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Remove any residual chlorine (by letting it evaporate or by titration after sodium thiosulfate addition).
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Sample dilution: when diluting the sample, the sample volume should not be less than 1% the BOD bottle volume. Make serial dilutions if
necessary
7.4.2 Dilution Water Preparation:
Prepare dilution water according to established methods.
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Use distilled, reverse osmosis, tap or receiving water free of metals and toxic substances.
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Use clean containers free of metals, organics or toxic substances. Preferably use glass containers. Clean containers periodically with a
bleach solution.
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Sparge the dilution water with clean tubing dedicated only for this purpose. The DO of the dilution water should be at least 7.5, but not
oversaturated. If it is oversaturated, lower the DO level by shaking or sparging the dilution water.
7.4.3 Seed Preparation:
Seed, when needed, as described in established methods.
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Seed source can be from a biological waste treatment system (e.g., settled domestic wastewater, primary effluent, diluted mixed liquor) or
from a synthetic seed source. Follow the supplier's instructions on use.
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Seed source should not be filtered but decanted if needed.
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If sparging of the seed water is needed, use clean tubing dedicated only for this purpose.
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If running a cBOD batch, add your nitrification inhibitor to your seed water, or add the inhibitor manually to your BOD bottles.
7 .5 QC SAMPlE (GGA STANDARD):
•
Prepare Glucose - Glutamic Acid (GGA) standard as described in established methods
Note on preparation: Pipette, in each BOD bottle used for QC Samples, an amount of your Glucose-Glutamic Acid standard so that your
final concentration will be of 3 mg/L glucose and 3 mg/L glutamic acid. The stock standard preparation being at 150 mg/L, this means
a volume of 6 ml of stock standard in a 300 ml bottle, and a volume of 1.2 ml of stock standard in a 60 ml bottle.
7 .6 SEED VOl (ml):
The amount of seed should be less when using 60 ml bottles than 300 ml bottles.
Note on preparation: The amount of seed added to Seed Controls should give a dissolved oxygen depletion after incubation of at least
2 mg/L O
2
(see Admin-Tools tab, QC Controls, Seed depletion).
The amount of seed added to QC samples and unknown samples should account for a dissolved oxygen uptake of 0.6 to 1.0 mg/L O
2
, out of
the total depletion for that bottle. In addition, the amount of seed should be adjusted from this volume range to that required to provide a GGA
result of 198 ± 30.5 mg/L O
2
for EPA method.
NOTE
NOTE
