Towards reducing DBP formation potential of drinking water by favouring direct ozone over hydroxyl radical reactions during ozonation

De Vera, Glen Andrew, Stalter, Daniel, Gernjak, Wolfgang, Weinberg, Howard S., Keller, Jurg and Farre, Maria José (2015) Towards reducing DBP formation potential of drinking water by favouring direct ozone over hydroxyl radical reactions during ozonation. Water Research, 87 49-58. doi:10.1016/j.watres.2015.09.007

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Author De Vera, Glen Andrew
Stalter, Daniel
Gernjak, Wolfgang
Weinberg, Howard S.
Keller, Jurg
Farre, Maria José
Title Towards reducing DBP formation potential of drinking water by favouring direct ozone over hydroxyl radical reactions during ozonation
Journal name Water Research   Check publisher's open access policy
ISSN 1879-2448
0043-1354
Publication date 2015-12-15
Sub-type Article (original research)
DOI 10.1016/j.watres.2015.09.007
Open Access Status File (Author Post-print)
Volume 87
Start page 49
End page 58
Total pages 10
Place of publication London, United Kingdom
Publisher I W A Publishing
Collection year 2016
Language eng
Formatted abstract
When ozonation is employed in advanced water treatment plants to produce drinking water, dissolved organic matter reacts with ozone (O3) and/or hydroxyl radicals (radical dotOH) affecting disinfection byproduct (DBP) formation with subsequently used chlorine-based disinfectants. This study presents the effects of varying exposures of O3 and radical •OH on DBP concentrations and their associated toxicity generated after subsequent chlorination. DBP formation potential tests and in vitro bioassays were conducted after batch ozonation experiments of coagulated surface water with and without addition of tertiary butanol (t-BuOH, 10 mM) and hydrogen peroxide (H2O2, 1 mg/mg O3), and at different pH (6–8) and transferred ozone doses (0–1 mg/mg TOC).

Although ozonation led to a 24–37% decrease in formation of total trihalomethanes, haloacetic acids, haloacetonitriles, and trihaloacetamides, an increase in formation of total trihalonitromethanes, chloral hydrate, and haloketones was observed. This effect however was less pronounced for samples ozonated at conditions favoring molecular ozone (e.g., pH 6 and in the presence of t-BuOH) over radical •OH reactions (e.g., pH 8 and in the presence of H2O2). Compared to ozonation only, addition of H2O2 consistently enhanced formation of all DBP groups (20–61%) except trihalonitromethanes. This proves that radical •OH-transformed organic matter is more susceptible to halogen incorporation. Analogously, adsorbable organic halogen (AOX) concentrations increased under conditions that favor radical •OH reactions. The ratio of unknown to known AOX, however, was greater at conditions that promote direct O3 reactions. Although significant correlation was found between AOX and genotoxicity with the p53 bioassay, toxicity tests using 4 in vitro bioassays showed relatively low absolute differences between various ozonation conditions.
Keyword Adsorbable organic halogens
Disinfection byproducts
Hydroxyl radicals
In vitro bioassays
Ozonation
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

 
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