Research On Improvement Of Urban River Water Quality Based On Multi-stage Constructed Wetland Of River Bypass Based On MIKE11 Model

In order to explore the effect of setting up river bypass artificial wetland to improve the water quality in urban rivers without water supply source,this study selected the Nanfei River,a heavily polluted tributary of Chaohu Lake,as the research object,and based on the analysis of the water quality and hydrodynamic characteristics of the river channel from the Dongpu Dam to the Nanfei River Bridge section,and according to the requirements of water quality improvement,the MIKE11model was used to establish a water quality hydrodynamic model for the river section,and the effects of different river bypass artificial wetland scales,wetland locations and wetland combination schemes on the improvement of river water quality were simulated and tested.Mastered the evolution of COD and NH3-N of major pollutants along the river,and analyzed the effect of simulated water quality improvement.The following are the main contents and conclusions of the study:?1?Using the hydrodynamic module?HD module?of the MIKE11 model to simulate regional flow and water level data and compare with the measured data.The simulation results show that the relative error between simulated flow and measured flow of Hefei station is 3.22%,and the relative error between simulated water level and measured water level of rubber dam is 6.31%.The simulation results are in good agreement with the measured data,indicating that the model can accurately reflect the hydrodynamic changes in the river section of the study area;?2?Using the convection-diffusion module of the MIKE11 model to simulate the concentration distribution of COD and NH₃-N pollutants in the area,and select Xixinzhuang as the model verification section to compare with the measured data in2015.The simulation results show that:two pollution factors The relative errors are8.89%and 11.42%,respectively.The simulation results are in good agreement with the measured data,indicating that the model can fit the temporal and spatial evolution of pollutant concentration within a reasonable error range.?3?By applying the MIKE11 model to simulate the effect of bypassed constructed wetland scale,wetland location and wetland combination scheme on the improvement of polluted river water quality,the Nanfei River is the research object,and the simulation results show that:when the river bypass artificial wetlands are set at points 1,2 and 3,respectively,and wetland daily processing capacity is 100,000cubic meters,the water quality improvement effect is better,and it's can reduce COD and NH₃-N average concentrations by 13.71mg·L^-11 and 4.06mg·L^-1,respectively,and the reduction rates are 35.60%and 70.72%,and the COD concentration of 100%of the river sections in the Nanfei river research area can reach the Class IV water quality standard,the NH₃-N concentration of 45%of the river sections reaches the Class IV water quality standard,and the NH₃-N concentration of 75%of the river sections reaches the Grade V water quality standard.?4?According to the MIKE11 model,the simulated pollutant concentration along the river is analyzed,and the influence of the scale of the constructed wetland,the location of the wetland and the wetland combination on the water quality improvement is studied,and it is possible to determine the best planning method for polluted urban inland river bypass constructed wetlands.It can broaden the new ideas for the application of the MIKE11 model,provide a basis for the water treatment of the Nanfei River,and provide a reference for the river pollution control of similar rivers,especially those without water supply source.