The EDI process produces industrial process water of very high purity, using less than 95% of the chemical products used in the conventional ion exchange processes. Two separation technologies, membranes and ion exchange, are combined into one sealed, self-contained unit. The distinct spiral-wound design of DOW™ EDI modules offer a chemical-free alternative to mixed-bed ion exchange resins for polishing RO permeate—an ideal choice for high purity water needs when combined with RO membranes and ion exchange resins.