[Reduction efficiencies of a biofilter and a bio-scrubber as bio-aerosols in two piggeries]

Biofilters and bioscrubbers are ultimate tools to control odour emissions from animal houses in pig and poultry production. Little is known about the efficiency of these devices to remove airborne particulate pollutants such as dust, microorganisms and endotoxins from the exhaust air of animal houses. Preliminary results of a one year field campaign in two piggeries show that the biofilter reduces the number of particles in the exhaust air by 79 to 96%. The efficiency of the bioscrubber was 22% only. The biofilter reduced the amount of mesophilic bacteria by 11% and 71%, respectively, the amount of thermotolerant fungi by 71%. The concentration of endotoxin and mesophilic fungi in the clean air after the bioscrubber was 3.8 times resp. 2.7 times higher than in the air of the piggery. The washing water which is regularly recirculated in both systems was highly contaminated with varying amounts of air contaminants. It seems that the quality of the washing water distinctly influences the reduction efficiency of both systems.