Freshwater microalgae selection for simultaneous wastewater nutrient removal and lipid production

Microalgae are a promising bioenergy source as well as wastewater pollution reducers. This study aims to determine which species better satisfies the double objective of lipid production and wastewater nutrient removal. Seven species were cultured in batch under laboratory conditions in real wastewater and synthetic medium aiming to perform a meaningful comparison among them. Biomass productivity was higher in the wastewater than in the synthetic medium for the strains Chlorella vulgaris, Chlorella kessleri and Scenedesmus obliquus, the latter species yielding the highest biomass concentration (1.4 g/L), lipid content (36.75%) and lipid productivity (29.8 mg lipids/L·d) while C. vulgaris reached the highest biomass productivity (0.107 g/L·d). On the other hand, Neochloris oleoabundans did not grow in wastewater. Algae were not able to remove nitrogen from wastewater and as they were not nitrogen starved their lipid content was lower than when cultured in synthetic medium. The species that achieved maximum daily nitrogen removal from wastewater was C. sorokiniana (6.6 mg Total-N/L·d) followed by S. obliquus (4.4 mg Total-N/L·d). S. obliquus was better than C. sorokiniana at achieving the double objective of nutrient removal and lipid production in wastewater.