Biochemical degradation of tetrachloroethylene using generator columns containing residual DNAPL

Abstract

The goal of this project was to study the feasibility of cleaning up solvents present in residual amounts in the saturated zone using an in situ biochemical treatment. Tetrachloroethylene (PCE) was chosen as a model compound because it is the most commonly found organic groundwater contaminant. A mixture of vitamin B₁₂ with titanium citrate was pumped as the remedial solution through a column containing 100 μL of PCE residual. The rate of reaction was found to be first order with respect to the concentration of PCE and to the concentration of vitamin B_]2. At 10 ppm B₁₂, more than 85% PCE was degraded to trichloroethylene (TCE) and dichloroethylene (DCE) in two hours. The major advantages of the biochemical system over the use of anaerobic bacteria are:

1. There is no need for the careful balance of nutrients or the addition of an extraneous carbon source.

2. There is no restriction in the concentration range of the compound to be treated, because there is no problem with toxicity, and

3. The delivery of the treatment is easy because vitamin B12 is highly water soluble.