Water pollution affects rivers, lakes, and oceans around the world—but engineers design systems to help clean it up. In this hands-on water pollution cleanup STEM challenge, kids create a model polluted water system and test different tools and materials to remove contaminants.
This water pollution experiment for kids introduces environmental science, engineering design, and real-world problem solving in a simple, engaging way.
This investigation works well as part of an environmental science unit, an Earth Day STEM activity, or a classroom engineering challenge using recycled materials. It also helps students understand how environmental engineers protect ecosystems and clean water sources.
You can pair this activity with our stormwater runoff experiment for kids to learn how pollution enters waterways and our water filtration science project for kids to explore how engineers clean and protect our water supply.
Water Pollution STEM Activity at a Glance
Field: Environmental Science & Engineering
Best Grades: 2–6
Concepts Explored: Water pollution, environmental engineering, separating mixtures, problem solving, engineering design process
👉 This activity is part of a larger environmental science unit. Find more structured investigations and printable lessons in our environmental science lesson plan guide.
NGSS Guiding Questions
• How do human activities affect Earth’s water systems?
• How can engineers design solutions to reduce pollution?
• How can models help us understand environmental problems?
Why Teach Pollution Cleanup?
Environmental engineers work to protect ecosystems and drinking water by removing harmful substances from water. Kids can explore these same ideas by designing and testing cleanup methods in a simple classroom model.
This activity connects directly to real-world topics such as:
• oil spill cleanup
• stormwater runoff
• water treatment systems
• environmental protection
👉 Explore more projects like this in our Engineering STEM Activities hub.
Supplies Needed
- Clear container, tray, or bin
- Water
- Small recyclable container (bottle cap, cup, or tray)
- Cooking oil
- Dirt or sand
- Small pieces of paper
- Leaves or grass
- Feathers, cotton balls, or sponge pieces
- Recycled tools such as:
- – spoons
- – cardboard pieces
- – craft sticks
- – droppers or pipettes
- – paper towels
- – cotton balls
- Optional: dish soap
How to Set Up the Pollution Cleanup Challenge
STEP 1: Create the polluted water model
Fill a clear container halfway with water.
Add pollutants such as:
• cooking oil
• dirt or sand
• paper pieces
• leaves
• small debris
Observe what happens when pollutants mix with water.
STEP 2: Observe the pollution
Ask students:
What floats?
What sinks?
What spreads across the surface?
This helps them understand different types of pollution.
STEP 3: Design a cleanup solution
Provide recycled tools and materials. Students must design a method to remove as much pollution as possible.
Encourage testing tools such as:
• scooping tools
• absorbent materials
• barriers
• filters
This introduces the engineering design process.
STEP 4: Test and improve the design
The Science Behind Pollution Cleanup
Water pollution includes substances that harm ecosystems and make water unsafe.
Different pollutants behave differently:
- Oil floats because it is less dense than water.
- Sand sinks because it is heavier.
- Some materials absorb liquids.
Engineers use multiple methods to clean water, including:
- skimming
- filtration
- absorption
- settling
Students model these same processes in this activity.
💡 Learn more about these processes in our water filtration science project and oil spill cleanup experiment.
Engineering Challenge Extension
Challenge students to design the most effective cleanup system.
Test questions such as:
- Which tool removes oil best?
- Which material absorbs water fastest?
- Does cleanup order matter?
Students can redesign and improve their solutions. This mirrors how environmental engineers solve real problems.
👉 Explore more design challenges in our Engineering STEM Projects hub.
Make It a Science Project (Optional)
Turn this into a simple science investigation. You can learn more about using the scientific method including writing a hypothesis, choosing variables, and making observations.
Example Question: Which material removes oil from water most effectively?
Example Hypothesis: If cotton balls are used, then more oil will be removed because cotton absorbs liquids.
Variables
Independent variable: Cleanup material
Dependent variable: Amount of pollution removed
Controlled variables: Water amount, container size, pollution type
Data Collection Ideas
Measure:
- amount of pollution removed
- cleanup time
- water clarity
Students can present results using a science fair board.
👉 See our science fair project guide for help.
Science Fair Questions: Water Pollution & Cleanup
Which material removes pollution from water most effectively?
Test materials such as cotton balls, sand, charcoal, sponge, or paper towels to compare cleaning effectiveness.
Does the order of filtration materials affect how clean the water becomes?
Change the layer order and observe differences in water clarity.
Which cleanup method works best for removing floating pollutants from water?
Compare tools such as spoons, absorbent materials, mesh, or cloth.
Does filtering water multiple times make it cleaner?
Run water through the same filter repeatedly and record changes.
Which material absorbs oil from water most effectively?
Test feathers, cotton, sponge, paper towel, or fabric.
Does slower filtration produce cleaner water?
Compare filters that allow water to move quickly versus slowly.
How does particle size affect filtration effectiveness?
Test removing large debris versus fine sediment.
Can recycled materials work as well as store-bought filtration materials?
Compare cardboard, fabric scraps, or recycled packing materials with standard supplies.
Real-World Connection: Environmental Engineering
Environmental engineers design systems to:
- clean drinking water
- protect wildlife habitats
- remove oil spills
- reduce pollution
Students explore these same ideas through hands-on design.
This activity pairs well with:
• Model stormwater runoff experiment (how pollution enters water)
• DIY water filtration experiment (how pollution is removed)
• Ocean spill clean-up experiment (ocean pollution clean-up)
• Earth Day STEM activities (environmental problem solving)
Cleaning polluted water is only one part of protecting our environment. Explore ways to protect natural resources with our water conservation activities for kids.
FAQ
What does this activity teach?
This activity helps kids understand how water pollution affects the environment and how engineers design systems to remove pollutants. Students explore concepts such as separating mixtures, absorption, and environmental protection.
Is this activity safe for kids?
Yes, this activity uses common household and recycled materials. The water is only for observation and experimentation and should not be consumed.
What age group is this best for?
This activity works well for grades 2–6. Younger students can focus on observation and simple cleanup tools, while older students can design experiments and compare results.
How is this connected to real-world engineering?
Environmental engineers use similar methods—such as skimming, filtering, and absorbing—to clean oil spills, treat wastewater, and protect natural water sources.
Can this be used as a science fair project?
Yes. Students can test different cleanup materials or methods, collect data, and present their findings. Pair this activity with a water filtration science project to explore additional cleanup solutions.
Continue exploring water conservation efforts
Continue exploring water science and sustainability with our Water Conservation Activities Pack and Water Study Unit, filled with hands-on STEM projects, experiments, and printable investigations designed for elementary learners.
