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Acid mine drainage (AMD) occurs at about 70% of the world’s mine sites. It is a naturally occurring process that leads to the contamination of water and occurs when water and oxygen react with exposed sulphide minerals in waste rock, tailings, rock cuts and underground workings, picking up heavy metals such as copper, zinc, cadmium, nickel, cobalt and arsenic. The result is a cocktail of heavy metals dissolved in weak acidic water which is toxic to the environment.
Because acid mine drainage can create an environmental liability that remains long after a mine has ceased operations, it is fully regulated in most jurisdictions and must be treated. Environmental regulations around the world make the treatment of contaminated water and its sources the mining industry’s single greatest liability.
BioteQ has developed innovative processes to treat acid mine drainage. The company’s BioSulphide® and ChemSulphide™ Processes can selectively recover metals from acidic waste water, producing a saleable metal product and clean water that can be safely discharged to the environment. Metals recovered for sale include copper, zinc, nickel and cobalt. Toxic metals such as arsenic, antimony, cadmium, lead, molybdenum and manganese are also removed from the water. In addition, BioteQ’s Sulf-IX™ process removes sulphate from water following metal removal. Click here to read more about BioteQ’s technology.
BioteQ operates water treatment plants for acid mine drainage at the Bisbee mine site in Arizona, and the Raglan mine site in Quebec. Plants are under construction at the Mt. Gordon mine in Australia, the Dexing mine in China, and the Lluvia de Oro mine in Mexico. Click here to read more about BioteQ’s operations.
Historically, acidic and metal contaminated mine water has been treated by adding lime (calcium oxide or hydroxide), or sometimes caustic soda, to precipitate metals as hydroxides to form a voluminous solid product termed sludge. Lime treatment essentially transfers the heavy metal contaminants from one medium (water) to another medium (sludge); because the sludge contains heavy metals, it must be stored and managed to prevent metals from re-dissolving and entering the environment. This creates a long-term environmental liability for mining firms.
While lime treatment technology is widely used, easily engineered, relatively simple to operate and, for the most part, has been successful in meeting water quality discharge standards in most jurisdictions, many jurisdictions are adopting stricter regulations for water treatment. Furthermore, regulations surrounding the reduction of the concentration of dissolved sulphate, always present in association with dissolved metals in acidic mine drainage, are now being instituted at levels well below the capability of all lime plants – requiring an entirely new approach to the treatment of effluents from mining projects.
- BioteQ’s process does not produce a toxic sludge, eliminating the long-term environmental liability associated with lime sludge.
- BioteQ’s process produces better quality water that meets strict water quality criteria, and can be safely discharged to the environment.
- BioteQ’s process can cost less than conventional lime treatment, over the long-term.
- BioteQ’s process removes metals from the environment; these metals can be sold to offset water treatment costs. In lime treatment, all metal values are lost to the sludge.
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