Date of Award
5-12-2024
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Civil and Environmental Engineering
Advisor(s)
Teng Zeng
Second Advisor
Tao Wen
Keywords
chloramination;N-nitroso compounds;NDMA;wastewater treatment
Subject Categories
Civil and Environmental Engineering | Engineering | Environmental Engineering
Abstract
N-Nitrosamines form as byproducts during oxidative water treatment or occur as impurities in consumer and industrial products. N-Nitrosamines and their precursors pose significant concerns for water utilities exploiting wastewater-impacted water supplies, as many N-nitrosamines are potential human carcinogens and have genotoxicity. To date, research on N-nitrosamines in environmental engineering has primarily focused on the occurrence, sources, formation, and control of N-nitrosodimethylamine (NDMA) in the broad context of drinking water and wastewater treatment. However, NDMA and the few other N-nitrosamines of current interest only constitute a fraction of the larger pool of total N-nitrosamines (TONO) in source waters and wastewater, while the rest of N-nitrosamines in the TONO pool remains largely unidentified. Even less is known about the origins, fate, and toxicological relevance of these uncharacterized N-nitrosamines. In the first study (Chapter 2), I compared the performance of acidic triiodide-based chemiluminescence method (HI3-CL) and ultraviolet photolysis-based chemiluminescence (UV-CL) method for TONO measurements in wastewater samples. Sixty-six N-nitroso compounds showed varied conversion efficiencies relative to NDMA with both chemiluminescence methods. On average, TONO levels in raw and chloraminated wastewater samples measured by the HI3-CL method were 2.1 ± 1.1 times those measured by the UV-CL method, suggesting potential matrix interferences for denitrosation by UV photolysis as further confirmed by spike recovery tests. This comparison addressed methodological gaps in TONO analysis, highlighted several practical considerations when implementing the HI3-CL and UV-CL methods for TONO analysis in wastewater, and validated an experimental platform for subsequent chapters. In the second study (Chapter 3), I developed an integrated analytical workflow combining solid phase extraction, TONO analysis, and liquid chromatography-high-resolution mass spectrometry (LC-HRMS) for systematic quantification and nontarget screening of N-nitrosamines in wastewater samples. A scoring scheme named TONO response factor was developed to enable a quantitative comparison between TONO and specific N-nitrosamine concentrations and was applied to refine the compositional analysis of TONO reported by the literature. To address gaps regarding the fate of TONO components in conventional wastewater treatment plants (WWTPs), the concentrations of specific N-nitrosamines and TONO in samples collected along the treatment trains of eight full-scale facilities in New York were consolidated by treatment steps for comparative analysis. Nontarget screening of raw and chloraminated samples from these facilities also led to the identification and confirmation of additional N-nitrosamines beyond commonly detected species such as NDMA. Of these newly identified N-nitrosamines, one was the N-nitroso derivative of a secondary amine-containing pharmaceutical – desloratadine, which was further evaluated in Chapter 4. Complementary measurements of wastewater samples using fluorescence spectroscopy, on the other hand, provided initial evidence for the proteinaceous nature of uncharacterized TONO precursors. This work provided information on the fate of TONO and their precursors in conventional WWTPs with varying treatment configurations and provided new insights into the possible identities of precursors to uncharacterized TONO components. In the third study (Chapter 4), I evaluated the formation of N-nitroso derivatives upon chloramination using non-labeled and 15N-labeled preformed monochloramine on 17 secondary amine-containing pharmaceuticals commonly detected in wastewater. LC-HRMS identified nine N-nitroso derivatives predicted to form via nitrosation of their secondary amine moieties, with reference to custom-synthesized standards. Chloramination of nine secondary-amine pharmaceuticals led to the formation of corresponding N-nitroso derivatives, confirmed by data dependent-MS2 spectra. The formation of N-nitroso derivatives was inhibited by radical scavengers or in the absence of dissolved oxygen, suggesting the involvement of radical intermediates and molecular oxygen. Hypothesized formation pathways were then proposed based on the detection of reaction intermediates on LC-HRMS. Molar yields of N-nitrosation reaction mixtures determined via chemiluminescence detection were higher than those measured by LC-HRMS, possibly due to the contribution from other N-nitrosamines. This work provided insight into an overlooked formation pathway of N-nitroso derivatives from secondary amine containing pharmaceuticals.
Access
Open Access
Recommended Citation
Pu, Changcheng, "Fate, Composition and Formation of Unknown N-Nitrosamines in Wastewater and Wastewater-Impacted Waters" (2024). Dissertations - ALL. 1968.
https://surface.syr.edu/etd/1968
