Matching Items (21)
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- All Subjects: Environmental engineering
- Creators: Torres, César I
- Member of: ASU Electronic Theses and Dissertations
Description
Uranium (U) contamination has been attracting public concern, and many researchers are investigating principles and applications of U remediation. The overall goal of my research is to understand the versatile roles of sulfate-reducing bacteria (SRB) in uranium bioremediation, including direct involvement (reducing U) and indirect involvement (protecting U reoxidation). I pursue this goal by studying Desulfovibro vuglaris, a representative SRB. For direct involvement, I performed experiments on uranium bioreduction and uraninite (UO2) production in batch tests and in a H2-based membrane biofilm reactor (MBfR) inoculated with D. vuglaris. In summary, D. vuglaris was able to immobilize soluble U(VI) by enzymatically reducing it to insoluble U(IV), and the nanocrystallinte UO2 was associated with the biomass. In the MBfR system, although D. vuglaris failed to form a biofilm, other microbial groups capable of U(VI) reduction formed a biofilm, and up to 95% U removal was achieved during a long-term operation. For the indirect involvement, I studied the production and characterization of and biogenic iron sulfide (FeS) in batch tests. In summary, D. vuglaris produced nanocrystalline FeS, a potential redox buffer to protect UO2 from remobilization by O2. My results demonstrate that a variety of controllable environmental parameters, including pH, free sulfide, and types of Fe sources and electron donors, significantly determined the characteristics of both biogenic solids, and those characteristics should affect U-sequestrating performance by SRB. Overall, my results provide a baseline for exploiting effective and sustainable approaches to U bioremediation, including the application of the novel MBfR technology to U sequestration from groundwater and biogenic FeS for protecting remobilization of sequestrated U, as well as the microbe-relevant tools to optimize U sequestration applicable in reality.
ContributorsZhou, Chen (Author) / Rittmann, Bruce E. (Thesis advisor) / Krajmalnik-Brown, Rosa (Committee member) / Torres, César I (Committee member) / Arizona State University (Publisher)
Created2014
Description
An eco-industrial park (EIP) is an industrial ecosystem in which a group of co-located firms are involved in collective resource optimization with each other and with the local community through physical exchanges of energy, water, materials, byproducts and services - referenced in the industrial ecology literature as "industrial symbiosis". EIPs, when compared with standard industrial resource sharing networks, prove to be of greater public advantage as they offer improved environmental and economic benefits, and higher operational efficiencies both upstream and downstream in their supply chain.
Although there have been many attempts to adapt EIP methodology to existing industrial sharing networks, most of them have failed for various factors: geographic restrictions by governmental organizations on use of technology, cost of technology, the inability of industries to effectively communicate their upstream and downstream resource usage, and to diminishing natural resources such as water, land and non-renewable energy (NRE) sources for energy production.
This paper presents a feasibility study conducted to evaluate the comparative environmental, economic, and geographic impacts arising from the use of renewable energy (RE) and NRE to power EIPs. Life Cycle Assessment (LCA) methodology, which is used in a variety of sectors to evaluate the environmental merits and demerits of different kinds of products and processes, was employed for comparison between these two energy production methods based on factors such as greenhouse gas emission, acidification potential, eutrophication potential, human toxicity potential, fresh water usage and land usage. To complement the environmental LCA analysis, levelized cost of electricity was used to evaluate the economic impact. This model was analyzed for two different geographic locations; United States and Europe, for 12 different energy production technologies.
The outcome of this study points out the environmental, economic and geographic superiority of one energy source over the other, including the total carbon dioxide equivalent emissions, which can then be related to the total number of carbon credits that can be earned or used to mitigate the overall carbon emission and move closer towards a net zero carbon footprint goal thus making the EIPs truly sustainable.
Although there have been many attempts to adapt EIP methodology to existing industrial sharing networks, most of them have failed for various factors: geographic restrictions by governmental organizations on use of technology, cost of technology, the inability of industries to effectively communicate their upstream and downstream resource usage, and to diminishing natural resources such as water, land and non-renewable energy (NRE) sources for energy production.
This paper presents a feasibility study conducted to evaluate the comparative environmental, economic, and geographic impacts arising from the use of renewable energy (RE) and NRE to power EIPs. Life Cycle Assessment (LCA) methodology, which is used in a variety of sectors to evaluate the environmental merits and demerits of different kinds of products and processes, was employed for comparison between these two energy production methods based on factors such as greenhouse gas emission, acidification potential, eutrophication potential, human toxicity potential, fresh water usage and land usage. To complement the environmental LCA analysis, levelized cost of electricity was used to evaluate the economic impact. This model was analyzed for two different geographic locations; United States and Europe, for 12 different energy production technologies.
The outcome of this study points out the environmental, economic and geographic superiority of one energy source over the other, including the total carbon dioxide equivalent emissions, which can then be related to the total number of carbon credits that can be earned or used to mitigate the overall carbon emission and move closer towards a net zero carbon footprint goal thus making the EIPs truly sustainable.
ContributorsGupta, Vaibhav (Author) / Calhoun, Ronald J (Thesis advisor) / Dooley, Kevin (Committee member) / Phelan, Patrick (Committee member) / Arizona State University (Publisher)
Created2014
Description
As the demand for power increases in populated areas, so will the demand for water. Current power plant technology relies heavily on the Rankine cycle in coal, nuclear and solar thermal power systems which ultimately use condensers to cool the steam in the system. In dry climates, the amount of water to cool off the condenser can be extremely large. Current wet cooling technologies such as cooling towers lose water from evaporation. One alternative to prevent this would be to implement a radiative cooling system. More specifically, a system that utilizes the volumetric radiation emission from water to the night sky could be implemented. This thesis analyzes the validity of a radiative cooling system that uses direct radiant emission to cool water. A brief study on potential infrared transparent cover materials such as polyethylene (PE) and polyvinyl carbonate (PVC) was performed. Also, two different experiments to determine the cooling power from radiation were developed and run. The results showed a minimum cooling power of 33.7 W/m2 for a vacuum insulated glass system and 37.57 W/m2 for a tray system with a maximum of 98.61 Wm-2 at a point when conduction and convection heat fluxes were considered to be zero. The results also showed that PE proved to be the best cover material. The minimum numerical results compared well with other studies performed in the field using similar techniques and materials. The results show that a radiative cooling system for a power plant could be feasible given that the cover material selection is narrowed down, an ample amount of land is available and an economic analysis is performed proving it to be cost competitive with conventional systems.
ContributorsOvermann, William (Author) / Phelan, Patrick (Thesis advisor) / Trimble, Steve (Committee member) / Taylor, Robert (Committee member) / Arizona State University (Publisher)
Created2011
Description
A method of determining nanoparticle temperature through fluorescence intensity levels is described. Intracellular processes are often tracked through the use of fluorescence tagging, and ideal temperatures for many of these processes are unknown. Through the use of fluorescence-based thermometry, cellular processes such as intracellular enzyme movement can be studied and their respective temperatures established simultaneously. Polystyrene and silica nanoparticles are synthesized with a variety of temperature-sensitive dyes such as BODIPY, rose Bengal, Rhodamine dyes 6G, 700, and 800, and Nile Blue A and Nile Red. Photographs are taken with a QImaging QM1 Questar EXi Retiga camera while particles are heated from 25 to 70 C and excited at 532 nm with a Coherent DPSS-532 laser. Photographs are converted to intensity images in MATLAB and analyzed for fluorescence intensity, and plots are generated in MATLAB to describe each dye's intensity vs temperature. Regression curves are created to describe change in fluorescence intensity over temperature. Dyes are compared as nanoparticle core material is varied. Large particles are also created to match the camera's optical resolution capabilities, and it is established that intensity values increase proportionally with nanoparticle size. Nile Red yielded the closest-fit model, with R2 values greater than 0.99 for a second-order polynomial fit. By contrast, Rhodamine 6G only yielded an R2 value of 0.88 for a third-order polynomial fit, making it the least reliable dye for temperature measurements using the polynomial model. Of particular interest in this work is Nile Blue A, whose fluorescence-temperature curve yielded a much different shape from the other dyes. It is recommended that future work describe a broader range of dyes and nanoparticle sizes, and use multiple excitation wavelengths to better quantify each dye's quantum efficiency. Further research into the effects of nanoparticle size on fluorescence intensity levels should be considered as the particles used here greatly exceed 2 ìm. In addition, Nile Blue A should be further investigated as to why its fluorescence-temperature curve did not take on a characteristic shape for a temperature-sensitive dye in these experiments.
ContributorsTomforde, Christine (Author) / Phelan, Patrick (Thesis advisor) / Dai, Lenore (Committee member) / Adrian, Ronald (Committee member) / Arizona State University (Publisher)
Created2011
Description
This research explores microbial chain elongation as a pathway for production of complex organic compounds in soils with implication for the carbon cycle. In chain elongation, simple substrates such as ethanol and short chain carboxylates such as acetate can be converted to longer carbon chain carboxylates under anaerobic conditions through cyclic, reverse β oxidation. This pathway elongates the carboxylate by two carbons. The chain elongation process is overall thermodynamically feasible, and microorganisms gain energy through this process. There have been limited insights into the versatility of chain elongating substrates, understanding the chain elongating microbial community, and its importance in sequestering carbon in the soils.
We used ethanol, methanol, butanol, and hydrogen as electron donors and acetate and propionate as electron acceptors to test the occurrence of microbial chain elongation in four soils with different physicochemical properties and microbial communities. Common chain elongation products were the even numbered chains butyrate, caproate, and butanol, the odd numbered carboxylates valerate and heptanoate, along with molecular hydrogen. At a near neutral pH and mesophilic temperature, we observed a stable and sustained production of longer fatty acids along with hydrogen. Microbial community analysis show phylotypes from families such as Clostridiaceae, Bacillaceae, and Ruminococcaceae in all tested conditions. Through chain elongation, the products formed are less biodegradable. They may undergo transformations and end up as organic carbon, decreasing the greenhouse gas emissions, thus, making this process important to study.
We used ethanol, methanol, butanol, and hydrogen as electron donors and acetate and propionate as electron acceptors to test the occurrence of microbial chain elongation in four soils with different physicochemical properties and microbial communities. Common chain elongation products were the even numbered chains butyrate, caproate, and butanol, the odd numbered carboxylates valerate and heptanoate, along with molecular hydrogen. At a near neutral pH and mesophilic temperature, we observed a stable and sustained production of longer fatty acids along with hydrogen. Microbial community analysis show phylotypes from families such as Clostridiaceae, Bacillaceae, and Ruminococcaceae in all tested conditions. Through chain elongation, the products formed are less biodegradable. They may undergo transformations and end up as organic carbon, decreasing the greenhouse gas emissions, thus, making this process important to study.
ContributorsJoshi, Sayalee (Author) / Delgado, Anca G (Thesis advisor) / Torres, César I (Committee member) / van Paassen, Leon (Committee member) / Arizona State University (Publisher)
Created2018
Description
Understanding and predicting climate changes at the urban scale have been an important yet challenging problem in environmental engineering. The lack of reliable long-term observations at the urban scale makes it difficult to even assess past climate changes. Numerical modeling plays an important role in filling the gap of observation and predicting future changes. Numerical studies on the climatic effect of desert urbanization have focused on basic meteorological fields such as temperature and wind. For desert cities, urban expansion can lead to substantial changes in the local production of wind-blown dust, which have implications for air quality and public health. This study expands the existing framework of numerical simulation for desert urbanization to include the computation of dust generation related to urban land-use changes. This is accomplished by connecting a suite of numerical models, including a meso-scale meteorological model, a land-surface model, an urban canopy model, and a turbulence model, to produce the key parameters that control the surface fluxes of wind-blown dust. Those models generate the near-surface turbulence intensity, soil moisture, and land-surface properties, which are used to determine the dust fluxes from a set of laboratory-based empirical formulas. This framework is applied to a series of simulations for the desert city of Erbil across a period of rapid urbanization. The changes in surface dust fluxes associated with urbanization are quantified. An analysis of the model output further reveals the dependence of surface dust fluxes on local meteorological conditions. Future applications of the models to environmental prediction are discussed.
ContributorsTahir, Sherzad Tahseen (Author) / Huang, Huei-Ping (Thesis advisor) / Phelan, Patrick (Committee member) / Herrmann, Marcus (Committee member) / Chen, Kangping (Committee member) / Clarke, Amanda (Committee member) / Arizona State University (Publisher)
Created2019
Description
Microbial electrochemical cells (MxCs) are a novel technology that use anode-respiring bacteria (ARB) to bioremediate wastewaters and respire an electrical current, which can then be used directly to produce value-added products like hydrogen peroxide (H2O2). Ninety-five percent of the world’s H2O2 is currently produced using the anthraquinone process, whose production requires expensive and potentially carcinogenic catalysts and high amounts of electricity. However, the amount of H2O2 that can be produced from these microbial peroxide-producing cells (MPPCs) has not been thoroughly investigated. Predicting potential H2O2 production in MxCs is further complicated by a lack of mathematical models to predict performance utilizing complex waste streams like primary sludge (PS).
A reactor design methodology was developed for MPPCs to systematically optimize H2O2 production with minimal energy consumption. H2O2 stability was evaluated with different catholytes, membranes, and catalysts materials, and the findings used to design and operate long-term a dual-chamber, flat-plate MPPC using different catholytes, ferrochelating stabilizers, and hydraulic retention times (HRT). Up to 3.1 ± 0.37 g H2O2 L-1 was produced at a 4-h HRT in an MPPC with as little as 1.13 W-h g-1 H2O2 power input using NaCl catholytes. Attempts to improve H2O2 production by using weak acid buffers as catholytes or ferrochelating stabilizers failed for different reasons.
A non-steady-state mathematical model, MYAnode, was developed combinging existing wastewater treatment, anode biofilm, and chemical speciation models to predict MxC performance utilizing complex substrates. The model simulated the large-scale trends observed when operating an MPPC with PS substrate. At HRTs ≥ 12-d, the model demonstrated up to 20% Coulombic recovery. At these conditions, ARB required additional alkalinity production by ≥ 100 mgVSS/L of acetoclastic methanogens to prevent pH inhibition when little influent alkalinity is available. At lower HRTs, methanogens are unable to produce the alkalinity required to prevent ARB inhibition due to washout and rapid acidification of the system during fermentation. At ≥ 100 mgVSS/L of methanogens, increasing the diffusion layer thickness from 500 to 1000 μm improved Coulombic efficiency by 13.9%, while increasing particulate COD hydrolysis rates to 0.25/d only improved Coulombic efficiency by 3.9%.
A reactor design methodology was developed for MPPCs to systematically optimize H2O2 production with minimal energy consumption. H2O2 stability was evaluated with different catholytes, membranes, and catalysts materials, and the findings used to design and operate long-term a dual-chamber, flat-plate MPPC using different catholytes, ferrochelating stabilizers, and hydraulic retention times (HRT). Up to 3.1 ± 0.37 g H2O2 L-1 was produced at a 4-h HRT in an MPPC with as little as 1.13 W-h g-1 H2O2 power input using NaCl catholytes. Attempts to improve H2O2 production by using weak acid buffers as catholytes or ferrochelating stabilizers failed for different reasons.
A non-steady-state mathematical model, MYAnode, was developed combinging existing wastewater treatment, anode biofilm, and chemical speciation models to predict MxC performance utilizing complex substrates. The model simulated the large-scale trends observed when operating an MPPC with PS substrate. At HRTs ≥ 12-d, the model demonstrated up to 20% Coulombic recovery. At these conditions, ARB required additional alkalinity production by ≥ 100 mgVSS/L of acetoclastic methanogens to prevent pH inhibition when little influent alkalinity is available. At lower HRTs, methanogens are unable to produce the alkalinity required to prevent ARB inhibition due to washout and rapid acidification of the system during fermentation. At ≥ 100 mgVSS/L of methanogens, increasing the diffusion layer thickness from 500 to 1000 μm improved Coulombic efficiency by 13.9%, while increasing particulate COD hydrolysis rates to 0.25/d only improved Coulombic efficiency by 3.9%.
ContributorsYoung, Michelle Nichole (Author) / Rittmann, Bruce E. (Thesis advisor) / Torres, César I (Committee member) / Marcus, Andrew K (Committee member) / Arizona State University (Publisher)
Created2018
Description
Microbial electrochemical cells (MXCs) serve as an alternative anaerobic technology to anaerobic digestion for efficient energy recovery from high-strength organic wastes such as primary sludge (PS). The overarching goal of my research was to address energy conversion from PS to useful resources (e.g. hydrogen or hydrogen peroxide) through bio- and electro-chemical anaerobic conversion processes in MXCs.
First, a new flat-pate microbial electrolysis cell (MEC) was designed with high surface area anodes using carbon fibers, but without creating a large distance between the anode and the cathode (<0.5 cm) to reduce Ohmic overpotential. Through the improved design, operation, and electrochemical characterization, the applied voltages were reduced from 1.1 to ~0.85 V, at 10 A m-2. Second, PS conversion was examined through hydrolysis, fermentation, methanogenesis, and/or anode respiration. Since pretreatment often is required to accelerate hydrolysis of organic solids, I evaluated pulsed electric field technology on PS showing a modest improvement of energy conversion through methanogenesis and fermentation, as compared to the conversion from waste activated sludge (WAS) or WAS+PS. Then, a two-stage system (prefermented PS-fed MEC) yielded successful performance in terms of Coulombic efficiency (95%), Coulombic recovery (CR, 80%), and COD-removal efficiency (85%). However, overall PS conversion to electrical current (or CR) through pre-fermentation and MEC, was just ~16%. Next, a single-stage system (direct PS-fed MEC) with semi-continuous operation showed 34% CR at a 9-day hydraulic retention time. The PS-fed MEC also showed an important pH dependency, in which high pH (> 8) in the anode chamber improved anode respiration along with methanogen inhibition. Finally, H2O2 was produced in a PS-fed microbial electrochemical cell with a low energy requirement (~0.87 kWh per kg H2O2). These research developments will provide groundbreaking knowledge for MXC design, commercial application, and anaerobic energy conversion from other high-strength organic wastes to resources.
First, a new flat-pate microbial electrolysis cell (MEC) was designed with high surface area anodes using carbon fibers, but without creating a large distance between the anode and the cathode (<0.5 cm) to reduce Ohmic overpotential. Through the improved design, operation, and electrochemical characterization, the applied voltages were reduced from 1.1 to ~0.85 V, at 10 A m-2. Second, PS conversion was examined through hydrolysis, fermentation, methanogenesis, and/or anode respiration. Since pretreatment often is required to accelerate hydrolysis of organic solids, I evaluated pulsed electric field technology on PS showing a modest improvement of energy conversion through methanogenesis and fermentation, as compared to the conversion from waste activated sludge (WAS) or WAS+PS. Then, a two-stage system (prefermented PS-fed MEC) yielded successful performance in terms of Coulombic efficiency (95%), Coulombic recovery (CR, 80%), and COD-removal efficiency (85%). However, overall PS conversion to electrical current (or CR) through pre-fermentation and MEC, was just ~16%. Next, a single-stage system (direct PS-fed MEC) with semi-continuous operation showed 34% CR at a 9-day hydraulic retention time. The PS-fed MEC also showed an important pH dependency, in which high pH (> 8) in the anode chamber improved anode respiration along with methanogen inhibition. Finally, H2O2 was produced in a PS-fed microbial electrochemical cell with a low energy requirement (~0.87 kWh per kg H2O2). These research developments will provide groundbreaking knowledge for MXC design, commercial application, and anaerobic energy conversion from other high-strength organic wastes to resources.
ContributorsKi, Dong Won (Author) / Torres, César I (Thesis advisor) / Rittmann, Bruce E. (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Parameswaran, Prathap (Committee member) / Popat, Sudeep C (Committee member) / Arizona State University (Publisher)
Created2016
Description
The finite supply of current energy production materials has created opportunities for the investigation of alternative energy sources in many fields. One example is the use of microorganisms in bioenergy applications, such as microbial fuel cells. Present in many types of environments, microorganisms with the ability to respire solid electron acceptors have become of increasing relevance to alternative energy and wastewater treatment research. In this dissertation, several aspects of anode respiration are investigated, with the goal of increasing the limited understanding of the mechanisms of electron transport through the use of advanced electrochemical methods. Biofilms of Geobacter sulfurreducens, the model anode respiring organism, as well as its alkaliphilic relative, Geoalkalibacter ferrihydriticus, were investigated using chronoamperometry, electrochemical impedance spectroscopy, and cyclic voltammetry.
In G. sulfurreducens, two distinct pathways of electron transport were observed through the application of advanced electrochemical techniques on anode biofilms in microbial electrochemical cells. These pathways were found to be preferentially expressed, based on the poised anode potential (redox potential) of the electrode. In Glk. ferrihydriticus, four pathways for electron transport were found, showing an even greater diversity in electron transport pathway utilization as compared to G. sulfurreducens. These observations provide insights into the diversity of electron transport pathways present in anode-respiring bacteria and introduce the necessity of further characterization for pathway identification.
Essential to science today, communication of pressing scientific issues to the lay audience may present certain difficulties. This can be seen especially with the topics that are considered socio-scientific issues, those considered controversial in society but not for scientists. This dissertation explores the presentation of alternative and renewable energy technologies and climate change in undergraduate education. In introductory-level Biology, Chemistry, and Physics textbooks, the content and terminology presented were analyzed for individual textbooks and used to evaluate discipline-based trends. Additional extensions were made between teaching climate change with the active learning technique of citizen science using past research gains from studies of evolution. These observations reveal patterns in textbook content for energy technologies and climate change, as well as exploring new aspects of teaching techniques.
In G. sulfurreducens, two distinct pathways of electron transport were observed through the application of advanced electrochemical techniques on anode biofilms in microbial electrochemical cells. These pathways were found to be preferentially expressed, based on the poised anode potential (redox potential) of the electrode. In Glk. ferrihydriticus, four pathways for electron transport were found, showing an even greater diversity in electron transport pathway utilization as compared to G. sulfurreducens. These observations provide insights into the diversity of electron transport pathways present in anode-respiring bacteria and introduce the necessity of further characterization for pathway identification.
Essential to science today, communication of pressing scientific issues to the lay audience may present certain difficulties. This can be seen especially with the topics that are considered socio-scientific issues, those considered controversial in society but not for scientists. This dissertation explores the presentation of alternative and renewable energy technologies and climate change in undergraduate education. In introductory-level Biology, Chemistry, and Physics textbooks, the content and terminology presented were analyzed for individual textbooks and used to evaluate discipline-based trends. Additional extensions were made between teaching climate change with the active learning technique of citizen science using past research gains from studies of evolution. These observations reveal patterns in textbook content for energy technologies and climate change, as well as exploring new aspects of teaching techniques.
ContributorsYoho, Rachel Ann (Author) / Torres, César I (Thesis advisor) / Rittmann, Bruce E. (Committee member) / Popat, Sudeep C (Committee member) / Vanmali, Binaben H (Committee member) / Arizona State University (Publisher)
Created2016
Description
The application of microalgal biofilms in wastewater treatment has great advantages such as abolishing the need for energy intensive aerators and recovering nutrients as energy, thus reducing the energy requirement of wastewater treatment several-fold. A 162 cm2 algal biofilm reactor with good wastewater treatment performance and a regular harvesting procedure was studied at lab scale to gain an understanding of effectual parameters such as hydraulic retention time (HRT; 2.6 and 1.3 hrs), liquid level (LL; 0.5 and 1.0 cm), and solids retention time (SRT; 3 and 1.5 wks). A revised synthetic wastewater “Syntho 3.7” was used as a surrogate of domestic primary effluent for nutrient concentration consistency in the feed lines. In the base case (2.6 hr HRT, 0.5 cm LL, and 3 wk SRT), percent removals of 69 ± 2 for total nitrogen (TN), 54 ± 21 for total phosphorous (TP), and 60 ± 7 for chemical oxygen demand (COD) were achieved and 4.0 ± 1.6 g/m2/d dry biomass was produced. A diffusion limitation was encountered when increasing the liquid level, while the potential to further decrease the HRT remains. Nonlinear growth kinetics was observed in comparing SRT variations, and promoting autotrophic growth seems possible. Future work will look towards producing a mathematical model and further testing the aptness of this system for large-scale implementation.
ContributorsHalloum, Ibrahim (Author) / Torres, César I (Thesis advisor) / Popat, Sudeep C (Committee member) / Rittmann, Bruce E. (Committee member) / Arizona State University (Publisher)
Created2016