GPS-X Technical Reference

145 Suspended Growth Models
33. Growth of methylotrophs on methanol using NO 2 as electron acceptor:
This represents the second step of denitrification. The stoichiometry of this
process is developed by considering partial reduction of NO 2-N to N 2-N.
The rate expression for the process uses an inhibition term for oxygen and a
saturation term for the NO 2-N. The reaction rate expression also reduces the
amount of biomass mediating the reaction by the fraction of NO 2-N to total
NO X nitrogen available in the system. It is assumed that when the
methylotroph biomass is converting NO 2-N to N 2-N, it is not participating in
the conversion of NO 3-N to NO 2-N.
34. Decay of methylotrophs: Decay of methylotrophs is modelled using first
order reaction rate, with respect to the biomass concentration.
Processes mediated by Anaerobic Microorganisms
The MANTIS2 model includes processes mediated by anaerobic microorganisms. These
processes present the key transformations observed in strict anaerobic environment like
anaerobic digester and other modifications of anaerobic treatment technology. These
processes are adapted from the anaerobic digestion model developed at University of
Cape Town (UCTADM1). The process rate and stoichiometry was converted from molar
units to COD units. The process stoichiometry was also modified to include the mass
balances for phosphorus, Ca, Mg, K, cation and anion species. The scheme of anaerobic
biodegradation assumes that the anaerobic biomass decay takes place according to the
decay processes listed above. The slowly degradable substrate is then hydrolyzed
anaerobically according to process 4. The resulting soluble fermentable substrate is then
converted to CH 4 and H 2 by the processes described below.
35. Growth of fermentive bacteria at low H 2: This process models the
fermentation by acidogens under low H 2 partial pressure. The process
stoichiometry is developed based on a conversion of model fermentable
substrate (glucose) to acetic acid, H 2 and CO 2. The kinetic expression for the
process uses a H 2 inhibition term to reduce the reaction rate as the partial
pressure of H 2 increases.
36. Growth of fermentive bacteria at high H 2: This process models the
fermentation by acidogens under high H 2 partial pressure. The process
stoichiometry is developed based on a conversion of model fermentable
substrate (glucose) to acetic acid, propionic acid, H 2 and CO 2. The kinetic
expression for the process uses a H 2 saturation term to account for increased
rate at higher partial pressure of H 2
GPS-X Technical Reference