Abstract: A method is provided for treating industrial waste water, such as aqueous effluents obtained in the hydrometallurgy of zinc to remove metal ion impurities therefrom, the method comprising, neutralizing the waste water with slaked lime to provide a final pH of at least 8.5 to precipitate hydroxides of metals which form precipitatable hydroxides at said pH and provide an aqueous effluent containing residual quantities of metal ions such as cadmium and manganese, capable of being removed from solution by the addition of a soluble silicate solution, separating the aqueous effluent from the hydroxide precipitate, adding to the effluent a soluble silicate solution in an amount at least sufficient to remove the residual metal ions from solution, and then separating the treated effluent from said precipitate.