Practice Test: Question Set - 18
1. Disposal to sewage in large cities, is done in
- (A) Irrigation
- (B) Dilution
- (C) Oxidation
- (D) Purification
2. 3.0 ml of raw sewage is diluted to 300 ml. 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 D.O. concentration was 5 mg/l. The BOD of raw sewerage is
- (A) 100 mg/l
- (B) 200 mg/l
- (C) 300 mg/l
- (D) 400 mg/l
3. The digested sludge from septic tanks, is removed after a maximum period of
- (A) 3 years
- (B) 3.5 years
- (C) 4 years
- (D) 5 years
4. Assertion (A): The minimum self cleansing velocity in the sewer, at least once a day, must be generated.
Reason (R):
If certain deposition takes place and is not removed, it obstructs free flow
and causes further deposition leading to complete blocking of the sewer.
- (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
5. The presence of free ammonia in sewage, is detected by
- (A) Boiling
- (B) Adding
potassium permanganate
- (C) Adding
sulphuric acid
- (D) Phenol-di-sulphuric
acid
6. Dry water flow in a combined sewer, is
- (A) Industrial
sewage
- (B) Domestic
sewage
- (C) Storm
water
- (D) Inclusive
of domestic and industrial sewage but excludes storm water
7. The porosity of sediments in sewer pipes, is usually taken as
- (A) 0.010
- (B) 0.011
- (C) 0.012
- (D) 0.013
8. In sewage having fully oxidized organic matter, the nitrogen exists in the form of
- (A) Nitrites
- (B) Nitrates
- (C) Free
ammonia
- (D) Aluminoid
nitrogen
9. The minimum diameter of sewer to be adopted is
- (A) 10 cm
- (B) 12.5 cm
- (C) 15 cm
- (D) 25 cm
10. If the diameter of sewer is 225 mm, the gradient required for generating self cleansing velocity, is
- (A) 1 in 60
- (B) 1 in 100
- (C) 1 in 120
- (D) None of
these
11. The sewerage system consists of
- (A) House sewer
- (B) Lateral
sewer
- (C) Branch
sewer
- (D) All
of these
12. Clogging of sewers, is caused due to
- (A) Silting
- (B) Low
discharge
- (C) Greasy
and oily matters
- (D) All
the above
13. Oxidation process results in the formation of
- (A) Carbon
dioxide
- (B) Nitrates
- (C) Sulphates
- (D) All
the above
14. The sewage is pumped up
- (A) From
low lying areas
- (B) From flat
areas
- (C) From
basements
- (D) All
the above
15. The angle subtended by the surface of sewer water with partial flow, at sewer centre is 120°, the depth of sewerage is
- (A) 20 cm
- (B) 25 cm
- (C) 40 cm
- (D) 50 cm
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