Cost analysis of treatment of exhausted cooling-oil emulsions

Exhausted cooling-oil emulsions from the metallurgical industry were treated. Total content of organic substances, expressed as COD, was 200,000 mg O2/l. Total amount of copper in emulsions was 6630 mg/l. Four treatment procedures were tested and costs of electric energy consumption, materials and recovered copper were determined. The optimal procedure consisted of the separation of part of the emulsion, the electrochemical isolation of copper contained in the aqueous phase using programmed current density, and the thermocatalytic treatment of the remaining part of the emulsion. The lowest removal costs in the optimum procedure amounted to 1.83 US $/m3. The content of copper was reduced to 36 mg/l of exhausted emulsions. This means that the recovery degree amounts to 99.46%. COD of wastewaters decreased to 1460 mg O2/l, a reduction degree of 99.24%. The total removal of copper was found to be possible.