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Source
Chloride (Cl-1) is one of the major anions found in water and are generally combined with calcium, magnesium, or sodium. Since almost all chloride salts are highly soluble in water, the chloride content ranges from 10 to 100 mg/I. Sea water contains over 30,000 mg/i as NaC1. Chloride is associated with the corrosion of piping because of the compounds formed with it; for example, magnesium chloride can generate hydrochloric acid when heated. Corrosion rates and the iron dissolved into the water from piping increases as the sodium chloride content of the water is increased. The chloride ion is instrumental in breaking down passivating films that protect ferrous metals and alloys from corrosion, and is one of the main causes for the pitting corrosion of stainless steel. The SMCL (suggested maximum contaminant level) for chloride is 250 mg/i which is due strictly to the objectionable salty taste produced in drinking water.
Treatment
Reverse Osmosis will remove 90 - 95% of the chlorides because of its salt rejection capabilities. Electrodialysis and distillation are two more processes that can be used to reduce the chloride content of water. Strong base anion exchanger which is the later portion of a two-column deionizer does an excellent job at removing chlorides for industrial applications.
