LaMotte MINI BOD5 TEST KIT M-B - Manual (Page 4)

PRO CE DURE FOR BOD DE TER MI NA TION (con tin ued)
6. After 5 days, run a dissolved oxygen determination on the two incubated
BOD bottles (Step 4). Record the dissolved oxygen content of the incubated
diluted sample (Step 2) as D
2
. Record the dissolved oxygen content of the
incubated dilution water for control (Step 3) as C
2
. There should not be an
increase or decrease of more than 0.2 mg/L of dissolved oxygen between C1
and C2. Use same dissolved oxygen procedure as previously in the Dissolved
Oxygen Determination Procedure.
7. Use the following equation to determine BOD
5
:
mg/L BOD
5
= 100 (D
1
–D
2
)/P = 60(D
1
–D
2
)/S
P = % of sample added = (S/60)100
S = Volume of sample added to 60 mL BOD Bottle
D
1
= DO of diluted sample immediately after preparation
D
2
= DO of Diluted Sample after 5 day incubation at 20°C
Data attained is considered reliable if there is a minimum residual dissolved
oxygen level of 1 mg/L and minimum dissolved oxygen depletion (C
1
–C
2
) of 2
mg/L.
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F. Replace cap and Titrator and continue titrating until the blue color
just disappears. Where the plunger tip meets the titrator scale, read the
test result in ppm dissolved oxygen. Each minor division on the titrator
scale equals 0.2 ppm.
G. If the plunger tip reaches the bottom line on the titrator scale
(10 ppm) before the endpoint color change occurs, refill the Titrator
and continue the titration. When recording the test result, be sure to
include the value of the original amount of reagent dispensed (10
ppm).