Engineering Questions with Answers - Multiple Choice Questions
Environmental Engineering MCQ’s – 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-chlorinationAnswer: c
Explanation: By Re-carbonation of water softened by excess lime treatment, excess lime is converted into bicarbonate.
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.