Municipal wastewater treatment by lime/ferrous sulfate and dissolved air flotation

In this work a chemical treatment system for municipal wastewater using copper cementation effluent and lime as coagulants in combination with dissolved air flotation, was investigated. Copper cementation effluent (CCE) containing about 45% dissolved solids (density=1.31) is a liquid waste from a leaching process, which is disposed in large ponds by several copper mines in the North of Chile. CCE contains a combination of ferrous iron, sulfate, chlorine, magnesium, sodium, residual copper and other ions. For its use as a coagulant, CCE was treated using a low cost process. Ferric hydroxide flocs precipitated after CCE addition were efficiently removed by dissolved air flotation producing a low density froth. High suspended solid removal efficiency, process flexibility, short overall residence time in addition to low cost of chemicals used and precipitation of varied proportions of contaminants, including bacteria from wastewater, are the main features of this chemical treatment system.