Abstract: In a sludge thickener water/wastewater treatment system, sludge solids are recirculated with a mixer positioned in the influent column or offset from the center column and within the stilling well, in order to produce essentially constant sludge solids concentration in the sludge withdrawn from the thickener. This solves the problem of thickeners producing inconsistent underflow solids concentration and often exhibiting problems with binding of rake arms due to sometimes very high sludge concentrations. Also, dewatering steps that follow thickening typically require a relatively constant solids concentration for efficient operation.

Abstract: A clarifier in a wastewater treatment plant is provided with a submerged launder for effluent, the launder preferably having an integral density current baffle and scum baffle. In one embodiment an existing launder is modified, with its vertical leg replaced with a sloped plate defining launder conduit triangular in cross section, and with a sloping portion of the plate forming a density current baffle. Openings in the sloped plate permit entry of effluent liquid, and the liquid level in a clarifier is controlled without an overflow weir plate. In another form submerged pipe with entry holes serves as the launder, with support brackets integral with a density current baffle. A third form of the launder is a box formed beneath the shelf of an existing internal launder in the clarifier, again with a density current baffle extending down from the box. In another version an existing launder is covered and sealed, and holes are drilled through the launder wall to admit effluent.

Abstract: A clarifier in a wastewater treatment plant is provided with a submerged launder for effluent, the launder preferably having an integral density current baffle and scum baffle. In one embodiment an existing launder is modified, with its vertical leg replaced with a sloped plate defining launder conduit triangular in cross section, and with a sloping portion of the plate forming a density current baffle. Openings in the sloped plate permit entry of effluent liquid, and the liquid level in a clarifier is controlled without an overflow weir plate. In another form submerged pipe with entry holes serves as the launder, with support brackets integral with a density current baffle. A third form of the launder is a box formed beneath the shelf of an existing internal launder in the clarifier, again with a density current baffle extending down from the box. In another version an existing launder is covered and sealed, and holes are drilled through the launder wall to admit effluent.

Abstract: In a sludge thickener water/wastewater treatment system, sludge solids are recirculated with a mixer positioned in the influent column or offset from the center column and within the stilling well, in order to produce essentially constant sludge solids concentration in the sludge withdrawn from the thickener. This solves the problem of thickeners producing inconsistent underflow solids concentration and often exhibiting problems with binding of rake arms due to sometimes very high sludge concentrations. Also, dewatering steps that follow thickening typically require a relatively constant solids concentration for efficient operation.

Abstract: In a wastewater treatment system, a suction duct clarifier is converted to a suction pipe clarifier without penetrating existing concrete at the base of the tank. An elevated sludge collection box is added, positioned on the center column to rotate with rake arms, and a series of sludge riser pipes extend from the rake arms up into the sludge collection box for sludge delivery by hydraulic pressure differential. A sludge discharge downpipe is provided within the center/influent column for delivery of sludge from the collection box, and at the bottom of this pipe, above the tank floor, the discharge pipe exits through an opening in the center/influent column. At the outside of this opening is a sludge transfer box that receives sludge exiting the discharge pipe and conveys it down through the existing floor opening and to the existing under-floor RAS return pipe.

Abstract: In a wastewater treatment system, a suction duct clarifier is converted to a suction pipe clarifier without penetrating existing concrete at the base of the tank. An elevated sludge collection box is added, positioned on the center column to rotate with rake arms, and a series of sludge riser pipes extend from the rake arms up into the sludge collection box for sludge delivery by hydraulic pressure differential. A sludge discharge downpipe is provided within the center/influent column for delivery of sludge from the collection box, and at the bottom of this pipe, above the tank floor, the discharge pipe exits through an opening in the center/influent column. At the outside of this opening is a sludge transfer box that receives sludge exiting the discharge pipe and conveys it down through the existing floor opening and to the existing under-floor RAS return pipe.