Category: Environmental Engineering Objective Questions

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.

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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.

Environmental Engineering Multiple Choice Questions on “Biological Characteristic of Water”.

1. Which type of bacteria has a rod shaped structure?
a) Bacilli
b) Cocci
c) Spirilla
d) Vibrio
Answer: a
Clarification: Bacilli (Singular-Bacillus) has a rod shaped structure. Cocci has a spherically shaped structure, Spirilla has a spiral shaped structure and Vibrio has a comma shaped structure.

2. ________ represents the bacterial density that is most likely to be present in water.
a) BOD
b) COD
c) MPN
d) Coliform index
Answer: c
Clarification: Most Probable Number is a number that indicates the bacterial density present in water.BOD and COD are the terms related to the oxygen required by microorganism to oxidize organic and inorganic matter.

3. Which of the following is a better test to identify Coliforms?
a) Coliform index
b) Multiple tube fermentation
c) MPN test
d) Membrane filter technique
Answer: d
Clarification: Membrane filter technique is a better and simpler technique to identify Coliforms. Various results are obtained in a shorter time than the multiple tube fermentation technique. MPN test and coliform index are not used now.

4. What is the temperature at which MPN test is performed?
a) 35^oC
b) 37 ^oC
c) 40^oC
d) 45 ^oC
Answer: b
Clarification: MPN test is performed at 37^oC where different samples of water are mixed with lactose broth and incubated in test tubes for 48 hours.

5. Which of the following statement is/are correct regarding coliform bacteria?
i. It is gram negative
ii. It is rod shaped bacteria
iii. It is a harmless aerobic microorganism
a) i, ii, iii
b) ii, iii
c) i, iii
d) i, ii
Answer: a
Clarification: Coliform bacteria is a gram negative, rod shaped and harmless aerobic microorganism which is found in the intestine of warm blooded animals including human beings.

6. Which of the following is the disease caused by bacterial infections?
a) Amoebic dysentery
b) Infectious hepatitis
c) Typhoid fever
d) Poliomyelitis
Answer: c
Clarification: Amoebic dysentery is caused by protozoan infection, Infectious hepatitis and Poliomyelitis are caused by a viral infection and Typhoid fever is caused by a bacterial infection.

7. The number of bacterial colonies by Agar plate count test should not exceed ____ per ml for potable water.
a) 1
b) 10
c) 100
d) 1000
Answer: c
Clarification: Agar plate count test is a test to count the number of bacterial colonies growing on a specified medium and the permissible limit for the number of bacterial colonies is 100 per ml.

8. If the acid and gas are formed in the multiple tube fermentation technique, the test is _____
a) Positive
b) Continued
c) Negative
d) Discarded
Answer: a
Clarification: The acid and gas formation in the Multiple tube fermentation technique indicates that the test is positive and there are coliform bacteria in the sample.

9. Which bacteria cause the reddish brown deposits in the tank?
a) Escherichia coli bacteria
b) Bacterium coli bacteria
c) Iron bacteria
d) Sulphur bacteria
Answer: c
Clarification: The growth of Iron bacteria causes the discoloration of tank due to reddish brown deposits and turbidity in water.

10. Which bacteria results in the corrosion of iron and steel pipes embedded in soil?
a) Escherichia coli bacteria
b) Bacterium coli bacteria
c) Iron bacteria
d) Sulphur bacteria
Answer: d
Clarification: Sulphur bacteria cause the corrosion of iron and steel pipes embedded in soil. They are both aerobic and anaerobic and are more destructive in marshy or clay soils where anaerobic conditions prevails.

11. Gelatin liquefying bacteria are helpful in the manufacturing of photographic films.
a) True
b) False
Answer: a
Clarification: These bacteria are capable of producing proteolytic ferments that digest and liquefy gelatin. So, their presence in water is helpful in photographic films and glue industries.

Environmental Engineering Multiple Choice Questions on “Various Other Filters”.

1. In which type of filter, water flows in upward direction?
a) Slow sand filter
b) Rapid sand filter
c) Pressure filter
d) Up flow filter
Answer: d
Clarification: Up flow filter is a rectangular or round shape filter in which water flows in upward direction.

2. The up flow filter is used in domestic water supply.
a) True
b) False
Answer: b
Clarification: The up-flow filter is not used in domestic water supply because sudden variation in pressure breaks the sand bridge and cause the bed to expand.

3. In which type of filter, the filtration is done in two opposite directions at the same time?
a) Dual media filter
b) Mixed media filter
c) Bi-flow filter
d) Rapid sand filter
Answer: c
Clarification: In Bi-flow filter, the filtration is done in the opposite direction at the same time. It is divided into single media and dual media bi-flow filter.

4. Which material is provided for the down-flow bed in dual media bi-flow filter?
a) Coal sand
b) Garnet sand
c) Rice husk
d) Graphite
Answer: a
Clarification: In dual media bi-flow filter, coal sand is provided, If the sand is finer than that provided in rapid sand filter, excessive amount of sand will rise into coal bed and sand will become coarser.

5. The rate of filtration of a Micro-Strainer is __________ litres / hour.
a) 10,000-20,000
b) 20,000-30,000
c) 40,000-60,000
d) 50,000-80,000
Answer: d
Clarification: The rate of filtration of a Micro-Strainer is 50,000-80,000 litres per hour. It cannot remove color and other finely divided particles.

6. Which material is provided for the up flow bed in dual media bi-flow filter?
a) Anthracite
b) Sand
c) Rice husk
d) Graphite
Answer: b
Clarification: Sand is provided for the up-flow bed in dual media bi-flow filter. The quality of effluent obtained from up-flow bed in dual media bi-flow filter is inferior than that of the mixed media filter.

7. Which device is used for screening stored water which do not contain microscopic sized particles?
a) Tube settler
b) Clarifier
c) Flocculator
d) Micro-Strainers
Answer: d
Clarification: Micro-Strainers are stainless steel wire cloth that is used for screening stored water that do not contain algae, plankton and micro sized particles.

8. What is the diameter of drum of a Micro-Strainer?
a) 1m
b) 2m
c) 3m
d) 4m
Answer: c
Clarification: The diameter of a drum of Micro-Strainer is 3m and it is 3m wide and single unit of it can deal with about 50,000-80,000 litres/ hour.

9. What is the thickness of a layer of a diatomite filter?
a) 1mm
b) 2mm
c) 3mm
d) 4mm
Answer: c
Clarification: Diatomite filter consists of a layer of diatomaceous earth, having a thickness of 3mm supported on a filter element called the septum.

10. The diatomite is applied on the septum at the rate of ______
a) 100gm/m²
b) 200gm/m²
c) 300gm/m²
d) 400gm/m²
Answer: c
Clarification: The diatomite is applied on the septum at the rate of 300gm/m² to form a precoat of filter media.

11. Consider the following statements regarding diatomite filters.
i. They are not used for water having high turbidity.
ii. They are not suitable for municipal water supplies.
iii. They are not used for temporary and shifting camps.
Which of the above statement is/are false?
a) i, ii, iii
b) i only
c) ii only
d) iii only
Answer: d
Clarification: The diatomite filter is useful for temporary and shifting camps because they require less space, are lighter in weight and are more mobile.