- Program Areas
- Energy and Water
- Environmental Restoration
- Munitions Response
- Resource Conservation and Climate Change
- Weapons Systems and Platforms
Bioaugmentation for Aerobic Bioremediation of RDX-Contaminated Groundwater
Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) is a common contaminant in soils and groundwater at military sites worldwide. RDX can be mobile and persistent in groundwater under the aerobic conditions present in many aquifers and thus tends to form large, dilute plumes. Although multiple studies have demonstrated in situ RDX biodegradation under anaerobic conditions, creating and maintaining anaerobic conditions across large areas is costly and technically challenging.
The objective of this project is to demonstrate an innovative application of bioaugmentation to enhance RDX biodegradation in contaminated groundwater under aerobic conditions. The project will provide field data to support both a technical evaluation and a cost-benefit analysis of this approach.
The Umatilla Chemical Depot (UMCD) has been identified as an ideal site for the demonstration. At UMCD, RDX is widespread in an aerobic, highly permeable groundwater aquifer. RDX concentrations range from 2 to 300 μg/L over the approximately 200-acre plume. This demonstration will be performed using a three-phased approach where each phase provides data required to optimize subsequent phases. Phase I consists of field site characterization and laboratory testing to select and develop a suitable bioaugmentation culture and to optimize conditions that facilitate growth, RDX-degrading activity, and cell transport under field conditions at the UMCD. Phase II consists of short duration push-pull tests conducted prior to substrate and culture injections to quantify RDX sorption to aquifer materials and cell transport tests to confirm that field test parameters selected based on Phase I test results are suitable for distributing cells at field-scale. Phase III consists of field-scale (~ 100 m3), low concentration (~10 mM ethanol) substrate injections in the aerobic biostimulation and aerobic bioaugmentation field plots and culture injection in the bioaugmentation plot only, followed by high concentration (50-100 mM corn syrup or ethanol) substrate injections in the anaerobic biostimulation field plot. In situ RDX degradation rates will be determined by triplicate push-pull tests in injection wells and downgradient wells within the treatment plots twice over a ~ 3-month period. Phase III will provide field-scale information on bioaugmentation culture transport, viability and xplA gene transfer, RDX degradation rates over time, and data needed to perform a cost-benefit analysis for implementation of the aerobic bioaugmentation approach for RDX treatment at UMCD.
Aerobic bioaugmentation should be less costly and more technically implementable than anaerobic biodegradation for large aerobic RDX plumes. Moreover, this aerobic approach will result in less degradation of groundwater quality than traditional anaerobic biodegradation (e.g., sulfide production and reduction and mobilization of Fe, Mn, and As). This demonstration will provide critical information concerning the potential utilization of aerobic bioaugmentation as an innovative technology for the full-scale treatment of large RDX plumes at UMCD, OR; the Milan Army Ammunition Plant, TN; Fort Wingate, NM; the former Hastings Naval Ammunition Depot, NE; the former Nebraska Ordnance Plant, NE; and the Massachusetts Military Reservation. (Anticipated Project Completion - 2015)
Points of Contact
Dr. Mandy Michalsen
U.S. Army Corps of Engineers
SERDP and ESTCP
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