Using resources

• How can we obtain potable water?

  By treating fresh water sources or desalinating seawater
• What are the three criteria for water to be considered potable?

  Low levels of dissolved substances, pH between 6.5 and 8.5, and no microorganisms
• What is fresh water?

  Water that doesn't have much dissolved in it
• What are groundwater sources?

  Water found under the ground, like aquifers
• What are surface water sources?

  Lakes, rivers, and reservoirs
• What is desalination?

  A technique used to extract potable water from seawater
• What are the two main techniques used for desalination?

  Distillation and reverse osmosis
• What is the main challenge of desalination techniques?

  They require a lot of energy and are expensive
• What happens in reverse osmosis?

  Salty water is passed through a membrane that allows only water molecules to pass
• How does distillation work in desalination?

  By boiling salty water and collecting the water vapor
• What are the steps involved in treating fresh water to make it potable?

  1. Pass through a wire mesh to filter out large particles
  2. Pass through a bed of sand and gravel to filter smaller solids
  3. Sterilize to kill harmful microbes
• What are the advantages and disadvantages of using surface water versus groundwater?

  Advantages of surface water:

  • Easy to access
  • Frequently replenished by rain

  
  

  Disadvantages of surface water:

  • Can dry up in hot weather

  
  

  Advantages of groundwater:

  • Less affected by weather conditions

  
  

  Disadvantages of groundwater:

  • More difficult to access
• What are the methods of sterilizing water and their purposes?

  Methods:

  • Bubbling chlorine gas: Kills bacteria
  • Exposing to ozone: Kills microorganisms
  • Ultraviolet light: Disinfects water
• What are the two main purposes of treating wastewater?

  To reuse it or safely return it to natural water sources
• What are the three main sources of wastewater?

  • Domestic
  • Agricultural
  • Industrial
• Where does domestic wastewater go after being flushed?

  It goes into the sewers and heads for sewage treatment plants
• What type of wastewater is produced by agriculture?

  Nutrient runoff from fields and animal waste from farms
• What do industrial sources of wastewater typically include?

  Waste from factories that make and use chemicals
• What is generally required for treating domestic and agricultural sewage?

  Removing organic matter and harmful microbes
• What are the three main steps in sewage treatment?

  1. Screening to remove large objects
  2. Sedimentation to separate sludge and effluent
  3. Biological breakdown of organic matter
• What additional steps are needed for industrial wastewater treatment?

  Extra steps to remove harmful chemicals
• What conditions are maintained in the effluent tank during biological breakdown?

  Aerobic conditions with oxygen supplied
• What conditions are maintained in the sludge tank during biological breakdown?

  Anaerobic conditions with little or no oxygen
• What is the result of anaerobic digestion in the sludge tank?

  Methane is produced, which can be captured for energy
• What can the remaining digested waste from the sludge be used for?

  As a fertilizer rich in nutrients
• Why is it important to treat wastewater before disposal?

  To prevent environmental pollution and protect public health
• What additional stages may be required for wastewater containing toxic substances?

  Adding chemicals to precipitate metals or using ultraviolet radiation
• How does treating wastewater compare to desalinating salt water?

  Treating wastewater requires less effort than desalinating salt water
• Why do some countries rely on treating wastewater for drinking supplies?

  Because they have a limited water supply
• What are the four main stages of a life cycle assessment?

  1. Extracting and processing raw materials
  2. Manufacturing and packaging the product
  3. Using the product
  4. Disposing of the product
• How does extracting resources from nature impact the environment?

  It often directly damages the local environment, such as cutting down forests or mining.
• What are some indirect environmental damages caused by processing materials?

  Processing materials can require huge amounts of energy and release pollutants.
• What are the three main problems associated with manufacturing and packaging?

  The problems are energy use, pollution release, and production of waste products.
• What can happen to waste products from manufacturing?

  They can sometimes be used as raw materials, but usually they are useless and need disposal.
• What two factors should be considered when assessing the impact of using a product?

  How much damage it does during its lifetime and how long the product is used for.
• What are the consequences of disposing of a product in landfill?

  It takes up space that could be used for nature and chemicals might seep into ecosystems.
• What happens if waste products are burned?

  They might release pollutants into the atmosphere.
• What is the raw material for plastic bags?

  Crude oil, which is a finite resource.
• How are paper bags made?

  They are made from wood, which reduces habitat for animals and plants.
• What is required for manufacturing plastic bags?

  Hydrocarbons from fractional distillation need to be cracked to make alkenes, which undergo polymerization.