Multiple choice question for engineering
Set 1
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
Answer: b [Reason:] 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
Answer: b [Reason:] 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
Answer: c [Reason:] 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
Answer: a [Reason:] 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
Answer: c [Reason:] 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
Answer: c [Reason:] 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 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
Answer: c [Reason:] Biological filters are used in septic tank for treatment of sewage when the percolation rate is >60minutes. The percolation rate is the rate at which water flows through the soil.
Set 2
1. Which of the following method is not used for desalination?
a) Distillation
b) Coagulation
c) Reverse osmosis
d) Freezing
Answer
Answer: a [Reason:] Coagulation is not used for desalination. It is done for removing the suspended impurities from water.
2. Which of the following is not a type of distillation plant?
a) Vertical tube evaporator
b) Multistage flash evaporator
c) Tube settler
d) Multi-effect multistage flash evaporator
Answer
Answer: c [Reason:] Tube settler is not a type of distillation plant. It is used for shallow depth sedimentation.
3. Multistage flash evaporator produces _____ kg of water per kg of prime steam.
a) 5
b) 10
c) 15
d) 20
Answer
Answer: d [Reason:] Multistage flash evaporator produces 20 kg of water per kg of prime steam.
They operate on the brine recycling basis.
4. Which of the following is the best evaporative desalinating method?
a) Vertical tube evaporator
b) Multistage flash evaporator
c) Tube settler
d) Multi-effect multistage flash evaporator
Answer
Answer: b [Reason:] Multistage flash evaporator is the best evaporative desalinating method in which efficiency of multistage flash evaporator can be further improved by the use of flash enhancers.
5. The number of stages involved in the desalination using a multistage flash evaporator is
a) 20
b) 38
c) 49
d) 69
Answer
Answer: d [Reason:] Multistage flash evaporator uses 69 stages in the desalination process. The vapors released during flash each stage condenses to heat the incoming sea water and gives fresh water.
6. Which of the following desalination method is more suitable for brackish water than sea water?
a) Distillation
b) Solar evaporation
c) Reverse osmosis
d) Freezing
Answer
Answer: c [Reason:] Reverse osmosis is more suitable for brackish water than sea water. In this process, some part of water permeates the membrane and is collected as fresh water while the remaining water passed through the turbine for recovery.
7. The process in which the brackish water is forced across a permeable membrane by mechanical forces is called as
a) Filtration
b) Semi filtration
c) Coagulation
d) Hyper filtration
Answer
Answer: d [Reason:] The process in which the brackish water is forced across a permeable membrane by mechanical forces is called as hyper filtration. The pressure applied must be greater than the osmotic pressure.
8. In which desalination process, the salt ions are removed from seawater by means of electric current?
a) Distillation
b) Electro-dialysis
c) Reverse osmosis
d) Freezing
Answer
Answer: b [Reason:] In Electro dialysis, the salt ions are removed from seawater by means of electric current where two membranes are used- one who is more selective to anode and another who is more selective to cathode.
9. In Electro-dialysis, the electric energy which required is
a) Directly proportional to cation permeable membrane
b) Directly proportional to anion permeable membrane
c) Directly proportional to salt concentration
d) Inversely proportional to salt concentration
Answer
Answer: c [Reason:] In Electro-dialysis, the passage of electric current helps the diffusion of cation and anion permeable membrane and the energy required is directly proportional to the concentration of salt in the saline water.
10. The maximum salt concentration up to which desalination of brackish water is possible by Electro-dialysis is
a) 1000ppm
b) 2000ppm
c) 3000ppm
d) 5000ppm
Answer
Answer: d [Reason:] Electro-dialysis is suitable for brackish water with a total concentration of salt up to 5000ppm and leaving 100ppm in the treated water.
11. In which desalination process, the cooling of sea water is done to obtain fresh water?
a) Distillation
b) Electro-dialysis
c) Reverse osmosis
d) Freezing
Answer
Answer: d [Reason:] In freezing method of desalination, cooling of the water takes place to obtain fresh water by separation of the ice and brine liquor.
12. State whether the following statement is true or false.
The pressure freezing process works on the vacuum free vapor compression principle.
a)True
b)False
Answer
Answer: b [Reason:] Zarchin colt freezing process works on the vacuum free vapor compression principle. In this process, water is used as a refrigerant.
13. In which desalination process, solar energy is used?
a) Reverse osmosis
b) Freezing
c) Electro-dialysis
d) Solar evaporation
Answer
Answer: d [Reason:] In the solar evaporation, the solar energy is used as a source of heat energy. The solar energy striking the earth is estimated to be a 250BTU / day/m2.
14. The solar evaporation can yield about ___ kg of fresh water per day per m2 of basin surface.
a) 5
b) 10
c) 15
d) 20
Answer
Answer: a [Reason:] The solar evaporation can yield about 5 kg of fresh water per day per m2 of basin surface under good sunshine conditions. The solar energy is absorbed by salt water and fresh water is produced.
Set 3
1. Which of the following is used in ceramic industries?
a) Electrostatic precipitator
b) Dynamic precipitator
c) Spray tower
d) Wet cyclonic scrubber
Answer
Answer: b [Reason:] Dynamic precipitator is used in ceramics, woodworking industries. It uses centrifugal force to remove gaseous matter.
2. Wet scrubbers are classified into ____ types.
a) 2
b) 3
c) 5
d) 6
Answer
Answer: b [Reason:] Web scrubbers are used to remove air pollutants and are classified into Spray towers, Wet cyclonic scrubber and Venturi scrubber.
3. The centrifugal collectors are classified into how many types?
a) 3
b) 4
c) 5
d) 2
Answer
Answer: d [Reason:] The Centrifugal collectors are classified into the Cyclone collector and Dynamic precipitator.
4. Which of the following air pollution control device has maximum efficiency?
a) Electrostatic precipitator
b) Dynamic precipitator
c) Spray tower
d) Wet cyclonic scrubber
Answer
Answer: a [Reason:] Electrostatic precipitator has the maximum efficiency among the rest with a value of 99%.
5. Which of the following fluid is used in web scrubbers?
a) Lime
b) MgSO4
c) NaCl
d) K2Cr2O7
Answer
Answer: a [Reason:] Apart from lime, K2CO3, a slurry of MnO and MgO and water can be used in Web scrubber.
6. Which of the following is incorrect regarding fabric filter?
a) They can remove very small particle
b) They are liable to chemical attack
c) They have low efficiency in comparison to venturi scrubber
d) They can handle large volume of gas at relatively high speed
Answer
Answer: c [Reason:] The efficiency of Electrostatic precipitator is <99%, whereas the efficiency of Fabric filter is >99%.
7. Which of the following removes both gaseous and particulate contaminants?
a) Venturi scrubber
b) Gravitational settling chamber
c) Dynamic precipitator
d) Wet scrubber
Answer
Answer: a [Reason:] Venturi scrubber removes both both gaseous and particulate contaminants. The minimum particle size removal is 0.5μm and its efficiency is < 99%.
8. Identify the correct statement regarding Electrostatic precipitator.
a) Minimum particle size removal is <0.5μm
b) They can be operated at high temperature
c) It has low maintenance cost
d) It does not cause any freezing problem
Answer
Answer: b [Reason:] Electrostatic precipitator can be operated at high temperature between 3000C to 4500C, has a high maintenance cost, can cause freezing problem and minimum particle size removal is < 1μm.
Set 4
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
Answer: b [Reason:] 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
Answer: d [Reason:] 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
Answer: a [Reason:] 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
Answer: b [Reason:] 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
Answer: c [Reason:] Anthracite is used as a top layer in dual media filter having a thickness of 30-40cm.
6. How the performance of 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
Answer: a [Reason:] 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
Answer: b [Reason:] 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
Answer: d [Reason:] 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
Answer: c [Reason:] 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
Answer: d [Reason:] 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
Answer: b [Reason:] 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
Answer: d [Reason:] 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.
Set 5
1. Which of the following is not commonly used as a filter material in the treatment of water?
a) Sand
b) Anthracite
c) Crushed rock
d) Garnet sand
Answer
Answer: c [Reason:] Sand, Anthracite and Garnet sand are used as a filter material but crushed rock is not used in the treatment of water.
2. Which of the following is correct regarding the cheapest filter material used in water treatment?
a) Sand>Anthracite>Garnet sand
b) Sand<Anthracite>Garnet sand
c) Sand<Anthracite<Garnet sand
d) Sand=Anthracite>Garnet sand
Answer
Answer: a [Reason:] Sand is the cheapest filter material followed by anthracite whereas Garnet sand is the costliest among them and is not used as a sole filter material but as a constituent in mixed media filter.
3. Consider the following statements regarding sand as filter material.
1. It should be free from clay or silt
2. Organic matter should be present in the sand
3. It should be nonuniform
Which of the above statement is/are correct?
a) 1, 2
b) 1 only
c) 2, 3
d) 1, 2, 3
Answer
Answer: b [Reason:] Sand used as a filter material should be free from clay, silt, organic matter or other impurity. It should be uniform and of proper size.
4. The uniformity characteristics of sand expressed in terms of .
a) Effective size
b) Effective size and uniformity coefficient
c) Uniformity coefficient
d) Mean velocity
Answer
Answer: b [Reason:] The uniformity characteristics of sand are expressed in terms of effective size and uniformity coefficient. Effective size is called as effective diameter and uniformity coefficient is a measure of particle range.
5. ____ represents the size of sand particle such that 10% of particles are finer than this size.
a) D0.1
b) D1
c) D10
d) D100
Answer
Answer: c [Reason:] D10 represents the size of sand particle such that 10% of particles are finer than this size. It is also called the effective size or effective diameter and is measured in mm.
6. What is CU in the expression CU= D60/D10 where D60 and D10 are the sizes of particle such that 60% and 10% of the particles are finer than these sizes respectively?
a) Coefficient of compaction
b) Coefficient of consolidation
c) Uniformity coefficient
d) Effective size
Answer
Answer: c [Reason:] The uniformity coefficient is a measure of particle range and it is the ratio of D60 and D10 sizes. It is denoted by CU.
7. The effective size of sand of the slow sand filter is
a) 0.1-0.2mm
b) 0.2-0.3mm
c) 0.4-0.7mm
d) 1-2mm
Answer
Answer: b [Reason:] The effective size of sand of the slow sand filter is 0.2-0.3mm and for rapid sand filter, the effective size is 0.4-0.7mm.
8. What is the value of specific gravity of sand filter?
a) 2
b) 2.6
c) 3.1
d) 3.5
Answer
Answer: b [Reason:] The specific gravity of sand filter lies in the range of 2.55-2.65. So, the value 2.6 lies in the range of specific gravity of sand filter.
9. The value of uniformity coefficient for uniformly graded sand is ______
a) 0
b) 1
c) 10
d) 100
Answer
Answer: b [Reason:] Uniformity coefficient CU= D60/D10
For uniformly graded sand, CU= 1
So, D60 = D10.
10. The value of specific gravity for Garnet sand is ____
a) 2.1
b) 3.6
c) 4.2
d) 5.1
Answer
Answer: c [Reason:] Garnet sand is a dense material with a specific gravity of 4.2 and is used as a constituent in mixed media filter. It is a costlier filter material.
11. Which of the following statement is correct?
a) Ignition loss of filter should not exceed 3%
b) Wearing loss of filter sand should not exceed 5%
c) The range of CU for the slow sand filter is 3-5
d) The range of CU for the rapid sand filter is 3-5
Answer
Answer: c [Reason:] The ignition loss of filter should not exceed 0.7%, wearing loss of filter sand should not exceed 3%, range of CU for the slow sand filter is 3-5 and for the rapid sand filter is between 1.3 and 1.7.