Microorganisms in the generation of acid drainage. Alternatives for their mitigation

DONATI E.R.; PLAZA CAZÓN, J.; CASTRO, C.; URBIETA, M. S.

Arequipa

Congreso; 1st International Congress of Biotechnology and Bioengineering-V COPEBIOT 2021; 2021

Universidad Nacional de San Agustin (UNSA), Arequipa-Perú

The economy of many countries in the world and mainly in Latin America, has metalliferous mining as one of most relevant pillars. The technologies used in large-scale mining make the recovery of metals economically profitable and are usually less polluting than the methods used in small-scale mining. Nevertheless, large-scale tailings are generated mainly because it is necessary to process huge volumes of ore to obtain small quantities of the metals of interest. The impact of these tailings covers different dimensions, but undoubtedly the most serious aspect is the contamination of water resources and soils, which can occur through different routes, among which acid minedrainage (AMD) should be distinguished as the highest risk. AMD is generated by the exposure of sulfide minerals (especially those sulfides such as pyrite) to oxygen and water, which causes their oxidation, usually accompanied by acidification and solubilization of heavy metals in the aqueous medium. These highly acidic, metal-loaded drainages can affect watercourses and ecosystems even at great distances from their source. Although the AMD formation process can develop under abiotic conditions, the presence of iron and sulfur oxidizing microorganisms drastically increases its speed due to the generation of ferric ion, which becomes the main oxidizing agent. There aredifferent physicochemical and biological alternatives to prevent the formation of AMD and/or to buffer its effects on the environment. Limiting the access of oxygen (usually by flooding) is usually an acceptable alternative with some hydrogeological consequences; in addition, the microorganisms mentioned can also act -much more slowly- under anaerobic conditions, so that inhibition of the microorganisms by adding different substances or even antagonistic microorganisms is a more promising alternative. Finally, the treatment of AMD using natural or artificial wetlands would make it possible to reduce the metal load and the acidity of these drains so that they can be discharged with a minimum effect on the environment