Environmental Engineering Questions and Answers – Types of Unit Operations

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

1. How many types of aerators are commonly used in the treatment of wastewater?
a) 2
b) 3
c) 4
d) 5
View Answer

Answer: c
Explanation: There are 4 types of aerators namely Gravity aerators, Spray aerators, Diffusers and Mechanical aerators.

2. Organic contaminants are removed from the wastewater by ____________
a) Water softening
b) Demineralization
c) Absorption
d) Adsorption
View Answer

Answer: d
Explanation: Organic contaminants are removed from the wastewater by the attraction and accumulation of one substance on the surface of another.

3. By which process, odor producing substances are oxidized?
a) Chlorination
b) Liming
c) Re-carbonation
d) Super-chlorination
View Answer

Answer: d
Explanation: By addition of chlorine dioxide to wastewater, odor producing substances are oxidized.
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4. Which of the following process is used to remove the colloidal particles from the effluent?
a) Chemical precipitation
b) Chemical coagulation
c) Ion exchange
d) Adsorption
View Answer

Answer: b
Explanation: Chemical coagulation is used to remove colloidal particles by the use of coagulants which increase the particle size and they settle down.

5. In which form of solute stabilization, hydrogen sulfide in the effluent is oxidized into sulfate?
a) Chlorination
b) Liming
c) Re-carbonation
d) Super-chlorination
View Answer

Answer: a
Explanation: By the process of chlorination, effluent gets stabilized by the conversion of hydrogen sulfide into sulfate.

6. In which unit operation, gases are released or absorbed in the effluent?
a) Gas transfer
b) Ion transfer
c) Solute stabilization
d) Solids Transfer
View Answer

Answer: a
Explanation: In Gas transfer, gases are released or absorbed in the effluent by exposing the wastewater through aeration under normal, increased or reduced pressure.

7. In which process, excess lime is converted into bicarbonate?
a) Chlorination
b) Liming
c) Re-carbonation
d) Super-chlorination
View Answer

Answer: c
Explanation: By Re-carbonation of water softened by excess lime treatment, excess lime is converted into bicarbonate.
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8. Flocculation of iron from water by the addition of lime is an example of which of the following process?
a) Chemical precipitation
b) Chemical coagulation
c) Ion exchange
d) Adsorption
View Answer

Answer: a
Explanation: Chemical precipitation removes the dissolved substance from the effluent through ion transfer where precipitation of dissolved impurities takes place.

9. Which form of solute stabilization occurs when effluent passes through limestone?
a) Chlorination
b) Liming
c) Re-carbonation
d) Super-chlorination
View Answer

Answer: b
Explanation: When effluent passes through limestone, carbon dioxide in excess gets converted into soluble bicarbonate.
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10. Solids are removed from the wastewater by which of the following unit operation?
a) Inter facial contact
b) Solid stabilization
c) Ion transfer
d) Solids transfer
View Answer

Answer: d
Explanation: During solids transfer, solids are removed from wastewater by straining, sedimentation, flotation and filtration.

11. In which unit operation objectionable solutes are converted into unobjectionable forms without removal?
a) Gas transfer
b) Ion transfer
c) Solute stabilization
d) Solids Transfer
View Answer

Answer: c
Explanation: In solute stabilization, effluent is stabilized by chlorination or liming so that objectionable solutes are converted into unobjectionable form.

12. Dealkalization results in removal of all the ions from the wastewater.
a) True
b) False
View Answer

Answer: b
Explanation: Dealkalization results in removal of hydroxides, carbonates and bicarbonates of calcium, sodium and magnesium from wastewater. Demineralization results in removal of all the ions from the wastewater.

Sanfoundry Global Education & Learning Series – Environmental Engineering.

To practice all areas of Environmental Engineering, 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 - Founder & CTO at Sanfoundry
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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