title: Anaerobic biodegradation of iso-butanol and ethanol and their relative effects on BTEX biodegradation in aquifer materials.
abstract: Biologically produced iso-butanol is currently being considered as an additive in gasoline blends. To evaluate its potential environmental fate in groundwater aquifers, a laboratory microcosm study was performed to evaluate iso-butanol biodegradation under various anaerobic conditions (nitrate-reducing, sulfate-reducing and methanogenic). The impacts of iso-butanol on benzene, toluene, ethylbenzene, and total xylenes (BTEX) biodegradation were also assessed, and microcosms prepared using ethanol instead of iso-butanol were evaluated to provide a basis for comparison. Iso-butanol was biodegraded under all conditions studied, with an observed apparent first-order rate constant ranging from approximately 0.2 d⁻¹ (nitrate-reducing) to approximately 0.02 d⁻¹ (sulfate-reducing). Iso-butanol typically was degraded in a time frame that was shorter than or similar to BTEX compounds. Iso-butyric acid and trace levels of iso-butylaldehyde were identified as transient intermediates, and both of these compounds were subsequently degraded within the time frame of the experiments. Iso-butanol and ethanol were biodegraded in similar time frames under methanogenic conditions. Under sulfate-reducing conditions, iso-butanol biodegradation initially proceeded more slowly than ethanol, and then increased to a rate greater than that observed for ethanol; this observation likely was due to the growth of iso-butanol degrading bacteria. Iso-butanol generally exhibited less adverse impacts on BTEX biodegradations than ethanol under the anaerobic conditions studied. In some cases, addition of iso-butanol enhanced the rate of TEX biodegradation.
authors.affiliation: Shaw Environmental Inc., Lawrenceville, NJ 08648, USA.
authors.forename: Charles E
authors.initials: CE
authors.lastname: Schaefer
authors.forename: Xiaomin
authors.initials: X
authors.lastname: Yang
authors.forename: Oliver
authors.initials: O
authors.lastname: Pelz
authors.forename: David T
authors.initials: DT
authors.lastname: Tsao
authors.forename: Sheryl H
authors.initials: SH
authors.lastname: Streger
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Steffan
mesh_terms: D001421:Bacteria, Anaerobic / Q000378:metabolism; D001554:Benzene / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D001555:Benzene Derivatives / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D001673:Biodegradation, Environmental; D000440:Butanols / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D000431:Ethanol / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D005618:Fresh Water / Q000737:chemistry; D019015:Geologic Sediments / Q000737:chemistry; D014050:Toluene / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry / Q000378:metabolism*; D014992:Xylenes / Q000032:analysis / Q000737:chemistry / Q000378:metabolism
chemical_list: D001555:Benzene Derivatives; D000440:Butanols; D014874:Water Pollutants, Chemical; D014992:Xylenes; D014050:Toluene; D000431:Ethanol; C040507:isobutyl alcohol; D001554:Benzene; C004912:ethylbenzene