A treatment device (10, 20, 30, 40, 50) for turning an effluent composed of liquid and of solid particles into a treated effluent, characterised in that it comprises: • a primary filtration device filtering by gravity separation onto a rotating canvas, said device having an inlet intended to receive the effluent to be treated and a first and a second outlet, the filtration device being intended to separate the effluent into a first and a second flow, the first flow comprising the treated effluent, the second flow comprising sludge comprising solid particles of the effluent to be treated, the first flow exiting the filtration device via the first outlet and the second flow exiting the filtration device via the second outlet; • at least one recirculation device intended to recirculate at least part of the sludge of the second flow, which part is intended to be directed towards a treatment unit, towards the inlet of the filtration device, said second outlet being connected to at least one recirculation device, in that the filtration device comprises a first filter having a mesh with a first diameter intended to retain, on the first filter, the solid particles of the effluent to be treated with a diameter that is greater than the first diameter, and in that the first filter is configured so as to form, in combination with the solid particles of the effluent to be treated that are retained on the first filter, a second filter having a porosity corresponding to a cut-off threshold that is less than the first diameter, and in that it comprises a separation device configured to separate the particles of the sludge of the effluent to be treated from the second flow as a function of their size or their density, so as to recirculate the particles of the effluent to be treated that are bigger than a predefined size or a density towards the inlet of the filtration device. • a primary filtration device filtering by gravity separation onto a rotating canvas, said device having an inlet intended to receive the effluent to be treated and a first and a second outlet, the filtration device being intended to separate the effluent into a first and a second flow, the first flow comprising the treated effluent, the second flow comprising sludge comprising solid particles of the effluent to be treated, the first flow exiting the filtration device via the first outlet and the second flow exiting the filtration device via the second outlet; • at least one recirculation device intended to recirculate at least part of the sludge of the second flow, which part is intended to be directed towards a treatment unit, towards the inlet of the filtration device, said second outlet being connected to at least one recirculation device, in that the filtration device comprises a first filter having a mesh with a first diameter intended to retain, on the first filter, the solid particles of the effluent to be treated with a diameter that is greater than the first diameter, and in that the first filter is configured so as to form, in combination with the solid particles of the effluent to be treated that are retained on the first filter, a second filter having a porosity corresponding to a cut-off threshold that is less than the first diameter,