Variability and Speciation of Halogenated Disinfection By-Products in Chloraminated Drinking Waters and Their Regulatory Implications

Temporal and spatial variability has been examined in the speciation and concentration of disinfection by-products (DBFs) at two drinking water treatment plants practicing chloramination in the United States. This work was part of an epidemiological study in which a specific suspected reproductive health effect of these DBFs was being characterized. Comparative analysis has been conducted to evaluate the weekly variability in concentration and speciation of halogenated DBFs at the two sites (Site 1 and Site 3), specifically for four trihalomethanes (THM4), nine haloacetic acids (HAA9), and total organic halide (TOX). A third water (Site 2), with low levels of all DBFs, was used as a control for the health impacts component of the study. The spatial and temporal variability in the DBF levels in these waters were also examined through several short-term intensive sampling events. The total organic carbon (TOC) concentrations are similar at Site 1 and 3, averaging between 5-8 mg/L and the total THM4 and HAA9 concentrations are also similar at the two sites. The average of 52 weekly THM4 measurements taken in 2003 was 62.4 μg/L at Site 1 and 58.3 μg/L at Site 3; the average HAA9 concentration for 2003 was 49.0 μg/L at Site 1 and 46.0 μg/L at Site3. However, the two plants treat surface waters with sufficiently different bromide concentrations to significantly impact DBF speciation. The source water at Site 1 exhibits very low bromide concentrations near the limit of practical quantitation (20-30 μg/L) and produces mostly chlorine-substituted DBFs while at Site 3 the source water has higher concentrations of bromide (150-400 μ/L) and more highly bromine-substituted DBFs are produced. This difference is apparent in the bromine incorporation factors (BIFs), a measure of the amount of bromine being incorporated into a DBP group, at these two sites. The average THM4 BIF at Site 1 is 0.3 while at Site 3 it is approximately four times larger at 1.3, indicating the influence of source water bromide concentrationon DBP speciation. Regulation of trihalomethanes (THMs) and haloacetic acids (HAAs) in drinking water is currently approached as a group measurement, THM4 and HAAS, where HAAS is a subset of HAA9 that does not include four of the bromine-containing HAAs. It is suspected that the health risks associated with individual DBP species vary, and that the brominated by-products may be associated with more negative health impacts than the chlorinated species. Therefore, the current summation-based regulatory approach may not accurately reflect or protect against THM and HAA exposure to consumers. This report addresses these regulatory weaknesses and provides suggestions for alternative means of monitoring THMs and HAAs in drinking waters.Master of Science in Environmental Engineerin