Overview
- The study site was a shallow aquifer impacted by chlorinated solvents.
- Historical groundwater monitoring indicated an accumulation of cis-dichloroethene (DCE).
- Groundwater total organic carbon (TOC) concentrations were low suggesting reductive dechlorination was limited by a lack of suitable electron donors.
Question
Will injection of a commercial electron donor stimulate growth of Dehalococcoides and promote complete reductive dechlorination?
Analyses Requested
CENSUS – Reductive Dechlorination
- Dehalococcoides (qDHC)
- Vinyl Chloride Reductase (qBAV)
- Vinyl Chloride Reductase (qVCR)
Results
- The relatively low Dehalococcoides population (103 cells/bead) and the accumulation of the daughter product DCE indicated that monitored natural attenuation (MNA) would not meet remediation goals in an acceptable timeframe.
- Following electron donor injection to promote reductive dechlorination, the Dehalococcoides population increased to 106 - 107 cells/bead with a corresponding decrease in DCE.
- Vinyl chloride (VC) concentrations temporarily increased due to the reductive dechlorination of DCE.
- As indicated by the high number of Dehalococcoides spp. and vinyl chloride reductase genes however, microorganisms capable of reductive dechlorination of VC were present.
- VC concentrations decreased after the initial spike with a corresponding increase in ethene.
Answer
Electron donor injection resulted in
- increases in Dehalococcoides populations,
- increases in vinyl chloride reductase genes, and
- enhanced reductive dechlorination.
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