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Carbon supplementation and bioaugmentation to improve denitrifying woodchip bioreactor performance under cold conditions
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  • Gary Feyereisen,
  • Hao Wang,
  • Ping Wang,
  • Emily Anderson,
  • Jeonghwan Jang,
  • Ehsan Ghane,
  • Jeffrey Coulter,
  • Carl Rosen,
  • Michael Sadowsky,
  • Satoshi Ishii
Gary Feyereisen
USDA-ARS, USDA-ARS
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Hao Wang
Department of Soil, Water, and Climate, Department of Soil, Water, and Climate
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Ping Wang
BioTechnology Institute, BioTechnology Institute

Corresponding Author:[email protected]

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Emily Anderson
Department of Soil, Water, and Climate, Department of Soil, Water, and Climate
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Jeonghwan Jang
Division of Biotechnology, Division of Biotechnology
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Ehsan Ghane
Department of Biosystems and Agricultural Engineering, Department of Biosystems and Agricultural Engineering
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Jeffrey Coulter
Department of Agronomy and Plant Genetics, Department of Agronomy and Plant Genetics
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Carl Rosen
Department of Soil, Water, and Climate, Department of Soil, Water, and Climate
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Michael Sadowsky
Department of Soil, Department of Soil, Water, and Climate
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Satoshi Ishii
Department of Soil, Water, and Climate, Department of Soil, Water, and Climate
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Abstract

Cold temperatures limit nitrate-N load reductions of woodchip bioreactors in higher-latitude climates. This two-year, on-farm (Willmar, Minnesota, USA) study was conducted to determine whether field-scale nitrate-N removal of woodchip bioreactors can be improved by the addition of cold-adapted, locally isolated bacterial denitrifying strains (bioaugmentation) or dosing with a carbon (C) source (biostimulation). In Spring 2017, biostimulation removed 66% of the nitrate-N load, compared to 21% and 18% for bioaugmentation and control, respectively. The biostimulation nitrate-N removal rate (NRR) was also significantly greater, 15.0 g N m-1 d-1, versus 5.8 and 4.4 g N m-1 d-1, for bioaugmentation and control, respectively. Bioclogging of the biostimulation beds limited dosing for the remainder of the experiment; NRR was greater for biostimulation in Fall 2017, but in Spring 2018 there were no differences among treatments. Carbon dosing did not increase outflow dissolved organic C concentration. The abundance of one of the inoculated strains, Cellulomonas sp. strain WB94, increased over time, while another, Microvirgula aerodenitrificans strain BE2.4, increased briefly, returning to background levels after 42 days. Eleven days after inoculation in Spring 2017, outflow nitrate-N concentrations of bioaugmentation were sporadically reduced compared to the control for two weeks but were insignificant over the study period. The study suggests that biostimulation and bioaugmentation are promising technologies to enhance nitrate removal during cold conditions. A means of controlling bioclogging is needed for biostimulation, and improved means of inoculation and maintaining abundance of introduced strains is needed for bioaugmentation. In conclusion, biostimulation showed greater potential than bioaugmentation for increasing nitrate removal in a woodchip bioreactor, whereas both methods need improvement before implementation at the field scale.