EDI (Electrodeionization)

Mit Water supplies Electrodeionization (EDI) modules and complete EDI systems for continuous production of high-purity water without chemical regeneration. EDI combines ion exchange membranes and ion exchange resins with a DC electric field to remove ionised species from water.

Working Principle

Feed water passes through alternating cation- and anion-permeable membranes arranged between two electrodes. Under an applied DC voltage, cations migrate toward the cathode and anions toward the anode. Ion exchange resin packed within the diluting compartments facilitates ion transport. Purified water exits the diluting compartments while concentrated brine is discharged separately. This continuous process eliminates the chemical regeneration cycle required by conventional mixed-bed ion exchange.

System Configuration

A typical EDI system consists of EDI membrane stacks, a DC rectifier power supply, conductivity monitoring instruments, flow control valves, and a PLC-based control panel. The complete unit is mounted on a stainless steel skid frame with pre-piped connections. EDI is normally installed downstream of reverse osmosis (RO) as a polishing step to achieve ultrapure water quality with resistivity up to 18.2 MOhm-cm.