Exploration of rapid start-up of the CANON process from activated sludge inoculum in a sequencing biofilm batch reactor (SBBR)

In this study, a laboratory-scale sequencing biofilm batch reactor (SBBR) was employed to explore a fast start-up of completely autotrophic nitrogen removal over nitrite (CANON) process. Partial nitrification was achieved by controlling free ammonia concentration and operating at above 30 degrees C; then the reactor was immediately operatedwith alternating periods of aerobiosis and anaerobiosis to start the anammox process. The CANON processwas successfully achieved in less than 50 d, and the total-nitrogen removal efficiency and the nitrogen removal ratewere 81% and 0.14 kg-N m(-3) d(-1) respectively. Afterwards, with the increasing of ammonium loading rate a maximum nitrogen removal rate of 0.39 kg-N m(-3) d(-1) was achieved on day 94. DNA analysis showed that 'Candidatus Brocadia' was the dominant anammox species and Nitrosomonas was the dominant aerobic ammonium-oxidizing bacteria in the CANON reactor. This study revealed that due to shortening the persistent and stable nitrite accumulation period the long start-up time of the CANON process can be significantly reduced.