Advanced nitrogen removal from landfill leachate via a two-stage combined process of partial nitrification-Anammox (PNA) and partial denitrification-Anammox (PDA).

Abstract

In this study, a two-stage combined process of partial nitrification-Anammox (PNA) and partial denitrification-Anammox (PDA) was established achieving advanced nitrogen removal from landfill leachate. The PNA sludge used to treat reject water adapted to the leachate in 37\u202fdays, resulting in fast start-up of the PNA process with a nitrogen removal rate (NRR) of 0.22\u202fkgN/(m3·d). Partial denitrification (PD) was induced using sodium acetate and proceeded in a stepwise manner using sludge fermentation liquid (SFL), achieving a NO3--N to NO2--N transformation ratio (NTR) of 52.1\u202f±\u202f1.1% within 16\u202fdays. PDA was established via the addition of mature Anammox biofilms. The nitrogen removal efficiency (NRE) of this system was 97.6\u202f±\u202f1.5%, of which PNA and PDA contributed 74.8\u202f±\u202f4.0% and 18.7\u202f±\u202f4.1%, respectively. Nitrosomonas (2.6% in PNA), Thauera (16.0% in PDA) and Candidatus Brocadia (23.0% in PNA, 1.4% in PDA) were dominant in the two-stage system. This study provides valuable and novel insights, supporting the practical application of PNA-PDA processes in landfill sites.