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Efficient bioremediation from metallurgical effluents through the use of microalgae isolated from the amazonic and highlands of Ecuador

Abstract:

Mining operations in the south of Ecuador have increased their activity in the last decades due to the great auriferous wealth of the region. Nevertheless, gold extraction involves processes that cause dangerous impacts to the environment, such as the release of metal ions and inorganic compounds, which are discharged into aquatic systems or to the earth’s surface, interacting adversely with various organisms. Due to this problem, the aim of this research was to evaluate the removal efficiency of mercury, phosphates, sulfates, and nitrates from the gold mining wastewater through a phytoremediation process. The study collected and applied microalgae species of the Andes and the Ecuadorian Amazon such as Pleurococcus sp., Scenedesmus sp., and Chlorella sp. The adaptation of the microalgae was evaluated, as well as the absorption capacity of the pollutants of the wastewater collected from one of the gold processing plants located on the riverside of the Calera River, province of El Oro. The microalgae strains were cultivated individually and as a consortium in photobioreactors for the treatment. The physical and chemical parameters of the wastewater and the treated water were characterized. The results determined that all the treatments were efficient, since the concentration of contaminants was considerably reduced. Pleurococcus was the genus of microalgae with the highest percentage of mercury removal, with 86 %, while in the removal of sulfates, phosphates, and nitrates, the microalgae consortium achieved results greater than 76 %, 93 % and 97 %, respectively. Thus, the use of isolated microalgae on the lacustrine systems of the Andes and the Ecuadorian Amazonia represents a promising source of germplasm for environmental bioremediation applications.