OUR measures how fast the biomass uses oxygen. A sudden drop can signal toxicity.
Oxygen Uptake Rate (OUR)
Formula
OUR, mg/L/h = (Starting DO - Ending DO) / minutes x 60
Inputs used
- Starting DO (mg/L)
- Ending DO (mg/L)
- Elapsed time (min)
Worked example (White River WRRF, fictional)
- OUR = (6.8 - 2.3) / 10 x 60 = 27.0 mg/L/h
Tips
- Start with DO near 6 to 8 mg/L and record until about 1 to 2 mg/L.
- Use the straight line part of the DO drop.
Results are estimates for operator use. Check units and inputs, and confirm decisions with plant data and procedures.