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Civil Engineering :: Waste Water Engineering

  1. Sewer pipes need be checked for

  2. A.
    minimum flow
    B.

    maximum flow

    C.

    both (a) and (b)

    D.

    none of these.

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  3. If D.O. concentration falls down to zero in any natural drainage, it indicates the zone of

  4. A.

    degradation

    B.

    active decomposition

    C.
    recovery
    D.

    cleaner water

    E.
    none of these.

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  5. The ratio of design discharge to the surface area of a sedimentation tank is called

  6. A.

    surface loading

    B.
    overflow rate
    C.

    overflow velocity

    D.

    all of these

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  7. The value of Chezy's constant

     C = \( \frac { [23+0.00155/s ]+1/n} { 1+[23+0.00155/s]+n\sqrt{}r} \)

  8. A.

    Chezy's formula

    B.

    Bazin's formula

    C.
    Kutter's
    D.

    Manning's formula.


  9. In the activated sludge process

  10. A.

    aeration is continued till stability

    B.
    aeration is done with an admixture of previously aerated sludge
    C.
    sludge is activated by constant stirring
    D.
    water is removed by centrifugal action.

  11. The minimum diameter of a sewer is kept

  12. A.

    10 cm

    B.
    15 cm
    C.

    20 cm

    D.

    25 cm

    E.

    30 cm.

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  13. The minimum diameter of sewer to be adopted is

  14. A.
    10 cm
    B.

    12.5 cm

    C.
    15 cm
    D.

    25 cm.

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  15. To test chemical oxygen demand (C.O.D.) of sewage, organic matter is oxidised by pottassium dichromate in the presence of

  16. A.

    Hydrochloric acid

    B.

    Sulphuric acid

    C.

    Nitric acid

    D.

    Citric acid.

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  17. The discharge per unit plan area of a sedimentation tank, is generally called

  18. A.

    over flow rate

    B.

    surface loading

    C.

    over flow velocity

    D.

    all the above.

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  19. In a sedimentation tank (length L, width B, depth D) the settling velocity of a particle for a discharge Q, is

  20. A.

    \(\frac { Q } { B\times D} \)

    B.

    \(\frac { Q } { L\times D} \)

    C.

    \(\frac { Q } { L } \)

    D.

    \(\frac { Q } { B\times L} \)

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  21. D is the diameter of a circular sewer and α is the side of a square section sewer. If both are hydraulically equivalent, the relationship which holds good, is

  22. A.
    πD8/3 = 4 b8/3
    B.

    πD3/8 = 4 b3/8

    C.

    πD2/3 = 4 b2/3

    D.
    πD3/2 = 4 b3/2
    E.
    none of these.

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  23. For detecting the nitrites in the sewage, the matching colour may be developed by adding

  24. A.

    Pottassium permanganate

    B.

    Sulphuric acid and napthamine

    C.

    Phenol-di-sulphuric acid pottassium hydroxide

    D.

    None of these.

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  25. The suitable cross-section of sewers to carry combined flow, is

  26. A.
    circular
    B.
    egg shaped
    C.

    rectangular

    D.
    horse shoe shaped.

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  27. Hazin's formula Vs = 418 (Gs - Gw)d [ \([\frac { 3T +70 } { 100 } ]\)is used for the settlement velocity of the particles of diameter

  28. A.

    less than 0.01 mm

    B.

    less than 0.05 mm

    C.
    less than 0.1 mm
    D.

    greater than 0.1 mm.


  29. If the diameter of a sewer is 100 mm, the gradient required for generating self cleansing velocity, is

  30. A.
    1 in 60
    B.
    1 in 100
    C.

    1 in 120

    D.

    none of these.

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  31.  

    Stone ware pipes are

  32. A.

    highly resistant to sulphide corrosion

    B.

    highly impervious

    C.
    hydraulically efficient because of their smooth interior surface
    D.
    specially suited to pressure pipes
    E.

    none of these.

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  33. Skimming tanks are

  34. A.

    used to remove the grease and oil

    B.

    those from which sludge is skimmed out

    C.

    tanks provided with self-cleansing screens

    D.
    improved version of grit chambers

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  35.  

    In a sludge digestion tank if the moisture content of sludge V1 litres is reduced from p1 % to p2 % the volume V2 is

  36. A.

    \(\frac { 100+P1 } { 100-P2} \) V1 

    B.

    \([\frac { 100-P1 } { 100+P2} ]V1\)

    C.

    \([\frac { 100-P1 } { 100-P2} ]V1\)

    D.

    \([\frac { 100+P2 } { 100-P1} ]V1\)


  37. Assertion (A) : The determination of pH value of sewerage is important.

    Reason (R) : The efficiency of certain treatment methods depends upon the availability of pH value.

  38. A.
    Both A and R are true and R is the correct explanation of A
    B.

    Both A and R are true but R is not a correct explanation of A

    C.

    A is true but R is false

    D.
    A is false but R is true.

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  39. With self cleansing velocity in sewers

  40. A.

    silting occurs at bottom

    B.

    scouring occurs at bottom

    C.

    both silting and scouring occur at bottom

    D.
    neither silting nor scouring occurs at bottom.

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  41. Aerobic activity is maximum

  42. A.

    in freshly produced sewage

    B.

    at sewer pipes

    C.

    in sewer treatment plants

    D.

    none of these.

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  43.  

    In sewers designed with self cleansing velocity,

  44. A.

    the bottom is silted

    B.

    the bottom is scoured

    C.

    both silting and scouring occur at the bottom

    D.
    neither silting nor scouring occurs at the bottom.

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  45.  

    Which one of the following resists hydrogen sulphide corrosion

  46. A.
    R.C.C.
    B.

    Glazed stone wares

    C.

    Asbestos cement

    D.

    Glazed ware.

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  47.  

    The sewerage system consists of

  48. A.
    house sewer
    B.

    lateral sewer

    C.

    branch sewer

    D.

    main sewer

    E.

    all of these.

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  49.  

    Hume steel pipes are

  50. A.

    steel pipes

    B.

    R.C.C. pipes

    C.

    steel shell coated from inside with cement mortar

    D.

    steel shell coated from outside with cement mortar

    E.

    both (c) and (d).

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  51. Drop manholes are the manholes

  52. A.

    without entry ladders

    B.

    without manhole covers

    C.

    with depths more than 3.5 m

    D.

    having drains at different levels.

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  53.  

    Boussinesq's equation for ascertaining unit pressure at a depth H on sewers due to traffic loads, is

  54. A.

    Pt = \(\frac { 3 H^3P } { 2 nZ^5} \)

    B.

    Pt = \(\frac { 2 H^3P } { 3 nZ^5} \)

    C.

    Pt = \(\frac { 3 H^3P } { 2 Z^5} \)

    D.

    Pt = \(\frac { 2 nH^3P } { 3 Z^5} \)

    E.

    none of these.


  55. The laying of sewers is done with

  56. A.

    magnetic compass

    B.

    theodolite

    C.
    level
    D.
    clinometer
    E.

    plane table.

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  57. The rational formula for peak drainage discharge, was evolved by

  58. A.

    Fruhling

    B.
    Lloyd David
    C.

    Kuichling

    D.

    All of these.

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  59. The sewage treatment in septic tanks is due to

  60. A.

    anaerobic decomposition

    B.

    aerobic decomposition

    C.

    parasitic decomposition

    D.
    none of these.

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  61. In 1000 kg of sewage, the total solids approximate

  62. A.
    0.5 to 1.0 kg
    B.

    1 kg to 2.0 kg

    C.

    5 kg to 7.5 kg

    D.
    7.5 kg to 10 kg.

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  63. Pathogens (or pathogentic bacterias) in water may cause

  64. A.

    typhoid

    B.
    cholera
    C.
    dysentery
    D.

    infectious hepatitis

    E.

    all the above.

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  65.  

    Sewer manholes are generally provided at

  66. A.

    the change of gradient

    B.
    the change of direction
    C.
    the junctions of sewers
    D.
    all of these.

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  67. The sewers

  68. A.
    must be of adequate size to avoid over flow
    B.

    must flow under gravity \( \frac { 1 } { 2 } \) to \( \frac { 3 } { 4} \) full

    C.

    must be laid at least 2 to 3 m deep to collect /water from the basements

    D.

    all the above.


  69. Before discharging the foul sewage into rivers, it is generally treated by

  70. A.

    screening

    B.

    sedimentation

    C.

    oxidation

    D.

    sludge digestion and disinfection

    E.

    all the above.

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  71. The settlement of a particle in sedimentation tank, is affected by

  72. A.
    velocity of flow
    B.

    viscosity of water

    C.

    size and shape of solid

    D.

    specific gravity of solid

    E.

    all the above.

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  73.  

    If the length of overland flow from the critical point to the mouth of drain is 13.58 km and difference in level between the critical point and drain mouth is 10 m, the inlet time is

  74. A.

    2 hours

    B.

    4 hours

    C.
    6 hours
    D.

    8 hours.

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  75. Oxidation process results in the formation of

  76. A.

    carbon dioxide

    B.
    nitrates
    C.
    sulphates
    D.
    all the above.

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  77. Dry weather flow is :

  78. A.
    average daily rate of flow
    B.

    average monthly rate of flow

    C.

    average annual rate of flow

    D.
    water supply allowance per capita
    E.
    none of these.

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  79. As compared to fresh river water, sea water contains oxygen

  80. A.

    10% less

    B.
    20% less
    C.

    10% more

    D.

    20% more.

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  81. The settlement velocity of a solid (diameter 0.5 mm, specific gravity 1.75) in water having temperature 10°C, is

  82. A.
    213.5 cm/sec
    B.

    313.5 cm/sec

    C.

    413.5 cm/sec

    D.

    500 cm/sec.

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  83. If γw is the unit weight of water, r the hydraulic mean depth of the sewer and S the bed slope of the sewer, then the tractive force exerted by flowing water, is

  84. A.

    γw . r . S

    B.
    γw r1/2 . S
    C.

    γw \(\sqrt{S}\)

    D.

    γw r2/3\(\sqrt{S}\)


  85. In detritus tanks,

  86. A.
    flow velocity is kept 0.09 m/sec
    B.
    detention period is kept 3 to 4 minutes
    C.

    organic and inorganic materials are separated

    D.

    all the above.

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  87. The width of a settling tank with 2 hour detention period for treating sewage 378 cu m per hour, is

  88. A.

    5 m

    B.

    5.5 m

    C.

    6 m

    D.

    6.5 m

    E.

    7 m.

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  89.  

    In areas where rainy season is limited to a few months, the type of sewerage system recommended is

  90. A.
    combined system
    B.
    partially separate system
    C.

    separate system

    D.
    none of these.

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  91.  \(\frac { 3 } { 4 } \) rd or  \(\frac { 1 } { 4 } \)th extra space is left in sewer pipes at maximum discharge for

  92. A.
    low estimates of the average and maximum flows
    B.

    large scale infiltration of storm water

    C.

    large scale infiltration of storm water

    D.

    all the above.


  93.  

    If n is the rugosity coefficient, r is the hydraulic depth, s is the bed slope of sewer, the velocity of flow in m/sec may be obtained by the formula  V = \(\frac { 1 } { n } r^2/3 s^1/2\)

  94. A.

    Chezy

    B.

    Manning

    C.

    Bazin

    D.

    Kutter.


  95. Pick up the correct statement from the following :

  96. A.
    anaerobic bacteria flourish in the absence of oxygen
    B.
    aerobic bacteria flourish in the presence of oxygen
    C.
    facultative bacteria flourish with or without oxygen
    D.

    all the above.

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  97. Antisyphonage pipe is fitted

  98. A.

    at the end of septic tanks

    B.

    on manholes

    C.

    with a W.C. trap

    D.
    at the beginning of sewer line.

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  99.  

    For drains up to 15 cumecs, the depth d and width B are related by

  100. A.

    d = 0.2 \(\sqrt{B}\)

    B.

    d = 0.5 \(\sqrt{B}\)

    C.

    B = 0.2\(\sqrt{d}\)

    D.

    B = \(\sqrt 0.5{d}\)