Denitrification in Anaerobic Lagoons Used to Treat Swine Wastewater
- P. G. Hunt *,
- T. A. Matheny,
- K. S. Ro,
- M. B. Vanotti and
- T. F. Ducey
- USDA–ARS, Coastal Plain Soil, Water, and Plant Research Center, Florence, SC. Assigned to Associate Editor Philippe Vidon. Mention of trade name, proprietary product, or vendor is for information only and does not constitute a guarantee or warranty of the product by the USDA and does not imply its approval to the exclusion of other products or vendors that may also be suitable
Anaerobic lagoons are commonly used for the treatment of swine wastewater. Although these lagoons were once thought to be relatively simple, their physical, chemical, and biological processes are very complex. This study of anaerobic lagoons had two objectives: (i) to quantify denitrification enzyme activity (DEA) and (ii) to evaluate the influence of lagoon characteristics on the DEA. The DEA was measured by the acetylene inhibition method. Wastewater samples and physical and chemical measurements were taken from the wastewater column of nine anaerobic swine lagoons from May 2006 to May 2009. These lagoons were typical for anaerobic swine lagoons in the Carolinas relative to their size, operation, and chemical and physical characteristics. Their mean value for DEA was 87 mg N2O–N m−3 d−1 In a lagoon with 2-m depth, this rate of DEA would be compatible with 1.74 kg N ha−1 d−1 loss. When nonlimiting nitrate was added, the highest DEA was compatible with 4.38 kg N ha−1 d−1 loss. Using stepwise regression for this treatment, the lagoon characteristics (i.e., soluble organic carbon, total nitrogen, temperature, and NO3–N) provided a final step model R 2 of 0.69. Nitrous oxide from incomplete denitrification was not a significant part of the system nitrogen balance. Although alternate pathways of denitrification may exist within or beneath the wastewater column, this paper documents the lack of sufficient denitrification enzyme activity within the wastewater column of these anaerobic lagoons to support large N2 gas losses via classical nitrification and denitrification.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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