Accumulation and capture of nitrogen and sulfur in biofilters treating aerial emissions from swine production facilities

Scope and Method of Study. Biofiltration is used to reduce ammonia (NH3-N) and hydrogen sulfide (H2S) emissions from livestock facilities. Current research evaluates the effectiveness of a biofiltration system as percentage total target gas removed from the inlet air. Alternative loss pathways from a single-layer open biofiltration system operating under field conditions are not addressed. The objectives are (1) to compare the NH3-N, nitrate (NO3-N), total nitrogen (TN) and total sulfur (TS) content as well as the carbon to nitrogen ratio (C:N) of the straw and compost biofilter media and (2) to compare the NH 3-N, NO3-N and TN and TS present in the soil below and adjacent to the biofilters. Four replications of straw and compost media were sampled with the media divided into top half, bottom half, and soil surface litter. The soil below and adjacent to the biofilter was sampled at the depths of 0-5 cm, 5-10 cm and 10-15 cm. All samples were analyzed for NH 3-N, NO3-N, TN, TS and total organic carbon (TC).Findings and Conclusions. Straw media NH4-N and NO3-N, TN and TS content increased while TC content decreased with depth. The compost media had similar concentrations of NH4-N and TS throughout the media profile while NO3-N concentration increased with depth and had a stable TC and TN content. The capacity of a media to capture and accumulate inorganic-N and TS appears to be different based on the availability of TC and is likely due to the activity of media specific microbial populations. The inorganic-N concentration is greater beneath the biofilter than outside the biofilter regardless of media, while TS concentration was greater adjacent to the biofilter. The elevated presence of NO3-N below the biofilter suggests that a clay, concrete or plastic liner should be installed below the biofilter to collect the leachate. A liner and pipe system connected to the animal waste storage lagoon would be an appropriate alteration of the single layer open biofiltration system. The TS concentration is elevated adjacent to the biofilter for both treatments. The prevention of H2S passage through the biofilter and subsequent deposition could be mitigated through increased moisture control which would facilitate the transfer of H2S into the biofilm.