Date of Award

Fall 2025

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

First Advisor

Susan D. Richardson

Abstract

Drinking water disinfection is critical to prevent the occurrence of waterborne pathogens in drinking water. However, disinfection causes the unintended formation of disinfection byproducts (DBPs) through the reaction of disinfectants (e.g., chlorine, chloramine) with natural organic matter (NOM), algal matter, or anthropogenic pollutants present in source waters. Exposure to DBPs is associated with increased bladder cancer, colorectal cancer, miscarriage, and birth defects. The U.S. EPA currently regulates eleven DBPs in drinking water—four trihalomethanes, five haloacetic acids, bromate, and chlorite. However, research shows that DBP related toxicity in drinking water is driven mainly by other, non-regulated DBPs, particularly iodinated DBPs and nitrogenous DBPs, which are generally far more toxic than those regulated.

We developed a solventless method utilizing headspace solid phase extraction with application of vacuum to extract six iodinated-trihalomethane (I-THM) disinfection byproducts from drinking water and urine. Vacuum-assisted sorbent extraction (VASE) provides improved analyte recovery, and reduced matrix interference compared to liquid-liquid extraction, and when paired with gas chromatography-tandem mass spectrometry, allows low ng/L detection of I-THMs.

A new liquid-liquid extraction-gas chromatography-tandem mass spectrometry (LLE-GC-MS/MS) method was developed with the first analysis by gas chromatography- tandem mass spectrometry of 23 priority unregulated DBPs including 13 haloacetamides, 3 haloacetic acids, 2 haloacetonitriles, 1 haloacetaldehyde, 2 haloketones, and 2 halonitromethanes. When combined with our previous GC-MS/MS method for haloacetic acids this enables analysis of 62 regulated and priority unregulated DBPs. Limits of quantification (LOQs) for most DBPs are between 5 and 30 ng/L, and are an average of 9 times lower than liquid-liquid extraction paired with GC-single MS.

Ash material can significantly impact drinking water when it enters source waters through rain run-off. Chlor(am)ination of the water-soluble fraction of structural ashes from a wildland-urban interface wildfire caused formation of high levels of brominated, iodinated, and nitrogenous DBPs due to high levels of water-soluble bromide, iodide, and nitrogenous precursors. Chloramination did not significantly reduce DBP formation or calculated cytotoxicity vs. chlorine due to enhanced formation of iodinated and nitrogenous DBPs. Structural ash leachates leached less dissolved organic carbon than vegetation ash and contribute lower levels of DBP precursors. However, these precursors can increase the toxicity of drinking water due to a shift towards more toxic DBP species.

While disinfection byproducts (DBPs) are typically measured at drinking water treatment plants, levels can change dramatically within the distribution system before reaching the consumer. Disinfection byproduct levels generally decrease with increasing detention time in distribution systems utilizing residual chlorine, and vice versa in distribution systems with residual chlorine. Additionally, calculated cytotoxicity generally decreases with increasing detention time with both residual disinfectants. This is due to a decrease in highly cytotoxic nitrogenous DBPs with increasing detention time with both disinfectants and a shift in speciation towards relatively low cytotoxicity trihalomethanes.

Rights

© 2025, Patrick Thomas Justen

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