ARS | Publication request: Denitrification enzyme activity in swine wastewater lagoons

Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: May 25, 2007
Publication Date: June 17, 2007
Citation: Hunt, P.G., Matheny, T.A., Ro, K.S., Vanotti, M.B., Reddy, G.B. 2007. Denitrification enzyme activity in swine wastewater lagoons. In: Proceedings of American Society of Agricultural and Biological Engineers Annual International Meeting,17-20 June, Minneapolis, Minnesota. Paper Number 07-4055, 5 p. CDROM

Technical Abstract: Recent publications of high levels of di-nitrogen emissions and high levels of potential surficial oxygen transfer indicated that large amounts of nitrogen may be removed via denitrification in anaerobic lagoons. If this denitrification is occurring via classical denitrification, the denitrification enzyme levels should be correspondingly high. We measured denitrification enzyme activity (DEA) in five lagoons with varying loads of swine wastewater. The lagoons varied from lightly loaded with oxidative reductive potentials (ORP) that favored aerobic processes to heavier loaded with ORPs that favored anaerobic processes. The Acetylene inhibition method was used to access DEA in the untreated control conditions. Acetylene was added to block nitrous oxide conversion to di-nitrogen gas and allow total denitrification to be accessed via nitrous oxide measurements. Samples were taken in four quadrants of the lagoons at the surface, midway to the bottom, and just above the bottom of the lagoon. Initial results indicate that the quadrants were reasonably similar, but the depths were somewhat variable. Two commercial lagoons with COD values >1800 had surprisingly low DEA. These results suggest that di-nitrogen may be produced at different levels and by different means in different lagoons.