Dynamic Membrane Microfiltration

To separate molecules or particles from a solution by cross-flow filtration through a membrane, it is necessary to circulate the fluid at a speed of 3–6 ms 1 in a tubular or plane membrane in order to prevent the buildup of a layer of rejected solutes on the membrane while exerting a pressure on the fluid to produce a filtrate. The combination of high feed pressure and flow rate requires powerful and expensive pumps that consume energy and the friction creates a pressure decay along the membrane which reduces the transmembrane pressure (TMP). In addition, the rejected molecules or particles can create a cake on a microfiltration (MF) membrane which reduces both filtration rate and solute transmission through the membrane. Dynamic filtration is a recent alternative to classical cross-flow filtration (Lee et al. 1995; Jaffrin 2008) consisting in creating a high shear rate (velocity gradient) at the membrane by a disk or a rotor rotating near the membrane or by using rotating or vibrating membranes, while using a low feed flow rate, only slightly larger than the permeate flow rate. Advantages and Drawbacks of Dynamic Filtration