EDI

Waterex uses electrodeionisation (EDI) as the demineralisation process of choice to remove dissolved ion salts from water. Waterex use EDI modules as polishers to demineralise permeate from reverse osmosis (RO) arrays without resorting to the use of chemical reagents.

EDI is utilised to produce demineralised water in place of traditional or other technologies that include regenerable mixed bed deionisation, ion exchange, and two pass reverse osmosis.

The EDI modules combine two well established water purification technologies, electrodialysis and ion exchange deionisation. Through this revolutionary technique, dissolved salts are removed with low energy cost and without the use of hazardous reagents. This compact clean technology uses the ion exchange process efficiently to remove ionised species from water by exchanging them for H+ and OH- ions. Water passes through one or more chambers filled with ion exchange resins held between cation or anion selective membranes. The membranes are used to isolate ions from their counter-ions. Where carbon dioxide needs to be removed membrane technology is used in combination with the EDI.

The result is a high quality demineralised water, up to 18 megaohm/cm, which can be readily produced continuously at substantial flow rates. Permeate flowrates up to 1,400m3/h can be achieved using up to 99% recovery. When used in combination with RO, 99.9% of ions can be removed from feed water.

Waterex supplies stand alone skid mounted PLC controlled EDI plants, with the pre-treatment reverse osmosis plant if required. Package plants can be installed in customised air-conditioned containers.

Applications
Waterex uses EDI to provide solutions for many applications including:

  • High purity water for power station turbines
  • High purity water for high pressure boilers
  • Pharmaceutical water
  • Reduction of ionisable SiO2
  • Reduction of total organic carbon
  • Laboratory water

Waterex Electrodeionisation.pdf