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.

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.

A shearing device, an arrangement and uses thereof. The shearing device is connectable to a drive assembly of the arrangement for separating solids from liquid. The shearing device includes an attachment arrangement arranged in a first end of the device for connecting the shearing device to the drive assembly. The shearing device further includes a shearing arrangement arranged to define a shearing element that is angled with the lengthwise direction of the device and intervals therebetween. The shearing device has a proximal portion closer to the first end and a distal portion closer to a second end of the device opposite to the first end. The average width of the shearing elements arranged in the distal portion is greater than average width of the shearing elements arranged in the proximal portion.

A shearing device, an arrangement and uses thereof. The shearing device is connectable to a drive assembly of the arrangement for separating solids from liquid. The shearing device includes an attachment arrangement arranged in a first end of the device for connecting the shearing device to the drive assembly. The shearing device further includes a shearing arrangement arranged to define a shearing element that is angled with the lengthwise direction of the device and intervals therebetween. The shearing device has a proximal portion closer to the first end and a distal portion closer to a second end of the device opposite to the first end. The average width of the shearing elements arranged in the distal portion is greater than average width of the shearing elements arranged in the proximal portion.

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.

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.

A system for sludge removal in a circular settling tank having a side wall (106) comprises a rotatable drive ring (130) adapted to be interconnected to a scraper arm provided with scraper blades, wherein the drive ring having a plurality of engagement surfaces (134) A traction assembly (140) is fixedly attached to the side wall and comprises a drive wheel (142). By providing a drive wheel with a plurality of engagement rolls (148) adapted to engage the engagement surfaces of the drive ring during rotation of the drive wheel, the drive ring can be rotated essentially without exerting any radial forces on the drive ring.

A system for sludge removal in a circular settling tank having a side wall (106) comprises a rotatable drive ring (130) adapted to be interconnected to a scraper arm provided with scraper blades, wherein the drive ring having a plurality of engagement surfaces (134) A traction assembly (140) is fixedly attached to the side wall and comprises a drive wheel (142). By providing a drive wheel with a plurality of engagement rolls (148) adapted to engage the engagement surfaces of the drive ring during rotation of the drive wheel, the drive ring can be rotated essentially without exerting any radial forces on the drive ring.

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.

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.