Impact of storm events on disinfection byproduct precursors in a drinking water source in the Northeastern United States

Mohammad Kiron Shakhawat; Rakesh K Gelda; Karen E Moore; Rajith Mukundan; Mariana Lanzarini-Lopes; Sean T McBeath; Christian D Guzman; Dave Reckhow

doi:10.1016/j.watres.2024.121445

Impact of storm events on disinfection byproduct precursors in a drinking water source in the Northeastern United States

Water Res. 2024 May 15:255:121445. doi: 10.1016/j.watres.2024.121445. Epub 2024 Mar 10.

Authors

Mohammad Kiron Shakhawat¹, Rakesh K Gelda², Karen E Moore², Rajith Mukundan², Mariana Lanzarini-Lopes³, Sean T McBeath³, Christian D Guzman³, Dave Reckhow³

Affiliations

¹ Civil and Environmental Engineering, Engineering Laboratory II (Elab II), 101 North Service road, Rm#210, UMass Amherst, Amherst MA 01003-9345, United States. Electronic address: mshakhawat@umass.edu.
² Bureau of Water Supply, NYC Department of Environmental Protection, 71 Smith Ave, Kingston, NY 12401, United States.
³ Civil and Environmental Engineering, Engineering Laboratory II (Elab II), 101 North Service road, Rm#210, UMass Amherst, Amherst MA 01003-9345, United States.

PMID: 38503182
DOI: 10.1016/j.watres.2024.121445

Abstract

Storm events play a crucial role in organic matter transport within watersheds and can increase the concentration and alter the composition of NOMs and DBP formation potential. To assess the impact that storm events can have on drinking water quality, samples were collected and analyzed across four storm events in the Neversink River, Catskill region, New York in 2019 and 2022. Source water natural organic matter (NOM) was characterized, and the change of NOM quality was evaluated due to storm impacts. During storm events, a high level of NOM mobilization is initiated by heavy precipitation causing overland flow and a rise in the water table. In this way, storms result in increased access to stored NOM pools that are generated during inter-storm periods. A significant correlation was observed between several organic water quality parameters such as UV absorbance (UV₂₅₄), dissolved organic carbon (DOC) and chlorine demand. Precursors for the total trihalomethanes (TTHM), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) exhibited comparable patterns with UV₂₅₄, DOC, and chlorine demand for four storms. Despite the potential for increased dilution resulting from higher discharges, all organic water quality parameters, including yields of disinfection byproducts (i.e., DBP precursors), exhibited elevated concentrations during periods of higher flows. Three of the four storms showed hysteresis patterns with higher observed concentrations of organic constituents in the falling limb of the hydrographs. Precursors for the nitrogenous DBPs (N-DBPs) were proportional to the DOC for all four storms. The coefficient of determination (R²) for TTHM, DCAA, TCAA with UV₂₅₄ is higher (R² 0.92-0.98) than corresponding correlations with DOC (R² 0.89-0.92). The R² for UV₂₅₄ showed the following hierarchy: DCAA≈TCAA>TTHM. Additionally, the R² for DOC and specific ultraviolet absorbance (SUVA) had the following hierarchy: DCAA>TCAA>TTHM and TCAA>DCAA>TTHM respectively. A significant correlation between UV₂₅₄ and DOC (R = 0.99) for all storms was observed. Chlorine demand also yielded a strong correlation (R = 0.91∼0.98) with UV₂₅₄ and DOC. This research indicates that a significant and disproportionate export of NOM to source waters occurs during storm events compared to baseflow conditions. Consequently, it is recommended for drinking water treatment facilities to reassess chlorine dosages during these events. Treatment plants can employ UV₂₅₄ as a tool to determine appropriate chlorine dosages, aiming to mitigate DBP formation in treated waters.

Keywords: DBp formation; Drinking water sources; Hysteresis; NOM characteristics changes; Storm impacts; Water quality parameters.