Browsing by Author "De Long, Susan, committee member"

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Embargo
Addressing barriers to the wide-scale implementation of roof runoff and stormwater collection and use projects for non-potable end uses in the U.S.
(Colorado State University. Libraries, 2023) Alja'fari, Jumana Hamdi Mahmoud, author; Sharvelle, Sybil, advisor; Arabi, Mazdak, committee member; De Long, Susan, committee member; Nelson, Tracy, committee member
Roof runoff and stormwater have the potential to serve as important local water sources and diversify the water budget portfolio in regions with dwindling water supplies and increasing populations. Due to the lack of guidance regulating the use of roof runoff for non-potable end uses, characterizing its microbial quality is necessary to promote roof runoff use across the U.S. Similarly, the degree of stormwater microbial contamination is still not well understood, and uncertainty about the required treatment is a barrier for the implementation of stormwater capture and use (SCU) projects. Stormwater runoff could become contaminated with human fecal matter in areas with aging infrastructure where raw wastewater exfiltrate from sewer networks to stormwater collection networks, areas with homeless encampments, or areas with sanitary sewer overflows (SSOs). Stormwater practitioners wanting to benefit from stormwater to augment the available water resources struggle with the selection and design of efficient stormwater treatment trains that are protective of public health for the designated end use. Knowledge of the degree to which stormwater is contaminated with human fecal matter, termed here as the human fecal contamination analog (HFCA), is critical for the design process and estimating the required pathogen log reduction targets (LRTs).To address the barrier to wide-scale implementations of roof runoff collection and use projects, a 2-year research study was designed to examine roof runoff microbial quality in four U.S. cities: Fort Collins, CO; Tucson, AZ; Baltimore, MD; and Miami, FL. Sample collection was conducted as part of a citizen science approach. The occurrence and concentrations of indicator organisms (E. coli and enterococci) and potentially human-infectious pathogens (PHIPs) including Salmonella spp., Campylobacter spp., Giardia duodenalis, and Cryptosporidium parvum in roof runoff were determined using culture methods and digital droplet polymerase chain reaction (ddPCR), respectively. E. coli and enterococci were detected in 73.4% and 96.2% of the analyzed samples, respectively. Concentrations of both E. coli and enterococci ranged from <0 log10 to >3.38 log10 MPN/100 mL. Salmonella spp. invA, Campylobacter spp. ceuE, and G. duodenalis β – giardin gene targets were detected in 8.9%, 2.5%, and 5.1% of the analyzed samples, respectively. Campylobacter spp. mapA and C. parvum 18S rRNA gene targets were not detected in any of the analyzed samples. This dataset represents the largest-scale study to date of enteric pathogens in U.S. roof runoff collections and will inform treatment targets for different non-potable end uses for roof runoff. To address barriers to the wide-scale implementation of SCU projects for non-potable end uses, stormwater microbial contamination originating from human fecal matter was examined using the detection frequencies and concentrations of human microbial source tracking (MST) markers and PHIPs observed in stormwater. Measurements of human MST markers in wet weather flows, dry weather flows, and influent wastewater in addition to measurements of viral and protozoan pathogens in wet weather flows and influent wastewater were compiled through a systematic review. Human MST marker and PHIP datasets were statistically analyzed and used to estimate HFCAs based on relative concentrations of microbial contaminants in stormwater compared to municipal wastewater. Analytical statistical distributions of the original data, unpaired Monte Carlo simulation, and paired Monte Carlo simulation were applied for the estimates of HFCAs in wet and dry weather flows. Estimates of human MST-based HFCAs are more reliable than PHIP-based HFCAs because the current PHIP datasets are limited by detection limits and the range of data observed within the statistical distributions. Unpaired Monte Carlo simulations and analytical statistical distributions were found to be the best methods for the estimation of human MST-based HFCAs in wet and dry weather flows which ranged from <10-7.0 to 10-1.5 and 10-12 to 10-2.6, respectively. Pathogen LRTs were determined in this study using HFCAHuman MST Markers and previously published quantitative microbial risk assessments (QMRAs) to guide the selection of stormwater treatment process trains based on the intended end use (e.g., unrestricted irrigation or indoor use) of stormwater. Combinations of stormwater treatment trains at varying HFCA levels were evaluated based on complexity and reliability of the suggested trains. To use stormwater safely for unrestricted irrigation and indoor uses, treatment trains containing both filtration and disinfection unit processes are required. The HFCA threshold beyond which the complexity of stormwater trains becomes considerably higher is 10-4. Performance evaluation of the suggested stormwater treatment trains revealed that trains consisting of membrane filtration and at least two disinfection unit treatment processes, specifically ultraviolet (UV) and ozone (O3) or UV and chloramine are recommended at HFCA values of 10-3, 10-2, and 10-1. At HFCA value of 10-4, a treatment train consisting of membrane filtration and O3 or chloramine is recommended. The use of free chlorination at all HFCA levels is not recommended due to the high continuous monitoring requirements associated with the use of free Cl2.
Open Access
Analysis of life cycle assessment of food/energy/waste systems and development and analysis of microalgae cultivation/wastewater treatment inclusive system
(Colorado State University. Libraries, 2013) Armstrong, Kristina Ochsner, author; Bradley, Thomas H., advisor; De Long, Susan, committee member; Marchese, Anthony, committee member
Across the world, crises in food, energy, land and water resources, as well as waste and greenhouse gas accumulation are inspiring research into the interactions among these environmental pressures. In the food/energy/waste problem set, most of the research is focused on describing the antagonistic relationships between food, energy and waste; these relationships are often analyzed with life cycle assessment (LCA). These analyses often include reporting of metrics of environmental performance with few functional units, often focusing on energy use, productivity and environmental impact while neglecting water use, food nutrition and safety. Additionally, they are often attributional studies with small scope which report location-specific parameters only. This thesis puts forth a series of recommendations to amend the current practice of LCA to combat these limitations and then utilizes these suggestions to analyze a synergistic food/waste/energy system. As an example analysis, this thesis describes the effect of combining wastewater treatment and microalgae cultivation on the productivity and scalability of the synergistic system. To ameliorate the high nutrient and water demands of microalgae cultivation, many studies suggest that microalgae be cultivated in wastewater so as to achieve large scale and low environmental costs. While cultivation studies have found this to be true, none explore the viability of the substitution in terms of productivity and scale-up. The results of this study suggest that while the integrated system may be suitable for low-intensity microalgae cultivation, for freshwater microalgae species or wastewater treatment it is not suitable for high intensity salt water microalgae cultivation. This study shows that the integration could result in reduced lipid content, high wastewater requirements, no greenhouse gas emissions benefit and only a small energy benefit.
Embargo
Cattle manure characteristics in relation to manure accumulation period and seasonal impacts in the intermountain west
(Colorado State University. Libraries, 2023) Bhowmik, Priya R., author; Sharvelle, Sybil, advisor; De Long, Susan, committee member; Olsen, Daniel, committee member
Anaerobic digestion (AD) of organic waste has been studied and implemented in practice more recently than ever. AD is used to produce biogas, which mainly consists of methane gas that has multiple purposes. Arguably the most important purpose methane gas has is that it is a renewable energy source. Organic waste that can serve as feedstock for AD ranges from food waste to animal waste, including manure. There are limited application of AD technology to process beef cattle manure compared to other manure sources due to factors such as method of collection processes (i.e., scraped on dry lots) and inconsistent methane gas produced due to varied conditions. This study focuses on beef cattle manure from the intermountain west, home to many cattle feedlots producing millions of tons of manure a year. Beef cattle feedlots pens typically have a base of compacted manure with no roof covering the pen. With no roof over the beef cattle feedlots and low collection frequency, the manure is exposed to seasonal change with varying weather conditions and often contains low water content and high inorganic material compared to other animal feeding operation manure. To improve the methane production of beef cattle manure in AD processes, more information is needed on the quality of beef cattle manure over varying collection frequency and seasons. The objective of this research is to determine biochemical methane potential (BMP) for differing accumulation time periods and seasonal impact. Four sample collections were conducted at one concentrated animal feeding operation (CAFO) from different months with different seasonal effects. For each sample collection, different manure accumulation periods were selected ranging from 7 to 90-day old manure. For each accumulation period, three cattle pens were selected based on the similar number of cattle and same feed. All manure was collected from each pen and was weighed with subsequent testing for characteristics. Based on the total solids (TS) from each pen in each manure accumulation period the composite sample was created for the manure accumulation period which was tested for BMP. A second manure collection technique was used due to complications with collecting lower manure accumulation periods with the first collection technique such as an uneven surface of the pen. The second technique applied land surveying one singular pen for a 10- and 20-day manure accumulation period to attempt to only collect newly deposited manure over the accumulation period. The BMP data is expressed as the volume of methane (CH4) produced per unit of volatile solids (VS) added, typically represented as mL CH4/ g VS feedstock. VS is the portion of the material that is organic and for this study in terms of volatile mass per dry mass. The sample collections from this study BMP results ranged from 200-276 mL CH4/ g VS feedstock. A literature review was conducted comparing over 13 studies that tested beef manure in AD. Results from this study were above the average of the literature review which was 160 mL CH4/ g VS feedstock. One of the sample collections occurred in May, which was the only data which represented a parallel trend between manure accumulation periods and BMP results, with BMP decreasing with longer accumulation periods. The May sample collection produced the highest measured ultimate BMP and was considered the most precise manure collection. Statically different trends were not observed for samples collected over seasons, leading to inconclusive results on seasonal impacts on BMP. The land surveying technique for manure collection resulted in variable quality manure, which emphasized the struggle of replication of manure collected and the possibility of obtaining only the desired manure accumulation period without obtaining any of the manure pad. Overall, results indicated the potential for increased methane production potential for more frequently collected manure at beef feedlots. However, the study also indicated that more frequent collection of only freshly deposited manure would be difficult to implement in practice.
Open Access
Characterization of osseointegrative phosphatidylserine and cholesterol orthopaedic implant coatings
(Colorado State University. Libraries, 2013) Rodgers, William Paul, author; James, Susan, advisor; Popat, Ketul, committee member; Ehrhart, Nicole, committee member; De Long, Susan, committee member
Total joint arthroplasties/replacements are one of the most successful surgeries available today for improving patients’ quality of life. By 2030 in the US, demand for primary total hip and knee arthroplasties are expected to grow by 174% and 673% respectively to a combined total of over 4 million procedures performed annually, driven largely by an ageing population and an increased occurrence of obesity. Current patient options for load-bearing bone integrating implants have significant shortcomings. Nearly a third of patients require a revision surgery before the implant is 15 years old, and those who have revision surgeries are at an increased risk of requiring additional reoperations. A recent implant technology that has shown to be effective at improving bone to implant integration is the use of phosphatidylserine (DOPS) coatings. These coatings are challenging to analyze and measure due to their highly dynamic, soft, rough, thick, and optically diffractive properties. Previous work had difficulty investigating pertinent parameters for these coating’s development due in large part to a lack of available analytical techniques and a dearth of understanding of the micro- and nano-structural configuration of the coatings. This work addresses the lack of techniques available for use with DOPS coatings through the development of original methods of measurement, including the use of scanning white light interferometry and nanoindentation. These techniques were then applied for the characterization of DOPS coatings and the study of effects from several factors: 1. the influence of adding calcium and cholesterol to the coatings, 2. the effect of composition and roughness on aqueous contact angles, and 3. the impact of ageing and storage environment on the coatings. This project lays a foundation for the continued development and improvement of DOPS coatings, which have the promise of significantly improving current patient options for bone integrating implants. Using these newly developed and highly repeatable quantitative analysis methods, this study sheds light on the microstructural configuration of the DOPS coatings and elucidates previously unexplained phenomena of the coatings. Cholesterol was found to supersaturate in the coatings at high concentration and phase separate into an anhydrous crystalline form, while lower concentrations were found to significantly harden the coatings. Morphological and microstructural changes were detected in the coatings over the course of as little as two weeks that were dependent on the storage environment. The results and understanding gained pave the path for focused future research effort. Additionally, the methods and techniques developed for the analysis of DOPS coatings have a broader application for the measurement and analysis of other problematic biological materials and surfaces.
Open Access
Characterization of water quality pollution in mixed land use watersheds
(Colorado State University. Libraries, 2020) Ludwig, Madeline, author; Arabi, Mazdak, advisor; De Long, Susan, committee member; Wilkins, Michael, committee member
Anthropogenic sources of pollution often lead to degraded surface water quality in urban and agricultural streams. The Clean Water Act was developed to mitigate the negative effects of urbanization on water quality through the development of water quality targets and the Total Maximum Daily Load program. In this study, a probabilistic framework was developed to quantitatively assess how indicators of human influence impact vulnerability to E. coli impairment and nutrient concentrations in mixed land use watersheds across the state of Colorado. The models derived using this method can be used to predict instream pollutant concentrations and help regulatory agencies create sampling programs for at risk waterbodies. Specifically, the first part of this study explores vulnerability to E. coli impairment under varying levels of upstream anthropogenic influences and develops a probabilistic method for assessing E. coli pollution based on the regulatory monitoring program. In this study, vulnerability is defined as the probability that ambient instream pollutant concentrations exceed numeric water quality standards. The study objective was examined for 28 sites along the Cache la Poudre River and its tributaries including: Boxelder Creek, Fossil Creek, and Spring Creek in northern Colorado. Indicators of urban influence include land use, wastewater treatment plant discharge capacity, combined animal feeding operation capacity, and population. Multiple linear regressions analysis between anthropogenic indicators, E. coli concentrations and vulnerability provide significant (p < 0.05) and strong (R2 > 0.7) relationships. In general, land use predictor variables were able to accurately predict E. coli load, however the most important indicator of human influence differed between E. coli concentration response variables. Additionally, the second part of this study expands upon the multiple linear regression framework to develop regression models that can predict base level nutrient concentrations for stream segments in three regions of Colorado. Regression models were developed using data from 89 sampling locations upstream of wastewater treatment plants and 84 sampling locations downstream of wastewater treatment plants. An initial analysis of gaged sampling locations showed that flow was a significantly influenced instream nutrient concentrations. Area and slope of the contributing sub watershed were then analyzed in a regression analysis and were found to be a surrogate for streamflow. Strong (R2 > 0.7) and significant (p < 0.05) regression models for upstream and downstream locations were developed using area and slope, hydrologic, point, and non-point source predictor variables. The models showed that agricultural and urban activity significantly impacted instream baseline nutrient concentrations. The methodology developed in this study can be used to predict instream pollutant concentration and assist in the development of monitoring programs for at risk waterbodies.
Open Access
Diagenesis and geochemistry of the Lower Permian Ingleside Formation, Owl Canyon area, Larimer County, Colorado
(Colorado State University. Libraries, 2018) Issa, Ahmad, author; Sutton, Sally, advisor; Ridley, John, committee member; De Long, Susan, committee member
The purpose of this study is to determine the diagenetic history and timing of hydrocarbon migration in the Lower Permian Ingleside Formation as revealed in the Ingleside roadcut at Owl Canyon area, Colorado. The studied exposure is divided into fourteen beds composed of quartz arenite sandstone, limestone, dolomite, or siltstone. Observations from outcrop and thin sections, including calcite veins, carbonate-hosted vugs, and carbonate cement, suggest carbonate mobility throughout the outcrop. Stylolites parallel to bedding may have formed by pressure solution related to compaction, and pressure solution of carbonates is one possible source of carbonate that could have precipitated in veins or as cement. The formation was affected by other diagenetic processes, in addition to compaction and carbonate cementation, including feldspar dissolution and alteration and several stages of cementation. Cements include hematite, calcite, dolomite, kaolinite, and quartz overgrowth cement. Hematite cement was determined to have precipitated very early. Poikilotopic carbonate cement was precipitated very early, but after the precipitation of the hematite cement. Blocky calcite and blocky dolomite cements, the most common cements within the formation, were precipitated after the hematite and poikilotopic cements. Kaolinite cement was probably precipitated in association with feldspar dissolution and alteration, or occurred with feldspar dissolution during modern weathering. Hydrocarbon migration probably occurred before the precipitation of the blocky carbonate cement. The relationship between S and MgO in some sandstone samples may indicate that Mg and S have been added by diagenetic fluids. Also, K2O correlates with Al2O3 probably because both elements are mainly in the same phases, clay minerals, micas, K-feldspar, or glauconite. This study of the Ingleside outcrop provides some information about the diagenesis, possible timing of possible hydrocarbon migration through the Ingleside Formation, and geochemical and mineralogical composition of the exposure, which was used to interpret the diagenetic history throughout the outcrop. Therefore, this study adds to understanding of hydrocarbon migration and the hydrocarbon pathways in this part of the Denver Basin.
Open Access
Enhancement of liquid flow through a leach bed reactor for anaerobic digestion of high solids cattle manure
(Colorado State University. Libraries, 2017) Wu, Rongxi, author; Sharvelle, Sybil, advisor; De Long, Susan, committee member; Butters, Greg, committee member
Due to animal production waste increases in Colorado, anaerobic digestion (AD) has become increasingly considered as a technology to convert organic solid waste (OSW) into renewable energy. The arid climate with water resource limitation in Colorado results in high solids cattle manure (HSCM) production, containing between 50% and 90% total solids (TS). Conventional AD for animal manure is best option to treat manure with less than 20% TS, but limited feasibility for conventional anaerobic digesters treats manure in Colorado. The multi-stage anaerobic digester (MSAD) investigated in this study can digest HSCM. An integral part of the MSAD is the Leach Bed Reactor (LBR), which is loaded with HSCM (up to 90% TS). A small quantity of water percolates into the LBR and is recirculated through the LBR where hydrolysis occurs until a large amount of organic material is solubilized into the leachate. A review of the literature has indicated that clogging can be an issue in operation of manure LBRs. Since sustaining liquid flow through LBRs can be a challenge, research was conducted to better understand how to use this technology to treat HSCM. The objectives of this research were to 1) assess the performance of the LBR component of the MSAD technology with different top layer materials and flow regimes to enhance duration of sustained flow, 2) assess the ability of varying top layer materials and flow regimes to enhance hydraulic conductivity of the manure bed in the LBR to maximize hydrolysis in the LBR. For this study, downward flow and upward flow LBR configuration experiments were conducted. The combination of a sand layer on top of the manure beds and an improved top filter for the LBR was added in the upward flow LBR configuration. HSCM samples from each stage of the experiment were analyzed for TS, fixed solids (FS), and volatile solids (VS), and the leachate samples were analyzed for chemical oxygen demand (COD). The leachate outflow rate and column pressure head were also measured daily. Due to failure of all downward flow experiments, the upward flow LBR configuration was evaluated. The clogging issues and leachate flow through the LBR improved by changing to the upward flow LBR configuration. The average operation time of the upward flow experiment was prolonged to 21 days comparing with downward flow experiment, which operated for an average of only 7 days. The percentage reduction of VS in upward flow experiments was on average above 40% indicating successful hydrolysis in the LBRs, comparable to VS reduction observed by other researchers (Uke and Stentiford, 2012). The COD concentration of the upward flow experiments started at an average of 45 g COD/ L and approached the LST's COD concentration of 10 g COD/L at day 10. This indicates that the MSAD was effectively degrading the HSCM throughout the batch digestion period. The constant pressure head of upward flow experiments indicated that no pressure built up inside the LBRs resulting in improved flow through the manure in these systems. In summary, this research showed that the upward flow LBR configuration with the combination of a sand layer on top of the manure bed and improved top cap filter can sustain leachate flow through the LBR for 21 days of operation.
Open Access
Enhancing hydraulic performance of a multi-stage anaerobic digester for high solids cattle manure
(Colorado State University. Libraries, 2019) Young, Kadin Catlin, author; Sharvelle, Sybil, advisor; De Long, Susan, committee member; Olsen, Daniel, committee member
Anaerobic digestion is an attractive technology for waste handling because it converts low value waste material into energy and other useful products while performing necessary treatment for proper waste disposal. Conventional anaerobic digestion technology, however, has been met with many economic challenges when being applied to high solids substrate such as dry-lot cattle manure. In Colorado and the rest of the arid west, feedlot practices and dry climate combine to form a waste product that is very high in total solids (TS) content, from 50% up to 90% TS. Since the most common conventional digestion practices typically can only treat wastes up to a maximum of 15% TS, other options must be considered to digest this abundant waste product and convert it to a valuable resource. Research at Colorado State University has led to the development of an innovative multi-stage anaerobic digester (MSAD) technology capable of digesting high solids content waste with very low water addition. The CSU MSAD has demonstrated the ability to successfully digest high solids content waste like that found at the many Colorado feedlots. This system differs from conventional technology in that hydrolysis takes place in one reactor and methane generation takes place in a separate high rate digester. The development of the MSAD for digestion of high solids cattle manure leads to the promising opportunity for valorization of a prevalent waste product in Colorado to create valuable products including methane biogas, compost, and fertilizers. The present research aims to advance the technology by assessing the performance of the MSAD running in a fully linked configuration including each of its individual components: the Upflow Solid-State Hydrolysis Reactor (USSHR), the Leachate Feed Tank (LFT), and the Fixed Film Reactor (FFR). A fully functional Central Leachate Processing System (CLPS) was constructed to demonstrate the technology, to facilitate column scale studies, and to link with the prototype USSHR (P-USSHR) to enable the evaluation of an improved liquid distribution system. The MSAD was constructed at column scale to evaluate the impact on organic leaching potential of varying hydraulic loading rate (HLR) through the USSHR using HLRs of 20, 41, and 75 cm/day for 16-day cycles. This experiment was the first successful demonstration of a fully linked MSAD system using cattle manure as feedstock. It was found that the higher HLR of 75 cm/day yields 25% more COD leached over the 16-day operating period than the two lower loading rates. Additionally, it was found that the P-USSHR achieved notable improvements over the previous operation in hydraulic distribution through the reactor and therefore improved digestion performance and volatile solids destruction, though areas for further improvement were noted.
Open Access
Evaluation of dose enhancement due to CuATSM uptake in hypoxic environments with external radiation
(Colorado State University. Libraries, 2019) Martinez, Stephen K., author; Leary, Del, advisor; Boss, Keara, committee member; Brandl, Alexander, committee member; De Long, Susan, committee member; Kato, Takamitsu, committee member
Most solid tumors contain areas of chronic hypoxia caused by limited diffusion of oxygen from tumor microvasculature. Hypoxic regions have been found to be radioresistant and their presence results in a worse prognosis for tumor control. Metal radiosensitizers have been employed to alleviate the radioresistance in hypoxic tumors by increasing dose through additional photoelectrons and Auger cascades. In recent years, gold nanoparticles (GNP) have been explored for their potential as an enhancer of external beam radiation and become the standard-bearer for the treatment modality; however, GNP have lower cellular uptake in anoxic and hypoxic conditions than under normoxic conditions. Additionally, the large size of nanoparticles decreases their diffusivity, reducing their ability to penetrate into tumor tissue distant from vasculature. The chelator diacetylbis (N(4)-methylthiosemicarbazonato) copper II (CuATSM) provides the potential to overcome the hypoxic barrier by preferentially depositing copper into tumor regions previously inaccessible to treatment. The characteristics of CuATSM have led to its utilization in positron emission tomography (PET) imaging of hypoxic regions. These PET images have also been investigated as a method for dose painting, amplification of intensity modulated radiation therapy (IMRT) dose to hypoxic regions. Additionally, radioactive ⁶⁴CuATSM has been investigated for implementation in brachytherapy for hypoxic tumors. The Auger electrons ejected upon decay of the radioisotope have been shown to be highly damaging to DNA. The intention of this study is to evaluate the potential of CuATSM as an external beam radiosensitizer. This project investigates radiosensitization of CuATSM by Monte Carlo (MC) modeling of different energy external beam spectra available clinically with Electron Gamma Shower (EGSnrc) and Geometry and Tracking (Geant4) and evaluating dose enhancement with CuATSM. These MC models are informed by and evaluated against cell models. Research indicates that CuATSM at high concentrations with low energy photons has efficacy for enhancing dose in hypoxic tumor regions.
Open Access
Rational design and novel bioprocesses for low-carbon biofuels and bioproducts
(Colorado State University. Libraries, 2023) Bartholet, Danielle, author; Reardon, Kenneth, advisor; Foust, Thomas, advisor; De Long, Susan, committee member; Peebles, Christie, committee member; Windom, Bret, committee member
The reduction of fossil fuel consumption and carbon emissions is one of the greatest challenges of our time, and innovative solutions are necessary to prevent climate catastrophe while maintaining economic development and modern ways of life. Biofuels and bioproducts can provide low-carbon alternatives to petroleum fuels and petroleum-based chemical processes. However, several limitations have impeded the wide-scale implementation of bio-based technologies. Biologically derived chemicals frequently do not possess ideal fuel properties due to high oxygen content and lower energy density. Furthermore, petroleum processes remain economically favorable to biological alternatives due to the high costs and low yields associated with bioprocesses. Rational design approaches to the development of new fuels and chemicals combined with improved bioconversion processes are strategies that address multiple aspects of sustainable development for a circular carbon economy. The broad purpose of this work was to explore and develop low-carbon alternatives to petrochemical products and processes. We begin by proposing a group of novel fuel additive molecules, then explore alternative technologies for their production. In Chapter 2 of this work, a rational design approach was used to identify "ideal" diesel fuel additive molecules. The desired characteristics of a liquid transportation fuel include high efficiency and engine performance, low particulate emissions, compatibility with current engines and infrastructure, and low risk of environmental contamination. In this work, we use computational tools to propose structures for diesel fuel additives that meet these criteria. Starting with the chemical structure of dimethoxymethane (DMM), a class of oxygenated molecules, called polyoxymethylene ethers (POMEs) is proposed by varying oxygen content in the backbone length and carbon content in the end group length. Additional structural variations, including iso-alkyl end groups and tertiary branches, are considered here for the first time. The ten candidate molecules identified consist largely of butyl-terminated POMEs. Synthesis chemistry for butyl-terminated POMEs was developed, utilizing an acid-catalyzed transacetalization reaction of butanol with methyl-terminated POMEs. To improve the sustainability of POME production, it is desirable to produce precursors from biomass using bioconversion processes. Therefore, the focus of this work pivoted to bioprocess technologies for improved production of butanol and other fuel precursor molecules. Butanol and other molecules of interest are highly reduced metabolic products, requiring the input of electrons through intracellular reducing equivalents. Frequently, the yields of these reduced products are limited due to redox constraints of metabolic pathways. Electro-enhancement, which refers to the direct supplementation of electrons from solid electrodes, may overcome redox constraints by enabling "unbalanced fermentations". While electro-enhancement of processes like fermentation (electro-fermentation) and anaerobic digestion (electro-AD) has been reported to successfully induce metabolic shifts and alter product profiles, much remains unknown about the mechanisms leading to observed shifts. Chapter 3 provides a detailed review of the literature in this field, highlighting the challenges and shortcomings of electro-enhancement research. Methods developed to improve the study of bioelectrochemical systems are also presented here. In Chapter 4, we apply these methods to pure culture electro-fermentations of Clostridium pasteurianum with the objective of increasing butanol production. Our results indicate that applied potentials may affect metabolite profiles through redox control but did not provide sufficient evidence for direct bacterial/electrode interaction. In Chapter 5, these methods are applied to electro-AD of food waste inoculated with wastewater sludge. Applied potentials are shown to have a wide range of effects on product profile and microbial communities. These results suggest that electro-enhancement may provide a method for fine-tuning product profiles in heterogeneous, mixed culture systems. However, further experiments are required in both pure and mixed culture systems to fully elucidate the effect of electro-enhancement on cellular processes. Through this work, new methods were developed to facilitate future research in bioelectrochemical systems and enable the design of improved electro-enhanced bioprocesses.
Open Access
Remediation of soil impacted with chlorinated organic compounds: soil mixing with zero valent iron and clay
(Colorado State University. Libraries, 2014) Olson, Mitchell R., author; Sale, Tom, advisor; Dandy, David, committee member; De Long, Susan, committee member; Shackelford, Charles, committee member
Chlorinated solvents in the environment continue to present an enormous remediation challenge. A primary reason for the difficulty in cleaning up chlorinated solvent source zones involves heterogeneous distributions of permeability and contaminants in natural porous media. A method that can be used to overcome heterogeneity involves use of soil mixing techniques to deliver reagents and homogenize soils. A typical soil mixing application involves admixing contaminated soil with zero valent iron (ZVI) and bentonite (clay). This technology, herein referred to as ZVI-Clay, combines ZVI-mediated degradation of chlorinated solvents with bentonite-induced stabilization. As of December 2013, ZVI-Clay has been applied in 13 field applications, all of which have been viewed as being successful in achieving site remediation objectives. However, our understanding of the processes governing treatment in the ZVI-Clay mixed soil system is rather limited. The overarching goal of the research presented herein is to broaden our understanding of the processes controlling degradation and transport in soils treated via soil mixing with ZVI (or similar reactive media) and bentonite. In support of this objective, research included (a) analysis of field data, (b) initial rate studies, (c) hydraulic conductivity testing, (d) reactive-transport modeling coupled with column experiments, and (e) treatment of hydrophobic compounds. Field data analysis was based on performance data from a ZVI-Clay field application at Camp Lejeune, NC, in which 23,000 m3 of soil initially contaminated with trichloroethene (TCE) and 1,1,2,2-tetrachloroethane (TeCA) were treated with 2% ZVI and 3% bentonite. Within one year of treatment, total chlorinated organic compound (COC) concentrations in soils were decreased by average and median values of 97% and >99%, respectively. Total COC concentrations in groundwater were reduced by average and median values of 81% and >99%, respectively. Total COC reductions by 99.9% or greater were observed in most soil and water sampling locations. Hydraulic conductivity in the treated soil zone was reduced by an average of about 2.5 orders of magnitude. To explain the variations in kinetic data observed following ZVI-Clay field applications, initial-rate batch-reactor studies were conducted under a range of initial TCE concentrations and ZVI concentrations. When TCE concentrations were less than solubility, the Michaelis-Menton kinetic model provided an excellent fit of experimental data. When TCE concentrations were above solubility (i.e., NAPL was present), the degradation rate was independent of the amount of NAPL in the system. The presence of NAPL appears to have had a minor impact (~20% reduction) on the TCE degradation rate. A linear relationship between TCE degradation rate and ZVI amount was observed. Hydraulic characteristics of soils mixed with bentonite were evaluated by conducting column studies and MODFLOW modeling of field-scale systems. Experiments were conducted to evaluate the hydraulic conductivity, K, in two soils types mixed with 0.5 to 4% bentonite (i.e., the range of values typical for ZVI-Clay field applications). In a well-sorted fine sand, with a moderately high initial K (10-4 m/s), the value of K was reduced by about a factor of 10 for each 1% bentonite added to the soils. In a moderately-sorted fine sand with silt, with a low initial K (10-8 m/s), addition of up to 4% bentonite had only minor impacts on K. MODFLOW modeling indicated that surrounding groundwater flow patterns tend to bypass the treated soil body, under steady state conditions, given a reduction in K by at least an order of magnitude. Within the treated soil body, contaminant residence time is extended in approximate proportion to the reduction in K. The concepts of NAPL dissolution, ZVI-mediated degradation, and flow reduction were combined in a mathematical model. The model was then tested using column reactor studies containing NAPL-phase TCE and soils treated with 2% ZVI. The model adequately described TCE elution and formation of degradation products. The model was then used to predict treatment performance following field-scale implementation of ZVI-Clay. Model output predicts that the benefits of reaction are most effectively utilized with a reduction in flow rate by at least 2 orders of magnitude. Finally, enhancements to the ZVI-Clay treatment process were evaluated for treatment of polychlorinated biphenyls (PCBs). Due to their strong hydrophobicity and stable molecular structure, PCBs in the environment have been shown to be much more difficult to degrade than many of the common chlorinated solvents. Thus, alternative types of reactive media were evaluated. Batch experiments were conducted to evaluate zero valent metals (ZVM), ZVM + Pd-catalysis, and emulsified zero valent iron (EZVI) for dechlorination of PCBs in systems with and without soil. In water-based systems, ZVM with a Pd-catalyst facilitated rapid destruction of 2-chlorobiphenyl (half-life < 2 hr), while ZVM alone did not achieve any measurable degradation. In the presence of soils, EZVI was the only approach that resulted in a clear enhancement in PCB dechlorination rates. The results suggest treatment of PCBs in the presence of soil presents a much greater challenge than treatment of aqueous phase PCBs; however, treatment of PCBs in soil can benefit from enhanced desorption and a persistent reactive media.
Open Access
The development and demonstration of a multiple stage anaerobic digester for the treatment of high solids wastes
(Colorado State University. Libraries, 2018) Loetscher, Lucas H., author; Sharvelle, Sybil, advisor; De Long, Susan, committee member; Davis, Jessica, committee member
The semi-arid Great Plains of the central United States is home to numerous high-density, confined animal feeding operations (CAFOs) that utilize outdoor animal pens. These facilities generate a desiccated manure very different from the wastes generated from similar enclosed facilities in other parts of the country. These high-solids wastes present challenges to the conventional digestion systems commonly used on wastes with lower solids contents. Therefore, it was determined that there was a need in the industry for a new technological approach to improve feasibility of the digestion of these challenging wastes. A first principle design technique was applied to the conceptual design of an innovative technology better suited to such a challenging substrate. This system, named the CSU multiple-stage anaerobic digester (MSAD) technology, is a promising technical alternative to existing AD technologies. The CSU MSAD technology demonstrated the ability to overcome various limitations in previous anaerobic digestion technologies and ultimately demonstrated the ability to be used in the digestion of a wider variety of substrates. A demonstration-scale CSU MSAD system was constructed and operated for a duration of four months. The demonstration-scale equipment was constructed as a stand-alone mobile pilot lab that could function with various substrates and hydrolysis reactor configurations. In addition to the demonstration of the MSAD system on manure wastes, experiments were conducted on the digestion and inoculation of food wastes. Findings from these experiments indicated that substrate inoculation became less important as the digestion system operated for a longer duration. Inferring from these findings, it is expected that commercial MSAD digesters will not benefit from substrate inoculation after the system completes a successful startup process. An analysis of the existing state of the MSAD technology was completed based on review of previous research efforts. To prioritize future research efforts, a modified technology development risk analysis using qualitative scores was applied to development needs of the technology that currently have unknown and potentially risky outcomes. This approach has led to a series of recommended future development efforts for the commercialization of this technology.