American Chemical Society
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Haloacetic acid and Trihalomethane Formation from the Chlorination and Bromination of Aliphatic β-Dicarbonyl Acid Model Compounds

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journal contribution
posted on 2020-04-03, 10:10 authored by Eric R. V. Dickenson, R. Scott Summers, Jean-Philippe Croué, Hervé Gallard
While it is known that resorcinol- and phenol-type aromatic structures within natural organic matter (NOM) react during drinking water chlorination to form trihalomethanes (THMs), limited studies have examined aliphatic-type structures as THM and haloacetic acid (HAA) precursors. A suite of aliphatic acid model compounds were chlorinated and brominated separately in controlled laboratory-scale batch experiments. Four and two β-dicarbonyl acid compounds were found to be important precursors for the formation of THMs (chloroform and bromoform (71–91% mol/mol)), and dihaloacetic acids (DXAAs) (dichloroacetic acid and dibromoacetic acid (5–68% mol/mol)), respectively, after 24 h at pH 8. Based upon adsorbable organic halide formation, THMs and DXAAs, and to a lesser extent mono and trihaloacetic acids, were the majority (>80%) of the byproducts produced for most of the aliphatic β-dicarbonyl acid compounds. Aliphatic β-diketone-acid-type and β-keto-acid-type structures could be possible fast- and slow-reacting THM precursors, respectively, and aliphatic β-keto-acid-type structures are possible slow-reacting DXAA precursors. Aliphatic β-dicarbonyl acid moieties in natural organic matter, particularly in the hydrophilic fraction, could contribute to the significant formation of THMs and DXAAs observed after chlorination of natural waters.