hydraulic retention time

Hydraulic Retention Time (HRT) is the average time that water spends inside a treatment process or tank, such as a wastewater treatment plant. It is calculated by dividing the volume of the tank or system by the flow rate of water entering it. For example, if a tank holds 1,000 gallons and water flows in at 100 gallons per hour, the HRT would be 10 hours. This measure helps engineers ensure that water is treated thoroughly, giving enough time for contaminants to be reduced before the water moves on in the process.