Hach-Lange BODTRACK II User Manual - Manual (Page 19)

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, Hach GGA or Hach Standard Method.
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 18.
Hach GGA (glucose/glutamic acid) results
The seed blank and seeded GGA sample results are necessary for the
Hach GGA procedure results.
1. Push the channel selection key for the seed blank bottle. The results
are shown.
2. Push the channel selection key for the seeded GGA sample bottle.
The results are shown.
3. Calculate the results:
BOD mg/L = seeded GGA sample result – seed blank result
Hach Standard Method results
1. Push the channel selection key for the Hach Standard Method
sample bottle. The results are shown.
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 (
Sample dilution
on page 18).
2. Find the dilution factor based on the selected range ( Table 6
on page 14). 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, calculate the results with this
equation and the corrected results: BOD (mg/L) = A – [B x (SA÷SB)]
Where:
• A = corrected BOD of the seeded sample
• B = 120 mg/L BOD
• SA = 20 mL
• SB = 110 mL
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
Typical curves
Refer to the expanded version of the manual for information about
specific procedures.
Figure 3 shows typical curves through a 10 day test period. For incorrect
curves, refer to Figure 4 on page 20.
English 17