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Multiple choice question for engineering

Set 1

1. The design solid surface loading in an activated sludge process is
a) 10 kg/m2/day
b) 25 kg/m2/day
c) 15 kg/m2/day
d) 35 kg/m2/day

View Answer

Answer: b [Reason:] The design solid surface loading during a gravity thickening process in an activated sludge plant lies between 25 to 30 kg/m2/day.

2. Which of the following plant nutrient is not found in municipal sewage?
a) Arsenic
b) Phosphorous
c) Potassium
d) Nitrogen

View Answer

Answer: a [Reason:] Potassium, Phosphorous and Nitrogen are found in municipal sewage having maximum plant nutrient concentration of 3.3% of total municipal waste as nitrogen.

3. The design pressure of ____ is applied on pressure type flotation device.
a) 1kg/cm2
b) 2kg/cm2
c) 3kg/cm2
d) 6kg/cm2

View Answer

Answer: c [Reason:] In pressure type flotation device, 3-5kg/cm2 pressure is applied to the sludge thickening process.

4. The design Hydraulic loading rate of the gravity thickener is _______ m3/m2/day.
a) 20
b) 39
c) 40
d) 85

View Answer

Answer: a [Reason:] The range of design Hydraulic loading rate of the gravity thickener is 20-25m3/m2/day.

5. Which of the following process is not involved in sludge thickening?
a) Gravity thickening
b) Vacuum filter
c) Air flotation
d) Centrifugation

View Answer

Answer: b [Reason:] The process involved in sludge thickening are gravity thickening, air flotation and centrifugation.

6. 7% of solids concentration of thickened sludge is obtained from gravity thickener.What is the type of sludge?
a) Primary sludge
b) Secondary sludge
c) Tertiary sludge
d) Activated sludge

View Answer

Answer: d [Reason:] When the thickened sludge, solid concentration is between 7-9, the type of sludge obtained from gravity thickner is activated.

7. Which of the following is not used for drying of sludge?
a) Multiple effect evaporation
b) Dual effect evaporation
c) Rotary dryer
d) Spray dryer

View Answer

Answer: b [Reason:] The process used for drying of sludge is multiple effect evaporation, rotary dryer, spray dryer and flash dryer.

8. In which of the following method, the sludge is rotated for dewatering process?
a) Centrifugation
b) Drying lagoon
c) Drying bed
d) Vacuum filter

View Answer

Answer: a [Reason:] In the centrifugation process, the force is applied so that rotation of sludge takes place which helps in the dewatering of sludge.

9. The dewatered sludge cannot be disposed by
a) Composting
b) Heat drying
c) Acid fermentation
d) Incineration

View Answer

Answer: c [Reason:] Acid fermentation is a sludge digestion process and composting, heat drying and incineration are the methods of disposal of dewatered sludge.

10. In which of the following process, the sludge is dried and disposed in land?
a) Centrifugation
b) Drying lagoon
c) Drying bed
d) Vacuum filter

View Answer

Answer: c [Reason:] Good amount of dried solids is produced by drying bed process and they are commonly used in the sludge dewatering process due to their low cost and better efficiency.

11. Which of the following is not a drying bed?
a) Wedwire beds
b) Artificial media
c) Filter press
d) Conventional sand

View Answer

Answer: c [Reason:] There are 5 types of drying beds, namely wedwire beds, artificial media, conventional sand, paved and vacuum assisted drying bed.

12. Which of the following is not suitable for dewatering of raw sludge?
a) Centrifugation
b) Drying lagoon
c) Drying bed
d) Vacuum filter

View Answer

Answer: b [Reason:] In drying lagoon, if raw sludge is used that contain supernatant liquor, foul smell and fly nuisance occur in the dewatering process.

13. Which of the following is not a part of dewatering process?
a) Drying bed
b) Air flotation
c) Vacuum filter
d) Drying lagoon

View Answer

Answer: b [Reason:] Air flotation is a part of the sludge thickening process and drying bed, drying lagoon and vacuum filter are the part of the dewatering process.

Set 2

Answer question 1 to 4 using the figure given below.

environmental-engineering-questions-answers-stormwater-flow-q1-q2-q3-q4

Figure 54.1: Hourly variation of sewage flow

1. Which of the following represents the minimum flow?
a) A
b) B
c) C
d) D

View Answer

Answer: a [Reason:] The figure clearly shows that the minimum flow occurs at point A and its magnitude is 50.

2. Which of the following represents the peak flow?
a) A
b) B
c) C
d) D

View Answer

Answer: b [Reason:] The peak flow is the maximum flow which occurs at point B and its magnitude is 170.

3. The point R in the figure represents the ________
a) Minimum flow
b) Maximum flow
c) Average rate of flow
d) Peak flow

View Answer

Answer: c [Reason:] The average rate of flow lies between the maximum and minimum flow. Here, R represents the average rate of flow which lies between point B and A.

4. At what time the peak flow takes place?
a) 3hours
b) 7hours
c) 10hours
d) 14hours

View Answer

Answer: c [Reason:] The peak flow takes place at point B and the corresponding time is 10 hours.

5. In India, the maximum sewage flow occurs normally in which month?
a) July
b) January
c) February
d) December

View Answer

Answer: a: [Reason:] In India, the maximum sewage flow occurs during June and July as maximum utilization of water takes place.

6. The minimum sewage flow occurs normally in which month in India?
a) March
b) January
c) August
d) July

View Answer

Answer: b [Reason:] The minimum sewage flow in India is assumed to occur during December or January.

7. The peaking factor is defined by
a) Peak flow * Average flow
b) Peak flow – Average flow
c) Peak flow + Average flow
d) Peak flow / Average flow

View Answer

Answer: d [Reason:] The peaking factor is the ratio of Peak flow to the Average flow and it is highest for domestic sewer as they receive the flow directly from the source.

8. Which of the following has a maximum peaking factor?
a) Domestic sewer
b) Branch sewer
c) Main sewer
d) Trunk sewer

View Answer

Answer: a [Reason:] The domestic sewer has the maximum peaking factor of 6 while Branch sewer, Main sewer and Truck sewer has a peaking factor of 3, 2.5 and 2 respectively.

9. The Lateral sewer has a peaking factor of ___
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: d [Reason:] The peaking factor of lateral sewer lies between 4 to 6 which is greater than Branch sewer, Main sewer and Truck sewer.

10. The population of the city is 30,000. What is the peaking factor?
a) 1
b) 2
c) 2.25
d) 2.5

View Answer

Answer: d [Reason:] When the population of the city is between 20,000 to 50,000, the peaking factor is 2.5.

11. State whether the following statement is true or false.
The peaking factor is directly proportional to the population of the city.
a) True
b) False

View Answer

Answer: b [Reason:] When the population of the city is less than 20,000, the peaking factor is 3.5 and when the population of the city is above 7,50,000, the peaking factor is 2. So, the peaking factor varies inversely with the population.

12. _________ flow persists for various time duration.
a) Minimum sewage
b) Maximum sewage
c) Sustained
d) Average sewage

View Answer

Answer: c [Reason:] Sustained flow persists for various time duration. They are important in sewage design when they are higher or lower than than average flow.

13. The wet weather flow is also known by ______
a) Minimum sewage flow
b) Maximum sewage flow
c) Storm water flow
d) Average rate of flow

View Answer

Answer: c [Reason:] The wet weather is also known by the storm water flow and is commonly abbreviated as W.W.F.

14. Consider the following statement.
The storm water flow depends on
1. Catchment area
2. Ground slope
3. Quality of water
4. Rainfall duration
Which of the following is correct?
a) 1, 2
b) 1, 2, 3
c) 1, 2, 4
d) 1, 4

View Answer

Answer: c [Reason:] The storm water flow depends on the catchment area, ground slope, permeability of ground, extent of vegetative growth, rainfall intensity and duration, condition of the ground and climatic conditions.

Set 3

1. Which of the following statement is wrong regarding filtration?
a) It removes fine particle
b) It removes suspended solids not removed by sedimentation
c) It does not remove turbidity
d) It removes color

View Answer

Answer: c [Reason:] Filtration is a primary turbidity removal process.It also removes color, suspended solids and fine particle.

2. In which action of filtration, particles coarser than the void size is arrested?
a) Mechanical Straining
b) Sedimentation
c) Biological mechanism
d) Electrolytic action

View Answer

Answer: a [Reason:] In Mechanical Straining, particles coarser than the void size is arrested. The water passing the voids will be free from such particles.

3. In which action of filtration, colloidal particles is removed?
a) Mechanical Straining
b) Sedimentation
c) Biological mechanism
d) Electrolytic action

View Answer

Answer: b [Reason:] In the sedimentation action of filtration, colloidal particles arrested in the voids attract other finer particle, settle down in the voids and get removed.

4. Which is the first zone of purification in a sand bed?
a) Autotrophic zone
b) Heterotrophic zone
c) Schmutzdecke zone
d) Electrolytic zone

View Answer

Answer: c [Reason:] Schmutzdecke zone is the first zone of purification in a sand bed. It comes under the biological action of filtration. Schmutzdecke is known as the surface coating.

5. State whether the following statement is true or false.
Schmutzdecke acts as an extremely fine meshed straining mat.
a) True
b) False

View Answer

Answer: a [Reason:] Schmutzdecke is a film of algae, bacteria and protozoa formed on the uppermost layer of sand which helps in the breakdown of organic impurities into harmless compounds acting as a fine mesh straining mat.

6. In which action of filtration, removal of particulate matter takes place?
a) Mechanical Straining
b) Sedimentation
c) Biological mechanism
d) Electrolytic action

View Answer

Answer: d [Reason:] Filter removes the particulate matter by electrostatic exchange where the charge of the filter medium neutralizes the charge of the floc and permitting it to be removed.

7. In which type of filter, rate of filtration is low?
a) Slow sand filter
b) Rapid sand filter
c) Gravity filter
d) Pressure filter

View Answer

Answer: a [Reason:] In Slow sand filter, rate of filtration is low and due to this they requires large land and are expensive to install.

8. What is the color of the surface coating formed during the filtration process?
a) White
b) Brown
c) Green
d) Reddish brown

View Answer

Answer: d [Reason:] The surface coating is formed by the reddish brown deposit of partially decomposed organic matter together with Iron, Alumina, Manganese and Silica.

9. In the ________ zone of purification in filter media, bacteria oxidizes the organic matter completely.
a) Autotrophic
b) Heterotrophic
c) Schmutzdecke
d) Electrolytic

View Answer

Answer: b [Reason:] In Heterotrophic zone, bacteria multiplies in large number, breaks down not only the organic matter but also destroys each other to maintain a balance of life in the filter.

10. The filtration rate of a slow sand filter is _____ litres of water per square metre.
a) 20
b) 30
c) 50
d) 100

View Answer

Answer: d [Reason:] The surface area of the slow sand filter lies between 50m2 to 1000m2 and its filtration rate lies between 100 to 200 litres of water per m2.

11. Identify the correct statement from the following options.
a) Rapid sand filter has a high initial cost
b) Coagulation is essential in slow sand filter
c) Slow sand filter requires skilled supervision
d) Period of cleaning of Rapid sand filter is 1-2 days

View Answer

Answer: d [Reason:] Rapid sand filter is cheap and economical and its period of cleaning is 1-2 days. Neither the coagulation nor the skilled supervision is required in slow sand filter.

Set 4

1. When impurities are separated by the gravitation of settling particles, the operation is called _____
a) Sedimentation with coagulant
b) Plain sedimentation
c) Secondary sedimentation
d) Disinfection

View Answer

Answer: b [Reason:] In plain sedimentation, impurities are separated from a suspending fluid by use of natural forces like gravitational forces..

2. In which type of settling, sedimentation of discrete particles takes place?
a) Zone settling
b) Compression settling
c) Hindered settling
d) Discrete settling

View Answer

Answer: d [Reason:] In Discrete settling, sedimentation of discrete particles takes place where the particles have little tendency to flocculate..

3. In which settling type, dilute suspension of particles takes place?
a) Zone settling
b) Compression settling
c) Hindered settling
d) Discrete settling

View Answer

Answer: c [Reason:] In this type of settling, particle mass increase and it settle down due to flocculation.

4. In which type of sedimentation, flocculent suspension of intermediate concentration takes place?
a) Type I sedimentation
b) Type II sedimentation
c) Type III sedimentation
d) Type IV sedimentation

View Answer

Answer: c [Reason:] In type III sedimentation, inter-particle forces hold the particle together and flocculent suspension of intermediate concentration takes place..

5. In which type of sedimentation, flocculent suspension of high concentration takes place?
a) Type I sedimentation
b) Type II sedimentation
c) Type III sedimentation
d) Type IV sedimentation

View Answer

Answer: d [Reason:] In type IV sedimentation, flocculent suspension of high concentration takes place and particles comes in contact with each other resulting in the formation of structure..

6. What is the settling velocity of the particle if its diameter is 2 * 10-3cm. Given G=2.65, viscosity v=8 * 10-3cm2/Sec?
a) 0.01cm/Sec
b) 0.13cm/Sec
c) 0.24cm/Sec
d) 0.36cm/Sec

View Answer

Answer: b [Reason:] Settling velocity of the particle is given by vs=g (G-1) d2/18v Specific gravity G=1, g=981cm2/Sec, viscosity v=8 * 10-3cm2/Sec vs = 981* (2.65-1) *0.002*0.002/(18*.008) = 0.13cm/Sec..

7. In a rectangular horizontal flow tank, the maximum permissible velocity is ____ m/Sec.
a) 3
b) 0.3
c) 0.03
d) 0.003

View Answer

Answer: b [Reason:] In the rectangular tank, the ideal conditions are that the flow is horizontal, velocity is uniform in all directions and the maximum permissible limit of velocity is .03m/Sec..

8. The time period for which the water is stored in a sedimentation tank is called _____
a) Time of flow
b) Frequency of flow
c) Settling time
d) Detention period

View Answer

Answer: d [Reason:] Detention period is the time period at which the water is stored in a tank. It varies for different purposes like in the septic tank or oxidation pond, its value is higher..

9. Settling velocity of a spherical body in a viscous fluid is given by
a) Reynolds law
b) Newton’s law
c) Stokes law
d) Charles law

View Answer

Answer: c [Reason:] According to Stokes law, settling velocity of the particle is given by vs=g (G-1) d2/18v where G is the specific gravity, d is the diameter of spherical particles and v is the viscosity..

10. In a fill and draw type sedimentation tank, a detention period of ____ hours is provided.
a) 6
b) 12
c) 18
d) 24

View Answer

Answer: d [Reason:] In this tank, water is detained for 24 hours. Then cleaning is done for 6-12 hours, so, the whole cycle of operations takes around 30-36 hours..

11. Which of the following represents the correct relation between displacement velocity and diameter of the particle?
a) v1 = (8Bg (G-1) d/f) 1/2
b) v1 = (8Bg (G-1) d2/f)2
c) v1 = (8Bg (G-1) d/f)
d) v1 = (8Bg (G-1) d/f)2

View Answer

Answer: a [Reason:] Displacement velocity is given by v1 = (8Bg (G-1) d/f)1/2 where B is a constant with value range 0.04-0.06, G is specific gravity, d is the diameter of the particle and f is the Darcy Weisbach friction factor..

Set 5

1. Which of the following is incorrect regarding cast iron pipes?
a) They are non corrosive
b) They are durable
c) They can be produced by centrifugal process
d) Their length varies from 80-100cm

View Answer

Answer: d [Reason:] Cast iron pipes are resistant to corrosion, has long life, can be produced by centrifugal process and their length varies from 3-6m.

2. Horizontally cast iron pipes are called _________
a) Mcwane pipes
b) Pit cast pipes
c) Galvanized iron pipes
d) Wrought iron pipes

View Answer

Answer: a [Reason:] The cast iron pipes which are horizontally cast are called Mcwane pipes while those that are vertically cast are called as Pit cast pipes.

3. Mcwane pipes are ___ stronger in tension than Pit cast pipes.
a) 20%
b) 30%
c) 50%
d) 100%

View Answer

Answer: d [Reason:] Mcwane pipes are 100% stronger in tension and 50% stronger in rupture than Pit cast pipes.

4. The enlarged end of a cast iron pipe is called ________
a) Lead
b) Socket
c) Hemp
d) Spigot end

View Answer

Answer: b [Reason:] The enlarged end of a cast iron pipe is called Socket. It accommodates the spigot end.

5. What is the quantity of lead required for a 15cm diameter cast iron pipe?
a) 5kg
b) 10kg
c) 15kg
d) 20kg

View Answer

Answer: a [Reason:] The quantity of lead required depends on the diameter of cast iron pipe. For 15cm diameter cast iron pipe, it requires 5kg lead, whereas for 120 cm diameter pipe, it requires 55kg lead.

6. Which of the following joint is called run lead joint?
a) Tyton joint
b) Coupled joint
c) Spigot and socket joint
d) Flanged joint

View Answer

Answer: c [Reason:] Spigot and socket joint is called run lead joint as it contains molten lead, which is heated at 4000C and applied at the joints.

7. In which of the following joint, pipes do not have sockets or spigots?
a) Tyton joint
b) Coupled joint
c) Spigot and socket joint
d) Expansion joint

View Answer

Answer: b [Reason:] In Coupled joints, pipes do not have sockets or spigots. There are two types of coupling joints- dresser coupling and victaulic coupling joints. These joints are highly flexible.

8. Which of the following joint is highly influenced by temperature?
a) Tyton joint
b) Coupled joint
c) Spigot and socket joint
d) Expansion joint

View Answer

Answer: d [Reason:] Expansion joints allow the expansion and contraction of the joint due to change in temperature. The space between the socket and spigot in this joint is filled with an elastic gasket.

9. Which of the following is the advantage of cast iron pipes?
a) They are subjected to tuberculation in certain water
b) They are fragile
c) They are heavier
d) They are resistant to corrosion.

View Answer

Answer: d [Reason:] The cast iron pipes are subjected to tuberculation which reduce their carrying capacity, they are fragile, heavier, resulting in more cost when their diameter exceeds 120cm and they are resistant to corrosion.

10. Which grade of concrete is used in Reinforced concrete pipes?
a) M10
b) M15
c) M20
d) M25

View Answer

Answer: d [Reason:] M20 grade of concrete is used for making Reinforced concrete pipes with longitudinal reinforcement equal to at least 0.25% of cross sectional area of concrete.

11. The pre-stressed concrete pipes are used for heads ____
a) <8m
b) <61m
c) >60m
d) <35m

View Answer

Answer: c [Reason:] The pre-stressed concrete pipes are used for heads greater than 60m, plain cement concrete up to 7m and reinforced concrete up to 60m.

12. Which of the following is correct regarding Cement concrete pipes?
a) They are corrosive
b) The maintenance cost is high
c) Unreinforced pipes are liable to tensile crack
d) It is easy to repair them

View Answer

Answer: c [Reason:] Cement concrete pipes are anti corrosive with low maintenance cost, difficult to repair and the unreinforced pipes are subjected to tensile cracks.

13. The tensile strength of Asbestos cement pipes is _____
a) 200kg/cm2
b) 300kg/cm2
c) 400kg/cm2
d) 600kg/cm2

View Answer

Answer: a [Reason:] The tensile strength of Asbestos cement pipes is 200kg/cm2 and its compressive strength is 600kg/cm2.

14. Which of the following is a disadvantage of Asbestos cement pipe?
a) They are light weight
b) They have smooth internal surface
c) They are anti corrosive
d) They are soft and brittle.

View Answer

Answer: d [Reason:] The disadvantage of Asbestos cement pipe is that it is soft and brittle, so they are weak under impact loading due to moving traffic.

15. State whether the following statement is true or false.
Lead pipes are used in water supply mains.
a) True
b) False

View Answer

Answer: b [Reason:] Lead pipes are used in service connection and in internal plumbing, but are not used in water supply mains due to the poisonous effect of lead.

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