Electro-deionization (EDI) is a water treatment process that removes ionizable species from liquids using electrically active media and an electrical potential to effect ion transport. It differs from other water purification technologies such as conventional ion exchange in that it does not require the use of chemicals such as acid and caustic for reactivation. EDI is commonly used as a polishing process to further remove trace ionic salts of the Reverse Osmosis (RO) permeate to high purity water of multi-megaohm-cm quality.
EDI utilizes chemical-free regeneration. This means a safer workplace because there is no need to store or handle hazardous acid and caustic. There are fewer regulation concerns due to the absence of these corrosive chemicals and there is no waste, neutralization or environmental hazards.
EDI is a continuous process. The ion exchange resins are being continuously being regenerated by the DC electric field. There is no "breakthrough" of ions as happens in conventional ion exchange operations, therefore the quality of the water remains at a constant high level of purity. The electric field also provides a bacteriostatic environment inside of the EDI cell, inhibiting the growth of bacteria and other organisms.
EDI has significantly lower operating costs than conventional ion exchange processes. Only a relatively small amount of electric power is needed to provide high purity water. The lack of acid and caustic regeneration means less operator attention and lower labor costs. Capital costs can also expect to be lower, especially because no chemical storage, pumping and neutralization equipment is required.
EDI has a significantly smaller footprint than conventional ion exchange processes. This means less plant space will be required to provide the same quantity of water.