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ADVANCES IN BIOTREATMENT OF ACID MINE DRAINAGE AND BIORECOVERY OF METALS: 1. METAL PRECIPITATION FOR RECOVERY AND RECYCLE
Citation:
Tabak*, H H., R A. Scharp*, J O. Burckle, F K. Kawahara*, AND R. Govind. ADVANCES IN BIOTREATMENT OF ACID MINE DRAINAGE AND BIORECOVERY OF METALS: 1. METAL PRECIPITATION FOR RECOVERY AND RECYCLE. B.E. Rittmann (ed.), BIODEGRADATION. Kluwer Academic Publishers, Hingham, MA, 14(6):423-436, (2003).
Description:
Acid-mine drainage (AMD) is a severe pollution problem attributed to past mining activities. AMD is an acidic, metal-bearing wastewater generated by the oxidation of metal sulfides to sulfates by Thiobacillus bacteria in both active and abandoned mining operations. The wastewaters contain substantial quantities of dissolved solids with the particular pollutants (metal sulfates) dependent upon the mineralization occurring at the mined rock surfaces. The exposure of post-mining residuals to water and air results in a series of chemical and biological oxidation reactions that produce an effluent which is highly acidic and contains high concentrations of various metal sulfates. The metals (metal sulfates) usually encountered and considered of concern for human risk assessment are: arsenic, cadmium, iron, lead, manganese, zinc, and copper. These metals as well as sulfate are considered serious pollutants of the acid mine drainage. The pollution generated by abandoned mining activities in the area of Butte, Montana has resulted in the designation of the Silver Bow Creek-Butte area known as Berkeley Pit, the largest superfund (National Protection List) site in the U.S. This paper reports on bench-scale studies conducted to develop a resource metal recovery based remediation process for the cleanup of the Berkeley Pit acid mine water.
The process utilizes selective, sequential precipitation (SSP) of metal hydroxides and sulfides such as copper, zinc, aluminum, iron and manganese from the Berkeley Pit AMD for their removal from the acidic water and purification in a form for additional processing into marketable precipitates and pigments. Unique, four stage and six stage processes for metal sequential precipitation/separation and purification have been developed for the above metals using biogenic hydrogen sulfide produced by the sulfate reducing activity of sulfate reducing bacteria (SRB) in separate bioreactor systems for the treatment of AMD. The six stage SSP system based on appropriate optimized operating conditions (pH, temperature, etc.), was shown to produce high recoveries of the above metals from the Berkeley Pit acid mine water, high purity metal precipitates and an agriculturally usable water (for irrigation purposes) that meets USEPA's Gold Standard criterion. Data generated from these studies provide information on the % recovery and purity of the heavy metals from the four stage and six stage metal precipitator-settler reactor systems and on the quality of the water effluent. This metal SSP process is unique in that it is only intended for the treatment of the Berkeley Pit acid mine water as well as other acidic mine waters (from other mine water pit lakes and effluents from acid mines), but it is also a remediation process based on metal resource recovery and recycle.
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Advances in biotreatment of acid mine drainage and biorecovery of metals: 1. Metal precipitation for recovery and recycle