Environmental Engineering Questions and Answers – Population Equivalent and Relative Stability

This set of Environmental Engineering Questions and Answers for Entrance exams focuses on “Population Equivalent and Relative Stability”.

1. The average standard BOD of domestic sewage is measured in ____________
a) ppm
b) Kg/day
c) Kg per person per day
d) Number of persons per day
View Answer

Answer: c
Explanation: The average standard BOD of domestic sewage is measured in 0.08Kg per person per day.

2. Which of the following id the correct expression of population equivalent?
a) BOD of industrial sewage in kg/day * 0.08
b) 0.08 * BOD of industrial sewage kg/day
c) BOD of industrial sewage kg/day / 0.08kg/person/day
d) BOD of industrial sewage kg/day + 0.08
View Answer

Answer: c
Explanation: BOD of industrial sewage kg/day /(0.08kg/person/day) where 0.08 represents the average standard BOD of domestic sewage.

3. The expression of relative stability at 20oC is given by ___________
a) S = (1-(0.794)T20)
b) S = 100 (1-(0.794)T20)
c) S = 1-(0.794)T20
d) S = 100 (0.794)T20
View Answer

Answer: b
Explanation: The expression of relative stability at 20oC is given by
S=100 (1-(0.794)T20) where T20 represents the incubation period at 20oC.
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4. The expression of relative stability at 37oC is given by ___________
a) S = (1-(0.794)T37)
b) S = 100 (1-(0.794)T37)
c) S = 1-(0.794)T20
d) S = 100 (1-(0.630)T37)
View Answer

Answer: d
Explanation: The expression of relative stability at 37oC is given by
S = 100 (1-(0.630)T37) where T37 represents the incubation period at 37oC.

5. What is the value of BOD of industrial sewage in kg/day, given population equivalent as 6000 persons?
a) 480
b) 160
c) 270
d) 100
View Answer

Answer: a
Explanation: BOD of industrial sewage in kg/day = Population equivalent * Average standard BOD of domestic sewage = 6000*0.08 = 480kg/day.
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6. Calculate the percentage of relative stability, given 5 day incubation period at 370C.
a) 50%
b) 60%
c) 90%
d) 99%
View Answer

Answer: c
Explanation: Relative stability at 370C is given by, S = 100 (1-(0.630) T37) = 100 (1-(0.630)5) = 90.08% which is approximately 90%.

7. _____ is the amount of oxygen required to oxidize both organic and inorganic matter in sewage.
a) Turbidity
b) BOD
c) COD
d) DO
View Answer

Answer: c
Explanation: COD is the amount of oxygen required to oxidize both organic and inorganic matter in sewage. It is always greater than BOD.
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8. COD is abbreviated as ___________
a) Chemical oxygen demand
b) Complex oxygen demand
c) Customary oxygen demand
d) Chemical oxygen deficit
View Answer

Answer: a
Explanation: COD is abbreviated as chemical oxygen demand. It is measured in ppm or mg/L.

9. The oxidizing agent used in COD test is ___________
a) Potassium chloride
b) Potassium per-manganate
c) Potassium chromate
d) Potassium dichromate
View Answer

Answer: d
Explanation: In COD test, oxidization of organic matter takes place by potassium dichromate in the presence of sulphuric acid using ferroin as indicator.
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10. 5 days BOD at 20oC is ___ of total demand.
a) 20%
b) 47%
c) 68%
d) 100%
View Answer

Answer: c
Explanation: 5 days BOD at 20oC is the standard BOD which is 68% of total demand, whereas 10 days BOD at 20oC is 90% of total demand.

11. Which of the following expression is correct regarding deoxygenation constant where symbols have their usual meaning?
a) KDT = KD20 + (1.047)T-20
b) KDT = KD20 / (1.047)T-20
c) KDT = KD20 (1.047)T-20
d) KDT = KD20 (1.04T)
View Answer

Answer: c
Explanation: KDT = KD20 (1.047)T-20 where, KDT is the deoxygenation constant at temperature ‘T’ and KD20 is the deoxygenation constant at 20oC.

Sanfoundry Global Education & Learning Series – Environmental Engineering.

To practice all areas of Environmental Engineering for Entrance exams, here is complete set of 1000+ Multiple Choice Questions and Answers.

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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