Electro-Deionisation

CEDI units were first developed in the 80’s as an alternative method of polishing deionised water post Reverse Osmosis, however the early systems were expensive and prone to fouling and leaks.

Since those early days CEDI technology has developed into a reliable and recognised process for a wide range of industries from Power Generation, Biotechnology, Steam Generation, Food and Beverage, to Pharmaceutical Production and Semi Conductor Manufacturing. The process is primarily used as post treatment to Reverse Osmosis and due to its modular nature, systems with flow rates up to 100m3/hr are not uncommon. The cost of the systems have dramatically reduced as Technological advances are made making the systems simpler to manufacture coupled with the economies of scale afforded to larger production plants.

Modern CEDI systems utilise Ion selective membranes to remove the Anions and Cations present in the Reverse Osmosis permeate feed source. By alternating these ion selective membranes, filling the spaces between (dilute compartments) with cationic or anionic resins and applying a DC current the Ions pass through their respective membranes to the concentrate flow compartment. The water within the dilute compartment becomes depleted of ions and the water within the concentrate compartment become concentrated with ions. Each compartment has its own inlet and outlet connection allowing a continual flow through the various compartments. In this way Purified water with a typical water quality between 10 and 18 meg-ohm can be produced on a continual basis.