Autotrophic denitrification of NO for effectively recovering N 2 O through using thiosulfate as sole electron donor.

To reclaim nitrous oxide (N ₂ O) as an energy resource economically, this study developed an autotrophic denitrification-based system with thiosulfate (S ₂ O ₃ ^2- ) and nitric oxide (NO) as electron donor and acceptor, respectively. NO from flue gases is absorbed on Fe(II)EDTA to overcome its low solubility in liquid phase by forming Fe(II)EDTA-NO. Short-term batch tests and long-term continuous experiments were conducted to investigate the N ₂ O production profile and NO conversion efficiency from thiosulfate-based denitrification under varied Fe (II)EDTA-NO conditions (5-20 mM). Up to 39% of NO was converted to gaseous N ₂ O at 20 mM Fe(II)EDTA-NO amid batch test due to the inhibition of key enzymatic activities by NO and the acidic conditions following thiosulfate oxidation. Higher Fe(II)EDTA-NO levels induced lower enzymatic activities with N ₂ OR being suppressed harder than NOR. Microbial diversity was reduced in the continuous thiosulfate-driven Fe(II)EDTA-NO-based denitrification system. NO-resistant bacteria and sulfide-tolerant denitrifiers were enriched, facilitating NO conversion to N ₂ O thereafter.
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