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Water Treatment Plant Operator Test Questions > Corrosion Control > Flashcards

Corrosion Control Flashcards

1
Q

What parameter is calculated to determine smoothness of the interior of a pipe?

A

C. Factor

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2
Q

The marble test determines what water condition?

A

Scaling or corrosiveness of the water and stability of the water

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3
Q

Besides the marble test, what other devices determine the stability of water?

A

Enslow column and langular index

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4
Q

⭐ When a operator took marble retest, initial pH, alkalinity, and hardness did not change after adding calcium carbonate to water. What does this indicate?

A

Water is just saturated/stable

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5
Q

⭐. After adding 5 mL of calcium carbonate to the marble test sample, the pH, alkalinity, and hardness all went up. What does this indicate?

A

The water was undersaturated or corrosive

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6
Q

⭐. After adding 5 mL of calcium carbonate to the marble test sample, the pH, alkalinity, and hardness all went down. What does this indicate?

A

The water was over-saturated or scaling

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7
Q

⭐. How is the pH calculated?

A

Temperature, TDS, calcium, and alkalinity

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8
Q

How is langlier index determined?

A

Subtract the pHs from the pH

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9
Q

⭐. The pH is 8.6 and the pHs is 8.8. What is the L.L. ?

A
  • 0.2
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10
Q

What is the action level for lead in water?

A

0.015 MG/L

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11
Q

What is the action level for copper?

A

1.3 mg/L

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12
Q

What is the SMCL for iron?

A

0.3 mg/l

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13
Q

When is a water system deemed to be in violation of lead and copper rule?

A

When the 90th percentile test exceeds the action level for copper and lead

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14
Q

What disease is associated with excess amounts of lead and water?

A

Mental retardation in children

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15
Q

What disease is associated with excess amounts of copper in the water?

A

Wilson’s disease known as liver problems

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16
Q

If water systems have exceeded the action level for lead or copper, what action must be taken?

A

pH. Adjustment/ publicnification and education/ add a polyphosphate in the filter Influent /adcalcium carbonate

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17
Q

The water spigots aerator must remain on when drawing, lead or copper samples true or false?

A

True true

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18
Q

The destruction of metallic matter by a chemical or electrochemical reaction is called?

A

Corrosion

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19
Q

What type of corrosion originates outside the homes plumbing system?

A

Stray current (also known as electrolysis)

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20
Q

If the water velocity increases, what else will increase

A

Corrosion rate

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21
Q

What type of corrosion is associated with copper pipe?

A

Erosion corrosion

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22
Q

What kind of corrosion is caused by connecting two dissimilar metals together?

A

Galvanic corrosion

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23
Q

What is the largest source of lead in water systems?

A

Plumbing fixtures

24
Q

What causes black water?

25
Q

Red stain indicates what type of corrosion?

26
Q

Black stains I’m plumbing fixtures indicate what type of corrosion is taking place

27
Q

What causes red water?

A

Iron bacteria

28
Q

A water system using manganese green sand is getting customer complaints regarding red water. What is the likeliest cause?

A

Iron bacteria/greensound filter has to be regenerated with potassium premagnate / polyphosphate reverted to orthophosphate

29
Q

If adding polyphosphate and chlorine during pretreatment, which chemical must come first?

A

Polyphosphate

30
Q

What conditions are ideal for corrosion?

A

Hi TDS, low hardness, low pH, high DO content, high temperature, high velocity/ s also chlorine residual, bacterial, soil moisture, or high pressure

31
Q

For corrosion to take place what must be present?

32
Q

How can a water system best prevent slime from forming in the distribution system?

A

Maintain 0.2 MG/L chlorine residual

33
Q

Which electrical system prevents corrosion and pitting of metal surfaces?

A

Cathodic protection

34
Q

When water is stored in an open reservoir, which phosphate compound should you avoid using?

A

Zinc phosphate because it causes algae bloom

35
Q

The WTP operator notices brown stains on the walls of the water filters. What does this indicate

A

Insoluble iron

36
Q

The WTP operator notices black stains on the walls of the water filter. What does this indicate?

A

Insoluble manganese

37
Q

The WTP operator notices brown and black stains on the walls of the water filters. What does this indicate

A

Insoluble iron and manganese

38
Q

How can you tell when there is corrosion in the water main?

A

Rusty or red water/ musty smell / dip in DO of water since it left the WTP

39
Q

How do you measure the corrosiveness of soil?

A

Soil resistance meter

40
Q

How do you determine the correct chemical dosage for water?

A

Jar test/ marble test/ enslow column /trial and error experiment with computer /graphics

41
Q

Iron in ferrous form is

42
Q

Iron as ferric hydroxide is?

43
Q

Corrosion can be slowed by adding what to the water?

A

Corrosion inhibitor

44
Q

What do you call a piece of metal that is inserted into a water main?

A

Coupon and is used to measure corrosion

45
Q

What type of corrosion is caused by connecting to dissimilar metals?

A

Galvanic corrosion

46
Q

A common corrosion in iron pipes is?

A

Tuberculation

47
Q

The negative pole is called

48
Q

The dissolved oxygen (DO) was lower at the customer’s home than when it left the WTP. What does this indicate? Or what caused this to happen?

A

Corrosion /organic matter in the water

49
Q

The operator measured the DO at point A. He then measured it at point B downstream from point A. What does this indicate? Or what caused this to happen?

A

Corrosion /organic matter in the water

50
Q

The operator dropped HCI on the copper gate of a valve? The reaction was an effervescent bubbling. What does this indicate?

A

A thin coat of CaCO3 on the valve part indicating the water was just saturated

51
Q

What term is used to measure current?

52
Q

What term is used to measure resistance

53
Q

CaCO3 is less soluble in hot water than in cold water. True or false?

54
Q

What is the most common source of lead found in customer’s homes?

A

Plumbing fixtures

55
Q

What can inhibit corrosion?

A

Thin layer of CACO3

56
Q

What do you call a ring-shaped space located between two circular objects,?

A

Annular space

Water Treatment Plant Operator Test Questions (16 decks)

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