Date of Graduation

9-2025

Document Type

Thesis

Degree Name

Doctor of Philosophy in Engineering (PhD)

Degree Level

Graduate

Department

Civil Engineering

Advisor/Mentor

Zhang, Wen

Committee Member

Julian Fairey

Second Committee Member

Lei Guo

Keywords

advanced water treatment; antibiotic resistance genes; water reuse

Abstract

More areas across the globe are becoming affected by water stress or water scarcity. The decrease in available freshwater due to overconsumption reveals the direct need to consider other sources for necessities such as drinking water or food production. Agricultural irrigation uses 70% of the world’s freshwater, making the focus on safe and reliable reclaimed water for agricultural reuse imperative. However, contaminants of emerging concern (CECs), such as antibiotics and their resulting antibiotic resistance genes (ARGs), can spread and affect human health if reclaimed water is not treated to the proper level. Antibiotics are widely used in human medicine and animal husbandry, developing into the problem of antibiotic resistance. ARGs can multiply throughout the environment via vertical or horizontal gene transfer (HGT) and can be present as intra- or extracellular DNA (iDNA and eDNA, respectively). eDNA can bind to sediment and particulate matter, shielding it from possible degradation and inactivation by wastewater treatment plant (WWTP) processes. WWTPs are typically unable to target and remove eARGs; however, advanced treatment processes for reclaimed water may be able to remove them. This study measured ARGs in various environmental samples, including lakes, ponds and wastewater treatment facilities with a pilot advanced treatment train. Five ARGs corresponding with resistance to different antibiotic classes (tetracyclines, sulfonamides, and macrolides) were quantified using qPCR. Different levels of ARGs were detected in all samples collected. A separation protocol was also tested for iDNA and eDNA in water samples by investigating the recovery efficiency of each. However, results from this study showed that the proposed separation protocol has a low recovery efficiency for eDNA, and that more research on iDNA and eDNA separation is needed in the future. Moreover, the advanced treatment processes in the pilot facility exhibited inconsistent ARG removal rates at all ozone dosages tested, which is most likely attributed to the differences in individual ARG structures, as well as the sequence of advanced treatment processes.

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