Potable Water Flashcards
What is potable water ?
Water that is safe to drink
Is potable water pure ?
No
What is the PH of potable water ?
6.5-8.5
What are the three criteria of potable water ?
- Needs to be free of harmful microbes
- Water has PH of 6.5-8.5
- Levels of dissolved substances need to be fairly low
What are the three criteria of pure water ?
- No dissolved substances inside
- PH of 7
- BP is fixed at 100*c
What are the two supplies of water ?
Ground water and sea water
What are surfaces water sources ?
- lakes
- Rivers
- reservoirs
Bodies of water that are exposed at their surface
Where are ground water sources?
Aquifers: Permeable rock under the ground that trap water
What is the benefit of using a surface water sources such as a lake ?
Easy to access
Replaced frequently by the rain
What is a limitation of using a surface water source ?
If it’s sunny it can dry up so in warmer areas they rely on ground water
How do we treat water ?
- Filter through filter beds and wire mesh: removes solids
- Passed through bed of sand and gravel which filters the smaller solids
- Sterilise it to kill any microbes
What are the three methods of sterilisation ?
- Bubbling chlorine gas through it
- Exposing it to Ozone
- Exposing it to ultraviolet light
If a country doesn’t have a good supply on fresh water what might they rely on ?
Desalination which extracts potable water from sea water
What is a benefit of using sea water?
Limitless supply
What are the two teachniqes for desalination ?
Reverse Osmosis
Distillation
What are the negatives of using desalination ?
Both methods, distillation and reverse osmosis, require lots of energy
Really expensive
This makes them impractical for producing large quantities of water
How do we desalinate water through distillation ?
Same as normal distillation where the water is boiled then condensed to give us distilled water
Except
It’s in larger quantiles of sea water being boiled and the apparatus will look different
How does reverse osmosis work ?
The salty water is passed through a membrane which only allows for water molecules to pass through
Therefore
The larger ions and molecules get trapped and separated leaving us with pure distilled water
