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D2 Practice Questions > D2 Practice 2 > Flashcards

D2 Practice 2 Flashcards

1
Q

Which process converts ammonia to nitrite and nitrate?

A

Nitrification

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2
Q

What is the maximum advisable rate of chlorine gas removal from a 150 lb. cylinder?

A

40 lbs/day

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3
Q

What is a type of positive displacement water meter?

A

Nutating-disc meter

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4
Q

_____ is a power-operated mechanism for opening amd closing a valve.

A

Actuator

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5
Q

What is required if a routine sample tests positive for total coliform bacteria?

A

Take repeat samples

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6
Q

Why is a grid layout better than a tree (branching) layout for a water distribution system?

A

Less dead-end mains

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7
Q

In general, at what depths is shoring required for a trench, if you’re excavating in soil?

A

5 feet or deeper

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8
Q

What is the purpose of a reduced pressure principle assembly?

A

Prevents back-pressure and back-siphonage

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9
Q

What occurs after breakpoint chlorination is achieved?

A

Free available chlorine residual is directly proportional to the amount of chlorine added

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10
Q

What is used to automatically shut-off the flow into a tank when the water level reaches a predetermined level?

A

Altitude valve

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11
Q

What could be used to find a chlorine gas leak, which produces white smoke when it reacts with this substance?

A

Spray ammonia solution vapor near leak

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12
Q

What causes staining of plumbing fixtures?

A

Iron and manganese

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13
Q

How long should you flush the water before you collect a bacteriological sample?

A

As long as necessary to flush stagnant water from the service pipe

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14
Q

What is the purpose of a surge tank?

A

Protect pipelines from sudden high pressure

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15
Q

What is recommended if a chlorine gas cylinder is leaking?

A

Rotate the cylinder and turn the leak upwards

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16
Q

What is the purpose of primary MCL?

A

To protect human health

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17
Q

What problem could be caused by water with a pH of 5.3?

A

Corrosion

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18
Q

What is a common way to connect a new pipe to an existing pipe, while the latter is pressurized and in-service?

A

Wet tap or hot tap

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19
Q

What impact would organics have on chlorine demand?

A

Increase chlorine demand

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20
Q

What is dichloramine?

A

Combined chlorine residual

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21
Q

What impact does tuberculation have on the interior of a water main?

A

Causes rough interior of the water main due to corrosion

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22
Q

What is used to neutralize chlorine residuals when collecting a water sample for bacteriological analysis?

A

Sodium thiosulfate

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23
Q

What are electrodes and ultrasonic signals used for in a tank?

A

Monitor water level

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24
Q

Which part of the water main should a new service tap be installed?

A

45 degrees from the top of the water main

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25
Q

What is the purpose of a vacuum breaker?

A

Prevent back-siphonage

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26
Q

Which type of valve is commonly used to isolate water mains during repairs to minimize service outages?

A

Gate valve

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27
Q

Pumping water level - static water level=

A

Drawdown

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28
Q

What is purple pipe used for?

A

Reclaimed water

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29
Q

Where is the correct location to install an air release valve?

A

Top of pipe

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30
Q

What must be performed prior to entering a confined space?

A

Test for oxygen deficiency/enrichment, combustible gases, and toxic gases

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31
Q

What does the C-factor of a pipe represent?

A

Roughness of pipe interior

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32
Q

Why should you never empty an underground storage tank when the groundwater level is high?

A

It may float the tank and cause damage to the facility

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33
Q

What is used to determine the bacteriological quality of a water supply?

A

Presence-absence of coliform bacteria

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34
Q

Which valve is available as a swing, double door, or slanting disc?

A

Check valve

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35
Q

What is used to check the effectiveness of disinfection?

A

Test for coliform bacteria (bacteriological result)

36
Q

What are used to protect water mains and tanks from corrosion?

A

Anodes

37
Q

What is a common customer complaint during or immediately after flushing the water main?

A

Cloudiness and color in water

38
Q

What is total dynamic head?

A

Total static head plus head loss, when pump is operating

39
Q

What is a connection between a potable water system and an unapproved water supply?

A

Cross connection

40
Q

What is tested in the field during the collection of a bacteriological sample?

A

Test for chlorine residual

41
Q

Which type of water meter diverts some of the flow through a bypass meter, which is calibrated to register the total flow through the main pipeline?

A

Proportional meter

42
Q

What must be true if trihalomethane is detected in the water?

A

Disinfection by-products have formed

43
Q

What causes a pump to sound like it is pumping rocks?

A

Cavitation

44
Q

What are the three most commonly used forms of chlorine for disinfection in the water industry?

A

Chlorine gas, calcium hypochlorite, and sodium hypochlorite

45
Q

What will reduce flow rate in a pipe?

A

Encrustation

46
Q

What is the source of E. coli?

A

Intestinal tract of warm-blooded animals

47
Q

What is the primary purpose of a listening device?

A

Locate leaks

48
Q

What does a positive result from a presence-absence test indicate?

A

Biological problem

49
Q

Which part of a chlorinator is fitted with a Venturi nozzle, and creates a vacuum that moves the chlorine gas?

A

Ejector

50
Q

What should be installed on the pipeline if the flow changes directions?

A

Thrust block or restraint

51
Q

What has the least impact to the disinfection capabilities of chlorine?

A

Hardness

52
Q

What is commonly used to protect the exterior of ductile iron pipe from corrosion?

A

Polyethylene encasement

53
Q

What causes water to appear red?

A

Iron

54
Q

What could be used to identify the corrosiveness of water?

A

pH

55
Q

What will happen to the maximum flow rate from a chlorine gas cylinder if the temperature of the cylinder decreases?

A

Decreases

56
Q

What is a white tablet with 65% available chlorine?

A

Calcium hypochlorite

57
Q

Which type of water storage facility has a height that is greater than its diameter?

A

Standpipe

58
Q

What is required if you cannot perform a bacteriological test within one hour of sampling?

A

Refrigerate the sample

59
Q

What causes scaling in a pipe?

A

Hardness

60
Q

Which valve has a movable disc that rotates on a vertical shaft to stop the flow of water?

A

Butterfly valve

61
Q

What will happen if the pressure in the water main drops below zero?

A

Back-siphonage

62
Q

What is a buried valve that connects a water main to a service lateral?

A

Corporation stop

63
Q

What is one of the drawbacks of a dead-end water main?

A

You have to flush more

64
Q

What is required before a new water main is placed in-service?

A

Test for coliform bacteria

65
Q

A solution with a pH of 6 is a _______

A

Weak acid

66
Q

What is required before discharging chlorinated water to the environment?

A

Dechlorinate the water

67
Q

What is the purpose of painting or coating the interior of a steel tank?

A

Minimize corrosion

68
Q

What’s an approved backflow prevention device for a service connection that does not pose a health hazard?

A

Double check valve

69
Q

What is used to add head to water and convey it to higher elevations?

A

Booster pumps

70
Q

Which standards are commonly used to disinfect a new water main?

A

AWWA

71
Q

If the organic concentration in a new water main increases, what is the impact to chlorine demand?

A

Chlorine demand Increases

72
Q

What are essential for killing harmful bacteria in water?

A

Adequate chlorine contact time and chlorine residual concentration

73
Q

If a tank was disinfected due to possible contamination, what would be true?

A

It cannot be returned to service until bacteriological test results show that samples tested negative for coliform bacteria

74
Q

What is used to prevent backflow into a pump?

A

Check valve

75
Q

What is the primary problem with installing PVC pipe (C-900) near a gas station?

A

Gasoline can permeate into the pipe

76
Q

What is a source of water main contamination that is unique to rural areas?

A

Septic leach fields

77
Q

What is formed when chlorine reacts with natural organic matter?

A

Trihalomethane (THM)

78
Q

An environment with the presence of free oxygen is known as ______

A

Aerobic

79
Q

What could happen if the water pressure on the customer’s side exceeds the pressure in the water main?

A

Back-pressure

80
Q

What is always required after coating the tank interior?

A

Disinfection

81
Q

What is a process by which water vapor passes into the atmosphere from living plants?

A

Evapotranspiration

82
Q

What is installed at the top of a well to prevent contamination of groundwater from the surface?

A

Sanitary seal

83
Q

Safe access and egress, such as a ladder, must be located within ______ feet from all workers in a trench that is 4 feet or deeper

A

25

84
Q

______ is a type of positive displacement pump

A

Reciprocating or piston pump

85
Q

Underground layer of porous, water bearing material from which groundwater can be extracted using a well.

A

Aquifer

D2 Practice Questions (3 decks)

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