Bacterial Adhesion and Fouling of Reverse Osmosis Membranes

Abstract

Adhesion of selected bacteria to cellulose actetate (CA) reverse osmosis (RO) membranes used in wastewater reclamation processes was investigated to determine its role in membrane fouling and reduced process efficiency. Adhesion of a Mycobacterium sp. previously isolated from an early stage of RO membrane biofouling was relatively unaffected by large variations in the ionic strength or pH of the buffer system. However, trace quantities of a polyoxyethylene ether nonionic detergent almost completely inhibited attachment. The mycobacteria were found to adhere to the CA membrane surface (or to a CA‐affinity column) approximately 25‐fold more effectively than a wild‐type strain of Escherichia coli The ability of Mycobacterium and E. coli to adhere to the membrane was correlated with their relative surface hydrophobicities as determined by their affinities for n‐hexadecane. A similar correlation was established between a hydrophilic wild‐type strain of Acinetobacter phosphadevorus containing a single 17.8 mega‐Dalton plasmid (PYG1) and a more hydrophobic isogenic derivative strain (P7P‐) lacking the PYG1 plasmid. Unlike the P7WT parent strain, the P7P‐derivative produced more fimbrialike appendages, which may account for its enhanced hydrophobic and adhesive properties. The results suggest that hydrophobic interactions between bacterial cell surface components and the CA membrane surface play an important role in the initial stages of bacterial adhesion and RO membrane biofilm formation.