Investigating the Effect of Additional Organic Matter on Disinfection Byproduct Formation: Sweetened Beverages and Spring Runoff
Creators: Wawryk, Nicholas J.P.
Publisher: name: University of Alberta Library
Year: 2024

<p>A significant effort is made to remove organic matter from source water prior to disinfection during water treatment. Any remaining organic matter in source water can react with disinfectants to form disinfection by-products (DBPs). Importantly, epidemiological studies have found associations between disinfected water and several adverse human health effects. Additionally, in vitro and in vivo toxicology studies have identified many DBPs as cyto- and genotoxic. Therefore, significant effort has been made to identify and monitor the formation of DBPs. Chapter 1 includes a review of current drinking water disinfection research focusing on the natural and anthropogenic influences on DBP formation as well as analytical methodology.<br>
    Most research on the formation of DBPs focuses on the disinfection step during water treatment. However, drinking water contains residual disinfectant to prevent against opportunistic waterborne pathogens within the distribution system. Therefore, any organic matter added to finished drinking water, such as during beverage preparation, could react with residual disinfectants. Chapter 2 investigated the formation of DBPs when aspartame (APM), a common artificial sweetener, was added to water containing residual chlorine. Nontargeted analysis with high performance liquid chromatography and quadrupole time-of-flight mass spectrometry (HPLC-QTOF-MS) enabled the tentative identification of eight novel chlorinated transformation products of APM. Further, targeted analysis using HPLC tandem mass spectrometry (MS/MS) was used to identify APM as a precursor to halobenzoquinones (HBQs), specifically 2,6-dichloro-1,4-benzoquinone (DCBQ), a toxicologically significant class of DBPs. Non-chlorinated transformation products of APM and ways to prevent formation were also examined.<br>
     Snow melt during spring can cause a significant change in the type and quantity of organic matter in source water. The effect of this phenomenon, referred to as spring runoff, was investigated in Chapter 3-5. One of the significant challenges for water treatment associated with spring runoff is an increase in taste and odour complaints. In Chapter 3, the concentration of free amino acids (AAs) was monitored during spring to evaluate their ability to predict the onset of odour events. Over the three years that were studied, a significant difference in the concentration of AAs was found which corresponded with the strongest reported odour intensities. Further, the formation of N-chloroaldimines from four AAs (phenylalanine, valine, leucine, and isoleucine) was found using HPLC-QTOF-MS. Subsequent analysis with HPLC-MS/MS investigated their formation under realistic water treatment conditions and stability in a simulated distribution system. These results indicate that AAs may signal the onset of spring runoff and represent the small polar compounds which can act as precursors to odourous DBPs.<br>
    In Chapter 4, the effect of spring runoff on the formation of HBQs was studied using HPLC-MS/MS. The results over three spring sampling periods demonstrated that spring runoff may contribute to variation in the formation of DCBQ. During spring runoff events, common water quality parameters, measured in source water, correlated well with the concentration of DCBQ determined in finished drinking water. The concentration of aromatic AAs determined in source water followed the same trend as the concentrations of DCBQ determined in finished drinking water. Additionally, a possible correlation was found between the concentration of DCBQ determined immediately following the addition of chlorine and OH-DCBQ detected in finished drinking water.<br>
    In Chapter 5, nontargeted analysis with HPLC-QTOF-MS, with ChloroDBPFinder and MS-DIAL for data processing, was used to investigate chemical changes in complex environmental samples. ChloroDBPFinder uses machine learning to extract chlorine (Cl)-containing features in high resolution mass spectrometry (HRMS) data. This program was able to extract several hundred (~500-700) Cl-containing features in laboratory reactions with model precursors and in authentic water samples collected during spring runoff. Principal component analysis (PCA) revealed differences in the chemical composition during laboratory reactions as well as temporal trends during spring runoff. Further, Spearman’s correlation analysis was used to identify chemical features that were correlated with water quality parameters during spring runoff events. This thesis highlights the effect of changes in organic matter on DBP formation and the importance of sensitive analytical methodologies for environmental analysis.</p>