Wastewater treatment by membrane ultrafiltration enhanced with ultrasound: Effect of membrane flux and ultrasonic frequency

Membrane ultrafiltration is increasingly applied for wastewater treatment and reuse, even though membrane fouling still represents one of the main drawbacks of this technology. In the last years, innovative strategies for membrane fouling control have been developed, such as the combination of membrane processes with ultrasound (US). In present work, the application of membrane ultrafiltration and its combination with US were studied, evaluating the influence on the performance of the treatment and membrane fouling formation of two membrane fluxes, 75 and 150 L/m2 h, along with two US frequencies, 35 and 150 kHz. The results observed showed that the combination of membrane ultrafiltration with US, respect to the filtration process alone, reduced membrane fouling rates to a greater extent at the higher membrane flux and lower US frequency applied, reaching a reduction of 57.33% at 150 L/m2 h and 35 kHz. Furthermore, higher organic matter and turbidity removals were observed at higher frequency (130 kHz). The results obtained highlights the applicability of this combined process for the upgrading of membrane ultrafiltration and as an alternative option to conventional tertiary wastewater treatments.