Co-processes of electrocoagulation and mixotrophic growth of Desmodesmus subspicatus in sugarcane vinasse

Abstract

Brazil is the world's largest producer of ethanol from sugarcane, and this process generates considerable amounts of vinasse, its main wastewater. Because of its high nutrient content, especially potassium and nitrogen, and organic matter, vinasse can be considered a fertilizer. However, due to the large volumes generated, there are several researches about their treatment and reuse. The cultivation of microalgae in certain conditions would lead to the consumption of carbon and nutrients from wastewaters with generation of biomass could be used to obtain bioproducts of commercial interest. Thus, in order to enhance the development of these microorganisms in vinasse, electrocoagulation as a pretreatment stage would contribute to the removal of part of the matter, reducing turbidity and allowing an adequate light incidence capable of supporting the microalgae's mixotrophic metabolism in vinasse. In this context, the present research aims to evaluate the co-processes of electrocoagulation with sequential cultivation of the Chlorophycea microalgae Desmodesmus subspicatus in sugarcane vinasse with the biomass production and organic matter/nitrogen removal. The electrocoagulation step will be conducted under different experimental conditions, such as mixing, type of material and arrangement of the electrodes. Later, the influence of this pretreatment on microalga cultivation will be studied, monitoring the growth, removal of carbon and nitrogen, as well as the composition of the biomass generated in terms of proteins and lipids. With the results, it is expected that the present study will be the basis for the development of a technology that can produce microalgal biomass in wastewater, generally limited by turbidity, integrating the electrocoagulation process with the subsequent microalgae culture through incorporation of part of the constituents of the vinasse. (AU)