Antibiotic Contamination in Wastewater Treatment Plants of a Highly Urbanized City in Vietnam: Occurrence, Removal, and Environmental Risks

—This study evaluated the occurrence, removal efficiency, and environmental risks of ten commonly used antibiotics in two Municipal Wastewater Treatment Plants (WWTPs) in Ho Chi Minh City, Vietnam, one of the most densely populated urban areas in Southeast Asia. Fluoroquinolones were the most frequently detected antibiotics in influent samples, with concentrations reaching the µg/L range, followed by sulfonamides and trimethoprim. In contrast, macrolides were detected at low or undetectable levels in raw wastewater. Although overall antibiotic concentrations were significantly reduced after treatment, residual fluoroquinolones persisted in the effluent, and macrolide concentrations unexpectedly increased. Ecological risk assessment of receiving waters indicated moderate risks associated with azithromycin, levofloxacin, and ciprofloxacin. These findings underscore the limitations of conventional treatment technologies in fully mitigating antibiotic pollution and raise concerns about the potential for the propagation of antimicrobial resistance and long-term ecological harm. Further research is recommended to assess antibiotic residues in dewatered sludge, which may serve as a persistent environmental reservoir, particularly where sludge is reused or disposed of on land.