Lesson 5: Down the Drain

Lesson Information

Summary: Students investigate the types of hazardous waste that go down the drain in their homes and communities.
Duration: 30 to 40 minutes
Group size: Several groups of three to five students
Materials: A transparent container filled with water; food colouring; Resource Sheet 3: Hazardous Waste Symbols; Resource Sheet 4: Alternatives and Proper Disposal of Some Common Household Waste; Resource Sheet 5: Control Garden Pests Naturally

Learning Outcomes

Students will be able to identify community-based sources of hazardous wastes that enter the ocean through watersheds and the atmosphere.

Background

As we saw in Lesson 4, everything that goes down the drain eventually ends up in a natural body of water — a river, lake, groundwater, or the ocean. Outdoor drains on streets, playgrounds, and parking lots usually lead directly to a river, lake, or estuary. Indoor drains often lead first to a sewage treatment plant. However, most treatment plants are designed to control only bacterial disease. Chemicals, metals, viruses, and excess nutrients pass freely into the ocean. These contaminants accumulate in mud, water, and the bodies of aquatic species. Since people eat some of these animals and plants, contaminants also accumulate in human bodies.

Much of this pollution comes from households that dump cleaning powders and fluids, motor oil, fertilizers, pesticides, paints and thinners, and other harmful substances down drains. Sewage treatment plants do not remove these contaminants. To protect our own community water supplies and our ocean communities, we can use safe alternatives to some of these products and take hazardous wastes to special collection depots, where they are sealed in special containers away from water.

Procedure

1. Have your students watch you add some food colouring to a transparent container filled with water. Ask them to think of ways to remove the colour. Explain that once something is dissolved in water, it is very difficult to get out. Some substances are found naturally in water (oxygen, carbon dioxide, some nutrients). Life on Earth has adapted to them. Others are dumped into water by people. The chemical or biological nature of many of these substances makes them harmful to ecosystems, plants, and animals, including humans. Inform the students that it is much easier to stop dumping hazardous wastes than it is to clean water once it is polluted. Ask students to recall Lesson 4: Tracing a Path to the Sea.
2. Brainstorm with your students about possible sources of hazardous wastes in human communities and list their responses.
3. Challenge the students to go on a hazardous waste search at home or at school. Focus on items that contain the hazardous waste symbols listed on Resource Sheet 3. Advise the students to have an adult with them and not to touch any of the materials or open any containers. Have them make a list of the items found and, with the help of an adult, answer these questions:
   • While the item is being used, does any of it go down the drain?
   • What happens to small amounts that are left over?
   • What happens to the container once it is empty?
4. Ask students for the general results of their search. How many found hazardous materials? Did any of these materials end up down the drain? Summarize their results and discuss ways to minimize hazardous wastes going down the drain (for example, proper disposal and use of non-hazardous alternatives). Emphasize the following points:
• Other sources of hazardous wastes in communities include pesticides sprayed on lawns, gardens, and crops as well as contaminants that enter the air through the burning of fuels like gasoline.
• One reason why people pour hazardous wastes down the drain is that they don=t think about the rivers or lakes the drain leads to, the fish that live there, or the people who play there and drink the water.
• Students can help prevent pollution in their homes by taking Resource Sheets 4 and 5 home and encouraging their parents to follow the recommendations.
• Students can help prevent pollution in their communities by taking actions (such as those described in Lesson 7: Pollution Solutions) and by explaining to other classes how to properly dispose of waste, how to reduce the use of hazardous chemicals, and how to minimize air pollution.

Evaluation

Ask your students to create informational posters promoting the proper disposal of household wastes and alternatives to pesticides.