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Browsing by Author "Ippolito, James A., committee member"

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    Dairy farm phosphorus recovery and re-use to reduce water quality risk and improve phosphorus cycling in agriculture
    (Colorado State University. Libraries, 2008) Massey, Michael Stanley, author; Archibeque, Shawn L., advisor; Ippolito, James A., committee member; Sheffield, Ron E., committee member; Davis, Jessica G., committee member; Peterson, Gary A., 1940-, committee member
    Phosphorus (P) is a limited natural resource, and its efficient use and cycling are important for the long-term sustainability of agricultural and industrial production. The over-application of P in dairy wastewater to fields, in addition to being inefficient, can lead to the degradation of water quality through P-induced eutrophication from agricultural runoff. This is especially true in areas where dairies and other livestock operations are increasingly concentrated around sources of fresh water such as rivers. Phosphorus recovery and re-use has the potential to reduce the amount of P applied to fields near the dairy while providing a useful, marketable, and easily transportable P fertilizer. This study evaluated the efficiency of magnesium (Mg) phosphate recovery on dairy farms using actual wastewater under field conditions, the nature of various recovered products including magnesium ammonium phosphate hexahydrate (struvite) and magnesium ammonium phosphate hydrate (dittmarite), and the feasibility of using Mg phosphates as fertilizers in slightly acidic and alkaline soil conditions. Dairy wastewater was treated using a cone-shaped fluidized bed reactor and two treatment processes which differed in the chemicals used for pH manipulation. The "conventional" process made use of hydrochloric acid and anhydrous ammonia for pH adjustment, while the "new" process used acetic acid and potassium hydroxide. The "new" process has the potential to produce a certified organic soil amendment with minimal modification to current organic production standards. After wastewater treatment, the recovered P products, along with other samples of recovered Mg phosphates including crystalline struvite and dittmarite, were examined with powder x-ray diffraction, scanning electron microscopy, and energy dispersive x-ray spectroscopy. Finally, struvite, dittmarite, and a heterogeneous recovered product were applied in greenhouse fertilizer trials alongside commercial triple superphosphate (TSP) and certified organic rock phosphate (RP). The fertilizers' performance was tested at two application rates (45 kg ha- 1 and 90 kg ha-1 ) and two soil pH levels (6.5 and 7.6). The "conventional" treatment method removed 14% of the total phosphorus (TP) in the dairy wastewater, while the "new" method removed 9% of TP, along with 12% and 9% of the Mg for the conventional and new methods, respectively. Detailed analysis and characterization of the products, as well as recovered struvite and dittmarite, showed great variation among the chemical, microscopic, and macroscopic characteristics of the different types of recovered Mg phosphates. Fertilizer trials found that TSP and recovered struvite and dittmarite crystals increased plant P concentration in spring wheat (Triticum aestivum L.) grown in slightly acidic soil. At high soil pH, the recovered Mg phosphates increased plant dry matter production over the control and also performed similarly to TSP. The results of the current study indicate that P recovery through Mg phosphate precipitation is possible on dairy farms, but improvements must be made in removal efficiency and consistency of product characteristics. Furthermore, the resulting recovered phosphates may be useful as fertilizers in both acidic and alkaline soils.
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    Implications of solid and liquid waste co-disposal on biodegradation and biochemical compatibility
    (Colorado State University. Libraries, 2018) Cook, Emily M., author; Bareither, Christopher A., advisor; Sharvelle, Sybil E., advisor; Ippolito, James A., committee member
    Co-disposal of solid and liquid waste in municipal solid waste (MSW) landfills can benefit landfill operations via enhancing waste moisture content and accelerating in situ waste biodegradation. However, implications of co-disposal on organic waste biodegradation are currently unknown and co-disposal in full-scale landfills is ad hoc. The objective of this study was to evaluate waste biodegradation and biochemical compatibility for different co-disposed solid and liquid wastes in MSW. To meet this objective, laboratory-scale reactors were operated to evaluate the potential impacts of co-disposal and ultimately to provide guidance for full-scale MSW landfill operations. Waste collected for this project was identified as MSW, special solid waste (SW), liquid waste (LW), and sludge waste (Sludge), such that reactor experiments were conducted with representative co-disposal combinations of MSW-SW, MSW-LW, and MSW-Sludge. The MSW-SW and MSW-Sludge reactors included landfill leachate as a liquid source to generate effluent; MSW-LW reactors were operated with unique liquid wastes. The MSW-LW reactors remained in the acid formation phase of biodegradation for the duration of the experiment. The liquid waste addition in the MSW-LW reactors was not an effective means to initiate biodegradation and is not recommended as an additive to fresh MSW without an inoculum that contains methanogenic microorganisms. All MSW-Sludge waste reactors and all but one set of the MSW-SW reactors reached methanogenesis. The solid and sludge wastes did not exhibit signs of biochemical incompatibility. The use of biochemical methane potential (BMP) assays as a selection tool for waste co-disposal was also evaluated. The BMP assays did not show good agreement with data from reactors that generated methane; therefore, use of BMP assays alone as a selection tool is not recommended.
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    Modeling nonpoint-source uranium pollution in an irrigated stream-aquifer system: calibration and simulation
    (Colorado State University. Libraries, 2024) Qurban, Ibraheem A., author; Gates, Timothy K., advisor; Bailey, Ryan T., committee member; Grigg, Neil S., committee member; Ippolito, James A., committee member
    The Lower Arkansas River Valley (LARV) in southeastern Colorado has been a source of significant agricultural productivity for well over a century, primarily due to extensive irrigation practices. Mirroring trends seen in other semi-arid irrigated areas globally, however, irrigated agriculture in the LARV has resulted in several challenges for the region. In addition to the emergence of waterlogging and soil salinization, leading to decreased crop yields, elevated levels of nutrients and trace elements have appeared in the soil and water. Among these constituents, uranium (U), along with co-contaminants selenium (Se) and nitrate (NO3), has shown particularly high concentrations in groundwater, surface water, and soils. These heightened concentrations pose environmental concerns, impacting human health and the well-being of aquatic life such as fish and waterfowl. Careful monitoring and management practices are crucial to prevent potential harm to water resources. The main goal of this research is to develop a comprehensive numerical model for assessing U pollution in a stream-aquifer system within a large irrigated area. To achieve this, a computational model is built and tested that can predict with reasonable accuracy how U, along with Se and NO3, are mobilized and move within a coupled system of streams and groundwater. The approach combines two key modeling components: a MODFLOW package, which handles the simulation of groundwater and stream flow dynamics, and an RT3D package, which addresses the reactive transport of U, Se, and nitrogen (N) species in both groundwater and interconnected streams. RT3D relies on the simulated flows generated by MODFLOW to track the movement of U, Se, and N species between streams and the aquifer in the irrigated landscape, updating daily to adequately capture changes over time. This integrated model provides an understanding of how these contaminants behave and interact within the stream-aquifer system, aiding in effective pollution assessment and providing insights valuable to the planning of management strategies. The coupled MODFLOW-RT3D flow and reactive transport model is applied to a 550 km² area within the LARV, stretching from Lamar, Colorado, to the Colorado-Kansas border and spanning a period of 14 years. The flow package is compared with observations of groundwater hydraulic head and stream flow, along with estimates of return flow along the Arkansas River. The reactive transport package is assessed by comparing predicted U, Se, and NO3 concentrations against data collected from groundwater monitoring wells and stream sampling sites along with estimates of solute mass loads to the river. To calibrate and refine the model, the PESTPP-iES iterative ensemble smoother (iES) software is employed. This calibration process is dedicated to enhancing the model's accuracy in predicting both flow and transport dynamics. PESTPP-iES addresses calibration uncertainty by establishing prior frequency distributions for key model parameters based on data and expertise, then iteratively adjusts these parameters during calibration to align model predictions with observed data. Post-calibration, posterior distributions reflect updated parameter values and reduced uncertainties. Demonstrating a strong alignment with concentrations of CNO3, CSe, and CU values found in groundwater, streams, and the mass loading entering the Arkansas River, outcomes of the model-based simulations reveal a substantial violation of the Colorado chronic standard (85th percentile = 30 μg/L) for CU throughout the study region. On average, simulated CNO3, CSe, and CU values for groundwater in non-riparian areas in the region are 3.6 mg/L, 41 µg/L, and 126 µg/L, compared to respective averages of 4 mg/L, 53 µg/L, and 112 µg/L observed in monitoring wells. When considering the 85th percentile of simulated CNO3, CSe, and CU values, the figures for non-riparian groundwater are 6 mg/L, 50 µg/L, and 218 µg/L, respectively. Groundwater in riparian areas shows lower average simulated CNO3, CSe, and CU values of 3 mg/L, 26 µg/L, and 72 µg/L, respectively, and 85th percentile values of 5 mg/L, 41 µg/L, and 152 µg/L. Additionally, simulated average mass loading rates for NO3, Se, and U along the river are 8.8 kg/day per km, 0.05 kg/day per km, and 0.27 kg/day/km respectively, compared to stochastic mass balance estimates of 9.2 kg/day per km , 0.06 kg/day per km , and 0.23 kg/day per km. The simulated 85th percentile CNO3, CSe, and CU values in the Arkansas River are 1 mg/L, 11 μg/L, and 87 μg/L, respectively. Notably, the simulated U levels in groundwater exceed the chronic standard across 44% of the region. Along the Arkansas River, concentrations consistently surpass the chronic standard, averaging 2.9 times higher. Predicted Se concentrations also show significant exceedances of the chronic standard, while NO3 violations are slight to moderate. The varying pollutant levels across the region highlight specific areas of concern that require targeted attention, indicating potential contributing factors to these hotspots. Findings outline how serious and widespread the problem is in the LARV, providing a starting point for comparing potential pollution reduction from alternative water and land best management strategies (BMPs) to be explored in future applications of the calibrated model.