Improved sludge dewatering process assisted by flocculating reactant and plant for the implementation of such a process

Method for dewatering sludge, comprising injecting a flocculating reagent (3) into the sludge (2) and dewatering the sludge. The injection of flocculating reagent occurs during or upstream a preliminary step (7) that consists of mixing the sludge in a mixer (4) comprising a cylindrical chamber (4a) provided with blades (4c) rotatably mounted on a shaft (4b). The blades rotate about an axis at a speed between 500 and 4000 rpm to destructure the sludge and reduce its viscosity. The sludge is discharged from the mixer to the dewatering step (1) via a network (11) including a pump (12). The method further comprises a step of depressurising the mixer and network resulting in the lysis of the sludge by cavitation, said depressurisation step being performed for a duration of at least 0.1 seconds and causing cavitation of the pump. The invention provides for reduced consumption of the flocculating reagent while improving dryness of the sludge after the dewatering step.