Xu, L.; Holmberg, K.; Magner, J. The Evaluation of a Novel Denitrifying Woodchip Bioreactor: Fairmont, MN, USA. Nitrogen2024, 5, 152-162.
Xu, L.; Holmberg, K.; Magner, J. The Evaluation of a Novel Denitrifying Woodchip Bioreactor: Fairmont, MN, USA. Nitrogen 2024, 5, 152-162.
Xu, L.; Holmberg, K.; Magner, J. The Evaluation of a Novel Denitrifying Woodchip Bioreactor: Fairmont, MN, USA. Nitrogen2024, 5, 152-162.
Xu, L.; Holmberg, K.; Magner, J. The Evaluation of a Novel Denitrifying Woodchip Bioreactor: Fairmont, MN, USA. Nitrogen 2024, 5, 152-162.
Abstract
The risk of nitrate contamination became a reality for Fairmont in Minnesota, when water rich in NO3-N exceeded the drinking water standard of 10-mg/L. This was unexpected because this city draws its municipal water from a chain of lakes that were fed primarily by shallow groundwater under row-crop land use. Spring soil thaw drives cold water into subsurface pipe where almost no NO3-N reduction occurs. This paper focuses on NO3-N reduction before entering the lakes and no other nitrogen management practices in the watershed. A novel denitrifying bioreactor was constructed behind a sediment forebay which then flowed into a chamber covered by a greenhouse, before entering a woodchip bioreactor. In 2022 and 2023, water depth, dissolved oxygen, and temperature were measured at several locations and continuous NO3-N concentration at the entry and exit of the bioreactor. The results showed better performance at a low water depth with lower dissolved oxygen, and higher water temperature. The greenhouse raised the inlet temperature in 2022 but did not in 2023. The forebay and the greenhouse may have impeded the denitrification process due to the high dissolved oxygen concentrations in the influent and the stratification of dissolved oxygen caused by algae in the bioreactor.
Copyright:
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