4. Sedimentation phase
The treatment phase is followed by a 2-hour
sedimentation phase. Any solids contained
in the sewage as well as the activated slud-
ge settle on the bottom of the tank and a
clear water layer thus forms in the upper
area, while a sludge layer made up of
microorganisms forms on the bottom.
5. Extracting the clear water
(clear water extraction)
Clear water now remains above this sludge
layer and is fed via the air syphon for the
clear water extraction into the preclarifier or
infiltration plant.
6. Repumping the activated sludge
(sludge extraction)
Excess activated sludge is pumped back
into the preliminary sedimentation.
2. General
104