From Brine to Beverage: Solar-Powered Salt Removal

Make Your Saltwater

1. Add 4 cups of water to the liquid measuring cup.
2. Wash and cut up your beets into chunks on a cutting board and add them to the liquid measuring cup. Use caution and have an adult supervise when handling the knife. If you are using food coloring instead of beets, add a few drops of the coloring to the water. The coloring "marks" the water with a contaminant, just like those that exist in real saltwater.
   
   
   
   

   Figure 2. This shows the liquid measuring cup filled with 4 cups of water and two chopped beets.
3. Put the liquid measuring cup and its contents inside the microwave. Turn the microwave on high power until the water comes to a boil. If you are using beets, boil the water in the microwave for an additional 3-4 minutes. If you are using food coloring, turn off the microwave as soon as it comes to a boil. Remove the liquid measuring cup carefully from the microwave using an oven mitt. Be careful with the hot water so you don't get burned.
4. Lay out newspaper on your work surface because beets and red food coloring both stain.
5. Add 1 teaspoon of salt to each of three bowls. These will be your low-salinity bowls. Label them by amount of salinity, with a "D" for "Desalinator," and a number to keep track of them individually, as follows: Low Salinity D1, Low Salinity D2, and Low Salinity D3,with sticky notes.
6. Add 3 tablespoons of salt to each of three bowls. These will be your high-salinity bowls. Label them by amount of salinity, with a "D" for "Desalinator," and a number to keep track of them individually, as follows: High Salinity D1, High Salinity D2, and High Salinity D3,with sticky notes.
   
   
   
   

   Figure 3. This shows how to prepare the bowls for the addition of hot water.
7. Using your dry measuring cup, add ½ a cup of hot red water from your liquid measuring cup to each of the six bowls. Use caution when pouring the hot water so you don't get burned.
8. Stir the water in each of the bowls with a spoon for 1-2 minutes to help the salt dissolve. Now you have six bowls, each representing the Red Sea, one of the saltiest bodies of water in the world!

Make Your Six Desalinators

1. Figure 4 shows the components of a desalinator and how it should be assembled.
   
   
   

   
   Figure 4. This is how to assemble a desalinator.
2. Place each of your six small cups inside each of the six bowls. Position the cups in the middle of the bottom of the bowls.
3. Cover the top of each bowl with a large piece of plastic wrap. Leave extra around the edges. Press down slightly with your fingers into the middle of each piece of plastic so that it sags down toward the cup.
4. Fasten the elastic bands around the top of each bowl so that there is a tight seal between the plastic wrap and each bowl, but still a sag in the middle, toward the cup.
5. Place 1-3 rocks or other small heavy objects on the sagging portion of the plastic, directly over the small cup. You may need to tug the overhanging plastic slightly to get the plastic to sag evenly over the cup.
6. Your assembled desalinators should look similar to the examples in Figure 5.
   
   
   
   

   Figure 5. Here are two assembled desalinators filled with low- and high-salinity saltwater.

Test Your Desalinators

1. Find a location where your desalinators can receive direct sunlight. Carefully set your desalinators side by side in the sun. Note: warmer climates have faster rates of desalination than cooler climates, so if you live in a cooler climate, start your test in the morning so you have enough daylight hours to complete the test.
2. Check on your desalinators once every hour to make sure they are all still in the sunlight. If they are not, gently move them to a sunny location.
3. Also peek through the plastic and look at the water that has collected in the small cups once every hour. If any of the cups look like they are about three-quarters full, then stop the desalination. Otherwise, continue to leave the desalinators out in the sun.
4. Stop the desalination when any of the small collection cups are at least three-quarters full, or if the sunlight has ended for the day. Carefully and slowly remove the weights, elastic bands, and plastic wrap from each desalinator.
5. Look in your small collection cups. What is the color of the collected water? Was your desalinator able to remove the red contaminant? Write down your observations in your lab notebook.
6. For each desalinator, pour the water you collected in the small cup into the medicine cup, as shown in Figure 6, and measure what you collected. Record your measurements in a data table, like the one below. Then pour the contents of the medicine cup back into the small collection cup and place it back inside its corresponding bowl.
   
   

   Figure 6. This shows the collected water ready to be poured into a medicine cup for measurement.
   
   

   Water Collection Data Chart
   	Amount Collected for Low Salinity (mL or tsp)	Amount Collected for High Salinity (mL or tsp)
   Desalinator 1 (D1)
   Desalinator 2 (D2)
   Desalinator 3 (D3)
   Sum
   Average

   
   
   Once you have measured all your collected water, dip your finger into one of the collection cups and taste what you collected. Now dip your finger into the red saltwater and taste that. Is there a big difference between the taste of the two waters? Write down your observations for each bowl. Compare the average freshwater collected from the low-salinity desalinators with the average freshwater collected from the high-salinity desalinators. Which type of desalinator produced the most freshwater?