potable water

• Why do we need to drink water?

  To stay alive
• What does it mean for water to be potable?

  It is safe for human consumption
• Why do we treat water to make it potable?

  To reduce harmful substances dissolved in it
• What must be drastically reduced to make water potable?

  The number of microbes
• What is required to reduce the concentrations of dissolved minerals and salts in water?

  They must be reduced, not completely eradicated
• Does potable water have to be chemically pure?

  No, it does not
• What are the sources of potable water?

  • Fresh water
  • Seawater
  • Waste water
• What is the treatment process for fresh water?

  It only needs filtering and sterilising
• Why is seawater the most expensive source to treat?

  Due to the large energy needed for desalination
• How does the energy requirement for treating waste water compare to seawater?

  Less energy is used for waste water treatment
• What are the steps involved in treating waste water?

  • Collection of waste water
  • Preliminary treatment (screening and grit removal)
  • Primary treatment (sedimentation)
  • Secondary treatment (biological processes)
  • Tertiary treatment (filtration and disinfection)