C10

• Life cycle assessment stages

  1. Extracting and processing the raw materials

  2. Manufacturing and packaging the product

  3. Using the product

  4. Disposing of the product
• When extracting resources from nature, the local environment can be directly damaged, e.g., cutting down forests or digging mines
• Processing materials can indirectly damage the environment due to energy requirements and release of pollutants
• Main problems during manufacturing and packaging include energy use, release of pollution, and production of waste products
• Impact of using a product is determined by the damage during its lifetime and how long it is used for
• Disposal methods like landfill or incineration have environmental consequences
• Raw materials for plastic bags

  • Crude oil
• Raw materials for paper bags

  • Wood from trees
• Plastic bags are made from crude oil, while paper bags are made from wood
• Plastic bags can be reused multiple times, while paper bags are usually single-use
• Plastic bags are not biodegradable, taking up space in landfills and harming wildlife, while paper bags are biodegradable and non-toxic
• Limitations of life cycle assessments include the complexity of quantifying all steps and the potential for manipulation to support specific companies
• Potable water

  Water that is safe to drink
• How to get potable water

  1. Treating fresh water sources

  2. Desalinating seawater
• Pure water in chemistry

  Contains only H2O molecules
• Portable water often contains other dissolved substances which makes it impure
• Criteria for water to be considered potable

  • Levels of dissolved substances need to be fairly low
  • pH between 6.5 and 8.5
  • No microorganisms like bacteria or fungi present
• Most countries have a good supply of fresh water, either surface water or ground water
• Surface water sources


  • Lakes
  • Rivers
  • Reservoirs
• Groundwater sources

  • Aquifers
• Benefit of using surface water

  Easy to access and gets replaced frequently by rain
• Challenge of using surface water

  Can dry up in hot and sunny conditions
• Treating fresh water

  1. Filtering through wire mesh

  2. Filtering through sand and gravel

  3. Sterilizing to kill harmful microbes like bacteria
• Methods to sterilize water

  • Bubbling chlorine gas
  • Exposing to ozone
  • Exposing to ultraviolet light
• In some countries like those in the Middle East, desalination is used due to lack of fresh water supply
• Desalination techniques

  • Distillation
  • Reverse osmosis
• Distillation and reverse osmosis techniques for desalination require a lot of energy and are expensive
• Distillation desalination process


  Boiling large quantities of salty water, collecting water vapor, and condensing it to get pure distilled water
• Reverse osmosis desalination process


  Passing salty water through a membrane that only allows water molecules to pass through, trapping ions and larger molecules to separate them from water
• 1. First, pass the water through a wire mesh. This will filter out any large objects like plastic bottles or leaves.
  2. Second, pass the water through a bed of sand and gravel. This will filter out smaller things like bits of rock.
  3. Lastly, sterilise the water to kill any microorganisms. There are three different ways to do this: 1) bubbling chlorine gas through it, 2) exposing it to ozone, 3) exposing it to ultraviolet radiation. 
• Wastewater treatment

  1. Screening

  2. Sedimentation

  3. Biological breakdown by microorganisms
• Three main sources of wastewater

  • Domestic
  • Agricultural
  • Industrial
• Domestic waste

  Refers to household waste like water from showers, sinks, and toilets
• Domestic waste goes into sewers and heads for sewage treatment plants
• Agricultural wastewater includes nutrient runoff from fields and animal waste from farms
• Industrial wastewater comes from factories that make and use chemicals
• All wastewater needs to be treated to make it safe before disposal
• Sewage treatment

  1. Screening

  2. Sedimentation

  3. Biological breakdown by microorganisms
• Screening involves removing large items like twigs or plastic bottles
• Sedimentation allows solid bits to sink to the bottom forming sludge and separates the effluent at the top