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Denitrification Enzyme Activity in Swine Wastewater Effluent of a Nitrification/Denitrification Treatment System

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Transactions of the ASABE. 55(1): 159-165. (doi: 10.13031/2013.41265) @2012
Authors:   P. G. Hunt, T. A. Matheny, M. B. Vanotti, K. C. Stone, A. A. Szogi
Keywords:   Carbon, Denitrification, Nitrate, Swine wastewater, Treatment system

Intensification of swine production in the U.S. and around the world requires advanced manure management. For swine manure management in the state of North Carolina, one system met all of the required advanced management criteria, and it was qualified as an environmentally superior technology. This investigation was part of the testing for this superior technology. The objectives of this investigation were to assess: (1) the denitrification enzyme activity (DEA) in the treatment systems homogenization tank and denitrification tank, and (2) the impact of the wastewater characteristics on this DEA. The DEA was measured by the acetylene inhibition method. Wastewater in the homogenization tank was fresh-flushed directly from the swine houses. Consequently, it was more concentrated than wastewaters in either the denitrification tank or typical swine wastewater lagoons; it had soluble biochemical oxygen demand (sBOD) of 676 mg L-1 and an electrical conductivity (EC) of 8.9 mS cm-1. However, the DEA in the homogenization tank was significantly limited by the low level of NO3-N, which was 0.1 mg L-1. Conversely, the DEA of the denitrification tank was limited by its lower level of carbon; it had only 53 mg L-1 sBOD. However, it had a NO3-N concentration of 150 mg L-1. When non-limiting glucose-C and NO3-N were added to the wastewaters of the homogenization and denitrification tanks, the homogenization tank had a significantly higher level of potential DEA: 17,943 vs. 10,055 mg N2O-N m-3 d-1, respectively. The DEA was generally well correlated by stepwise regression to the measured physiochemical characteristics. The findings of this investigation document that the DEA within this treated swine wastewater can be altered by manageable constituents of the processed swine wastewater, in particular soluble carbon and oxidized nitrogen.

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