Study On The Development And Application Of Water Environment Simulation Model Of Urban River Network Embedded With Purification Device Effects

Urban rivers are indispensable basic conditions for city development.However,rivers in cities are mostly closed water bodies with low water exchange and poor self-purification ability,which are easily affected by human activities.There are many kinds of urban river treatment technologies,and the mechanism and purification effect of various treatment technologies are also affected by many factors.Therefore,study on the purification effects of the membrane aeration biofilm reactor（MABR）-ecological floating bed combination device,the construction of the numerical simulation model of the river network water environment simulation model in the center of Tianjin city,is of great significance to the improvement of urban river water quality and the guarantee of high-quality living environment.Based on the national science and technology major project“Research and Demonstration of Integrated Control Technology for Linkage Water Purification of Haihe River Network”,this research took the river network in Tianjin as the research object,and explored the purification effects of the integrated device of MABR-ecological floating bed.The main research contents and results are:（1）Through the physical model experiment,the purification effects of MABR,ecological floating bed and its integrated device under different hydrodynamic conditions were studied.Considering the multiple pollutant indexes,the integrated device has the best purification effect in hydrodynamic water,and the ecological floating bed purification effect is relatively weak;the purification rate of NH₄⁺-N in the integrated device reaches its peak under hydrodynamic conditions of 20m/h,which is0.14 mg/（L·d）;for COD_Mn and TP,the purification rate reach the maximum under hydrodynamic conditions of 10 m/h,respectively to be 0.2 mg/（L·d）and 0.024mg/（L·d）.（2）Based on the St.Venant equations and the one-dimensional transport-diffusion equation,the relationship between the purification rate K of the integrated device and the flow velocity and the pollutant concentration was embedded in the one-dimensional river hydrodynamic-water quality model.According to the situ-survey and monitoring of the river network in Tianjin from April 2018 to August 2019,the current water quality situation of river network was analyzed.In the dry season（October-May）,the water quality in Tianjin could basically meet the national standard,while in the rainy season（June-September）,the water quality is generally V or worse,especially the NH₄⁺-N and COD.Based on this,a numerical simulation model of the river network water environment of the center of Tianjin was established,and the water network model of the river network was verified by the continuous monitoring data of water quality in May 2015.The verification results were good.（3）Aiming at the water quality problems in the river network of Tianjin,the research area was divided into 6 areas according to the situation of river communication,water quality change and flow rate distribution.The water circulation process and pollutant concentration changes under various types of control strategies such as the deployment of purification devices were simulated.The results showed that the scheme of small-flow cooperated with purification device has the smallest water consumption of 3.6 million m³,which could save 2.1 million m³ compared with the scheme of large-flow.The optimal layout scheme of the purification device for seriously polluted river network was proposed according to previous study.