Fouling of membranes during microfiltration of surimi wash water: Roles of pore blocking and surface cake formation

Studies were conducted to investigate the development of membrane fouling in the microfiltration of protein solutions such as surimi wash water, containing both soluble and suspended proteinaceous solids. A laboratory scale plate-and-frame crossflow membrane filtration unit was fabricated and installed. Continuous filtration was performed to recover the suspended myofibrillar proteins from the wash water at refrigerated temperatures (12-15 degrees C) using polysulfone membranes. The transmembrane pressure was controlled at a constant pressure of 34.5+/-2.2 KPa, and the feed was pumped to the filtration unit at a crossflow velocity of 0.262+/-0.026 m/s. It was hypothesized that the development of membrane fouling was a dynamic process of two distinctive stages. The pore blocking resistance was the dominant resistance at the initial period of filtration, and the cake resistance began to dominate following the initial pore blocking. Experimental results showed that the initial membrane fouling process could be modeled by the standard pore blocking law, and the development of fouling continued with a continuous process of cake formation. A new concentration-dependent power law cake resistance model was found. The filtration resistance of the cake layer increased with the feed concentration and was found to be one order in magnitude higher than the initial dominant pore blocking resistance. (C) 1998 Elsevier Science B.V.