The correlation between biofilm biopolymer composition and membrane fouling in submerged membrane bioreactors

Abstract

Biofouling, the combined effect of microorganism and biopolymer accumulation, significantly reduces the process efficiency of membrane bioreactors (MBRs). Here, four biofilm components, alpha-polysaccharides, beta-polysaccharides, proteins and microorganisms, were quantified in MBRs. The biomass of each component was positively correlated with the transmembrane pressure increase in MBRs. Proteins were the most abundant biopolymer in biofilms and showed the fastest rate of increase. The spatial distribution and co-localization analysis of the biofouling components indicated at least 60% of the extracellular polysaccharide (EPS) components were associated with the microbial cells when the transmembrane pressure (TMP) entered the jump phase, suggesting that the EPS components were either secreted by the biofilm cells or that the deposition of these components facilitated biofilm formation. It is suggested that biofilm formation and the accumulation of EPS are intrinsically coupled, resulting in biofouling and loss of system performance. Therefore, strategies that control biofilm formation on membranes may result in a significant improvement of MBR performance.

Keywords:

• biofouling
• cake layer
• biofilm
• transmembrane pressure
• co-localization
• extracellular polymeric substances

Acknowledgements

This research was supported by a research grant [MEWRC651/06/177] from the Environment and Water Industry Programme Office of Singapore. The authors also thank GE Singapore Water Technology Centre for providing the ZeeWeed 500 membrane.