Optimization of a membrane hybrid process for oil-in-water emulsions treatment using Taguchi experimental design

AbstractA coagulation–centrifugation/ultrafiltration hybrid process has been performed for the treatment of a commercial oil-in-water emulsion used in metalworking operations. The effect of pre-treatment stage on membrane fouling was evaluated to ascertain the main fouling mechanism and to establish the best membrane cleaning procedure. The hybrid process was optimized in terms of the maximum ultrafiltration (UF) permeate flux. Destabilization temperature, transmembrane pressure, feed flow rate to the UF module, and coagulant salt molar concentration were selected as factors. The experiments were designed using Taguchi method, and the contribution of each factor was determined using a statistical analysis of variance. Experimental results were also discussed in terms of environmental parameters (chemical oxygen demand [COD], conductivity, pH, and turbidity) for the main process streams. The best fit to experimental data of permeate flux decline corresponded to the cake/gel layer formation model. The clean...