ABSTRACT
Treatises on the filtration of liquids with the objective of achieving a sterile effluent are
typically replete with detailed discussions of the physical and chemical characteristics of
filters and the various mechanisms at play in retention. Rarely does one find a careful
consideration of the microbiological considerations of filtration in spite of the simple
truth that the retention of microorganisms is a nearly all-consuming component of the
filter validation exercise. It must also be said that “sterility” of the effluent is arguably the
aspect of filtration that receives the greatest regulatory scrutiny both in product dossier
review and in plant inspection.
