Pollution Processes And Management Researches On Urban Rainfall Runoff In Shanghai

With the development of urbanization, the areas of impervious surfaces like roads parking lots and rooftops increase constantly, which leads to the happening about lots of runoff from impervious surfaces during raining .especially storm water, and the runoff with lots of contaminants, for example, sediment , heavy metals, N P nutrition, toxicity organic compounds drain to the urban rivers, lakes and estuaries and become the main pollution source which decline the water quality. So urban runoff pollution is the typical urban non-point pollution. The region of research in the paper is the center of Shanghai city, which included road runoff in different function area and roof runoff in different roof materials. It analyzes the pollution process and researched the management practice. Among the content, the important points include the space-time rule of contaminants in runoff, first flush effects, the estimation of load of contaminants in runoff using models and management practice of urban runoff in Shanghai city basing on BMPs.It is founded by analysis samples from roof runoff and road runoff in lab that there is evident time rule about contaminants regulation in runoff in Shanghai city. The result indicates that the instant concentration of contaminants in runoff changes constantly during the process of rainfall. For roof runoff, the concentration of contaminants presents the evident index attenuation rule with the increasing of flow time. But for road runoff, the time rule of concentration of contaminants is different in different function areas. The concentration of contaminants presents the index attenuation rule with the increasing of flow time in industrial area, commercial area and residential area. But in traffic area, the phenomena never happens because the continuous pollution source from the complicated human and vehicles activities.The EMCs (event mean concentration) of runoff can be quantitative analysis of contaminants in runoff. In road runoff, the EMCs of contaminants are all high and different in different function areas. The order of mean EMCs of TSS, COD_Cr B0D₅ TN, NH₄⁺-N TP DP is : traffic area> commercial area > industrial area > residential area. The order of mean EMCs of N0₃-N NO₂-N is : traffic area > industrial area > commercial area> residential area. The highest mean EMCs of heavy metals is in industrial area, then is traffic area and commercial area, and the residential area is thelowest.In roof runoff, the order of mean EMCs of TSS> COD_Cr TN TP in the four kinds of roofs is : old concrete roof > old clay roof > new concrete roof > new clay roof; the order of the NH₄⁺ -N is : old concrete roof > new concrete roof > old clay roof > new clay roof; the order of NO₃-N is: new concrete roof > old concrete roof > old clay roof > new clay roof.It is analyzed about first flush effects of contaminants in roof runoff and road runoff by using dimensionless cumulative curve. The main contaminants including TSS C0D_Cr present the first flush effects in roof runoff, the other contaminants present the phenomena to different degree. The result indicates the first flush effects is existent. In road runoff, the first flush effects presents weakly, the phenomena never exist for some contaminants. The contaminants and the degree of first flush have differentiation in the industrial area, commercial area and residential area. The result from the former twice samples the first flush of TSS COD_Cr BOD5 is very evident, and 50-80% of the pollution load is transferred in the first 40% of event volume. The other contaminants are different in different areas. The analysis of samples from May indicate that the intensity of rainfall can affect the first flush heavily. In May, the intensity of rainfall was very small and the intensity of washout was also small, so the contaminants enter the runoff slowly, the first flush in four areas is not evident. The first flush never exist for other contaminants and areas except the Cr, Mn in residential area.It depicts the models about estimation the load of contami...