Spiral Blade Design

DESCRIPTION: 

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.