Water Treatment & Filtration

Transcription

1 Water Treatment & Filtration Subject Area: Natural Resources Unit Title: Source Water Protection Grade Level: 4th & 5th grade Objectives: To help students understand the importance of protecting Colorado s valuable water resources. Colorado Content Standards to be covered: GEOGRAPHY Standard V- Students understand the effects of interactions between human and physical systems and changes in meaning, use, distribution, and importance of resources. SCIENCE Standard I - Students understand the processes of scientific investigation and design, conduct, communicate about, and evaluate such investigations. Standard III - Life Science: Students know and understand the characteristics and structure of living things, the processes of life and how living things interact with each other and their environment. Standard V- Students know and understand interrelationships among science, technology and human activity and how they can affect the world. Materials: water filtration handout 2 liters of swamp water (you might find some standing water outside your home that has started to turn green or just add 1 cup of dirt to your 2 liters of water) 1-two liter plastic soft drink bottle with its cap 2-two liter plastic soft drink bottles, one with its bottom cut off and one with the top cut off 1 large beaker or measuring bowl that will hold the inverted two liter bottle 2 tablespoons of alum (potassium aluminum sulfate) found in spice aisle at grocery store 1 1/2 cups of fine sand found in home improvement/hardware store or landscaping supply 1 1/2 cups of coarse sand found in home improvement/hardware store or landscaping supply 1 cup of small pebbles (or aquarium rocks) coffee filter rubber band tablespoon for measuring large spoon for stirring stopwatch Anticipatory Set: Ask the students to fill in the first column of the included Vocabulary Knowledge Rating Chart indicating how well they know each vocabulary word before the lesson (first column). Input: Where does water come from? 1

2 Whether source water comes from the surface or from the ground, it most often isn t safe for people to drink. It must be cleaned or treated. Depending on the quality of the source water, water may be treated differently. Sometimes all that is needed is for the water to be filtered. Other times, water needs to be treated by a more complicated process. Many drinking water treatment systems have two main parts: treatment and distribution. Water is treated. Then it is stored and then delivered to all of us. Let s follow water as it goes through a treatment process. Water is collected and screened to remove large objects such as sticks, leaves, and trash. Water may be stored in reservoirs where natural purification takes place. It can then be treated with chemicals to kill harmful germs, remove pollutants, or bad tastes and odors. This process is called coagulation. The chemicals used and any particles settle to the bottom during the sedimentation process. Next, the water is filtered through layers of sand, gravel and charcoal. This is called filtration. The last step is adding a small amount of chlorine to kill any left over bacteria. This part of the process is called disinfection. After the water has been treated, it is stored in tanks, water towers, reservoirs or sent directly to homes and businesses through water pipes. Sometimes water needs additional treatment which might include: fluoridation or adding fluoride to water to help prevent tooth decay. Water conditioning or softening may be used when water is hard because it has too much salt or minerals. Some small communities have a community well where they get their water. This water may or may not be treated. It depends on the quality of the water. Some people who live in the country get their water from their own well. If this is the case, the water is probably not treated. Checking for Understanding: At the end of this section, choose one of the following for a quick check: ask the students to partner share and think, pair and share, do a quick 3 word write up as an exit slip, do a quick sketch or give each other a quick thumbs up or down to check for understanding. Determine the level of mastery for each student and provide individual remediation as needed. Procedures/Activities: Build Your Own Water Filtration System Please note: The water you will filter is unsafe to drink. 1. Pour your swamp water into the two liter bottle with cap. 2. Notice how the water looks and smells. 3. Ask yourself: Would you want to drink it? 4. Our first step in the filtration process is to add air to the water. It allows gases trapped in the water to escape and adds oxygen to the water. Place the cap on the bottle and vigorously shake the bottle for 30 seconds. Continue the aeration process by pouring the water into another bottle or the beaker, then pour the water back and forth between them about 10 times. Once aerated, gases have escaped, and bubbles should be gone. 5. Pour your aerated water into your bottle with its top cut off. Coagulation is the process which allows dirt and other suspended solid particles to chemically stick together into floc or clumps of alum and sediment so they can easily be removed from water. Add 2 tablespoons of alum to the aerated water. 6. Slowly stir the mixture for 5 minutes. You will see particles clinging together to make large clumps. This makes it harder for them to get through a filter in the plant. 7. Sedimentation is the process that occurs when gravity pulls the particles of floc to the bottom of the cylinder. Allow the water to stand undisturbed in the cylinder. Observe the water at 5 minute intervals for a total of 20 minutes. Write down what you see. What is the appearance of the water now? 8. At a treatment plant, there are settling beds that collect floc that sinks to the bottom, allowing the clear water to be drained from the top of the bed and continue through the process. 9. Construct a filter from the bottle with its bottom cut off as follows: attach the coffee filter to the outside neck 2

3 of the bottle with a rubber band, completely covering the hole in the top of the bottle. Turn the bottle upside down and place it in your beaker or two liter bottle with the top cut off. Pour the pebbles into the bottle. Pour the coarse sand on top of the pebbles. Pour the fine sand on top of the coarse sand. Clean the filter by slowly and carefully pouring through about 2 liters of clean tap water. Try not to disturb the top layer of sand as you pour the rinsed water out of the container. 10. Filtration through a sand and pebble filter removes most of the impurities in the water. Take your swamp water and carefully pour the top two-thirds of the water through the filter. The sediment on the bottom of your swamp water bottle should remain, just as it would in a settling bed. Once the filter has stopped dripping, compare the finished water with the swamp water. What are the differences? Is it clearer, does it still smell? 11. The last step in a treatment process is disinfection to purify the water and kill any organisms that may have made it through the treatment process. Because disinfectants are dangerous and must be handled carefully, we do not recommend this step. The water you just filtered is unsafe to drink. from the United States Environmental Protection Agency website: Closure: Review and clarify the key points of the lesson including the new vocabulary words. Have the students return to the Vocabulary Knowledge Rating Chart and rate their understanding of each vocabulary word after the lesson. Then have them write down the definition and provide at least one example. You may want to visit your local water utility to see this process on a large scale. Each water utility system must decide, given the water source they must use, the best treatment process for them. 3

4 Vocabulary Knowledge Rating Chart Before the Lesson: In the first column, indicate how well you know each vocabulary word by using 1 to represent I know what it means, 2 I sort of know what it means, or 3 for I don t know what it means. After the Lesson: In the second column, indicate how well you know each vocabulary word after the lesson, by using 1 I know what it means, 2 I sort of know what it means, or 3 I don t know what it means. Next write down the definition and give at least one example or use the word in a sentence. Vocabulary Word Before After Definition Example/Sentence Lesson Lesson coagulation sedimentation filtration disinfection 4

5 Vocabulary Knowledge Rating Chart KEY Before the Lesson: In the first column, indicate how well you know each vocabulary word by using 1 to represent I know what it means, 2 I sort of know what it means, or 3 for I don t know what it means. After the Lesson: In the second column, indicate how well you know each vocabulary word after the lesson, by using 1 I know what it means, 2 I sort of know what it means, or 3 I don t know what it means. Next, write down the definition and give at least one example or use the word in a sentence. Vocabulary Word Before After Definition Example/Sentence Lesson Lesson coagulation sedimentation filtration disinfection when water is treated with chemicals to kill harmful germs, remove pollutants, or bad tastes and odors when the chemicals used and any particles settle to the bottom water is filtered through layers of sand, gravel and charcoal adding a small amount chlorine to kill any left over bacteria answers will vary 5