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Description
Bioremediation of trichloroethene (TCE) using Dehalococcoides mccartyi-containing microbial cultures is a recognized and successful remediation technology. Our work with an upflow anaerobic sludge blanket (UASB) reactor has shown that high-performance, fast-rate dechlorination of TCE can be achieved by promoting bioflocculation of Dehalococcoides mccartyi-containing cultures. The bioreactor achieved high maximum conversion rates of 1.63 ± 0.012 mmol Cl- Lculture-1 h-1 at an HRT of 3.6 hours and >97% dechlorination of TCE to ethene while continuously fed 2 mM TCE. The UASB generated bioflocs from a microbially heterogeneous dechlorinating culture and produced Dehalococcoides mccartyi densities of 1.73x10-13 cells Lculture-1 indicating that bioflocculation of Dehalococcoides mccartyi-containing cultures can lead to high density inocula and high-performance, fast-rate bioaugmentation culture for in situ treatment. The successful operation of our pilot scale bioreactor led to the assessment of the technology as an onsite ex-situ treatment system. The bioreactor was then fed TCE-contaminated groundwater from the Motorola Inc. 52nd Street Plant Superfund site in Phoenix, AZ augmented with the lactate and methanol. The bioreactor maintained >99% dechlorination of TCE to ethene during continuous operation at an HRT of 3.2 hours. Microbial community analysis under both experimental conditions reveals shifts in the community structure although maintaining high rate dechlorination. High density dechlorinating cultures containing bioflocs can provide new ways to 1) produce dense bioaugmentation cultures, 2) perform ex-situ bioremediation of TCE, and 3) increase our understanding of Dehalococcoides mccartyi critical microbial interactions that can be exploited at contaminated sites in order to improve long-term bioremediation schemes.
ContributorsFajardo-Williams, Devyn (Author) / Krajmalnik-Brown, Rosa (Thesis advisor) / Torres, César I (Committee member) / Popat, Sudeep C (Committee member) / Arizona State University (Publisher)
Created2015
Description
N-nitrosodimethylamine (NDMA) is a probable human carcinogen and drinking water disinfection by-product. NDMA forms as the product of reactions between chloramines and precursor compounds in water. This dissertation aims to provide insight into the removal of NDMA precursors, their nature, and a method to aid in their identification. Watershed-derived precursors accounted for more of and greater variability to NDMA formation upon chloramination than polymer-derived precursors in environmental samples. Coagulation polymers are quaternary amines, which have low NDMA yield but high use rates. Watershed-derived precursors were removed up to 90% by sorption to activated carbon, but activated carbon exhibited much less (<10%) sorption of polymer-derived precursors. Combined with literature NDMA molar yields of model anthropogenic compounds, where anthropogenic chemicals in some cases have NDMA yields >90% and biological compounds always have yields <2%, trace, organic, amine containing, anthropogenic chemicals were implicated as the most likely source of NDMA precursors in the watershed. Although activated carbon removes these precursors well, identification of individual compounds may result in more cost effective mitigation strategies. Therefore, I developed a method to isolate NDMA precursors from other organic matter into methanol to facilitate their identification. Optimization of the method resulted in a median recovery of NDMA precursors of 82% from 10 surface waters and one wastewater. The method produces 1,000X concentrated NDMA precursors and, in collaboration with the University of Colorado Center for Environmental Mass Spectrometry, time of flight mass spectrometry (TOF-MS) was performed on multiple treated wastewater and raw drinking water isolates. During TOF-MS, tertiary amines can cleave to form a neutral loss and an R group ion that is dependent on the original structure and I wrote a software program to “trawl” exported TOF-MS spectra for the diagnostic neutral loss resulting from fragmentation of tertiary amines. Methadone was identified as one new NDMA precursor that occurs at concentrations that form physiologically relevant levels of NDMA in surface water and wastewater. The approach used here to identify NDMA precursors is adaptable to other unknown disinfection by-product precursors given that a functional group is known that can 1)control sorption and 2)produce a predictable diagnostic fragment.
ContributorsHanigan, David (Author) / Westerhoff, Paul (Thesis advisor) / Rittmann, Bruce (Committee member) / Herckes, Pierre (Committee member) / Arizona State University (Publisher)
Created2015
Description
This dissertation studies the larger issue of antibiotic resistance with respect to how antibiotics are being introduced into the environment, focusing on two major anthropogenic pathways: animal husbandry for human consumption, and the recycling of wastewater and municipal sludge generated during conventional biological sewage treatment.
For animal production on land (agriculture) antibiotics are often used for growth enhancement and increased feed efficiency. For animal production in water (aquaculture) antibiotics are often used as a prophylactic. I found that the same antibiotics are being used in both industries and that the same strains of human pathogens have also been isolated from both sources, expressing identical resistance mechanisms. In U.S. seafood, five out of 47 antibiotics screened for were detected at levels of 0.3 to 7.7 ng/g fresh weight. Although compliant with FDA regulations, the risk for resistance still exists, as even low antibiotic concentrations have been shown to exert selective pressure on bacteria.
Similarly low concentrations of antibiotics were found in U.S. biosolids at levels of 0.6 to 19.1 ng/g dry weight. Of the five antibiotics detected, two have never been reported before in biosolids. Three have never been reported before in U.S. biosolids. Using the raw numbers obtained from antibiotic screenings in biosolids, I assessed the impact of employing four different LC-MS/MS methods, concluding that analysts should experimentally determine the most appropriate quantitation method based on the analyte targeted, matrix investigated, and research goals pursued. Preferred quantitation approaches included the isotope dilution method with use of an analogous standard and, although time and resource demanding, the method of standard addition.
In conclusion, antibiotics introduced into the environment via agriculture, aquaculture, and wastewater recycling pose a combination of chemical and biological threats. Aside from exerting outright chemical toxicity to non-target organisms, antibiotic residues can promote the development of multi-drug resistance in human pathogens. Public health protection approaches to stem the risks posed by animal husbandry may include reserving drugs for exclusive, human use, decreasing their usage altogether, improving reporting efforts, reevaluating existing regulations on agricultural and aquacultural antibiotic usage, and improved risk assessment for biosolids application on land.
For animal production on land (agriculture) antibiotics are often used for growth enhancement and increased feed efficiency. For animal production in water (aquaculture) antibiotics are often used as a prophylactic. I found that the same antibiotics are being used in both industries and that the same strains of human pathogens have also been isolated from both sources, expressing identical resistance mechanisms. In U.S. seafood, five out of 47 antibiotics screened for were detected at levels of 0.3 to 7.7 ng/g fresh weight. Although compliant with FDA regulations, the risk for resistance still exists, as even low antibiotic concentrations have been shown to exert selective pressure on bacteria.
Similarly low concentrations of antibiotics were found in U.S. biosolids at levels of 0.6 to 19.1 ng/g dry weight. Of the five antibiotics detected, two have never been reported before in biosolids. Three have never been reported before in U.S. biosolids. Using the raw numbers obtained from antibiotic screenings in biosolids, I assessed the impact of employing four different LC-MS/MS methods, concluding that analysts should experimentally determine the most appropriate quantitation method based on the analyte targeted, matrix investigated, and research goals pursued. Preferred quantitation approaches included the isotope dilution method with use of an analogous standard and, although time and resource demanding, the method of standard addition.
In conclusion, antibiotics introduced into the environment via agriculture, aquaculture, and wastewater recycling pose a combination of chemical and biological threats. Aside from exerting outright chemical toxicity to non-target organisms, antibiotic residues can promote the development of multi-drug resistance in human pathogens. Public health protection approaches to stem the risks posed by animal husbandry may include reserving drugs for exclusive, human use, decreasing their usage altogether, improving reporting efforts, reevaluating existing regulations on agricultural and aquacultural antibiotic usage, and improved risk assessment for biosolids application on land.
ContributorsDone, Hansa Yi-Yun (Author) / Halden, Rolf U. (Thesis advisor) / Haydel, Shelley E (Committee member) / Abbaszadegan, Morteza (Committee member) / Arizona State University (Publisher)
Created2015
Description
Ion exchange sorbents embedded with metal oxide nanoparticles can have high affinity and high capacity to simultaneously remove multiple oxygenated anion contaminants from drinking water. This research pursued answering the question, “Can synthesis methods of nano-composite sorbents be improved to increase sustainability and feasibility to remove hexavalent chromium and arsenic simultaneously from groundwater compared to existing sorbents?” Preliminary nano-composite sorbents outperformed existing sorbents in equilibrium tests, but struggled in packed bed applications and at low influent concentrations. The synthesis process was then tailored for weak base anion exchange (WBAX) while comparing titanium dioxide against iron hydroxide nanoparticles (Ti-WBAX and Fe-WBAX, respectively). Increasing metal precursor concentration increased the metal content of the created sorbents, but pollutant removal performance and usable surface area declined due to pore blockage and nanoparticle agglomeration. An acid-post rinse was required for Fe-WBAX to restore chromium removal capacity. Anticipatory life cycle assessment identified critical design constraints to improve environmental and human health performance like minimizing oven heating time, improving pollutant removal capacity, and efficiently reusing metal precursor solution. The life cycle environmental impact of Ti-WBAX was lower than Fe-WBAX as well as a mixed bed of WBAX and granular ferric hydroxide for all studied categories. A separate life cycle assessment found the total number of cancer and non-cancer cases prevented by drinking safer water outweighed those created by manufacture and use of water treatment materials and energy. However, treatment relocated who bore the health risk, concentrated it in a sub-population, and changed the primary manifestation from cancer to non-cancer disease. This tradeoff was partially mitigated by avoiding use of pH control chemicals. When properly synthesized, Fe-WBAX and Ti-WBAX sorbents maintained chromium removal capacity while significantly increasing arsenic removal capacity compared to the parent resin. The hybrid sorbent performance was demonstrated in packed beds using a challenging water matrix and low pollutant influent conditions. Breakthrough curves hint that the hexavalent chromium is removed by anion exchange and the arsenic is removed by metal oxide sorption. Overall, the hybrid nano-sorbent synthesis methods increased sustainability, improved sorbent characteristics, and increased simultaneous removal of chromium and arsenic for drinking water.
ContributorsGifford, James McKay (Author) / Westerhoff, Paul (Thesis advisor) / Hristovski, Kiril (Thesis advisor) / Chester, Mikhail (Committee member) / Arizona State University (Publisher)
Created2016
Description
Biomass synthesis is a competing factor in biological systems geared towards generation of commodity and specialty chemicals, ultimately limiting maximum titer and yield; in this thesis, a widely generalizable, modular approach focused on decoupling biomass synthesis from the production of the phenylalanine in a genetically modified strain of E. coli BW25113 was explored with the use of synthetic trans-encoded small RNA (sRNA) to achieve greater efficiency. The naturally occurring sRNA MicC was used as a scaffold, and combined on a plasmid with a promoter for anhydrous tetracycline (aTc) and a T1/TE terminator. The coding sequence corresponding to the target binding site for fourteen potentially growth-essential gene targets as well as non-essential lacZ was placed in the seed region of the of the sRNA scaffold and transformed into BW25113, effectively generating a unique strain for each gene target. The BW25113 strain corresponding to each gene target was screened in M9 minimal media; decreased optical density and elongated cell morphology changes were observed and quantified in all induced sRNA cases where growth-essential genes were targeted. Six of the strains targeting different aspects of cell division that effectively suppressed growth and resulted in increased cell size were then screened for viability and metabolic activity in a scaled-up shaker flask experiment; all six strains were shown to be viable during stationary phase, and a metabolite analysis showed increased specific glucose consumption rates in induced strains, with unaffected specific glucose consumption rates in uninduced strains. The growth suppression, morphology and metabolic activity of the induced strains in BW25113 was compared to the bacteriostatic additives chloramphenicol, tetracycline, and streptomycin. At this same scale, the sRNA plasmid targeting the gene murA was transformed into BW25113 pINT-GA, a phenylalanine overproducer with the feedback resistant genes aroG and pheA overexpressed. Two induction times were explored during exponential phase, and while the optimal induction time was found to increase titer and yield amongst the BW25113 pINT-GA murA sRNA variant, overall this did not have as great a titer or yield as the BW25113 pINT-GA strain without the sRNA plasmid; this may be a result of the cell filamentation.
ContributorsHerschel, Daniel Jordan (Author) / Nielsen, David R (Thesis advisor) / Torres, César I (Committee member) / Wang, Xuan (Committee member) / Arizona State University (Publisher)
Created2016
Description
Microbial Electrochemical Cell (MXC) technology harnesses the power stored in wastewater by using anode respiring bacteria (ARB) as a biofilm catalyst to convert the energy stored in waste into hydrogen or electricity. ARB, or exoelectrogens, are able to convert the chemical energy stored in wastes into electrical energy by transporting electrons extracellularly and then transferring them to an electrode. If MXC technology is to be feasible for ‘real world’ applications, it is essential that diverse ARB are discovered and their unique physiologies elucidated- ones which are capable of consuming a broad spectrum of wastes from different contaminated water sources.
This dissertation examines the use of Gram-positive thermophilic (60 ◦C) ARB in MXCs since very little is known regarding the behavior of these microorganisms in this setting. Here, we begin with the draft sequence of the Thermincola ferriacetica genome and reveal the presence of 35 multiheme c-type cytochromes. In addition, we employ electrochemical techniques including cyclic voltammetry (CV) and chronoamperometry (CA) to gain insight into the presence of multiple pathways for extracellular electron transport (EET) and current production (j) limitations in T. ferriacetica biofilms.
Next, Thermoanaerobacter pseudethanolicus, a fermentative ARB, is investigated for its ability to ferment pentose and hexose sugars prior to using its fermentation products, including acetate and lactate, for current production in an MXC. Using CA, current production is tracked over time with the generation and consumption of fermentation products. Using CV, the midpoint potential (EKA) of the T. pseudethanolicus EET pathway is revealed.
Lastly, a cellulolytic microbial consortium was employed for the purpose ofassessing the feasibility of using thermophilic MXCs for the conversion of solid waste into current production. Here, a highly enriched consortium of bacteria, predominately from the Firmicutes phylum, is capable of generating current from solid cellulosic materials.
This dissertation examines the use of Gram-positive thermophilic (60 ◦C) ARB in MXCs since very little is known regarding the behavior of these microorganisms in this setting. Here, we begin with the draft sequence of the Thermincola ferriacetica genome and reveal the presence of 35 multiheme c-type cytochromes. In addition, we employ electrochemical techniques including cyclic voltammetry (CV) and chronoamperometry (CA) to gain insight into the presence of multiple pathways for extracellular electron transport (EET) and current production (j) limitations in T. ferriacetica biofilms.
Next, Thermoanaerobacter pseudethanolicus, a fermentative ARB, is investigated for its ability to ferment pentose and hexose sugars prior to using its fermentation products, including acetate and lactate, for current production in an MXC. Using CA, current production is tracked over time with the generation and consumption of fermentation products. Using CV, the midpoint potential (EKA) of the T. pseudethanolicus EET pathway is revealed.
Lastly, a cellulolytic microbial consortium was employed for the purpose ofassessing the feasibility of using thermophilic MXCs for the conversion of solid waste into current production. Here, a highly enriched consortium of bacteria, predominately from the Firmicutes phylum, is capable of generating current from solid cellulosic materials.
ContributorsLusk, Bradley (Author) / Torres, César I (Thesis advisor) / Rittmann, Bruce E. (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Arizona State University (Publisher)
Created2015
Description
Since its first report in 1976, many outbreaks linked to Legionella have been reported in the world. These outbreaks are a public health concern because of legionellosis, which is found in two forms, Pontiac fever and Legionnaires disease. Legionnaires disease is a type of pneumonia responsible for the majority of the illness in the reported outbreaks of legionellosis. This study consists of an extensive literature review and experimental work on the aerosolization and UV inactivation of E.coli and Legionella under laboratory conditions. The literature review summarizes Legionella general information, occurrence, environmental conditions for its survival, transmission to human, collection and detection methodologies and Legionella disinfection in air and during water treatment processes.
E. coli was used as an surrogate for Legionella in experimentation due to their similar bacterial properties such as size, gram-negative rod-shaped, un-encapsulated and non-spore-forming bacterial cells. The accessibility and non-pathogenicity of E. coli also served as factors for the substitution.
Three methods of bacterial aerosolization were examined, these included an electric spray gun, an air spray gun and a hand-held spray bottle. A set of experiments were performed to examine E. coli aerosolization and transport in the aerosolization chamber (an air tight box) placed in a Biological Safety Cabinet. Spiked sample was sprayed through the opening from one side of the aerosolization chamber using the selected aerosolization methods. The air sampler was placed at the other side to collect 100 L air sample from the aerosolization chamber. A Tryptic Soy Agar plate was placed inside the air sampler to collect and subsequently culture E. coli cells from air. Results showed that the air spray gun has the best capability of aerosolizing bacteria cells under all the conditions examined in this study compared to the other two spray methods. In this study, we provide a practical and efficient method of bacterial aerosolization technique for microbial dispersion in air. The suggested method can be used in future research for microbial dispersion and transmission studies.
A set of experiments were performed to examine UV inactivation of E. coli and Legionella cells in air. Spiked samples were sprayed through the opening from one side of the aerosolization chamber using the air spray gun. A UV-C germicidal lamp inside the Biological Safety Cabinet was turned on after each spray. The air samples were collected as previously described. The application of UV-C for the inactivation of bacterial cells resulted in removing aerosolized E. coli and Legionella cells in air. A 1 log reduction was achieved with 5 seconds UV exposure time while 10 seconds UV exposure resulted in a 2 log bacterial reduction for both bacteria. This study shows the applicability of UV inactivation of pathogenic bacterial cells in air by short UV exposure time. This method may be applicable for the inactivation of Legionella in air ducts by installing germicidal UV lamps for protecting susceptible populations in certain indoor settings such as nursing homes or other community rooms.
E. coli was used as an surrogate for Legionella in experimentation due to their similar bacterial properties such as size, gram-negative rod-shaped, un-encapsulated and non-spore-forming bacterial cells. The accessibility and non-pathogenicity of E. coli also served as factors for the substitution.
Three methods of bacterial aerosolization were examined, these included an electric spray gun, an air spray gun and a hand-held spray bottle. A set of experiments were performed to examine E. coli aerosolization and transport in the aerosolization chamber (an air tight box) placed in a Biological Safety Cabinet. Spiked sample was sprayed through the opening from one side of the aerosolization chamber using the selected aerosolization methods. The air sampler was placed at the other side to collect 100 L air sample from the aerosolization chamber. A Tryptic Soy Agar plate was placed inside the air sampler to collect and subsequently culture E. coli cells from air. Results showed that the air spray gun has the best capability of aerosolizing bacteria cells under all the conditions examined in this study compared to the other two spray methods. In this study, we provide a practical and efficient method of bacterial aerosolization technique for microbial dispersion in air. The suggested method can be used in future research for microbial dispersion and transmission studies.
A set of experiments were performed to examine UV inactivation of E. coli and Legionella cells in air. Spiked samples were sprayed through the opening from one side of the aerosolization chamber using the air spray gun. A UV-C germicidal lamp inside the Biological Safety Cabinet was turned on after each spray. The air samples were collected as previously described. The application of UV-C for the inactivation of bacterial cells resulted in removing aerosolized E. coli and Legionella cells in air. A 1 log reduction was achieved with 5 seconds UV exposure time while 10 seconds UV exposure resulted in a 2 log bacterial reduction for both bacteria. This study shows the applicability of UV inactivation of pathogenic bacterial cells in air by short UV exposure time. This method may be applicable for the inactivation of Legionella in air ducts by installing germicidal UV lamps for protecting susceptible populations in certain indoor settings such as nursing homes or other community rooms.
ContributorsYao, Wei (Author) / Abbaszadegan, Morteza (Thesis advisor) / Fox, Peter (Committee member) / Alum, Absar (Committee member) / Arizona State University (Publisher)
Created2015
Description
In desert riparian ecosystems, rivers provide free water but access to that water diminishes with distance producing a steep gradient in the relative importance of water for growth and reproduction of riparian animals and hence, their biodiversity. Previous work suggests that water limited riparian predators eat more prey to meet their water demand where free water is not available. Here I explore the effect of water limitation on prey selection and per capita interaction strengths between a predatory spider ( Hogna antelucana) and two prey species occupying different trophic levels using a controlled field experiment conducted in the riparian forest of the San Pedro River, Cochise County, AZ. Lab measurements of water and energy content revealed that intermediate predators (smaller spiders in the genus Pardosa) had 100-fold higher energy: water ratios than an alternate prey species more basal in the food web (crickets in the genus Gryllus). Given this observation, I hypothesized that water-stressed predatory wolf spiders would select more water-laden crickets but switch to more energy rich Pardosa when water stress was experimentally eliminated. Additionally, I hypothesized that switching by quenched Hogna to Pardosa would reduce predation by Pardosa on Gryllus leading to increased abundance of the basal resource. Finally, I hypothesized that water mediated switching and release of basal prey would be stronger when male Hogna was the apex predator, because female Hogna have higher energetic costs of reproduction and hence, stronger energy limitation. Experimental water additions caused both sexes of Hogna to consume significantly higher numbers of Pardosa but this difference (between water and no-water treatments) did not vary significantly between male and female Hogna treatments. Similarly, strong negative interaction strengths between Hogna and Pardosa led to release of the basal prey species and positive interaction strengths of Hogna on Gryllus. Again strong positive, indirect effects of Hogna on Gryllus did not depend on the sex of the Hogna predator. However, water mediated indirect effects of Hogna (either sex) on Gryllus were the strongest for male Gryllus. These results suggest that water and energy co-dominate foraging decisions by predators and that in managing water-energy balance; predators can modify interaction pathways, sex-ratios of prey populations and trophic dynamics.
ContributorsLeinbach, Israel (Author) / Sabo, John (Thesis advisor) / Harrison, Jon (Committee member) / Johnson, Chadwick (Committee member) / Arizona State University (Publisher)
Created2015
Description
An insect society needs to share information about important resources in order to collectively exploit them. This task poses a dilemma if the colony must consider multiple resource types, such as food and nest sites. How does it allocate workers appropriately to each resource, and how does it adapt its recruitment communication to the specific needs of each resource type? In this dissertation, I investigate these questions in the ant Temnothorax rugatulus.
In Chapter 1, I summarize relevant past work on food and nest recruitment. Then I describe T. rugatulus and its recruitment behavior, tandem running, and I explain its suitability for these questions. In Chapter 2, I investigate whether food and nest recruiters behave differently. I report two novel behaviors used by recruiters during their interaction with nestmates. Food recruiters perform these behaviors more often than nest recruiters, suggesting that they convey information about target type. In Chapter 3, I investigate whether colonies respond to a tradeoff between foraging and emigration by allocating their workforce adaptively. I describe how colonies responded when I posed a tradeoff by manipulating colony need for food and shelter and presenting both resources simultaneously. Recruitment and visitation to each target partially matched the predictions of the tradeoff hypothesis. In Chapter 4, I address the tuned error hypothesis, which states that the error rate in recruitment is adaptively tuned to the patch area of the target. Food tandem leaders lost followers at a higher rate than nest tandem leaders. This supports the tuned error hypothesis, because food targets generally have larger patch areas than nest targets with small entrances.
This work shows that animal groups face tradeoffs as individual animals do. It also suggests that colonies spatially allocate their workforce according to resource type. Investigating recruitment for multiple resource types gives a better understanding of exploitation of each resource type, how colonies make collective decisions under conflicting goals, as well as how colonies manage the exploitation of multiple types of resources differently. This has implications for managing the health of economically important social insects such as honeybees or invasive fire ants.
In Chapter 1, I summarize relevant past work on food and nest recruitment. Then I describe T. rugatulus and its recruitment behavior, tandem running, and I explain its suitability for these questions. In Chapter 2, I investigate whether food and nest recruiters behave differently. I report two novel behaviors used by recruiters during their interaction with nestmates. Food recruiters perform these behaviors more often than nest recruiters, suggesting that they convey information about target type. In Chapter 3, I investigate whether colonies respond to a tradeoff between foraging and emigration by allocating their workforce adaptively. I describe how colonies responded when I posed a tradeoff by manipulating colony need for food and shelter and presenting both resources simultaneously. Recruitment and visitation to each target partially matched the predictions of the tradeoff hypothesis. In Chapter 4, I address the tuned error hypothesis, which states that the error rate in recruitment is adaptively tuned to the patch area of the target. Food tandem leaders lost followers at a higher rate than nest tandem leaders. This supports the tuned error hypothesis, because food targets generally have larger patch areas than nest targets with small entrances.
This work shows that animal groups face tradeoffs as individual animals do. It also suggests that colonies spatially allocate their workforce according to resource type. Investigating recruitment for multiple resource types gives a better understanding of exploitation of each resource type, how colonies make collective decisions under conflicting goals, as well as how colonies manage the exploitation of multiple types of resources differently. This has implications for managing the health of economically important social insects such as honeybees or invasive fire ants.
ContributorsCho, John Yohan (Author) / Pratt, Stephen C (Thesis advisor) / Hölldobler, Bert (Committee member) / Liebig, Jürgen R (Committee member) / Amazeen, Polemnia G (Committee member) / Rutowski, Ronald L (Committee member) / Arizona State University (Publisher)
Created2019
Description
This study reports on the treatment of ammunition wastewater containing RDX (1,3,5-Trinitro-1,3,5-triazinane), HMX (1,3,5,7-Tetranitro-1,3,5,7-tetrazoctane), and the oxyanion co-contaminants nitrate (NO3-) and perchlorate (ClO4-) in a membrane biofilm reactor (MBfR), a Palladium (Pd)-coated MBfR (Pd-MBfR), and an abiotic Pd-coated film reactor (Pd-film reactor). A consortium of nitrate- and perchlorate-reducing bacteria, continuously fed with synesthetic ammunition wastewater featuring 4 mM nitrate and 0.1-2 mM perchlorate, formed robust biofilms on the membrane surfaces in the MBfR and Pd-MBfR. PdNPs with diameter 4-5-nm auto-assembled and stabilized on the surfaces of membrane and biofilm in MPfR and Pd-MBfR. Nitrate and perchlorate were rapidly reduced by the biofilms in the MBfR and Pd-MBfR, but they were not catalytically reduced through PdNPs alone in the MPfR. In contrast, RDX or HMX was recalcitrant to enzymatic degradation in MBfR, but was rapidly reduced through Pd-catalytic denitration in the MPfR and Pd-MBfR to form ‒N‒NHOH or ‒N‒H. Based on the experimental results, the synergistic coupling of Pd-based catalysis and microbial activity in the Pd-MBfR should be a viable new technology for treating ammunition wastewater.
ContributorsZheng, Chenwei (Author) / Rittmann, Bruce (Thesis advisor) / Delgado, Anca (Committee member) / Lai, Yen-Jung (Committee member) / Arizona State University (Publisher)
Created2019