Removal of trichloroethylene in reduced soil columns.

A continuous soil column experiment was conducted to investigate reductive dechlorination of trichloroethylene (TCE) in soil system reductively manipulated by three types of reductants (Fe(II), dithionite, and Fe(II) + dithionite (combined treatment of Fe(II) and dithionite)). The soil column reduced by Fe(II) + dithionite has the greatest bed volumes (51.8) treated to breakthrough indicating that the combined treatment of Fe(II) and dithionite is more effective for the reductive dechlorination of TCE in the reduced soil column than the separate treatment of Fe(II) or dithionite. The measured bed volumes to breakthrough in control and treated soil columns were similar to the estimated bed volumes based on the result of batch kinetic experiment, differing by a factor of 0.96-1.02. The relative concentration of bromide (non-reactive tracer) reached the approximate value of 1 between 0.87 and 1.03 bed volume. C2 hydrocarbons (acetylene, ethylene, and ethane) were observed as transformation products in the effluents of soil columns treated by the reductants. However, no chlorinated intermediates were observed at the concentrations above detection limits throughout the experiment. Chloride was observed in the effluents of soil columns reduced by dithionite and Fe(II) + dithionite.