TasteThresholds of Monochloramine and Chlorine in Water

ReportNo WSAA 10

December 1989

SYNOPSIS

Aseries of experiments are reported which investigated the effects of chlorineand chloramine species on the taste of water. The psychophysical method of constantstimuli was employed throughout in order to establish taste thresholds. Initialattempts to locate a specific threshold for monochloramine in distilled waterfailed since the highest tested concentration of 5.2 mgL^-1 wasinsufficient to alter the taste. Subsequent trials showed that the thresholdwas considerably higher, at approximately 17 mgL^-1. Furtherexperiments conducted with monochloramine in tap water showed a comparabletaste threshold.

Animportant feature encountered throughout the study was the undesired presenceof free chlorine in all samples containing monochloramine. This chlorine couldbe minimised by letting the solutions stand in the open for several hours, butsignificant quantities remained for the higher concentrations of chloramine. Wedemonstrated that the thresholds for taste and odour of free chlorine wereapproximately 0.4 mgL^-1 and 0.2 mgL^-1, respectively. Iftastes and odours are to be minimised in chloraminated drinking water, it istherefore essential that every effort is made to eliminate free chlorine.

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