Antifouling microfiltration strategies to harvest microalgae for biofuel

▸ Three high lipid content microalgae species were concentrated at lab/pilot scale. ▸ Dynamic filtration improved permeability compared with tangential cross-flow filtration. ▸ Pre-concentration step substantially improved posterior dynamic filtration. ▸ Dynamic filtration is more economic efficient than tangential cross-flow filtration. Microalgae are microorganisms that can fix CO2 by using the energy from the sun and transforming it into organic molecules such as lipids (i.e. feedstock for biodiesel production). Microfiltration is a promising method to be considered in the harvesting step. In this study, two antifouling methods were tested in order to minimize permeability decrease over time, at low trans-membrane pressure filtration. Preliminary experiments were performed to find optimum conditions of transmembrane pressure, rotational speed and membrane pore size. Pilot experiments were carried out in the optimal conditions using microalgae obtained from the culture step and from a previous concentration process based on sedimentation. Fouling was significantly minimized, and the permeability plateau increased up to 600L/h/m2/bar. Three microalgae species were tested: Phaeodactylum tricornutum (Pht), Nannochloropsis gaditana (Nng) and Chaetoceros calcitrans (Chc). An economic assessment was also performed, which demonstrated that dynamic filtration is economically more efficient than tangential cross-flow filtration.