Field Demonstration of a Monitoring Toolbox for In Situ Biogeochemical Transformation
Presented on Tuesday, May 6, 2014
Ryan Wymore, P.E.1, Nathan Smith2 and Patrick Evans3, (1)CDM Smith Inc., Denver, CO, (2)Environmental Management Division, CDM Smith, Denver, CO, (3)CDM Smith, Bellevue, WA
In situ biogeochemical transformation involves biological formation of reactive minerals that can destroy chlorinated solvents without accumulation of intermediates like vinyl chloride. An AFCEC-funded field demonstration was conducted to develop a monitoring toolbox to assess biogeochemical transformation at two existing mulch biowalls at Altus AFB to treat VOC-contaminated groundwater. Three segments of the Altus OU1 biowall were monitored—(1) segment recently rejuvenated with electron donor and iron, (2) segment recently rejuvenated with electron donor only, and (3) segment with no rejuvenation. In addition, a segment of the Altus SS-17 biowall (no rejuvenation) was monitored.
Monitoring data were collected quarterly for 18 months for groundwater velocity, electron acceptor loading rates (i.e., mass per day per unit volume of treatment zone), electron donor concentrations, geochemical conditions, reactive minerals, microbiological activity, and VOCs.
The SS17 biowall showed a biogeochemical transformation pattern based on a high VOC destruction without accumulation of daughter products. Factors that appeared to promote VOC removal included: (1) high volumetric sulfate consumption rates, (2) high concentrations of total iron in the biowall matrix, (3) low dissolved sulfide concentrations, and (4) relatively high oxidation-reduction potentials. These results contrast to the low total molar VOC destruction observed in the unamended OU1 biowall section, which had (1) low volumetric sulfate consumption rates, (2) low total iron concentrations, (3) high dissolved sulfide concentrations, and (4) more negative ORP.
For the organic-amended and organic-iron amended OU1 biowall segments, sulfide concentrations decreased and total molar VOC destruction increased following rejuvenation. These data suggest that amendment with organics and not iron was primarily responsible for biowall rejuvenation.
Monitoring tools that provided useful data during this demonstration were VOC removal, dissolved sulfide concentration, oxidation-reduction potential, volumetric sulfate consumption rate measured using passive flux meters, total biowall iron concentrations, total volatile fatty acids, pH, and electron microprobe analysis.
Ryan Wymore, P.E.
CDM Smith Inc., Denver, CO
Ryan Wymore is a principal environmental engineer with CDM Smith in Denver, Colorado, where he serves as the company’s environmental remediation market leader. He has spent the last 15 years specializing in innovative groundwater remediation technologies. He also serves as the administrator for CDM Smith’s Research and Development Program. Wymore joined ITRC in 2002, and has had membership on seven technical teams. He holds a B.S. in Biological Systems Engineering from the University of Nebraska-Lincoln, and an M.S. in Civil/Environmental Engineering from the University of Idaho.
Nathan Smith
Environmental Management Division, CDM Smith, Denver, CO
Nathan Smith is a senior project manager and environmental scientist specializing in bioremediation of chlorinated solvents and mining-influenced water.
Patrick Evans
CDM Smith, Bellevue, WA
Dr. Evans is a Vice President with CDM Smith in Bellevue, Washington and has 30 years of research and development experience in the areas of hazardous waste remediation, energy, drinking water treatment, and waste water treatment. He received his B.S. and Ph.D. degrees in chemical engineering from the University of Michigan and his M.S. degree in chemical engineering from Rutgers, The State University of New Jersey. He also completed postdoctoral research in environmental microbiology at New York University Medical Center. Dr. Evans has been a Principal Investigator on numerous research projects including ones funded by the Department of Defense Environmental Security Technology Certification Program (ESTCP) and the Water Research Foundation. He is the recipient of the Water Environment Federation McKee Award, and two Research Grand Awards and one Superior Achievement Award from the American Academy of Environmental Engineers and Scientists. He is the author of over 40 publications and holds 4 patents.
