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Home >> Toxicity >> Dissolved Oxygen Uptake Test

DISSOLVED OXYGEN UPTAKE RATE TEST (DOUR) PROCEDURE

Materials Required

  • - Dissolved Oxygen probe and meter
  • - BOD bottler
  • - Stopwatch
  • - Graph paper

1. Take sample of mixed liquor from aeration basin, preferably near an aerator if accessible.

2. Immediately pour the sample into a BOD (DBO) bottle. Fill the bottle all the way so that there are no air bubbles and the liquid overflows when the DO (dissolved oxygen) probe is inserted.

3. Take a dissolved oxygen measurement and record time and DO level.

4. If DO level is above 2.0 mg/L proceed to step 5. If DO reading is below 2.0 mg/L, pour a small amount of the mixed liquor out of the bottle and shake it vigorously. Fill the bottle to the top so that the liquid overflows again. Proceed to step 5.

5. Record DO readings at the following times:

0 sec 4.0 min
30 sec 5.0 min
60 sec 6.0 min
90 sec 7.5 min
120 sec 10.0 min
180 sec 12.0 min

6. Plot the DO vs. time

7. Calculate the DOUR according to the following equation:

Notes: The test should be run as soon as possible after the sample is taken. Readings to calculate DOUR should be taken from the flat portion of the slope.