At this point students will be asked to suggest ways to save water and protect its quality. Hopefully students will come up with some of the following:
1. Stop letting the water run when you are brushing your teeth, or waiting for a cold glass or water from the tap.
2. Have any dripping faucets fixed. A leaky faucet with a drip of just 1/16 of an inch in diameter can waste 10 gallons of water a day.
3. Don’t fill a washing machine or dish washer unless you have a full load.
4. Close the hose when you are watering the grass or flowers, or washing your car.
5. Limit the use of pesticides and/or use natural lawn care products.
6. Don’t throw toxic chemicals, or oil down the storm drains.
7. Dispose of containers and left over cleaners at the recycling center in your town.
8. Become active in water conservation and government policies that will help the water supply.
Students will be asked to take their ideas about water conservation and quality and make up posters. These can be hung in the classroom or displayed throughout the school so students can share what they are learning with others. If possible students might be given the chance to share what they have learned with younger students.
For the culminating activity of the unit I hoped to do an activity which would become the class science fair project. What I have decided on is for students to do a demonstration of the water filtering process. This experiment is based on the idea presented in the U.S. Environmental Protection Agency web site. 23As part of our study we would visit the regional water treatment plant which is very good about having school children visit its plant. The visit would show the basic five step approach that most water treatment facilities utilize: (1) aeration ;( 2) coagulation ;( 3) sedimentation; (4) filtration; and (5) disinfection.
Objective: To show students how water purification is done
Materials:
5 liters of swamp water or add 2 cups of dirt to 5 liters of water
1 two liter plastic soda bottle with its cap
2 two liter plastic soda bottles – one with the top removed and one with the bottom removed
1 one and one half liter (or larger) beaker or the bottom of another soda bottle
20 grams of alum (available in the pharmacy or spice isle of the supermarket
Fine sand (about800ml)
Coarse sand (about 800 ml)
Small Pebbles (washed natural aquarium stones are fine)
1 large (500ml or larger) beaker or jar
1 coffee filter
1 rubber band
1 tablespoon
A clock with a second hand or stopwatch
Procedure:
1. Pour about 1.5L of the Swamp Water into a 2L Bottle/ have students pass it around and describe its appearance.
2. The first step in cleaning the water is aeration. This means allowing trapped gases in the water to exit and adding oxygen to the water. Put the cap on the bottle and shake it vigorously for 30 seconds. Continue the process by pouring the water into one o the cut off bottles, and then pour it back into the other going back and forth 10 times. Students should describe any changes they see. Pour the aerated water into a bottle with its top cut off.
3. The next part of the process – coagulation- is a way of getting particles within the water to stick together so they can be more easily removed. This is accomplished by adding 20 g of alum crystals to the water. The mixture is then stirred slowly for 5 minutes
4. Sedimentation is the next process that is used in cleaning the water. Gravity pulls the alum and the impurities down to the bottom of the container. The water after stirring now must sit undisturbed. Students should observe the container for the next 20 minutes at 5 minute intervals and list their observations concerning the changes in the water.
5. The next step is to construct a filter using the bottle with its bottom cut off.
a. Attach the coffee filter to the outside neck of the bottle with a rubber band. Turn the
bottle upside down and pour a layer of pebbles into the bottle - the filter will keep
the pebbles from falling out of the neck.
b. Pour the coarse sand on top of the pebbles.
c. Pour the fine sand on top of the coarse sand.
d. Pour 5L (or more) of clean water over the filter. Try not to disturb the layer of sand.
6. Now you can carefully pour the swamp water into the filter being careful not to disturb the sediment which should now be on the bottom of the bottle. After pouring about two-thirds of the water into the filter pour the rest back into the bottle of swamp water. Compare the treated and untreated water.
The final step used by actual filtering plants ends with the addition of disinfectants to the water to purify it and kill any organisms that could be harmful. These chemicals are potentially harmful and so this experiment skips this step. While the water may seem clean it is not fit to drink.
I hope that throughout the unit my students will share what they are learning with their families and that we will share with other classes. It was also suggested to me that the students might have a water fair where they would show off the things they learned to their friends and family. I’m certain that would be a celebration they would enjoy.
This unit is a very small beginning in dealing with environmental concerns. There is a myriad of information on the web and there are numerous activities that students can do. There are many other areas which I have not had time to explore like dealing with how people can affect change and how difficult change is in our industrialized society.
As with all teaching this is a beginning effort and there are many other avenues which this unit can explore. I hope that it will spark interest in my students and that it will expand and contract with new materials as I use it.
