Teaching about water treatment can be a challenge. Municipal water treatment facilities are far removed from students' everyday lives, so the idea that water is already treated before it enters their house may come as a surprise to students. Students have ideas about what makes water clean and how this happens, and they have basic rules they use to decide if water is clean enough to drink. For example, students may think that if water looks clean, or is clear, they can drink the water. Other students may think that all water must be filtered before it can be used for drinking. Today, many students have experiences with home filtration systems on their faucets or via pitchers. Few students actually know how these work, let alone how water treatment and filtration occur at larger scales. They may realize that sewage is treated at some point, but may not readily identify drinking-water treatment. In addition, the materials used to filter water may surprise students, especially materials such as charcoal. Discussing home filtration and large-scale drinking-water treatment and sewage treatment can help students better understand the different types of treatment we use on our water.

Watch this video of 6th grade students in San Diego, California—a coastal community. The purpose of this classroom video is to see students discuss water treatment as they design and build water filters.