The primary objective of this study was to investigate the use of hydrogen as a
structural substitute or as a reducing equivalent in the anaerobic biodegradation of
methanol, methyl tert—butyl ether (MTBE), toluene, phenol, and 2,4—dichlorophenol. In
addition, biodegradation rates of these compounds at various initial concentrations with
and without inhibition of sulfate reducing bacteria were determined along with anaerobic
biodegradation rate constants for each of the compounds studied.
Rates of methanol biodegradation were only slightly altered in molybdate
amended microcosms indicating that methanol is a noncompetitive substrate in
Blacksburg soil. MTBE biodegradation was slow and followed first order kinetics with
respect to initial concentration. Molybdate had no affect on MTBE biodegradation
alone, but increased the biodegradation rate in MTBE microcosms which were amended
with ethanol. Toluene, phenol, and 2,4-dichlorophenol biodegradation proceeded at two
different rate versus initial concentration relationships for lower and upper concentration
ranges. Phenol biodegradation followed first order kinetics. The 2,4-dichlorophenol
biodegradation rate order varied from 0.78 to 1.75. Monod kinetics were followed by
methanol, toluene, and phenol, but not by MTBE, ethanol amended MTBE, or
2,4-dichlorophenol.
Addition of molybdate to inhibit sulfate reduction increased the degradation
rates more for compounds which may require hydrogen in a structural position
(2,4-dichlorophenol, MTBE) than those which require hydrogen for proton reduction
(methanol). Biodegradation or recalcitrant compounds may be stimulated by the
addition of organics (such as ethanol) which produce hydrogen upon biodegradation.
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