Manganese is the second most common constituent after iron of impounded water and many well waters. It causes difficulties in public supplies and in industrial supplies. In this study, the oxidation of Manganese(II) is studied in batch reactors in which the concentrations of manganese(IV) was in the range 0-300 mg/L. This study has demonstrated the catalytic effect of MN(IV) on the Mn(II) oxidation by air to the MN(IV) levels of 100 mg/L. A quadratic equation has been obtained to determine the catalytic reaction rate constant, kcat, as a function of Mn(IV).