EDI provides continuous demineralization at recovery rates of 90% or more. In EDI, just as in conventional ion exchange, cations and anions in the feed water are exchanged for hydrogen and hydroxyl ions in the ion exchange resins, producing demineralized water. The key operational difference is that with EDI, the ion exchange resin is regenerated continuously, while with conventional ion exchange, chemical regeneration is performed intermittently.
Continuous electro-deionization (CEDI) is the most advanced generation of ion exchange technology and it is achieved electrochemically, by means of ion conducting membranes and an imposed electric current. The continuous electro-regeneration enables CEDI systems to produce multi-megohm water without the need for chemical regeneration or downtime so CEDI is a chemical-free operation and therefore environmentally friendly, a continuous production, and has extremely low operating costs when compared to chemically regenerated ion exchange technology.
CEDI is often selected for projects requiring ultra-high purity water, as well as for projects with stringent wastewater requirements. It is typically used in industries requiring higher purity than RO alone can produce.