Cleaning membranes with focused ultrasound beams for drinking water treatment

Traditional methods for water treatment are not effective to remove micro pollutants such as harmful organics and cannot meet the demand for high-quality drinking water. Membrane technologies are known to produce drinking water of the highest quality. However, membrane fouling is a significant problem, which limits a widespread use of these technologies. Currently, chemical cleaning is used to control fouling, which interrupts the water production process during cleaning, produces secondary pollutants, shortens membrane life due to chemical erosion, adds costs of cleanup, handling, and transporting dangerous chemicals, and waste energy and the cleaned water. Ultrasound has been demonstrated effective for membrane cleaning and does not have the problems of chemical cleaning. However, current ultrasound methods have high energy consumption, require transducers that can handle high power, and are expensive to clean a large membrane area needed for a typical water treatment plant. In this paper, a focused ultrasound beam is used to create a high intensity at focus to produce cavitations for membrane cleaning. This method may save energy and potentially allow inexpensive low-power transducers such as polymeric transducers to be used. Combined with the beamforming technology that is widely used in medical ultrasound, the focused beams can be swept over a large surface area of membranes for cleaning. An experiment was performed and preliminary results show that the method is promising for membrane cleaning.