Feel the Burn: Disinfection Byproduct Formation and Cytotoxicity during Chlorine Burn Events

Abstract

Nitrification and biofilm growth within distribution systems remain major issues for drinking water treatment plants utilizing chloramine disinfection. Many chloraminated plants periodically switch to chlorine disinfection for several weeks to mitigate these issues, known as “chlorine burns”. The evaluation of disinfection byproduct (DBP) formation during chlorine burns beyond regulated DBPs is scarce. Here, we quantified an extensive suite of 80 regulated and emerging, unregulated DBPs from 10 DBP classes in drinking water from two U.S. drinking water plants during chlorine burn and chloramination treatments. Total organic halogen (TOX), including total organic chlorine, total organic bromine, and total organic iodine, was also quantified, and mammalian cell cytotoxicity of whole water mixtures was assessed in chlorine burn waters for the first time. TOX and most DBPs increased in concentration during chlorine burns, and one emerging DBP, trichloroacetaldehyde, reached 99 μg/L. THMs and HAAs reached concentrations of 249 and 271 μg/L, respectively. Two highly cytotoxic nitrogenous DBP classes, haloacetamides and haloacetonitriles, increased during chlorine burns, reaching up to 14.2 and 19.3 μg/L, respectively. Cytotoxicity did not always increase from chloramine treatment to chlorine burn, but a 100% increase in cytotoxicity was observed for one plant. These data highlight that consumer DBP exposure during chlorine burns can be substantial.

Fluorescent Dissolved Organic Matter Components as Surrogates for Disinfection Byproduct Formation in Drinking Water: A Critical Review

“…However, in excess of 700 DBPs have been identified to date, the vast majority of which are unregulated with many thoughts of being potentially carcinogenic . Moreover, a recent study estimated that 32–81% of total organic halogen (TOX) loads, produced during chemical disinfection, are attributable to as yet unidentified DBPs, highlighting the likely importance of new and emerging classes over the coming years …”

Fluorescent Dissolved Organic Matter Constituents as Surrogates for Disinfection Byproduct Formation in Drinking Water Treatment: A Critical Review

“…For instance, emerging DBP classes, including HKs, HALs, HNMs, HANs, HAMs, NAs, I-HAAs and I-THMs need to be screened more frequently with advanced analytical methods to potentially established relationships with PARAFAC components. 5,111 The potentially greater carcinogenic concerns associated with HANs and I-HAAs means these two classes should be prioritized in future investigations. 12 In addition, various disinfectant methods might have, from a mechanistic point of view, various precursors and formation pathways with contrasting effects on a single PARAFAC component.…”

“…4 Moreover, a recent study estimated that between 32−81% of the total halogen component content constitutes unidentified DBPs. 5 DOM in freshwaters is comprised of many different organic carbon compounds, derived from autochthonous sources, such as algae/bacteria, and allochthonous sources, such as leaf/soil, material, 6 whose hydrological export varies spatially and temporally within river basins around the world 7 . Humic and fulvic acids from allochthonous sources, comprising high molecular weight and aromaticity humic substances are considered to be the primary DOM precursors for carbonaceous DBPs (C-DBPs).…”

Formation of Larger Molecular Weight Disinfection Byproducts from Acetaminophen in Chlorine Disinfection

“…Chlorine is the most widely used disinfectant in drinking water treatment, , yet it can react with natural organic matter (NOM) and organic pollutants in source water to generate potentially harmful disinfection byproducts (DBPs). − Acetaminophen shows high reactivity toward chlorine and can readily undergo conversion during chlorination. − N -Acetyl- p -benzoquinone imine (NAPQI) and 1,4-benzoquinone have already been identified as chlorination products of acetaminophen; after a one-hour treatment with 4 mg/L chlorine, the two byproducts accounted for 25% and 1.5%, respectively, of the initial acetaminophen concentration. In addition, the formation of chlorinated acetaminophen has been reported in previous studies. , …”

“…12 The presence of acetaminophen and other pharmaceuticals in the water environment has become one of the key challenges to safe drinking water supplies and continues to be a major public health concern. 12,13 Chlorine is the most widely used disinfectant in drinking water treatment, 14,15 yet it can react with natural organic matter (NOM) and organic pollutants in source water to generate potentially harmful disinfection byproducts (DBPs). 16−30 Acetaminophen shows high reactivity toward chlorine and can readily undergo conversion during chlorination.…”