Spiral Blade Clarifiers

Settled sludge is rapidly collected continuously along the spiral rake blade pushing it towards the center with one or two passes of the rake arm.

On larger units (>100’ diameter multiple spiral blade rakes will the used.  Depending on sludge volume to be removed, 2 stub arms may be added also to keep the sludge hopper full (minimizing “rat holing”).

Spiral Blade Design

The spiral scraper blade has a constant attack angle of 30 to 35 degrees and generally increases in depth towards the center of the clarifier.

ADVANTAGES:

1.  Nothing to “plug up” under water.
   2.    Regardless of solids loading settled sludge will be transported to the settled sludge
   pit, and/or rotating sludge manifold.
   3.    The settled sludge transport time is significantly decreased over the segmented
          blade design. Many consider the spiral blade clarifier to be a rapid solids removal
          clarifier.

DISADVANTAGES:

1.  Increased capital costs.
   2.    Increased installation costs.
   3.    Larger clarifiers (>120’) will require multiple spiral blades.

VARIATIONS:

1.  Change the attack angle of the blade to the radius.
   2.    Add two half radius arms to aid in solids transport near the clarifier center.
   3.    Dual slope bottom (steeper near the center) to decrease the solids inventory in the
   bottom of the clarifier.