Low-pressure membrane filtration for removing Giardia and microbial indicators

Low pressure ultrafiltration at 10-40 psi, using hollow fibre membranes, was evaluated as a means of removing micro-organisms from water. Pilot studies on 4 different source waters were undertaken. Their quality differed considerably; turbidity was 0.46-9 ntu and TOC 0.9-3.6 mg per litre. Natural bacteria were monitored in addition to added MS2 virus, total coliform bacteria and Giardia muris. No viruses or coliform bacteria were detected in permeates and G. muris was removed to better than 99.99 per cent. In all, there was a 6 logs removal of MS2 virus and 4 logs removal of G. muris. Performance deteriorated if any fibres were broken, as diagnosed by a standard air percolation test. Particle counting proved to be more sensitive than turbidity in monitoring performance. There are 41 references.