Making Bod Determinations; Oxygen Utilization Rate (Our) And Specific Oxygen Utilization Rate (Sour) Tests - Hach sension8 Manual

SECTION 3,
continued

3.6 Making BOD Determinations

3.7 Oxygen Utilization Rate (OUR) and Specific Oxygen Utilization
Rate (SOUR) Tests
Use the Hach BOD Accessory Kit with a magnetic stir plate and a
standard 300-mL BOD bottle.
1. Fill a standard 300-mL BOD bottle with the water sample and
insert the overflow funnel.
2. Insert the DO probe into the funnel and bottle.
3. Place the BOD bottle on a magnetic stirrer so that the probe is
over the center of the stir plate.
4. Start the magnetic stirrer and increase the speed until the
rotor loses its cycle. Adjust until the rotor regains its cycle.
Mark this point on the speed scale of the stirrer. This
identifies the optimum working point. Insufficient stirring
will cause low results.
Note: If air bubbles develop below or on the probe membrane, allow the
stirrer about five seconds to remove, or hold the probe at a slight
angle and tap gently.
1. If running the OUR test, skip to step 2.
If running the SOUR test, determine the total solids in mg/L
(Hach Method 8271) or the volatile suspended solids in
mg/L, depending on reporting requirements.
Note: Some regulations require the sample to be at 20 °C when
measured. Keep the sample aerated until the test is run.
2. Shake or aerate the sample to ensure that it contains an
adequate oxygen concentration.
3. Fill a standard 300-mL BOD bottle with the water sample and
insert the overflow funnel.
4. Place the BOD bottle on a magnetic stirrer so that the probe is
over the center of the stir plate.
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