
Agricultural and Biosystems Engineering Publications
Campus Units
Agricultural and Biosystems Engineering, Civil, Construction and Environmental Engineering
Document Type
Article
Publication Version
Published Version
Publication Date
2020
Journal or Book Title
Transactions of the ASABE
Volume
63
Issue
2
First Page
407
Last Page
416
Research Focus Area(s)
Land and Water Resources Engineering
DOI
10.13031/trans.13709
Abstract
There is a lack of information on denitrifying bioreactors treating subsurface drainage water at the end of their initial design life due to the relative newness of the technology and the relatively long estimated life. A denitrifying bioreactor (15 m L x 7.6 m W x 1.1 m D) installed in August 2008 in Greene County, Iowa, was recharged with new woodchips in November 2017 (age 9.25 years), providing the opportunity to evaluate the properties of the wood media at the end of design life. The objective was to pair a battery of physical, chemical, and nitrate-N removal tests on the wood media harvested from the bioreactor with field observations to assess likely reasons why denitrifying bioreactors treating tile drainage may need to be recharged. The two types of wood media harvested from the bioreactor (termed woodchips and mixed shreds) had median particle sizes (D50) of 12.1 and 7.7 mm, respectively, and saturated hydraulic conductivities of 4.2 ±3.0 and 3.1 ±1.0 cm s-1 (mean ± standard deviation), which were within the range of reported values for woodchips, albeit at the low end. The wood media carbon content and quality had degraded (e.g., lignocellulose indices of 0.63 to 0.74, nearing the range of decomposition stabilization), although batch tests suggested the robustness of wood as a carbon source to support nitrate removal (e.g., 65% nitrate concentration reduction in drainage water). Woodchip degradation along with sedimentation from the drainage system likely reduced conductivities over time. Development of preferential flow paths through the bioreactor was indicated by low bioreactor outflow rates (i.e., reduced permeability) and reduced hydraulic efficiency based on conservative tracer testing. These changes in media properties and linked impacts resulted in the need to recharge this bioreactor after nine years.
Access
Open
Rights
Works produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted.
Language
en
File Format
application/pdf
Recommended Citation
Christianson, Laura E.; Feyereisen, Gary W.; Hay, Christopher; Tschirner, Ulrike W.; Kult, Keegan; Wickramarathne, Niranga M.; Hoover, Natasha L.; and Soupir, Michelle L., "Denitrifying Bioreactor Woodchip Recharge: Media Properties after Nine Years" (2020). Agricultural and Biosystems Engineering Publications. 1132.
https://lib.dr.iastate.edu/abe_eng_pubs/1132
Included in
Agriculture Commons, Bioresource and Agricultural Engineering Commons, Water Resource Management Commons
Comments
This article is published as Feyereisen, Gary W., Christopher Hay, Ulrike W. Tschirner, Keegan Kult, Niranga M. Wickramarathne, Natasha Hoover, and Michelle L. Soupir. "Denitrifying Bioreactor Woodchip Recharge: Media Properties after Nine Years." Transactions of the ASABE 63, no. 2 (2020): 407-416. DOI: 10.13031/trans.13709.