GPS-X Technical Reference

211 Suspended Growth Models
TEMPERATURE MODELLING
The current GPS-X model uses a user-defined temperature in the biological unit processes. In
using these models, it is assumed that the user has previous knowledge about the expected
temperature in different biological reactors. In this project, it was decided to estimate the
temperature in the biological units based on the heat balance in the tank considering heat losses
and gains.
A simple heat balance model as proposed by van der Graff (1976) and later validated by
Gillot and Vanrolleghem (2003) was used to model the temperature change in a biological tank.
The model was appropriately modified to account for the heat generation in denitrification and
nitrifications reactions. The details of the model are described in following sections.
The equations described in Gillot and Vanrolleghem (2003) were developed for a completely
mixed basin under steady state conditions. These equations were appropriately modified to model
the temperature under dynamic conditions. The completely mixed hypothesis assumes that the
water temperature is uniform over the basin, and equals the outlet temperature. The energy
balance over the reactor can be expressed with following equation.
Equation 6.77
where:
V = volume of the reactor, m 3
p w = density of water, kg/m 3
c pw
= the specific heat of water, J/kg/°C
Q w = the wastewater flow rate, m 3 /s
T wi = the influent temperature, °C
T wo = the water temperature in reactor, °C
ΔH = enthalpy change due to heat transfer, J/s
GPS-X Technical Reference