Multi-objective Optimization Of Pollutant Discharge Amount At River Sewage Outlets Based On EFDC

As the contradictions between people's needs and environmental protection become increasingly prominent,environmental improvement and governance problems have gradually become the focus of social attention.During the"Thirteenth Five-Year Plan"period,the National Development and Reform Commission proposed to promote the construction of ecological civilization,in order to promote the realization of the integrated management of the water environment of the river basin,to adapt to local conditions,and to carry out the construction of related projects such as the comprehensive management of water environment in the river basin.The main cause of water pollution is the discharge of sewage into the river sewage outlet,so the optimization of the sewage outlet is very important for the protection of water resources and the improvement of water pollution.Therefore,applying scientific methods to deal with river water pollution is an important part of water pollution control.This article takes the long-polluted Ashi River as the research object,references the EFDC water environment model,and uses the analytic hierarchy process,water quality target method,and water environment capacity calculation method to formulate a pollutant discharge reduction plan,and analyzes the pollutant discharge at each sewage outlet.The response to the water quality of the Ashi River under the scenario of volume reduction simulation,finally came to a more effective scheme.First,establish the water environment model of the Ashi River,generalize the river channel to 23 boundaries including tributaries and discharge outlets,establish a hydrological model,use COD and NH₃-N as indicators to establish a water quality model,and verify with measured water level and water quality data.The results show that the simulation situation It is in good agreement with the actual situation,and the simulation results are more reliable.The development of the Ashi River emission reduction plan is based on three goals.First,the suitability assessment of the Ashi River centralized sewage outlet was used as the main research object.The results show that the Xinyigou Sewage Treatment Plant,Tuanjie Town Outlet,and the province The discharge level of the youth farm is poor;the second is to target the water quality of the monitoring section of the Ashi River,and the water quality of the main monitoring section of the Ashi River is analyzed.The results show that the section on the Xinyi Goukou does not meet the standards during the ice-sealing period.The water quality did not meet the Class IV standard,and there were inferior Class V water bodies in the cross-section of the Ashi River estuary throughout the year.Finally,the water environmental capacity of the Ashi River Basin in the ice-sealed,high-water,and flat-water periods was calculated,and the calculation result was COD of 7692.3 t/a,NH3-N is 978.98t/a.Compared with the pollution load,we can know that the pollution load in the outer area far exceeds the water environmental capacity.This article draws up three types of sewage reduction plans for the Ashi River,targeting eight centralized sewage outlets,non-point source pollution,and the heavily polluted tributary Dongfeng Gully.The targets are a single sewage outlet concentration,a single sewage outlet flow,multiple Sewage outlet combination schemes were developed and scenarios were simulated in the EFDC water environment model of the Ashi River.The results show that when the concentration of a single sewage outlet is selected for reduction,Option 1.4 is the best for the upper section of the Xinyi ditch mouth.The cross section of the Shihe Estuary is 1.10 as the best;when the discharge of a single sewage outlet is selected to reduce,the COD of the cross section on the Xinyi Gully is selected as the best of 2.3,and the NH3-N is the best of Scheme2.2.The COD of the cross section of the Ashi River Estuary is the best.The best solution for both NH3-N and NH3-N is 2.7;the combined reduction of multiple sewage outlets is better than a single sewage outlet.The research results have important practical significance for the integrated management and early warning of the water environment of the Ashi River,and can provide a reference for the supervision and water quality improvement of sewage outlets across the country.