Hach BODTrak, Instrument Manual, Page: 16 / 63

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BOD test results help determine general oxygen uptake patterns.
This allows operators to estimate plant operating efficiency and
determine proper treatment procedures.
The BODTrak method is an easy and direct method of measuring
BOD. It makes complex chemical analysis unnecessary because
the BODTrak instrument takes a physical measurement of the
oxygen consumed by a test sample.
Advantages to using the BODTrak method over the dilution
method are listed below:
• Minimal sample preparation time.
• Reduced total testing time (titrations and dilutions are
unnecessary).
• The BODTrak test is easy to monitor.
• The sample is stirred constantly and maintained under natural
conditions. The BODTrak has an initial head space containing
21% oxygen above the water sample. Continuous stirring
replenishes dissolved oxygen to the sample. This makes the
BODTrak results similar to occurrences found in a natural
environment. The dilution method supplies no additional
oxygen to the sample; this causes a higher percentage of
oxygen depletion, sometimes as much as 89 percent.
• The BOD rate can be observed daily without disturbing the
sample. Pressure changes within the closed BODTrak system
are displayed graphically in milligrams per liter (mg/L) on
an LCD. The system supplies 480 evenly spaced data points
over the selected period (5.25, 7, or 10.5 days).
NOTE: You can either manually stop the test at 5.0 or 10.0 days, or
scroll back (using the arrow keys) to 5.0 or 10.0 days on the display to
see the final BOD value. If downloading, you can also disregard the last
data points to collect exactly 5.0 or 10.0 days (i.e., disregard the last 23
points when doing the 5.25 day test).
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