New results in metal working wastewater treatment using membrane technology

Abstract

This study is dedicated to the application of membrane technology for wastewater treatment of metal working fluids and more precisely of oily emulsions stabilized by anionic surfactants. Previous studies have involved the now classical treatment of macroemulsions using ultrafiltration membranes and have clearly demonstrated the limits of this membrane process: on the one hand, the permeate fluxes are low, especially when the concentration ratio increases and, on the other hand, problems of fouling appear with time. These points could limit the industrial applications of the ultrafiltration process. The present study suggests innovative solutions which could be used to limit the above-mentioned problems: 1. 1. The permeate fluxes have been considerably increased by the adjunction of a reactive salt at a very low concentration in the feed solution. After this treatment, the ultrafiltration membrane behaves as an efficient surface coalescer. This treatment and procedure reduce the polarization layer resistance thus giving an increased permeate flux which is nearly constant and independent of the concentration ratio. 2. 2. The application of specific micellar cleaning solutions to fouled membranes restores their initial water permeability and their initial hydrophilic properties.