Trihalomethanes in Groundwater Systems

M. M. Varma
A. Balram
H. M. Katz

DOI: 10.2190/JPMV-NJV2-GKRF-0UC1


Aqueous chlorine reacts with certain precursors in water to form trihalomethanes which are suspected carcinogens-mutagens. In the past, much attention has been given to the formation of THM's in surface waters, but little attention has been given to groundwater systems. In this study, groundwater supplies in six small towns in Maryland were studied. Samples of both raw and finished water were collected and analyzed for THM's and for THM formation potential at ambient pH and at pH9. In raw water samples, the only THM detected was chloroform, and the highest concentration was 2.5 μg/ℓ. In finished water samples, chloroform concentrations were somewhat higher and no other species were detected, except for one supply where the chloroform concentration was 24.8 μg/ℓ and total THM's were 103.5 μg/ℓ, the difference being brominated compounds. Significant amounts of brominated compounds were found in only one other supply, but total THM's were relatively low. The results of THM formation potential generally followed the same pattern, and showed a slight increase in formation potential at higher pH. The results indicate that more attention needs to be given to monitoring groundwater supplies in small towns.

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