The genus of Raoultella belongs to the family of Enterobacteriaceae, and some strains of Raoultella sp. have the function of degrading chemical pollutants in the environment. A Raoultella sp. strain was isolated from activated sludge through enrichment cultured with heterotrophic nitrification medium. This strain was named Raoultella sp. sari01. Single-factor and response surface methodology experiments results showed that efficient heterotrophic nitrification of strain sari01 occurred with sodium citrate as the carbon source, at pH of 7.0-7.5, temperature of 30℃, C/N ratio of 15, inoculation volume of 7.5% and loading volume of 50 mL, while the removal rate of nitrogen was 99.9%, of which 33.7% was converted to gaseous product and escaped to air, and the residual nitrogen was fixed in cell biomass. Using nitrite and nitrate as the sole nitrogen source, the nitrogen degradation ratios were 98.4% and 65.2%, respectively. Hence, strain sari01 could remove nitrogen by heterotrophic nitrification-aerobic denitrification independently, quickly and effectively, which demonstrated that strain sari01 has the potential to be used in wastewater treatment.
Keywords: Raoultella sp.; aerobic denitrification; biological removal of nitrogen; heterotrophic nitrification; response surface methodology (RSM).