Optimization of Membrane Fouling Using Experimental Design: An Example from Dairy Wastewater Treatment

The aim of the present study was to investigate the advanced treatment and reuse of dairy industry wastewater using an integrated membrane process that involves nanofiltration (NF) and reverse osmosis (RO). The Taguchi L-16 (4(4)) experimental design was used to determine the optimal conditions for the NF process used in the first phase of this study. The following parameters were selected for optimization of the experimental conditions: NF membrane type (NF 90, Desal 5DL, FM NP010, or NF 270), pH (4, 6, 8, or 10), temperature (20, 25, 30, or 35 degrees C), and transmembrane pressure (TMP; 12, 16, 20, or 24 bar). Membrane fouling was optimized by calculating the signal-to-noise (S/N) ratio of the parameters. Analysis of variance (ANOVA) was applied, and the results revealed that the pH is the most effective factor. A confirmation experiment performed under the optimum conditions showed good agreement between the observed and calculated results. In addition, the fouling on the membrane was also evaluated by atomic force microscopy (AFM) and contact-angle measurements. In the second phase of this study, the composite permeate obtained from the confirmation experiment in the first part was further purified for reuse with an RO membrane under TMPs of 20 and 40 bar.