Electrodeionization, also referred to as Continuous Electrodeionization (CEDI/EDI) is a process that reduces ions in water. The process has similarities to conventional ion exchange, whereby the water passes through an ion exchange resin. While the water is being deionized, the EDI regenerates the resin with an electric current, and also simultaneously removes the contaminants by an electrical charge.

Where is Electrodeionization used?

Electrodeionization is used in water treatment services for process water and ultrapure water treatment plants to remove trace levels of ionic salts. This process also be used in many applications, such as semiconductor manufacturing. These water treatment services are designed to reduce the energy required to treat water to a specified level of purity at a given pressure. EDI systems are an extremely versatile water purification technology. They can be designed to treat from less than 1 to over 10,000 gallons per minute (GPM).

Advantages of Electrodeionization

The main benefit of EDI is an improved quality of water, available at lower operating costs. The main difference between EDI water treatment services and reverse osmosis is the effect each process has on the treated water. Where reverse osmosis turns highly saline water into “semi-pure” water, electrodeionization converts the “semi-pure” water into the water close to theoretical purity. Ions in EDI product water are typically measured 1 to 5 parts per billion (ppb) and sometimes below ppb, measured in parts per trillion (ppt).

Another benefit of EDI is that it does not produce much wastewater. This can be of particular importance in larger flow rates, where gallons per minute can be recovered back into the raw water break tank. In such a case, the EDI concentrate water is of better quality than the raw water feed, so it actually improves the pretreatment performance while operating the EDI effectively at 100% recovery.