Section 8 Determination Of Results; Simplified Sample Results; Hach Standard Method Results - Hach BODTrak II User Manual

13. Push and hold 14. Do steps 10
ON to start a test. A through 13 again to
graph will show. set the test range
Note: To cancel a test, and start each of the
push and hold OFF.
six channels. It is not
There is a built-in 1
necessary to operate
hour instrument/sample
all six channels if
equilibration period
less than six
before data collection.
samples are
The display shows
available.
"DELAY" during this
period.

Section 8 Determination of results

After the end of the selected test period (5, 7 or 10 days), the display
shows "END". The results are given based on the selected procedure:
Simplified or Hach Standard Method.

8.1 Simplified sample results

The simplified procedure results are shown on the BODTrak II display.
Push the applicable channel selection key to show the results.
Note: If the sample was pre-diluted, apply a dilution factor to the instrument
reading. Refer to Sample dilution on page 15.

8.2 Hach Standard Method results

1. Push the channel selection key for the Hach Standard Method
sample bottles, and the seed blank bottle and GGA bottle when
applicable. The results are shown.
14 English
Note: Treat the seed blank the same as all other samples. If the sample was
pre-diluted, apply a dilution factor to the instrument reading
on page 15).
2. Find the dilution factor based on the selected range
on page 11). For example, if the sample range selected is 0 to
350 mg/L BOD, the dilution factor is 1.45.
3. Calculate the corrected results:
BOD mg/L = BOD mg/L (instrument reading) x dilution factor
Example:
• Instrument Reading = 200 mg/L
• BOD dilution factor = 1.45
200 mg/L x 1.45 = 290 mg/L BOD (corrected result)
4. When the samples are seeded (not GGA), calculate the results with
the equation that follows and the corrected results:
BOD (mg/L) = A – [B x (SA÷SB)]
Where:
• A = corrected BOD of the seeded sample
• B = corrected BOD of the seed blank
• SA = volume of seed in seeded sample
• SB = volume of sample in seeded sample
Example:
• A = 290 mg/L BOD
• B = 120 mg/L BOD
• SA = 20 mL
• SB = 110 mL
BOD (mg/L) = 290 mg/L - [120 mg/L x (20 mL÷110 mL)]
BOD mg/L = 268 mg/L
5. For GGA, calculate the results of the GGA with the equation that
follows and the corrected BOD of the seed blank:
BOD (mg/L) = C – [B x (SA÷SC)]
Where:
• C = instrument reading on seeded GGA
(Sample dilution
(Table 5