This set of Waste Water Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Adsorption by Activated Carbon”.
1. Activated carbon removes microbial contaminants effectively.
a) True
b) False
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: Charred wood, bones and coconut charcoals were used during 18th and 19th 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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
View Answer
Explanation: 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.
Sanfoundry Global Education & Learning Series – Waste Water Engineering.
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