Microfilters

Microfilters are filtration devices or membranes designed to remove small particles from liquids or gases. They operate with pore sizes typically in the range of 0.1 to 10 micrometers, enabling retention of suspended solids, colloids, and many bacteria while allowing water and smaller dissolved substances to pass through. Microfiltration is widely used as a pretreatment step before more fine filtration processes such as ultrafiltration, as well as for direct clarification tasks.

In liquid systems, microfiltration is usually pressure-driven and can be configured as dead-end filtration, where the feed passes perpendicularly through the membrane, or crossflow (tangential) filtration, where the feed flows parallel to the surface to reduce fouling. Membrane modules come in several configurations, including cartridge filters, hollow-fiber assemblies, and flat-sheet membranes housed in plate-and-frame or spiral-wound formats. Common membrane materials include polymers such as polyethersulfone, polysulfone, cellulose acetate, polypropylene, and PVDF, as well as ceramic variants used in more demanding applications.

Applications span municipal and industrial water treatment, beverage and dairy processing (clarification of juices, wine, beer, and milk), pharmaceutical and biotech manufacturing (clarification of cell cultures and fermentation broths), and laboratory filtration for research and quality control. Microfilters are valued for relatively high flow rates, compatibility with cleaning-in-place and sterilization-in-place procedures, and the ability to operate at moderate pressures.

Limitations include membrane fouling and the need for pretreatment to extend life, membrane integrity monitoring, and the handling of concentrate waste. Selection of pore size, membrane material, and module design depends on the intended fluid, contaminant profile, and operating conditions.