Optimal Control Of Intercepted And Separated Rainwater Runoff In An Industrial Park In Ganluo County,Liangshan Prefecture

In recent years,with the acceleration of urbanization,large areas of permeable areas in cities have gradually been covered by non permeable structures such as gray high-rise buildings and hard roads,hindering rainwater infiltration and significantly increasing surface discharge coefficient.During the confluence process,most surface runoff can only flow through the urban drainage system,which greatly increases the pressure on the urban drainage system.At present,urbanization in China is being vigorously promoted,but in many cities,supporting facilities such as drainage are still immature,and there is still a long exploration process in the design process of drainage systems.This article first reviews and analyzes the research and application progress of the concept of drainage systems both domestically and internationally,and points out the shortcomings of current research.Afterwards,taking an industrial park in Ganluo County,Liangshan Prefecture,Sichuan Province as an example,based on the characteristics of the research area,and based on the park’s diversion system,a current rainwater system model was constructed based on the model’s calibrated parameter data.The drainage system was transformed,and based on the complete diversion interception diversion system,the problems of mixed rainwater and sewage pipes,initial rainwater pollution,and insufficient rainwater utilization in the traditional drainage system were solved,Through the coupling of the optimized drainage system and low impact development facilities,process simulation of rainfall,confluence,pollutant accumulation and other processes was carried out at different rainstorm intensities,to explore the best regulation scheme suitable for the study area,to maximize efficiency,and to conduct preliminary design of rainwater reuse facilities in combination with the water quality data after regulation.The main conclusions are as follows:（1）Based on the current situation of the drainage system in the industrial park,the advantages and disadvantages of the improved drainage system were analyzed through model software simulation verification.Combined with the verification results,the optimized and improved intercepting drainage system was determined as the optimal drainage system.At the same time,the calculation method for relevant parameters such as intercepting wells and storage tanks was determined.（2）Based on the current drainage system in the research area,a pipeline network model,runoff model,and water quality model were constructed and analyzed.The simulation results of the current rainwater system in the research area showed that under different return periods,the maximum flow rate in the same sub catchment area gradually increased,and the cumulative flow rate gradually increased,but the maximum flow rate appeared at the same time.At return periods 1a,3a,and 5a,as the return period increases,the operating pressure of the pipeline network increases.When the return period is 5a,the overflow inspection well approaches 3/4,and the drainage capacity of the pipeline network is poor;The peak time of each pollutant is basically the same,but the peak value does not gradually increase.The peak concentration of COD is COD_50a>COD_20a>COD_10a>COD_5a>COD_1a>COD_3a,the peak concentration of SS is SS_50a>SS_20a>SS_10a>SS_5a>SS_3a>SS_1a,the peak concentration of TP is TP_50a>TP_20a>TP_10a>TP_5a>TP_3a>TP_1a,and the peak concentration of NH₃-N_50a>NH₃-N_20a>NH₃-N_10a>NH₃-N_5a>NH₃-N_3a>NH₃-N_1a.During the same period,the concentrations of the four pollutants SS,COD,TP,and NH3-N were 32.37 times,2.42 times,1.05 times,and 1.32 times higher than the standards for recycled water,respectively,indicating a higher pollution level to the receiving water body.（3）The simulation results of the optimized interception diversion system show that after adding interception wells and storage tanks,the peak water level of the pipeline in front of the discharge outlet decreased from 1776.608m to 1776.393m,a decrease of 0.215m;The peak flow rate of the pipeline has decreased from 0.719m3/s to 0.678m3/s,with a flow reduction rate of 5.70%.This indicates that the optimized drainage system has to some extent alleviated the overload operation of pipelines and reduced the risk of waterlogging.（4）In response to the shortcomings of the current drainage system in the research area,such as rainwater runoff pollution and insufficient utilization of rainwater resources,an optimized drainage system coupled with Low Impact Development Facilities（LID）facility was adopted to optimize and control rainwater runoff and pollution.The results showed that the reduction effect of the facility on the total inflow and peak flow of the discharge outlet showed a decreasing trend,but the peak time was delayed by 13.5-22.5 minutes compared to the original time when no facilities were added,During the three rainfall return periods,the total reduction rates of surface runoff in the industrial park were 38.46%,34.68%,27.14%,24.35%,19.58%,15.35%,respectively,and the runoff coefficient decreased by 39.43%,33.63%,26.63%,21.87%,17.2%,14.39%,with significant effects;The LID measure delayed the storage time of rainwater and pushed back the discharge process,resulting in a higher flow rate of the later process line than the state without the addition of LID measures.Compared with the direct drainage rainwater method without LID,the delayed discharge of LID measures is more in line with the requirements;After the rainwater is regulated by the green rainwater system,in order to ensure the quality of the effluent,a preliminary design of rainwater reuse system process facilities has been made to improve the effluent quality based on the actual situation of initial rainwater,and a water quality detection device has been designed to detect whether the effluent meets the standard requirements,further ensuring the effluent quality requirements.