MEMBRANE PERFORMANCE WITH PLUG SCREW FEEDER PRESSATE - OPERATING-CONDITIONS AND MEMBRANE-PROPERTIES

Membrane performance can be significantly affected by operating condit ions. The effects of transmembrane pressure and cross flow velocity ar e discussed for various membranes during ultrafiltration of a pulp mil l effluent. The effluent contained suspended solids, colloidal particl es such as resin and fatty acids and materials with a wide molecular w eight distribution. This effluent had severe membrane fouling characte ristics, the nature of which complicated interpretation of the results . A variety of commercially available membranes made with different po lymers and pore sizes were evaluated. Permeation experiments were perf ormed using thin-channel, flat sheet, test cells. Cross-flow velocitie s varied from 0.4 to 1.2 m/s and the transmembrane pressure from 345 t o 1,035 kPa. Flux decline occurred by several mechanisms and the selec tion of the membrane material, pore size and the operating conditions determined the relative contribution of these mechanisms. A modified s eries resistance model using flux loss ratios qualitatively explained changes in membrane performance under different operating conditions.