Advanced nitrogen removal had been realized from mature landfill leachate via three-stage anaerobic ammonium oxidation (Anammox) system during the previous study. However, the Anammox system was influenced by factors such as influent nitrite and organic concentrations and needed to be optimized. To optimize the Anammox system, this study investigated Anammox Sequence Batch Reactor (ASBR) with different feeding modes and influent organic concentrations. The results showed that with influent ammonia and nitrite concentrations of 250 +/- 20 and 320 +/- 20 mg/L, respectively, a continuous feeding mode reduced the adverse effect of high influent nitrite concentration on Anammox. A small amount of organics improved rather than inhibited nitrogen removal. However, as influent COD increased (from 600 +/- 50 to 800 +/- 50 mg/L), Anammox was gradually inhibited. Influent organics concentration should be kept below 800 mg/L, which facilitated Anammox. (C) 2015 Elsevier Ltd. All rights reserved.