Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
Displaying 1 - 7 of 7
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- All Subjects: Environmental engineering
- Creators: Boyer, Treavor
Description
This research aims to develop an understanding of how interventions designed to improve water quality in buildings can be used to mitigate Legionella pneumophila concentrations. Intervention methods can be described as any approach that can be used to improve microbial water quality. In order to provide a foundation of background knowledge, a literature review was conducted to identify similar studies and collect relevant and timely research similar to the subject. The information gathered from the literature review was used to structure the sampling process and parameters. Using the research collected from the literature review, a review table was created to summarize the differences in the studies conducted and to determine research gaps. To categorize the studies, intervention methods, contaminants addressed, and water quality meta-data were differentiated for each of the articles. For the purpose of the sampling process, the three interventions analyzed consist of flushing, water heater set point change, and both flushing and water heater set point change. The locations of the sampling consisted of the city drinking water inlet, the basement janitor's closet, basement shower, 2nd floor, 3rd floor, and 7th floor break rooms and restrooms of the Interdisciplinary Science and Technology Building IV at ASU. For the flushing intervention, the sampling results demonstrated an increase in free and total chlorine concentration post flushing which aligns with the research found in the literature review. In addition, it was observed that iron concentrations drastically increased for both the cold and hot water by flushing. There was a significant decrease detected for ATP concentrations post flush in the hot line. However through the sampling session, the flushing intervention did not yield statistically significant results for Legionella concentrations.
ContributorsCahill, Molly (Author) / Call, Kathryn (Co-author) / Johnson, Elizabeth (Co-author) / Kotta, Vishnu (Co-author) / Hamilton, Kerry (Thesis director) / Boyer, Treavor (Committee member) / Barrett, The Honors College (Contributor) / School of Sustainable Engineering & Built Envirnmt (Contributor)
Created2023-05
Description
Efforts to enhance the quality of life and promote better health have led to improved water quality standards. Adequate daily fluid intake, primarily from tap water, is crucial for human health. By improving drinking water quality, negative health effects associated with consuming inadequate water can be mitigated. Although the United States Environmental Protection Agency (EPA) sets and enforces federal water quality limits at water treatment plants, water quality reaching end users degrades during the water delivery process, emphasizing the need for proactive control systems in buildings to ensure safe drinking water.Future commercial and institutional buildings are anticipated to feature real-time water quality sensors, automated flushing and filtration systems, temperature control devices, and chemical boosters. Integrating these technologies with a reliable water quality control system that optimizes the use of chemical additives, filtration, flushing, and temperature adjustments ensures users consistently have access to water of adequate quality. Additionally, existing buildings can be retrofitted with these technologies at a reasonable cost, guaranteeing user safety.
In the absence of smart buildings with the required technology, Chapter 2 describes developing an EPANET-MSX (a multi-species extension of EPA’s water simulation tool) model for a typical 5-story building. Chapter 3 involves creating accurate nonlinear approximation models of EPANET-MSX’s complex fluid dynamics and chemical reactions and developing an open-loop water quality control system that can regulate the water quality based on the approximated state of water quality. To address potential sudden changes in water quality, improve predictions, and reduce the gap between approximated and true state of water quality, a feedback control loop is developed in Chapter 4.
Lastly, this dissertation includes the development of a reinforcement learning (RL) based water quality control system for cases where the approximation models prove inadequate and cause instability during implementation with a real building water network. The RL-based control system can be implemented in various buildings without the need to develop new hydraulic models and can handle the stochastic nature of water demand, ensuring the proactive control system’s effectiveness in maintaining water quality within safe limits for consumption.
ContributorsGhasemzadeh, Kiarash (Author) / Mirchandani, Pitu (Thesis advisor) / Boyer, Treavor (Committee member) / Ju, Feng (Committee member) / Pedrielli, Giulia (Committee member) / Arizona State University (Publisher)
Created2023
Description
The current level of carbon dioxide in ambient air is increasing and reinforcing the severity of global warming. Several techniques have been developed to capture the gas directly from the air. Moisture swing absorption (MSA) is a mechanism through which a reactive surface, namely resin beads, absorbs carbon dioxide when dry and releases it when wet. The ionic complexity of the surface of the bead interacts with CO2 when H2O contents are low, and CO2 diffuses as bicarbonate or carbonate. Hence, diffusion-drift-reaction equations describe the moving species behavior MS sorbent. A numerical model has been developed previously applying finite difference scheme (FDS) to estimate the evolution of species concentrations over uniform time and space intervals. The methodology was based on a specific membrane and bead geometry. In this study, FDS was employed again with modifications over the boundary conditions. Neumann boundary condition was replaced by Robin boundary condition which enforced diffusion and drift fluxes at the center of the sorbent. Furthermore, the generic equations were approximated by another numerical scheme, Finite volume scheme (FVS), which discretizes the spatial domain into cells that conserves the mass of species within. The model was predicted to reduce the total carbon mass loss within the system. Both schemes were accommodated with a simulated model of isolated chamber that contained arbitrary sorbent. Moreover, to derive the outcomes of absorption/desorption cycles and validate the performance of FVS, Langmuir curve was utilized to obtain CO2 saturation in the sorbent and examine two scenarios: one by varying the partial pressure of CO2 (PCO2) in the chamber at constant H2O (PH2O), or changing PH2O at constant PCO2. The results from FDS approximation, when adjusting the center with Robin boundary condition, show 0.11% lower carbon mass gain than when applying Neumann boundary condition. On the other hand, FVS minimizes the mass loss by 0.3% lower than the original total carbon mass and achieves sorbent saturation without any adjustment. Moreover, the isotherm curve demonstrates that increasing PH2O reduces CO2 saturation and is dependent on the linear and non-linear correlations used to estimate water concentration on the surface.
ContributorsMejbel, Meteb (Author) / Lackner, Klaus (Thesis advisor) / Boyer, Treavor (Committee member) / Wang, Zhihua (Committee member) / Arizona State University (Publisher)
Created2021
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
Humans are exposed up to thousands of per- and polyfluoroalkyl substances (PFAS) in the environment, but most of the research and action has been directed towards only two PFAS compounds. These two compounds are part of a subcategory of PFAS called perfluoroalkyl acids (PFAAs). It has been a challenge for the environmental community to mitigate risks caused by PFAAs due to their high persistence and lack of effective measures to remove them from the environment, especially in heavily impacted areas like fire-training sites. The goal of this work was to further answer some questions regarding the removal of PFAAs in the environment by looking at anion exchange resin characteristics and presence of a competing compound, natural organic matter (NOM), in the adsorption of environmentally relevant PFAS compounds including the two often monitored 8-carbon chain PFAAs. Two different resins were tested with two forms of counterions, in both groundwater and NOM impacted groundwater. Resin polymer matrix was the most important property in the adsorption of PFAAs, the two resins used A520E and A860 had similar properties except for their matrices polystyrene (PS) and polyacrylic (PA), respectively. The PS base is most effective at PFAAs adsorption, while the PA is most effective at NOM adsorption. The change in the counterion did not negatively affect the adsorption of PFAAs and is, therefore, a viable alternative for future studies that include regeneration and destruction of PFAAs. The presence of NOM also did not significantly affect the adsorption of PFAAs in the PS resin A520E, although for some PFAAs compounds it did affect adsorption for the PA resin. Ultimately, PS macroporous resins with a strong Type I or Type II base work best in PFAAs removal.
Contributorsdel Moral, Lerys Laura (Author) / Boyer, Treavor (Thesis advisor) / Abbaszadegan, Morteza (Committee member) / Hamilton, Kerry (Committee member) / Arizona State University (Publisher)
Created2019
Description
The escalating global demand for food production underscores the urgent need for sustainable agricultural innovations. This research contributes new insights into the environmental benefits of using urine-derived phosphorus (P) fertilizers by closing the nutrient loop and applying the technology to agricultural food systems. Anticipatory life cycle assessment was used to quantify the environmental impacts of replacing conventionally mined P fertilizer with recovered urine-derived P fertilizer within the production of beef and plant-based burgers. Results shows that implementing recovered P fertilizer provides greater environmental benefits for all environmental impact categories, with global warming, eutrophication, and water consumption being the main impact categories examined in this study. Urine-derived P fertilizer use in beef burger production led to a 4% reduction in global warming impacts (3% for plant-based), 15% reduction in eutrophication (2% for plant-based), and 42% reduction in water consumption (46% for plant-based). Uncertainty in the results was accounted for using Monte Carlo simulation with 10,000 runs to rank the four burger production scenarios (e.g., conventional and urine-derived beef burger and conventional and urine-derived plant-based burger) based on their environmental impact on global warming, eutrophication, and water use under conditions of baseline, realistic, and maximum uncertainty. Under conditions of realistic uncertainty, implementing urine-derived P fertilizer for beef burger production was considered beneficial for global warming, eutrophication, and water consumption, with 78%, 99%, and 89% of the runs showing environmental benefits, respectively. Due to the lower P fertilizer requirements in plant-based burger production, uncertainty assessment under realistic conditions showed that a reduction in water use was the only expected benefit of implementing recovered P fertilizer, with 71% of the runs providing water use benefits. These results show that closing the nutrient loop by implementing urine-derived P fertilizers can be beneficial when applied to the correct agricultural food system (e.g., beef burger production) and is expected to have the most pronounced benefits with regard to water savings.
ContributorsEvans, Dilan (Author) / Boyer, Treavor (Thesis advisor) / Ravikumar, Dwarak (Thesis advisor) / Westerhoff, Paul (Committee member) / Arizona State University (Publisher)
Created2024
Description
Waterborne opportunistic pathogens, particularly non-tuberculous mycobacteria(NTM), pose significant challenges to public health. This study aims to address critical gaps in understanding mycobacterial succession within premise plumbing systems, focusing on diversity, morphology, and factors influencing persistence. A premise plumbing pipe rack experiment was conducted with various pipe materials under real-world conditions. Water samples were collected and analyzed for NTM presence using culture-based and molecular techniques. During the cultivation of various isolates, two main morphologies were noted, revealing insights into the dynamics of mycobacterial communities within premise plumbing systems. Polymerase chain reaction (PCR) analysis attributed the yellow colonies to M. intracellulare or M. chimaera, while the white colonies represented unidentified mycobacterial species. The temporal dynamics of mycobacterial presence, assessed through PCR analysis over 7 weeks, demonstrated fluctuations influenced by source water conditions and disinfectant levels. Different pipe materials exhibited varying levels of mycobacterial colonization, with PVC pipes showing the highest percent positive. Species-level PCR analysis revealed dominance of M. intracellulare/M. chimaera in copper and PEX pipes, while "other" species were more prevalent in PVC pipes. The dominance of human-relevant species raises concerns for health, particularly among immunocompromised individuals. Future sequencing work is necessary to distinguish between M. intracellulare and M. chimaera, a differentiation that could provide valuable insights into the sources and transmission routes of these pathogens in the environment.
ContributorsCahill, Molly (Author) / Hamilton, Kerry A (Thesis advisor) / Boyer, Treavor (Committee member) / Voth-Gaeddert, Lee (Committee member) / Arizona State University (Publisher)
Created2024