Enhancing autotrophic nitrogen removal with a novel dissolved oxygen-differentiated airlift internal circulation reactor: Long-term operational performance and microbial characteristics

Autotrophic nitrogen removal (ANR) processes have not been widely applied in wastewater treatment due to their long start-up time and unstable performance. In this study, a novel dissolved oxygen-differentiated airlift internal circulation reactor was developed enhance ANR from wastewater. During 200 days of continuous operation, the achieved within 30 days; high total efficiency 80% stably maintained under an aeration rate 0.90 L/min hydraulic retention 6 h. Additionally, color sludge went light yellow dark red, amount size micro-granules increased obviously. Medium-sized (1.0–2.5 mm) accounted for 72.4% on day 190. The specific anammox activity 0.53 1.43 g-N/g-VSS/d, while SNOA decreased 0.93 0.08 g-N/g-VSS/d. Furthermore, microbial analysis showed that Nitrosomonas (4.2%) Candidatus Brocadia (22.6%) were enriched formed after reactor's long-term operation. results indicate configuration realizes partitioning oxygen (DO), optimizes nitritation reactions, accelerates biochemical thereby enhancing This study provides practical alternative performance scientific basis development application reactors.