Study of growth kinetics of microalgae cultivated in brackish/waste water for bioenergetic purposes

Abstract

The production of microalgae biomass as a raw material for the production of biodiesel has shown great potential. Cellular stress can occur as a result of the environment in which the species under study has been cultivated, which may be brackish water or wastewater. The present work studied the growth kinetics and the feasibility of producing biodiesel from two species of microalgae. Synthetic brackish media and a mixture of brackish water from wells and effluents from septic tanks as an exclusive source of nutrients were used as a culture medium. The species studied were Chlorella sp. and Scenedesmus acuminatus. As for growth kinetics, the best results in synthetic media were obtained in media with lower salinity (2.0 g.L^-1 of NaCl) for Scenedesmus acuminatus. In Chlorella sp., the best results occurred in the 4.0 g.L^-1 NaCl concentration. In cultures from a mixture of wastewater and brackish well, Scenedesmus acuminatus had its growth favored in media with low concentrations of nutrients and Chlorella sp. in high concentrations. As for the potential of biodiesel production, Scenedesmus acuminatus proved to be more viable, since the lipid percentage varied between 23% and 28% in synthetic brackish crops and 31% and 62% in crops that used wastewater as a source of nutrients. In addition to the kinetic study and feasibility of biofuel production, it was also possible to observe the nutrient removal rate in the mixture of well water and septic tank effluent, where a significant decrease in ammonia levels in the media was observed.