Objective  Aiming at the problem of being difficult to treat the high concentration of NH₄⁺-N in farming wastewater, one heterotrophic nitrification bacterium was isolated and screened from the lake sediment.

Method  The screened strains were subjected to Gram staining, scanning electron microscopy and strain identification. Homology analysis of 16SrDNA sequencing results was performed in the Blast database and phylogenetic trees were constructed. The heterotrophic nitrification and aerobic denitrification properties of this strain under different nitrogen sources were studied, and the denitrification characteristics were studied with different inoculum levels, carbon source, initial pH, temperature, C/N, and initial NH₄⁺-N concentration as environmental factors. Finally, the strain was added to the actual rural pig wastewater to evaluate its application ability.

Result  The strain of heterotrophic nitrification strain was identified as Acinetobacter sp and named L-1. Univariate experiments showed that L-1 had the best heterotrophic nitrification effect under inoculation ratio of 2%, carbon source of sodium citrate, pH 6-9, temperature 20-30 ℃, C/N 10-20, and NH₄⁺-N initial concentration of 50 mg/L. In the actual pig wastewater, L-1 was added to the wastewater for nitrogen removal, in which the 1 000 mg/L NH₄⁺-N wastewater was reduced to 298.46 mg/L at the 96th hour. The removal rate of NH₄⁺-N reached 70.15%, which was 45.78% higher than that of the blank control group, while both concentrations of NO₃^--N and NO₂^--N were decreased.

Conclusion  The strain L-1 has the ability of heterotrophic nitrification and aerobic denitrification, which has certain reference value in the study of heterotrophic nitrification bacteria for the treatment of pig wastewater.