Process for treating silt to dry and clean it, involves sifting and/or filtering, submission to a first hydrocyclone separation stage to eliminate sand, a second hydrocyclone separation stage to separate the fines, and then dehydrating and cleaning the fines from the second separation stage The dehydration stage involves coagulating or flocculating the silt before decanting to obtain on the one hand dried mud and on the other water. The crude silt is diluted with the water from the dehydration stage before the process starts. The silt passes through a desalination stage before dehydration and the dehydrated silt is stabilized. Waste floated from the first separation stage is dehydrated separately. The granulometry of the silt after the first separation is analyzed and the cut point of the second separation is determined as a result. Installation for carrying out the above process, comprising a sieving and/or filtering unit (1), an abrasion cell (2), a first hydrocyclone (3), at least one floatation cell (4), at least one second hydrocyclone (5) in series, a fines cleaning unit (6) and at least one dehydration unit (7). A desalination unit (8) and a silt stabilization unit (9) can also be included. The installation is mobile.
