Development of water scrubbers to reduce fine dust emission from poultry houses

Poultry housings with litter are a major contributor to fine dust emissions (PM10/PM2.5) in the Netherlands. Poultry producers are in need of dust mitigation options that are cost effective. Such an option could be provided by adequately designed water scrubbers. Catchment of dust particles by water droplets and deposition of dust particles on the surface of wetted packing material will lead to removal of dust from ventilation air. The aim of this research was to test water scrubbers under real poultry farm conditions. Prototypes of two water scrubber concepts were tested: prototype A was based on treating outlet air in a cross flow scrubbing setup. Synthetic packing material is continuously drained with a specified large volume of water, that is recirculated from a storage basin below. Prototype B was based on spraying of water by high pressure nozzles in an open treatment chamber, through which the ventilated air was led. A drip catcher was constructed at the outlet of this chamber to prevent loss of water. For prototype A an indicative measurement scheme was carried out on a poultry farm with non-productive raising pullets on cages. Four measurements based on 24 h sampling periods were carried out during which dust removal was measured by a gravimetrical method. Mean removal percentages for PM2.5 and PM10 amounted 9 and 62% respectively. The observed removal percentage for PM10 was in accordance with an earlier theoretical assessment study. It is concluded that this prototype can be used as a basis to develop of this water scrubber for use in poultry production. Prototype B was tested on a broiler farm. First measurements based on gravimetrical methods showed negative removal results. To avoid biasing effects of high humidity on the results, subsequent gravimetrical measurements in the outlet air of the scrubber were carried out after heating and drying the outlet air to lower humidity levels. Accompanying particle counter measurement in particle size classes from 1 to 25 micrometer were carried out in both untreated and treated air. PM10 removal performance was negative, and particle numbers especially increased in the smaller size classes. Inspection of outlet dust samples by electron microscopy indicated that formation of salt aerosols might provide an explanation for this increase. It is concluded in general that humidity effects on dust measurement methods and potential salt crystal formation may complicate dust removal performance of scrubbers and should be more deeply investigated.