Research And Control Of Runoff Pollution And Waterlogging In Urban Residential Areas Of Northern Coastal Cities

In recent years,China's urbanization has reached 60%.With the completion of the city,the impervious rate of the surface is rising,and the waterlogging is common.In addition,as the degree of the urban point source pollution controlling increases,the industrial parks are moved or vigorously improved.The point source pollution treatment in the urban industrial area has obvious effects,and the industrial areas are well managed,but the pollution of the urban water has not been fundamentally solved.At this point,the urban non-point source pollution has gradually entered people's sight,The climate in the northern coastal areas is quite different from that in the south,according to the requirements of local conditions in the construction of sponge city,it is of great significance to carry out a more in-depth and detailed study on runoff pollution and waterlogging in the typical areas of northern coastal cities,so as to promote the construction of sponge city in China.Under the new situation of new urbanization and sponge city construction,this paper is based on the control concept of "infiltration,storage,stagnation,purification,utilization and drainage" of sponge city and the project of national natural science foundation of China,this paper selected a completed residential area in Qingdao as the research area.The water quality of runoff in this area was measured by field sampling,and the concentration level,correlation and initial scouring effect of pollutants were analyzed.Then SWMM model was built for the study area and parameters were corrected based on the data of rainfall.Based on SWMM model,Waterlogging risk assessment and water quality simulation in this residential area were simulated and analyzed with the recurrence periods of 1 year,2 years,3 years,5 years and 10 years respectively.Finally,according to the characteristics of residential areas,permeable pavement,green roof and rainwater garden are selected to be laid out,and the control effects of three control measures on Waterlogging and water quality were analyzed in five recurrence periods.The main research results are as follows:(1)The EMC?First flush effect and the correlation of pollutants of four rainfall times were analyzed.The runoff pollutant concentration in this residential area basically increased first,then decreased and finally tended to be stable with the runoff time.Cu and Pb have a direct decreasing trend.The EMC ranges of pollutants are: TSS is 91.69-248.89 mg/L,COD is 31.48-85.79 mg/L,TN is 0.112-0.389 mg/L,TP is 0.179-0.409 mg/L,Cu is 0.037-0.114 mg/L,Zn is 0.327-0.432 mg/L,and Pb is 0.063-0.194 mg/L.Among the major cities in China,this pollution level is below the average;All the pollutants have initial scour phenomenon and the scour intensity is affected by rainfall intensity.COD,TN and TP were significantly correlated with TSS.Heavy metals were not correlated with TSS,but Cu was correlated with Pb.In addition,the factors of runoff pollution are analyzed.The results show that:runoff duration and rainfall intensity both affect runoff pollution concentration,and the two effects of rainfall erosion and dilution work together.In the residential areas with better sanitation management,the early drought days have little influence on runoff pollution concentration.(2)Simulation shows that the node overflow is not serious and there is a risk of waterlogging but it will not occur in a large area when the recurrence period was 1,2 and 3 years.when the recurrence period was 1 year,Serious node overflow occurred in the downstream of branch pipe and pipe network,and the overflow node accounted for 32.5%.In 10 years,there were 27 overflow nodes with large overflow flow,and the whole area was at risk of waterlogging.In terms of water quality,the pollutant load increases with the recurrence period,and the overall pollution load is huge.(3)LID measures should be arranged according to the proportion of 15%-20% permeable pavement,3%-5% rainwater garden and 40%-50% green roof,The reduction rates of peak flow were 37.5%,37%,34.8%,30.4% and 9.2%;Total emissions were cut by 32.8% to 42.4%;The peak time and runoff time was no significant reduction.In the recurrence period of 1,2 and 3 years,all overflow nodes disappeared,and the overflow nodes in 5 and 10 years were reduced by 78.9% and 40.7%.In terms of water quality,the reduction rates of total pollution load and peak pollutant concentration were 42.3%-65.8% and 23.7%-41.0%.On the whole,permeable pavement,green roof and rain garden had obvious effect on runoff pollution and waterlogging control but the effect was weakened when the recurrence period was large.