Airborne distribution of bio-aerosols of different size and composition after passing a bio-scrubber

Rising concerns about detrimental emissions from animal housings, such as dust particles, odours, gases and microorganisms led to an increasing enforcement to install abatement techniques, especially exhaust filtration systems, both in existing and new-built animal houses. A promising method is the combination of bio-washers and bio-filters: after a washing step where larger particles, some gases and odours are partially removed from of the exhaust air, the air flows through a packed layer of irrigated materials (e.g. wood scrubs or ceramic pellets) where the remaining pollutants are absorbed by a thin bio-film on the surface of the packing material. Microorganisms, including bacteria and fungi are immobilized in this bio-film and degrade the transferred pollutants. Reduction efficiencies of up to 90 % are reported. However, recent studies show that particles in the air stream before and behind such a bio-scrubber not only differ in their bacterial load but also in their size. Little is known about the distribution of such small particles leaving a bio-filter system in the ambient air. Therefore, a model was applied to compare the dispersion of of raw and clean gas particulates. an atmospheric dispersion modelling was conducted to evaluate the differences in the dispersion of raw and clean gas particulates.