Flux enhancement in cross-flow membrane filtration by flow reversal: A case study on ultrafiltration of BSA

Fouling problems are perhaps the single most important reason for relatively slow acceptance of ultrafiltration in many areas of chemical and biological processing. To overcome the losses in permeate flux associated with concentration polarization and fouling, in cross-flow membrane filtration, we investigated the concept of flow reversal as a method to enhance membrane flux in ultrafiltration. Conceptually, flow reversal prevents the formation of stable hydrodynamic and concentration boundary layers at or near the membrane surface. Furthermore, periodic reversal of the flow direction of the feed stream at the membrane surface results in prevention and mitigation of membrane fouling. Consequently, these advantages are expected to enhance membrane flux significantly. BSA is a well-studied model solute in membrane filtration known for its fouling and concentration polarization capabilities. Laboratory-scale tests on a hollow-fiber ultrafiltration membrane module using bovine serum albumin (BSA) solution as feed show that under flow reversal conditions, the permeate flux is significantly enhanced when compared with the conventional unidirectional flow. The flux enhancement is dramatic (by an order of magnitude) with increased feed concentration and operating transmembrane pressure.