1. UNIT I & II - MCQ

2. 1. 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
Answer : a)

3. 2. Pick up the correct statement: The sewer pipes
does not carry sewage as gravity conduits
Are designed for generating self-cleansing velocities at different discharge
Should not resist the wear and tear caused due to abrasion
will not carry storm water
Answer : b)

4. 3. Pick up the incorrect statement from the following for allowing workers to enter sewers
The particular manhole and one manhole on upstream and one manhole on downstream should remain open for 30 minutes
Proper tests for the presence of poisonous gases must be carried out
The men entering the manhole should be advised to smoke in the sewer
Warning signals should be erected
Answer : c)

5. 4. To prevent settling down of sewage both at the bottom and on the sides of a large sewer, self cleaning velocity recommended for Indian conditions, is
0.50 m/sec
0.60 m/sec
0.70 m/sec
0.75 m/sec
Answer : d)

6. 5. The temperature in the waste water
lower that of the water supply
increase the viscosity of water
decrease the bacterial activity
does not affect the aquatic life
Answer : b)

7. 6. The sewer that unloads the sewage at the point of treatment is called
Main sewer
Outfall sewer
Branch sewer
House sewer
Answer : b)

8. 7. Dry weather flow is: Average daily rate of flow
Average monthly rate of flow
Average annual rate of flow
Water supply allowance per capita
Answer : d)

9. 8. Pick up the incorrect statement from the following
The mixture of water and waste products, is called sewage
The treated sewage effluents, are generally used for irrigating the crops
The process of collecting, treating and disposing off the sewage, is called sewerage
The old convergence system was definitely better than water carried sewerage system
Answer : d)

10. 9. Hydraulic mean radius is
Mean radius of sewer
Difference in heads between two points in circular pipes
Mean of radii in a pipe line of varying cross-sections
Cross-sectional area/wetted perimeter
Answer : d)

11. 10. Traps Are water seals which prevent the entry of foul gases
Are used to trap the rats entering sewers
Dissolve the foul gases
Create symphonic action to increase the quick disposal of sewerage
Answer : a)

12. 11. If the diameter of a sewer is 150 mm, the gradient required for generating self cleansing velocity, is
1 in 60
1 in 100
1 in 120
1 in 150
Answer : b)

13. 12. The sewer which received discharge from two or more main sewers, is known as
A branch or trunk sewer
An outfall sewer
A main sewer
An intercepting sewer
Answer : a)

14. 13. The sludge does not contain waste water from
Bath rooms
Wash basins
Kitchen sinks
Toilets
Answer : d)

15. 14. 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
Answer : b)

16. 15. Which of the following shape of sewer gives the maximum area for a given perimeter and provided for separate sewerage system
Rectangular section
Ovoid Section
Circular section
Trapizoidal section
Answer : c)

17. 16. A sewer which receives sewage from a relatively small area usually a few laterals and discharge into main sewer is called as
A Branch sewer
An outfall sewer
A main sewer
An intercepting sewer
Answer : a)

18. 17. The sewer which resists sulphide corrosion, is
Brick sewer
Cast iron sewer
R.C.C. sewer
Lead sewer
Answer : d)

19. 18. The amount of oxygen consumed by the aerobic bacterias which cause the aerobic biological decomposition of sewage, is known
Bio-Chemical Oxygen Demand (B.O.D.)
Dissolved Oxygen (D.O.)
Chemical Oxygen Demand (C.O.D.)
Oxygen Demand
Answer : b)

20. 19. Water content of sewage is about
90 %
95 %
99 %
99.9 %
Answer : d)

21. 20. The most efficient cross-section of sewers in a combined sewerage system is
Parabolic
Circular
Rectangular
New egged
Answer : b)

22. 21. Self-cleansing velocity is
Velocity at dry weather flow
Velocity of water at flushing
Velocity at which no accumulation remains in the drains
Velocity of water in a pressure filter
Answer : c)

23. 22. 5 days-biochemical oxygen demand (BOD5) is taken at a temperature of
Answer : c)

24. 23. A well oxidized sewage contains nitrogen mainly as
Nitrates
Nitrites
Free ammonia
Albuminoid ammonia
Answer : a)

25. 24. The average temperature of sewage in India, is
10°C
15°C
20°C
25°C
Answer : c)

26. 25. If the discharge of a sewer running half is 628 1. p. s. , i = 0
25. If the discharge of a sewer running half is p.s., i = 0.001, and n = 0.010, the diameter of the sewer, is
1.39 m
1.49 m
1.59 m
1.69 m
Answer : d)