Denitrification beds are promoted to reduce nitrate load in agricultural subsurface drainage water to alleviate the adverse environmental effects associated with nitrate pollution of surface water. In this system, drainage water flows through a trench filled with a carbon media where nitrate is transformed into nitrogen gas under anaerobic conditions. The main objectives of this study were to model a denitrification bed treating drainage water and evaluate its adverse greenhouse gas emissions. Field experiments were conducted at an existing denitrification bed. Evaluations showed very low greenhouse gas emissions (mean N2O emission of 0.12μgNm-2min-1) from the denitrification bed surface. Field experiments indicated that nitrate removal rate was described by Michaelis-Menten kinetics with the Michaelis-Menten constant of 7.2mgNL-1. We developed a novel denitrification bed model based on the governing equations for water flow and nitrate removal kinetics. The model evaluation statistics showed satisfactory prediction of bed outflow nitrate concentration during subsurface drainage flow. The model can be used to design denitrification beds with efficient nitrate removal which in turn leads to enhanced drainage water quality.
Bibliographical noteFunding Information:
Funding of this research was provided in part by Ohio Agricultural and Research Development Center grant number 2013-098 ; Ohio State University Graduate School Presidential Fellowship to lead author; Overholt Drainage Education and Research Program; Department of Food, Agricultural and Biological Engineering; College of Food, Agricultural, and Environmental Sciences ; and USDA-Natural Resources Conservation Service CIG grant number 69-5E34-10-053 . The funding sources were not involved in the study design, collection, analysis, interpretation of data, and preparation of the manuscript.
- Bromide tracer
- Drainage water
- Greenhouse gas
- Woodchip bioreactor