[Optimization of Tidal-Combined Flow Constructed Wetland System and Its Removal Effect on Antibiotic Resistance Genes]

Antibiotic resistance genes (ARGs) pose a serious threat to environmental biology and public health, along with the discharge and spread of wastewater. The advanced treatment of ARGs in wastewater therefore deserves special attention. In our previous study, we found that tidal flow constructed wetlands can effectively remove multiple ammonia from wastewater. In this study, we further optimized tidal flow constructed wetland systems by adding baffles and cultivating plants; we investigated the influence of process optimization on the removal of ARGs and the influence of functional microorganism distribution on nitrogen removal. The results show that the addition of baffles and plants can effectively improve the removal efficiency of ARGs, with the maximum removal rate of 21 resistance genes, in 7 categories, reaching 83.82%-100.0% with the simultaneous addition of baffles and plants. These removal rates were significantly higher than the increase resulting from a single baffle or plant group. From the comparison of the absolute abundance of ARGs in the substrate and plants, it is clear that the baffles can promote the enrichment of ARGs in the wetland substrate, while uptake by plants is also a way of removing ARGs. Combined with the results of nitrogen-cycle functional gene sequencing, system optimization can increase the diversity and richness of nitrification and denitrification functional microorganisms in the substrate, which is consistent with the higher removal rate of nitrification and total nitrogen in wastewater.