A plant for purifying slurry, comprising: - a homogenization tank, which contains slurry with bacteria, and wherein a homogenizer is mounted for homogenizing the slurry; - a first biological reactor, connected to the homogenization tank for receiving slurry, and inside of which first aeration means are mounted for supplying oxygen, in order to enable the bacteria to aerobically decompose the slurry; - a nitrate remover, for receiving slurry from the first biological reactor, for removing nitrogen from the slurry by means of an anaerobic action of the bacteria; - stirring means, mounted within the nitrate remover, for putting the slurry in contact with the bacteria; - a decanter, which receives the denitrified slurry, for decanting the slurry by separating said slurry into purified water and sludge; and - recirculation means, for recirculating sludge to the homogenization tank, and that comprise a first pumping device for pumping sludge from the decanter to the homogenization tank and a second pumping device for pumping sludge from the first biological reactor to the homogenization tank; the plant being characterized in that it additionally comprises a stratified basin for feeding slurry to the homogenization tank, and that comprises the following three layers: • a first layer, which is deeper down, made up of sludge; • a second layer, in the upper portion, comprising clean water and plant species, such as algae; and • a third layer, inserted between the first layer and the second layer, with a murky intermediate composition; wherein the plant additionally comprises pumping means for pumping the contents of the first layer and the third layer to the homogenization tank. - a homogenization tank, which contains slurry with bacteria, and wherein a homogenizer is mounted for homogenizing the slurry; - a first biological reactor, connected to the homogenization tank for receiving slurry, and inside of which first aeration means are mounted for supplying oxygen, in order to enable the bacteria to aerobically decompose the slurry; - a nitrate remover, for receiving slurry from the first biological reactor, for removing nitrogen from the slurry by means of an anaerobic action of the bacteria; - stirring means, mounted within the nitrate remover, for putting the slurry in contact with the bacteria; - a decanter, which receives the denitrified slurry, for decanting the slurry by separating said slurry into purified water and sludge; and - recirculation means, for recirculating sludge to the homogenization tank, and that comprise a first pumping device for pumping sludge from the decanter to the homogenization tank and a second pumping device for pumping sludge from the first biological reactor to the homogenization tank; the plant being characterized in that it additionally comprises a stratified basin for feeding slurry to the homogenization tank, and that comprises the following three layers: • a first layer, which is deeper down, made up of sludge; • a second layer, in the upper portion, comprising clean water and plant species, such as algae; and • a third layer, inserted between the first layer and the second layer, with a murky intermediate composition; wherein the plant additionally comprises pumping means for pumping the contents of the first layer and the third layer to the homogenization tank. • a first layer, which is deeper down, made up of sludge; • a second layer, in the upper portion, comprising clean water and plant species, such as algae; and • a third layer, inserted between the first layer and the second layer, with a murky intermediate composition;