1. Further treatment of water

2. Further treatment of water: chlorination Chlorination Chlorine is added into water Small portion is enough to kill micro- organisms Distillation needs high cost $$$$ Chlorine can kill micro-organisms in water. Chlorine is a chemical. It has a strange smell. It is used in swimming pool.

3. Further treatment of water: fluoridation Food remains in mouth Bacteria grows and produce acids Acids attack teeth Tooth decay

4. Further treatment of water: fluoridation Fluoride protects teeth Fluoridation Fluoride is added to drinking water We drink fluoride in water Prevent teeth decay

5. Fluoride is added into water to protect our teeth but some people do not agree. Do you? Further treatment of water: fluoridation