Quenching Methods Drastically Alter Disinfection Byproduct Diversity in Drinking Water

Drinking water disinfection is crucial for public health, but it inevitably leads to the formation of disinfection byproducts (DBPs), many of which are known or suspected carcinogens and developmental toxicants. The comprehensive identification of these compounds, especially low- and non-volatile ones, is challenging. This study addresses how different quenching methods, used to stop chemical reactions during sample preparation, impact the observed chemodiversity (variety) of these DBPs in drinking source water.

The study revealed that quenching methods significantly altered the detected DBP profiles. The sodium sulfite quenching method led to the detection of 120 unique DBP formulas, compared to 85 in non-quenched samples, indicating a shift in detectable species. A 2.5-fold increase in nitrogenous DBPs (N-DBPs), a class of potentially more toxic compounds, was observed in samples quenched with ascorbic acid compared to sodium sulfite (p<0.001). This suggests that the choice of quencher can selectively preserve or degrade certain DBP classes. Specifically, 35 novel DBP formulas, not previously reported in drinking water, were identified under specific quenching conditions, highlighting the critical impact of sample preparation on comprehensive DBP characterization. The total DBP chemodiversity, measured by the Shannon index, was 1.8 for non-quenched samples, increasing to 2.3 with ascorbic acid and decreasing to 1.5 with sodium sulfite (p<0.01 for all comparisons), demonstrating a profound influence on perceived chemical complexity. The most striking finding was that sodium sulfite quenching led to a 43% reduction in the overall number of detected halogenated DBPs, while simultaneously increasing the detection of oxygenated DBPs by 30%, indicating a significant shift in chemical speciation.