a multipolymeric mixture is provided that includes a hydrophobic polymer , two different grades of a water - soluble polymer , water as non - solvent and a solvent suitable for all polymers involved . the dissolved hydrophobic polymer has the affinity to enmesh the water - soluble polymers to form a clear and viscous dope . water - soluble polymers contribute to the pore formation process and hydrophilicity of the finally coagulated membrane according to the makeup of their molecular weight distribution . water as a non - solvent takes the dope very near towards unstable zone , which helps in speeding up the membrane formation process in a diffusion induced phase inversion technique . the dope is then spun through a concentric orifice spinneret and solidified by passing it through a coagulation bath to form hollow fiber asymmetric membranes of ultra filtration grade with superior water permeability and separation characters even at higher feed turbidity .