GPS-X Technical Reference

193 Suspended Growth Models
Calculation of DO Saturation Concentration at Field Conditions
The DO saturation concentration at field conditions is calculated as follows:
Equation 6.58
where:
τ
β
Ω
= temperature correction factor (unitless)
= correction factor for sales, particulates, and surface-active substances
(unitless)
= pressure correction factor (unitless)
C * ∞20 = DO saturation concentration at 20°C and 1 atm (mg/L)
The correction factors are used to adjust the DO saturation concentration to account for
the temperature of the liquid, the pressure at the submergence level of the diffusers, and
the salts, precipitates, and surface-active substances found in the wastewater.
The temperature correction factor is calculated as follows:
Equation 6.3
where:
C * st
C * s20
= surface DO saturation concentration at temperature of t and 1 atm air
pressure (mg/L)
= surface DO saturation concentration at 20°C and 1 atm pressure (mg/L)
The surface DO saturation concentration at liquid temperature t and an air pressure of
1 atm is obtained using a look-up table in GPS-X that is based on temperature. The lookup
table data were taken from Appendix C of the USEPA Design Manual – Fine Pore
Aeration Systems (USEPA, 1989). When the temperature falls between two data points
in the table, GPS-X uses linear interpolation to determine the C * st value. The value of
C * s20 is 9.09 mg/L.
GPS-X Technical Reference