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Comparison of Chemical Composition of Complex Disinfection Byproduct (DBP) Mixtures Produced by Different Treatment Methods
Citation:
Parvez, S., D. McCurry, G. E. RICE, L. K. TEUSCHLER, T. F. SPETH, R. J. MILTNER, AND J. G. PRESSMAN. Comparison of Chemical Composition of Complex Disinfection Byproduct (DBP) Mixtures Produced by Different Treatment Methods. Presented at Society of Risk Analysis 2011 Annual Meeting, Charleston, SC, December 04 - 07, 2011.
Impact/Purpose:
To inform the public.
Description:
Analyses of the chemical composition of complex DBP mixtures, produced by different drinking water treatment processes, are essential to generate toxicity data required for assessing their risks to humans. For mixture risk assessments, whole mixture toxicology studies generally are preferred to component studies. A concern with whole mixture studies is the similarity of the tested mixture to the mixture of concern in the environment. We evaluated the chemical composition of three chlorinated DBP mixture concentrates (A, B, C) formed by different concentration methods. We compared their DBP composition to a reference chlorinated mixture (R) at 1x dilution of the disinfected source water. Tukey studentized tests and statistical power tests were performed (at α = 0.2, 0.1, 0.05, 0.01) to examine differences among 19 individual DBPs and 4 DBP classes. Preliminary results suggested concentrate C and R are similar except for levels of 3 individual DBPs. Concentrates A and B differed significantly from C and R based on concentrations of trihalomethanes, haloacetic acids, total organic halogens (TOX), and other individual DBPs. Statistical analyses at different α levels yielded consistent results for most of the DBP fractions including TOX, suggesting that these results are robust. However, the percent TOX associated with measured individual DBPs (MTOX) and unknown (UTOX) fractions varied across the concentrates; MTOX and UTOX each comprised ~50% of TOX in R; in concentrates A, B, and C, the percentage of UTOX was 70%, 70%, and 64%, respectively. This suggested that among the three concentrates, concentrate C is quite similar to R for measured DBPs and MTOX, but the UTOX fractions of all concentrates differ. We conclude that the concentrate C has DBP concentrations that are most similar to that of R. [The views expressed in this abstract are those of the authors and do not necessarily reflect the views or policies of the U.S. EPA.]