LaMotte BOD5 TEST KIT BOD - Manual (Page 4)

DISSOLVED OXYGEN DETERMINATION PROCEDURE
A. Use a 1.0 mL transfer pipet (2-2170) to add 1.0 mL of the *Manganous
Sulfate Solution (4167) to the sample in the BOD bottle. Hold the tip of the
pipet under the surface of the sample. Rinse pipet.
B.
Use a second pipet to add 1.0 mL of *Alkaline Potassium Iodide Azide
Reagent (7166). Stopper and invert several times to mix.
C.
Allow sample to stand to settle precipitate.
D. Use a third pipet to add 1.0 mL of *Sulfuric Acid, Conc. (5172). Stopper
and invert several times to mix.
E.
Use the 100 mL graduated cylinder (0419) to measure and transfer 202
mL of the treated sample. Transfer to 500 mL Erlenmeyer flask (0435).
F.
Fill the Automatic Buret (0997) with *Sodium Thiosulfate, 0.025N
(4169). Titrate the sample in the flask to a light yellow color.
G.
Use the fourth pipet to add 5 drops of Starch Solution (4170). The
sample will turn blue. Continue titration until the blue color just disappears.
Record buret reading in mL.
H.
Dissolved Oxygen, mg/L = mL 0.025N Sodium Thiosulfate
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
.
NOTE: There should not be an increase or decrease of more than 0.2 mg/L
of dissolved oxygen between C
1
and C
2
. Use Dissolved Oxygen
Determination procedure described above.
7. Use the following equation to determine BOD
5
:
mg/L BOD
5
= 100 (D
1
- D
2
)/P = 300(D
1
- D
2
)/S
P = % of sample added (S/300)100
S = Volume of sample added to 300 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 (D
1
- D
2
) of 2
mg/L.
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