Electrodeionization (EDI) is a water treatment technology that has gone from an unproven and unknown commodity to one that has revolutionized the industry in the past 20 years.
The technology was first introduced to the market in 1987 by Ionpure Technologies.
EDI is used in small and large applications. Laboratories use EDI in systems as low as 360 gallons per day (gpd), while power plants, semiconductor industries or other industrial systems may use EDI systems as large as 13,500 gallons per minute (gpm). The available products are well-suited for all flows in-between.
EDI takes the place of chemically regenerated mixed beds, both on-site and off-site regenerated. EDI uses electrical power to split water molecules which regenerate resin rather than acid and caustic hazardous chemicals. The hydrogen (H+) ions and hydroxyl (OH-) ions continuously regenerate the mixed resin in the EDI module.
Water splitting replaces the chemical regeneration process. For illustrative purposes, where R is impurity trapped on the mixed bed resin
In traditional ion exchange units, after the contaminants are trapped onto the resin sites, the resin continues to exhaust and lose capacity. In EDI, the contaminates are continuously removed as they are attracted to one of the two electrical charges, and then migrate through the resin bed, through ion exchange membranes and into the concentrate stream where they are removed from the device. EDI is a polishing technology and requires reverse osmosis (RO) as pre-treatment. The combination of RO-EDI provides the customer with a continuous, chemical-free system.
EDI replaces on-site regenerated mixed-bed resin where end users do not wish to store, handle and neutralize chemicals. EDI also replaces service deionization (SDI) or off-site regenerated mixed beds, as EDI is more reliable, cost effective and requires little maintenance. Under environmental pressure, companies are turning away from their traditional regeneration facilities and electing instead to provide a service contract and lease EDI systems.