# Environmental Engineering Questions and Answers – Types of Settling Tanks

This set of Environmental Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Types of Settling Tanks”.

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

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. 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

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

3. 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

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. 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

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

5. 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

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

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. 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

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

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.

Sanfoundry Global Education & Learning Series – Environmental Engineering.