Civil Engineering Waste Water Engineering Quiz (or) MCQ

1 .

What is Waste Water Engineering?

A)

providing safe drinking water

B)

removing and disposing of human waste

C)

use of engineering approaches to enhance the cleanliness of human populations

D)

All of the above

Correct Answer : All of the above

Explanation : Sanitary engineering, often known as public health engineering or waste water engineering, is the use of engineering approaches to enhance the cleanliness of human populations, typically by removing and disposing of human waste and providing safe drinking water.

2 .

Removal of oil and grease from sewage, is known_____.

A)

skimming

B)

filtration

C)

screening

D)

None of the above

Correct Answer : skimming

3 .

The gas which may cause explosion in sewers, is

A)

ammonia

B)

methane

C)

carbondioxide

D)

carbon monoxide

Correct Answer : methane

4 .

Pick up the incorrect statement from the following :

A)

Sludge digestion is carried out in sludge tank

B)

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

C)

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

D)

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

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

5 .

Pick up the correct statement from the following :

A)

The circular sewers are provided for separate sewerage system

B)

The circular section of sewers provides maximum hydraulic mean depth

C)

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

D)

All of the above

Correct Answer : All of the above

Explaination : * The circular sewers are provided for separate sewerage system
* The circular section of sewers provides maximum hydraulic mean depth
* The circular sewers work efficiently if the sections run at least half full
* Two sewers of different shapes are said to be hydraulically equivalent if they discharge at the same rate while running full on the same grade

6 .

The underground sewers are more subjected to

A)

bending force

B)

compressive force

C)

tensile force

D)

shearing force

Correct Answer : compressive force

7 .

How is Chemical Oxygen Demand (COD) calculated?

A)

Waste water is oxidised chemically using sodium in acid solutions

B)

Waste water is oxidised chemically using bromine in acid solutions

C)

Waste water is oxidised chemically using dichromate in acid solutions

D)

Waste water is oxidised chemically using strontium in acid solutions

Correct Answer : Waste water is oxidised chemically using dichromate in acid solutions

Explanation : Waste water is oxidised chemically using dichromate in acid solutions. High COD value indicates that the presence of inorganic compounds is high. Inorganic compounds get chemically oxidised and this results in the increase of organic compounds in the sample.

8 .

Which of the following is the next step after water abstraction in waste water treatment?

A)

Treatment

B)

Supply to consumers

C)

Combine with stormwater

D)

Supply to receiving body

Correct Answer : Treatment

Explanation : Initially, water is abstracted from the river, lake or water table and has a certain quality. Hence water is sent for treatment, where it undergoes transformation to be able to comply with intended uses.

9 .

The most dangerous pollutant in vehicular emissions is

A)

CO

B)

Oâ‚ƒ

C)

COâ‚‚

D)

SOâ‚‚

Correct Answer : CO

10 .

If the depletion of oxygen is found to be 2.5 mg/litre after incubating 2.5 ml of sewage diluted to 250 ml for 5 days at 20Â°C, B.O.D. of the sewage is

A)

100 mg/l

B)

150 mg/l

C)

200 mg/l

D)

250 mg/l

Correct Answer : 250 mg/l

11 .

The clarigesters are_______.

A)

circular septic tanks

B)

rectangular septic tanks

C)

circular Imhoff double tanks with bottom hoppers

D)

circular Imhoff double storey tanks without bottom hoppers

Correct Answer : circular Imhoff double storey tanks without bottom hoppers

12 .

Rate of flow of sewage is generally assumed

A)

at 150 litres per capita

B)

equal to the rate of water supply

C)

less than the rate of water supply

D)

more than the rate of water supply

Correct Answer : less than the rate of water supply

13 .

The pH value of fresh sewage is usually

A)

more than 7

B)

less than 7

C)

equal to 7

D)

equal to zero

Correct Answer : more than 7

14 .

The moisture content of a sludge is reduced from 90% to 80% in a sludge digestion tank. The percentage decrease in the volume of sludge, is

A)

10%

B)

25%

C)

50%

D)

None of the above

Correct Answer : 50%

15 .

Sewer pipes need be checked for________.

A)

minimum flow

B)

maximum flow

C)

Both (A) and (B)

D)

None of the above

Correct Answer : Both (A) and (B)

16 .

In areas where light rains are uniformly distributed throughout the year, the type of sewerage system to be adopted is______.

A)

separate system

B)

combined system

C)

partially combined system

D)

None of the above

Correct Answer : combined system

17 .

Which of the following type of treatment methods are used for municipal and industrial waste waters?

A)

Slow rate

B)

Overflow

C)

Main stream

D)

Rapid infiltration

Correct Answer : Slow rate

Explanation : Slow Rate (SR) systems are the predominant form of land treatment for municipal and industrial waste-water. Such a technology incorporates waste-water treatment, water reuse, crop utilization of nutrients and waste-water disposal.

18 .

The sewage is pumped up

A)

from basements

B)

from low lying areas

C)

across a high ridge

D)

All of the above

Correct Answer : All of the above

19 .

In sewers the effect of scouring is more on

A)

top side

B)

bottom side

C)

horizontal side

D)

all sides

Correct Answer : bottom side

20 .

You are asked to design sewer pipes of diameters 0.4 m to 0.9 m at maximum flow, you will assume the sewer flow running at

A)

half full

B)

full depth

C)

two third full

D)

three fourth full

Correct Answer : half full

21 .

For sewer mains of 0.5 to 1 m diameter, the ratio of maximum daily sewage flow to the average daily sewage flow is assumed

A)

3.0

B)

2.5

C)

2.0

D)

1.5

Correct Answer : 2.0

22 .

The normal values of over flow rates for secondary sedimentation tanks, 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 10, 000 litres/sqm/day

Correct Answer : 25, 000 to 35, 000 litres/sqm/day

23 .

What is the wastewater flow in a sewer system during the periods of dry weather with minimum infiltration called?

A)

Wet flow

B)

Dry flow

C)

Wet weather flow

D)

Dry weather flow

Correct Answer : Wet weather flow

Explanation : Summers are usually dry. Hence the rainfall is minimum and is called as dry weather flow in sewers. During the rainy season or periods of high rainfall or storm, the sewers will be full and are called wet weather flow.

24 .

Which of the following factors does the dry weather does not depend on?

A)

Population growth

B)

Rate of water supply

C)

Infiltration of groundwater

D)

Design of sewer system

Correct Answer : Design of sewer system

Explanation : Dry weather flow depends on the type of area served, rate of water supply, population growth, infiltration of groundwater. Design of sewer system is to determine the size of a sewer system in peak conditions. It has nothing to do with the factors responsible for dry weather flow.

25 .

Which of the following common unit is used to express the rate of water supply to a city or town?

A)

Litres/capita/second

B)

Litres/capita/day

C)

Millilitres/capita/day

D)

Millilitres/capita/hour

Correct Answer : Litres/capita/day

Explanation : The common unit used to express the rate of water supply to a city or town is in terms of litres per person for a day. Capita refers to each person or an individual. Hence the unit is litres/capita/day.

26 .

What is night soil?

A)

Human excreta

B)

Animal excreta

C)

Soil containing urea

D)

Human excreta, animal excreta and urea

Correct Answer : Human excreta, animal excreta and urea

Explanation : Human excrement collected at night from buckets, cesspools, privies and sometimes used as manure is called night soil. The night soil consists of human excreta, animal excreta and urea originating at privies, water closets, urinals and stables.

27 .

Maximum permissible velocity 1.5 m/sec, is adopted in drains

A)

lined with stones

B)

with beds of rocks and gravels

C)

Both (A) and (B)

D)

Neither (A) nor (B)

Correct Answer : Both (A) and (B)

28 .

The digested sludge from septic tanks, is removed after a maximum period of

A)

3 years

B)

4 years

C)

5 years

D)

6 years

Correct Answer : 3 years

29 .

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

Correct Answer : 150 m to 300 m

30 .

If the peak discharge of a storm water drain (S.W. Drain) is e.xpected to exceed 150 cumecs, the free board to be provided, is

A)

50 cm

B)

90 cm

C)

100 cm

D)

None of the above

Correct Answer : 100 cm

31 .

The quantity of sanitary sewage entering the sewers would be ___________ the total quantity of water supplied.

A)

Less than

B)

Equal to

C)

More than

D)

Greater than

Correct Answer : Less than

Explanation : The quantity of sanitary sewerage entering the sewers would be less than the total quantity of water supplied because the water is lost in domestic consumption, evaporation, lawn sprinkling, fire fighting and industrial consumption.

32 .

If D.O. concentration falls down to zero in any natural drainage, it indicates the zone of

A)

recovery

B)

degradation

C)

cleaner water

D)

active decomposition

Correct Answer : active decomposition

33 .

For detecting the nitrates in sewage, the colour may be developed by adding_____.

A)

Pottassium permanganate

B)

Sulphuric acid and napthamine

C)

Phenol-di-sulphuric acid and pottassium hydroxide

D)

All of the above

Correct Answer : Phenol-di-sulphuric acid and pottassium hydroxide

34 .

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)

Kutter

C)

William-Hazen

D)

Crimp and Bruge

Correct Answer : Crimp and Bruge

35 .

The ratio of design discharge to the surface area of a sedimentation tank is called

A)

overflow rate

B)

surface loading

C)

overflow velocity

D)

All of the above

Correct Answer : All of the above

36 .

In the activated sludge process

A)

aeration is done with an admixture of previously aerated sludge

B)

aeration is continued till stability

C)

water is removed by centrifugal action

D)

sludge is activated by constant stirring

Correct Answer : aeration is done with an admixture of previously aerated sludge

37 .

For laying a sewer line in a trench of 2 m width, an offset line is marked on the ground parallel to the given centre line at a distance of

A)

160 cm

B)

180 cm

C)

120 cm

D)

140 cm

Correct Answer : 180 cm

38 .

The area of land where all the precipitation falls will flow downhill into a specific stream called _______

A)

Reservoirs

B)

Water tanks

C)

Drainage basin

D)

Water towers

Correct Answer : Drainage basin

Explanation : The water that falls on the ground and flows across the surface until it hits a stream is called runoff. Each waterway has a drainage basin, which is an area of land where all precipitation that falls will flow downhill into a specific stream.

39 .

What is the drainage basin also called as?

A)

Wetland

B)

Water pond

C)

Watershed

D)

Runoff area

Correct Answer : Watershed

Explanation : Each waterway has a drainage basin which is an area of land where all the precipitation that falls will flow downhill into a specific stream and it is also called watershed.

Watershed management is the process of creating and implementing programs, plans and projects to sustain and enhance watershed functions that affect the plant, animal and human communities within a watershed boundary.

40 .

The part of the precipitation, snowmelt or irrigation water that appears in uncontrolled surface streams is generally called as _______

A)

Runoff

B)

Rivers

C)

Sewers

D)

Drains

Correct Answer : Runoff

Explanation : Runoff can be described as a part of the water cycle that flows over a land as the surface water instead of being absorbed into groundwater or evaporate into the atmosphere. Runoff increases the water volume of surface water bodies.

41 .

What is the minimum diameter of pipes used for drainage of waste water?

A)

50 mm

B)

75 mm

C)

100 mm

D)

105 mm

Correct Answer : 75 mm

Explanation : Waste water is from showers, basins, kitchen sinks, washing machines and the like. This is also called grey water. Normally a minimum of 75 mm diameter pipes is used for drainage of waste water.

42 .

Which of the following type of waste water treatment process is used for treating waste water or industrial waste water using aeration and biological flocs?

A)

Active sludge process

B)

Aeration

C)

Anaerobic digestion

D)

Biological aeration

Correct Answer : Active sludge process

Explanation : One of the sewer waste water treatment processes is a biological treatment known as activated-sludge process. Waste water is agitated and aerated to remove solids and oxidation methods are introduced to activate decomposition.

43 .

The asbestos cement pipes are generally laid________.

A)

horizontally

B)

vertically

C)

at an angle of 30Â°

D)

at an angle of 60Â°

Correct Answer : vertically

44 .

Chlorination of water is done for the removal of_________.

A)

sediments

B)

hardness

C)

bacterias

D)

suspended solids

Correct Answer : bacterias

45 .

In septic tanks, decomposition of organic bacteria, is done by

A)

anaerobic bacteria

B)

aerobic bacteria

C)

Both (A) and (B)

D)

None of the above

Correct Answer : anaerobic bacteria

46 .

'Cowl' is provided at_____.

A)

first step in manhole

B)

upper end of the manhole

C)

lower end of ventilating column

D)

upper end of ventilating column

Correct Answer : upper end of ventilating column

47 .

The sewer which transports the sewage to the point of treatment, is called____.

A)

lateral

B)

house sewer

C)

branch sewer

D)

out-fall sewer

Correct Answer : out-fall sewer

48 .

The Brake Horse power of the motor (efficiency 60%) required for a pump of capacity 0.075 cumec for a total lift of 12 m, is___.

A)

10

B)

15

C)

20

D)

25

Correct Answer : 20

49 .

The sewer which collects the discharge from a collecting system and delivers it to a treatment plant, is known

A)

house sewer

B)

sewer outfall

C)

branch sewer

D)

lateral sewer

Correct Answer : sewer outfall

50 .

If the depletion of oxygen is found to be 5 ppm after incubating a 2.5% solution of sewage sample for 5 days at 21Â°C, B.O.D. of the sewage is

A)

200 ppm

B)

150 ppm

C)

100 ppm

D)

50 ppm

Correct Answer : 200 ppm

51 .

Wastewater from different sources like bathrooms, kitchens and wash basins is called ______

A)

Sewage

B)

Sullage

C)

Garbage

D)

Discharge

Correct Answer : Sullage

Explanation : Dry wastes such as dry leaves, paper and grass are called garbage. Discharge is the outflow of water or wastewater. Sewage is the wastewater from various houses. Sullage is the wastewater from bathroom, kitchen, wash basins, etc.

52 .

Which of the following conditions is not suitable for the disposal of excreta or sewage?

A)

It does not give odour nuisance

B)

It is not exposed to the atmosphere

C)

It should be accessible for children

D)

The waste does not pollute the ground surface

Correct Answer : It should be accessible for children

Explanation : The place and criteria for the disposal of waste play a major role. It should be off the sight of the people so it doesn’t cause displease for the vision and it must not be accessible for children and household pets with respect to health aspects.

53 .

For providing an Indian type W.C., the R.C.C. slabs in the toilet portion

A)

should be sunk by 20 cm

B)

should be sunk by 50 cm

C)

should be kept 20 cm above the adjacent portion

D)

need not be sunk

Correct Answer : should be sunk by 50 cm

54 .

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)

2 hours

B)

1 hour and 30 minutes

C)

1 hour

D)

30 minutes

Correct Answer : 2 hours

55 .

The drop man holes are generally provided in sewers for

A)

large town ships

B)

cities in plains

C)

industrial areas

D)

hilly town ships

Correct Answer : hilly town ships

56 .

Depletion of ozone layer in the outer atmosphere may cause

A)

skin cancer

B)

bronchitis

C)

lung cancer

D)

heart disorder

Correct Answer : skin cancer

57 .

The quantity of sanitary sewage directly depends on ______

A)

Area

B)

Precipitation

C)

Population

D)

Rate of water supply

Correct Answer : Population

Explanation : As the population increases the rate of water consumption also increases which leads to the direct increase in sanitary sewage. This also increases water demand. Hence the quantity of sanitary sewage directly depends on the population.

58 .

The minimum diameter of a sewer is kept________.

A)

10 cm

B)

15 cm

C)

20 cm

D)

25 cm

Correct Answer : 15 cm

59 .

The minimum diameter of sewer to be adopted is

A)

25 cm

B)

15 cm

C)

12 cm

D)

10 cm

Correct Answer : 15 cm

60 .

To test chemical oxygen demand (C.O.D.) of sewage, organic matter is oxidised by pottassium dichromate in the presence of

A)

Nitric acid

B)

Citric acid

C)

Hydrochloric acid

D)

Sulphuric acid

Correct Answer : Sulphuric acid

61 .

The sewage treatment units in which anaerobic decomposition of organic matter is used, are called_____.

A)

trickling filters

B)

imhoff tanks

C)

sludge sedimentation tanks

D)

None of the above

Correct Answer : trickling filters

62 .

What is the body of permeable rock which can contain or transmit groundwater called?

A)

Canal

B)

Aquifer

C)

Bore well

D)

Water table

Correct Answer : Canal

Explanation : An aquifer is an underground layer of water-bearing permeable rock, rock features or unconsolidated material from which groundwater can be extracted using a water well

63 .

The water supply consists of a connection point from where the fire fighters can tap water and is called as _______

A)

Ditches

B)

Fire point

C)

Fire hydrant

D)

Water towers

Correct Answer : Fire hydrant

Explanation : A fire hydrant also called as a fire plug is a connection point by which fire fighters can tap water from a water supply. It is a component of active fire protection. It helps in emergency situations and rescues.

64 .

What percentage of solids does waste water contain?

A)

0%

B)

0.1%

C)

0.5%

D)

1%

Correct Answer : 0.1%

Explanation : Waste water contains 99.9% water and 0.1% solids. The goal is to remove this 0.1% of solids. Waste water is the water generated by industries and communities.

65 .

When alum is added to the waste water containing calcium ions which compound is formed as a precipitate?

A)

Al(OH)â‚ƒ

B)

CaCOâ‚ƒ

C)

Ca(OH)â‚‚

D)

Alâ‚‚ (SOâ‚„)â‚ƒ

Correct Answer : Al(OH)â‚ƒ

Explanation : When alum is added to a waste water containing calcium salts Al(OH)â‚ƒ is precipitated. This sis a gelatinous floc. This reaction sweeps out suspended particles

66 .

For evaporation and measurement of settlable solids, the apparatus used, is

A)

a jar

B)

a breaker

C)

a test tube

D)

an Imhoff cone

Correct Answer : an Imhoff cone

67 .

In SI units the power of sound is represented in______.

A)

kgs

B)

joules

C)

watts

D)

neutons

Correct Answer : watts

68 .

Kjedahl nitrogen is a mixture of_____.

A)

ammonia and nitrogen

B)

organic nitrogen and ammonia

C)

nitrogen and organic nitrogen

D)

All of the above

Correct Answer : All of the above

69 .

In sewers the velocity of flow should not be______.

A)

less than 10 m/sec

B)

less than the self-cleansing velocity

C)

more than 20 m/sec

D)

more than the self-cleansing velocity

Correct Answer : less than the self-cleansing velocity

70 .

Setting out the alignments of sewers may start from_______.

A)

tail end

B)

city

C)

out-fall

D)

any point

Correct Answer : tail end

71 .

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

A)

Oxygen

B)

Methane

C)

Carbon dioxide

D)

Hydrogen sulphide

Correct Answer : Methane

72 .

The system to collect night soil, garbage etc. in separate vessels or deposited in pools and pits is called _______

A)

Waste pit

B)

Waste deposition system

C)

Conservancy system

D)

Waste allocation system

Correct Answer : Conservancy system

Explanation : Conservancy system is an old system in which various types of wastes such as night soil, garbage, etc. are collected separately in vessels and deposited in pools or pits and then removed periodically once in 24 hours.

73 .

In urban cities like Bangalore, which of the water carriage system is used?

A)

Combined system

B)

Partially combined system

C)

Separate system

D)

Partially separate system

Correct Answer : Separate system

Explanation : Urban cities have a large area and high population, therefore water usage is more and sewage generated will also be more. Hence, a separate system to carry sewage and stormwater is necessary. Whereas in rural areas, precipitation will be absorbed by the ground and infiltered. Therefore only a little amount of precipitation forms storm. Hence the combined system is preferred.

74 .

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 of the above

Correct Answer : All of the above

75 .

In case of Imhoff tanks,_______.

A)

the shape is rectangular

B)

detention period is 2 hours

C)

the velocity of flow is restricted to 0.30 m/minute

D)

All of the above

Correct Answer : All of the above

Explanation : * the shape is rectangular
* detention period is 2 hours
* the velocity of flow is restricted to 0.30 m/minute
* surface loading is limited to 30, 000 litres/m of plan area per day

76 .

The spacing of bars of perforations of fine screens used for the treatment of sewage, is_______.

A)

2 to 3 mm

B)

3 to 5 mm

C)

5 to 8 mm

D)

8 to 10 mm

Correct Answer : 2 to 3 mm

77 .

The self-cleansing velocity of water flowing through pipe lines, is_______.

A)

0.25 metre/sec.

B)

2 metres/sec

C)

1 metre/sec

D)

0.5 metre/sec

Correct Answer : 2 metres/sec

78 .

Ventilating shafts are provided to a sewer line at every______.

A)

500 m

B)

300 m

C)

200 m

D)

150 m

Correct Answer : 500 m

79 .

The quantity of water supply is equal to the rate of supply multiplied by the ______

A)

Area

B)

Net usage

C)

Population

D)

Quantity of sewage

Correct Answer : Population

Explanation : The rate of usage of water varies from individual to individual and different sectors. Hence the total quantity of water supplied is equal to the rate of supply multiplied by population.

80 .

Wet weather flow is _________ than the dry weather flow.

A)

Higher

B)

Lower

C)

Equal to

D)

Not equal to

Correct Answer : Lower

Explanation : Wet weather flow is higher than the dry weather flow because of the inflow and infiltration in the sewer system. Wet weather flow is the combination of stormwater and sanitary sewage but dry weather flow consists of only sanitary sewage.

81 .

D is the diameter of a circular sewer and α is the side of a square section sewer. If both are hydraulically equivalent, the relationship which holds good, is

A)

πD^8/3 = 4 b^8/3

B)

πD^3/8 = 4 b^3/8

C)

πD^2/3 = 4 b^2/3

D)

πD^3/2 = 4 b^3/2

Correct Answer : πD^8/3 = 4 b^8/3

82 .

For detecting the nitrites in the sewage, the matching colour may be developed by adding____.

A)

Pottassium permanganate

B)

Sulphuric acid and napthamine

C)

Phenol-di-sulphuric acid pottassium hydroxide

D)

All of the above

Correct Answer : Sulphuric acid and napthamine

83 .

The most efficient cross section of sewers in a separate sewerage system is_____.

A)

circular

B)

parabolic

C)

rectangular

D)

new egged

Correct Answer : circular

84 .

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

A)

100 mg/l

B)

200 mg/l

C)

300 mg/l

D)

400 mg/l

Correct Answer : 400 mg/l

85 .

_____ is used to lift surface water and move it to a nearby treatment plant.

A)

Pumps

B)

Water carriers

C)

Low-lift pumps

D)

Water suppliers

Correct Answer : Low-lift pumps

Explanation : Many kinds of pumps are used in the distribution system. Pumps that lift surface water and move it to a nearby treatment plant are called low-lift pumps. Pumps that discharge treated water into arterial mains are called high-lift pumps.

86 .

What are the facilities including pumps and equipment for pumping fluids from one place to another are called?

A)

Pumpers

B)

Pumping stations

C)

Pumping area

D)

Pumping facilities

Correct Answer : Pumping stations

Explanation : Pumps are used in a variety of infrastructure systems such as the supply of water to canals, the drainage of low lying land, etc. Pumping stations are facilities including pumps and equipment for such activities.

87 .

What is an artificial channel for conveying water, typically in the form of a bridge across a valley or other gap called?

A)

Canals

B)

Tunnel

C)

Aqueduct

D)

Aquifer

Correct Answer : Aqueduct

Explanation : A body of permeable rock which can contain or transmit groundwater is called aquifer. A small duct in the body of fluids is called an aqueduct. The canal is an artificial tubular duct for the inland waterways.

88 .

What is the lowest waste water flow in hospitals?

A)

700 lpcd

B)

900 lpcd

C)

40 lpcd

D)

50 gpcd

Correct Answer : 700 lpcd

Explanation : The unit lpcd stands for litres per capita per day and gpcd stands for gallons per capita per day. 40 lpcd indicates the minimum water usage for places like kids play home and schools. 700 lpcd is for hospitals.

89 .

How many forms of nitrogen are present in waste water?

A)

5

B)

4

C)

3

D)

2

Correct Answer : 4

Explanation : There are different types of nitrogen present in waste water. Basically, our types of nitrogen are present. They are organic nitrogen, ammonia nitrogen, nitrate nitrogen and nitrite nitrogen.

90 .

Which of the following is the controlled application of waste water onto the land surface to achieve a specified level of treatment?

A)

Water treatment

B)

Waste water treatment

C)

Soil treatment

D)

Land treatment

Correct Answer : Land treatment

Explanation : The controlled application of waste water onto the land surface to achieve a specified level of treatment through natural physical, chemical, and biological processes within the plant soil-water matrix is called land treatment.

91 .

The maximum velocity in a channel section often occurs _______ the water surface.

A)

Above

B)

Below

C)

Top

D)

Between

Correct Answer : Below

Explanation : A closed or an open conduit always has different velocities of flow within the section. The bottom of the channel is provided with the certain slope for the water carrying foreign particles to flow easily. Hence the velocity is maximum at the bottom of the water surface.

92 .

What is the maximum velocity of tap water such that the flow causes low noise?

A)

0.2-0.3 m/s

B)

0.5-0.7 m/s

C)

1.0-2.5 m/s

D)

1.5-2.5 m/s

Correct Answer : 0.5-0.7 m/s

Explanation : The high rate of flow of water can lead to increasing sound levels of flow which leads to noise. Hence minimum flow of water should be considered. 0.5-0.7 m/s is the maximum velocity of tap water that produces less noise levels. 1.0-2.5 m/s of water flow leads to high noise levels.

93 .

Disposal to sewage in large cities, is done in

A)

dilution

B)

oxidation

C)

irrigation

D)

putrifaction

Correct Answer : dilution

94 .

For the COD test of sewage, organic matter is oxidised by Kâ‚‚Crâ‚‚0â‚‡ in the presence of

A)

HCl

B)

HNOâ‚ƒ

C)

Hâ‚‚SOâ‚„

D)

None of the above

Correct Answer : Hâ‚‚SOâ‚„

95 .

If D is the diameter of a circular sewer and D' is the top horizontal diameter of an equivalent egg shaped section, the relationship which holds good, is____.

A)

D' = 0.84 D

B)

D' = 0.74 D

C)

D' = 0.64 D

D)

D' = 0.54 D

Correct Answer : D' = 0.84 D

96 .

If a paper moistened with lead acetate for five minutes when placed in manhole turns black. The sewer certainly contains____.

A)

Oxygen

B)

Methane

C)

Carbon dioxide

D)

Hydrogen sulphide

Correct Answer : Hydrogen sulphide

97 .

The design period of sewage treatment works in normally____.

A)

5 - 10 years

B)

15 - 20 years

C)

30 - 40 years

D)

40 - 50 years

Correct Answer : 15 - 20 years

98 .

What are the structures that are constructed at suitable intervals along the sewerage system called?

A)

Pumps

B)

Manholes

C)

Catch basins

D)

Sewer appurtenances

Correct Answer : Sewer appurtenances

Explanation : Sewer appurtenances are the structures that are constructed at suitable intervals along the sewerage system. These include many structures such as manholes, drop manholes, lamp holes, clean-outs, catch basins, etc.

99 .

A masonry or R.C.C. chamber constructed at suitable intervals along the sewer lines, for providing access into them is called ________

A)

Manhole

B)

Clean-outs

C)

Flushing tanks

D)

Inverted siphons

Correct Answer : Manhole

Explanation : The manhole helps in inspection, cleaning and maintenance of sewer. These are provided at every junction, change of diameter or change of gradient of the sewer.

100 .

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)

1.49 m

B)

1.59 m

C)

1.69 m

D)

1.79 m

Correct Answer : 1.69 m

101 .

A manhole is generally provided at each

A)

bend

B)

junction

C)

change of gradient

D)

All of the above

Correct Answer : All of the above

Explanation : * bend
* junction
* change of gradient
* change of sewer diameter

102 .

For sewers, inverted siphon is provided for_______.

A)

four pipes

B)

three pipes

C)

two pipes

D)

one pipe

Correct Answer : three pipes

103 .

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

A)

alum

B)

ferric chloride

C)

ferric sulphate

D)

chlorinated copperas

Correct Answer : alum

104 .

Fresh sewage is generally______.

A)

acidic

B)

highly decomposed

C)

alkaline

D)

a source of objectionable odour

Correct Answer : alkaline

105 .

Which of the following is an advantage of the conservancy system over water carriage system?

A)

Labour force

B)

Water consumption

C)

Spread of epidemic

D)

Compact house design

Correct Answer : Water consumption

Explanation : In the conservancy system, compact house design is not possible, a large labour force is required and there is a spread of an epidemic. Hence, little water consumption is an advantage of the conservancy system over water carriage system.

106 .

The means of promoting hygiene through the prevention of human contact with the hazards of wastes especially feces is called ________

A)

Sanitation

B)

Hygiene

C)

Hygiene control

D)

Disease prevention

Correct Answer : Sanitation

Explanation : Sanitation generally refers to hygiene by the prevention of wastes coming into human contact especially feces. The various measures taken to reduce the occurrence of diseases are called disease prevention.

107 .

The presence of free ammonia in sewage, is detected by_____.

A)

adding sulphuric acid

B)

phenol-di-sulphuric acid

C)

adding pottassium permanganate

D)

boiling

Correct Answer : boiling

108 .

The amount of oxygen consumed by the aerobic bacterias which cause the aerobic biological decomposition of sewage, is known______.

A)

Dissolved Oxygen (D.O.)

B)

Chemical Oxygen Demand (C.O.D.)

C)

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

D)

None of the above

Correct Answer : Dissolved Oxygen (D.O.)

109 .

Which one of the following part of human body withstands minimum radiation

A)

eyes

B)

thyroid

C)

ovaries/testis

D)

kidneys

Correct Answer : ovaries/testis

110 .

The sludge does not contain waste water from_____.

A)

bath rooms

B)

toilets

C)

wash basins

D)

kitchen sinks

Correct Answer : toilets

111 .

Dry weather flow+ storm water=_________

A)

Stormwater

B)

Sanitary sewage

C)

Wet weather flow

D)

Dry weather flow

Correct Answer : Wet weather flow

Explanation : Dry weather flow is the wastewater flow in sewers during dry weather. Dry weather flow in combination with stormwater is called as wet weather flow.

112 .

_________ in residential areas resemble water usage patterns in those areas.

A)

Daily flow

B)

Hydrographs

C)

Dry period patterns

D)

Sewage flow patterns

Correct Answer : Sewage flow patterns

Explanation : The water usage depends upon the population, number oh houses and the type of water usage in that area. Sewage flow in turn depends upon these activities. Hence sewage flow patterns in residential areas resemble water usage patterns in those areas.

113 .

A graph showing discharge versus time past a specific point in a conduit carrying flow is called?

A)

Hydrograph

B)

Water flow graph

C)

Variation graph

D)

A graph showing discharge versus time at a specific point in a conduit carrying flow or river is called â€˜hydrographâ€™. Hydrograph helps in understanding the flow characteristics of water at different time intervals.

Correct Answer : Hydrograph

114 .

The suitable cross-section of sewers to carry combined flow, is

A)

circular

B)

egg shaped

C)

rectangular

D)

horse shoe shaped

Correct Answer : egg shaped

115 .

If the diameter of a sewer is 100 mm, the gradient required for generating self cleansing velocity, is

A)

1 in 60

B)

1 in 100

C)

1 in 120

D)

None of the above

Correct Answer : 1 in 60

116 .

Stone ware pipes are______.

A)

highly impervious

B)

highly resistant to sulphide corrosion

C)

specially suited to pressure pipes

D)

hydraulically efficient because of their smooth interior surface

Correct Answer : specially suited to pressure pipes

117 .

Skimming tanks are_______.

A)

improved version of grit chambers.

B)

those from which sludge is skimmed out

C)

tanks provided with self-cleansing screens

D)

used to remove the grease and oil

Correct Answer : used to remove the grease and oil

118 .

With self cleansing velocity in sewers_________.

A)

silting occurs at bottom

B)

scouring occurs at bottom

C)

both silting and scouring occur at bottom

D)

neither silting nor scouring occurs at bottom

Correct Answer : neither silting nor scouring occurs at bottom

119 .

Aerobic activity is maximum______.

A)

at sewer pipes

B)

in freshly produced sewage

C)

in sewer treatment plants

D)

None of the above

Correct Answer : in freshly produced sewage

120 .

Which one of the following resists hydrogen sulphide corrosion_________.

A)

Glazed ware

B)

R.C.C.

C)

Asbestos cement

D)

Glazed stone wares

Correct Answer : Glazed ware

121 .

Hume steel pipes are_____.

A)

R.C.C. pipes

B)

steel shell coated from inside with cement mortar

C)

steel shell coated from outside with cement mortar

D)

Both (B) and (C)

Correct Answer : Both (B) and (C)

122 .

The quantity of liquid waste which flows in sewers during the period of rainfall, is known______.

A)

storm sewage

B)

sanitary sewage

C)

industrial waste

D)

None of the above

Correct Answer : storm sewage

123 .

In a sludge tank, the gas mainly produced, is_______.

A)

Oxygen

B)

Methane

C)

Hydrogen

D)

Carbon dioxide

Correct Answer : Methane

124 .

The intensity of rain is expressed in_____.

A)

cm/day

B)

cm/hour

C)

cm/minute

D)

None of the above

Correct Answer : cm/hour

125 .

The normal values of over flow rates for sedimentation tanks using coagulent, 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

Correct Answer : 50, 000 to 60, 000 litres/sqm/day

126 .

An apparatus for raising, driving or compressing fluids or gases is called _________

A)

Pump

B)

Piston

C)

Compressor

D)

Force drive

Correct Answer : Pump

Explanation : A pump is a device used to transfer or force the liquid or gas against gravity. There are different types of pumps based on the requirements and the pumps are designed for different loads.

127 .

________ pumps produce a head and a flow by increasing the velocity of the liquid with the help of the rotating vane impeller.

A)

Positive pumps

B)

Rotating pumps

C)

Displacement pumps

D)

Centrifugal pumps

Correct Answer : Centrifugal pumps

Explanation : Centrifugal pumps produce a head and a flow by increasing the velocity of the liquid with the help of the rotating vane impeller. Centrifugal pumps include radial, axial and mixed flow units.

128 .

What are the pumps that operate by alternately filling a cavity and then displacing a given volume of liquid called?

A)

Rotating pump

B)

Centrifugal pump

C)

Roto-dynamic pump

D)

Positive displacement pump

Correct Answer : Positive displacement pump

Explanation : A positive displacement pump alternately fills a cavity and then displaces a given volume of liquid. For each cycle, this pump delivers a constant volume of liquid independent of discharge pressure or head.

129 .

In a centrifugal pump, the flow is _______ when the viscosity is increased.

A)

Same

B)

Reduced

C)

Greater

D)

Increased

Correct Answer : Reduced

Explanation : In a centrifugal pump, the flow is reduced when the viscosity is increased. This is because the viscosity of any fluid restricts its capacity to flow easily. On thickening the solution or liquid, the flow is reduced.

130 .

Which of these equations is used to calculate the water velocity inside of a pipe?

A)

A=Q/I

B)

L=C*Q

C)

Q=A*V

D)

V=0.408 Q/ DÂ²

Correct Answer : V=0.408 Q/ DÂ²

Explanation : The first formula is used to calculate the infiltration area. The third formula is used to calculate the load of wastewater. The fourth formula is used to calculate the rate of flow. The second formula is used to calculate the velocity of flow inside of a pipe (V) where Q stands for flow rate of water inside pipe and D stands for pipe diameter (inside).

131 .

What is the minimum velocity required in sewers to keep the foreign particles from settling?

A)

3 ft/sec

B)

5 ft/sec

C)

10 ft/sec

D)

12 ft/sec

Correct Answer : 3 ft/sec

Explanation : If the velocity is too less then the solid or foreign particles which are very minute in size may settle down. Hence a minimum velocity is required to keep these particles moving along the flow is likely to be 3 ft/sec.

132 .

In R.C. sewer pipes, the percentage longitudinal reinforcement to the cross-sectional area of concrete is kept

A)

10.0

B)

5.0

C)

0.25

D)

2.0

Correct Answer : 0.25

133 .

Dilution method of disposing off sewage, is not preferred to_____.

A)

when sewage is fresh

B)

when the diluting water is having flow currents

C)

when diluting water has high dissolved oxygen content

D)

when diluting water is used for water supply near the point of sewage disposed

Correct Answer : when diluting water is used for water supply near the point of sewage disposed

134 .

For house drainage minimum gradient is

A)

1 in 80

B)

1 in 60

C)

1 in 10

D)

None of the above

Correct Answer : 1 in 60

135 .

If the side of a square sewer is 1000 mm, the diameter of a hydraulically equivalent circular section, is___.

A)

1095 mm

B)

1075 mm

C)

1065 mm

D)

1045 mm

Correct Answer : 1095 mm

136 .

The ratio of minimum hourly flow to the average flow of sewage is____.

A)

1/2

B)

1/3

C)

1/4

D)

3/4

Correct Answer : 1/3

137 .

The porosity of sediments in sewer pipes, is usually taken as____.

A)

0.011

B)

0.012

C)

0.013

D)

0.020

Correct Answer : 0.013

138 .

For a peak discharge of 0.0157 cumec, with a velocity of 0.9 m/sec, the diameter of the sewer main, is____.

A)

10 cm

B)

12 cm

C)

15 cm

D)

18 cm

Correct Answer : 15 cm

139 .

What is the spacing of manholes for pipe diameter of greater than 2 m?

A)

45-90 m

B)

90-150 m

C)

150-200 m

D)

300 m

Correct Answer : 300 m

Explanation : For smaller sewers that are of pipe diameter less than 0.9 m, the spacing given in between manholes is 45 m. In case of pipe diameter of sewers greater than 2 m, the spacing is 300 m.

140 .

What are the manholes having a depth greater than 1.5 m called?

A)

Deep manholes

B)

Normal manholes

C)

Shallow manholes

D)

Straight manholes

Correct Answer : Deep manholes

Explanation : The manholes having a depth of 0.7-0.9 m are called shallow manholes. The manholes having a depth of 1.5 m are called normal manholes. The manholes having depth greater than 1.5 m are called deep manholes.

141 .

In a trickling filter is_______.

A)

biological action is used

B)

filtration process is used

C)

Both (A) and (B)

D)

None of the above

Correct Answer : filtration process is used

142 .

Cement concrete sewers are only suitable if non-scouring velocity is between____.

A)

2.5 to 3.0 m/sec

B)

3.0 to 4.0 m/sec

C)

3.5 to 4.5 m/sec

D)

4.5 to 5.5 m/sec

Correct Answer : 2.5 to 3.0 m/sec

143 .

The grit chambers of sewage treatment plants, are generally cleaned after

A)

5 days

B)

7 days

C)

12 days

D)

14 days

Correct Answer : 14 days

144 .

The spacing of bars for perforations in coarse screens used for the treatment of sewage, is_____.

A)

30 mm

B)

40 mm

C)

50 mm

D)

100 mm

Correct Answer : 50 mm

145 .

In very first stage of decomposition of the organic matter in sewage____.

A)

nitrates are formed

B)

ammonia is formed

C)

nitrites are formed

D)

carbondioxide is formed

Correct Answer : ammonia is formed

146 .

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

A)

90 days

B)

60 days

C)

30 days

D)

15 days

Correct Answer : 90 days

147 .

The relatively clean wastewater from baths, sinks, washing machines and other kitchen appliances is called ________

A)

Wastewater

B)

Grey water

C)

Black water

D)

Yellow water

Correct Answer : Grey water

Explanation : Yellow water refers to the wastewater containing only feces. Black water is the wastewater from bathrooms and toilets. Wastewater generally refers to the water that cannot be used or water produced out of various uses.

148 .

The standard B.O.D. of water is taken for____.

A)

2 days

B)

3 days

C)

5 days

D)

10 days

Correct Answer : 5 days

149 .

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____.

A)

0.50 m/sec

B)

0.60 m/sec

C)

0.70 m/sec

D)

0.75 m/sec

Correct Answer : 0.75 m/sec

150 .

In sewers the gas generally found, is_____.

A)

Methane (CHâ‚„)

B)

Carbon dioxide (COâ‚‚)

C)

Hydrogen sulphide (Hâ‚‚S)

D)

All of the above

Correct Answer : All of the above

151 .

A manhole is classified as shallow if its depth is between______.

A)

0.7 to 0.9 m

B)

0.9 to 1.20 m

C)

1.2 to 1.50 m

D)

None of the above

Correct Answer : 0.7 to 0.9 m

152 .

For design purposes, the normal rate of infiltration of ground water into the sewer, is______.

A)

2500 litres/km/cm

B)

2000 litres/km/cm

C)

1500 litres/km/cm

D)

1000 litres/km/cm

Correct Answer : 2000 litres/km/cm

153 .

The maximum diameter of sewers adopted in the designs is______

A)

1.0 m

B)

2.0 m

C)

3.0 m

D)

4.0 m

Correct Answer : 3.0 m

154 .

Sluge banks are formed if sewage is disposed of in____.

A)

seas

B)

lakes

C)

rivers

D)

None of the above

Correct Answer : seas

155 .

The pH value of sewage is determined with the help of______.

A)

Imhoff Cone

B)

turbidimeter

C)

Both (A) and (B)

D)

potentiometer

Correct Answer : potentiometer

156 .

Lead caulked joints are used for laying______.

A)

C.I. pipes

B)

G.I. pipes

C)

stone ware pipes

D)

earthern ware pipes

Correct Answer : G.I. pipes

157 .

The laying of sewers is done with_____.

A)

level

B)

theodolite

C)

clinometer

D)

magnetic compass

Correct Answer : level

158 .

The rational formula for peak drainage discharge, was evolved by_____.

A)

Fruhling

B)

Kuichling

C)

Lloyd David

D)

All of the above

Correct Answer : All of the above

159 .

The sewage treatment in septic tanks is due to_______.

A)

aerobic decomposition

B)

parasitic decomposition

C)

Both (A) and (B)

D)

anaerobic decomposition

Correct Answer : anaerobic decomposition

160 .

In 1000 kg of sewage, the total solids approximate

A)

0.5 to 1.0 kg

B)

1 kg to 2.0 kg

C)

5 kg to 7.5 kg

D)

7.5 kg to 10 kg

Correct Answer : 0.5 to 1.0 kg

161 .

Why are booster pumps used?

A)

Chop solids

B)

Higher flow

C)

Boost pressure

D)

Maintain flow

Correct Answer : Boost pressure

Explanation : Booster pumps are used to further boost the pressure in a system. It may be in-line circulator, horizontal split case, or vertical turbine in a can type of pump. Chopper Pumps are designed to chop up solids and stringy material as it pumps.

162 .

Why are cryogenic pumps used?

A)

Boost pressure

B)

Handle low temperature liquids

C)

Handle high temperature liquids

D)

Pump small quantities of liquids

Correct Answer : Handle low temperature liquids

Explanation : Cryogenic pumps are used to handle very low temperature liquids. Booster pumps are used to further boost the pressure in a system. Drum pumps are used to pump out small quantities of liquid of out of drums and carboys.

163 .

What is the maximum allowable velocity in public water mains?

A)

3 ft/sec

B)

8 ft/sec

C)

10 ft/sec

D)

12 ft/sec

Correct Answer : 8 ft/sec

Explanation : The velocity of 3 ft/sec is considered to be minimum to keep the foreign particles moving in sewers. The Washington State Department of Health (DOH) recommends a maximum velocity of 8 ft/sec but permits greater velocities during fire flow conditions.

164 .

Storm water is collected from streets into the __________ which in turn discharged into main drains of open type.

A)

Sub mains

B)

Lateral drains

C)

Interseptal mains

D)

Link drains

Correct Answer : Link drains

Explanation : Lateral drains are small diameters of pipe which is aligned on one side of the curb line that collects wastewater from different sources like residences, schools, etc. Link drains collect storm water from streets and conveys it to the min drains.

165 .

Clogging of sewers, is caused due to__________.

A)

silting

B)

low discharge

C)

greasy and oily matters

D)

All of the above

Correct Answer : All of the above

166 .

A sewer pipe contains 1 mm sand particles of specific gravity 2.65 and 5 mm organic particles of specific gravity 1.2, the minimum velocity required for removing the sewerage, is________.

A)

0.45 m/sec

B)

0.40 m/sec

C)

0.35 m/sec

D)

0.30 m/sec

Correct Answer : 0.45 m/sec

167 .

House connections to the laterals is generally made by

A)

P.C.C.

B)

R.C.C.

C)

Cast iron

D)

Glazed stonewares

Correct Answer : Glazed stonewares

168 .

The ratio of maximum sewage flow to average sewage flow for mains up to 1 m in diameter, is

A)

4.0

B)

3.0

C)

2.0

D)

1.5

Correct Answer : 2.0

169 .

The dimensions of a rectangular settling tank are : length 24 m, width 6 m and depth 3 m. If 2 hour detention period for tanks is recommended, the rate of flow of sewage per hour, is______.

A)

220 cu m

B)

216 cu m

C)

212 cu m

D)

208 cu m

Correct Answer : 216 cu m

170 .

In primary sedimentation, the 0.2 mm inorganic solids get separated if specific gravity is______.

A)

2.75

B)

2.65

C)

2.55

D)

2.50

Correct Answer : 2.65

171 .

For design of sewers, percentage of sewage discharge is assumed______.

A)

75 to 80%

B)

70 to 75%

C)

65 to 70%

D)

None of the above

Correct Answer : 75 to 80%

172 .

The sewerage system originates from_____.

A)

main sewers

B)

branch sewers

C)

lateral sewers

D)

house sewers

Correct Answer : house sewers

173 .

If the grit in grit chambers is 4.5 million litres per day, its cleaning is done_____.

A)

electrically

B)

mechanically

C)

manually

D)

hydraulically

Correct Answer : manually

174 .

The reduced levels of the string at the consecutive sight rails A and B are 203.575 m, 203.475 m respectively. If the difference of their R.D.s is 10 m, the gradient of the sewer line is

A)

1 in 100 upward

B)

1 in 500 upward

C)

1 in 100 downward

D)

None of the above

Correct Answer : 1 in 100 downward

175 .

In a residential colony, sewers of diameters 100 mm, 150 mm and 225 mm were laid with a gradient 1 in 120. Which portion of the sewage system does not choke in due course of time______.

A)

150 mm dia.

B)

225 mm dia

C)

100 mm dia

D)

None of the above

Correct Answer : 225 mm dia

176 .

If D is the diameter of upper circular portion, the overall depth of New Egg shaped sewer section, is________.

A)

1.625 D

B)

1.425 D

C)

1.350 D

D)

1.250 D

Correct Answer : 1.625 D

177 .

What is a sewer that runs full under gravity, flow at a pressure above the atmosphere in the sewer called?

A)

Siphon

B)

Curb inlet

C)

Flushing manhole

D)

Inverted siphon

Correct Answer : Inverted siphon

Explanation : Inverted siphons are used to pass on obstacles such as buried pipes, subways, etc. This terminology ‘siphon’ is misnomer as there is no siphon action in the depressed sewer.

178 .

What is the facility provided to stop the entry of heavy debris present in the storm water into the sewers called?

A)

Catch basin

B)

Curb inlet

C)

Clean-outs

D)

Gutter inlet

Correct Answer : Catch basin

Explanation : Clean-out is a pipe which is connected to the underground sewer. Curb inlets are vertical opening in the road curbs through which stormwater flow enters the stormwater drains. Gutter inlets are horizontal openings in the gutter which is covered by one or more grating through which stormwater is admitted.

179 .

What is the arrangement for diverting excess sewage from the combined sewer called?

A)

Leaping weir

B)

Siphon gateway

C)

Siphon spillway

D)

Intercepting sewer

Correct Answer : Siphon spillway

Explanation : The overflow channel is connected to the combined sewer through the siphon. At the crest level of siphon an air pipe is provided to activate the siphon when water will reach in the combined sewer at a stipulated level and is called siphon spillway.

180 .

The normal value of over flow rates for plain primary sedimentation tanks, 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

Correct Answer : 40, 000 to 50, 000 litres/sqm/day

181 .

Bottom openings 15 cm x 15 cm in the standing baffle wall are provided______.

A)

75 cm c/c

B)

50 cm c/c

C)

30 cm c/c

D)

22.5 cm c/c

Correct Answer : 22.5 cm c/c

182 .

The ratio of maximum sewage flow to average sewage flow for trunk mains having diameters more than 1.25 m, is_______.

A)

1.5

B)

2.0

C)

3.0

D)

4.0

Correct Answer : 1.5

183 .

The effluent of a septic tank is

A)

fit for discharge into any open drain

B)

as good as that from a complete treatment

C)

foul and contains dissolved and suspended solids

D)

All of the above

Correct Answer : fit for discharge into any open drain

184 .

The detention period for plain sedimentation water tanks, is usually______.

A)

24 to 36 hours

B)

16 to 24 hours

C)

4 to 8 hours

D)

2 to 3 hours

Correct Answer : 4 to 8 hours

185 .

Primary treatment of sewage consists of removal of_______.

A)

sand and girt

B)

oil and grease

C)

floating materials

D)

large suspended organic solids

Correct Answer : large suspended organic solids

186 .

The rainfall at any place may be determined by______.

A)

its intensity

B)

its direction

C)

its frequency

D)

All of the above

Correct Answer : All of the above

187 .

Which one of the following gases is most significant as air pollutant_______.

A)

Oxygen

B)

Sulphurdioxide

C)

Nitrogen

D)

Carbondioxide

Correct Answer : Sulphurdioxide

188 .

In circular sewers if depth of flow is 0.2 times the full depth, the nominal gradient,_______.

A)

is doubled

B)

is trebled

C)

is not enough

D)

is only provided

Correct Answer : is doubled

189 .

Pathogens (or pathogentic bacterias) in water may cause__________.

A)

cholera

B)

dysentery

C)

infectious hepatitis

D)

All of the above

Correct Answer : All of the above

190 .

As compared to fresh river water, sea water contains oxygen

A)

10% less

B)

20% less

C)

10% more

D)

20% more

Correct Answer : 20% less

191 .

End suction pumps are the common type of _________ pumps.

A)

Drum pumps

B)

Grinder pumps

C)

Centrifugal pumps

D)

Positive displacement pumps

Correct Answer : Drum pumps

Explanation : End suction pumps are the common type of centrifugal pump. It has a horizontal shaft with an overhung impeller. The flow goes in the end of the casing, and out the top.

192 .

Which type of pump is designed to handle rocks and other solids?

A)

Slurry pumps

B)

Trash pumps

C)

Submersible pumps

D)

Self-priming pumps

Correct Answer : Trash pumps

Explanation : Trash pumps are a type of submersible centrifugal pump designed to handle rocks and other solids while dewatering. It is used in dewatering construction sites, mines, and utility pits.

193 .

In an activated sludge process which type of pump is used to recirculate the sludge?

A)

Vane Pump

B)

Booster Pump

C)

Centrifugal Pump

D)

Vertical Turbine Pump

Correct Answer : Centrifugal Pump

Explanation : The activated sludge does not contain any solids. Also, it is not very viscous. Hence a centrifugal pump can be used for this application.

194 .

The depth in open drain should preferably be kept _______ the man height.

A)

Less than

B)

Equal to

C)

Greater than

D)

Sufficient to

Correct Answer : Less than

Explanation : Open drains often carry storm water. In rainy seasons the water level increases in the drains. If it contains clogging or any operations to be done, it becomes difficult if the depth is more.

195 .

If the over land flow from the critical point to the drain is 8 km and the difference in level is 12.4 m, the inlet time is

A)

1 hour

B)

2 hours

C)

3 hours

D)

4 hours

Correct Answer : 4 hours

196 .

A rainfall may be classified as acidic if its pH value is less or equal to______.

A)

2

B)

5

C)

6

D)

7

Correct Answer : 5

197 .

When drainage to sewage ratio is 20, the peak dry weather flow is________.

A)

20% of the design discharge

B)

slightly more than 5% of the design discharge

C)

slightly less than 5% of the design discharge

D)

None of the above

Correct Answer : slightly less than 5% of the design discharge

198 .

For treating the sewage of a large city, you will recommend__________.

A)

a sedimentation tank and an activated sludge treatment plant

B)

sedimentation tanks with high rate trickling filters

C)

a plant consisting of Imhoff tanks with low rate trickling filters

D)

None of the above

Correct Answer : a sedimentation tank and an activated sludge treatment plant

199 .

Pick up the correct statement from the following :

A)

In treated sewage, 4 PPm of D.O. is essential

B)

Only very fresh sewage contains some dissolved oxygen

C)

The solubility of oxygen in sewage is 95% that is in distilled water

D)

All of the above

Correct Answer : All of the above

200 .

The surface water quality is affected by _______ and infiltration from rainfall.

A)

Run off

B)

Farming

C)

Wetlands

D)

Precipitation

Correct Answer : Run off

Explanation : Even when the catchment area is preserved in its natural condition, the surface water quality is affected by run off and infiltration resulting from rainfall. The impact of these is dependant on the contact of the water with the impurities.

201 .

_______ are constructed for water supply, electricity generation, recreation, irrigation and others.

A)

Tanks

B)

Ponds

C)

Reservoirs

D)

Swimming pools

Correct Answer : Reservoirs

Explanation : There are multiple uses assigned to water bodies, resulting in the necessity of satisfying diverse quality criteria. Reservoirs are constructed for water supply, electricity generation, etc.

202 .

Which of the following requires aesthetically pleasant water?

A)

Industrial use

B)

Irrigation

C)

Aquaculture

D)

Domestic use

Correct Answer : Industrial use

Explanation : Industries need aesthetically pleasant water with low turbidity, colour, taste and odour, absence of macro-organisms. The water should be free from organisms harmful to health.

203 .

Which of the following related to the aerobic organic matter is true?

A)

Essential nutrients for growth

B)

Development of septic conditions

C)

Development of sludge deposits

D)

Growth of undesirable aquatic life

Correct Answer : Development of septic conditions

Explanation : Both nitrogen and phosphorus are essential nutrients for growth. These nutrients can lead to the growth of undesirable aquatic life. Their biological stabilization can lead to the depletion of natural oxygen resources and to the development of septic conditions.

204 .

_____ tend to resist conventional methods of wastewater treatment.

A)

Nutrients

B)

Suspended solids

C)

Priority pollutants

D)

Refractory organics

Correct Answer : Refractory organics

Explanation : Refractory organics tend to resist conventional methods of wastewater treatment. Typical examples include surfactants, phenols, and agricultural pesticides.

205 .

Organic matter + nutrients + O2 â†’ CO2 + H2O + _______

A)

Oâ‚‚

B)

Nutrients

C)

Biomass

D)

Organic matter

Correct Answer : Biomass

Explanation : This is the general form of the equation for decomposition of organic matter during the BOD test. It should be noted that oxygen is consumed in the reaction and biomass is the catalyst for the reaction.

206 .

Which among these is the alternative BOD test for determining the oxygen consuming potential of a wastewater sample?

A)

COD

B)

BOD

C)

TOC

D)

ThOD

Correct Answer : COD

Explanation : An alternative to the BOD test for determining the oxygen consuming potential of a wastewater sample is the chemical oxygen demand (COD) test. As the name implies, the carbonaceous oxygen demand is oxidized chemically in the COD test.

207 .

What does SWOT stand for?

A)

Solid Waste Operation and Treatment

B)

Supercritical Water Oxidation

C)

Storm Water Operation and Treatment

D)

Storm and Wastewater Operation and Treatment

Correct Answer : Supercritical Water Oxidation

Explanation : Supercritical water oxidation (SCWO) is an intensive version of the WAO process. SCWO has become a rapidly developing innovative waste treatment technology for the oxidation of organic wastes and hazardous materials in water.

208 .

Unit operations are the ______ operations to remove the impurities.

A)

Chemical

B)

Physical

C)

Biological

D)

Biochemical

Correct Answer : Physical

Explanation : The physical operations to remove the impurities present in the water and waste water are called unit operations where as the unit processes are the chemical and biological conversion on the status of the impurities that they will be converted to a form that can be easily separated.

209 .

What did the structures use to prevent floating matter that enters into pumps and pumping systems?

A)

Bioreactor

B)

Grit chamber

C)

Aeration units

D)

Screens

Correct Answer : Screens

Explanation : Screens are in use from the intake structure where they prevent the floating matter enters into the pumping units, and fine and coarse screens are in use to treat waste water to prevent the entry of floating wastes and coarse solids into the treatment.

210 .

________ is simply detaining water for a sufficient time.

A)

Filtration

B)

Coagulation

C)

Flocculation

D)

Sedimentation

Correct Answer : Sedimentation

Explanation : Sedimentation is simply detaining water for a sufficient time mostly in stagnant or relatively stagnant position to make the flow velocity of water less than the settling velocity of the solid particles that they without being driven by horizontal force settles down by gravity.

211 .

For the survival of fish in a river stream, the minimum dissolved oxygen is prescribed

A)

3 PPm

B)

4 PPm

C)

5 PPm

D)

10 ppm

Correct Answer : 4 PPm

212 .

Self-cleansing velocity is_________.

A)

velocity at dry weather flow

B)

velocity of water at flushing

C)

velocity of water in a pressure filter

D)

velocity at which no accumulation remains in the drains

Correct Answer : velocity at which no accumulation remains in the drains

213 .

If the diameter of sewer is 225 mm, the gradient required for generating self cleansing velocity, is

A)

1 in 60

B)

1 in 100

C)

1 in 120

D)

None of the above

Correct Answer : 1 in 120

214 .

The width of a rectangular sewer is twice its depth while discharging 1.5 m/sec. The width of the sewer is

A)

1.36 m

B)

1.76 m

C)

0.68 m

D)

0.88 m

Correct Answer : 1.36 m

215 .

The rate of accumulation of sludge in septic tanks is recommended as

A)

25 litres/person/year

B)

30 litres/person/year

C)

25 litres/person/month

D)

30 litres/person/month

Correct Answer : 30 litres/person/year

216 .

Drop manholes at the junctions of sewer lines, are provided if_________.

A)

two sewer lines intersect

B)

sewer line runs along a main road

C)

ordinary manhole cannot be built

D)

invert level of a branch sewer is more than 60 cm that of the main sewer

Correct Answer : invert level of a branch sewer is more than 60 cm that of the main sewer

217 .

In sewage, the solids in mg per litre is_____

A)

100 to 500

B)

500 to 1000

C)

1000 to 1500

D)

1500 to 2000

Correct Answer : 500 to 1000

218 .

The sewer which received discharge from two or more main sewers, is known as

A)

a main sewer

B)

an outfall sewer

C)

a trunk sewer

D)

an intercepting sewer

Correct Answer : a trunk sewer

219 .

The arrangement made for passing the sewer line below an obstruction below the hydraulic gradient lines called

A)

sag pipe

B)

depressed sewer

C)

inverted syphon

D)

All of the above

Correct Answer : All of the above

220 .

The angle subtended by the surface of sewer water with partial flow, at sewer centre is 120Â°, the depth of sewerage is_____.

A)

50 cm

B)

40 cm

C)

25 cm

D)

20 cm

Correct Answer : 50 cm

221 .

The sewage discharge in a detritus tank of a treatment plant is 576 litres/sec with flow velocity of 0.2 m/sec. If the ratio of width to depth is 2, the depth is

A)

150 cm

B)

120 cm

C)

110 cm

D)

100 cm

Correct Answer : 120 cm

222 .

A cylindrical ejector having its height 2 m fills after every 10 minutes with a peak sewage discharge of 0.0157 cumec. The diameter of the ejector chamber, is______.

A)

2.30 m

B)

2.40 m

C)

2.45 m

D)

2.50 m

Correct Answer : 2.45 m

223 .

The flow velocity in detritus tanks is________.

A)

0.05 m/sec

B)

0.09 m/sec

C)

1.25 m/sec

D)

None of the above

Correct Answer : 0.09 m/sec

224 .

In normal conditions, the period for sludge digestion, is

A)

90 days

B)

60 days

C)

30 days

D)

20 days

Correct Answer : 30 days

225 .

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 of the above

Correct Answer : All of the above

Explanation : * 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
* capacity of the tank for 24 hours, is kept equal to maximum daily flow of sewage

226 .

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 the above

Correct Answer : centrifugal pump

227 .

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

A)

60%

B)

55%

C)

50%

D)

45%

Correct Answer : 55%

228 .

R.M.O. expenses include______.

A)

running expenses

B)

operation expenses

C)

maintenance expenses

D)

All of the above

Correct Answer : All of the above

229 .

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

A)

water test

B)

straightness test

C)

smoke test

D)

All of the above

Correct Answer : smoke test

230 .

Dry water flow in a combined sewer, is

A)

storm water

B)

domestic sewage

C)

industrial sewage

D)

inclusive of domestic and industrial sewage but excludes storm water

Correct Answer : inclusive of domestic and industrial sewage but excludes storm water

231 .

If D is the diameter of upper circular portion, the overall depth of a standard egg shaped section, is____.

A)

D

B)

1.25 D

C)

1.5 D

D)

1.75 D

Correct Answer : 1.5 D

232 .

A nuisance is experienced in diluting water if dilution factor is less than___.

A)

20

B)

40

C)

60

D)

100

Correct Answer : 20

233 .

For estimating the peak run off the rational formula Q = 0.0278 KpA was evolved by_____.

A)

Frubling

B)

Kinchling

C)

Lloyd Davis

D)

All of the above

Correct Answer : All of the above

234 .

Nitrogen cycle of sewage, is______.

A)

Liberation of nitrogen-formation of nitrates-formation of nitrites-liberation of ammonia

B)

Liberation of ammonia-formation of nitrites-formation of nitrates-liberation of nitrogen

C)

Formation of nitrates-formation of nitrites-liberation of nitrates-liberation of nitrates

D)

Liberation of nitrogen-liberation of ammonia-formation of nitrites- formation of nitrates

Correct Answer : Liberation of ammonia-formation of nitrites-formation of nitrates-liberation of nitrogen

235 .

In sewers the highest non-scouring velocity is achieved in_______.

A)

cast iron sewers

B)

glazed bricks sewers

C)

stone ware sewers

D)

cement concrete sewers

Correct Answer : glazed bricks sewers

236 .

In sewage having fully oxidised organic matter, the nitrogen exists in the form of________.

A)

nitrites

B)

free ammonia

C)

nitrates

D)

aluminoid nitrogen

Correct Answer : nitrates

237 .

The maximum spacing of manholes specified by Indian standard in sewers upto 0.3 m diameter is______.

A)

45 m

B)

30 m

C)

20 m

D)

75 m

Correct Answer : 45 m

238 .

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 of the above

Correct Answer : All of the above

Explaination : * size of the sewer
* shape of the sewer
* roughness of sewer surface
* hydraulic characteristics of sewer

239 .

Afive day B.O.D. at 15°C of the sewage of a town is 100 kg/day. If the 5 day B.O.D. per head at 15°C for standard sewage is 0.1 kg/day, the population equivalent is

A)

10000

B)

5000

C)

1000

D)

100

Correct Answer : 10000

240 .

The settlement velocity of a solid (diameter 0.5 mm, specific gravity 1.75) in water having temperature 10°C, is

A)

213.5 cm/sec

B)

313.5 cm/sec

C)

413.5 cm/sec

D)

500 cm/sec

Correct Answer : 313.5 cm/sec

241 .

The width of a settling tank with 2 hour detention period for treating sewage 378 cu m per hour, is________.

A)

6 m

B)

6.5 m

C)

7 m

D)

None of the above

Correct Answer : 7 m

242 .

For drains up to 15 cumecs, the depth d and width B are related by

A)

d = 0.2 √B

B)

d = 0.5 √B

C)

B = 0.2 √d

D)

B = √0.5 d

Correct Answer : d = 0.5 √B

243 .

Newton's law is used for_______

A)

Spiral flow

B)

Turbulent flows

C)

Laminar flow

D)

Non-turbulent flows

Correct Answer : Turbulent flows

Explanation : Newton’s law is used for turbulent flows. The Reynolds number is in the range of 103-104. The particle size is greater than 1mm for a specific gravity of 2.65 and temperature is 20ËšC for Newton’s law for settling of discrete particles.

244 .

Non-spherical particles will settle _______ spherical particles.

A)

Same as

B)

Equal as

C)

Faster than

D)

Slower than

Correct Answer : Slower than

Explanation : Non-spherical particles will settle more slowly than spherical particles of the same volume and density. For all flow conditions other than laminar the drag coefficient is also a function of the shape of the particle and must be determined experimentally.

245 .

Which of the following is not correct with respect to ultrafiltration?

A)

Compact plant size

B)

Chemicals required

C)

Good product quality

D)

Good pathogen removal

Correct Answer : Chemicals required

Explanation : The plant size required for the operation of ultrafiltration is compact and the product quality is good with good pathogen removal. There are no chemicals required for the process.

246 .

Macromolecules deposited uniformly on pore walls is called ______

A)

Blocking

B)

Complete blocking

C)

Standard blocking

D)

Intermediate blocking

Correct Answer : Standard blocking

Explanation : Macromolecules deposited uniformly on pore walls is called standard blocking. The membrane pore completely sealed by a macromolecule is called complete blocking.

247 .

What is the amount of phosphorus present in municipal wastewater?

A)

5-20 mg/L

B)

4-12 mg/L

C)

2-8 mg/L

D)

1-2 mg/L

Correct Answer : 5-20 mg/L

Explanation : Municipal wastewaters may contain from 5 to 20 mg/l of total phosphorous, of which 1-5 mg/l is organic and the rest in inorganic. The individual contribution tends to increase because phosphorous is one of the main constituents of synthetic detergents.

248 .

What is the average phosphorus contribution per person per day?

A)

1.2 g

B)

2.18 g

C)

3.26 g

D)

4.25 g

Correct Answer : 2.18 g

Explanation : The individual phosphorous contribution varies between 0.65 and 4.80 g/inhabitant per day with an average of about 2.18 g.

249 .

What is the phosphorus available for a biological process called?

A)

Phosphate

B)

Polyphosphate

C)

Biophosphorus

D)

Orthophosphate

Correct Answer : Orthophosphate

Explanation : Orthophosphates are available for biological metabolism without a further breakdown. Molecules with two or more phosphorous atoms, oxygen and in some cases hydrogen atoms combine in a complex molecule to form polyphosphates.

250 .

The addition of substances or energy forms that directly or indirectly alter the nature of the water body is called?

A)

Sanitation

B)

Water treatment

C)

Water pollution

D)

Water contamination

Correct Answer : Water pollution

Explanation : Water pollution is the addition of substances or energy forms that directly or indirectly alter the nature of the water body in such a manner that negatively affects its legitimate uses.

251 .

What is the combination of using a photocatalyst and UV or visible light for the treatment of wastewater and gaseous pollutants is called?

A)

Photocatalysis

B)

Wet air oxidation

C)

Advanced oxidation process

D)

Super critical water oxidation

Correct Answer : Photocatalysis

Explanation : Photocatalysis is the combination of using a photocatalyst and UV or visible light for the treatment of wastewaters and gaseous pollutants. When illuminating a photocatalyst using UV or visible light, various organic compounds can be oxidized and mineralized at the photocatalyst surface or oxidized in solution ambient and atmospheric condition.

252 .

How is iconic strength related to total dissolved solids?

A)

I= 2.5 TDS

B)

I = 2.5 x10 TDS

C)

I = (2.5 Ã— 10âµ) TDS

D)

I= (2.5 x 10â»âµ)TDS

Correct Answer : I= (2.5 x 10â»âµ)TDS

Explanation : I = (2.5×10â»âµ) TDS .This correlation was defined by Stumm and Morgan in 1996. The ionic strength can be found if the TDS is known. TDS is measured in mg/L.

253 .

What is the value of activity coefficients for monovalent and divalent ions for a potable water at an ionic strength of 0.01 M?

A)

0.9 in both the cases

B)

0.9 and 0.66 respectively.

C)

0.66 in both the cases

D)

0.66 and 0.9 respectively

Correct Answer : 0.9 and 0.66 respectively.

Explanation : The value of the activity coefficient for the monovalent ion is 0.9. The value of the activity coefficient for the divalent ion is 0.66. The activity coefficients for neutral species is negligible.

254 .

What is the maximum approach velocity to be considered for a mechanical screen while designing it?

A)

0.6-1m/s

B)

2 m/s

C)

1-1.5m/s

D)

0.3-0.5m/s

Correct Answer : 0.6-1m/s

Explanation : The maximum approach velocity for a mechanical screen would be in the range 0.6-1m/s. The minimum approach velocity would be in the range 0.3-0.5m/s. These mechanical screens reduce manual labour.

255 .

What is the detention time considered while designing a Grit chamber?

A)

10-20 sec

B)

20-40 sec

C)

45-90 sec

D)

90-120 sec

Correct Answer : 45-90 sec

Explanation : The detention time considered while designing a Grit chamber is 45-90 sec. Usually, 60 secs is considered as the detention time in most of the cases. The typical head loss considered is 30-40%.

256 .

Which of these process is involved in the removal of chemical flocs?

A)

Hindered settling

B)

Compression settling

C)

Flocculent settling

D)

Ballasted flocculent settling

Correct Answer : Flocculent settling

Explanation : Flocculent settling is involved in the removal of chemical flocs from the waste water. This also removes a portion of the TSS from the untreated waste water in primary settling tanks. By coalescing, the mass increases and thus the particles settle faster.

257 .

For a discrete particle settling which of these mathematical equations is true?

A)

Q=A/V

B)

Q=A/t

C)

Q= A X t

D)

Q= A Xv

Correct Answer : Q= A Xv

Explanation : For a discrete particle settling process Q=AX v. Where Q is the flow rate. A is the area of the sedimentation basin and v is the velocity.

258 .

Which of the following materials are used for high temperature applications?

A)

Polypropylene

B)

Ceramic

C)

Polylactic acid

D)

Cellulose acetate

Correct Answer : Ceramic

Explanation : Most ultrafiltration membranes use polymer materials such as polypropylene, cellulose acetate and Polylactic acid. However, ceramic membranes are used for high temperature applications.

259 .

How much amount of phosphorus is removed by secondary treatment?

A)

0.5-1 mg/l

B)

0.2-0.3 mg/l

C)

0.4-0.6 mg/l

D)

1-2 mg/l

Correct Answer : 1-2 mg/l

Explanation : Normally secondary treatment can only remove 1-2 mg/l, so a large excess of phosphorous is discharged in the final effluent, causing eutrophication in surface waters.

260 .

What does PAO stand for?

A)

Polyphosphate-accumulating organisms

B)

Poly-ammonium oxygenate

C)

Poly-ammonium organisms

D)

Phosphate-ammonium organisms

Correct Answer : Polyphosphate-accumulating organisms

Explanation : A group of heterotrophic bacteria, called polyphosphate-accumulating organisms (PAO) are selectively enriched in the bacterial community within the activated sludge.

261 .

What is the type of pollution where the pollutants reach the water body in points called?

A)

Diffuse pollution

B)

Diffuse contamination

C)

Point-source pollution

D)

Point-source contamination

Correct Answer : Point-source pollution

Explanation : In point-source pollution, the pollutants reach the water body in points concentrated in space. Usually, the discharge of domestic and industrial wastewater generates point-source pollution.

262 .

The optimum temperature for bacterial activity is in what range?

A)

25-35 degree Celsius

B)

20 degree Celsius

C)

40 degree Celsius

D)

50 degree Celsius

Correct Answer : 25-35 degree Celsius

Explanation : The optimum temperature for bacterial activity is 25-35 degree Celsius. Aerobic digestion and nitrification stop when the temperature increases up to 50 degree Celsius. When the temperature drops to 15 degree Celsius methane producing bacteria become inactive.

263 .

The algae dies out in the zone of

A)

recovery

B)

degradation

C)

cleaner water

D)

active decomposition

Correct Answer : degradation

264 .

A)

1 minute

B)

2 minutes

C)

3 minutes

D)

5 minutes

Correct Answer : 1 minute

265 .

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

A)

unexpected increase in the population

B)

under estimates of maximum and average flows

C)

unexpected large scale infiltration of stream water

D)

All of the above

Correct Answer : All of the above

266 .

5 days-biochemical oxygen demand (BODâ‚…) is taken at a temperature of

A)

0°C

B)

15°C

C)

20°C

D)

25°C

Correct Answer : 20°C

267 .

What is the growth of huge amounts of algae and other aquatic plants leading to the deterioration of the water quality called?

A)

Algae growth

B)

Eutrophication

C)

Denitrification

D)

Nitrification

Correct Answer : Eutrophication

Explanation : Eutrophication is the growth of huge amounts of algae and other aquatic plants leading to the deterioration of water quality. The untreated wastewater is rich in organic matter which demands oxygen.