Waste Water Treatment

• Where can waste water come from?

  Households, industries, agriculture, it then goes into sewers towards sewage treatment plants.
• What two processes does waste water first undergo in order to be treated?

  1. Screening - large bits of material is removed - twigs, plastic bags.
  2. Sedimentation - where heavier suspended solids sink to the bottom to produce sludge while lighter effluents stay at the top in a settlement tank.
• What happens to the effluent after sedimentation?

  The effluent is removed from the settlement tank and undergoes aerobic digestion - air is pumped through the water to encourage aerobic bacteria to break down organis water (microbes) in the water. After this, it is released back into the environment where it can undergo filtration and sterilisation before use.
• What happens to sludge after sedimentation?


  Removed from the settlement tank to get broken down by bacteria through anaerobic digestion. This is where organic matter is broken down in the sludge, releasing methane gas in the process, which can be used as an energy source. The remaining waste can be used as a fertilizer.
• Where is methane gas released and what can it be used for?


  Released during anaerobic digestion of sludge during waste water treatement. Can be used as an energy source.
• What is anaerobic digestion?


  Process of breaking down organic matter in the absence of oxygen to produce biogas (methane) and fertilizers during waste water treatment.
• What is aerobic digestion in waste water treatment?


  Where air is pumped through the effluent after sedimentation to encourage aerobic bacteria to break down any organic matter.