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Nitrous oxide (N2O) is not only recognized as a potent greenhouse gas, but it is also used in industry as a clean energy source. In this study, different electrode materials of carbon felt and graphite were equipped in the ΔnosZP. aeruginosa/microbial electrolysis cell (MEC) systems to explore the optimization mechanism for long-term N2O recovery during incineration leachate treatment. The carbon felt group showed a better performance in N2O recovery across 45 days of operation. The N2O conversion efficiency was above 80% and the proportion of N2O in biogas accounted for 80.6% in the carbon felt group. qRT-PCR analysis was conducted to evaluate the expression of genes involved in denitrification (norB) and electroactivity (phzG, phzM, and phzH) of ΔnosZ P. aeruginosa. The results showed a significant upregulation in the suspended biomass (day 21) and the electron-attached biomass (day 45) from the carbon felt-equipped reactor, which was highly related to the opportunity of biomass exposed to the phenazine derivatives. By the carbon felt optimization in the system, 82.6% of the Pseudomonas genus survived after 45 days of operation. These results indicate that the carbon felt electrode has a more sustainable performance for N2O recovery in the ΔnosZ P. aeruginosa/MEC system.

In this study, a quorum sensing (QS) signal molecule, 3-oxo-C12-HSL, was supplied into ΔnosZ Pseudomonas microbial electrolysis cell system for strengthening the N

High concentrations of nitrous oxide were recovered from partial nitrification treated leachate in a microbial electrolysis cell (MEC) inoculated with a nosZ-deficient strain of Pseudomonas aeruginosa. N2O conversion efficiencies > 90% were achieved when a potential of 0.8 V was applied to the MEC. The ΔnosZ strain was enriched in the 0.8 V MEC, but Achromobacter dominated the non-current control. Nitric oxide reductase genes were highly expressed by ΔnosZ cells growing in the 0.8 V MEC, consistent with enhanced nitrous oxide production rates. Concentrations of phenazine derivatives and transcripts from phenazine biosynthesis genes were also high in the 0.8 V MEC. Phenazine derivatives are known to act as electron shuttles, enhance biofilm formation, and help ward off competitors, thereby increasing the survivability of the ΔnosZ strain in the MEC. These results show that applied current stabilized growth of the ΔnosZ strain in the reactor and allowed it to sustainably generate high concentrations of nitrous oxide.

In this study, nitrous oxide was recovered from a lab-scale moving-bed biofilm reactor (MBBR) treating partial nitrification-treated leachate supplemented with a nosZ-deficient strain of Pseudomonas aeruginosa. Batch culture tests with the nosZ-deficient strain determined that the threshold for free nitrous acid (FNA) inhibition was 0.016 mg/L and that FNA concentrations above this threshold severely inhibited denitrification and transcription of genes from the dissimilatory nitrate reduction pathway (narG, nirS, and norB). High nitrite removal and N2O conversion efficiencies (>95%) were achieved with long-term operation of this MBBR. N2O accounted for the majority of biogas (80%) produced when the MBBR was fed partial nitrification-treated leachate with high nitrite concentrations and the drainage ratio was adjusted to 30%. Bacterial community analysis revealed that the nosZ-deficient Pseudomonas strain remained metabolically active and was primarily responsible for denitrification processes in the reactor. This study presents a promising method for N2O recovery from incineration leachate.