

Raking blades turned at an approximately 45-degree angle are supported from two structural support arms. The settled sludge is plowed inward from one blade to another until it is deposited into a sludge pit.
ADVANTAGES:
- Simple design.
- Nothing to “plug up” under water.
- Regardless of solids loading settled sludge will be transported to the
sludge pit.
DISADVANTAGES:
- Sludge transport from the outside may take many hours, especially on
large (>100’ diameter) units, leading to the potential of septicity.
- Under high flows and/or high solids loading conditions, the raking
mechanism may not be able to transport solids as quickly as they are
settling, causing a buildup of solids in the basin. The deeper sludge
blanket can lead to scouring and short circuiting.
VARIATIONS:
- Change to the angle of the blade to the radius.
- Increase the depth of all the blades.
- Increase the depth of each blade as it gets nearer to the center and
settle sludge sump.
- Add two more half radius arms to aid in solids transport for clarifiers
larger than 100’ diameter.