Degree

Doctor of Philosophy (PhD)

Department

Civil and Environmental Engineering

Document Type

Dissertation

Abstract

The persistence of pharmaceutical micropollutants in treated wastewater presents a growing challenge to conventional treatment systems, particularly as water reuse becomes central to sustainable water management. Advanced oxidation processes (AOPs) offer a pathway for degrading recalcitrant contaminants, yet their efficiency is often constrained by dissolved organic matter (DOM), energy demands, and limited control over reactive species generation. This dissertation advances UV-driven chlorine and chloramine photolysis as tunable, infrastructurecompatible oxidation platforms capable of overcoming these limitations. Through systematic control of wavelength, pH, and irradiation mode, this work demonstrates that reactive oxygen species (ROS) and reactive chlorine species (RCS) distributions can be selectively engineered to enhance micropollutant degradation while mitigating matrix interference. Using carbamazepine and acetaminophen as model contaminants, the study integrates in-situ electron paramagnetic resonance (EPR) spin trapping, kinetic analyses, quenching experiments, and high-resolution mass spectrometry to resolve dominant radical pathways and transformation mechanisms. Particular emphasis is placed on distinguishing the roles of •OH, Cl•, Cl2⁻•, ClO•, NHCl•, 1O3, and O3 under varying photochemical conditions. A key innovation of this work is the exploration of pulsed UV irradiation as a strategy to modulate radical formation dynamics. Frequency and duty cycle control produced distinct reactive species signatures, revealing new opportunities for energy-efficient radical control beyond conventional continuous irradiation. Additionally, monochloramine photolysis is mechanistically characterized, expanding the applicability of UV-based advanced oxidation in chloraminated systems. The influence of DOM on radical selectivity and degradation efficiency is systematically evaluated, demonstrating that selective oxidants such as ozone and reactive chlorine species can outperform non-selective hydroxyl radical pathways in complexx water matrices. Transformation product profiling and Microtoxicity bioassays further elucidate toxicity evolution during treatment, highlighting the balance between contaminant removal and byproduct formation. Collectively, this research establishes a mechanistic framework for engineering spectrally controlled, oxidant-flexible photochemical treatment systems. By linking radical chemistry, operational parameters, and ecotoxicological outcomes, the findings support the development of adaptive, energy-conscious tertiary treatment technologies suitable for potable reuse and advanced wastewater reclamation applications.

Date

4-2-2026

Committee Chair

Snow, Samuel D.

LSU Acknowledgement

1

LSU Accessibility Acknowledgment

1

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