Using axial vibration membrane process to mitigate membrane fouling and reject extracellular organic matter in microalgae harvesting

Abstract

Membrane fouling caused by algae cells and extracellular organic matter (EOM) is a major challenge in microalgae harvesting. In the present study, the axial vibration membrane (AVM) process can effectively reduce membrane fouling by increasing vibration frequency. An equation was obtained to explain why the vibration frequency has a more important impact on critical flux than the amplitude. During the continuous filtration, the flux decline rate was only 3.6% at the frequency of 10Hz and amplitude of 1cm. While at the frequency of 5 and 0Hz the decline rates were 34% and 64.2%, respectively. At high frequency, AVM can not only prevent the deposition of algae cells on membrane, but also reduce the adsorption of EOM on membrane. Scanning electron microscope and fourier transform infrared spectroscopy analysis showed that AVM can effectively reduce EOM adsorbing on membrane at 10Hz. AVM had better rejections of protein (28–39%) and polysaccharide (about 35%) at 10Hz, compared with 0 and 5Hz. Membranes had obvious rejection of low molecular weight EOM, regardless of at high or low frequency; however, compared to low frequency at high frequency AVM could reject more high molecular weight organics.