The extent of flux recovery is independent of the length of sonication time and increases with ultrasonic power. The use of surfactants in combination with ultrasonic irradiation shows a synergistic effect, providing a better efficiency than either cleaning process alone. Repetitive use of ultrasonic cleaning over a 1 month period does not result in any significant change in the permeate flux of a cleaned membrane, indicating that the ultrasonic treatment does not appear to damage the membrane structure itself.
