Screening and identification of aerobic denitrifier with nitrite as substrate

Enrichment of aerobic denitrifier in activated sludge system was investigated, using intermittent aeration mode and nitrite as substrate in sequencing batch reactor (SBR). 70% of TN removal was observed when DO was 4-5mg/L, which indicated that aerobic denitrification occurred in activated sludge system. 30 strains were isolated from activated sludge, 10 strains of which had a high TN removal efficiency of more than 60%. Especially, 90.25% of TN removal was observed by strain Y23. The life cycle of Y23 was determined as 4 days and aerobic denitrification was mainly occurred at logarithmic phase (12-36h). After 4-day cultivation, TN removal efficiency and maximum removal rate was 90.25% and 3.47mg/ (L-h), respectively. In whole aerobic denitrification process, only 0.32mg/L NO3-N was accumulated. The characteristics of colony were circular, white and opaque, viscous and the cell of Y23 was rod, gram negative under microscope. Moreover, Y23 was identified as Acinetobacter sp. by 16S rDNA sequences analysis.