Hydraulic Retention Time (HRT) Calculator
A hydraulic retention time calculator is a tool used in water treatment to compute the average time that water or wastewater remains in a treatment system.
A wastewater treatment tank with a volume of 1000 cubic meters receiving a flow of 100 cubic meters per hour. The HRT calculator would determine that the average retention time in this tank is 10 hours.Hydraulic Retention Time Calculation Chart
| Treatment Unit | Volume (m³) | Flow Rate (m³/h) | HRT (hours) |
|---|---|---|---|
| Primary Clarifier | 500 | 50 | 10 |
| Aeration Basin | 2000 | 100 | 20 |
| Secondary Clarifier | 800 | 80 | 10 |
| Anaerobic Digester | 5000 | 25 | 200 |
| Chlorine Contact Chamber | 100 | 200 | 0.5 |
Hydraulic Retention Time Formula
The formula for calculating Hydraulic Retention Time is:
HRT = V / QWhere:
- HRT is the Hydraulic Retention Time
- V is the volume of the treatment unit
- Q is the flow rate through the unit
Let’s calculate the HRT for a sedimentation tank:
- Volume (V) = 1500 m³
- Flow rate (Q) = 75 m³/h
Applying the formula: HRT = 1500 / 75 = 20 hours
This means that, on average, water spends 20 hours in the sedimentation tank.How Do You Find Hydraulic Retention Time?
To find the hydraulic retention time, follow these steps:
Measure the volume of the treatment unit in cubic meters (m³).
Determine the flow rate through the unit in cubic meters per hour (m³/h).
Divide the volume by the flow rate to get the HRT in hours.
Let’s walk through an example for a biological reactor:
- Volume of the reactor: 3000 m³
- Influent flow rate: 125 m³/h
- HRT = 3000 / 125 = 24 hours
The hydraulic retention time for this biological reactor is 24 hours. This means that, on average, wastewater remains in the reactor for 24 hours, allowing sufficient time for biological treatment processes to occur.More Chemistry Tools