Innovative hybrid anaerobic ammonium oxidation system enhances nitrogen and sulfur elimination in landfill leachate treatment.

Under anaerobic conditions, ammonia nitrogen (NH4+) reacts with nitrite (NO2-) and sulfate (SO42-), i.e., nitrite-ammonia oxidation (Nir Anammox) and sulfate-ammonia oxidation (Sulfammox). In this study, a combined system of internal circulation (IC) reactor and biological aerated filter (BAF) was used for landfill leachate treatment: the IC reactor performs anaerobic digestion to remove organic matter (COD) and facilitate sulfate reduction, while the BAF achieves partial nitritation and anaerobic ammonium oxidation under intermittent aeration. After 300 days of operation, the nitrogen removal efficiency (TNRE) reached a maximum of 97.1 %, the volumetric nitrogen removal rate (NRR) reached a maximum of 1.04 kg N/(m3·d), and the sulfate removal rate reached 53.4 %. Post-treatment significantly reduced each fluorescence peak intensity in waste liquid and effectively removed proteins and other organics. In summary, combining nitrite-type and sulfate-type anaerobic ammonium oxidation can enhance nitrogen and sulfur removal efficiency, offering a novel strategy for treating landfill leachate.