For municipal wastewater treatment

a continuous anoxic/aerobic system (A/O) combined with flow separate filler was developed to investigate nitrogen removal performance. A/O was running stably for 113 days under oxygen-enriched condition (dissolved oxygen

DO>1.5 mg·L-1). Removal of ammonia nitrogen and total nitrogen reached 50%

while nitrite and nitrate were not accumulating during the stable process. Simultaneous nitrification and denitrification was obvious in the aerobic zone. 16S rDNA results showed that functional bacterias were aerobic denitrifying bacteria (ADB) in the biofilm of the aerobic zone

and FISH results showed the activities of ADB along the aerobic zone. Aerobic denitrification was the main form of simultaneous nitrification and denitrification in the system

consuming nitrite and nitrate from nitrification. A nitrogen removal pathway model via simultaneous nitrification and denitrification in the biofilm under oxygen-rich water environment was established.