Scaling up the chemical treatment of spent oil-in-water emulsions from a non-ferrous metal-processing plant

The treatment of spent oil-in-water emulsion (SOWE) from a non-ferrous metal-processing plant by using aluminum sulfate and hydrated lime was studied in order to determine the purification efficiency, optimize the operating conditions and scale up the treatment process. The purification efficiency was estimated by comparing the compositions of the SOWE and the processed wastewater. The treatment efficiency does not depend on the type of mineral oil and filter aid. The optimum doses of aluminum sulfate and hydrated lime must be experimentally determined for each batch of SOWEs, but the results obtained at laboratory level are applicable at pilot level. The processed wastewater and the filter cake from the process can be safely disposed into public sewage systems and at municipal waste landfills, respectively. The purification efficiency was higher than 98% with respect to total suspended solids, chemical oxygen demand and oil and grease, and was comparable to the known treatment processes based on coagulation/flocculation followed by sedimentation.