Field evaluation of wood bark-based down-flow biofilters for mitigation of odor, ammonia, and hydrogen sulfide emissions from confined swine nursery barns

Abstract

Two down-flow wood bark-based biofilters were evaluated for their effectiveness in treating odor, NH3 and H2S under actual swine farm conditions. The water requirement for maintaining proper media moisture contents (MC) under different ventilation rates and intervals were determined. The effect of media depth and MC on the biofilters' performance was also evaluated. The aerodynamic resistance on biofilters was studied using computational fluid dynamics (CFD) software. Water requirements for biofilters were obtained in the range of 3.8–556.0 L/m3/d for ventilation duration of 1–24 h/d (depending on the age of the pig and environmental conditions). The highest reductions in odor, NH3 and H2S, obtained in this study at empty bed residence times (EBRT) of 1.6–3.1 s, were 73.5–76.9%, 95.2–97.9% and 95.8–100.0%, respectively. The pressure drop was 28.8–68.8 Pa for a media depth of 381 mm at an EBRT of 1.6–3.1 s and an MC of 64–65%. The pressure drop followed a secondary order polynomial line with both airflow rate and media MC (R2 = 0.927–0.982). The results of odor, NH3 and H2S reduction efficiency and pressure drop suggest a media depth of ≥254 mm, MC ≥ 35–50% and EBRT of 2–3 s for successful operations of the wood bark-based biofilters. A high correlation was found between the measured and predicted pressured drops obtained using CFD software (R2 = 0.921, RMSE = 0.145).