Study On Runoff Pollution Of Typical Plots In Suzhou Sponge City Pilot Area

With the expansion of the scale of cities and the increase of impervious surface area,rainfall runoff pollution has become an important factor affecting the urban water environment.In recent years,the construction of sponge cities with runoff pollution control as one of the important goals is being carried out in full swing,and there are continuous research results on the control of surface runoff by the construction of sponge cities and the reduction of pollutants by sponge facilities.Carry out sponge city construction based on the runoff pollution of plots,and conduct research on the runoff pollution control capabilities of sponge facilities and plots after completion,which has important practical value for rainfall runoff pollution control,sponge facility optimization and sponge city construction.This paper takes two typical plots in the Suzhou sponge pilot area as the research object.Based on the analysis of rainfall runoff pollution characteristics,combined with the construction conditions,needs and goals of the plots,the sponge transformation design was carried out and according to local conditions,and the construction process was tracked and summarized.After the sponge transformation of plots,the runoff water quality of the single sponge facility is monitored and analyzed.The evaluation model of plot runoff control was built to evaluate the effectiveness of plot runoff pollution control.The main conclusions of this research are as follows:（1）The dynamic change process of the pollutant concentration in the rainfall runoff of the road and roof in the study area shows a certain regularity.The regularity of SS and COD is the most obvious,and its concentration rises to the peak concentration with runoff time and then tends to be stable.The concentration of TN,NH₃-N,and TP fluctuate greatly with runoff time.The polution in the study area is very serious.In many rainfall events,SS,COD,TN,NH₃-N,TP of roads and roofs were different degrees of beyond the surface water environment quality standards and the integrated wastewater discharge standard.The runoff pollution degree of different plots and underlying surfaces is generally represented by residential quarters>public buildings,roads>roofs.（2）There is a strong correlation between SS,COD,TN,NH₃-N and TP in road and roof runoff,and the correlation between SS and COD is the most significant.It shows that it is reasonable to use the reduction rate of SS to measure the control of conventional pollutants in runoff.Both road and roof runoff pollutants have the first flush effect,but the pollutant load carried by the first 30%of the runoff is less than 60%,indicating that the first flush effect is not significant.In order to better control runoff pollution,runoff process control should be strengthened.（3）On the basis of field investigations,follow the process of“assessment of current conditions and problems-determination of sponge transformation goals-design of sponge transformation schemes-construction drawing design-sponge transformation construction-evaluation of effects after completion".Carry out the spongy transformation of typical plots with runoff pollution control as the main goal.The results show that sponge transformation can achieve plot renewal while controlling runoff pollution.It can be used as an important path in urban renewal.However,it should be ensured that the selection and design of sponge facilities are reasonable,the construction is accurate and the operation and maintenance are scientific.（4）Analyed the runoff pollution reduction capabilities of nine sponge facilities by monitoring the quality of outflow water.On different underlying surfaces,the average removal rates of SS in runoff rainwater for permeable steel slag brick paving and permeable steel slag concrete paving can reach 67.94%,67.63%,and 75.29%.The average removal rates of SS in runoff rainwater from different underlying surfaces in biological retention ponds,rain gardens,and high-level flower beds were 73.63%,77.80%,74.45%,72.46%,78.25%,71.89%.The runoff pollution reduction capacity of sponge facilities on different underlying surfaces is roof>road surface,combined facilities>single facilities.（5）Build a model system to evaluate the runoff and runoff pollution control capabilities of typical plots after sponge transformation,and analyze the effectiveness of plot runoff pollution control.After the sponge transformation,the runoff control capabilities of residential quarters and public building plots have increased by 30.7%and 40.4%,respectively.The reduction rate of SS,COD,TN,NH₃-N,and TP in residential district plots can reach 58.44%,55.44%,39.71%,33.71%,and 39.71%respectively.The reduction rate of SS,COD,TN,NH₃-N,and TP in public building plots can reach 58.96%,54.08%,36.80%,36.80%,and 38.68%respectively.It can be seen that reasonable sponge city construction on the plot can effectively control runoff pollution.