This report describes a series of laboratory and full-scale tests to develop a process for improving the flotation characteristics of lime-treated wastewater. Unknown substances in the wastewater reduced the flotation efficiency of the metal sulfides. An estimated annual loss of 795,000 lb cu, 232,000 lb mo, 5,625 tr oz ag, and 617 tr oz au would result from recycling the total flow from the lime treatment plant to the flotation mill in an effort to conserve water and reduce associated expense. The tests indicated that aeration or treatment with activated carbon significantly improved the water quality. The improvements in molybdenum recovery averaged 8 pct for aeration, 11 pct for activated carbon, and 16 pct for combined aeration and activated carbon. The combination of the two processes produced water quality as good as or better than that of normal feed water.