Science Fair Water Treatment

A look at Chemical Engineering for children.

How do We Get Clean Water?

Where does the water from your sink come from? How come it is clean when it comes out of my sink but dirty in the river? These are questions that all curious kids ask. Their curiosity leads to a new generation of new scientists and engineers. Luckily for me, this curiosity was fostered in my home by helping me find the answers. Sometimes this was in a book or through experimentation. So, I am writing this post to show how to get clean water at home.

Before water can be brought to your house it goes to a water treatment plant. Listed below are the steps most towns use to provide their citizens with clean water (Combest, n.d.).

Step 1: Collect the water from a lake, river, or ground.

Step 2: Filter out all the gross stuff. After all, nobody wants trash, sand, sticks, fish, or poop in their drinking water.

Step 3: Add chemicals to the water. These chemicals react with harmful particles in the water causing them to become solids in the water. This is like a chemical grabbing onto the salt in saltwater. Since it wants the salt more than the water, it pulls it out from liquid to solid. This turns the saltwater into normal water. This is called a precipitation reaction.

Step 4: Mix the water really fast. The mixing speeds up the precipitation reaction and causes the small solid partials to clump together into bigger pieces.

Step 5: Remove the new solids from the water. The first step to do this is to let the solids sink to the bottom. The water can then move to the second step. This second step is to filter the water of any remaining solids.

Step 6: Disinfect the water of germs. Like washing your hands to kill germs, the water is washed to kill germs.

Water Treatment Experiment

To demonstrate how water is treated, a basic precipitation experiment can be performed at home. The experiment will make use of steps 3-5 of the water treatment. This experiment uses ice melt and baking soda to form the solid Calcium Carbonate or chalk. The chalk can be removed from the water using a coffee filter and funnel.

Materials

The following items will be needed to perform this experiment.

· 2 clear glass mixing bowls (4 cups or larger)

· 1 spoon

· 1 funnel

· 1 coffee filter

· 1 large jar

· 1 tablespoon (Tbsp.) of Calcium Chloride salt (or 3 Tbsp. of ice melt)

· 2½ cups of water (use 4 cups if 3 Tbsp. of ice melt is used)

· 1 teaspoon (tsp.) of baking soda

Experimental Steps

Step 1: Collect the 1 Tbsp. of Calcium Chloride (CaCl2) from the ice melt. (I used Road Runner ice melt, but any ice melt containing CaCl2 will work.) I sorted the CaCl2, the spherical white crystals seen below, from the ice melt salt mixture. Pure ice melt can be used but it requires a larger quantity (3 Tbsp.) and may be less effective.

Step 2 (Optional): Crush the CaCl2 so that it will dissolve faster.

Step 3: Measure out 2½ cups of water (4 cups if pure ice melt is used) in one of the glass bowls.

Step 4: Pour the CaCl2 into the water and stir using the spoon for two minutes or until all the CaCl2 has dissolved.

Step 5: If any of CaCl2 salt remains after two minutes of stirring, carefully pour the water from the first glass bowl into the second glass bowl. If all the CaCl2 dissolved move onto Step 6.

Step 6: Add the 1 tsp. of baking soda to the water and stir for 1 minute, demonstrating steps 3-4 of the water treatment process. This should turn the water from clear to cloudy. The cause of the cloudiness is the formation of Calcium Carbonate/chalk.

Step 7: Place the coffee filter in a funnel and rest the funnel over a large jar. Slowly pour the cloudy water solution into the funnel. Be careful not to overfill the funnel (it will take a while to filter and multiple pours may be needed). This demonstrates step 5 of the water treatment process.

Step 8: Once fully drained, the water in the jar should be clear and the filter should have a white substance on it. If allowed to dry for 24 hours, the power will resemble and feel like chalk that was created.

Step 9: Clean up and put away all the equipment.

For help performing the experiment, please watch the video I made below.

https://www.youtube.com/watch?v=VKaHviIloFE

References:

Combest, Tymn., Municipal Water Treatment Processes (n.d.). Los Angeles, CA; Los Angeles Department of Water and Power.