Bioremediation of 1,1,1-Trichloroethane and 1,1-Dichloroethene at a Confidential Site

Background

CL-Out® bioaugmentation was used to remediate ground water contaminated by 1,1,1-trichloroethane (1,1,1-TCA) and 1,1-dichloroethene (1,1-DCE). The 1,1-DCE was formed as a product of the natural abiotic degradation of 1,1,1-TCA. The bioremediation was implemented as a pilot study and a subsequent interim action for source removal.

Remediation Approach and Results

CL-Out® was introduced into the contaminated ground water in the suspected source area by injection through temporary well points up gradient of the monitoring point. The initial application was in March 2007 and a subsequent application was completed in September 2007.

The ground water treatment results were monitored by analysis of ground water samples for the contaminants of concern. The 30-day monitoring results after the first application showed an immediate decrease in the contaminant concentrations. After 30 days, the 1,1,1-TCA concentration decreased from 1,000 µg/L to 190 µg/L and the 1,1-DCE concentration decreased from 160 µg/L to 27 µg/L . Long-term monitoring after the second application showed that the concentrations of both compounds were reduced to 1.4 µg/L. The following chart shows the long-term contaminant concentrations.

Conclusions

This project demonstrates several of the benefits of aerobic bioaugmentation. CL-Out® organisms were able to metabolize the parent chloroethane compound and the daughter product, which was a chloroethene compound. The metabolic diversity of the CL-Out® organisms facilitates enables the bioremediation of mingled plumes and multiple contaminants. Bioaugmentation provides active control of the site as effective organisms compatible with the site conditions were injected where they were needed for quick contaminant removal.