UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.

More information is available at Theses and Dissertations at University of Maryland Libraries.

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2015 - 20182

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    Fate of antimicrobials and nutrients in dairy manure management systems
    (2018) Schueler, Jenna E; Lansing, Stephanie; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Anaerobic digestion (AD) and composting manure management strategies were explored at the field scale to monitor antimicrobial degradation, nutrient transformations, and optimize mitigation of these pollutants in manure fertilizer to decrease their entry to waterways. Removal of antimicrobials and antimicrobial resistance genes (ARGs) were explored at the bench scale, where AD degraded >85% of antimicrobials. At the field-scale, antimicrobials were not consistently removed, persisting in concentrations up to 34,000 ng/g DW in the AD effluent. The tetM genes were reduced during bench-scale AD suggesting that AD could be an effective treatment for removing tetracycline ARGs from manure. The 100% reduction of sulfadimethoxine antimicrobials during AD did not correspond with Sul1 reduction, illustrating differences in antimicrobial versus gene reductions during manure treatment. Antimicrobials did not degrade significantly during field scale composting, likely due to a shortened composting period (33-days). The field-scale results illuminate limitations of tracking antimicrobials in complex treatment systems.
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    INVESTIGATING COMPOSTING AS A METHOD FOR REDUCING ESTROGENICTY IN POULTRY LITTER AND BIOSOLIDS
    (2015) Hammett, Kirsten; Yonkos, Lance; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Biosolids and poultry litter contain the natural estrogens 17β-estradiol and estrone, which can be transported to receiving waters via runoff when these materials are used as fertilizers. Estrogens are of concern because of their ability to act as endocrine disruptors and feminize fish. In this study, In-Vessel Aerated and Turned composting was investigated for its efficacy at mitigating estrogen concerns in BS and PL. Pre- and post- composted, BS and PL samples were investigated for total estrogenicity and estrogen species concentrations. In addition, conversion of estrone to 17β-estradiol was investigated by measuring the creation of deuterated 17β-estradiol from a deuterium-labeled estrone stock within aqueous PL mixtures. Data from these studies indicates that there may be efficacy in composting BS and PL prior to land application and suggest that estrone is capable of converting to the more potent 17β-estradiol species as a result of entering microbially active environments.