Pseudomonas aeroginosa is a potential coloniser of water system networks and is similar in size to E-coli. Ceramic filters will therefore reduce this bacteria much the same as for E-coli. However, since this organism is rapid growing and may recover quickly, a <99.99% barrier maybe insufficient. A limited number of cells may pass through the filter which, unlike E-coli, may form colonies downstream of the filter. It would be best to combine filtration with a ultra-violet disinfection stage to ensure removal of Pseudomonas aeroginosa.