Which factor is NOT included in calculating Hydraulic Residence Time?

Hydraulic Residence Time (HRT) is a crucial parameter in water treatment that reflects the average time water spends in a treatment facility or a specific basin. To calculate HRT, the essential factors are the volume of the basin and the influent flow rate.

The volume of the basin indicates how much water the system can hold at any given time, while the influent flow rate determines how quickly water enters the basin. The formula for calculating HRT is typically expressed as:

[ \text{HRT} = \frac{\text{Volume of the basin}}{\text{Influent flow rate}} ]

The time a molecule stays in the basin—often viewed as the residence time of water—can also be derived from HRT, making it a related but not directly calculated factor.

In contrast, temperature does not directly influence the calculation of Hydraulic Residence Time. While temperature can impact water quality and treatment processes (such as reaction rates of certain chemical treatments), it is not a parameter needed in the mathematical determination of HRT. This is why temperature is the factor that does not belong in the calculation.