Options for In Situ Remediation of Soil Contaminated with a Mixture of Perchlorinated Compounds

Environments contaminated with mixtures of chlorinated hydrocarbons represent a formidable challenge for bioremediation because biodegradation of all components of the mixture must be demonstrated. In this study a soil site contaminated with hexachloro-1,3-butadiene (HCBD), hexachlorobenzene (HCB), and perchloroethene (PCE) was investigated. Environmental parameters (including toxicity) and microbial community composition were characterized. The lack of scientific literature on HCBD biodegradation led to attempts to develop HCBD-respiring enrichment cultures and to test the hypothesis that known PCE-degrading cultures could dechlorinate HCBD. No HCBD dechlorination was observed. An alternative approach, using electron shuttles to degrade the mixture of chlorinated hydrocarbons, was compared with the activity of zero-valent iron. The authors conclude that electron shuttles offer promise for the in situ treatment of mixtures of chlorinated hydrocarbons.