Patent ID: 7754074

Claim:
A filtering device, comprising: a filtering apparatus composed of a vessel with a filtrate accumulation space provided in an upper side thereof and a filter contained in the vessel; a feed inlet line for introducing feed into the filtering apparatus; a filtrate outlet line for letting filtrate flow out of the filtering apparatus; the filter filtering the feed to let filtered feed flow as the filtrate; a back wash tank for storing back wash water to be supplied into the filtering apparatus, with a partition which easily passes liquid component and hardly passes gas component to separate the back wash tank into a first compartment and a second compartment; the first compartment being adapted for connecting a gas supply line capable of controlling gas pressure and for supplying the gas to the filtering apparatus, and a make-up water supply line for supplying the back wash water to the filtering apparatus; and the second compartment being connected to the filtrate accumulation space of the filtering apparatus.