Lesson: Splish, Splash, I was Takin' a Bath!

Contributed by: Integrated Teaching and Learning Program, College of Engineering, University of Colorado Boulder
A colorful drawing depicts the World's water supply as percents and images. Shown is a pie, made up of 97% ocean water, with a 3% slice representing fresh water. Of the 3% slice, 99% of it is in the form of glaciers or stored in aquifers, and 1% of it is in lakes, rivers and streams.
Figure 1. The World's Water Supply


In this lesson, students will explore the causes of water pollution and its effects on the environment through the use of models and scientific investigation. In the accompanying activities, they will investigate filtration and aeration processes as they are used for removing pollutants from water. Lastly, they will learn about the role of engineers in water treatment systems.

Engineering Connection

To benefit society, engineers design and build systems to keep our global water supplies clean. This requires that engineers investigate the water source, and route it travels before it is used by people, and study previous methods that have successfully cleaned our water supplies.

Educational Standards

Learning Objectives

After this lesson, students should be able to:
  • Understand the role of engineers in water treatment systems.
  • Understand how contaminants leach into the soil and ground water and how they are absorbed by plants.
  • Understand the natural water filtration process.
  • Examine how much water is consumed by humans in a lifetime.


Did you know that 97% of the water on Earth is salt water? The other 3% is fresh water, but of this amount, 2% is actually frozen in ice caps. So, that means that only 1% of the Earth's water is available for drinking and growing food.
On average, Americans use approximately 80 gallons of water per person per day. The U.S. population keeps growing year to year, and so does the use of water. The majority of water used by Americans goes through a waste water treatment facility that was designed by an engineer and eventually returns to the water supply. This means — for the bulk of American residents — that the water you used this morning to brush your teeth travels through the water system, gets cleaned up at a treatment facility and returns to the community water supply and, subsequently, your own sink!
Water is essential to all life on Earth. The human body is made up of 60%-70% water. Although much of the water in the body is recirculated, a human must have fresh water daily (obtained from eating and drinking) because some of our body's water is removed each day (through the natural processes of urination, breathing, perspiration, etc.).
Where does a body get its supply of water? Ask the students to list some liquids that a person drinks that contain water. Record their suggestions on the board. Next, ask the students to list some foods that a person eats that contain water. Record their suggestions on the board.
Water must be clean for humans and animals. Water pollution can cause poisoning and/or diseases in both animals and humans because they may either drink the contaminated water or eat the plants that grew from the contaminated water. What are some sources of water pollution? Ask the students to list some possible sources of water pollution. Record their suggestions on the board.
Globally, water pollution is a big problem. The United Nations reports that at least 1.7 billion people do not have an adequate supply of drinking water. At least 30,000 people die everyday in the poorest parts of the world because of either a lack of water or unsafe drinking water (about 10 million each year).
Engineers explore and design ways to keep water clean. They study water supplies (where water comes from) and methods for cleaning water. Water engineers' goal, of course, is to develop a process that keeps the water in our faucets — and everywhere else water is used — clean and healthy for the people who use it. Can you think of some additional reasons why clean water is important?

Lesson Background and Concepts for Teachers

Interesting Water Facts

 A colorful pie chart depicts the percentage of water consumption for average North Americans. The following water uses are shown: toilet flushing: 28%, washing machines: 22%, showers: 21%, faucets: 12%, baths: 9%, toilet leaks: 5% and dishwashers: 3%.
Figure 2. Percent Water Consumption
  • Average North American uses 300 liters of water per day (see Figure 2).
  • A dripping faucet that leaks just one drop of water every second will waste 4 gallons of water a day (1,400 gallons in a year). Yet, it usually only costs a few dollars to repair.
  • Irrigation has played a roll in human lives for nearly 5,000 years. The Pharaohs in ancient Egypt ordered people build channels to carry water to dry fields. In about 1,000 B.C., a farmer with a bucket and a pole could irrigate about ¼ acre a day. Then, in about 1,000 A.D., a farmer using a buffalo to turn a wheel could irrigate about 5 acres a day. Today, in industrialized countries using advanced technology, a farmer can pump 1,000 gallons of water per minute over a 160-acre area. On average, crops require about 2,200 lbs of water to produce 2.2 lbs of food.
  • The Exxon Valdez, carrying millions of gallons of crude oil, ran aground in Prince William Sound, Alaska, in March 1989. Over 11 million gallons of oil spilled into the sea. It eventually spread over 1,100 miles of coastline and killed as many as 100,000 birds and 1,000 sea otters as well as other shore life.
  • During the Gulf War in 1991, Iraq deliberately dumped 240 million gallons of crude oil from Kuwaiti oil reserves in an attempt to halt U.S. marine operations. Reports estimate that 8 million gallons ran directly into the Persian Gulf.
  • Safe and abundant water is listed as fourth of the 20 greatest engineering achievements of the 20th century (according to NAE, the National Academy of Engineers).
  • Typhoid fever, cholera, dysentery and diarrhea killed many people in the early 1900s. Because of water treatment systems created by engineers starting in the 1940s in the United Stated, these diseases were almost eradicated. Furthermore, water was moved into areas that were previously inhabitable.

Causes of Water Pollution

Point source pollution is the leading cause of water pollution. Point source pollution is pollution that comes from a definite source, such as: direct industrial discharge and dumping, accidents, deep-well injection, leaky landfills, leaking underground storage tanks, abandoned hazardous waste sites, septic tanks, etc. Point source pollution can usually be measured and there is strict government regulations on its discharge (i.e., permits must be obtained from the local government for permission to discharge such pollutants into the environment). Following are some examples of how point source pollution exists today.
A colorful 3-D graphic of a slice of landscape depicting various sources of pollution. Shown in a city, an urban community and a rural farm, each contributing to environmental pollution.
Figure 3. Sources of Pollution
  • City and Industrial Waste – Such waste includes chemical waste produced by factories, raw/partly treated sewage from cities (that contains dangerous, sometimes deadly, bacteria), and garbage that is irresponsibly dumped straight into water. This type of water pollution is the most heavily regulated today.
  • Deep Well Injection – Industrial liquid waste is injected into porous areas that are sealed off from the aquifers above and below by a layer of impermeable rock. The rock can develop cracks, and sometimes the chemical wastes corrode through the impermeable rock. Also, the lining of the well can leak.
  • Landfills – Leachate is a liquid that is produced when rainwater mixes with the substances that are buried in a landfill. This liquid leaks from the landfill and often seeps into the groundwater.
  • Heat – Some industrial companies use water to cool their equipment (like nuclear power plants). The water is heated up above its normal temperature and is drained back into the original water source. This results in animals dying (when the temperature is outside their range of tolerance) and an increase in algae growth — eutrophication — of the types that grow more quickly in warmer water.
  • Saltwater Infiltration – occurs when too much water is taken from a freshwater aquifer near the ocean, allowing salt water to infiltrate, and contaminate, the aquifer.
  • Natural – This type of water pollution occurs in many ways including: blue-green algae that can poison fresh-water ponds, rapid algae growth called "red tides," dust/ash/heat from erupting volcanoes, germs (bacteria), and floods.
Nonpoint source pollution follows point source pollution in terms of its cause for polluting our waters, but is still a major contributing factor. Nonpoint source pollution is described as water that runs over the ground and picks up — and then carries away — natural and human-made pollutants. This water is then deposited into our lakes, streams, coastal waters and even underground sources of drinking water, resulting in harmful effects on drinking water supplies, recreation and wildlife. Sources for nonpoint source pollution include: agricultural runoff, urban runoff, mining, logging, grazing, etc.
A photograph of oil-slicked ocks along the coastal shoreline of Prince William Sound after the Exxon Valdez ran aground in 1989.
Figure 4. A coastal oil spill.
  • Farmland Runoff – Irrigation runoff carries nitrates/phosphates (from fertilizer) and pesticide/insecticides to water sources. Runoff water also carries large quantities of soil which settle on the bottom of lakes and rivers.
  • Transportation – This includes the use of waterways for industrial shipping (such as the large and widely used Mississippi River) and the transportation of materials through pipelines (natural gases, liquids, oil, or coal in a water "slurry" carried from Black Mesa Coal Mine in Arizona to Mojave, Nevada).
  • Crude Oil - More than 50% of crude oil comes from land-based, nonpoint sources (40% of it from car owners changing their oil and disposing of it improperly, and the rest from leaking oil pipes from oil production and transportation sites). About 10% of crude oil pollution comes from oil spills. The rest results from marine operations (such as when ships clean out their fuel tanks).
  • Household Hazardous Waste Products – It is estimated that 300,000 tons of household hazardous waste (household chemicals, detergent, bleach, etc.) products enter the water system by way of household drains or go unchecked into landfills each year (1992 Environmental Almanac, World Resource Institute).

Effects of Water Pollution

A photograph of a bird covered in oil as a result of the Exxon Valdez Oil Spill in 1989.
Figure 5. The effects of a coastal oil spill.
Water pollution can cause diseases and poisoning in animals because they may drink the contaminated water or eat the plants that grow from the contaminated water. In essence, the pollution may very well prevent their survival and reproduction.
Phosphates and nitrates, in lakes, coastal waters, rivers, wetlands, etc. throw off the natural balance so that there is too much food for plants and too little oxygen for animals. Such pollutants can cause algae to grow too quickly, which uses up all the nutrients in the water. The algae then die and decompose which uses up all the oxygen in the water. Subsequently, without oxygen the fish die. In large doses, nitrates may cause cancer in humans, which may result in death.
Oil spills may kill aquatic animals, and ultimately, the oil covers ocean floors and beaches. Such large amounts of oil do not allow organisms to reproduce effectively or at all, and prevents normal animal activities (such as, oil-slicked feathers preventing birds from flying and staying warm).
Another effect of water pollution is in our bodies of water that are used for recreation or commercial fishing. Severe pollution restricts commercial fishing because there is little aquatic life left to fish for or because what aquatic life remains is contaminated. And, recreational activities that involve water may not be enjoyed if pollution is present.
There is an excellent history and time-line about water by The National Academy of Engineers at: http://www.greatachievements.org/


Aeration: The process of adding air to water, which is often done as part of the water purification process.
Algal Bloom: A period of excessive, unnatural growth of algae caused by an increase in nutrients (like phosphorus and nitrogen) in the water. It can lead to a decrease in the amount of oxygen available for other aquatic life.
Aquifer: The space below the water table in which layers of soil and rock are saturated with water. Water in aquifers can generally be pumped out.
Biochemical Oxygen Demand (BOD): The amount of oxygen required by an organism to perform biochemical functions.
Contaminants: Usually measured in parts per million (ppm) or parts per billion (ppb). This means that there is one molecule of contaminant for every million (or billion) molecules of water. (For example, pretend you have a wealthy relative who dies and has $10,000,000 dollars to distribute. If you receive an inheritance of 5 ppb, then you will get 5 cents!)
Desalinization: A process that separates salt and water, leaving the saltwater drinkable.
Eutrophication: A process by which the oxygen in a body of water is used up by the decaying bodies of microorganisms (algae with high BOD) that were stimulated into overgrowth by an abundance of nutrients. It is a common result of nitrate pollution.
Groundwater: Water found between underground particles of soil and rock (how much depends on the permeability and porosity of the particles) that supplies wells and springs. It makes up approximately 97% of the freshwater on Earth. Some of the groundwater that we use today fell as rain hundreds or even thousands of years ago. Water falls to the earth and seeps through the particles of the soil that make up the crust of the Earth. It filters down until it reaches a water-saturated zone. The top of this zone is the water table and the part below it is called an aquifer.
Leachate: Contaminated liquid produced by water seeping through solid waste (for example, rainfall seeping through a landfill).
Nonpoint Pollution: Pollution that cannot be traced to a single source because it comes from many different sources (for example, pesticides that wash off farm crops). This type of pollution is difficult to control and requires many people working together to make a change.
Runoff: Water that "runs off" the surface of soil (into a sewer or body of water) instead of soaking into the ground.
Water Table: The top portion of an underground area where the soil and rock particles are saturated with water. The bottom portion is called an aquifer.

Associated Activities

  • What's Gotten Into You? - Students will use models to investigate the process and consequences of water contamination on the land, groundwater and plants. This is a good introduction to building water filters found in the associated activity, The Dirty Water Project.
  • The Dirty Water Project - Students investigate different methods (aeration and filtration) for removing pollutants from water. They will design their own water filters.

Lesson Closure

Go to http://sandiego.surfrider.org/ to get tips on how little changes in everyday life can help prevent pollution. Emphasize that ordinary people can do ordinary things to prevent water pollution. Ask the students to describe one thing they could do to help clean up water pollution.
Read the following poem "Recycled," by Verne N. Rockcastle. Then, discuss with the students how the water they drank this morning may return to their children's glass many years from now using the water cycle. Why might engineers need to know about this process?
The glass of water you're about to drink
Deserves a second thought, I think.
For Avogadro, oceans and those you follow
Are all involved in every swallow.
The molecules of water in a single glass
In number, at least five times, outclass
The glasses of water in stream and sea,
Or wherever else that water can be.
The water in you is between and betwixt,
And having traversed is thoroughly mixed,
So someone quenching a future thirst
Could easily drink what you drank first!
The water you are about to taste
No doubt represents a bit of waste
From prehistoric beast and bird—
A notion you may find absurd.
The fountain spraying in the park
Could well spout bits of Joan of Arc,
Or Adam, Eve, and all their kin;
You'd be surprised where your drink has been!
Just think! The water you cannot retain
Will some day hence return as rain,
Or be held as the purest dew.
Though long ago it passed through you!
Source: Wisconsin Department of Natural Resources, http://dnr.wi.gov/org/caer/ce/eek/earth/groundwater/poem.htm


Pre-Lesson Assessment

Brainstorming: Have students generate a number of possible ideas about a lesson or activity. Encourage wild ideas and discourage criticism of any ideas.
  • Ask the students to list different liquids that a person drinks that contain water. Record their suggestions on the board. (Possible answers: milk, juice, coffee, tea, soft drinks, etc.)
  • Ask the students to list different foods that a person eats that contain water. Record their suggestions on the board. (Possible answers: most fruits and vegetables, meat, cheese, etc.)

Post-Introduction Assessment

Discussion Question: Ask students to suggest reasons why clean water is important. Write suggestions on the board. (Possible answers: water is a necessity of life, it provides many entertainment/recreation options, many people earn their living by commercial fishing, etc.)

Lesson Summary Assessment

Problem Solving: Present the class with a problem and ask the students to calculate how much water they think the average person consumes in a lifetime. (Note: The water can be directly from drinking water or from other foods and liquids.) They can suggest the number in terms of 8-ounce glasses, gallons, swimming pools, etc.
  • As a class, calculate how many 8-ounce glasses of water the average person consumes from food and liquid each year. (Answer: 8 glasses/day X 365 days/year = 2,920 glasses/year.)
  • Ask students to suggest the how many years the average person lives. (Answer: 75 years)
  • As a class, calculate how many 8-ounce glasses of water the average person consumes in a lifetime. (Answer: Assuming the average lifespan is 75 years, 75 years/life X 2,920 glasses/year = 219,000 glasses/lifetime.)
  • To help students better understand this calculated amount, ask them to complete the How Much? Worksheet (in small groups). (Note: Each calculation addresses a different skill level; consider the skill level of your students before arranging groups for this activity.) Discuss the results of the group calculations.


Quiz: Have students take the Water Pollution Quiz. Review answers during the next class period.

Lesson Extension Activities

  • Investigate factories in your local area. Inquire about taking a tour of the facility. What do they make? What types of water waste do they produce? How do they dispose of the waste? Research the company on the US EPA website (http://www.epa.gov/).
  • Invite a representative from the local wastewater or drinking water treatment plant to visit your classroom. Or, plan a field trip to the plant.
  • Invite a local farmer or agricultural engineer into the classroom to talk about water-friendly farming practices.
  • Ask students to locate the water meter in their home. Have them read the meter one night and then again at the same time a week later. Compare the results between readings of the same household and between students in class. Determine how much water per person is being used in each household. Are some households more water efficient? What are the reasons for this?
  • Locate the water meter at your home or school, and read it at the same time everyday for five days. Record and graph the results. Discuss ways to save water at home or at school. Create a bulletin board display in your school to urge others to make similar changes.
  • Contact the Bureau of Reclamation to inquire about their educational programs. They often have wonderful, hands-on demonstrations that they can bring to your class for little or no fee.
  • Read "Rachel Carson and Shirley Briggs – Friends for Life" (from Environmental Portraits – People Making a Difference for the Environment, by Kim Sakamoto Steidl, Good Apple, Inc., 1993). Research and discuss the book Silent Spring, by Rachel Carson (Houghton Mifflin Company, 1962). What impact did this information have on our current water pollution laws and practices?
  • Complete the PCBs Worksheet and Desalination Handout (attached) to develop content area reading activities.
  • Investigate the US Geological Survey's Water Science for Schools website at: http://ga.water.usgs.gov/edu/.


Carson, Rachel. Silent Spring, New York, NY: Houghton Mifflin Company, 1962.

Glencoe Science: An Introduction to the Life, Earth and Physical Sciences, Student Edition, Blacklick, Ohio: Glencoe/McGraw-Hill, 2002.

Hopkins, Jean, Johnson, Susan and McLaughlin, Charles William. "How Many Cans of Soda Pop?" Ecology Earth's Natural Resources Activity Book, New Jersey: Prentice Hall, Inc., 1993 (ISBN 0-13-987090-3).

Kerrod, Robin and Evans, Ted. The Environment (Let's Investigate Science), New York: Benchmark Books, 1993.

Lucas, Eileen. Water: A Resource in Crisis, Chicago: Childrens Press, Inc., 1991.

Sakamoto Steidl, Kim. Environmental Portraits – People Making a Difference for the Environment, Boulder, CO: Good Apple, Inc., 1993.

Stille, Darlene R. The New True Book – Water Pollution, Chicago: Childrens Press, Inc., 1990.

The National Academy of Engineer's ranking of the 20 best engineering achievements of the 20th century: http://www.greatachievements.org/

US Environmental Protection Agency: http://www.epa.gov/owow/nps/qa.html

US Geological Survey: http://ga.water.usgs.gov/edu/waterquality.html

Wisconsin Department of Natural Resources:http://dnr.wi.gov/org/caer/ce/eek/earth/recycle/index.htm


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


© 2005 by Regents of the University of Colorado.

Supporting Program

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


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: November 25, 2015

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