BOOK OF ABSTRACTS 219 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Hall A Poster Session / Environment, Agriculture, and Forestry P4.3 Wildfires As Important Sources of Haloaromatic Disinfection Byproducts in California Water Systems Vincent T. DiPietri1, William Mitch2 1 Stanford University, Department of Civil and Environmental Engineering, 473 Via Ortega Drive, Stanford, CA 94305, vxncxnt@stanford.edu 2 Stanford University, Department of Civil and Environmental Engineering, 473 Via Ortega Drive, Stanford, CA 94305, wamitch@stanford.edu Wildfire occurrence and severity are increasing globally, posing significant threats to downstream water sources and drinking water reservoirs by altering the chemical composition of natural organic matter and ultimately influencing the formation of disinfection byproducts (DBPs) in potable waters. While the characterization of 1-2 carbon DBPs from wildfire-impacted watersheds is better understood, the impacts on >2 carbons DBPs are severely understudied. This project investigates different fuel types (e.g., oak versus pine woods), burn temperature (300-700 °C), fire age (Glass Fire samples from 2020 and 2025), and fire type (wildfire versus prescribed burn) as variables affecting overall water quality and DBP formation in waters disinfected with chlorine and chloramines. Pyrogenic dissolved organic matter obtained from laboratory pyrolysis of fuels were used as a source of DBP Precursors. Analysis of >2 carbon DBPs via liquid-chromatography massspectrometry reveals concentrations of halonitrophenols, halophenols, and halosalicylic acids increase significantly after chlorination of pyDOM for most temperatures evaluated, up to 400% after 24 h. For chloramination, total concentrations of >2 carbon DBPs remained relatively stable throughout disinfection and typically formed within the first 1 h of free chlorine contact prior to conversion into chloramines. Of the three >2 carbon DBP classes examined, halosalicylic acids are formed at the highest concentrations constituting approximately 93% of total >2 carbon DBPs formed. More generally, halosalicylic acids typically form at the highest concentrations relative to halonitrophenols and halophenols in all samples for both disinfectants. Concentrations of 1-2 carbon DBPs align well with previous literature showing that as temperature increases, decreases in water extractable organic carbon released from pyrolyzed material subsequently decreases the formation of 1-2 carbon DBPs.
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