Abstract
The mining industry is the major producer of acid mine drainage (AMD). The problem of AMD concerns at active and abandoned mine sites. Acid mine drainage needs to be treated since it can contaminate surface water. Constructed wetlands (CW), a passive treatment technology, combines naturally-occurring biogeochemical, geochemical, and physical processes. This technology can be used for the long-term remediation of AMD. The challenge is to overcome some factors, for instance, chemical characteristics of AMD such a high acidity and toxic metals concentrations, to achieve efficient CW systems. Design criteria, conformational arrangements, and careful selection of each component must be considered to achieve the treatment. The main objective of this review is to summarize the current advances, applications, and the prevalent difficulties and opportunities to apply the CW technology for AMD treatment. According to the cited literature, sub-surface CW (SS-CW) systems are suggested for an efficient AMD treatment. The synergistic interactions between CW components determine heavy metal removal from water solution. The microorganism-plant interaction is considered the most important since it implies symbiosis mechanisms for heavy metal removal and tolerance. In addition, formation of litter and biofilm layers contributes to heavy metal removal by adsorption mechanisms. The addition of organic amendments to the substrate material and AMD bacterial consortium inoculation are some of the strategies to improve heavy metal removal. Adequate experimental design from laboratory to full scale systems need to be used to optimize equilibria between CW components selection and construction and operational costs. The principal limitations for CW treating AMD is the toxicity effect that heavy metals produce on CW plants and microorganisms. However, these aspects can be solved partially by choosing carefully constructed wetlands components suitable for the AMD characteristics. From the economic point of view, a variety of factors affects the cost of constructed wetlands, such as: detention time, treatment goals, media type, pretreatment type, number of cells, source, and availability of gravel media, and land requirements, among others.
Highlights
The mining industry is the major producer of acid mine drainage (AMD)
Heavy Metal Uptake Mechanisms in Constructed Wetlands In Constructed wetlands (CW) for AMD treatment systems metals are removed by a series of mechanisms that are usually attributed to a particular CW component
Türker et al [41] compared the accumulation of B by T. latifolia and P. australis in a polyculture CW receiving mining effluent, the results showed that T. latifolia can accumulate more B in its tissues (250 mg/Kg) than P. australis
Summary
Acid mine drainage (AMD) forms when sulfide minerals are exposed to oxidizing conditions during and following mining operations, highway construction, and other large-scale excavations [1,2]. When the residues are forming sulfides, their exposure to oxygen and water, accompanied by microbial activity leads to the formation of sulfate, metal, and acid drainage called AMD. Kinetic tests attempt to mimic natural oxidation reactions of the field setting and provide information on the rate of sulfide mineral oxidation and acid production Tests such as humidity cell, soxhelet extraction, column, British Columbia Research Confirmation, batch reactor, and field scale are examples of kinetic tests. AMD and liquid waste generated during the extraction and processing of minerals under the term water impacted by mining (MIW) are grouped. Presence of Pb and Uranium in concentrations 0.01 mg/L and less than 0.02 mg/L; * Presence of Pb and Uranium in concentrations 2.1 mg/L and 12.3 mg/L, respectively
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