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"Cleaning Our Water"

Sean Powell

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Objective:

To demonstrate the procedures that municipal water plants use to purify water for drinking.

 

Grade: 4

Materials: swamp water, 1 2L plastic bottle w/cap, 2 2L bottles (one w/top removed, one w/bottom removed), large beaker, 20g Alum, fine sand, coarse sand, small pebbles, nylon hose, rubber band

 

Procedure:

1. Describe the appearance and smell of swamp water before beginning purification process.
2. Aeration is the addition of air to water. It allows gases trapped in the water to escape and adds oxygen to the water. Begin aerating the swamp water as follows;
   1. put the cap on the bottle and shake the water vigorously for 30secs.
   2. Continue the aeration process by pouring the water back and fourth between the cut off bottles 10x.
3. Does the aeration process change the appearance or smell of the water?
4. Coagulation is the process by which the dirt and other suspended solid particles are chemically stuck together into floc so they can be removed from the water.
   1. With a table spoon, add 20g of alum crystals to the swamp water. Slowly mix the two for 5min.
   2. Sedimentation is the process that occurs when gravity pulls the floc to the bottom of the bottle.
5. Construct a filter from the bottle with the bottom cut off as follows:
   1. Attach the nylon to the outside of the neck of the bottle with the rubber band. Turn the bottle upside down, and pour a layer of pebbles into the bottle. Pour the coarse sand on top of the pebbles. Pour the fine sand on top rof the coarse sand. Clean the filter by pouring 5L of clean water through it.

   

6. Filtration through a sand-and-pebble filter removes most of the impurities remaining in water after coagulation and sedimentation are completed. After a large amount of sediment has settled on the bottom of the bottle, carefully (without disturbing the sediment) pour the top 2/3 of the swamp water through the filter. Pour the remaining 1/3 swamp water and Floc into a bucket.

   

Your treatment of the swamp water is complete. Compare it with the swamp water before it was treated. How has the treatment changed its appearance and smell?

 

WORKSHEET:

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Name:_________________________ Date:__________________________


"Cleaning Up Water"


1. Describe the appearance and smell of your "swamp" water.

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2. Aeration is the addition of air (oxygen) to water. Put the cap on your bottle of water and shake for 10 seconds. Take the cap off and let the bottle "breathe". Shake for 10 seconds. "Breathe". Shake for 10 seconds. Does aeration change the appearance or smell of the water?

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3. Coagulation is the process by which dirt and other suspended solids are chemically stuck together into Floc (clumps of impurities) so that they can be removed from the water.
Add two tablespoons (20g) of Alum (aluminum potassium sulfate) to the swamp water. Allow to sit at least 10 minutes (the longer the better). Is there any change in the water's appearance? Explain.

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4. Construct a filter from the cut-off bottle as follows:
Attach the nylon screen to the outside of the neck of the bottle with a rubber band. Turn the bottle upside down with the neck pointed into a large beaker. Pour a layer of pebbles into the bottle (approximately 1/3 full); then pour a layer of coarse sand on top of the pebbles. Pour fine sand on top of the coarse sand. Clean the filter by pouring 4L or more of clean tap water through it. Try not to disturb the top layer of sand as you pour the water onto it.

5. Now, carefully pour your "swamp" water- without disturbing the sediment at the bottom of the bottle- through the filter. Collect the filtered water in to the beaker. Compare the filtered water to swamp water that has not been filtered. Can you see or smell a difference between the two. Explain.


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