Activity 10: Water Purification

1. Prepare a table like the following, for each of your water samples:

2. Pour approximately 30mL of the muddy water into a test tube and label. Describe the appearance and observe any microorganisms under a microscope; determine the pH of the water sample using litmus paper.

3. Allow the muddy water to settle overnight and pour off the top liquid into a beaker.

4. Pour approximately 30mL of the liquid into a test tube and repeat the observations from step 1.

5. Test the pH of the liquid in the beaker, if it is acidic, add enough baking soda to produce a slightly basic solution. (This step is important because in order for the alum to coagulate the fine clay particles still in the water, and the water needs to be basic).

6. Add 30g of alum to the water in the beaker, observe any immediate changes. Stir the mixture thoroughly and allow it to settle overnight.

7. Make your observations as in step 1, and then pour approximately 30mL of the top liquid (leaving the coagulated material at the bottom of the beaker) into a test tube, label and make your observations.

8. Make a sand and gravel filter (with the sand on top of the gravel). Pour the remaining liquid left in the beaker, into the filter. Again describe its appearance and make observations as in step 1.

9. Answer the discussion questions.

Discussion Questions: Water Purification

1. What did you observe after the muddy water was left over night?

2. What change was observed when the alum was added? If the liquid appeared to be clear, where did the particles come from?

3. Which sample was clearest (After each of the 4 treatments)?

4. Is the clearest water drinkable? Explain why or why not.

5. There will still be substances dissolved in the water. How are these substances removed from the solution?

6. Unlike Canada may countries have little fresh water.

A. Why can the salt water not be used to drink?

B. How can the salt water be removed?

C. Approximately 97% of the Earth's water is in the oceans. Why do we not remove the salt and use the water for drinking and irrigation?

7. Suggest some substances at a water treatment plant that are removed to make the water drinkable.

A. Why is chlorine gas added to the water during the purification process?

B. Do fluorides have to be added? Why are fluorides added to drinking water?