Modeling And Optimization Of Rainwzsater System Based On LID Regulation

Rainwater occupies an important position in human activity.With the acceleration of the urbanization process,various areas of China have been flooding.With the development of science and technology,urban builders should choose the best urban construction plans not only to inprove the people’s living standard,but also collect and use the valuable freshwater resouixes.The application of computer model in engineering field has been basically popularized.In the use of simulation,a large number of practical difficult problems have been solved and the huge cost has been saved.Therefore,it is very significant to optimize the urban pollution and sewage abatement scheme using computer.Comparison of domestic and foreign engineering examples and design manuals of-some universities in the United States,the concept and measures of various pollutant emission reduction were conpared.Finally,the LID source control was selected.According to the different characteristics of LID measures,pollutant removal and runof’f reduction,we finally chose the Bio-retention Cell,Vegetabled swale,Permeable Pavement and Infiltration Trench as the focus of this study.According to the results of the existing stormwater pipe network consti’uction model,this paper discussed the advantages and disadvantages of various models,and finally selected SWMM to build the rainwater pipe network model of JZ City.The pipe and node sections and flooding problems could be found out by operating the SWMM simulation of urban rainwater system.NSGA-Ⅱ algorithm was used to calculate the minimum value of the multi-objective optimization equation.Add the weight coefficient of each target in the optimization equation,which was set by the actual need.Then,we got the optimization results.In the base of the optimization results,the types of LID measures and the construction area were determined for each sub-watershed,and the feasibility of the scheme and the logical compliance were determined.Through the program optimization and evaluation,it could be concluded that the LID measure has a significant effect on pollutant removal.At the P = 3a recovery period,the COD removal rate of each plot reached 63%～84%,and most of the rate more than 70%.The removal rate of TSS reached 64%～85%,the removal rate of most plots was more than 80%;The removal rate of TN reached 41%～79%,most of them were more than 60%;The removal rate of TP was 35%to 80%,and only individual plots was less than 40%,most of the land’s removal rate was more than 50%.The runoff reduction reached more than 10%,however,with the re-emergence period of P = 20a and above,the capacity of runoff reduction began to decrease.Therefore,LID could not take the dominant position in flood control and drainage.