Biofilter media mixture ratio of wood chips and compost treating swine odors

Biofilter media mixtures were compared in 18 pilot-scale biofilters treating pit gases from a swine facility. The compost and wood chips mixtures ranged from 100% wood chips to a 50-50 blend in 10% increments. The effect of three media moisture contents (low, medium, and high) on biofilter performance was also evaluated. Odor and hydrogen sulfide reduction did not change significantly for mixtures with greater than 20% compost. For efficient odor, hydrogen sulfide, and ammonia reduction media moisture must be greater than 40% wb. Media moisture content influenced odor, hydrogen sulfide, and ammonia reduction more than the ratio of compost and wood chips. The count of heterotrophic or sulfur-oxidizing bacteria did not change in a discernable pattern with respect to media mixture or moisture content. As the amount of compost increased in the media mixtures, the pressure drop also increased. Based on this experiment, the recommended mixing ratio of compost to wood chips for biofilters on swine facilities is minimum 30% compost and 70% wood chips by weight.