Novel membrane processes in ultrafiltration and microfiltration have been developed by a combination of ultrasound process. The feasibility of applying various sound frequencies to the membrane system is demonstrated in cleaning of fouling membrane and in enhancing flux through the filtration operation. For ultrasound-associated membrane cleaning, ultrasound was applied to peptone solution and milk aqueous solution. The membrane operations were performed by cross-flow filtration in ultrasound field having 28, 45 and 100 kHz frequency. It was found that water cleaning under sonication is effective in a recovery of permeate flux for the fouled membrane, especially in 28 kHz field. The low frequency effect of ultrasound on the membrane cleaning was proved by sonic wave detection at the membrane surface. It was also discussed that ultrasound assisted in the enhanced permeation and decreased membrane fouling during the operation with the low frequency. We focus on ultrasound effect on both membrane cleaning and the flux enhancement from a viewpoint of technical fundamentals and the application of ultrasound associated membrane processes.
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