waste water treatment

• pollutants in waste water:

  • human waste contains harmful bacteria and high levels of nitrogen which can harm aqautic ecosystems
  • industrial waste water can contain toxic metal compounds
  • agricultural waste water can contain fertilisers
• treating waste water:

  • sewage from homes or businesses cleaned
  • water parts through large screens and grit removal to remove large particles
  • sedimentation allows large particles to settle to bottom
  • effluent and sewage sludge produced
  • sewage sludge anaerobically digested by specific bacteria so harmful organic matter reduced
  • used as fertiiliser - has minerals for plants
  • effluent aerobically digested so any solid particles broken down
  • water sterilised so bacteria killed
• treating fresh water:

  • fresh water from rivers or lakes used
  • water passes through large screens and grit removal to remove large particles
  • water passes through filter beds so undissolved solids removed
  • water sterilised so bacteria killed
  • done by ozone, ultraviolet light, chlorine