Degradation of sulfamethoxazole and antibiotic resistance genes from surface water in the photocatalyst-loading bionic ecosystems

The behavior and removal of sulfamethoxazole (SMX) and 3 typical corresponding antibiotic resistance genes (ARGs) including sul1, sul2, sul3, and 16S rDNA in surface water were investigated in the photocatalyst-loading bionic ecosystems (PCBEs). Synthesized composite photocatalyst g-C₃N₄/TiO₂ showing higher catalytic activity than Fe/g-C₃N₄/TiO₂ was selected in the PCBEs. Five PCBEs, i.e., A-the control (without bionic grass or photocatalyst), B-bionic grass loaded with 4.12 g/m² g-C₃N₄/TiO₂, C-bionic grass loaded with 8.25 g/m² g-C₃N₄/TiO₂, D-bionic grass loaded with 12.37 g/m² g-C₃N₄/TiO₂, and E-bionic grass loaded with 16.5 g/m² g-C₃N₄/TiO₂ were constructed and operated in a medium-scale running cyclical flume. SMX could be photolyzed efficiently by g-C₃N₄/TiO₂ with an optimal unit load on the bionic grass of 12.37 g/m². 3-amino-5-methylisooxazole and p-aminobenzene sulfonamide were selected as main intermediates through the analyses of SMX degradation mechanisms and pathways, and detected in the aqueous phase and bionic grass. The intermediates were higher in the underwater part of the bionic grass than the above-water part. The overall removal of SMX ranged from 31.7 % to 82.3 % in 5 PCBEs, and the removal of sul1and sul2 were 0.2 %- 62.9 % in the aqueous phase and 8.4 %-63.2 % in the sediment. PCBE D might be the best construction when SMX and ARGs' removal was considered comprehensively. Moreover, the microbial structures showed Proteobacteria as the most dominant bacterial species had a relative abundance of 22.2 %-26.6 % and 33.4 %-68.2 % in the aquatic phase and sediment respectively, illustrating that the removal of the antibiotic and ARGs was bound up with the variations of dominant bacteria in the ecosystems. The findings illustrated that ecosystems with bionic grass and photocatalysts could be a promising technology for the removal of typical antibiotics and ARGs from surface water.