Analysis And Research Of MBR Sewage Treatment Characteristics Based On CFD

In the field of sewage treatment,membrane bioreactor(MBR)has been widely used for its advantages of strong treatment capacity,small footprint and low residual sludge.However,membrane fouling has always been an important factor limiting the efficiency and application of MBR treatment.Therefore.using CFD and Fluent software to carry out in-depth research on MBR wastewater treatment characteristics optimization has important practical significance for slowing down membrane fouling.This paper builds a membrane module simulation model based on computational fluid dynamics(CFD)method and using Fluent software.Using simulation model to analyze the processing characteristics of MBR wastewater treatment process and adjust the operating conditions and parameters of the MBR system to improve the treatment effect of MBR and improve the efficiency of membrane fouling treatment.First of all,this paper summarizes the mechanism and types of MBR membrane fouling.inductives influencing factors and main control methods for MBR membrane fouling and tease out the flow characteristics and membrane flux distribution characteristics of membrane modules in MBR.According to different MBR fluid research objects,a variety of MBR calculation models and basic equations of fluid mechanics were selected.The MBR membrane module and single hollow fiber membrane tube were model built and meshed by Fluent software.Secondly,Fluent software was used for flux simulation and axial simulation of the established Membrane module CFD model.The shell movement characteristics were analyzed.Simulation results show that the lateral uneven flow of tube and shell in the hollow fiber membrane module could affect the efficiency of membrane fouling treatment.The CFD model of single hollow fiber membrane was axial simulated.The characteristics of membrane flux distribution were analyzed.Simulation results confirm that the flux distribution will affect the processing efficiency of hollow fiber membrane.When the flux of some membrane increases.high penetration index will increase.As a result,the membrane module produces transmembrane differential pressure throughout the whole.This pressure difference leads to an uneven distribution of flux in the membrane assembly.Therefore,the energy efficiency of membrane modules is affected.Finally,the boundary conditions of the hollow fiber membrane simulation model were set by Fluent software.The simulation method of simulate gas flushing first and then simulate hydraulic backwashing was adopted.Three different gas flushing speeds,0.156M/s,0.396M/s and 0.565M/s,were selected to analyze the movement of bubble flow in the reactor,the magnitude of the shear force on the membrane surface and the change of the flow field.The speed of 0.396m/s was determined as the optimal gas flushing speed.It is concluded that the lower part of the membrane filament is a region with high shear force.At this time,the bubbles are active in the lower part of the membrane module and could form higher shear force.Higher shear force can further improve the effect of pollution removal at the lower end of hollow fiber membrane.Simulation results prove that the inhomogeneity of shell motion and flux distribution of the membrane components can be reduced by using the cleaning method of gas flushing first and then hydraulic backwashing.The cleaning method of gas flushing first and then hydraulic backwashing could remove contaminants from the membrane surface more effectively,alleviate membrane fouling in hollow fiber membrane system and improve the pollution treatment efficiency of hollow fiber membrane.