/pdf/a-comprehensive-review-on-the-applications-of-coal-fly-ash-mt8gcj5phv.pdf

A comprehensive review on the applications of coal fly ash

growing scientifi c evidence of the negative impacts . Our analyses of current studies and water-quality data from WV streams revealed serious environmental impacts that mitigation practices successfully Published studies human health impacts.

/pdf/mountaintop-mining-consequences-2epsulfugd.pdf

Mountaintop mining consequences

https://www.mde.maryland.gov/programs/Marylander/Documents/Canedo-Arguelles_13_SalinisationOfRivers_UrgentEcologicalIssue.pdf

Salinisation of rivers: An urgent ecological issue

Acid mine drainage (AMD), characterized by low pH and high concentrations of sulfate and heavy metals, is an important and widespread environmental problem related to the mining industry. Sulfate-reducing passive bioreactors have received much attention lately as promising biotechnologies for AMD treatment. They offer advantages such as high metal removal at low pH, stable sludge, very low operation costs, and minimal energy consumption. Sulfide precipitation is the desired mechanism of contaminant removal; however, many mechanisms including adsorption and precipitation of metal carbonates and hydroxides occur in passive bioreactors. The efficiency of sulfate-reducing passive bioreactors is sometimes limited because they rely on the activity of an anaerobic microflora [including sulfate-reducing bacteria (SRB)] which is controlled primarily by the reactive mixture composition. The most important mixture component is the organic carbon source. The performance of field bioreactors can also be limited by AMD load and metal toxicity. Several studies conducted to find the best mixture of natural organic substrates for SRB are reviewed. Moreover, critical parameters for design and long-term operation are discussed. Additional work needs to be done to properly assess the long-term efficiency of reactive mixtures and the metal removal mechanisms. Furthermore, metal speciation and ecotoxicological assessment of treated effluent from on-site passive bioreactors have yet to be performed.

Passive treatment of acid mine drainage in bioreactors using sulfate-reducing bacteria: critical review and research needs.

Acid mine drainage: Prevention, treatment options, and resource recovery: A review

Acid mine drainage control and treatment.

When appropriately designed and maintained, passive systems can provide long-term, efficient, and effective treatment for many acid mine drainage (AMD) sources. Passive AMD treatment relies on natural processes to neutralize acidity and to oxidize or reduce and precipitate metal contaminants. Passive treatment is most suitable for small to moderate AMD discharges of appropriate chemistry, but periodic inspection and maintenance plus eventual renovation are generally required. Passive treatment technologies can be separated into biological and geochemical types. Biological passive treatment technologies generally rely on bacterial activity, and may use organic matter to stimulate microbial sulfate reduction and to adsorb contaminants; constructed wetlands, vertical flow wetlands, and bioreactors are all examples. Geochemical systems place alkalinity-generating materials such as limestone in contact with AMD (direct treatment) or with fresh water up-gradient of the AMD. Most passive treatment systems employ multiple methods, often in series, to promote acid neutralization and oxidation and precipitation of the resulting metal flocs. Before selecting an appropriate treatment technology, the AMD conditions and chemistry must be characterized. Flow, acidity and alkalinity, metal, and dissolved oxygen concentrations are critical parameters. This paper reviews the current state of passive system technology development, provides results for various system types, and provides guidance for sizing and effective operation.

/pdf/review-of-passive-systems-for-acid-mine-drainage-treatment-22ltzj2ncj.pdf

Review of Passive Systems for Acid Mine Drainage Treatment

Much attention has been devoted to developing inexpensive, limestone-based systems for treating acid mine drainage (AMD) with little or no maintenance. Treatment of AMD with limestone results in a surface coating of metal hydroxides, a process known as limestone armoring. Once armored, limestone is assumed to cease dissolution and acid neutralization. Laboratory and field experiments determined acidity changes in AMD when contacted by armored and unarmored limestone and investigated the implications of armoring on the construction of open limestone channels for treating AMD. Results of a laboratory titration study indicated armored limestone was only 2 to 45% less effective in neutralizing a hydrochloric acid solution as unarmored limestone. A laboratory container study showed that armored limestone was 90% as effective in neutralizing AMD as unarmored limestone. The field study surveyed 2- to 8-yr-old, rock-lined channels constructed of sandstone or limestone, and measured water quality changes down the length of the channel. Open limestone channels, though armored, reduced more acidity in AMD (4-62%) than the sandstone channel (2%). The results from open limestone channels were compared to an acid neutralization kinetics model that predicts the rate of acid neutralization for a specified channel size, and AMD flow and acidity concentration. The open limestone channels in the field neutralized more acidity than the model predicted. Open limestone channels show promise for neutralizing AMD in watershed restoration projects and abandoned mine land (AML) reclamation projects where one-time installation costs are incurred, little to no maintenance is required, and systems do not have to meet specific water quality standards.

Acid Mine Drainage Treatment with Armored Limestone in Open Limestone Channels

State and federal reclamation programs, mining operators,
and citizen-based watershed organizations have constructed
hundreds of passive systems in the eastern U S over the past
20 years to provide reliable, low cost, low maintenance mine
water treatment in remote locations While performance has been
reported for individual systems, there has not been a
comprehensive evaluation of the performance of each treatment
type for a wide variety of conditions We evaluated 83 systems;
five types in eight states Each system was monitored for
influent and effluent flow, ph, net acidity, and metal
concentrations Performance was normalized among types by
calclating acid loading reductions and removals, and by
converting construction cost, projected service life, and metric
tonnes of acid load treated into cost per tonne of acid treated
Of the 83 systems, 82 reduced acid load Average acid load
reductions were 99 t/yr for open limestone channels (OLC), 101
t/yr for vertical flow wetland (VFW), 119 t/yr for anaerobic
wetlands (AnW), 166 t/yr for limestone leach beds (LSB), and
222 t/yr for anoxic limestone drains (ALD) Average costs for
acid removal varied from $83/t/yr for ALDs to $527 for AnWs
Average acid removals were 25
g/m2/day for AnWs, 62
g/m2/day for VFWs, 22 g/day/t for
OLCs, 28 g/day/t for LSBs, and 56 g/day/t for ALDs It appears
that the majority of passive systems are effective but there was
wide variation within each system type, so improved reliability
and efficiency are needed This report is an initial step in
determining passive treatment system performance; additional
work is needed to refine system designs and monitoring

Paul F. Ziemkiewicz

Papers

Acid mine drainage control and treatment.

Review of Passive Systems for Acid Mine Drainage Treatment

Acid Mine Drainage Treatment with Armored Limestone in Open Limestone Channels

Long-term Performance of Passive Acid Mine Drainage Treatment Systems

Acid mine drainage formation, control and treatment: Approaches and strategies