David R. Yonge

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A mixed culture was enriched from surface soil obtained from an eastern United States site highly contaminated with chromate. Growth of the culture was inhibited by a chromium concentration of 12 mg/L. Another mixed culture was enriched from subsurface soil obtained from the Hanford reservation, at the fringe of a chromate plume. The enrichment medium was(More)
Hexavalent chromium [Cr(VI)] is a major industrial pollutant. Bioremediation of Cr(VI) to Cr(III) is a viable clean-up approach. However, Cr(VI) bioreduction also produces soluble organo-Cr(III) complexes, and little is known about their behavior in the environment. When tested with soil columns, citrate-Cr(III) showed little sorption to soil;(More)
Chromium(VI) was reduced by Enterobacter cloacae strain HO1 grown with sucrose as a carbon source and nitrate as the initial terminal electron acceptor. Under excess substrate conditions, the Cr(VI) concentration, initially at 5 and 10 mg/l, was reduced to less than 100 mg/l.
Biological treatment of high-salinity industrial wastewaters using halophilic bacteria can be used to remove organic compounds without first decreasing the salt concentration. While halophilic degradation of phenol and other organics has been investigated, there exists a general absence of kinetic data in current literature to allow evaluation of this(More)
The process of naphthalene degradation by indigenous, introduced, and transconjugant strains was studied in laboratory soil microcosms. Conjugation transfer of catabolic plasmids was demonstrated in naphthalene-contaminated soil. Both indigenous microorganisms and an introduced laboratory strain BS394 (pNF142::TnMod-OTc) served as donors of these plasmids.(More)
The distribution of chromium in subcellular components was examined with a fresh and starved denitrifying consortium by performing Cr+6 equilibration and cell fractionation tests. The cell wall fraction of 50 day starved cells adsorbed approximately 100% more chromium than did the cell wall fraction in fresh cells. The soluble fraction of 50 day old cells(More)
Chlorpyrifos, one of the most widely used insecticides, has been detected in air, rain, marine sediments, surface waters, drinking water wells, and solid and liquid dietary samples collected from urban and rural areas. Its metabolite, TCP, has also been widely detected in urinary samples collected from people of various age groups. With a goal of(More)
A fractional factorial statistical experimental design was used to ascertain which experimental parameters affect the rate at which Cr6+ is sorbed by a consortium of denitrifying bacteria. Data from this set of experiments indicates that the amount of chromium sorbed as a function of time could be described by an exponential rise function. Additionally, the(More)
The accumulation of metal ions on to biological materials is a promising method for removing these toxic materials from waste or ground-waters. A fractional factorial statistical experimental design was used to ascertain which experimental parameters affect the sorption of Cr6+ by a consortium of denitrifying bacteria using a minimum number of experiments.(More)
Irreversible adsorption has been shown to influence activated carbon adsorption equilibria. To gain a better understanding of irreversible adsorption and its influence on adsorption equilibria, batch and continuous-flow single-solute adsorption experiments were conducted on five low molecular weight substituted phenols. Sorbate functional group type and(More)