Waste Water Engineering problems
- 1. If the depletion of oxygen is found to be 2.5 mg/litre after incubating 2.5 ml of sewage diluted to 250 ml for 5 days at 20°C, B.O.D. of the sewage is
Options- A. 50 mg/l
- B. 100 mg/l
- C. 150 mg/l
- D. 200 mg/l
- E. 250 mg/l. Discuss
Correct Answer: 250 mg/l.
- 2. It is customary to design a sewer for D.W.F. on the basis of
Options- A. average demand
- B. twice the average demand
- C. thrice the average demand
- D. four times the average demand. Discuss
Correct Answer: thrice the average demand
- 3. The detention period for plain sedimentation water tanks, is usually
Options- A. 4 to 8 hours
- B. 8 to 16 hours
- C. 16 to 24 hours
- D. 24 to 36 hours. Discuss
Correct Answer: 4 to 8 hours
- 4. Sewer ventilating columns are generally placed at
Options- A. distances 150 m to 300 m
- B. upper ends of branch sewers
- C. every change in the size of sewers
- D. all the above. Discuss
Correct Answer: all the above.
- 5. In case of Imhoff tanks,
Options- A. the shape is rectangular
- B. detention period is 2 hours
- C. the velocity of flow is restricted to 0.30 m/minute
- D. surface loading is limited to 30, 000 litres/m of plan area per day
- E. All the above. Discuss
Correct Answer: All the above.
- 6. Pick up the correct statement from the following :
Options- A. The materials separated by screens, is called screenings
- B. The screenings are disposed off either by burning or by burial or by dumping
- C. The process of burning the screenings, is called incineration
- D. The process of burning the screenings, is known as compositing
- E. All the above. Discuss
Correct Answer: All the above.
- 7. In sewers the highest non-scouring velocity is achieved in
Options- A. glazed bricks sewers
- B. cast iron sewers
- C. cement concrete sewers
- D. stone ware sewers. Discuss
Correct Answer: glazed bricks sewers
- 8. The standard B.O.D. of water is taken for
Options- A. 1 day
- B. 2 days
- C. 3 days
- D. 5 days
- E. 10 days. Discuss
Correct Answer: 5 days
- 9. The ratio of the diameter of a circular section and the side of a square section hydraulically equivalent, is
Options- A. 1.095
- B. 1.085
- C. 1.075
- D. 1.065 Discuss
Correct Answer: 1.095
- 10. The digested sludge from septic tanks, is removed after a maximum period of
Options- A. 3 years
- B. 3.5 years
- C. 4 years
- D. 5 years. Discuss
Correct Answer: 3 years
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