Elimination of Ammonia in Air Stream by a Fern-Chip Biofilter

Abstract

Biofiltration is a process for removing contaminants in air using microorganisms immobilized on a solid support media surface. This technique is economically attractive, and has been adopted successfully to treat a number of air contaminants such as volatile organic compounds (VOCs) or odors. The performance of biofiltration for removal of ammonia from air streams was studied in a pilot-scale biofilter consisted of two columns [40 cm (w) × 40 cm (L) × 70 cm (H) acrylic column] arranged in a series. A medium consisting solely of fern chips, on which biofilms were cultivated, was used as a packing material. The biofilter was tested continuously for 110 days, measuring the removal efficiency, empty bed residence time (EBRT), removal capacity, pressure drop, moisture content, and pH. Most of ammonia was eliminated in the first biofiltration column, and the removal efficiency was increased with the increase in EBRT. Complete removal of the influent ammonia (20–120 ppm) was obtained with the ammonia loading as high as 5.4 g N kg⁻¹ dry media day⁻¹ during the experiment. The Michaelis-Menten equation was tested to be adequate for modeling the ammonia elimination kinetics in the biofilter and the maximum removal rate (V _m ) and the half-saturation constant (K _s ) were estimated to be 28.2 g N kg⁻¹ dry media day⁻¹ and 129 ppm, respectively.