Evaluation of pH as a Limiting Factor for TCE Dechlorination in Savannah River Site Sediment

Details

• Personal Author:
  Aelion CM ; Flora JR ; Rust CM
• Description:
  In situ pH control may be a viable method for enhancing remediation of contaminated groundwater and sediment. pH can limit certain anaerobic subsurface microbes employed in bioremediation efforts. Investigations into pH control must begin with an evaluation of the effect of pH on microbes actively metabolizing contaminants in sediment from a potential site. The Department of Energy's Savannah River Site (SRS) was chosen as a possible site for in situ pH control due to extensive contamination of the groundwater with TCE (trichloroethylene). Limited success has been reported at this site for removal of TCE from the groundwater and sediment via the reductive dechlorination pathway. Near neutral pH has been shown to optimize TCE reductive dehalogenase activity in purified enzyme solutions, cell extracts, and cell suspensions, though this pH effect has not been tested in subsurface sediment. The groundwater at SRS ranges in pH from 4.5 to 5.5. Sediment obtained from a TCE-contaminated aquifer at SRS was packed into 160-ml serum bottles and spiked with 0.2 mg/kg TCE and nutrients. The pH in the sediment slurry was adjusted to different set points (4.0, 5.5, 7.0, 8.5, 10.0) using 0.5 M NaOH or HCl. TCE and its metabolites, cis-dichloroethylene and vinyl chloride, and methane were analyzed by GC-FID for 50 days. Carbon and nutrient analyses were performed on sediment extracts. Metabolites were formed at low concentrations (3 mg/L) without methanogenesis. Statistically, maximum vinyl chloride production occurred at a pH of 4 (p<0.0001). The results implied that a pH of 7 will not necessarily optimize TCE dechlorination in sediment even if it does so in enrichment cultures such as cell suspensions. Though pH appeared to have an effect on TCE dechlorination, the low production of reduced metabolites indicated that in situ pH control would not be efficacious for promoting reductive dechlorination at SRS. [Description provided by NIOSH]
• Subjects:
  Environmental Monitoring Environmental Pollution Microbiology Occupational Health Safety
• Keywords:
  Environmental Contamination Environmental Monitoring Ground Water Microorganisms Soil Bacteria Trichloroethylene
• Publisher:
  SETAC (Society of Environmental Toxicology and Chemistry)
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Abstract or Summary
• Place as Subject:
  OSHA Region 4 ; South Carolina
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Pages in Document:
  236-237
• NIOSHTIC Number:
  nn:20057789
• Citation:
  SETAC 22nd Annual Meeting: Changing Environmental Awareness: Societal Concerns and Scientific Responses, November 11-25, 2001, Baltimore, Maryland. Pensacola, FL: SETAC (Society of Environmental Toxicology and Chemistry), 2001 Nov; :236-237
• CAS Registry Number:
  Trichloroethylene (CAS RN 79-01-6)
• Federal Fiscal Year:
  2002
• Performing Organization:
  Arnold School of Public Health, University of South Carolina, Columbia
• Peer Reviewed:
  False
• Start Date:
  19940701
• Source Full Name:
  SETAC 22nd Annual Meeting: Changing Environmental Awareness: Societal Concerns and Scientific Responses, November 11-25, 2001, Baltimore, Maryland
• End Date:
  20040630
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:2a9b6b1db9190b9dfb83e82bf3c11f5e7a7657fd3efec54fca0add6108857b2224a6950e0c02ae92453b84b8303e0652831fc855e8eceecc0475e3cb1ec9aaec
• Download URL:
  https://stacks.cdc.gov/view/cdc/215021/cdc_215021_DS1.pdf
• File Type:
  [PDF - 137.53 KB ]