A nozzle is provided for a header conduit. The nozzle includes an inlet that is resistant to clogs caused by flat materials covering the inlet. The inlet generally includes multiple pathways to an elongated passageway through which waste liquid and sludge (waste) are guided and enter the header conduit. In one embodiment, the elongated passageway is oriented to guide the waste along a path that is tangential to at least the inner surface of the header conduit which such incoming waste first contacts. When the conduit has an inner surface of circular cross-section, the passageway may optionally be elongated enough that the incoming waste enters the header conduit along a path tangential to the circular surface. To better assure axial flow of the waste in the conduit to an outlet, in one embodiment the passageway provides both the tangential flow and is at an acute angle to the longitudinal axis of the conduit. The incoming waste is thereby provided with an axial component. In this manner, the passageway assures that the energy and momentum of the incoming waste is helical in direction. The waste previously admitted into the header conduit is urged by the newly entering waste to continue to flow helically in the conduit. The passageways are provided at spaced intervals along the length of the conduit to collect sludge from a wide area of the bottom of the basin. Because of the tangential orientation of each of the passageways and the resulting initial tangential flow of the incoming waste, the waste incoming from each of those multiple passageways reinforces the existing helical flow of waste in the conduit.

A rake classifier assembly including an elongate rake member reciprocally movable up an inclined surface to move solid material thereup is described. A pair of guide arrangements are provided each with a pivotally mounted elongate guide track along which respective wheels connected to the elongate rake member are movable. The guide tracks are selectively movable between first and second alignments, with the guide tracks extending substantially parallel to the inclined surface in the first alignment such that the elongate rake member can be moved up the inclined surface moving solid materials thereup, and in the second alignment the guide tracks diverge downwardly away from the inclined surface, such that as the elongate rake member is moved downwardly the elongate rake member also moves away from the inclined surface.

Rapid removal of settled solids in secondary clarifiers is critical in sewage treatment plants having nutrient removal permits, especially phosphorus, to prevent solids from surfacing after going aerobic and releasing phosphorus. Release of phosphorus could impact the plant's permit limit. This is addressed by the described design of rake blade flights and squeegees that quickly move solids on the clarifier floor to the sludge pickup tubes, usually in one revolution. In a preferred form the blade flights are curved and may be spiral in shape, causing gathered sludge to advance outwardly toward the pickup tube at each flight, usually in one revolution. Previous blade flights included angled linear sections that progressively move the sludge in incremental movements with each revolution of the clarifier mechanism.