曝气条件对浸没式膜生物反应器内流场的影响

为深入研究流场动力学特性对浸没式膜生物反应器系统内膜面污染的控制,应用fluent软件对浸没式膜生物反应器内气液两相流动进行了三维数值模拟研究。采用标准k-ε湍流模型和欧拉多相流模型,考察了改变曝气条件对膜面气液速度场及气含率分布的影响。模拟结果表明,在相同曝气强度下,1 mm曝气孔径下膜面气液两相的速度增加较孔径2 mm、3 mm的快;曝气孔径为1 mm时,膜面的液相速度随着曝气强度的增加逐渐增大;曝气孔径为1 mm时,曝气量为5.5 m3/h所形成的漩涡区较大,膜面气含率值较高且分布较均匀,气液两相接触面积较大,膜面冲刷效果较好;模拟观察到反应器底部靠近壁面局部气含率较低,不利于活性污泥中微生物的生长,需要进一步优化曝气和反应器结构。

Effect of aeration conditions on flow field in submerged membrane bioreactor

For further research on flow field dynamics of submerged membrane bioreactor system for control membrane surface pollution, a 3D numerical simulation of gas liquid two-phase flow was carried out by fluent software. The standard k-ε turbulence model and Euler multiphase flow model were used. The effect of changed aeration conditions in the reactor on the gas holdup and gas-liquid velocity distribution in the reactor was studied. The simulation results showed that the liquid and gas velocities of 1mm hole aerated at the membrane surface increased faster than 2 mm and 3 mm aeration holes at the 4.5 m3/h aeration rate. At the same aeration hole, with the increase of aeration rate,the liquid and gas velocities at the membrane surface increased. At the 1mm aeration hole and 5.5 m3/h aeration rate, the vortex area was larger and gas holdup was higher, gas and liquid were contacting well and the membrane surface scouring effect was better. The simulation also showed that local gas holdup was lower at close to the wall at the bottom of the reactor, which was not conducive to the growth of microorganisms, so it needs further study on optimizing the structure of aeration and reactor. The study laid a foundation on controlling membrane pollution of membrane bioreactor.