Anaerobic digestion is one of the most promising management options for dairy manure treatment. Manure wastewater from dairy farms has been used for methane production for decades. However, performance failure due to inadequate mixing is routine. In general, the mixng of anaerobic digester is achived throguh mechnical stirring, liquid circulation, and gas circulation, among which the gas circulation proves to be the most effcient way. In this work, we studied the liquid flow pattern of two differetn type of gas-circualtion based anaerobic digesters, with the aim to understand the effects of hydrodynamic behavior of the digesting liquid on the anaerobic digestion performance, so a better mixing strategy can be provided. We used two 20-L gas circulation based anaerobic digesters with confined (gas-lift) and unconfined (bubble column) design. The anaerobic digestion performance and mixing behaviors were studied at different gas recirculation rate. It was found that the biogas production from the bubble column was constantly higher than that from gas-lift digester. However, the overall flow of the two digesters, which is indicated by residence time distribution (RTD), showed a similar pattern. Furhter investigation of local liquid flow behavior using Computational Fluid Dynamic (CFD) indicate that the bubble column accumulated higher portion of sludge in the bottom of the digester, which has a higher TS and VS, COD, and biomethane production potential than those from the gas-lift digester. This is the reason that the biogas production from the bubble column is higher than the gas-lift digester. Through this study, a thorough characterization of the flow behavior of the anaerobic digester were developed, and provided a deep insight of its influence on the anaerobic digestion performance. / Master of Science

Bioelectrochemical systems (BES) is a platform technology that is able to realize versatile engineering functions and recover valuable resources in an energy-efficient manner. One of the potential applications of BES is to remove and recover nutrients simultaneously from nutrient-rich wastewater, such as digested manure from livestock. A four-chamber BES was developed and used in this study to explore the potential to remove and recover hexavalent Chromium from synthetic wastewater, and ammonia and phosphate from digested manure. The BES was able to achieve 99.6% removal of Chromium by membrane adsorption in 5 days but failed to recover in the concentration chamber. Nutrients were removed from the waste stream and recovered in the recirculated catholyte by the electrical field generated from the waste. The BES was demonstrated to achieve substantial COD removal, nutrients removal and recovery. On average, the removal efficiencies were about 50% for COD, 85% for NH4-N and 40% for PO4-P, and the concentration of NH4-N recovered in the catholyte was 670 mg/L after 5 cycles under an applied voltage of 0.8 V. PO4-P was not recovered in solution, probably because it has precipitated under the alkaline condition together with Mg2+ and Ca2+ concentrated in the catholyte. It was also demonstrated that nutrients removal and recovery depended on the current generation and were mostly completed at high current. To sum up, the BES was proven to be an effective and sustainable approach to remove and recover nutrients from digested manure. / Master of Science

The objectives of this study were to (1) determine an intermittent aeration strategy that could be used to conserve nitrogen (N) via nitrification in dairy manure, (2) determine the effect of recycled flush water on the bio-availability of N during nitrification, and (3) determine effective and economical dosages of chemicals to remove phosphorus (P) from liquid dairy manure. Intermittent aeration strategies, defined in terms of time the aerator is on and off (ON h:OFF h), could be used to conserve N in dairy manure. Testing of four treatments (continuous aeration [100%], 1h:0.33h [75%], 1h:0.67h [60%], and 1h:1h [50%]) showed that only treatments using air provided for 100% and 75% of the time could support nitrification. The 100% and 75% aeration treatments conserved an average of 38% and 25% of influent total ammonia nitrogen (TAN) as nitrite-N+nitrate-N, respectively. Less than 2% of influent TAN was conserved using 60% and 50% treatments. The effect of manure handling technique on N bioavailability and nitrification was tested using flushed and scraped dairy manure. Nitrification was inhibited in scraped manure. Four aluminum- and iron-based salts and five cationic polyacrylamide polymers were evaluated for P removal using jar tests. Ferric chloride (FeCl3·6H2O), aluminum sulfate (Al2[SO4]3·13H2O, alum), and Superfloc 4512 were selected for further study. Polymer addition enhanced floc size and improved P removal. Treatment of manure (0.89% total solids) from Tank 2 at Virginia Tech's dairy using either FeCl3 or alum in combination with polymer resulted in more than 90% P removal. Chemical treatment and transport of P-rich sludge from a 2,270 cubic meter storage tank would result in an estimated 40% cost savings over transport of the entire manure volume offsite for land application elsewhere. The manure treatment strategies tested provide some solutions to dairy farmers regarding adjustment of N:P ratios so that manure can be applied to meet nutrient needs of crops while adhering to regulations set forth by nutrient management plans. / Master of Science

The aim of this study was to examine how manure-derived value-added products via anaerobic digestion impact the environment and economics of dairy farming. An on-farm anaerobic digester (AD) at Virginia dairy was used in this study. The AD performance evaluated for: (i) biogas production (ii) waste stabilization; and (iii) production of organic fertilizer. Locally available organic waste streams were evaluated for co-digestion with dairy manure to increase biomethane production at the on-farm AD. The effective pasteurization temperature and duration to reduce fecal coliform, E. coli, and Salmonella concentrations in the AD effluent to acceptable levels for use as an organic fertilizer were determined. A partial environmental and economic analysis was conducted on the AD system to determine its effects on the environmental-economic sustainability of dairy farming. The results showed that the manure-derived value-added products from the AD improved environmental health and had the potential to improve the economic sustainability of the dairy farm. The AD stabilized the manure adequately and produced 400 KW of electricity, enough to power 230 US homes. Blending manure with locally available organic materials increased volatile fatty acid production, suggesting the potential to increase biomethane yields. Pasteurization at 70°C is sufficient to reduce pathogen indicating organisms to acceptable levels for the manure to be used as an organic fertilizer. The payback periods range from 4.6 to 11.8 years for the AD investment costs and reductions in direct manure methane emissions of 2,436 tonnes CO2e per year. / Master of Science

Phosphorus (P) released in overland flow is related to P form, soil solution P concentration and the release rate of P from soil. Models relating soil test P (STP) to water soluble P (WSP) and the degree of P saturation (DPS) to STP are used in Virginia to estimate P loss potential. Typically the reservoir of biologically available P in eastern soils has been attributed to P sorbed onto surface sites of non-crystalline aluminum (Al) and iron (Fe) oxides, extractable in ammonium oxalate. More recently, soils with a long-term history of manure application have exhibited properties that indicate calcium (Ca) may also be limiting P, especially in soils impacted by poultry manure. Accurate estimation of P loss potential is critical for justification of long-term management approaches. To evaluate the accuracy of model estimation of P loss potential and P source, we evaluated the (i) soil chemical properties, (ii) soil solution equilibria, (iii) inorganic speciation, and (iv) P desorption capacity of soils impacted over a long period of time by poultry litter (broiler and layer), dairy manure and commercial fertilizer applications. Soil chemical properties were measured with various extractions, while soil solution was measured in samples equilibrated at field capacity. Inorganic material was analyzed using scanning electron microscopy with electron dispersive capacities. Phosphorus desorption capacity was determined by calculating the rate of P release into a 0.01 M NaCl batch reactor. Out of the said analysis, we found that Al and Ca were the primary soil chemical elements limiting soil test P extractability and release. Soils with a high P sorbing capacity (PSC), that were not yet saturated, retained the most total soil P over a 60 hr. batch release experiment. Phase diagrams show that all soils were supersaturated with respect to common Al-, and Fe â P minerals. Saturation indices calculated with Visual Minteq were correlated with the degree of P saturation, and suggested that as the DPS increased, formation of less soluble Ca -P minerals occurs. The soils found to be supersaturated with respect to tri-calcium phosphate (TCP) and octa-calcium (OCP) had the highest P release rate coefficients for both the first (k1) and second (k2) phases of release. Scanning electron microscopy with electron dispersive analysis (SEM-EDS) found that for some manure impacted soils, Al formed associations with P that are stable over a large soil to solution ratio. Additionally, it appears that as non-crystalline Al becomes saturated with P, Ca-P forms may act as an additional reservoir of P in soils with a long-term history of poultry manure application. / Master of Science

Hormones are endocrine disrupting compounds, which have been shown to alter the sexual development of aquatic organisms. Animal manure applications to agricultural fields for nutrient management can be a source of environmental hormones. This dissertation investigates the occurrence of hormones in fields applied with various manures and their adjacent streams, as well as the effect of manure application technologies on the fate of hormones in soils, sediments, and runoff. A total of 11 hormone compounds were studied. All studied analytes were quantified using liquid chromatography and triple-quadrupole mass spectrometry following various sample extraction and clean-up strategies. The spatial and temporal distribution of manure-associated hormones in a manure surface applied agricultural field and adjacent stream was studied at time points up to 7.5 months after a routine manure application. Hormones were detected mainly in the top 0-5cm soils. Significantly higher levels of hormones were found in the drystack applied area of the field when compared to dairy manure slurry applied portion. New technologies for the subsurface application of poultry litter show promise as a tool to reduce the transportation of environmental hormones in surface runoff. Once adequate sampling protocols were established; it was determined that subsurface injection of both dairy manure and poultry litter reduced the impact of manure surface runoff. Hormones also showed little vertical and lateral movement in the soil. The transformation rates of 1,4-androstadiene-3,17-dione, 4-androstene-3,17-dione and estrone were studied comparing the effects of temperature, soil type, and application type. The calculated half-life of 1,4-androstadiene-3,17-dione in poultry litter surface-applied soils was 1.9 times higher than that in the poultry litter subsurface-injected soils, indicating a faster dissipation rate in the injection slits. Estrone persisted at detectable levels for the duration of the study in all treatments. The continued use of best management practices and innovative manure management techniques for the reduction of nutrients, sediment and other contaminants has the potential to also reduce hormone transport to the natural environment. Monitoring many different types of hormones in all areas of an environmental system will continue to provide better information on the occurrence and fate of hormones sourced from manure amended soils. / Ph. D. / Hormones can contaminate streams and cause harm in the environment by interfering with the sexual development of aquatic organisms. Hormones are naturally occurring in animal manure, which is applied to agricultural fields for nutrients. Animal manures are usually spread on the surface of the soil and hormones can travel from the field to the streams when it rains. There are new technologies where the manure is injected into the soil instead of spread on the surface that could reduce the environmental impact of hormones in manure. This dissertation investigated the how hormones behave in fields applied with animal manures using the surface application technique and the subsurface injection technique. We investigated how long hormones persist in the soil, and their levels in manures, runoff from precipitation, and in waterways. Hormones were shown to stay in the top 0-5cm of soil, and to remain in the manure injection slit, showing that they do not easily move in the environment. Hormones were only detected in runoff water from soils that had surface applied manures. The transformation rate of hormones that were found at the highest levels in all the manures analyzed in this research was studied. It was determined that manure subsurface injection caused one of the compounds to transform at a faster rate in the soil. Overall, hormones were detected for up to 9 weeks in soils that were applied with animal manures. Best management practices such as manure subsurface injection and using a buffer zone between an agricultural field and a stream are promising tools for preventing hormones in animal manure from entering the natural environment.

Over the last two decades, livestock operations have become highly concentrated due to growing trends towards larger, more confined facilities and a decrease in cropland on smaller farms. This has led to greater amounts of excess manure nutrients on farms, increasing the potential for nutrient pollution of water bodies from runoff. The purpose of this study was to determine if enhanced biological phosphorus removal (EBPR) is a viable alternative for managing excess manure nutrients on dairy farms. Assessment of EBPR involved the investigation of various aspects of wastewater treatment modeling and design and farm nutrient management. The fermentation potential (volatile fatty acid (VFA) production) of dairy manure was determined through laboratory analysis to be 15.3% of the total COD. Total VFA production was composed of 57, 23, and 20% acetic, propionic, and butyric acids, respectively. The EBPR component of the BioWin wastewater treatment model was evaluated through a sensitivity analysis. The parameters to which effluent phosphate (PO4) concentration was most sensitive were maximum specific growth rate, growth yield, aerobic PO4 uptake rate per unit poly-b-hydroxybutyrate (PHB) utilized, PHB yield from VFA, PO4 release per unit VFA uptake, and fraction of releasable PO4. An EBPR sequencing batch reactor (SBR) was designed for a dairy farm with 700 lactating cows and 325 ha of corn silage. An economic analysis of EBPR for dairy farms employing P-based manure applications was completed. The cost of hauling excess manure to nutrient deficient farms was the most significant expense in comparing costs of manure management with and without EBPR. For a herd of 700 lactating cows, utilizing EBPR was more economical for farms with 270 ha or less cropland, while EBPR did not offer an economic advantage for farms over 270 ha. / Master of Science

In an effort to develop cost-effective technologies for the removal of ammonium nitrogen from dairy waste, a novel biological wastewater treatment process, utilizing anaerobic ammonium oxidation (anammox), referred to as Oxygen-Limited Autotrophic Nitrification and Denitrification (OLAND) was examined. Due to the potential use of OLAND-based systems in dairy manure management, a detailed water quality assessment of a modern dairy farm manure treatment-system was conducted. The Johnson Highland Dairy Farm, Glade Spring, Virginia, was selected for this assessment and a comprehensive analysis of the wastewater characteristics throughout the confined animal feeding operation was completed. The results suggest that ammonia concentrations in the anaerobic storage facility was high enough to justify use of treatment technologies that reduce ammonia loads in stored dairy waste. A lightly loaded Fixed Film Bioreactor (FFBR), in which the OLAND process was desired to occur, was then constructed in the laboratory and monitored over 51 days. Of particular interest was the time taken to achieve stable performance of this OLAND system. Furthermore, a protocol was developed to determine whether OLAND based metabolism was occurring. Ammonium nitrogen removal efficiency in the FFBR throughout the 51-day monitoring period was high, averaging approximately 95 % for the length of the study. From day 32 to 51, simultaneous removal of both ammonium and nitrite with a low level of concomitant nitrate production was observed, a key indicator of possible anammox activity. Stoichiometric ratios calculated for the FFBR compared favorably with those already established for OLAND systems. The developed protocol, incorporating anaerobic and aerobic batch experiments, to verify the occurrence of OLAND based metabolism did not yield expected results and described poorly what was being observed in the FFBR. Volatilization of ammonia during the experimental test was suspected and should be controlled when the protocol is performed in the future. / Master of Science

Cattle are commonly treated with antibiotics that may survive digestion and promote antibiotic resistance when manure or composted manure is used as a soil amendment for crop production. This study was conducted to determine the effects of antibiotic administration and soil amendment practices on microbial diversity and antibiotic resistance of bacteria recovered from the surfaces of lettuce and radishes grown using recommended application rates. Vegetables were planted in field plots amended with raw manure from antibiotic-treated dairy cows, composted-manure from cows with different histories of antibiotic administration, or a chemical fertilizer control (12 plots, n=3). Culture-based methods, 16SrDNA amplicon sequencing, qPCR and shot-gun metagenomics were utilized to profile bacteria and characterize the different gene markers for antibiotic resistance. Culture-based methodologies revealed that lettuce grown in soils amended with BSAs had significantly larger clindamycin resistant populations compared to control conditions. Growth in BSAs was associated with significant changes to the bacterial community composition of radish and lettuce. Total sul1 copies were 160X more abundant on lettuce grown in manure and total tet(W) copies were 30X more abundant on radishes grown in manure. Analysis of shotgun metagenomic data revealed that lettuce grown in manure-amended soils possessed resistance genes for three additional antibiotic classes compared to other treatments. This study demonstrates that raw, antibiotic-exposed manure may alter microbiota and the antibiotic resistance genes present on vegetables. Proper composting of BSAs as recommended by the U.S. Department of Agriculture and Environmental Protection Agency is recommended to mitigate the spread of resistance to vegetable surfaces. / MSLFS / Antibiotics are drugs responsible for killing infectious diseases in both humans and animals. In cows, antibiotics are frequently used when they get infections in their udders. These drugs can be excreted through manure and urine and end up in the environment. Manure or composted manure is often applied as a soil amendment for crop production. The presence of antibiotics in soil may promote antibiotic resistance, meaning bacteria that carry antibiotic resistance genes (ARGs) are capable of surviving exposure to drugs that would normally kill them. Such bacteria may eventually pass their ARGs to pathogens, which then could no longer be treated effectively by antibiotics when there is an infection. Thus, there is concern that overuse of antibiotics in agriculture can contribute to reduced effectiveness of antibiotics and the growing global antibiotic resistance health crisis. This study sought to determine if prior antibiotic administration affected the antibiotic resistance of bacteria found on the surfaces of vegetables grown in soil amended with manure or compost from dairy cows. Lettuce and radishes were grown in the field in plots amended with raw manure from antibiotic-treated dairy cows, compost from cows with different histories of antibiotic administration, or a chemical fertilizer control. Mature vegetables were harvested and used to enumerate antibiotic-resistant bacterial colonies. Additionally, the 16S rRNA gene, which is a ubiquitous gene found in all bacteria, was sequenced to identify the kinds of microbes that colonized the radish and lettuce surfaces when grown under the different conditions. DNA was extracted from the bacteria collected from the vegetable surfaces to and different methods were used to identify the kinds of ARGs present and to which kinds of antibiotics they encode resistance. The results of the study indicated that raw, antibiotic-exposed manure may increase the bacteria found on vegetables in addition to their ARGs. Proper composting of manure, as recommended by the U.S. Department of Agriculture (USDA) and the Environmental Protection Agency (EPA), is recommended to mitigate resistance and control microbial populations on fresh vegetables.

The study was done in Adaa district which is one of the 12 districts in East Shoa zone in Oromia regional state of Ethiopia. It is located southeast of Addis Ababa at 38o51’ 43.63’’ to 39o04’ 58.59’’ E and 8o46’ 16.20’’ to 8o59’ 16.38’’ N, on the western margin of the Great East African Rift Valley. The altitude ranges from 1 500 to ≥ 2 000 meters above sea level. The district has a high potential for mixed livestock and crop production systems. The purpose of this study was to make up for the paucity of information on livestock and environment interaction by assessing the relationship of livestock, soil, water, land, climate and crops under mixed crop-livestock production systems in central Ethiopian highlands. The objectives of the study were: (a) to assess the effect of change in land management on carbon storage and the contribution of livestock to carbon storage; (b) to examine the impact of livestock on natural resources and the environment; (c) to assess the effects of the change in traditional agricultural practices, expansion of factories, slaughter houses, greenhouses and flower farms on water and soil quality; (d) to evaluate the effect of climate change on livestock production under small-scale agriculture; and (e) to recommend options for mitigation and adaptation to environmental changes. The research design was non-experimental and did not involve the manipulation of the situation, circumstances or experiences of the interviewees. The design was comparative research that compared two or more groups on one or more variables, such as the effect of agricultural land use management, tillage type etc. on carbon storage in the soil. This research also applied a longitudinal design that examined variables such as the performance exhibited by groups over time. Purposive sampling was often used to measure the effect of agricultural, industrial effluent and human interferences on the environment by measuring nutrient contents at sources in the soil, water and manure. Biological data were complemented by key socio-economic survey by interviewing individual farmers and focus groups from sampling sites. Secondary data were also reviewed to measure soil degradation and run-off attributed to livestock. Results showed that animal waste and farmyard manure had the highest contribution in the addition of carbon in the soil. This implied that for most of carbon inputs livestock products and by-products had a greater place in the carbon sink. Therefore, livestock production could be considered as one of the major agricultural production systems in soil carbon storage. Similarly, livestock production systems also play an important role in maintaining the eco-system balance through nutrient recycling. On the average, the number of livestock per household for most species increased during the Derge regime in the 1990s compared to the Haile Sellassie regime in the 1970s when people did not own land; and then the number declined in the 2000s except for equines, crossbreeds and oxen. The change to crop intensification led to the change in the purpose for livestock keeping. Farmers started keeping certain types of animals for specific purposes unlike before when livestock was kept for prestige and economic security. The major drive for the change of attitude towards the purpose of keeping livestock was scarcity of resources, mainly feed and water. Equine ownership has significantly increased due to their low off-take rate and their feeding habits which allowed them to survive in harsh environments where feed resources were extremely scarce. There was a significant difference in crop response to manure application. Vegetables produced higher yields with manure than chemical fertilizers. Cereals on the other hand responded more to chemical fertilizers than to manure. Therefore, combining manure and chemical fertilizers was the best option for the sustainability of crop production in the study area. Some of the limitations to the use of manure as an organic fertilizer were inadequate manure production, high labour cost, bulkiness and high cost of transport to the fields and weed infestation. Manure management systems in the study area were affected by livestock husbandry practices. Only crossbred cattle (5%) were zero-grazed and used; and manure was stored in pits as slurry. Indigenous cattle were grazed outdoors in the fields during the day and at night they were kept in kraals near homesteads. There was a substantial loss of nutrients during the day when animals were grazing in the fields through leaching and trampling of dung and urine patches. Indoor or zero grazing of livestock could reduce nutrient losses. The use of manure as fuel in the study area had no significant effect on CO2 emissions at household or local level, but had a negative impact on soil organic carbon storage and soil fertility. Therefore, for improved yield and balanced eco-systems manure burning has to be replaced by other alternative energy sources such as bio-gas and kerosene. The largest carbon equivalent emissions were from CH4 (72.6%), N2O (24%) and CO2 (3.4%) which indicated the need to improve livestock and manure management systems under smallholder agriculture. Overall, there was an indication of a decline in water resources on per capita basis. The major contributing factors were combined pressure of human and animal population on natural resources that led to excessive deforestation, loss of biological diversity, overgrazing, soil degradation and various forms of pollution and contamination. The global climate change also played a role in the decline in water resources due to the decrease in annual precipitation and increasing temperatures. Urbanization and economic growth increased the demand for milk and meat, which required additional water use for each unit of increased animal protein. The demand for milk and meat is expected to double in the next 20 years with an annual growth rate of between 2.5 to 4%. From the sixty-year meteorological data (1951-2009) there was an established increase in rainfall by 2% per annum; and maximum and minimum temperature by 0.08oC per decade, which amounted to a cumulative temperature increase of 0.5oC in the last decade. The increase in precipitation and temperature favoured the adaption of lowland crops like maize and sorghum to highland agro-ecology. Climate prediction models forecasted that most of the highlands in Ethiopia will remain suitable for cereals like wheat and Teff for the next 50 to100 years. However, the perception of farmers indicated that they felt more heat and warm weather than they have experienced before. They reported that rainfall is now more erratic or comes late and stops earlier before plants completed their vegetative growth. / Environmental Sciences / D. Litt. et Phil. (Environmental Science)