waste water engineering MCQs – Page 6

Practise focused waste water engineering questions with marked answers for exam preparation and subject revision.

waste water engineering Mcqs
251. If the depth of partial flow in a sewer of diameter 2 m, is 50 cm, its wetted perimeter is____________________ ?
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A. 3-Jan

B. 0/2

C. 2 /3

D. 0/3

252. Stone ware pipes are_______________?
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A. Highly resistant to sulphide corrosion

B. Especially suited to pressure pipes

C. Highly impervious

D. Hydraulically efficient because of their smooth interior surface

253. A drop manhole is provided if__________________?
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A. None of these

B. A sewer drops from a height

C. A lamp is inserted to check obstruction

D. A branch sewer joins the main sewer at higher level
254. 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_______________?
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A. 25%

B. 50 %

C. 5%

D. 10%

255. The formula which accepts the value of rugosity coefficient n = 0.012 to be used in Mannings formula, is given by______________________?
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A. Kutter

B. William-Hazen

C. Crimp and Bruges

D. Bazin

256. For large sewers, maximum distance between manholes may be_______________?
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A. 300 m

B. 100 m

C. 50 m

D. 200 m

257. The sewage is pumped up_______________?
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A. From low lying areas

B. From flat areas

C. All the above

D. From basements

258. The value of Chezys constant C = 157.6/(1.81 + K/ ) is used in__________________?
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A. Chezys formula

B. Kutters formula

C. Bazins formula

D. Mannings formula

259. The use of coarse screens for the disposal of sewage, may be dispensed with by______________?
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A. Comminutor

B. Shredder

C. Both A. and B.

D. Neither A. nor B.

260. Facultative bacteria survive in_____________________?
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A. The presence of oxygen

B. The absence of oxygen

C. Both cases A. and B.

D. Neither A. nor B.

261. A circular sewer section is preferred to because__________________?
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A. All the above

B. It is cheaper in construction

C. It provides maximum area for a given perimeter

D. It provides maximum hydraulic mean depth

262. Discrete or granular particles change their_________________ ?
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A. Weight

B. None of these

C. Size

D. Shape

263. A safety lamp when inserted in the upper portion of a manhole causes flames. It indicates the presence of______________?
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A. Methane gas

B. Carbondioxide gas

C. Petrol vapours

D. Hydrogen sulphide gas

264. In detritus tanks______________________?
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A. All the above

B. Organic and inorganic materials are separated

C. Detention period is kept 3 to 4 minutes

D. Flow velocity is kept 0.09 m/sec

265. The most widely used pump for lifting sewage is_________________?
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A. Pneumatic ejector

B. Reciprocating pump

C. Air pressure pump

D. Centrifugal pump
266. If the depletion of oxygen is found to be 5 ppm after incubating a 2.5% solution of sewage sample for 5 days at 21C, B.O.D. of the sewage is_____________________?
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A. 50 ppm

B. 150 ppm

C. 200 ppm

D. 100 ppm

267. Which one of the following gases is most significant as air pollutant ?
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A. Sulphur-dioxide

B. Carbondioxide

C. Oxygen

D. Nitrogen

268. If a 2% solution of sewage sample is incubated for 5 days at 20C and the dissolved oxygen depletion was found to be 8 mg/l. The BOD of the sewage is_________________?
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A. 300 mg/l

B. 400 mg/l

C. 200 mg/l

D. 100 mg/l

269. A well oxidized sewage contains nitrogen mainly as___________________?
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A. None of these

B. Free ammonia

C. Nitrites

D. Nitrates
270. Setting out the alignments of sewers may start from__________________?
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A. City

B. Tail end

C. Any point

D. Out-fall

271. The stone ware sewers_________________?
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A. Are used for carrying sewage and drainage from houses

B. All the above

C. After casting are dried and burnt at temperature 150C, 700C and 1200C

D. Are manufactured from clays and shale

272. The underground sewers are more subjected to________________?
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A. Bending force

B. Shearing force

C. Compressive force

D. Tensile force

273. The spacing of bars for perforations in coarse screens used for the treatment of sewage, is ____________________?
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A. 50 mm

B. 20 mm

C. 40 mm

D. 30 mm

274. Lead acetate test in sewer manhole is done to test the presence of ____________________?
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A. Diesel vapours

B. Hydrogen sulphide

C. Carbondioxide gas

D. Methane gas

275. The maximum depth of sedimentation tanks, is kept__________________?
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A. 3 m

B. 3.5 m

C. 4.5 m

D. 4 m

276. The ratio of the diameter of a circular section and the side of a square section hydraulically equivalent, is____________________?
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A. 1.085

B. 1.095

C. 1.075

D. 1.065

277. The factor responsible for purification of sewage in river is________________?
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A. Dissolved oxygen in water

B. All the above

C. Hydrology

D. Temperature

278. A five day B.O.D. at 15C of the sewage of a town is 100 kg/day. If the 5 day B.O.D. per head at 15C for standard sewage is 0.1 kg/day, the population equivalent is____________________?
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A. 1000

B. 10000

C. 100

D. 5000

279. Sewer pipes need be checked for_________________?
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A. Minimum flow

B. Maximum flow

C. Both A. and B.

D. None of these

280. The minimum diameter of a sewer is kept __________________?
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A. 25 cm

B. 15 cm

C. 10 cm

D. 20 cm

281. The width of a settling tank with 2 hour detention period for treating sewage 378 cu m per hour, is __________________?
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A. 6.5 m

B. 7 m

C. 5 m

D. 5.5 m

282. If the depth of flow in a circular sewer is 1/4th of its diameter D, the wetted perimeter is______________?
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A. /2

B. D

C. /3

D. /4

283. Imhoff cone is used to measure________________?
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A. Total organic solids

B. Settleable solids

C. Total solids

D. Total in organic solids

284. In a sedimentation tank (length L, width B, depth D) the settling velocity of a particle for a discharge Q, is____________________?
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A. Q/(B D)

B. Q/(B L)

C. Q/(L D)

D. Q/L

285. The grit and silt of the grit chambers, may not be used for_________________?
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A. Raising low lying areas by dumping

B. Concreting

C. Both A. and B.

D. Neither A. nor B

286. For the COD test of sewage, organic matter is oxidised by K2Cr2O7 in the presence of________________?
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A. HCl

B. H2SO4

C. HNO3

D. None of these

287. The sewer that unloads the sewage at the point of treatment is called_________________?
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A. Outfall sewer

B. Main sewer

C. Branch sewer

D. House sewer

288. If the flame of a miners safety lamp in a manhole extinguishes within 5 minutes, the sewer certainly contains_______________?
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A. Hydrogen sulphide

B. Carbon dioxide

C. Oxygen

D. Methane

289. Pick up the correct statement from the following?
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A. All the above

B. Inlets are provided on the road surface at the lowest point for draining rain water

C. Inlets having horizontal openings, are called horizontal inlets

D. Inlets are generally provided at an interval of 30 m to 60 m along straight roads

290. Sewer pipes are designed for maximum discharge with 25% to 33% vacant cross-sectional area for__________________?
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A. Unexpected increase in the population

B. Unexpected large scale infiltration of stream water

C. All of the above

D. Under estimates of maximum and average flows

291. The layers of vegetable wastes and night soil alternatively piled above the ground to form a mound, is called_______________?
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A. A heap

B. Windrow

C. Plateau

D. None of these
292. Sewer ventilating columns are generally placed at_______________?
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A. All the above

B. Every change in the size of sewers

C. Upper ends of branch sewers

D. Distances 150 m to 300 m

293. For a grit chamber, if the recommended velocity of flow is 0.2 m/sec and detention period is 2 minutes, the length of the tank, is__________________?
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A. 30 m

B. 20 m

C. 24 m

D. 16 m

294. Pick up the correct statement from the following?
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A. The circular section of sewers provides maximum hydraulic mean depth

B. The circular sewers work efficiently if the sections run at least half full

C. The circular sewers are provided for separate sewerage system

D. All the above
295. Pick up the correct statement from the following?
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A. pH value indicates acidity and alkalinity of sewage

B. In acidic sewage, the pH value is less than 7

C. In alkaline sewage, the pH value is more than 7

D. All the above
296. The amount of oxygen consumed by the aerobic bacterias which cause the aerobic biological decomposition of sewage, is known_________________?
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A. Chemical Oxygen Demand (C.O.D.)

B. Dissolved Oxygen (D.O.)

C. None of these

D. Bio-Chemical Oxygen Demand (B.O.D.)

297. In sewers the effect of scouring is more on__________________?
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A. Horizontal side

B. Bottom side

C. All sides

D. Top side

298. Pick up the correct statement from the following?
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A. Aerobic bacteria flourish in the presence of oxygen

B. Anaerobic bacteria flourish in the absence of oxygen

C. Facultative bacteria flourish with or without oxygen

D. . All the above
299. Pick up the correct statement from the following ?
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A. All the above

B. The black colour indicates septic sewage

C. The sewage omits offensive odours after four hours

D. Turbidity is more in strong sewage

300. Dilution method of disposing of sewage, is not preferred to_______________?
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A. When diluting water has high dissolved oxygen content

B. When diluting water is used for water supply near the point of sewage disposed

C. When the diluting water is having flow currents

D. When sewage is fresh