title: Experimental evaluation and mathematical modeling of microbially enhanced tetrachloroethene (PCE) dissolution.
abstract: Experiments to assess metabolic reductive dechlorination (chlororespiration) at high concentration levels consistent with the presence of free-phase tetrachloroethene (PCE) were performed using three PCE-to-cis-1,2-dichloroethene (cis-DCE) dechlorinating pure cultures (Sulfurospirillum multivorans, Desulfuromonas michiganensis strain BB1, and Geobacter lovleyi strain SZ) and Desulfitobacterium sp. strain Viet1, a PCE-to-trichloroethene (TCE) dechlorinating isolate. Despite recent evidence suggesting bacterial PCE-to-cis-DCE dechlorination occurs at or near PCE saturation (0.9-1.2 mM), all cultures tested ceased dechlorinating at approximately 0.54 mM PCE. In the presence of PCE dense nonaqueous phase liquid (DNAPL), strains BB1 and SZ initially dechlorinated, but TCE and cis-DCE production ceased when aqueous PCE concentrations reached inhibitory levels. For S. multivorans, dechlorination proceeded at a rate sufficient to maintain PCE concentrations below inhibitory levels, resulting in continuous cis-DCE production and complete dissolution of the PCE DNAPL. A novel mathematical model, which accounts for loss of dechlorinating activity at inhibitory PCE concentrations, was developed to simultaneously describe PCE-DNAPL dissolution and reductive dechlorination kinetics. The model predicted that conditions corresponding to a bioavailability number (Bn) less than 1.25 x 10(-2) will lead to dissolution enhancement with the tested cultures, while conditions corresponding to a Bn greater than this threshold value can result in accumulation of PCE to inhibitory dissolved-phase levels, limiting PCE transformation and dissolution enhancement. These results suggest that microorganisms incapable of dechlorinating at high PCE concentrations can enhance the dissolution and transformation of PCE from free-phase DNAPL.
authors.affiliation: School of Civil and Environmental Engineering and School of Biology, Georgia Institute of Technology, 311 Ferst Drive, Atlanta, Georgia 30332-0512, USA.
authors.forename: Benjamin K
authors.initials: BK
authors.lastname: Amos
authors.forename: John A
authors.initials: JA
authors.lastname: Christ
authors.forename: Linda M
authors.initials: LM
authors.lastname: Abriola
authors.forename: Kurt D
authors.initials: KD
authors.lastname: Pennell
authors.forename: Frank E
authors.initials: FE
authors.lastname: Löffler
mesh_terms: D000693:Anaerobiosis; D001421:Bacteria, Anaerobic / Q000378:metabolism*; D001673:Biodegradation, Environmental; D002713:Chlorine / Q000378:metabolism*; D020564:Deltaproteobacteria / Q000378:metabolism; D045858:Desulfitobacterium / Q000378:metabolism; D045285:Desulfovibrio desulfuricans / Q000378:metabolism; D004000:Dichloroethylenes / Q000378:metabolism; D045302:Geobacter / Q000378:metabolism; D007700:Kinetics; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D012989:Soil Pollutants / Q000378:metabolism*; D013237:Stereoisomerism; D013750:Tetrachloroethylene / Q000378:metabolism*
chemical_list: D004000:Dichloroethylenes; D012989:Soil Pollutants; D002713:Chlorine; D013750:Tetrachloroethylene; C035384:1,2-dichloroethylene