Highly efficient of nitrogen removal from mature landfill leachate using a combined DN-PN-Anammox process with a dual recycling system

An efficient and stable combined denitrification-partial nitrification-Anammox process with a dual recycling system was used to remove nitrogen from mature landfill leachate. After 155 d of operation, the NO3− as the PN-Anammox byproduct was almost treated with biodegradable organic carbon in raw wastewater in a pre-denitrification reactor by external recycling system. When raw landfill leachate with NH4+-N concentration of 1900 mg/L was treated, an integrated reactor with airlift recycling was combined with the PN and Anammox reactions to efficiently remove NH4+ from the inflow. The total nitrogen concentration of effluent stabilized at 20 mg/L and total nitrogen removal efficiency was 99%. The maximum NO2− production rate in the aerobic zone was 2.2 kg/(m3·d) and the maximum nitrogen removal rate in the anaerobic zone was 21.4 kg/(m3·d). The most common phyla among the nitrification and the Anammox functional bacteria were Nitrosomonas, Candidatus Kuenenia, and Candidatus Brocadia after landfill leachate treatment.