Skim milk ultrafiltration with a PES membrane: Effect of milk thermal pretreatment and concentration on the irreversible fouling

摘要

The skim milk ultrafiltration (UF) is widely used industrially to standardize milk protein concentration before cheese making. These UF membranes are made of polyethersulfone (70% of the market for HFK 131, Koch) and are used on several consecutive stages. During production cycles the membrane is fouled with skim milk components. It leads to flux and selectivity decrease. To restore membrane performances, a chemical cleaning is performed at least once a day (2-3 h of cleaning every 6-8h of production). The irreversible fouling that remains after the water rinsing is the target of the cleaning. Cleaning procedures actually performed cannot avoid a decrease of about 50% of the production flux over several months nor sometimes an alteration of the membrane selectivity. This justifies the fundamental studies on cleaning optimization and the need of information on the nature of the overall and irreversible fouling.