Practice Test: Question Set - 08
1. For design of sewers, percentage of sewage discharge is assumed
- (A) 65 to 70 %
- (B) 70 to 75 %
- (C) 75 to 80 %
- (D) 85 %
2. The grit chambers of sewage treatment plants, are generally cleaned after
- (A) 2 days
- (B) 7 days
- (C) 12 days
- (D) 14 days
3. Maximum permissible velocity 1.5 m/sec, is adopted in drains
- (A) With
beds of rocks and gravels
- (B) Lined
with stones
- (C) Both (a) and
(b)
- (D) Neither (a)
nor (b)
4. The average temperature of sewage in India, is
- (A) 10°C
- (B) 15°C
- (C) 20°C
- (D) 25°C
5. 'Cowl' is provided at
- (A) Lower end of
ventilating column
- (B) Upper end of
ventilating column
- (C) Upper end of
the manhole
- (D) First step
in manhole
6. If the discharge of a sewer running half is 628 1.p.s., i = 0.001, and n = 0.010, the diameter of the sewer, is
- (A) 1.39 m
- (B) 1.49 m
- (C) 1.59 m
- (D) 1.69 m
7. A drop manhole is provided if
- (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
8. For a circular sewer of diameter ‘D’ running partially full with central angle ‘α’,
- (A) d/D
= ½ (1 - cosα/2)
- (B) a/A
= [(π/360°) - (sinα/2π)]
- (C) r/R
= [1 - 360° sinα/2πα)]
- (D) All the
above
9. The use of coarse screens for the disposal of sewage, may be dispensed with by
- (A) Comminutor
- (B) Shredder
- (C) Both (a) and
(b)
- (D) Neither (a)
nor (b)
10. In the activated sludge process
- (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. For detecting the nitrates in sewage, the color may be developed by adding
- (A) Potassium
permanganate
- (B) Sulphuric
acid and napthamine
- (C) Phenol-di-sulphuric
acid and potassium hydroxide
- (D) None of
these
12. The settling velocity of a spherical particle of diameter less than 0.1 mm as per Stock's law, is
- (A) Vs = 418 (Gs - Gw)d [(3T + 70)/100]
- (B) Vs = 418 (Gs - Gw)d² [(3T + 70)/100]
- (C) Vs = 218 (Gs - Gw)d² [(3T + 70)/100]
- (D) Vs = 218 (Gs - Gw)d [(3T + 70)/100]
13. In septic tanks,
- (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) All the
above
14. Inter-distance between ventilation columns in a sewer line is kept
- (A) 25 to 50 m
- (B) 50 m to 100
m
- (C) 100 m to 150
m
- (D) 150 m to 300
m
15. Stone ware pipes are
- (A) Highly
resistant to sulphide corrosion
- (B) Highly
impervious
- (C) Hydraulically
efficient because of their smooth interior surface
- (D) Especially
suited to pressure pipes
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