GPS-X Technical Reference

167 Suspended Growth Models
If you wish to have a membrane “relaxation” period (rather than a backwash
period), set the duration and frequency as normal, but set the backwash flow rate
to zero. This will cause the permeate flow to cease for the appropriate period of
time, but there will be no backwash flow into the tank. This can be done in both
the Intermediate and Advanced modes.
There is no steady-state solution for the model in Advanced Mode. The
discontinuous backwashing and cleaning cycles render the model without a true
steady equilibrium state (similar to why the SBR object does not have a steadystate
solution). When using Advanced Mode, you may wish to run a long
dynamic simulation (~100 days) to allow time for the system to reach a cyclic or
periodic equilibrium. Due to the fact that there is no backwashing or cleaning in
Simple Mode, the steady-state solver can be used.
A summary of the default values of the GPS-X MBR model parameters are shown below
in Table 6-4:
Table 6-4 – GPS-X MBR Model – Default Parameter Values
Model Parameter Unit Default Value Comment/Reference
Default value was
selected to provide a
permeate TSS
Solids capture rate - 0.9999
concentration of 1
mg/L or less for typical
MBR MLSS
concentrations
Density of dry cake
solids
kg/m 3 1,020 Hydromantis (2003)
Porosity of cake layer - 0.15 Chang et al. (1999)
Calibrated using data
Solids backwash
1/m
removal rate
100
in Garcia and Kanj
(2002)
Cross-flow solids
removal rate
Intrinsic membrane
resistance
Maximum fouling
resistance
kg/m 200,000
Calibrated using data
in Garcia and Kanj
(2002)
1/m 1.0e+11 Chang et al. (1999)
- 1.0e+12
Fouling rate constant 1/d 0.005
Calibrated using data
in Merlo et al. (2000)
Calibrated using data
in Merlo et al. (2000)
GPS-X Technical Reference