1. In which unit operation, gases are released or absorbed in the water?
a) Gas transfer
b) Ion transfer
c) Solute stabilization
d) Solids Transfer
Answer: a
Explanation: In Gas transfer, gases are released or absorbed in water by exposing the water through aeration under normal, increased or reduced pressure.

2. How many types of aerators are commonly used in the treatment of water?
a) 2
b) 3
c) 4
d) 5
Answer: c
Explanation: There are 4 types of aerators namely Gravity aerators, Spray aerators, Diffusers and Mechanical aerators.

3. Which of the following process is used to remove the colloidal particles from water?
a) Chemical precipitation
b) Chemical coagulation
c) Ion exchange
d) Adsorption
Answer: b
Explanation: Chemical coagulation is used to remove colloidal particles by the use of coagulants which increase the particle size and they settle down.

4. 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
Explanation: Chemical precipitation removes the dissolved substance from water through ion transfer where precipitation of dissolved impurities takes place.

5. 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
Explanation: In solute stabilization, water is stabilized by chlorination or liming so that objectionable solutes are converted into unobjectionable form.

6. In which form of solute stabilization, hydrogen sulfide in water is oxidized into sulfate?
a) Chlorination
b) Liming
c) Re-carbonation
d) Super-chlorination
Answer: a
Explanation: By the process of chlorination, water gets stabilized by the conversion of hydrogen sulfide into sulfate.

7. Which form of solute stabilization occurs when water passes through limestone?
a) Chlorination
b) Liming
c) Re-carbonation
d) Super-chlorination
Answer: b
Explanation: When water passes through limestone, carbon dioxide in excess get converted into soluble bicarbonate.

8. In which process, excess lime is converted into bicarbonate?
a) Chlorination
b) Liming
c) Re-carbonation
d) Super-chlorination
Answer: c
Explanation: By Re-carbonation of water softened by excess lime treatment, excess lime is converted into bicarbonate.

9. By which process, odour producing substances is oxidized?
a) Chlorination
b) Liming
c) Re-carbonation
d) Super-chlorination
Answer: d
Explanation: By addition of chlorine dioxide to water, odour producing substances are oxidized.

10. Solids are removed from the water by which of the following unit operation?
a) Inter facial contact
b) Solid stabilization
c) Ion transfer
d) Solids transfer
Answer: d
Explanation: During solids transfer, solids are removed from water by straining, sedimentation, flotation and filtration.

11. Dealkalization results in the removal of all the ions from the water.
a) True
b) False
Answer: b
Explanation: Dealkalization results in removal of hydroxides, carbonates and bicarbonates of calcium, sodium and magnesium from water. Demineralization results in removal of all the ions from the water.

12. Organic contaminants are removed from the water by the process of ______
a) Water softening
b) Demineralization
c) Absorption
d) Adsorption
Answer: d
Explanation: Organic contaminants are removed from the water by the attraction and accumulation of one substance on the surface of another.

13. Which process of water treatment is done to avoid floating debris, branches, trees or other large particles suspended in water?
a) Screening
b) Aeration
c) Primary sedimentation
d) Secondary sedimentation
Answer: a
Explanation: Screens are used as a pretreatment process for purification of water to avoid large size suspended materials from water.

14. What is the size of the coarse screen used in pretreatment of water?
a) 25mm
b) 50mm
c) 75mm
d) 100mm
Answer: a
Explanation: Coarse screens are used in the form of bars of 25mm diameter size and are spaced at 75 to 100mm centers.

15. The coarse screen is inclined at _____ to facilitate the cleaning or raking.
a) 300
b) 350
c) 450
d) 900
Answer: c
Explanation: The coarse screen is inclined at 450-600 so that they can be easily cleaned with a rake. Moreover, it reduces the flow velocity which also helps in cleaning the screen.

16. The head loss through screen depends on _______________
a) Shape of screen elements
b) Open area, block area
c) Approach velocity
d) Nature of their construction, approach velocity
Answer: d
Explanation: The head loss through the screen is given by, h=B (w/b) 4/3h1*sinx Where h=head loss, h1=approach velocity head, b=minimum width, x=angle of rack, B=shape factor. It also depends on the nature of their construction.

17. The shape factor for circular rods in finding the head loss through the screen is _____
a) 1.79
b) 2.42
c) 1.83
d) 1.45
Answer: a
Explanation: The shape factor rectangular bar with sharp edges is 2.42, for semicircular face is 1.83 and for circular rod is 1.79.

18. Micro strainers are used to remove color in water.
a) True
b) False
Answer: b
Explanation: Micro strainers are used for screening stored water which contains plankton, algae and other microscopic particles.

19. Identify the incorrect statement regarding aeration process.
a) It removes taste and odor
b) It increases the dissolved oxygen content of water
c) It increases the carbon dioxide content of water
d) It is used for mixing chemicals with water
Answer: c
Explanation: Aeration reduces the carbon dioxide content and corrosiveness of water and hence, raises the pH value of water.

20. The reduction of carbon dioxide by cascade aerators is in the range of __________
a) 10-20%
b) 20-30%
c) 40-50%
d) 50-60%
Answer: d
Explanation: Cascade aerators are the gravity aerators in which water falls from 1-3m height such that it comes in contact with air and reduces carbon dioxide content to 50-60%.

21. In which type of aerator, the flow of water is divided into fine streams and small droplets?
a) Cascade aerator
b) Inclined apron aerator
c) Spray aerator
d) Gravel bed aerator
Answer: a
Explanation: In Cascade aerator, the flow of water is divided into fine streams and small droplets such that they come in contact with air in their trajectories and reduces CO2 by 70-90%.

22. ______ are used in fine screen so that they do not get clogged up.
a) Automatic strainers
b) Spray aerators
c) Cascade aerators
d) Gravel bed aerators
Answer: a
Explanation: Automatic strainers are self cleaning devices that remove solids from the flowing liquid continuously and help in a fine screen so that it does not get clogged up.

23. Ferric chloride is effective over a pH range of __________
a) 3.5-6
b) 6.5-8
c) 3.5-6.5
d) 2-5
Answer: c
Explanation: Ferric chloride is effective over a pH range of 3.5-6.5 and above 8.5 whereas if Ferric sulfate is used then, it is effective over a pH range of 4-7 and above 9.

24. Why Magnesium carbonate is not commonly preferred as coagulant?
a) It is expensive
b) It does not remove color
c) Formation of sludge
d) The time required for floc formation is less
Answer: c
Explanation: When magnesium carbonate and lime are dissolved in water, magnesium hydroxide and calcium carbonate are formed which are soluble in water and sludge is formed in slurry form, so they are not commonly used.

25. Which of the following statement is wrong regarding Iron salt?
a) Iron salt produces less floc than Alum
b) Detention time for sedimentation by using Iron salt as coagulant is less
c) Handling of Iron salt requires some skills
d) Iron removes H2S, taste and odor
Answer: a
Explanation: Iron salt produces heavy floc due to which more suspended matter is removed than with alum.

26. Alum is effective when pH of water is between ____
a) 8-10
b) 6-8
c) 6.5-8.5
d) 7-9
Answer: c
Explanation: Alum is effective when pH of water is between 6.5-8.5. Its dose depends on turbidity, color, taste, pH and temperature of water.

27. Why Alum is preferred over other coagulants?
a) It is easy to dewater the sludge formed
b) It imparts corrosiveness to water
c) It reduces taste and odor in addition to turbidity
d) The time required for floc formation is less
Answer: c
Explanation: Alum is preferred over other coagulants because it reduces the taste and odor in addition to turbidity and produce lighter flocs that can be broken easily.

28. What is the normal value of the detention period adopted in a flocculator for design purpose?
a) 30min
b) 60min
c) 90min
d) 100min
Answer: a
Explanation: The detention period in a flocculator for design purpose should be in the range of 10-40min and its normal value should be 30min.

29. The design value of the velocity of flow in a flocculator is _______
a) 0.2-0.8m/s
b) 0.3-0.5m/s
c) 0.6-0.8m/s
d) 0.1-0.5m/s
Answer: a
Explanation:The normal value of the velocity of flow in a flocculator is 0.4m/s and its range is 0.2-0.8m/s.

30. What is the detention period of a clarifier used in the treatment of water?
a) 1hour
b) 2hours
c) 3hours
d) 4hours
Answer: c
Explanation: The detention period of a clarifier is lower than in the plain sedimentation tank and its range is 2.5 to 3 hours.

31. The pulsator clarifier is a type of __________
a) Horizontal flow sludge tank
b) Vertical flow sludge tank
c) Circular sludge tank
d) Plain sedimentation tank
Answer: b
Explanation: The pulsator clarifier is a vertical flow sludge tank in which pulse is generated at interval of 30Sec to give rapid flow for 5-10Sec resulting in the alternative rising up of the sludge blanket.

32. Which device solved the problem of unstable hydraulic conditions and operation of sludge removal equipment?
a) Centrifugal pump
b) Pulsator clarifier
c) Tube settler
d) Flocculator
Answer: c
Explanation: Tube settler solved the problem of unstable hydraulic conditions and operation of sludge removal equipment by providing laminar flow conditions for sedimentation.

33. In which device, the primary mixing is followed by a secondary reaction zone resulting in formation of sludge blanket?
a) Centrifugal pump
b) Flocculator
c) Tube settler
d) Solid contact clarifier
Answer: d
Explanation: In Solid contact clarifier, sludge blanket is formed where straining action occurs to remove some of the finer particles. The thickness of the blanket is 1m.

34. In which type of tube settler, tubes are slightly inclined in the direction of normal flow?
a) Solid contact clarifier
b) Steeply inclined tube settler
c) Vertical tube settler
d) Horizontal tube settler
Answer: d
Explanation: In Horizontal tube settler, the tubes are slightly inclined in the direction of normal flow and the sludge settled is drained by filter backwash.They are used in small plants.

35. 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
Answer: c
Explanation: Filtration is a primary turbidity removal process. It also removes color, suspended solids and fine particles.

36. In which action of filtration, particles coarser than the void size is arrested?
a) Mechanical Straining
b) Sedimentation
c) Biological mechanism
d) Electrolytic action
Answer: a
Explanation: In Mechanical Straining, particles coarser than the void size is arrested. The water passing the voids will be free from such particles.

37. In which action of filtration, colloidal particles are removed?
a) Mechanical Straining
b) Sedimentation
c) Biological mechanism
d) Electrolytic action
Answer: b
Explanation: In the sedimentation action of filtration, colloidal particles arrested in the voids attract other finer particle, settle down in the voids and get removed.

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

39. Schmutzdecke acts as an extremely fine meshed straining mat.
a) True
b) False
Answer: a
Explanation: 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.

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

41. In which type of filter, rate of filtration is low?
a) Slow sand filter
b) Rapid sand filter
c) Gravity filter
d) Pressure filter
Answer: a
Explanation: In Slow sand filter, rate of filtration is low and due to this they requires large land and are expensive to install.

42. What is the colour of the surface coating formed during the filtration process?
a) White
b) Brown
c) Green
d) Reddish brown
Answer: d
Explanation: The surface coating is formed by the reddish brown deposit of partially decomposed organic matter together with Iron, Alumina, Manganese and Silica.

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

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

45. In which of the following filters, the rate of filtration is highest?
a) Slow sand filter
b) Rapid sand filter
c) Pressure filter
d) Roughing filter
Answer: c
Explanation: The rate of filtration is highest in pressure filter and its filtration rate lies between 6000 to 15000 litres per hour per m2 of filter area while in rapid sand and roughing filter, it is between 6000 to 8000 litres per hour per m2 of filter area.

46. The final loss of head in slow sand filter is ______ than rapid sand filter.
a) Higher
b) Lower
c) Slightly Lower
d) Equivalent
Answer: b
Explanation: The loss of head in slow sand filter lies between 15-100cm and of rapid sand filter lies between 30-300cm.The final loss of head in slow sand filter is 100cm while in rapid sand filter is 300cm.

47. The turbidity of water applied to rapid sand filter is less than _______
a) 35-40ppm
b) 10-20ppm
c) 30-40ppm
d) 10-15ppm
Answer: a
Explanation: As before filtration, sedimentation and coagulation process is done, so the turbidity of water should be less than 35-40ppm.

48. The period of cleaning of a slow sand filter is ______ than rapid sand filter.
a) Smaller
b) Larger
c) Slightly smaller
d) Slightly larger
Answer: b
Explanation: The period of cleaning of a slow sand filter is 1-2 months and that of the rapid sand filter is 2-3 days.

49. The bacterial removal efficiency of the rapid sand filter is ______ in comparison to slow sand filter.
a) More
b) Less
c) Equal
d) Better
Answer: b
Explanation: The bacterial removal efficiency of the rapid sand filter is90-99%, whereas of a slow sand filter is 98-99%.

50. How is the grain size distribution of sand in rapid sand filter?
a) Stratified
b) Unlayered
c) Layered with heaviest grains at the top
d) Layered with lightest grains at the top
Answer: d
Explanation: The grain size distribution of sand in rapid sand filter is stratified with lightest grains at the top and heaviest grains at the bottom.

51. Consider the following statement.
i. The penetration of suspended matter is deep in the slow sand filter
ii. The penetration of suspended matter is superficial in the rapid sand filter
iii. Coagulation is not required in the slow sand filter
Which of the above statement is/are correct?
a) Only iii
b) i, ii
c) i, ii, iii
d) ii, iii
Answer: a
Explanation: The penetration of suspended matter is deep in rapid sand filter, whereas the penetration of suspended matter is superficial in slow sand filter.

52. Consider the following statement.
i. The slow sand filter is not efficient in removing turbidity
ii. The slow sand filter has a high initial cost
iii. Skilled supervision is required in slow sand filter
Which of the above statement is/are correct?
a) Only iii
b) i, ii
c) i, ii, iii
d) ii, iii
Answer: b
Explanation: Skilled supervision is not required in the slow sand filter but it is essential in the case of the rapid sand filter.

53. The filter run in rapid sand filter should not be less than _____ hours.
a) 1
b) 6
c) 12
d) 24
Answer: d
Explanation: The filter run in rapid sand filter should not be less than 24 hours and its head loss should not exceed 2m.

54. Consider the following statement.
i. Slow sand filter is not flexible in variation in demand
ii. The rapid sand filter is flexible in fluctuations in demand
iii. The method of cleaning of a slow sand filter involves agitation and back-washing
Which of the above statement is/are correct?
a) i, ii
b) i, ii, iii
c) ii, iii
d) Only iii
Answer: a
Explanation: The method of cleaning of a slow sand filter involves scrapping of top layer to 15 to 25mm whereas in rapid sand filter involves agitation and back-washing.

55. Rapid sand filters are very efficient in the removal of colour.
a) True
b) False
Answer: a
Explanation: Rapid sand filters are very efficient in the removal of color and the intensity of color can be brought down below 3 on cobalt scale.

1. What is called for the collection of rainwater for use?
a) Rain collection
b) Rainwater harvesting
c) Rain digging
d) Rain water pumping
Answer: b
Explanation: Rainwater harvesting is a technique of collection and storage of rainwater into natural reservoirs or tanks. Rainwater can be collected from rivers, roofs and in many places. The stored water can be used in needy situation.

2. What is the name of the process to clean water using filters?
a) Sublimation
b) Oxidation
c) Rainwater harvesting
d) Purification
Answer: d
Explanation: Purification of water is the process of removing undesirable chemicals, biological contaminants and gases from water. Water filter, the device uses small scale quality improvement clean the water for domestic purposes.

3. What is called for the method of removing dust and other particles from water using filters?
a) Filtration
b) Sublimation
c) Rainwater harvesting
d) Evaporation
Answer: a
Explanation: Filtration is a process that removes particles from suspension in water. Removal of particles takes place by a number of mechanisms that include straining, flocculation, surface capture and more types.

4. Which one of the following is the best way to conserve water?
a) Taking shower with less water
b) Taking shower with more water
c) Not taking shower
d) Using other liquids instead of water for shower
Answer: a
Explanation: Using less water in shower save water and it also saves time for shower. Various methods like installation of a low-flow showerhead, turning off the tap when not using, spending less time in shower can conserve water efficiently.

5. What is the gallon to use in new toilets according to Federal plumbing standards?
a) 1.6
b) 2.5
c) 3.9
d) 4.3
Answer: a
Explanation: Old toilets can use 3.5, 5, or even up to 7 gallons of water with every flush. Federal plumbing standards now specify that new toilets can only use up to 1.6 gallons per flush and high efficiency toilets that use up to 1.28 gallons.

6. We only use water for drinking.
a) True
b) False
Answer: b
Explanation: We don’t just use water for drinking. We use water for washing and we use water to produce everything from food to clothing. Fresh water supplies are being used faster than ever for crop production.

7. How many methods of rainwater harvesting are there?
a) One
b) Two
c) Three
d) Four
Answer: b
Explanation: There are two ways of harvesting rainwater, 1. Surface runoff harvesting: In urban area rainwater flows away as surface runoff, this runoff can be used for recharging aquifers. 2. Roof top rainwater harvesting: It is a system of catching rainwater where it falls.

8. How can we increase the water-efficient irrigation system?
a) By pouring unnecessary water to the land
b) By not supplying adequate water
c) By applying drip irrigation method
d) By using more manures
Answer: c
Explanation: Drip irrigation is a method of controlled irrigation in which water is slowly delivered to the root system of multiple plants. Drip irrigation increases the water efficient irrigation system and hence it is very helpful in water conservation.

9. What are the two main types of drip irrigation?
a) Surface and Subsurface drip irrigation
b) Under and Subsurface drip irrigation
c) Top and Surface drip irrigation
d) Top and Under drip irrigation
Answer: a
Explanation: Surface drip irrigation and subsurface drip irrigation are the two main types of drip irrigation. In surface drip irrigation the water is delivered to the surface of the soil directly above the root system of the plants. In subsurface drip irrigation the water is applied directly to the root system.

10. Why should people implement rainwater harvesting?
a) In order to play with the water
b) In order to use during scarcity of water
c) In order to pour the rain water directly to the sewage
d) In order to time pass
Answer: b
Explanation: Rainwater harvesting helps to store the rain water and it can be used during the scarcity of water. We can use as per convince either directly or for recharging groundwater as the rain falling on the surface to flow away fast.

11. Which one of the following is the benefit of rainwater harvesting?
a) Flood mitigation
b) Provide a lot of water to play
c) Create good aesthetic view
d) Decrease the ground water level
Answer: a
Explanation: Rainwater harvesting helps for flood mitigation. Appropriate designed recharges in open public spaces will help to keep the roads from flooding. When water is not allowed to leave the premises there is less chance for choking up of the roads.

12. Which one of the following is an effective way of conserving water?
a) Increase food waste
b) Eat less meat
c) Always turn on the taps
d) Boil the water when there is no need
Answer: b
Explanation: Eat less meat is one of the effective ways of conserving water. Rearing animals for meat and dairy is incredibly water intensive. By cutting down on the amount of meat consume we can save water drastically.

13. What is called for an area surrounding a body of water in which that body of water is subject to?
a) Rainwater harvesting
b) Watershed
c) Water pumping
d) Water cycle
Answer: b
Explanation: Watersheds include groundwater flow as well slowly flows through deep soil. For example, if a river is flowing through a city, its watershed would be the surrounding land that is sloped towards the river including forests.

14. Rainwater harvesting increases the groundwater levels.
a) True
b) False
Answer: a
Explanation: Rainwater harvesting increases the ground water level, it marked the improvement of both the quantity as well as the quality of the groundwater in areas which have implemented rainwater harvesting.

15. 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
Answer: d
Explanation: Cast iron pipes are resistant to corrosion, has long life, can be produced by the centrifugal process and their length varies from 3-6m.

16. Horizontally cast iron pipes are called _________
a) Mcwane pipes
b) Pit cast pipes
c) Galvanized iron pipes
d) Wrought iron pipes
Answer: a
Explanation: The cast iron pipes which are horizontally cast are called Mcwane pipes while those that are vertically cast are called as Pit cast pipes.

17. Mcwane pipes are ___ stronger in tension than Pit cast pipes.
a) 20%
b) 30%
c) 50%
d) 100%
Answer: d
Explanation: Mcwane pipes are 100% stronger in tension and 50% stronger in rupture than Pit cast pipes.

18. The enlarged end of a cast iron pipe is called ________
a) Lead
b) Socket
c) Hemp
d) Spigot end
Answer: b
Explanation: The enlarged end of a cast iron pipe is called Socket. It accommodates the spigot end.

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

20. Which of the following joint is called run lead joint?
a) Tyton joint
b) Coupled joint
c) Spigot and socket joint
d) Flanged joint
Answer: c
Explanation: Spigot and socket joint is called run lead joint as it contains molten lead, which is heated at 4000C and applied at the joints.

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

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

23. 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.
Answer: d
Explanation: The cast iron pipes are subjected to tuberculation which reduces their carrying capacity, they are fragile, heavier, resulting in more cost when their diameter exceeds 120cm and they are resistant to corrosion.

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

25. 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
Explanation: 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.

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

27. 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
Explanation: Sluice valves are used to stop the water supplies when required. They are also helpful in dividing the water mains into suitable sections.

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

29. _______ 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
Explanation: 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.

30. _________ valve allows water to flow in one direction only.
a) Air relief valve
b) Sluice valve
c) Reflux valve
d) Altitude valve
Answer: c
Explanation: 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.

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

32. 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
Explanation: Pressure relief valve is known as automatic cut off or safety valves. They are located at points where pressure is likely to be maximized.

33. 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
Explanation: Reflux valve is known as non-return valve or check valve. They are placed in water pipes which obtain water directly from the pumps.

34. 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
Explanation: 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.

35. A Service connection is a connection from the distribution system to the ______
a) Factory
b) School
c) Industry
d) Consumer
Answer: d
Explanation: A consumer can be a single house, an apartment or a planned block development. A connection to a single house involves tapping the main and installing a corporation cock.

36. Which of the following is not a component of domestic service connection?
a) Water meter
b) Stopcock
c) Tube settler
d) Gooseneck
Answer: c
Explanation: The various components of a domestic service connection are Brass ferrule, Gooseneck, Stopcock, Mains service pipe and Water meter.

37. The length of Goose neck in a domestic service connection is ____________
a) 10cm
b) 20cm
c) 30cm
d) 40cm
Answer: d
Explanation: The Goose neck consists of 40-50cm curved piece of pipe which prevents the breaking of the main service pipe.

38. Which device is used to measure the quantity of water consumed by the consumer?
a) Water meter
b) Stopcock
c) Tube settler
d) Gooseneck
Answer: a
Explanation: Water meter is used to measure the quantity of water consumed by the consumer. It is installed in a suitable chamber with cover.

39. Which of the following is incorrect regarding water meter?
a) Should be durable
b) Easy to maintain and repair
c) Should allow backflow of water
d) Should be rugged
Answer: c
Explanation: Water meter should prevent the back flow of water passing through it. It should not be liable to clogging.

40. Which device is used to measure the velocity of flow for high flows?
a) Water meter
b) Inferential meter
c) Globe valve
d) Gate valve
Answer: b
Explanation: Inferential meter measures the velocity of flow across a cross section whose area is known. They are only used for high flows.

41. Which of the following is an example of Inferential meter?
a) Turbine meter
b) Hydrometer
c) Water meter
d) Gate valve
Answer: a
Explanation: Turbine and rotary meters are examples of Inferential meter. It is also called as velocity meter as they measure the velocity of flow.

42. Which device is used to measure velocity for low flows?
a) Water meter
b) Inferential meter
c) Globe valve
d) Displacement meter
Answer: d
Explanation: Displacement meter is used to measure velocity for flows. Reciprocating, Rotary, Oscillating and Nutating disc meter are the examples of Displacement meter.

43. The method of distribution of water is divided into how many types?
a) 1
b) 2
c) 3
d) 4
Answer: c
Explanation: The method of distribution of water is divided into 3 types and it includes gravity system, pumping system and combined gravity and pumping system.

44. In which of the following distribution system, the clean water flows entirely under gravity?
a) Gravity system
b) Pressure system
c) Combined gravity and pumping system
d) Pumping system
Answer: a
Explanation: The purified water in gravity system flow entirely under gravity. It is the most reliable and economical distribution system.

45. The pressure in the distribution mains does not depend on ____________
a) Altitude to supply water
b) Fire fighting requirements
c) Availability of funds
d) Quality of water
Answer: d
Explanation: The pressure in the distribution mains depends on the height to which water is required to be supplied, fire fighting requirements, whether the supply is metered or not and availability of funds.

48. The pressure in distribution mains in a residential building up to three storeys is ____________
a) 2kg/cm2
b) 5kg/cm2
c) 7kg/cm2
d) 10kg/cm2
Answer: a
Explanation: The pressure in distribution mains in a residential building up to three storeys is 2kg/cm2 and when it is between 3-6 storeys, the pressure is 3kg/cm2.

49. There is a 8 storey residential building in Lucknow. What is the pressure in the distribution mains?
a) 2kg/cm2
b) 5kg/cm2
c) 7kg/cm2
d) 10kg/cm2
Answer: b
Explanation: When the height of residential building is between 6 to 10 storey, the pressure in the distribution mains lies between 4 to 5.5kg/cm2.

50. The velocity of water in a 10 cm diameter pipe should be ____________
a) 0.2m/Sec
b) 0.5m/Sec
c) 0.9m/Sec
d) 1.2m/Sec
Answer: c
Explanation: The velocity of water in a 10 cm diameter pipe should be 0.9m/Sec
Which is 1.2m/Sec when the diameter of pipe is 15cm.

51. In which system of water supply, water is available for 24 hours but uneconomically used?
a) Continuous supply
b) Fixed supply
c) Intermittent supply
d) Low supply
Answer: a
Explanation: In continuous water supply, water is wasted due to a continuous supply of water for 24 hours of the day or long duration of flow.

52. In which system of water supply, water is supplied only during fixed hours of the day?
a) Continuous supply
b) Fixed supply
c) Intermittent supply
d) Low supply
Answer: c
Explanation: In Intermittent supply, water is supplied to the consumer during fixed hours of the day and is adopted when sufficient pressure is not available or sufficient quantity of water is not available.

53. The velocity of water in the pipe is 1.8m/Sec. What is the diameter of pipe used?
a) 10cm
b) 15cm
c) 25cm
d) 40cm
Answer: d
Explanation: It is the maximum diameter of the pipe for which the velocity of water should not be less than 1.8m/Sec.

54. The hourly demand rate is constant throughout the day.
a) True
b) False
Answer: b
Explanation: The hourly demand rate is not constant throughout the day, it is more during morning and evening and less during other parts of the day.

1. _________ is the flow through sewers available during the non-rainfall period.
a) Gradually varied flow
b) Rapidly varied flow
c) Dry weather flow
d) Storm water flow
Answer: c
Explanation: Dry weather flow is the flow through sewers available during non-rainfall period. It consists of domestic sewage and waste water sewage.

2. _______ is the additional flow occurring during rainy season.
a) Gradually varied flow
b) Rapidly varied flow
c) Dry weather flow
d) Storm water flow
Answer: d
Explanation: The storm water flow is the additional flow occurring during the rainy season. It consists of runoff from roofs, streets or open spaces during rainfall.

3. Which flow is also called sanitary sewage?
a) Dry weather flow
b) Storm weather flow
c) Uniform flow
d) Non uniform flow
Answer: a
Explanation: Dry weather flow is the quantity of wastewater that flows through a sewer in dry weather when no storm water is present in the sewer.

4. Which of the following factor does not affect the dry weather flow?
a) Rate of water supply
b) Temperature conditions
c) Population growth
d) Infiltration of groundwater
Answer: b
Explanation: There are four factors that affect the dry weather flow, namely the rate of water supply, population growth, type of area served and infiltration of ground water.

5. The quantity of wastewater is assumed to be ___________ % of the quantity of water supply.
a) 40
b) 50
c) 60
d) 80
Answer: d
Explanation: The quantity of waste water is assumed to be 80 % of the quantity of water supply when no extra water enters the sewer.

6. The sewer should be designed for a minimum of ______ litres of waste water per capita per day.
a) 50
b) 100
c) 150
d) 1000
Answer: c
Explanation: Sewer is an underground carriage system that takes impure water from houses and commercial buildings through pipes to treatment units and they should be designed for a minimum of 150 litres of waste water per capita per day.

7. The size of the town is 15,000. What is the density of population per hectare?
a) 50
b) 75
c) 100
d) 200
Answer: d
Explanation: When the size of the town is between 5000 and 20,000, the density of population per hectare is between 150 and 200.

8. The design period of main and branch sewer is ___________
a) 5years
b) 10years
c) 30years
d) 40years
Answer: c
Explanation: The main and branch sewer is designed for the population that may occur at the end of one generation of 30 years.This period of 30 years is called a design period.

9. ___________ is the process in which groundwater unfiltrate into the sewers.
a) Exfiltration
b) Infiltration
c) Filtration
d) Osmosis
Answer: b
Explanation: Infiltration is the process in which groundwater unfiltrate into the sewers. It increases the load on the treatment work.

10. ________ is the process that indicates the flow of wastewater from the sewer into the ground.
a) Exfiltration
b) Infiltration
c) Filtration
d) Osmosis
Answer: a
Explanation: Exfiltration is the reverse process of Infiltration where flow through sewer decreases and pollution of the ground water increases.

11. In India, the maximum sewage flow occurs normally in which month?
a) July
b) January
c) February
d) December
Answer: a
Explanation: In India, the maximum sewage flow occurs during June and July as maximum utilization of water takes place.

12. The minimum sewage flow occurs normally in which month in India?
a) March
b) January
c) August
d) July
Answer: b
Explanation: The minimum sewage flow in India is assumed to occur during December or January.

13. 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
Answer: d
Explanation: 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.

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

15. The Lateral sewer has a peaking factor of ____________
a) 1
b) 2
c) 3
d) 4
Answer: d
Explanation: The peaking factor of lateral sewer lies between 4 to 6 which is greater than Branch sewer, Main sewer and Truck sewer.

16. The population of the city is 30,000. What is the peaking factor?
a) 1
b) 2
c) 2.25
d) 2.5
Answer: d
Explanation: When the population of the city is between 20,000 to 50,000, the peaking factor is 2.5.

17. The peaking factor is directly proportional to the population of the city.
a) True
b) False
Answer: b
Explanation: 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.

18. _________ flow persists for various time duration.
a) Minimum sewage
b) Maximum sewage
c) Sustained
d) Average sewage
Answer: c
Explanation: Sustained flow persists for various time duration. They are important in sewage design when they are higher or lower than than average flow.

19. 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
Answer: c
Explanation: The wet weather is also known by the storm water flow and is commonly abbreviated as W.W.F.

20. Consider the following statement.
The storm water flow depends on
i. Catchment area
ii. Ground slope
iii. Quality of water
vi. Rainfall duration
Which of the following is correct?
a) i, ii
b) i, ii, iii
c) i, ii, iv
d) i, iv
Answer: c
Explanation: 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.

21. Which type of sewer serves as an outlet for large territory?
a) Lateral sewer
b) Main sewer
c) Branch sewer
d) Separate sewer
Answer: b
Explanation: Main sewer acts as an outlet for the large territory as it receives sewage from many tributary branches.

22. Which sewer collects sewage directly from the house?
a) Main sewer
b) Outfall sewer
c) Lateral sewer
d) Intercepting sewer
Answer: c
Explanation: The first stage of collection of sewage starts from the house which is done by Lateral sewer.

23. _______ sewer collects sewage from the collecting system to a disposal plant?
a) House sewer
b) Outfall sewer
c) Lateral sewer
d) Separate sewer
Answer: b
Explanation: The Outfall sewer is a sewer that carries the sewage from collecting systems and transfers it to a point of final discharge i.e a disposal plant.

24. Which sewer carries both sewage and stormwater?
a) Outfall sewer
b) Separate sewer
c) Main sewer
d) Combined sewer
Answer: d
Explanation: Combined sewer carries both the sewage and the rain water from the roofs of the house and from the street.

25. Which sewer is also called a submarine sewer?
a) Branch sewer
b) Separate sewer
c) Main sewer
d) Lateral sewer
Answer: a
Explanation: Sub main sewer receives sewage from the small area which finally gets discharged into the main sewer. It is also called a branch sewer.

26. Which sewer is used to carry the excess flow of the existing sewer?
a) Branch sewer
b) Relief sewer
c) Main sewer
d) Lateral sewer
Answer: a
Explanation: The Relief sewer is used to carry the excess flow of the existing sewer. It is also called as overflow sewer.

27. Asbestos cement sewers are made from __________
a) Cement, silica
b) Asbestos fibre, copper
c) Asbestos fibre, cement, silica
d) Asbestos fibre, magnesium
Answer: c
Explanation: Asbestos cement sewers are made from the composition of asbestos fibre, cement, silica asbestos fibre acts as a reinforcing material.

28. Which of the following is a disadvantage of asbestos cement sewer?
a) They are light weight
b) They can be easily jointed
c) They are brittle
d) Inside surface is smooth
Answer: c
Explanation: Asbestos cement sewer is weak against the impact force and requires care in handling.

29. Asbestos cement sewer offers resistance to sulfide corrosion.
a) True
b) False
Answer: b
Explanation: Asbestos cement sewer is used as verticals only because they are prone to sulfide corrosion.

30. Which of the following is called a depressed sewer?
a) Lateral sewer
b) Outfall sewer
c) Inverted siphon
d) Main sewer
Answer: c
Explanation: Inverted siphon is also caused as depressed sewer as the pipes between the inlet and the outlet chamber is depressed due to obstruction like roads, bridges etc.

31. The sewage in inverted siphon will flow under __________
a) Air
b) Vacuum
c) Pressure
d) Gravity
Answer: c
Explanation: The sewage in inverted siphon will flow under pressure greater than the atmospheric pressure and it will not flow under gravity.

32. The design self cleansing velocity of an inverted siphon is __________
a) 0.9m/Sec
b) 0.6m/Sec
c) 0.7m/Sec
d) 0.4m/Sec
Answer: a
Explanation: The design self cleansing velocity of an inverted siphon is 0.9m/Sec for caring minimum, maximum and combined sanitary sewage.

33. The minimum diameter of an inverted siphon is __________
a) 5cm
b) 10cm
c) 15cm
d) 25cm
Answer: c
Explanation: The inverted siphon has a minimum diameter of 15cm and it is made of siphon tubes.

34. Which sewer appurtenance discharges the excess sewage flow to relief sewer?
a) Flushing tank
b) Drop manhole
c) Lamp hole
d) Storm regulators
Answer: d
Explanation: Storm regulators prevents the overloading of sewage treatment plants by discharging the excess sewage flow into relief sewer.

35. Storm regulators are classified into how many types?
a) 2
b) 3
c) 4
d) 6
Answer: b
Explanation: Storm regulator is classified into 3 types, namely Overflow weir, Siphon spillway and Leap weir.

36. Which of the following is most effective in preventing the overloading of treatment plants?
a) Street inlets
b) Overflow weir
c) Siphon valley
d) Leap weir
Answer: b
Explanation: In Siphon valley, the siphonic action takes place when the sewage quantity in combined sewer exceeds the fixed level and it get stopped as soon as it falls below that fixed level.

37. Which of the following is called a sewage ejector pump?
a) Solid handling pump
b) Air lift pump
c) Diaphragm pump
d) Reciprocating pump
Answer: a
Explanation: Solid handling pump is also called as sewage ejector pump where pumping of raw sewage takes place which are mostly in solid form.

38. Which of the following pump is used for the removal of grit?
a) Centrifugal pump
b) Pneumatic ejector
c) Rotary screw pump
d) Air lift pump
Answer: c
Explanation: At the Rotary screw pump, the motor rotates on a shaft to lift the solid waste material to a higher level and they are used in grit chambers for removing grit.

39. The septic tank and pump chamber should be kept as deep as possible.
a) True
b) False
Answer: b
Explanation: The septic tank and pump chamber should be placed at shallow depth as it will result in easier inspection, repairment and maintenance of them.

40. Which of the following represents the physical characteristics of water?
a) Chloride content
b) BOD
c) Turbidity
d) COD
Answer: c
Explanation: Turbidity represents the physical characteristic of water, whereas BOD, COD and chloride content represents the chemical characteristic of water.

41. Which of the following is measured in mg/L?
a) Unit weight
b) Coefficient of cohesion
c) Discharge
d) Turbidity
Answer: d
Explanation: The turbidity of waste water is measured in mg/L. The other units of turbidity are ppm, NTU and JTU.

42. Which of the following instrument is used to measure turbidity?
a) Olfactometer
b) Turbidity meter
c) Colorimeter
d) Spectrophotometer
Answer: b
Explanation: Turbidity can be measured by Jackson’s turbidity meter, Baylis turbidity meter, turbidity rod and Nephelometer.

43. When the sewage becomes stronger, the turbidity of wastewater?
a) Increases
b) Decreases
c) Becomes constant
d) Slightly decrease
Answer: a
Explanation: When the sewage becomes stronger, the milkiness in water increases and thus, the turbidity increases.

44. Which colour indicates the fresh sewage?
a) Pink
b) Red
c) Black
d) Grey
Answer: d
Explanation: If the color of sewage is grey, yellow and light brown, then it means that the sewage is fresh.

45. The color of the septic sewage is __________
a) Pink
b) Red
c) Black
d) Grey
Answer: c
Explanation: The color of septic sewage is black or dark brown. It contains either little or no oxygen.

46. The odor in wastewater is measured by __________
a) Osmoscope
b) Chromatography
c) Olfactometer
d) Turbidity meter
Answer: a
Explanation: The odor in waste water is measured by Osmoscope which consist of two 10mm diameter glass tubes which is 300mm long and 8mm wide.

47. In India, the average temperature of sewage is __________
a) 10oC
b) 20oC
c) 40oC
d) 80oC
Answer: b
Explanation: The average temperature of sewage is 20oC. The temperature of sewage is higher than that of the water supply.

48. Identify the incorrect statement from the following?
a) High odor intensity indicates odorless water
b) Fresh sewage is odorless
c) Turbidity can be measured by turbidity rod
d) NTU is a unit of turbidity
Answer: a
Explanation: If the odor intensity of water is 6, it indicates extremely strong odor and when it is 0, it indicates the odorless water.

49. _______ indicates the freshness of sewage.
a) Turbidity
b) Color
c) Temperature
d) COD
Answer: b
Explanation: The color indicates the freshness of sewage. It can be detected easily by the naked eye.

50. The temperature of sewage increases. What will be the effect on the dissolved oxygen in sewage?
a) Remains constant
b) Increase
c) Decrease
d) No effect
Answer: c
Explanation: The temperature and dissolved oxygen are inversely proportional to each other.

51. What is the minimum quantity of dissolved oxygen that should be present in the treated sewage?
a) 6ppm
b) 4ppm
c) 1ppm
d) 10ppm
Answer: b
Explanation: At least, 4ppm of dissolved oxygen should be present in treating sewage otherwise, fishes will die due to lack of dissolved oxygen.

52. The presence of which of the following in sewage indicates nitrogen content before decomposition of sewage?
a) Nitrites
b) Nitrates
c) Free ammonia
d) Albuminoid nitrogen
Answer: d
Explanation: The presence of Albuminoid nitrogen in water indicates the decomposition of sewage has not taken place.It nitrogen is also called as organic nitrogen.

53. The presence of free ammonia in sewage represents ____________
a) Air pollution
b) Old pollution
c) Recent pollution
d) Water pollution
Answer: c
Explanation: The presence of free ammonia in sewage represents recent pollution. Which can be removed from wastewater by the nitrification process.

54. Which chemical is used for the titration of waste water for finding its chloride content?
a) Potassium chloride
b) Sodium chloride
c) Potassium chromate
d) Potassium dichromate
Answer: c
Explanation: Potassium chromate is used for the titration of waste water with silver nitrate solution for finding the chloride content.

55. The type of solids which floats in sewage is __________
a) Suspended solids
b) Settleable solids
c) Dissolved solids
d) Total solids
Answer: a
Explanation: The suspended solids float in sewage. 1000kg of sewage contain 0.112 kg of suspended solids.

56. The presence of which of the following indicates old pollution?
a) Nitrates
b) Nitrites
c) H2S
d) Sulfates
Answer: d
Explanation: The presence of nitrates indicates the old pollution. It also means that the nitrogen is fully oxidized in sewage.

57. ________ is used to find the D.O content of sewage.
a) Winkler method
b) Chromatography
c) Kjeldahl method
d) Olfactometer
Answer: b
Explanation: Wrinkler method is used to find the D.O content of sewage where the D.O content is proportional to the titration of iodine with S2O32- solution.

58. The permissible dose of chloride in domestic sewage is __________
a) 120ppm
b) 10ppm
c) 1ppm
d) 250ppm
Answer: a
Explanation: Domestic sewage includes waste from kitchen, laundry, toilet, bathroom, etc., which contain higher amount of chloride content, so the permissible dose of 120ppm is kept for domestic sewage.

59. Imhoff cone is used to measure the _______
a) Suspended solids
b) Settleable solids
c) Dissolved solids
d) Total solids
Answer: b
Explanation: Imhoff cone is used to measure the settleable solids where wastewater is allowed to stand for a specific time, solids get settled down and the readings are taken through the graduations on the cone.

1. Activated sludge process uses micro-organisms to degrade organics from wastewater.
a) True
b) False
Answer: a
Explanation: An activated sludge process refers to a multi-chamber reactor unit that makes use of highly concentrated micro-organisms to degrade organics and remove nutrients from wastewater to produce a high quality effluent.

2. Activated sludge process degrade organics and _________
a) Improve nutrients
b) Remove nutrients
c) Remove odour
d) Remove taste
Answer: b
Explanation: Highly concentrated micro-organisms are used to degrade organics and remove nutrients from wastewater to produce a high quality effluent that is activated sludge process.

3. What is required to keep the activated sludge suspended?
a) Carbon-dioxide
b) Nitrogen
c) Oxygen
d) Ammonia
Answer: c
Explanation: To maintain the aerobic conditions and to keep the activated sludge suspended, a continuous and well-timed supply of oxygen is required. Flocs of bacteria, which are suspended and mixed with wastewater is used for the process.

4. What does the bacterium use to grow?
a) Oxygen
b) Organic pollutants
c) Water
d) Carbon-dioxide
Answer: b
Explanation: The bacteria use the organic pollutants to grow and transform it to energy, water, carbon-dioxide and new cell material. The bacterium is present in the form of flocs which are suspended and mixed with wastewater.

5. Activated sludge process can be used for treating all types of wastewater.
a) True
b) False
Answer: b
Explanation: Activated sludge systems are suspended-growth type and are used in conventional high-tech wastewater treatment plants to treat almost every wastewater influent as long as it is biodegradable.

6. ________ combines aeration basin and secondary clarifier into a single unit.
a) Primary clarifier
b) Aerobic unit
c) Sequential batch reactor
d) Secondary clarifier
Answer: c
Explanation: An SBR essentially combines the aeration basin and the secondary clarifier of a traditional activated sludge system into a single basin. While the system is in aeration mode, air is supplied by the aeration system and influent enters the basin.

7. What does SBR stand for?
a) Secondary batch reactor
b) Sequential biological reactor
c) Secondary biological reactor
d) Sequential batch reactor
Answer: d
Explanation: SBR stands for a Sequential batch reactor. An SBR essentially combines the aeration basin and the secondary clarifier of a traditional activated sludge system into a single basin.

8. SBR operates as ________ process.
a) Batch
b) Continuous
c) Semi-continuous
d) Discontinuous
Answer: a
Explanation: SBR operates as a batch process. Because sequential batch reactors operate as a batch process, the level of the basin starts out low and the basin fills over several hours as influent enters.

9. When the aeration system shuts off, the basin begins to perform as a ______
a) Primary clarifier
b) Secondary clarifier
c) Anaerobic unit
d) Aeration unit
Answer: b
Explanation: When the filling/ aeration phase is complete, the aeration system shuts off and the basin begins to function as a secondary clarifier. Suspended solids and micro-organisms settle to the bottom of the tank and clarified water is left near the surface.

10. _______ provides the dual purpose of providing DO and mixing of the mixed liquor and wastewater.
a) Flocculation
b) Aeration
c) Sedimentation
d) Clarification
Answer: b
Explanation: Aeration serves the dual purpose of providing dissolved oxygen and mixing of the mixed liquor and wastewater in the aeration tank. Two methods are commonly used to disperse oxygen from the air to the micro-organisms; Surface Aeration and Diffused Aeration.

11. Aeration consumes less energy in the activated sludge process compared to other processes.
a) True
b) False
Answer: b
Explanation: Aeration occurs in many water and wastewater treatment processes, but in the activated sludge process and its variants, it consumes more energy than other processes, by far.

12. What does OTR stand for?
a) Oxygen transfer rate in standard conditions
b) Oxygen transfer rate in clean water
c) Oxygen transfer efficiency in clean water
d) Oxygen transfer efficiency in standard conditions in the clean water
Answer: b
Explanation: OTR stands for oxygen transfer rate in clean water. SOTR stands for oxygen transfer rate in clean water. OTE stands for Oxygen transfer efficiency in the clean water. SOTE stands for oxygen transfer efficiency in standard conditions in clean water.

13. Which of the following is not a standard condition for aeration?
a) 40˚C
b) 1 atm
c) Zero salinity
d) Zero DO
Answer: a
Explanation: Various standard conditions are mentioned for the aeration process. The standard temperature is considered to be 20˚C along with 1 atmospheric pressure, zero salinity and zero dissolved oxygen.

14. What is the symbol used to define the ratio of the process to clean water mass transfer?
a) Alpha
b) Beta
c) Gamma
d) Sigma
Answer: a
Explanation: The ratio of the process to clean water mass transfer is called alpha factor and is symbolized by alpha.

15. _________ is the actual mass of oxygen transferred per unit time.
a) OTR
b) SOTR
c) OTE
d) SOTE
Answer: a
Explanation: The OTR is the actual mass of oxygen transferred per unit time and it is the key process variable for design. The DO saturation concentration is the concentration of dissolved oxygen at saturation with no reactions in the liquid.

16. High solubility of CO2 ______ pH.
a) Maintains
b) Reduces
c) Increases
d) Nullifies
Answer: b
Explanation: High solubility of CO2 reduces the pH of water which causes excessive consumption of lime or other neutralizing agents in coagulation and softening process. The corrosiveness of water is also higher at lower pH values.

17. What is the range of pH above which aeration is required?
a) 2 mg/L
b) 5 mg/L
c) 8 mg/L
d) 10 mg/L
Answer: d
Explanation: Exposure of water droplets to air for 2 seconds will lower the CO2 by 70-90%. If CO2 > 10mg/L aeration is recommended. Otherwise, the lime addition should be used to neutralize the CO2.

18. H2S is highly soluble in water.
a) Tue
b) False
Answer: a
Explanation: H2S is highly soluble in water. Hydrogen sulphide poisoning is one of the leading causes of accidents. If its concentration is above 5 ppm moderate odour is present. If its concentration increases above 300 ppm, it leads to unconsciousness and death.

19. Which of the following is not used for iron removal?
a) Oxidation
b) Reduction
c) Gasification
d) Absorption
Answer: b
Explanation: Oxygenation of water is done by gasification and absorption. The removal of iron from water or wastewater can be done by various methods such as oxidation, gasification and absorption.

20. How many types of aerators are present?
a) 2
b) 3
c) 4
d) 5
Answer: c
Explanation: There are four types of aerators. They are gravity aerators, spray aerators, diffused air aeration systems and mechanical aerators. Air stripping is done to remove toxic volatile organics and volatile compounds.

21. Which of the following is a prime lake pollutant?
a) Iodine
b) Phosphorous
c) Potassium
d) Sodium
Answer: b
Explanation: Phosphorous is a prime lake pollutant that promotes the algal bloom and destroys the quality and appearance of a lake.

22. The turbulence decreases the DO content of water.
a) True
b) False
Answer: b
Explanation: The turbulence increases the DO content of water, however, beyond a certain limit, it scours the sediments placed at the bottom.

23. The dilution factor is expressed by _____________
a) Volume of diluted sample + Volume of sewage
b) Volume of diluted sample / Volume of sewage
c) Volume of diluted sample – Volume of sewage
d) Volume of diluted sample* Volume of sewage
Answer: b
Explanation: The dilution factor is the ratio of volume of diluted sample of water to the volume of sewage. It is used in finding the BOD of water.

24. The tolerance limit of BOD of sewage to be disposed on land is ____________
a) 100ppm
b) 200ppm
c) 500ppm
d) 400ppm
Answer: c
Explanation: The tolerance limit of BOD of sewage to be discharged into sea water is 100ppm while to be disposed on land is 500ppm.

25. The tolerance limit of pH value of sewage to be discharged into sea water is ____________
a) 1-5ppm
b) 2-9ppm
c) 5.5-9ppm
d) 6-10ppm
Answer: c
Explanation: The tolerance limit of pH value of sewage to be discharged into sea water or to be disposed on land is between 5.5 and 9ppm.

26. The dilution factor is 400. What should be the type of treatment given to the water?
a) Preliminary treatment
b) Sedimentation, Flocculation
c) Complete treatment
d) No treatment
Answer: a
Explanation: When the dilution factor lies between 300 and 500, then preliminary treatment is given to the water.

27. The tolerance limit of oil and grease of sewage to be disposed on land is ____________
a) 40ppm
b) 30ppm
c) 20ppm
d) 10ppm
Answer:b
Explanation: The tolerance limit of oil and grease of sewage to be disposed on land is 30ppm while on sea water is 20ppm.

28. The minimum depth to which sewage should be discharged of sea water is ____________
a) 0.5m
b) 1m
c) 2m
d) 3m
Answer: d
Explanation: The minimum depth to which sewage should be discharged of sea water is 3m to avoid marine pollution.

29. The tolerance limit of COD of sewage to be discharged in sea water is ____________
a) 250ppm
b) 100ppm
c) 40ppm
d) 20ppm
Answer: a
Explanation: The tolerance limit of COD of sewage to be discharged in sea water and on land for irrigation purpose is 250ppm.

30. Which of the following is called as a conventional trickling filter?
a) Rapid sand filter
b) Slow sand filter
c) High rate trickling filter
d) Low rate trickling filter
Answer: d
Explanation: Low rate trickling filter is called as a conventional trickling filter. It is also called a standard rate and percolating filter.

31. The BOD after the filtration of sewage from the low rate trickling filter is ___________
a) 40-50%
b) 80-90%
c) 70-80%
d) 90-99%
Answer: b
Explanation: The BOD of the effluent obtained after the filtration of sewage from the low rate trickling filter is between 80 to 90% and the effluent obtained is highly nitrified and stabilized.

32. Which of the following is the correct expression of the aeration period in hours?
a) V/Q
b) 24V/Q
c) V/24Q
d) Q/V
Answer: b
Explanation: Aeration period = 24V/Q where V is the volume of the tank and Q is the quantity of sewage. It is measured in hours.

33. Which of the following activated sludge process has minimum food to microorganism ratio?
a) Extended aeration
b) Step aeration
c) Modified aeration
d) Conventional
Answer: a
Explanation: Extended aeration process has minimum food to microorganism ratio of 0.5 which means it has the maximum BOD removal efficiency.

34. The maximum aeration period for a conventional activated sludge system is ___________
a) 2 hours
b) 3 hours
c) 4 hours
d) 6 hours
Answer: d
Explanation: The detention period for a conventional activated sludge system is between 4 to 6 hours.

35. The organic loading in an activated sludge plant is defined as ___________
a) Mass of BOD per day/Volume of the aeration tank
b) Volume of aeration tank/Mass of BOD per day
c) The mass of BOD per day/Volume of secondary clarifier
d) Aeration period * Volume of aeration tank
Answer: a
Explanation: The organic loading in an activated sludge plant is defined as the mass of BOD to the aeration tank in grams per unit volume of aeration tank in m3.

36. _________ is defined as a volume in ml occupied by 1 gram of solid in the mixed liquor after 30 minutes of settling.
a) BOD loading
b) Suspended solid volume
c) Sludge volume index
d) Organic loading
Answer: c
Explanation: Sludge volume index is used to indicate the settling behavior of sludge. It is measured in ml/gm.

37. The design value of food to microorganism ratio in the tapered aeration sludge process is ___________
a) 0.1
b) 0.2
c) 0.4
d) 0.8
Answer: c
Explanation: The design value of food to microorganism ratio is 0.3-0.4 for a tapered aeration sludge process.

38. Which of the following sludge process has maximum aeration period?
a) Conventional process
b) Extended process
c) Step aeration process
d) Tapered aeration
Answer: b
Explanation: Extended process has a maximum aeration period of 12 to 24 hours.

39. The maximum BOD removal efficiency of the Step aeration process of the activated sludge system is ___________
a) 92%
b) 80%
c) 99%
d) 78%
Answer: a
Explanation: The BOD removal efficiency of the step aeration process of the activated sludge system is between 85% to 92%.

40. BOD of sewage is dependent on food to microorganism ratio.
a) True
b) False
Answer: a
Explanation: If the food to microorganism ratio increases, BOD removal from the sewage will decrease.

41. _________ is the time at which sewage is detained in the aeration tank.
a) Average time
b) Detention time
c) Aeration period
d) Reaeration period
Answer: c
Explanation: Aeration period decides the loading rate at which sewage is introduced in the aeration tank.

42. Which of the following has minimum hydraulic retention time?
a) Conventional process
b) Extended process
c) Modified aeration process
d) Complete mix process
Answer: c
Explanation: Modified aeration process has a minimum hydraulic retention time with an aeration period of 1.5 hours.

1. What is the principle behind which opacity monitors/transmissometers work?
a) Change in capacitance for various gaseous media, between two stationary plates
b) Pressure exerted by a fixed volume of gas enclosed in a container of specific dimension
c) Scattering of light transmitted through a gas stream
d) None of the mentioned
Answer: c
Explanation: Like the name suggests, opacity monitors or transmissometers work by transmitting light into a particular stream of gas, and gives information regarding the combustion conditions and efficiency.

2. Are any of the following monitors used to measure the concentration of particular gases from the exhaust generated in vehicles?
a) Opacity monitors
b) Gaseous emission monitors
c) Opacity & Gaseous emission monitors
d) None of the mentioned
Answer: b
Explanation: These monitors are used to measure the concentrations of certain gases such as oxygen, carbon monoxide, oxides of sulphur and nitrogen from the exhaust.

3. What does the abbreviation NDIR stand for, in the category of spectrometric analysers?
a) Non-Destructive Integrated Restoration
b) Neo-Destructive Integrated Radiation
c) Non-Dispersive Infrared
d) Neo-Dispersive Integrated Radiation
Answer: c
Explanation: NDIR detectors/analysers are used to monitor sulphur dioxide, oxides of nitrogen and carbon, hydrocarbons, etc.

4. Non-Dispersive Ultraviolet (NDUV) analysers are primarily used to detect which of the following two gases?
a) Oxygen and Carbon Dioxide
b) Oxygen and Nitrogen Dioxide
c) Nitrogen Dioxide and Sulphur Dioxide
d) Sulphur Dioxide and Oxygen
Answer: c
Explanation: NDUV analysers are mainly used to detect nitrogen dioxide and sulphur dioxide.

5. NDUV monitors use a reference gas to analyse other gases.
a) True
b) False
Answer: b
Explanation: NDIR monitors use a reference gas for analysis and not NDUV, which is the main difference between the two.

6. NDUV analysis is also known as differential absorption.
a) True
b) False
Answer: a
Explanation: NDUV method uses a reference wavelength which has less absorption capabilities to find out variations in absorption with respect to this reference wavelength in different media.

7. Fluorescence analysers are used to analyse which of the following gases?
a) Nitrogen dioxide
b) Sulphur dioxide
c) Sulphur trioxide
d) Nitrous oxide
Answer: b
Explanation: Fluorescence occurs when a molecule is excited by light energy of specific wavelength and emits light energy of another wavelength.

8. Electroanalytical monitors rely on which of the following methods?
a) Polarography and amperometric analysis
b) Polarography and electrocatalysis
c) Polarography, electrocatalysis and conductivity
d) All of the mentioned
Answer: d
Explanation: Electroanalytical instruments rely on polarography, conductivity, electrocatalysis and amperometric analysis.

9. Which of the following analyser is used for oxygen analysis?
a) Electrocatalytic
b) Polarographic
c) Conductive
d) Amperometric
Answer: a
Explanation: Electrocatalytic analysers are used for oxygen monitoring.

10. In-situ cross-stack analysers work behind which of the following principles?
a) Differential absorption spectroscopy
b) Gas-filter correlation spectroscopy
c) Differential absorption & Gas-filter correlation spectroscopy
d) None of the mentioned
Answer: c
Explanation: Cross stack analysers work behind the principles of differential absorption/gas-filter correlation spectroscopy.

11. In-situ in-stack analysers are used for measuring concentrations of which of the following gases?
a) Ammonia
b) Sulphur dioxide
c) Nitrogen monoxide
d) All of the mentioned
Answer: d
Explanation: In-site in-stack analysers work on the principle of second derivative spectroscopy to measure concentrations of ammonia, sulphur dioxide and nitrogen monoxide.

12. What is the disadvantage of using conductometric analysers?
a) Low sensitivity
b) Interfering gases must be removed before monitoring process
c) Medium used to measure change in conductivity is expensive
d) All of the mentioned
Answer: b
Explanation: Conductometric analysis is a non-specific method and hence requires interfering gases to be removed before monitoring process.

13. Flame photometric analysers are specific to sulphur compounds.
a) True
b) False
Answer: a
Explanation: Flame photometric analysers work behind the principle of luminescence through molecule/flame interaction and their use is limited to detect sulphur compounds alone.

14. Airshed modelling takes into account the effects of only stationary sources and not the mobile sources of pollution.
a) True
b) False
Answer: b
Explanation: Airshed modelling takes into account the effects of both mobile and stationary sources scattered in a small geographical region.

15. Which of the following is used in ceramic industries?
a) Electrostatic precipitator
b) Dynamic precipitator
c) Spray tower
d) Wet cyclonic scrubber
Answer: b
Explanation: Dynamic precipitator is used in ceramics, woodworking industries. It uses centrifugal force to remove gaseous matter.

16. Wet scrubbers are classified into ____ types.
a) 2
b) 3
c) 5
d) 6
Answer: b
Explanation: Web scrubbers are used to remove air pollutants and are classified into Spray towers, Wet cyclonic scrubber and Venturi scrubber.

17. The centrifugal collectors are classified into how many types?
a) 3
b) 4
c) 5
d) 2
Answer: d
Explanation: The Centrifugal collectors are classified into the Cyclone collector and Dynamic precipitator.

18. 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: a
Explanation: Electrostatic precipitator has the maximum efficiency among the rest with a value of 99%.

19. Which of the following fluid is used in web scrubbers?
a) Lime
b) MgSO4
c) NaCl
d) K2Cr2O7
Answer: a
Explanation: Apart from lime, K2CO3, a slurry of MnO and MgO and water can be used in Web scrubber.

20. Which of the following is incorrect regarding the 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: c
Explanation: The efficiency of Electrostatic precipitator is <99%, whereas the efficiency of Fabric filter is >99%.

21. Which of the following removes both gaseous and particulate contaminants?
a) Venturi scrubber
b) Gravitational settling chamber
c) Dynamic precipitator
d) Wet scrubber
Answer: a
Explanation: Venturi scrubber removes both gaseous and particulate contaminants. The minimum particle size removal is 0.5μm and its efficiency is < 99%.

22. Identify the correct statement regarding the Electrostatic precipitator.
a) Minimum particle size removal is <0.5μm
b) They can be operated at high temperature
c) It has a low maintenance cost
d) It does not cause any freezing problem
Answer: b
Explanation: Electrostatic precipitator can be operated at a high temperature between 3000C to 4500C, has a high maintenance cost, can cause a freezing problem and minimum particle size removal is < 1μm.

23. What is the primary standard level for carbon monoxide for assuring air quality?
a) 10ppm
b) 90ppm
c) 1ppm
d) 9ppm
Answer: d
Explanation: The primary standard level for carbon monoxide is 9ppm.

24. The pulmonary section of the respiratory tract consists of ___________
a) Nose and mouth as well as down till epiglottis and larynx
b) Bronchi down till the end of bronchiole
c) Respiratory bronchiole, alveoli and alveoli ducts
d) Alveoli ducts and alveoli
Answer: c
Explanation: Respiratory bronchiole, alveoli and alveoli ducts are categorised under the pulmonary section of the respiratory tract.

25. What is the primary function(s) of the alveoli?
a) Transfer of oxygen to the blood
b) Removal of carbon dioxide from the blood
c) Transfer of toxic substances to the blood
d) All of the mentioned
Answer: d
Explanation: The thin walls of the alveoli contain capillaries which aid in transfer of oxygen and toxic substances into the blood and removal of carbon dioxide.

26. The velocity of air reduces to zero by the time it reaches the bronchi.
a) True
b) False
Answer: b
Explanation: The velocity of air reduces to zero only when it reaches the alveoli and not the bronchi.

27. Particles of what size are filtered by the nasal passage?
a) >10micrometre
b) >500 micrometre
c) >1 mm
d) >5 micrometre
Answer: a
Explanation: The moist nasal passage can capture dust particles above 10 micrometre.

28. What is the effect of ozone on the human respiratory system?
a) It has higher affinity to bind with haemoglobin and does not allow binding of oxygen
b) It causes the disfigurement of the alveoli reducing the surface area for gaseous transfer
c) It damages lung tissues and aggravates asthma
d) All of the mentioned
Answer: c
Explanation: Ozone scars lung tissues when exposed for a long time and it intensifies asthma by increasing the individual’s sensitivity towards allergens.

29. Which of the following pollutants is the major contributor to photochemical smog?
a) Peroxynitrates
b) Hydroperoxides
c) Nitrogen dioxide
d) Ozone
Answer: d
Explanation: Ozone is the major constituent of photo-chemical smog.

30. What are the effects of sulphur dioxide on the human body?
a) It causes the malfunction of liver and kidney
b) It breaks down body’s immunity towards particulate matter and bacteria
c) It causes blood cells to dilate thereby affecting blood flow through the circulatory system
d) All of the mentioned
Answer: b
Explanation: Sulphur dioxide interrupts our immunity towards particulate matter and allows bacteria to enter through our respiratory system.

31. How does an increase in temperature affect air pollution?
a) Higher temperatures reduce air pollution
b) Higher temperatures increase air pollution
c) Temperature does not affect the air pollution levels
d) Humidity factor is also necessary to predict variance of air pollution with temperature
Answer: b
Explanation: Generally, air pollution increases with increase in temperature because it leads to increase in ground level ozone, nitrogen dioxide concentrations increase since higher temperature favours the oxidation of nitrogen monoxide.

32. Ocean is a source for carbon monoxide.
a) True
b) False
Answer: a
Explanation: It was earlier assumed oceans served as a sink, but marine organisms contribute enough carbon monoxide to highly saturate the ocean surface.

33. What range of air quality index has the most severe impact on human health?
a) 101-200
b) 201-300
c) 301-400
d) 401-500
Answer: d
Explanation: Air quality is regarded as severe when it has an index of 401-500, and affects even healthy people and impacts them even during simple activity.

34. Hazardous pollutants are those pollutants for which air quality standards have been devised.
a) True
b) False
Answer: b
Explanation: Hazardous pollutants do not have a defined air quality standard but contribute to severe health damage and mortality rate.

35. Which of the following devices is NOT used to control particulate emissions?
a) Electrostatic precipitator
b) Bag filters
c) Catalytic converters
d) All of the mentioned
Answer: c
Explanation: Catalytic converters are used to remove vapour phase and gaseous pollutants whereas, electrostatic precipitator and bag filters are used for particulate removal.

36. Which of the mentioned devices are used for removing vapour phase/ gaseous pollutants?
a) Absorption towers
b) Catalytic converters
c) Thermal oxidisers
d) All of the mentioned
Answer: d
Explanation: Absorption tower, catalytic converters and thermal oxidisers filter out harmful gaseous pollutants from the air.

37. How many fundamental ways in which noise can b controlled?
a) One
b) Two
c) Three
d) Four
Answer: d
Explanation: There are four fundamental ways in which noise can be controlled. a) Reduce noise at the source. b) Block the path of noise. c) Increase the path length. d) Protect the recipient. These four noise controlling ways reduce the noise pollution.

38. Which is the best way to control noise pollution among the four fundamental ways?
a) Reduce noise at the source
b) Block the path of noise
c) Increase the path length
d) Protect the recipient
Answer: a
Explanation: The best control method for noise pollution is to reduce the noise levels at the source. We a noise is reduced at the source tan pollution won’t occurrence in the proceeding steps and thus it won’t affect any organisms.

39. How can we reduce the noise in industries?
a) By not using the heavy machinery
b) By using rigid sealed enclosures
c) By using more robotics
d) By reduce the production of the industries
Answer: b
Explanation: In industries, noise reduction can be done by using rigid sealed enclosures around machinery, lined with acoustic absorbing material. Isolated machines and their enclosures from the floor can reduce the noise pollution at the source.

40. What is the main source of vehicular noise?
a) High speed
b) Movement of the vehicle’s tyres on the pavement
c) Low pressure
d) Fuel engine
Answer: b
Explanation: Most of the vehicular noise comes from the movement of the vehicle’s tyres on the pavement and wind resistance. Poorly maintained vehicles can also increase the noise pollution in the vehicles.

41. Which of the following is a way to reduce the traffic noise in the highway?
a) Constructing the vertical barriers
b) Increase the speed of the vehicles
c) Using old engine vehicles
d) Horning in unnecessary time
Answer: a
Explanation: The path of traffic noise can be locked by constructing vertical barriers along the highways. Proper highway planning and design are essential for controlling traffic noise. Establishing lower speed limits for highways also reduced the noise.

42. Noise levels at construction sites can be controlled using proper construction planning and scheduling techniques.
a) True
b) False
Answer: a
Explanation: Noise levels at construction sites can be controlled using proper construction planning and scheduling techniques. Certain techniques should be used in order to reduce the noise generated by machineries. Avoid construction timings during the night in order to disturbed the surrounding places.

43. What is the best way to reduce the noise pollution around houses?
a) Throwing all noisy machines
b) Built a noise resistant shield across the house
c) Use of ear buds to reduce the noise
d) Planting trees around houses
Answer: d
Explanation: To block the path of noise, planting trees around houses can be an effective way. In some situations trees will reduce noise levels up to 50% but to be effective we need a trees barrier that is at least 50 feet deep.

44. In order to reduce the roadside noise which of the following product Australian Government designed?
a) Sound tube
b) Ear buds
c) Ear repellent
d) Noise repellent
Answer: a
Explanation: In Melbourne, Australia a special instrument called as a sound tube is designed. This sound tube reduced the roadway noise without detracting from the area’s aesthetics and thus it lowers the noise pollution.

45. What is the best way to reduce aircraft noise?
a) By using shield around aircraft
b) By using quieter jet engines
c) By using heavy propellants
d) By using white paint
Answer: b
Explanation: Aircraft noise can be reduced significantly by using quieter jet engines. The old engines which cause more noise should be replaced by the new engines which cause less noise. Altering paths and time of day runway is also reduced the noise pollution.

46. What is used during sleep in order to avoid noise pollution?
a) Mask
b) Earplugs
c) Cotton shirts
d) Jackets
Answer: b
Explanation: Earplugs reduced the noise pollution which can help humans to sleep peacefully. Earplugs are a cheap drugstore purchase that makes humans sleep by barring the noise. Noise canceling headphones are also used while sleeping to reduce noise.