Category: Environmental Engineering Objective Questions

Environmental Engineering Multiple Choice Questions on ” Dual Media and Mixed Media Filter”.

1. What is the specific gravity of Anthracite used in a dual media filter?
a) 1
b) 1.4
c) 2.4
d) 4.2
Answer: b
Clarification: The specific gravity of Anthracite is 1.4 and due to this, the beds of it can be expanded at a same backwash rate as sand bed when the size of anthracite grains is twice of sand grains.

2. In which of the following filter, two layers filtering media is provided for filtration?
a) Slow sand filter
b) Pressure filter
c) Rapid sand filter
d) Dual media filter
Answer: d
Clarification: In dual media filter, filtration takes place from coarse to fine media by the provision of two layers filtering media called as dual media and that is why it is called as a dual media filter.

3. What is the size of sand used in a dual media filter?
a) 0.5-1mm
b) 1-2mm
c) 2-3mm
d) 3.5-4mm
Answer: a
Clarification: The size of sand used in a dual media filter is 0.5-1mm and it has a thickness of 20 to 30 cm.

4. The coarser layer used in a dual media filter is of __________
a) Sand
b) Anthracite
c) Garnet sand
d) Rice husk
Answer: b
Clarification: Anthracite is a coarser filter medium used in the dual media filter. It is costlier than sand and it is used as a substitute for sand.

5. The thickness of Anthracite used in dual media filter is __________
a) 10-20cm
b) 20-30cm
c) 30-40cm
d) 40-50cm
Answer: c
Clarification: Anthracite is used as a top layer in dual media filter having a thickness of 30-40cm.

6. How the performance of the rapid sand filter can be improved?
a) Replacing the top 15 cm layer of sand with Anthracite
b) Replacing the bottom15 cm layer of sand with Anthracite
c) Increasing the thickness of a layer of sand
d) Replacing 15 cm layer of Anthracite with sand
Answer: a
Clarification: The performance of rapid sand filter can be improved by capping sand filters with coal where the top 15 cm layer of sand is replaced with Anthracite.

7. The size of Anthracite used in dual media filter is __________
a) 1-2mm
b) 1.25-2.5mm
c) 3-4mm
d) 4-5mm
Answer: b
Clarification: The size of Anthracite used in dual media filter is 1.25-2.5mm and it is placed over a sand of 0.5 to 1mm size.

8. In mixed media filter, the filtration is done from ______
a) Fine to finer
b) Coarse to coarser
c) Fine to coarse
d) Coarse to fine
Answer: d
Clarification: In mixed media filter, the filtration is from coarse to fine and impurities and suspended matter are stored and removed throughout the full depth of the bed.

9. What is the ratio in which coal, sand and garnet are present in the mixed media filter?
a) 2 : 3 : 5
b) 4 : 2 : 1
c) 6 : 3 : 1
d) 1 : 2 : 3
Answer: c
Clarification: In mixed media filter, the coal is placed on top, sand in the middle and garnet at the bottom in the proportion of 60%, 30%, 10% respectively.

10. Which of the following order is correct regarding the specific gravity of the materials used in the mixed media filter?
a) Anthracite coal < Sand > Garnet sand
b) Anthracite coal > Sand > Garnet sand
c) Anthracite coal = Sand = Garnet sand
d) Anthracite coal < Sand < Garnet sand
Answer: d
Clarification: Anthracite coal has a specific gravity of 1.42, sand has a specific gravity of 2.65 and Garnet sand has a specific gravity of 4.2. So, coal has lower, sand has medium and Garnet sand has the highest specific gravity between them.

11. Which of the following order is correct regarding the thickness of layer of the materials used in the mixed media filter?
a) Anthracite coal < Sand > Garnet sand
b) Anthracite coal > Sand > Garnet sand
c) Anthracite coal = Sand = Garnet sand
d) Anthracite coal < Sand < Garnet sand
Answer: b
Clarification: Anthracite coal has a thickness of 45 cm, sand has a thickness of 22.5cm and Garnet sand has a thickness of 7.5 cm. So, coal has highest, sand has medium and Garnet sand has a lower thickness of layer between them.

12. Which of the following is the best filter in terms of rate of filtration?
a) Pressure filter
b) Rapid sand filter
c) Dual media filter
d) Mixed media filter
Answer: d
Clarification: Dual media filter has greater depth of filter media in comparison to rapid sand filter, whereas mixed media filter is an improved version of dual media filter having three materials for filter layers resulting in increased filter run times and water quality.

Environmental Engineering Multiple Choice Questions on “Centrifugal Pump”.

1. The impeller in the volute pump is surrounded by _____________
a) Discharge pipe
b) Throat
c) Suction pipe
d) Volute chamber
Answer: d
Clarification: The impeller in the volute pump is surrounded by a spiral shaped casing called as volute chamber. The shape of the casing is such that the sectional area of flow around impeller increases from the tongue to delivery tube.

2. The advance version of volute chamber is designed by _____________
a) V. Richardson
b) J. Thomson
c) Darcy Weisbach
d) Bernoulli
Answer: b
Clarification: The advance version of volute chamber is designed by J. Thomson where a circular chamber called vortex chamber is provided between the impeller and the volute chamber.

3. Consider the following statements regarding vortex chamber.
i. Reduce the velocity of the pump
ii. Convert pressure energy into kinetic energy
iii. Decrease the efficiency of the pump
Which of the above statement is correct?
a) Only i
b) Only ii
c) Only iii
d) i, ii, iii
Answer: a
Clarification: The vortex chamber reduces the velocity of pump, converts the kinetic energy into pressure energy and increase the efficiency of the pump.

4. A diffuser pump is also called as _______ pump.
a) Reciprocating pump
b) Volute pump
c) Turbine pump
d) Rotary pump
Answer: c
Clarification: A diffuser pump is a reverse pump, so it is also called a turbine pump. It contains a series of guide vanes surrounding the impeller.

5. Depending on the number of impellers, the centrifugal pump is divided into ______________ types.
a) Two
b) Three
c) Four
d) Six
Answer: a
Clarification: The centrifugal pump is divided into a single stage and multistage pump depending on the number of impellers.

6. The each stage in centrifugal pump increase the head by ______________
a) 10m
b) 20m
c) 30m
d) 60m
Answer: c
Clarification: The each stage in centrifugal pump increase the head from 30 to 45m. There can be six stages in a centrifugal pump.

7. Radial flow pump is a pump classified on the basis of _____________
a) Direction of flow
b) Number of impellers
c) Number of entrances to the impeller
d) On the basis of shaft
Answer: a
Clarification: Depending on the basis of the direction of flow, the centrifugal pump is divided into the radial flow pump, mixed flow pump and axial flow pump.

8. Which of the following type of pump is based on the number of entrances to the impeller?
a) Single stage pump
b) Single suction pump
c) Mixed flow pump
d) Horizontal pump
Answer: b
Clarification: Based on the number of entrances to the impeller, the centrifugal pump is divided into single suction and double suction pump. In a single suction pump, the liquid enters from one side of the impeller.

9. The specific speed of a pump is given by _____________
a) NQ^1/2 / H²
b) NQ^1/2 / H^3/4
c) NQ / H^3/4
d) NQ ^1/2 / H^1/4
Answer: b
Clarification: The specific speed of a centrifugal pump is given by NQ^1/2 / H^3/4 Where, N is the rotational speed in rates per minute, Q is the discharge in litres/Sec and H is the head in metres.

10. When the specific speed of the pump is <2600, the type of pump is _____________
a) Reciprocating pump
b) Centrifugal pump
c) Mixed flow pump
d) Axial flow pump
Answer: b
Clarification: The specific speed of the pump is given by NS = NQ^1/2 / H^3/4 and when NS > 2600, the type of pump is centrifugal pump.

Environmental Engineering Questions for Experienced people on “Egg Shaped Sewers and Other Sewer Sections”.

1. Which of the following sewer is called as an ovoid sewer?
a) Asbestos cement sewer
b) Egg shaped sewer
c) Plain cement sewer
d) Salt glazed sewer
Answer: b
Clarification: Egg shaped sewer is an oval shaped sewer and is also called as an ovoid sewer.

2. Egg shaped sewers are more suitable in a combined system during dry weather flow.
a) True
b) False
Answer: b
Clarification: Egg shaped sewers are more suitable in a combined system during maximum rain water flow as for low flows, they give sufficient velocity.

3. Which of the following is incorrect regarding Egg shaped sewer?
a) It is cheap
b) It is difficult to construct
c) It is less stable
d) It is mainly circular in shape
Answer: a
Clarification: The Egg shaped sewer is expensive as more material is required than other sewer. Moreover, the cost of construction is high.

4. The upper portion of Egg shaped sewer is called as _____
a) Level
b) Arch
c) Invert
d) Wedge
Answer: b
Clarification: The upper portion of Egg shaped sewer is called as arch which is circular in shape and is larger than the lower circular section.

5. The Egg shaped sewer provides ____ velocity for low flows over the circular sewer of equal capacity.
a) Lesser
b) Higher
c) Slightly higher
d) Very high
Answer: c
Clarification: The Egg shaped sewer provides slightly higher velocity for low flows over the circular sewer of equal capacity. This makes it useful during a combined sewerage system.

6. The lower portion of Egg shaped sewer is known as _____
a) Roof
b) Invert
c) Arch
d) Wedge
Answer: b
Clarification: The lower portion of Egg shaped sewer is known as invert which is circular in shape and is smaller than the arch.

7. The height of standard section of Egg shaped sewer is ______ the new shaped section.
a) Equal to
b) Twice of
c) Less than
d) Half of
Answer: a
Clarification: The height of both the standard and a new shaped section of Egg shaped sewer is 3 times the radius of sewer. So, their heights are equal.

8. The ratio of the width of the standard section and new shaped section of Egg shaped section is __________
a) 1:2
b) 2:1
c) 1:1
d) 1:3
Answer: c
Clarification: Width of standard section = 2 times radius of sewer
Width of new shaped section = 2 times radius of sewer
So, their ratio = 1:1.

9. The radius of invert of the standard section of Egg shaped sewer is ____ of the new shaped section.
a) Twice
b) Thrice
c) Half
d) Equivalent
Answer: a
Clarification: Let k be the radius of sewer. The radius of invert of the standard section= 0.5k and the radius of invert of the new shaped section = 0.25k. So, radius of invert of the standard section is twice the new shaped section of Ovoid sewer.

10. _______ denotes the characteristic size of circular cross section of sewer.
a) DN
b) MN
c) QW
d) SE
Answer: a
Clarification: DN denotes the internal diameter of circular cross section of sewer. It is measured in mm.

11. The arch cross section is divided into how many types?
a) 2
b) 3
c) 4
d) 5
Answer: b
Clarification: The arch cross section is divided into 3 types, namely Normal, Extended and Squashed arch cross section.

12. One side walkway is a type of __________
a) Circular cross section
b) Channel cross section
c) Ovoid cross section
d) Arch cross section
Answer: b
Clarification: The channel cross section is divided into 2 types. It includes One side walkway and Two side walkway channel cross section.

13. Which of the following ovoid cross section has the maximum nominal size range?
a) Squashed
b) Extended
c) Normal
d) Wide
Answer: a
Clarification: Squashed ovoid cross section has the maximum nominal size range with breadth and height as 3200mm.

14. There is less deposition of waste in ovoid cross-section.
a) True
b) False
Answer: a
Clarification: Ovoid sewer cross-section offers less deposition of waste which results in better handling of waste in sewage treatment plant during dry weather and reduced emission of waste during wet weather.

To practice all areas of Environmental Engineering for Experienced people, .

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.

Environmental Engineering Multiple Choice Questions on “Construction of Septic Tank”.

1. The disposal of sewage from the septic tank is done by which of the following?
a) Clarifier
b) Soak pit
c) Aerated lagoon
d) Lamp holes
Answer: b
Clarification: Soak pit is a circular pit through which sewage is disposed in the soil.

2. The detention period of a septic tank is ___________
a) 2 hours
b) 12-36 hours
c) 4 hours
d) 1 week
Answer: b
Clarification: The septic tank has a long detention period in comparison to sedimentation than with a detention period of 12 to 36 hours.

3. The concentration of biodegradable organic matter after the septic tank is ___________
a) 50ppm
b) 100ppm
c) 200ppm
d) 75ppm
Answer: c
Clarification: The effluent contains 200-250 ppm of biodegradable organic matter after the treatment from the septic tank.

4. What is the maximum design flow of sewage in a septic tank?
a) 70 liters per person per day
b) 100 liters per person per day
c) 30 liters per person per day
d) 40 liters per person per day
Answer: a
Clarification: The design flow of sewage in a septic tank lies between 40 to 70 liters per person per day.

5. Which of the following is not the method of disposal of sewage from septic tank?
a) Upflow anaerobic filter
b) Soil absorption system
c) Vacuum filter
d) Biological filters
Answer: c
Clarification: Vacuum filter is used in the sludge dewatering process and upflow anaerobic filter, soil absorption system and biological filter are the method of disposal of sewage from the septic tank.

6. The minimum depth of septic tank as per design consideration is ___________
a) 1.8m
b) 1m
c) 1.2m
d) 1.5m
Answer: c
Clarification: The design depth of septic tank lies between 1.2m and 1.8m, so its minimum depth is 1.2m.

7. What is the type of filter used in the septic tank when the rate of percolation is 90 minutes?
a) Slow sand filter
b) Rapid sand filter
c) Biological filter
d) Trickling filter
Answer: c
Clarification: Biological filters are used in a septic tank for the treatment of sewage when the percolation rate is >60minutes. The percolation rate is the rate at which water flows through the soil.