[Screening and Nitrogen Removing Characteristics of Heterotrophic Nitrification-Aerobic Denitrification Bacteria SLWX2 from Sea Water].

In this study, an efficient heterotrophic nitrifying-aerobic denitrifying bacteria strain SLWX2 was screened from 7 strains isolated from Stichopus japonicus culture ponds, with removal rates of NH4+-N, NO2--N and NO3--N up to 100%, 99.5% and 85.6% within 24 h, respectively. Through morphologic observation, physiological characteristics and 16S rDNA sequence analysis, strain SLWX2 was identified as Bacillus hwajinpoensis. The results of nitrogen removal characterization experiments indicated that, when NH4+-N, NO2--N and NO3--N existed at the same time, SLWX2 utilized NH4+-N firstly, then utilized NO2--N and NO3--N, and removed almost all the inorganic nitrogen within 72 h, suggesting that it could achieve simultaneous nitrification and denitrification itself. The results of nitrogen tolerance examination indicated that strain SLWX2 showed perfect nitrogen removal ability when the ammonia load was not above 500 mg·L-1, nitrite load was not above 100 mg·L-1 and nitrate load was not above 200 mg·L-1, the maximal removal of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen withinn 96 h reached 180 mg, 30 mg and 120 mg, respectively. Moreover, there was no NO2--N accumulation during nitrification. This strain showed great potential in biological nitrogen removal of wastewater with high salt and nitrogen from mariculture and industries.