51. Air binding phenomena in rapid sand filters occur due to
a) excessive negative head
b) mud ball formation
c) higher turbidity in the effluent
d) low temperature
Ans:a
52. The percentage of filtered water, which is used for back washing in rapid sand filters, is about
a) 0.2 to 0.4
b) 0.4 to 1.0
c) 2 to 4
d) 5 to 7
Ans:c
53. Period of cleaning of slow sand filters is about
a) 24 – 48 hours
b) 10-12 days
c) 2-3 months
d) 1-2 year
Ans:c
54. The rate of Alteration of pressure filters is
a) less than that of slow sand filters
b) in between the filtration rate of slow sand filters and rapid sand filters
c) greater than that of rapid sand filters
d) equal to that of slow sand filters
Ans:c
55. Double filtration is used
a) to increase the filtration slow sand filters capacity of
b) to increase the filtration rapid sand filters capacity of
c) for isolated buildings like pools, hotels etc swimming
d) all of the above
Ans:a
56. Cleaning is done by
i) scraping and removal in filters slow sand
ii) back washing in slow sand filters
iii) scraping and removal in filters rapid sand
iv) back washing in rapid sand filters
The correct answer is
a) (i) and (ii)
b) (ii) and (iii)
c) (i) and (iv)
d) (ii) and (iv)
Ans:c
57. Disinfection of water results in
a) removal of turbidity
b) removal of hardness
c) killing of disease bacteria
d) complete sterilisation
Ans:c
58. The disinfection efficiency of chlorine increases by
i) decreasing the time of contact
ii) decreasing the temperature of water
iii) increasing the temperature of water
The correct answer is
a) only (i)
b) both (i) and (ii)
c) both (i) and (iii)
d) only (iii)
Ans:d
59. Chlorine demand of water is equal to
a) applied chlorine
b) residual chlorine
c) sum of applied and residual chlorine
d) difference of applied and residual chlorine
Ans:d
60. The process in which the chlorination is done beyond the break point is known as
a) prechlorination
b) post chlorination
c) super chlorination
d) break point chlorination
Ans:c
61. The percentage of chlorine in fresh bleaching powder is about
a) 10 to 15
b) 20 to 25
c) 30 to 35
d) 40 to 50
Ans:c
62. The treatment of water with bleaching powder is known as
a) prechlorination
b) super chlorination
c) dechlorination
d) hypochlorination
Ans:d
63. The suitable method for disinfection of swimming pool water is
a) ultra violet rays treatment
b) lime treatment
c) by using potassium permanganate
d) chlorination
Ans:a
64. Which of the following chemical compounds can be used for dechlorination of water ?
a) carbon dioxide
b) bleaching powder
c) sulphur dioxide
d) chloramines
Ans:c
65. In chlorination, with the rise in temperature of water, death rate of bacteria
a) increases
b) decreases
c) remains unaffected
d) none of the above
Ans:a
66. As compared to higher pH values, the contact period required for efficient chlorination at lower pH values is
a) smaller
b) larger
c) same
d) none of the above
Ans:a
67. Disinfection efficiency is
a) reduced at higher pH value of water
b) unaffected by pH value of water
c) increased at higher pH value of water
d) highest at pH value equal to 7
Ans:a
68. In lime-soda process
a) only carbonate hardness is removed
b) only non-carbonate hardness is re-moved
c) lime reduces the carbonate hardness and soda-ash removes the non-carbonate hardness
d) lime reduces the non-carbonate hardness and soda-ash removes the carbonate hardness
Ans:c
69. The major disadvantage of lime soda process of water softening is that
a) it is unsuitable for turbid and acidic water
b) huge amount of precipitate is formed which creates a disposal problem
c) the effluent cannot be reduced to zero hardness
d) it is unsuitable for softening the water of excessive hardness
Ans:b
70. Which of the following compounds is widely used for algae control ?
a) sodium sulphate
b) copper sulphate
c) sodium chloride
d) calcium chloride
Ans:b
71. Activated carbon is used for
a) disinfection
b) removing hardness
c) removing odours
d) removing corrosiveness
Ans:c
72. As compared to cast iron pipes, steel pipes are
a) heavier
b) stronger
c) costlier
d) less susceptible to corrosion
Ans:b
73. The suitable layout of a distribution system for irregularly growing town is
a) dead end system
b) grid iron system
c) radial system
d) ring system
Ans:a
74. The layout of distribution system in which water flows towards the outer periphery is
a) ring system
b) dead end system
c) radial system
d) grid iron system
Ans:c
75. The suitable layout of distribution system for a city with roads of rectangular pattern is
a) grid iron system
b) dead end system
c) ring system
d) radial system
Ans:a