A coupled system of half-nitritation and ANAMMOX for mature landfill leachate nitrogen removal

A coupled system of membrane bioreactor-nitritation (MBR-nitritation) and up-flow anaerobic sludge blanket-anaerobic ammonium oxidation (UASB-ANAMMOX) was employed to treat mature landfill leachate containing high ammonia nitrogen and low C/N. MBR-nitritation was successfully realized for undiluted mature landfill leachate with initial concentrations of 900-1500mg/L NH4+ - N and 2000-4000mg/L chemical oxygen demand. The effluent NO2- - N concentration and the NO2- - N accumulation efficiency were 889mg/L and 97% at 125d, respectively. Half-nitritation was quickly realized by adjustment of hydraulic retention time and dissolved oxygen (DO), and a low DO control strategy could allow long-term stable operation. The UASB-ANAMMOX system showed high effective nitrogen removal at a low concentration of mature landfill leachate. The nitrogen removal efficiency was inhibited at excessive influent substrate concentration and the nitrogen removal efficiency of the system decreased as the concentration of mature landfill leachate increased. The MBR-nitritation and UASB-ANAMMOX processes were coupled for mature landfill leachate treatment and together resulted in high effective nitrogen removal. The effluent average total nitrogen concentration and removal efficiency values were 176mg/L and 83%, respectively. However, the average nitrogen removal load decreased from 2.16 to 0.77g/(Ld) at higher concentrations of mature landfill leachate.