Abstract: The invention concerns a system for putting back in suspension a sediment that has, by deposition, formed a layer (3) on the bottom (1b) of a tank (1) with a floating roof (2) containing crude oil, said device comprising: —at least one pipe (11) for sucking out and re-injecting the oil contained in said tank (1); —a pump (7) for providing circulation of the oil in said pipe (11); —a filtration device (9) intended to eliminate the inorganic elements contained in the crude oil; and —injection lances (5) each comprising at least one injection orifice (8a, 8b, 8c) sending a jet in the direction of the layer of sediment; the filtration device (9) comprises at least a first (15a) and a second filter (15b) mounted in parallel and connected to the suction and re-injection pipe (11) by means of a switching device (16, 17) for directing the flow of oil selectively to the first (15a) or second filter (15b). The invention also concerns a method of putting a layer of sediment back in suspension.