Constructed wetlands as nature-based solutions for the removal of antibiotics: performance, microbial response, and emergence of antimicrobial resistance (AMR)

Antibiotics and antibiotic resistance genes (ARGs) have been regarded as emerging pollutants and pose significant threats to the aquatic environment and to human health. This study aimed to investigate the removal of nutrients, antibiotics, and the emergency of ARGs in domestic sewage by means of constructed wetlands (CWs) filled with an electroconductive media, i.e., coke. In this study, the antibiotics removal efficiencies ranged from 13% to 100%, which were significantly higher in the system filled with coke compared with the CWs filled with common quartz sand (7%~100%). Moreover, the presence of wetland plants could also significantly improve the removal of nutrients and tetracyclines. The results also demonstrated the importance of substrate selection and wetland plants in CWs on the alternation of microbial communities and structures, where the electroconductive media showed a promising effect on increasing the removal of antibiotics in CWs. In terms of the emergency of ARGs, the CWs filled with coke retained the most ARGs (10,690 copies/g) compare with the control groups (8576–7934 copies/g) in the substrate. As the accumulated ARGs could be released back to the watercourse due to the environmental/operation condition changes, the application of such an advanced substrate in CWs may pose a more significant potential threat to the environment. With these results, this study provided new insight into selection of the substrates and plants for wastewater treatment to achieve a sustainable and secure water future.