Comparison of approaches to minimize fouling of a UF ceramic membrane in filtration of seawater

Abstract

In this study, several anti-fouling approaches including coagulation conditions (FeCl3 dosage and feed pH), air-enhanced backwash (AEB) conditions (backwash interval and AEB duration) and chemical cleaning conditions (reagents, soak time and temperature) were evaluated to enhance the feasibility of a commercial ultrafiltration (UF) membrane as a pretreatment of RO seawater desalination. A tubular commercial ceramic UF membrane with a surface layer of zirconium dioxide (ZrO2) and a supporting layer of α-alumina oxide (α-Al2O3) was employed in this study. The results showed that ferric coagulation was functional to enhance the performance of ceramic UF for seawater treatment, especially on COD removal. The trial of cleaning demonstrated that the performance of NaClO was much better than that of HNO3 under various evaluated pH values. The relevant additional experiments showed that the cleaning efficiency increased with NaClO concentration, soak time and soak temperature but decreases when soak temperature was up to 60°C. An important finding of this study is that the fouled membrane from coagulation-filtration trial can be easily and quickly recovered by acid cleaning regents followed by NaClO solution. Furthermore, short backwash interval performed more efficiently. However, it is certain that both backwash interval and AEB duration enhanced less than other approaches on the permeate quality. This study finally summarized the operating condition of each anti-fouling approach for the further potential application of UF ceramic membrane as a pretreatment of RO seawater desalination.