EVALUATION OF PROCESS MODELS FOR FOULING CONTROL OF REVERSE-OSMOSIS OF CHEESE WHEY

Long-term fouling of reverse-osmosis membranes processing dairy products can be caused by two phenomena: (1) an increasing thickness of the protein gel layer; (2) deposit formation due to precipitation of calcium phosphate/protein complexes. Mechanistic models describing these two phenomena are evaluated for a tubular reverse-osmosis pilot-plant for concentrating cheese whey during a 20 hour period. The experimental variables were the initial pressure after start-up, flow velocity, concentration ratio and process temperature. The results indicate that the model of a growing gel layer does not fit the process of long-term fouling. However, a precipitation model for calcium phosphate showed good agreement with the experimental results. Finally, experimental results and a modified form of the precipitation model are applied to explore possibilities for controlling fouling by adapting the controlling variables flow velocity, pressure and temperature.