Optimizing anammox capacity for weak wastewater in an AnSBBR using aerobic activated sludge as inoculation

Process optimization is essential for improving the efficiency of anaerobic ammonium oxidation (anammox) process in a practical application. In this study, an anaerobic sequence biofilm batch reactor (AnSBBR) inoculated with aerobic activated sludge was chosen as an efficient mainstream anammox reactor for treating low-nitrogen wastewater. To optimize the AnSBBR-anammox process, eight different operation stages lasting for a total of 215 days were conducted by regulating key process parameters. Principal components analysis revealed significant effects of the substrate ratio (SR) and volumetric exchange ratio (VER) on anammox performance, while other parameters (cycle time, hydraulic retention time and nitrogen loading rate) played minor roles. The highest removal efficiencies for ammonia and total nitrogen, respectively, reached 99.8% and 95.3% under optimal conditions. High-throughput sequencing found the anammox species Candidatus Brocadia and Candidatus Kuenenia made up as much as 8.5% and 3.5%, respectively, of the microbial community. Redundancy analysis indicated that these taxa were also greatly influenced by operating parameters, particularly SR and VER. This research helps to decode the correlations among nitrogen removal capacity, process parameters and the microbial community to enhance anammox in an AnSBBR system.