GPS-X Technical Reference

Suspended Growth Models 128
The heterotrophic processes include the aerobic growth on two substrates
(processes 4 and 5), their corresponding anoxic growth (processes 6 and 7). The
fermentation of organic material under anaerobic conditions is also accounted for by
process 8. This process has been identified as one requiring more research into its
understanding. Since little is known about this process, a large range of kinetic
parameters for this rate may be found during the modelling exercise. Process 9 models
the death and lysis of the heterotrophs.
Processes 10-15 describe the phosphorus accumulating bacteria:
1. the internal storage of fermentable products (process 10);
2. the internal storage of poly-phosphate (process 11);
3. the aerobic growth of polyP bacteria (process 12); and
4. the lysis of the bacteria and their corresponding internally stored products
(processes 13-15)
The final two processes in the model are the aerobic growth of the nitrifiers (process 16)
and their death and lysis (process 17). The kinetic parameters of this model, like those of
the mantis model, are temperature dependent. A similar Arrhenius type function is used
to describe this dependency.
This model is a minor extension of the original asm2 model. It includes two additional
processes to account for phosphorus accumulating organisms (PAOs) using cell internal
storage products for denitrification. Whereas the asm2 model assumed PAOs to grow
only under aerobic conditions, the asm2d model includes denitrifying PAOs.
ACTIVATED SLUDGE MODEL NO. 3 (ASM3)
The Activated Sludge Model No. 3 (Gujer et al., 1999) relates to ASM1 and corrects for some
inadequacies of ASM1. The main features of the model are:
Hydrolysis is independent of the electron donor, and occurs at the same rate under
aerobic and anoxic conditions.
Lower anoxic yield coefficients are introduced.
Decay of biomass is modelled as endogenous respiration (vs. the “death regeneration”
concept used in asm1).
Storage of COD by heterotrophs under anoxic and aerobic conditions is modelled.
GPS-X Technical Reference