Numerical simulation of membrane bioreactor hydrodynamics

Abstract

Computational Fluid Dynamic (CFD) is becoming more advanced with a wide range of capabilities to simulate most real-life applications. This study focuses on the hydrodynamic characteristics of a Membrane bioreactor (MBR) using a simplified form of a Bubble column reactor (BCR) model. Results obtained from this project will be used to explain and validate observations obtained from previous research.

The BCR model consists of an air sparging inlet situated at the central bottom of the column and a membrane placed at the radial centre of the column at two location heights of 0.3m and 0.6m. GAMBIT is used to pre-process and prepare the model, which is simulated using FLUENT. Multiphase mixture model and the realisable k–ε turbulence model are used. This project aims to build on the previous work by revising the model construction particularly by modifying the membrane module from Block to Fibre structure and cross-examining the data from the current Fibre model with that of the previous Block model.

Both graphical data and numerical results are obtained and examined. The Fibre model data and the Block model data generally follow the same trend except the TKE against air flow rates and the air fraction profile along the x-axis. Difference in membrane position is observed to have significance on flow pattern across column height. Preliminary data validation shows great potential in the improvement brought by the Fibre model. It is strongly recommended that detailed cross-examination of the current data with the experimental data and porosity characteristics to be done in the future to improve on the existing model and increase the CFD modelling accuracy.