Trihalomethane Levels in Canadian Drinking Water

Abstract

The presence of the trihalomethanes chloroform, bromodichloro-methane, chlorodibromomethane and bromoform in drinking water which had been treated with chlorine was reported by workers in Holland (Rook, 1974) and the United States (Bellar et al, 1974). It was postulated that the chloroform was formed by the reaction of the chlorine, via the haloform reaction, with the natural organics present in the raw water supply (Rook, 1974; Bellar et al, 1974). The brominated trihalomethanes were thought to be produced by the reaction of chlorine with bromide ion present in the raw water (Rook, 1974; Bunn et al, 1975). Bunn and co-workers (1975) have shown, under laboratory conditions, that this is true with both bromide and iodide ions and have obtained all ten trihalomethanes containing chlorine, bromine and iodine atoms. However, most methods of analysis have been optimised to detect only the four trihalomethanes containing chlorine and bromine atoms. The classical haloform reaction occurs with compounds containing the methyl ketone structure (-CO.CH₃) but Rook (1974) demonstrated that compounds containing 1,3-dione or resorcinol type structures also underwent the haloform reaction.