The main drawback of Membrane BioReactors (MBRs) is the fouling of the membrane. One way to reduce this fouling is by controlling the hydrodynamics of the two-phase slug flow near the membrane surface. Literature has shown that the slug flow pattern has a higher scouring effect for removing particulates due to the high shear stresses and high mass transfer between the membrane surface and the bulk region. However, calculating the mass transfer coefficient in an efficient and accurate way is not straightforward. Indeed, for accurate determination, numerous complex experimental measurements are required. Therefore, this work proposes an alternative method that uses existing heat transfer relationships for two-phase flow and links them through a dimensionless number to the mass transfer coefficient (Sherwood number) to obtain an empirical relationship which can be used to determine the shear stress. (C) 2012 Elsevier Ltd. All rights reserved.