Specific Oxygen Uptake Rate SOUR

Because toxicity affects cellular structure and cellular activity, a decrease in the number of active bacteria in the activated sludge process occurs. With a smaller number of active bacteria, less oxygen is consumed as less BOD is degraded. Therefore, a higher dissolved concentration is maintained in the activated sludge process and a decreased specific oxygen uptake rate (SOUR) occurs (Tables 19.19 and 19.20). SOUR (mg/hr/g VSS) is determined by the following calculation:

DO uptake rate (mg/liter)/minute x 60 (minutes/hour) x 1000mg/g/VSS (mg/liter)

Oxygen Uptake Rate Activated Sludge
FIGURE 19.8 Healthy free-living nematode.
FIGURE 19.9 Dispersed free-living nematode.
TABLE 19.19 Significance of SOUR Values

Values (mg/hr/g VSS)

Rate of Oxygen Consumption




Not enough solids for the BOD loading



Good BOD removal and sludge settling



Too many solids or presence of toxicity

TABLE 19.20 Typical Ranges of Specific Oxygen Uptake Rates (SOUR) for Various Modifications of the Activated Sludge Process at Aeration Tank Effluent9

Process Modification SOUR Range (mg/hr/g VSS)

Conventional 8-20

Step aeration 8-20

Extended aeration 3-12

Contact stabilization 5-15


a Values should be relatively consistent—that is, +2-3 mg/hr/g VSS. SOURs should be taken from the same aeration tank at approximately the same time each day (nearly identical loading conditions on a daily basis) for troubleshooting purposes including the identification of toxicity.

TABLE 19.21 Examples of the Ranges in Concentrations (mg/liter) of Heavy Metals that Cause Toxicity

Metal cBOD Removal nBOD Removal

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  • Dillon
    What are typical valeus for sour dour wastewater?
    4 years ago
  • jasmine
    How to perform a SOUR in wastewater?
    1 year ago
  • elle
    How to estimate oxygen uptake rate given dissolved oxygen and feed rates?
    8 months ago
  • obo whitfoot
    What is a good oxygen uptake rate in a extended wastewater plant?
    8 months ago

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