Research On Aerator Arrangement Of Aeration Tank Based On CFD-PBM Coupling Model

With the rapid increase in China’s urban population,the discharge of domestic and production sewage has increased year after year,and the problem that a large amount of sewage needs to be treated to meet the standards and then discharged has become more serious.As an important facility for secondary treatment of wastewater,the operation of the aeration tank has a great impact on the treatment effect of wastewater.In this paper,the Euler-Euler multiphase flow model,the standard k-εturbulence model and the PBM model are used to numerically simulate the gas-liquid two-phase flow in the aeration tank of a university water station,and the following conclusions are obtained by comparing and analyzing the flow field parameters in the aeration tank with the simulated values on the surface of each characteristic section under different discharging conditions of the aerator,and get the following conclusion:(1)Model validation I concluded that the selected Euler-Euler multiphase flow model and the standard k-ε turbulence model and bubble size coupled PBM model are suitable for simulation studies of aeration basins,and both model validation II and model validation III selected the previous models for numerical simulation studies of two external aeration basins,and the simulation results are in good agreement with the experimental results.Thus,it was verified that the selected models have general applicability in the numerical simulation of the aeration basin.(2)When the aerators are arranged in four rows at the bottom of the aeration basin,the flow patterns on the characteristic sections of the aeration basin are almost unchanged,and more circulation zones are formed than in the other two conditions.(3)By comparing the gas volume fraction clouds on the characteristic sections at different heights,the gas distribution is wider when the aerators are arranged uniformly in four rows at the bottom of the aeration tank than under the other two conditions,so it is considered that this aerator arrangement is more favorable for oxygen transfer.(4)By comparing and analyzing the liquid vertical velocity clouds of different height characteristic sections under different working conditions,it can be seen that when the aerator is divided into four rows and evenly arranged at the bottom of the aeration tank,the liquid vertical velocity on the characteristic section is the largest,the no-flow velocity zone is the smallest,and the liquid phase flow velocity inhomogeneity coefficient is also the smallest,which indicates that this arrangement method has a better effect on the sewage mixing in the aeration tank and can better prevent the activated sludge from settling.(5)Comparing the average turbulence parameters in the aeration tank under different working conditions,the average values of turbulent energy and turbulent energy dissipation rate are greater when the aerators are arranged in four rows uniformly at the bottom of the aeration tank.This indicates that the turbulent flow in the aeration tank is more intense and more oxygen enters the effluent under the condition one aerator arrangement.