Wind-Driven Surficial Oxygen Transfer and Dinitrogen Gas Emission from Treatment Lagoons

摘要

Surficial oxygen transfer plays an important role, when analyzing the complex biochemical and physical processes responsible for ammonia and dinitrogen gas emission in 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 O_2 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 N_2 emission, followed by partial nitrification-denitrification pathway, then by classical nitrification-denitrification pathway. In order to estimate stoichiometric amount (i.e., maximum) of N_2 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 N_2 emission data were below the maximum N_2 emission potentials by the classical nitrification-denitrification pathway. However, one value of observed N_2 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.