Quality And Biofiltration Of Stormwater Runoff

For Xi'an is lacking of water seriously,many methods that can be used to prom -ote the ability and efficiency of utilizing the stormwater is not only a way to solve the problem of lacking of water in Xi'an,but also the way to achieve fully using of water resource and sustainable development.This paper is based on the experiment of monitoring the stormwater runoff quality from the office building of environment engineering institution of Xi'an University of architecture and technology,and by researching the effect of biofiltration systems treatment,some basis and technical support of utilizing stormwater in Xi'an city are obtained.This paper is also based on a large number of domestic and foreign literatures and their application.Subsequently,different kinds of methods in urban stormwater runoff utilization,the pollution and water characteristic of stormwater runoff of office build -ing,as well as the feasibility of urban stormwater runoff using have been analyzed and summarized,the biofiltration system has also been built in this experiment.During the experiment,stormwater runoff was collected and percolated.The stored stormwater can be used in the growth of surface plant through capillary action of soil,thus,the quantity of irrigating water can be decreased.The results and conclusions of this paper are as follows:(1)The early stormwater runoff in spring is seriously polluted,which contains 90～30mg/l COD_Mn(6～2 times higher than surface water standard classâ…¤),10～6 mg/l NH₃-N(5～3 times higher than surface water standard classâ…¤),thus,it is superâ…¤class water,however,the quality of stormwater runoff in late rainy season do not exceed the surface water standard classâ…¤;in summer,the stormwater runoff contains few contaminated element,such as 14～3mg/l COD_Mn,4～0.1 mg/l NH₃-N,the average value is 5.6 mg/l and 0.62mg/l respectively,consequently,it isâ…¢class water.(2) The biofiltration system has strong ability in removing turbidity,SS,COD_Mn, NH₃-N,TN,and TP of roof stormwater runoff.The average removal rate is:turbidity 80%,SS 95%,COD_Mn 44%,NH₃-N 83%,TN 61%,and TP 79%.(3)The result of experimental research has shown that the growth of poa annua in biofiltration system is better than which in normal green,because the sand ratio in artificial soil is more proper,and the nutrition in stormwater runoff can offer a better condition for the growth of poa annua.(4)The water-reserving ability of biofiltration system soil is superior to ordinary green,and the infiltrating water in the bottom of experiment equipment can reach to surface through capillary action to support the growth of plants;the system had operated for 6 months,though the superficial poa annua of biofiltration system had never been maintained and managed during the time,however,only few of the poa annua was scorched.(5)Simulated green system can modify the quality of stormwater runoff efficiently, and,quantity of N and P in stormwater runoff was absorbed by plants,instead of enriching in soil.