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Title: Experimental study of gravity tectonics
Author: Blay, Paul Kwesi
ISNI:       0000 0001 3467 8547
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1974
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The use of energy in wastewater treatment is becoming a significant issue in both the public and private sectors, with municipal water and waste treatment in the USA accounting for 1.4% of the total national electricity usage and estimated to cost in excess of $4 billion annually. Lowering electricity consumption in this area will help to reduce CO2 emissions and offset the economic cost of wastewater treatment. Research into renewablefuel technology has begun to attempt to address the issue of utilising the metabolic diversity of certain prokaryotes housed within "microbial fuel cells" (MFCs) as a means of electricity generation from waste materials. A novel continuous flow MFC was developed in this project in which the fuel cell housing is made from an electrically conductive and chemically resistant conductive carbon composite, enabling direct electrical connections to be easily achieved between the internal electrode materials. The uniform and efficient flow of liquid across the electrode material achieved through the use of calming channels at the inflow and effluent paints will minimise the possibility of electron donor or acceptor limitation within the MFCs. This continuous flow MFC generated higher power outputs, voltages and currents, than a Htype system previously used. Environmental samples, obtained from Crosby Marine Lake (CML) and the Albert Dock (AD) Liverpool, were subjected to a series of enrichment steps within the continuous MFC system. The enrichment strategies employed in generating diverse microbial populations and the subsequent changes to the operational conditions of the MFC stack configurations, led to an improvement in the electrical output and the coulombic efficiency of the system in comparison to experiments using Shewanella oneidensis as a model organism. It was found that an electrically "in parallel" configuration was associated with a higher level of performance and avoided the detrimental voltage reversals found in the stacks connected electrically "in series". The maximum series stack voltage achieved was 1,222 mV, while the maximum parallel stack current and power density were 2.307 mA and 95 W m-3 of total anodic compartment. Because the CML-MFC and AD-MFC enrichments generated highest currents, voltages, and power outputs over extended time periods in a number of experimental runs.Microbial populations were selected for phylogenetic analysis using high throughput 454 pyrosequencing. A volatile fatty acid (VFA) waste stream obtained from a novel anaerobic wastewater treatment process was used within the MFC system, initially as both the inoculum source and to provide the organic compounds necessary to power the device. In both configurations the MFCs using the VFA performed poorly in comparison with the experiments using complex or defined growth media as model waste streams. The enrichment strategy employed to generate the diverse highly active microbial populations in this investigation led to an improvement in terms of both the electrical output and the coulombic efficiency of the system in comparison to the previous experiments using S. oneidensis. Phylogenetic analysis using high throughput sequencing methods revealed that at the class level the CML / CML-MFC.2 and AD / AD-MFC.2 amplicon library pairs contained a number of shared taxa. However at the species level the most numerically dominant OTUs present in the MFC enrichments were not identified in the original environmental samples. Dominant taxa found in the CML-MFC.2 and AD-MFC.2 amplicon libraries had a greater degree of similarity down to the genus level, with a number of species common to both MFC enrichments being identified. The most common species identified in the two MFC enrichments were quite rare, only accounting for 1.28 % of the normalized amplicon libraries. Both the MFC enrichments generated in this investigation were dominated by reads assigned to the phyla Proteobacteria and Firmicutes and their associated classes, which have also been found in other studies investigating the bacterial populations present within MFCs.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available