The comparison between vibration and aeration on the membrane performance in algae harvesting

Abstract

Membrane fouling is a main problem in algae harvesting and retarding membrane fouling is significant to increase filtration efficiency and reduce harvesting cost. The aeration membrane system could mitigate membrane fouling by the coarse bubbles and the vibration membrane system could produce high shear by the vibration of membrane to mitigate fouling. In the critical flux experiment, the aeration membrane had a low critical flux of 34 L/(m2h) compared with the vibration membrane (49 L/(m2h)). After experiencing 12-h continuous filtration, the flux decline rates of vibration and aeration membrane were 3.6% and 46%, respectively. Based on the Extended Derjaguin–Landau–Verwey–Overbeek (XDLVO) theory, the free energy of fouled vibration and aeration membranes were −53.76 and −62.51 mJ/m2, respectively, indicating that vibration could better reduce the interaction of algae cells and membrane, compared with aeration. Moreover, vibration also had a better effect on the rejection of extracellular organic matter (EOM), which could reduce secondary pollution of the water body. The different working mechanism of vibration and aeration acting on membrane was draw, suggesting that the fluid velocity induced by vibration mainly acting on membrane surface could decrease membrane fouling, while the fluid velocity induced by aeration basically could not act on membrane.