Date of Award
5-14-2024
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Wastewater is a common waste produced from municipal, agricultural, and industrial processes. As the world’s population increases, the amount of wastewater produced globally is expected to reach approximately 450 billion m3 in the next two decades. Issues surrounding water, food, and energy accessibility will also become more imminent as the population grows. Interestingly, wastewater is an unconventional source of resources including water, nutrients (e.g., NH4+ and PO43-), and energy. However, conventional wastewater treatment processes focus primarily on the removal of containments rather than the recovery of resources. Bioelectrochemical systems (BES) have the ability to recover resources from wastewater. These engineered systems take advantage of microbial oxidation of organics to generate electricity. Incorporation of ion exchange membranes can also promote the separation of nutrients. Two common types of BES are microbial fuel cells (MFCs) and microbial electrolysis cells (MECs). However, shortcomings including relatively low energy production and high material costs oftentimes deter justification of BES implementation over conventional methods. Other processes and technologies such as forward osmosis (FO), membrane contactor (MC), and thermoelectric generators (TEGs) have similar issues when comparing the advantages and disadvantages of the recovery system. Coupling BES with other recovery approaches could potentially achieve synergy and optimize resource recovery from wastewater. However, systematic investigation of BES coupled systems to understand their potential as effective recovery systems is insufficient. This dissertation has three research objectives: (1) investigate forward osmosis as a pretreatment step for microbial fuel cell treatment, (2) explore membrane contactor integration with microbial fuel cell technology as a sustainable resource recovery method, and (3) investigate thermoelectric generators as an alternative power supply for microbial electrolysis cells. 1. Investigate forward osmosis as a pretreatment step for microbial fuel cell treatment. Chapter 2 describes methods used for removal and recovery of reverse fluxed solutes during FO operation. Chapter 3 investigates two draw solutes (NaCl and NH4HCO3) for FO water recovery and the effects that draw solutes have on coupled MFC performance. Holistic evaluations based on energy consumption, COD removal, ammonium removal and recovery, and water recovery were used to compare the coupled systems. 2. Explore membrane contactor integration with microbial fuel cell technology as a sustainable resource recovery method. Chapter 4 explores MC as a non-energy intensive approach to recover volatile fatty acids (VFAs) and ammonium. The effect osmotic distillation has on VFA and ammonium recovery, economic feasibility, and optimal operation conditions are explored as well. Chapter 5 incorporates MC into MFC treatment to compare air stripping and membrane separation as ammonium recovery methods. Different system configurations and parameters were analyzed to determine optimal operation conditions. 3. Investigate thermoelectric generators as an alternative power supply for microbial electrolysis cells. Chapter 6 presents TEGs as an alternative energy source that can be used to power an MEC for hydrogen generation. First, the TEGs were characterized for performance based on temperature gradient and recirculation rate of the hot and cold sources. Then, the TEG powered MEC was evaluated based on variables including Coulombic efficiency, hydrogen production rate, and maximum power density. Overall, this dissertation seeks to better understand the synergy that can be achieved by coupling BES with membrane processes and alternative energy sources, as well as how we evaluate these systems in terms of their effectiveness. It also seeks to provide insight on challenges that need to be addressed for real world implementation of these coupled systems.
Language
English (en)
Chair
Zhen He