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Sierra-Alvarez, R. (2006). Biological treatment of heavy metals in acid mine drainage using sulfate reducing bioreactors. Water Sci. Technol., 54(2), 179–185.
Abstract: The uncontrolled release of acid mine drainage (AMD) from abandoned mines and tailing piles threatens water resources in many sites worldwide. AMD introduces elevated concentrations of sulfate ions and dissolved heavy metals as well as high acidity levels to groundwater and receiving surface water. Anaerobic biological processes relying on the activity of sulfate reducing bacteria are being considered for the treatment of AMD and other heavy metal containing effluents. Biogenic sulfides form insoluble complexes with heavy metals resulting in their precipitation. The objective of this study was to investigate the remediation of AMD in sulfate reducing bioreactors inoculated with anaerobic granular sludge and fed V with an influent containing ethanol. Biological treatment of an acidic (pH 4.0) synthetic AMD containing high concentrations of heavy metals (100 Mg Cu2+vertical bar(-1); 10 mg Ni2+vertical bar(-1), 10 mg Zn2+vertical bar(-1)) increased the effluent pH level to 7.0-7.2 and resulted in metal removal efficiencies exceeding 99.2%. The highest metal precipitation Cn rates attained for Cu, Ni and Zn averaged 92.5, 14.6 and 15.8 mg metal l(-1) of reactor d(-1). The results of this work demonstrate that an ethanol-fed sulfidogenic reactor was highly effective to remove heavy metal contamination and neutralized the acidity of the synthetic wastewater.
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Bamforth, S. M. (2006). Manganese removal from mine waters – investigating the occurrence and importance of manganese carbonates. Appl. Geochem., 21(8), 1274–1287.
Abstract: Manganese is a common contaminant of mine water and other waste waters. Due to its high solubility over a wide pH range, it is notoriously difficult to remove from contaminated waters. Previous systems that effectively remove Mn from mine waters have involved oxidising the soluble Mn(II) species at an elevated pH using substrates such as limestone and dolomites. However it is currently unclear what effect the substrate type has upon abiotic Mn removal compared to biotic removal by in situ micro-organisms (biofilms). In order to investigate the relationship between substrate type, Mn precipitation and the biofilm community, net-alkaline Mn-contaminated mine water was treated in reactors containing one of the pure materials: dolomite, limestone, magnesite and quartzite. Mine water chemistry and Mn removal rates were monitored over a 3-month period in continuous-flow reactors. For all substrates except quartzite, Mn was removed from the mine water during this period, and Mn minerals precipitated in all cases. In addition, the plastic from which the reactor was made played a role in Mn removal. Manganese oxyhydroxides were formed in all the reactors; however, Mn carbonates (specifically kutnahorite) were only identified in the reactors containing quartzite and on the reactor plastic. Magnesium-rich calcites were identified in the dolomite and magnesite reactors, suggesting that the Mg from the substrate minerals may have inhibited Mn carbonate formation. Biofilm community development and composition on all the substrates was also monitored over the 3-month period using denaturing gradient gel electrophoresis (DGGE). The DGGE profiles in all reactors showed no change with time and no difference between substrate types, suggesting that any microbiological effects are independent of mineral substrate. The identification of Mn carbonates in these systems has important implications for the design of Mn treatment systems in that the provision of a carbonate-rich substrate may not be necessary for successful Mn precipitation. (c) 2006 Elsevier Ltd. All rights reserved.
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Jong, T. (2006). Microbial sulfate reduction under sequentially acidic conditions in an upflow anaerobic packed bed bioreactor. Water Research, 40(13), 2561–2571.
Abstract: The aim of this study was to operate an upflow anaerobic packed bed reactor (UAPB) containing sulfate reducing bacteria (SRB) under acidic conditions similar to those found in acid mine drainage (AMD). The UAPB was filled with sand and operated under continuous flow at progressively lower pH and was shown to be capable of supporting sulfate reduction at pH values of 6.0, 5.0, 4.5, 4.0 and 3.5 in a synthetic medium containing 53.5 mmol l(-1) lactate. Sulfate reduction rates of 553-1052 mmol m(-3) d(-1) were obtained when the influent solution pH was progressively lowered from pH 6.0 to 4.0, under an optimal flow rate of 2.61 ml min(-1). When the influent pH was further lowered to pH 3.5, sulfate reduction was substantially reduced with only about 1% sulfate removed at a rate of 3.35 mmol m(-3) d(-1) after 20 days of operation. However, viable SRB were recovered from the column, indicating that the SRB population was capable of surviving and metabolizing at low levels even at pH 3.5 conditions for at least 20 days. The changes in conductivity in the SRB column did not always occur with changes in pH and redox potential, suggesting that conductivity measurements may be more sensitive to SRB activity and could be used as an additional tool for monitoring SRB activity. The bioreactor containing SRB was able to reduce sulfate and generate alkalinity even when challenged with influent as low as pH 3.5, indicating that such treatment systems have potential for bioremediating highly acidic, sulfate contaminated waste waters. (c) 2006 Elsevier Ltd. All rights reserved.
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Jarvis, A. P. (2006). Effective remediation of grossly polluted acidic, and metal-rich, spoil heap drainage using a novel, low-cost, permeable reactive barrier in Northumberland, UK. Environmental Pollution, 143(2), 261–268.
Abstract: A permeable reactive barrier (PRB) for remediation of coal spoil heap drainage in Northumberland, UK, is described. The drainage has typical chemical characteristics of pH < 4, [acidity] > 1400 mg/L as CaCO3, [Fe] > 300 mg/L, [Mn] > 165 mg/L, [Al] > 100 mg/L and IS041 > 6500 mg/L. During 2 years of operation the PRB has typically removed 50% of the iron and 40% of the sulphate from this subsurface spoil drainage. Bacterial sulphate reduction appears to be a key process of this remediation. Treatment of the effluent from the PRB results in further attenuation; overall reductions in iron and sulphate concentrations are 95% and 67% respectively, and acidity concentration is reduced by an order of magnitude. The mechanisms of attenuation of these, and other, contaminants in the drainage are discussed. Future research and operational objectives for this novel, low-cost, treatment system are also outlined. (c) 2005 Elsevier Ltd. All rights reserved.
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Driussi, C. (2006). Technological options for waste minimisation in the mining industry. J. Cleaner Prod., 14(8), 682–688.
Abstract: Just as the application of technology in mining processes can cause pollution, it can also be harnessed to minimise, and sometimes eliminate, mine-related contaminants. Waste minimisation can be achieved through decreased waste production, waste collection, waste recycling, and the neutralisation of pollutants into detoxified forms. This article reviews examples of how technology can be used to minimise air, water, land and noise pollution in the mining industry. (c) 2005 Elsevier Ltd. All rights reserved.
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