A feedwell assembly for a thickener/clarifier includes a feedwell body, at least one infeed conduit connected at a downstream end to the body, and at least one spin or rotation inducement element disposed as part of the infeed conduit for imparting rotation or spin to a slurry stream fed to the feedwell body via the infeed conduit. The spin or rotation inducement element may be a fixed and rigid structural member such as a vane or baffle, or include actively operated elements. Multiple such spin or rotation inducement elements may be provided in various locations in or adjacent the infeed conduit.