Use of microalgae Spirulina platensis in wastewater treatment and biofuel production

Abstract

This study evaluated the efficiency of microalgae Spirulina platensis in the treatment of cattle wastewater and, simultaneously, in the production of biomass for biodiesel. Cultivation in effluents, without additives, demonstrated high bioremediation efficacy, with removals of 86 to 99% of Chemical Oxygen Demand (COD), 86 to 99% of Biochemical Oxygen Demand (BOD), and 98 to 100% of Ammoniacal Nitrogen (NH??). Dry biomass volumetric productivity reached 2.018 g L?¹ day?¹ in one of the experiments, with an average of 0.846 g L?¹ day?¹ in the four scenarios tested, exceeding values ??reported in the literature for similar media. CO? biofixation reached 3401 mg L?¹ day?¹ in the highest productivity experiment. The generated biomass presented lipid contents between 6.3% and 8%, with palmitic acid (C16:0) being the majority (~47%). The biodiesel produced met several quality parameters, although the linolenic acid (C18:3) content was between 17-22%, above the 12% limit established by EN14214 standard. The treated effluent met the discharge and reuse standards of the National Environment Council (CONAMA) Resolutions No. 430/2011 and No. 357/2005, respectively, for most parameters, except for pH, which requires simple and low-cost correction. It is concluded that the cultivation of Spirulina platensis in wastewater is a viable and efficient strategy, integrating effluent treatment with sustainable biofuel production.