FULL SCALE BIOAUGMENTATION FOR ANAEROBIC DECHLORINATION OF PCE AND DCE
Sami A. Fam, Ph.D., P.E. L.S.P., Innovative Engineering Solutions, Inc., Sam Fogel, Ph.D.,
Margaret Findlay, Ph.D., Bioremediation Consulting, Inc., Mike Gaudette, Vopak USA.
This paper describes an on-going site remedial program in California, that includes bioagmentation of the groundwater with etheneogen rich water from another project site in New Jersey. Lactate and potassium phosphate are also added to the groundwater to enhance anaerobic degradation of chlorinated organics.
This is likely one of the largest and first full-scale bioaugmentation projects for anaerobic dechlorination in the world. The remedial measures involve extraction of impacted groundwater (50 gallons per minute) from a network of 8 extraction wells (3-acre area). Electron donors (approximately 10,000 lbs./yr.) and nutrients are added to the extracted groundwater, along with a few gallons per day of bioaugmentation water prior to recharge to reinjection trenches.
The initial biogeochemical investigation showed that extensive biodegradation is occurring at the site, but that electron donor deficiencies may be limiting degradation. Microcosm studies further indicated that dechlorination past cis-dichloroethene was not possible due to the lack of ethenogens at the site. The microcosms further indicated that full dechlorination to ethene was possible with bioaugmentation with ethenogen rich water that was collected from another project site. Severeal bioaugmentation cultures were tested prior to choosing the selected culture. The various microcosm bottles were analyzed at different times for VOCs, electron donors, and degradation products.
The bioaugmentation water was transferred to the site in a custom made 2 gallon reactor and was transferred to a 100 gallon tank at the site under anaerobic conditions. Testing over the past six months has shown that the 100-gallon reactor contains vigorous etheneogens.
The remediation system was started up in November 2000. Ethene was not detected at the site in July 1999, July 2000, or November 2000, but was detected at low concentrations in six wells in 2001. The amendments and bioaugmentation program have increased dechlorination of VOCs in the subsurface. Furthermore, methane levels in several wells have increased slightly over the past several months indicating that the areas around these wells are becoming more anaerobic.
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