Using resources

• What is potable water

  Water that is safe to drink
• How is freshwater treated

  • filtered through wired mesh to remove large insoluble contaminants
  • Filtered again through sand and gravel to remove smaller microbes
  • Sterilised using chlorine, ozone (O3) or UV light to kill harmful microbes
• What is desalination x

  Techniques used to remove dissolved substances and extracting potable water from sea water
• What is Distallation

  Sea water heated until boiled which leaves salt in the liquid due to high boiling point

  Steam is cool and condensed to make potable water

  High temp kills microbes
• Downside of Distallation

  Generates waste which is expensive and difficult to get rid of

  Expensive as it requires lots of energy
• What is reverse osmosis

  Water is put under high pressure and passed through a membrane which has tiny holes to allow water molecules through but also prevents most ions and molecules from passing through
• Downside of reverse osmosis 


  Membranes are expensive

  Produces large volume of waste water therefore low efficiency
• What is the process of waste water and sewage treatment

  • Screening which removes large debris and rubbish
  • Sedimentation - sewage is left to sit to allow heavier particles to fall to the bottom of the tank which form sludge, the top layer is effluent which is separated into different tanks
  • Sludge is anaerobically digested
  • Effluent if aerobically digested to be released into rivers and seas