Role of Temperature and Nitrate Concentration in Controlling Denitrification in Field Scale Denitrification Beds.

Denitrification beds are becoming established as a relatively simple approach for removing nitrate from point source discharges such as wastewater stream and tile drain-flow. Denitrification beds are essentially large lined containers filled with a solid carbon substrate often a softwood chip or sawdust. It has been convincingly demonstrated that the main mechanism for nitrate removal is denitrification where microorganisms utilise decaying wood material as an energy source and nitrate as a terminal electron acceptor. The end-product is predominantly nitrogen gas released to the atmosphere. To allow appropriate design and sizing, environmental factors that control the rate of nitrate removal need to be quantified. Here, we determine whether nitrate removal rate is controlled by nitrate concentration following Michaelis-Menten kinetics and specifically attempt to determine values for Km for different carbon substrates. Secondly, we measure changes in nitrate removal as a function of temperature in several field scale denitrification beds throughout a year to determine whether this relationship can be predicted using the Arrhenius function. Combining an improved understanding of kinetic controls of nitrate removal with temperature response of denitrification will improve our ability to appropriately size denitrification beds for use in human dominated landscapes.