Rotation and Concentration Effects in High-Shear Ultrafiltration

A parametric waste-specific study was conducted to assess the effects of membrane rotational speed and feed oil concentration on the pressure independent “limiting” flux in a high-shear rotary ultrafiltration (HSRUF) system. The limiting flux data were adequately described by the thin-film model. The transition from pressure dependent to pressure independent behavior occurred at lower oil concentrations as membrane rotational speed was decreased and pressure was increased due to an increase in the thickness of the solute boundary layer at the membrane surface. A gel layer oil concentration, OCgel, of 39% was reported, and OCgel was determined to be constant with respect to average transmembrane pressure and membrane rotational speed. The solute mass transfer coefficient increased with membrane rotation and was greater than reported for conventional ultrafiltration systems. The greater mass transfer characteristics determined for the HSRUF system were attributed to the efficient delivery of “cleaning energy” to the membrane surface due to the effective decoupling of feed pressurization from recirculation∕hydraulic turbulence.