Prediction Research On Confluence Of Overflow And Rainwater Runoff In Yuzhong District Of Chongqing City Based On ICM Model

With the continuous evolution of urbanization,large-scale development and construction has caused the proportion of urban undersurface hardening to increase sharply,and the problems of confluent overflow（CSOs）and non-point source pollution have become increasingly prominent,which has become a problem for many urban water environment governance.The use of advanced technical means to study the urban confluence drainage system has begun to receive widespread attention.In this paper,the typical combined drainage system in the old city of Chongqing is taken as the research object.The Info Works ICM model is used to analyze the changes of overflow water volume and water quality under different recurrence periods,and to simulate the combined drainage system to the receiving water body under the typical annual rainfall conditions.Pollution characteristics;comparative analysis of the change of pollution load before and after the combined drainage system;explore the influence mechanism of the intercepted combined drainage system on the water quantity and quality of the terminal sewage treatment plant.Finally,the CSOs pollution control measures are proposed based on the actual conditions of the old city.The main conclusions are as follows:（1）The measured water quality data of the intercepting wells in the rainy season is used to rate and verify the model.The average correlation coefficient R,relative errorδand Nash-Sutcliffe efficiency coefficient Ens of the COD simulated values and measured values obtained from the rate and verification period are:0.84,19.30%and0.76;NH3-N:0.88,19.98%and 0.85;TN:0.88,18.56%and 0.77;TP:0.84,22.64%and0.79;SS:0.71,28.13%and 0.60.The simulations of COD,NH3-N,TN,and TP have higher accuracy,and SS is slightly worse.（2）Using typical annual rainfall events,the simulation predicts that the average annual overflow frequency of 16 overflows in Yuzhong District is 3 to 27 times,and the cumulative overflow water volume is 2.123 million m³.The total pollution load of BOD,COD,NH₃-N,TN,TP and SS were 53.71t,261.87t,5.54t,15.50t,1.78t,715.50t respectively.The area and confluence multiple of the confluence system are the main factors affecting the overflow frequency,water volume and total pollution load of Yuzhong District.（3）The impact of rainfall intensity on overflow water quantity and water quality was simulated and analyzed under the rain recurrence period of 1a,3a,5a,10a,30a and50a.The greater the rain intensity,the larger the overflow water volume and the early stage of overflow The higher the comprehensive pollutant concentration,the faster the decay rate and the lower the valley concentration.In the total CSOs pollution load,the total rainfall runoff pollution load accounts for 10%to 40%.The comprehensive concentration of various pollutants in the confluence system,the initial intercepted mixed sewage>dry stream domestic sewage>mixed sewage before the overflow>overflow sewage.（4）Comparative analysis of the pollution law before and after the current combined drainage system and the combined drainage system found that after the combined drainage system was reformed,the inflow of water increased by 163.76%,the total BOD pollution load increased by 1.10%,and the total COD pollution load An increase of200.20%,a total reduction of NH₃-N pollution load by 97.74%,a reduction of TN pollution load by 20.82%,and an increase of SS pollution load by 171.86%.The shunt system reform has a significant reduction effect on NH₃-N,TN and TP,NH₃-N is the most significant,and at the same time,the total pollution load of COD and SS increases significantly after the transformation.There are risks of increasing the pollution load by adopting the diversion system reform measures.The pollution load of the combined drainage system on the receiving water body is not necessarily higher than that of the diversion system.（5）Under the conditions of small and medium rains,the inflow of the sewage plant at the end of the combined drainage system shows a weak positive correlation with the rainfall intensity,and the trend of the influent pollutant concentration decline is not obvious.For heavy rains and rainstorms,due to the overflow measures taken by the sewage plant,the influent volume and rainfall intensity show a strong negative correlation,and the concentration of influent pollutants shows a declining trend with the increase of rainfall intensity.The effluent quality of the sewage treatment plant reached the standard throughout the year.（6）Consolidation Yuzhong District International Situation,Submission General Construction Jianchi District Subsurface Remodeling,Permeable Gluing,Green Sufficient Subdivision Construction of Submerged Green or Rainwater Garden,Municipal Road,Square and Commercial Area Rainwater Mouth Reform,Rainwater Inlet,Binjie Public Park,etc.Jiyuan Shukensa Pond or Shenzhen City,Shenzhen,formation"green color"sum"gray color"combination,source,middle halfway end terminal total flow diameter rainwater control bureau,effective term solution old city ward confluence overflow flooding problem.