Hazardous Waste Management Multiple Choice Questions on “Physical Treatment – Stripping”.
1. Stripping is widely used to remove _________
a) Volatile components
b) Organic matter
c) Inorganic matter
d) Chemicals
Answer: a
Clarification: Stripping is widely used to remove volatile components of a liquid mixture by passing stream of gas.
2. Gases passed in stripping process can be ________
a) Evaporated
b) Boiled
c) Condensed
d) Cooled
Answer: c
Clarification: Gases passed in stripping process can be condensed which may yield the organic matter directly.
3. Exotic gases can be used for stripping.
a) True
b) False
Answer: a
Clarification: Air and steam (which assist volatilisation) are frequently used for stripping, but more exotic gases are used in special cases.
4. Which of the following aqueous waste can be subjected to stripping?
a) Lead
b) Platinum
c) Ammonia
d) Arsenic
Answer: c
Clarification: Ammonia rich aqueous waste, phenolic waste, any aqueous waste with volatile organic compounds or contaminants can be subjected to stripping.
5. What do CG stands for in stripping theory (Henry’s law)?
a) Contaminant
b) Contaminant in gaseous phase
c) Contaminant in liquid phase
d) Contaminant in solid phase
Answer: b
Clarification: Stripping theory is given by H = CG / CL. Where, CL is the ratio of the contaminant at equilibrium in the liquid phase, CG is the contaminant in the gaseous phase and H is Henry’s constant.
6. Height of packed stripping tower affects ________
a) Removal efficiency
b) Contaminants
c) Standards
d) Temperature
Answer: a
Clarification: The height of packed stripping tower affects the removal efficiency of the contaminant.
7. _________ flow through the air stripper will control the removal rate of the contaminants.
a) Air-to-water
b) Boiling point-to-air
c) Heating point-to-water
d) Water-to-air
Answer: a
Clarification: Increase in air-to-water flow ratio will usually result in greater removal rates of contaminants.
8. The pressure drop in tower should be between _________ N/m2 per meter of tower height to prevent flooding.
a) 100 to 200
b) 200 to 300
c) 200 to 400
d) 400 to 500
Answer: c
Clarification: The pressure drop in the tower should be between 200 to 400 N/m2 per meter of tower height to avoid flooding. The flooding velocity depends upon the type and size of packing and liquid mass velocity of the contaminant.
9. The air stripper is an example of a _________ contactor.
a) Liquid-gas
b) Liquid-liquid
c) Liquid-solid
d) Liquid-plasma
Answer: a
Clarification: The air stripper is an example of a liquid-gas contactor and the most efficient type of liquid-gas contactor is the packed tower for better contaminant removal.
10. Smaller packing material size in stripping increases ____________
a) Contaminant removal
b) Air removal
c) Waste removal
d) Gas removal
Answer: a
Clarification: Smaller packing material size in stripping increases the area available for stripping and improves the transfer process, thus maximises contaminant removal.
11. Rotary air stripping uses ____________ force.
a) Centripetal
b) Centrifugal
c) Gravitational
d) Pressure