MEASUREMENT AND MODELLING OF AMMONIA EMISSIONS AT WASTE TREATMENT LAGOON-ATMOSPHERIC INTERFACE

Abstract

Global emissions of ammonia are approximately 75 Tg N/yr (1 Tg = 10 12 g). The major global source is excreta from domestic animals (∼ 32 Tg N −1 yr −1 ). Waste storage and treatment lagoons are used to treat the excreta of hogs in North Carolina (NC). Proteins and nitrogen rich compounds in the lagoon are converted to ammonia, through a series of biological and chemical transformations. The process of ammonia emission has been investigated using two different model approaches: (1) Coupled Mass Transfer with Chemical Reaction Model (Model I), and (2) Mass Transport without Chemical Reaction Model (Model II). A sensitivity analysis is performed with the models, and the model results are compared with ammonia emission experiments at a swine waste storage and treatment lagoon in NC using a dynamic emission flux chamber. Results of model predictions of emission flux indicate an exponential increase in ammonia flux with increasing lagoon temperature and pH, a linear increase with increasing lagoon total ammoni- acal nitrogen (TAN), and a secondary degree increase with the increasing wind speed. In addition, the fluxes predicted by Model I are consistently larger than fluxes predicted by Model II. Experimental values of flux agreed well with model predictions, with the experimental values lying in different po- sitions between the two model predictions under different physical and chemical conditions. Further, when compared to diurnal and seasonal experimental flux values, Model I corroborates the results in calm meteorological conditions (wind speed U10 = 1.5 m s −1 ). However, the observed results are better predicted by Model II during unstable conditions, when wind speeds are higher than 2.0 m s −1