Research On The Theory And Practice Of Source Control And Pollution Interception Of Urban Water System

Our country has made remarkable achievements in the development of economic,construction of ecological civilization and other fields in recent years.However,for a long time,low-end manufacturing industry characterized by rough and labor-intensive has caused serious environmental pollution,especially in the aspect of water environment pollution.At the same time,the rapid urbanization accelerated the deterioration of urban ecosystem,reducing the self-purification capacity and water environmental capacity of urban water system.The prominent focus was that almost every city was facing severe problems of black and odorous water treatment.Therefore,from the point of view of system theory,this paper taked every link of urban water system as the research object,and then analysed the relationship between the change process of hydrological,the basic situation of hydrodynamics,the change rule of water environmental quality,the evolution of water ecosystem and the change of water environmental capacity.Based on the mathematical model of the water environment,the research object was simulated and analyzed.The basic theory and key elements of source control and pollution interception of urban water system were explored by comparing the actual data,it is intended to provide theoretical reference for the source control and pollutant interception,original clean-up and ecosystem reconstruction(sponge city construction)of urban water system,providing the preliminary tentative research on the improvement of the scientificalness and accuracy of comprehensive control of urban water environment,the ecology and compatibility of sponge city construction(shore and water),the healthy development of environmental capacity of urban inland river and river basin systems.Based on the theroretical study of water environment capacity and source control and pollutant interception,this paper analyzed water environment and pollution source load in Yangshe town,Zhangjiagang comprehensively,a mathematical model of the water environment in the study area was established by using the rainfall runoff module(NAM),hydrodynamic module(HD)and convection-diffusion module(AD)of MIKE11 model.Besides,the parameters of the model were calibrated by using the measured data of section water level,flow rate and water quality in the study area,and the spatial and temporal distribution rules of CODMn and ammonia nitrogen in the downtown water system of Zhangjiagang were mastered.In the end,the improvement effect of water quality and water environmental capacity of the river that optimized by source control and pollutant interception and sewage treatment plant upgrade can be simulated and predicted.The study results show that:(1)The MIKE11 model has good practicability for the simulation study of the river channel in the study area,and can reflect the actual hydrodynamic and water quality changes.For the rainfall-runoff module and the hydrodynamic module,the relative error of water level simulation and the Nash-Suttcliffe coefficient are 6.4%±4.2%,0.864~0.882,and the relative error of flow simulation and the Nash-Suttcliffe coefficient are 4.8%±3.2%,0.874~0.896,respectively.For the water quality module,the average error range of CODMn is 10.3%~14.5%,and that of ammonia nitrogen is 9.2%~13.7%.(2)The water environmental capacity formula method based on MIKE11 model,comprehensively considers hydrological conditions,current water quality,rainfall runoff,self-purification of pollutants,etc.,which more objectively reflects the dynamic characteristics of water environmental capacity.The water environmental capacity of COD and ammonia nitrogen in the study area showed a certain rule,that is,high water period >middle water period >low water period,and the water environmental capacity of the lower reaches of some rivers was higher than that of the upper and middle reaches.(3)Different treatment schemes have different improvement effects on the water environment of the river,among which source control and pollutant interception is the key to improve the water quality and water environment capacity of the river.When the initial rainwater interception time is 30~40min,the concentration of CODMn in the river decreases by 21.97%~28.16%,the concentration of ammonia nitrogen decreases by 18.91%~25.07%,and the COD capacity of water environment increases by 30.52%~38.44%.The increase range of ammonia nitrogen capacity of water environmental is 24.79%~31.92%.At the same time,more than 70% of the river reaches the water quality target can be achieved through controlling source and intercepting pollution and upgrading of sewage treatment plant.This study can provide reference and basis for decision-making of comprehensive improvement of urban water environment.