Browsing by Author "Carlson, Kenneth H., committee member"
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Item Open Access Air quality impacts from unconventional oil and gas development(Colorado State University. Libraries, 2024) Ku, I-Ting, author; Collett, Jeffrey L., Jr., advisor; Fischer, Emily V., committee member; Carlson, Kenneth H., committee member; Kreidenweis, Sonia, committee memberUnconventional oil and natural gas development (UOGD) has expanded rapidly across the United States raising concerns about associated air quality impacts. While significant effort has been made to quantify and limit methane emissions, relatively few observations have been made of emitted Volatile Organic Compounds (VOCs). Extensive air monitoring during development of several large, multi-well pads in Broomfield, Colorado, in the Denver-Julesburg Basin, provides a novel opportunity to examine changes in local concentrations of air toxics and other VOCs during drilling and completions of new wells. With simultaneous measurements of methane and 50 VOCs from October 2018 to December 2022 at as many as 19 sites near well pads, in adjacent neighborhoods, and at a more distant reference location, we identify impacts from each phase of well development and production. In Part 1, we report how emissions from Broomfield pre-production and production operations influence air toxics and other VOC concentrations at nearby locations. Use of weekly, time-integrated canisters, a Proton Transfer Reaction Mass Spectrometer (PTR-MS), continuous photoionization detectors (PID) to trigger canister collection upon detection of VOC-rich plumes, and an instrumented vehicle, provided a powerful suite of measurements to characterize both transient plumes and longer-term changes in air quality. Prior to the start of well development, VOC gradients were small across Broomfield. Once drilling commenced, concentrations of oil and gas (O&G) related VOCs, including alkanes and aromatics, increased around active well pads. Concentration increases were clearly apparent during certain operations, including drilling, coil tubing/millout operations, and production tubing installation. Emissions of C8-C10 n-alkanes during drilling operations highlighted the importance of VOC emissions from a synthetic drilling mud chosen to reduce odor impacts. More than 90 transient plumes were sampled and connected with specific UOGD operations. The chemical signatures of these plumes differed by operation type. Concentrations of individual, O&G-related VOCs in these plumes were often several orders of magnitude higher than in background air, with maximum ethane and benzene concentrations of 79,600 and 819 ppbv, respectively. Study measurements highlight future emission mitigation opportunities during UOGD operations, including better control of emissions from shakers that separate drill cuttings from drilling mud, production separator maintenance operations, and periodic emptying of sand cans during flowback operations. In Part 2 OH reactivities (OHR) were calculated to examine the potential of emitted VOCs to contribute to regional ozone formation. NO2 was the largest contributor to OHR during winter when OHR values peaked, while VOCs dominated OH sinks during summer. Oxygenated VOCs and C3-C7 n-alkanes, closely associated with O&G activities, were primary contributors to OHR levels during the summer ozone season. In Part 3 we leverage observations from Broomfield and other Colorado O&G air quality studies to examine relationships between O&G emissions of methane and VOCs. A key goal is to determine whether more commonly measured methane emissions can serve as a surrogate to estimate emissions of less frequently measured compounds such as benzene, a key air toxic. While strong correlations are observed between benzene and methane emissions in some situations, considerable variability is observed in this relationship across locations and operations suggesting caution in assuming that reductions in methane emissions will yield proportionate reductions in releases of air toxics.Item Open Access An evaluation of hydraulic retention time on BMP water quality performance(Colorado State University. Libraries, 2011) Messamer, Jason, author; Roesner, Larry A., advisor; Stednick, John D., committee member; Carlson, Kenneth H., committee memberUrban stormwater contains elevated concentrations of pollutants that are carried to receiving waters as runoff travels over roads, rooftops, and other hard surfaces. Structural best management practices (BMPs) are used to mitigate the negative impacts of urbanization by improving the water quality of stormwater runoff. Volume-based BMPs attenuate the peak flow of runoff and increase the hydraulic retention time (HRT) of runoff allowing pollutants to be removed through settling, adsorption, and other physiochemical processes. When BMPs provide longer HRTs for runoff events, the capacity for pollutant removal is increased because there is greater opportunity for pollutants to settle out of the water column and more time for plant and biological uptake. However, increasing the HRT that a BMP provides requires more storage volume, costs more to construct, and takes away land that could be developed for other uses. There is a tradeoff between the size of a BMP, the cost to build a BMP, and the capacity for pollutant removal. Two regional BMPs that serve the downtown area of Fort Collins, CO, were investigated in an effort to relate the HRT of a BMP to its water quality performance. The Udall Natural Area (Udall WP) is a wet extended detention basin that provided storm HRTs of over 80 hours. Contrastingly, the Howes St. BMP has an unregulated outlet and provided storm HRTs less than 20 hours. Stormwater quality data was collected from 2009-2011 at the inlet and outlet of each facility. The pollutant removal at each BMP was quantified for various runoff constituents including heavy metals, total suspended solids (TSS), bacteria, and nutrients. The Udall WP consistently had cleaner TSS effluent than the Howes St. BMP had and also removed significant amounts of heavy metals. The cleaner effluent at the Udall WP can be attributed to the longer HRT that the BMP provided. If the Howes St. BMP were modified to have a water quality outlet, it is believed that the BMP could enhance water quality more consistently and that it would actually be more cost-effective than the Udall WP. Furthermore, the degree of pollutant removal from the undersized and unregulated outlet at the Howes St. BMP was enough to warrant the suggestion that the Udall WP was constructed larger than necessary for significant pollutant removal. To further develop the relationship between HRT and water quality enhancement, additional stormwater studies for wet ponds and extended detention basins were investigated from the International BMP Database. A lognormal approximation was used to estimate the average HRT provided by a BMP based on the volume of runoff recorded at the BMP inlet during a storm event. The computed storm HRTs were matched with effluent water quality results for TSS, total recoverable zinc, total recoverable copper, and total phosphorous. Results were binned into HRT groups and a statistical analysis was conducted to determine whether longer HRTs enhanced the water quality at the BMP outlet. The analysis did not focus on water quality enhancement from inlet to outlet, but was aimed at determining whether additional treatment occurred from longer HRTs at the outlet. The results indicated that additional pollutant removal was not achieved in wet ponds when HRTs longer than 12 hours were provided. The only exception was total phosphorous, which was statistically lower in concentration when extremely long HRTs were provided. For dry extended detention basins, better pollutant removal was achieved when longer HRTs were provided, and longer HRTs (greater than 60 hours) may be required if total phosphorous or heavy metal reduction is desired. The findings could be used to refine BMP design criteria for the optimal HRT that will provide significant enhancements in water quality.Item Open Access Financial and environmental impacts of new technologies in the energy sector(Colorado State University. Libraries, 2015) Duthu, Ray C., III, author; Bradley, Thomas H., advisor; Bandhauer, Todd M., committee member; Carlson, Kenneth H., committee member; Suryanarayanan, Siddharth, committee memberEnergy industries (generation, transmission and distribution of fuels and electricity) have a long history as the key elements of the US energy economy and have operated within a mostly consistent niche in our society for the past century. However, varieties of interrelated drivers are forcing changes to these industries’ business practices, relationship to their customers, and function in society. In the electric utility industry, the customer is moving towards acting as a fuller partner in the energy economy: buying, selling, and dispatching its demand according to its own incentives. Natural gas exploration and production has long operated out in rural areas farther from public concerns or regulations, but now, due to hydraulic fracturing, new exploration is occurring in more urbanized, developed regions of the country and is creating significant public concern. For these industries, the challenges to their economic development and to improvements to the energy sector are not necessarily technological; but are social, business, and policy problems. This dissertation seeks to understand and design towards these issues by building economic and life cycle assessment models that quantify value, potential monetization, and the potential difference between the monetization and value for two new technologies: customer-owned distributed generation systems and integrated development plans with pipeline water transport in hydraulically fractured oil and gas fields. An inclusive business model of a generic customer in Fort Collins, Co and its surrounding utilities demonstrates that traditional utility rates provide customers with incentives that encourage over-monetization of a customer’s distributed generation resource at the expense of the utilities. Another model which compares customer behavior incented by traditional rates in three New England cities with the behavior incented through a real-time pricing market corroborates this conclusion. Daily customer load peak-shaving is shown to have a negligible and unreliable value in reducing the average cost of electricity and in some cases can increase these costs. These models support the hypothesis that distributed generation systems provide much greater value when operated during a few significant electricity price events than according to a daily cycle. New business practices which foster greater cooperation between customers and utilities, such as a real-time price market with a higher fidelity price signal, reconnect distributed generation’s potential monetization to its value in the marketplace. These new business models are required to ensure that these new technologies are integrated into the electric grid and into the energy market in such a way that all of the market participants are interested and invested stakeholders. The truck transport of water associated with hydraulic fracturing creates significant local costs. A life cycle analysis of a hypothetical oil and gas field generic to the northern Colorado Denver-Julesburg basin quantifies the economic, environmental, and social costs associated with truck transport and compares these results with water pipeline systems. A literature review of incident data demonstrates that pipelines historically have spilled less hazardous material and caused fewer injuries and fatalities than truck transport systems. The life cycle analysis demonstrates that pipeline systems also emit less pollutants and cause less local road damage than comparable trucking systems. Pipeline systems are shown to be superior to trucking systems across all the metrics considered in this project. In each of these domains, this research has developed expanded-scope models of these new technologies and systems to quantify the tradeoffs that are present between monetization, environment, and economic value. The results point towards those business models, policies, and management practices that enable the development of more equitable, efficient, and sustainable energy systems.Item Open Access Mathematical modeling of groundwater anomaly detection(Colorado State University. Libraries, 2016) Gu, Jianli, author; Liu, Jiangguo, advisor; Carlson, Kenneth H., committee member; Zhou, Yongcheng, committee memberPublic concerns about groundwater quality have increased in recent years due to the massive exploitation of shale gas through hydraulic fracturing which raises the risk of groundwater contamination. Groundwater monitoring can fill the gap between the public fears and the industrial production. However, the studies of groundwater anomaly detection are still insufficient. The complicated sequential data patterns generated from subsurface water environment bring many challenges that need comprehensive modeling techniques in mathematics, statistics and machine learning for effective solutions. In this reseach, Multivariate State Estimation Technique (MSET) and One-class Support Vector Machine (1-SVM) methods are utilized and improved for real-time groundwater anomaly detection. The effectiveness of the two methods are validated based upon different data patterns coming from the historic data of Colorado Water Watch (CWW) program. Meanwhile, to ensure the real-time responsiveness of these methods, a groundwater event with contaminant transport was simulated by means of finite difference methods (FDMs). The numerical results indicate the change of contaminant concentration of chloride with groundwater flow over time. By coupling the transport simulation and groundwater monitoring, the reliability of these methods for detecting groundwater contamination event is tested. This research resolves issues encountered when conducting real-time groundwater monitoring, and the implementation of these methods based on Python can be easily transfered and extended to engineering practices.Item Open Access Treatment of shale oil and gas produced water using membrane distillation combined with effective pretreatment(Colorado State University. Libraries, 2019) Zhang, Zuoyou, author; Tong, Tiezheng, advisor; Carlson, Kenneth H., committee member; Zahran, Sammy J., committee memberFossil energy is indispensable for society development. Shale oil and gas as unconventional energy resource plays an important role in improving the energy security of U.S. But the exploitation of shale oil and gas is accompanied by substantial freshwater consumption and wastewater generation. The wastewater generated from shale oil and gas production contains large amounts of salts, particles, and petroleum-associated pollutants, inevitably imposing harmful consequences to the ecological environment if not properly treated. Effective treatment of shale oil and gas wastewater, ideally for beneficial reuse, is essential in promoting sustainability of shale oil and gas production at the water-energy nexus. In this thesis, I am focusing on developing an integrated treatment train that enables effective treatment of shale oil and gas produced water. Membrane distillation (MD), an emerging membrane desalination technology, was performed in tandem with simple and inexpensive pretreatment steps, namely precipitative softening (PS) and walnut shell filtration (WSF). A laboratory-scale MD system was designed and built at Colorado State University, and produced water generated from the Wattenberg field in northeast Colorado was collected and treated by the PS-WSF-MD system. My results demonstrated that PS removed various particulate, organic, and inorganic foulants, and thus mitigate fouling and scaling potential of the produced water. WSF displayed exceptional efficiencies (≥95%) in eliminating volatile toxic compounds including benzene, ethylbenzene, toluene, and xylenes (BTEX) along with additional gasoline and diesel range organic contaminants. With pretreatment, the water vapor flux of MD decreased by only 10% at a total water recovery of 82.5%, with boron and total BTEX concentrations in the MD distillate meeting the regulatory requirements for irrigation and typical discharge limits, respectively. The use of pretreatment also led to robust membrane reusability within three consecutive treatment cycles, with MD water flux fully restored after physical membrane cleaning. The results of this thesis highlight the necessity of pretreatment prior to MD treatment of produced water and demonstrate the potential of the developed treatment train to achieve a cost-effective and on-site wastewater treatment system that improves the sustainability of the shale oil and gas industry. At last, an economic and technical assessment of MD-based wastewater treatment system was performed. The cost of the treatment system developed in this thesis was evaluated, and the results indicated that the cost of MD-based treatment system is around $0.29-$0.87/barrel. Further investigation is needed to validate the economic feasibility of MD-based treatment system when applied at full-scale in the oil and gas fields.Item Open Access Waste heat driven turbo-compression cooling(Colorado State University. Libraries, 2018) Garland, Shane Daniel, author; Bandhauer, Todd M., advisor; Marchese, Anthony J., committee member; Carlson, Kenneth H., committee memberWaste heat recovery systems utilize exhaust heat from power generation systems to produce mechanical work, provide cooling, or create high temperature thermal energy. One waste heat recovery application is to use the exhaust heat from a Natural Gas Combined Cycle Power Plant (NGCC) to drive a heat activated cooling system that can offset a portion of the plant condenser load. There are several heat activated cooling systems available including absorption, adsorption, ORVC, and ejector, but each has disadvantages. One system that can overcome the disadvantages of typical heat activated cooling systems is a turbo-compression cooling system (TCCS). In this system, the exhaust heat enters an organic Rankine cycle at the boiler and vaporizes the fluid that passes through a turbine. The turbine power is directly transferred to a compressor via a hermetically sealed shaft that is made possible by a magnetic coupling. The compressor operates a vapor-compression system which provides a cooling effect in the evaporator. The hermetic seal between the turbine and compressor allows for two separate fluids on the power and cooling cycles, which maximizes the efficiency of the turbine and compressor simultaneously. This study presents a thermodynamic modeling approach that makes system performance predictions for the baseline design case, and for off-design performance conditions. The off-design modeling approach uses turbo-compressor performance maps and a heat exchanger UA scaling methodology to accurately simulate system operation for a broad range of temperatures and cooling loads. A 250 kWth cooling capacity TCCS was constructed and tested to validate the modeling approach. The test facility simulates a 138:1 scaled NGCC power plant configuration in which the TCCS extracts 106°C waste heat from the flue gases and produces a cooling effect that offsets a portion of the NGCC condenser load. The design target for the test facility was to achieve a COP of 2.1 while chilling water from 17.2°C to 16°C at an ambient temperature of 15°C. Although the final design point was not tested for this study due to facility limitations, the off-design performance methodology was utilized to predict the performance for an ambient condition of 27.5°C and power and cooling cycle mass flow rate range between 0.35 kg s-1 - 0.5 kg s-1 and 0.65 kg s-1 – 0.85 kg s-1, respectively. The comparison between the experimental and modeling data suggested strong correlation over the data range presented with a maximum error in COP of only 2.0% among the selected data points. Future experimental data over a larger range of ambient temperatures and system conditions is suggested to further validate the system modeling. Regardless, the results in the present study show that the TCCS compares favorably with other heat activated cooling systems.