Cleaning of spiralwound ultrafiltration membranes using ultrasound and alkaline solution of EDTA

Cleaning effects of ultrasound and alkaline solution of EDTA individually and together on spiralwound ultrafiltration membrane were studied. Several frequencies of 28,45 and 100 kHz and alternative waveforms of ultrasound, alkaline solutions of EDTA (pH 11, 1 mM and 3 mM) as well as their interaction effects were used as cleaning agents of spiralwound membranes that fouled using 1% solution of skim milk. The flux recovery and hydrodynamic resistance of each treated membrane were measured during and after cleaning process and cleaning efficiency of each factor was also calculated during various time intervals on treated membranes. The obtained data statistically analyzed in ANOVA table using multifactor design. The overall results showed that the cleaning efficiency of each treatment including different frequencies of ultrasound and alkaline solutions of EDTA individually is relatively low. However, the cleaning efficiency of ultrasound and EDTA increased when applied altogether. The maximum cleaning effects were obtained in the first seconds and after 5 min and additional cleaning process were not necessary. The best results were obtained when mixed waveform of ultrasound and 3 mM EDTA were used together. This effect may be due to a synergistic sonochemical effect of ultrasound and EDTA as cleaning factors. (C) 2010 Elsevier B.V. All rights reserved.