Differences in Chloroform Levels from Drinking Water Samples Analysed Using Various Sampling and Analytical Techniques

Abstract

During an investigation of disinfection by-products in drinking water from Canadian treatment facilities, chloroform was determined using either Purge & Trap or liquid-liquid extraction techniques on water samples treated with different dechlorinating preservatives and/or pH adjustment. The addition of dechlorinating preservatives to the sampled water altered the sample pH which had a significant effect on the chloroform levels. Initial results indicated lower chloroform levels for water samples where the pH was decreased by the addition of acid or preservative. The effect due to pH adjustment was usually greatest for samples taken at the treatment plant and diminished with distance (time) in the distribution system. The magnitude of the differences appeared to be also dependent on other variables such as water source quality and water treatment processes. To obtain an accurate estimation of human exposure to chloroform from drinking water, samples should be collected at the consumer tap and not at the treatment plant.