Nitric Oxide-Targeted Anammox (NOTA): A Novel Pathway for Nitrogen Flux Regulation

Closed landfill leachate (CLL) contains elevated levels of ammoniacal nitrogen and humic substances that have accumulated over decades, disrupting global nitrogen and carbon biogeochemical cycles. This study examines the nitric oxide-targeted anammox (NOTA), a novel biochemical pathway for nitrogen and carbon recovery from CLL, utilizing waste-activated sludge (WAS) as the inoculum. Notably, during the anammox process the nitric oxide pathway was preferred over the hydrazine pathway. Aerated (ANR) and stirred NOTA reactors (SNR) exhibited ammoniacal nitrogen removal efficiencies of 98% and 92%, respectively, and biological oxygen demand (BOD) removal rates of 60.2% and 43.4%, demonstrating the impact of active (ANR) and passive aeration (SNR) on NOTA performance. Metagenomic analysis revealed microbial community shifts, with an increased presence of nitrogen and carbon degrading bacteria. These findings contribute to the advancement of sustainable CLL treatment with minimal aeration and reinforce the role of NOTA in enhancing biological nitrogen and carbon cycling.