A. James Clark School of Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/1654
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item NUTRIENT MOVEMENT IN A VEGETATED COMPOST BLANKET AMENDING A VEGETATED FILTER STRIP ON A HIGHWAY SLOPE(2022) Forgione, Erica Rose; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Excess stormwater runoff caused by rapid urbanization and exacerbated by climate change generates many challenges for public safety and the environment. Large runoff volumes contribute to flooding and pollutants in stormwater runoff pose risks to human and environmental health, including toxicity to the aquatic environment caused by heavy metals and nutrient pollution leading to eutrophication, the cause of harmful algal blooms. An effort is being made to improve the efficiency of existing highway stormwater control systems which have limited performance in terms of volume reduction and pollutant removal. To address this issue, amendment of highway Vegetated Filter Strips (VFS) with a Vegetated Compost Blanket (VCB), a layer of seeded compost placed on an established slope, has been proposed. Compost has high water holding capacity and organic matter content which can immobilize contaminants of concern. However, the high nutrient content of compost poses a threat to net beneficial performance since excess nutrient leaching occurs after application. This research has posed the question: Can a VCB be used as a stormwater control measure (SCM) while avoiding excessive nutrient leaching?The VCB/VFS system was assessed through lab-scale, greenhouse-scale, and field-scale experiments. Hydrologic performance was evaluated in field and greenhouse experiments through evaluation of dynamic flow modification, event volume storage, and cumulative volume retention. Water quality performance was assessed through analysis of Total Suspended Solids (TSS), Nitrate + Nitrite (NOx), Total Kjeldahl Nitrogen (TKN), Total Nitrogen (TN), Total Phosphorus (TP), filtered and total Copper, and total Zinc concentrations. Nitrogen (N) and phosphorus (P) in compost are naturally transformed from organic to inorganic, soluble forms through the microbially-mediated process of mineralization. Nutrient removal occurs through adsorption as compost leachate passes through the VFS soil layer. To further investigate nutrient movement, small scale laboratory experiments were completed to determine the N and P compost mineralization rates and theoretical soil adsorption capacities. Nutrient data from greenhouse and field experiments were empirically evaluated using the lab-obtained mineralization data. Nutrient release was simulated and compared to experimental field data using a new open-source software, OpenHydroQual, which combines hydraulic and water quality modeling. VCBs were found to have a significant impact on both flow and volume reduction, though at the highest flowrates, VCBs were unable to significantly reduce flow and instead acted as conveyance. A useful design estimate for representative storage capacity using the saturated moisture content and wilting point of both the VCB and VFS was determined. Significant TSS removal was observed in both the field and greenhouse studies and particulate metals were largely removed; however dissolved copper leaching was observed in the field experiment, as has been observed previously for some compost in stormwater systems. Highly elevated concentrations of nutrients (as high as 100 mg/L TN and 12 mg/L TP) were observed in the effluent of both field and greenhouse experiments, resulting in net nutrient leaching and concentrations above recommended EPA freshwater limits even after 1-2 years. Additionally, mass loading rates at the field site (as high as 41 kg/ac/yr for TN and 14 kg/ac/yr for TP) were 1-2 magnitudes higher than observed influent mass loading rates (~3.8 kg/ha/yr for TN and ~0.47 kg/ha/yr for TP). Through laboratory mineralization studies, N and P mineralization rates were found to differ between compost batches, with initial nutrient content and age/leaching of compost being important factors. Adsorption experiments indicated increasing P adsorption from compost leachate with increasing soil Al+Fe content. Comparisons to greenhouse and field data showed differences in N speciation, likely due to differences in moisture content and temperature causing differing amounts of nitrification and volatilization. OpenHydroQual modeling showed modest results, with varying levels of accuracy for storm hydrograph simulation and mass release. VCBs are not currently recommended for use due to the risk of nutrient and metals pollution, especially in nutrient and metals sensitive watersheds. However, several impactful factors were identified that may reduce nutrient leaching, including compost composition, compost age/leaching, and VFS soil type.Item ENERGY CONSUMPTION REDUCTION OF COMMERCIAL BUILDINGS THROUGH THE IMPLEMENTATION OF VIRTUAL AND EXPERIMENTAL ENERGY AUDIT ANALYSIS(2022) Bae, Ji Han; Ohadi, Michael; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)According to the U.S. Energy Information Administration (EIA), about 38 quads of the total U.S. energy consumption was consumed by residential and commercial buildings in 2017, which is about 39% of the total 2017 annual U.S. energy consumption (EIA, 2018). Additionally, the building sector is responsible for about 75% of the total U.S. electricity consumption as well as for about 70% of the projected growth in the U.S. electricity demand through 2040. It is clear that the potential for energy savings and greenhouse gas emissions reduction in existing buildings today remain largely untapped and that there is still much left to explore in respect to determining the best protocols for reducing building energy consumption on a national and even a global scale. The present work investigates the effectiveness of coupling an initial virtual energy audit screening with the conventional, hands-on, energy audit processes to more quickly and less costly obtain the potential energy savings for high energy consumption buildings. The virtual screening tool takes advantage of a customized cloud-based energy efficiency management software and the readily available building energy consumption data to identify the buildings that have the highest energy savings potential and should be given priority for performing onsite walkthroughs, detailed energy audits, and the subsequent implementation of the identified energy conservation measures (ECMs). By applying the proposed procedure to a group of buildings, the results of this study demonstrated that a combination of the software-based screening tools and a detailed experimental/onsite energy audit as necessary can effectively take advantage of the potential energy consumption and carbon footprint reduction in existing buildings today and that the low-cost/no-cost energy conservation measures alone can oftentimes result in significant savings as documented in this thesis. However, selection of the appropriate software was deemed critically important, as certain software limitations were observed to hinder the obtainment of some energy savings opportunities.Item Application of Advanced Statistical Methods to Assess Atmospheric and Soil Pollution Mitigation and Potential Risks(2020) Yang, Zijiang; Torrents, Alba; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In environmental engineering field studies, data analysis plays an important role when presenting data into useful information that can be used by engineers and policy makers. However, traditional and currently used approaches have significant limitations due to the nature of the field data, such as high temporal variability, high spatial variability, and high heterogeneity. Such uncertainty may be better handled with more realistic statistical models than traditional statistical models with normal approximation. Additionally, a more robust incorporation of heterogeneity and variability may help to modify environmental fate models to achieve more accurate predictions. Therefore, this dissertation applied some advanced data analysis techniques to four case studies.First, reparameterization was applied to modify the Gaussian plume model to predict dispersion of air pollutant emission from a ground-level active-discharge releasing source. Cross-validation was applied for model selection. The results showed that predictive accuracy of the modified GPM was greatly improved compared with the original model. Second, dispersion of particulate matter was accessed, and a dispersion correction factor was developed to enhance the performance of the regulatory air dispersion model (AERMOD) for low-level sources. Cross-validation was used for model comparison. The results showed that predictive accuracy of the corrected model was greatly improved. Third, carbon amendments were applied to a historically contaminated field to investigate the feasibility for mitigating bioaccumulation. The effect of carbon amendments on bioaccumulation were evaluated. The results showed some evidence of the mitigation effect of compost, and in the meanwhile, the need of a robust statistical method was highlighted due to great spatial variability. Lastly, the Bayesian hierarchical model (BHM) was applied to the field measurement dataset to characterize pollutant concentrations and bioaccumulation. Cross-validation and information criteria were used to evaluate model performance between the BHM and traditional model. The results showed that the BHM was preferred for smaller predictive errors and ability to handle data with larger observational error. These case studies demonstrate the capability of advanced statistical methods for dealing with different environmental research problems. Such statistical methods will be useful for model modification with more specific situations, for data analysis with limited sample size and/or great variability and observational error, for environmental and ecological risk assessment, for evaluation of environmental mitigation strategies, for simulation of real-time pollutant distribution and forecasting with integration of monitoring and modelling approaches, and for minimization of sample size to meet with the accuracy requirement and lower the cost. In conclusion, advanced statistical methods are useful tools for environmental research.Item REAL-TIME COMPARISON OF PHYSICAL AND CHEMICAL AEROSOL MEASUREMENT METHODS(2019) OYEBANJO, FRANCIS; Asa-Awuku, Akua; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Atmospheric aerosols are major contributors to air pollution. Overexposure to these particles can cause severe respiratory and cardiovascular impairments. Aerosols also affect the planet's climate through radiative forcing. Various techniques exist to monitor the physical and chemical characteristic of aerosols but few allow for real-time analysis. In this thesis, real-time field measurements of aerosol particles were compared with values reported by state regulatory agencies. These values were also compared to mass concentrations of PM2.5 in order to determine if a correlation exists between the two. Lastly, the relationship between particle mobility-size and chemical characterization using Raman spectroscopy is explored in an effort to obtain quantitative semi-continuous spectral data. This study found no variation between local and regional particulate matter measurements and no discernable correlation between PM2.5 mass and particle number concentration. The relationship between particle size and Raman intensity remains unknown due to the non-uniformity of mobility-size selected particles.Item ANALYSIS OF TEMPERATURE AND SPECIFIC HUMIDITY DEPENDENCE OF MOVES OUTPUT FOR MOTOR VEHICLE EMISSIONS(2017) Varada, Sai Sreedhar; Ehrman, Sheryl H; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Air pollution and climate change are some of the important consequences of modern industrialization. In a large developed country like the United States of America, these changes have a greater impact due to the country’s high energy demands. This project focuses on air pollution caused by emissions released by combustion of fuels in automobile engines. The mobile emissions inventory for the National Emissions Inventory (NEI) is based on the estimates from MOtor Vehicle Emissions Simulator (MOVES), which is a software program used to model automobile emissions. Analysis of in-situ roadside monitor observations shows that emissions from automobile sources, especially CO and NOx emissions are correlated with ambient temperature and humidity. In this research, I compared the MOVES model output dependence on ambient temperature and specific humidity to observations from an Air quality Monitoring Site which is located in Maryland on Interstate-95 (I-95) and adjusted the model output to nearly match the observations. The adjusted model was used to obtain emissions estimates of another month (here, Nov 2014) and these estimated ratios nearly matched with the observations.Item Mitigation of High Alkalinity in Leachates of Aged Steel Slag(2015) Ozkok, Enes; Davis, Allen P; Aydilek, Ahmet H; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Steel slag, an abundant by-product of the steel-making industry, after it is aged, has a huge potential for use as an aggregate in road construction. However, the high pH of steel slag seepage (pH≥12) is a major impediment in its beneficial use. Analyses on aged steel slag samples demonstrated that the alkalinity producing capacity of aged steel slag samples strongly correlated to Ca(OH)2 dissolution and that prolonged aging periods have marginal effects on overall alkalinity. Treatment methods that included bitumen-coating, bathing in Al(III) solutions and addition of an alum-based drinking water treatment residual (WTR) were evaluated based on reduction in pH levels and leachate alkalinity. 10% (wt./wt.) alum-based drinking water treatment residual (WTR) addition to slag was determined to be the most successful mitigation method, providing 65−70% reduction in alkalinity both in batch-type and column leach tests, but final leachate pH was only 0.5−1 units lower and leachates were contaminated by dissolved Al(+III) (≥3−4 mM). Based on the interpretation of calculated saturation indices and SEM and EDX analyses, formation of calcium sulfoaluminate phases (i.e., ettringite and monosulfate) was suggested as the mechanism behind alkalinity mitigation upon WTR-modification. The residual alkalinity in WTR-amended slag leachates was able to be completely eliminated utilizing a biosolids compost with high base neutralization capacity. In column leach tests, effluent pH levels below 7 were maintained for 58−74 pore volumes worth of WTR-amended slag leachate using 0.13 kg compost (dry wt.) per 1 kg WTR-amended slag on average; also, dissolved Al(+III) was strongly retained on the compost.Item Effect of Free Chlorine Oxidation on the Deposition Kinetics of Bacteriophage MS2 on a Silica Surface(2015) Stephens, Heungkook Noriomoral; Mi, Baoxia; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Understanding the transport kinetics of water contaminates such as pathogenic viruses around solid surfaces is important in controlling groundwater contaminant plumes and optimizing contaminant removal in sand filtration units. The effect of increasing oxidative stress, in the form of small doses of free chlorine, on the deposition behavior of bacteriophage MS2 onto a silica surface was examined using a quartz crystal microbalance with dissipation (QCM-D). MS2 deposition rates were analyzed by reaction time and inactivation level. A statistically significant increase in the deposition rate was identified between MS2 test solutions not exposed to free chlorine and most test solutions that were exposed. However, as exposure to free chlorine was increased, no relationship was able to be deduced from the collected deposition data. Potential explanations based on previous work were discussed. Observations also indicated that more comprehensive purification procedures in comparison to previous studies were necessary to obtain accurate QCM-D data.Item A MODEL SYSTEM TO EVALUATE THE IMPACTS OF VEHICLE-RELATED TAXATION POLICIES ON HOUSEHOLD GREENHOUSE GAS EMISSIONS(2014) LIU, YAN; Cirillo, Cinzia; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This thesis proposes a model system to forecast household-level greenhouse gas emissions (GHGEs) from private transportation and to evaluate effects of car-related taxation schemes on vehicle emissions. The system contains four sub-models which specifically capture households' vehicle type and vintage, quantity, usage, and greenhouse gas emissions rates for different vehicle types. An integrated discrete-continuous vehicle ownership model is successfully implemented, while MOVES2014 (Motor Vehicle Emission Simulator 2014) is utilized. The model system has been applied to the Washington D.C. Metropolitan Area. The 2009 National Household Travel Survey (NHTS) with supplementary data from the Consumer Reports, the American Fact Finder and the 2009 State Motor Vehicle Registrations (SMVR) are used for estimations and predictions. Three tax schemes, vehicle ownership tax, purchase tax and fuel tax, have been proposed and their impacts on vehicle GHGEs reduction are predicted. The proposed model system can be extended to other regions, counties, states and nations.Item AN EXPERIMENTAL INVESTIGATION ON SOLUTE NATURAL CONVECTION IN A VERTICAL HELE-SHAW CELL(2014) Ehyaei, Dana; Kiger, Ken T; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)An experimental analogue was developed to investigate instability propagation of a multicomponent fluid system in porous media. This type of flow pattern has been observed in a broad range of applications from oil enhanced recovery to geological storage of byproduct materials such as CO2. The main focus of this study is on the engineering instrumentation and implementation of experimental measurement techniques in microfluidic systems, more specifically in a thin-gap device that is used as a model for a saturated porous medium. Initially, quantitative in-plane velocity measurement by means of particle image velocimetry (PIV) within thin gap devices subject to a large depth-of-focus and Poiseuille flow conditions is studied extensively. The temporal velocity measurement is then coupled with a simultaneous concentration measurement by means of LED induced fluorescence (LIF). The primary obstacles to a reliable quantitative PIV measurement are due to the effects of the inherent wall-normal velocity gradient and the inertial migration of particles in the wall-normal direction. After quantification of both effects, a novel measurement technique is proposed to make quantitative velocity measurement in microfluidic systems and narrow devices by manipulating the particles to their equilibrium position through inertial induced migration. This single camera technique is significantly simpler and cheaper to apply comparing to the existing multi-camera systems as well as micro-PIV implementations, which are restricted to a small field-of-view. A demonstration of a reliable PIV measurement under appropriate parameter design is then discussed for diffusive Rayleigh-Bénard convection in a Hele Shaw cell. For concentration measurements, the main difficulty of making LIF quantitative is its highly sensitive response to the experimental settings due to extreme sensitivity of the fluorescence to the environment factors and illumination conditions. A calibration procedure is required prior to performing any meaningful quantitative measurements. Additionally, the effect of photobleaching can be significant, which impairs the measurement as will be discussed later in further detail. Eventually after calibration and correction methods for velocity and concentration measurement techniques, a simultaneous PIV/LIF is performed to quantify the behavior of instability fingers in the developed experimental system.Item Reevaluting the CERCLA Process: A Case Study at Beaverdam Road Landfill(2012) Michaelson, Daniel; Torrents, Alba; McConnel, Laura; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This case study consists of a reassessment of the decision making process and chosen remedial action for the Beaverdam Road Landfill (BDRLF) Superfund site. Analyses incorporate case study review, site data, and experimental results to assess whether the chosen remedial action meets the EPA goals of protecting human health and the environment. The case study evaluation produced conclusions used to assess the chosen remedial action. For site analysis, I reassessed the original data interpretation using pertinent soil gas, soil, surface water, and groundwater data. Experimental work consisted of a batch experiment testing the ability of various biowall media and amendments to degrade TCE relative to site soil and a negative control. I concluded that although CERCLA was generally followed, absence of clear remedial goals and limited interpretation of site data resulted in a remedial action which does not meet the EPA's goal of protecting human health and the environment.