Abstract: A system for purifying dredging water comprises a mixing compartment and an agitating means that mixes water with a coagulating agent. A discharge means collects the coagulated sediment and delivers it to a centrifugal sediment water separating means. An outlet at the top of the fluid container collects the purified water. Recirculation means connects the decanter with the container such that the water extracted from the sludge is returned to the mixing compartment. A conveyor means collects and transports decanted sediment. Preferably, baffles partially separate the container into compartments configured to promote mixing and sedimentation. The conveyor means may comprise a solidification reaction acceleration agent injector to mix this agent with the sediment to further dehydrate and solidify it.