Research On Combined Sewer Overflows Control Based On Sponge City Construction

In recent years,with the advancement of urbanization,the problem of combined sewer overflows pollution has become more and more serious.The control of combined sewer overflows pollution has become the focus of urban water environment management.In the meanwhile,sponge city construction provides a good opportunity for control of combined sewer overflows pollution.Compared with the traditional end-of-pipe governance,the sponge city emphasizes source reduction and system management which is more advantageous.Therefore,it is of great practical significance and application value to study the control of combined sewer overflows pollution based on the construction of sponge city.Taking the combined sewer area in the Tongzhou National Sponge Pilot as the research object,the drainage numerical model was constructed based on the data collected by on-site monitoring and field investigation.Based on the model simulation calculation,the optimal control scheme of the combined sewer overflows was determined.The main research achievements of this paper are as follows:(1)In this paper,the distribution process of typical rainfall and the change of pollution load in rainwater are revealed.Meanwhile,the spatial distribution difference of different pollution load indicators in dry season and rainy season is clarified.Moreover,under different rainfall conditions,the variation characteristics of overflow and discharge are proved.(2)Based on SWMM software,a numerical model of regional drainage is constructed.Using two measured rainfall data,the model was determined,based on the calculation of Nash coefficient(NSE)and mean relative deviation(BIAS).Comparing the simulated water quality and water quality results with the measured data,the rationality and accuracy of the SWMM model are verified.(3)The characteristics of the combined overflow under the condition of the underlying surface are clarified.It reveals the response law of the combined flow overflow to different rainfall events under the control of single-link control of source sponge modification or interception pipe network.Finally,the effect of each link on the overflow control of the combined flow is quantified.(4)Using the long series of rainfall data as the model input,the long series overflow simulation results are obtained.Based on the simulation results,the field overflow is divided,and the correlation between the overflow and the overflow pollution load is proved.The water quality control capacity of the receiving water body is taken as the water quality control target,and the water quantity control target is proposed on the premise of meeting the water quality control target.(5)The CSO control plan is formulated through the confluence of the overflow control target,and the cost of each plan is estimated.It is determined that when the interception multiple is n=3 and the total volume of the combined storage tank is28148m3,the economical cost of the combined overflow control scheme is the smallest,about 193.83 million yuan.