Biomedical Engineering Reference
In-Depth Information
conditions, methanol was degraded with stoichiometric amounts of
nitrate consumed. However, under sulfate-reducing conditions the
researchers concluded that the sulfate-reducing bacteria were not
utilizing the methanol. Generally speaking, high concentrations of
methanol are not used by sulfate-reducing bacteria to an environ-
mentally significant extent. However, sulfate reducers have been found
to contribute to methanol depletion in other studies, and at least four
species of sulfate-reducing bacteria have been isolated that can utilize
methanol (Nanninga and Gottschal, 1986; Esnault et al., 1988).
Other laboratory studies have reported the biodegradation of metha-
nol under various redox conditions and by microorganisms from diverse
environments. For example, the methanogenic degradation of methanol
was demonstrated for an enrichment culture derived from an anaerobic
digester as well as for a pure culture. The rates of methanol degradation
by the enrichment and pure cultures without acclimation periods were
reported to be 1.92 and 1.37 ppm/min (extrapolated from Figures 2 and
6B, respectively, of Bagley and Gossett, 1995). Fitch et al. (1996) also
grew methanol-utilizing cultures in a chemostat culture at methanol
concentrations of 1500-2700 ppm and found the cell yield of methanol-
grown cells to be consistent with what has previously been reported for
methanotrophs. Florencio et al. (1993) investigated the anaerobic
biodegradation of methanol at a range of pH values by a culture derived
from an anaerobic granular sludge reactor used to treat alcohol distillery
wastewater. Florencio et al. (1995) monitored the anaerobic removal of
methanol by methanogens and acetogens in upflow anaerobic sludge
blanket reactors. Results from these studies showed that methylotrophic
methanogens dominated in a broad pH range (4.2-7.2), while signifi-
cant acetogenesis occurred in the presence of high methanol concen-
trations. Finally, Beeman and Suflita (1987) measured methanol
biodegradation in microcosms from a shallow anoxic aquifer under-
lying a municipal landfill in Oklahoma. By recovering 70-100% of the
methane produced during methanogenesis, they were able to demon-
strate that methanogenesis of methanol was occurring.
Adsorption Another methanol loss mechanism from the groundwater
is adsorption to soil materials. However, adsorption would not
