Abstract: Porous track membranes are produced by exposing a polymeric film to a bombardment of heavy ions to provide the film with a track density, and etching pores into the resulting tracked film with an etching solution to provide the film with a density of the pores corresponding to the track density under conditions to maintain turbulent flow. An alkaline etching solution is used that contains salts of alkali metals in sufficient concentration to increase the boiling point of the resulting alkali-metal-containing solution to temperatures in excess of about 100 up to about 150° C.

Abstract: Processes are provided for producing porous track membranes, membrane cards, membrane packages, separation elements, separation units and separation systems, for using the same for the separation of materials from fluids, and for determining the maximum pore diameter of membranes. Porous track membranes are produced by exposing a polymeric film to a bombardment of heavy ions to provide the film with a track density, etching pores into the resulting tracked film with an etching solution to provide the film with a density of the pores corresponding to the track density and laminating the resulting porous track membrane to a porous backing by means of an adhesive to produce membrane cards. Membrane packages and a turbulizer are spirally wound around a fluid collection tube to form a separation unit.

Abstract: An upright filter unit (10) is disclosed which comprises a membrane (16) consisting of a perforated, vertical permeate pipe (12) and a plurality of leaves (14) of semipermeable material which permits water to pass through it. The semi-permeable material defines a plurality of solids retention passages and a plurality of permeate passages. The leaves (14) are wound around the perforated vertical pipe (12) into which the permeate water flows, the membrane being inside a casing (40). An inlet (24) at the bottom of the unit allows raw water under pressure to flow to the solids retention passages of the membrane. An air inlet (32) at the upper end of the unit permits air under pressure to enter the upper end of the unit, and hence the upper ends of the solids retention passages, until the air and water pressures are balanced.