This study aimed to investigate the harvesting of microalgae by microfiltration (MF) on a ceramic membrane at relatively high cross-flow velocity (CFV) of interest for commercial processes. Pilot-scale harvesting was conducted with algal suspensions (Chlorella vulgaris and Tisochrysis lutea (T-Iso)) and algal supernatants (Porphyridium cruentum) to assess the effect of feedstock characteristics and understand flux decline mechanisms. In total recycle mode (C. vulgaris, 1 g/L), high steady-state permeation flux around 200 L/m2/h was achieved. Total filtration resistance was mainly due to cake resistance (Rc, 57%) and pore adsorption and blocking (Ra, 40%). The process hydrodynamic conditions seemed to have relatively little effect on Chlorella cell integrity. In concentration mode, average permeate flux decreased from 441 to 73 L/m2/h with increasing feed concentration (C. vulgaris, 0.25-1 g/L); the contribution of Rc decreased (82 to 57%), while that of Ra rose (7 to 40%). With T-Iso suspensions and P. cruentum supernatants at 1 g/L, average permeate flux was 59 and 49 L/m2/h, respectively, with predominance of Rc and Ra, respectively. Distinct fouling mechanisms were inferred to explain the superior filterability of C. vulgaris. The results show that ceramic membrane MF at relatively high CFV could be a suitable option for harvesting certain microalgae including C. vulgaris.
Keywords: Alumina membrane; Chlorella vulgaris; Cross-flow microfiltration; Fouling mechanisms; Microalgae harvesting; Tangential velocity.