A method for the phyto-depuration of zootechnical sewage, in particular from pigs, comprising the following steps: a) Collection of sewage; b) Separation of the liquid fraction of the sewage from the solid part by means for the mechanical separation, wherein said means is a helical separator; c) Sedimentation of said liquid fraction of the sewage; d) Oxidation of the liquid fraction of the sewage in the presence of effective micro-organisms; e) Collection of the liquid fraction of the sewage in a first charging tank; and from this point, f) At first, at least two subsequent passages of the liquid fraction of the sewage through vertical submerged flow phyto-depuration basins, each basin having an inlet side and an outlet side, from which respectively the liquid fraction of the sewage subjected to phyto-depuration enters and exits; and subsequently g) At least two subsequent passages of the liquid fraction of the sewage through horizontal submerged flow phyto-depuration basins, each horizontal submerged flow phyto-depuration basin having an inlet side and an outlet side, from which the liquid fraction of the sewage subjected to phyto-depuration respectively enters and exits; wherein said effective micro-organisms comprise Lactobacilli, Yeasts, Photosynthetic bacteria, Actinomycetes, fermentative fungi; wherein said vertical submerged flow phyto-depuration basins and said horizontal submerged flow phyto-depuration basins contain a filling medium (50, 53), comprising gravels (51, 54) and/or sand having different granulometries, and macrophyte aquatic plants; wherein said filling medium of the vertical submerged flow phyto-depuration basins is constituted by: round river gravel having granulometry comprised between 16 and 32 mm and forming a first filling layer on the bottom of the basins, fluvial sand having granulometry comprised between 0 and 3 mm forming an intermediate filling layer, round river gravel having granulometry comprised between 8 and 16 mm and forming a basin filling surface layer; wherein said filling medium of the horizontal submerged flow phyto-depuration basins is formed by: round river gravel having granulometry of about 3 cm and round river gravel having granulometry comprised between 0.8 and 1.6 cm, and wherein the gravel having granulometry of about 3cm occupies a first region near the inlet side and a second region near the outlet side of the horizontal submerged flow phyto-depuration basins whereas the gravel having granulometry comprised between 0.8 and 1.6 cm occupies a third region interposed between the other two regions. a) Collection of sewage; b) Separation of the liquid fraction of the sewage from the solid part by means for the mechanical separation, wherein said means is a helical separator; c) Sedimentation of said liquid fraction of the sewage; d) Oxidation of the liquid fraction of the sewage in the presence of effective micro-organisms; e) Collection of the liquid fraction of the sewage in a first charging tank; and from this point, f) At first, at least two subsequent passages of the liquid fraction of the sewage through vertical submerged flow phyto-depuration basins, each basin having an inlet side and an outlet side, from which respectively the liquid fraction of the sewage subjected to phyto-depuration enters and exits; and subsequently g) At least two subsequent passages of the liquid fraction of the sewage through horizontal submerged flow phyto-depuration basins, each horizontal submerged flow phyto-depuration basin having an inlet side and an outlet side, from which the liquid fraction of the sewage subjected to phyto-depuration respectively enters and exits; wherein said effective micro-organisms comprise Lactobacilli, Yeasts, Photosynthetic bacteria, Actinomycetes, fermentative fungi; wherein said vertical submerged flow phyto-depuration basins and said horizontal submerged flow phyto-depuration basins contain a filling medium (50, 53), comprising gravels (51, 54) and/or sand having different granulometries, and macrophyte aquatic plants; wherein said filling medium of the vertical submerged flow phyto-depuration basins is constituted by: round river gravel having granulometry comprised between 16 and 32 mm and forming a first filling layer on the bottom of the basins, fluvial sand having granulometry comprised between 0 and 3 mm forming an intermediate filling layer, round river gravel having granulometry comprised between 8 and 16 mm and forming a basin filling surface layer; wherein said filling medium of the horizontal submerged flow phyto-depuration basins is formed by: round river gravel having granulometry of about 3 cm and round river gravel having granulometry comprised between 0.8 and 1.6 cm, and wherein the gravel having granulometry of about 3cm occupies a first region near the inlet side and a second region near the outlet side of the horizontal submerged flow phyto-depuration basins whereas the gravel having granulometry comprised between 0.8 and 1.6 cm occupies a third region interposed between the other two regions.