Multiple Choice Questions on Wastewater Treatment - Set 08 - ObjectiveBooks

# 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 ‘Î±’,
(A) d/D = ½ (1 - cosÎ±/2)
(B) a/A = [(Ï€/360°) - (sinÎ±/2Ï€)]
(C) r/R = [1 - 360° sinÎ±/2Ï€Î±)]
(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) [(3T + 70)/100]
(C) Vs = 218 (Gs - Gw) [(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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