Abstract: A filtration membrane for micro- or ultra-filtration is formed from a complex of PVDF and calcined .alpha.-alumina (".alpha.-Al") particles, in which complex the particles are reacted and dispersed. The suspended complex is then mixed with a hydrophilic polymer such as polyvinyl alcohol (40%-90% hydrolyzed) referred to herein as HPVA, which reacts with the complex imparting hydrophilicity to the polymer. The novel membrane provides about 50% higher specific flux than a membrane made with the same polymer but without the .alpha.-Al particles. Unexpectedly, the net flux is improved by treating the membrane with a solution of sodium hypochlorite which fails to remove the HPVA from the novel membrane but does remove it from the prior art membrane which does not contain the .alpha.-Al. The preferred membrane comprises a macroporous support coated on its outer surface with a thin tubular asymmetric semipermeable film of polymer containing less than about 50% by weight of .alpha.-Al particles.

Abstract: A filtration membrane for micro- or ultra-filtration is formed from a complex of PVDF and calcined .alpha.-alumina (".alpha.-Al") particles, in which complex the particles are reacted and dispersed. The suspended complex is then mixed with a hydrophilic polymer such as polyvinyl alcohol (40%-90% hydrolyzed) referred to herein as HPVA, which reacts with the complex imparting hydrophilicity to the polymer. The novel membrane provides about 50% higher specific flux than a membrane made with the same polymer but without the .alpha.-Al particles. Unexpectedly, the net flux is improved by treating the membrane with a solution of sodium hypochlorite which fails to remove the HPVA from the novel membrane but does remove it from the prior art membrane which does not contain the .alpha.-Al. The preferred membrane comprises a macroporous support coated on its outer surface with a thin tubular asymmetric semipermeable film of polymer containing less than about 50% by is weight of .alpha.-A1 particles.

Abstract: A filtration device is provided for withdrawing permeate essentially continuously from a multicomponent aqueous substrate containing growing microorganisms in a reservoir. A vertical skein of fiber is scrubbed with coarse bubbles which emanate from a conversion baffle positioned under the skein. The substrate is aerated with fine bubbles in a size range small enough to transfer oxygen to the substrate efficiently. The baffle traps the fine bubbles and converts them to coarse bubbles which are effective to scrub the fibers. In the most preferred embodiment, the finished headers of the skein are derived from composite headers comprising a fixing lamina of resin in which the fibers are potted near their terminal ends, and a fugitive lamina of fugitive powdery material in which the terminal ends of the fibers are potted. The fugitive lamina is removed, preferably by dissolving the powder, e.g. finely divided common salt in water.

Abstract: A gas-scrubbed vertical cylindrical skein of "fibers" has their opposed terminal portions held in headers unconfined in a modular shell, and aerated with a cleansing gas supplied by a gas-distribution means which produces a mass of bubbles serving the function of a scrub-brush for the outer surfaces of the fibers. The skein is surprisingly effective with relatively little cleansing gas, the specific flux through the membranes reaching an essentially constant relatively high value because the vertical deployment of fibers allows bubbles to rise upwards along the outer surfaces of the fibers. The effectiveness is critically dependent upon the length of each fiber in the skein. That length is in the range from at least 0.1% more than the fixed distance between opposed faces of the skein's headers, but less than 5% greater than the fixed distance.

Abstract: A vertical skein of "fibers", opposed terminal portions of which are held in headers unconfined in a modular shell, is aerated with a gas-distribution means which produces a mass of bubbles serving the function of a scrub-brash for the outer surfaces of the fibers. The membrane device is surprisingly effective with relatively little cleansing gas, the specific flux through the membranes reaching an essentially constant relatively high value because the vertical deployment of fibers allows bubbles to rise upwards along the outer surfaces of the fibers. Further, bubbles flowing along the outer surfaces of the fibers make the fibers surprisingly resistant to being fouled by build-up of deposits of inanimate particles or microorganisms in the substrate provided that the length of each fiber is only slightly greater than the direct center-to-center distance between opposed faces of the headers, preferably in the range from at least 0.1% to about 5% greater.