Water treatment

• In the UK we get our water from:

  • Surface water
  • eg. lakes, rivers, reservoirs
  • Groundwater
  • eg. aquifers
• Water is purified in water treatment plants:

  1. Filtration
  2. Sedimentation
  3. Chlorination
• 1. Filtration

  • Wire mesh blocks large twigs and rocks
  • Gravel and sand beds filter out any other solid bits

  1. Sedimentation

  • Iron sulfate is added to the water, causing fine particles to clump together and settle at the bottom

  1. Chlorination

  • Chlorine gas is bubbled through to kill harmful bacteria

  
• Tap water still contains impurities such as:

  • Nitrate residues
  • Excess fertiliser run-off into lakes and rivers
  • Lead compounds
  • From old lead pipes
  • Pesticide residues
  • From spraying pesticides too close to rivers and lakes
• You can get fresh water by distilling sea water

  • However it is very expensive as it requires lots of energy