Abstract: Suspended solid particles are separated from a fluid flow by dividing the flow into partial fluid flows in flow channels having an upper filter surface travelling upstreams and a lower filter surface travelling downstreams, controlling the flow velocity in the channels such that the flow is turbulent but at the same time low enough to allow for sedimentation of the suspended material to form a clear top layer off so that more than half of the liquid fed to the channel is filtered through the upper filter surface, suctioning less than half of the liquid fed into the channel through a sediment formed on the lower filter surface, and finally removing the sediment from the lower surface.