GPS-X Technical Reference

155 Suspended Growth Models
SUGGESTIONS FOR SELECTING AN ACTIVATED SLUDGE MODEL
With a large number of models available in the provided literature and used in GPS-X, it can be a
challenge to select which model is best for each modelling application. The following simple
guide gives a few suggestions and “rules of thumb” for selecting an activated sludge model.
1. The first choice to be made is the GPS-X macro library. If you are only concerned with
carbon and nitrogen processes, then you should use the CN (1-step nitrification) library.
If you are interested in modelling phosphorus, then the CNP or Comprehensive libraries
should be used. If you are interested in modelling pH, inorganic precipitation and/or side
stream processes, use the Comprehensive library. Extra user-defined components can be
added to the models by selecting the associated IP (Industrial Pollutant) library – CNIP or
CNPIP.
2. It is a good rule of practice to keep the model as simple as possible at the beginning, until
you interpret the results and are comfortable with that model's level of complexity. You
can then move to more complicated models. If you are unsure of which model to start
with we recommend using asm1, or mantis.
3. The choice of model should depend on the amount and type of data that is available to
support its use. For example, if you have little information about different substrate types
in your system, it is advisable to use models that have fewer substrates.
4. If you are modelling a plant that has recycling of flows back from the solids handling
process back to the activated sludge line, the Mantis2 model is best suited for handling
this situation. The Comprehensive (Mantis2) library contains a full set of state variables
that cover both activated sludge and anaerobic digestion processes.
The choice of model should reflect the need to simulate certain processes. For example, if you are
interested in exploring P-removal or alkalinity control, you will need to use models that contain
processes that are relevant to those components. Table 6-2 summarizes the processes in each
model, and may be useful in choosing a model. You can consult the model descriptions earlier in
this chapter or the Model matrices found in Appendix A to see the details of the processes
contained in each model.
GPS-X Technical Reference