Patent ID: 7758758

Claim:
A method for removing metals from metal-containing acidic mine wastewater, in which a basic sludge produced by said method is used in treating said wastewater, comprising the steps of: (a) mixing said wastewater with a lime slurry and with said basic sludge to form a mixture having a pH in the range of 4 to 6; (b) allowing said mixture to separate into an aqueous effluent and an acidic sludge to remove said metals, said acidic sludge containing ferric iron and stable metal precipitates; (c) sending said acidic sludge to disposal, wherein a portion of said acidic sludge is recycled; (d) mixing said aqueous effluent of step (b) with a lime slurry, lignin derivatives, and said portion of acidic sludge, to produce a mixture including coprecipitated metals; and (e) allowing said mixture of step (d) to separate into an aqueous effluent and said basic sludge, wherein said basic sludge contains unstable metal precipitates.