Woodchip Denitrification Bioreactors: Impact of Temperature and Hydraulic Retention Time on Nitrate Removal

Hoover, Natasha L.; Bhandari, Alok; Soupir, Michelle L.; Moorman, Thomas B.

doi:10.2134/jeq2015.03.0161

Cited by 120 publications

(104 citation statements)

References 50 publications

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“…The average gravitational and internal porosity of the woodchip media were 0.52 ± 0.01 and 0.32 ± 0.03, respectively, yielding a total porosity of 0.84, which was comparable to 0.84 and 0.89 reported by Robertson (2010) and Hoover et al (2015), respectively.…”

Section: Reactor Vessel and Packingsupporting

confidence: 59%

“…Conventionally, hydrolysis products of woodchips are used as the sole electron donor in woodchip bioreactors. As is typical for biologically mediated reactions, decreasing temperatures result in lower reaction rates (Feyereisen et al, 2016;Hoover et al, 2015). For most bioreactor processes that are not mass-transfer limited, shorter HRTs are also associated with decreasing fractional nitrogen removal in these systems (Hoover et al, 2015).…”

Section: Theorymentioning

confidence: 99%

“…As is typical for biologically mediated reactions, decreasing temperatures result in lower reaction rates (Feyereisen et al, 2016;Hoover et al, 2015). For most bioreactor processes that are not mass-transfer limited, shorter HRTs are also associated with decreasing fractional nitrogen removal in these systems (Hoover et al, 2015). By stimulating the bioreactors with electricity, additional electrons can be readily produced to enhance the denitrification processes (Prosnansky et al, 2002;Thrash and Coates, 2008).…”

Section: Theorymentioning

confidence: 99%

“…Tubing was replaced when flow rates decreased significantly. Synthetic nutrient solution containing 30 mg/L of NO 3 -N, and other micronutrients (detailed in supplementary information) required for optimal bacterial growth (Nadelhoffer, 1990), was used to represent tile drain water (Hoover et al, 2015). The solution was prepared in a 170 L container as influent solution for all columns.…”

Section: Fluid Handling Systemmentioning

confidence: 99%

“…A comparative study of field bioreactors at four separate locations in Iowa reported an average nitrate removal of 43 percent for treated drainage water (Christianson et al, 2012), demonstrating that such systems could achieve reductions close to those targeted by the Hypoxia Task Force. However, the performance of bioreactors is highly variable, with lower removal efficiencies occurring when temperatures are low, or flow is high (i.e., when hydraulic retention time (HRT) are low) (Hoover et al, 2015;Robertson et al, 2008). This is one of the motivations to improve bioreactor performance under such conditions, which typically occur in the early spring or high-flow season.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Electrical stimulation for enhanced denitrification in woodchip bioreactors: Opportunities and challenges

Law

Soupir

Raman

et al. 2018

Ecological Engineering

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Woodchip bioreactors are being implemented for the removal of nitrates in groundwater and tile water drainage. However, low nitrate removals in denitrifying woodchip bioreactors have been observed for short hydraulic retention time (HRT) and low water temperature (°C). One potential approach to improve woodchip bioreactor performance is to provide an alternative and readily available electron source to the denitrifying microorganisms through electrical stimulation. Previous work has demonstrated the capability of bio-electrochemical reactors (BER) to remove a variety of water contaminants, including nitrate, in the presence of a soluble carbon source. The objective of this study was to evaluate the denitrification efficiency of electrically augmented woodchip bioreactors and conduct a simple techno-economic analysis (TEA) to understand the possibilities and limitations for full-scale BER implementation for treatment of agricultural drainage. Up-flow column woodchip bioreactors were studied included two controls (non-energized, and without electrodes), two electrically enhanced bioreactors, each using a single 316 stainless steel anode coupled with graphite cathodes, and two electrically enhanced bioreactors, each with graphite for both anode and cathodes. Both pairs of electrically enhanced bioreactors demonstrated higher denitrification efficiencies than controls when 500 mA of current was applied. While this technology appeared promising, the technoeconomic analysis showed that the normalized N removal cost ($/kg N) for BERs was 2-10 times higher than the base cost with no electrical stimulation. With our current reactor design, opportunities to make this technology cost effective require denitrification efficiency of 85% at 100 mA. This work informs the process and design of electrically stimulated woodchip bioreactors with optimized performance to achieve lower capital and maintenance costs, and thus lower N removal cost. RightsWorks 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. A B S T R A C TWoodchip bioreactors are being implemented for the removal of nitrates in groundwater and tile water drainage. However, low nitrate removals in denitrifying woodchip bioreactors have been observed for short hydraulic retention time (HRT) and low water temperature (< 10°C). One potential approach to improve woodchip bioreactor performance is to provide an alternative and readily available electron source to the denitrifying microorganisms through electrical stimulation. Previous work has demonstrated the capability of bio-electrochemical reactors (BER) to remove a variety of water contaminants, including nitrate, in the presence of a soluble carbon source. The objective of this study was to evaluate the denitrification efficiency of electrically augmented woodchip bioreactors and conduct a simple techno-economic analysis (TEA) to understand the possibilities and limitations for full-scale BER im...

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Section: Reactor Vessel and Packingsupporting

confidence: 59%

Section: Theorymentioning

confidence: 99%

Section: Theorymentioning

confidence: 99%

Section: Fluid Handling Systemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Electrical stimulation for enhanced denitrification in woodchip bioreactors: Opportunities and challenges

Law

Soupir

Raman

et al. 2018

Ecological Engineering

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Nitrate removal and nitrous oxide production from upflow and downflow column woodchip bioreactors

Feyereisen

Spokas

Strock

et al. 2020

Agricultural & Env Letters

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Woodchip denitrifying bioreactors (WDBR) reduce off-field tile drainage nitrogen (N) losses from agricultural fields. Limited evaluation exists regarding the influence of flow direction through WDBRs. Changing flow direction could reduce short circuiting. This study evaluated the dependency of nitrate-N removal and dissolved nitrous oxide (dN 2 O) production rates on vertical flow direction in triplicate column bioreactors at 12-h (without carbon dosing) and 2-h (with carbon dosing) hydraulic residence times. Results presented demonstrate that there was no significant difference in overall N removal rates from these column bioreactors as a function of flow direction. There was the suggestion of lower N 2 O production in the downflow direction, although this was not statistically significant due to the high variability of the N 2 O production observed in the upflow direction. Carbon addition led to bioclogging of downflow columns; future work needs to identify dosing rate, placement, and conditions that prevent biofilm formation. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Impact of flow on woodchip properties and subsidence in denitrifying bioreactors

Schaefer

Werning

Hoover

et al. 2021

Agrosystems Geosci & Env

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Woodchip bioreactors are edge‐of‐field practices that remove nutrients from agricultural drainage water, with an effective lifespan estimated between 10 and 30 yr. Subsidence, or bioreactor settling and subsequent depression formation, is a concern of producers and stakeholders and little is known regarding its effect on bioreactor performance. Six woodchip bioreactors set at three different hydraulic residence times (HRTs 2, 8, and 16 h) were excavated after 2 yr of operation, with wood samples collected from multiple depths and distances from the bioreactor inlet. Subsidence was observed in all six bioreactors and was greater near the inlet. Particle‐size distribution did not change over the study period, indicating that smaller woodchips were not degrading preferentially or washing out of the bioreactor while the macropore space was simultaneously decreasing. Flow path analysis showed an increase in Morrill Dispersion Indices and short‐circuiting as well as decreases in drainable porosity and hydraulic efficiency; these changes were uniform across all three HRTs, suggesting that the decline in hydraulic properties was independent of flow. Further, despite increased woodchip decomposition as measured by C/N ratio in the 2‐h HRT bioreactors (mean ± SD = 64.9 ± 13.7) compared with the 8‐ and 16‐h HRT systems (90.3 ± 19.0, 95.6 ± 27.2, respectively), denitrification was still supported at all HRTs based on the results from a batch denitrification test. To offset wood aging, bioreactor fill material nearest the inlet could be replenished without excavation of the entire bioreactor.

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Woodchip Denitrification Bioreactors: Impact of Temperature and Hydraulic Retention Time on Nitrate Removal

Cited by 120 publications

References 50 publications

Electrical stimulation for enhanced denitrification in woodchip bioreactors: Opportunities and challenges

Electrical stimulation for enhanced denitrification in woodchip bioreactors: Opportunities and challenges

Nitrate removal and nitrous oxide production from upflow and downflow column woodchip bioreactors

Impact of flow on woodchip properties and subsidence in denitrifying bioreactors

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