Anaerobic dechlorination and redox activities after full-scale Electrical Resistance Heating (ERH) of a TCE-contaminated aquifer

• Published in: Journal of contaminant hydrology 2006-12, Vol.88 (3), p.219-234
• Main Authors: Friis, A.K., Heron, G., Albrechtsen, H.-J., Udell, K.S., Bjerg, P.L.
• Format: Article
• Language: English
• Subjects: anaerobes; anaerobic conditions; aquifers; Biodegradation, Environmental; bioremediation; Chlorinated ethenes; chlorinated hydrocarbons; Contamination; Dechlorination; Earth sciences; Earth, ocean, space; Electric Impedance; electrical resistance heating; electrical treatment; Exact sciences and technology; Geologic Sediments - chemistry; groundwater contamination; heat treatment; Hot Temperature; Hydrogeology; Hydrology. Hydrogeology; Oxidation-Reduction; Redox activities; redox potential; Remediation; Thermal treatment; trichloroethene; Trichloroethylene - metabolism; Water Pollutants, Chemical - metabolism; Water Purification - methods
• ISSN: 0169-7722; 1873-6009
• DOI: 10.1016/j.jconhyd.2006.07.001

The effects of Electrical Resistance Heating (ERH) on dechlorination of TCE and redox conditions were investigated in this study. Aquifer and groundwater samples were collected prior to and after ERH treatment, where sediments were heated to approximately 100 °C. Sediment samples were collected from three locations and examined in microcosms for 250 to 400 days of incubation. Redox activities, in terms of consumed electron acceptors, were low in unamended microcosms with field-heated sediments, although they increased upon lactate-amendment. TCE was not dechlorinated or stalled at cDCE with field-heated sediments, which was similar or lower compared to the degree of dechlorination in unheated microcosms. However, in microcosms which were bioaugmented with a mixed anaerobic dechlorinating culture (KB-1™) and lactate, dechlorination past cDCE to ethene was observed in field-heated sediments. Dechlorination and redox activities in microcosms with field-heated sediments were furthermore compared with controlled laboratory-heated microcosms, which were heated to 100 °C for 10 days and then slowly cooled to 10 °C. In laboratory-heated microcosms, TCE was not dechlorinated and redox activities remained low in unamended and lactate-amended sediments, although organic carbon was released to the aqueous phase. In contrast, in field-heated sediments, high aqueous concentrations of organic carbon were not observed in unamended microcosms, and TCE was dechlorinated to cDCE upon lactate amendment. This suggests that dechlorinating microorganisms survived the ERH or that groundwater flow through field-heated sediments carried microorganisms into the treated area and transported dissolved organic carbon downstream.