Anaerobic/anoxic/oxic (AAO)-biological aerated filter (BAF) is a two-sludge system with different SRT

which can remove nitrogen and phosphorus simultaneously in the low C/N condition. The startup of a pilot-scaled AAO-BAF system with capacity of 40—100 m3·d-1 used for treating real domestic sewage was studied in this experiment. The AAO and BAF run independently in order to cultivate and acclimate the phosphorus accumulating organisms (PAOs) and nitrifying bacterial biofilms

respectively. When the TP concentration of AAO effluent and concentration of BAF effluent were found keeping stable

the two parts were combined. With this operation strategy

the effluent concentration of COD

TN

TP

NTU and SS was lower than 50 mg·L-1

5 mg·L-1

15 mg·L-1

0.5 mg·L-1

5 NTU and 10 mg·L-1 in the 58th day

respectively

indicating the successful setup of the pilot-scaled process. Comparing with the lab-scale study

the separate running had more advantage in cultivating PAOs. The formation of natural biofilm in BAF was more convenient than the method of inoculated sludge

but needed longer time. According to the analysis of microbial community diversity

the abundance of nitrobacteria was less than 3% in the AAO system

however

it was higher than 12% on the biofilm in BAF. This experiment can provide a reference for practical engineering application of the process.