Identification and Synergistic Denitrification of Two Heterotrophic Nitrification-Aerobic Denitrification Bacteria.

The study aimed to isolate heterotrophic nitrification–aerobic denitrification strains (HNAD) and improve the denitrification efficiency of these strains. Two HNAD were selected as the research objects. The nitrification, denitrification, and simultaneous nitrification–denitrification performance of NO-5 and NH-3, as well as the synergistic simultaneous nitrification–denitrification performance of the two strains were studied. Then, the synergistic denitrification conditions of the two strains were optimized through an orthogonal experiment. The results showed that the denitrification efficiencies of NO-5 and NH-3 were 38.19% and 32.78%, and their nitrification efficiencies were 78.64% and 82.16%, respectively. Both NO-5 and NH-3 also exhibited simultaneous nitrification–denitrification. The total nitrogen(TN) removal rate of NH-3 was 74.32%, which was higher than that of NO-5 (64.60%). When the two strains co-operate exhibiting simultaneous nitrification–aerobic denitrification, the maximum TN removal rate was 91.93%. Compared with simultaneous nitrification–aerobic denitrification, the synergistic denitrification performance of the two strains was better. The optimum conditions improved through the orthogonal experiment were as follows: carbon source composition (sodium succinate:sodium citrate) was 1:1, nitrogen source composition (NO₃⁻-N:NH₄⁺-N) was 2:3, strain composition (NO-5:NH-3) was 3:2, inoculation ratio was 1:100, salt concentration was 0.3%, and C: N was 20:1. Under the optimal conditions, the synergistic denitrification efficiency of the two strains was 95.45%, which was 4.18% higher than that without optimization. Finally, two strains of bacteria were applied to the biofilter experiment, and the results showed that the membrane formation of the mixed high-efficiency bacteria only took 8 days, with shorter start-up time, good stability, and strong resistance to load impact, which has good engineering application significance. [ABSTRACT FROM AUTHOR]