Study On Water Quality Standard Scheme Of Qing’an River Based On MIKE11 Water Quality Model

Small and medium-sized rivers are most closely related to the quality of human living environment,and are also carriers of water environment that are easily disturbed by human activities.Point source and non-point source pollution directly affect the water environment quality and river health.This study aimed at Qing’an river channel water pollution characteristics and hydrodynamic features,using the model of river health to Qing’an river channel health index evaluation,on the basis of convection diffusion module（AD）and based on the hydrodynamic module（HD）built Qing’an river channel quality evolution model,application of the model analysis of the distribution of TP and ammonia nitrogen of clear ain,Different measures such as cutting off pollution from industrial pollution sources,urban household pollution sources and simple treatment of agricultural non-point source pollution sources along the belt and roAD,improving the discharge standards of sewage treatment plants,and comprehensive treatment will be taken to compare the changes in water quality,so as to provide the best scheme for water quality control up to standard.The research contents and main conclusions are as follows:（1）The HD model was used to establish the hydrodynamic model of the river,and the measured data of river depth and flow in 2020 were used to ADjust the bed roughness parameters;The model parameters were corrected by using the measured data of the section downstream of the second sewage plant and Huai’an Agricultural School.The simulation results show that the relative error of water depth downstream is 3.92%.The relative error of Huai’an agricultural school flow is 1.19%.Therefore,the hydrodynamic model constructed in this study has a small error in simulating the hydrodynamic conditions of the Qing’an river channel,which can provide a dynamic basis for the further establishment of water quality model.（2）Based on HD model of Qing’an river channel,convection diffusion model（AD）was used to simulate water quality evolution of the reach,and the attenuation and longitudinal diffusion coefficients of ammonia nitrogen and total phosphorus were ADjusted.The model parameters were calibrated using the measured data of the downstream of the secondary sewage plant and the section of Huai’an Agricultural School.The simulation results show that the average relative errors of ammonia nitrogen and total phosphorus in the downstream section of the second sewage plant are 0.87%and 2.56%,respectively,and the average relative errors of ammonia nitrogen and total phosphorus in the Huai’an Agricultural section are 1.89%and 3.25%,respectively.It can be seen that the simulation evolution and measured values of water quality in the Qing’an river channel have small errors,and the AD model is more accurate.（3）The water quality model established by MIKE 11 was used to predict the treatment effects of different water quality control measures for point source and non-point source pollution along the Qing’an river channel.According to the objective of water quality improvement in Qing’an river channel,the model simulation shows that the effect of scheme 3 is better than that of the other two schemes.Scheme 3 could decrease the concentration of ammonia nitrogen by 10.42 mg/l and 0.37 mg/l in average during the flood period,with a reduction of 64.9%and 52.6%,respectively,and could decrease the concentration of ammonia nitrogen by 7.01 mg/l during the flood period,the reduction rate was 73.1%,and the concentration of total phosphorus was reduced by 0.75 mg/l,the reduction rate was 64.4%.The maximum lengths of ammonia nitrogen and total phosphorus that meet the requirements of class IV water in the simulated river reach in the normal water period account for 86%and 21%of the total length,respectively are 82%and 0%.It is concluded that the results of this study can provide technical support for the prevention and control of water pollution in the Qing’an river channel basin,and provide reference and basis for the decision-making of the comprehensive river control project.