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

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

Arequipa

Congreso; V COPEBIOT / I Congreso Internacional de Biotecnología y Bioingeniería; 2024

Universidad Nacional de San Agustin, Arequipa, Perú

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