using resources

• drinking water has to have low levels of salt
• drinking water must have low levels of what

  salt
• drinking water cant have high levels of microbes such as 


  bacteria
• drinking water cant have microbes such as bacteria
• water that is safe to drink is called potable water
• what is water that is safe to drink called

  potable water
• potable water and pure water are not the same
• what is the difference between pure water and potable water

  potable water contains some dissolved substances and pure water does not
• where does rainwater collect

  aquifers , lakes , rivers , reservoirs
• how to make potable water

  take fresh water

  pass through filter beds to remove leaves and suspended particles

  water is sterilised to kill microbes ( with chlorine or UV light )
• sea water is made potable through desalination
• what does desalination do

  reduce the levels of dissolved minerals to a safe level
• one way of carrying out desalination is to use distillation
• one way of carring out desalination is by reverse osmosis
• desalination is very expensive
• what are resources used for

  warmth , shelter , food , transport
• what are resources produced by

  agriculture
• many resources are produced by agriculture
• what are trees used for

  timber or fuel
• agriculture helps us use the earth resources more efficiently
• some natural resources are finite
• what does it mean if a resource is finite

  it cant be replaced as quickly as it is used
• what do natural resources provide

  food , timber , clothes , fuel
• finite resources from the earth provide energy and materials
• what natural products have been replaced by synthetic versions or agricultural versions

  rubber

  fertilisers
• drinking water has to have low levels of dissolved salts
• what is potable water

  water that is safe to drink
• potable water and pure water are not the same
• sources of fresh water

  aquifers

  lakes

  rivers

  reservoirs
• how to produce potable water

  find a good source of fresh water

  pass water through filter beds

  sterilise water with chlorine ( or ozone or UV light )
• ways of carrying out desalination

  distillation

  reverse osmosis
• you can carry out desalination using reverse osmosis and distillation
• reverse osmosis and distillation both require large amounts of energy making them expensive
• methods of producing potable water depend on available water supply and local conditions
• waste water must be treated before being released into the environment
• what is the purpose of screening waste water

  removes solid and bits of grit by passing through a mesh
• what is the purpose of sedimentation tanks

  it produces a liquid effluent and a sludge which sinks

  the sludge gets taken away and digested by anaerobic bacteria

  if there is no oxygen the bacteria produce biogas which can be burned for energy
• sedimentation tanks produce sludge and effluent
• what can the digested sludge in waste water treatment be used for

  fertilisers for farming
• the digested sludge can be used as fertilisers for farming