Waste water treatment

• What is the process called that converts sea water into potable water?

  Desalination
• Why is it preferable to make potable water from fresh water reserves rather than from sea water?


  Because removing sodium chloride from sea water requires a lot of energy
• How much sodium chloride is present in every kilogram of sea water?


  35 grams
• What are the two main methods of desalination?

  • Distillation
  • Reverse osmosis
• What is the process of distillation in desalination?


  1. Sea water is heated until it boils.
  2. Salt remains in the liquid.
  3. Steam is collected and cooled to condense into pure water.
• What are the energy requirements of the distillation process?


  It requires a lot of energy to boil the water and to cool the steam
• What is a significant environmental concern associated with distillation?


  The waste water is very salty and can harm marine ecosystems
• How does reverse osmosis work in desalination?


  1. Water is put under high pressure.
  2. It passes through a membrane with tiny pores.
  3. The pores allow water molecules through but prevent most ions and molecules.
• What are the drawbacks of reverse osmosis?


  It requires expensive membranes and produces a large volume of waste water
• How does the efficiency of reverse osmosis compare to other desalination methods?


  Its efficiency is often quite low compared to other methods
• What is the correlation mentioned in the study material regarding global population and copper demand?


  • Increase in global population
  • Increase in demand for copper