Nitrogen removal from landfill leachate by single-stage anammox and partial-nitritation process: effects of microaerobic condition on performance and microbial activities

Abstract Nitrogen levels in landfill leachate (LL) could potentially pollute water bodies and surrounding groundwater, when discharged untreated. Against this backdrop, pollutant removal from leachate generated at landfill sites is essential. However, a cost-efficient approach, which could concurrently remove various pollutants within LL via single-stage approach, and under microaerobic conditions, has not been fully explored. In this study, single-stage nitrogen removal using anammox and partial-nitritation (SNAP) process was proposed and employed to treat LL under microaerobic condition in an upflow sludge blanket. When reactor dissolved oxygen-(DO) of 0.2 mg/L was implemented along with nitrogen loading rate-(NLR) ranging 0.31-1.84 kg/m3·d, 99.5% NH4+-N, 94.3% TN and 31.04% chemical oxygen demand (COD) removals was concurrently achieved. Conversely, when DO was elevated to 0.6 mg/L, nitrogen removal was curtailed to