Organic matter (chemical oxygen demand, COD) removal with decolorization in waste distillery slops and copper removal in a semiconductor industry wastewater were achieved in a single step mixing and precipitation/coagulation treatment system. The process utilized the complementary properties of the positively charged copper ions in semiconductor wastewater and net negative charge of melanoidin (organic chromophoric pollutant) in distillery slops to mutually neutralize each other. Copper ions served as coagulant for slops and melanoidin served as precipitant for copper. The volumetric ratio of the wastewater and pH were optimized to attain maximum removal of organic matter and copper. The optimum volumetric ratio for the evaluated semiconductor wastewater to distillery slops was found to be 2-3 with an equilibrium pH of around pH 6. At optimum conditions, average removals of COD and copper were 86% and 92%, respectively, in an actual and undiluted system. Decolorization efficiency using the diluted distillery slops was 89%. The process can be considered an effective pretreatment procedure for simultaneous gross removal of copper and color/COD, particularly in highly concentrated waste streams. (c) 2005 Society of Chemical Industry.