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Evaluación comparativa de dos tipos de floculantes para la cosecha de biomasa de microalgas a escala piloto

Abstract:

The high energy cost of conventional harvesting methods for microalgal biomass for different commercial applications makes their production economically unfeasible. A new method proposed to solve this kind of problem is the biological flocculation using plant extracts. Flocculation capacity of three native Ecuadorian strains were tested: CMIE-A1-004 of the genus Chlorella sp.1 and CMIE-A3-006 of the genus Scenedesmus sp. from Cotopaxi National Park and CMIE-I4.2-002 of the genus Chlorella sp.2 from Llanganates National Park. The tannins used as biologic flocculants were extracted from the flour obtained from the pods of the specie Caesalpina spinosa, by dissolving 150 g of four in 1500 mL of a solution 50% of methanol and destilled water. Tannins were added in the microalgae media culture in three different volumes of 60 mL, 100 mL and 160 mL at a final concentration of 0,5 g/mL, 0,3 g/mL y 0,188 g/mL respectively. In order to obtain more microalgal biomass at the harvest, the pH was adjusted into three ranges: 5, 8 and 11. The results revealed than from all treatments analyzed, strain CMIE-A1-004 of the genus Chlorella sp.1 and CMIE-A3-006 of the genus Scenedesmus sp. both with 100 mL of tannins and pH 11 do not show significant differences compared to the positive control aluminium sulfate (chemical flocculant). By analyzing each factor and their interactions, the pH and the combination of strains*pH are highly significant. The stain CMIE-A3-006 of the genus Scenedesmus sp. has a better flocculation ability. Between tannin volumes there are no significant differences. However, volumes of 100 mL and 160 mL are more effective. Finally, pH 11 had the better yield in the floculation. Although all strains of microalgae studied have a better flocculation with pH 11 and high volumes of tannins, biomass dry weight in grams obtained was lower compared to the biomass obtained with the positive control.