Types of Activated Sludge Processes


Plug Flow - wastewater is routed through a series of channels constructed in the aeration basin.

Complete Mix - wastewater may be immediately mixed throughout the entire contents of the aeration basin (mixed with oxygen and bacteria).

Contact Stabilization -

Extended Aeration -

Other Modifications (less common)

Oxidation ditch - similar to plug flow but uses a circulator aeration basin.

Step feed - microbes gradually feed organics in a step feed mode at multiple points along the tank plug flow.

Tapered aeration - air flow rate to the aeration basin may be tapered along the length of the basin.

Kraus Process - The anaerobically digested sludge and digester supernatant may be added to the return sludge, thus improving settling of the floc.

Denser anaerobically digested sludge settles rapidly and is added to the lighter secondary sludge to add weight and improve settling.