Compressibility of Membrane Bioreactor Sludge: Modelling Cake Build-up and Specific Cake Resistance

Membrane bioreactors (MBRs) are applied for municipal wastewater treatment with advantages such as high effluent quality and low footprint. However, membrane fouling is inevitable even at low fluxes. This study aims to provide a deeper understanding of fouling mechanisms and filter cake characteristics based on modeling and results from both full, pilot and lab-scale MBRs. It has been found that MBR sludge is highly compressible and applying this knowledge enabled modeling of the cake build-up and changes in specific cake resistance in MBR systems with both synthetic and real wastewater feed. Thus, the established model might enable optimization of operation parameters such as pressure level and relaxation frequency from lab-scale experiments with the same sludge and feed conditions.