Evaluation of a newly isolated Klebsiella sp. DL-1 and its interaction with Klebsiella sp. FD-3 in regenerating nitrogen oxide scrubbing liquor using ethylenediaminetetraacetic acid iron(II) as absorbent

•A new Klebsiella sp. strain (DL-1) was isolated for Fe(II)EDTA-NO reduction.•DL-1 was efficient in denitrifying, and the reduction rate was 4.29 mmol gDCW−1 h−1.•The interaction of DL-1 and FD-3 in the NOx removal system was investigated.•DL-1 inhibited Fe(III)EDTA reduction, while FD-3 promoted Fe(II)EDTA-NO reduction.•Fe(II)EDTA-NO and Fe(III)EDTA could be effectively reduced by the mixed strains.

A highly effective strain, referred to as DL-1 and identified as Klebsiella sp., was applied to Fe(II)EDTA-NO reduction. The average reduction rate was approximately 4.29 mmol g DCW−1 h−1, which was higher than those reported in the literature. The relationship between cell growth and Fe(II)EDTA-NO reduction was characterized, and a model was developed based on a logistic equation. To ensure that the simultaneous reduction of Fe(II)EDTA-NO and Fe(III)EDTA was feasible in the integrated NOx removal process of chemical absorption and biological reduction, DL-1 was mixed with a Fe(III)EDTA-reducing bacterium FD-3 to regenerate the scrubbing liquor. There was carbon and nitrogen source competition between these two strains in the mixed system. DL-1 was incapable of reducing Fe(III)EDTA, but FD-3 was capable of reducing Fe(II)EDTA-NO. Therefore, DL-1 would inhibit Fe(III)EDTA reduction, and FD-3 would enhance Fe(II)EDTA-NO reduction. The performance of the mixed strains was also investigated. The system could maintain stable and high reduction efficiencies, after 7 h, the reduction efficiency of Fe(II)EDTA-NO and Fe(III)EDTA were 84.9% and 77.1%, respectively.