The Sewage Aerated Tank (SAT) is, as the name indicates, a holding tank for sewage.
However, unlike a regular holding tank, this tank is being aerated through air diffusers installed in the tank and an air blower, usually outside the tank, provides the airflow into the tank.
A control panel must be installed to indicate the levels as the tank is filled up, and a light to indicate that it is time to have the tank pumped out.
This panel also have a high level warning with audible & visual alarm.
The reasons for aeration is that by infusing air (oxygen) into the liquid it lowers the Biochemical Oxygen Demand (BOD) which is the amount of oxygen required to break down the nutrients in the waste water. The oxygen also prevents the sewage from going septic (decompose) and therefore no noxious gasses or odours are produced.
Aeration, to a certain degree keeps the sludge from settling.

CLICK on the pictures below for a larger view.
The drawing show a Aerated Sewage Holding Tanks.