GPS-X Technical Reference

Suspended Growth Models 140
3. Anoxic hydrolysis: This hydrolysis process is active under anoxic
conditions. The oxygen saturation term in aerobic hydrolysis rate expression
is replaced with an oxygen inhibition term. A NO X (NO 2-N+NO 3-N)
saturation term is added to the rate expression. The specific hydrolysis rate is
reduced by anoxic hydrolysis reduction factor (η nox).
4. Anaerobic hydrolysis: This hydrolysis process is active only under
anaerobic conditions. The rate expression contains oxygen and NO X
inhibition terms. The specific hydrolysis rate is reduced by anaerobic
hydrolysis reduction factor (η anaer).
5. Ammonification: The ammonification process converts soluble organic
nitrogen to ammonia nitrogen. Both the ordinary heterotrophic organism and
fermentative organism are considered to participate in the ammonification
process. The kinetics of ammonification is similar to that provided in ASM1.
6. Growth on fermentable substrate (ss) using O 2 as electron acceptor: The
process of heterotrophic growth takes place under aerobic conditions. The
reaction rate for this process is formulated considering the concept of multi
substrate kinetics outlined in ASM2d model. The growth rate is considered
proportional to the ratio of fermentable substrate to total soluble substrate
(ss+sac+spro) available to heterotrophic biomass. The main difference in the
growth stoichiometry of different biomass is the uptake of N and P, Ca, Mg,
K, anion and cation during the biomass growth. In this implementation, it is
assumed that concentration of Ca, Mg and K is non-limiting during growth.
If required, the saturation terms for each micronutrient can be added easily in
the model equations. The growth kinetics does not use the alkalinity
saturation function as it is planned to add a pH inhibition term in the growth
kinetics at a later date.
7. Growth on acetate (sac) using O 2 as electron acceptor: The process of
aerobic heterotrophic growth on acetate is similar to the process #6, except
that the growth rate is proportional to the ratio of acetate concentration to the
total soluble substrate (ss+sac+spro) available to heterotrophic biomass.
8. Growth on propionate (spro) using O 2 as electron acceptor: The process of
aerobic heterotrophic growth on acetate is similar to the process #6, except
that the growth rate is proportional to the ratio of propionate concentration to
the total soluble substrate (ss+sac+spro) available to heterotrophic biomass.
GPS-X Technical Reference