GPS-X Technical Reference

Suspended Growth Models 172
Figure 6-18 - Regular SBR - Operation Cycle Parameters
1. Mix (and fill): The unit is modelled as a CSTR without aeration (i.e. air flow, power
or KLa set to 0.0). This phase is usually the starting phase, used while the tank has
just started filling with liquid. This phase represents the first of four mixing phases.
2. Aerate (and fill): The unit is modelled as a CSTR with aeration. This represents the
second mixing phase, and is used while the tank is filling after the aeration has been
turned on.
3. Mix only: The unit is modelled as a CSTR without aeration. This represents the third
mixing phase usually occurring sometime after the tank has finished filling. It is
typically used as a denitrifying phase.
4. Aerate: The unit is modelled as a CSTR with aeration. This is the last mixing phase
generally used to re-aerate the sludge so that it will settle properly.
5. Settle: The unit is modelled as a settler, with or without biological reactions,
depending on the model selected. The mixing is turned off to allow the content of the
tank to become quiescent and to promote settling.
6. Decant: The unit is modelled as a settler. During this phase, the user-specified decant
flow is activated.
7. Desludge: The unit is modelled as a settler. This phase occurs at the end of the cycle,
and the user-specified wastage flow is activated.
GPS-X Technical Reference