Continuous electrodeionisation systems (CEDI) that produce high-purity water with chemical-free operation
Continuous electrodeionisation systems (CEDI) polish reverse osmosis permeate to produce high-purity water of up to 18MΩ.cm with flow rates ranging from 1.4 to 40.8m3/hr. CEDI overcomes the limitations of ion exchange resin beds, notably the release of ions as the beds exhaust, and the associated need to change or regenerate the resins.
Reverse osmosis (and sometimes membrane degassing) is typically used prior to CEDI to ensure that the CEDI stack is not overloaded with high levels of salts. CEDI offers chemical-free operation and produces a continuous flow of consistent water quality, and is available with short lead times, quick installation and start-up.
What is Pure Water?
Pure water is water which has been processed to remove all contaminants and impurities. Tap water, for example, typically contains various harmless minerals such as calcium, magnesium, sodium, potassium and phosphorus. Electrodeionisation (EDI) is a highly efficient process that removes these dissolved minerals. This is achieved using resins, ion-exchange membranes and electricity to separate the dissolved impurities (ions) from the water.
The ionic purity of water can be determined by measuring its resistivity or conductivity. This is a measure of the water's opposition (resistance) to the flow of electricity or its inverse. The water's electrical resistivity or conductivity is directly related to the amount of ionic material (mineral salts) dissolved in the water. The quantity of minerals dissolved in water is commonly referred to as total dissolved solids or TDS. Water with low TDS will be more resistant to the flow of electricity and water with higher levels of TDS will have lower resistivity. The ionic purity of water is typically quoted in mega-ohm per centimetre at 25 degrees celsius. The Veolia CEDI pure water system delivers high-purity water at up to 18MΩ.cm.