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Grades 8–10 Intermediate About 20 min Version 1 Awaiting review Premium

Making muddy river water safe to drink

River and pond water can contain mud, sand and invisible germs such as bacteria. Water can look perfectly clear and still make people ill. Purifying water usually takes several steps. Letting it stand (sedimentation) lets heavy mud settle. Filtering removes smaller particles. Finally, disinfection kills germs: boiling the water, or adding chlorine, are common ways to do this.

What you will learn

  • Describe the steps used to purify water.
  • Explain why clear water is not necessarily safe to drink.
  • Compare boiling and chlorination as methods of disinfection.

Before you start

  • Know about sedimentation and filtration. Try "Sedimentation and decantation" and "Filtration: cleaning muddy water" first.

Materials

  • Muddy river water
  • Chlorine tablet

Equipment

  • Beakers
  • Conical flask with funnel and filter paper
  • Hot plate

Procedure

  1. Beaker A holds freshly stirred muddy river water. Leave it to settle.
  2. Filter the settled water into Flask B.
  3. Pour the filtered water into Beaker C and boil it for 5 minutes, or into Beaker D and add a chlorine tablet, then wait 30 minutes.

How this simulation is simplified

  • Germs cannot be seen; the simulation tells you when they are present.
  • Settling time is shortened. Boiling for 5 minutes or 30 minutes with chlorine kills all the germs in this model.