The present invention finds application in systems for dewatering a stream of slurry, comprising a first separator, for separating object above a first size from a stream of slurry, to produce a stream of primary treated slurry, a second separator for receiving the stream of primary treated slurry and for separating objects above a second size from the stream primary treated slurry to produce a stream of secondary treated slurry, the second size being smaller than the first size and, optionally, a third separator for receiving the stream of secondary treated slurry and for separating objects above a third size from the stream of secondary treated slurry, the third size being smaller than the first and second sizes. In a first aspect, the first separator preferably comprises a plurality of sieve mat supports alternately connected to a main support frame section and a movable support frame section so that the flexible sieve mat can be agitated by the movable support frame section, a collector being provided for collecting the primary treated slurry passing through the flexible sieve mat. A duct for feeding water having solid suspended therein in the third separator comprises an inlet portion for receiving a flow of water having a solid suspended therein, the inlet portion defining an inlet flow direction and having an inlet maximum width in a direction normal to the inlet flow direction, an outlet portion for delivering a flow of water having the solid suspended therein, the outlet portion defining an outlet flow direction and having an outlet maximum width in a direction normal to the outlet flow direction, the outlet maximum width being greater than the inlet maximum width, and a duct section connecting the inlet portion and the outlet portion. A gas feed is provided within the inlet portion or duct section, for allowing gas to be fed into the flow of water having solid suspended therein, to lighten the weight of the fluid In a fourth, optional step, water is removed from solid which has been separated from the slurry by being fed into a vessel which has a first section and a second section which are separated by a filter screen, a pump assembly being provided for removing fluid from the second section and for reducing the pressure in the second section relative to the first section.