To maintain a filtration critical particle system and a filter medium strength while filtration of a water system liquid of drinking water, industrial water, or the like is taken as a use by a method wherein an average pore size in a specific condition, the maximum pore size, a wetting index, and a filter flow rate of pure water at a differential pressure are composed of not less than specific nonwoven fabrics.
In the case where filter media are used in order to remove an iron rust from a pipe line, suspension contained in wash wastewater or the like in a general home, or water plant or the like generated when reserved in a water storage tank or the like, in order to make its filtration crytical particle system at least about 22 μm, an average pore size of a nonwoven fabric composed of a fiber of polybutylene terephthalate comprising the filter media to 1 to 25 μm, the maximum pore size to at most 50 μm, the wetting index to at least 54, and a filter flow rate of pure water at 1 cmH2O in a differential pressure are respectively set to at least 3 L/m2.min. Thereby, while filtration of a water system liquid of drinking water, industrial water, river water, wastewater, etc., is taken as a use, the filtration crytical particle size and a filter medium strength can be maintained.
ISHIBE HISAO
YAMAGISHI TAKASHI
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