A review of antibiotic effects on wastewater denitrification: From process inhibition to microbial resistance mechanism

Antibiotics, as emerging pollutants, are frequently detected in wastewater treatment systems, and their impact on biological denitrification has garnered increasing attention. This review comprehensively summarized the effects of antibiotics on heterotrophic, autotrophic, and mixotrophic denitrification performances, considering various factors such as antibiotic types, concentrations, environmental conditions and exposure time. It delves into antibiotic effects on nitrate removal, intermediate product accumulation, and greenhouse gas emissions. The review also elucidates the mechanisms underlying these effects from the angles of denitrifying microbial community structures and functional genes. Furthermore, it clarifies the defense mechanisms employed by microorganisms to counteract antibiotic effects, such as biodegradation, extracellular polymeric substance (EPS) secretion, and antibiotic resistance genes (ARGs) acquisition. These mechanisms enable microorganisms to maintain denitrification capabilities under antibiotic pressure. Finally, the review identifies gaps in current research and suggest future directions, emphasizing the need for studies on low-concentration antibiotics, combined pollution effects, microbial adaptation mechanisms, and ARGs dissemination pathways.