A STUDY OF MEMBRANE FILTRATION FOR THE REMOVAL OF CYANOBACTERIAL CELLS

Low-pressure membrane filtration, particularly microfiltration (MF) an d ultrafiltration (UF), has received considerable attention recently a nd in some cases can be considered as an economically viable alternati ve to conventional water treatment techniques. In principle, membrane filtration appears to be an attractive method of algal removal. This i s because its removal efficiency should be less influenced by some raw water quality parameters which have an overriding influence on the pe rformance of other conventional treatment processes. In this study, a specially designed experimental flat sheet membrane filtration unit wa s employed to examine the removal of the toxic cyanobacterium, Microcy stis aeruginosa, which is commonly found in drinking water reservoirs. The study focused mainly on the effect of membrane filtration on the cyanobacterial cells. Two commercially available flat sheet membranes, MF and UF. operated under both dead-end (DE) and cross-flow (CF) mode s were evaluated. Measurements used to assess their effect included fl uorescence microscopy with fluorochromes to determine cell integrity ( total cell count and cell viability); and leakage of cell pigment (chl orophyll-a) and toxin (microcystin-LR) into the filtrate as an indicat or of eel membrane damage and release of cell metabolites. The results showed that only a small proportion of the cells were damaged by the treatment but there was no significant increase of toxin in the permea te with all modes of filtration.