Purification of Water

• Process:

  1. Water pumped into screens to remove solid insoluble impurities
  2. Aluminum sulfate added to make small clay pieces stick together and are then removed
  3. Water filtered through sand and gravel to remove larger, insoluble debris
  4. Water encounters flocculants and is filtered through coarse sand. 
  5. Chlorine gas bubbled into water to kill bacteria
• The acidic effect of chlorine gas on the water is reversed by adding an alkali, sodium hydroxide
• flocculants are chemicals that make particles sink to the bottom of water
• Some countries add fluoride to water to reduce tooth decay