Removal of nitrogen by heterotrophic nitrification-aerobic denitrification of a phosphate accumulating bacterium Pseudomonas stutzeri YG-24

Phosphate accumulating bacterium Pseudomonas stutzeri YG-24 exhibited efficient heterotrophic nitrification and aerobic denitrification ability. Single factor experiments showed that both heterotrophic nitrification and aerobic denitrification occurred with sodium citrate as carbon source and lower C/N ratio of 8. High average NH₄⁺-N, NO₂^--N and NO₃^--N removal rates of 8.75, 7.51 and 7.73mgL^-1h^-1 were achieved. The application of strain YG-24 in wastewater samples resulted in TN, NH₄⁺-N, NO₂^--N, NO₃^--N and P removal efficiencies of 85.28%, 88.13%, 86.15%, 70.83% and 51.21%. Sequencing and quantitative amplification by real-time PCR of napA, nirS and ppk showed that nitrogen removal pathway of strain YG-24 was achieved through heterotrophic ammonium nitrification coupled with fast nitrite denitrification (NH₄⁺-N to NO₂^--N and then to gaseous nitrogen) directly. These results demonstrated the strain as a suitable candidate to simultaneously remove both nitrogen and phosphate in wastewater treatment.