Many water purification plants using MF or UF membrane filtration processes have been constructed and in operation throughout the world. Feed water quality of these plants may change site by site from the view points of suspended particles (turbidity) and characteristics of natural organic matter (NOM). One of the important issues that affect membrane filtration performance is “membrane fouling”. To overcome “membrane fouling”, we studied the design of both pure water permeability and membrane surface pore size distribution. As a result, TORAY has achieved to obtain the series of low fouling hollow fiber membranes by unique composite hollow fiber membrane morphologies. These composite hollow fiber membranes are made from high strength supporting layer and low fouling layers, which determine the surface pore size. Based on this technology, TORAY line-upped three PVDF hollow fiber membrane modules, which should be selected for water purification plant depending on the feed water qualities. The hollow fiber membranes are successfully made into extremely large casing type modules, which have 8inches diameter, 2 meter length and 75 square meter surface area. These modules make it possible to achieve small footprint area of membrane filtration plants, low cost and stable operation.
