SOUR is OUR per gram of volatile solids. It compares activity between days and plants.
Specific Oxygen Uptake Rate (SOUR)
Formula
SOUR, mg O₂/g VSS/h = OUR, mg/L/h / (VSS, mg/L / 1,000) SOUR at 20 °C = SOUR(T) x 1.05^(20 - T)
Inputs used
- OUR (mg/L/h)
- MLVSS (or VSS of the sample) (mg/L)
- Sample temperature (optional, for 20 °C correction) (°C)
Worked example (White River WRRF, fictional)
- SOUR = 27 / 2.34 = 11.54 mg O₂/g VSS/h
- At 20 °C = 11.54 x 1.05^(20 - 24) = 9.49
Tips
- Many conventional plants see about 8 to 20 mg O2/g VSS/h; learn your own normal.
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.