GPS-X Technical Reference

263 Sedimentation and Flotation Models
FLOTATION MODEL
This section of the chapter describes the flotation model (simple1d) associated with the DAF
unit.
The flotation model is closely related to the one-dimensional sedimentation model. It is partly
based on the double-exponential function, but the model is inverted to promote flotation of solids
as opposed to sedimentation of solids. The flotation model includes a solids flux component to
account for floating of solids. This floating component is primarily controlled by an air-to-solids
ratio and a polymer dosage, specified by the user.
One-Dimensional Model
The one-dimensional flotation model will predict the amount of solids removal achieved
by the DAF unit. Solids are removed from the top of the unit in the float stream. Effluent
is removed from the bottom of the DAF unit in the effluent stream. The one-dimensional
flotation model is primarily based on the solids flux theory presented previously in this
chapter, but it is modified to account for flotation as opposed to sedimentation. The major
difference between the flotation and sedimentation models is the direction of solids flux
and the parameters controlling it.
In the one-dimensional flotation model, the DAF unit is divided into a number of layers
(10 by default) of equal thickness, depicted in Figure 8-6.
The following assumptions are made:
1. Incoming solids are distributed instantaneously and uniformly across the entire
cross-sectional area of the feed layer.
2. Only vertical flow is considered.
GPS-X Technical Reference