Optimal operating conditions of micro- and ultra-filtration systems for produced-water purification: Taguchi method and economic investigation

In this study, treatment of two real produced waters was studied using microfiltration (MF) and ultrafiltration. In the first step, the effects of operating parameters including temperature, transmembrane pressure (TMP), cross-flow velocity (CFV), and back pulse time (BPT) (in the MF system) at three levels on the amount of permeate flux were investigated using ceramic and polymeric membranes. To design the experiments and optimize the experimental results, the L-9 (3(4)) and L-9 (3(3)) orthogonal arrays of the Taguchi method and a response category of the-larger-the-better were applied. Analysis of variance was used to determine the most important parameters affecting the permeate flux. The optimum conditions were found at the third level of temperature, TMP, and CFV and at the first level of BPT in the MF system. In the second step, the performance of ceramic and polymeric membranes was studied under the optimum conditions and 99% oil and turbidity and 100% total suspended solids rejection were obtained. Moreover, the range of total organic components removal was 63-77%. Finally, the management cost of produced-water treatment by the MF system was estimated as $0.304/bbl (similar to$0.002/L).