Water Waste engg-4

Question No. 61

The sludge does not contain waste water from

(A) Bath rooms

(B) Wash basins

(C) Kitchen sinks

(D) Toilets

Answer: Option D

Question No. 62

In sewers the velocity of flow should not be

(A) More than the self-cleansing velocity

(B) Less than the self-cleansing velocity

(C) Less than 10 m/sec

(D) More than 20 m/sec

Answer: Option B

Question No. 63

Pick up the correct statement from the following:

(A) Hydrogen sulphide gas in excess, may cause corrosion of concrete sewers

(B) 4 ppm of Dissolved Oxygen (D.O.) is ensured before discharging the treated sewage in river

(C) Solubility of oxygen in sewage is 95% of that of distilled water

(D) All the above

Answer: Option D

Question No. 64

In sewers the effect of scouring is more on

(A) Top side

(B) Bottom side

(C) Horizontal side

(D) All sides

Answer: Option B

Question No. 65

The rainfall at any place may be determined by

(A) Its intensity

(B) Its direction

(C) Its frequency

(D) All the above

Answer: Option D

Question No. 66

Pick up the correct statement from the following:

(A) The circular section of sewers provides maximum hydraulic mean depth

(B) The circular sewers are provided for separate sewerage system

(C) The circular sewers work efficiently if the sections run at least half full

(D) All the above

Answer: Option D

Question No. 67

Pick up the correct statement from the following:

(A) Rate of digestion of sludge is more at higher temperature

(B) Thermophilic organisms digest the sludge if the temperature ranges from 40° to 60°C

(C) Mesophilic organisms digest the sludge if the temperature is between 25° and 40°C

(D) All the above

Answer: Option D

Question No. 68

Sewer ventilating columns are generally placed at

(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

Answer: Option D

Question No. 69

The sewer which resists sulphide corrosion, is

(A) Brick sewer

(B) Cast iron sewer

(C) R.C.C. sewer

(D) Lead sewer

Answer: Option D

Question No. 70

In a sedimentation tank (length L, width B, depth D) the settling velocity of a particle for a

discharge Q, is

(A) Q/(B × D)

(B) Q/(L × D)

(C) Q/L

(D) Q/(B × L)

Answer: Option D

Question No. 71

The formula which accepts the value of rugosity coefficient n = 0.012 to be used in Manning's

formula, is given by

(A) Bazin

(B) Crimp and Bruges

(C) William-Hazen

(D) Kutter

Answer: Option B

Question No. 72

The amount of oxygen consumed by the aerobic bacterias which cause the aerobic biological

decomposition of sewage, is known

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

(B) Dissolved Oxygen (D.O.)

(C) Chemical Oxygen Demand (C.O.D.)

(D) None of these

Answer: Option B

Question No. 73

Water content of sewage is about

(A) 90 %

(B) 95 %

(C) 99 %

(D) 9.9 %

Answer: Option D

Question No. 74

Skimming tanks are

(A) Used to remove the grease and oil

(B) Those from which sludge is skimmed out

(C) Tanks provided with self-cleansing screens

(D) Improved version of grit chambers

Answer: Option A

Question No. 75

The most efficient cross-section of sewers in a combined sewerage system is

(A) Parabolic

(B) Circular

(C) Rectangular

(D) New egged

Answer: Option B

Question No. 76

The detention period for plain sedimentation water tanks, is usually

(A) 4 to 8 hours

(B) 8 to 16 hours

(C) 16 to 24 hours

(D) 24 to 36 hours

Answer: Option A

Question No. 77

The factor responsible for purification of sewage in river is

(A) Hydrology

(B) Dissolved oxygen in water

(C) Temperature

(D) All the above

Answer: Option D

Question No. 78

Hume steel pipes are

(A) Steel pipes

(B) Steel shell coated from inside with cement mortar

(C) Steel shell coated from outside with cement mortar

(D) Both (B) and (C)

Answer: Option D

Question No. 79

To maintain aerobic biological activity, the moisture content of the compost mass should be about

(A) 45 %

(B) 50 %

(C) 55 %

(D) 60 %

Answer: Option C

Waste Water Engineering -2

Question No. 21

The Chezy's constant C in the formula V = C √rs depends upon

(A) Size of the sewer

(B) Shape of the sewer

(C) Roughness of sewer surface

(D) All the above

Answer: Option D

Question No. 22

The discharge per unit plan area of a sedimentation tank, is generally called

(A) Over flow rate

(B) Surface loading

(C) Over flow velocity

(D) All the above

Answer: Option D

Question No. 23

Pick up the incorrect statement from the following for allowing workers to enter sewers

(A) The particular manhole and one manhole on upstream and one manhole on downstream

should remain open for 30 minutes

(B) Proper tests for the presence of poisonous gases must be carried out

(C) The men entering the manhole should be advised to smoke in the sewer

(D) Warning signals should be erected

Answer: Option C

Question No. 24

For the open drain (N = 0.025) shown in the below figure, the discharge is

(A) 26.88 cumecs

(B) 27.88 cumecs

(C) 28.88 cumecs

(D) 29.88 cumecs

Answer: Option C

Question No. 25

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

(A) 0.50 m/sec

(B) 0.60 m/sec

(C) 0.70 m/sec

(D) 0.75 m/sec

Answer: Option D

Question No. 26

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.

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

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

(C) A is true but R is false

(D) A is false but R is true

Answer: Option A

Question No. 27

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

(A) 25,000 to 35,000 litres/sqm/day

(B) 40,000 to 50,000 litres/sqm/day

(C) 50,000 to 60,000 litres/sqm/day

(D) 80,000 to 100,000 litres/sqm/day

Answer: Option C

Question No. 28

The drainage area of a town is 12 hectares. Its 40% area is hard pavement (K = 0.85), the 40% area

is unpaved streets (K = 0.20) and the remaining is wooded areas (K = 0.15). Assuming the time of

concentration for the areas as 30 minutes and using the formula Ps = 900/(t + 60) the maximum

run off is

(A) 0.10 cumec

(B) 0.12 cumec

(C) 0.15 cumec

(D) 0.20 cumec

Answer: Option C

Question No. 29

Sewer pipes are designed for maximum discharge with 25% to 33% vacant cross-sectional area for

(A) Unexpected large scale infiltration of stream water

(B) Unexpected increase in the population

(C) Under estimates of maximum and average flows

(D) All of the above

Answer: Option D

Question No. 30

The rational formula for peak drainage discharge, was evolved by

(A) Fruhling

(B) Lloyd David

(C) Kuichling

(D) All of these

Answer: Option D

Question No. 31

The sewer that unloads the sewage at the point of treatment is called

(A) Main sewer

(B) Outfall sewer

(C) Branch sewer

(D) House sewer

Answer: Option B

Question No. 32

During preliminary treatment of a sewage

(A) Oil and grease are removed from skimming tanks

(B) Floating materials are removed by screening

(C) Girt and sand are removed by girt chambers

(D) All the above

Answer: Option D

Question No. 33

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

(A) 16 m

(B) 20 m

(C) 24 m

(D) 30 m

Answer: Option C

Question No. 34

Dry weather flow is:

(A) Average daily rate of flow

(B) Average monthly rate of flow

(C) Average annual rate of flow

(D) Water supply allowance per capita

Answer: Option D

Question No. 35

Pick up the incorrect statement from the following:

(A) The mixture of water and waste products, is called sewage

(B) The treated sewage effluents, are generally used for irrigating the crops

(C) The process of collecting, treating and disposing off the sewage, is called sewerage

(D) The old convergence system was definitely better than water carried sewerage system

Answer: Option D

Question No. 36

Pick up the correct statement from the following:

(A) The maximum rate of storm runoff is called peak drainage discharge

(B) Rational method of estimating peak run off, may be used precisely for areas less than 50

hectares

(C) The period after which the entire area starts contributing to the runoff, is called the time of

concentration

(D) All the above

Answer: Option D

Question No. 37

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

(A) Q = [(4 + √P)/(18 + √P)] q

(B) Q = [(18 + P)/(4 + √P)] q

(C) Q = [(18 + √P)/(4 + √P)] q

(D) Q = [(5 + √P)/((15 + √P)] q

Answer: Option C

Question No. 38

¾th or ¼th extra space is left in sewer pipes at maximum discharge for

(A) Low estimates of the average and maximum flows

(B) Large scale infiltration of storm water

(C) Unexpected increase in population

(D) All the above

Answer: Option D

Question No. 39

If the flame of a miner's safety lamp in a manhole extinguishes within 5 minutes, the sewer

certainly contains

(A) Hydrogen sulphide

(B) Carbon dioxide

(C) Methane

(D) Oxygen

Answer: Option B

Question No. 40

Hydraulic mean radius is

(A) Mean radius of sewer

(B) Difference in heads between two points in circular pipes

(C) Mean of radii in a pipe line of varying cross-sections

(D) Cross-sectional area/wetted perimeter

Answer: Option D

Waste Water Part - 1

Waste Water Engineering

Question No. 01

For a continuous flow type of sedimentation tanks

(A) Width of the tank is normally kept about 6 m

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

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

(D) All the above

Answer: Option D

Question No. 02

The asbestos cement sewers are

(A) Light in weight

(B) Not structurally strong to bear large compressive stress

(C) Susceptible to corrosion by sulphuric acid

(D) All the above

Answer: Option D

Question No. 03

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

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

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

(C) Both (a) and (b)

(D) Neither (a) nor (b)

Answer: Option C

Question No. 04

Pick up the correct statement from the following:

(A) The sewer pipes of sizes less than 0.4 m diameter are designed as running full at maximum

discharge

(B) The sewer pipes of sizes greater than 0.4 m diameter are designed as running 2/3rd or 3/4th

full at maximum discharge

(C) The minimum design velocity of sewer pipes is taken as 0.8 m/sec

(D) All the above

Answer: Option D

Question No. 05

Pick up the correct statement from the following:

(A) Maximum daily flow = 2 times the average daily flow

(B) Maximum daily flow = ⅔ × average daily flow

(C) Sewers are designed for minimum permissible velocity at minimum flow

(D) All the above

Answer: Option D

Question No. 06

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

(A) 15 cm c/c

(B) 22.5 cm c/c

(C) 30 cm c/c

(D) 50 cm c/c

Answer: Option B

Question No. 07

The pressure exerted by

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

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

(C) Pressure sewers are designed to be safe in tension

(D) All the above

Answer: Option D

Question No. 08

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

(A) Water test

(B) Smoke test

(C) Straightness test

(D) All the above

Answer: Option B

Question No. 09

No treatment of the sewage is given if dilution factor is

(A) Less than 150

(B) Between 150 to 200

(C) Between 200 to 300

(D) More than 500

Answer: Option D

Question No. 10

Which of the following pumps in used to pump sewage solids with liquid sewage without clogging

the pump is?

(A) Centrifugal pump

(B) Pneumatic ejector

(C) Reciprocating pump

(D) None of these

Answer: Option A

Question No. 11

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

(A) 15 days

(B) 30 days

(C) 60 days

(D) 90 days

Answer: Option D

Question No. 12

Pick up the correct statement from the following:

(A) Small sewers are cleaned by flushing

(B) Medium sewers are cleaned by cane rodding

(C) Medium sewers may be cleaned by pills

(D) All the above

Answer: Option D

Question No. 13

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

(A) Alum

(B) Ferric chloride

(C) Ferric sulphate

(D) Chlorinated copperas

Answer: Option A

Question No. 14

The layers of vegetable wastes and night soil alternatively piled above the ground to form a

mound, is called

(A) A heap

(B) Plateau

(C) Windrow

(D) None of these

Answer: Option D

Question No. 15

If the flame of a miner's safety lamp in the upper layers of the sewer forms an explosive, the

sewer certainly contains

(A) Hydrogen sulphide

(B) Carbon dioxide

(C) Methane

(D) Oxygen

Answer: Option C

Question No. 16

The gas which may cause explosion in sewers, is

(A) Carbondioxide

(B) Methane

(C) Ammonia

(D) Carbon monoxide

Answer: Option B

Question No. 17

Pick up the correct statement from the following:

(A) The water supply pipes carry pure water free from solid particles

(B) The water supply pipes get clogged if flow velocity is less than self cleansing velocity

(C) The sewers may be carried up and down the hills and valleys

(D) The sewer pipes are generally laid along level hills

Answer: Option A

Question No. 18

Pick up the incorrect statement from the following:

(A) The process of decomposing the organic matter under controlled anaerobic conditions, is

called sludge digestion

(B) Sludge digestion is carried out in sludge tank

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

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

Answer: Option C

Question No. 19

The sewer pipes

(A) Carry sewage as gravity conduits

(B) Are designed for generating self-cleansing velocities at different discharge

(C) Should resist the wear and tear caused due to abrasion

(D) All the above

Answer: Option D

Question No. 20

The settling velocity of the particles larger than 0.06 mm in a settling tank of depth 2.4 is 0.33 m

per sec. The detention period recommended for the tank, is

(A) 30 minutes

(B) 1 hour

(C) 1 hour and 30 minutes

(D) 2 hours

Answer: Option D