Waste Water Treatment

• What should you be able to describe by the end of the video?

  How wastewater is treated
• What is potable water?

  Water that is safe to drink
• What percentage of water is used for drinking?

  A small percentage
• What are some uses of water besides drinking?

  Personal hygiene, flushing toilets, washing clothes
• What does wastewater contain a large amount of?

  Organic molecules
• Why must wastewater be treated before release?

  To remove harmful microorganisms and organic molecules
• What is the first stage of wastewater treatment?

  Sewage is screened through a mesh
• What happens to sewage after screening?

  It settles in large sedimentation tanks
• What is produced after sewage settles in sedimentation tanks?

  Liquid effluent and semi-solid sludge
• What happens to the sludge after sedimentation?

  It is taken away and digested by anaerobic bacteria
• What do anaerobic bacteria produce from undigested sludge?

  Biogas
• How can biogas be used?

  It can be burned for electricity
• What can the digested sludge be used for?

  Fertilizers for farming
• What needs to be reduced in the liquid effluent before discharge?

  Organic molecules and harmful microorganisms
• What is done to the liquid effluent to aid treatment?

  Air is bubbled through it
• What do aerobic bacteria do in the treatment process?

  They digest organic molecules and harmful microorganisms
• Where can the treated liquid effluent be safely discharged?

  Into nearby rivers or the sea
• What is a common industrial use of water?

  Making paper and chemicals
• What must be removed from industrial wastewater before treatment?

  Harmful chemicals
• What is done after harmful chemicals are removed from industrial wastewater?

  It enters general sewage treatment
• Is treated sewage used to produce potable water in the UK?

  No, it is not carried out
• What is the easiest way to produce potable water?

  Using groundwater from aquifers
• What must be done to groundwater from aquifers before drinking?

  It needs to be treated with chlorine
• What can pollute aquifers?

  Fertilizers from farms
• What is required to produce potable water from salt water?

  Desalination
• What is a drawback of desalination?

  It requires a lot of energy and is expensive
• Where can you find questions on wastewater treatment?

  In the vision workbook
• What should you be able to compare regarding potable water production?

  Groundwater sources, salt water, and wastewater
• How does the treatment of wastewater differ from groundwater treatment?

  Wastewater requires more purification steps
• Why is wastewater treatment important for the environment?

  It prevents harmful substances from entering ecosystems