GPS-X Technical Reference

Suspended Growth Models 194
The correction factor for salts, particulates, and surface-active substances, β, is a
parameter that must be measured or estimated for the wastewater of interest. In GPS-X, a
default value of 0.95 is used.
The pressure correction factor is calculated as follows:
Equation 6.18
where:
P b
P s
p v
= barometric pressure at elevation and air temperature (kPa)
= standard barometric pressure (101.325 kPa)
= vapour pressure of water at liquid temperature (kPa)
The barometric pressure at elevation and air temperature is calculated using the following
formula taken from Appendix B-2 of Metcalf and Eddy (2003):
Equation 6.5
where:
g
M
R
T air
zi
= acceleration due to gravity (9.81 m/s2)
= molecular weight of air (28.964 kg/kg-mole)
= universal gas constant (8314 N•m/kg-mole•K)
= air temperature (K)
= elevation at position “i” (m)
GPS-X Technical Reference