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Author Mitchell, P.; Wheaton, A. isbn  openurl
  Title From environmental burden to natural resource; new reagents for cost-effective treatment of, and metal recovery from, acid rock drainage Type Book Chapter
  Year 1999 Publication Sudbury '99; Mining and the environment II; Conference proceedings Abbreviated Journal  
  Volume Issue Pages  
  Keywords acid mine drainage Bunker Hill Mine cost decontamination Idaho metal ores mines mitigation natural resources pollution reagents recovery Shoshone County Idaho sludge United States zinc ores 22 Environmental geology 27A Economic geology, geology of ore deposits  
  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.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor Goldsack, D.E.; Belzile, N.; Yearwood, P.; Hall, G.J.  
  Language Summary Language Original Title (up)  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN ISBN 0886670470 Medium  
  Area Expedition Conference  
  Notes From environmental burden to natural resource; new reagents for cost-effective treatment of, and metal recovery from, acid rock drainage; GeoRef; English; 2000-048642; Sudbury '99; Mining and the environment II, Sudbury, ON, Canada, Sept. 13-17, 1999 References: 3; illus. incl. 5 tables Approved no  
  Call Number CBU @ c.wolke @ 16593 Serial 296  
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Author Mitchell, P.; Rybock, J.; Wheaton, A. openurl 
  Title Treatment and prevention of ARID using silica micro encapsulation Type Book Chapter
  Year 1999 Publication Proceedings of the 16th annual National meeting of the American Society for Surface Mining and Reclamation; Mining and reclamation for the next millennium Abbreviated Journal  
  Volume Issue Pages 657-661  
  Keywords acid mine drainage Bunker Hill Mine Idaho mines pollution Shoshone County Idaho United States water treatment 22, Environmental geology  
  Abstract In response to the known drawbacks of liming and the ever-increasing regulatory demands on the mining industry, KEECO has developed a silica micro encapsulation (SME) process. SME is a cost-effective, high performance reagent that is utilized in conjunction with simple chemical delivery systems. By encapsulating metals in a silica matrix formation and rapidly precipitating them into a sand-like sludge, it offers all the advantages of liming without the negative drawbacks. Utilizing an injection technique via a high shear mixing device, a slurry from of the SME product called KB-1 (super TM) was applied to ARD at the Bunker Hill Mine in Idaho and to ARD pumped from collection ponds at a remote mine site in the Sierra Nevada Mountains. Flow rates at both sites ranged from 500 to 800 gallons per minute. Treated water from the Bunker Hill Mine operation achieved the site's NPDES criteria for all evaluated metals and U.S. Drinking Water quality for arsenic, cadmium, chromium, lead and zinc with a dosage rate of 1.34 grams KB-1 (super TM) per liter. Treated water from the Sierra Nevada project focused on the control of aluminum, arsenic, copper, iron and nickel. All water samples displayed a >99.5% reduction in these metals, as well as an 84%-87% reduction in the concentration of sulfate. Testing on sludge generated from both operations achieved TCLP Action Limits. The SME process is currently under evaluation as a means to coat the pyrite surfaces of newly generated mine tailings to prevent oxidation and future acid generation.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication 16 Editor Bengson, S.A.; Bland, D.M.  
  Language Summary Language Original Title (up)  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN ISBN Medium  
  Area Expedition Conference  
  Notes Treatment and prevention of ARID using silica micro encapsulation; GeoRef; English; 2001-047986; 16th annual National meeting of the American Society for Surface Mining and Reclamation, Scottsdale, AZ, United States, Aug. 13-19, 1999 2 tables Approved no  
  Call Number CBU @ c.wolke @ 16602 Serial 297  
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