External Flashcards
What are the four types of impurities?
Suspended matter
Dissolved solids
Dissolved gases
PH values
Which dissolved solids are considered soft scale? Hard scale?
Soft scale - bicarbonates
Hard scale - sulphates
The bicarbonates cause…
Temporary hardness
The sulphates cause…
Permanent hardness
What types of dissolved gases cause pitting/corrosion?
Oxygen and carbon dioxide
How are dissolved gases removed from the water?
By the use of a deaerator, which boils the water causing the gases to be vented out through the steam vent
What are the methods of external water treatment
Filtration
Water softening
Deaerating
What are the three types of filters
Pressure filter
Tubular filter
Cartridge filter
What must you do when a pressure type filter becomes plugged?
Backwash
The process of removing the calcium and magnesium and replacing them with sodium is called
Water softening
What are the three types of water softeners
Lime soda
Sodium zeolite
Demineralizers
What causes water hardness
Calcium and magnesium dissolved in the water
What makes water “soft”
The sodium from water softeners replacing the calcium and magnesium
Which softener uses the principle of cat ion exchange
Sodium zeolite
What must you do when a sodium zeolite softener has given up all of its sodium cations?
Regenerate it
