Long-term characterization of trihalomethane levels in drinking water

Abstract

Water chlorination leads to the formation of trihalomethanes (THM). In this case study, the levels of THM during the chlorination process of the drinking water in Valencia (Spain) were determined over a 12-year period. Different control areas and points were strategically sampled and samples were analyzed by gas chromatography. Temporal tendencies, as well as spatial and seasonal variations, were established. The individual distribution of THM was also evaluated. Factors such as distances from chlorination points and inter-month seasonal distribution, including ambient temperature effect, were assessed. The range of total THM concentrations measured in the water network goes from 4 to 184 μg L-1. However, from the year 2000, coinciding with an improvement in the quality scheme of the analytical method, no more than one sample per year is above the limiting level of 100 μg L-1 and the annual data dispersion becomes lower. Although the levels of THM virtually do not exceed the limits established by law, the variability in their concentrations suggests the need for adaptable control plans combined with factors such as ambient temperature and distances from disinfection points. © 2010 Taylor & Francis.