Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 121-128). Also available on the World Wide Web.

Microbial fuel cells (MFCs) are alternative energy resources that generate electricity from organic matter, where microorganisms such as the Geobacter species oxidize organic waste and transfer electrons to an electrode. Mathematical models are used to study biofilm processes, in hopes of developing MFCs into commercial applications. Existing biofilm models are based on Nernst-Monod type expressions, and are restricted to studying extracellular electrochemical/microbiological components, separated from the metabolic behavior of microorganisms. In this thesis, a model was developed combining extracellular biofilm conditions, with the intracellular metabolic fluxes of microorganisms under spatial heterogeneities (electron donor/acceptor levels) across the biofilm. This model predicts biofilm processes under varying extracellular conditions (presence/absence of NH4+, shear stress in continuous mode MFCs), and intracellular conditions (ATP maintenance fluxes); and also provides a preliminary evaluation of the pH changes across the biofilm. A sensitivity analysis based on the cell density and the biofilm conductivity was also conducted.

Microbial fuel cells (MFCs) are alternative energy resources that generate electricity from organic matter, where microorganisms such as the Geobacter species oxidize organic waste and transfer electrons to an electrode. Mathematical models are used to study biofilm processes, in hopes of developing MFCs into commercial applications. Existing biofilm models are based on Nernst-Monod type expressions, and are restricted to studying extracellular electrochemical/microbiological components, separated from the metabolic behavior of microorganisms. In this thesis, a model was developed combining extracellular biofilm conditions, with the intracellular metabolic fluxes of microorganisms under spatial heterogeneities (electron donor/acceptor levels) across the biofilm. This model predicts biofilm processes under varying extracellular conditions (presence/absence of NH4+, shear stress in continuous mode MFCs), and intracellular conditions (ATP maintenance fluxes); and also provides a preliminary evaluation of the pH changes across the biofilm. A sensitivity analysis based on the cell density and the biofilm conductivity was also conducted.

Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 92-100). Also available on the World Wide Web.

Thesis (PhD)--Montana State University--Bozeman, 2010. / Typescript. Chairperson, Graduate Committee: Ron Larsen. Includes bibliographical references (leaves 106-114).

Wastewater treatment is an energy intensive process and sustainable processes/technologies for the treatment of wastewaters need to be considered. One such contender might be the microbial fuel cell (MFC), a subset of bioelectrochemical system (BES) which generates electricity in the process of electrogenic (generating electrons) degradation of soluble organic contaminants present in the water (or wastewater) by electrogens (electron producing bacteria) at the anode in absence of oxygen. Several issues related to the power performance (also somewhat linked to the cost) of MFCs exist causing barriers in the deployment of up-scaled MFC system and the continual research from a multitude of discipline is focusing on overcoming these issues. Implementation of an MFC system for wastewater treatment would require a large array of MFCs to meet the treatment capacity of the wastewater treatment plant. Commissioning and continual operation of such MFCs would require rapid and cost-effective start-up and improvement in their performance. Optimisation of the power performance is addressed through a systems approach in this study, where improvement in the performance is sought through the system design and control strategies applied to the MFCs. The start-up rate of MFCs has been reduced by 45% using maximum power point tracking (MPPT), which is believed to be cost-effective as exogenous energy (such as in the case of poised-potential) is not required for the rapid start-up. The control of MFC power would need to be considered when up-scaled MFC system is realised. The controller implementation benefits from linearised system models. The viability of such piecewise linearisation of the nonlinear MFC system was demonstrated and the data were shown to be reasonably represented by the 1st order process models throughout its operating range. The occurrence of voltage reversal during stack operation of MFCs is a concern in large arrays particularly, and has been shown to be avoidable by adopting the hybrid stack connectivity. Further enhancement of the performance was sought through the detailed design and fluid dynamics modeling to obtain highly mixed anolyte at low input power, using improved helical anodes which increased the MFC performance at all the tested flow rates (1, 3 and 8 mL min-1) compared to previously studied helical anodes. The up-scaling of MFCs by modularisation was demonstrated and it was shown that the use of improved helical anodes can increase the modular length of the MFC without compromising the power performance. Aggregated power produced from the multi-module MFC (containing 5 modules) was 28.05 ± 3.5 mW (19.75 ± 2.47 W m-3) with an PhD Thesis – Hitesh Chandubhai Boghani 2014 V individual MFC power of 5.61 ± 0.7 mW, when fed with 10 mM sodium acetate at 3 mL min-1 flow rate and at 22 ± 3 °C. So, this thesis presents the strategies for improvement in the performance of MFCs for their applications in wastewater treatment and such strategies may also be transferable to their other applications.

One contemporary issue experienced worldwide is the climate change due to the combustion of fossil fuels. Microbial Electrochemical Systems pose as an alternative for energy generation. In this technology, microorganisms are primarily responsible for electricity production. To improve the performance it is reasonable to think that bacteria from diverse environments, such as the brine pools of the Red Sea, can be utilized in these systems. Samples from three brine pools: Atlantis II, Valdivia, and Kebrit Deeps, were analyzed using Microbial Electrochemical Cells, with a poised potential at +0.2 V (vs. Ag/AgCl) and acetate as electron donor, to evaluate the exoelectrogenic activity by the present microorganisms. Only samples from Valdivia Deep were able to produce a noticeable current of 6 A/m2. This result, along with acetate consumption and changes on the redox activity measured with cyclic voltammetry, provides arguments to con rm the presence of exoelectrogenic bacteria in this environment. Further characterization using microscopy and molecular biology techniques is required, to obtain the most amount of information about these microorganisms and their potential use in bioelectrochemical technologies.

Microbial fuel cells (MFCs) are potentially advantageous as an energy-efficient approach to wastewater treatment. For single-chamber tubular MFCs, anode effluent is used as catholyte instead of tap water or buffer solutions. Therefore, exposing cathode electrode to atmosphere could be also considered as a passive aeration for further aerobic oxidation of organics and nitrification. Based on several bench-scale studies, a 200-L scale MFC system with passive aeration process has been developed for treating actual municipal wastewater after primary clarification. The integrated system was able to remove over 80% organic contaminants and solid content from primary effluent. Through parallel and serial electricity connection, the power output of ~200 mW and the conversion efficiency of ~80% for charging capacitors were achieved by using commercially available energy harvesting device (BQ 25504). The treatment system is energy-efficient for the energy saving from aeration and sludge treatment while partial energy recovery as direct electricity can be utilized on site to power small electric devices. However, the post treatments are required to polish the effluent for nutrients removal. / Ph. D.

Microbial fuel cells (MFCs) are potentially advantageous as an energy-efficient approach for wastewater treatment. Integrating membrane filtration with MFCs could be a viable option for advanced wastewater treatment with a low energy input. Such an integration is termed as membrane bioelectrochemical reactors (MBERs). Comparing to the conventional membrane bioreactors or anaerobic membrane bioreactors, MBER could be a competitive technology, due to the its advantages on energy consumption and nutrients removal. By installing the membrane in the cathodic compartment or applying granular activated carbon as fluidized bed materials, membrane fouling issue could be alleviated significantly. In order to drive MBER technology to become a more versatile platform, applying anion exchange membrane (AEM) could be an option for nutrients removal in MBERs. Wastewater can be reclaimed and reused for subsequent fermentation use after a series MFC-MBR treatment process. Such a synergistic configuration not only provide a solution for sustainable wastewater treatment, but also save water and chemical usage from other non-renewable resource. Integrating membrane process with microbial fuel cells through an external configuration provides another solution on sustainable wastewater treatment through a minimal maintenance requirement. / Ph. D.

A dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science. April, 2015 / Microbial fuel cell (MFC) technology presents great potential for use as a dual system for industrial waste water remediation and electricity generation. The hurdle in up-scaling this technology has been identified as MFC-bioreactor architecture, both with regards to bioremediation and carbon source to electricity conversion rates. In addition to the latter’s limitations, the use of expensive mediators and membrane to enhance MFC performance renders the technology uneconomic to employ industrially. A 60mm high double chamber membrane and mediator-less MFC-bioreactor was designed, and constructed. The novel MFC-bioreactor made of transparent polyacrylic plastic had a total working volume of 8 litres with the anode chamber situated at the bottom and the cathode chamber at the top separated by a 10cm deep artificial membrane made up of glass wool, glass beads and marble balls. The MFC was operated under various operating parameters including; feeding modes (batch and continuous), with different substrate concentration at a range of external resistance (100-9000Ω) .The voltage produced during MFC operation was monitored and used to estimate the power density output of the MFC. The pseudo membrane was able to sufficiently separate the anode and cathode chambers allowing the development of potential difference and hence generation of current. The MFC demonstrated the potential for sustainable operation by producing and maintaining a stable power density of 2000mW/m2 when operated with an external resistance of 1000Ω. This power density was accompanied by a 73% remediation efficiency of the synthetic wastewater. It was concluded that the results of this research show proof of concept for a membrane-less MFC that can produce electrical energy in the absence of an electron shuffling mediator.