Engineering Questions with Answers - Multiple Choice Questions

Environmental Engineering MCQ – Types of Unit Operations

1 - Question

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 - Question

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 - Question

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.




4 - Question

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 - Question

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 - Question

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 - Question

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.




8 - Question

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 - Question

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.




10 - Question

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 - Question

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 - Question

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.

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