Potable Water

• Potable water is water you can drink

  • it is water that is been treated or is naturally safe for humans to drink - essentials for life
  • chemists wouldn't call it pure - pure water only contains H2O molecules whereas potable water can contain lots of other dissolved substances
  • the important thing is that the levels of dissolved salts aren't too high, that it has a pH between 6.5 and 8.5 and also that there aren't any nasties swimming around in it
• Potable Water is Produced Depends on Where you are - pt1

  1.Rainwater is a type of fresh water - water that doesn't have much dissolved in it

  2. when it rains water can either collect as surface area or groundwater

  3. in the uk the source of fresh water used to depend on location. surface area tends to dry up first so in warm areas
• Potable Water is Produced Depends on Where you are - pt2

  4. even though it has low levels of dissolved substances it still needs to be treated:

  • Filtration - a wire mesh screens out large twigs etc, and then gravel and sand beds filter out other solid bits
  • sterilisation - the water is sterilised to kill any harmful bacteria or microbes - bubbling chlorine gas through it or ozone/uv light.

  5. in some dry countries there's not enough surface or ground water and instead seawater must be treated by desalination - potable water

  6. distillation can be used to desalinate sea water
• Potable Water is Produced Depends on Where you are - pt3

  7. distillation

  • test the PH of water until it's pH is 7
  • set up the apparatus
  • as the water heats up, it will evaporate and will enter the condenser as steam
  • the drop in temperature inside the condenser due to cold water around it will cause steam to condense back into liquid
  • collect the water running out of the condenser in a beaker
  • retest the pH of the water with pH of the water out of the condenser in a beaker
  • reset the pH of the water
  • you can tell whether the salts because they will be crystalised
• Potable Water is Produced Depends on Where you are - pt4

  8. sea water can also be treated by the process that uses membranes like reverse osmosis, salty water is passed througjh a membrane that only allows water molecules to pass through

  9. both distillation and reverse osmosis need a lot of energy so it is very expensive and not practical for producing large quantities of water