This pilot study investigated the effects of in situ formed manganese dioxide (in situ delta MnO2), produced from KMnO4 reduction, on the removal efficiency for turbidity and particles and the run length of filters through this pilot-scale study. The sedimentation effluent showed an insignificant difference in turbidity but a remarkable decrease in particle concentration after dosing KMnO4. The residual particle concentration decreased from 1504 units/mL to 359, 302, 164 units/mL in the anthracite filter effluent and from 994 units/mL to 219, 134, 99 units/mL in the granular activated carbon (GAC) effluent at KMnO4 dosages of 0.2, 0.3, and 0.4 mg/L respectively. However, this effect was achieved at the expense of a rapid increase of water head loss (WHL), and the average run length decreased from 70 h to 54, 52, and 48 h accordingly. After dosing KMnO4 at 0.2, 0.3, and 0.4 mg/L, the contributive ratios of the uppermost 200 mm layers on WHL increased from 68.5% to 81.9%, 76.0%, and 82.2%, respectively. (C) 2013 Elsevier B.V. All rights reserved.