GPS-X Technical Reference

249 Attached-Growth Models
HYBRID SYSTEM
The Hybrid-System model in GPS-X is based on a combination of the standard plug flow tank
configuration with suspended growth biomass, and the GPS-X biofilm model representing fixed
film growth on the media inserted into the tank. Any type of media will be represented in the
model as long as the specific surface area is set correctly. Thus the model is able to represent
commercial systems such as MBBR, Ringlace, Captor, Bionet and other types of hybrid systems,
whether they contain sludge recycle or not.
Biological Component
The hybrid-system uses the same biological reactions found in the suspended-growth
models. For more specific information on biological models, please consult Chapter 6
(page 94).
Biofilm Component
The existing biofilm model in GPS-X is based on Spengel and Dzombak (1992). This
model was adapted to the hybrid-system. The model handles soluble material diffusion,
biofilm growth, and particulate attachment and detachment. Details are described in the
Trickling Filter Model section of this chapter.
Model Parameters
Physical
This section of the chapter discusses the various model parameters and inputs that the
user will encounter when using this model.
The physical parameters are found under the Parameters sub-menu item Physical. It
contains physical dimensions to describe the hybrid-system, and model dimensions which
allow the user to specify how the physical system will be modelled.
The hybrid-system requires inputs such as the specific surface of media, the water
displaced by media, and the specific density of media.
GPS-X Technical Reference