Mixed bed deionized water treatment machine is 50/50 mixture of cation and anion resin combined in a single ion exchange column. With proper pretreatment, product water purified from a single pass through a mixed bed ion exchange column is the purest that can be made. Most commonly, mixed bed demineralizers are used for final water polishing to clean the last few ions within water prior to use. Small mixed bed deionization units have no regeneration capability. Commercial mixed bed deionization units have elaborate internal water and regenerant distribution systems for regeneration. A control system operates pumps and valves for the regenerants of spent anions and cations resins within the ion exchange column. Each is regenerated separately, then remixed during the regeneration process. Because of the high quality of product water achieved, and because of the expense and difficulty of regeneration, mixed bed demineralizers are used only when the highest purity water is required. 

EDI (Electrodeionization) is a revolutionary water treatment technology; it is a membrane filtration and desalination technology that skillfully combined the electrodialysis technology and ion exchange technology together, which is high-tech, green and eco-friendly technology.

EDI equipment uses the RO outlet water as feed water. The resistivity of RO outlet water is normally 40-2μS/cm (25℃), and the resistivity of EDI outlet water can normally reach 18MΩ.cm (25℃). According to the application of deionization water and the setup of the system, EDI outlet water can meet the requirements for resistivity of 1-18.2MΩ.cm (25℃).

Calcium and magnesium ions are atoms having a positive electrical charge, as do sodium and potassium ions. Ions of the same charge can be exchanged. In the ion exchange process,a granular substance(usually a resin)that is coated with sodium or potassium ions comes into contact with water containing calcium and magnesium ions. Two positively charged sodium or potassium ions are exchanged (released into the water) for every calcium or magnesium ion that is held by the resin. This "exchange or trade"happens because sodium or potassium are loosely held by the resin. In this way, calcium and magnesium ions responsible for hardness are removed from the water, held by the resin,and replaced by sodium or potassium ions in the water. This process makes water"soft".Eventually, a point is reached when very few sodium or potassium ions remain on the resin, thus no more calcium or magnesium ions can be removed from the incoming water. The resin at this point is said to be"exhausted"or"spent",and must be"recharged"or"regenerated".