Dechlorination Chemical Summary
Currently, sodium bisulfite, sodium sulfite and sodium thiosulfate are most frequently used by water utilities for
dechlorination. The choice of a particular dechlorination chemical is dictated by site-specific issues such as the nature of
water release, strength of chlorine, volume of water release, and distance from receiving waters. Sodium bisulfite is used by
some utilities due to its lower cost and higher rate of dechlorination. Sodium sulfite tablets are chosen by utilities due to
ease of storage and handling, and its ease of use for dechlorinating constant, low flow rate releases. Sodium thiosulfate is
used for dechlorination since it is less hazardous and consumes less oxygen than sodium bisulfite and sodium sulfite.
Ascorbic acid and sodium ascorbate are used because they do not impact DO concentrations.
Knowledge on dechlorination efficiencies of various chemicals is incomplete. A comprehensive study evaluating
all the chemicals for various chlorinated water release scenarios is not currently available.