Although industry has historically constructed larger and deeper circu
lar clarifiers-thickeners, municipal wastewater facility design practi
ce has been to utilize multiple small and shallow clarifiers. The latt
er practice has resulted in lower areal capacity and more complex faci
lities that are proving to be more difficult and costly to expand. The
capital costs of larger units with more reserve peak flow capacity ar
e equal or lower and plant operation is simplified.