1. Have the whole class sit in a circle around a large bucket of water. Dip a clear plastic cup into this water and then pour the water back and forth between the two clear cups. Ask the students to observe, listen and think about their favorite body of water. Have them close their eyes and continue to listen and imagine this special place. What are they doing there? Who else is there? What does it smell like? While the students have their eyes closed, add green food coloring and mud to the cup of water and continue pouring. Ask the students to open their eyes. Discuss their reactions to the changes in the water. Tell them they will learn how water becomes polluted and how it is cleaned up again.
2. Explain that the bucket of water represents a lake that has slowly been polluted over the years by various sources. Explain that each student will represent someone who lives or works near the lake. Give each student a labelled film cannister containing pollutant material. Tell the students that you are going to describe the lake and the pollutants that affect it. As each source of pollution is mentioned, have the student holding the corresponding pollutant dump the contents of his or her cannister into the water jug.
3. Describe the lake to the class. Recount the lake's history. For example, back in 1960 only a dairy farm and apple orchard bordered the lake. Later a small fishing access and parking lot were built to allow for public boating. A campground with a store and laundromat followed and attracted many summer visitors. Then in the 1980's, summer houses were built along the shore, and several are now under construction. The water quality in the lake has slowly changed over the years. Mention the farmer, whose fertilizers and manure are washed into the lake by the rain; the orchard, whose pesticides are washed into the lake by rain; the motorboat driver/fishermen, whose fuel and engine exhaust enter the water; the campers, whose litter gets into the water; the campground laundromat, whose washing machines' leaky underground drainpipe adds soapy water to the lake; the homeowner, whose household waste water drains into the lake; the new building sites, where erosion and runoff add sediments to the lake; the careless house painter, whose unused paint and turpentine seeps into the lake; and the motorists, whose cars parked near the lake contribute polluting oil drips, antifreeze, and windshield wiper fluid. By the end of your description of the lake, the water in the jar should be dirty.
4. Ask the students who polluted the lake. Who is going to clean the lake up? How? Discuss what actions the students might take if they lived around the lake to prevent the pollution from continuing.
5. Divide the class into small groups. Give each group a quart container of dirty water from the bucket and a cleanup kit. Explain that they will play the role of managers of the water-treatment plant that has been built to clean up this lake. They will work to clean the lake, represented by the water in the jar. Show them the materials they have to use for this task. Explain that pickling alum will be available for any group that wants to use it. A ½ teaspoon full will coagulate small particles, causing them to stick together and sink to the bottom where they can be removed.
6. Set a time limit and ask the students to produce the cleanest water possible, using any or all of the materials in their kits. They should try to lose as little water as possible. Have them designate one person in each group as a recorder to write down cleanup steps as they are performed. Have each group keep its cleaned water in a clear quart jar.
7. When the allotted time is up, have all the groups set their jars of treated water side-by-side. Compare the results and vote which group produced the cleanest water. Have these students list their treatment steps and compare cleaning processes with other groups to decide which steps were most effective.
Extensions: a. Read the book THE MAGIC SCHOOL BUS AT THE WATERWORKS, by Joanna Cole (Scholastic, 1983). Compare methods used by the class to those encountered by Mrs. Frizzle and her class.
b. Let the students experiment with additional steps to try to improve the quality of their water.
c. Go on a field trip to the local water-treatment facility.
d. Have the students design their own watershed. Place two or three plastic cups upside-down on a lunch tray. Have the students mold tin foil over the cups to create mountains, valleys and rivers. When the watershed is finished, invite the students to develop and discuss the types of land use that take place in their watershed: agriculture, homes, industry, highways, malls, and ski resorts, to name a few! Do these land-use activities have any effect on the water quality? Have the students sprinkle water tinted with unsweetened Kool-Aid over the land-use areas of their watershed that they think will cause pollution to the water. What will happen when it rains? Use a watering can to simulate a rain shower in their watershed. Where did the water travel? What happened to the color of the water after traveling through the land-use areas?