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Environmental Engineering Multiple Choice Questions on “Various Unit Operations”.
1. In which unit operation, gases are released or absorbed in the water?
a) Gas transfer
b) Ion transfer
c) Solute stabilization
d) Solids Transfer
Answer: a
Clarification: In Gas transfer, gases are released or absorbed in water by exposing the water through aeration under normal, increased or reduced pressure.
2. How many types of aerators are commonly used in the treatment of water?
a) 2
b) 3
c) 4
d) 5
Answer: c
Clarification: There are 4 types of aerators namely Gravity aerators, Spray aerators, Diffusers and Mechanical aerators.
3. Which of the following process is used to remove the colloidal particles from water?
a) Chemical precipitation
b) Chemical coagulation
c) Ion exchange
d) Adsorption
Answer: b
Clarification: Chemical coagulation is used to remove colloidal particles by the use of coagulants which increase the particle size and they settle down.
3. 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
Answer: a
Clarification: Chemical precipitation removes the dissolved substance from water through ion transfer where precipitation of dissolved impurities takes place.
4. 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
Answer: c
Clarification: In solute stabilization, water is stabilized by chlorination or liming so that objectionable solutes are converted into unobjectionable form.
5. In which form of solute stabilization, hydrogen sulfide in water is oxidized into sulfate?
a) Chlorination
b) Liming
c) Re-carbonation
d) Super-chlorination
Answer: a
Clarification: By the process of chlorination, water gets stabilized by the conversion of hydrogen sulfide into sulfate.
6. Which form of solute stabilization occurs when water passes through limestone?
a) Chlorination
b) Liming
c) Re-carbonation
d) Super-chlorination
Answer: b
Clarification: When water passes through limestone, carbon dioxide in excess get converted into soluble bicarbonate.
7. In which process, excess lime is converted into bicarbonate?
a) Chlorination
b) Liming
c) Re-carbonation
d) Super-chlorination
Answer: c
Clarification: By Re-carbonation of water softened by excess lime treatment, excess lime is converted into bicarbonate.
8. By which process, odour producing substances is oxidized?
a) Chlorination
b) Liming
c) Re-carbonation
d) Super-chlorination
Answer: d
Clarification: By addition of chlorine dioxide to water, odour producing substances are oxidized.
9. Solids are removed from the water by which of the following unit operation?
a) Inter facial contact
b) Solid stabilization
c) Ion transfer
d) Solids transfer
Answer: d
Clarification: During solids transfer, solids are removed from water by straining, sedimentation, flotation and filtration.
10. Dealkalization results in removal of all the ions from the water.
a) True
b) False
Answer: b
Clarification: Dealkalization results in removal of hydroxides, carbonates and bicarbonates of calcium, sodium and magnesium from water. Demineralization results in removal of all the ions from the water.
11. Organic contaminants are removed from the water by the process of ______
a) Water softening
b) Demineralization
c) Absorption
d) Adsorption
Answer: d
Clarification: Organic contaminants are removed from the water by the attraction and accumulation of one substance on the surface of another.