Dissertation
URANIUM IMMOBILIZATION IN SUBSURFACE SEDIMENTS
Doctor of Philosophy (PhD), Washington State University
01/2011
Handle:
https://hdl.handle.net/2376/111945
Abstract
The groundwater at the U.S. Department of Energy Hanford 300 Area (300A) site remains contaminated with uranium (U) despite decades of remediation efforts. The objective of this study was to investigate U immobilization in Hanford 300A subsurface sediments. The first part of this research involved U(VI) immobilization from groundwater to 300A subsurface sediments through organic stimulation of indigenous 300A sediment microorganisms carried out by mimicking the in situ environment in the laboratory. Results revealed that reductive U(VI) immobilization by stimulating indigenous microorganisms could be effective for U remediation in the 300A subsurface environment. Scanning electron microscopy images of organic-stimulated 300A sediments revealed the presence of surface-attached cells embedded in extracellular polymeric substances (EPS) (i.e., sediment biofilms). In the second part of this research, indigenous microorganisms were isolated from 300A subsurface sediment under biofilm forming conditions. Paenibacillus sp. 300A was one of the biofilm isolates which rapidly catalyzed Fe(III) reduction and promoted U(VI) immobilization. Since ~50-80% of the biofilm biomass is composed of EPS, the quantified contribution of EPS in U(VI) immobilization using Shewanella sp. HRCR-1 bacteria isolated from Hanford reach Columbia River was investigated. Results reveled that EPS immobilized U(VI) through both reduction and adsorption, and it played a significant role especially at lower U(VI) concentration.
Overall outcomes from this research include extending the current understanding of i) U interaction with subsurface geochemistry and indigenous microorganisms, ii) the role of indigenous microorganisms in U(VI) immobilization, and iii) the role of EPS in U(VI) immobilization.
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Details
- Title
- URANIUM IMMOBILIZATION IN SUBSURFACE SEDIMENTS
- Creators
- Bulbul Ahmed
- Contributors
- Haluk Beyenal (Advisor)James Petersen (Committee Member)Nehal Abu-Lail (Committee Member)Richard Zollars (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Chemical Engineering and Bioengineering, School of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 247
- Identifiers
- 99900581857801842
- Language
- English
- Resource Type
- Dissertation