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Civil Engineering :: Waste Water Engineering

  1. The most dangerous pollutant in vehicular emissions is

  2. A.
    CO
    B.
    SO2
    C.

    CO2

    D.

    O3.


  3. If the depletion of oxygen is found to be 2.5 mg/litre after incubating 2.5 ml of sewage diluted to 250 ml for 5 days at 20°C, B.O.D. of the sewage is

  4. A.

    50 mg/l

    B.
    100 mg/l
    C.
    150 mg/l
    D.

    200 mg/l

    E.
    250 mg/l.

  5. The clarigesters are

  6. A.

    circular septic tanks

    B.

    rectangular septic tanks

    C.

    circular Imhoff double tanks with bottom hoppers

    D.
    circular Imhoff double storey tanks without bottom hoppers.

  7. Rate of flow of sewage is generally assumed

  8. A.

    more than the rate of water supply

    B.

    equal to the rate of water supply

    C.

    less than the rate of water supply

    D.

    at 150 litres per capita.


  9. Maximum permissible velocity 1.5 m/sec, is adopted in drains

  10. A.

    with beds of rocks and gravels

    B.

    lined with stones

    C.
    both (a) and (b)
    D.
    neither (a) nor (b).

  11. The digested sludge from septic tanks, is removed after a maximum period of

  12. A.
    3 years
    B.

    3.5 years

    C.

    4 years

    D.
    5 years.

  13. For providing an Indian type W.C., the R.C.C. slabs in the toilet portion

  14. A.

    should be sunk by 20 cm

    B.
    should be kept 20 cm above the adjacent portion
    C.

    should be sunk by 50 cm

    D.

    need not be sunk.


  15. The gradient of sewers depends upon

  16. A.

    velocity of flow

    B.

    diameter of the sewer

    C.

    discharge

    D.
    all the above.

  17. The settling velocity of the particles larger than 0.06 mm in a settling tank of depth 2.4 is 0.33 m per sec. The detention period recommended for the tank, is

  18. A.
    30 minutes
    B.

    1 hour

    C.

    1 hour and 30 minutes

    D.

    2 hours

    E.
    3 hours.

  19. The drop man holes are generally provided in sewers for

  20. A.

    industrial areas

    B.

    large town ships

    C.
    hilly town ships
    D.
    cities in plains.

  21.  

    Sewer ventilating columns are generally placed at

  22. A.

    distances 150 m to 300 m

    B.

    upper ends of branch sewers

    C.

    every change in the size of sewers

    D.

    all the above.


  23. In case of Imhoff tanks,

  24. A.
    the shape is rectangular
    B.

    detention period is 2 hours

    C.

    the velocity of flow is restricted to 0.30 m/minute

    D.

    surface loading is limited to 30, 000 litres/m of plan area per day

    E.

    All the above.


  25. If the depth of partial flow in a sewer of diameter 2 m, is 50 cm, its wetted perimeter is

  26. A.

    π

    B.

    \(\frac { n } { 2 } \)

    C.

    \(\frac { n } { 3 } \)

    D.

    \(\frac { 2n } { 3 } \)

    E.

    \(\frac { 3n } { 2 } \)


  27. A drop manhole is provided if

  28. A.

    a sewer drops from a height

    B.

    a branch sewer joins the main sewer at higher level

    C.

    a lamp is inserted to check obstruction

    D.
    none of these.

  29. In a city the ratio of the drainage to sewage is 20, the percentage discharge passing through non-monsoon periods, is

  30. A.
    5
    B.

    10

    C.

    15

    D.

    20


  31. Pick up the correct statement from the following :

  32. A.

    Indore method of composting involves decomposition under aerobic conditions

    B.
    Bangalore method of composting involves decomposing under anaerobic conditions
    C.

    Fully stabilised refuse by the Bangalore method of compositing is a powdery mass called humus

    D.

    all of these.


  33. The liquid wastes from kitchens, bath rooms and wash basins, is not called

  34. A.
    liquid waste
    B.

    sullage

    C.

    sewage

    D.

    none of these.


  35.  

    The presence of free ammonia in sewage, is detected by

  36. A.

    boiling

    B.

    adding pottassium permanganate

    C.

    adding sulphuric acid

    D.

    phenol-di-sulphuric acid.


  37. The amount of oxygen consumed by the aerobic bacterias which cause the aerobic biological decomposition of sewage, is known

  38. A.

    Bio-Chemical Oxygen Demand (B.O.D.)

    B.

    Dissolved Oxygen (D.O.)

    C.

    Chemical Oxygen Demand (C.O.D.)

    D.

    None of these.


  39.  

    The standard B.O.D. of water is taken for

  40. A.
    1 day
    B.

    2 days

    C.
    3 days
    D.

    5 days

    E.

    10 days.


  41.  

    To prevent settling down of sewage both at the bottom and on the sides of a large sewer, self-cleaning velocity recommended for Indian conditions, is

  42. A.
    0.50 m/sec
    B.

    0.60 m/sec

    C.
    0.70 m/sec
    D.

    0.75 m/sec

    E.

    1.0 m/sec.


  43.  

    Pick up the correct statement from the following :

  44. A.

    Turbidity is more in strong sewage

    B.

    The black colour indicates septic sewage

    C.

    The fresh sewage is practically odourless

    D.

    The fresh sewage is practically odourless

    E.

    All the above.


  45. In sewers the gas generally found, is

  46. A.
    Hydrogen sulphide (H2S)
    B.

    Carbon dioxide (CO2)

    C.

    Methane (CH4)

    D.
    Petrol vapours
    E.

    All the above.


  47. A sewer running partially full and hurried with back filled, fails in compression due to

  48. A.

    weight of the pipe

    B.
    weight of the back fill
    C.

    superimposed traffic loads

    D.
    all the above.

  49. A manhole is classified as shallow if its depth is between

  50. A.

    0.4 to 0.5 m

    B.

    0.5 to 0.7 m

    C.

    0.7 to 0.9 m

    D.
    0.9 to 1.20 m
    E.

    1.2 to 1.50 m.


  51. For a circular sewer of diameter D running partially full with central angle α,

  52. A.

    \( \frac { d} { D } \) = \(\frac { 1 } { 2 } \) [ 1- cos \(\frac { α } { 2 } \) ] 

    B.

    \(\frac { a} { A } \) = [ \(\frac { n} { 360^0 } \) - \(\frac { sina ​​} { 2n } \)]

    C.

    \(\frac { D } { P } \) = [ \(\frac { α} { 360^0 } \)

    D.

    \(\frac { r } { R }\) = [ 1-\( \frac { 360^0 sinα} { 2nα } \) ]

    E.

    all the above.


  53. For design purposes, the normal rate of infiltration of ground water into the sewer, is

  54. A.
    500 litres/km/cm
    B.

    1000 litres/km/cm

    C.
    1500 litres/km/cm
    D.

    2000 litres/km/cm

    E.

    2500 litres/km/cm.


  55. The effluent of a septic tank is

  56. A.

    fit for discharge into any open drain

    B.

    foul and contains dissolved and suspended solids

    C.

    as good as that from a complete treatment

    D.
    none of these.

  57.  

    The drainage area of a town is 12 hectares. Its 40% area is hard pavement (K = 0.85), the 40% area is unpaved streets (K = 0.20) and the remaining is wooded areas (K = 0.15). Assuming the time of concentration for the areas as 30 minutes and using theformula  ps = \( \frac { 900 } { t+60 } \)the maximum run off is

  58. A.

    0.10 cumec

    B.

    0.12 cumec

    C.

    0.15 cumec

    D.

    0.20 cumec.


  59. The detention period for plain sedimentation water tanks, is usually

  60. A.

    4 to 8 hours

    B.

    8 to 16 hours

    C.

    16 to 24 hours

    D.

    16 to 24 hours


  61.  

    Fresh sewage may become stale in

  62. A.

    one hour

    B.

    two to three hours

    C.

    three to four hours

    D.

    six hours.

    E.

    ten hours.


  63. The small sewers are cleaned by

  64. A.
    flushing
    B.

    cane rodding

    C.
    wooden pills
    D.
    none of these.

  65. Dry water flow in a combined sewer, is

  66. A.

    industrial sewage

    B.
    domestic sewage
    C.

    storm water

    D.

    inclusive of domestic and industrial sewage but excludes storm water.


  67. Which one of the following tests is used for testing sewer pipes :

  68. A.
    water test
    B.
    ball test
    C.

    mirror test

    D.

    all of these.


  69. Nitrogen cycle of sewage, is

  70. A.
    Liberation of ammonia-formation of nitrites-formation of nitrates-liberation of nitrogen
    B.

    Liberation of nitrogen-liberation of ammonia-formation of nitrites- formation of nitrates

    C.

    Liberation of nitrogen-formation of nitrates-formation of nitrites-liberation of ammonia

    D.
    Formation of nitrates-formation of nitrites-liberation of nitrates-liberation of nitrates
    E.
    None of these.

  71. In sewers the highest non-scouring velocity is achieved in

  72. A.

    glazed bricks sewers

    B.
    cast iron sewers
    C.

    cement concrete sewers

    D.

    stone ware sewers.


  73. In sewage having fully oxidised organic matter, the nitrogen exists in the form of

  74. A.
    nitrites
    B.

    nitrates

    C.

    free ammonia

    D.
    aluminoid nitrogen
    E.
    none of these.

  75.  

    It is customary to design a sewer for D.W.F. on the basis of

  76. A.

    average demand

    B.
    twice the average demand
    C.

    thrice the average demand

    D.
    four times the average demand.

  77. During preliminary treatment of a sewage

  78. A.

    Oil and grease are removed from skimming tanks

    B.

    Floating materials are removed by screening

    C.

    Girt and sand are removed by girt chambers

    D.

    All the above.


  79. Pick up the correct statement from the following :

  80. A.

    The larger the sewer in size, more will be velocity

    B.
    The smaller the sewer in size, less will be velocity
    C.

    The larger the sewer in size, no deposition will take place

    D.

    The larger the sewer in size, deposition will take place.


  81. In septic tanks,

  82. A.
    free board of 0.3 m may be provided
    B.

    the baffles or tees are extended up to top level of scum

    C.
    the clear space between the baffle top and covering slab is about 7.5 cm
    D.

    the inlet is kept 30 cm below the sewage line and outlet is kept at a level 40% depth of the sewage

    E.

    all the above.


  83. The sewer pipe which carries sewage from a building for immediate disposal is

  84. A.

    house sewer

    B.

    lateral sewer

    C.

    intercepting sewer

    D.

    main sewer.


  85. The algae dies out in the zone of

  86. A.

    degradation

    B.

    active decomposition

    C.

    recovery

    D.

    cleaner water.


  87. The recommended detention period for grit chambers is

  88. A.

    1 minute

    B.

    2 minutes

    C.

    3 minutes

    D.

    5 minutes.


  89. Pick up the correct statement from the following :

  90. A.

    The materials separated by screens, is called screenings

    B.

    The screenings are disposed off either by burning or by burial or by dumping

    C.
    The process of burning the screenings, is called incineration
    D.
    The process of burning the screenings, is known as compositing
    E.

    All the above.


  91. The ratio of the diameter of a circular section and the side of a square section hydraulically equivalent, is

  92. A.
    1.095
    B.

    1.085

    C.

    1.075

    D.
    1.065

  93. Pick up the correct statement from the following :

  94. A.

    The maximum rate of storm run off is called peak drainage discharge

    B.

    Rational method of estimating peak run off, may be used precisely for areas less than 50 hectares

    C.
    The period after which the entire area starts contributing to the run off, is called the time of concentration
    D.
    The time required by water to reach the outlet of a catchment from the most remote point, is called time of concentration
    E.

    All the above.


  95. For trunk and out-fall, the type of sewers generally used, is

  96. A.

    standard egg shaped

    B.
    circular shaped
    C.

    horse shoe shaped

    D.

    parabolic shaped

    E.

    semi-elliptical shaped.


  97. Pick up the incorrect statement from the following :

  98. A.

    Septic tanks are horizontal continuous flow type of sedimentation tanks

    B.

    Septic tanks are generally provided a detention period of 12 to 36 hours

    C.

    Septic tanks are completely covered and high vent shafts are provided for the escape of foul gases

    D.
    Septic tanks are generally classified as tanks which work on the principle of anaerobic decomposition
    E.
    None of these.

  99. Hydraulic mean radius is

  100. A.

    mean radius of sewer

    B.

    difference in heads between two points in circular pipes

    C.

    mean of radii in a pipe line of varying cross-sections

    D.
    cross-sectional area/wetted perimeter.