P. Hofschreuder

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

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.

Validation of the Cyclone as a Pre-Separator for Airborne Fine Dust Sampling in Animal Houses

The aim of this study was to verify the overloading of greased impaction pre-separators (IPs) in samplers for PM10 and PM2.5. Furthermore, the use of cyclone pre-separators (CPs) as equivalent samplers, which are less vulnerable for overloading, was validated. In the overloading test, the greased plates of IPs were replaced by new ones at different time intervals. Additional validating tests were conducted in different animal houses (pigs and poultry), in a technical lab, and in ambient air. Seventy-five pairs of 24-h measurements, 36 for PM10 and 39 for PM2.5, consisting of results for 1 IP and 2 CPs were obtained in total. The equivalence analysis was performed according to EU prescription. Results from the overloading test showed that measured PM2.5 concentrations notably increased with increasing intervals of replacement of the greased plates. PM10 concentrations were not affected by replacement intervals. Results from the validation tests showed comparable results for PM10 with CP and IP in the whole concentration range. PM2.5 concentrations, however, were significantly higher for IP than for CP in animal houses. At low concentrations in the lab and in the outside air, results were comparable. It was concluded that PM2.5 measurements in animal houses cannot be performed with an IP, because of overloading. A CP seems to give reliable results, both for PM10, as for PM2.5 measurements.