Produção de biomassa microalgal cultivada em vinhaça e água residuária de usina de cana-de-açúcar

Abstract

Brazil is one of the world's largest producers of sugar cane. In the sugar-alcohol industry, a large portion of sugarcane processing is used to produce bioethanol. However, this product generates large amounts of wastewater with a high pollution potential. This wastewater is often returned to the fields without prior treatment, causing serious problems for soil and water due to the high organic load and the presence of toxic substances. For this reason, several studies have been carried out on the minimization of the impact of wastes from the sugar-alcohol industry, such as vinasse. The cultivation of microalgae in sugarcane vinasse is an alternative way to treat this waste, and is also capable of achieving significant yields and being used as a low value raw material. However, some authors have highlighted the need to dilute the medium in order to cultivate efficiently in high concentrations of vinasse. The sugar-alcohol industry is an intensive user of water in its processes, but it also has a large amount of wastewater from the industrial process, which together with vinasse could be a strategic alternative for use as a growing medium. In addition, the recirculation of water in the system can contribute to the adaptation and yield of algal biomass. Therefore, this study evaluated the cultivation of microalgae in wastewater from the sugar-alcohol industry, as well as in the recirculated medium used to dilute vinasse water. The cultivation phases (P) were carried out under controlled conditions. P1 evaluated the cultivation of microalgae in vinasse in dilutions (1%, 5%, 10%, 15%, 20%), P2 tested the best dilutions (1%, 5%, 10%) in P1 and evaluated the possibility of reusing the culture medium in dilutions of 1% (S1%) and 5% (S5%). Then the cultivation phases P3, P4 and P5 were then carried out. In P3, different dilutions (25%, 50%, 75%, 100%) of industrial wastewater mixed with 5% vinasse ware evaluated. The best dilution combined with 5% vinasse was 50%. P4 and P5 showed that the effluent from the industrial process, together with the supernatant from the culture recirculation, can be used to satisfy the water demand of the system. In this way, the combination of effluents was satisfactory, achieving high efficiencies in the removal of pollutants as well as high biomass yields, ensuring the viability of the recirculated water in the system.