W17 Making drinking water safe

HygieneWater Supply

Obtaining safe drinking water is a struggle for many people. The microbes that spread diarrhoea are often found in dirty water. Water becomes dirty in many ways. It may contain faeces and urine, soap from washing or chemicals from industry. Dirty water can be used for washing clothes. However, if we drink or cook with dirty water, we can become ill. Let muddy water settle for a day and then pour off the clearest water into a clean container. Repeat this a day later. This will produce clearer water that can be made safe for drinking in several ways.

We can boil the water for a few minutes if we have enough fuel. We can add chemicals such as chlorine bleach, being very careful to follow the instructions on the bottle. We can make and use a sand filter.

Another easy way is to use the sun’s energy. Collect some clean, clear large plastic bottles that are not too scratched. Fill each bottle 34 full and shake it for 20 seconds to add oxygen. This will help kill microbes in the water. Then fill to the top with more water. Place the bottles on their side in full sun for at least six hours on a roof, table or bench. If possible place them on a piece of black plastic or cloth. Cool the bottles. Keep the lids on until needed to keep the water safe to drink. If the weather is cloudy, there may not be enough sun and the method will not work.


  • Where do people in our community go to collect their water during the wet season and during the dry season?
  • When safe drinking water is hard to get, people often drink unsafe, dirty water. How can we try to improve this situation in our community?
  • How many homes in our area collect rainwater from their roofs at present? What reasons stop people doing this? What are the best ways of collecting and storing this rainwater?
  • Boiling water or adding chlorine makes water safe to drink. However, it can change its taste. Too much chlorine will make the water taste bad but the right amount should give a good taste. Have people tried these methods? How does the water taste?
  • Do people have any experience of making and using sand filters?
  • If moringa trees grow in our area, the ripe seeds can be ground into a paste and stirred into a bucket of water. This helps to make water safer to drink. Does anyone have any experience of using moringa in this way?
  • Using the sun’s energy to clean water is very easy to do. Do people have any experience of using this method? (It is often known as SODIS.)
  • Shaking the bottle for 20 seconds is very important to make sure the microbes are removed by the action of the sun and oxygen in the water. Can people think of easy ways to count to 20 seconds? (For example, by counting out loud ‘one second’, ‘two seconds’ up to 20 seconds.)
  • Could you put together a simple role-play to teach people about how to use the sun to make drinking water safe?
  • Who could we ask to find out more about making water safe to drink?