Abstract
The study evaluates the performance of the novel ADES (alkaline diffusive exchange System), SDES (sulfidogenic diffusive exchange system) and DAS (Dispersed Alkaline Substrate) technologies for the passive treatment of high-strength acid mine drainage (AMD) from copper mining (pH~3, 633 mg Cu L−1). The chemical DAS and ADES prototypes showed the best performance in the removal of Cu, Al, and Zn (98–100%), while the biochemical SDES reactors achieved a high sulfate removal rate (average of 0.28 mol m−3 day-1). Notably, the DES technology was effective in protecting the sulfate-reducing communities from the high toxicity of the AMD, and also in maintaining bed permeability, an aspect that was key in the ADES reactor. The DAS reactor showed the highest reactivity, accumulating the metallic precipitates in a lower reactor volume, allowing to conclude that it requires the lowest hydraulic residence time among all the reactors. However, the concentration of precipitates resulted in the formation of a hardpan, which may trigger the need of removing it to avoid compromising the continuity of the treatment process. This study suggests the development of new treatment alternatives by combining the strengths of each technology in combined or serial treatments.
Highlights
Acid mine drainage (AMD) is an effluent from the mining industry generated by the interaction of mining waste derived from the extraction and processing of the ore, with environmental factors, mainly water, oxygen and microorganisms [1,2,3]
All had in common a 20 cm layer of coarse sand (0.5–5 mm grain size) at the base, a 100 cm reactive substrate bed, a 10 cm layer of coarse sand (0.5–5 mm grain size) on top, and a 10 cm zone of free water. Three of these prototypes worked with DES technology, including a metal screen tube attached to their bases, of 6 cm internal diameter
The fourth prototype corresponded to a dispersed alkaline system (DAS) reactor
Summary
Acid mine drainage (AMD) is an effluent from the mining industry generated by the interaction of mining waste derived from the extraction and processing of the ore (waste rock deposits and tailing dams), with environmental factors, mainly water, oxygen and microorganisms [1,2,3]. The acidic pH between −3.6 and 6 and the high concentrations of sulfate and heavy metals that characterize AMD are the result of oxidation reactions of sulfur minerals and leaching of associated elements [4]. The most significant sources of AMD are the cordilleran copper deposits during snowmelt, which are located in the central zone of the country. A particularity of this AMD is that it presents high concentrations of copper, which can be recovered economically [8]. In the United States, copper mining is significant in Utah and New Mexico, where
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