Autotrophic denitrification of NO for effectively recovering N2O through using thiosulfate as sole electron donor

Abstract

To reclaim nitrous oxide (N2O) as an energy resource economically, this study developed an autotrophic denitrification-based system with thiosulfate (S2O32-) 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 N2O 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 N2O 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 N2OR 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 N2O thereafter.