GPS-X Technical Reference

Sludge Blanket Threshold Concentration
Sedimentation and Flotation Models 258
This variable is used to define the sludge blanket height for display purposes. If the
concentration in a settler layer is above this threshold value (searching from top to bottom
layer), then the sludge blanket is defined as the height of that layer.
Critical Sludge Blanket Level
This parameter is used to define the height of the sludge blanket in order for the dissolved
oxygen in the underflow and pumped streams to be zero.
Soluble and Particulate Components
The soluble state variables in the nonreactive models are subject to a complete mix zone,
unlike the particulate components, which move from layer to layer. If the user wishes to
subject the soluble components to a number of tanks in series, then they must select a
reactive type settler. In this case all of the state variables are transported from cell to cell
according to the bulk fluid motion (but only the particulate components will be affected
by a settling term). The feed layer then will become an important term in fixing the
number of layers in series through which the soluble components will flow.
Correlation to Sludge Volume Index and Clarification
A feature of the sedimentation models in GPS-X (secondary clarifiers only) is the
correlation provided between the settling parameters and Sludge Volume Index (SVI)
measurements.
The SVI test characterizes the sedimentation, which occurs in the high solids
concentration band of a clarifier. To specify the sedimentation characteristics over the
full concentration spectrum, another parameter, the Clarification factor, is needed to
specify the settling behavior in the flocculant or low solids concentration regions. This
factor is a relative clarification index; a high number (1.0) indicates good clarification
and a low number (0.1) indicates poor clarification.
GPS-X Technical Reference