Application of membrane bioreactor for completely autotrophic nitrogen removal over nitrite (CANON) process

• CANON was started-up in MBR at ambient temperature during 50 days.
• Average NRR reached to 0.7 kg m−3 d−1 with a removal efficiency of 88%.
• AFR/ALR should be maintained below 0.28 for stable CANON.
• MBR was suitable for enrichment of AnAOB and CANON operation.
• Distribution of AerAOB and AnAOB was detected by FISH.

A membrane bioreactor (MBR) was adopted for completely autotrophic nitrogen removal over nitrite (CANON) process at ambient temperature. CANON was rapidly started-up within around 50 d under oxygen-limited condition. The average nitrogen removal rate reached to 0.70 kg N m−3 d−1 with a removal efficiency of 88%. The ratio of air flow rate to volumetric ammonium loading rate should be maintained below 0.28 Lair min−1 kg−1 N m3 d for stable CANON. The feasibility of MBR for CANON process was proved in batch experiments. FISH results showed that aerobic ammonium-oxidizing bacteria predominated in the reactor sludge, whereas anaerobic ammonium-oxidizing bacteria predominated in the membrane biofilm. This study demonstrated that MBR was a suitable experimental setup for the operation of CANON process.