Q.1

Which one of the following statements regarding septic tanks is wrong :

  • a gap of 7.5 cm between the bottom of the covering slab and the top level of scum is provided
  • the outlet invert level is kept 5 to 7.5 cm below the inlet invert level
  • the minimum width of septic level is 90 cm
  • the depth of tank is kept equal to its width.
Q.2

In septic tanks, decomposition of organic bacteria, is done by

  • anaerobic bacteria
  • aerobic bacteria
  • both types of bacterias
  • none of these.
Q.3

The average temperature of sewage in India, is

  • 10°C
  • 15°C
  • 20°C
  • 25°C
  • 30°C.
Q.4

3.0 ml of raw sewage is diluted toml. The D.O. concentration of the diluted sample at the beginning of the test was 8 mg/l. After 5 day-incubation at 20°C, the DO. concentration was 5 mg/l. The BOD of raw sewerage is

  • 100 mg/l
  • 200 mg/l
  • 300 mg/l
  • 400 mg/l.
Q.5

Pick up the incorrect statement from the following :

  • The process of decomposing the organic matter under controlled anaerobic conditions, is called sludge digestion
  • Sludge digestion is carried out in sludge tank
  • The gases produced in sludge digestion process, contain 75% carbon dioxide
  • The gases produced in sludge digestion process, contain 75% methane.
Q.6

In a residential colony, sewers of diametersmm,mm andmm were laid with a gradient 1 inWhich portion of the sewage system does not choke in due course of time

  • 100 mm dia.
  • 150 mm dia.
  • 225 mm dia.
  • all of these.
Q.7

Pick up the correct statement from the following :

  • The water supply pipes carry pure water free from solid particles
  • The water supply pipes get clogged if flow velocity is less than self cleansing velocity
  • The sewers may be carried up and down the hills and valleys
  • The sewer pipes are generally laid along level hills
  • None of these.
Q.8

If the grit in grit chambers is 4.5 million litres per day, its cleaning is done

  • manually
  • mechanically
  • hydraulically
  • electrically.
Q.9

The pH value of sewage is determined with the help of

  • Imhoff Cone
  • turbidimeter
  • potentiometer
  • none of these.
Q.10

A well oxidized sewage contains nitrogen mainly as

  • nitrates
  • nitrites
  • free ammonia
  • none of these.
Q.11

Drop manholes at the junctions of sewer lines, are provided if

  • invert level of a branch sewer is more than 60 cm that of the main sewer
  • sewer line runs along a main road
  • ordinary manhole cannot be built
  • two sewer lines intersect.
Q.12

The self-cleansing velocity of water flowing through pipe lines, is

  • 2 metres/sec
  • 1 metre/sec
  • 0.5 metre/sec
  • 0.25 metre/sec.
Q.13

In circular sewers if depth of flow is 0.2 times the full depth, the nominal gradient,

  • is only provided
  • is doubled
  • is trebled
  • is not enough.
Q.14

The stone ware sewers

  • are used for carrying sewage and drainage from houses
  • are manufactured from clays and shales
  • after casting are dried and burnt at temperature 150°C, 700°C and 1200°C
  • are generally provided with a water proof cover by vaporising sodium chloride
  • all the above.
Q.15

The most widely used pump for lifting sewage is

  • centrifugal pump
  • reciprocating pump
  • pneumatic ejector
  • air pressure pump.
Q.16

The arrangement made for passing the sewer line below an obstruction below the hydraulic gradient lines called

  • inverted syphon
  • depressed sewer
  • sag pipe
  • all of these.
Q.17

The pH value of sewage is determined with the help of

  • Imhoff Cone
  • turbidimeter
  • potentiometer
  • none of these.
Q.18

Pick up the correct statement from the following :

  • The circular section of sewers provides maximum hydraulic mean depth
  • The circular sewers are provided for separate sewerage system
  • The circular sewers work efficiently if the sections run at least half full
  • Two sewers of different shapes are said to be hydraulically equivalent if they discharge at the same rate while running full on the same grade
  • All the above.
Q.19

If D is the diameter of upper circular portion, the overall depth of New Egg shaped sewer section, is

  • 1.250 D
  • 1.350 D
  • 1.425 D
  • 1.625 D.
Q.20

For trunk sewers more than 1.m in diameter, the ratio of the maximum daily sewage flow to the average daily sewage flow is assumed

  • 1.5
  • 2.0
  • 2.5
  • 3.0
  • 3.5
Q.21

The gas evolved in sewers is

  • Carbondioxide
  • Hydrogen sulphide
  • Methane
  • All of these.
Q.22

A safety lamp when inserted in the upper portion of a manhole causes flames. It indicates the presence of

  • Carbondioxide gas
  • Hydrogen sulphide gas
  • Methane gas
  • Petrol vapours.
Q.23

The most effective arrangement for diverting excess storm water into a natural drainage, is

  • leaping weir
  • overflow weir
  • siphon spill way
  • none of these.
Q.24

'Cowl' is provided at

  • lower end of ventilating column
  • upper end of ventilating column
  • upper end of the manhole
  • first step in manhole.
Q.25

The sewer which resists sulphide corrosion, is

  • Brick sewer
  • Cast iron sewer
  • R.C.C. sewer
  • Lead sewer
  • None of these.
Q.26

The angle subtended by the surface of sewer water with partial flow, at sewer centre is 120°, the depth of sewerage is

  • 20 cm
  • 25 cm
  • 40 cm
  • 50 cm
  • 60 cm.
Q.27

You are asked to design sewer pipes of diameters 0.4 m to 0.9 m at maximum flow, you will assume the sewer flow running at

  • full depth
  • half full
  • two third full
  • three fourth full.
Q.28

Discrete or granular particles change their

  • size
  • shape
  • weight
  • none of these.
Q.29

In sewers the velocity of flow should not be

  • more than the self-cleansing velocity
  • less than the self-cleansing velocity
  • less than 10 m/sec
  • more than 20 m/sec.
Q.30

During putrifaction process of sewage the gas given off, is

  • carbon dioxide
  • hydrogen
  • ammonia
  • methane
  • all the above.
Q.31

At the junction of sewers

  • top of smaller sewer is kept lower
  • top of larger sewer is kept lower
  • tops of both the sewers are at the same level
  • none of these.
Q.32

The maximum depth of sedimentation tanks, is kept

  • 3 m
  • 3.5 m
  • 4 m
  • 4.5 m.
Q.33

Assertion (A) : A free board of 0.3 m is provided above the top sewage line in septic tanks.

Reason (R) : It helps to accommodate the scum in the septic tank.

  • Both A and R are true and R is the correct explanation of A
  • Both A and R are true but R is not a correct explanation of A
  • A is true but R is false
  • A is false but R is true.
Q.34

Large diameter sewers subjected to external pressure alone, are reinforced

  • near the inner surface of the pipe
  • near the outer surface of the pipe
  • both (a) and (b)
  • with elliptical cage
  • none of these.
Q.35

The sewer which transports the sewage to the point of treatment, is called

  • house sewer
  • out-fall sewer
  • branch sewer
  • lateral
  • main sewer.
Q.36

The sewer which resists sulphide corrosion, is

  • Brick sewer
  • Cast iron sewer
  • R.C.C. sewer
  • Lead sewer
  • None of these.
Q.37

Imhoff cone is used to determine

  • settlable solids
  • suspended solids
  • dissolved solids
  • none of these.
Q.38

Ventilating shafts are provided to a sewer line at every

  • 100 m
  • 150 m
  • 200 m
  • 300 m
  • 500 m.
Q.39

For a peak discharge of 0.cumec, with a velocity of 0.9 m/sec, the diameter of the sewer main, is

  • 10 cm
  • 12 cm
  • 15 cm
  • 18 cm
  • 20 cm.
Q.40

If D is the diameter of a circular sewer and D' is the top horizontal diameter of an equivalent egg shaped section, the relationship which holds good, is

  • D' = 0.64 D
  • D' = 0.74 D
  • D' = 0.84 D
  • D' = 0.94 D.
Q.41

Sewer pipes are designed for maximum discharge withtovacant cross-sectional area for

  • unexpected large scale infiltration of stream water
  • unexpected increase in the population
  • under estimates of maximum and average flows
  • All of the above.
Q.42

A circular sewer section is preferred to because

  • it is cheaper in construction
  • it provides maximum area for a given perimeter
  • it provides maximum hydraulic mean depth
  • all the above.
Q.43

Primary treatment of sewage consists of removal of

  • large suspended organic solids
  • oil and grease
  • sand and girt
  • floating materials
  • none of these.
Q.44

The reduced levels of the string at the consecutive sight rails A and B are 203.m, 203.m respectively. If the difference of their R.D.s ism, the gradient of the sewer line is

  • 1 in 100 upward
  • 1 in 500 upward
  • 1 in 100 downward
  • 1 in 503 upward.
Q.45

Pick up the correct statement from the following :

  • The ratio of the quantity of the diluting water to that of the sewage, is known as dilution factor
  • The automatic purification of polluted water, is known self purification phenomenon
  • The photosynthesis is carried out in the presence of sun light
  • Grab sample is generally obtained from the surface where turbulence mixes the sewage particles
  • All the above.
Q.46

Kjedahl nitrogen is a mixture of

  • ammonia and nitrogen
  • nitrogen and organic nitrogen
  • organic nitrogen and ammonia
  • all the above.
Q.47

The sewage discharge in a detritus tank of a treatment plant islitres/sec with flow velocity of 0.2 m/sec. If the ratio of width to depth isthe depth is

  • 100 cm
  • 110 cm
  • 120 cm
  • 150 cm.
Q.48

Which one of the following part of human body withstands minimum radiation

  • thyroid
  • kidneys
  • eyes
  • ovaries/testis.
Q.49

The pH value of fresh sewage is usually

  • equal to 7
  • more than 7
  • less than 7
  • equal to zero.
Q.50

A nuisance is experienced in diluting water if dilution factor is less than

  • 100
  • 60
  • 40
  • 20
  • 10
0 h : 0 m : 1 s