3. Porous membrane separations

3.1 Microfiltration

Separation by microfiltration (MF) concerns particles that are generally non-settleable, but whose size is greater than 0.2 to 0.5 µm. Values differ from one author to another, but in practice, microfiltration membrane separation operations are encountered when clarifying a medium, seeking to remove colloidal and particulate matter, prior to use or post-treatment of the medium (e.g. by chromatography, fermentation, enzymatic reaction or other). Another major application of this technique concerns the ability of microfiltration membranes to retain micro-organisms such as bacteria: the permeate flowing down the low-pressure side of the membrane contains very few bacteria (log reductions of 6 to 8 are observed, depending on the micro-organisms observed, the type of...