GPS-X Technical Reference

Attached Growth Models 234
For the SBC the process is the same as the RBC (conceptually shown in Figure 7-9). The
concentration of each particulate state variable is converted to volume based on the dry
material content of biofilm and its density input by the user. When the volume of each
layer is filled (based on maximum biofilm thickness and number of biofilm layers) the
next layer begins to fill. When the film thickness starts to approach the specified
maximum, increasing detachment of biofilm will occur.
Mathematical Model
The mathematical equations used within each layer of the biofilm are provided in the
corresponding Model matrix (for example, see Appendix A for the mantis model). The
equation used for the diffusion of the state variables from the bulk liquid into the biofilm
is provided in the trickling filter section.
Model Parameters
Physical
This section of the chapter discusses the model parameters and inputs that the user will
encounter using this model, in particular those different from the other fixed film models.
The example and discussion below pertains to the mantis model in the Carbon - Nitrogen
(CN) library.
These menu items are found under Parameters > Physical, and contain both real
physical dimensions to describe the actual submerged biological contactor being
modelled, and model dimensions which allow the user to specify how the physical system
will be modelled. there are two items under the heading Speed, which allow the user to
optimize the simulation speed of this model by changing the frequency of integration for
the soluble components.
As seen in Figure 7-12, the real dimensions of the submerged biological contactor
require inputs such as:
1. tanks in series
2. volume set up method
3. SBC liquid volume in tanks
4. SBC media volume in tanks
5. SBC total volume
6. SBC total media volume
7. volume fractions
8. Specific surface of media (which will provide an estimation of the total biofilm
surface area in the model.)
GPS-X Technical Reference