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CFD simulation of gas-liquid-sludge three-phase flow in membrane bioreactor

Authors： LI HuiQiang, LIU Qiao, WANG Qing, XU Nong, DONG Qiang, DING AiQin, FAN Long

Units： 1 School of Energy, Materials and Chemical Engineering, Hefei University, 230601, Hefei 2Stage Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, 100190, Beijing 3Nanjing Tech. University, State Key Laboratory of Materials-Oriented Chemical Engineering, 211816, Nanjing

KeyWords： gas-liquid-solid three-phase flow; computational fluid dynamics; membrane bioreactor; sludge sedimentation

ClassificationCode：TQ028.5, O359

year,volume(issue):pagination： 2023,43(2):138-149

Abstract：

The gas-water-sludge three-phase flow in an aerated membrane bioreactor (MBR) is simulated using computational fluid dynamics software FLUENT. The activated sludge is treated as a single phase. Not only the flow and the distribution of gas in the reactor are obtained, but also the hydrodynamics and settling characteristic of sludge are presented. The possible area for sludge settling, i.e. the consequent membrane pollution area, is provided. Furthermore, the effects of aeration bubble diameter, aeration area, and aeration location on the flow and sludge sedimentation are investigated. Both the operation conditions and the reactor structure are optimized to minimize membrane pollution. In the simulated range, the potential to have membrane fouling is minimal when the distance between the aeration surface and the bottom of the membrane unit is 350 mm, the width of the simplified aeration surface is 2 mm, and the bubble diameter is between 4-6 mm. Since the data for gas-liquid-solid three-phase flow in MBR are scarce, the gas-liquid two-phase flow is simulated for the purpose of verification. The mixture of water and sludge is treated as one single liquid phase. The comparison of two-phase simulation with literature proved the reliability of the simulation method and results.

Funds：

安徽省重点研究和开发计划项目（2022a05020041）；安徽省教育厅重点项目（KJ2021A1015，KJ2020A0669）；中国科学院过程工程研究所生化国家重点实验室开放基金项目；南京工业大学材料化学工程国家重点实验室开放基金项目（KL21-04）。

AuthorIntro：

李会强（1996—），男，安徽霍邱人，硕士研究生，研究方向为计算流体力学。E-mail：lhqstu127@163.com

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