Removal of Particulate Matter (PM10) by Air Scrubbers at Livestock Facilities: Results of an On-Farm Monitoring Program

Abstract

Air scrubbers are commonly used for removal of ammonia and odor from exhaust air of animal houses in the Netherlands. In addition, air scrubbers remove a part of the particulate matter. In this article, the results of an on-farm monitoring are presented in which PM10 removal was monitored at 24 scrubbers. It was found that scrubbers with long air contact times (empty bed residence time (EBRT) > 3 s) achieved relatively high PM10 removal efficiencies (on average 79%). However, at short air contact times (EBRT < 3 s), efficiencies were lower (on average 49%). As dust particles travel through the humid scrubber environment, they grow in size and mass, which increases their chance of being intercepted and removed from the air. The results suggest that the maximum particle size is reached within this period of 3 s, but a controlled experimental setup is required to prove this assumption. Possible formation of salt aerosols inside the scrubbers may have affected measured removal efficiencies, especially for acid scrubbers, that are operated at EBRT < 3 s. As multi-stage scrubbers have a higher average air residence time, they show a higher PM10 removal efficiency than acid scrubbers and bioscrubbers. In addition, it is suggested that the gravimetric PM10 determination method might need to be improved to eliminate the effect of differences in moisture levels between scrubber inlet and outlet air on particle cutoff.