Students are asked to design methods to filter water using ordinary materials, while also considering their designs' material and cost efficiencies. They learn about the importance of water and its role in our everyday lives. They come to understand what must occur each day so that they can have clean water.

Clean water is not available in all parts of the world. Many people live with polluted water that is unhealthy for them to drink and bath in. Civil, environmental , materials and mechanical engineers all contributoe to developing technologies and systems to purify unclean water. Purifying water can be done easily if it is a small amount that is fairly clean, but larger amounts that are very polluted are much more complicated. Typical steps for full water treatment include aeration, coagulation, sedimentation, filtration, and disinfection clean water filter filtration water Understanding of how filtration works. Creative design methods. Problem solving. Mathematics (multiplication) reinforcement. Teamwork to solve a challenge. 1 liter of water with soil and sand in it until it is thin but relatively opaque 3 test tubes prepared with the water standards "A," "B," and "C" (C is filtered through some grass, B is filtered through a coffee filter, and A is filtered through 2 coffee filters with a paper towel in the middle) cotton balls gauze squares tulle/netting tissue paper towels coffee filters gravel (aquarium gravel works great) sand 3 test tubes per student test tube racks graduated cylinders One of our most valuable and often overlooked resources is water. We can survive for a few weeks without food, but only a few days without water. Having clean water to drink is a luxury. The water that eventually comes out of our faucets often did not start off being safe to drink. In most cases, it has gone through a water treatment plant designed by engineers prior to reaching our faucets. This is a great activity for students to experience some "real-life" engineering. Any materials you have in your classroom can be adapted as filtration materials. Water from lakes and rivers often has contaminants that make it unfit for drinking. The water may contain dirt, rocks, and other objects that can be easily identified. Water may also contain bacteria and other microscopic organisms that cannot be seen easily. For these reasons, water that is delivered to our homes must go through a water treatment process. This is typically a five-part process that consists of aeration, coagulation, sedimentation, filtration, and disinfection. This activity is only concerned with filtration, which removes most but not all of the impurities from the water. Make sure students know that in this activity the filtered water is still unfit to drink. Recommended Resources: Information on the water treatment process and drinking water standards: http://www.epa.gov/safewater/ Technology library with information on different types of filters and filtration processes: http://www.osmonics.com/library/library.htm Make the liter of dirty water and the "A," "B," and "C" tubes. Tell the students they have been hired by (Your last name) Water Supply. There has been a drought and there is little water for all the things we need to supply - people, animals and plants. Tell them that they will each be given a sample of the dirty water they have remaining, and show them the tubes "A," "B," and "C". A is nearly ready for human use, B is nearly ready for animal use, and C is nearly ready to feed the plants. Remind them that no one must taste anything in the lab. They will be paid for their supply of filtered water: A gets $10 per ml, B gets $5 per ml, and C gets $1 per ml. Put trays of materials in front of the students. Let them decide in teams what materials they would like to use to filter their water. Have them draw schematics of the layers. Once completed, they can receive 25 ml of the dirty water and begin filtering into their test tubes. Once filtering is complete, have them bring the test tubes to you for observation. You will decide if the water is A, B, or C grade and help them measure their sample in a graduated cylinder. They must return to their desks and do the math to come up with their $ value. Have the students put their $ values on the board. Rubric for Performance Assessment (pdf) Rubric for Performance Assessment (doc) What was the best filtering agent and why? What are other ways we purify our water? Design a package for your "clean" water. Use the attached Rubric for Performance Assessment to evaluate students design projects using criteria for the final fitering system and their teamwork effort.