Top 10 viva/interview questions on Biological Oxygen Demand (BOD) test

The biochemical oxygen demand determination is a chemical procedure for determining the amount of dissolved oxygen needed by aerobic organisms in a water body to break the organic materials present in the given water sample at certain temperature over a specific period of time.

1. Biochemical oxygen demand (BOD) is an important measure of

a) the oxygen using potential of water and wastewater
b) oxygen content of water and wastewater
c) an organism's natural level of oxygen requirement
d) a measure of the biological activity of water and wastewater

2. In BOD test, dilution water is aerated

a) for supplementing air
b) for cooling the sample
c) for super saturation
d) for diluting the sample

3. Which of the following is added as nutrient

a) Calcium chloride
b) Calcium sulphate
c) Magnesium chloride
d) Magnesium phosphate

4. Seeding is the process of addition of

a) seeds
b) live microbes
c) cold water
d) nutrients

5. After the incubation period of BOD which is 5 days at 20°C,

a) all the organic content would be exhausted.
b) all organisms present will die
c) practical convenience
d) all the nutrients would be exhausted.

6. In a treatment plant when the influent BOD is 245 mg/L and the effluent BOD is 22 mg/L, the percentage of BOD removed is

a) 19%
b) 91%
c) 9%
d) 86%

7. The reaction that occurs between iodine and sodium thiosulphate result in ______.

a) Sodium iodide
b) Disodium iodide
c) Disodium thioiodide
d) Sodium thio iodide

8. Manganous hydroxide takes up dissolved oxygen in molecular form to form Manganous oxide.

a) Manganous oxide
b) Manganous di oxide
c) Manganic di oxide
d) Manganic oxide

9. Sulphuric acid is added to

a) reduce tetravalent manganese to trivalent manganese
b) reduce tetravalent manganese to divalent manganese
c) reduce tetravalent manganese to manganese
d) make acidic pH

10. The increased level of BOD in water indicate that

a) it is not fit for potable use
b) it is fit for potable use
c) it tastes better
d) it smells pleasant

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