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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
Hydrogen is a key indicator of microbial activity in soils/sediments and groundwater because of its role as an electron donor for reducing sulfate and nitrate and carrying out other metabolic processes. The goal of this study was to quantitatively measure the total biological hydrogen demand (TBHD) of soils and sediments in anaerobic environments. We define the total biological hydrogen demand as the sum of all electron acceptors that can be used by hydrogen-oxidizing microorganisms. Three sets of anaerobic microcosms were set up with different soils/sediments, named Carolina, Garden, and ASM. The microcosms included 25g of soil/sediment and 75 mL of anaerobic medium. 10 mL of hydrogen were pulse-fed for 100 days. Hydrogen consumption and methane production were tracked using gas chromatography. Chemical analysis of each soil was performed at the beginning of the experiment to determine the concentration of electron acceptors in the soils/sediments, including nitrate, sulfate, iron and bicarbonate. An analysis of the microbial community was done at t = 0 and at the end of the 100 days to examine changes in the microbial community due to the metabolic processes occurring as hydrogen was consumed. Carolina consumed 9810 43 mol of hydrogen and produced 19,572 2075 mol of methane. Garden consumed 4006 33 mol of hydrogen and produced 7,239 543 mol of methane. Lastly, ASM consumed 1557 84 mol of hydrogen and produced 1,325 715 mol of methane. I conclude that the concentration of bicarbonate initially present in the soil had the most influence over the hydrogen demand and microbial community enrichment. To improve this research, I recommend that future studies include a chemical analysis of final soil geochemistry conditions, as this will provide with a better idea of what pathway the hydrogen is taking in each soil.
ContributorsLuna Aguero, Marisol (Author) / Krajmalnik-Brown, Rosa (Thesis director) / Delgado, Anca (Committee member) / Civil, Environmental and Sustainable Engineering Programs (Contributor) / School of Sustainability (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
The effect of an anaerobic reductive environment produced by the oxidation of zero valent iron (ZVI) on the microbial reductive dechlorination of trichloroethylene and its applicability to in-situ bioremediation processes was investigated using microcosms and soil column studies. I learned that microbial dechlorination requires a highly reductive environment, as represented by negative values for oxidation-reduction potential (ORP), which can be maintained through the addition of reducing agents such as ZVI, or to a lesser extent, the fermentation of added substrates such as lactate. Microcosm conditions represented distance from an in-situ treatment injection well and contained different types of iron species and dechlorinating bioaugmentation cultures. Diminishing efficacy of microbial reductive dechlorination along a gradient away from the injection zone was observed, characterized by increasing ORP and decreasing pH. Results also suggested that the use of particular biostimulation substrates is key to prioritizing the dechlorination reaction against competing microbial and abiotic processes by supplying electrons needed for microbial dechlorination.
ContributorsMouti, Aatikah (Author) / Krajmalnik-Brown, Rosa (Thesis director) / Delgado, Anca (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-12
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
While most household surfactants are biodegradable in aerobic conditions, their presence in a microbiological treatment process can lead to the proliferation of antimicrobial-resistance genes (ARG) in bacteria, such as Pseudomonas aeruginosa. Surfactants can be cationic, anionic, or zwitterionic, and these different classes may have different effects on the proliferation of ARG. This study evaluated how the three classes of surfactants affected the microbial community’s structure and ARG in O2-based membrane biofilm reactors (O2-MBfRs) that provided at least 98% surfactant removal. Cationic cetrimonium bromide (CTAB) had by far the strongest impact with highest ARG abundance in the biofilm. In particular, Pseudomonas and Stenotrophomonas, the two main genera in the biofilm treating CTAB, were highly correlated to the abundance of ARG for efflux pumps and antibiotic inactivation. CTAB also promoted potential of horizontal gene transfer (HGT) of ARG. Combining results from the metabolome and metagenome identified four possible pathways for CTAB biodegradation. Of special important is a new pathway: β-carbon oxidation of CTAB to produce betaine. An insufficient nitrogen source could lead to irreversible ARB and ARG enrichment in the MBfR biofilm. Finally, a two-stage O2-MBfR successfully removed a high concentration (730 mg/L) of CTAB: Partial CTAB removal in the Lead reactor relieved inhibition in the Lag reactor. Metagenomic analysis also revealed that the Lag reactor was enriched in genes for CTAB and metabolite oxygenation.
ContributorsZheng, Chenwei (Author) / Rittmann, Bruce (Thesis advisor) / Delgado, Anca (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Lai, Yen-Jung (Committee member) / Arizona State University (Publisher)
Created2023
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
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
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
Nutrient rich agricultural runoff is a major source of phosphorus (P) and nitrogen (N) loading to surface waters, resulting in eutrophication and harmful algal blooms. The most effective nutrient removal technologies often have cost, land, or operational requirements that limits use in the decentralized areas that need it most. This dissertation investigated combined physical-chemical and microbiological technologies for combined P and N removal from nonpoint sources. Chapter 2 investigated the combination of basic oxygen furnace (BOF) steel slag and woody mulch for P removal by mineral precipitation and N removal by microbial denitrification. When combined with mulch in column experiments, slag with high fines content achieved complete P removal under unsaturated conditions. Batch experiments showed that microbial denitrification occurred under the highly alkaline conditions created by steel slag, but the timescale differential between P and N removal was a critical barrier to combining these treatment technologies. Chapter 3 evaluated a field-scale slag filter to treat agricultural tile drainage and lab-scale column experiments to provide insight on field conditions that impacted P removal. Increases in alkalinity had negative influences on P removal through inhibition of P mineral precipitation by BOF slag, while blast furnace (BF) steel slag was less impacted by alkalinity due to primarily adsorptive P removal. Regeneration strategies were identified based on water quality and slag type.Chapters 4 and 5 explored biological ion exchange (BIEX) as an option for addressing the timescale offset identified in Chapter 1. In Chapter 4 columns fed with dissolved organic matter (DOM) were not regenerated and over 50% DOM removal was observed, with the primary mechanism of removal identified as secondary ion exchange (SIEX)
between sulfate and DOM fractions with high affinities for ion exchange. Chapter 5 aimed to expand BIEX to N treatment through batch denitrification and adsorption experiments, which revealed a positive relationship between molecular weight of organic molecules and their ability to displace nitrate. This work shows that by having an improved understanding of impacted water characteristics, the information presented in this work can be used to select and implement effective treatment technologies for decentralized areas.
ContributorsEdgar, Michael Garrett (Author) / Boyer, Treavor H (Thesis advisor) / Hamdan, Nasser (Committee member) / Delgado, Anca (Committee member) / Arizona State University (Publisher)
Created2022
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