Practice Test: Question Set - 07
1. In areas where light rains are uniformly distributed throughout the year, the type of sewerage system to be adopted is
- (A) Separate
system
- (B) Combined
system
- (C) Partially
combined system
- (D) None of
these
2. Self-cleansing velocity is
- (A) Velocity at
dry weather flow
- (B) Velocity of
water at flushing
- (C) Velocity at
which no accumulation remains in the drains
- (D) Velocity of
water in a pressure filter
3. 5 days-biochemical oxygen demand (BOD5) is taken at a temperature of
- (A) 0°C
- (B) 15°C
- (C) 20°C
- (D) 25°C
4. Pick up the correct statement from the following:
- (A) Inlets
are provided on the road surface at the lowest point for draining rain water
- (B) Inlets are
generally provided at an interval of 30 m to 60 m along straight roads
- (C) Inlets
having horizontal openings, are called horizontal inlets
- (D) All the
above
5. If a 2% solution of sewage sample is incubated for 5 days at 20°C and the dissolved oxygen depletion was found to be 8 mg/l. The BOD of the sewage is
- (A) 100 mg/l
- (B) 200 mg/l
- (C) 300 mg/l
- (D) 400 mg/l
6. Pick up the incorrect statement from the following:
- (A) Manholes are
provided in sewer pipes at suitable intervals
- (B) Catch basins
are generally provided in sewers for carrying drainage discharge
- (C) Inlets are
generally provided in all sewers
- (D) None of
these
7. The moisture content of sludge is reduced from 90% to 80% in a sludge digestion tank. The percentage decrease in the volume of sludge, is
- (A) 25 %
- (B) 50 %
- (C) 10 %
- (D) 5 %
8. A well oxidized sewage contains nitrogen mainly as
- (A) Nitrates
- (B) Nitrites
- (C) Free
ammonia
- (D) None
of these
9. In a sludge tank, the gas mainly produced, is
- (A) Oxygen
- (B) Nitrogen
- (C) Hydrogen
- (D) Carbon
dioxide
10. Bio-chemical oxygen demand (BOD) for the first 20 days in generally referred to
- (A) Initial
demand
- (B) First
stage demand
- (C) Carbonaceous
demand
- (D) All of these
11. Stoneware sewers are available in size
- (A) 10 cm
- (B) 15 cm
- (C) 20 cm
- (D) All
the above
12. If ‘D’ is the diameter of upper circular portion, the overall depth of New Egg shaped sewer section, is
- (A) 1.250 D
- (B) 1.350 D
- (C) 1.425 D
- (D) 1.625 D
13. In normal conditions, the period for sludge digestion, is
- (A) 10 days
- (B) 20 days
- (C) 30 days
- (D) 60 days
14. For evaporation and measurement of settable solids, the apparatus used, is
- (A) A jar
- (B) A breaker
- (C) A test tube
- (D) An Imhoff
cone
15. In trickling filter, B.O.D. is reduced to
- (A) 30 to 40%
- (B) 40 to 60%
- (C) 60 to 80%
- (D) 80 to 90%
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