[Screening, denitrification characteristics, and anaerobic ammonium oxidation ability of denitrifying bacterium aHD7]

A highly efficient denitrifying bacterium aHD7 was screened from activated sludge. After static culture at 30 degrees C for 3 days, the denitrification rate of the aHD7 reached 91.7%, and during denitrification, nitrite had lower accumulation, with its concentration basically maintained at 1.8 mg x L(-1). The microscopy observation demonstrated that the aHD7 was a gram-negative bacillus, with an average size of 0.5 microm x (1.5-2.5) microm. Based on its biochemical/morphological characteristics and homologic analysis of 16S rDNA sequence, the aHD7 was identified as Pseudomonas mendocina. The investigation on the factors affecting the denitrification capacity of aHD7 showed that at the initial concentration of nitrate nitrogen being less than 276.95 mg x L(-1), the denitrification rate was almost 100%, and when the initial concentration of nitrate nitrogen was as high as 553.59 mg x L(-1), the denitrification rate could reach 66.8%, with little nitrite accumulated. Ethanol was the most suitable carbon source. C/N ratio 6-8 and pH value 6-9 benefited the denitrification. The aHD7 had a good ability of anaerobic ammonium oxidation, and its average ammonium utilization rate reached 4.56 mg x L(-1) x d(-1).