Short tests to couple N₂O emission mitigation and nitrogen removal strategies for landfill leachate recirculation

Landfills implemented with onsite leachate recirculation can efficiently remove pollutants, but currently they are reckoned as N₂O emission hot spots. In this project, we evaluated the relationship between N₂O emission and nitrogen (N) removal efficiency with different types of leachate recirculated. Nitrate supplemented leachate showed low N₂O emission rates with the highest N removal efficiency (~70%), which was equivalent to ~1% nitrogen emitted as N₂O. Although in nitrite containing leachates' N removal efficiencies also reached to ~60%, their emitted N₂O comprised ~40% of total removed nitrogen. Increasing nitrogen load promoted N₂O emission and N removal efficiency, except in ammonia type leachate. When the ratio of BOD to total nitrogen increased from 0.2 to 0.4, the N₂O emission flux from nitrate supplemented leachate decreased from ~25 to <0.5μgN/kg-soil·h. We argue prior to leachate in situ recirculation, sufficient pre-aeration is critical to mitigate N₂O surges and simultaneously enhance nitrogen removal efficiency.