Human Use of Resources—Dirty Water, Clean Water

Summary: Where does dirty water go when it leaves your home? This topic guide focuses on wastewater movement and treatment in municipal areas.

Concepts to teach: Storm water, wastewater, water treatment plant, septic system

Goals: Students recognize that water is an important resource used by humans, and that wastewater must be managed in order to conserve resources and to prevent harmful contaminants from escaping into the environment. They learn about various engineering solutions to wastewater management, including sewer systems, water treatment facilities, and septic systems.

S6.4D.1, S6.4D.3

Specific Objectives:

  1. Describe the difference between sewer lines and stormwater lines.
  2. Trace the route toilet water takes after it is flushed, and explain what happens to the water at each stage along its route.
  3. Illustrate how a septic tank works.

Activity Links and Resources:

  • Review the Water Use topic guide from the Land and Water Use focus area in this module
  • Contact your local city planning department or soil and water conservation districts for maps of local sewer lines. For example:
  • Dirty Water Clean Water—This investigation from Alaska Sea Grant’s “Alaska Seas and Rivers Curriculum” is designed for younger students, but the basic structure can apply to middle school students as well. Invite a wastewater expert to the classroom, or take a field trip to a wastewater treatment facility.
  • Virtual tours of wastewater treatment plants in locations outside the Pacific Northwest are also available:
  • Septic Tanks
    • What is a Septic Tank?—This activity has students create a model septic tank. To make this lesson inquiry-based for middle schoolers, ask students to make their own septic tank model and explain how it works.
    • Background article to help students make their model: What Happens After the Flush?
  • EPA’s Enviromapper—This website provides access to several EPA databases to provide information about environmental activities that may affect air, water and land anywhere in the U.S. See which facilities in your zip code have permits to discharge wastewater into rivers
  • The Story of Dryville from USGS—Water management in a fictional, growing town.


  • Discuss differences between sewer lines and stormwater lines.
  • Trace the route toilet water takes after it is flushed, and explain what happens to the water at each stage along its route.
  • Using a drawing or model, describe how a septic tank works.