SUCCESSFUL BIOREMEDIATION OF A DILUTE 44-ACRE PLUME
Sami A. Fam, Ph.D., P.E. L.S.P., David Falatko, P.E., Jason Blackburn, P.G., Innovative Engineering Solutions, Inc.,
George Pon, Ph.D., Bioremediation & Treatability Center. Michael Gaudette, Univar USA Inc.
Abstract
We have been conducting a large scale (19 acre) enhanced anaerobic dechlorination (EAD) pilot test since May 2006. The highly successful (98% decline in VOC concentrations and conversion to ethene) bioremediation of the (initial) 19 acres has lead the way to design of a final remedy to cover the entire 44-acre dilute VOC plume. The EAD pilot test used a groundwater recirculation system that includes 6 extraction wells and thirteen injection wells spanning an area that is approximately 300 feet wide. Groundwater (contaminated with 2 to 3 ppm of TCE and its breakdown products) is recirculated within this area at an approximate flow rate of 30 gallons per minute within the sandy aquifer. The amendment dose is approximately 15,000 pounds/month of total organic carbon (TOC) using a whey solution stabilized with molasses (molwhey). We have also used emulsified vegetable oil and sodium lactate as further supplements to the mixed substrate feeding system. Molwhey is the lowest cost electron donor that is available and appears to be an ideal substrate lasting up to one year in the aquifer. Coupled with the site's high groundwater velocity (1,500 feet per year), our enhancement system has fed 19 acres in roughly 1.5 years. Bioaugmentation was conducted using the NJ-14 culture and there is evidence that it has migrated to distances exceeding 700 feet.
The major benefit of the high groundwater flow velocity is greater areal coverage by the remediation system. The major downside is the high consumption of electron donor (est. $200,000/year for 3 years for the 44 acres), however in consideration that we are remediating such a large area, the cost of the electron donor is considered acceptable. The final remedy calls for installation of a second bioremediation zone and expansion of the initial installation (pilot 19 acre zone) for eventual remediation of approximately 44 acres. There is evidence that at the downgradient plume fringe co-metabolic degradation is also taking place (methane as a co-metabolite).
System operational results, mixed substrate feeding, remediation of dilute plumes and the combination of EAD and co-metabolic degradation for large plumes will be discussed.
