4. Function of the SBR system
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Step 3:
Settling phase
This step is a rest phase in which no aeration takes place. The activated sludge settles with
gravity (sedimentation phase). A clear water zone forms at the top and a sludge layer at the
bottom. Any floating sludge is on top of the clear water zone.
Step 4:
Clear water extraction
In this phase, the biologically cleaned waste water (clear water) is drawn out of the SBR
stage. It is pumped out by an air lift (or mammoth) pump, which uses compressed air. The
air lift pump is designed such that any floating sludge present at the layer of clear water is
not pumped out and a minimum water level is retained in the SBR stage without further
components.
Step 5:
Removal of excess sludge
In this phase, excess activated sludge is pumped by an air lift pump from the SBR reactor
chamber to the sludge reservoir chamber, where it is stored. This excess sludge is pumped
out of the base of the SBR chamber.
Once the 5th step is complete, the cleaning process starts again with step 1.
The cycle described above is usually undertaken four times a day. The switching times and
number of cycles can be adapted following discussion with the manufacturer. They may only be
adapted by an authorised maintenance specialist.
The system can also be manually switched to holiday mode.
When in holiday mode, system operation is greatly reduced during long periods without a supply
of wastewater.
