title: Kinetics of 1,2-dichloroethane and 1,2-dibromoethane biodegradation in anaerobic enrichment cultures.
abstract: 1,2-Dichloroethane (1,2-DCA) and 1,2-dibromoethane (ethylene dibromide [EDB]) contaminate groundwater at many hazardous waste sites. The objectives of this study were to measure yields, maximum specific growth rates (μ), and half-saturation coefficients (K(S)) in enrichment cultures that use 1,2-DCA and EDB as terminal electron acceptors and lactate as the electron donor and to evaluate if the presence of EDB has an effect on the kinetics of 1,2-DCA dehalogenation and vice versa. Biodegradation was evaluated at the high concentrations found at some industrial sites (>10 mg/liter) and at lower concentrations found at former leaded-gasoline sites (1.9 to 3.7 mg/liter). At higher concentrations, the Dehalococcoides yield was 1 order of magnitude higher when bacteria were grown with 1,2-DCA than when they were grown with EDB, while μ's were similar for the two compounds, ranging from 0.19 to 0.52 day(-1) with 1,2-DCA to 0.28 to 0.36 day(-1) for EDB. K(S) was larger for 1,2-DCA (15 to 25 mg/liter) than for EDB (1.8 to 3.7 mg/liter). In treatments that received both compounds, EDB was always consumed first and adversely impacted the kinetics of 1,2-DCA utilization. Furthermore, 1,2-DCA dechlorination was interrupted by the addition of EDB at a concentration 100 times lower than that of the remaining 1,2-DCA; use of 1,2-DCA did not resume until the EDB level decreased close to its maximum contaminant level (MCL). In lower-concentration experiments, the preferential consumption of EDB over 1,2-DCA was confirmed; both compounds were eventually dehalogenated to their respective MCLs (5 μg/liter for 1,2-DCA, 0.05 μg/liter for EDB). The enrichment culture grown with 1,2-DCA has the advantage of a more rapid transition to 1,2-DCA after EDB is consumed.
authors.affiliation: Department of Environmental Engineering and Earth Sciences, Clemson University, Clemson, South Carolina, USA.
authors.forename: Rong
authors.initials: R
authors.lastname: Yu
authors.forename: Hari S
authors.initials: HS
authors.lastname: Peethambaram
authors.forename: Ronald W
authors.initials: RW
authors.lastname: Falta
authors.forename: Matthew F
authors.initials: MF
authors.lastname: Verce
authors.forename: James K
authors.initials: JK
authors.lastname: Henderson
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Bagwell
authors.forename: Robin L
authors.initials: RL
authors.lastname: Brigmon
authors.forename: David L
authors.initials: DL
authors.lastname: Freedman
mesh_terms: D000693:Anaerobiosis; D058491:Bacterial Load; D001711:Biotransformation; D041862:Chloroflexi / Q000254:growth & development / Q000378:metabolism; D004783:Environmental Microbiology; D015946:Ethylene Dibromide / Q000378:metabolism*; D005025:Ethylene Dichlorides / Q000378:metabolism*; D007773:Lactates / Q000378:metabolism; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D005025:Ethylene Dichlorides; D007773:Lactates; D014874:Water Pollutants, Chemical; D015946:Ethylene Dibromide; C024565:ethylene dichloride