What are the 3 main sources of waste water?

  1. Households (domestic).
  2. Agriculture.
  3. Industrial processes.

Answer in your head, out loud, or on paper, then tap the card to flip.

What 2 things must be removed from sewage and agricultural waste water?

  1. Organic matter.
  2. Harmful microbes.

Answer in your head, out loud, or on paper, then tap the card to flip.

Why does water from industrial processes require additional treatment?

It may contain harmful chemicals that were formed during the industrial chemical reactions.

Answer in your head, out loud, or on paper, then tap the card to flip.

Outline the steps in the treatment of sewage.

  1. Screening - the sewage is passed through gratings and meshes to remove anything large.
  2. Sedimentation - the sewage is left to sit in a settlement tank, so that the heavier particles settle at the bottom as sludge, while the lighter particles settle at the top as effluent. 
  3. Aerobic digestion - air is pumped through the effluent to supply the bacteria with oxygen.
  4. Anaerobic digestion - the sludge is sealed in a container to prevent the entry of air, which ensures anaerobic respiration.

Answer in your head, out loud, or on paper, then tap the card to flip.

After sewage treatment, what can the products of the anaerobic digestion process be used for?

The methane (gas) can be burned as an energy source.


The sludge can be used as a fertiliser.

Answer in your head, out loud, or on paper, then tap the card to flip.