GPS-X Technical Reference

315 Others Models
The optimal polymer dosage and sludge treatability are used to define the performance
of the unit. The minimal sludge concentration for processing is a limit concentration
under which the unit will not operate. The cake dry material content is a function of the
treatability and the expected content from easy to treat sludge at optimal polymer
dosage, hard to treat sludge at optimal, and no polymer dosage.
Using the following mass balance, the output flow rates (Q o and Q s) can be computed:
Equation 11.13
Press Model
The press model is based on the simple model but has, in addition, a parameter for the
filter press surface area and a maximum load on the press. These two parameters are
used to model the reduced efficiency of dewatering as the loading on the press increases.
The dewatering object should not be confused with the thickener object. The thickener is
configured like a nonreactive settling tank. The Sedimentation Models are described in
Chapter 8 (page 253).
Differential Model
In certain solid-liquid separation devices (centrifuges, vortex separator etc.), the
inorganic particulate matter may be removed at higher efficiency than the organic
particulate matter due to difference in the density. Further, depending on the nature of
aggregation/particle size of particulate matter, there may be differences in the relative
removal efficiencies of different organic particulate matters.
In some of the sludge reduction systems (i.e. Cannibal Process), it is suggested that the
inert organic material is preferentially removed by the solid-liquid separation device in
the process. To model such processes, an empirical solid-liquid separation model
(differential) is implemented in dewatering unit process considering differential removal
of particulates depending on the characteristics of each particulate state variable.
GPS-X Technical Reference