Fate of antibiotic resistance genes and bacteria in a coupled water-processing system with wastewater treatment plants and constructed wetlands in coastal eco-industrial parks

In coastal eco-industrial zones, wastewater treatment plants (WWTPs) and constructed wetlands (CWs) can alleviate the challenge of water shortage and the negative effect of sewage discharge, while the problems of antibiotic resistance genes (ARGs) have not attracted enough attention. In this research, the Wafergen SmartChip system was adopted to investigate the ARG profiles in a coupled system combined WWTPs and CWs in a coastal industrial park. Potential risks of antibiotic resistance in chemical industrial wastewater were confirmed due to the higher abundance of target ARGs (> 107 copies/mL). General decline with partial enrichment in absolute and relative abundance of ARGs from the WWTPs to CWs revealed the effective removal of ARGs in the coupled system, while the fate of different ARG types varied greatly. Aminoglycoside and sulfonamide ARGs were detected with higher abundance (up to 5.34 ×107 and 3.61 ×107 copies/mL), especially aac(6′)-Ib and sul1. Denitrification, secondary sedimentation, and acid hydrolysis contributed to the removal of aminoglycoside, sulfonamide, β-lactamase, chloramphenicol, and multidrug ARGs. Catalytic ozonation contributed to the removal of tetracycline and MLSB ARGs. Subsurface CWs worked effectively for the removal of sulfonamide, tetracycline, and multidrug ARGs, especially tetX, cphA, tetG, and strB. Close correlations between ARGs and MGEs emphasized the vital roles of anthropogenic pollutants and horizontal gene transfer on the diffusion of ARGs. Actinobacteria, Bacteroidota, and Cyanobacteria were dominant in the CWs, while Proteobacteria, Firmicutes, and Planctomycetota were prevalent in the WWTPs. Redundancy analysis and variance partitioning analysis indicated that transposase and water quality posed greater influences on the distribution of ARGs. Co-occurrence network revealed that potential multiple antibiotic resistant pathogenic bacteria decreased in the CWs. The coupled system has a limited effect on the reduction of ARGs and potential ARG hosts, providing a comprehensive insight into the fate of ARGs in conventional water-processing systems.