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- Creators: Hindemith, Paul, 1895-1963
Description
Nitrate is the most prevalent water pollutant limiting the use of groundwater as a potable water source. The overarching goal of this dissertation was to leverage advances in nanotechnology to improve nitrate photocatalysis and transition treatment to the full-scale. The research objectives were to (1) examine commercial and synthesized photocatalysts, (2) determine the effect of water quality parameters (e.g., pH), (3) conduct responsible engineering by ensuring detection methods were in place for novel materials, and (4) develop a conceptual framework for designing nitrate-specific photocatalysts. The key issues for implementing photocatalysis for nitrate drinking water treatment were efficient nitrate removal at neutral pH and by-product selectivity toward nitrogen gases, rather than by-products that pose a human health concern (e.g., nitrite). Photocatalytic nitrate reduction was found to follow a series of proton-coupled electron transfers. The nitrate reduction rate was limited by the electron-hole recombination rate, and the addition of an electron donor (e.g., formate) was necessary to reduce the recombination rate and achieve efficient nitrate removal. Nano-sized photocatalysts with high surface areas mitigated the negative effects of competing aqueous anions. The key water quality parameter impacting by-product selectivity was pH. For pH < 4, the by-product selectivity was mostly N-gas with some NH4+, but this shifted to NO2- above pH = 4, which suggests the need for proton localization to move beyond NO2-. Co-catalysts that form a Schottky barrier, allowing for localization of electrons, were best for nitrate reduction. Silver was optimal in heterogeneous systems because of its ability to improve nitrate reduction activity and N-gas by-product selectivity, and graphene was optimal in two-electrode systems because of its ability to shuttle electrons to the working electrode. "Environmentally responsible use of nanomaterials" is to ensure that detection methods are in place for the nanomaterials tested. While methods exist for the metals and metal oxides examined, there are currently none for carbon nanotubes (CNTs) and graphene. Acknowledging that risk assessment encompasses dose-response and exposure, new analytical methods were developed for extracting and detecting CNTs and graphene in complex organic environmental (e.g., urban air) and biological matrices (e.g. rat lungs).
ContributorsDoudrick, Kyle (Author) / Westerhoff, Paul (Thesis advisor) / Halden, Rolf (Committee member) / Hristovski, Kiril (Committee member) / Arizona State University (Publisher)
Created2013
Description
The influence of climate variability and reclaimed wastewater on the water supply necessitates improved understanding of the treatability of trace and bulk organic matter. Dissolved organic matter (DOM) mobilized during extreme weather events and in treated wastewater includes natural organic matter (NOM), contaminants of emerging concern (CECs), and microbial extracellular polymeric substances (EPS). The goal of my dissertation was to quantify the impacts of extreme weather events on DOM in surface water and downstream treatment processes, and to improve membrane filtration efficiency and CECs oxidation efficiency during water reclamation with ozone. Surface water quality, air quality and hydrologic flow rate data were used to quantify changes in DOM and turbidity following dust storms, flooding, or runoff from wildfire burn areas in central Arizona. The subsequent impacts to treatment processes and public perception of water quality were also discussed. Findings showed a correlation between dust storm events and change in surface water turbidity (R2=0.6), attenuation of increased DOM through reservoir systems, a 30-40% increase in organic carbon and a 120-600% increase in turbidity following severe flooding, and differing impacts of upland and lowland wildfires. The use of ozone to reduce membrane fouling caused by vesicles (a subcomponent of EPS) and oxidize CECs through increased hydroxyl radical (HO●) production was investigated. An "ozone dose threshold" was observed above which addition of hydrogen peroxide increased HO● production; indicating the presence of ambient promoters in wastewater. Ozonation of CECs in secondary effluent over titanium dioxide or activated carbon did not increase radial production. Vesicles fouled ultrafiltration membranes faster (20 times greater flux decline) than polysaccharides, fatty acids, or NOM. Based upon the estimated carbon distribution of secondary effluent, vesicles could be responsible for 20-60% of fouling during ultrafiltration and may play a vital role in other environmental processes as well. Ozone reduced vesicle-caused membrane fouling that, in conjunction with the presence of ambient promoters, helps to explain why low ozone dosages improve membrane flux during full-scale water reclamation.
ContributorsBarry, Michelle (Author) / Barry, Michelle C (Thesis advisor) / Westerhoff, Paul (Committee member) / Fox, Peter (Committee member) / Halden, Rolf (Committee member) / Hristovski, Kiril (Committee member) / Arizona State University (Publisher)
Created2014
Description
Arsenic (As) and chromium (Cr) occur naturally in AZ surface and groundwaters, pose different health impacts, and exhibit different treatment efficacies. Hexavalent chromium (Cr(VI)) has newly recognized human health concerns, and State and Federal agencies are evaluating a low Cr(VI)-specific maximum contaminant level (MCL) for drinking water. Occurrence of Cr and As in municipal drinking waters and industrial cooling tower waters was quantified by grab samples and compared with sampling results obtained from a new passive sampler developed specifically for Cr(VI). Cr(VI) and As concentrations in groundwater used for cooling tower make-up water concentrations were ~3 ppb and ~4 ppb, respectively, and were concentrated significantly in blowdown water (~20 ppb and ~40 ppb). Based upon pending Cr(VI), As, and other metal regulations, these blowdown waters will need routine monitoring and treatment. Cr(VI) concentrations in a water treatment plant (WTP) raw and finished water samples varied from 0.5 and 2 ppb for grab samples collected every 4 hours for 7 consecutive days using an ISCO sampler. The development of an ion exchange (IX) based passive sampler was validated in the field at the WTP and yielded an average exposure within 1 standard deviation of ISCO sampler grab data. Sampling at both the WTP and cooling towers suggested sources of Cr(III) from treatment chemicals or wood preservatives may exist. Since both facilities use chlorine oxidants, I quantified the apparent (pH=5) second-order rate constant for aqueous chlorine (HOCl/OCl-) with Cr(III) to form Cr(VI) as 0.7 M-1s-1. Under typical conditions (2 ppb Cr(III) ; 2 mg/L Cl2) the half-life for the conversion of Cr(III) to the more toxic form Cr(VI) is 4.7 hours. The occurrence studies in AZ and CA show the Cr(VI) and As treatment of groundwaters will be required to meet stringent Cr(VI) regulations. IX technologies, both strong base anion (SBA) and weak base anion (WBA) resin types were screened (and compared) for Cr removal. The SBA IX process for As removal was optimized by utilizing a reactive iron coagulation and filtration (RCF) process to treat spent IX brine, which was then reused to for SBA resin regeneration.
ContributorsBowen, Alexandra (Author) / Paul, Westerhoff K. (Thesis advisor) / Hristovski, Kiril (Committee member) / Halden, Rolf (Committee member) / Arizona State University (Publisher)
Created2014
Description
In an effort to stress the benefits of the application of renewable energy to the next generation of science, technology, engineering, arts, and mathematics (STEAM) professionals, instructional modules on energy and biogas were integrated into a summer camp curriculum that challenged students to apply STEAM concepts in the design and development of chain reaction machines. Each module comprised an interactive presentations and a hands-on component where students operated a manipulative relevant to the content. During summer 2013, this camp was implemented at two high schools in Arizona and one in Trinidad and Tobago. Assessments showed that the overall modules were effective in helping students learn and retain the information presented on energy and biogas production. To improve future implementations of these modules, specifically the module on biogas production, the anaerobic digester was redesigned. In addition, a designed experiment was conducted to determine how to optimize the influent and operational environment that is available in an average high school classroom to generate maximum biogas yield. Eight plug-flow anaerobic digesters made of PVC piping and fixtures were used in a 2x3 factorial design assessing: co-digestion (20mL or 50mL) used cooking oil, temperature (25°C or 40°C), and addition of inoculum (0mL or 200mL). Biogas production was captured at two intervals over a 30-day period, and the experiments were replicated three times. Results showed that temperature at 40°C significantly increased biogas production and should be used over 25°C when using anaerobic digesters. Other factors that may potentially increase biogas production are combination of temperature at 40°C and 50mL of used cooking oil. In the future, the improvements made in the design of the anaerobic digester, and the applications of the finding from the experimental design, are expected to lead to an improved manipulative for teaching students about biogas production.
ContributorsMcCall, Shakira Renee (Author) / Dalrymple, Odesma O (Thesis advisor) / Bradley, Rogers (Committee member) / Hristovski, Kiril (Committee member) / Arizona State University (Publisher)
Created2014
Description
A new photocatalytic material was synthesized to investigate its performance for the photoreduction of carbon dioxide (CO2) in the presence of water vapor (H2O) to valuable products such as carbon monoxide (CO) and methane (CH4). The performance was studied using a gas chromatograph (GC) with a flame ionization detector (FID) and a thermal conductivity detector (TCD). The new photocatalytic material was an ionic liquid functionalized reduced graphite oxide (IL-RGO (high conductive surface))-TiO2 (photocatalyst) nanocomposite. Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and UV-vis absorption spectroscopy techniques were employed to characterize the new catalyst. In the series of experiments performed, the nanocomposite material was confined in a UV-quartz batch reactor, exposed to CO2 and H2O and illuminated by UV light. The primary product formed was CO with a maximum production ranging from 0.18-1.02 µmol(gcatalyst-hour)-1 for TiO2 and 0.41-1.41 µmol(gcatalyst-hour)-1 for IL-RGO-TiO2. A trace amount of CH4 was also formed with its maximum ranging from 0.009-0.01 µmol(gcatalyst-hour)-1 for TiO2 and 0.01-0.04 µmol(gcatalyst-hour)-1 for IL-RGO-TiO2. A series of background experiments were conducted and results showed that; (a) the use of a ionic liquid functionalized reduced graphite oxide -TiO2 produced more products as compared to commercial TiO2, (b) the addition of methanol as a hole scavenger boosted the production of CO but not CH4, (c) a higher and lower reduction time of IL-RGO as compared to the usual 24 hours of reduction presented basically the same production of CO and CH4, (d) the positive effect of having an ionic liquid was demonstrated by the double production of CO obtained for IL-RGO-TiO2 as compared to RGO-TiO2 and (e) a change in the amount of IL-RGO in the IL-RGO-TiO2 represented a small difference in the CO production but not in the CH4 production. This work ultimately demonstrated the huge potential of the utility of a UV-responsive ionic liquid functionalized reduced graphite oxide-TiO2 nano-composite for the reduction of CO2 in the presence of H2O for the production of fuels.
ContributorsCastañeda Flores, Alejandro (Author) / Andino, Jean M (Thesis advisor) / Forzani, Erica (Committee member) / Torres, Cesar (Committee member) / Arizona State University (Publisher)
Created2014
Description
The goal of the study was twofold: (i) to investigate the synthesis of hematite-impregnated granular activated carbon (Fe-GAC) by hydrolysis of Fe (III) and (ii) to assess the effectiveness of the fabricated media in removal of arsenic from water. Fe-GAC was synthesized by hydrolysis of Fe(III) salts under two Fe (III) initial dosages (0.5M and 2M) and two hydrolysis periods (24 hrs and 72 hrs). The iron content of the fabricated Fe-GAC media ranged from 0.9% to 4.4% Fe/g of the dry media. Pseudo-equilibrium batch test data at pH = 7.7±0.2 in 1mM NaHCO3 buffered ultrapure water and challenge groundwater representative of the Arizona Mexico border region were fitted to a Freundlich isotherm model. The findings suggested that the arsenic adsorption capacity of the metal (hydr)oxide modified GAC media is primarily controlled by the surface area of the media, while the metal content exhibited lesser effect. The adsorption capacity of the media in the model Mexican groundwater matrix was significantly lower for all adsorbent media. Continuous flow short bed adsorber tests (SBA) demonstrated that the adsorption capacity for arsenic in the challenge groundwater was reduced by a factor of 3 to 4 as a result of the mass transport effects. When compared on metal basis, the iron (hydr)oxide modified media performed comparably well as existing commercial media for treatment of arsenic. On dry mass basis, the fabricated media in this study removed less arsenic than their commercial counterparts because the metal content of the commercial media was significantly higher.
ContributorsJain, Arti (Author) / Hristovski, Kiril (Thesis advisor) / Olson, Larry (Committee member) / Madar, David (Committee member) / Edwards, David (Committee member) / Arizona State University (Publisher)
Created2011
Description
Population growth and fresh water depletion challenge drinking water utilities. Surface water quality is impacted significantly by climate variability, human activities, and extreme events like natural disasters. Dissolved organic carbon (DOC) is an important water quality index and the precursor of disinfection by-products (DBPs) that varies with both hydrologic and anthropogenic factors. Granular activated carbon (GAC) is a best available technology for utilities to meet Stage 2 D/DBP rule compliance and to remove contaminants of emerging concern (CECs) (e.g., pharmaceutical, personal care products (PCPs), etc.). Utilities can operate GAC with more efficient and flexible strategies with the understanding of organic occurrence in source water and a model capable predicting DOC occurrence. In this dissertation, it was found that DOC loading significantly correlated with spring runoff and was intensified by dry-duration antecedent to first flush. Dynamic modeling based on reservoir management (e.g., pump-back operation) was established to simulate the DOC transport in the reservoir system. Additionally, summer water recreational activities were found to raise the level of PCPs, especially skin-applied products, in raw waters. GAC was examined in this dissertation for both carbonaceous and emerging nitrogenous DBP (N-DBP) precursors (i.e., dissolved organic nitrogen (DON)) removal. Based on the experimental findings, GAC preferentially removes UV254-absorbing material, and DOC is preferentially removed over DON which may be composed primarily of hydrophilic organic and results in the low affinity for adsorption by GAC. The presence of organic nitrogen can elevate the toxicity of DBPs by forming N-DBPs, and this could be a major drawback for facilities considering installation of a GAC adsorber owing to the poor removal efficiency of DON by GAC. A modeling approach was established for predicting DOC and DON breakthrough during GAC operation. However, installation of GAC adsorber is a burden for utilities with respect to operational and maintenance cost. It is common for utilities to regenerate saturated GAC in order to save the cost of purchasing fresh GAC. The traditional thermal regeneration technology for saturated GAC is an energy intensive process requiring high temperature of incineration. Additionally, small water treatment sites usually ship saturated GAC to specialized facilities for regeneration increasing the already significant carbon footprint of thermal regeneration. An innovative GAC regeneration technique was investigated in this dissertation for the feasibility as on-site water treatment process. Virgin GAC was first saturated by organic contaminant then regenerated in-situ by iron oxide nanocatalysts mixed with hydrogen peroxide. At least 70 % of adsorption capacity of GAC can be regenerated repeatedly for experiments using modeling compound (phenol) or natural organic matter (Suwannee River humic acid). The regeneration efficiency increases with increasing adsorbate concentration. Used-iron nanocatalysts can be recovered repeatedly without significant loss of catalytic ability. This in-situ regeneration technique provides cost and energy efficient solution for water utilities considering GAC installation. Overall, patterns were found for DOC and CEC variations in drinking water sources. Increasing concentrations of bulk (DOC and DON) and/or trace organics challenge GAC operation in utilities that have limited numbers of bed-volume treated before regeneration is required. In-situ regeneration using iron nanocatalysts and hydrogen peroxide provides utilities an alternative energy-efficient operation mode when considering installation of GAC adsorber.
ContributorsChiu, Chao-An (Author) / Westerhoff, Paul (Thesis advisor) / Rittmann, Bruce (Committee member) / Hristovski, Kiril (Committee member) / Arizona State University (Publisher)
Created2012
Description
Titanium dioxide (TiO2) nanomaterial use is becoming more prevalent as is the likelihood of human exposure and environmental release. The goal of this thesis is to develop analytical techniques to quantify the level of TiO2 in complex matrices to support environmental, health, and safety research of TiO2 nanomaterials. A pharmacokinetic model showed that the inhalation of TiO2 nanomaterials caused the highest amount to be absorbed and distributed throughout the body. Smaller nanomaterials (< 5nm) accumulated in the kidneys before clearance. Nanoparticles of 25 nm diameter accumulated in the liver and spleen and were cleared from the body slower than smaller nanomaterials. A digestion method using nitric acid, hydrofluoric acid, and hydrogen peroxide was found to digest organic materials and TiO2 with a recovery of >80%. The samples were measured by inductively coupled plasma-mass spectrometry (ICP-MS) and the method detection limit was 600 ng of Ti. An intratracheal instillation study of TiO2 nanomaterials in rats found anatase TiO2 nanoparticles in the caudal lung lobe of rats 1 day post instillation at a concentration of 1.2 ug/mg dry tissue, the highest deposition rate of any TiO2 nanomaterial. For all TiO2 nanomaterial morphologies the concentrations in the caudal lobes were significantly higher than those in the cranial lobes. In a study of TiO2 concentration in food products, white colored foods or foods with a hard outer shell had higher concentrations of TiO2. Hostess Powdered Donettes were found to have the highest Ti mass per serving with 200 mg Ti. As much as 3.8% of the total TiO2 mass was able to pass through a 0.45 um indicating that some of the TiO2 is likely nanosized. In a study of TiO2 concentrations in personal care products and paints, the concentration of TiO2 was as high as 117 ug/mg in Benjamin Moore white paint and 70 ug/mg in a Neutrogena sunscreen. Greater than 6% of Ti in one sunscreen was able to pass through a 0.45 um filter. The nanosized TiO2 in food products and personal care products may release as much as 16 mg of nanosized TiO2 per individual per day to wastewater.
ContributorsWeir, Alex Alan (Author) / Westerhoff, Paul K (Thesis advisor) / Hristovski, Kiril (Committee member) / Herckes, Pierre (Committee member) / Arizona State University (Publisher)
Created2011
Description
Local municipalities in the Phoenix Metropolitan Area have voiced an interest in purchasing alternate source water with lower DBP precursors. Along the primary source is a hydroelectric dam in which water will be diverted from. This project is an assessment of optimizing the potential blends of source water to a water treatment plant in an effort to enable them to more readily meet DBP regulations. To perform this analysis existing water treatment models were used in conjunction with historic water quality sampling data to predict chemical usage necessary to meet DBP regulations. A retrospective analysis was performed for the summer months of 2007 regarding potential for the WTP to reduce cost through optimizing the source water by an average of 30% over the four-month period, accumulating to overall treatment savings of $154 per MG ($82 per AF).
ContributorsRice, Jacelyn (Author) / Westerhoff, Paul (Thesis advisor) / Fox, Peter (Committee member) / Hristovski, Kiril (Committee member) / Arizona State University (Publisher)
Created2011
Description
Over the past years, an interest has arisen in resolving two major issues: increased carbon dioxide (CO2) emissions and depleting energy resources. A convenient solution would be a process that could simultaneously use CO2 while producing energy. The photocatalytic reduction of CO2 to fuels over the photocatalyst titanium dioxide (TiO2) is such a process. However, this process is presently inefficient and unsuitable for industrial applications. A step toward making this process more effective is to alter TiO2 based photocatalysts to improve their activity. The interactions of CO2 with oxygen-deficient and unmodified (210) surfaces of brookite TiO2 were studied using first-principle calculations on cluster systems. Charge and spin density analyses were implemented to determine if charge transfer to the CO2 molecule occurred and whether this charge transfer was comparable to that seen with the oxygen-deficient and unmodified anatase TiO2 (101) surfaces. Although the unmodified brookite (210) surface provided energetically similar CO2 interactions as compared to the unmodified anatase (101) surface, the unmodified brookite surface had negligible charge transfer to the CO2 molecule. This result suggests that unmodified brookite is not a suitable catalyst for the reduction of CO2. However, the results also suggest that modification of the brookite surface through the creation of oxygen vacancies may lead to enhancements in CO2 reduction. The computational results were supported with laboratory data for CO2 interaction with perfect brookite and oxygen-deficient brookite. The laboratory data, generated using diffuse reflectance Fourier transform infrared spectroscopy, confirms the presence of CO2- on only the oxygen-deficient brookite. Additional computational work was performed on I-doped anatase (101) and I-doped brookite (210) surface clusters. Adsorption energies and charge and spin density analyses were performed and the results compared. While charge and spin density analyses showed minute charge transfer to CO2, the calculated adsorption energies demonstrated an increased affinity for CO2adsorption onto the I-doped brookite surface. Gathering the results from all calculations, the computational work on oxygen-deficient, I-doped, and unmodified anatase and brookite surface structures suggest that brookite TiO2 is a potential photocatalysts for CO2 photoreduction.
ContributorsRodriguez, Monique M (Author) / Andino, Jean M (Thesis advisor) / Nielsen, David R (Committee member) / Dai, Lenore (Committee member) / Arizona State University (Publisher)
Created2012