Research On Optimal Regulation Strategy Of Urban River Inlet Based On MIKE21

2021 is the beginning of the"14th Five-Year Plan"development plan,which points out that it is necessary to further fight the battle against water environmental pollution and continue to improve the goal of water environmental protection.With the increase of the intensity of environmental governance in China,the emission of pollutants has been controlled to a certain extent,but its total amount is still at a high level.The rational setting and scientific management of outfalls are crucial to the health of the regional water environment.The arbitrary setting of outfalls in rivers,lakes and reservoirs poses a serious threat to the safety of water supply,the health of the population and the protection of water resources in the region.In this thesis,the outfall of the sewage treatment plant of Yancheng City,Jiangsu Province,is used as an example to propose a strategy for the optimal regulation of the river outfall,using numerical simulation as the main technical method.Firstly,the basic situation of the study area is investigated and analysed,and the current situation of the river outfalls is investigated.Secondly,the MIKE21 model is used to simulate and analyse the possible environmental risks of the proposed river outfalls,and to study the optimal control strategy of the river outfalls,which provided a reference for the scientific management of the sewage outlet,which is of great significance to the improvement of water environment,water ecological quality and water resources protection.This thesis mainly including the following results and conclusions:（1）Based on the information collected from the study area,we understood the basic overview of Xinyang Port and the actual and planned discharges of the outfall,and clarified the treatment process after the completion and operation of the sewage treatment plant and the discharge standard of the effluent from the outfall;according to the water function zone assessment requirements of the river section where the outfall is located,two inlet pollutants,COD and NH₃-N,were selected as predictive indicators.（2）According to the model comparison and combined with the actual situation of the study area,the MIKE21 model was selected as a simulation tool.The model was validated by using the topographic data,river cross-sections and hydrological data collected from local environmental protection departments,and the key parameters that determine the accuracy of the model were verified based on the measured data,and the accuracy of the model results was evaluated by introducing the Nash coefficient.The results show that the model simulation results fit well with the measured results,which proves the applicability of the MIKE21-based outfall pollutant prediction model,and lays a good foundation for further simulation work in the following.（3）On the basis of the sewage outlet planning scheme,two kinds of sewage outlet optimization and control schemes are formulated,and the MIKE21 model is used to explore the changes in the impact of pollutants discharged into the downstream under the conditions of normal discharge of sewage outlets and accident discharge under the conditions of the dry period and the flat water period from the perspective of changing the location of sewage outlets and reducing the concentration of discharges,extracts the simulation results of sewage outlet discharges under each scheme and compares them,and analyzes the changes in the influence trend of pollutants entering the river on the water quality of downstream water bodies under each scheme.The results showed that both schemes had a certain improvement effect compared with the planned schemes,and the method of reducing the concentration of pollutants entering the river by increasing surface flow wetlands works better.