An apparatus for separating materials suspended in a fluid stream; the apparatus comprising: a support structure; a separator unit (202, 204, 206) rotatably mounted on the support structure; means for rotating the separator unit on the support structure; the separator unit having a longitudinal axis of rotation extending through a longitudinal tube disposed centrally within the separator unit; the longitudinal tube being connected or connectable to a pressurised source of fluid requiring separation, the longitudinal tube having one or more openings for receiving fluid under pressure from the said source and one or more lateral openings for introducing the fluid into the separator unit; wherein the separator unit comprises, in addition to the longitudinal tube: (aa) a centrifugal separation chamber for separating suspended material from the fluid stream; (bb) a collector for collecting either (i) suspended material separated from the fluid stream; or (ii) fluid from which at least some of the suspended material has been removed; and (cc) an array of vanes or nozzles and means for directing the fluid stream or fluid output from the separator unit over the vanes or through the nozzles to form a turbine which can drive rotation of the separator unit; characterised in that the collector is disposed radially outwardly of the separator unit and is associated with the centrifugal separation chamber; and in that the apparatus further comprises (dd) first and second outlets through which separated components of the fluid stream can pass, wherein suspended material separated from the fluid stream can pass out through one outlet and the fluid stream from which suspended material has been removed can pass out through the other outlet. a support structure; a separator unit (202, 204, 206) rotatably mounted on the support structure; means for rotating the separator unit on the support structure; the separator unit having a longitudinal axis of rotation extending through a longitudinal tube disposed centrally within the separator unit; the longitudinal tube being connected or connectable to a pressurised source of fluid requiring separation, the longitudinal tube having one or more openings for receiving fluid under pressure from the said source and one or more lateral openings for introducing the fluid into the separator unit; wherein the separator unit comprises, in addition to the longitudinal tube: (aa) a centrifugal separation chamber for separating suspended material from the fluid stream; (bb) a collector for collecting either (i) suspended material separated from the fluid stream; or (ii) fluid from which at least some of the suspended material has been removed; and (cc) an array of vanes or nozzles and means for directing the fluid stream or fluid output from the separator unit over the vanes or through the nozzles to form a turbine which can drive rotation of the separator unit; characterised in that the collector is disposed radially outwardly of the separator unit and is associated with the centrifugal separation chamber; and in that the apparatus further comprises (dd) first and second outlets through which separated components of the fluid stream can pass, wherein suspended material separated from the fluid stream can pass out through one outlet and the fluid stream from which suspended material has been removed can pass out through the other outlet. (aa) a centrifugal separation chamber for separating suspended material from the fluid stream; (bb) a collector for collecting either (i) suspended material separated from the fluid stream; or (ii) fluid from which at least some of the suspended material has been removed; and (cc) an array of vanes or nozzles and means for directing the fluid stream or fluid output from the separator unit over the vanes or through the nozzles to form a turbine which can drive rotation of the separator unit; characterised in that the collector is disposed radially outwardly of the separator unit and is associated with the centrifugal separation chamber; and in that the apparatus further comprises (dd) first and second outlets through which separated components of the fluid stream can pass, wherein suspended material separated from the fluid stream can pass out through one outlet and the fluid stream from which suspended material has been removed can pass out through the other outlet.