OPTIMUM FILTER AID OF PRECOAT FILTERING TYPE WATER TREATING SYSTEM

摘要

PURPOSE:To increase the filtering life of a filter aid by carrying out precoat again during water sampling to prolong an internal filtering time and, at the same time, to prevent the crack generation of the filter aid by adding a fibrous substance to said filter aid used in precoat during water sampling. CONSTITUTION:A filter aid is sent into a filtering and desalting tower 6 from a precoat tank 8 to form a precoat layer on the surface of an element 13. In this state, condensed water is sent into the tower 6 and the impurity removed condensed water is sent to the succeeding stage process as treated water. In addition, the filter aid containing a fibrous substance is mixed with water in a precoat tank 10 by a stirrer 9 to form a slurry and this slurry is sent into the tower 6 under a purification process of condensed water by a pump 12. By this operation, one precoat layer is further formed on the precoat layer previously formed on the element 13. Because this second precoat layer is increased in the elasticity thereof by mutual entanglement of the fibrous substance, stress due to the shrinkage of a resin layer with ion exchange and stress due to deformation of the element 13 with the rising of filtering pressure are absorbed.