Anaerobic methane oxidation drives simultaneous nitrite and nitrous oxide removal

Denitrifying anaerobic methane oxidation (DAMO) processes have been proven effective for nitrogen removal while contributing to the sustainable operation of wastewater treatment plants. However, it remains unclear whether DAMO-centric technologies can simultaneously remove nitrous oxide (N₂O). Here, we demonstrated high removal performance of nitrite and N₂O with methane as the electron donor over a prolonged period. The DAMO bacteria Candidatus Methylomirabilis always dominated the community during the synchronous removal of nitrite and N₂O, meanwhile microorganisms with complete denitrification pathways thrived. Metabolic profiles revealed that their synergy effects were responsible for anaerobic methane oxidation driven simultaneous removal of nitrite and N₂O, where the electrons for nitrite and N₂O reduction originated from methane or its metabolic intermediates. This enables them to remove N₂O efficiently and flexibly. This finding suggests that DAMO-centric technologies harbor great potential for N₂O removal, contributing to strengthen greenhouse gases reduction under the increasingly severe climate change.