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- All Subjects: Environmental engineering
- Genre: Masters Thesis
- Member of: ASU Electronic Theses and Dissertations
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Description
Iodide (I-) in surface and groundwaters is a potential precursor for the formation of iodinated disinfection by-products (I-DBPs) during drinking water treatment. The aim of this thesis is to provide a perspective on the sources and occurrence of I- in United States (US) source waters based on ~9200 surface water (SW) and groundwater (GW) sampling locations. The median I- concentrations observed was 16 μg/l and 14 μg/l, respectively in SW and GW. However, these samples were rarely collected at water treatment plant (WTP) intakes, where such iodide occurrence data is needed to understand impacts on DBPs. Most samples were collected in association with geochemical studies. We conclude that I- occurrence appears to be influenced by geological features, including halite rock/river basin formations, saline aquifers and organic rich shale/oil formations. Halide ratios (Cl-/I-, Br-/I- and Cl-/Br-) were analyzed to determine the I- origin in source waters. SW and GW had median Cl-/I- ratios of ~3600 μg/μg and median Br-/I- ratios of ~15 μg/μg. For states with I- concentration >50 μg/l (e.g., Montana and North Dakota), a single source (i.e., organic rich formations) can be identified. However, for states like California and Texas that have wide-ranging I- concentration of below detection limit to >250 μg/l, I- occurrence can be attributed to a mixture of marine and organic signatures. The lack of information of organic iodine, inorganic I- and IO3- in source waters limits our ability to predict I-DBPs formed during drinking water treatment, and new occurrence studies are needed to fill these data gaps. This is first of its kind study to understand the I- occurrence through historical data, however we also identify the shortcomings of existing databases used to carry out this study.
ContributorsSharma, Naushita (Author) / Westerhoff, Paul (Thesis advisor) / Lackner, Klaus (Committee member) / Herckes, Pierre (Committee member) / Arizona State University (Publisher)
Created2018
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
Mobile sources emit a number of different gases including nitrogen oxides (NOx) and volatile organic compounds (VOCs) as well as particulate matter (PM10, PM2.5). As a result, mobile sources are major contributors to urban air pollution and can be the dominant source of some local air pollution problems. In general, mobile sources are divided into two categories: on-road mobile sources and non-road mobile sources. In Maricopa County, the Maricopa County Air Quality Department prepares inventories of all local sources [11], [12]. These inventories report that for Maricopa County, on-road mobile sources emit about 23% of total PM2.5 annually, 58% of the total NOx, and 8% of the total VOCs. To understand how future changes how vehicles might impact local air quality, this work focuses on comparing current inventories of PM2.5, black carbon (BC), NOx, and VOCs to what may be expected emissions in future years based on different scenarios of penetration of hybrid gas-electric vehicles (HEV) and electric vehicles (EV) as well as continued reduction in emissions from conventional internal combustion (IC) vehicles. A range of scenarios has been developed as part of this thesis based on literature reports [6], [8], air quality improvement plan documentation [5], projected vehicle sales and registration [3], [4], as well as using EPA’s Motor Vehicle Emission Simulator (MOVES) [9]. Thus, these created scenarios can be used to evaluate what factors will make the most significant difference in improving local air quality through reduced emissions of PM2.5, BC, NOx and VOCs in the future. Specifically, the impact of a greater fraction of cleaner alternative vehicles such as hybrid-electric and electric vehicles will be compared to the impact of continual reductions in emissions from traditional internal combustion vehicles to reducing urban air pollution emissions in Maricopa County.
ContributorsAlboaijan, Fahad A M S (Author) / Fraser, Matthew (Thesis advisor) / Andino, Jean (Committee member) / Lackner, Klaus (Committee member) / Arizona State University (Publisher)
Created2020