Browsing by Author "Stewart, Barry R."
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- The influence of fly ash additions on acid mine drainage production from coarse coal refuseStewart, Barry R. (Virginia Tech, 1995)The exclusion of coal fly ash from regulation as a hazardous waste has led to increased interest in returning ash to the coalfields for disposal. Bulk-blending alkaline fly ash with acid forming coal refuse may present a disposal option that aids in the control of acid mine drainage. A preliminary column leaching study examined the leachate quality from acid-forming coal refuse:fly ash blends. Coal refuse (2.2 % total-S), and two refuse:fly ash blends (20% and 33% ash w/w) were packed into leaching columns and leached under unsaturated conditions for over four years. The coal refuse columns acidified quickly, producing peak leachate levels of acidity (pH 1.7), Fe (10,000 mg 1-1), SO4(30,000 mg 1-1), and Mn (300 mg 1-1). Both ash blended treatments provided alkaline leachate with low metal levels. A second column study used a refuse with higher potential acidity (4% total-S), and two alkaline ash sources; one blended at two rates (20% and 33%) and one at four rates (5%, 10%, 20%, and 33%). Bulk-blended ground agricultural limestone, rock phosphate ore, and topsoil treatments were also studied. The unamended refuse treatment acidified rapidly and produced acidic (pH 1.7) leachates with high peak dissolved metal levels (>15,000 mg 1-1 Fe; 200 mg 1-1 Mn). Treatments blended with 33% ash produced alkaline (pH >8.4) leachates with low metal levels (Al <1.0 mg 1-1; Cu-0.10 mg 1-1; Fe < 2.0 mg 1-1; Mn <3.0 mg 1-1). Treatments containing less ash eventually acidified and ash bound metals (Mn and Cu) were stripped from the ash and eluted in quantities proportionate to the amount of ash in the blend. A field experiment with water sampling lysimeters examined bulk-blended refuse (0.8% S) with two acidic and one alkaline ash. The ash treatments did not produce consistent negative impacts on leachate water quality, and produced positive effects on plant biomass production compared to unamended controls. Overall, the inhibition of pyrite oxidation by high ash blends was attributed to alkalinity effects, chemisorption, decreased hydraulic conductivity, and decreased oxygen diffusion to pyritic surfaces. Ash alkalinity and refuse potential acidity must be balanced for environmental safety in this co-disposal environment.
- Physical and chemical properties of coarse coal refuse from Southwest VirginiaStewart, Barry R. (Virginia Tech, 1990)Coarse coal refuse is difficult to reclaim due to high potential acidity and coarse fragment content, low water holding capacity, low fertility, and other problems. Little is known about coal refuse properties, particularly as they relate to revegetation potential. This study was undertaken to determine the physical and chemical properties of composite samples from 27 coal waste piles of varying age. Selected physical and chemical properties varied widely across this sample set. The mean coarse fragment (>2mm) content of these materials was 60%. The average texture of the fine (<2mm) fraction was a sandy loam with 15% clay. The mean water retention difference, between 0.03 MPa and 1.5 MPa of soil moisture tension, on a whole sample basis was 0.08 g water/g refuse. The pH values varied from 8.3 to 3.0, and the older piles generally had lower pH values than the more recent piles. The saturated paste electrical conductivity (EC) was higher in the younger coal waste materials. Total elemental analysis revealed that Si, Al, Fe, and K were the most abundant elements in these materials. The mineralogy of three selected samples was found to be dominated by quartz in the sand and silt fraction and mica in the clay fraction. The physical factor most limiting to plant growth was found to be low water holding capacity. Low pH was found to be the chemical factor most limiting to plant survival. These findings indicate that some refuse piles may be suitable for direct seeding, but many will require heavy lime and/or organic treatments.
- Reclamation of Coal Refuse Disposal AreasDaniels, W. Lee; Stewart, Barry R.; Zipper, Carl E. (Virginia Cooperative Extension, 2018-03-16)Discusses coal refuse, its storage in the ground, and ways to mitigate and reclaim such lands.
- Reclamation of Coal Refuse Disposal AreasDaniels, W. Lee; Stewart, Barry R.; Zipper, Carl E. (Virginia Cooperative Extension, 2010-10-21)This publication reviews problems associated with stabilization and revegetation of coal refuse disposal areas and suggests strategies for their successful long-term reclamation and closure.