Occurrence, fate and correlation analysis of antibiotics and antibiotic resistance genes (ARGs) in rural domestic wastewater treatment facilities.

Antibiotics and antibiotic resistance genes (ARGs) are emerging contaminants of increasing concern in rural wastewater treatment systems. This study examined the occurrence, removal, and ecological risks of 42 antibiotics and related ARGs across the rural facilities utilizing three treatment processes: anaerobic digestion with soil infiltration systems (AD + SIS), anaerobic-anoxic-oxic (A/A/O), and fixed-bed membrane bioreactor coupled with constructed wetlands (FMBR + CW). Eighteen antibiotics were frequently detected in influents, with concentrations up to 2644 ng/L. FMBR + CW systems exhibited the highest removal efficiencies, while AD + SIS showed limited or negative removal for some antibiotics. Sludge samples revealed significant accumulation of hydrophobic antibiotics, particularly quinolones and tetracyclines (>16,000 μg/kg). ARGs such as sul1 and ErmB were commonly detected, with FMBR + CW achieving >96 % removal due to synergistic effects of redox conditions and plant-microbe interactions. Microbial analysis indicated distinct community structures across treatment stages, with potential links to antibiotic and ARG attenuation. Correlation analysis revealed strong associations between specific antibiotics and ARGs, suggesting co-selection mechanisms. These findings provide critical insight into contaminant fate in decentralized systems and highlight the potential of integrated biological-ecological treatment technologies for mitigating antibiotic and ARG pollution in rural areas.