Master of Science in Environmental Engineering

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Master of Science in Environmental Engineering

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https://hdl.handle.net/1853/76032

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Degree Series

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School of Civil and Environmental Engineering

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Now showing 1 - 10 of 80

Impacts of Fuel Prices and Regulations on Electricity Generation Emissions and Urban Air Quality

(Georgia Institute of Technology, 2023-07-25) Mei, Eric John

Regulatory actions and fuel price trends have decreased emissions from electricity generating units (EGUs) in the United States. The objective of this thesis is to separate the impacts of regulations and fuel prices on EGU emissions and air pollution in Atlanta and New York City (NYC) between 2006 and 2019. We used observed fuel prices, electricity demand, EGU emissions, and air pollutant concentrations to estimate what air pollutant concentrations would have been under different (counterfactual) fuel price and regulatory scenarios. By comparing the actual and counterfactual scenarios, we find that fuel prices influenced EGU dispatch, which reduced ozone and PM2.5 in Atlanta beginning 2009 and PM2.5 in NYC beginning 2012. Beginning 2008, installation of emissions controls due to the Clean Air Interstate Rule reduced PM2.5 year-round but increased ozone during winter months. Coal EGU retirements due to the combined influence of the Cross-State Air Pollution Rule, Mercury and Air Toxics Standards, and other market and policy factors account for the remaining long-term reductions in PM2.5 and ozone. Such information can be used to estimate the air quality and health benefits of past controls and aid the development of effective future emissions reductions strategies.
Analysis of local climate action in Atlanta through a systemic equity lens

(Georgia Institute of Technology, 2023-05-02) Desai, Aditya Girish

Many cities around the world are engaged in either the planning or implementation of their climate strategies. With political power and will, city-level climate action plans have the potential to combat climate change at a local level by leveraging support from international collaboration. While many climate action planning frameworks exist, there is a need for a standard to be able to benchmark and report progress on agreed upon targets while also ensuring data transparency. Mumbai and Nairobi are one of the most recent examples of cities taking charge to combat climate change and its effects locally. The hazards and risks that climate change poses to these two cities are different, and their socioeconomic and political constructs have unique characteristics. The City of Atlanta’s climate policies and the goal to transition to 100% clean energy usage by 2035 is ambitious. The transition plan adopted in 2019 establishes guidelines for periodic assessment of progress and targets which is vital for an initiative as broad and long-term as this one. Estimating the effectiveness of such a long-term policy over its inception years is not optimal. However, employing an equity-centric framework like the one presented in this work will make comparative analysis much more robust and give decision-makers a unique equity and human health centered tool to assess the performance of their climate policies.
Applications of Systemic Equity in Controlled and Uncontrolled Socioecological Systems

(Georgia Institute of Technology, 2023-05-02) Aggarwal, Ayushi

The present research proposed a broad classification of two types of social and ecological (socioecological) systems – i.e., uncontrolled and controlled systems - that were investigated and analyzed for their implications using the Systemic Equity framework and the Wells-Du Bois Protocol. This framework, definitions of inequities, and the tools to help tackle such inequities are explained in Chapter 1, followed by two case studies in Chapters 2 and 3. The first case study showcases an uncontrolled system and its inequities. Agriculture was chosen as the focal point here to demonstrate the application of the Systemic Equity framework concerning historical environmental exposures by the Monsanto Company. Following this, a case study on the food expenditure patterns across sociodemographic subgroups (i.e., race and ethnicity) in the United States are analyzed for its inherent biases. Specifically, a machine learning (ML) tool – i.e., clustering - was used to model and test the presence of in-built biases followed by the application of the Wells-Du Bois Protocol to demonstrate a use case in mitigating socioecological biases in ML systems. The use of these tools and the Systemic Equity framework are discussed as a means to promote equity-centered decision making moving forward.
Machine Learning Applied to Chlorine Residual Data

(Georgia Institute of Technology, 2022-12-13) Helm, Wiley Speir

Chlorine disinfection systems are ubiquitous in drinking water treatment plants and provide a method for reliable, safe, potable water. The concentration of free chlorine residual (FCR) leaving drinking water treatment plants must be between a federally regulated margin of 4.00 and 0.20 mg/L as Cl2. Dosing chlorine is tricky as oxidizable constituents in the water will consume the FRC generating a chlorine demand and altering the final concentration. The chlorine dose is often determined by the plant operator who relies on personal experience to predict the chlorine demand and the FCR leaving the plant. A machine learning model was applied to historic water treatment plant data to see if the FCR could be predicted with readily available water quality data. The model used a CatBoost regression tool, based on a form of gradient boosting, to predict the FCR. The data spanned from March 2021 to March 2022, and a data frame of 33 input parameters and 7,851 rows of data was used to train the model. The model went through four iterations, with the best predictive results providing a coefficient of determination, R2, of 0.937. Shapely additive explanation values were used to interpret the results of the model. This tool provided elegant visual interpretations into the function of the model and how it used individual parameters to make predictions. It was found that the model relied heavily on non-causal parameters to make the most accurate predictions. The relationship, if any, between the non-causal parameters and the FCR is not clear.
THE EFFECTS OF CLIMATE CHANGE ON ELECTRICITY GENERATION AND FUEL SUPPLY IN 2050: A STUDY OF LOUISIANA, CALIFORNIA, NEW YORK, AND WASHINGTON’S CONVENTIONAL GRID

(Georgia Institute of Technology, 2021-05-17) Burns, Diana A.

Climate change due to increased greenhouse gas emissions can impact energy infrastructure in a variety of ways. Climate impacts on power grid reliability in 2050 for Louisiana, California, New York, and Washington were studied in this paper. Projected electric loads, reserve margins, ramping needs, and flexible reserves were calculated for each state in 2050 to form a baseline to analyze the effect of extreme temperatures and drought on electricity generation and fuel supply, which can in turn impact grid reliability. Reduced capacity of natural gas combined cycle power plants from increased heat, combined with increased electrical demand, is projected to affect all states, especially California and Louisiana. These states also are projected to have some of the most severe heat in the country in 2050. Reduced thermal plant capacity from increased cooling water temperatures or low cooling water supply is an issue, however its effects on in-state generation in these states is projected to be minimal. Decreases in hydropower generation are also projected to have minimal effect on all states, however it had the greatest impact on California. Lastly, natural gas supply loss is projected to impact all states, especially Louisiana and California. Overall, geographic location, seasons, time of day, fuel mix, and policy are all factors to be considered when analysing the effects of climate change on the reliability of the power grid.
KINETIC MODELING TO PROBE THE ADVANCED OXIDATION PROCESSES IN A FE(II)-PAA-ABTS, A FE(VI)-PAA AND A FE(VI)-AMINE SYSTEMS

(Georgia Institute of Technology, 2021-05-11) Sadhasivan, Manasa

Pharmaceuticals are one of the major groups of emerging environmental contaminants in recent years. Advanced oxidation processes (AOPs) are known to be more efficient than conventional treatment processes in the degradation of pharmaceutical micropollutants. Novel AOPs use several oxidants such as ferrate (Fe(VI)) and peracetic acid (PAA) in order to generate highly reactive species which further degrade micropollutants. Furthermore, suitable activators can be combined with the oxidants to produce enhanced efficient in AOPs. The overall objective of this study is to investigate qualitatively and quantitatively the reaction mechanisms of the iron intermediate species (Fe(V) and Fe(IV)) in three different AOP systems that exploit the oxidizing potential of Fe(VI) or activated Fe(II). The three systems investigated are the Fe(II)-PAA-ABTS (2,2′-azino-bis(3-ethyl-benzothiazoline-6-sulfonic acid), Fe(VI)-PAA and Fe(VI)-DMA systems. The experimental results are collected and examined in depth by constructing robust kinetic models for the respective oxidative systems to study the mechanisms involved. Sensitivity analysis and goodness-of-fit tests are further conducted to validate the kinetic models. Overall, this study presents a useful methodology and new modeling tools to quantitatively probe the advanced oxidation systems to gain new insights in the mechanism involved.
Optimization of The Scaled-Up Coaxial-Electrode Copper Ionization Cell for Water Disinfection

(Georgia Institute of Technology, 2020-12-09) Gore-Datar, Nissim

Over 800 million people worldwide lack access to clean, uncontaminated drinking water, and over 1.1 million people in America lack a piped water connection. The public health consequences of this issue have been worsened by the ongoing pandemic, which has made the availability of clean water for hand washing more important. Centralized solutions to this issue, such as chlorination or membrane filtration, are too costly and energy intensive for widespread application in the developing world, and sometimes even pose their own risks, such as the formation of carcinogenic disinfection by-products (DBPs). Point-of-use solutions such as chlorine tablets or UV disinfection are more practical, but can also be energy intensive and pose DBP risks. The coaxial-electrode copper ionization cell (CECIC) is a water disinfection system developed to fill this gap using the biocidal properties of copper aided by other mechanisms such as electrophoresis, strong localized electric fields, and in-situ generation of copper ions. The CECIC has been proven to be highly effective (>6-log inactivation of E. coli with ~200 μg/l Cu) when tested with DI water at low flow rates in a reactor with an effective volume of 10 ml. In order to meet real-world conditions, it is necessary to scale up the system to a larger prototype and test its performance with more conductive waters at higher flow rates. This presents several challenges, such as maintaining a strong localized electric field with a low voltage in spite of the larger radius (inter-electrode distance) of the cell, keeping copper concentrations low in spite of a higher rate of copper release in more conductive water, and ensuring high bacterial inactivation in spite of a reduced hydraulic retention time (HRT). On the other hand, the larger cell of the scaled-up CECIC also allows for more flexibility with the anode configuration. More wires can be installed parallel to the flow and equidistant from the axis to reduce the gap between the electrodes, in turn creating more regions with enhanced electric field strength. The anode can also be positioned at an angle to the flow so as to increase mixing and contact with bacteria. Various experiments are designed and conducted in order to test these configurations and optimize the performance of the scaled-up CECIC under high-conductivity, high-flow conditions. Configurations consisting of 1, 3 and 6 wires positioned parallel to the flow as well as 3 wires positioned inclined to the flow are tested for their response to different flow rates (100 – 250 ml/min) at the same voltage (3 V) and to different voltages (0.5 – 7 V) at the same flow rate (150 ml/min). The results of these experiments show that inclining the wires reduces the disinfection performance rather than increasing it, but do not clearly indicate whether increasing the number of wires helps improve performance. Further testing is carried out with the original configuration (1 coaxial wire) to ascertain the synergetic role played by the electric field and copper concentration gradients by controlling the current supplied to the cell. These experiments demonstrate that the synergetic effect does play an important role even in the scaled-up reactor, with the disinfection performance improving significantly as the electric field strength increased. Lastly, the scaled-up system is tested with real water samples (river water and rain water) that are pre-treated to remove experimental interference from suspended solids and pre-existing microorganisms while preserving the real water matrix. Over 99% of bacteria are inactivated by the CECIC in both cases, with an effluent copper concentration of ~550 μg/l. This performance is lower than that achieved at the same conditions with synthetic water, likely due to interference from dissolved substances in the real water. However, this demonstrates that the scaled-up CECIC can disinfect real water samples too, which is an important stepping stone to pilot studies and field deployment.
Effect of peracetic acid on anaerobic treatment of poultry processing wastewater

(Georgia Institute of Technology, 2019-06-10) Lin, Ding Hsiang

Peracetic acid (PAA) is a powerful disinfectant against a wide spectrum of microbes, used in healthcare, water treatment, and food industry. In poultry processing plants, PAA is used in chicken chiller tanks as well as for the disinfection of processing equipment as an antimicrobial agent. Residual PAA in poultry processing wastewater may be carried to biological wastewater treatment systems with potential adverse effects. The overall goal of this research was to evaluate if anaerobic treatment of PAA-carrying poultry processing wastewater is feasible. The specific objectives of this research were to investigate: i) the effect of PAA on a mixed fermentative/methanogenic culture, acetoclastic methanogens, and hydrogenotrophic methanogens; and ii) the effect of PAA on the anaerobic treatment of poultry processing wastewater (dissolved air floatation effluent) and compare the effect of pre-decomposed and direct PAA addition to semi-continuously-fed, laboratory-scale anaerobic reactors, conditions reflecting normal operation and accidental spills, respectively, in poultry processing plants. The findings of the present study suggest that pre-decomposed PAA addition does not impact fermentative/methanogenic systems, especially acetoclastic methanogens, and hydrogenotrophic methanogens. On the other hand, direct 40 and 100 mg/L impacted the fermentative/methanogenic culture and acetoclastic methanogens, which recovered over time. Hydrogenotrophic methanogens were more resistant to direct PAA addition, given that hydrogenotrophic methanogens were not affected by direct 40 mg/L PAA addition. Thus, anaerobic processes can be used to treat poultry processing wastewater carrying PAA, at least up to 80 mg/L PAA. Even in the case of an accidental PAA spill, anaerobic treatment systems can recover over time providing that corrective measures are implemented (e.g., temporary wastewater diversion, pH adjustment).
A preliminary assessment of population exposures resulting from truck idling at port gates

(Georgia Institute of Technology, 2017-12-14) Wilson, Alana

The work presented in this thesis is the contributions to a larger research effort studying emissions associated with port operations. My contribution can be split into three components: literature review, environmental justice mapping, and dispersion modeling. The literature review for this project includes looking at past population exposure studies, past studies for measuring truck emissions, and existing efforts to reduce port emissions. The environmental justice mapping portion of this work includes mapping population demographics for areas surrounding the Port of Los Angeles, Port of Long Beach, Port of Houston, Port of Savannah, and Port of Brunswick. The data used for this section was taken from the US Census Bureau and from the EPA’s EJSCREEN tool and includes data on income, race, housing occupancy, house and family size, age, linguistic isolation, and education. The dispersion modeling component of this analysis looks at emissions from truck drivers queuing at part gates. These emissions were modeled in AERMOD on three different spatial scales and then mapped using ArcGIS’s interpolation tool. The modeling portion of this thesis evaluates the effect vehicle age, meteorological data, and characterization of the roughness parameter has on estimated concentrations.
Mechanistic modeling of an aquaponic controlled-environment agriculture system: nutrient and water dynamics, harvest productivity, and waste treatment

(Georgia Institute of Technology, 2017-12-11) Debrota, Kathleen H.

Aquaponics, the symbiotic co-culturing of fish and vegetable crops, is a promising technology for both food production and waste mitigation. As part of an urban ecosystem, controlled-environment-agriculture (CEA) systems would serve as nutrient transformation hubs, generating food and removing nutrient pollutants from local organic waste and wastewater. A mechanistic model of the nutrient and water dynamics of this emerging system is proposed here, based on Monod kinetics and the International Water Association’s Activated Sludge Models (ASM). This model functions to dynamically predict the nutrient transformation and food production capacity of an aquaponics CEA, and allows the optimization of crop and fish species selection, planting and stocking densities, fish food composition, feeding rate, maximum harvest rates, and other important factors with important economic, policy, and design decision implications.