Study On The Agglomeration Characteristics Of Biochemical Sludge In MBR Membrane Pool Based On DPM

Membrane bioreactor is a new sewage treatment device combining membrane separation process and activated sludge method.It is widely used in industrial,agricultural and urban sewage treatment fields because it can optimize water quality and produce water efficiently.However,the problem of membrane pollution is relatively serious,which has a great impact on the operation efficiency of membrane filaments.In this paper,the computational fluid dynamics software Fluent was used to simulate the solid-liquid two-phase flow characteristics in membrane bioreactor,and the hydraulic characteristics and particle movement rule near the membrane filament were studied,which has important guiding significance for further optimization of membrane components and improvement of membrane component operating efficiency.The main work is as follows:Firstly,a simplified model of the membrane component was constructed,and the hydrodynamic characteristics and regularities of particle motion near a single membrane filament were studied using the k-ε turbulence model,the porous medium model,and DPM discrete phase model.The results showed that the inlet location,inlet velocity,and length of the membrane filament had significant effects on the permeability of the membrane.By comparing different inlet height,inlet velocity and membrane component structure of different lengths,the best working conditions were obtained.When the inlet position was near the top of the membrane wire,the inlet velocity was 2m/s,and the length of the membrane wire was 250 mm,the liquid velocity of different height sections was evenly distributed and the turbulent kinetic energy fluctuation was obvious,and the particle concentration near the surface of the membrane wire was low.It is not easy to block the membrane hole in a wide range,which enhances the penetration effect of the membrane filaments.In order to better explore the law of solid-liquid two-phase flow between membrane filaments,a single membrane filament was expanded into a single row membrane filament structure for research.The results showed that appropriate membrane filament spacing had a very important influence on the enhancement of membrane flux.When the membrane filament spacing was too small,the liquid phase velocity and turbulent kinetic energy were not easy to flow into the gap region between membrane filaments due to the narrow flow channel space between membrane filaments.The scour effect in the gap area between membrane filaments was weak,leading to serious sludge particle accumulation in the area between membrane filaments,which was easy to block the membrane holes between membrane filaments,increased the membrane resistance,and reduced the antipollution ability of the membrane surface.When the spacing between membrane filaments was too large,the gap between membrane filaments was close to the width of membrane filaments,and a large number of sludge particles would adhere to the membrane surface,causing serious membrane pollution.Only when the spacing between membrane filaments was 4mm,moderate membrane spacing increases the flow channel space between membrane filaments,and liquid phase velocity and turbulent kinetic energy were distributed between membrane filaments,effectively scour the gap between membrane filaments.The accumulation of sludge particles on the surface of the membrane silk was less,which reduced the resistance of the membrane,improved the anti-pollution ability of the membrane surface,and was conducive to better enhancing the permeability effect of the membrane silk.Based on the single row of membrane filaments,in order to further studied the effect of the arrangement of membrane filaments on the solid-liquid two-phase flow law of membrane components,the single row of membrane filaments was amplified again to expand the multi-row membrane filaments structure.The results showed that,when the membrane filaments were neatly arranged and misaligned along the Y-axis,due to the influence of hydraulic conditions,The outer region of the membrane filament was easy to be covered by sludge particles,and the accumulation degree of particles is serious,which would increase the resistance of the outer region of the membrane filament,causing serious blockage of the outer region of the membrane filament,reducing the anti-pollution ability of the membrane filament and reducing the permeability of the outer region of the membrane filament.When the arrangement of the membrane filament was misplaced,the accumulation of sludge particles in the outer region of the membrane filament was less.Due to the effect of liquid velocity and turbulent kinetic energy between membrane filaments,the gap area between membrane filaments was scoured,and the concentration of sludge particles was low,which did not cause a lot of blockage of membrane holes between membrane filaments,which was conducive to enhancing the penetration effect between membrane filaments.When the direction of inlet was changed,the membrane component structure with different arrangement modes of membrane filaments along the X-axis was compared.When the arrangement mode was orderly,the liquid phase velocity and turbulent kinetic energy had a great influence on the membrane filaments only on the unilateral surface.When the arrangement mode of membrane filaments was changed to dislocation arrangement,the liquid phase velocity and turbulent kinetic energy had a great influence on the surface area between membrane filaments.However,due to the effect of turbulent kinetic energy,the local accumulation of sludge particles between membrane filaments was also relatively serious.However,by comprehensive comparison,the structure of misaligned membrane filaments was more conducive to enhancing the permeability effect of membrane filaments.