Efficient nitrous oxide recovery from incineration leachate by a nosZ-deficient strain of Pseudomonas aeruginosa

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.