Oak Ridge National Laboratory
Description
Many technologies designed to remediate organic contamination either directly depend on increasing populations of bacteria that can degrade the compounds, such as the methane injection, or lead to increases in degradative populations as a secondary result of nonbiological remediation, such as the biological benefits of venting-bioventing. Microbial monitoring is needed to demonstrate the effectiveness of bioremediation and to demonstrate additional bioremediation benefits from other technologies (e.g., bioventing benefits from soil venting). The various advanced monitoring techniques, developed and applied, (e.g., DNA probe analysis, lipid analysis, activity and biomass measurements) all contribute to documenting the necessary changes in microbial populations. In addition, these techniques permit feedback during operation so that procedures may be changed (e.g., changing nutrients) to increase effectiveness of the remediation.
Technical Performance Data
Microbial population changes were monitored in soil and groundwater samples from the Savannah River Site (SRS). Microbial biomass was evaluated using measurements of colony forming units, MPN techniques for methanotroph and methylotroph population and PFLA analysis. Microbial activity was assessed using the acetate incorporation techniques and by measurement of trichloroethylene (TCE) degradation in enrichments. DNA probes are used to enumerate specific groups of bacteria such as methanotrophs, toluene degraders, and others. Several new probes have been developed as part of this work.
The monitoring has been very effective in documenting significant changes in the microbial community in response to the remediation. The results of this effort indicate that there have been substantial changes in biological activity and biomass with increasingly aggressive measures to promote TCE degration in the subsurface. However, there are some indications of a leveling off or a decrease in some of these measures as the 4% methane injection proceeds. Thus, the data indicate the success in stimulating TCE degrading populations in the subsurface and now may be indicating a limitation of further increases or the potential for decreases in critical populations. Other nutrients may be becoming limiting, and a further phase (methane injection with nutrient addition) may be necessary to increase critical population levels and degradative activity further.
Analysis can be completed in 2 days to 1 month, depending on the techniques used.
Cost. Costs will vary with the intensity of the sampling techniques used. Costs at SRS were high because of the redundancy built into the sampling that was needed to develop the data on the reliability of individual monitoring techniques. Costs for a more focused effort would be lower. Sample costs vary from less than $100 to greater than $500.
Projected Performance
This technology is expected to demonstrate the effectiveness of bioremediation and give feedback during operations to increase the effectiveness of bioremediation technologies.
Waste Applicability
This technology is applicable to the monitoring of populations that can degrade organic compounds.
Status
Materials and equipment are off-the-shelf except for the DNA probes that are not commercially available.
Regulatory Considerations
Ecological impacts are not anticipated from user of this technology. The potential exists for exposure to solvents and low-levels of radionuclides.
Potential Commercial Applications
This technology has potential commercial applicatyions at any site undergoing bioremediation.
Baseline Technology
The baseline technology is mass balance measurements that are limited in monitoring critical changes in the microbial populations.
Intelectual Property Rights
Patent Ownership: None
For more information, please contact:
References
Go to the Characterization and Monitoring Technology Profiles Index