FULL SCALE ANAEROBIC BIOREMEDIATION USING ACETATE AND
LACTATE ELECTRON DONORS
Sami A. Fam, Ph.D., P.E., L.S.P., Innovative Engineering Solutions, Inc., Margaret Findlay, Ph.D., Bioremediation Consulting, Inc.,
Sam Fogel, Ph.D., Bioremediation Consulting, Inc., Tony Pirelli, P.G., Tom Sullivan, P.G. , Bascor Environmental. Inc.
This paper describes an on-going site remedial program, which includes addition of acetate, lactate and ammonium phosphate to the groundwater to enhance anaerobic degradation of chlorinated organics. This is likely one of the largest full scale anaerobic dechlorination systems in the world. The remedial measures involve extraction of impacted groundwater from a network of 36 extraction wells (3-acre area). Electron donors and nutrients are added to the subsurface via non pumping extraction wells. The pumping and non-pumping wells are alternated every month.
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 using anaerobic sterile technique into multiple 160 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 and lactate were found in the groundwater (already acclimated microorganisms), and are likely the most naturally available electron donors (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.
The full scale bioenhancement system has been operating for 21 months and has greatly improved site conditions. Total VOC concentrations have dropped from 460 mg/L to approximately 41 mg/L (in September 1999) in the most impacted well (OW-3). Of the 41 mg/l of total VOCs in OW-3, approximately 25 mg/l are vinyl chloride and chloroethane . In contrast, prior to initiating remediation vinyl chloride and chloroethane represented only 7% of the total VOCs in OW-3. Concentrations of ethane and ethene in the observation wells have increased by approximately 50 fold in the impacted zone since initiation of the bio-enhancement program. To date we estimate that 50,000 pounds of VOCs have been removed/degraded.
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