Category: Environmental Engineering Objective Questions

Environmental Engineering online quiz on “Effects of Air Pollution, Design of Stack Height”.

1. Which of the following is not a part of photochemical smog?
a) NO₂
b) O₃
c) PAN
d) SPM
Answer: d
Clarification: Photochemical smog includes NO₂, O₃ and PAN. The damage to vegetation is caused by NO₂, O₃ and PAN.

2. Which air pollutant cause corrosion of building?
a) SO₂
b) SO₃
c) CO
d) NO₂
Answer: a
Clarification: SO₂ is a colorless and irritant gas that causes corrosion of building.

3. Which of the following air pollutant effects plants the most?
a) Fluorine
b) SO₂
c) PAN
d) HCl
Answer: a
Clarification: Fluorine is the most dangerous air pollutant that affects plant, whereas SO₂, PAN and HCl effects the leaf of the plant.

4. The size of cigarette particles is ______________
a) 1μm
b) 10μm
c) 10μm
Answer: c
Clarification: Cigarette particles are <1μm and >25% particles are deposited in the lungs.

5. Concentration of fluorine that cause a phototoxicological effect on the plant is ___________
a) 0.1μg/m³
b) 0.3μg/m³
c) 0.5μg/m³
d) 1μg/m³
Answer: b
Clarification: Fluorine is produced through aluminium or glass industries and it causes a phototoxicological effect on the plant at a concentration of 0.3μg/m³.

6. Which of the following gas is not colorless?
a) NO
b) O₃
c) Pb
d) SO₃
Answer: a
Clarification: NO is a highly reactive gas which is reddish brown in color, whereas O₃, Pb and SO₃ are colorless gas.

7. The effective height of stack is given by ___________
a) Plume height / Actual height of the stack
b) Plume height * Actual height of the stack
c) Plume height – Actual height of the stack
d) Plume height + Actual height of the stack
Answer: d
Clarification: Effective height of the stack, H = h₁ + h₂ where, h₁ is the plume height and h₂ is the actual height of stack.

8. The chimney is emitting particulate matter. Which of the following is the correct expression of the height of the chimney? Here ‘Kp’ represents the emission of particulate matter.
a) HC = 74 K_p^0.27
b) HC = 14 K_p^0.27
c) HC = 14 K_p^0.47
d) HC = 74 K_p^0.33
Answer: a
Clarification: Height of the chimney HC = 74 K_p^0.27 where HC is in metre and ‘Kp’ is in tonnes per hours.

9. What is the minimum height of the chimney in a thermal power plant of capacity 350MW?
a) 100m
b) 220m
c) 380m
d) 60m
Answer: b
Clarification: As the capacity of the thermal plant lies between 200MW and 500MW, the minimum height height of the chimney is 220m.

10. Which of the following is the correct expression of the height of chimney emitting sulfur dioxide?
a) HC = 74 K_p^0.27
b) HC = 14 K_p^0.33
c) HC = 14 K_p^0.47
d) HC = 74 K_p^0.33
Answer: b
Clarification: Height of the chimney, HC = 14 K_p^0.33 when the chimney is emitting sulfur dioxide. Here, the unit of ‘Kp’ is in kg/hour and HC is in metre.

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Environmental Science Multiple Choice Questions on “Particulates”.

1. What is the size range of respirable suspended particulate matter?
a) Less than 1 micrometre
b) Less than 10 micrometre
c) Less than 100 micrometre
d) Less than 0.1 micrometre
Answer: b
Clarification: Particulate matter of size less than 10 micrometre, fall under the category of suspended particulate matter.

2. Air-borne particulates are classified as group 1 carcinogens.
a) True
b) False
Answer: a
Clarification: Air borne particulate matter is classified as group 1 carcinogen by WHO and IARC.

3. Which of the following is a viable particulate?
a) Smoke
b) Mist
c) Dust
d) Moulds
Answer: d
Clarification: Viable particulate matter consists of miniscule living organisms that float in the atmosphere.

4. Which type of particulate is condensed form of vapours?
a) Mist
b) Dust
c) Fumes
d) Smoke
Answer: c
Clarification: Fumes are condensed vapours, especially metallic vapour and is regarded as a type of particulate matter.

5. What is the composition of photochemical smog?
a) Nitrogen oxides, ketones and ozone
b) VOCs and hydrocarbons
c) Peroxy-acetyl-nitrate, peroxy-benzoyl-nitrate, peroxy fornyl-nitrate
d) All of the mentioned
Answer: d
Clarification: The photochemical smog constitutes of oxides of nitrogen, aldehydes, ketones, ground level ozone as well as PAN, PBN, PFN which are the free radicals formed due to reaction of ketones, nitrogen oxides and oxygen in the presence of sunlight.

6. Which of the following constituent of photochemical smog causes the bronzing of plants?
a) PBN
b) PAN
c) PFN
d) Ketones
Answer: b
Clarification: Peroxy-acetyl-nitrate is known to have sever effects on plants and causes it’s surface to bronze and glaze.

7. What is the reason behind the yellow colour of smog?
a) Nitrogen dioxide
b) Sulphur dioxide
c) Sulphate ions
d) Nitrate ions
Answer: c
Clarification: Sulphate ions formed by the conversion of sulphur dioxide due to high humidity and low temperature, is responsible for the yellow colour of smog.

8. Which of the following aerosols have the best absorbing properties?
a) Carbon black
b) Soot
c) Elemental Carbon
d) All of the mentioned
Answer: d
Clarification: Elemental carbon (also called soot/ carbon black/ black carbon) is a type of aerosol with the best absorbing property and used to absorb poisonous gases.

9. What is the size range of atmospheric particulate matter?
a) 0.1 – 10 microns
b) 0.1 – 1 micron
c) 1 – 10 microns
d) 10 – 100 microns
Answer: a
Clarification: Atmospheric particulate matter comprises of particles of sizes in the range of 0.1 – 10 micrometres.

10. In rural areas, what has contributed significantly to particulate pollution?
a) Incomplete combustion in vehicles
b) Using wood for fire and cooking
c) Fertilisers
d) All of the mentioned
Answer: b
Clarification: In rural areas, due to usage of wood for fire and cooking leading to the emission of soot and other organic gases has significantly contributed to particulate pollution.

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Environmental Engineering Problems on “Design Elements of Sedimentation”.

1. The detention period of a rectangular tank is given by _______
a) t0 = LBH/Q
b) t0 = LB/HQ
c) t0 = Q/LBH
d) t0 = HQ/LB
Answer: a
Clarification: The detention period of a rectangular tank is given by t0 = LBH/Q where L is the length, B, is the breadth and H is the height of rectangular tank and Q = discharge rate.

2. The average time required by water to pass through the settling tank is called _______
a) Detention time
b) Flowing through period
c) Time of flow
d) Mean time
Answer: b
Clarification: The average time required by water to pass through the settling tank is called ‘flowing through period’ which is always less than the detention period.

3. Range of Displacement efficiency in the plain sedimentation tank is ___________
a) 0.25-0.5
b) 0.1-0.2
c) 0.5-0.8
d) 0.3-0.6
Answer: a
Clarification: Displacement efficiency is defined as the ratio of flowing through period to the detention period and varies from 0.25 to 0.5 in the plain sedimentation tank.

4. The quantity of water flowing per hour per unit horizontal area is called ________
a) Detention time
b) Flowing through period
c) Displacement time
d) Overflow rate
Answer: d
Clarification: Overflow rate = Q/A where Q is discharge rate in litre per day, A is the horizontal area in m².

5. Settling tank efficiency is reduced by _______
i. Eddy current
ii. Surface current
iii. Density current
a) i, ii
b) i, ii, iii
c) ii, iii
d) i, iii
Answer: b
Clarification: Eddy current is set up by the inertia of the incoming fluid, surface current is induced due to wind in open tank and density current cause cold water to under run the warm water to flow across its surface.

6. 1cm per second settling velocity corresponds to a surface loading of ______ litre per day per m².
a) 36000
b) 864000
c) 24000
d) 6000
Answer: b
Clarification: Surface loading = 864000*settling velocity = 864000*1=864000litre per day per m² where settling velocity is in cm/Sec.

7. What will be the surface area of the basin for a flow of 2*10⁶ litre per day having a surface loading rate 10,000 litre/day/m²?
a) 100
b) 200
c) 300
d) 400
Answer: b
Clarification: Surface area of basin = flow of water/surface loading rate = 2000000/10000=200m².

8. The detention period of the vertical flow clarifier is _______
a) 1-1.5
b) 2
c) 3.5
d) 4
Answer: a
Clarification: Typical design value of the detention period for the vertical flow clarifier is between 1 to 1.5 hours. They normally remove the flocculent.

9. The design value of surface loading for horizontal flow circular sedimentation is _______
a) 30-40m³/m²/d
b) 20-30m³/m²/d
c) 10-20m³/m²/d
d) 50-100m³/m²/d
Answer: a
Clarification: For the design of horizontal flow circular sedimentation, the surface loading rate is 30-40m³/m²/d and its design detention period period is 2-2.5 hours.

10. Detention time for a circular tank is given by _______
a) t = D (D + 0.785H) /Q
b) t = D (0.1D + 0.785H) /Q
c) t = D2 (0.01D + 0.785H)
d) t = D2 (0.01D + 0.785H) /Q
Answer: d
Clarification: Detention time for a circular tank is given by t = D2 (0.01D + 0.785H) /Q where D is the diameter of the tank, H is the vertical depth of wall and Q is the discharge rate.

11. The sedimentation basin should be made as deep as possible.
a) True
b) False
Answer: b
Clarification: The particle settling efficiency is independent of the depth of the basin and should be made as shallow as possible.

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Environmental Engineering Assessment Questions on “Factors Affecting Chlorination”.

1. When turbidity in water increases, the efficiency of chlorine?
a) Decreases
b) Increases
c) Slightly increases
d) Remains constant
Answer: a
Clarification: The presence of turbidity in water makes it difficult to obtain free residual chlorine. So, it is preferred to apply chlorine after filtration when water is free from turbidity.

2. The presence of metallic compounds in water _______ the efficiency of chlorine.
a) Decreases
b) Increases
c) Slightly decreases
d) Remains constant
Answer: a
Clarification: The presence of metallic compounds like iron and manganese utilized a large amount of chlorine and decrease the efficiency of chlorine for disinfection.

3. The amount of hypochlorous acid formed when pH of water is 8 is _______________
a) 95% of total free chlorine
b) 80% of total free chlorine
c) 30% of total free chlorine
d) 5% of total free chlorine
Answer: c
Clarification: When chlorine is added to water, the amount of hypocholorous acid decreases as pH of water increases. It is 95% of total free chlorine when pH < 6.7 and 30% of total free chlorine when pH of water is 8.

4. Which type of chlorine is represented by the green line as shown in the following figure?

Figure: Kill rates of E-coli
a) Free residual chlorine
b) Ammonia chlorine
c) Combined residual chlorine
d) Residual chloramine
Answer: a
Clarification: Free residual chlorine composed of dissolved hypochlorite ions, hypochlorous acid and chlorine gas present in water. It is represented by the green line in the above figure.

5. Which type of chlorine is represented by the red line as shown in the following figure?

Figure: Kill rates of E-coli
a) Free residual chlorine
b) Ammonia chlorine
c) Combined residual chlorine
d) Residual chloramine
Answer: b
Clarification: Ammonia chlorine is represented by the red line in the figure which results in speedy disinfection, it contains ammonia and chlorine in the ratio of 1:1 in the following figure.

6. The efficiency of chlorine increase by ______________
a) Presence of metallic compounds
b) When the pH of the water increases
c) When the pH of the water decreases
d) Turbid water
Answer: c
Clarification: The efficiency of chlorine is inversely proportional to the pH of water. When the pH of the water containing chlorine decreases, the efficiency of chlorine increases.

7. The contact time for disinfection by free chlorine is ______________
a) 20 minutes
b) 30 minutes
c) 40 minutes
d) 60minutes
Answer: a
Clarification: The contact time for disinfection by free chlorine is 20 minutes and it depends on pH, temperature, type and concentration of microorganism.

8. The contact time for disinfection by combined chlorine is ______________
a) 20 minutes
b) 30 minutes
c) 40 minutes
d) 60 minutes
Answer: d
Clarification: The contact time for disinfection by combined chlorine is 60 minutes. The % kill of bacteria depends upon the time of contact between chlorine and microorganism.

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Environmental Engineering Multiple Choice Questions on “Types of Valves”.

1. Which of the following is known as Shut off valve?
a) Air relief valve
b) Sluice valve
c) Pressure relief valve
d) Altitude valve
Answer: b
Clarification: Sluice valve is called as shut off valve as the water in pipes can be shut off from them. They offer no resistance to the flow of water when the valve is wide open.

2. The spacing between the Sluice valves is ____________
a) 10m
b) 30m
c) 80m
d) 180m
Answer: d
Clarification: The spacing between the Sluice valves lies between 150-300m. They can be placed at street corners or where the two pipelines intersect.

3. Which of the following is used to stop the water supplies when required?
a) Air relief valve
b) Sluice valve
c) Pressure relief valve
d) Altitude valve
Answer: b
Clarification: Sluice valves are used to stop the water supplies when required. They are also helpful in dividing the water mains into suitable sections.

4. The Gate valves are made of _______ with brass mountings.
a) Cement concrete
b) Reinforced concrete
c) Cast iron
d) Galvanized iron
Answer: c
Clarification: The Gate valves are made of cast iron with brass mountings. They are of two types, namely solid wedge type and double disk type.

5. _______ valves are used to discharge air from the water pipelines.
a) Air relief valve
b) Sluice valve
c) Pressure relief valve
d) Altitude valve
Answer: a
Clarification: The water flowing through the water pipelines contains some air, which may interfere with the flow. So, it is removed with the help of Air relief valves.

6. _________ valve allows water to flow in one direction only.
a) Air relief valve
b) Sluice valve
c) Reflux valve
d) Altitude valve
Answer: c
Clarification: Reflux valves are an automatic device that allows water to flow in one direction only and avoids the back flow of water or prevents the damage of the pump.

7. Which of the following is known as washout valve?
a) Scour valve
b) Sluice valve
c) Reflux valve
d) Altitude valve
Answer: a
Clarification: Scour valve is known as washout valve. They are either located at the dead ends or at the lowest point in the mains.

8. Which of the following valve is known as a safety valve?
a) Scour valve
b) Pressure relief valve
c) Reflux valve
d) Altitude valve
Answer: b
Clarification: Pressure relief valve is known as automatic cut off or safety valves. They are located at points where pressure is likely to be maximized.

9. Which of the following is also known as a check valve?
a) Scour valve
b) Pressure relief valve
c) Altitude valve
d) Reflux valve
Answer: d
Clarification: Reflux valve is known as non-return valve or check valve. They are placed in water pipes which obtain water directly from the pumps.

10. The valve which is preferred in elevated tanks and stand pipes is ____________
a) Altitude valve
b) Pressure relief valve
c) Reflux valve
d) Air relief valve
Answer: a
Clarification: Altitude valve is preferred in elevated tanks and stand pipes. They are open when the pressure on the pump side is less than the tank side of the valve.

11. ______ valves are used to remove sand and silt from the pipelines.
a) Air relief valve
b) Sluice valve
c) Scour valve
d) Altitude valve
Answer: c
Clarification: Scour valves are provided to blow off the sand and silt deposited in the pipeline. This operation is done manually.

Environmental Engineering Multiple Choice Questions on “Devices Associated with Sewer”.

1. Which of the following is not a sewer appurtenance?
a) Storm regulator
b) Flushing tank
c) Water tank
d) Manholes
Answer: c
Clarification: Sewer appurtenance are the structures that are constructed for the efficient performance and maintenance of sewers. The water tank is not a sewer appurtenance.

2. ______ provides the working space for maintenance and inspection of sewers.
a) Lamp holes
b) Manholes
c) Flushing tanks
d) Working chamber
Answer: d
Clarification: Working chamber provides the working space for maintenance and inspection of sewers. It is situated at the lower part of the manhole.

3. The minimum thickness of the side wall of the manhole is __________
a) 50mm
b) 100mm
c) 225mm
d) 300mm
Answer: c
Clarification: The minimum thickness of the side wall of the manhole is 225mm and they are commonly made of bricks.

4. Which of the following is situated above the working chamber in a deep manhole?
a) Main sewer
b) Access shaft
c) Branch sewer
d) Channel
Answer: b
Clarification: The access shaft lies above the working chamber which is just below the manhole cover.

5. If the depth of excavation is 4m. What is the thickness of the brick wall of manhole?
a) 12cm
b) 16cm
c) 20cm
d) 26cm
Answer: d
Clarification: The thickness of brick wall of manhole (in cm) = 10 + 4*depth of excavation (in m) = 10 + 4*4 = 26cm.

6. Into how many types manholes are classified on the basis of depth of manhole?
a) 3
b) 5
c) 6
d) 7
Answer: a
Clarification: Manholes are classified into Shallow, Normal and Deep on the basis of depth of the manhole.

7. The minimum diameter of the access shaft for a circular manhole is __________
a) 60cm
b) 20cm
c) 30cm
d) 10cm
Answer: a
Clarification: Access shaft is the upper portion of manhole whose minimum diameter for a circular manhole is 60cm.

8. The manhole in which inclined pipe for transfer of sewage from branch to main sewer is __________
a) Deep manhole
b) Ramp
c) Drop manhole
d) Normal manhole
Answer: b
Clarification: Ramp has an inclined pipe for the transfer of sewage which is used when the drop is less.

9. The thickness of the manhole frame is __________
a) 10cm
b) 15cm
c) 20cm
d) 40cm
Answer: c
Clarification: The manhole frame is made of cast iron having 10cm width and the thickness is 20cm.

10. The minimum diameter of the working chamber for a circular manhole is __________
a) 0.8m
b) 0.9m
c) 1m
d) 1.2m
Answer: d
Clarification: The working chamber is the lower portion of the manhole having a minimum diameter of 1.2 m.

11. The manhole in which vertical pipe is used for the transfer of sewage from branch to main sewer is __________
a) Deep manhole
b) Ramp
c) Drop manhole
d) Normal manhole
Answer: c
Clarification: Drop manholes are provided with vertical pipe so that the sewage does not fall on the people working at manhole.

12. Which sewer appurtenance allows lamp in the sewer?
a) Catch basin
b) Drop manhole
c) Lamp hole
d) Storm regulators
Answer: c
Clarification: The lamp hole is acting as an inspection device where lamps are inserted. It is used when the construction of manhole is difficult.

13. Which sewer appurtenance is used for removing rainwater from the roads?
a) Catch basin
b) Gullies
c) Lamp hole
d) Storm regulators
Answer: b
Clarification: Gullies are placed along the roadside at an interval of 30-60m to remove the rainwater from the road.

14. ________ removes oil and grease from the sewage.
a) Catch basin
b) Gullies
c) Grease and oil traps
d) Storm regulators
Answer: c
Clarification: The oil and grease sticks to the sides of the sewer and reduces the sewer capacity. So, it is essential to remove oil and grease, which can be done by the device called as Grease and oil traps.

15. Which device is used to prevent the clogging of sewer pipes?
a) Flushing tank
b) Drop manhole
c) Lamp hole
d) Storm regulators
Answer: a
Clarification: Flushing tank is used to flush and clean the sewer to prevent it from clogging. This is done either by automatic flushing tank or by hand operated flushing tank.