Membrane antifouling methods and alternatives: Ultrasound approach

Membranes are widely used in separation processes. Various industries use membranes as part of their production processes. However, one of the main problems in membrane separation processes is fouling. The fouling mechanism is briefly reviewed in this paper. Fouling can be controlled before it happens. Alternatively, membranes can be cleaned after fouling occurs. Several control methods such as feed pre-treatment, material selection and membrane surface modification can be applied. Cleaning methods can be categorized into several techniques: chemical, mechanical, hydrodynamic, electrical and ultrasonic cleaning methods. This paper focuses on the ultrasonic cleaning method, which is an additional force that aids filtration. The mechanism of the ultrasonic wave that reduces fouling by cavitation and acoustic streaming is reviewed. The advantages and disadvantages of ultrasound irradiation as a cleaning method are also discussed in this paper. The apparatus design and factors that influence the effectiveness of ultrasound treatments, including frequency, power intensity, feed properties, membrane properties, cross-flow velocity, temperature and pressure, are analysed. Recently, ultrasound irradiation combined with other techniques has gained increasing attention. It has been discovered that a combination of other cleaning methods with ultrasound irradiation led to the removal of the fouling layers from the membrane surface.