摘要
膜污染是膜生物反应器系统在污水和废水处理应用中最主要的问题之一。针对这一问题,通过计算流体动力学(CFD)仿真模拟,研究了单个气泡以及气泡群在平板膜中的水力学特征,包括气泡速度和膜表面剪切应力等,以达到优化膜组件几何特征和运行条件的目的。模拟结果表明,对于单个气泡而言,随着气泡尺寸的增加,气泡上升速度开始随着直径的增加而升高,在气泡直径为4 mm时,其可达到最大值,随后随着直径的增加反而降低。此外,对于直径为4 mm的气泡,随着膜间隙距离的增加,气泡上升速度明显呈升高的趋势,而剪切应力呈现下降趋势。考虑到实际运行中的膜堵塞问题,建议在平板膜组件中使用7 mm的膜间距,以适当增强膜表面剪切应力。气泡群的模拟结果表明,当膜间液相上升流速较大时,气相和液相所产生的剪切应力相当。而当膜间液相上升流速较小时,气相产生的剪切应力占主导。以上研究结果可为膜生物反应器的设计及运行提供参考。
Membrane fouling is the major obstacle hindering the wide application of membrane bioreactors system(MBR) configured with different membrane modules in wastewater treatment. Aiming at this problem,the computational fluid dynamics(CFD) simulation was used to study the behaviors of single bubbles and bubble swarms during their rise in the membrane channel, such as the bubble rising rate and shear stress on the membrane surface, and achieve the goal of optimizing the geometrical characteristic module and operating conditions of the flat sheet membrane. The simulation results showed that for single bubble, its velocity first increased with the increase of bubble size(diameter), and reached the maximum value at the bubble diameter of 4 mm, then decreased when bubble size further increased. In addition, for bubbles with diameter of 4 mm, with increasing gap distance of membranes, the bubble rising velocity increased significantly, while the shear stress decreased. Considering the clogging problem in practice, it is recommended that a channel gap depth of 7 mm should be applied to the MBR system for the shear stress enhancement. The simulation results of bubble swarms indicated that the shear stresses in liquid and gas phases were close at high upwards flow rate, while the shear stresses in gas phase dominated at a relatively low flow rate. This work can provide the theoretical basis and technical support for the design and operation of MBR system.
作者
曹迎晨
SONNENBURG Alexander
URBAN Wilhelm
CAO Yingchen;SONNENBURG Alexander;URBAN Wilhelm(IWAR Institute,Technical University of Darmstadt,Darmstadt 64287,Germany;IWW Water Center Site Rhein-Main,Biebesheim 64584,Germany)
出处
《环境工程学报》
CAS
CSCD
北大核心
2020年第2期414-422,共9页
Chinese Journal of Environmental Engineering
关键词
CFD模拟
平板膜
膜污染
剪切力
单气泡
气泡群
CFD simulations
flat sheet membrane
membrane fouling
shear stress
single bubble
bubble swarms
