EVALUATION OF NATURAL AND IN-SITU REMEDIATION TECHNOLOGIES FOR A COAL-RELATED METALS PLUME
Metals contamination exceeding drinking water standards (MCLs) is associated with acidic leachate generated from a coal pile runoff basin at the Savannah River Site (SRS) in Aiken, South Carolina. The metals plume extends over 100 acres with its' distal boundary about onehalf mile from the Savannah River. Based on the large plume extent and high dissolved iron and aluminum concentrations, conventional treatment technologies are likely to be ineffective and cost prohibitive. In-situ bioremediation using existing groundwater microbes is being evaluated as a promising alternative technology for effective treatment, along with consideration of natural attenuation of the lower concentration portions of the plume to meet remedial goals. Treatment of the high concentration portion of the groundwater plume by sulfate-reducing bacteria (SRB) is being evaluated through laboratory microcosm testing and a field-scale demonstration. Organic substrates are added to promote SRB growth. These bacteria use dissolved sulfate as an electron acceptor and ultimately precipitate dissolved metals as metal sulfides. Laboratory microcosm testing indicate SRB are present in groundwater despite low pH conditions, and that their growth can be stimulated by soybean oil and sodium lactate. The field demonstration consists of substrate injection into a 30-foot deep by 240-foot long permeable trench. Microbial activity is demonstrated by an increase in pH from 3 to 6 within the trench. Downgradient monitoring will be used to evaluate the effectiveness of SRB in reducing metal concentrations. Natural attenuation (NA) is being evaluated for the low concentration portion of the plume. A decrease in metal mobility can occur through a variety of abiotically and/or biotically mediated mechanisms. Quantification of these mechanisms is necessary to more accurately predict contaminant attenuation using groundwater transport models that have historically relied on simplified conservative assumptions. Result s from matched soil/porewater samples indicate higher soil/water partition coefficients (Kds) with increasing distance from the source. In addition, site-specific metals availability is being assessed using sequential extraction techniques, which more accurately represent environmental conditions as compared to default EPA extraction methods. Due to elevated sulfate levels in the plume, SRB are most likely to be the dominant biotic contributor to NA processes.
- Research Organization:
- Bechtel Savannah River Inc., Environmental Restoration Division, Aiken, SC 29808; Westinghouse Savannah River Company, Savannah River Technology Center, Aiken, SC 29808 (US)
- Sponsoring Organization:
- US Department of Energy (US)
- OSTI ID:
- 827229
- Resource Relation:
- Conference: Waste Management 2003 Symposium, Tucson, AZ (US), 02/23/2003--02/27/2003; Other Information: PBD: 27 Feb 2003
- Country of Publication:
- United States
- Language:
- English
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