Taste Thresholds of Monochloramine and Chlorine in Water

Report No WSAA 10

December 1989

 

SYNOPSIS

 

A series of experiments are reported which investigated the effects of chlorine and chloramine species on the taste of water. The psychophysical method of constant stimuli was employed throughout in order to establish taste thresholds. Initial attempts to locate a specific threshold for monochloramine in distilled water failed since the highest tested concentration of 5.2 mgL^-1 was insufficient to alter the taste. Subsequent trials showed that the threshold was considerably higher, at approximately 17 mgL^-1. Further experiments conducted with monochloramine in tap water showed a comparable taste threshold.

 

An important feature encountered throughout the study was the undesired presence of free chlorine in all samples containing monochloramine. This chlorine could be minimised by letting the solutions stand in the open for several hours, but significant quantities remained for the higher concentrations of chloramine. We demonstrated that the thresholds for taste and odour of free chlorine were approximately 0.4 mgL^-1 and 0.2 mgL^-1, respectively. If tastes and odours are to be minimised in chloraminated drinking water, it is therefore essential that every effort is made to eliminate free chlorine.

 

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