Apparatus for treating at least one fluid, at least in one section comprising a horizontal ferrule; - at least a first particulate material filling a volume emerging on either side of the ferrule section in which the fluid flows in a horizontal direction, the first particulate material being maintained in the volume through two perforated grids placed at the 2 ends of the ferrule section; - one or a plurality of loading ports located on the upper part of the ferrule providing access to the volume, - at least one deflector comprising 2 volumes (V3a) and (V3b) having four side faces (S3-c), (S3-d), (S3-e) and (S3-f) contiguous to both said perforated gratings located at both ends of the section of the ferrule, and defined by the inner casing of the body and secondly by the lower surfaces (S3a) and (S3b) forming with a horizontal plane an angle (α) greater than the angle of repose of the first particulate material, - at least one volume connecting volumes (V3a) and (V3b) of the deflector made up of the following: -- a flexible and sealed membrane that is: --- contiguous to volumes (V3a) and (V3b) of the deflector along the entire length of the section of the ferrule, and --- attached laterally to the vertical walls of volumes 3-a and 3-b, and --- supported by the first particulate material; -- a second particulate material having a density greater than the density of the first particulate material filling the volume; the second particulate material being in the space formed by the membrane and the inner envelope of the ferrule, volumes (V3a) (V3b) and being located in the upper half of the horizontal section of the horizontal ferrule. - at least a first particulate material filling a volume emerging on either side of the ferrule section in which the fluid flows in a horizontal direction, the first particulate material being maintained in the volume through two perforated grids placed at the 2 ends of the ferrule section; - one or a plurality of loading ports located on the upper part of the ferrule providing access to the volume, - at least one deflector comprising 2 volumes (V3a) and (V3b) having four side faces (S3-c), (S3-d), (S3-e) and (S3-f) contiguous to both said perforated gratings located at both ends of the section of the ferrule, and defined by the inner casing of the body and secondly by the lower surfaces (S3a) and (S3b) forming with a horizontal plane an angle (α) greater than the angle of repose of the first particulate material, - at least one volume connecting volumes (V3a) and (V3b) of the deflector made up of the following: -- a flexible and sealed membrane that is: --- contiguous to volumes (V3a) and (V3b) of the deflector along the entire length of the section of the ferrule, and --- attached laterally to the vertical walls of volumes 3-a and 3-b, and --- supported by the first particulate material; -- a second particulate material having a density greater than the density of the first particulate material filling the volume; the second particulate material being in the space formed by the membrane and the inner envelope of the ferrule, volumes (V3a) (V3b) and being located in the upper half of the horizontal section of the horizontal ferrule. -- a flexible and sealed membrane that is: --- contiguous to volumes (V3a) and (V3b) of the deflector along the entire length of the section of the ferrule, and --- attached laterally to the vertical walls of volumes 3-a and 3-b, and --- supported by the first particulate material; -- a second particulate material having a density greater than the density of the first particulate material filling the volume;