Detention time is tank volume divided by flow.
Detention Time
Formula
Detention time, hours = Volume, gal / Flow, gpd x 24
Inputs used
- Tank volume (gal)
- Flow through the tank (MGD)
Worked example (White River WRRF, fictional)
- DT = 893,554 / 8,000,000 x 24 = 2.68 hours
Tips
- For aeration basins, decide whether to include RAS in the flow and say which.
Results are estimates for operator use. Check units and inputs, and confirm decisions with plant data and procedures.
This calculator also appears on ActivatedSludge.com, our consulting site. Results are for training and operator use; always follow your plant’s procedures.