waste water treatment

• What is potable water?

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

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

  Personal hygiene, flushing toilets, washing clothes, and agriculture
• What does wastewater contain that makes it necessary to treat?

  Organic molecules and harmful microorganisms
• What is the first stage of wastewater treatment?

  Sewage is screened by passing through a mesh
• What is produced after sewage settles in sedimentation tanks?

  A liquid effluent and semi-solid sludge
• What happens to the sludge in wastewater treatment?

  It is taken away and digested by anaerobic bacteria
• What do anaerobic bacteria produce during the digestion of sludge?

  Biogas
• How can biogas produced from sludge be used?

  It can be burned for electricity
• What must be done to the liquid effluent before it is discharged into the environment?

  Reduce organic molecules and harmful microorganisms
• How are aerobic bacteria involved in wastewater treatment?

  They digest organic molecules and harmful microorganisms in the presence of oxygen
• Where can liquid effluent be safely discharged after treatment?

  Into nearby rivers or the sea
• How is treated sewage used in some parts of the world?

  To produce potable water directly
• What is the first step in treating industrial wastewater?

  Removing harmful chemicals
• Why is groundwater from aquifers the easiest source for producing potable water?

  It is usually safe to drink once 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
• What are the steps involved in wastewater treatment?

  1. Screening sewage through a mesh
  2. Settling in sedimentation tanks
  3. Digestion of sludge by anaerobic bacteria
  4. Aeration to promote aerobic bacteria
  5. Discharging treated liquid effluent into rivers or the sea
• Compare the sources of potable water: groundwater, salt water, and wastewater.

  • Groundwater: Usually safe after chlorine treatment, but can be polluted.
  • Salt water: Requires desalination, which is energy-intensive and costly.
  • Wastewater: Can be treated to produce potable water, but involves many purification steps.
• What are the main uses of water in human activities?

  • Personal hygiene (baths, showers)
  • Flushing toilets
  • Washing clothes
  • Agriculture