Trihalomethane precursors: Land use hot spots, persistence during transport, and management options

Robert S Eckard; Brian A Bergamaschi; Brian A Pellerin; Tamara Kraus; Peter J Hernes

doi:10.1016/j.scitotenv.2020.140571

Trihalomethane precursors: Land use hot spots, persistence during transport, and management options

Sci Total Environ. 2020 Nov 10:742:140571. doi: 10.1016/j.scitotenv.2020.140571. Epub 2020 Jun 29.

Authors

Robert S Eckard¹, Brian A Bergamaschi², Brian A Pellerin³, Tamara Kraus⁴, Peter J Hernes⁵

Affiliations

¹ Department of Land, Air, and Water Resources, University of California, One Shields Ave., Davis, CA 95616, United States of America. Electronic address: reckard@rseanalytics.com.
² U.S. Geological Survey, 6000 J Street, Placer Hall, Sacramento, CA 95819, United States of America. Electronic address: bbergama@usgs.gov.
³ U.S. Geological Survey, 12201 Sunrise Valley Drive, Reston, VA 20192, United States of America. Electronic address: bpeller@usgs.gov.
⁴ U.S. Geological Survey, 6000 J Street, Placer Hall, Sacramento, CA 95819, United States of America. Electronic address: tkraus@usgs.gov.
⁵ Department of Land Air, and Water Resources, University of California, One Shields Ave., Davis, CA 95616, United States of America. Electronic address: pjhernes@ucdavis.edu.

PMID: 32640387
DOI: 10.1016/j.scitotenv.2020.140571

Abstract

To meet drinking water regulations, rather than investing in costly treatment plant operations, managers can look for ways to improve source water quality; this requires understanding watershed sources and fates of constituents of concern. Trihalomethanes (THMs) are one of the major classes of regulated disinfection byproducts, formed when a specific fraction of the organic carbon pool-referred to as THM precursors-reacts with chorine and/or bromine during treatment. Understanding the source, fate, timing and duration of the organic compounds that react to form THMs will allow identification of targeted and effective management actions. In this study we evaluated THM precursor contributions from multiple land use categories and hydrologic contexts, including novel data for urban land uses that demonstrate strong potential to release water with high THM formation potential (THMFP; median 618 μg L^-1): greater than storm runoff integrated across a mixed-use (1/3 natural, 2/3 agricultural) watershed (median 460 μg L^-1), irrigation runoff from agricultural systems (357 μg L^-1), or runoff from a natural forested (median 123 μg L^-1) and shrubland/grassland (median 259 μg L^-1) watersheds. While individual storm events released high THM precursor concentrations over short periods, dry season agricultural irrigation as well as urban landscapes have the potential to release water high in THM precursors for several months. Experimental bioassays and sampling along 333 miles of the California Aqueduct confirmed bioavailability and photooxidation potential of less than 10% for THM precursors, suggesting that rivers with residence times of days to weeks may act as THM precursor conduits, shuttling THM precursors from hundreds of miles away to drinking water intakes with minimal degradation. This finding has considerable implications for water managers, who may therefore consider THM precursor management strategies that target even sources located far upstream.

Keywords: DBPs; Disinfection byproduct precursors; Disinfection byproducts; Dissolved organic carbon; Dissolved organic matter; Trihalomethanes.