Efficiency of activated and nano activated carbon catalyzed ozonation for inactivation of antibiotic resistant bacteria and abatement of resistance genes in hospital wastewater

Abstract Antimicrobial resistance (AMR) is a leading global health threat, and hospital wastewater is a critical hotspot for its emergence and dissemination. Hospital wastewater is a major reservoir for antibiotic-resistant bacteria (ARBs) like Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, and their resistance genes (ARGs). We assessed ARB/ARG removal via catalytic ozonation (CATO) enhanced with AC or NAC (20–60 mg L −1 ) in 24-h hospital wastewater composites. Sterilized samples were spiked to 10 6 or 10 8 CFU mL −1 . Ozone (22 mg L −1 at 0.2 L min −1 ) delivered TOD of 11–45 mg L −1 . ARB viability was assessed by selective plating; ARGs ( sul1 , bla CTX-M , bla TEM , bla VIM , qnrS ) and the 16S rRNA reference gene by PMA-qPCR. Statistics (R): one-way ANOVA with Bonferroni-corrected pairwise comparisons, Kruskal–Wallis with Dunn's post-hoc and Bonferroni correction, paired and independent two-sample t-tests; significance set at p < 0.05. Bacterial inactivation was significantly TOD dependent at 10 8 CFU mL −1 , with 40 mg L −1 NAC optimal at TOD = 45 mg L −1 , whereas no catalyst effect was detected at 10 6 CFU mL −1 . ARG abatement ( sul1 , bla CTX-M , bla TEM ) was greatest at higher TOD and 60 mg L −1 NAC, while bla VIM remained comparatively resistant. E. coli and A. baumannii showed generally greater ARG reduction than P. aeruginosa . SEM indicated preliminary NAC stability after single cycle ozonation. Under the tested high load batch conditions, the process reduced culturable ARB counts and viable cell associated ARG loads, while bla VIM in P. aeruginosa remained the most recalcitrant carbapenem resistance marker. These findings indicate that NAC assisted ozonation may improve treatment performance in hospital effluents; however, because the study was conducted in a sterilized, spiked batch matrix and did not include catalyst-only or non-ozonated blank controls, validation in continuous-flow systems treating native hospital wastewater and across multiple catalyst-reuse cycles is required before operational deployment.