GPS-X Technical Reference

Suspended Growth Models 122
For example the slowly biodegradable material, designated Xs, may include soluble
and/or colloidal material. This approach greatly facilitates the model development;
however it invariably introduces some error into the models. The issues of wastewater
characterization are important and the modeller should refer to the papers listed with the
individual models discussed below.
Model Matrix
Most biological process models now follow a standard matrix format. An example of
this format is shown in Table 6-1.
Table 6-1 – Example Model Matrix (Wentzel et al., 1987a)
In this table, the components or state variables of the Monod-Herbert model
(Herbert, 1958), designated by a variable with a subscript i, are numbered and listed
across the top. Three state variables are defined (Xb, S S and S o), each having its own
column. Names and units for each state variable are provided in the bottom row of each
of these columns. The important processes, designated pj, in the system, which result in
changes in the state variables, are shown in separate rows; the actual process rate (kinetic
expression or rate equation) is shown in the rightmost column of each of these rows. All
the necessary kinetic parameters are defined in the lower right-hand corner of the table.
GPS-X Technical Reference