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Lesson: Dirty Water Project

Water

(Lesson from TeachEngineering.com, contributed by the Integrated Teaching and Learning Program, College of Engineering, University of Colorado at Boulder)

Civil, chemical, and environmental engineers work together to develop new water treatment systems or to improve existing ones. In this activity, teams of students in grades 3 – 5  investigate different methods (aeration and filtering) for removing pollutants from water, then design and build their own water filters.

Grade level: 3 – 5

Time: 90 minutes (Add a 15-minute session at the beginning if you decide to make the “polluted” water and set up the aeration as a class.)

Learning Objectives

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.
Standards

International Technology Education Association
  • B. Waste must be appropriately recycled or disposed of to prevent unnecessary harm to the environment.

Common Core State Mathematics Standards

  • 3. Use multiplication and division within 100 to solve word problems in situations involving equal groups, arrays, and measurement quantities, e.g., by using drawings and equations with a symbol for the unknown number to represent the problem. [Grade 3]
  • d. Compare two fractions with the same numerator or the same denominator by reasoning about their size. Recognize that comparisons are valid only when the two fractions refer to the same whole.[Grade 3]
  • 2. Read and write multidigit whole numbers using base-ten numerals, number names, and expanded form. Compare two multidigit numbers based on meanings of the digits in each place. [Grade 4]

Figure 1. Picture of 2-liter bottle, intact and cut in half lengthwise. Copyright © University of Colorado at Boulder, Integrated Teaching and Learning Program and Laboratory, 2004.

Materials

Each group of 3 students should have:

  • 1 copy of the Data Collection Worksheet (7 pages)
  • 1 2-liter plastic 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.)
  • 1 3-inch square of mesh (fine nylon screen, fine cheese-cloth, etc.)

For groups to share:

  • Filter materials: Filter paper or large coffee filter (at least 6″ in diameter); 6 cotton balls; roughly 6 cups soil; roughly 6 cups sand; 1 dozen large and small pebbles (total); roughly 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)
  • 1 rubber band
  • 1 spoon or other stirring utensil (chopsticks work well)
  • “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 + Other ‘pollutants’ you wish to include

Introduction

Water is often considered the “universal solvent” because it can mix with organic (natural) or synthetic (man made) substances. Some of these products break down easily in water, others break down very slowly or never. Water naturally cleans itself through filtration through the ground and evaporation in the water cycle.

Many societies used to dispose of waste and garbage directly into lakes, streams, and oceans. Now, most countries require polluted water to be treated. Environmental, chemical, and civil engineers wrk to improve existing water treatment systems and design new ones to ensure a steady supply of safe, clean water now and in the future.

Generally, there are three ways to treat raw sewage (waste) water. 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.

Pipe filter lets a Nigerian woman drink from a pond
Pipe filter lets a Nigerian woman drink from a pond

Procedure
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.
  • 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.)

    A 2-liter bottle with a standard coffee filter placed in the bottom

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.)
  • 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

Astronauts water filtration system
Astronaut’s water filtration system

Remind 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

  • 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.

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.

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

  • 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?
  • Have students add food coloring to the water. Do their filters work to remove dye and such other minute substances as germs?
  • Have students test the local tap water and send in results for World Water Monitoring Day (through Dec. 31)

Activity Scaling

  • 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.

Additional Resources

Aquaduct Mobile Water-filtration bike. [YouTube video, 2:00] The Aquaduct, a pedal powered vehicle that transports, filters, and stores water for the developing world, was an award-winning 2007 entry in the Innovate or Die contest put on by Google and Specialized.

Interactive Water Cycle (requires Flash) from the U.S. Environmental Protection Agency’s Drinking & Ground Water for Kids.

Water STEM Filtration activity (Grades 6 -10). One of 17 standards-based water-purification lessons from the University of Illinois, Urbana-Champaign’s Water Campws, a program from the Center of Advanced Materials for the Purification of Water with Systems.

Video: Engineers Without Borders, California Polytechnic, San Luis Obispo chapter, designs and installs a water filtration systme for six rural Thai villages. [YouTube, 9:40]

Water Purification: A Systems and Global Engineering Project – Nine week collaborate project for students in grades 9 -12 developed by the Stevens Institute’s Center for Innovation in Engineering and Science Education.

Build a Water Filter Part 1 (dirt) and Part 2 (salt). PBS’s Zoom kids activities using half a large soda bottle to rid water of dirt or salt.

Contributors: Amy Kolenbrander, Jessica Todd, Malinda Schaefer Zarske, Janet Yowell; Copyright © 2005 by Regents of the University of Colorado; last updated May 2011.

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