Abstract: Porous fibers which are much preferred for having various functionalities such as ion exchangeability, catalytic activity, etc. can be produced by impregnating a mixed monomer liquid of at least one monovinyl monomer and at least one polyvinyl monomer which contains a polymerization initiator in substrate fibers capable of being swollen by 30 - 500 volume % with the mixed monomer liquid, polymerizing the monomers in the state of being absorbed in the fibers and then removing said substrate fibers.

Abstract: Waste water containing finely divided oily materials and solid materials suspended therein can be clarified by (1) forwarding the waste water successively through a plurality of fibrous strata which are arranged along a path of the waste water and each of said strata is composed of a mass of hydrophilic organic polymer fibers compressed in such a manner that the closer the location of a fibrous stratum is to the supply source of the waste water, the greater the gaps on the average are formed between the fibers in the stratum, while allowing the particles of the finely divided oily materials to coarsen and to catch and collect finely divided solid materials into the coarsened particles; (2) after passing through each of the fibrous strata, introducing the waste water into a space in which the coarsened particles are allowed to float and form a separate layer of the oily materials containing the solid materials on the upper surface of the waste water in the space; (3) discharging the oily materials containing t