Role of microbial activities in nitrogen transformation under antibiotic stress in wastewater systems: A review of emerging treatment technologies

The presence of antibiotics in wastewater critically hampers biological nitrogen removal (BNR) processes by disrupting microbial populations and metabolic functions. This review assesses advanced microbial-based treatment strategies aimed at enhancing nitrogen removal amid antibiotic stress, considering difficult wastewater regulations. BNR includes methods like nitrification/denitrification (N/DN), partial nitrification (PN), anaerobic ammonia oxidation (PN-ANAMMOX), and integrated approaches such as simultaneous nitrification, anammox, and denitrification (SNAD). While these systems can effectively remove nitrogen, antibiotic exposure negatively impacts their efficiency by inhibiting nitrifiers and denitrifiers, leading to altered community structures and functional gene expressions. This situation also poses risks of increasing antibiotic-resistant bacteria and genes, raising environmental and public health concerns. The review discusses microbial pathways for antibiotic degradation, focusing on nitrogen transformation and the conditions that enhance biotransformation efficiency. It also addresses ecological risks of degradation products, such as tetracycline-derived compounds that may be more persistent and bioaccumulative than their precursors. When compared to energy-heavy physicochemical methods, BNR processes present a more sustainable alternative for removing nitrogen and antibiotics concurrently. Moreover, this study highlights recent progress in reactor design, operational control, microbial engineering, and optimization strategies, pointing out existing challenges and future research needs. Understanding microbial reactions to antibiotic stress is key to developing effective, resilient, and environmentally friendly BNR technologies to tackle evolving wastewater treatment challenges.