One of the steps in making lake water clean and pure is called filtration. How does it work? Try this.
You will need
- a paper towel
- scissors
- a funnel
- clean sand (from the beach or the sandbox)
- 2 clear glasses or jars
- a spoon
- water
- dirt from the back yard
- Cut a circle from the paper towel. Fold it in half, then in half again.
- Open the folded circle a little to make a paper cone.
- Put the cone inside the funnel and set the funnel in one of the glasses or jars.
- Fill the cone with clean sand.
- Fill the other jar with water. Add 3 or 4 spoonfuls of dirt to the water and stir it.
- Slowly pour the muddy water into the sand in the funnel.
- Look at the water coming out of the funnel.
The funnel filled with sand is a filter. What happened to the dirt as the muddy water passed through the filter? Is the water in the bottom jar clear? Or is it still a little bit muddy? If it still looks muddy, the dirt particles were small enough to pass through the spaces between the sand in the filter.
That's why more than one kind of filtration is used at the water treatment plant. Do you think your sand filter would remove germs from the water? (Hint: how big are germs?)
(Copyright © Monroe County Water Authority)
