C10: Potable Water

Question 1

What is potable water?

Answer 1

Water that’s been treated or is naturally safe for humans to drink - it’s essential for life.

Question 2

Is potable water pure?

Answer 2

No - pure water only contains H2O molecules whereas potable water can contain lots of other dissolved substances

Question 3

What does the pH of potable water need to be between?

Answer 3

6.5 and 8.5 so there aren’t any bacteria or other microbes in it

Question 4

How is rainwater collected?

Answer 4

Rainwater is a type of fresh water = doesn’t have much dissolved into it

Can collect as surface water (in lakes, rivers and reservoirs) as groundwater (in rocks called aquifers that trap water underground)

Question 5

Where does freshwater come from in the UK?

Answer 5

The source depends on location

Surface water dries up first - warm areas (eg. most water south-east comes from groundwater)

Question 6

How is the water from these fresh water sources treated?

Answer 6

Filtration: wire mesh screens out large twigs, then gravel and sand beds filter out any other solid bits
Sterilisation: to kill harmful bacteria, don’t by bubbling chlorine gas through it, or by using ozone or ultraviolet

Question 7

What happens in very dry countries where there’s not enough surface or groundwater?

Answer 7

Seawater can be desalinated through distillation to provide potable water.

Question 8

Other than desalination, how can seawater be treated?

Answer 8

By processes that use membranes - like reverse osmosis
Salty water passed through membrane that only allows water molecules through
Ions &larger molecules are trapped by membrane and separated from the water

Question 9

Why aren’t distillation and reverse osmosis practical?

Answer 9

They need lots of energy so are expensive and impractical for producing large quantities of fresh water