Dechlorination techniques to improve sensory odor testing of geosmin and 2‐MIB

Chlorine in finished water can mask the more subtle odors of geosmin and 2‐methylisoborneol (2‐MIB), two chemicals that often trigger consumer complaints when present at even nanogram‐per‐litre concentrations. These are two of the odors that are revealed as chlorine dissipates in the distribution system, which is typically at the consumer's end. As a result, odor monitoring at the treatment plant may not identify unpleasant smells because chlorine levels at the plant are typically high and mask the other odors. Proper sensory evaluation of these odor‐causing substances requires that the chlorine odor first be reduced or eliminated so that the secondary odor can be identified. In this study, ascorbic acid, hydrogen peroxide, oxalic acid, sodium thiosulfate, and ultraviolet (UV) irradiation were evaluated for their effectiveness in reducing chlorine solutions and for their subsequent usefulness in sensory analysis. Oxalic acid and UV irradiation were inefficient dechlorinators, and sodium thiosulfate produced a rotten‐egg odor under the study conditions. Triangle testing and flavor profile analysis showed that ascorbic acid and hydrogen peroxide were effective in reducing chlorinous odors without producing new odors, and they did not alter the testers' sensory perceptions of geosmin and 2‐MIB.