Wiktionary
hydraulic retention time
n. a measure of the average length of time that a soluble compound remains in a constructed reactor
Wikipedia
Hydraulic retention time
The hydraulic retention time (HRT), also known as hydraulic residence time or t (tau), is a measure of the average length of time that a compound (ex. water) remains in a storage unit (ex. lake, pond, ocean).
Hydraulic retention time is the volume of the storage unit divided by the influent flowrate:
$HRT = \frac{Volume\; of\; aeration\; tank}{influent\; flowrate}$
where using SI Units Volume is in [m] and Influent flowrate is in [m/h]. HRT is usually expressed in hours (or sometimes days).
Category:Hydrology Category:Environmental engineering Category:Hydraulic engineering Category:Chemical engineering Category:Waste treatment technology