Superfund Research Program
Bioremediation of Chlorinated Solvent Compounds: In Situ Remediation Strategies and Predictive Tools for Controlling Contaminated Plumes
Project Leader: John Ferguson
Grant Number: P42ES004696
Funding Period: 1995 - 2006
Studies with perchloroethylene (PCE)-dehalogenating enrichments have continued along with numerical models for their application in reactor systems. The experimental results and simulations indicate that complete conversion of chloroethenes to ethene is very difficult in a reactor because of slow kinetics of conversion of vinyl chloride. Studies have also shown the dependence of dehalogenation on hydrogen levels in the enrichments; these results indicate that dehalogenators are effective scavengers for hydrogen in methanogenic communities. Studies were also conducted with 1,1,2,2-tetrachloroethane which showed abiotic and biotic transformations, leading to complete removal and possible conversion to unchlorinated products. Anaerobic sulfidogenic bacteria have been isolated from the PCE-dehalogenating culture on two media and will be characterized for their ability to dechlorinate PCE and c-DCE.
Chemostats have been constructed for study of the filamentous phenol-degrading isolate (A-1) and Pseudomonas cepacia G4 in pure culture. G4 grows well and degrades trichloroethylene (TCE) rapidly under chemostat growth conditions. Strain A-1 grows poorly in pure culture with phenol as the sole source of carbon, and it does not degrade TCE under these conditions. Experiments with a mixed culture growing on phenol under nitrogen limited conditions and dominated by the filaments showed that TCE degradation was poor unless phenol concentrations reached high levels during intermittent feeding (20 mg/L). At these levels the mixed culture was able to degrade TCE at rates comparable to G4. The 16S rDNA was sequenced. A preliminary phylogenetic analysis of this data supports earlier whole cell fatty acid evidence that this strain is a member of the subdivision of the Proteobacteria, and that its closest neighbor is Comomonas (Pseudomonas) testosteroni. The strain represents a new species, possibly a new genus.
The genus Rhodococcus is involved in the degradation of hydrocarbon compounds. This work has centered on the ability of this genus to emulsify crude oil hydrocarbons. Wild type Rhodococcus strain NO-1 produces a capsule that is involved in its emulsification activities. An unencapsulated "rough" mutant of NO-1 has been isolated which has much less emulsification capability.