Microbial community and carbon-nitrogen metabolism pathways in integrated vertical flow constructed wetlands treating wastewater containing antibiotics.

This study demonstrates effects of sulfamethoxazole (SMX) on carbon-nitrogen transformation pathways and microbial community and metabolic function response mechanisms in constructed wetlands. Findings showed co-metabolism of SMX with organic pollutants resulted in high removal of 98.92 ± 0.25% at influent concentrations of 103.08 ± 13.70 μg/L (SMX) and 601.92 ± 22.69 mg/L (COD), and 2 d hydraulic retention. Microbial community, co-occurrence networks, and metabolic pathways analyses showed SMX promoted enrichment of COD and SMX co-metabolizing bacteria like Mycobacterium, Chryseobacterium and Comamonas. Relative abundances of co-metabolic pathways like Amino acid, carbohydrate, and Xenobiotics biodegradation and metabolism were elevated. SMX also increased relative abundances of the resistant heterotrophic nitrification-aerobic denitrification bacteria Paracoccus and Comamonas and functional genes nxrA, narI, norC and nosZ involved in simultaneous heterotrophic nitrification-aerobic denitrification. Consequently, denitrification rate increased by 1.30 mg/(L∙d). However, insufficient reaction substrate and accumulation of 15.29 ± 2.30 mg/L NO-N exacerbate inhibitory effects of SMX on expression of some denitrification genes.