Potable Water Flashcards
What is potable water?
water that has been treated or is naturally safe for humans to drink-it is essential for life
is potable water pure?
no, it does not only contain H2O molecules it also has lots of other dissolved substances
what makes water potable?
-it should not have levels of salt that are too high
-must have a pH between 6.5 and 8.5
-must not have anything like bacteria or microbes swimming in it
how can water be collected when it rains?
-it can be collected as surface water from lakes rives or reservoirs
-it can be collected as groundwater in rocks called aquifers that trap water underground
In the UK the source of fresh water usually depends on….?
location
-in warm areas like the south east most domestic water supply comes from groundwater as surface water dries up
How is water from fresh water sources treated?
by filtration and sterilisation
how is filtration used to treat water?
a wire mesh screens out large twigs etc, and then gravel and sand beds filter out any solid bits
how is sterilisation used to treat water?
the water is sterilised to kill any harmful bacteria or microbes. This can be done by bubbling chlorine gas through it or by using ozone or ultraviolet light
where is desalination (the process of removing salt from seawater) used to provide potable water and how?
-in very dry countries where there is not enough groundwater or surface water.
-This can be done through distillationor reverse osmosis
How can you purify water in a lab using distillation?
1)test the pH of the water using a pH meter. if the pH is too high or low you have to neutralise it by adding some acid if the sample is alkaline or alkali if the sample is acidic until the pH is 7
2)set up your equipment by placing a rounded bottom flask with the water sample inside over a bunsen burner and connect this to a condenser with a beaker under
3)the drop in temperature inside the condenser due to the cold water around it will cause the steam to condense back to liquid water
4)collect the water running out of the condenser in the beaker and retest the pH to see if its neutral
5) you can see whether there were salts in your initial sample by checking if there are any crystals in the rounded bottom flask after the water has been distilled
how can reverse osmosis be used for desalination?
the salty water is passed through a membrane that only allows water molecules to pass through. Ions and larger molecules are trapped by the membrane so separated from the water
What are the disadvantages of distillation and reverse osmosis to treat water?
-they both require alot of energy so are really expensive and not practical for producing large quantities of fresh water
