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Goulet, R. R. (2001). The evaluation of metal retention by a constructed wetland using the pulmonate gastropod Helisoma trivolvis (Say). Archives of Environmental Contamination and Toxicology, 40(3), 303–310.
Abstract: Constructed wetlands are built because they can act as sinks fur many pollutants, thereby protecting the water quality of downstream ecosystems. The treatment performance is generally assessed using mass balance calculations. Along with the mass balance approach, we compared the metal content of populations of a common pond snail (Helisoma trivolvis Say) collected upstream and downstream of a 3-year-old constructed wetland. Snails were collected in early May, June, and August 1998. At the same time, water samples for particulate and dissolved metals were taken every 3 days for the duration of the experiment. Overall, the wetland retained most dissolved metals, including Fe, Mn, Cu, Zn, Ni, and Pb, but released dissolved As. However, the wetland released particulate Fe and Mn. With the exception of Zn, the metal concentrations of the downstream snails were on average higher than those measured in the upstream population. The higher metal content of downstream snails was likely related to the significant export of particulate metals by the wetland, despite the overall retention of dissolved metals. This study points to the need for biological as well as chemical monitoring to determine the treatment efficiency and toxicological risk associated with constructed wetlands.
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Younger, P. L. (2000). Holistic remedial strategies for short- and long-term water pollution from abandoned mines. Transactions of the Institution of Mining and Metallurgy Section a-Mining Technology, 109, A210–A218.
Abstract: Where mining proceeds below the water-table-as it has extensively in Britain and elsewhere-water ingress is not only a hindrance during mineral extraction but also a potential liability after abandonment. This is because the cessation of dewatering that commonly follows mine closure leads to a rise in the water-table and associated, often rapid, changes in the chemical regime of the subsurface. Studies over the past two decades have provided insights into the nature and time-scales of these changes and provide a basis for rational planning of mine-water management during and after mine abandonment. The same insights into mine-water chemistry provide hints for the efficient remediation of pollution (typically due to Fe, Mn and Al and, in some cases, Zn, Cd, Pb and other metals). Intensive treatment (by chemical dosing with enhanced sedimentation or alternative processes, such as sulphidization or reverse osmosis) is often necessary only during the first few years following complete flooding of mine voids. Passive treatment (by the use of gravity-flow geochemical reactors and wetlands) may be both more cost-effective and ecologically more responsible in the long term. By the end of 1999 a total of 28 passive systems had been installed at United Kingdom mine sites, including examples of system types currently unique to the United Kingdom. Early performance data for all the systems are summarized and shown to demonstrate the efficacy of passive treatment when appropriately applied.
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Gatzweiler, R. (2001). Cover design for radioactive and AMD-producing mine waste in the Ronneburg area, Eastern Thuringia. Waste Management, 21(2), 175–184.
Abstract: At the former uranium mining site of Ronneburg, large scale underground and open pit mining for nearly 40 years resulted in a production of about 113 000 tonnes of uranium and about 200 million cubic metres of mine waste. In their present state, these materials cause risks to human health and strong environmental impacts and therefore demand remedial action. The remediation options available are relocation of mine spoil into the open pit and on site remediation by landscaping/contouring, placement of a cover and revegetation. A suitable vegetated cover system combined with a surface water drainage system provides long-term stability against erosion and reduces acid generation thereby meeting the main remediation objectives which are long-term reduction of radiological exposure and contaminant emissions and recultivation. The design of the cover system includes the evaluation of geotechnical, radiological, hydrological, geochemical and ecological criteria and models. The optimized overall model for the cover system has to comply with general conditions as, e.g. economic efficiency, public acceptance and sustainability. Most critical elements for the long-term performance of the cover system designed for the Beerwalde dump are the barrier system and its long-term integrity and a largely self-sustainable vegetation. (C) 2001 Elsevier Science Ltd. All rights reserved.
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Zou, L. H. (2000). Sulfide precipitation flotation for treatment of acidic mine waste water. Transactions of Nonferrous Metals Society of China, 10, 106–109.
Abstract: Sulfide precipitation flotation of copper-iron-bearing acidic waste water from a large copper mine and the stimulated waste water were studied. The pH of the waste water was 2.2, with 130 mg/L Cu2+ and 500 mg/L Fe3+ (Fe2+). Results show that, when Na2S was added as precipitating agent, sodium butylxanthate as collector and at pH 2.0, the removal of copper could be as high as 99.7 % and the residual copper decreased to 0.2 mg/L, however, almost no iron was removed. When the floated solution was neutralized to pH = 8.0, more than 98 % iron was precipitated and the residual iron was less than 10 mg/L. In experiment on actual mine effluents, after the use of precipitate flotation technology to recover copper and pH neutralization to precipitate iron, the treated waste water does meet the emission standards for sewage and valuable floating copper graded 37.12%. The chemical calculation and mechanism of solution were also presented.
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Barton, C. D. (1999). Renovation of a failed constructed wetland treating acid mine drainage. Environmental Geology, 39(1), 39–50.
Abstract: Acid mine drainage (AMD) from abandoned underground mines significantly impairs water quality in the Tones Branch watershed in McCreary Co., Kentucky, USA. A 1022-m(2) surface-flow wetland was constructed in 1989 to reduce the I AMD effects, however, the system failed after six months due to insufficient utilization of the treatment area, inadequate alkalinity production and metal overloading. In an attempt to improve treatment efficiencies, a renovation project was designed incorporating two anoxic limestone drains (ALDs) and a series of anaerobic subsurface drains that promote vertical now or mine water through a successive alkalinity producing system (SAPS) of limestone beds overlain by organic compost. Analytical results from the 19-month post-renovation period are very encouraging. Mean iron concentrations have decreased from 787 to 39 mg l(-1), pH increased from 3.38 to 6.46 and acidity has been reduced from 2244 to 199 mg l(-1) (CaCO3 equivalent). Mass removal rates averaged 98% for Al, 95% for Fe, 94% for acidity, 55% for sulfate and 49% for Mn during the study period. The results indicate increased alkalinity production from limestone dissolution and longer residence time have contributed to sufficient buffering and metal retention. The combination of ALDs and SAPS technologies used in the renovation and the sequence in which they were implemented within the wetland system proved to be an adequate and very promising design for the treatment of this and other sources of high metal load AMD.
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