The feasibility of using endpoint pH control to achieve stable partial nitritation (PN) in an SBR for landfill leachate treatment was investigated. By imposing a fixed-time anoxia followed by variable-time aeration in an SBR cycle, successful partial nitritation was maintained for 182 days at a nitrogen loading rate of 0.30-0.89 kg/m(3)/day. The effluent NO2--N/NH4+-N ratio and the effluent NO3--N concentration were 1.30 +/- 0.22 and 16 +/- 9 mg/L, respectively. High free ammonia (FA) and low dissolved oxygen (DO) concentrations were inhibition factors of nitrate formation. The termination of aeration at a suitable endpoint pH was the key to achieve an effluent NO2--N/NH4+-N ratio close to the stoichiometric value. This endpoint pH control strategy represents practical potentials in the engineered application of combined PN-ANAMMOX processes. (C) 2013 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.