Ultrasound irradiation combined with hydraulic cleaning on fouled polyethersulfone and polyvinylidene fluoride membranes.

ABSTRACT

In this study, an ultrasonic irradiation technique was utilized to mitigate the fouling of polyethersulfone (PES) and polyvinylidene fluoride (PVDF) membranes. The use of ultrasound at 20 kHz was applied to a dead-end microfiltration cell in order to mitigate fouling caused by the presence of colloidal bentonite particles. The effect of ultrasonic power and pulse duration on the permeate flux recovery was examined. Measurements indicate that an increase in ultrasonic power and longer pulse duration results to a higher permeate flux recovery. In order to reduce power consumption, a low to high power shift (LHPS) and pulsation method, were investigated. Methods of cleaning such as ultrasonic irradiation, ultrasonic cleaning with forward flushing and ultrasonic cleaning with backwashing were utilized and their cleaning efficiencies were examined. The cleaning performance was assessed using the clean water flux method and scanning electron microscope analysis of the cleaned membranes. Results showed that LHPS and pulsation method both improve the permeate flux recovery but were not able to attain the 93.97 and 74.88% flux recovery for PES and PVDF that was achieved by constant-15 W ultrasonic cleaning. In addition, forward flushing and backwashing may enhance the performance of ultrasonic cleaning at 9 W but could become disadvantageous at 15 W.