topic 10

• Potable water

  • water safe to drink
• Method to produce potable water

  • appropriate fresh water source
  • water passed through filter beds
  • water is then sterilized to kill microbes
  • if sea water, desalination is required
• desalination

  • can be done by distillation
  • or can be done using processes with membranes ( reverse osmosis )
  • both very expensive
• Quality water production

  • screening
  • sedimentation
  • anaerobic digestion of sludge
  • aerobic respiration of effluence
  • water sterilised with chlorine to kill any microbes left
• Phyto mining

  • uses plants to absorb metal compounds
  • plants are harvested and then burned to produce ash with metal compounds in
• Bioleaching

  • uses bacteria to produce leachate solutions that contain metal compounds
• What is potable water?

  Water that is safe to drink
• Why is potable water treated?

  To ensure it is safe for drinking
• What pH range is considered safe for potable water?

  6.5 to 8.5
• What is the significance of dissolved salts in potable water?

  They should not be too high
• How does the source of potable water vary by location?

  It depends on local conditions
• What is the primary source of potable water in temperate areas?

  Surface water from lakes and rivers
• Why is groundwater usually purer than surface water?

  It is filtered through rock
• What happens to water during the treatment process?

  It is filtered and sterilized
• What is the first step in the potable water treatment process?

  Screening to remove large debris
• How is sterilization achieved in water treatment?

  By using chlorine gas or UV light
• What is desalination?

  Treating seawater to make it potable
• What is the purpose of distillation in water treatment?

  To remove dissolved salts from water
• How can you test for sodium ions in water?

  By performing a flame test
• What indicates the presence of chloride ions in water?

  A white precipitate forms with silver nitrate
• What happens during the distillation process?

  Water boils and leaves dissolved salts behind
• What is reverse osmosis?

  A membrane process to purify water
• Why are distillation and reverse osmosis expensive?

  They require a lot of energy
• What is waste water?

  Water that has been used and contaminated
• What are common sources of waste water?

  Household drains, agriculture, and industry
• What is sewage?

  Waste water containing organic waste
• Why must sewage be treated?

  To remove organic waste and harmful microbes
• What are the stages of sewage treatment?

  Screening, primary treatment, secondary treatment
• What happens during primary treatment of sewage?

  Solid sediments settle to produce liquid effluent
• What is the role of aerobic bacteria in sewage treatment?

  They break down organic matter in water
• What is anaerobic digestion?

  Breaking down organic matter without oxygen
• What is produced during anaerobic digestion?

  Methane gas (biogas)
• What additional treatments may be needed for toxic waste water?

  Chemicals, UV radiation, or membranes
• Why is recycling waste water important?

  To prevent pollution and reuse water
• What is the Haber process used for?

  To produce ammonia from nitrogen and hydrogen
• What is the significance of NPK fertilizers?

  They provide essential elements for plant growth
• What are the sources of phosphate and potassium for fertilizers?

  Mined compounds
• Why is recycling important for sustainability?

  It reduces the use of finite resources
• What is sustainable development?

  Development that meets present needs without harming future generations
• How can chemists improve sustainability?

  By developing processes that use fewer resources