Guo Xingfei, Wang Yaowu, Zhang Hongwei, Li Pengfei, Ma Cong
State Key Laboratory of Separation Membranes and Membrane Processes, Tianjin Polytechnic University, Tianjin 300387, China E-mail:
School of Environmental and Chemical Engineering, Tianjin Polytechnic University, Tianjin 300387, China.
Water Sci Technol. 2017 Sep;76(5-6):1283-1299. doi: 10.2166/wst.2017.228.
Membrane fouling has limited extensive applications for hollow fiber membranes in water treatment. Backwashing and air scouring can effectively solve this problem in the submerged outside-in hollow fiber membrane system. In this study, variation of the fouling layer on the membrane surface during backwashing and the impact of shear stress caused by air scouring on fouling removal were investigated through computational fluid dynamics (CFD) simulation. The backwashing and air scouring process were simulated using CFD and the results were verified by experimental studies. The results of experimental studies are in accordance with the simulation results. During the backwashing process, the velocity profile inside the reactor was presented, and visualization of the particle movement to illustrate the dynamic peeling process of the fouling layer on the membrane surface was also shown. The formation of uneven cleaning reveals that the upper region of the fibers has an excellent cleaning effect during backwashing. After that, the supporting role of air scouring was investigated in the study. It is concluded that the lower part and the middle region of the fibers suffer greater shear stress by analyzing the velocity contours and vectors, and the analysis results indicated that air scouring can further remove membrane fouling.
膜污染限制了中空纤维膜在水处理中的广泛应用。反冲洗和空气擦洗可以有效解决浸没式外压中空纤维膜系统中的这一问题。在本研究中，通过计算流体动力学（CFD）模拟研究了反冲洗过程中膜表面污垢层的变化以及空气擦洗引起的剪切应力对污垢去除的影响。利用CFD模拟了反冲洗和空气擦洗过程，并通过实验研究对结果进行了验证。实验研究结果与模拟结果一致。在反冲洗过程中，给出了反应器内部的速度分布，并展示了颗粒运动的可视化，以说明膜表面污垢层的动态剥离过程。不均匀清洗的形成表明，纤维的上部区域在反冲洗过程中具有良好的清洗效果。之后，在研究中考察了空气擦洗的辅助作用。通过分析速度等值线和矢量得出，纤维的下部和中部区域承受的剪切应力更大，分析结果表明空气擦洗可以进一步去除膜污染。
