Environmental Engineering Multiple Choice Questions on “Disposal of Sewage”.
1. Which of the following is a prime lake pollutant?
a) Iodine
b) Phosphorous
c) Potassium
d) Sodium
Answer: b
Clarification: Phosphorous is a prime lake pollutant that promotes the algal bloom and destroys the quality and appearance of a lake.
2. The turbulence decreases the DO content of water.
a) True
b) False
Answer: b
Clarification: The turbulence increases the DO content of water, however, beyond a certain limit, it scours the sediments placed at the bottom.
3. The dilution factor is expressed by _____________
a) Volume of diluted sample + Volume of sewage
b) Volume of diluted sample / Volume of sewage
c) Volume of diluted sample – Volume of sewage
d) Volume of diluted sample* Volume of sewage
Answer: b
Clarification: The dilution factor is the ratio of volume of diluted sample of water to the volume of sewage. It is used in finding the BOD of water.
4. The tolerance limit of BOD of sewage to be disposed on land is ____________
a) 100ppm
b) 200ppm
c) 500ppm
d) 400ppm
Answer: c
Clarification: The tolerance limit of BOD of sewage to be discharged into sea water is 100ppm while to be disposed on land is 500ppm.
5. The tolerance limit of pH value of sewage to be discharged into sea water is ____________
a) 1-5ppm
b) 2-9ppm
c) 5.5-9ppm
d) 6-10ppm
Answer: c
Clarification: The tolerance limit of pH value of sewage to be discharged into sea water or to be disposed on land is between 5.5 and 9ppm.
6. The dilution factor is 400. What should be the type of treatment given to the water?
a) Preliminary treatment
b) Sedimentation, Flocculation
c) Complete treatment
d) No treatment
Answer: a
Clarification: When the dilution factor lies between 300 and 500, then preliminary treatment is given to the water.
7. The tolerance limit of oil and grease of sewage to be disposed on land is ____________
a) 40ppm
b) 30ppm
c) 20ppm
d) 10ppm
Answer:b
Clarification: The tolerance limit of oil and grease of sewage to be disposed on land is 30ppm while on sea water is 20ppm.
8. The minimum depth to which sewage should be discharged of sea water is ____________
a) 0.5m
b) 1m
c) 2m
d) 3m
Answer: d
Clarification: The minimum depth to which sewage should be discharged of sea water is 3m to avoid marine pollution.
9. The tolerance limit of COD of sewage to be discharged in sea water is ____________
a) 250ppm
b) 100ppm
c) 40ppm
d) 20ppm
Answer: a
Clarification: The tolerance limit of COD of sewage to be discharged in sea water and on land for irrigation purpose is 250ppm.