Matching Items (32)
Description
Large quantities of sodic and alkaline bauxite residue are produced globally as a by-product from alumina refineries. Ecological stoichiometry of key elements [nitrogen (N) and phosphorus (P)] plays a critical role in establishing vegetation cover in bauxite residue sand (BRS). Here we examined how changes in soil chemical properties over time in rehabilitated sodic and alkaline BRS affected leaf N to P stoichiometry of native species used for rehabilitation. Both Ca and soil pH influenced the shifts in leaf N:P ratios of the study species as supported by consistently significant positive relationships (P < 0.001) between these soil indices and leaf N:P ratios. Shifts from N to P limitation were evident for N-fixing species, while N limitation was consistently experienced by non-N-fixing plant species. In older rehabilitated BRS embankments, soil and plant indices (Ca, Na, pH, EC, ESP and leaf N:P ratios) tended to align with those of the natural ecosystem, suggesting improved rehabilitation performance. These findings highlight that leaf N:P stoichiometry can effectively provide a meaningful assessment on understanding nutrient limitation and productivity of native species used for vegetating highly sodic and alkaline BRS, and is a crucial indicator for assessing ecological rehabilitation performance.
ContributorsGoloran, Johnvie B. (Author) / Chen, Chengrong (Author) / Phillips, Ian R. (Author) / Elser, James (Author) / College of Liberal Arts and Sciences (Contributor) / School of Life Sciences (Contributor)
Created2015-10-07
Composition and Dynamics of Microbiomes Involved in Chain Elongation Driven Reductive Dehalogenation
Description
Microbial chain elongation (CE) has been shown at laboratory scale to drive reductive dehalogenation (RD) of chlorinated ethenes through both primary (oxidation of ethanol) and secondary (fermentation of medium chain carboxylates) hydrogen (H2) production. This process can offer engineers a sustainable in situ bioremediation alternative to address the challenges of conventional treatment technologies and processes. To aid in moving this process into field scale applications, a greater understanding of the specific microbiomes involved in both primary and secondary processes is needed. In this study, microbial community analysis was conducted on groundwater microcosms under various CE substrate combinations to quantify the extent of CE and the effect on RD of cis-1,2-dichloroethene (cis-DCE). Taxonomic classification of amplicon sequence variants obtained from DNA extracted from groundwater microcosms were used to characterize microbiomes using QIIME 2. Pielou’s eveness and beta diversity (via unweighted UniFrac distances) analyses were performed to assess the diversity of microbiomes. Overall, low concentration microcosms (excluding L-7:1 EtOH:Butyrate and L-9:1 EtOH:Acetate + Soil) underwent complete RD, as evidenced by significant ethene production. Alpha and beta diversity analyses confirm the findings of chemical data that the overall substrate concentrations played a major role in determining the extent of CE and RD.
ContributorsGaura, Alex (Author) / Delgado, Anca (Thesis director) / Robles, Aide (Committee member) / Barrett, The Honors College (Contributor) / School of Sustainable Engineering & Built Envirnmt (Contributor)
Created2023-05
Description
Chlorinated ethene contamination is present at hundreds of sites around the U.S. and threatens the health and quality of living in many communities. Complete reductive dechlorination of chlorinated ethenes to ethene is possible by the anaerobic bacteria Dehalococcoides mccartyi which uses H2 as an electron donor for the process. Microbial chain elongation (MCE) has recently shown viability as an H2 producing process for reductive dechlorination. This study examined the presence of native chain-elongating organisms in soil and groundwater samples from a Superfund site contaminated with chlorinated ethenes using batch microcosms experiments. The study’s findings have implications for the use of MCE to promote detoxification of chlorinated ethenes at contaminated sites.
ContributorsSilverman, Maxwell (Author) / Delgado, Anca (Thesis director) / Robles, Aide (Committee member) / Barrett, The Honors College (Contributor) / School of Politics and Global Studies (Contributor) / School of Sustainable Engineering & Built Envirnmt (Contributor)
Created2022-05
Description
In the realm of environmental engineering, the compound N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD), has recently emerged as an environmental concern. 6PPD serves as a tire additive to prolong the lifespan of rubber but can transform into a more toxic derivative, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine-quinone (6PPD-quinone), when exposed to ground-level ozone. Initially, my research sought to investigate the biodegradation of 6PPD and 6PPD-quinone using microbial cultures. However, unexpected challenges arising from limited solubility and potential toxicity to microorganisms led to a shift in research objectives. The study then refocused on developing methods for detecting and quantifying 6PPD and 6PPD-quinone. The scarcity of literature available on the environmental fate and transport of these compounds underscores the pressing need for further research to gain a comprehensive understanding of the behavior of these chemicals. Consequently, the development of effective detection strategies will enable the development of effective remediation strategies to safeguard aquatic ecosystems.
ContributorsKoenig-Vinicombe, Ryan (Author) / Delgado, Anca (Thesis director) / Skinner, Justin (Committee member) / Barrett, The Honors College (Contributor) / College of Integrative Sciences and Arts (Contributor) / School of Sustainability (Contributor) / School of Sustainable Engineering & Built Envirnmt (Contributor)
Created2023-12
Description
Lactate and methanol have been the most commonly used electron donors in the Krajmalnik-Brown laboratory for efficient microbial dechlorination of trichloroethene (TCE). Our goal was to assess the technical and economic feasibility of molasses and ethanol, two alternative electron donors by evaluating their costs and ability support complete TCE dechlorination to ethene. First, ethanol and molasses, with and without methanol, were evaluated for their abilities to support complete dechlorination in batch serum bottles. Molasses, the cheapest alternative, supported a similar dechlorination performance to lactate in batch experiments, so we then used it in an upflow anaerobic bioreactor (UABR) to test its ability to support rapid dechlorination in this continuous system. Molasses supported 88% TCE conversion to ethene at a hydraulic retention time (HRT) of 13 hours after 80 days of operation in continuous mode. Compared to the UABR operated previously using lactate and methanol, molasses led to a reduction of TCE conversion to ethene, and a possible increase in time required to produce culture. Additionally, when molasses was used as the electron donor, we encountered new difficulties in the operation of the UABR, such as drastic pH changes. Therefore, I conclude that the savings from using molasses is outweighed by the costs associated with the reduction in dechlorination performance and increase in reactor maintenance. I recommend that lactate and methanol continue to be used as the electron donors in the Krajmalnik- Brown dechlorination lab to support fast-rate and cost-effective production of dechlorinating culture in an UABR. Because molasses supported fast rates of dechlorination in the batch experiment, however, it is potentially a better option than lactate and methanol for batch production of culture or for biostimulation, where the aquifer resembles a batch system. I recommend that further studies be done to reach a general conclusion about the feasibility of molasses as an electron donor for other enhanced bioremediation projects.
ContributorsBondank, Emily Nicole (Author) / Krajmalnik-Brown, Rosa (Thesis director) / Delgado, Anca (Committee member) / Torres, Cesar (Committee member) / Civil, Environmental and Sustainable Engineering Programs (Contributor) / Barrett, The Honors College (Contributor)
Created2014-12
Description
It is common to use crumb rubber as modifier in bitumen. Good performance of crumb rubber in bitumen has been reported in terms of improving characteristics like higher skid resistance, reducing noise, higher rutting resistance and longevity. However, due to the vulcanization, the polymeric crosslinked structure of crumb rubber suffers from inadequate dispersion and incompatibility in bitumen where storage stability becomes an issue. To solve this problem, partial surface devulcanization of the rubber via chemical and microbial surface activation was examined in this study showing both method can be effective to enhance rubber-bitumen interactions and subsequently storage stability of the rubberized bitumen. To ensure proper surface activation, it is important to thoroughly understand chemo-mechanics of bitumen containing rubber particles as well as underlying interaction mechanism at the molecular level. Therefore, this study integrates a multi-scale approach using density functional theory based computational modeling and laboratory experiments to provide an in-depth understanding of the mechanisms of interaction between surface activated rubber and bitumen. To do so, efficacy of various bio-modifiers was examined and compared it terms of both surface activation capability and durability of resulting rubberized bitumen. It was found that biomodifiers with various compositions can have either synergistic or antagonistic effect onchemo-mechanics of rubberized bitumen. The study was further extended to study the interplay of Polyphosphoric Acid (PPA) and these biomodified rubberized bitumens showing not all modifiers have high synergy with PPA in bitumens. Finally, durability of rubberized bitumen was studied in terms of its resistance to Ultraviolet (UV) aging. It was shown that there is a strong relation between composition of biomodified rubberized bitumen and its resistance to UV-aging.
ContributorsKabir, Sk Faisal (Author) / Fini, Elham (Thesis advisor) / Kaloush, Kamil (Committee member) / Lamanna, Anthony (Committee member) / Delgado, Anca (Committee member) / Poulikakos, Lily (Committee member) / Arizona State University (Publisher)
Created2020
Description
The study was to analyze the extent of bacterial transport in a two-dimensional tank under saturated conditions. The experiments were done in a 2-D tank packed with 3,700 in3 of fine grained, homogenous, chemically inert sand under saturated conditions. The tank used for transport was decontaminated by backwashing with 0.6% chlorine solution with subsequent backwashing with chlorine-neutral water (tap water and Na2S2O3) thus ensuring no residual chlorine in the tank. The transport of bacteria was measured using samples collected from ports at vertical distances of 5, 15 and 25 inches (12.7, 38.1 and 63.5 cm) from the surface of the sand on both sides for the 2-D tank. An influent concentration of 105 CFU/mL was set as a baseline for both microbes and the percolation rate was set at 11.37 inches/day using a peristaltic pump at the bottom outlet. At depths of 5, 15 and 25 inches, E. coli breakthroughs were recorded at 5, 17 and 28 hours for the ports on the right side and 7, 17 and 29 hours for the ports on the left sides, respectively. At respective distances Legionella breakthroughs were recorded at 8, 22 and 35 hours for the ports on the right side and 9, 24, 36 hours for the ports on the left side, respectively which is homologous to its pleomorphic nature. A tracer test was done and the visual breakthroughs were recorded at the same depths as the microbes. The breakthroughs for the dye at depths of 5, 15 and 25 inches, were recorded at 13.5, 41 and 67 hours for the ports on the right side and 15, 42.5 and 69 hours for the ports on the left side, respectively. However, these are based on visual estimates and the physical breakthrough could have happened at the respective heights before the reported times. This study provided a good basis for the premise that transport of bacterial cells and chemicals exists under recharge practices.
ContributorsMondal, Indrayudh (Author) / Abbaszadegan, Morteza (Thesis advisor) / Dahlen, Paul (Committee member) / Delgado, Anca (Committee member) / Arizona State University (Publisher)
Created2019
Description
Urease, an amidohydrolase, is an essential ingredient in the emerging engineering technique of biocementation. When free urease enzyme is used this carbonate precipitation process is often referred to as enzyme induced carbonate precipitation (EICP). To date, most engineering applications of EICP have used commercially available powdered urease. However, the high cost of commercially available urease is a major barrier to adoption of engineering applications of EICP in practice. The objective of this dissertation was to develop a simple and inexpensive enzyme production technique using agricultural resources. The specific objectives of this dissertation were (i) to develop a simple extraction process to obtain urease from common agricultural resources and identify a preferred agricultural resource for further study, (ii) to reduce the cost of enzyme production by eliminating the use of a buffer, centrifugation, and dehusking of the beans during the extraction process, (iii) investigate the stability of the extracted enzyme both in solution and after reduction to a powder by lyophilization (freeze-drying), and (iv) to study the kinetics of the extracted enzyme.
The results presented in this dissertation confirmed that inexpensive crude extracts of urease from agricultural products, including jack beans, soybeans, and watermelon seeds, are effective at catalyzing urea hydrolysis for carbonate precipitation. Based upon unit yield, jack beans were identified as the preferred agricultural resource for urease extraction. Results also showed that the jack bean extract retained its activity even after replacing the buffer with tap water and eliminating acetone fractionation, centrifugation, and dehusking. It was also found that the lyophilized crude extract maintained its activity during storage for at least one year and more effectively than either the crude extract solution or rehydrated commercial urease. The kinetics of the extracted enzyme was studied to gain greater insight into the optimum concentration of urea in engineering applications of EICP. Results showed higher values for the half-saturation coefficient of the crude extract compared to the commercial enzymes.
The results presented in this dissertation demonstrate the potential for a significant reduction in the cost of applying EICP in engineering practice by mass production of urease enzyme via a simple extraction process.
ContributorsJavadi, Neda (Author) / Kavazanjian, Edward (Thesis advisor) / Khodadadi Tirkolaei, Hamed (Committee member) / Hamadan, Naser (Committee member) / Delgado, Anca (Committee member) / Arizona State University (Publisher)
Created2021
Description
Phosphate production, the main component of fertilizers, generates a byproduct phosphogypsum (PG; CaSO4•H2O). In this work, I present a sustainable biotechnological method to recover elemental sulfur (S0) from PG using membrane biofilm reactors (MBfRs) with the first step of sulfate reduction to soluble sulfide in the hydrogen (H2)-based MBfR and second step as soluble-sulfide oxidation to elemental sulfur (S0) in the oxygen (O2)-based MBfR. I evaluated the H2-MBfR to reduce sulfate leached from phosphogypsum water (PG water). In-depth alkalinity, precipitation, and mass balance analysis revealed that inorganic precipitation, mainly calcium sulfate, competed with sulfate reduction to soluble sulfide especially when H2 delivery was lower due to CO2 accumulation in the fibers’ lumen. The H2-MBfR is a feasible biotechnology to reduce sulfate from PG water to soluble sulfide and its long-term operation success for sulfur recovery requires calcium removal and ensuring hydrogen availability by venting CO2 when delivered through the fibers.
I removed calcium from PG water via cation-exchange and re-evaluated the H2-MBfR. A high sulfate reduction flux was achieved, double the flux achieved when calcium was present but soluble sulfide concentrations remained low. Shallow metagenomic analysis of the collected biofilm sample revealed several bacteria genera competing for H2 and SO42-. A careful control of H2 is needed to minimize the growth of competing bacteria and a pH control method is needed to promote dissimilatory sulfate reduction pathway to increase soluble sulfide in the effluent.
I optimized the O2-MBfR to partially oxidize sulfide into S0 using a synthetic high-sulfide wastewater. I found that the ratio of O2-delivery capacity to the O2 surface loading for partial oxidation of sulfide to S0 1.5 gO2/gO2 to simultaneously achieve high degrees sulfide oxidation and S0 recovery. To be able to control S0 recovery in the O2-MBfR, I tested a biofilm management method, hydraulic-flow reversal, in which I applied a reverse recirculation to gently shear off the retained S0. All the retained S0 was released but performance declined to 70%. Further development of the frequency of hydraulic-induced detachment is needed to determine its best application and its effects on the biofilm and S0 formation.
ContributorsAlsanea, Anwar (Author) / Rittmann, Bruce (Thesis advisor) / Delgado, Anca (Committee member) / Zhou, Chen (Committee member) / Arizona State University (Publisher)
Created2024
Description
In order to optimize the ability of Geobacter sulfurreducens to produce electrical current and remediate wastewater, several physiological challenges must be overcome. The accumulation of protons at the electrode surface of a microbial fuel cell (MFC) decreases the pH, and, thus, the ability of the bacteria to maintain baseline metabolic conditions. To evaluate the extent to which this pH change hinders performance, the buffer concentration supplied to G. sulfurreducens reactors was varied. The resulting biofilms were subjected to chronoamperometry, cyclic voltammetry, and confocal microscopy to determine metabolic function and biofilm thickness. Biofilms grown with a 30-mM bicarbonate buffer experienced limitations on cell function and current output due to proton accumulation, while 90- and 150-mM conditions alleviated these limitations most of the measurements. Based on the current output, estimated biofilm thickness, and the medium-rate and slow-rate scan rate cyclic voltammetry, benefits exist for buffer concentrations greater than 30 mM. If the kinetics of G. sulfurreducens electron transfer are optimized, the potential of the technique to be implemented for energy recovery is improved.
ContributorsCoulam, Jordan (Author) / Torres, Cesar (Thesis advisor) / Delgado, Anca (Committee member) / Rittmann, Bruce (Committee member) / Arizona State University (Publisher)
Created2024