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Title: Bioelectrochemically-enhanced remediation of contaminated groundwater
Author: Hedbavna, Petra
ISNI:       0000 0004 5992 0557
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2016
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Plumes of organic chemicals in groundwater are frequently anaerobic due to limitations in the availability and aqueous solubility of oxygen. As biodegradation rates for anaerobic processes are usually slower than for aerobic processes, plumes of organic contaminants may persist in groundwater. A novel, but under-developed, approach to enhance the anaerobic bioremediation of organic compounds in groundwater is to couple the exchange of electrons between bacteria and solid state electrodes. In this case, electrodes inserted into the subsurface serve as an inexhaustible electron acceptor for microbial metabolism of organic compounds. It was shown in laboratory bioelectrochemical systems (BESs) that the presence of an electrode can enhance biodegradation of organic contaminants such as petroleum hydrocarbons, phenol, benzene, naphthalene, phenanthrene and pyrene. However, these laboratory experiments used inocula from sources other than groundwater and often supplied bacteria with mineral media, nutrients, vitamins and single carbon sources. This fails to represent the in situ conditions in most aquifers. In this thesis, the biodegradation rate of phenols and their metabolites in contaminated groundwater was evaluated in a laboratory-scale microbial fuel cell (MFC). The groundwater microbial community development in the MFC was studied subsequently. The tested contaminated groundwater contained a mixture of phenolic compounds (phenol and isomers of cresols and xylenols) and acetate as a product of fermentation of phenols. The electro-active bacteria, likely to be Desulfuromonas sp. from Geobacteraceae family, attached to the electrode and used acetate as an electron donor for electricity generation (~1.8 mW/m2 of projected electrode surface area). Biodegradation of acetate was enhanced in the presence of an electrode acting as an electron acceptor. Enhanced biodegradation of phenols occurred after complete acetate removal. The original groundwater microbial community was more diverse than the community developed in the MFCs as only a few bacterial species were dominating the latter. The results demonstrate that it is crucial to identify compound(s) utilised by exoelectrogens as electron donor(s) to implement bioelectrochemically-enhanced remediation of organic contaminants. It is likely that electro-active bacteria will not directly degrade the contaminants but utilise their metabolites. Microbial community will undergo significant changes after the introduction of BES electrodes in the aquifer. Hence, knowledge of biodegradation pathways of the parent compound(s) to the electron donating metabolite and their regulation, as well as the cell-cell interactions and carbon flow in the microbial community, is critical for successful application of remediation BESs at the field scale.
Supervisor: Thornton, Steven F. ; Rolfe, Stephen A. ; Huang, Wei E. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available