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- Title
Dynamics of reductive TCE dechlorination in two distinct H<sub>2</sub> supply scenarios and at various temperatures.
- Authors
Heimann, A. C.; Friis, A. K.; Scheutz, C.; Jakobsen, R.
- Abstract
Anaerobic microbial dechlorination of trichloroethene (TCE) by a mixed, Dehalococcoides containing culture was investigated at different temperatures (4-60 °C) using propionate and lactate as a slow- and fast-releasing hydrogen (H2) source, respectively. Distinct temperature-dependent dynamics of substrate fermentation and H2 levels could explain observed patterns of dechlorination. While varying the temperature caused changes in rate, the overall pattern of dechlorination was characteristic of the supplied electron donor. Feeding cultures with a rapidly fermentable substrate such as lactate generally resulted in high H2 concentrations and fast and complete dechlorination accompanied by rapid methanogenesis. In contrast, low H2 release rates resulting from fermentation of propionate were associated with 2 to 3--fold longer time frames necessary for complete dechlorination at intermediate temperatures (15-30 °C). A lag-phase prior to dechlorination of cis-dichloroethene (cDCE), together with a characteristic build-up of H2 and methane, was consistently observed at slow H2 supply. At temperatures of 10 °C and lower, the system remained in this lag phase and no dechlorination past cDCE was observed within the experimental time frame. However, when lactate was the substrate, complete dechlorination of TCE occurred within 74 days at 10 °C, accompanied by methane production. The choice of fermentable substrate decisively influenced the rate and degree of dechlorination at an electron donor/TCE ratio as high as 666:1. Temperature-dependent H2 levels resulting from fermentation of different substrates could be satisfactorily explained through thermodynamic calculations of the Gibbs free energy yield assuming a constant metabolic energy threshold of -20 kJ/(mol reaction).
- Subjects
FERMENTATION; MICROBIOLOGICAL synthesis; CHLORINATION; HYDROGEN; BACTERIAL growth; BACTERIA; LACTATES; TEMPERATURE
- Publication
Biodegradation, 2007, Vol 18, Issue 2, p167
- ISSN
0923-9820
- Publication type
Article
- DOI
10.1007/s10532-006-9052-z