Membrane performance with plug screw feeder pressate: Operating conditions and membrane properties

Membrane performance can be significantly affected by operating conditions. The effects of transmembrane pressure and cross flow velocity are discussed for various membranes during ultrafiltration of a pulp mill effluent. The effluent contained suspended solids, colloidal particles such as resin and fatty acids and materials with a wide molecular weight distribution. This effluent had severe membrane fouling characteristics, the nature of which complicated interpretation of the results. A variety of commercially available membranes made with different polymers and pore sizes were evaluated. Permeation experiments were performed using thin-channel, flat sheet, test cells. Cross-flow velocities varied from 0.4 to 1.2 m/s and the transmembrane pressure from 345 to 1,035 kPa. Flux decline occurred by several mechanisms and the selection of the membrane material, pore size and the operating conditions determined the relative contribution of these mechanisms. A modified series resistance model using flux loss ratios qualitatively explained changes in membrane performance under different operating conditions.