Water Supply Engineering

51. Corrosion of a pipe

1. Reduces its life span
2. Reduces its carrying capacity
3. Adds colour to water
4. All the above

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52. Corrosion of well pipes may not be reduced by

1. Reducing the draw down and the pumping rate
2. Reducing the flow velocity
3. Using thicker pipes
4. Using screens having larger area of openings

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53. Critical time for developing a water hammer, is the time required for

1. Closing the valve
2. The wave to travel from valve to the reservoir
3. The wave to travel from the valve to the reservoir and back
4. None of these

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54. Dead storage of a reservoir of Q capacity generally provided for silt deposition during its life time, is generally kept

1. 1/8th Q
2. 1/6th Q
3. 1/5th Q
4. 1/4th Q

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55. De-chlorination is followed by

1. Post-chlorination
2. Pre-chlorination
3. Double-chlorination
4. Super-chlorination

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56. Demand for public uses in a city, does not include water required for

1. Watering of public parks
2. Watering of public gardens
3. Sprinkling on roads
4. Drinking purposes

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57. Derivation of Thiem's formula Q = 2πT(s₁ - s₂)/2.3 log₁₀ (r₂/r₁) is based on the assumption

1. The aquifer is homogeneous, isotropic and of infinite depth and area
2. The well is sunk through the full depth of the aquifer
3. The flow lines are radial and horizontal, and the flow is laminar
4. All the above

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58. Detention period of a settling tank is

1. Average theoretical time required for water to flow through the tank
2. Time required for flow of water to fill the tank fully
3. Average time for which water is retained in tank
4. All the above

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59. Detention time for plain sedimentation tank usually ranges from

1. 2 to 4 hours
2. 4 to 8 hours
3. 6 to 10 hours
4. 8 to 12 hours

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60. Disappearance of pink colour of water of a well due of KMnO4 indicates that water contains

1. Acidity
2. Alkalinity
3. Turbidity
4. Organic matter

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