External Flashcards

1
Q

What are the four types of impurities?

A

Suspended matter
Dissolved solids
Dissolved gases
PH values

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2
Q

Which dissolved solids are considered soft scale? Hard scale?

A

Soft scale - bicarbonates

Hard scale - sulphates

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3
Q

The bicarbonates cause…

A

Temporary hardness

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4
Q

The sulphates cause…

A

Permanent hardness

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5
Q

What types of dissolved gases cause pitting/corrosion?

A

Oxygen and carbon dioxide

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6
Q

How are dissolved gases removed from the water?

A

By the use of a deaerator, which boils the water causing the gases to be vented out through the steam vent

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7
Q

What are the methods of external water treatment

A

Filtration
Water softening
Deaerating

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8
Q

What are the three types of filters

A

Pressure filter
Tubular filter
Cartridge filter

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9
Q

What must you do when a pressure type filter becomes plugged?

A

Backwash

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10
Q

The process of removing the calcium and magnesium and replacing them with sodium is called

A

Water softening

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11
Q

What are the three types of water softeners

A

Lime soda
Sodium zeolite
Demineralizers

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12
Q

What causes water hardness

A

Calcium and magnesium dissolved in the water

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13
Q

What makes water “soft”

A

The sodium from water softeners replacing the calcium and magnesium

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14
Q

Which softener uses the principle of cat ion exchange

A

Sodium zeolite

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15
Q

What must you do when a sodium zeolite softener has given up all of its sodium cations?

A

Regenerate it

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16
Q

What are the four main steps in operation of a sodium zeolite softener

A
  • service
  • backwash
  • regenerate
  • rinsing
17
Q

Explain the function of a Deaerator

A

It removes dissolved gases such as oxygen and carbon dioxide by raising the water to its boiling point and releasing the gases by steam to the atmosphere

18
Q

What is the normal operating pressure in a deaerator

A

70-100 kPa

19
Q

What is the regenerant used to regenerate a cation exchanger in a demineralizer?

A

Sulphuric acid