Abstract: A system for treating wastewater and improving the quality of wastewater effluent by preventing solids from being discharged in the effluent is disclosed. Wastewater having a concentration of waste solids flows into a wastewater collection container through a waste-water inlet and solids are allowed to distribute into a lower horizontal sludge layer and an upper horizontal scum layer with a horizontal layer of liquid therebetween. A substantially upstanding elongate tube is immersed in the wastewater within the container and the interior of the tube is exposed to the horizontal layer of liquid through a plurality of inclined slots in the tube. Liquid flows from the horizontal liquid layer through the slots into the interior of the tube and thereafter through a liquid effluent outlet of the container. Preferably, the slots extend vertically along a majority of the depth of the wastewater in the container.