Abstract: A system for treating effluents such a sewage includes a mixing chamber and a separation chamber. In the mixing chamber various chemical additives are introduced in to the effluent and thoroughly mixed to act as a flocculent to extract the solid materials in the separating chamber. In the separating chamber the mixed materials are caused to flow longitudinally in a laminar flow condition to allow stratification of the liquid from the solid materials. In the mixing chamber there is provided a plurality of transverse baffles spaced longitudinally and rotated angularly relatively to a longitudinal axis of the tube. Each baffle has tapered holes to act as a venturi to mix the materials. In the separation chamber there is provided an auger flight rotating slowly which has holes through the flight thus generating a laminar flow to provide improved separation of the solid and the liquid components.