A system for the automatic measurement of the settling rate (Vsed) and of the volume of settled sludge (Vf) present in purifying treatments, comprising: a device for drawing and sending a predefined quantity of sludge to be treated from and to a containment body which extends along a substantially vertical axis, an image acquisition device, configured to acquire a plurality of digital images of said containment body containing said sludge to be treated at a respective plurality of moments in time (t1, t2, t3) after the sending of said sludge to be treated to said containment body, said image acquisition device comprising a video camera device adapted to acquire said digital images of said containment body containing said sludge to be treated in said moments in time (t1, t2, t3), and a processing device, configured to: - extract at least two columns of pixels from each one of said digital images of said containment body containing the sludge to be treated, - identify a variation in light intensity of said pixels, for each one of said at least two extracted columns of pixels, in order to detect an interface point between the settled sludge and the liquid fraction of the sludge along the respective column of pixels, characterized in that the processing device is also configured to: - determine an average value of a level of said settled sludge inside said containment body, on the basis of said interface points detected along said at least two columns of pixels, at each one of said moments in time (t1, t2, t3), and - determine a settling rate (Vsed) and a volume of settled sludge (Vf) at a predetermined moment in time of said plurality of moments in time (t1, t2, t3), using known calculation formulas and on the basis of said average values determined at said plurality of moments in time (t1, t2, t3). a device for drawing and sending a predefined quantity of sludge to be treated from and to a containment body which extends along a substantially vertical axis, an image acquisition device, configured to acquire a plurality of digital images of said containment body containing said sludge to be treated at a respective plurality of moments in time (t1, t2, t3) after the sending of said sludge to be treated to said containment body, said image acquisition device comprising a video camera device adapted to acquire said digital images of said containment body containing said sludge to be treated in said moments in time (t1, t2, t3), and a processing device, configured to: - extract at least two columns of pixels from each one of said digital images of said containment body containing the sludge to be treated, - identify a variation in light intensity of said pixels, for each one of said at least two extracted columns of pixels, in order to detect an interface point between the settled sludge and the liquid fraction of the sludge along the respective column of pixels, characterized in that the processing device is also configured to: - determine an average value of a level of said settled sludge inside said containment body, on the basis of said interface points detected along said at least two columns of pixels, at each one of said moments in time (t1, t2, t3), and - determine a settling rate (Vsed) and a volume of settled sludge (Vf) at a predetermined moment in time of said plurality of moments in time (t1, t2, t3), using known calculation formulas and on the basis of said average values determined at said plurality of moments in time (t1, t2, t3). - extract at least two columns of pixels from each one of said digital images of said containment body containing the sludge to be treated, - identify a variation in light intensity of said pixels, for each one of said at least two extracted columns of pixels, in order to detect an interface point between the settled sludge and the liquid fraction of the sludge along the respective column of pixels, characterized in that the processing device is also configured to: - determine an average value of a level of said settled sludge inside said containment body, on the basis of said interface points detected along said at least two columns of pixels, at each one of said moments in time (t1, t2, t3), and - determine a settling rate (Vsed) and a volume of settled sludge (Vf) at a predetermined moment in time of said plurality of moments in time (t1, t2, t3), using known calculation formulas and on the basis of said average values determined at said plurality of moments in time (t1, t2, t3). - determine an average value of a level of said settled sludge inside said containment body, on the basis of said interface points detected along said at least two columns of pixels, at each one of said moments in time (t1, t2, t3), and - determine a settling rate (Vsed) and a volume of settled sludge (Vf) at a predetermined moment in time of said plurality of moments in time (t1, t2, t3), using known calculation formulas and on the basis of said average values determined at said plurality of moments in time (t1, t2, t3).