Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 25, 2006
Publication Date: November 1, 2006
Citation: Ro, K.S., Hunt, P.G. 2006. A new unified equation for wind-driven surficial oxygen transfer into stationary water bodies. Transactions of the American Society of Agricultural and Biological Engineers. 49(5):1615-1622. Interpretive Summary: Oxygen is an important compound driving biological reactions responsible for nitrogen gas formation. Scientists have generally thought that nitrogen gas should not be formed in animal-waste treatment lagoons because of insufficient amounts of oxygen prevalent in these lagoons. Recently, unexpected observations of large nitrogen gas emission from swine treatment lagoons puzzled the scientific community. Our objective was to clarify a hypothesis that enough masses of atmospheric oxygen were supplied to treatment lagoons, and supported the biological processes responsible for the nitrogen gas formation. An approach of reviewing literature data and developing an oxygen transfer equation was taken. Initially 297 relevant experimental data published in the last 5 decades were obtained. From the compiled data, a new equation was then formulated for predicting oxygen absorption rates into treatment lagoons under relevant weather conditions. The predicted oxygen absorption rates were used to calculate the amounts of nitrogen-gas emission that could be supported according to well-known 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: When analyzing the complex biochemical and physical processes responsible for ammonia and dinitrogen gas emission in the animal waste treatment lagoons, surficial oxygen transfer plays an important role. This part-II of a two-part in-series paper 1) presents the synthesis of a new, unified equation for oxygen mass transfer coefficient based on the gas transfer data in the literature of the last 50 years, and 2) discusses the potential nitrogen pathways responsible for the dinitrogen gas emissions observed from the treatment lagoons. The new empirical oxygen-transfer equation is a function of Schmidt number, wind speed, and temperature. With this new equation, the maximum surficial oxygen fluxes into the treatment lagoons were estimated. The stoichiometric amounts of the maximum dinitrogen gas production per unit mass of O2 transferred were calculated based on three most likely biochemical pathways for ammonia removal in the treatment lagoons -- classical nitrification-denitrification, partial nitrification-denitrification, and partial nitrification-Anammox. When the maximum N2 production potentials were compared with the observed N2 emission data, the classical nitrification-denitrification pathway appears to explain most of the N2 emission data. However, one N2 emission data set with a very high value suggests yet unknown biological processes and/or non-biological nitrogen processes such as chemodenitrification may also be important in these treatment lagoons.