Analytical and experimental investigation of vibration for reducing cleaning time of water filtration membranes

Abstract

Membrane technology is one of the most reliable and efficient separation processes for water treatment. However, one of the main limiting factors in the membrane filtration process is fouling, which is the deposition or adsorption of contaminants on the membrane surface or inside the membrane pores. In this paper, induced-vibrations is proposed as a cleaning-aid by preventing and reducing membrane fouling. The response of the membrane to periodic displacement at its boundaries is found mathematically and experiments are performed using a tabletop shaker to verify the model. Humic Acid (HA), a common water foulant in filtration systems, are distributed on the surface and their motion is observed at various forcing frequencies. Here we aim to utilize induced vibrations to excite the membrane’s resonances and take advantage of the spatial non-uniformity of the resulting mode shapes. In these modes, there will be regions of the membrane which vibrate out-of-phase with one another, potentially reducing the deposition of particles on the membrane surface (fouling) further by creating instability in the fluid near the membrane surface. Because the amplitude of vibration varies across the membrane surface, the deposition of foulants will also occur unevenly. These uneven patterns of fouling may be able to be removed from the membrane more easily during subsequent cleaning.