Potable water

Question 1

What is potable water?

Answer 1

• Water that is safe to drink
• Doesn’t mean that the water is pure

Question 2

What are the 3 criteria for water to be considered potable?

Answer 2

• Levels of dissolved susbtances needs to be fairly low
• The pH needs to be between 6.5 and 8.5
• There should be no micro-organisms in the water

Question 3

What are the different places that fresh water can collect and their pros and cons?

Answer 3

• Can collect as surface water (lakes and rivers) or as ground water (aquifiers)
• Surface water is easy to access and replaced frequently by can dry up if it gets too hot. In this case, ground water is used

Question 4

Steps of water treatment

Answer 4

• Passing it through a wire mesh - filters out any big things
• Passing it through a bed of sand or gravel - filters out smaller bits
• Sterilise it to kill any microbes

Question 5

Different methods of sterilising water

Answer 5

• Bubbling chorine gas through it
• Exposing it to ozone
• Exposing it to ultraviolet light

Question 6

What is desalination and why is it used?

Answer 6

• Desalination is a method of extracting potable water from sea water
• It is used in areas which have a poor supply of fresh water (little rain)

Question 7

Different methods of desalination and its pros and cons

Answer 7

• Desalination can be done via distillation or reverse osmosis
• Pros: lots of sea water so ltos of available water to sterilise
• Cons: uses tons of energy and not easily feasable

Question 8

How is desalination done through distillation?

Answer 8

• Water is heated to evaporate and then condensed to get pure distilled water

Question 9

How is desalination done through reverse osmosis?

Answer 9

• Salty water is passed through a membrane which only allows the water molecules to pass through, leaving us with pure water