waste water treatment

• what is the first step of treating water waste

  the sewage is screened by passing through a mesh which removes solids and pieces of grit
• what is the second step of treating water waste

  now the sewage can settle in large sedimentation tanks, this produces a liquid efficient and a semi solid sludge which sinks
• what is the third step of treating water waste

  the sludge is taken away and digested by anaerobic bacteria, in the absence of oxygen these bacteria produce biogas which can be turned into electricity
• what is the fourth step of treating biogas

  the digested sludge can be used as fertilisers for farming
• what is the easiest way to produce potable water

  use ground water from aquifiers, safe to drink once treated with chlorine
• what are some issues with aquifiers

  can sometimes be polluted eg fertilisers from farms
• we can make potable water directly from waste water such as sewage, what are the negatives of this

  1. takes many purification steps so its only done in places where water is scarce
• salt water needs to be desalinated so its potable, what are the negatives

  1. requires lots of energy
  2. expensive