Harvesting of Microalgae Biomass Using Ceramic Microfiltration at High Cross-Flow Velocity

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 (R_c, 57%) and pore adsorption and blocking (R_a, 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 R_c decreased (82 to 57%), while that of R_a 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 R_c and R_a, 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.