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Chemosphere
Vol. 67, No: xx, 2007, Pages: : 816–825


Dechlorination after thermal treatment of a TCE-contaminated aquifer: Laboratory experiments

A.K. Friisa,*,1, E.A. Edwardsb, H.-J. Albrechtsena, K.S. Udellc,2, M. Duhamelb,3, P.L. Bjerga

Institute of Environment & Resources, Technical University of Denmark, building 115, Bygningstorvet, DK-2800 Kgs. Lyngby, Denmark.

Abstract

A microcosm study was conducted to evaluate dechlorination of trichloroethene (TCE) to ethene and survival of dechlorinating bacteria after a thermal treatment in order to explore the potential for post-thermal bioremediation. Unamended microcosms containing groundwater and aquifer material from a contaminated site dechlorinated TCE to cis-1,2-dichloroethene (cDCE), while lactate-amended microcosms dechlorinated TCE to cDCE or ethene. A thermal treatment was simulated by heating a sub-set of microcosms to 100 oC for 10 d followed by cooling to 10 oC over 150 d. The heated microcosms demonstrated no dechlorination when unamended. However, when amended with lactate, cDCE was produced in 2 out of 6 microcosms within 300 d after heating. Dechlorination of TCE to cDCE thus occurred in fewer heated (2 out of 12) than unheated (10 out of 12) microcosms. In unheated microcosms, the presence of dechlorinating microorganisms, including Dehalococcoides, was confirmed using nested PCR of 16S rRNA genes. Dechlorinating microorganisms were detected in fewer microcosms after heating, and Dehalococcoides were not detected in any microcosms after heating. Dechlorination may therefore be limited after a thermal treatment in areas that have been heated to 100 oC. Thus, inflow of groundwater containing dechlorinating microorganisms and/or bioaugmention may be needed for anaerobic dechlorination to occur after a thermal treatment.

Keywords:Remediation,Dechlorination,Groundwater,Chlorinatedethenes,Thermaltreatment,16SrRNA genes,Dehalococcoides,dechlorination of trichloroethene,bioremediation.


Corresponding author: Tel +45 3025 2030; fax +45 4593 2850

E-mail: akf@er.dtu.dk

 

 
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