Fate of an antibiotic and its effects on nitrogen transformation functional bacteria in integrated vertical flow constructed wetlands

This study aims to provide insights into the fate and effects of the antibiotic sulfamethoxazole (SMX) on nitrogen transformation processes in integrated vertical-flow constructed wetlands (IVCW), which is useful to create strategies to improve their degradation and combat antibiotic resistance dissemination. Findings indicated chronic exposure to SMX to cause moderate deterioration of IVCW performance for nitrogen removal (p < 0.05), with average TN removal efficiency reductions of circa 10%. High-throughput sequencing and network analysis demonstrated chronic exposure of antibiotics to impact functional bacteria, ammonium oxidizing bacteria (AOB) and ANAMMOX, significantly. ANNAMMOX emerged as a potential pathway of nitrogen removal in the IVCW, albeit with considerable accumulation of NO3--N (12.76 mg/L) and carbon deficiency (C/N = 0.99). Nonetheless, IVCW provides a promising technology for the advanced treatment of antibiotic-containing wastewater, demonstrated by a high and stable removal efficiency (circa 95%) of sulfamethoxazole. Biodegradation, primarily in the first stage of the IVCW, represented the major removal pathway of SMX. Microbial network analysis and the enrichment of Pseudomonas, Bradyrhizobium, Sphingomonas and Luteimonas demonstrated potential for the biodegradation of SMX. These results provide a theoretical reference for the enhancement of nitrogen and antibiotics removal in constructed wetlands.

Automated summary

This study found that chronic exposure to SMX can lead to a decline in nitrogen removal performance of IVCW, but IVCW still demonstrates a high removal efficiency of sulfamethoxazole. ANAMMOX may be a potential pathway for nitrogen removal, but it can result in the accumulation of NO3--N and carbon deficiency. Through biodegradation, IVCW shows a potential for treating wastewater containing antibiotics.