Considering that an adequate characterization of the drainage produced by mining operations enables a correct selection of their treatment system. The use of the best available techniques (BAT) is essential to develop methodologies for the characterization and treatment of acid mine water, such as total acidity, which includes mineral acidity as well as protonic acidity, accompanied by neutralization and precipitation tests that promote the formation of physical and chemical processes that modify the Eh and pH conditions of discharges, favoring the formation of insoluble species and the removal of metallic load dissolved in the water.
In these acid water characterization tests, the most important are the determination of hydrolysis zones and the formation of initial solid phases of iron and aluminum that precipitate as hydroxides, oxyhydroxides or hydroxysulfates at pH values between 2.7 and 6, which induce the adsorption and coprecipitation of metals even those dissolved such as zinc, cadmium, manganese and others. If tests continue at pH values between 6 and 11, the remaining hydrolysis zones of the other constituents dissolved in the water will continue to be identified. This aspect is linked to the pH-Eh ranges in which the metal load present in effluents can be removed.
This hydrogeochemical characterization methodology, based on the estimation of total acidity and the identification of the hydrolysis zones, makes it possible to dimension more efficient mine water treatment systems, known as direct and staged systems, which lead to lower consumption of reagents and better environmental control. In the case of staged neutralization processes, the sludge or solids generated in each stage are removed sequentially, in order to avoid the redissolution of solid phases, enhance the efficiency of the treatment system and reduce costs and reagent consumption.
This paper reviews the techniques for geochemical characterization of effluents that have contributed to develop more efficient treatment systems and that make it possible for discharges to receiving bodies to comply with current legal requirements stipulated by the Peruvian mining and environmental legislation.
