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Permeate polishing

The RO process removes over 99% of the dissolved solids from the feedwater, leaving approximately 1%, which is unacceptable for many applications. RO permeate is not considered of equal quality to demineralized or deionized water, nor is it considered ultrapure water. To achieve and maintain this level of purity, the RO permeate must be ‘polished.’  IDE offers two stages of permeate polishing:

Ion Exchange

Ion exchange is a method for exchanging one ion for another; thus, in water treatment, one or more undesirable ionic contaminants are removed from water by exchange with another non-objectionable or less objectionable ionic substance. Both the contaminant and the exchanged substance must be dissolved and have the same type of electrical charge (positive or negative).


The CEDI process uses an ion-exchange resin, ion-exchange membrane, and direct current to continuously deionize water without chemicals. As a result of CEDI technology, chemicals are avoided, your operating costs and maintenance costs are reduced, and your bottom line improves.

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