GPS-X Technical Reference

97 Suspended Growth Models
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 = acceleration due to gravity (9.81 m/s 2 )
M
= molecular weight of air (28.964 kg/kg-mole)
R = universal gas constant (8314 m/kg-mole K)
T air
z i
= air temperature (K)
= elevation at position i (m)
The vapour pressure of water at the liquid temperature is determined using the Antoine
equation (Felder & Rosseau, 1986):
Equation 6.6
where:
A, B, C, = Antoine coefficients
(found in System > Input Parameters >Physical form in GPS-X
under Physical Constants)
T
= wastewater temperature (°C)
GPS-X Technical Reference