Stacy Ragueneau, Clémence Cordier, Adeline Lange, Laurent Torres, P. Moulin
Microalgae can synthesize diverse bioactive compounds and rapidly adjust their biochemical composition in response to fluctuating cultivation conditions, making them a potentially inexhaustible resource with broad industrial applications. However, large-scale exploitation is constrained by biological and technical challenges, including contamination, predation, and the complexities of processing large water volumes. This study investigates seawater purification by ultrafiltration process to improve the growth of microalgae cultures from the laboratory to the industrial scale. Three species were selected for study: Odontella aurita , Phaeodactylum tricornutum and Dunaliella salina . The findings indicate a favourable effect of seawater ultrafiltration on the proliferation of microalgae, whatever the magnitude (from 0.2 L to 100 m 3 ) and the position of the cultivation (indoor/outdoor). The cultures maintained in ultrafiltered seawater exhibited a growth rate up to 128% higher than those under control conditions with different sensitivities to water quality depending on the microalgae grown, resulting in a 20–25% reduction in cultivation time and a 30% increase in fresh biomass productivity of O. aurita over a year of production. Over a nearly two-year period, the ultrafiltration unit was subjected to continuous monitoring, which revealed that the quality of the produced water remained constant in terms of bacterial removal (99%) and turbidity (<0.6 NTU). Additionally, membrane permeability remained near its initial level through the optimization of chemical backwashing.