Electro Deionisers

An EDI stack has the basic structure of a deionization chamber. The chamber contains a ion exchange resin, packed between a cationic exchange membrane and a anionic exchange membrane. Only the ions can pass through the membrane, the water is blocked.

Electrodeionization (EDI) is an electrically-driven water treatment technology that uses electricity, ion exchange membranes and resin to remove ionized species from water.

The typical EDI installation has the following components: anode and cathode, anion exchange membrane, cation exchange membrane, and resin. The most simplified configuration comprises 3 compartments. To increase production, the number of compartments or cells can be increased.

Electro deionization process is utilized predominantly for the production of high purity water. EDI is generally used as a post treatment, after a Reverse Osmosis to achieve high purity water. Typically EDI is used to achieve the treated water quality for the following applications

  • Semi conductor industry production water
  • Printed circuit board manufacturing
  • Solar cell manufacturing
  • Pharma grade water
  • Vaccines
  • Parental
  • Water for Injection

EDI utilizes and operates on the principle of migration of charged ions across a semi-permeable membrane which contains charged resin beds. The migration of membranes is initiated by applying current, by means of cathode and anode. This generates the migration of ions across the oppositely charged membranes. The oppositely charged ions permeate through the charged membranes and collect in the concentrate chamber. A constant flow is maintained in the concentrate chamber to continuously evacuate the ions into the reject stream.

The ultra pure water from the pure water chamber flows out continuously. The reject water is not wasted and is recycled back to the pre-treatment sections.