Demulsification of oily wastewater through a synergistic effect of ozone and salt

Emulsion wastewater is one of the important industrial wastewaters, which is resulting from the various manufacturing industries including the metal manufacturing and its processing. Wastewater treatment technologies utilizing flocculation and electrolysis have been used but these technologies have not been very helpful in resolving the problems in view of process consistency and economic merit. Selection of appropriate electrolytes and rapid separation techniques of the demulsified oil will be important factors to be considered for development of an efficient treatment system. The objective of this study was to investigate the roles of salt and ozone in the treatment of the emulsion wastewater by examining the effects of salt concentration, ozone intensity, pH, and emulsion concentration on the demulsification reaction. A synergistic effect of salt and ozone treatment on the demulsification was observed, where the demulsification efficiency was at least 40% higher than the only salt or ozone treatment. The economic level of salt concentration was evaluated to be 3%. Other conditions such as pH and the initial emulsion concentration did not critically affect the demulsification efficiency (95% at least) after 20 min reaction. The emulsion wastewater treatment technology utilizing the synergistic effect of salt and atone activities was found to be relatively simple in its process and moderate in the operation conditions, hence may be an attractive alternative technology to the conventional demulsification processes. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.