BOD Test Procedure
The BOD test involves multiple equipment and supplies which are listed below:
- BOD incubator
- Burette and stand
- 300ml BOD bottles: These bottles have glass toppers which ensure air-tight sealing.
- DO Meter
- Wash bottle
- Conical flask
- Measuring cylinder
- Pipette with an elongated tip
- Gloves and seal starch
The procedure is carried out in the following manner:
Neutralization of Sample
50 ml of water sample is added to 100 ml of water. The pH is adjusted at 7± 0.2 using sulfuric acid or sodium hydroxide according to the current pH.
Removal of Chlorine Content
To neutralize the chlorine, add the prescribed volume of sodium sulphite solution to the sample. The chlorine interferes with the proper measurement of the BOD value. Hence it needs to be neutralized.
Preparation of Phosphate Buffer Solution
The Phosphate buffer solution is prepared by dissolving potassium dihydrogen phosphate, 21.75 grams of dipotassium hydrogen phosphate, disodium hydrogen phosphate, and ammonium chloride in distilled water. Dilute the solution to a volume of 1 litre.
Alkali-Iodide-Azide Reagent
Dissolve sodium hydroxide and sodium iodide (NaI) in distilled water to make a 1000 ml solution. Then add and dissolve sodium azide in the solution.
Procedure to Test Dissolved Oxygen
The following steps are carried out to test for DO:
- Manganous Sulphate solution is added to the sample using a pipette tip along with an alkali-iodide-azide reagent.
- The solutions are kept for some time to allow for their reaction with dissolved oxygen.
- Once the precipitates are formed, sulphuric acid is added to dissolve the precipitates.
- The BOD sample is transferred to an Erlenmeyer flask. Then it is titrated with Sodium Thiosulfate solution using a starch indicator till the blue hue fades. The burette reading is noted.
- Perform a similar procedure to determine the burette reading for the blank sample.
What is BOD Test?
The BOD test acts as an important criterion for knowing the health of an ecosystem. The BOD Test of Water is done to know how impure or pure the water body is. The BOD test procedure involves the collection of the water sample in an air-tight container which is then kept in incubation for five days at 20 ℃. The sample of water contains microorganisms that have the function of decomposing organic matter. They utilize oxygen present in the water to do so. BOD measures the amount of oxygen that gets consumed.
Table of Content
- Definition of BOD
- Objectives of BOD Testing
- Principle of BOD Test
- Calculation of BOD
- BOD Test Procedure
- BOD Test Measurement Problems
- Importance of Biochemical Oxygen Demand
- Limitations of the BOD Test
Contact Us