Characteristics of salt taste and free chlorine or chloramine in drinking water

Salty taste with or without chlorine or chloramine flavour is one of the major consumer complaints to water utilities. The flavour profile analysis (FPA) taste panel method determined the average taste threshold concentration for salt (NaCl) in Milli-Q water to be 640 +/- 3 mg/L at pH 8. Chlorine and chloramine disinfectants have no antagonistic or synergistic effects on the taste of NaCl, salt, in Milli-Q water. The flavour threshold concentrations for chlorine or chloramine in Milli-Q water alone or in the presence of NaCl could not be estimated by the Weber-Fechner curves due to the chlorine or chloramine flavour outliers in the 0.2-0.8 mg/L concentration range. Apparently, NaCl is not equilibrated with the concentration of ions in the saliva in the mouth and the concentration of free chlorine or chloramines cannot be tasted correctly. Therefore, dechlorinated tap water may be the best background water to use for a particular drinking water evaluation of chlorine and chloramine thresholds. Laboratory FPA studies of free chlorine found that a 67% dilution of Central Arizona Project (CAP) (Tucson, AZ) water with Milli-O water was required to reduce the free chlorine flavour to a threshold value instead of a theoretical value of 80% (Krasner and Barrett, 1980). No synergistic effect was found for chlorine flavour on the dilution of CAP water with Milli-Q water. When Central Avra Valley (AVRA) groundwater was used for the dilution of CAP water, a synergistic effect of the TDS present was observed for the chlorine flavour. Apparently, the actual mineral content of drinking water, and not just NaCl in Milli-Q water, is needed for comparative flavour tests for chlorine and chloramines.