Abstract
Combinations of UV with oxidants can initiate advanced oxidation processes (AOPs) and enhance bacterial inactivation. However, the effectiveness and mechanisms of UV-AOPs in damaging nucleic acids (e.g., antibiotic resistance genes (ARGs)) and cell integrity represent a knowledge gap. This study comprehensively compared ARG degradation and cell membrane damage under three different UV-AOPs. The extracellular ARG (eARG) removal efficiency followed the order of UV/chlorine > UV/H2O2 > UV/peracetic acid (PAA). Hydroxyl radical (•OH) and reactive chlorine species (RCS) largely contributed to eARG removal, while organic radicals made a minor contribution. For intracellular ARGs (iARGs), UV/H2O2 did not remove better than UV alone due to the scavenging of •OH by cell components, whereas UV/PAA provided a modest synergism, likely due to diffusion of PAA into cells and intracellular •OH generation. Comparatively, UV/chlorine achieved significant synergistic iARG removal, suggesting the critical role of the RCS in resisting cellular scavenging and inactivating ARGs. Additionally, flow cytometry analysis demonstrated that membrane damage was mainly attributed to chlorine oxidation, while the impacts of radicals, H2O2, and PAA were negligible. These results provide mechanistic insights into bacterial inactivation and fate of ARGs during UV-AOPs, and shed light on the suitability of quantitative polymerase chain reaction (qPCR) and flow cytometry in assessing disinfection performance.
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