Filtration device

A filtration device comprising:

• a casing having a fluid inlet and a fluid outlet, and including, inside thereof, first and second raw fluid chambers communicating with the fluid inlet for storing fluid before being filtered, and a filtered-fluid chamber communicating with the fluid outlet for storing filtered fluid;
• a plurality of filter elements removably installed in parallel inside the casing, each of the plurality of filter elements having a filter medium and formed into a box or tube shape, and two opposite faces which are open to the first and second raw fluid chambers, respectively, to receive fluid from the first and second raw fluid chambers through the two opposite faces and allow the fluid to pass through from inside toward the filtered-fluid chamber outside thereof so as to filter the fluid, and having a backwashing mechanism inside thereof;
• and
• a backwash fluid discharge pipe which discharges backwash fluid from the backwashing mechanism to the outside of the casing,
• wherein the second raw fluid chamber communicates with the fluid inlet via the inside of the each of the plurality of filter elements and the first raw fluid chamber,
• wherein the backwashing mechanism includes:
• a fixed pipe fixed to the inside of the each of the plurality of filter elements and connected to the backwash fluid discharge pipe;
• a movable pipe fitted to the outside of the fixed pipe and provided to be movable in an axial direction thereof;
• and
• at least one backwash head attached to the movable pipe and having an inflow inlet arranged to come into surface contact with the filter medium to allow fluid outside of the each of the plurality of filter elements to pass through the filter medium as backwash fluid and flow into the inflow inlet in order to backwash the filter medium, and
• wherein the fixed pipe and the movable pipe movably guide the backwash head and form a discharge passage for backwash fluid.