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.


  1.  Simple design.
  2.  Nothing to “plug up” under water.
  3.  Regardless of solids loading settled sludge will be transported to the
    sludge pit.


  1.  Sludge transport from the outside may take many hours, especially on
    large (>100’ diameter) units, leading to the potential of septicity.
  2. 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.


  1.  Change to the angle of the blade to the radius.
  2. Increase the depth of all the blades.
  3. Increase the depth of each blade as it gets nearer to the center and
    settle sludge sump.
  4. Add two more half radius arms to aid in solids transport for clarifiers
           larger than 100’ diameter.

Segmented Blade Design


segmented blade design

Settled sludge is directed to the center by multiple blades pushing the sludge to the center over multiple passes of the rake arm.

raking blades

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