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Arango, I. (2002). Evaluation of the beneficial effects of the acidophilic alga Euglena mutabilis on acid mine drainage systems. Ph.D. thesis, Indiana State University,, Terre Haute.
Abstract: Euglena mutabilis is an acidophilic, photosynthetic protozoan that forms benthic mats in acid mine drainage (AMD) channels. At the Green Valley mine, western Indiana, E. mutabilis resides in AMD measuring <4.2 pH, with high concentrations of dissolved constituents (up to 22.67 g/l). One of the main factors influencing E. mutabilis distribution is water temperature. The microbe forms thick (>1 mm), extensive mats during spring and fall, when water temperature is between 13 and 28 degrees C. During winter and summer, when temperatures are outside this range, benthic communities have a very patchy distribution and are restricted to areas protected from extreme temperature changes. E. mutabilis also responds to rapid increases in pH, which are associated with rainfall events. During these events pH can increase above 4.0, causing precipitation of Fe and Al oxy-hydroxides that cover the mats. The microbe responds by moving through the precipitates, due to phototaxis, and reestablishing the community at the sediment-water interface within 12 hours. The biological activities of E. mutabilis may have a beneficial effect on AMD systems by removing iron from effluent via oxygenic photosynthesis, and/or by internal sequestration. Photosynthesis by E. mutabilis contributes elevated concentrations of dissolved oxygen (DO), up to 17.25 mg/l in the field and up to 11.83 mg/l in the laboratory, driving oxidation and precipitation of reduced metal species, especially Fe (II), which are dissolved in the effluent. In addition, preliminary electro-microscopic and staining analyses of the reddish intracellular granules in E. mutabilis indicate that the granules contain iron, suggesting that E. mutabilis sequesters iron from AMD. Inductive coupled plasma analysis of iron concentration in AMD with and without E. mutabilis also shows that E. mutabilis accelerates the rate of Fe removal from the media. Whether iron removal is accelerated by internal sequestration of iron and/or by precipitation via oxygenic photosynthesis has yet to be determined. These biological activities may play an important role in the natural remediation of AMD systems.
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Niyogi, D. K., McKnight, D. M., Lewis, W. M., Jr., & Kimball, B. A. (1999). Experimental diversion of acid mine drainage and the effects on a headwater stream. Water-Resources Investigations Report, Wri 99-4018-A, 123–130.
Abstract: An experimental diversion of acid mine drainage was set up near an abandoned mine in Saint Kevin Gulch, Colorado. A mass-balance approach using natural tracers was used to estimate flows into Saint Kevin Gulch. The diversion system collected about 85 percent of the mine water during its first year of operation (1994). In the first 2 months after the diversion, benthic algae in an experimental reach (stream reach around which mine drainage was diverted) became more abundant as water quality improved (increase in pH, decrease in zinc concentrations) and substrate quality changed (decrease in rate of metal hydroxide deposition). Further increases in pH to levels above 4.6, however, led to lower algal biomass in subsequent years (1995-97). An increase in deposition of aluminum precipitates at pH greater than 4.6 may account for the suppression of algal biomass. The pH in the experimental reach was lower in 1998 and algal biomass increased. Mine drainage presents a complex, interactive set of stresses on stream ecosystems. These interactions need to be considered in remediation goals and plans.
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Bilek, F., Werner, F., & Schöpke, R. (2003). Experimentelle und modellgestützte Entwicklung von Verfahren zur geochemischen Grundwasser- und Untergrundbehandlung zur Gefahrenabwehr im Nordraum des Senftenberger Sees.544.
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Houston, K. S., Milionis, P. N., Eppley, R. L., Harrington, J. M., & Harrington, J. G. (2005). Field Demonstration of In-Situ Treatment and Prevention of Acid Mine Drainage in the Abandoned Tide Mine, Indiana County, Pennsylvania.
Abstract: A field demonstration of the Green World Science® patented process technology was performed to address acid mine drainage (AMD) at an abandoned bituminous coal mine, the Tide Mine in Center Township, Indiana County, PA. ARCADIS owns an exclusive patent license of the Green World Science® process, which can be used in situ to transform an aerobic, AMD-producing mine pool to a biologically mediated, sulfate-reducing state. The Green World Science® process treats the entire mine pool to address the source of AMD in place. The project was conducted through a grant agreement between the Blacklick Creek Watershed Association, the Pennsylvania Department of Environmental Protection's Bureau of Abandoned Mine Reclamation, and ARCADIS. In conjunction with the characterization of mine pool hydraulics through injection of a bromide tracer, the in situ treatments implemented at Tide Mine include the initial addition of alkalinity to create an environment suitable for biological activity, injection of organic carbon into the mine pool to facilitate microbially mediated metals reduction and precipitation, and injection of carbon dioxide gas into the atmosphere above the mine pool to control the dominant source of oxygen that perpetuates the AMD process. Collectively, these treatments raised the pH from a baseline of approximately 2.5 to over 6 during the demonstration period. The mine pool subsequently maintains a pH above 5 through microbially produced (i.e., bicarbonate) alkalinity. Ferric iron has been reduced to non-detect concentrations within the anaerobic mine pool, and aluminum concentrations have decreased by approximately 30%, with additional metals removal expected as the system becomes controlled by ferrous sulfide precipitation. The injection of carbon dioxide gas into the mine workings decreased oxygen concentrations above the mine pool from over 20% (ambient air conditions) to less than 5% over approximately three months, thus mitigating the source of AMD within the mine.
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Mitchell, P., & Wheaton, A. (1999). From environmental burden to natural resource; new reagents for cost-effective treatment of, and metal recovery from, acid rock drainage. In D. E. Goldsack, N. Belzile, P. Yearwood, & G. J. Hall (Eds.), Sudbury '99; Mining and the environment II; Conference proceedings.
Abstract: Acid rock drainage remains the greatest environmental issue faced by the mining sector and as the new millennium approaches, low capital/operating cost treatments remain elusive. Therefore as part of an ongoing process to develop a leading edge, innovative and cost-effective approach, pilot trials were conducted by KEECO in collaboration with the New Bunker Hill Mining Company on a substantial and problematic metal-contaminated acid flow, emanating from underground workings at the Bunker Hill Mine, Idaho. The aims of the work were fourfold. First to assess the capacity of KEECO's unique Silica Micro Encapsulation (SME) reagents and associated dosing systems to cost-effectively decontaminate the acid flow to stringent standards set by the U.S. Environmental Protection Agency (USEPA), where alternative and standard technologies had failed. Second, to demonstrate that treatment using a compact system suitable for underground installation. Third, to demonstrate that the treatment sludge had enhanced chemical stability in absolute terms and relative to standard approaches. Fourth, to examine the potential for resource recovery via sequential precipitation. Although the focus to date has been the development of a cost-effective treatment technology, the latter aim was considered essential in light of the growing pressure on all industrial sectors to develop tools for environmentally sustainable economic growth and the growing demands of stakeholders for improved resource usage and recycling. Two phases of work were undertaken: a laboratory-based scoping exercise followed by installation within the mine workings of a compact reagent delivery/shear mixing unit capable of treating the full flow of 31 L s (super -1) . At a dose rate of 2.0 g L (super -1) (equivalent to a final treated water pH range of 7-9), the SME reagent KB-1 reduced metal concentrations to levels approaching the U.S. Drinking Water Standards, which no other treatment piloted at the site had achieved. Based on the USEPA's Toxicity Characteristic Leaching Procedure, the sludge arising from the treatment was classified as non-hazardous. Operating costs compared favourably with those of lime use, while estimated capital costs were considerably lower due to the compact nature of the reagent delivery system and the rapid settling characteristics of the treatment sediment. Resource recovery was attempted using a two-stage selective precipitation approach. The first stage involved pH adjustment to 5.5 (by addition of 1.5 g L (super -1) of KB-1) to produce a sludge enriched in aluminium, iron and manganese, with lesser amounts of arsenic, nickel, lead and zinc. Further KB-1 addition to a total of 2.1 g L (super -1) generated sludge enriched in zinc (33% by dry weight), demonstrating that resource recovery is theoretically feasible. Further work on downstream processing is required, although it is considered that the most likely route for zinc metal recovery will be high temperature/pressure due to the chemically inert nature of the zinc-rich sediment.
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