Molecular-Level Insights into the Formation of Traditional and Novel Halogenated Disinfection Byproducts

Abstract

Dissolved organic matter (DOM) composition influences the formation of disinfection byproducts (DBPs) during drinking water treatment, yet the role of DOM composition at the molecular level in forming both known and novel DBPs has not been established. We characterized the composition of DOM from drinking water utilities that draw from surface (n = 4) and groundwaters (n = 14), focusing on groundwater because the reactivity of its DOM is poorly understood. We quantified the formation of targeted DBPs, identified novel high molecular weight (HMW) halogenated DBPs, and analyzed DOM transformation after reaction with free available chlorine. Characterization by UV–visible spectroscopy and Fourier transform-ion cyclotron resonance mass spectrometry (FT-ICR MS) reveals a high degree of variability in DOM composition and reactivity with chlorine, particularly among groundwater samples. Despite the variability in DOM composition, novel DBPs with up to three halogens are compositionally similar among all waters and are positively correlated with trihalomethane and, to a lesser extent, haloacetonitrile formation. These relationships demonstrate that some low molecular weight DBPs and novel DBPs detected by FT-ICR MS share similar aromatic precursors, providing evidence that DBPs such as trihalomethanes are a useful proxy for the formation of their HMW counterparts.