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Title:Ex situ biodegradation of explosives using photosynthetic bacteria and biological granular activated carbon systems
Author(s):Millerick, Kayleigh
Director of Research:Finneran, Kevin T.
Doctoral Committee Chair(s):Werth, Charles J.
Doctoral Committee Member(s):Finneran, Kevin T.; Strathmann, Timothy J.; Freedman, David L.
Department / Program:Civil & Environmental Eng
Discipline:Environ Engr in Civil Engr
Degree Granting Institution:University of Illinois at Urbana-Champaign
Research Department Explosive (RDX)
Rhodobacter sphaeroides
Granular Activated Carbon (GAC)
electron shuttles
Abstract:Military explosives have been identified globally as anthropogenic groundwater contaminants. Communication with the US Army indicates that ex situ pump and treat, a strategy that intercepts contaminated groundwater and pumps it aboveground for treatment, will continue to be the default treatment approach for explosives-laden groundwater in the foreseeable future. This project investigates potential ex situ treatment strategies that could be used as alternatives to the unsustainable activated carbon systems currently in use. Part I examines current activated carbon practices and tests experimentally whether GAC pre-adsorbed with the high explosive RDX can be biologically regenerated. Part II evaluates photosynthetic Rhodobacter sphaeroides as a potential ex situ treatment option for explosives, to be used in lieu of activated carbon. Both focus on biotransformation by bacterial pure cultures. Experiments were conducted as small-scale batch reactors with amendments of both chemicals and bacteria (suspended cells and growing transfers). Reduction of adsorbed RDX was investigated using three different electron sources: biological, chemical, and a mixed biological-chemical system. Each experimental system was capable of ≥ 97.0% adsorbed RDX transformation. Formaldehyde (daughter product) was produced rapidly and was stoichiometric in chemical systems, which operated more rapidly than systems with bacteria. All systems were able to transform adsorbed RDX within 90 hours. This is the first study to successfully demonstrate biological transformation of RDX adsorbed to GAC. Following experimentation, GAC could be re-used for removal of RDX from water. These data suggest the masses of GAC waste currently produced by activated carbon at RDX remediation sites can be minimized. Photosynthetic studies demonstrate that Rhodobacter sphaeroides can biologically transform RDX and novel insensitive munitions (IMs), which will replace the explosive TNT in many next generation explosives. R. sphaeroides degraded RDX and IMs within 72 hours under light conditions. Photosynthetic electron transfer is identified as the degradation mechanism. Additional experiments with RDX showed that succinate and malate were the most effective reducing equivalents for photosynthetic reactions; however, biodiesel-derived waste glycerol was also utilized as an electron donor. RDX was transformed irrespective of the presence of carbon dioxide. Electron shuttling compounds increase degradation kinetics in the absence of CO2. In conditions where CO2 was present (and growth possible), the electron shuttling compound had no stimulatory effect. End products indicated that much of the RDX carbon became CO2 and biomass, but a fraction became a soluble, aqueous metabolite, characterized using 14C-labeled RDX. End products for IMs were consistent with reduction metabolites present in the literature. The presence of high explosive RDX did not inhibit photosynthetic growth of R. sphaeroides, and growing cultures consistently degraded spikes of RDX over 480 hours. These data are the first to suggest that photobiological RDX and insensitive munitions degradation is possible.
Issue Date:2014-05-30
Rights Information:Copyright 2014 Kayleigh Millerick
Date Available in IDEALS:2014-05-30
Date Deposited:2014-05

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