Filtering Water

Warm-up: Water in Your Life

1. Begin this lesson by discussing with your class the importance of water in our daily lives. Have your students brainstorm how many times today they have used water, and write their answers on the board.

a. Examples: drinking, flushing the toilet, taking a bath or shower, brushing teeth, watering yard or garden, washing dishes, filling a pet’s water dish or fishtank, cleaning, doing laundry, swimming, fishing, etc.


Activity One: Water, Water, Everywhere?

1. Lead students in a discussion about the overall scarcity of clean water on our planet, and the impact this has on humans around the world:

a) Although Earth is covered with water (over 70% of Earth’s surface), only about 3% of the water on our planet is not saltwater. Of this tiny amount of freshwater, much is locked up in ice and glaciers, and of the remainder, less and less is available to humans because of rising populations and increased pollution.

b)  What are some sources of water pollution? Oil spills, bacteria and other organisms, toxic chemicals, litter, run-off from city streets, industrial waste, human waste, agricultural waste, etc.

c) In the United States, we are lucky to have sources of freshwater, and sanitation facilities and water treatment plants to clean our water. We are also lucky that most of us have running water in our homes, schools and other buildings, and we can access clean water any time of day.

d) What would you do if you turned on your faucet at home, and no water came out? Where would you find water? Think of nearby bodies of water in your area. Is there a stream or river? A lake? The ocean?

e) What do these places look like? Could you drink the water? Cook with it? Bathe with it? Feed your pet?

f)  Many people around the world do not have running water in their homes, or even access to clean water. They must gather water from sources near their homes such as communal wells, sewers, rivers, streams, ponds, lakes or swamps. What do you think they find in this water? Fish, plants and other wildlife, trash, wastes, chemicals etc.

g) Depending on where they live, there could be all kinds of things in their water.


Activity Two: Water Pollution Collage

1. This discussion should have gotten students thinking about water sources near their homes. Take this further by defining a watershed for your students. Also known as catchment basins, these areas of land are defined by the flow patterns of rainwater or melting snow and ice; a geographic area where all water, sediments, and dissolved materials drain to a common outlet (stream, river system, reservoir, underground aquifer, or other body of water).

2. To further explain this concept, have students imagine: If a huge giant were to pour an imaginary pitcher of water over your landscape, how would the water flow? What areas would it run over and where would it drain?

3. Encourage your students to think about what their watershed might include? Does the water in your area likely come from glacial melting? Rainfall? Rivers? Streams?

4. What other people, animals, towns, industries, farms, etc. might share your water source? How might each of these contribute to the pollution of the watershed? Remember, water runs from higher elevation to lower (upstream to downstream). Where does your watershed start?

5. To take this further, visit the EPA Surf Your Watershed website: (Put this on a projector so the class can see.) Type in the school’s zip code to see your local watershed. Use the resulting information to answer the questions above. Think about water sources as well as sources of pollution. (There is a range of information on this site – feel free to go as in-depth as you wish.)

6. Pass out paper, pencils, markers, etc. and magazines.

7. Based on the discussion above, have students draw the water source near their home or school. Using magazine pictures or drawing, have them add the things that might be in the water. Think about plants and wildlife, human uses (boating, fishing, etc.), and nearby sources of pollution (roadways, factories, farms, landfills, runoff, litter, etc.). Tell them that it does not need to be drawn to scale, and they should think of tiny or invisible things in the water as well (bacteria, oil, chemicals, etc.). Encourage creativity!

8. If you have time, have your students share and discuss their collages.


Activity Three: Water Filter Activity

1. Break students into small groups, and pass out Reproducible #1 – Water Filter Procedure (one for each student, or one for each lab group) and Reproducible #2 – Water Filter Lab Worksheet (one for each student). Distribute lab supplies to each station (2-liter soda bottle pre-cut in half, filtration materials, “pollution” materials).

2. Have students think about the types of pollution they included in their collage. How could they represent these with the materials provided?

3. Have each group follow the procedure outlined in Reproducible #1 – Water Filter Procedure and answer the questions in Reproducible #2 – Water Filter Lab Worksheet.

4. Clean up.


Wrap Up: Water Filter Discussion

1. Have your students imagine again that they have no running water and no water treatment facilities, and they must collect water from sources near their homes. What might this water look like, taste like, smell like, etc. Would they like to use this water for drinking, cleaning, cooking, etc.?

2.  Based on the water filter activity, how would they design a water filter to clean the water they would be using?

a. What pollutants would they need to filter out?

b. What materials would they use to filter each kind of pollutant?

c. Are there any pollutants that they were not able to filter out with their hand-made filters?

d. Even if the water looked clean, is it possible that the water was still undrinkable?

e.  How might they remove contaminants from the water that cannot be filtered out?

f.  Would they feel safe and comfortable using and drinking the water after using a homemade filter? Would they get sick?

3. Think about microscopic organisms that are too tiny to see and possibly too small to filter. Also, think about contaminants that are dissolved in the water and thus would be difficult to filter.  How do water treatment plants and sanitation facilities solve this problem?  (Ex. they use chemical cleaners to treat the water.)

4. Remind your students that, although most citizens in the United States generally have reliable access to clean water, many people around the world are not so lucky and must collect and clean their own water. In addition, conditions such as drought, pollution, increased population and unequal distribution of natural resources threaten Earth’s water supply. This makes it necessary for each of us to conserve water and find ways to reduce our daily water usage.


Extension: Building a Water Filter and Adopt a Water Project

  1. Have students design a water filter they would use if they had to, including drawings. How much would a filter like this cost? Would it be hard or easy to make? Do they have access to all of these materials?
  2. Take a field trip to a water treatment facility! Find out more about the filtration process and other steps involved in purification.
  3. Have your students visit the Adopt-a-Water-Project section at After reading some of the project descriptions, do any of these problems seem solvable?
  4. Consider adopting a project! Have your students brainstorm ways to raise money to fund a water project somewhere in the world.



After completing this lesson, students will be more familiar with the issues of water pollution and access to clean water. Through experimentation with a simple, handmade water filter, they will have an idea of some methods of filtration.