Kinetics of nitrous oxide (N2O) formation and reduction by Paracoccus pantotrophus

B. L. Read-Daily, Elizabethtown College
F. Sabba, University of Notre Dame
J. P. Pavissich, Universidad Adolfo Ibáñez
R. Nerenberg, University of Notre Dame

Abstract

Nitrous oxide (N O) is a powerful greenhouse gas emitted from wastewater treatment, as well as natural systems, as a result of biological nitrification and denitrification. While denitrifying bacteria can be a significant source of N O, they can also reduce N O to N . More information on the kinetics of N O formation and reduction by denitrifying bacteria is needed to predict and quantify their impact on N O emissions. In this study, kinetic parameters were determined for Paracoccus pantotrophus, a common denitrifying bacterium. Parameters included the maximum specific reduction rates, q^, growth rates, μ ^, and yields, Y, for reduction of NO (nitrate) to nitrite (NO ), NO to N O, and N O to N , with acetate as the electron donor. The q^ values were 2.9 gN gCOD d for NO to NO , 1.4 gN gCOD d for NO to N O, and 5.3 gN gCOD d for N O to N . The μ ^ values were 2.7, 0.93, and 1.5 d , respectively. When N O and NO were added concurrently, the apparent (extant) kinetics, q^ , assuming reduction to N , were 6.3 gCOD gCOD d , compared to 5.4 gCOD gCOD d for NO as the sole added acceptor. The μ ^ was 1.6 d , compared to 2.5 d for NO alone. These results suggest that NO and N O were reduced concurrently. Based on this research, denitrifying bacteria like P. pantotrophus may serve as a significant sink for N O. With careful design and operation, treatment plants can use denitrifying bacteria to minimize N O emissions. 2 2 2 2 2 2 3 2 2 2 2 2 3 2 2 2 2 2 2 3 app 2 3 app 3 3 2 2 2 − − − −1 −1 − − −1 −1 − −1 −1 −1 − −1 −1 −1 −1 − −1 −1 − −