ADHESION OF WASTE-WATER BACTERIA TO REVERSE-OSMOSIS MEMBRANES

A stirred cell was used to study initial adhesion of three sewage bact eria belonging to the genus Pseudomonas to the three reverse osmosis ( RO) membranes BW30, PVD and CAB2, and the nanofiltration membrane NF45 . Membranes were immersed in suspensions containing 10(8) bacteria/ml for 10 min. All three strains were capable of rapidly colonising the f our membranes, but to different extents. It was found that bacteria wo uld sometimes aggregate upon adhering to particular RO membranes. The effects of solution ionic strength and pH, and conditioning of membran es (by prior exposure to filtrates of treated and untreated sewage) on the number of adherent bacteria were investigated. Minimal bacterial attachment occurred in a very low ionic strength milieu (deionised wat er). Salt concentrations corresponding to waste water and to twice tha t concentration resulted in significantly higher but statistically sim ilar numbers of attached microbes. Adhesion of he three isolates was n ot affected by pH in the range of 4-8. The number of bacteria attachin g to the membranes could be increased or reduced by conditioning films of sewage origin, conditioning films could also trigger or inhibit ag gregation of adherent cells. Some surface properties of the membranes (roughness, hydrophobicity) and bacterial cells (electrophoretic mobil ity, functional groups by affinity chromatography) were also investiga ted. (C) 1998 Published by Elsevier Science B.V.