to reduce the overall rate of TSS concentration is maintained at-26.1%to 60.8%,the average reduction rate of more than 35%;the concentration of TP overall reduction rate is maintained at-21.3%to 49.0%,the average reduction rate of more than 42.6%;concentration of TN overall reduction rate is maintained at-17.9%to 13.5%,the average reduction rate was 4.7%,well below the TP,TSS and other pollutants reduction rate;of the total ammonia concentration reduction rate is maintained at 41.1%to 69.7%,with an average reduction of 54.3%.A total of 23 games during the experiment complete rainfall detection,of which only three short rain overflow,and the rest are effective rainwater infiltration soil.Peak flow during rain gardens within a run rate of more than 95%reduction(2)Engineering applications rainwater garden monomer is 5 ×6m oval,the bus with a total area of about 520m2,the outermost layer of the water depth of about 20cm,artificial water during the test,the rain does not overflow occurs,the rainwater infiltration 2h or less,rain gardens average infiltration rate of 0.623m/d,preferably infiltration performance(3)Experimental zone of ecological ditches,experiments were carried out in 48 sessions,24 sessions before the concentration of pollutants in the water and under constant hydraulic load change the situation,the results showed that ammonia nitrogen removal rate was 27.1%,total nitrogen and 23%total phosphorus 60%;after 24 sessions in a water pollutant concentration changes under constant hydraulic load situation,ammonia nitrogen removal rate was 28%,total nitrogen and 27%of the phosphorus was 56.9%.Therefore,the indicators monitored,the ecological ditch filter pollutants phosphorus removal is better,and for the removal of nitrogen poor in phosphorus(4)Ecological ditch engineering application area of 81.5m2,which corresponds to the confluence area of 395.7m2,collected a total of 4 times effective rainfall,total rainfall single pollutant reduction rate of up to 57.8%,TN pollutant load reduction rate of up to 45.8%,TP load reduction rate of up to 56.7%,COD load reduction rate of up to 65.2%.