Iron Speciation in Acid Mine Effluents: Chemical and Microbial Controls : Final Report

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Title: Iron Speciation in Acid Mine Effluents: Chemical and Microbial Controls : Final Report
Creators: Bigham, Jerry M.; Tuovinen, Olli H.; Brady, Karen S.; Logan, Terry J.
Contributors: Ohio State University. Water Resources Center
Subjects (LCSH): Acid mine drainage -- Ohio
Water -- Purification -- Biological treatment
Issue Date: 1983
Publisher: Ohio State University. Water Resources Center
Series/Report no.: Project completion report (Ohio State University. Water Resources Center) ; no. 714437
Abstract: The Black Fork Creek watershed, located in Perry and Morgan Counties, Ohio, was selected as a representative field site for evaluating the solution chemistry of iron in streams receiving acid coal mine drainage. Water samples from a point source of acid discharge and a 2 km downstream section of the receiving stream were examined in detail. The total sulfate content, total iron content, Eh and pH of the acid effluent were 4500 ug/ml, 1250 ug/ml, + 584 mV and 2.9, respectively, at the time of sampling. Ferrous iron accounted for 95% of the total iron load. Both total and ferrous iron showed rapid, 10-fold decreases in the receiving stream even though pH of the stream water remained less than 3.5. The fraction of polymeric iron (> 0.1 um esd) increased from 6% in the acid effluent to almost 50% of the total iron load at points farthest downstream. UV- spectroscopic analyses of the stream water indicated that Fe(OH)2+ and Fe2(OH)24+ may be important intermediate species in polymer formation. Specific adsorption of SO42- appeared to lower polymer surface charge and promote precipitation of ferrihydrite, a poorly crystallized iron oxide with the general formula 5 Fe2O3 • 9 H2O. Ferrihydrite has a large specific surface area and a high affinity for many dissolved inorganic and organic species; thus, it could have a major impact on both water and sediment quality in streams receiving acid mine drainage. A laboratory bio-reactor was tested for potential use in the treatment of acid mine drainage. Cells of Thiobacillus ferrooxidans were immobilized in an alginate matrix and used in a packed-bed column reactor for the continuous oxidation of Fe(II) in synthetic ferrous sulfate solutions. Oxidation efficiencies of over 90% were attained within 14 to 35 days for aerated columns operating at room temperature with influent Fe(II) concentrations of 55 mM. The presence of mineral salts in the influent solution resulted in a shorter lag period before a steady state of iron oxidation was achieved. Chemical (abiotic) oxidation of Fe(II) was insignificant in the aerated columns, which were operated up to three months without a loss of activity. If developed on a commercial scale, bio-reactors of this type might prove useful to mining companies or environmental agencies concerned with the treatment and control of acid mine drainage.
Other Identifiers: OCLC #10744466 (print)
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