C10 - Using Resources

• The Earth's resources are used to provide warmth, shelter, food and transport
• Natural resources are supplemented by agriculture, provide food, timber, clothing and fuels
• Finite resources are from the earth, oceans and atmosphere are processed to provide energy and materials
• Renewable energy resources - sources of power that can quickly replenish themselves and be used again
• Finite resources - have a limited supply that will eventually run out
• Potable water - water that is safe to drink
• Potable water is not pure because it contains dissolved substances, although to be safe it must have sufficiently low levels of dissolved salts and microbes
• Uk Method to produce potable water:

  • An appropriate source of freshwater is selected (rain provides water with low levels of dissolved substances and this collects in the ground/rivers/lakes)
  • The water is passed through filter beds to remove different sized insoluble solids
  • The water is then sterilised to kill microbes (sterilising agents include: ozone, UV light or chlorine)
• If only salty water is available to produce potable water desalination is required.
• What is one disadvantage of desalination methods?

  It is very expensive
• Types of desalination methods:

  • Distillation
  • Membrane processes (reverse osmosis)
• Water of the correct quality is essential for life. It must be free of poisonous salts and harmful microbes.
• How correct quality water is produced:

  1. Water is passed through a mesh screen to remove large bits (e.g twigs or grit)
  2. Chemicals are added to make solids and microbes stick together to form sediment and sink
  3. There is then anaerobic digestion of sewage sludge
  4. The water is then sterilised with chlorine to kill any microbes left
• It is cheaper and easier to obtain potable water from groundwater and wastewater than salt water, although seawater is plentiful raw material, so is good for countries with little freshwater.
• Why and how is copper being extracted differently?

  Copper ores are becoming scarce and new ways of extracting copper from low-grade ores include phytomining and bioleaching. These methods avoid traditional mining methods of digging, moving and disposing of large amounts of rock
• Phytomining uses plants to absorb metal compounds. Plants are harvested and then burned to produce ash that contains metal compounds.
• Bioleaching uses bacteria to produce leachate solutions that contain metal compounds. The metal compounds can be processed to obtain the metal.
• What is an example of bioleaching?

  Copper can be obtained from solutions of copper compounds by displacement using scrap ions or by electrolysis
• Pure water only contains H20 molecules whereas potable water can contain lots of other dissolved substances
• In potable water it is important that the levels of salt aren't too high. It should have a pH between 6.5 and 8.5 and that any bacteria or microbes aren't contained.
• Freshwater is water that doesn't have much dissolved in it.
• Groundwater is water in rocks that trap aquifers that trap water underground.
• Surface water is in lakes, rivers and reservoirs.
• Surface water in the uk tends to dry up first, so in warm areas (e.g south-east), most of the domestic water supply comes from groundwater.
• Filtration - a wire mesh screens out large twigs etc and then gravel and sand beds filter out any other solid bits.
• Sterilisation -the water is sterilised to kill any harmful bacteria or microbes. This can be done by bubbling chlorine gas through it or by using ozone or ultraviolet
• Why are distillation and reverse osmosis expensive?

  They require loads of energy and not practical for producing large quantities of freshwater.
• Agricultural systems produce a lot of waste water including nutrient run-off from fields and slurry from animal farms.
• Potable/drinking water has low levels of:

  • Dissolved salts
  • Microbes
• Under ground water - ground water
• Potable water is collected by:

  1. Choosing an appropriate source of freshwater
  2. Passing the water through filter beds - sand and gravel layers remove solid particles
  3. Sterilising (killing microorganisms) - UV light, chlorine, ozone
• Water can only be fully purified by distillation
• Pure water is made of only H20 ions
• If fresh water supplies are limited we may have to desalinate salty water or seawater
• Describe how dirty water from a reservoir is made potable? (6 marks)

  Filtration - large meshes to remove bigger objects such as sticks and leaves

  Sedimentation - water is left in a large tank to allow sediment due to gravity

  A chemical is added which causes the solid particles (which would pass through a filter) to clump together into larger particles - flocculation. These particles then are allowed to settle out or may be filtered.
• Explain how reverse Osmosis works to desalinate water?

  Pressure is applied to seawater, forcing water molecules to move across a selectively permeable membrane from an area of low concentration to high concentration.
• Life Cycle Assessment stages:

  1. Extraction and processing of raw materials
  2. Manufacturing and packaging
  3. Use and reuse
  4. Disposal
  5. Transport and distribution at all stages
• What does the reduction in use, reuse and recycling of materials by end users do?

  It reduces the use of limited resources, energy sources, waste and environmental impacts
• What is mostly produced from limited raw materials?

  Metals, glass, building materials, clay ceramics and plastics
• Where does most energy for processes come from?

  Limited resources