Submitted to: Journal of Environmental Science and Health
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 6, 2006
Publication Date: November 26, 2006
Citation: Ro, K.S., Hunt, P.G., Poach, M.E. 2006. Wind-driven surficial oxygen transfer and dinitrogen gas emission from treatment lagoons. Journal of Environmental Science and Health. 41:1627-1638. Interpretive Summary: Oxygen is an important compound driving biological reactions responsible for nitrogen gas formation. Scientists have generally thought that nitrogen gas were not formed in animal-waste treatment lagoons because of insufficient amounts of oxygen. However, recent discoveries of large nitrogen gas emission from swine treatment lagoons have caused reconsideration of lagoon biochemical processes. Our objective was to clarify a hypothesis that enough atmospheric oxygen was supplied to treatment lagoons for the reported nitrogen formation. We predicted the maximum amount of wind-driven oxygen that can be absorbed into the treatment lagoons using the most recent knowledge on oxygen transfer in the literature. The predicted oxygen absorption rates were used to calculate the amounts of nitrogen-gas emission that could be supported according to well-known and recently discovered biological pathways. These predicted nitrogen-gas emission rates compared well with most of the observed emission data. However, one observed data set with a value much higher than others suggests that currently unknown pathways may also be important in animal waste treatment lagoons.
Technical Abstract: Surficial oxygen transfer plays an important role, when analyzing the complex biochemical and physical processes responsible for ammonia and dinitrogen gas emission in the animal waste treatment lagoons. This paper analyzes if currently-known nitrogen biochemical pathways can explain the enigmatic dinitrogen gas emissions recently observed from the treatment lagoons, based on the amount of wind-driven oxygen that can be transferred through the air-water interface. The stoichiometric amounts of the maximum dinitrogen gas production potential per unit mass of O2 transferred were calculated according to three most likely biochemical pathways for ammonia removal in the treatment lagoons -- classical nitrification-denitrification, partial nitrification-denitrification, and partial nitrification-Anammox. Partial nitrification-Anammox pathway would produce the largest N2 emission, followed by partial nitrification-denitrification pathway, then by classical nitrification-denitrification pathway. In order to estimate stoichiometric amount (i.e., maximum) of N2 emission from these pathways, we assumed that heterotrophic respiration was substantially inhibited due to high levels of free ammonia prevalent in treatment lagoons. Most observed N2 emission data were below the maximum N2 emission potentials by the classical nitrification-denitrification pathway. However, one value of observed N2 emission was much higher than that could be produced by even the partial nitrification-Anammox pathway. This finding suggests yet unknown biological processes and/or non-biological nitrogen processes such as chemodenitrification may also be important in these treatment lagoons.