How can we make clean water?

People need water to survive and yet 1.1 billion people in the world do not have access to safe, clean drinking water. Finding ways to clean water is important as dirty water can cause health problems. Filtration is a cleaning method that is used by water companies worldwide and is also a natural process that occurs when water seeps through materials, such as bunter sandstone and rocks, in the ground.

Use sand and rocks to create your own water filter. You will need some other materials to help.

Things you will need A 2 litre plastic water or pop bottle 300 g of fine sand 330 g of coarse sand 100 g of small stones or pebbles 1 coffee filter 1 rubber band 1 kitchen knife 1 ruler 1.5 litres of dirty water

Instructions 1. Use the knife to cut the water bottle in half. You will need both halves. 2. Take the top half of the bottle and remove the bottle cap. 3. Attach the coffee filter to the outside of the bottle neck using the elastic band. 3. Turn the bottle upside down. 3. First add a layer of compacted sand. 4. Second add a layer of coarse sand or gravel. 5. Third add a layer of pebbles. 6. Insert this filled half of the bottle, neck first, into the bottom half of the bottle. The top bottle is the filter and lower bottle is the water collector.

Water bottle top Small stones or pebbles Coarse sand Fine sand Coffee filter Water bottle bottom Elastic bando Dirty water Clean water

Pour muddy water into the top of the upturned bottle and see how the filter bed helps the water to come clearer and less dirty.

Which water would you prefer to use, the muddy water or the clear water?

How would you and your family cope if the water to your home was shut off tonight? Imagine you can only obtain water by walking to school (or the local police station) and collecting it. What would that be like? How often would you need to collect the water? If the source of water was not clean, how much would you need to filter before washing or cooking or drinking? How long would this take?

1 in every 6 people in the world doesn’t have access to safe water. Ask 1 in every 6 pupils to stand in a group to show this. Discuss – Do pupils think this is fair? Do pupils know why this is?

FURTHER HELPFUL WEB RESOURCES: Where our local water supplies come from across the UK amusing video and downloadable posters starring Kriss Akabusi on how to conserve water by taking shorter showers! Links to – 4 Minute urgency Pirate Scientists