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Demchak, J., Morrow, T., Skousen, J., Donovan, J. J., & Rose, A. W. (2001). Treatment of acid mine drainage by four vertical flow wetlands in Pennsylvania Evolution and remediation of acid-sulfate groundwater systems at reclaimed mine-sites. Geochemistry – Exploration, Environment, Analysis, 1(1), 71–80.
Abstract: Acid mine drainage (AMD) is a serious problem in many watersheds where coal is mined. Passive treatments, such as wetlands and anoxic limestone drains (ALDs), have been developed, but these technologies show varying treatment efficiencies. A new passive treatment technique is a vertical flow wetland or successive alkalinity producing system (SAPS). Four SAPS in Pennsylvania were studied to determine changes in water chemistry from inflow to outflow. The Howe Bridge SAPS removed about 130 mg l (super -1) (40%) of the inflow acidity concentration and about 100 mg l (super -1) (60%) iron (Fe). The Filson 1 SAPS removed 68 mg l (super -1) (26%) acidity, 20 mg l (super -1) (83%) Fe and 6 mg l (super -1) (35%) aluminium (Al). The Sommerville SAPS removed 112 mg l (super -1) (31%) acidity, exported Fe, and removed 13 mg l (super -1) (30%) Al. The McKinley SAPS removed 54 mg l (super -1) (91%) acidity and 5 mg l (super -1) (90%) Fe. Acid removal rates at our four sites were 17 (HB), 52 (Filson1), 18 (Sommerville) and 11 (McKinley) g of acid per m (super 2) of surface wetland area per day (g/m (super 2) d (super -1) ). Calcium (Ca) concentrations in the SAPS effluents were increased between 8 and 57 mg l (super -1) at these sites. Equilibrators, which were inserted into compost layers to evaluate redox conditions at our sites, showed that reducing conditions were generally found at 60 cm compost depths and oxidized conditions were found at 30 cm compost depths. Deeply oxidized zones substantiated observations that channel flow was occurring through some parts of the compost. The Howe Bridge site has not declined in treatment efficiency over a six year treatment life. The SAPS construction costs were equal to about seven years of NaOH chemical treatment costs and 30 years of lime treatment costs. So, if the SAPS treatment longevity is seven years or greater and comparable effluent water quality was achieved, the SAPS construction was cost effective compared to NaOH chemical treatment. Construction recommendations for SAPS include a minimum of 50 cm of compost thickness, periodic replacement or addition of fresh compost material, and increasing the number of drainage pipes underlying the limestone.
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Wieder, R. K. (1989). A survey of constructed wetlands for acid coal mine drainage treatment in the Eastern United States. Wetlands, 9(2), 299–315.
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Smit, J. P. (2000). Potable water from sulphate polluted mine sources. Mining Environmental Management, 8(6), 7–9.
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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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Haferkorn, B., Mueller, M., Zeh, E., Benthaus, F. K., Pester, L., Lietzow, A., et al. (1999). Schaffung von Tagebauseen im mitteldeutschen Bergbaurevier; die Wiederherstellung eines sich selbst regulierenden Wasserhaushaltes in den Braunkohleabbaugebieten des Freistaates Sachsen (Nordwestsachsen), des Landes Sachsen-Anhalt und des Freistaates Thueringen. Creation of open-pit lakes in central Germany mining district; the reclamation of some self-regulating water balance in abandoned lignite regions of the Saxony Free States Northwest Saxony), of the Saxony-Anhalt state and Free States. Berlin: Lmbv.
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