I order to remove metals from waters and aqueous effluents generally are employed traditional methods which involve neutralization, hydrolysis and precipitation of hydroxides using a base. Manganese must be removed from waters and aqueous effluents down to a concentration limited by Brazilian law which is of 0.1 mg/L for waters and 1.0 mg/L for aqueous effluents. The work carried out herein investigated the removal of manganese (II) using the following oxidants: oxygen, hydrogen peroxide, and Fenton reagent, with the aim to identify a process that could be more efficient than the simpler hydroxide precipitation. Results are discussed of experiments made with synthetic solutions of 1000 mg/L manganese (II) with the objective of developing a route that could favour the removal of that metal to the levels established by Brazilian environmental law (resolution CONAMA 20 / 1986).The experiments were conducted in pH 7 to 10, at temperature ambient and 80 oC, with reaction times of 5, 15 and 30 minutes. Hydrogen peroxide was used in excess levels of 100 and 200% for the reaction: Mn2+ (aq) + H2O2 (aq) -> MnO2 (s) + 2 H+ (aq) Amongst the conducted experiments, both hydrogen peroxide and the Fenton reagent were shown to be most effective, allowing final concentrations of manganese less than 0.3 mg/L, at ambient temperature, in pH values lower than those required for precipitation without oxidation or with O2 (air).