Patent ID: 8871073

Claim:
An electrodeionization apparatus for producing deionized water comprising at least one deionization treatment unit provided between a cathode and an anode that are opposite to each other, said deionization treatment unit including a deionization chamber and a pair of concentration chambers placed adjacent to said deionization chamber on opposite sides thereof and filled with anion exchangers, wherein said deionization chamber is partitioned by an ion exchange membrane into a first small deionization chamber adjacent to one of said pair of concentration chambers and a second small deionization chamber adjacent to the other of said pair of concentration chambers; wherein said first small deionization chamber is filled with an anion exchanger, and wherein said second small deionization chamber is filled with an anion exchanger and a cation exchanger in a sequence such that the ion exchanger, through which water that is to be treated finally passes, is the anion exchanger.