The 2, 700 cubic meter daily effluent flow from a zinc concentrate thickener contains 67 parts per million Cu(CN)₃^--, 14 parts per million CN^-, 301 parts per million ZnS, 1.29 parts per million CdS, 16.8 parts per million C₂H₅OCS₂^-, and 18 parts per million frother.
Sulphuric acid is added to the effluent and the Cu(CN)₃^-- is decomposed into CuCN, C₂H₅OCS₂Cu and CN^-, All components of effluent other than CN^- are then floated and separated from the water. The effluent water now containing 30 parts per million CN^- is recycled to the differential lead-zinc flotation circuit.
The NAGAHM flotation machine which makes this cleaning process possible was specifically developed to perform ion flotation, precipitation flotation, and ultra-fine particle flotation. Characteristics of the flotation machine are very high aeration rate, fine dispersal of air bubbles throughout the cell, smooth non-turbulent flow in the cell, and rapid removal of large quantities of froth.
Apart from the improvement of environmental quality the system has had three significant economic effects-the first improved mill recoveries, the second recovery of actual metals in the effluent, and third a reduction in reagent consumption.

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