Abstract: The rejection flow from a water ultrafiltration system is passed through a filtration means for removal of bacteria, viri, pyrogens, and colloids, the effluent of which is reintroduced into the affluent presented to the ultrafiltration surface. Treatment of the refjection flow prior to ultrafiltration after removal of bacteria, viri, pyrogens, and colloids may include carbon filtration followed by ion exchange treatment.

Abstract: A closed water recycling system produces potable drinking water from total domestic waste-water, including household sewage. The system includes filtration and demineralization units. An electronic controller, which is preferably a microprocessor, monitors the operation of the system and automatically cleans the filter assembly, operates the demineralizer when the monitored variables indicate this is necessary, acts as a failsafe monitor to insure water quality, and shuts down the system in case of a malfunction. For example, the demineralizer may include acid and base regenerated resin beds in an ion-exchange system. When a monitor indicates that the beds require regeneration, acid and base regenerating solutions are supplied to the beds. The flow of regenerating solution and rinse is controlled by the electronics which sense conditions at the bed outlet.

Abstract: Improvement in the reduction of Mg, Ca, Na, K and Al in crude phosphoric acid using an ion exchange resin bed, comprising preclarifying the feed acid with flocculant polymer and placing a filter aid precoat on the resin bed. As part of the preclarification process, a compatible soluble sodium compound, such as sodium carbonate, is added to the feed acid to speed the flocculation process.

Abstract: The invention concerns a process for preparation of a water for hemodialysis, particularly renal hemodialysis, and consists of fixing the acetate anions (CH.sub.3 COO.sup.-) on at least one water-insoluble anion-exchange resin contained in a column and passing a potable water through a bed of said resin which is thus prepared, in order to substitute the anions contained in the initial potable water for the acetate anions. The water which is obtained is devoid of ions which are undesirable for the hemodialysis process and is suitable for the preparation of a hemodialysis solution by means of a traditional type of aqueous solution.