Overview: Contaminants that can affect the quality of or usefulness of water for various uses can be categorized as either chemical, physical or biological. Generally, the most troublesome physical contaminant is sediment: silt, sand, organic debris. As you will see, not only does the presence of sediment affect the drinking quality of water, it can affect other uses of water. To understand and appreciate the significance of physical contaminant such as sediment, we need to know not only how to define and measure it, but also how to prevent it and how to clean up water affected by it. The ideas taught in this lesson should give you a better understanding of sediment as a contaminant.

Purpose: The purpose of this lesson/activity is to introduce students to the idea of physical contaminants in water, help them understand the significance of such contaminants, teach them how to measure or quantify sediment, and illustrate how to deal with sediment.

Ideas Taught:

Materials Needed:

Procedure:

1. ___ Before the class meets, place the jar of clean cold water and supplies on a table in front of the class.
2. ___ When the class begins, ask the students if they would like a drink of water. Assure them that there is nothing wrong with the water.
3. ___ Give a small drink from a jar to each child willing to take a drink. Ask them how it tastes and if they can can see any reason they would not want to drink the water.
4. ___ Explain that contaminants come in a variety of forms, some physical, some chemical, and some biological. Tell the class that you are going to look at a physical contaminant called sediment.
5. ___ Explain that sediment is the most frequently occurring and troublesome physical contaminant with which we deal in water supplies. Nearly all public water systems relying on surface water treat it to remove sediment before delivery to the home.
6. ___ Ask the class if they have any reason to believe there is any sediment in the water they just drank.
7. ___ Ask them to explain what sediment is and how it gets into water systems. Ask them to explain or list on the board some potential adverse effects sediment in water might have.
8. ___ After the discussion, pour the soil, peat, and/or coffee grounds into a jar full of water and mix it up.
9. ___ Ask the students how many would now like a drink of water. Compare the responses with the previous response to the clean water.
10. ___ Ask the students what effect the sediment might have. Allow the discussion to go as the students want it to.
11. ___ After the discussion, transfer the goldfish or aquatic insects to the jar with the sediment and ask the question again.
12. ___ Ask someone to define or explain what the word sediment means. Write the word "sediment" on the board.
13. ___ Explain that usually we call sediment the things that will settle out of the water, given enough time in calm water. Sediment can be easily treated by filtration or by sedimentation (settling).
14. ___ Pour the dirty water with the goldfish or aquatic insects through the filter paper, which has been placed in the funnel and put on top of the empty mason jar. If necessary, filter the water several times to remove all the sediment, the fish, the insects and the coffee grounds.
15. ___ The students should have realized and commented by now that the sediment can affect: (list on the board as the discussion leads to these topics)

• the drinking quality
• the cost of treatment
• the survival of fish
• the reproductive potential of fish (smothers the eggs)
• the survival and vitality of aquatic plants
• light penetration
• water temperature by influencing heat and light adsorption
• dissolved oxygen
• the rate at which impoundments fill in
• stream courses and channels
• the presence of other contaminants adsorbed on the sediment (this applies to fertilizers, pesticides,     other chemicals)
• bacterial, microorganisms, and insects living in the sediment

Lessons Learned: Sediment does not normally occur in ground water systems; the two primary sources of sedimant in surface water systems are: 1) land surface erosion or runoff, and 2) stream bank and stream bottom scouring.