Classification of resistance to permeation caused by fouling during ultrafiltration of whey and skim milk

To identify the cause of fouling of the membrane surface and pores during the ultrafiltration of whey or skim milk, these liquids were filtered through a membrane, allowed to adsorb to it, or both. Measurements of flux were made before and after gentle hand cleaning with a soft sponge, and resistance to permeation because of fouling was calculated and classified into four kinds: by adsorption to the surface, by adsorption in side the pores, because of filtration on the surface, and because of filtration in the pores. In the ultrafiltration of whey, resistance caused by fouling on the surface by filtration was great, and that caused by fouling in the pores by filtration was slight. In the ultrafiltration of skim milk, resistance caused by fouling by adsorption was great, and that caused by fouling on the surface by filtration was slight, probably because the casein micells in skim milk scrape fouling materials off the surface.