Study On Emission Reduction Of Black And Odorous River Pollution Source Based On WASP8

With the development of society and urbanization,higher and higher demands are being put on rivers,significantly increasing the degree of river development.However,many urban rivers are black and odorous perennially or seasonally.It has become one of the most common problems torturing in the urban water environment of China,seriously affecting the city image and ecological environment.In the next stage of urban development,how to solve the problem of black and odorous water body has become both the key point and a difficult one.Eliminating urban black and odorous water body is a systematic process,and it is necessary to propose targeted pollution reduction and treatment programs according to regional differences and their respective pollution status.Therefore,this study selects the Tianjin Beitang Sewage River as the research object,which is especially black and odorous among the problem-plagued rivers.Based on the WASP8model,the study simulates the river channel pollution indicators?COD,BOD,NH₃-N,TP,DO?.Based on the model results and the pollution index evaluation standard,a reverse analysis is conducted to obtain the emission reduction control target of the Beitang Sewage River and the river's water environment capacity is calculated.The model is then combined with the TMDL program,and,according to different grade standards,pollutant load reduction and distribution is proposed.In addition to these,the author also puts forward some management suggestions for addressing the pollution problem in the thesis.The main findings are as follows:1.Based on the survey of pollution source and historical documents,the point source pollution load is calculated,and the non-point source pollution load is calculated through the basin loss output coefficient model.The calculation result of point source pollution load is COD=1741 kg/d,BOD=1546 kg/d,NH₃-N=486 kg/d,TP=219 kg/d,and the calculation result of non-point source pollution load is COD=248.86 kg/a,BOD=253.97 kg/a,NH₃-N=344.0kg/a,TP=360.7 kg/a.2.Based on the historical data and documents of the Beitang Sewage River,a WASP model is established with DO,TP,NH₃-N,COD_Mn and BOD₅ as the indicators.The relative error of the model is between 1%and 20%,which can meet the accuracy requirement on the model.Based on the model simulation results,the prediction on the pollution index causing the Beitang Sewage River black and odorous in 2018 is made.According to the prediction result,the pollution has seriously exceeding the standard,especially the COD,which is 3-4 times higher than the standard.3.Based on the established model,a scenario simulation analysis is carried out.The scenario design adopts the enumeration method,with the initial reduction rate setting at 50%,and the step length at 10%.The scenario simulation results show that after reducing the pollution load by 50%,the whole river section is still substandard,especially the COD,which is higher by 1-2 times.After reducing the pollution load by 80%,the 50%-100%of the indicators can meet the standard.After reducing the pollution load by 90%,90%-100%of the indicator can meet the standard.4.Based on the model,the study selects ammonia nitrogen,total phosphorus,BOD,COD and DO as the control factors.According to the standard of black and odorous water body index of Tianjin City,the author adopts the trial and error method to calculate the water environment capacity of the Beitang Sewage River.The calculated water environment capacity is COD=55t/a,BOD=59 t/a,NH₃-N=20 t/a,TP=12 t/a respectively.5.Combining the model with the TMDL program,the author conducts pollutant load reduction and distribution at different levels?standard for black and odorous water body,surface water environmental quality standard VI level,V water quality standard?for the Beitang Sewage River.The results show that the COD reduction rate is between 78%-90%,the BOD reduction rate is between 86%-89%,the NH₃-N reduction rate is between 87%-96%,and the TP reduction rate is between 83%-93%.6.According to the current situation of the Beitang Sewage River and the combination of the model and the TMDL program,some management suggestions for the Beitang Sewage River are proposed:the management system and management measures should be improved,such as reducing the emission of pollutants from the pollution sources;engineering restoration measures should be carried out,such as re-aeration,microbial remediation,aquatic phytoremediation technology,ecological floating island,land treatment,etc.