Browsing by Subject "Biosystems and Agricultural Engineering"

Now showing 1 - 7 of 7
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    Adaptation of advanced MRI and NMR technique for low magnetic field MRI system.
    (2012-07) Li, Yun
    Nuclear magnetic resonance techniques, including nuclear magnetic imaging (MRI) and nuclear magnetic resonance (NMR) relaxometry are increasingly gaining interest and acceptance by food scientists and engineers. These techniques are being used to study moisture and fat content, water mobility, and distribution of water, fat, and temperature in foods. They are also used to determine freezing front and viscosity of foods. A unique advantage of NMR techniques is their non-invasive and non-destructive nature, making analysis faster and more reliable than conventional techniques. MRI work in the food area is primarily conducted using expensive and hard to operate large MRI systems. Most food companies, especially small companies, are not willing to use or cannot afford such large systems. Therefore, developing small systems specifically for food samples is an urgent need. NMR relaxometry has been used by food scientists for decades. However, only recently food scientists began to realize that the technique has more to offer. Research on the relationship between NMR relaxation times and physiochemical properties of foods is emerging. A suite of techniques were developed for the acquisition of reliable data and high quality images using low field MRI machines. My research has helped solve some key technical problems by improving the hardware configuration, pulse sequences, and data analysis techniques. In my research, advanced pulse sequences were adapted to our low field MRI machines for MRI imaging work and NMR relaxation work. Pulse sequences were tuned to obtain high quality images. New hardware was developed to accommodate unique samples. New NMR data acquisition schemes and data analysis techniques were developed to obtain additional information for the analysis of food stability. Models were designed for state diagrams. Coding programs were developed to calculate and analyze state diagram related parameters. My work involved both hardware and software improvements to facilitate adaptation and implementation of advanced techniques. It is my hope that these low field MRI machines be improved through my study so that they become an affordable, easy-to-operate, and relatively maintenance free analytical tool for food research and development and quality control labs.
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    Design, construction, and assessment of a self-Sustaining drainage ditch.
    (2011-08) Kramer, Geoffrie
    Agricultural drainage is a double-edged sword: helping farmers achieve everincreasing crop yields to meet consumers’ demands, while providing a short-circuit through the soil profile for excess water and nutrients. Drainage ditches are an important pathway as water moves downstream in headwater landscapes. As low order streams, ditches have the potential to remove and assimilate nutrients. In order to operate at their maximum nutrient removal potential, ditches should be healthy, self-sustaining ecosystems that function similarly to natural streams. The two-stage agricultural drainage ditch is an innovative solution for creating drainage ditches that behave more like natural streams. A low-flow channel provides sediment transport during low-flow periods, while benches within the ditch allow for overbank flow and energy dissipation during high-flow periods. The larger crosssectional area increases surface contact between water and the ditch at certain flow depths, which likely enhances nutrient removal. In this study, a two-stage agricultural drainage ditch was designed and then constructed in southern Minnesota, USA in the autumn of 2009. Extensive monitoring of the ditch has been conducted following construction; efforts have focused on establishing an understanding of the geomorphic, water source, and water quality aspects of the ditch. Analysis of field measurements from August 2010 show that between 10 and 15 percent of nitrate N entering the ditch was removed within the ditch reach. A slight increase in average channel thalweg elevation has been measured, while increased pool-riffle sequencing has also been observed. Channel cross-sectional surveys have showed slight changes in low-flow channel dimensions. Economic analyses have been performed to measure the feasibility of two-stage ditch construction. There are situations where predicted cost reductions in periodic ditch maintenance provide enough savings to offset two-stage channel construction costs. In other cases, subsidies may be required to economically justify a two-stage system. An analysis was performed to estimate the cost of additional nitrogen (N) removal ($/kg N removed) in two-stage ditches, using increased N removal as a basis for subsidies. Results show situations where N removal costs is less than $3 to $4 kg-1 of N removed, which is competitive with other Best Management Practices.
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    Estimating renewable water flux using landscape features.
    (2011-07) Peterson, Heidi Marie
    The complexity of vadose zone, groundwater and surface water interactions presents hydrological research challenges specifically in the area of quantifying groundwater recharge. To acknowledge unity of the surface and groundwater systems requires an interdisciplinary approach that organizes knowledge about an analysis domain based on hydrologic units rather than on aquifers, enabling an integrative, system viewpoint of the terrestrial hydrologic system. By establishing the relationship between landscape components and water balance characteristics, hydrologic response units are established. This dissertation hypothesizes that regionalization can identify hierarchical hydrogeological units (HHUs) composed of unique combinations of surface water, groundwater and vadose zone landscape characteristics with statistically different recharge rates (p<0.05), and that these units can be used to estimate the renewable water flux of the groundwater system. Three interdependent studies were pursued to address the hypothesis: (i)a statewide regionalization of mean annual streamflow that defined independent hydrologic regimes within Minnesota; (ii) a regionalization focusing on East Central Minnesota which established unique HHUs based on unique combinations of landscape characteristics with statistically significant differences in mean minimum recharge; (iii) a water management application which used the regionalization methodology to quantify the renewable groundwater flux and assess a water resources sustainability indicator within the Twin Cities Metropolitan Area. Results from the three studies indicate that landscape characteristics control the rate of renewable water flux within the groundwater system. The results identified at one analysis scale could be used to extrapolate data at refined scales where long-term hydrologic monitoring data is lacking but informed water management decisions are crucial for the sustainable future of freshwater resources. Within the state of Minnesota, five hydrologic regimes were identified, each with varying inter- and intra-annual flow characteristics. Kendall-tau results suggest that mean annual streamflow within the regimes is either increasing or remaining stable. Focusing on a smaller, regional analysis territory within East-Central Minnesota, regionalization using the Watershed Characteristics Approach (WCA) identified HHUs composed of unique combinations of hydrogeologic characteristics, bedrock material, Quaternary thickness, topography and available water capacity. These HHUs and their corresponding minimum monthly recharge rates represent the renewable groundwater flux. HHUs previously identified within the Twin Cities Metropolitan Area (TCMA) were used together with water use estimates to calculate the sustainability indicator for each community within the TCMA. Although the WCA has few assumptions, limitations of the methodology include that the hierarchical refinement is based on the availability of streamflow data, and the accuracy of the estimated recharge rates associated with each HHU is pre-determined by the resolution of spatial landscape attribute data. Future research should further evaluate the defined HHUs to confirm that they are consistent for all five of the hydrologic regimes identified within Minnesota.
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    Fermentative hydrogen production from liquid swine manure with glucose supplement using an anaerobic sequencing batch reactor.
    (2009-07) Wu, Xiao
    The idea of coupling renewable energy production and agricultural waste management inspired this thesis. The production of an important future fuel -hydrogen gas- from high strength waste stream-liquid swine manure- using anaerobic treatment processes makes the most sustainable sense for both wastewater utilization and energy generation. The objectives of this thesis were to develop a fermentation process for converting liquid swine manure to hydrogen and to maximize hydrogen productivity. Anaerobic sequencing batch reactor (ASBR) systems were constructed to carry out this fermentation process, and seed sludge obtained from a dairy manure anaerobic digester and pretreated by nutrient acclimation, heat and pH treatment was used as inoculum. High system stability was indicated by a short startup period of 12 days followed by stable hydrogen production, and successful sludge granulation occurred within 23 days of startup at a hydraulic retention time (HRT) of 24 hours. Operation at a progressively decreasing HRT from 24 to 8h gave rise to an increasing biogas production rate from 15.2-34.4L/d, while good linear relationships were observed between both total biogas and hydrogen production rates correlated to HRT, with R2 values of 0.993 and 0.997, respectively. The maximum hydrogen yield of 1.63 mol-H2/mol-hexose-feed occurred at HRT of 16h, while the HRT of 12h was highly suggested to achieve both high production rate and efficient yield. Hexose utilization efficiencies over 98%, considerable hydrogen production rate up to 14.3 L/d and hydrogen percentage of off-gas up to 43% (i.e., a CO2/H2 ratio of 1.2) with the absence of CH4 production throughout the whole course of experiment at a pH of 5.0 strongly validated the feasibility of the fermentative H2 production from liquid swine manure using an ASBR system. Ethanol as well as acetic, butyric and valeric acids were produced in the system accompanying the hydrogen production, with acetic acid being the dominant one, which contributed to 56-58% of the total soluble metabolite production, indicative of an acetic acid fermentation system, and acetate-to-butyrate ratio was found to be closely related to hydrogen yield. pH level influenced every aspect of the ASBR performance for hydrogen production. ASBR operation at five pHs ranging from 4.4 to 5.6 (4.4, 4.7, 5.0, 5.3, 5.6) showed distinct dynamic profiles of both biogas production and the changes of H2 and CH4 percentage in the biogas during a running period of 22 days. The H2 content in biogas, H2 production rate and H2 yield were all pH-dependent, in the range of 5.1-36.9 %, 0.71-8.97 L/d and 0.12-1.50 mol-H2/mol-glucose, respectively, and maximum values for all three responses were simultaneously achieved at pH 5.0. Methanogens appeared to be significantly activated at pH of 5.3 or higher since significant CH4 evolution and concurrent reduction in H2 production was observed at pH 5.3 and 5.6. Acetate, propionate, butyrate, valerate, and ethanol were main aqueous products in all pH tests and their distribution was influenced by pH. Analysis of kinetic models developed from modified Gompertz equations for batch experiments showed that pH had a profound effect on all kinetic parameters for hydrogen production including hydrogen potential, maximum hydrogen production rate and the length of the lag phase, as well as the maximum substrate utilization rate. The low pH of 4.4 gave the highest hydrogen production potential but with the lowest hydrogen production rate. A contrast experiment was conducted with an initial pH of 5.3 but not controlled, came up with a rapid pH decline, leading to a low hexose degradation efficiency of 33.2% and a significantly suppressed H2 production, indicating the importance of pH control and the effect of pH on H2 production and substrate consumption. pH 5.0 was verified as the optimal for the proposed fermentation system by kinetic models. An extremely linear relationship (R2= 0.993) between the maximum H2 production rate and the maximum hexose degradation rate suggested that the pH inhibition on H2 production was a result of the suppression on the bacterial activity for substrate utilization due to an unfavorable pH level. System optimization was realized through experiments conducted according to a response surface methodology, with a central composite design and empirical quadratic response equations obtained for three responses including the hydrogen content in the biogas, hydrogen evolution rate and hydrogen yield, against three independent variables, pH (4.4-5.6), HRT (8-24h) and substrate glucose concentrations (Cg, 0-20 g/L). Contour plots revealed that all three responses were significantly impacted by the variable and squared pH. Furthermore, pH and Cg had a significant interaction effect on H2 production rate, while HRT and glucose concentration were interdependent, or they had a mildly significant interaction effect on H2 production rate. The hydrogen content decreased when pH was greater than 5.0 or less than 4.6 and a largest value of 42.7% could be obtained at pH 4.8, HRT 8 h, and Cg of 18.7 g/L. The highest hydrogen production rate of 26.1 L/d happened under a pH of 4.6, HRT of 8h, and Cg of 20 g/L; Lower HRT and higher Cg was found to benefit the H2 production rate because they provide elevated organic loading and food to microorganism ratio for the system. HRT shorter than 17h resulted in declined hydrogen yield, while the glucose concentration up to 20 g/L did not cause suppression on hydrogen yield. The revised optimal condition of pH 4.8, HRT 11h, and Cg of 20 g/L, which could achieve 85% of the maximum values of all three hydrogen productivity responses, was determined by surface response methodology. Highly reproducible results from confirming experiments at the optimal condition indicated that the results modeled in this study possessed a high reliability, while the results of H2 content, H2 production rate and yield were obtained as 40.3%, 23.16 L/d, and 1.36mol H2/mol hexose, respectively. Results obtained in this study indicated that ASBR system using swine manure based substrate had significant potential of fermentative hydrogen production.
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    Surface aeration to reduce odor generation potential in swine manure lagoons.
    (2009-06) Dong, Chunying
    The odors originating from open liquid manure storages are one of the most persistent problems and present undesirable environmental situations that have caused conflicts between swine producers and their neighboring communities. A considerable amount of research effort has been spent on controlling odor emissions from swine manure storages with methods studied including aeration and anaerobic treatment. Surface aeration is the most cost-effective method. Therefore, more information is needed about the system improvement and optimal depth determination of surface aeration. This thesis presents investigations on gas injection in water, including a field-and-lab-scale study on surface aeration to reduce odor generation potential and laboratory-scale studies on aerator module development, liquid flow rate, alpha factor, surface aeration depth and temperature profiles on aeration efficiency. The purpose of the first investigation was to evaluate the effectiveness of a surface aeration system using venturi injectors, in which air was injected into a pipeline and discharged into the lagoon as a gas-liquid diffuser. This technique was shown to be an effective means of improving the dissolved oxygen levels and reduce odor generation potential in the lagoon. The purpose of the laboratory investigation was to better understand the effect of liquid flow rate, aerator module design, surface aeration depth and temperature on the surface aeration efficiency. Important fundamental results obtained in this thesis such as the field-scale surface aeration study and optimal surface aeration depth were very useful for many engineering applications, and pave the way for all animal producers (not just swine) who use liquid manure storages to adopt advanced aeration technologies for controlling manure odors.
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    A two-step fed sequencing batch reactor combined with pre-nitritation for treating swine wastewater.
    (2009-01) Wang, Liang
    Scientists have identified agricultural fertilizers as a primary culprit behind the eutrophication phenomenon booming in lakes and gulfs, among which the wastewater flushed from confined swine production and applied to cropland as fertilizers is identified to be one of the major responsible agricultural sources. When the scale of swine production keeps rising, manure that cannot be land applied according to the plant and soil testing has to be treated before discharge. Shortcut nitrification and denitrification (SND) is a novel nitrogen removal process that has drawn significant attention from researchers lately. In this study, the application of SND in swine wastewater treatment was investigated using two sequencing batch reactors (SBRs) connected in series in order to reduce the needs for energy and carbon uses. The first SBR produced a nitrite rich effluent that was subsequently fed to the second SBR where both nitrogen and phosphorus removal were taking place. Shortcut nitrification (also termed nitritation) is the first step of shortcut nitrogen removal from swine wastewater. As such, stably obtaining an effluent with a significant amount of nitrite becomes the premise to realize SND. The possibility of accumulating nitrite from swine wastewater was firstly investigated by adopting a continuous feeding strategy in an activated sludge SBR. The results showed that free ammonia and free nitrous acid in the system could reduce the activities of nitrite oxidizing bacteria, generating an effluent with 13-23% of NH4-N, 15-21% of NO3-N, and 56-72% of NO2-N. Two cyclic modes with HRTs of 3 days (the ratio of aerobic feeding to total aerobic reaction time was 0.33) and 1.5 days (the ratio was 0.77) were employed. The cycle comparison between the two modes with different HRTs shows that there is no big difference with regard to the whole nitritation process, which is characterized by continuous conversion of loaded ammonium to nitrite and nitrate in the aerobic feeding period and no further conversion after the loading was terminated, resulting relatively stable levels for all the three nitrogen components in the entire cycle. Compared to 3-day HRT mode, 1.5-day HRT cyclic mode has doubled daily output in volume. In order to better understand the process of nitrite accumulation, more bench experiments were performed including an effluent nitrogen composition stability test and a reducing load test. The nitrite production stability was tested using four different ammonium loading rates, 0.075, 0.062, 0.053, and 0.039 gNH4/gMLSS*d in a 2-month running period. The TIN composition in the effluent was not affected when the ammonium load was between 0.053 and 0.075 g NH4/g MLSS*d (64% NO2-N, 16% NO3-N, and 20% NH4-N). Under 0.039 g NH4/g MLSS*d, a little more NO2-N was transformed to NO3-N with an effluent of 60% NO2-N, 20% NO3-N, and 20% NH4-N. The reducing load test has revealed the relationship between a declining FNA concentration and the decreasing nitrite production. The NH4+ load was gradually decreased from 0.081 to 0.011 g/gMLSS*d. When the NH4+ load was between 0.081 and 0.035 g/gMLSS*d, the ratio of NO2-/( NO2-+ NO3-) was kept stable around 0.75. When the NH4+ load dropped from 0.035 to 0.024 g/gMLSS*d, the ratio dropped to 0.70, accompanied by an abrupt decline of FNA from 1.2 to 0.6. From that point forward, the nitrite dominance environment in the system was no longer existing. Combining the results from both reducing load and stability tests, it is concluded that an ammonium loading rate around 0.035 is the lower threshold for producing a nitrite dominance effluent from the activated sludge SBR. In the denitrification step, three COD/NOx-N ratios (3.6, 4.8 and 6) and two solid retention times (SRTs), 16 and 23 days, were selected to test the influence of carbon availability and SRT on the total inorganic nitrogen (TIN) reduction and phosphorus removal efficiencies for the step-fed SBR. The best operating combination of parameters would consist of a COD/NOx-N ratio of 4.8 and an SRT of 23 days to achieve 97% TIN and 67% dissolved phosphorus (DP) removals.