A method for reducing barium concentration in waste streams. Hydrous manganese oxide (HMO) is formed in solution/slurry and mixed with water containing barium such that the hydrous manganese oxide exhibits a negative charge at a desired pH. Barium from the water is adsorbed onto the negatively charged HMO surface. The HMO with adsorbed barium is separated from the water, producing treated effluent having a reduced barium concentration.