Untersuchungen zur Verbesserung der Mikro-, Ultrafiltration durch Ultraschall

In this thesis the possibilities for improvement of micro- and ultrafiltration via ultrasound were examined. Key findings were collected from the two fields of technology (membrane filtration and ultrasound) for the analysis of possible mechanisms of ultrasound that could lead to an improvement of membrane filtration. For the most important approaches of the use of ultrasound in membrane filtration, a system was developed. Numerous approaches have been investigated experimentally in exploratory experiments and evaluated. An important aspect for the evaluation of the methods was the scalability of the technology combinations. Clearly visible bubbles in the order of 10-500 microns were identified to have the most important role for the cleaning effect. The most successful method is the ultrasonically enhanced backwash. Based on these findings, a scale-up of ultrasonic cleaning was carried out with a commercial capillary membrane. In initial filtration experiments with natural surface water membrane damages could be detected, which were due to a local cavitation streamer at the coupling point of the ultrasound transducer. No membrane damages occurred when using lower ultrasonic power and higher ultrasonic frequencies. In comparison to a reference module without ultrasound significant improvements by the ultrasound irradiation could be detected in various fluid systems. The thesis concludes with suggestions for membrane modules with integrated power ultrasound, which appear advisable from a technical point of view after the experimental and theoretical work