Taking actual domestic wastewater (C/N=2.6-4.1) as influent substrate and polyurethane filler as biological carrier (filling rate was 25%)

the simultaneous nitrification and denitrification (SND) was achieved in sequencing batch biofilm reactor (SBBR) in a short period of time (98 d) with gradually increased nitrogen loading. The results of real-time qualitative polymerase chain reaction (qPCR) confirmed the enrichment of nitrifying bacteria in the reactor. The system had a good effect of organic matter and nitrogen removal in the formal running period. The concentration of COD

NH4+-N and TN of the effluent water was 38.28 mg·L-1

1.23 mg·L-1 and 8.23 mg·L-1

respectively. Most of COD was taken up and converted to polyhydroxyalkanoate (PHA)

and the storage products were used for denitrification

which removed a large amount of nitrate. The removal efficiency of TN and SND was calculated as 82.95% and 70.57%

respectively

and the NO2--N concentration always kept low level. Since the nitrification and denitrification reactions took place in the same reactor and conditions

the system could maintain pH in a steady conditions by that the increasing basicity in the denitrification process can complement the consuming basicity in the nitrification process. Furthermore

the reaction time can be effectively controlled and the power consumption can be decreased through the curve change of DO and pH to judge the operation status of SND.