Sludge granulation and microbial activity in a stable CANON process by DO controlling and operating parameter optimization

Abstract

Abstract We present a start-up method for complete autotrophic nitrogen removal via the nitrite (CANON) granular sludge process by controlling the DO concentration. More specifically, we initially increase the activity of anaerobic ammonia-oxidizing bacteria (AnAOB) and, subsequently, gradually increase the activity of ammonia oxidizing bacteria (AOB). The results indicate the optimum process parameters to be an 8\xa0h reaction period and an aeration/non-aeration time ratio of 1.0\xa0h/0.25\xa0h. These conditions maintain a high activity for both AOB and AnAOB and are also conducive to sludge granulation. Following 64 days of continuous operation, the mean particle size of the sludge increased to 992\xa0µm, while the proportion of granular sludge accounted for approximately 87.16%, and the proportion of sludge with a particle size ≥\xa01000\xa0µm was 36.66%. Both AOB and AnAOB became the dominant bacterial genera in the CANON reaction system, while nitrite-oxidizing bacteria were successfully discharged from the reaction system.