METHOD AND APPARATUS FOR REDUCING SCALING OF ELECTRODEIONIZATION SYSTEMS AND FOR IMPROVING EFFICIENCY THEREOF

摘要

A method and apparatus for inhibiting scaling in an electrodeionization syst em (10) or in a combined reverse osmosis/electrodeionization system (62, 10) fo r water treatment and, more particularly, for increasing tolerance to hardness in the feed water to an electrodeionization unit (10) to inhibit precipitati on of metal cations contained in the feed water and for increasing efficiency o f the electrodeionization system. Water to be purified is passed through an electrodeionization unit (10) in which a concentrate stream recycling (12) through concentrating compartments (18) and anode and cathode compartments (20, 22) contains effective amounts of an antiscalant to inhibit precipitati on of scale. One or more preliminary reverse osmosis units (62, 72, 74, 90, 100 , 110, 120, 130, 140) in series with the electrodeionization unit (10) preferably receives a portion of the antiscalants in the concentrate stream (12, 44). The antiscalant in the water fed to the reverse osmosis unit (62) can be supplemented and adjusted. Electrolyte can be provided to the concentrate stream (44) of the electrodeionization unit from products of the reverse osmosis.