Environmental Engineering Multiple Choice Questions 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
Answer: c
Clarification: 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
Answer: d
Clarification: 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
Answer: d
Clarification: By addition of chlorine dioxide to wastewater, odor producing substances are oxidized.
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
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.
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
Answer: a
Clarification: 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
Answer: a
Clarification: 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
Answer: c
Clarification: By Re-carbonation of water softened by excess lime treatment, excess lime is converted into bicarbonate.
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
Answer: a
Clarification: 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
Answer: b
Clarification: When effluent passes through limestone, carbon dioxide in excess gets converted into soluble bicarbonate.
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
Answer: d
Clarification: 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
Answer: c
Clarification: 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
Answer: b
Clarification: 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.