Study On Pollution Characteristics Simulation And Control Scheme Of Fuzhou River Based On QUAL2K Model

With the large-scale construction of urban sewage treatment plants in China,the problem of tail water discharge from sewage treatment plants affecting the quality of water environment becomes more and more prominent.For the water shortage areas in northern China,tail water discharge into the river becomes an important source of ecological water resources,which makes the original river water environment pollution more complex.In this paper,the Fuzhou River in Dalian city is taken as the research object.The huitou River,a tributary of the river,receives the tail water discharge from the sewage treatment plant.Because of the joint effect of non-point source pollution and tail water point source discharge in the river basin,it is difficult to reach the standard for a long time.Starting from the basic water environment characteristics of the Fuzhou River Basin,combined with the water quality data of each monitoring section to diagnose the main water environment problems.Based on the distribution of pollution sources,the QUAL2K model is established.Through simulating the engineering effect under different scenarios,the comparison and selection of technical schemes for environmental treatment of Fuzhou river water are carried out,and finally the feasibility of the scheme is evaluated,and the research results will reach the standard of the river water environment quality affected by the tail water discharge of the sewage plant Construction provides theoretical and technical support.The main conclusions of this study are as follows:（1）According to the seasonal characteristics of Fuzhou River,in 2018,the water quality was analyzed by on-site sampling for three times of high,medium and low water quality.Five indexes,pH,TN,COD_Mn,NH₃-N and TP,were selected as the research objects to evaluate the water quality of Caifangshen Bridge section,Fuzhouwan Bridge section and Santaizi section of Fuzhou river.The results show that the three sections do not meet the class III standard of the target water quality surface water,and the exceeding factors are mainly NH3-N and TP.（2）Collect information on the emission situation of pollution sources and identify the sources and composition of pollution.Based on the collected the annals of statistics Data and remote sensing images,estimate industrial point sources in the basin,rural life,agricultural planting and livestock and poultry breeding of four kinds of main pollution sources of NH₃-N and TP into the river pollution load.（3）Choose QUAL2K model to simulate Fuzhou river water quality,according to the drainage basin and the distribution characteristics of the river,the outlet of calibration parameters were tested,and measured error in the process of simulation precision can keep in a certain range,NH₃-N and TP Nash coefficient were greater than 0.8,QUAL2K model works well for Fuzhou river,the QUAL2K model can be used to simulate the NH₃-N and TP migration transformation rule for Fuzhou river.（4）Based on the calibrated Fuzhou river model,under the specific design hydrological conditions and water function zoning objectives,the scenario analysis method is used to simulate the water quality impact of the tailrace diversion project on the main stream of the Fuzhou River in the study area.After the implementation of the project,the water quality of the downstream National control section does not meet the water quality objectives.The exceeding times of NH₃-N,TP at Santaizi are 1.09,2.41 respectively.The exceeding times of NH₃-N and TP are 1.36 and 1.77 at Fuzhouwan respectively.At the same time,the effect of different engineering or engineering combination measures on the water quality improvement of inflow river of the Dongfeng water reservoir is simulated and studied,and the pollutant reduction rate of different engineering scenarios is calculated.Compared with that,the tail water treatment+river ecological engineering scheme is the most appropriate solution.It can achieve the target water quality requirements and has better reduction effect,with low engineering cost and operation cost,and at the same time,it improves the reuse of reclaimed water resources Effectiveness.