Abstract: In a vortex separator for use in at least partially removing suspended solids from a liquid containing suspended solids, the inlet port (8), whereby the liquid is introduced tangentially into a vortex chamber, has a substantially rectangular cross-section at a curved internal wall surface (2) of the chamber and the long axis of the rectangle is preferably aligned substantially parallel with the longitudinal axis of the curved internal wall surface (2). The inlet port (8) preferably has a short side dimension which is not substantially greater than the thickness of the boundary layer of the liquid in the vortex chamber in use, so that the introduced liquid is substantially maintained in the boundary layer of the liquid at the internal wall surface.