Equipment,reagent and calculation formula for BOD testing

EQUIPMENT, REAGENTS & BOD FORMULA

REAGENTS

Test reagents are as follows:

1.     Phosphate buffer solution

2.     Magnesium sulfate solution (MgSO4 7H2O) *

3.     Calcium chloride solution (CaCl2) *

4.     Ferric chloride solution (FeCl3) *

5.     Sodium hydroxide (NaOH), 1 N *

6.     Sulfuric acid (H2SO4), 1 N *

7.     Sodium sulfite (Na2SO3), 0.025 N

8.     Potassium iodide solution (KI), 10%

9.     Acetic acid solution (CH3CO2H), (1+1) *

10.   Sulfuric acid solution (H2SO4), (1+50) *

11.   Starch indicator solution

12.   Glucose‑glutamic acid solution

13.   Nitrification inhibitor (2‑chloro‑6‑(trichloromethyl) pyridine) *

14.   Distilled water.

NOTE:  Use only high‑grade distilled or deionized water. The water must contain less than 0.01 mg/L copper, and be free of chlorine, chloramines, caustic alkalinity, organic material, or acids.

        *      These reagents are poisonous or corrosive and should be handled with extreme caution.

EQUIPMENT

1.     BOD meter with probe for measurement of dissolved oxygen in 300 mL BOD bottles

2.     300 mL BOD bottles

3.     Incubator, capable of maintaining 20 +/‑ 1°C

4.     250 mL graduated cylinders

5.     100 mL graduated cylinders

6.     25 mL measuring pipettes (wide‑mouth)

7.     10 mL measuring pipettes (wide‑mouth)

8.     100 mL beaker

9.     1000 mL beaker

10.   250 mL Erlenmeyer flask

11.   Burette graduated to 0.1 mL

12.   Dilution water bottle of suitable volume for the number of tests to be performed

13.   Pipette bulb

14.   Equipment for pH measurements **

15.   Magnetic stirrer and stirring bars **

** Optional equipment

FORMULA

To determine the value of the BOD in mg/L, use the following formula:

BOD, mg/L = [(Initial DO ‑ Final DO) x 300]/mL sample

For example:

Initial DO = 8.2 mg/L

Final DO = 4.4 mg/L

Sample size = 5 mL

BOD mg/L = [(8.2 ‑ 4.4) x 300]/5 = (3.8 x 300)/5 = 1140/5 = 228 mg/L

Whenever a sample is dechlorinated, it must be seeded.  If the sample is seeded, a correction factor must be calculated to determine the effects that the seed material has on the DO depletion.  A number of BOD’s must be run on the seed material to determine the seed correction factor.

Reagent

Pipette

Dissolve oxygen meter