This article describes a methodology for managing solid and liquid waste generated in mining processes, as the way to reuse and recover by-products of mine effluents that have economic value. This aspect is known as the circular economy of mining waste.
To evaluate the possibilities of using solid mining waste such as mine clearings and tailings, it is necessary to characterise them geochemically to predict their behavior over time, and to identify their use and/or possible use in other activities of the mining process, or to identify their definitive storage in case of reactive residue (acidity generator). This way of proceeding reduces the volume of waste to be stored and chooses the most adequate coverage to ensure the physical, chemical and hydrological stability of the deposits where they will be permanently deposited.
In evaluating acid generation, we depend on static tests (ABA), short- term leaching tests (NAG, SPLP, SFE) and kinetic tests, which, through certain criteria and/or indicators, such as: the net neutralisation potential (NNP), acid/base ratio (NP/AP), sulfur content as sulfur, to evaluate leaching capacity and release of metal filler.
To these criteria, comparative studies are usually added, correlating them with other aspects such as the mineralogical and petrological composition of the residues, physicochemical characteristics of the excavated rock mass, storage conditions of these materials and residues, and the possibility that these materials come into contact with water and air.
With this geochemical characterisation, inert or non-acid generating waste can be put to new uses while wastes that generate acidity must be stored in watertight or waterproof tanks.
To control liquid mining waste such as effluents and contact waters, the effluent is treated before being discharged to a receiving body if it complies with the LMP limits and current ECA standards.
Prior to treatment we proceed to a geochemical characterisation of mine effluents and evaluate the possibilities of recovering by-products with economic value during the treatment. This makes the process more efficient, since in addition to the protonic acidity the mineral acidity is included, an aspect that usually is not considered in classic characterisation methods.
With this information we proceed to sizing the acidic water treatment system based on the acidity content and by stages (sequential), this allows, on the one hand, using less lime in the neutralisation process and on the other, recovering metals from the sludge of the process. This makes acidic water treatments more efficient, at lower cost with greater environmental control.
