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Publication

CONDUCTING BIOREMEDIATION IN A TOXIC SOURCE AREA ZONE

Sami A. Fam, Ph.D., P.E. L.S.P., Stewart Mountain, P.E., L.S.P., Innovative Engineering Solutions, Inc

Groundwater at the main source area (0.5 acre) contains over 1,400 mg/L of chlorinated VOCs including 1,1,1 TCA, PCE, TCE and the various breakdown products. In addition, the main source area contains thousands of mg/L of glycols, ketones and alcohols. The chemical soup provides a great electron donor supply for the downgradient plume, however the source area itself is generally toxic to the dechlorinators. Some source area wells contain as much as 90,000 nM/L of dissolved hydrogen that can not be utilized by the dechlorinators. Eight of the source area wells are PCR negative and contain low amounts of vinyl chloride and ethene. Non source area wells are generally all PCR positive and are extremely biologically active, showing very strong dechlorination trends. In fact, our commercially available NJ-14 dechlorinating culture (degrades PCE to ethene, 1,1,1 TCA to CA) originated from this project site. Microcosm testing has indicated that at 25%-50% strength, the main source area wells are hospitable to anaerobic dechlorination. A full scale recirculation based enhanced anaerobic dechlorination (EAD) system has been installed in 2004 that includes a vapor extraction and dual extraction component to recover vadose zone contamination and detoxify the main source area. Within a few months of source area detoxification, strong signs are emerging that dechlorination is underway and the VOC profile is changing dramatically to include more vinyl chloride, ethene, chloroethane and much less 1,1,1 TCA and PCE within the main source area.

Extensive work is underway by us and others to enable EAD application under such harsh conditions. Our work has enabled us to successfully degrade up to 550 mg/L of PCE to ethene in the laboratory by acclimating our cultures and by adding vitamin B12 to the microcosms. Until such time that these efforts are successful (to degrade over 1,000 ppm) detoxification and groundwater mixing (toxic with non toxic) presents viable options today. We will present our work for detoxification (degrading 1,400 ppm), groundwater mixing (degrading 600 ppm) and high concentration microcosm work (degrading 550 ppm).