Modeling Ammonia Removal and Biotransformation Within Laboratory-Scale Yard-Waste Compost Biofilters

摘要

Laboratory-scale yard-waste compost biofilters were constructed with inoculum to treat ammonia gas at concentrations below 140 ppm. Using adsorption equilibrium and NH3 removal rates, a model was developed to describe and predict biofilter activities in the field. Modeling was based on a clean humid air stream combined with anhydrous ammonia gas controlled from between 15 to 140 ppm NH3. Steady-state NH3 removal rates were based on the difference between inlet and outlet NH3 gas concentrations. Concentrations of total ammoniacal nitrogen (TAN) and nitrate (NO_3~-), pH and moisture content were measured throughout the experiments and used to develop a prediction model for NO_3~- concentrations and pH changes. The developed model was able to predict NH3 outlet from biofilters used in the model development. Using the model, TAN concentrations were overpredicted but predicted NO_3~-concentration were very close. The model also predicted a pH decrease that results from nitrification but did not predict well increases caused by high NH3 gas concentrations. This model presents a reasonable approach to predicting NH3 biotransformation and changes within a biofilter that treats NH3 in a clean air steam.