A filtration system and a method of cleaning a particle and/or colloidal fouled filtration membrane are provided. The filtration system includes at least one filtration membrane disposed in a casing, and at least one ultrasonic transducer in direct contact with a fluid to be filtered. Ultrasonic energy is emitted by the ultrasonic transducer in the direction of the filtration membrane. Dislodged particles cleaned by the ultrasonic energy from the filtration membrane are carried away in a cross-flow stream and wasted or recycled back to the beginning of the treatment process. The ultrasonic transducer can be fixed or movable. The filtration system can use different filtration membrane configurations such as, but not limited to, tubular, flat sheet, hollow fiber and spiral wound membranes.