Ceramic filter modules in series with piston backwash

An apparatus for filtering a liquid, comprising:

• a container for storing a liquid;
• a filter casing containing two modules joined in series, each of the modules comprising a plural number of pipe-like ceramic filters arranged in parallel and having plural passages therein, plural end plates equal in number to the number of ceramic filters and having plural through-holes into which the ceramic filters are inserted, plural supports placed between the end plates for supporting the end plates in a fixed manner, and packings placed between the end plates and the ceramic filters in clearances defined between the end plates and the ceramic filters so that the packings cover portions of end surfaces of the ceramic filters and provide a seal between the through-holes of the end plates and the ceramic filters, the through-holes having inner diameters greater than corresponding outer diameters of the ceramic filters;
• means for connecting the container with the filter casing so that the liquid stored in the container can be supplied into the filter casing;
• plural packing pressure plates for fixing the casing to the end plates, the pressure plates having plural holes at positions corresponding to the through-holes to the end plates and applying a pushing force onto the packings so as to substantially completely seal the filters, the pressure plates having holes communicating with outer sides of the filters;
• a back washing device attached to the filter casing which includes a hydraulic pressure device having a piston movable in a cylinder so that the filter can be back washed with filtrate moved by the piston when the hydraulic pressure device is actuated, and
• the piston being designed to move back to its original position after the back washing.