Temperature Effects on Rate of Trichloroethene Degradation in Fractured Sandstone Using a 14C-Assay

Abiotic and biologically mediated abiotic degradation of chlorinated ethenes has been documented at many sites. One of the challenges with relying on this mechanism is slow rates. A simple way to enhance the rates is to heat the subsurface, e.g., using borehole heat exchangers powered by solar photovoltaics. Raising the groundwater temperature by ~5 to 20°C has the potential to increase abiotic and biotic rates to an extent that will significantly reduce remediation times and/or the extent of a contaminant plume. The objective of this study was to assess the effect of heating on degradation of trichloroethene (TCE) using samples of crushed sandstone rock and groundwater. A 14C-TCE assay was developed to determine pseudo first-order rate coefficients for the degradation of TCE based on a crushed rock microcosm study. The assay involved the development of a first-order model that determined rate coefficients based on product accumulation while accounting for volumetric changes in the serum bottles due to sampling and corresponding changes to the distribution of TCE between the aqueous and gaseous phases. Results proved that increasing temperature subsequently increases the rate of TCE degradation by a factor of 1.3 in the unamended treatment and a factor of 2.6 in the lactate- amended treatment. These results come from increasing the temperature from ambient groundwater temperature 18°C to 30°C