Filter Sheets continue to be widely employed in beer filtration, typically for particulate filtration (trap filtration following DE), fine filtration (polishing and bio- reducing) and final filtration for microbiological removal.
Sheet filtration provides excellent beer quality and flexibility, but lacks the security of a cartridge filter with a fixed pore structure. Therefore, constant attention to operating conditions is necessary to prevent system pressure shocks and potential microorganism unloading from sheet filters.
Filter sheets used in breweries consist primarily of cellulose, DE, and per lite bound by a food quality resin. Sheets exhibit both surface and depth filtration mechanisms, and may have a zeta potential for absorptive effects. Large solids are retained on the sheet surface, whereas smaller particles are caught in the tortuous path of depth media.
Sheets are available in various grades (nominal micron ratings) for the required level of clarity or bio-reduction, and may have different formats depending on equipment used.