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Heterogeneous response to biostimulation for U(VI) reduction in replicated sediment microcosms
Jennifer L Nyman1, Terence L Marsh, Matthew A Ginder-Vogel
1Department of Civil and Environmental Engineering, M42 Terman Engineering Center, Stanford University, 380 Panama Mall, Stanford, CA 94305-4020, USA.
Biodegradation
|February 24, 2006
Summary
Biostimulation effectively reduced soluble uranium (U(VI)) in contaminated sediment by promoting microbial activity. However, uranium reduction rates can be limited by sulfate-reducing bacteria becoming substrate-limited, highlighting the need for efficient chemical delivery.
Area of Science:
- Environmental Science
- Microbiology
- Geochemistry
Background:
- Uranium contamination poses environmental risks.
- Bioremediation strategies are crucial for contaminant cleanup.
- Understanding microbial processes is key to effective uranium reduction.
Purpose of the Study:
- To assess the biostimulation of uranium reduction in contaminated sediment.
- To simulate field conditions using batch microcosms.
- To identify microbial communities involved in uranium reduction.
Main Methods:
- Batch microcosm experiments using contaminated sediment and inoculum.
- X-ray absorption near edge structure (XANES) spectroscopy for uranium speciation.
- Terminal restriction fragment length polymorphism (T-RFLP) for microbial community analysis.
- Chemical analyses for sulfate, acetate, and ethanol concentrations.
Main Results:
- Biostimulation led to decreased sulfate and soluble U(VI) concentrations.
- XANES confirmed U(IV) formation, indicating uranium reduction.
- T-RFLP identified denitrifying bacteria, including Acidovorax, involved in U(VI) reduction.
- Presence and activity of fermenting and sulfate-reducing bacteria were detected.
- Rebound in soluble U(VI) occurred when sulfate-reducing bacteria were substrate-limited.
Conclusions:
- Microbial biostimulation is effective for uranium reduction in contaminated sediments.
- Microbial and mineralogical heterogeneity can impact uranium reduction efficiency.
- Effective chemical delivery and understanding of serial/parallel microbial processes are vital for successful bioremediation.