Water And Wastewater Engineering Set 1 MCQs

Q1 | For a continuous flow type of sedimentation tanks

Width of the tank is normally kept about 6 m

Length of the tank is normally kept 4 to 5 times the width

) Maximum horizontal flow velocity is limited to 0.3 m/minute

All the above

Q2 | The asbestos cement sewers are

Light in weight

Not structurally strong to bear large compressive stress

Susceptible to corrosion by sulphuric acid

All the above

Q3 | For efficient working of a sewer, it must be ensured that

Minimum velocity of 0.45 m/sec, is maintained at its minimum flow

A maximum velocity of 0.90 m/sec, is maintained at its maximum flow

Both (a) and (b)

Neither (a) nor (b)

Q4 | Bottom openings 15 cm × 15 cm in the standing baffle wall are provided

15 cm c/c

22.5 cm c/c

30 cm c/c

50 cm c/c

Q5 | For drainage pipes in buildings the test applied before putting them to use, is

Water test

Smoke test

Straightness test

All the above

Q6 | The pressure exerted by

The sewage when running full from inside, is called internal pressure

The internal pressure if any, causes tensile stress in the pipe material

Pressure sewers are designed to be safe in tension

All the above

Q7 | No treatment of the sewage is given if dilution factor is

Less than 150

Between 150 to 200

Between 200 to 300

More than 500

Q8 | Which of the following pumps in used to pump sewage solids with liquid sewage withoutclogging the pump is?

Centrifugal pump

Pneumatic ejector

Reciprocating pump

None of these

Q9 | Acid regression stage of sludge digestion at a temperature 21°C extends over a period of

15 days

30 days

) 60 days

90 days

Q10 | The coagulant which is generally not used for treating the sewage, is

Alum

Ferric chloride

Ferric sulphate

Chlorinated copperas

Q11 | The layers of vegetable wastes and night soil alternatively piled above the ground to form a mound, is called

A heap

Plateau

Windrow

None of these

Q12 | If the flame of a miner's safety lamp in the upper layers of the sewer forms an explosive, thesewer certainly contains

Hydrogen sulphide

Carbon dioxide

Methane

Oxygen

Q13 | The gas which may cause explosion in sewers, is

Carbondioxide

Methane

Ammonia

Carbon monoxide

Q14 | Pick up the incorrect statement from the following:

The process of decomposing the organic matter under controlled anaerobic conditions, is called sludge digestion

Sludge digestion is carried out in sludge tank

The gases produced in sludge digestion process, contain 75% carbon dioxide

The gases produced in sludge digestion process, contain 75% methane

Q15 | The sewer pipes

Carry sewage as gravity conduits

Are designed for generating self-cleansing velocities at different discharge

Should resist the wear and tear caused due to abrasion

All the above

Q16 | The settling velocity of the particles larger than 0.06 mm in a settling tank of depth 2.4 is 0.33 mper sec. The detention period recommended for the tank, is

30 minutes

1 hour

1 hour and 30 minutes

2 hours

Q17 | The Chezy's constant C in the formula V = C ???? depends upon

Size of the sewer

Shape of the sewer

Roughness of sewer surface

All the above

Q18 | To prevent settling down of sewage both at the bottom and on the sides of a large sewer,selfcleaning velocity recommended for Indian conditions, is

0.50 m/sec

0.60 m/sec

0.70 m/sec

0.75 m/sec

Q19 | Assertion (A): The determination of pH value of sewerage is important. Reason (R): The efficiency of certain treatment methods depends upon the availability of pH value.

Both A and R are true and R is the correct explanation of A

Both A and R are true but R is not a correct explanation of A

A is true but R is false

A is false but R is true

Q20 | The normal values of over flow rates for sedimentation tanks using coagulant, ranges between

25,000 to 35,000 litres/sqm/day

40,000 to 50,000 litres/sqm/day

50,000 to 60,000 litres/sqm/day

80,000 to 100,000 litres/sqm/day

Q21 | During preliminary treatment of a sewage

Oil and grease are removed from skimming tanks

Floating materials are removed by screening

Girt and sand are removed by girt chambers

All the above

Q22 | Dry weather flow is:

Average daily rate of flow

Average monthly rate of flow

Average annual rate of flow

Water supply allowance per capita

Q23 | If q is the average sewage flow from a city of population P, the maximum sewage flow

Q = [(4 + ?? )/(18 + ?? )] q

Q = [(18 +p )/(4 + ?? )] q

Q = [(18 + ?? )/(4 + ?? )] q

Q = [(5 + ?? )/(15 + ?? )] q

Q24 | If the flame of a miner's safety lamp in a manhole extinguishes within 5 minutes, the sewercertainly contains

Hydrogen sulphide

Carbon dioxide

Methane

Oxygen

Q25 | 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