The Model Of Swmm Applied In Chaohu City Of Zhuanchihe Regional Non-point Source Pollution Simulation Research

With the development of the city,as well as the increase of domestic environmental protection,the point source pollution of industrial emissions has been controlled and treated effectively.However,the issues of urban non-point pollution into rivers and other water bodies are becoming major pollution sources.Therefore,through the research of non-point source pollution,effective strategies on treating water body pollutions such as river would be provided.Under the background of this thought,Zhuanchihe area of Chaohu city is considered as the research object.Through the collection of related data of the region and the scholars at home and abroad for reference,based on the field survey of cumulative erosion characteristics of non-point source pollution load on Zhuanchihe area,as well as topography and rain etc.,model is generalized on Zhuanchihe area.Rainstorm management model?SWMM?software is utilized to establish the quantitative research on the water quality model for Zhuanchihe area in Chaohu city.The reliability of the model is verified by the observed runoff data of rainfall and the simulation of empirical coefficient.In this paper,the analysis of SWMM is applied in non-point source pollution load research in Zhuanchihe area,aiming to solve problems of pool water body pollutions.The main research contents are shown in followings:the application of analyzing and studying the urban rainstorm model-SWMM on calculation non-point pollution load;the establishment of non-point pollution load calculation model based on SWMM in Zhuanchihe;the usage of SWMM model on different rainfall intensity?different return period?and LID facilities settings of former and later conditions to analyze the whole process of rainfall runoff as well as the production,transfer and weaken of pollutant.By comparison with the data found that rainfall COD concentration to the water body of pool almost no effect,average concentration of COD water stay near 18 mg/L.For total nitrogen,total phosphorus and ammonia nitrogen has a larger effect,after the rain water,total nitrogen,total phosphorus and ammonia nitrogen concentration are larger,the water content of total nitrogen and ammonia nitrogen after the rain,no rain season is about four times the size of the total phosphorus content is 1.5 times when no rain season.Rainfall on the water pollution is the greatest influence nitrides.During the water simulation analysis of different rainfall intensities,it can be concluded that runoff into the river is increased with increasing rainfall intensity.The relationship between total runoff volume and rainfall intensity is positive,rather than linear correlation.In terms of different return period,the drainage flow is basically the same as the rainfall changes,and the rate of increased flow is much higher than that of rainfall changes.The soil becomes saturated in heavy rains.For the soil of absorbing early rainwater,the water infiltration rate could be reduced greatly leading to more runoff.The rate of early rain drain flow is small,0 min-15 min,almost no runoff has been produced;this is the time of generation and collection;With the increase of rainfall intensity,drain flow rate value is increased.About the period of 15 min-45 min after raining,the flow will be raised exponentially.Under different return period,the changes of sub-catchment area of pollutant concentration trend are basically the same as the rainfall.Under different rainfall conditions,the sub-catchment area of TSS,COD,TN,TP unit time period into the river pollution load changes is basically the same with the continuing of rainfall.The greater the rainfall intensity,the greater the unit time period into the river pollution load,the greater the rate of changes.In terms of the child catchment area of S5,TSS and COD achieve highest concentrations,however,S2,S3,S4,S6 has a minimum concentration of TSS and COD.For sub-catchment area of S1,TN and TP have highest concentration,while child water catchment area of S4has lowest concentration of TN and TP.Through the analysis of different catchment areas of land property,the reason that causes high concentration of TSS and COD is almost all residential land in sub-catchment area of S5,contributing to higher runoff coefficient.Sub-catchment area of S1 has the highest concentration of TN and TP S1 plot has a percentage of the farmland,farmland nitrogen and phosphorus in the material into the runoff result in higher peak concentrations of TN and TP.Child S6 first stop runoff catchment area,water catchment area of S5 finally stop stop time of runoff.This is because the S5 area far from outfalls,and the main land use is residential,runoff coefficient is larger.S6 region nearest outfalls,runoff coefficient compared to other small catchment area.Under low impact development?LID?facilities,through the analysis of water quality of water in 1 year once,once every two years,once every five years,10 years of rainfall intensity,set the low impact development?LID?after the facilities of ChiHe area into the river traffic and the peak flow into the river are produced more obvious control action.Once every LID facilities for 1 year and 2 years in a heavy rain amount into the river and peak flow effect is obvious.When the rainfall intensity increasing,to once every 5 years or even a decade,the LID facilities for the total into the river and the weakening of the peak flow ability decreased significantly.LID facilities of water storage ability is limited,when LID facilities meet once every five years,10 years a huge water in case of rain the LID facilities of water storage space is full,the LID facilities effect will be greatly reduced.Son to once a year of rainfall,water catchment area of S3 and S5for outfalls 2?O₂?LID facilities set before and after the TSS and COD concentration are in decline after rising first,and after the LID facilities of TSS and COD concentrations are below the LID facilities set before.Proof LID facilities the peel of the pollutants in rainwater has a certain effect,can reduce of rainfall in the area of non-point source pollution,reduce the pollution load into the river.Can draw the following conclusion:the rain mouth set LID facilities,such as the infiltration ditch can control to enter into the flow of the river also has a key role.At the same time,which can effectively reduce the pollution into the river,to solve the urban river water pollution provides a new direction.