Integrated Process for the Removal of Emulsified Oils from Effluents in the Steel Industry

Abstract

Emulsified oils contained in aqueous effluents from cold-rolling mills of the steel industry can be effectively removed via an integrated process consisting of a coagulation/flocculation stage followed by ultrafiltration of the resulting aqueous phase. The effects of CaCl₂, NaOH, and lime on the stability of different industrial effluents were studied in the coagulation experiments. The flocculants tested were inorganic prehydrolyzed aluminum salts and quaternary polyamines. Ultrafiltration of the aqueous phase from the coagulation/flocculation stage was carried out in a stirred cell using Amicon PM30 and XM300 organic membranes. Permeate fluxes were measured for industrial effluents to which the indicated coagulants and flocculants had been added. Oil concentrations in the permeate were 75% lower than the limits established by all European Union countries. Complete regeneration of the membrane was accomplished with an aqueous solution of a commercial detergent.

Keywords:

• Coagulation
• Emulsified oil
• Flocculation
• Rolling mill
• Steel industry
• Ultrafiltration

ACKNOWLEDGMENTS

Financial support by the European Coal and Steel Community (ECSC) and by the Comisión Interministerial de Ciencia y Tecnología (CICYT) is gratefully acknowledged.