Matching Items (13)
Filtering by
- All Subjects: Environmental engineering
- Creators: Delgado, Anca G
- Resource Type: Text
Description
The goal of this research was to study the effect of dilution on ammonium and potassium removal from real hydrolyzed urine. The performance of two natural zeolites, clinoptilolite and chabazite, was studied and compared with the help of batch equilibrium experiments at four dilution levels: 100%, 10%, 1% and 0.1% (urine volume/total solution volume). Further, the sorption behavior of other exchangeable ions (sodium, calcium and magnesium) in clinoptilolite and chabazite was studied to improve the understanding of ion exchange stoichiometry. Ammonium and potassium removal were highest at undiluted level in samples treated with clinoptilolite. This is a key finding as it illustrates the benefit of urine source separation. Chabazite treated samples showed highest ammonium and potassium removal at undiluted level at lower doses. At higher doses, potassium removal was similar in undiluted and 10% urine solutions whereas ammonium removal was the highest in 10% urine solutions. In general, chabazite showed higher ammonium and potassium removal than clinoptilolite. The result showed that ion exchange was stoichiometric in solutions with higher urine volumes.
ContributorsRegmi, Urusha (Author) / Boyer, Treavor H (Thesis advisor) / Delgado, Anca G (Committee member) / Hamilton, Kerry (Committee member) / Arizona State University (Publisher)
Created2019
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
Petroleum contamination is ubiquitous during extraction, transportation, refining, and storage. Contamination damages the soil’s ecosystem function, reduces its aesthetics, and poses a potential threat to human beings. The overall goals of this dissertation are to advance understanding of the mechanisms behind ozonation of petroleum-contaminated soil and to configure an effective integrated bioremediation + ozonation remedial strategy to remove the overall organic carbon. Using a soil column, I conducted batch ozonation experiments for different soils and at different moisture levels. I measured multiple parameters: e.g., total petroleum hydrocarbons (TPH) and dissolved organic carbon (DOC), to build a full understanding of the data that led to the solid conclusions. I first demonstrated the feasibility of using ozone to attack heavy petroleum hydrocarbons in soil settings. I identified the physical and chemical hurdles (e.g., moisture, mass transfer, pH) needed to be overcome to make the integration of chemical oxidation and biodegradation more efficient and defines the mechanisms behind the experimental observations. Next, I completed a total carbon balance, which revealed that multiple components, including soil organic matter (SOM) and non-TPH petroleum, competed for ozone, although TPH was relatively more reactive. Further experiments showed that poor soil mixing and high soil-moisture content hindered mass transfer of ozone to react with the TPH. Finally, I pursued the theme of optimizing the integration of ozonation and biodegradation through a multi-stage strategy. I conducted multi-stages of ozonation and bioremediation for two benchmark soils with distinctly different oils to test if and how much ozonation enhanced biodegradation and vice versa. With pH and moisture optimized for each step, pre-ozonation versus post-ozonation was assessed for TPH removal and mineralization. Multi-cycle treatment was able to achieve the TPH regulatory standard when biodegradation alone could not. Ozonation did not directly enhance the biodegradation rate of TPH; instead, ozone converted TPH into DOC that was biodegraded and mineralized. The major take-home lesson from my studies is that multi-stage ozonation + biodegradation is a useful remediation tool for petroleum contamination in soil.
ContributorsChen, Tengfei (Author) / Rittmann, Bruce E. (Thesis advisor) / Westerhoff, Paul (Committee member) / Krajmalnik-Brown, Rosa (Committee member) / Delgado, Anca G (Committee member) / Arizona State University (Publisher)
Created2018
Description
Mineral weathering and industrial activities cause elevated concentration of hexavalent chromium (Cr(VI)) in groundwater, and this poses potential health concern (>10 ppb) to southwestern USA. The conversion of Cr(VI) to Cr(III) – a fairly soluble and non-toxic form at typical pH of groundwater is an effective method to control the mobility and carcinogenic effects of Cr(VI). In-situ chemical reduction using SnCl2 was investigated to initiate this redox process using jar testing with buffered ultrapure water and native Arizona groundwater spiked with varying Cr(VI) concentrations. Cr(VI) transformation by SnCl2 is super rapid (<60 seconds) and depends upon the molar dosage of Sn(II) to Cr(VI). Cr(VI) removal improved significantly at higher pH while was independent on Cr(VI) initial concentration and dissolved oxygen (DO) level. Co-existing oxyanions (As and W) competed with Cr(VI) for SnCl2 oxidation and adsorption sites of formed precipitates, thus resulted in lower Cr(VI) removal in the challenge water. SnCl2 reagent grade and commercial grade behaved similarly when freshly prepared, but the reducing strength of the commercial product decreased by 50% over a week after exposing to atmosphere. Equilibrium modeling with Visual MINTEQ suggested redox potential < 400 mV to reach Cr(VI) treatment goal of 10 ppb. Kinetics of Cr(VI) reduction was simulated via the rate expression: r=-k[H+]-0.25[Sn2+]0.5[Cr2O72-]3 with k = 0.146 uM-2.25s-1, which correlated consistently with experimental data under different pH and SnCl2 doses. These results proved SnCl2 reductive treatment is a simple and highly effective method to treat Cr(VI) in groundwater.
ContributorsNguyen, Duong Thanh (Author) / Westerhoff, Paul K (Thesis advisor) / Delgado, Anca G (Committee member) / Sinha, Shahnawaz (Committee member) / Arizona State University (Publisher)
Created2019
Description
This study was designed to provide insight into microbial transport kinetics which might be applied to bioremediation technology development and prevention of groundwater susceptibility to pathogen contamination. Several pilot-scale experiments were conducted in a saturated, 2 dimensional, packed porous media tank to investigate the transport of Escherichia coli bacteria, P22 bacteriophage, and a visual tracer and draw comparisons and/or conclusions. A constructed tank was packed with an approximate 3,700 cubic inches (in3) of a fine grained, homogeneous, chemically inert sand which allowed for a controlled system. Sampling ports were located at 5, 15, 25, and 25 vertical inches from the base of the 39 inch saturated zone and were used to assess the transport of the selected microorganisms. Approximately 105 cells of E. coli or P22 were injected into the tank and allowed to move through the media at approximately 10.02 inches per day. Samples were collected intermittently after injection based off of an estimated sampling schedule established from the visual tracer.
The results suggest that bacteriophages pass through soil faster and with greater recovery than bacteria. P22 in the tank reservoir experienced approximately 1 log reduction after 36 hours. After 85 hours, P22 was still detected in the reservoir after experiencing a 2 log reduction from the start of the experiment. E. coli either did not reach the outlet or died before sampling, while P22 was able to be recovered. Bacterial breakthrough curves were produced for the microbial indicators and illustrate the peak concentrations found for each sampling port. For E. coli, concentrations at the 5 inch port peaked at a maximum of 5170 CFU/mL, and eventually at the 25 inch port at a maximum of 90 CFU/mL. It is presumed that E. coli might have experienced significant filtration, straining and attachment, while P22 might have experienced little adsorption and instead was transported rapidly in long distances and was able to survive for the duration of the experiment.
The results suggest that bacteriophages pass through soil faster and with greater recovery than bacteria. P22 in the tank reservoir experienced approximately 1 log reduction after 36 hours. After 85 hours, P22 was still detected in the reservoir after experiencing a 2 log reduction from the start of the experiment. E. coli either did not reach the outlet or died before sampling, while P22 was able to be recovered. Bacterial breakthrough curves were produced for the microbial indicators and illustrate the peak concentrations found for each sampling port. For E. coli, concentrations at the 5 inch port peaked at a maximum of 5170 CFU/mL, and eventually at the 25 inch port at a maximum of 90 CFU/mL. It is presumed that E. coli might have experienced significant filtration, straining and attachment, while P22 might have experienced little adsorption and instead was transported rapidly in long distances and was able to survive for the duration of the experiment.
ContributorsAcosta, Jazlyn Cauren (Author) / Abbaszadegan, Morteza (Thesis advisor) / Dahlen, Paul (Committee member) / Fox, Peter (Committee member) / Arizona State University (Publisher)
Created2017
Description
The advantages and challenges of combining zero-valent iron (ZVI) and microbial reduction of trichloroethene (TCE) and perchlorate (ClO4-) in contaminated soil and groundwater are not well understood. The objective of this work was to identify the benefits and limitations of simultaneous application of ZVI and bioaugmentation for detoxification of TCE and ClO4- using conditions relevant to a specific contaminated site. We studied conditions representing a ZVI-injection zone and a downstream zone influenced Fe (II) produced, for simultaneous ZVI and microbial reductive dechlorination applications using bench scale semi-batch microcosm experiments. 16.5 g L-1 ZVI effectively reduced TCE to ethene and ethane but ClO4- was barely reduced. Microbial reductive dechlorination was limited by both ZVI as well as Fe (II) derived from oxidation of ZVI. In the case of TCE, rapid abiotic TCE reduction made the TCE unavailable for the dechlorinating bacteria. In the case of perchlorate, ZVI inhibited the indigenous perchlorate-reducing bacteria present in the soil and groundwater. Further, H2 generated by ZVI reactions stimulated competing microbial processes like sulfate reduction and methanogenesis. In the microcosms representing the ZVI downstream zone (Fe (II) only), we detected accumulation of cis-dichloroethene (cis-DCE) and vinyl chloride (VC) after 56 days. Some ethene also formed under these conditions. In the absence of ZVI or Fe (II), we detected complete TCE dechlorination to ethene and faster rates of ClO4- reduction. The results illustrate potential limitations of combining ZVI with microbial reduction of chlorinated compounds and show the potential that each technology has when applied separately.
ContributorsMohana Rangan, Srivatsan (Author) / Krajmalnik-Brown, Rosa (Thesis advisor) / Delgado, Anca G (Committee member) / Lowry, Gregory V. (Committee member) / Arizona State University (Publisher)
Created2017
Description
Trichloroethene (TCE) and hexavalent chromium (Cr (VI)) are ubiquitous subsurface contaminants affecting the water quality and threatening human health. Microorganisms capable of TCE and Cr (VI) reductions can be explored for bioremediation at contaminated sites. The goal of my dissertation research was to address challenges that decrease the efficiency of bioremediation in the subsurface. Specifically, I investigated strategies to (i) promote improve microbial reductive dechlorination extent through the addition of Fe0 and (ii) Cr (VI) bio-reduction through enrichment of specialized microbial consortia. Fe0 can enhance microbial TCE reduction by inducing anoxic conditions and generating H2 (electron donor). I first evaluated the effect of Fe0 on microbial reduction of TCE (with ClO4– as co-contaminant) using semi-batch soil microcosms. Results showed that high concentration of Fe0 expected during in situ remediation inhibited microbial TCE and ClO4– reduction when added together with Dehalococcoides mccartyi-containing cultures. A low concentration of aged Fe0 enhanced microbial TCE dechlorination to ethene and supported complete microbial ClO4– reduction. I then evaluated a decoupled Fe0 and biostimulation/bioaugmentation treatment approach using soil packed columns with continuous flow of groundwater. I demonstrated that microbial TCE reductive dechlorination to ethene can be benefitted by Fe0 abiotic reactions, when biostimulation and bioaugmentation are performed downstream of Fe0 addition. Furthermore, I showed that ethene production can be sustained in the presence of aerobic groundwater (after Fe0 exhaustion) by the addition of organic substrates. I hypothesized that some lessons learned from TCE Bioremediation can be applied also for other pollutants that can benefit from anaerobic reductions, like Cr (VI). Bioremediation of Cr (VI) has historically relied on biostimulation of native microbial communities, partially due to the lack of knowledge of the benefits of adding enriched consortia of specialized microorganisms (bioaugmentation). To determine the merits of a specialized consortium on bio-reduction of Cr (VI), I first enriched a culture on lactate and Cr (VI). The culture had high abundance of putative Morganella species and showed rapid and sustained Cr (VI) bio-reduction compared to a subculture grown with lactate only (without Morganella). Overall, this dissertation work documents possible strategies for synergistic abiotic and biotic chlorinated ethenes reduction, and highlights that specialized consortia may benefit Cr (VI) bio-reduction.
ContributorsMohana Rangan, Srivatsan (Author) / Krajmalnik-Brown, Rosa (Thesis advisor) / Delgado, Anca G (Thesis advisor) / Torres, César I (Committee member) / van Paassen, Leon (Committee member) / Arizona State University (Publisher)
Created2022
Description
The world currently faces hundreds of millions of cubic meters of soil contaminated with petroleum crude oil residuals. The application of ozone gas (O3) to contaminated soil is an effective means to oxidize petrogenic compounds and, when used with bioremediation, remove the oxidized byproducts. The overarching goal of this dissertation was to evaluate two areas of potential concern to large-scale O3 deployment: the capacity of O3-treated petroleum contaminated soils to support seed germination before bioremediation and the transport characteristics of O3 in soil columns. A matched study comparing the germination outcomes of radish (Raphanus sativus L.), grass (Lagurus ovatus), and lettuce (Lactuca sativa) in soils contaminated with three crude oils at various O3 total-dose levels showed that radish germination was sensitive to the soluble byproducts of oxidized petroleum (assayed as dissolved organic carbon [DOC]), but not sensitive to the unreacted petroleum (total petroleum hydrocarbon [TPH]). A multivariable logistic regression model based on the radish results showed that adverse germination outcomes varied with the DOC concentration and that DOC ecotoxicity decreased with increasing O3 dose-level and background organic material. The model was used to create a risk management map of conditions that created 10%, 25%, and 50% extra risks of adverse radish germination. Thus, while O3 effectively lowered TPH in soils, the byproducts exhibited ecotoxicity that inhibited radish germination. On the other hand, the sensitivity of radish germination to oxidized petroleum byproducts could be utilized to assess ecological risk. The feasibility of gas transport in the soil matrix is also of paramount concern to field-scale utilization of O3. A matched study comparing TPH removal at three field-relevant loading rates (4, 12, or 36 mgozone/ gsoil/ hr) and various total dose-levels showed an anisotropic pattern along the axial distance favoring the column inlet end. The asymmetry decreased as loading rate decreased and with concurrent improvements in O3-transport distance, O3 utilization, and heat balance. Overall, a low O3 loading rate significantly improved O3 transport and utilization efficiency, while also better distributing reaction-generated heat along the gas flow path for a depth typically utilized in bioremediation field settings.
ContributorsYavuz, Burcu Manolya (Author) / Rittmann, Bruce E (Thesis advisor) / Delgado, Anca G (Committee member) / Westerhoff, Paul (Committee member) / Arizona State University (Publisher)
Created2022
Description
Zero-Valent Metals (ZVM) are highly reactive materials and have been proved to be effective in contaminant reduction in soils and groundwater remediation. In fact, zero-Valent Iron (ZVI) has proven to be very effective in removing, particularly chlorinated organics, heavy metals, and odorous sulfides. Addition of ZVI has also been proved in enhancing the methane gas generation in anaerobic digestion of activated sludge. However, no studies have been conducted regarding the effect of ZVM stimulation to Municipal Solid Waste (MSW) degradation. Therefore, a collaborative study was developed to manipulate microbial activity in the landfill bioreactors to favor methane production by adding ZVMs. This study focuses on evaluating the effects of added ZVM on the leachate generated from replicated lab scale landfill bioreactors. The specific objective was to investigate the effects of ZVMs addition on the organic and inorganic pollutants in leachate. The hypothesis here evaluated was that adding ZVM including ZVI and Zero Valent Manganese (ZVMn) will enhance the removal rates of the organic pollutants present in the leachate, likely by a putative higher rate of microbial metabolism. Test with six (4.23 gallons) bioreactors assembled with MSW collected from the Salt River Landfill and Southwest Regional Landfill showed that under 5 grams /liter of ZVI and 0.625 grams/liter of ZVMn additions, no significant difference was observed in the pH and temperature data of the leachate generated from these reactors. The conductivity data suggested the steady rise across all reactors over the period of time. The removal efficiency of sCOD was highest (27.112 mg/lit/day) for the reactors added with ZVMn at the end of 150 days for bottom layer, however the removal rate was highest (16.955 mg/lit/day) for ZVI after the end of 150 days of the middle layer. Similar trends in the results was observed in TC analysis. HPLC study indicated the dominance of the concentration of heptanoate and isovalerate were leachate generated from the bottom layer across all reactors. Heptanoate continued to dominate in the ZVMn added leachate even after middle layer injection. IC analysis concluded the chloride was dominant in the leachate generated from all the reactors and there was a steady increase in the chloride content over the period of time. Along with chloride, fluoride, bromide, nitrate, nitrite, phosphate and sulfate were also detected in considerable concentrations. In the summary, the addition of the zero valent metals has proved to be efficient in removal of the organics present in the leachate.
ContributorsPandit, Gandhar Abhay (Author) / Cadillo – Quiroz, Hinsby (Thesis advisor) / Olson, Larry (Thesis advisor) / Boyer, Treavor (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