Theses and Dissertations from UMD
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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 give thesis/dissertation in DRUM
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Item Utilizing algal turf scrubbers for bioremediation and bioenergy production(2023) Delp, Danielle Marie; Lansing, Stephanie A; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)This dissertation researched the conversion of algal biomass that was generated as a byproduct of bioremediation by algal turf scrubbers (ATS) into bioenergy via anaerobic digestion. Anaerobic digestion is a bacterial process that converts organic material into bioenergy in the form of biogas that contains methane (CH4), the primary component of natural gas. Bioenergy yield was quantified as the volume of CH4 generated from digestion of the algae in relation to seasonal changes in algal biomass yield, different digester operational parameters, co-digestion of the biomass with more conventional digestion feedstock, and flocculation pre-treatment for dewatering of algae prior to digestion. The first study used a pilot-scale mesophilic digester at the Port of Baltimore (Baltimore, MD, USA) to continuously digest algae from a 122 m2 ATS on the Patapsco River over two years. Biomass generation was significantly correlated to maximum daily air temperature, water temperature, and flow rate in Year 1 but only water flow rate in Year 2. Algae of the taxa Ochrophyta dominated the algal turf, especially the filamentous diatom Melosira sp., in both years. In Year 1 of the study, two anaerobic digestion systems with variable hydraulic retention times (HRT), designated D1 (average HRT 45.0 ± 5.8 days) and D2-D3 (average HRT 61.0 ± 8.1 days) were used to digest the algae. The D1 generated 1090 L CH4 from 2416 L of algae over a 39-day HRT (59.1 ± 8.9 L algae/kg VS), and D2-D3 generated 1170 L CH4 from 2337 L of algae over a 53-day HRT (67.9 ± 11.0 L algae/kg VS). The difference in CH4 yield with two different HRTs was not significant. In Year 2, only the D2-D3 was operated and was modified to test the use of active recirculation and heating to improve digestion efficiency and CH4 yield. The D2-D3 system generated 4000 L of CH4 (163 ± 42 L algae/kg VS) from 3310 L of algae in Year 2. The second study consisted of laboratory-scale biomethane potential tests to test changes in CH4 yield when algae harvested from an Anacostia River (Bladensburg, MD, USA) ATS was co-digested with three wastes (dairy manure, food waste, and poultry litter) at algae:waste loading ratios of at 1:1, 1:2, 1:5, and 1:10 by organic material, or volatile solids (VS), content. The algal biomass was the least efficient substrate at generating CH4 when normalized by both mass VS digested (109 ± 4 mL CH4/g VS) and total mass of substrate digested (0.687 ± 0.025 mL CH4/g substrate). Co-digestion with all three of the wastes at all ratios tested significantly increased CH4 generation efficiency per mass VS compared to only digesting algae. However, the high moisture content of the algae (95.2%) relative to the other co-digestion wastes (29.0-84.6%) significantly decreased CH4 production on a mass basis for the dairy manure, food waste, and poultry litter when algae was added at any loading ratio. A lettuce growth experiment using the effluent of the digestion vessels showed no signs of acute toxicity when any of the diluted (8-fold) digester effluents were applied as fertilizer to the developing plants. The third and final study consisted of flocculation experiments that tested 500-mL of algae using four experimental treatments (FeCl3, electrocoagulation, chitosan, and Bacillus sp. RP 1137) to dewater algae harvested from the Anacostia River ATS and compared to gravity settling as a control. The experimental flocculants successfully increased the total solids (TS) of the ATS algae by 14-291% depending on the treatment, with electrocoagulation being the least effective and bacterial flocculation being the most effective flocculant. All treatments reduced total suspended solids (TSS) in the drained supernatant by >98%. The raw ATS algae and dewatered solids from the settling experiment were then digested for 35-days, with the algae yielding 49.6 ± 3.6 mL of CH4/g VS. The dewatered solids had reduced digestion efficiency by 29.6-71.0% compared to untreated algae. Dewatering pre-treatment increased CH4 yield from the algae when normalized by total g substrate fed to the reactor (1.65 ± 0.12 mL CH4/g substrate) for all treatments except bacteria 1x, however the effect was only significant for solids dewatered with electrocoagulation. The results from the three studies show that temperature drives algal growth patterns in temperate climates, which results in seasonally variable biomass yield from ATS, with a corresponding variability in CH4 production due to inconsistent availability of the algal feedstock. Algae can be co-digested with agricultural and food wastes that are generated year-round to reduce variability in feedstock availability. Thickening and dewatering the algae improves CH4 yield on a mass basis, however the digestion efficiency was reduced. In conclusion, the findings suggest that anaerobic digestion is a viable means of managing the algae harvested from ATS systems with and without co-digestion of the algal biomass.Item TWO MARINE SPONGES, LENDENFELDIA CHONDRODES AND HYMENIACIDON HELIOPHILA, AND THEIR MICROBIAL SYMBIONTS: ROLES IN MARINE PHOSPHORUS CYCLING.(2021) Jonas, Lauren; Hill, Russell; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Marine sponges have emerged as major players within coral reef biogeochemical cycles, facilitating intake and release of carbon, nitrogen, and phosphorus. The majority of studies have investigated the role of sponges in transforming dissolved carbon and nitrogen; however, the same breadth of insights has not been extended to phosphorus. This study uses 32P-labeled orthophosphate and ATP to determine that two marine sponges, Lendenfeldia chondrodes and Hymeniacidon heliophila, both rapidly take up ambient dissolved inorganic phosphate and dissolved organic phosphorus. Subsequent genetic analysis and chemical extraction showed that sponge symbionts store phosphorus in the form of energy-rich polyphosphate (poly-P). L. chondrodes, a sponge from oligotrophic habitats and with a microbiome dominated by cyanobacterial symbionts, stores more phosphorus as poly-P (6–8%) than H. heliophila (0.55%), a eutrophic sponge with low cyanobacterial abundance. This work adds new insights to the roles of the sponge holobiont in cycling the crucial element, phosphorus.Item RESPONSE OF PLANKTON COMMUNITIES IN COASTAL LAGOONS TO CHANGES IN NUTRIENT QUALITY AND QUANTITY: CASE STUDY OF FLORIDA BAY(2016) Shangguan, Yini; Glibert, Patricia M; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Comprehensive Everglades Restoration Plan was initiated to return Florida Bay to a more natural ecological state. The C-111 project, one phase of this plan and initiated in 2012, was designed to increase freshwater flow into northern Florida Bay. However, it also alters the nutrient regime and, potentially, phytoplankton biomass and assemblage. This dissertation investigated the combined effects of changes in discharge and nutrient on phytoplankton biomass and assemblage in several interconnected, mesohaline coastal lagoon systems (lakes) of Florida Bay using field observations, mesocosm experiments, and a statistical box model. Field measurements on nutrients and phytoplankton were performed before and after C-111 implementation. After C-111, increased freshwater flow and phosphorus (P) input, but decreased salinity and nitrogen (N) input were observed. One set of the lagoon lakes, previously highly eutrophic (average chlorophyll a >20 ug L-1), had a nearly 50% decline in overall phytoplankton biomass. The other set of lakes, originally oligotrophic (average chlorophyll a <2 ug L-1), had a doubling of phytoplankton biomass. Phytoplankton assemblage in both sets of lakes shifted to picocyanobacteria. Mesocosm experiments (5 independent experiments, 5-10 day duration, 1000 L tanks) were conducted to test the effects of nutrient additions. Phytoplankton biomass increased 3 to 10-fold in the +P treatments (alone or +N), but did not increase substantially in the +N alone treatments. The +N+P treatments, particularly the +NO3-+P at a +N:P molar ratio of 32 led to a 20-fold increase in diatoms, whereas N in the form of +NH4+ yielded a > 2-fold increase in picocyanobacteria. A statistical box model based on relationships measured in the field under different salinity regimes was developed to simulate flow, nutrients, and phytoplankton changes in the eutrophic lake chain. Model output showed that higher freshwater discharge decreased phytoplankton biomass in the upper of the connected lakes, but the lower lake had a high potential to generate algal blooms, which is consistent with the field data. Also, picocyanobacteria tripled following an increase in dissolved organic nitrogen (DON). This study recommends co-management of both P and N, particularly NH4+ and DON in Florida Bay if picocyanobacteria blooms are to be controlled.Item A Comparison of Organic Matter Amendments for Use in Extensive Green Roof Substrates(2015) Barton, Elizabeth Taussig; Lea-Cox, John D; Cohan, Steven M; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Organic matter is important for water retention and nutrient availability in green-roof systems. Yet few quantitative green-roof studies provide data for various sources of organic matter (OM). Coconut coir (CC), rice hulls (RH), SmartLeaf® (SL), and mushroom compost (MC) were used as green roof substrate amendments. The effects of OM on water-holding capacity, nutrient availability and plant establishment were measured. Growth of Phedimus kamtschaticus was greater with MC or SL compared to CC or RH. Substrate moisture and nutrient availability were significantly affected by OM source during an 8-month rooftop experiment and a 6-month growth chamber study. Coconut coir showed high moisture retention, low nutrient availability and low aboveground biomass, indicating that nutrient availability is crucial to successful plant growth and establishment on a green roof. Composted materials such as MC and SL that have higher levels of available nutrients, promote better growth than unprocessed materials like RH and CC.Item Does the Policy-Making Process Affect Farmer Compliance? A Three-State Case Study of Nutrient Management Regulations(2010) Perez, Michelle Reid; Nelson, Robert H.; Public Policy; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A series of fishkills in 1997 in the Chesapeake Bay were linked to Pfiesteria piscicida, a rare toxic microorganism, and to nutrient pollution from agricultural sources. Manure from poultry production on the Delmarva Peninsula was regarded as the primary source of the excess nutrients. These fishkills served as a focusing event for policy-makers in Maryland, Virginia, and Delaware to update their scientific guidance on phosphorus management, promulgate agricultural regulations, and depart from decades of relying on voluntary technical and financial assistance to improve farm-related water quality problems. This dissertation conducts a comparative case study of these three states to determine if 1) the policy-making process in each state affects compliance by farmers and 2) if the laws improved farmer nutrient management behavior. Data sources include information gathered from interviews with 60 corn farmers on the Peninsula that use broiler chicken manure as fertilizer; interviews with over 60 policy stakeholders; and reviews of primary and secondary documents. Analytical methods include: political analysis of the main stages of the policy development process; policy analysis of the effectiveness of plan-based regulations; statistical tests to determine significant differences between states regarding farmer responses to Likert Opinion Statements and questions about their nutrient management practices; logit regression analysis to determine factors influential to low manure application rates; and a review of compliance data collected by the state regulatory agencies. Answers to both research questions are, overall, "yes," though this answer depends on which dataset of compliance and which metric of improved nutrient management behavior is reviewed; there are "no" answers as well. Results of this dissertation highlight the serious difficulty of regulating dispersed nonpoint source agricultural nutrient pollution through nutrient management plans. Several findings arise, including: plan-based agricultural regulations are in reality voluntary; plans prepared by private and public sector planners result in non-uniform standards; gaining "buy-in" from rather than "alienating" the regulated community likely results in better overall outcomes; regulations that account for on-the-ground realities of farming and state regulatory capacity likely achieve better overall outcomes; and focusing events that turn out to be weak can undermine the justification for new regulatory policies.Item Microcosm Studies of Nutrient Cycling in Bahamian Stromatolites(2008-08-13) Jabro, Nicholas; Marinelli, Roberta; Harvey, Rodger; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)I report results of field observations and experiments that examine the oxygen and nutrient fluxes for stromatolites in Highborne Cay in the Exumas, Bahamas. The aim of this study is to determine whether nutrients play a role in the transition of the community structure within the mats that is thought to be responsible for lithification and, ultimately, mat growth and structure. The research includes nutrient monitoring of the sediment and water column, and measures of rates of oxygen and inorganic nutrient exchange from stirred microcosm chamber incubations of mats with varied community structure. On the basis of mat community composition, I hypothesized that different mat types would have different fluxes, and that Highborne mats would be limited by one or more nutrients that efficient recycling within the mats might otherwise help supply. Samples of the four major mat types were sealed in stirred microcosm flux chambers, incubated in a circulating water bath, and sampled for oxygen, NH4, NO3, PO4, and Silicate. Nutrient addition, treatments of PO4 and Si were employed to investigate whether they stimulate primary productivity, signaling that mats are limited in these solutes. Nutrients in Highborne Cay were high in nitrogen relative to P, with N:P as high as 30. There was no difference in nutrient flux or productivity among mat types, and the addition of nutrients did not change mat productivity. These observations suggest that mat development in Highborne Cay is not limited by nutrients, but more likely structured by external physical factors such as the rate of turbulent flow which may limit the recruitment of competitors such as macroalgae and benthic branching diatoms.Item Field Evaluation of Hydrologic and Water Quality Benefits of Grass Swales for Managing Highway Runoff(2006-09-22) Stagge, James Howard; Davis, Allen P; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Due to growing awareness of non-point source pollution treatment, the performance of grass swales as a highway runoff treatment and the effect of including a grass filter strip pretreatment area adjacent to the swale were evaluated using a field-scale input/output study on a Maryland highway. Results of this comparison for 22 rainfall events over 1.5 years show significant peak reduction (50-53%), delay of the peak flow (33-34 min) and reduction of total volume (46-54%). The grass swales exhibited statistically significant removals by mean concentration of total suspended solids (41-52%), nitrite (56-66%) and zinc (30-40%), lead (3-11%), copper (6-28%) and cadmium. Other monitored nutrients (nitrate, TKN, and total phosphorus) exhibited variable removal capabilities (-1-60%), while the swales exported chloride (216-499 mg/l) at a significant level. Results suggest the pretreatment grass filter strip imparts no significant water quantity or quality improvement and that the swale itself is the most important treatment mechanism.