Abstract: A solids-liquid separator comprises a basin in which liquid containing solids is introduced from an inlet port of the basin in a direction tangential to the side wall of the basin so as to produce a swirling flow of the liquid. The swirling flow also generates a secondary flow, and both flows promote the floating of floatable solids on the surface and the settling of settlable solids on the bottom. The solids floating on the surface are discharged by the overflowing liquid and the settled solids are discharged through a discharge pipe opening at the bottom of the basin. The liquid from which solids are separated is discharged outwardly from an outflow opening of the basin independent from the discharge of solids. The inlet port and outflow opening are separated circumferentially with respect to the flowing direction so that the circumferential separation thereof subtends at least 180 degrees about the center of the basin.