Waste water treatment

• Aquifers can sometimes be polluted and need careful testing before use
• Biogas produced by anaerobic bacteria can be burned for electricity
• Desalination of saltwater is required to produce potable water
• Treated water can be discharged into nearby rivers or the sea
• Uses of water

  • Personal hygiene (baths, showers)
  • Flushing toilets
  • Washing clothes
  • Agriculture
• Producing potable water directly from wastewater such as sewage requires many purification steps
• Digested sludge can be used as fertilizers for farming
• Wastewater must be carefully treated before being released back into the environment
• Air is bubbled through liquid effluent to allow aerobic bacteria to digest organic molecules and harmful microorganisms
• In some parts of the world, treated sewage is used directly to produce potable water
• Humans use a great deal of water, with only a small percentage used for drinking
• Desalination requires a lot of energy and is expensive
• Wastewater treatment

  1. Screening to remove solids and grit

  2. Settling in sedimentation tanks to produce liquid effluent and semi-solid sludge

  3. Anaerobic digestion of sludge by bacteria to produce biogas

  4. Aerobic digestion of liquid effluent by bacteria in the presence of oxygen

  5. Discharge of treated liquid effluent into nearby rivers or the sea
• Wastewater contains a large amount of organic molecules and harmful microorganisms
• Sludge is digested by anaerobic bacteria to produce biogas
• Screening of sewage removes solids and grit
• Industrial wastewater needs to have harmful chemicals removed before general sewage treatment
• Groundwater from aquifers is usually safe to drink after treatment with chlorine
• Sedimentation tanks produce liquid effluent and semi-solid sludge