Deionization systems purify water through ion exchange using cationic and anionic resins. They are widely used in manufacturing and industrial facilities requiring pure water. Resins can be placed in separate tanks or as a mixed bed in one tank.
Mixbed systems are typically used after reverse osmosis or cation–anion columns, reducing regeneration frequency by using low-conductivity feedwater. Regeneration is done with acid and caustic. These systems are not efficient for raw waters with conductivity above 1000 µs/cm. In such cases, reverse osmosis should precede the deionization unit. They can produce water with 0.2–5 µs/cm conductivity. For ultra-pure water (<0.2 µs/cm), double-pass RO + EDI systems are preferred.