In this hands-on activity, students investigate different methods—aeration and filtering—for removing pollutants from water. Working in teams, they design, build and test their own water filters—essentially conducting their own "dirty water projects." A guiding data collection worksheet is provided.
Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.
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- Colorado: Science
- a. Develop, communicate, and justify a procedure to separate simple mixtures based on physical properties (Grade 5)  ...show
- International Technology and Engineering Educators Association: Technology
- B. Waste must be appropriately recycled or disposed of to prevent unnecessary harm to the environment. (Grades 3 - 5)  ...show
- Next Generation Science Standards: Science
- Generate and compare multiple possible solutions to a problem based on how well each is likely to meet the criteria and constraints of the problem. (Grades 3 - 5)  ...show
- Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved. (Grades 3 - 5)  ...show
- Use sight and smell to identify pollutants in a water sample.
- Explore what types of pollutants are removed from water by aeration and filtration.
- Design, build and test a water filtration system.
- Explain the role of engineers in water treatment systems.
- Data Collection Worksheet, one per student
- 2-liter plastic bottle cut in half horizontally, as shown in Figure 1; ask students to bring empty bottles from home or get from local recycling center near you; wash before use; consider using the same ones used in Lesson 4's This Landfill is a Gas activity.)
- 3-inch square of mesh, such as fine nylon screen or fine cheese-cloth
- 1 rubber band
- 1 spoon or other stirring utensil; a chopstick works well
- filter materials, such as filter paper or large coffee filter (at least 6" in diameter), 6 cotton balls, ~6 cups soil, ~6 cups sand, 1 dozen large and small pebbles (total), ~6 cup activated charcoal (such as used for potting plants and in aquariums)
- aquarium aerator or a mechanical stirrer/mixer; aeration pumps for fish tanks work well
- measuring cups
- 2 large jugs/jars, ~1 gallon size, such as plastic gallon milk jugs with lids; for mixing/storing "polluted water" (recipe follows)
- "polluted water" made by mixing the following items in amounts at the teacher's discretion: water (enough to fill the jugs/jars ~¾ full), green liquid food coloring, soil, organic matter such as grass clippings and orange rinds, dishwashing detergent, vinegar, baking soda, salt, pepper, pieces of polystyrene foam (foam peanuts), small pieces of newspaper, and your own ideas for other items
Before the Activity
- Prepare the "polluted water" supply and let it ripen in a sunny spot for a day or two. Alternatively, do this as a class demonstration so that students know exactly what is in the water. If you have student create the "polluted water" supply, have them write down the ingredients and their sight and smell (not taste) observations about the solution as it changes.
- Place the aerator/mixer in one sample of "polluted water" and let it sit overnight before Part 1. You will probably need to aerate a large sample of water for a day or so before Part 2, depending on how many groups choose to use aerated water for their best filter. Note: Aeration, the process of adding air to water, is often part of the water purification process in order to help many harmful organic pollutants react with oxygen and change into non-threatening carbon dioxide and water.
- Be sure to mix the solution thoroughly before preparing the student samples.
- Prepare the 2-liter bottles: cut them in half horizontally. Place a square of mesh over the bottle opening and secure it with the rubber band. If you use cheese cloth, you will need to replace it before Part 2.
- Make copies of the Data Collection Worksheet, one per person.
- Make a transparency or large chart of the class data section for use in Part 1.
- Review the water cycle with the class. Pay special attention to where the water can be purified. See the following book for a great description: The Magic School Bus – Wet All Over: A Book about the Water Cycle by Joanna Cole and Pat Relf (New York, NY: Scholastic Books, Inc., 1996).
With the Students
- Divide the class into groups of three students each.
- Distribute a worksheet to each group.
- Remind the students that they are now working for the Clean Water Environmental Engineering Company and have been asked to design a new water filtration system for a small community with a polluted water supply. First, the company is going to look at different types of filter material to determine which ones work well. Then each group in the company will design a filtering system to clean up the polluted water.
- Give the following supplies to each group: a pre-cut 2-liter bottle, a ½-¾ cup (100-200 ml) sample of the "polluted water" in a beaker or cup, one type of "filter" (one group will not get a filter in order to test the mesh only), and a spoon.
- Ask each group to draw a picture of the "polluted water." Ask them to describe in words what it looks and smells like. Remind them to gently stir the solution and record their sight and smell observations on the worksheet. Remind students to never taste the solution.
- Ask students to write down on their worksheets their predictions for what they think their particular filter material will do.
- Ask students to set up their filters by placing the filter material into the inverted 2-liter bottle top, as shown in Figure 2. Note: Place the filter in the end of the bottle with the neck, so it functions like a funnel. Use the other half of the bottle as a stand. Prompt students to draw sketches of their setups on the worksheet.
- Ask students to gently stir the "polluted water" and then slowly pour it into the filter. Make sure the group with the filter paper is careful to not pour liquid above the top of the filter.
- Direct students to observe what happens during the filtration. Expect some filtrations to take longer than others. Remind students to record on their worksheets their observations and draw pictures of the filtered water.
- After all groups have collected data, share the results as a class by filling in the information on the transparency or chart made earlier. Have students record all team results in the class data section on the worksheets.
- As a class, look at the aerated sample. Discuss what aeration is and how it works (refer to the aeration explanation in the Before the Activity section).
- Ask students to work in their engineering design groups to design the best water filtration system given the filter material options and their choice of aerated or non-aerated water. Have them fill in the worksheet to record and explain their design choices. Permit them to use as many of the filtering materials as they want.
- Collect all supplies and dispose of used items properly. Rinse and save the 2-liter bottles Part 2.
- Have students sort into their Part 1 groups.
- Give each team a prepared 2-liter bottle, ½-¾ cup (100-200 ml) of the "polluted water" in a beaker or cup (aerated or non-aerated, whichever they chose) and a spoon.
- Distribute the filter materials as needed. Note: It helps if teams each send a designated "materials" person from to collect their supplies from a central classroom location.
- Ask students to fabricate their groups' water filter systems and draw pictures of them on their worksheets.
- For testing, direct students to gently stir the polluted water supply and then slowly pour an amount into the filter. For teams that used filter paper, remind them to be careful not to pour the liquid above the top of the filter.
- Alert students to carefully oberve and record on their worksheets what happens during the filtration process. Note: Some filtration systems take longer than others to process the "polluted water," so students should not worry if their filtration systems takes longer than other systems. Also have teams draw pictures on their worksheets of the filtered water.
- Direct students to record their results and answer the worksheet discussion questions, comparing answers with team members.
- After all the groups are finished, label and line up the filtered samples. Ask each team to present its filter system to the class (aka Clean Water Environmental Engineering Company).
- Conclude with a class vote and discussion about which water is the cleanest and why.
Pre-Activity Assessment: Part 1
Pre-Activity Assessment: Part 2
Activity Embedded Assessment: Parts 1 and 2
Post Activity Assessment: Part 1
Post Activity Assessment: Part 2
Cole, Joanna and Relf, Pat. The Magic School Bus – Wet All Over: A Book About the Water Cycle. New York, NY: Scholastic Inc., 1996 (ISBN 0-590-50833-4).
Glencoe Science: An Introduction to the Life, Earth and Physical Sciences. Student Edition. Blacklick, OH: Glencoe/McGraw-Hill, 2002.
Hassard, Jack. Science as Inquiry – Active Learning, Project-Based, Web-Assisted and Active Assessment Strategies to Enhance Student Learning. Tucson, AZ: Good Year Books, 1999. (ISBN 0-673-57731-7)
Lucas, Eileen. Water: A Resource in Crisis. Chicago, IL: Children's Press, Inc., 1991.
Prentice Hall Science. Ecology Earth's Natural Resources Activity Book. NJ: Prentice Hall, Inc., 1993.
Spurling Jennett, Pamela. Investigations in Science – Ecology. Westminster, CA: Creative Teaching Press, Inc., 1995.
Stille, Darlene. The New True Book – Water Pollution. Chicago, IL: Childrens Press, Inc., 1991.
Amy Kolenbrander, Jessica Todd, Malinda Schaefer Zarske, Janet Yowell
© 2005 by Regents of the University of Colorado
Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
Last modified: February 4, 2016