Advanced nitrogen removal from landfill leachate without addition of external carbon using a novel system coupling ASBR and modified SBR

In order to achieve advanced nitrogen removal from landfill leachate without the addition of external carbon sources, a novel system coupling an anaerobic sequencing batch reactor (ASBR) and sequencing batch reactor (SBR) was proposed for the treatment of real landfill leachate with NH 4 + -N and chemical oxygen demand (COD) concentrations of 1100 mg/L and 6000 mg/L, respectively. ASBR could remove 80% of the influent COD under a volumetric loading rate of 5 kg COD/(m3 d). Denitritation and simultaneous nitritation–denitritation were responsible for 50% of the TN removal in SBR under alternate anoxic/aerobic modes. Furthermore, advanced nitrogen removal was realized with a total inorganic nitrogen (TIN) removal efficiency of 99% at the expense of endogenous denitritation during a 26 h period, which led to effluent COD and TN values of 550–650 mg/L and 15–25 mgN/L, respectively. For the combined system, removal efficiencies of COD and total nitrogen (TN) were above 90% and 95%, respectively.