Denitrifying bioreactors are one possible solution to the problem of nitrate-nitrogen outflow from agricultural subsurface drainage to surface waters. This study was conducted to determine the effectiveness of a corn cob and wood chip mixture, comprised of an equal amount of each by weight, as a denitrifying bioreactor bed medium in comparison to both corn cobs and wood chips alone. The nitrate-nitrogen removal rates of these three media were tested by packing each into 15 cm by 50 cm PVC cylinders and pumping a solution with a 50 mg/L concentration of nitrate-nitrogen through them over a period of five months at a rate equivalent to a hydraulic resistance time of 12 hours. The entire apparatus was kept at 2˚ C as to imitate weather conditions common to Midwestern states in early spring. The average nitrate-nitrogen removal rates for the three media were: corn cob > mixture > wood chips.
This research was supported by the Undergraduate Research Opportunities Program (UROP). Additional funding provided by: the USDA-ARS Soil and Water Research Unit, the MN Agricultural Utilization Research Institute, and the MN Corn Growers Association.
Comparison of Three Agricultural Residue-Based Filter Media for Use In a Denitrifying Bioreactor.
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