13    BIODEGRADATION OF PHENOL IN UNDERGROUND COAL
GASIFICATION MATRIX MATERIALS
Godwin B.O. Biezugbe, Remediation Engineer
Geraghty & Miller, Inc., Environmental Services
Midland, Texas 79701
David H. Foster, Associate Professor
Department of Civil and Architectural Engineering
University of Wyoming
Laramie, Wyoming 82071
John P. Turner, Assistant Professor
Department of Civil and Architectural Engineering
University of Wyoming
Laramie, Wyoming 82071
INTRODUCTION AND BACKGROUND
Underground Coal Gasification (UCG) involves combustion of coal in-situ and subsequent recovery of combustible, low-BTU gas at the surface.1 A potential environmental impact of UCG is the
generation of soluble organic and inorganic compounds, including phenol, in the matrix materials
(coal) surrounding the combustion zone. The presence of phenol in the subsurface poses a potential
threat to groundwater. While traditional pump and treat methods have been used for cleanup of UCG
sites, results reported to date indicate only limited success.2 Bioremediation is a potentially more
effective approach to site cleanup and may have environmental as well as economical advantages over
pump and treat methods.
This paper describes a laboratory study to evaluate the potential for biodegradation of phenol in
UCG matrix materials. Two sets of laboratory tests were conducted using Wyoming subbituminous
coal treated with various concentrations of phenol. These include: 1) adsorption tests, to characterize
the isotherms for adsorption of phenol on representative UCG matrix materials, and 2) biodegradation tests, in which the Monod biokinetic parameters were determined as a function of initial phenol
concentration, bacterial type and density, and nutrient type.
METHODS AND MATERIALS
Coal samples were obtained from Eagle Butte coal mine near Gillette, Wyoming. The Eagle Butte
coal is a low-rank, subbituminous coal and is typical of Wyodak coals found in the Powder River
Basin. It comes from the same seam and is essentially the same coal that forms the matrix material at
Hoe Creek, a U.S Department of Energy UCG site a few away miles from Eagle Butte mine. Coal
samples were crushed and sieved to 1/4 inch. This size is assumed to approximate the surface area of
the fractured virgin coal seam surrounding the combustion zone following in situ combustion.3
ADSORPTION AND BIODEGRADATION TESTS
Adsorption tests were performed in a batch mode in 50-mL Teflon centrifuge tubes. Equilibrium
time of 96 hours was used, based upon previous work by Humenick et al.4 Tests were conducted at 5
initial aqueous-phase phenol concentrations, arranged in decreasing concentration order, at contact
times of 2, 4, 8, 24, 48, and 96 hours. This arrangement produces a constant solid to solution ratio
isotherm.'
Approximately one gram of weighed coal was contacted with 45 mL of phenol solution and placed
in a centrifuge tube. The tubes were sealed, placed in a wrist-action shaker, and allowed to equilibrate.
Following each of the equilibration times cited above, tubes were centrifuged for 1 hr at 3,000 rpm.
Supernatant from the tubes were decanted and phenol was extracted from each of the aqueous phases
47ih Purdue Industrial Waste Conference Proceedings, 1992 Lewis Publishers, Inc., Chelsea, Michigan 48118.
Printed in U.S.A.
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