Hach BODTrak, Instrument Manual, Page: 47 / 63

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For more information, Standard Methods for the Examination of
Water and Wastewater, 18th edition emphasizes the importance of
selecting the proper seed for specific wastes.
If the waste sample to be tested contains toxic materials such
as phenol, formaldehyde, or other microbic inhibitory agents,
use acclimated seed. Acclimate the seed in any non-metal or
stainless steel gallon container fitted with an aeration system.
Proceed as follows:
1. Aerate domestic sewage for about 24 hours. Allow one hour
settling time for heavier materials to settle.
2. After the one hour settling, siphon and discard the top two-
thirds of the volume.
3. Refill the container to the original volume with domestic
sewage containing 10% of the waste material in question.
4. Repeat steps 1-3, increasing the addition of waste material
by 10%. Stop the procedure when 100% waste material has
been reached.
4.6 pH Effect
Low BOD test results occur when the pH of a test waste material
exceeds the 6-8 range. The operator may maintain this pH to
simulate original sample conditions or may adjust the pH to
approach neutrality (buffered at pH 7). Neutralize samples
containing caustic alkalinity or acidity by using 1.0 N (or weaker)
sulfuric acid or sodium hydroxide, respectively.
4.7 Supersaturation
Reduce supersaturated cold samples (containing more than
9 mg/L dissolved oxygen at 20 °C) to saturation. To do so, first
bring the sample temperature to about 20 °C. Then partly fill a
sample bottle with sample and shake vigorously for two minutes,
or aerate with filtered compressed air for two hours.
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