ANAEROBIC BIOREMEDIATION OF CHLORINATED VOC'S
IN CONJUNCTION WITH DUAL EXTRACTION
Sami A. Fam, Ph.D., P.E., L.S.P., Innovative Engineering Solutions, Inc., Tony Pirelli, P.G., Van Waters & Rogers Inc.,
Tom Sullivan, P.G. , Bascor Environmental. Inc., Margaret Findlay, Ph.D., Bioremediation Consulting, Inc.,
Sam Fogel, Ph.D., Bioremediation Consulting, Inc.
This paper will describe a site remedial program which includes addition of acetate, and phosphate to the groundwater to enhance anaerobic degradation of chlorinated organics. The remedial measures involve dual extraction of impacted groundwater and soil vapor from a network of 36 extraction wells. Electron donors and nutrients are to be added to the subsurface via non pumping extraction wells. The dual extraction system will remediate the vadose zone and the dewatered soil, while the bioremediation system will remediate the portions of the saturated zone that are not dewatered. The dual extraction system was required in order to distribute nutrients in the fairly low permeability silty-clay formation (as well as for VOC mass removal).
The initial biogeochemical investigation showed that extensive biodegradation is occurring at the site, but that phosphate and electron donor deficiencies may be limiting degradation. A lab-scale treatability test was conducted to confirm that electron donor and phosphate addition would enhance biodegradation of the VOCs. The treatability test was also intended to provide a basis for initial dosing requirements for the selected amendments during full scale implementation.
Groundwater samples were collected from 2 site wells for treatability testing. The samples from each well were subdivided into multiple 100 ml. serum bottles, and each bottle was subjected to varying treatment scenarios as follows: 1) Killed immediately with HCl; 2)Unamended; 3)Amended with Phosphate (P) only; 4) Amended with Acetate (electron donor) and P; 5)Amended with Lactate (electron donor) and P;
The various bottles were analyzed at different times for VOCs, electron donors, and degradation products (ethane, ethene, CO2). In general, the data showed that TCE degradation at the site is enhanced by the addition of electron donor and phosphate. The greatest enhancement appeared to be from Phosphate and Acetate addition. This is to be expected, since acetate was found in the groundwater (already acclimated microorganisms), and is likely the most naturally available electron donor (acetate is produced from the degradation of many compounds such as methylene chloride, which is abundant at the site). c-DCE concentrations increased initially, concomitantly until TCE loss, consistent with conversion of TCE to DCE.
A final component of the site remedial program is the installation of a property boundary bio-enhancement reactive wall to enhance the biogeochemical conditions of the off-site impacted groundwater. The remediation system, which includes groundwater and vapor phase treatment using steam regenerable granular activated carbon, is currently being installed with a scheduled start-up in April 1998.
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