Lesson Plan

What Happens to the Water When We Brush and Flush?

Teacher and students gathered around an Enviroscape learning about wastewater.
Students learn how wastewater impacts our environment.


Water from homes and businesses enters sewers or septic tanks through pipes. This wastewater is kept with other dirty water because it is unhealthy and must be kept away from our drinking water. This sewer water is sent to a water treatment plant where the unhealthy parts are removed. The water is then returned to the river sometimes cleaner than it was originally. This lesson raises real world concerns, guiding students to become better stewards of our environment.


Students will:

  • Learn the process of water treatment
  • Discuss the various amounts of water used in everyday activities
  • Learn strategies for conserving water
  • View and discuss river conditions
  • Test river water with basic water testing kit


During water treatment, 60% of suspended solids are removed. Since we often let the water run as we complete our daily routines, much of the water is already clean when it goes down the drain. Less than 1% of wastewater is actually waste. Machines remove human waste, gravel, sand, oils, grease, rags, and other objects that could damage equipment in the treatment plant. Those and other objects found are sent to the landfill. Water is then sent through a secondary treatment where aerobic bacteria break down soap, detergent, and human and food wastes, Those items are said to floc together, or clump, to be removed. The bacteria provide a healthy solution to removing organic components that might cause harm to humans and animals. The water then goes through a tertiary treatment to be filtered and disinfected. Without adequate wastewater treatment, waterborne diseases (cholera, dysentery, and typhoid) would be more prevalent. The water is then returned to local waterways such as the Chattahoochee.


What They Know

Ask students what happens to the water after they brush there teeth and flush the toilet. Record their responses on a calk board or flip chart.

Ask students if they run the water as they brush their teeth. Discuss why this is unnecessary.

Ask students about how much water they believe they use for the following everyday activities:

  • Brushing your teeth
  • Using the dishwasher
  • Flushing the toilet 
  • Taking a shower or bath


  • Brushing your teeth? Tap on 2 gallons/minute - Tap off .25 gallons
  • Using the dishwasher? 10-15 gallons per load
  • Flushing the toilet? 3-5 to 5 gallons
  • Taking a shower or bath? Shower 7 to 10 gallons - Bath 30 to 50 gallons

Have several gallon and quart jugs handy so students can visualize as you explain water required for these activities. Explain that many people in other parts of the world exist on less than 3 gallons of water per day. We use that in one flush.

Treating Wastewater

Explain that water used in homes and businesses leaves through sewer pipes under the ground. Everything that is flushed or rinsed down the drain goes to a water treatment facility. There the water is thoroughly cleaned through a series of processes including coagulation, sedimentation, filtration, disinfection, and storage. Explain that many things that we might not even think about are in the water, such as phosphorus, nitrogen, and ammonia.

Discuss the positives and negatives of various elements in our water source and what they indicate (ie. phosphates enter our waters from fertilizers, cleaning products, and from human and animal wastes.  In high levels, phosphates can cause rapid plant growth and algal blooms in a body of water, which in turn reduces the amount of dissolved O2, thus causing organism to die; excess nitrogen comes from such things as fertilizers, animal feedlots, and septic systems.  Nitrogen is a needed nutrient; but it can cause reactions in fresh water which cause oxygen depletion; ammonia – which can enter water sources from municipal effluent discharges and the excretion of animal waste - is a form of nitrogen that directly has toxic effects on aquatic organisms.

Since the water from the treatment facility is returned to the river, these items >must be removed. Students will have an opportunity to test the river water to see if any of these contaminants are present.

Field Testing

Instruct students in basic water testing steps and how to test for nitrogen, phosphorus, and turbidity. Visit Chattahoochee River NRA or neighborhood park pointing out various water sources. Have students differentiate between a pond, stream, and a river as you walk through the park to discuss.

Ask students if they believe the water is clean. Lead students in safely collecting water to test. Use a test kit that uses tablets rather than liquid chemicals, thus making it much safer for children. Various tests, such as pH, phosphate, nitrogen, dissolved oxygen, and turbidity, can be performed. Share results of testing. Discuss the possibility that water was clean when it was returned to the river, but could have been contaminated again by point source and non-point source pollution.

Field Trip

Take your students on a field trip to your local sewage treatment plant or the Johns Creek Environmental Campus in Roswell, Georgia. Students will take a tour of the facility and participate in an interactive lesson on cleaning water. Students also learn about community contamination using an Enviroscape.


Students will answer the following questions using complete sentences in their journals after lesson conclusion:

  • Where the water in my home goes when it leaves the sink.
  • Name one step in the water treatment process.
  • List two things that are removed from the water during treatment.
  • Name where the water goes after it leaves the treatment facility.
  • Name two things that they can do to reduce the amount of water I use.

Park Connections

A number of units in CRNRA and a few county and municipal parks have easy access to the Chattahoochee River as well as streams and ponds. Students must use caution along shorelines while collecting water samples for test for contaminates.


Continue water testing at different locations in the park or in different water features.

Additional Resources

Johns Creek Environmental Campus: http://www.fultoncountyga.gov/home-jcec

Clean Water Campaign: http://www.cleanwatercampaign.com/html/index.htm

LaMotte: http://www.lamotte.com/en/

World Water Monitoring Challenge ™: http://www.monitorwater.org/



wastewater, treatment facility, contaminants, bacteria, conservation, floc, coagulation, sedimentation, filtration, disinfection, phosphorus, nitrogen, ammonia, point source pollution, non-point source pollution