Anion exchange units contain a resin that exchanges chloride or hydroxide ions for contaminant anions such as fluoride, nitrate, sulfate and bicarbonates to purify the water.

The chemical process where negative ions of one chemical are preferentially replaced by negative ions of another chemical. In water treatment, the net effect is the removal of an unwanted ion from a water supply. For example, some municipalities are installing anion exchange systems to remove nitrate from their water supplies.

Anion Exchange - Chemical process where negative ions of one chemical are preferentially replaced by negative ions of another chemical.