Proceedings

Membrane bioreactors (MBRs) are a recent innovation in wastewater treatment that combines a
membrane filtration unit with a biological process (Tchobanoglous et al. 2003).The focus of this study is
only on membrane filtration. It concentrates on the development of a mathematical model describing
filtration and fouling on micro-filtration membranes and this work is based on the earlier published model
by Liang et al. (2006). Initial modelling experiments with the Liang model showed its deficiencies at
predicting trans-membrane pressures over a wide range of membrane fluxes. A very basic structure of
this model and its behavioural character limit its applicability to only limited number of operational
regimes. In an endeavour to develop a more universal yet simple model, the Liang model has been
extended and modified to include: backwash mechanism, cake and SMP deposit compressibility effects,
various cake removal models (air scouring and cross-flow velocity) and flux dependent SMP deposition
rates. The model was developed in MATLAB/Simulink environment and validated on experimental data
from a flux stepping experiment performed on a pilot scale with a tubular crossflow 0.45m membrane. A
second validation exercise was performed on long-term filtration data from a membrane pilot plant
equipped with a hollow fibre 0.05 mm membrane. The model proved to be in good agreement with the
measurements in both validation studies.

Key Words
Cake, Filtration, Fouling, MBR, Modelling, Simulation, SMP, Wastewater