Primary sedimentation separates the readily settleable and floatable
solids from the wastewater for subsequent wastewater treatment.
Description
of Process
 |
Covered Primary Sedimentation Tanks |
Suspended particles may be classified as granular or flocculent.
Granular particles (sand and silt) settle at a constant velocity,
with no change in size, shape, or weight. Ideally, most such
particles are removed in upstream grit chambers. Flocculent
particles (organic matter, flocs formed by coagulants, or biological
growths) tend to cluster during settling, with attendant changes
in size, shape, and relative density. The clusters ordinarily
settle more rapidly than their individual particles.
Settleable solids, including portions of the granular and
flocculent material, settle under quiescent conditions within
a reasonable time.
Removal of floatables, including grease and scum, helps protect
downstream plant unit processes, reduces the pollutants discharged,
and improves the aesthetics of the plant effluent.