In animal feed industry, powder sizes as a result of spray drying is typically much larger than 10 microns. Where particulate matter (PM) pollution can be of concern, a wet scrubber is typically added after a spray dryer. A low energy scrubber would suffice for collection of particulate matter in excess of 10 microns (μm). Any smaller particles to be captured would have necessitate medium and high energy scrubbers. A water-to-gas ratio for simple spray tower is typically approximately 20L of water to 30m3 of gas. Total pressure drop (of gas/air) across the simple spray tower (including mist eliminator) would not have exceed 13cm/5inch of water gauge, hence the classification of simple spray tower as a low energy scrubber.
In the animal feed industry (especially when dealing with insoluble solids), scrubber effluent typically forms a layer of scum at the surface of the water which may necessitate incorporation of a scum scraper for the removal of organics at the effluent surface; cleaner water is discharged from the bottom of the effluent which can then be reused for further wet scrubbing. This method reduces the quantity of wastewater being produced, thus in the long term, reduces the overall operating cost for the wastewater treatment.