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.