Engineering Questions with Answers - Multiple Choice Questions

Environmental Engineering MCQ – Types of Settling Tanks

1 - Question

How many types of sedimentation tanks are there on the basis of the method of operation?
a) 2
b) 3
c) 4
d) 5

View Answer

Answer: a
Explanation: There are two types of sedimentation tanks on the basis of the method of operation, namely Fill and draw type and Continuous flow type.




2 - Question

In which type of sedimentation, the flocculent suspension of the intermediate concentration takes place?
a) Type I sedimentation
b) Type II sedimentation
c) Type III sedimentation
d) Type IV sedimentation

View Answer

Answer: c
Explanation: In type III sedimentation, the inter-particle forces hold the particle together and the flocculent suspension of the intermediate concentration takes place.




3 - Question

In which type of sedimentation, the flocculent suspension of high concentration takes place?
a) Type I sedimentation
b) Type II sedimentation
c) Type III sedimentation
d) Type IV sedimentation

View Answer

Answer: d
Explanation: In type IV sedimentation, the flocculent suspension of high concentration takes place and particles comes in contact with each other resulting in the formation of structure.




4 - Question

When the impurities are separated by the gravitation of settling particles, the operation is called ______
a) Sedimentation with coagulant
b) Plain sedimentation
c) Secondary sedimentation
d) Disinfection

View Answer

Answer: b
Explanation: In plain sedimentation, the impurities are separated from a suspending fluid by use of natural forces like gravitational forces.




5 - Question

What is the settling velocity of the particle in the wastewater if its diameter is 2 * 10-3cm. Given G=2.65, viscosity v=8 * 10-3cm2/Sec?
a) 0.01cm/Sec
b) 0.13cm/Sec
c) 0.24cm/Sec
d) 0.36cm/Sec

View Answer

Answer: b
Explanation: Settling velocity of the particle in wastewater is given by vs=g (G-1) d2/18v
Specific gravity G=1, g=981cm2/Sec, viscosity v=8 * 10-3cm2/Sec
vs = 981 * (2.65-1) * 0.002 * 0.002/(18 * 0.008) = 0.13cm/Sec.




6 - Question

In a rectangular horizontal flow tank, the maximum permissible velocity is ____ m/Sec.
a) 3
b) 0.3
c) 0.03
d) 0.003

View Answer

Answer: b
Explanation: In the rectangular tank, the ideal conditions are that the flow is horizontal, velocity is uniform in all directions and the maximum permissible limit of velocity is 0.03m/Sec.




7 - Question

The time period for which the water is stored in a sedimentation tank is called _____
a) Time of flow
b) Frequency of flow
c) Settling time
d) Detention period

View Answer

Answer: d
Explanation: Detention period is the time period at which the water is stored in a tank. It varies for different purposes like in the septic tank or oxidation pond, its value is higher.




8 - Question

In a fill and draw type sedimentation tank, a detention period of ____ hours is provided.
a) 6
b) 12
c) 18
d) 24

View Answer

Answer: d
Explanation: In this tank, water is detained for 24 hours. Then cleaning is done for 6-12 hours, so, the whole operation takes 30-36 hours.

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