{"id":{"repo_id":"iastate","oai_identifier":"oai:dr.lib.iastate.edu:20.500.12876/106779"},"canonical_url":"https://search.dev.ndltd.org/etd/iastate/oai:dr.lib.iastate.edu:20.500.12876/106779","repository":{"repo_id":"iastate","name":"Iowa State University","base_url":"https://dr.lib.iastate.edu/server/oai/request"},"display":{"title":"Improving performance and expanding application of denitrifying bioreactors for nutrient management in agricultural landscapes","abstract":"Subsurface tile drainage is widely implemented across agricultural landscapes in the U.S. Midwest, creating direct hydrologic pathways that transport excess nutrients from fields to surface waters. As a result, nitrate (NO₃) can bypass natural soil filtration and attenuation processes, contributing to elevated nutrient loads in downstream ecosystems and increasing risks to environmental and human health. To address these challenges, denitrifying bioreactors have been developed as an edge-of-field conservation practice to intercept tile drainage and promote microbial denitrification within a carbon-rich, anoxic environment. Optimizing the design and performance of these systems is critical for achieving regional nutrient reduction goals and mitigating downstream impacts. The first study (Chapter 3) evaluated the performance of corncob (CC) versus woodchip (WC) bioreactor media across a range of flow conditions and identified key drivers of performance. Results demonstrated that CC consistently outperformed WC, achieving greater nitrate removal efficiency (NRE) and NO3 load removal. Total organic carbon (TOC) and hydraulic residence time (HRT) were identified as primary drivers of performance, while targeted nitrogen-cycling gene abundances (nirS, nirK, nosZI, nosZII) were generally unreliable predictors of NRE in both media types. The second study (Chapter 4) used a four-year field-scale dataset to evaluate saturated water depth and test common hydraulic assumptions on bioreactor performance for NO3 removal. A saturated depth coefficient was developed using a grid search and then applied to inlet and outlet water depths to generate HRT estimates comparable to reference values derived from internal well measurements. The internal water table at this study site was found to be fundamentally non-linear, as typically assumed. Linear assumptions resulted in an overestimation of HRT and underestimation of NO3 load removal. The third study (Chapter 5) evaluated the potential to expand bioreactor application by determining if an existing system could effectively remove E. coli. A field-scale bioreactor was retrofitted with a pump to deliver surface water to the system, allowing comparison of pathogen removal between tile drainage and surface water sources. The system achieved significant E. coli removal, with influent E. coli concentration and water temperature significant to removal.","abstract_html":"Subsurface tile drainage is widely implemented across agricultural landscapes in the U.S. Midwest, creating direct hydrologic pathways that transport excess nutrients from fields to surface waters. As a result, nitrate (NO₃) can bypass natural soil filtration and attenuation processes, contributing to elevated nutrient loads in downstream ecosystems and increasing risks to environmental and human health. To address these challenges, denitrifying bioreactors have been developed as an edge-of-field conservation practice to intercept tile drainage and promote microbial denitrification within a carbon-rich, anoxic environment. Optimizing the design and performance of these systems is critical for achieving regional nutrient reduction goals and mitigating downstream impacts. The first study (Chapter 3) evaluated the performance of corncob (CC) versus woodchip (WC) bioreactor media across a range of flow conditions and identified key drivers of performance. Results demonstrated that CC consistently outperformed WC, achieving greater nitrate removal efficiency (NRE) and NO3 load removal. Total organic carbon (TOC) and hydraulic residence time (HRT) were identified as primary drivers of performance, while targeted nitrogen-cycling gene abundances (nirS, nirK, nosZI, nosZII) were generally unreliable predictors of NRE in both media types. The second study (Chapter 4) used a four-year field-scale dataset to evaluate saturated water depth and test common hydraulic assumptions on bioreactor performance for NO3 removal. A saturated depth coefficient was developed using a grid search and then applied to inlet and outlet water depths to generate HRT estimates comparable to reference values derived from internal well measurements. The internal water table at this study site was found to be fundamentally non-linear, as typically assumed. Linear assumptions resulted in an overestimation of HRT and underestimation of NO3 load removal. The third study (Chapter 5) evaluated the potential to expand bioreactor application by determining if an existing system could effectively remove E. coli. A field-scale bioreactor was retrofitted with a pump to deliver surface water to the system, allowing comparison of pathogen removal between tile drainage and surface water sources. The system achieved significant E. coli removal, with influent E. coli concentration and water temperature significant to removal.","abstract_has_math":false,"creators":["Vroman, Taylor"],"institution":"Iowa State University - Thesis & Dissertation","degree_name":"Doctor of Philosophy","degree_level":"dissertation","degree_discipline":"Environmental science","degree_department":null,"school":null,"contributors":[],"advisors":["Soupir, Michelle, L"],"committee_chairs":[],"committee_members":[],"year":2026,"date_issued":"2026-05","date_published":"2026-05","updated_at":"2026-07-24T02:37:49Z","subjects":["Agricultural and biosystems engineering"],"languages":["en_US"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://dr.lib.iastate.edu/handle/20.500.12876/106779","outbound_label":"Repository record","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Soupir, Michelle, L"]},{"key":"dc:creator","label":"Author","values":["Vroman, Taylor"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2026-06-09T22:35:06Z"]},{"key":"dc:date.issued","label":"Date","values":["2026-05"]},{"key":"dc:type","label":"Dc Type","values":["Text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Environmental science"]},{"key":"thesis:degree_level","label":"Degree Level","values":["dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Doctor of Philosophy"]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["Iowa State University - Thesis & Dissertation"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Agricultural and biosystems engineering"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en_US"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://dr.lib.iastate.edu/handle/20.500.12876/106779"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["May2026"]},{"key":"dc:description.abstract","label":"Abstract","values":["Subsurface tile drainage is widely implemented across agricultural landscapes in the U.S. Midwest, creating direct hydrologic pathways that transport excess nutrients from fields to surface waters. As a result, nitrate (NO₃) can bypass natural soil filtration and attenuation processes, contributing to elevated nutrient loads in downstream ecosystems and increasing risks to environmental and human health. To address these challenges, denitrifying bioreactors have been developed as an edge-of-field conservation practice to intercept tile drainage and promote microbial denitrification within a carbon-rich, anoxic environment. Optimizing the design and performance of these systems is critical for achieving regional nutrient reduction goals and mitigating downstream impacts. The first study (Chapter 3) evaluated the performance of corncob (CC) versus woodchip (WC) bioreactor media across a range of flow conditions and identified key drivers of performance. Results demonstrated that CC consistently outperformed WC, achieving greater nitrate removal efficiency (NRE) and NO3 load removal. Total organic carbon (TOC) and hydraulic residence time (HRT) were identified as primary drivers of performance, while targeted nitrogen-cycling gene abundances (nirS, nirK, nosZI, nosZII) were generally unreliable predictors of NRE in both media types. The second study (Chapter 4) used a four-year field-scale dataset to evaluate saturated water depth and test common hydraulic assumptions on bioreactor performance for NO3 removal. A saturated depth coefficient was developed using a grid search and then applied to inlet and outlet water depths to generate HRT estimates comparable to reference values derived from internal well measurements. The internal water table at this study site was found to be fundamentally non-linear, as typically assumed. Linear assumptions resulted in an overestimation of HRT and underestimation of NO3 load removal. The third study (Chapter 5) evaluated the potential to expand bioreactor application by determining if an existing system could effectively remove E. coli. A field-scale bioreactor was retrofitted with a pump to deliver surface water to the system, allowing comparison of pathogen removal between tile drainage and surface water sources. The system achieved significant E. coli removal, with influent E. coli concentration and water temperature significant to removal."]},{"key":"dc:format.mimetype","label":"Dc Format Mimetype","values":["PDF"]},{"key":"dc:title","label":"Title","values":["Improving performance and expanding application of denitrifying bioreactors for nutrient management in agricultural landscapes"]}]}],"canonical_facts":{"dc:contributor.advisor":["Soupir, Michelle, L"],"dc:creator":["Vroman, Taylor"],"dc:date.accessioned":["2026-06-09T22:35:06Z"],"dc:date.issued":["2026-05"],"dc:description":["May2026"],"dc:description.abstract":["Subsurface tile drainage is widely implemented across agricultural landscapes in the U.S. Midwest, creating direct hydrologic pathways that transport excess nutrients from fields to surface waters. As a result, nitrate (NO₃) can bypass natural soil filtration and attenuation processes, contributing to elevated nutrient loads in downstream ecosystems and increasing risks to environmental and human health. To address these challenges, denitrifying bioreactors have been developed as an edge-of-field conservation practice to intercept tile drainage and promote microbial denitrification within a carbon-rich, anoxic environment. Optimizing the design and performance of these systems is critical for achieving regional nutrient reduction goals and mitigating downstream impacts. The first study (Chapter 3) evaluated the performance of corncob (CC) versus woodchip (WC) bioreactor media across a range of flow conditions and identified key drivers of performance. Results demonstrated that CC consistently outperformed WC, achieving greater nitrate removal efficiency (NRE) and NO3 load removal. Total organic carbon (TOC) and hydraulic residence time (HRT) were identified as primary drivers of performance, while targeted nitrogen-cycling gene abundances (nirS, nirK, nosZI, nosZII) were generally unreliable predictors of NRE in both media types. The second study (Chapter 4) used a four-year field-scale dataset to evaluate saturated water depth and test common hydraulic assumptions on bioreactor performance for NO3 removal. A saturated depth coefficient was developed using a grid search and then applied to inlet and outlet water depths to generate HRT estimates comparable to reference values derived from internal well measurements. The internal water table at this study site was found to be fundamentally non-linear, as typically assumed. Linear assumptions resulted in an overestimation of HRT and underestimation of NO3 load removal. The third study (Chapter 5) evaluated the potential to expand bioreactor application by determining if an existing system could effectively remove E. coli. A field-scale bioreactor was retrofitted with a pump to deliver surface water to the system, allowing comparison of pathogen removal between tile drainage and surface water sources. The system achieved significant E. coli removal, with influent E. coli concentration and water temperature significant to removal."],"dc:format.mimetype":["PDF"],"dc:identifier.uri":["https://dr.lib.iastate.edu/handle/20.500.12876/106779"],"dc:language.iso":["en_US"],"dc:subject":["Agricultural and biosystems engineering"],"dc:title":["Improving performance and expanding application of denitrifying bioreactors for nutrient management in agricultural landscapes"],"dc:type":["Text"],"thesis:degree_discipline":["Environmental science"],"thesis:degree_level":["dissertation"],"thesis:degree_name":["Doctor of Philosophy"],"thesis:institution_name":["Iowa State University - Thesis & Dissertation"]},"updated_at":"2026-07-24T02:37:49Z"}