A model of manganese (Mn) adsorption and subsequent oxidation by chlorine was applied to experimental data from two pilot-scale postfiltration Mn contactors to estimate the oxidation rate constant. Experiments showed the ability of the contactors to adequately remove soluble Mn under varying operating conditions. A pseudo first-order rate expression was found to be more appropriate than a second-order rate expression. The fitted, pseudo first-order rate constant ranged from 2.8 x 10-4to 5.2 x 10-4/s and from 1.1 x 10-4 to 1.8 x 10-4/s in the two pilot-scale, post-filtration contactors. A sensitivity analysis showed the model was most sensitive to the adsorption isotherm constants and the oxidation rate constant, suggesting that these two processes controlled the removal of soluble Mn in the contactor. Combined with bench-scale experiments, the model described in this article could be used to predict the performance of a postfiltration contactor across a range of influent Mn concentrations and chlorine doses that might be encountered in a water treatment facility.