The first full-scale down-flow hanging sponge (DHS) reactor applied to post-treatment of effluent from an upflow anaerobic sludge blanket (UASB) reactor for the treatment of municipal sewage was evaluated, with emphasis on nitrification. The full-scale DHS reactor was successfully operated at a hydraulic retention time of 1.5 h for over 1800 days in India. The DHS reactor produced effluent with 6 mg L-1 ammonium nitrogen, corresponding to 79% removal efficiency. The total nitrogen removal by the DHS reactor was 65%. The high process performance of the DHS reactor was supported by its distinctive characteristics of (1) high dissolved oxygen of 5.4 mg L-1 in the DHS effluent without forced ventilation, (2) dense retained sludge in the range of 23-46 gVSS Lsponge(-1), and (3) adequate sludge activity of 52 mgN gVSS(-1) day(-1) for nitrification. The full-scale experiment has proven that the DHS reactor has practical applicability to developing countries. (C) 2016 Elsevier Ltd. All rights reserved.