Tackling CECs and antimicrobial resistant bacteria in hospital wastewater using biological and AOP hybrid...

This study investigated the disinfection, and removal of contaminants of emerging concern (CECs) and antibiotic-resistant bacteria (ARB) from hospital wastewater (HWW) using biological treatment followed by the LED photo-Fenton (BIO + LED-PF) and LED photo-Fenton followed by biological treatment (LED-PF + BIO). BIO was conducted by the Zahn Wellens method, while the LED-PF was applied in a pulse width modulation reactor (20 mg L^-1 Fe²⁺, 50 mg L^-1 H₂O₂, pH 2.8, 70 % duty cycle, 60 min). CECs removal exceeded 90 % using BIO + LED-PF and 71 % using LED-PF + BIO. Both treatments were efficient in removing targets CECs from non-spiked raw HWW achieving concentrations < 1 µg L^-1, except for trimethoprim in BIO + LED-PF. LED-PF + BIO removed 5 and 6 log₁₀ units of total coliforms (TC) and Escherichia coli (MPN/100 mL), respectively, while BIO + LED-PF achieved 5 log₁₀ units of removal of TC and E. coli (MPN/100 mL) elimination. Pathogens considered as "critical" priority by the World Health Organization detected in HWW by MALDI-TOF/MS (cephalosporin-resistant Enterococcus faecalis and E. coli and carbapenem-resistant Klebsiella pneumoniae) were also eliminated by both strategies. Approximately 3 logs₁₀ units of ARB were removed for both treatment strategies, yet bacterial regrowth was observed after the LED-PF + BIO (Staphylococcus warneri resistant to ciprofloxacin) and BIO (Citrobacter freundii resistant to ciprofloxacin with 2 log₁₀ units), emphasizing antimicrobial resistance risks. This regrowth was attributed to biomass proliferation and horizontal gene transfer in organic-rich environments. BIO + LED-PF also suppressed ARB, yet regrowth was detected for ARB resistant to SME + TRI. Overall, BIO + LED-PF was the most effective treatment, indicating the feasibility of its application in-situ in hospitals.