Page 25 - Simplified Wastewater Treatment Fundementals_Preliminary Treatment.exe
P. 25
Preliminary Treatment
Grit
Grit is removed by slowing wastewater velocity to less than 2 feet per second. Grit
removal is further assisted by aerating the wastewater. Aeration lowers the specific
gravity of the wastewater increasing the ability for fine grit and sand to rapidly settle.
Two general types of grit removal are Shallow Clarifier and Tea Cup.
Shallow Clarifier grit removal slows the wastewater velocity, providing a short
detention time allowing the grit and sand to settle. A collector drive sweeps the
bottom of the clarifier pushing the settled grit and sand into a center sump where it is
pumped as a slurry to the grit separator or classifier.
The Tea Cup shaped grit tank provides a centrifugal vortex to help separate grit, from
which the settled grit and sand is removed as a slurry and pumped to a classifier.
