10.2 Potable Water

• What is potable water?

  Water that is safe to drink
• How can we obtain potable water?

  By treating fresh water sources or desalinating seawater
• What does it mean for water to be pure in chemistry?

  It must contain only H2O molecules
• What makes potable water impure?

  It often contains other dissolved substances
• 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
• Why is pH important for potable water?

  It ensures the water is not too acidic or alkaline
• What types of water sources are generally used for potable water?

  Freshwater sources and desalinated seawater
• What is fresh water?

  Water that doesn't have much dissolved in it
• How does the UK obtain its fresh water?

  From rain, which collects as surface water or groundwater
• What are surface water sources?

  Lakes, rivers, and reservoirs
• What are groundwater sources?

  Water found under the ground, like aquifers
• What is the benefit of using surface water?

  It is easy to access and gets replaced frequently by rain
• What is a disadvantage of using surface water?

  It can dry up if it's hot and sunny
• What is the first step in treating fresh water?

  Passing it through a wire mesh to filter out large particles
• What is the second step in treating fresh water?

  Passing it through a bed of sand and gravel
• What is the final step in treating fresh water?

  Sterilizing it to kill harmful microbes
• What are the three methods of sterilizing water?

  Bubbling chlorine gas, exposing to ozone, or ultraviolet light
• Why do some countries rely on desalination?

  They have limited supplies of fresh water
• 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
• How does distillation work in desalination?

  It involves boiling salty water and collecting the water vapor
• What happens in reverse osmosis?

  Salty water is passed through a membrane that allows only water molecules to pass
• What is the result of both desalination techniques?

  Pure distilled water
• What are the steps involved in treating fresh water to make it potable?

  1. Pass through a wire mesh to filter 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 desalination for potable water?

  Advantages:

  • Provides a source of water in arid regions
  • Utilizes abundant seawater

  
  

  Disadvantages:

  • High energy requirements
  • Expensive processes
• What are the sources of fresh water used for potable water?

  • Surface water: lakes, rivers, reservoirs
  • Groundwater: aquifers