Treating Water

• What is potable water?

  Water that is safe to drink
• What are the types of water sources?

  • Ground water
  • Salt water
  • Wastewater
• What must be done to salt water to make it potable?

  It must be desalinated
• What is required for treating wastewater?

  It requires a lot of treatment
• What are the steps in treating ground water?

  1. Mesh to remove large debris
  2. Sand and gravel filtration for smaller solids
  3. Sterilisation using chlorine gas, ozone, or UV light
• What is used to sterilise ground water?

  Chlorine gas, ozone, or UV light
• How is rainwater treated in the UK?

  It is treated through filtration and sterilisation
• What are the two methods of desalination?

  1. Distillation

  • Boiling water to separate from salts

  1. Reverse osmosis

  • Passing water through a selective membrane
• Why is desalination necessary?

  To make sea water potable in dry areas
• What is the difference between distillation and reverse osmosis?

  Distillation boils water; reverse osmosis uses a membrane
• What is a potential drawback of desalination methods?

  They use lots of energy
• What are the steps in treating wastewater?

  1. Screening
  2. Sedimentation
  3. Aerobic digestion of organic matter
  4. Anaerobic digestion of organic matter
  5. Release of effluent back into the environment
• What happens to wastewater containing toxic substances?

  It may require extra radiation or chemical treatment
• What is sludge in wastewater treatment?

  Organic matter that is digested
• What is produced from anaerobic digestion of organic matter?

  Natural gas and fertiliser