Hydrosphere

• Pumping

  • First step in water treatment
  • Abstraction for water supply
• Screens

  • Second step in water treatment
  • Removes floating vegetation, plastic and paper
  • Water flows through metal grills or meshes
• Aeration

  • 3rd step in water treatment
  • Remove unpleasant tastes and odours
  • Air bubbled through water in a tank
• Flocculation

  • Fourth step in water treatment
  • Removes colloids, e.g. clay, as too small to settle out
  • Coagulant added, e.g. alum
• Sedimentation

  • 5th step in water treatment
  • Allows flocs to settle out
  • Water enters a setting tank, suspended solids settle out and water is carefully siphoned off
• Filtration

  • 6th step in water treatment
  • Filters out fine grained organic and inorganic material
  • Passed through sand beds underlined with gravel which traps particles
• Activated carbon treatment

  • 7th step in water treatment
  • Removes organic compounds
  • Water is passed over charcoal which has a very high SA and absorption capacity
• Sterilisation

  • 8th step in water treatment
  • Kills pathogens
  • Chlorine added and has high oxidising capacity penetrating pathogen cell wall. Ozone and UV also added
• pH adjustment

  • 9th step in water treatment
  • Reduces alkalinity or acidity
  • Lime is added to reduce acidity
• Ion exchange (in some areas)

  • 10th step in water treatment
  • Removes toxins such as lead, Mercury or arsenic
  • Toxic ions absorb onto polymer beds or particles of zeolite
• Fluoridation (in some areas)

  • Final step of water treatment before water is sent to customers
  • Fluorides added to water
  • To improve dental health