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- Creators: Barrett, The Honors College
- Creators: Kavazanjian, Edward
- Creators: Allenby, Braden
- Creators: Cadillo – Quiroz, Hinsby
Description
Microbial fuel cells (MFCs) promote the sustainable conversion of organic matter in black water to electrical current, enabling the production of hydrogen peroxide (H2O2) while making waste water treatment energy neutral or positive. H2O2 is useful in remote locations such as U.S. military forward operating bases (FOBs) for on-site tertiary water treatment or as a medical disinfectant, among many other uses. Various carbon-based catalysts and binders for use at the cathode of a an MFC for H2O2 production are explored using linear sweep voltammetry (LSV) and rotating ring-disk electrode (RRDE) techniques. The oxygen reduction reaction (ORR) at the cathode has slow kinetics at conditions present in the MFC, making it important to find a catalyst type and loading which promote a 2e- (rather than 4e-) reaction to maximize H2O2 formation. Using LSV methods, I compared the cathodic overpotentials associated with graphite and Vulcan carbon catalysts as well as Nafion and AS-4 binders. Vulcan carbon catalyst with Nafion binder produced the lowest overpotentials of any binder/catalyst combinations. Additionally, I determined that pH control may be required at the cathode due to large potential losses caused by hydroxide (OH-) concentration gradients. Furthermore, RRDE tests indicate that Vulcan carbon catalyst with a Nafion binder has a higher H2O2 production efficiency at lower catalyst loadings, but the trade-off is a greater potential loss due to higher activation energy. Therefore, an intermediate catalyst loading of 0.5 mg/cm2 Vulcan carbon with Nafion binder is recommended for the final MFC design. The chosen catalyst, binder, and loading will maximize H2O2 production, optimize MFC performance, and minimize the need for additional energy input into the system.
ContributorsStadie, Mikaela Johanna (Author) / Torres, Cesar (Thesis director) / Popat, Sudeep (Committee member) / Barrett, The Honors College (Contributor) / Chemical Engineering Program (Contributor)
Created2015-05
Description
Currently conventional Subtitle D landfills are the primary means of disposing of our waste in the United States. While this method of waste disposal aims at protecting the environment, it does so through the use of liners and caps that effectively freeze the breakdown of waste. Because this method can keep landfills active, and thus a potential groundwater threat for over a hundred years, I take an in depth look at the ability of bioreactor landfills to quickly stabilize waste. In the thesis I detail the current state of bioreactor landfill technologies, assessing the pros and cons of anaerobic and aerobic bioreactor technologies. Finally, with an industrial perspective, I conclude that moving on to bioreactor landfills as an alternative isn't as simple as it may first appear, and that it is a contextually specific solution that must be further refined before replacing current landfills.
ContributorsWhitten, George Avery (Author) / Kavazanjian, Edward (Thesis director) / Allenby, Braden (Committee member) / Houston, Sandra (Committee member) / Civil, Environmental and Sustainable Engineering Programs (Contributor) / Barrett, The Honors College (Contributor)
Created2013-05
Description
City managers and policy makers are increasing looking to environmental systems to provide beneficial services for urban systems. Constructed wetland systems (CWS), highly managed and designed wetland ecosystems, are being utilized to remove pollution, particularly excess nitrogen (N), from treated wastewater. Various wetland process remove N from effluent, such as denitrification, direct plant uptake, and soil accumulation. Emergent macrophytes provide direct uptake of N and improve conditions for microbially-mediated N processing. The role of different macrophytes species, however, is less understood and has primarily been examined in mesocosm and microcosm experiments and in mesic environments. I examined the effects of community composition on N removal and processing at the whole ecosystem scale in an aridland, constructed wetland (42 ha) through: 1) quantifying above- and belowground biomass and community composition from July 2011 \u2014 November 2012 using a non-destructive allometric technique, and; 2) quantifying macrophyte N content and direct macrophyte N uptake over the 2012 growing season. Average peak biomass in July 2011 & 2012 was 2,930 g dw/m2 and 2,340 g dw/m2, respectively. Typha spp. (Typha domingensis and Typha latifolia) comprised the majority (approximately 2/3) of live aboveground biomass throughout the sampling period. No statistically significant differences were observed in macrophyte N content among the six species present, with an overall average of 1.68% N in aboveground tissues and 1.29% N in belowground tissues. Per unit area of wetland, Typha spp. retained the most N (22 g/m2); total N retained by all species was 34 g/m2. System-wide direct plant N uptake was markedly lower than N input to the system and thus represented a small portion of system N processing. Soil accumulation of N also played a minor role, leaving denitrification as the likely process responsible for the majority of system N processing. Based on a literature review, macrophyte species composition likely influences denitrification through oxygen diffusion into soils and through the quality and quantity of carbon in leaf litter. While this study and the literature indicates Typha spp. may be the best species to promote wetland N processing, other considerations (e.g., bird habitat) and conditions (e.g., type of wastewater being treated) likely make mixed stands of macrophytes preferable in many applications. Additionally, this study demonstrated the importance of urban wetlands as scientific laboratories for scientists of all ages and as excellent stepping-off points for experiments of science-policy discourse.
ContributorsWeller, Nicholas Anton (Author) / Daniel L., Childers (Thesis director) / Grimm, Nancy (Committee member) / Turnbull, Laura (Committee member) / Barrett, The Honors College (Contributor) / School of Sustainability (Contributor) / School of Public Affairs (Contributor) / Graduate College (Contributor)
Created2013-05
Description
Duckponics is an unconventional form of aquaponics that has recently been implemented by a small community in Washington State as an experiment in sustainable methods of food production. The community created the Duckponics system to test the possibility of using the waste of ducks present on the farm to fertilize crop plants. This research paper examines aspects of the nitrogen cycle within this system to determine the efficacy of nitrogen removal by plants and microbes. More specifically, the research examines (1) the microbial activity occurring in selected beds of the system, (2) the ability of hydroponic grow beds to retain inorganic nitrogen, and (3) how periodic flushing of the system affects nitrogen retention. Water data was collected in all system tanks using aquarium test strips, but water samples were collected for flow injection analysis in (1) one of the grow beds, (2) the duck pond, and (3) a control bed with no plants but filled with gravel and inoculated with the same bacteria from the grow bed. Samples were then analyzed for ammonia (NH4+-N) and combined nitrite and nitrate (NOx-N) concentrations. The results show that the treatment type (control, duck pond, or grow bed) was a significant (p<0.05) predictor of NH4+-N, NOx-N, and total inorganic nitrogen (TIN) in the porewater of the treatment beds. The grow bed was found to have 100% removal of TIN, whereas the control had 0% TIN removal (195% increase). Timing of the sample in relation to the flushing events was a moderately significant predictor of TIN, NH4+-N and NOx-N in the duck pond (p = 0.07 for TIN, p = 0.12 for NH4+-N, p = 0.11 for NOx-N), with an overall decrease in TIN after flood pulses. NH4+-N concentrations at the inlet and outlet were found to be significantly different in the grow bed (p=0.037), but not the control, and moderately significantly different (p<0.15) for NOx-N and TIN in the grow bed (p=0.072 for NOx-N, p=0.075 for TIN), but significant for the control (p=0.043). These findings show evidence of nitrification in the grow bed and control, plant presence significantly contributing to nitrogen removal in the grow bed, and some hydrologic flushing of NOx-N out of the duck pond during pump cycles.
ContributorsPanfil, Daniela Kristiina (Author) / Doucette, Sonya (Thesis director) / Palta, Monica (Committee member) / Moody, Jack (Committee member) / Civil, Environmental and Sustainable Engineering Programs (Contributor) / School of Sustainability (Contributor) / W. P. Carey School of Business (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Characterization and Manipulation of Microbiomes From Arid Landfills for Improved Methane Production
Description
Environmentally harmful byproducts from solid waste’s decomposition, including methane (CH4) emissions, are managed through standardized landfill engineering and gas-capture mechanisms. Yet only a limited number of studies have analyzed the development and composition of Bacteria and Archaea involved in CH4 production from landfills. The objectives of this research were to compare microbiomes and bioactivity from CH4-producing communities in contrasting spatial areas of arid landfills and to tests a new technology to biostimulate CH4 production (methanogenesis) from solid waste under dynamic environmental conditions controlled in the laboratory. My hypothesis was that the diversity and abundance of methanogenic Archaea in municipal solid waste (MSW), or its leachate, play an important role on CH4 production partially attributed to the group’s wide hydrogen (H2) consumption capabilities. I tested this hypothesis by conducting complementary field observations and laboratory experiments. I describe niches of methanogenic Archaea in MSW leachate across defined areas within a single landfill, while demonstrating functional H2-dependent activity. To alleviate limited H2 bioavailability encountered in-situ, I present biostimulant feasibility and proof-of-concepts studies through the amendment of zero valent metals (ZVMs). My results demonstrate that older-aged MSW was minimally biostimulated for greater CH4 production relative to a control when exposed to iron (Fe0) or manganese (Mn0), due to highly discernable traits of soluble carbon, nitrogen, and unidentified fluorophores found in water extracts between young and old aged, starting MSW. Acetate and inhibitory H2 partial pressures accumulated in microcosms containing old-aged MSW. In a final experiment, repeated amendments of ZVMs to MSW in a 600 day mesocosm experiment mediated significantly higher CH4 concentrations and yields during the first of three ZVM injections. Fe0 and Mn0 experimental treatments at mesocosm-scale also highlighted accelerated development of seemingly important, but elusive Archaea including Methanobacteriaceae, a methane-producing family that is found in diverse environments. Also, prokaryotic classes including Candidatus Bathyarchaeota, an uncultured group commonly found in carbon-rich ecosystems, and Clostridia; All three taxa I identified as highly predictive in the time-dependent progression of MSW decomposition. Altogether, my experiments demonstrate the importance of H2 bioavailability on CH4 production and the consistent development of Methanobacteriaceae in productive MSW microbiomes.
ContributorsReynolds, Mark Christian (Author) / Cadillo-Quiroz, Hinsby (Thesis advisor) / Krajmalnik-Brown, Rosa (Thesis advisor) / Wang, Xuan (Committee member) / Kavazanjian, Edward (Committee member) / Arizona State University (Publisher)
Created2022
Description
Zero-Valent Metals (ZVM) are highly reactive materials and have been proved to be effective in contaminant reduction in soils and groundwater remediation. In fact, zero-Valent Iron (ZVI) has proven to be very effective in removing, particularly chlorinated organics, heavy metals, and odorous sulfides. Addition of ZVI has also been proved in enhancing the methane gas generation in anaerobic digestion of activated sludge. However, no studies have been conducted regarding the effect of ZVM stimulation to Municipal Solid Waste (MSW) degradation. Therefore, a collaborative study was developed to manipulate microbial activity in the landfill bioreactors to favor methane production by adding ZVMs. This study focuses on evaluating the effects of added ZVM on the leachate generated from replicated lab scale landfill bioreactors. The specific objective was to investigate the effects of ZVMs addition on the organic and inorganic pollutants in leachate. The hypothesis here evaluated was that adding ZVM including ZVI and Zero Valent Manganese (ZVMn) will enhance the removal rates of the organic pollutants present in the leachate, likely by a putative higher rate of microbial metabolism. Test with six (4.23 gallons) bioreactors assembled with MSW collected from the Salt River Landfill and Southwest Regional Landfill showed that under 5 grams /liter of ZVI and 0.625 grams/liter of ZVMn additions, no significant difference was observed in the pH and temperature data of the leachate generated from these reactors. The conductivity data suggested the steady rise across all reactors over the period of time. The removal efficiency of sCOD was highest (27.112 mg/lit/day) for the reactors added with ZVMn at the end of 150 days for bottom layer, however the removal rate was highest (16.955 mg/lit/day) for ZVI after the end of 150 days of the middle layer. Similar trends in the results was observed in TC analysis. HPLC study indicated the dominance of the concentration of heptanoate and isovalerate were leachate generated from the bottom layer across all reactors. Heptanoate continued to dominate in the ZVMn added leachate even after middle layer injection. IC analysis concluded the chloride was dominant in the leachate generated from all the reactors and there was a steady increase in the chloride content over the period of time. Along with chloride, fluoride, bromide, nitrate, nitrite, phosphate and sulfate were also detected in considerable concentrations. In the summary, the addition of the zero valent metals has proved to be efficient in removal of the organics present in the leachate.
ContributorsPandit, Gandhar Abhay (Author) / Cadillo – Quiroz, Hinsby (Thesis advisor) / Olson, Larry (Thesis advisor) / Boyer, Treavor (Committee member) / Arizona State University (Publisher)
Created2019
Description
Wastewater treatment plant (WWTP) utilization of combined heat and power (CHP) systems allows for the efficient use of on-site biogas production, as well as increased annual savings in utility costs. In this thesis, a literature review of six CHP prime mover technologies is presented. Even though there are different prime mover technologies, the main ones currently being implemented in WWTPs are micro turbines, fuel cells and reciprocating engines. These prime mover technologies offer varying efficiencies, installation costs and maintenance requirements. The prime movers are also all in different stages of development, leading some to be more currently-in-use than others in WWTPs. Currently reciprocating engines and micro turbines occupy the largest shares of the CHP in WWTP sector.
This thesis will also go in detail into equations and calculations created for a techno-economic assessment for installation and maintenance of a CHP system at a WWTP. The equations and calculations created here were then utilized with data from a typical WWTP in the Southwestern United States to create an accurate case study. In this case study, a payback of 5.7 years and a net present value of $709,000 can be achieved when the WWTP generates over 2,000,000 m3 of biogas per year and utilizes over 36,000 GJ of natural gas per year.
This thesis will also go in detail into equations and calculations created for a techno-economic assessment for installation and maintenance of a CHP system at a WWTP. The equations and calculations created here were then utilized with data from a typical WWTP in the Southwestern United States to create an accurate case study. In this case study, a payback of 5.7 years and a net present value of $709,000 can be achieved when the WWTP generates over 2,000,000 m3 of biogas per year and utilizes over 36,000 GJ of natural gas per year.
ContributorsRiley, Derall (Author) / Milcarek, Ryan (Thesis director) / Villalobos, Rene (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-12
Description
Water is a scarce resource that is recycled through wastewater treatment plants (WWTPs) to help fulfill the demand for water. Agriculture is a large consumer of water, indicating that WWTP-treated water is proportionally applied to crops at a high rate. Recycled water is highly regulated but is capable of containing high-risk pathogens and contaminants despite the efforts of physical and microbial treatments throughout the WWTP process. WWTPs are also producers of biosolids, treated sewage sludge regulated by the EPA that can be applied in agricultural settings to act as a fertilizer. Biosolids are a useful fertilizer as they are rich in nitrogen and contain many beneficial nutrients for soil and crops. Due to biosolids being a by-product of recycled water, they are susceptible to containing the same pathogens and contaminants that can be transferred in the WWTP systems. Antibiotic resistance (AR) is an ever-growing threat on a global scale and is one of the areas of concern for consideration of pathogen spread from WWTPs. Antibiotic resistance bacteria, created through mutation of bacterial plasmids producing antibiotic resistance genes (ARGs), have been quantified and studied to help mitigate the risk posed by continued AR spread in the environment. This study aims to produce a comprehensive collection of quantified ARG concentration data in biosolids, as well as producing a QMRA model integrating Monte Carlo distributions to provide groundwork for understanding of the direct dosage and consumption of ARGs to the standard U.S. citizen. The study determined that sul1, sul2, tetM, and tetO are ARGs of high concern in biosolid samples based on current concentration data of biosolid samples. The resulting dose models and gene concentration distributions provide data to support the need to mitigate AR risk presented by agricultural biosolid application.
ContributorsMorgan, Grace (Author) / Hamilton, Kerry (Thesis director) / Muenich, Rebecca (Committee member) / Barrett, The Honors College (Contributor) / Harrington Bioengineering Program (Contributor)
Created2022-05