GPS-X Technical Reference

Suspended Growth Models 136
State Variables
A complete description of the state variables in MANTIS2 model is located in the
Comprehensive Model Library (MANTIS2LIB) section of Chapter 3, GPS-X State
Variable Libraries.
The soluble states in the model can be classified into four categories: Soluble inert
organic; Soluble biodegradable organics; Soluble inorganic ions; and Dissolved gases.
The states in each category are described in following sections.
Soluble Inert Organics
1. Soluble inert organics (si)
The state represents the inert organics in the wastewater. The soluble inert organics are
not degraded in the wastewater treatment processes. MANTIS2 model considers the
generation of soluble inert organic during the hydrolysis of slowly biodegradable
substrate. By default, the fraction of soluble inert organic production is set to zero. In the
anaerobic digestion process, the fraction may be set to a non-zero value to calibrate the
soluble inert COD from the digesters.
Soluble Biodegradable Organics
1. acetate (sac)
2. propionate (spro)
3. methanol (smet)
4. fermentable substrate (ss)
5. colloidal substrate (scol)
The state of fermented substrate (slf) in ASM2D is split into two states of acetate (sac)
and propionate (spro). The inclusion of an additional state of spro is required as it is one
of the important intermediate products in anaerobic digestion.
The additional state of methanol (smet) is added to the model. It is now well accepted
that the single carbon methanol is degraded by special microorganism which have
different kinetics than the ordinary heterotrophic organism. This additional state is
helpful to track the degradation of methanol based on the degradation kinetics of
methylotrophic biomass.
GPS-X Technical Reference