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Hands-on Activity: The Dirty Water Project
Contributed by: Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder

Summary

In this activity, students investigate different methods (aeration and filtering) for removing pollutants from water. They will design and build their own water filters.

Engineering Connection

Engineering analysis or partial design

Civil, chemical and environmental engineers work together to make existing water treatment systems better, or to develop new water treatment systems. Some engineers design state-of-the-art seawater treatment system technologies that take water from the ocean and process it cost-effectively for safe domestic use.

Contents

  1. Learning Objectives
  2. Materials
  3. Introduction/Motivation
  4. Procedure
  5. Attachments
  6. Safety Issues
  7. Troubleshooting Tips
  8. Assessment
  9. Extensions
  10. Activity Scaling
  11. References

Grade Level: 5 (3-5) Group Size: 3
Time Required: 90 minutes
(An additional 15-minute session at the beginning if you decide to make the "polluted" water and set up the aeration as a class.)
Activity Dependency :None
Expendable Cost Per Group
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Learning Objectives (Return to Contents)

After this activity, students should be able to:
  • Identify the pollutants in a water sample using sight and smell.
  • Explore what types of pollutants are removed from water by aeration and filtration.
  • Design, build and test a water filtration system.
  • Understand the role of engineers in water treatment systems.

Materials List (Return to Contents)

Each group should have:
  • 1 copy of the Data Collection Worksheet set
  • 1 2-liter bottle cut in half horizontally, as in Figure 1. (Note: Ask students to bring these in or visit the recycling center near you. Be sure to wash the bottle before use. These can be the same ones that you used in the This Landfill is a Gas Activity of Lesson 4.)
A photograph of a standard 2-liter bottle (left), and cut in half lengthwise (right).
Figure 1. Picture of 2-liter bottle, intact and cut in half lengthwise.
  • 1 3-inch square of mesh (fine nylon screen, fine cheese-cloth, etc.)
  • 1 rubber band
  • 1 spoon or other stirring utensil (chopsticks work well)
For groups to share:
  • Filter materials: - 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 (used for potting plants and in aquariums)
  • 1 aquarium aerator or a mechanical stirrer/mixer (aeration pumps for fish tanks work well)
  • Measuring cups
  • 2 large jugs/jars (approximately 1 gallon size – plastic gallon milk jugs with lids are great), for mixing/storing "Polluted Water" (recipe follows)
  • "Polluted Water" (made by mixing the following, in amounts at your discretion): - Water (enough to fill the jugs/jars approximately ¾ full) - Green food coloring - Dirt - Organic matter (grass clippings, orange rinds, etc.) - Dishwashing detergent - Vinegar - Baking soda - Salt - Pepper - Pieces of polystyrene foam (foam peanuts) - Small pieces of newspaper - Your own ideas

Introduction/Motivation (Return to Contents)

Due to its incredible chemical properties, water is often considered the "universal solvent." It can mix with organic (natural) or synthetic (man made) substances. Some of these products easily break down in water, while others break down very slowly (or perhaps even never). Water naturally cleans itself through filtration through the ground and evaporation in the water cycle.
At one time, society just disposed of its waste and garbage directly into lakes, streams and oceans. Now, most countries require that if water is polluted, it be treated before it is allowed to enter into natural water formations (lakes, rivers, oceans, etc.).
Generally, there are three ways that raw sewage (waste) water is treated before it is released. First, the liquid is allowed to settle and then is exposed to oxygen by stirring or bubbling air through it (aeration). This allows many harmful organic pollutants to react with the oxygen and change into carbon dioxide and water. Second, the liquid can be filtered to remove the particulate matter. Lastly, the solution is treated chemically (with chlorine or ozone) to kill any remaining harmful things like bacteria.
Environmental, chemical and civil engineers work to improve existing water treatment systems and design new ones to ensure that we have clean water both now and in the future. Today, we are engineers working for the Clean Water Environmental Engineering Company. The company has been asked to design a new water filtration system for a small community with a polluted water supply. We are going to focus on the second step in the water treatment process, filtering. First, we are 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. The best filtering system will be used in the small community.

Before the Lesson

  • Prepare the "polluted" water sample and let it ripen in a sunny spot for a day or two. (Note: This can also be done as a class demonstration so that the students know exactly what is in the water. If you decide to do this, ask the students to write down the "ingredients" and make observations about the "polluted" water as it changes. They should use sight and smell, but do not let them taste the mixture.)
  • 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 is the process of adding air to water. It is often done as part of the water purification process. This allows many harmful organic pollutants to react with the oxygen and change into 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 Worksheets, 1 set per group.
  • Make a transparency or large chart of the class data section for use in Part 1.
  • Review the water cycle with the students. Pay special attention to where the water can be purified. 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) has a great description.

With the Students

Part 1
  • Divide the students into groups of 3.
  • Distribute a Data Collection Worksheet set 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 as they will 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 observations of that as well. They should record their answers on the Data Collection Worksheet. Remind students that they should never, ever taste the solution.
  • Ask students to write down a prediction for what they think their particular filter material will do. (There is a space for this on the Data Collection Worksheet.)
  • Ask students to set up their filters by placing the filter material into the inverted 2-liter bottle top, as in Figure 2. (Note: the filter should be place in the end of the bottle with the neck; it will function like a funnel. Use the other half of the bottle as a stand.) They should draw a picture of their set-up on the data sheet.
A photograph of a 2-liter bottle with a standard coffee filter placed in the bottom.
Figure 2. A 2-liter bottle with a standard coffee filter placed in the bottom.
  • Ask students to gently stir the polluted water and then slowly pour it into the filter. (Note: The group with the filter paper will need to be careful not to pour liquid above the top of the filter.)
  • They should observe what happens during the filtration. Some filtrations will take longer than others. They should record their observations and draw a picture of the filtered water on their data sheet.
  • After all the groups have collected their data, share the results as a class (fill in the information on the transparency or chart you made earlier). Students should record everyone's results in their class data section on their worksheet as well.
  • As a class, look at the aerated sample. Discuss what aeration is and how it works (see aeration explanation in the Before the Lesson section).
  • Ask students to work in their engineering design groups to design the best water filtration system given the filter choices and a choice of aerated or non-aerated water. There is a place on the Data Collection Worksheet for them to record and explain their choices. (They can use as many of the filtering items as they want.)
  • Collect all supplies and dispose of used items properly. (The 2-liter bottles will need to be rinsed and saved for Part 2.)
Part 2
  • Have students break into their groups assigned during Part 1.
  • Give each group 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: Assign a specific "materials" person from each group to collect the supplies from a central location in the room.)
  • Ask the students to build their groups' water filter system and draw a picture of it on the Data Collection Worksheet.
  • Ask students to gently stir the polluted water and then slowly pour it into the filter. (If filter paper has been used, students will need to be careful not to pour liquid above the top of the filter.)
A 2-liter bottle with a standard coffee filter placed in the bottom that has begun to trap particles of carbon.
Figure 3. A 2-liter bottle with a standard coffee filter placed in the bottom that has begun to trap contaminants (carbon, in this case).
  • They should observe what happens during the filtration process. (Note: Some filtrations will take longer than others; students should not panic if their filtration takes longer than another groups'.) Groups should record their observations and draw a picture of the filtered water on their Data Collection Worksheet.
  • Ask students to record their results and complete the discussion questions on the Data Collection Worksheet. Have them compare answers with a group member.
  • After all the groups are finished, label and line up the samples. Ask each group to present their filter system to the class (aka Clean Water Environmental Engineering Company). Have a class vote and discussion about which water is the cleanest and why.

Safety Issues (Return to Contents)

Remind the students that when they are making observations they should only use sight and smell; they should never taste the solution, even if it looks "clean."

Troubleshooting Tips (Return to Contents)

Be sure to have paper towels/rags on hand in-case spills occur.
Consider any students' allergies before creating the dirty water sample.
Help the students to fold the filter paper correctly. They will also need to pre-wet the paper so that it sticks to the sides of the "funnel." You may want to have an eyedropper and some tap water available for this purpose.
Remember to dispose of the waste from this experiment properly! Most times the "polluted" water can just be washed down the drain; however, if you have used any chemicals, you will need to dispose of it according to proper disposal methods.

Pre-Activity Assessment: Part 1

Picture Drawing: Ask each student to draw a picture of their group's "polluted water" in the space provided on their Data Collection Worksheet.
Prediction: Ask students to write down a prediction for what they think their particular filter material will do in the space provided on their Data Collection Worksheet.
Recorded Observations: Ask students to stir the solution and record their observations on their Data Collection Worksheet.

Pre-Activity Assessment: Part 2

Picture Drawing: Ask the students to draw a picture of their best water filter in the space provided on the Data Collection Worksheet.

Activity Embedded Assessment: Parts 1 and 2

Recorded Observations: Students should observe and record what happens during the filtration process.
Picture Drawing: Have students draw a picture of the filtered water in the space provided on their Data Collection Worksheet.

Post Activity Assessment: Part 1

Data Recording: After all the groups have collected their data, share the results as a class (fill in the information on the transparency or chart you made earlier). Students should record all groups' results in the Class Data Section on their Data Collection Worksheet as well.
Clean Water Environmental Engineering Company Design Project: Ask students to work in their engineering design groups to design the best water filter system given the filter choices and a choice of aerated or non-aerated water. There is space provided on their Data Collection Worksheet for them to record and explain their choices.

Post Activity Assessment: Part 2

Worksheet: Have students complete the discussion questions on their Data Collection Worksheets and compare answers with a group member.
Engineering Presentations: Ask each group to present their filter system to the class. Have a class vote and discussion about which water is the cleanest and why.

Activity Extensions (Return to Contents)

Have students use pH paper and a pH guide to help them determine the pH of the solution during different stages of the process (plain water, "polluted water" before treatment, after aeration, after filtering with one filter, and after using their final filter). Discuss how the different items in the solution affect the pH. How would the pH of the solution affect the rest of the environment? (Refer to pH table.)
Ask students to measure the volume before and after filtration. Younger students can describe it as more or less or even use measuring spoons/cups. Older students can use labeled beakers or graduated cylinders.
Try some simple chemical treatments. For example, adding chlorine to a water sample, etc. These may be better done as demos or with older students. Do not forget protective equipment when handling chemicals!
Ask the students if they think that the order of the layers matters. Why or why not?
Ask students to filter their sample more than once. They should keep a small sample after each filtration for comparison. Does the water get cleaner on subsequent filtrations? Why or why not?

Activity Scaling (Return to Contents)

For 3rd grade students, try this activity as a demo with only a couple of filter choices. Do each filter type individually and then ask the students to predict what will happen when you use both of the filter types together. Ask the students to draw pictures of the results.
For 4th grade students, do the activity as is.
For 5th grade students, groups can work a bit more independently so more time should be spent on the design piece. Ask students for their own suggestions for filters and other ways to treat the "polluted" water. Have students bring in some things from home to test as filters and have each group test their own items after you have modeled the filtration procedure.

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, Ohio: 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: Children's Press, Inc., 1991.

Prentice Hall Science. Ecology Earth's Natural Resources Activity Book, New Jersey: 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: Childrens Press, Inc., 1991.

Contributors

Amy Kolenbrander, Jessica Todd, Malinda Schaefer Zarske, Janet Yowell

Copyright

© 2005 by Regents of the University of Colorado.

Supporting Program (Return to Contents)

Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder

Acknowledgements (Return to Contents)

The contents of this digital library curriculum were developed under a grant from the Fund for the Improvement of Postsecondary Education (FIPSE), U.S. Department of Education and National Science Foundation GK-12 grant no. 0338326. However, these contents do not necessarily represent the policies of the Department of Education or National Science Foundation, and you should not assume endorsement by the federal government.
Last Modified: July 31, 2014
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