250+ TOP MCQs on Adsorption by Activated Carbon and Answers

Waste Water Engineering Multiple Choice Questions on “Adsorption by Activated Carbon”.

1. Activated carbon removes microbial contaminants effectively.
a) True
b) False
Answer: b
Clarification: Activated carbon is effective in removing certain organics, chlorine, fluorine or radon from drinking water or wastewater. However, it is not effective for microbial contaminants, metals, etc.

2. The filter once installed need not to be replaced in activated carbon filtration.
a) True
b) False
Answer: b
Clarification: Activated carbon filters are relatively easy to install but requires energy and skilled labour and can even have high costs due to the irregular replacement of the filter material.

3. ___________ has high degree of porosity.
a) Alum
b) Carbon
c) Aluminium
d) Zinc
Answer: b
Clarification: Charred wood, bones and coconut charcoals were used during 18^th and 19^th century. Activated carbon exhibits a high degree of porosity and an extended surface area.

4. Which of the following is not removed by activated carbon?
a) Odour
b) Chlorine
c) Microbes
d) Micro-pollutants
Answer: c
Clarification: Activated carbon filters are efficient to remove certain organics such as unwanted taste, odour and micro-pollutants, chlorine, fluorine or radon from drinking water or wastewater.

5. How many types of water filters are present?
a) 2
b) 3
c) 4
d) 5
Answer: a
Clarification: There are two basic types of water filters. Namely, particulate filters and adsorptive filters. Adsorptive filters contain a material that either adsorbs or reacts with a contamination in water.

6. On which principle does the particulate filters work?
a) Particle’s size
b) Absorb contaminant
c) Reacts with contaminant
d) Adsorb contaminant
Answer: a
Clarification: Adsorptive filters contain a material that either adsorbs or reacts with a contamination in water. Adsorptive activated carbon filtration contains the same principles as those of any other adsorption material. Particulate filters exclude particles by size.

7. What is the average surface area of one gram of carbon?
a) 1000 m²
b) 2000 m²
c) 3000 m²
d) 4000 m²
Answer: c
Clarification: Due to its high degree of micro porosity, just one gram of activated carbon has a surface area in excess of 3,000 m² (32,000 sq ft), as determined by gas adsorption. An activation level sufficient for useful application may be attained solely from high surface area.

8. For which of the following activated carbon is not used?
a) Spill cleanup
b) Air purification
c) Increase in oxygen quantity
d) Groundwater remediation
Answer: c
Clarification: For groundwater remediation, drinking water filtration, spill cleanup, air purification, volatile organic compounds capture from painting, dry cleaning and etc. activated carbon is used.

9. _______ stores natural gas.
a) Sponge
b) Activated carbon
c) Cotton
d) Zinc
Answer: b
Clarification: Activated carbon’s ability is more in storing natural gas and hydrogen gas. The porous material acts as a sponge for different types of gases.

10. What is the range of bonding energies of carbon?
a) 2-3 KJ per mol
b) 3-4 KJ per mol
c) 4-8 KJ per mol
d) 5-10 KJ per mol
Answer: d
Clarification: The gas is attracted to the carbon material via Van der Waals forces. Some carbons have been able to achieve bonding energies of 5–10 kJ per mol.

11. What is the minimum temperature required for carbonization?
a) 200˚C
b) 400˚C
c) 600˚C
d) 800˚C
Answer: c
Clarification: Material which has carbon content is pyrolysed at temperatures in the range of 600–900 °C, usually in the inert atmosphere with gases like argon or nitrogen.

12. Calculate the area of the activated carbon filter for the following details.
Flow: 2000 m³/h.
Rise Velocity: 15m/h
a) 118 m²
b) 135 m²
c) 122 m²
d) 136 m²
Answer: b
Clarification: The area of the filter is calculated based on the flow rate and the rise velocity. Area of the filter is calculated as Flow/ Rise Velocity. Area= 2000/15 =133.33 m² (Rounded off to 135 m²).

13. Calculate the backwash pump required for the activated carbon filter for the following details.
Flow: 1000 m³/h.
Rise Velocity: 15m/h
a) 1000 m³/hr
b) 1608 m³/hr
c) 1288 m³/hr
d) 1200 m³/hr
Answer: b
Clarification: The area of the filter is calculated based on the flow rate and the rise velocity. Area of the filter is calculated as Flow/ Rise Velocity. Area= 1000/15 =67 m². Backwash pump velocity is considered as 24 m/hr. Therefore the backwash pump required is area x velocity = 67 x 24= 1608 m³/hr.

14. What is the quality of Organic content obtained in the effluent by an activated carbon filter?
a) <1 ppm
b) 10 ppm
c) Below detection level
d) 1.5 ppm
Answer: c
Clarification: Organic content is removed by the activated carbon filter is below detection level in the effluent. The activated carbon removes organic content by adsorption. This organic content also contributes to COD, thus activated carbon filter is used in the removal of COD also.

15. What is the quality of Turbidity obtained in the effluent by an activated carbon filter?
a) <1 ppm
b) 10 ppm
c) Below detection level
d) <0.5 ppm
Answer: d
Clarification: Activated carbon removes colour. It also removes turbidity. The net turbidity obtained in the effluent is < 0.5 ppm.

16. Which of these are not removed by an activated carbon filter?
a) TSS
b) Turbidity
c) Colour
d) Odour
Answer: a
Clarification: Activated carbon removes odour and colour. It also removes organic content. It does not remove TSS.

17. Calculate the backwash water volume for the activated carbon filter for the following details.
Net Flow: 3000 m³/h.
Rise Velocity: 15m/h
a) 580 m³
b) 800 m³
c) 680 m³
d) 900 m³
Answer: b
Clarification: The area of the filter is calculated based on the flow rate and the rise velocity. Area of the filter is calculated as Flow/ Rise Velocity. Area= 3000/15 =200 m². Backwash pump velocity is considered as 24 m/hr. Therefore the backwash pump required is area x velocity = 200 x 24= 4800 m³/hr.Backwash is done for 10 mins.Hence the backwash volume = 4800 x 10/60 =800 m³.

18. Calculate the flow of backwash pump required for the activated carbon filter for the following details.
Flow: 2500 m³/h.
Rise Velocity: 15m/h
Backwash pump velocity: 24 m/h
a) 2500 m³/h
b) 3500 m³/h
c) 4000 m³/h
d) 4500 m³/h
Answer: c
Clarification: The area of the filter is calculated based on the flow rate and the rise velocity. Area of the filter is calculated as Flow/ Rise Velocity. Area= 2500/15 =167 m². The backwash pump capacity is calculated as Area of the filter x Backwash pump velocity. Back wash pump capacity required = 167 m² x 24 m/h = 4000 m³/h.