[Screening and identification of two heterotrophic nitrifying bacteria and characterization of their capacity for nitrogen removal].

OBJECTIVE

Two heterotrophic nitrifying bacteria, P2 and P9 isolated from piggery wastewater, were studied for their capacity of nitrification and nitrogen removal.

METHODS

Physiological characteristics and phylogenetic analysis based on 16S rDNA sequences of strains P2 and P9 were analyzed. The ammonia removal characteristics of strains P2 and P9 were investigated. Furthermore, nitrogen removal ability of strains P2 and P9 individually or mixed were evaluated in the treatment of actual piggery wastewater.

RESULTS

Strains P2 and P9 were identified as Paracoccus sp. and Shinella sp., respectively. Heterotrophic nitrification could occur by the strains when they utilized organics. After cultivation of 24 h, the ammonia removal rates by the strains were up to 80% approximately; meanwhile, there was almost no nitrite and nitrate accumulation. However, aerobic denitrification could not occur by the strains when NO3- or NO2- was provided as the sole nitrogen source, respectively. For heterotrophic nitrification, with strains P2 and P9, the optimal carbon source was sodium succinate, and the optimal C/N ratio was 9. Besides, the pH values rose from 6.8 to 8.9 in the whole ammonia removal process. The growth and nitrogen removal ability of the two strains depended much on the quantity of small molecule carbon source, and the nitrogen removal capability of strains P2 or P9 in wastewater with small molecule carbon source was improved evidently. The effect was strengthened especially when the two strains were mixed together.

CONCLUSION

Nitrogen removal ability of strains P2 and P9 was relatively strong, and they may exhibit broad application prospects in wastewater treatment.