Do biological-based strategies hold promise for biofouling control in membrane bioreactors?

Biofouling in membrane bioreactors (MBRs) remains a primary challenge for their wider application.
Biofouling in membrane bioreactors (MBRs) remains a primary challenge for their wider application.

Membrane bioreactors (MBRs) are now broadly applied as wastewater treatment technology that combines membrane processes and suspended growth bioreactors. However, biofouling in MBRs remains a primary challenge for their wider application, despite the growing acceptance of MBRs worldwide.

Research studies on membrane fouling are extensive in the literature, with more than 200 publications on MBR fouling in the last three years. But improvements in practice on biofouling control and management have been remarkably slow. Commonly applied cleaning methods are only partially effective, and membrane replacement often becomes frequent.

This slow progress in successful control of biofouling is largely attributed to the complex interactions of the biological compounds involved, and the lack of representative-for-practice experimental approaches to evaluate potential effective control strategies.

Biofouling is driven by microorganisms and their associated extra-cellular polymeric substances (EPS) and microbial products. Microorganisms and their products convene together to form matrices that are commonly treated as a ‘black box’ in conventional control approaches.

Biological-based antifouling strategies are a promising constituent of an effective integrated control approach, since they target the essence of biofouling problems. However, biological-based strategies are still in their developmental phase, and several questions need to be addressed to set a roadmap for translating existing and new information into sustainable and effective control techniques.

This review paper – by an international team in Saudi Arabia, Australia, The Netherlands, and Lebanon – investigates membrane biofouling in MBRs from the microbiological perspective, to evaluate the potential of biological-based strategies in offering viable control alternatives.

The limitations of available control methods highlight the importance of an integrated antifouling approach including biological strategies. Successful development of these strategies requires detailed characterisation of microorganisms and EPS through the proper selection of analytical tools and assembly of results.

Existing microbiological/EPS studies reveal a number of implications as well as knowledge gaps which justify future targeted research. Systematic and representative microbiological studies, complementary utilisation of molecular and biofilm characterisation tools, standardised experimental methods, and validation of successful biological-based antifouling strategies for MBR applications are needed.

Specifically, in addition, linking these studies to relevant operational conditions in MBRs is an essential step to ultimately develop a better understanding and a more effective and directed control strategy for biofouling.

Water Research, Volume 47, Issue 15, 1 October 2013, Pages 5447–5463.