E-cell Corporation

Robert Glegg

David Florian Tessier

Mark Philip Huehnergard

John H Barber

Steve Siverns

Tom Kosir

A method and apparatus is provided for inhibiting scaling in an electrodeionization system and, more particularly, for increasing tolerance to hardness in the feed water to an electrodeionization unit by inhibiting precipitation of scale-forming metallic cations contained in the feed water and thereby increasing efficiencies of the electrodeionization system. Water to be purified is passed through an electrodeionization unit in which the flow in the diluting compartment is countercurrent to the flow in the concentrating compartment. This is to impede the migration of scale-forming metallic cations from the diluting compartment, through the cation exchange membrane, into the concentrating compartment and towards the concentrating compartment side of the anion exchange membrane, thereby preventing scale formation on the anion exchange membrane. The electrodeionization unit may be further modified by dividing the concentrating compartments into first and second compartments by a porous diaphragm or ion-conducting membrane. The porous diaphragm or ion-conducting membrane effectively eliminates convective transport of scale-forming metallic cations from the cation exchange membrane side of the concentrating compartment to the anion exchange membrane side of the concentrating compartment, thereby inhibiting scale formation on the anion exchange membrane.

Method and apparatus for preventing scaling in electrodeionization units

A method and apparatus for inhibiting scaling in an electrodeionization system or in a combined reverse osmosis/electrodeionization system for water treatment and, more particularly, for increasing tolerance to hardness in the feed water to an electrodeionization unit to inhibit precipitation of metal cations contained in the feed water and for increasing efficiency of the electrodeionization system. Water to be purified is passed through a electrodeionization unit in which a concentrate stream recycling through concentrating compartments and anode and cathode compartments contains effective amounts of an antiscalant to inhibit precipitation of scale. One or more preliminary reverse osmosis units in series with the electrodeionization unit preferably receives a portion of the antiscalants in the concentrate stream. The antiscalant in the water fed to the reverse osmosis unit can be supplemented and adjusted. Electrolyte can be provided to the concentrate stream of the electrodeionization unit from products of the reverse osmosis.

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Campbellville, Canada

Robert Glegg