The CFD Analysis of Internal Flow Field Characteristics in a Membrane Bioreactor

Hui Jia, Zhiwei Ding, Yi Wu, Anhu Dang, Xianhui Li, Jie Wang



In this study, the characteristics of internal flow field in a membrane bioreactor (MBR) under different aeration intensities were investigated in membrane filtration & cleaning operation model by using the method of computational fluid dynamics (CFD) three dimensional simulations. The effects of different air/water ratios (10:1, 15:1, 20:1) on the membrane cleaning process were analyzed. The results showed that the shear force on membrane surface as well as the circular velocity was the greatest and the vortex was the most obvious when air/water ratio was 15:1. And the smaller interval of shear force on membrane surface was helpful to control the aeration intensity and alleviate the asymmetrical fouling of membrane fiber. Furthermore, the characteristics of the internal flow field in membrane filtration process were investigated at the optimal aeration intensity when the air/water ratio was 15:1. It demonstrated that the position of water inlet affected the internal flow field of the MBR. In the middle position of the MBR, the vortex was bigger, the streamline was more intensive and the velocity was higher. Asymmetrical fouling of membrane fiber was caused by the asymmetrical flow. Overall, the MBR could be optimized by changing the way of inlet water and the position of the membrane cassette.

Keywords: Computational fluid dynamics (CFD); membrane fouling; aeration intensity; membrane module; surface shear force