SummaryStudents experience the steps of the engineering design process as they design solutions for a real-world problem that could affect their health. After a quick review of the treatment processes that municipal water goes through before it comes from the tap, they learn about the still-present measurable contamination of drinking water due to anthropogenic (human-made) chemicals. Substances such as prescription medication, pesticides and hormones are detected in the drinking water supplies of American and European metropolitan cities. Using chlorine as a proxy for estrogen and other drugs found in water, student groups design and test prototype devices that remove the contamination as efficiently and effectively as possible. They use plastic tubing and assorted materials such as activated carbon, cotton balls, felt and cloth to create filters with the capability to regulate water flow to optimize the cleaning effect. They use water quality test strips to assess their success and redesign for improvement. They conclude by writing comprehensive summary design reports.
The water that comes from our faucets has passed through a complex system designed by many different types of engineers. Civil, chemical, electrical, environmental, geotechnical, hydraulic, structural and architectural engineers all play roles in the design, development and implementation of municipalities' drinking water supplies and delivery systems. Hydraulic engineers design systems that safely filter the water at a rate needed to supply a specific region and population. Chemical engineers precisely determine the amounts and types of chemicals added to source water for coagulation and decontamination to make the water safe to drink and not taste bad. Even so, modern pharmaceutical and agricultural practices persist in contaminating our water supplies. In this activity, students play the role of engineers challenged to design-build-test filtration devices to regulate flow and maximize output and decontamination.
Students should have prior knowledge of the water cycle, groundwater movement and how current day municipal water treatment plants operate.
After this activity, students should be able to:
- Explain how advances in medicine have resulted in pervasive water contamination.
- Describe how hormones, used in agriculture and medicine, are introduced to the groundwater.
- Describe the effects humans have on the quality of water on Earth.
- Follow the steps of the engineering design process while designing and building prototype devices to filter contaminants from a liquid solution.
- Design a system that regulates flow rate to maximize effectiveness of treatment.
- Filter out 75% of the chlorine from a provided chlorine solution.
- In a summary engineering design report, describe the materials used by explaining their use and effectiveness.
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Each TeachEngineering lesson or activity is correlated to one or more K-12 science,
technology, engineering or math (STEM) educational standards.
All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN),
a project of D2L (www.achievementstandards.org).
In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics;
within type by subtype, then by grade, etc.
Each TeachEngineering lesson or activity is correlated to one or more K-12 science, technology, engineering or math (STEM) educational standards.
All 100,000+ K-12 STEM standards covered in TeachEngineering are collected, maintained and packaged by the Achievement Standards Network (ASN), a project of D2L (www.achievementstandards.org).
In the ASN, standards are hierarchically structured: first by source; e.g., by state; within source by type; e.g., science or mathematics; within type by subtype, then by grade, etc.
- Apply scientific principles to design a method for monitoring and minimizing a human impact on the environment. (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment? Thanks for your feedback!
- Evaluate competing design solutions using a systematic process to determine how well they meet the criteria and constraints of the problem. (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment? Thanks for your feedback!
- Create a computational simulation to illustrate the relationships among management of natural resources, the sustainability of human populations, and biodiversity. (Grades 9 - 12) Details... View more aligned curriculum... Do you agree with this alignment? Thanks for your feedback!
- The management of waste produced by technological systems is an important societal issue. (Grades 6 - 8) Details... View more aligned curriculum... Do you agree with this alignment? Thanks for your feedback!
- Humans devise technologies to reduce the negative consequences of other technologies. (Grades 9 - 12) Details... View more aligned curriculum... Do you agree with this alignment? Thanks for your feedback!
Each group needs:
- 1.5 foot (.46 m) plastic tubing or PVC pipe with 1.5 inch (3.81 cm) or greater inner diameter; available at hardware stores (see Figure 1, which shows an example tube that is longer than 1.5 feet; it is recommend to cut tubes to 1.5 feet to avoid difficulties in removing filter materials)
- 2 250-ml beakers
- 50-100 ml chlorinated water; this 200 ppm solution is prepared by the teacher using Clorox® germicidal bleach; see instructions in the Procedure section
- 50-ml graduated cylinder
- plastic spoon, to load sands and activated carbon
- sieve, to separate small materials
- lab safety gloves, one pair per student per day, such as disposable nitrile gloves available at https://www.amazon.com/s/ref=nb_sb_noss_1?url=node%3D4954444011&field-keywords=disposable+nitrile+gloves&rh=n%3A4954444011%2Ck%3Adisposable+nitrile+gloves
- lab book or notebook, one per student; alternatively, have students record all necessary information throughout the activity on blank sheets of paper and staple them together to serve as a lab "book" for the activity
- safety goggles, enough so that each student in a team can wear goggles while handling and testing the chlorinated solution
- Engineering Design Process and Water Filtration Pre/Post-Test, two per student
- Engineering Design Report Scoring Rubric, one per student
To share with the entire class:
- activated carbon, either granules or pellets; for cleanup, pellets are easier to separate with a sieve at activity end; see material life expectations note, below
- filter media, such as cotton balls, fish filter media, carbon infused filter media, 50 micron felt pad, cheesecloth, cotton cloth or whatever is available
- fine-grained sand
- (for teacher use only!) Clorox® germicidal bleach; used to make a chlorinated water solution; 2 teaspoons bleach per gallon of water
- pitcher or other container large enough to hold a gallon of water, for preparing the chlorinated water
- "free" and total low-level chlorine water quality test strips, such as Hach's "Free & Total Chlorine Test Strips, 0-10 mg/l," 50 strips, 0-10 ppm, for $16.65 at http://www.hach.com/free-total-chlorine-test-strips-0-10-mg-l/product-details?id=7640211603
- sanitizer-strength chlorine test strips, such as LaMotte's "4250-BJ sanitizer strength chlorine test strips," 200 strips, 0-200 ppm, for $7.10 from Cole-Parmer at https://www.coleparmer.com/i/mn/9953231
- sink, tap water, soap, towels
Note: A pound of activated carbon can remove 200 ppm chlorine from 843 gallons, as calculated from http://www.waterprofessionals.com/process-water/dechlorination.html. Thus, a supply of activated carbon is reusable for several years of experiments.
With all of the steps that water goes through before coming out of our taps, we have to assume it is clean and safe, right? Who can tell me the typical treatment steps of municipal water treatment plants? (See what students know.) Water goes through many steps before it arrives at our taps. Larger particles are removed during the coagulation and sedimentation stages of water treatment. In the coagulation stage, alum, a material that causes particles to stick together, is added to the water. In the sedimentation stage, which comes after coagulation, the flow of the water is slowed down to so clumps of particles have time to settle out of the water column. Then the remaining smaller particles are removed by filtering the water through sand filters. Aeration enables some metals and chemicals to come out of the water and enter the atmosphere. (If you see calcium build-up on your shower head and bath spout it is because the water is not adequately aerated). Then, a chemical disinfectant, typically chlorine, is added to the water to kill any pathogens. But, after all that—is the water truly safe?
Since the early 1970s, pharmaceuticals and hormones have been detected in major metropolitan drinking water supplies including those in America and Europe. In 2002, the U.S. Geological Survey conducted a study of 139 streams across the country and found that 80% tested positive for at least one or more chemicals related to human and veterinary drugs, natural and synthetic hormones, and other detergents, plastics and insecticides. Studies have shown that increased estrogen in human males can have adverse effects such as enlarged breasts and decreased fertility. Additionally, studies on fish populations discovered that increased estrogen, and other chemicals that can mimic the hormone, in the river systems are causing male fish to develop female sexual organs. A major contribution to the increase in pharmaceuticals is from improper disposal of leftover medication or traces of medicine, sometimes overprescribed, and not taken up by the body. Additionally, agricultural antibiotics and hormones administered to livestock for increased production are excreted through waste and enter the water cycle in the form of runoff. In addition, the runoff is contaminated by herbicides and pesticides that have been applied to crops.
Some drugs and hormones are not able to be removed by current drinking water treatment processes and may be present in your tap water. Today, as if you were an environmental engineer, your challenge is to design a filtration device that could be implemented in a water treatment system to effectively remove estrogen and other organic compounds from drinking water as a final step in the filtration system.
aeration: Mixing air with a substance.
anthropogenic: Caused or produced by humans.
coagulation: The clumping of a material into larger particles. Example: Blood coagulates to stop a cut from bleeding.
estrogen: A hormone that is naturally found in the human body. This hormone maintains female characteristics of the body and is replicated in birth-control pills.
pharmaceutical: A drug that is used for medical reasons; may be available over-the-counter or prescribed by a doctor.
prototype: A first attempt or early model of a new product or creation. May be revised many times
sedimentation: The process of settling. Example: Particles settle to the bottom of a water column.
Activated carbon (or charcoal) and sand filtration are commonly used to remove particles, organic matter, bacteria and pathogens from water. To keep aquariums healthy for fish, filters with activated carbon are employed to remove tap water chemicals and the chemicals produced from fish waste. Typically, municipal water treatment facilities do not use activated carbon in their filtration processes in order to reduce system cost and maintenance.
Provide students with research (see the References section) that documents the successful use of activated carbon to remove estrogen, the disinfectant that is added to water and other harmful pollutants that may be present in drinking water. Activated carbon reduces the amount of estrogen in drinking water by 60-80%.
Before the Activity
- Gather materials and make copies of the Engineering Design Process and Water Filtration Pre/Post-Test (two per student) and the Engineering Design Report Scoring Rubric (one per student).
- Depending on available supplies, set a maximum material amount that can be used by each group. For example, if you have 40 ounces of activated carbon available and 10 groups, set a 4 oz. maximum per team. If you only have one 24 x 24-inch square of felt, then each group may use a maximum of 2.4 x 2.4-inch square.
- Prepare the chlorine solution: Pour 2 teaspoons of Clorox® germicidal bleach into 1 gallon of water to create a 200 ppm solution.
With the Students—Day 1
- Administer the pre-test, as described in the Assessment section.
- Present the Introduction/Motivation content to the class.
- Review lab safety with students. Inform them that they will be using a bleach solution. Ask them to tell you what lab safety procedures apply to this situation. Refer to the guidelines suggested in the Safety Issues section. Remind students to wear lab gloves and safety goggles when handling and testing the chlorinated water.
- As a class, review the steps of the engineering design process. Refer to https://www.teachengineering.org/engrdesignprocess.php (read and click through the steps.) The basic steps are: Identify the need and constraints, research the problem, develop possible solutions, build a prototype(s), test and evaluate the prototype(s), redesign as needed.
- Divide the class into groups of two or three students each. Or, if materials are scarce, organize the class into groups of three or four students each.
- Review the rubric with students so they understand the activity expectations and the assessment criteria.
- Explain to the class how activated carbon can attract and trap estrogen, organic compounds and chlorine. As water travels through students' prototype filter designs, it is important to be able to control the flow of the water in order to give the activated carbon time to remove the toxins. If the water goes through the activated carbon too fast, it will not purify the water because not enough contact time is provided; if water goes through the carbon too slowly, then the prototype is not efficient for practical use. In situations like this, engineers must find the balance that is most suitable for the purpose and goals of the device being designed.
- Inform students that they will be required to take apart their prototypes at the end of class and separate all materials. A sieve will be provided to separate any mixed sand and activated carbon. Other materials such as wool, filter media and felt will also be separated and returned to their designated storage spots.
- Do a few water quality tests in front of the class to demonstrate how to test water and read the results. First, use a 0-200 chlorine test strip to test the chlorinated solution that was made for the class. The solution should be 200 ppm chlorine. Then test the school's tap water, as taken from a drinking fountain or sink tap, using both the 0-200 chlorine test strip and the 0-10 chlorine test strip so you can compare the school's drinking water to the highly chlorinated water of the pre-made solution. Show students the test strips and how to compare their colors to the scale provided with each type.
- Give groups their filters (the tubes) and let them begin the design process. Inform them of the available supply of materials and any per group material limitations.
- Direct groups to start by brainstorming at least three different designs. Require (at least) one team member in each group to take notes and document all ideas from the brainstorming session, including sketching out various design ideas. Mention to students that throughout all the steps of the design process, engineers benefit from taking detailed notes of all their ideas and test results, including sketches.
- After groups have brainstormed multiple designs, direct them to discuss the merits of each design, comparing them to each other in order to select the most-promising design (or combine various ideas into one most-promising design). Next, have the teams create more detailed sketches of the chosen designs; make sure these drawings are labeled with dimensions/amounts and materials. Remind students to write down the reasoning behind the final design and each material selection, as well as how each is intended to function. Check each design sketch before permitting students to gather the necessary materials.
- Once teams have acquired their materials, direct them to begin creating their prototypes.
- When 15 minutes are remaining in the period, direct students to test their current designs and come up with solutions to any problems they may want to fix during the next day.
- Testing procedure:
- A group brings its prototype up to the teacher. They explain their design concept and the purpose of each layer in their filter prototype.
- Then students hold the prototype vertically above a 250-ml beaker while the teacher pours 50 ml of 200 ppm chlorinated water into the prototype.
- One student uses a stopwatch to record the time it takes for the water to move through the filter.
- Once the liquid has stopped dripping out of the bottom of the prototype (to a rate of about one drip every five seconds), the teacher uses a chlorine test strip to test the dripping water to determine if students have achieved the goal of lower than 50 ppm chlorine. If they have, then the teacher uses a 0-10 ppm chlorine test strip to determine the best estimate of the chlorine concentration of the water.
- Students also measure the amount of water retrieved from the filter.
- In their lab notebooks, students record the chlorine concentration, the time it took the water to move through the filter, and the amount of water retrieved from their filters.
- Direct the team to spend some time making notes about the "lessons learned" from the prototype testing. What worked? What did not work? What could be improved? What new ideas do you have? This prepares them for how to begin the next day.
- With five minutes left of the class period, have students disassemble their prototypes and separate all materials into piles of like materials so they are ready to be used for the next class.
With the Students—Day 2
- Direct students to redesign their filter prototypes with the same expectations of the previous day. This means that groups can modify or completely re-design their water filtration systems from the previous day.
- When teams have completed their revised prototype designs, they take them to the teacher and explain the purpose of each layer of the filter prototypes.
- With the teacher's help, groups test their (hopefully) improved prototypes. They measure the time it takes for water to pass through the system, the after-filtered chlorine concentration with the chlorine test strips, and the amount of water that was retrieved, as they did the previous day. Students record all results in their lab notebooks.
- Groups disassemble their filtration systems and separate the materials into piles for the next class or for storage.
- Direct students to answer the Guiding Questions in their lab books/journals, as provided in the Assessment section. Collect their lab books for grading.
- Direct students to begin individually writing up their observations and results into final engineering design reports, as described in the Assessment section. Give them a deadline to turn them in and grade them with guidance from the rubric.
- Administer the post-test, as described in the Assessment section.
Good lab practices for this activity:
- Wear safety goggles and gloves when handling and testing the chlorine solution and filter materials (because they are re-used and thus contain the chlorine solution).
- Bleach products at this level of concentration may cause skin irritation. If any chlorine solution gets in your eyes or mouths, immediately flush the area with water for 10 minutes.
- If any solution gets on skin, wash the skin with water and soap for five minutes.
- If any solution spills on a desk or the floor notify the teacher so the spill can be cleaned up.
Pre-Test: Before starting the activity, administer the 11-question Engineering Design Process and Water Filtration Pre/Post-Test to gauge student's base knowledge of the activity topics. The assessment contains multiple choice, fill in the blank and matching questions about the engineering design process and water filtration process.
Activity Embedded Assessment
Lab Book/Journal: Individually assess students based on the design and redesign documentation in their lab books or journals. Require each student's lab book to contain design ideas, prototype sketches and a description of the functionality and results from prototype testing. Expect students to include observations and hypotheses about their prototype designs and material use. Direct them to document their reasoning for each design they built and tested. For full credit, require students to answer the following Guiding Questions for the design portion of the lab book:
- What are you trying to accomplish in the design of your water filtration device?
- What are different ways to use the materials provided in your filtration device?
- How can you control water flow to enable the chlorinated water to react with the activated carbon?
- What is the purpose of each portion of the water filtration device your group decided to build?
- What are the results of your water filtration device's test?
- In what step of the water filtration process would you implement your design?
Summary Engineering Design Reports: Students prepare and hand in engineering reports on their design work completed on both days, including the pros and cons of their designs. Grade students on their ability to critique their designs and their improvements from Day 1 to Day 2 and suggestions to further improve the prototypes. Students whose designs did not improve can still obtain high-achieving grades by thoroughly explaining the ways that their second designs did not work compared to their first designs and how they can further improve their designs. Use the Engineering Design Report Scoring Rubric for guidance in assessing students' reports.
Post-Test: Administer the Engineering Design Process and Water Filtration Pre/Post-Test again to analyze student content knowledge on the engineering design process and water filtration steps. Compare pre/post scores to gauge changes in student comprehension.
If time permits, conduct a materials analysis of scaling the best design in the class to a full-scale water treatment system that can filter 4.5 million gallons per day, which is the city of Marlborough, MA's average daily water use.
Doheny, Kathleen. "Drugs in Our Drinking Water? Experts Put Potential Risks in Perspective After a Report that Drugs Are in the Water Supply." Published March 10, 2008. WebMD Feature, WebMD. Accessed July 2, 2014. http://www.webmd.com/a-to-z-guides/features/drugs-in-our-drinking-water
Rowsell, Victoria F., Dawn S.C. Pang, Foteini Tsafou and Nikolaos Voulvoulis. "Removal of steroid estrogens from wastewater using granular activated carbon: comparison between virgin and reactivated carbon." Water Environment Research. April 2009, 81(4): 394-400. Print.
Welch, Lyman. "Drugs in Drinking Water: New Report Explores Emerging Great Lakes Threat, Solutions." Posted March 4, 2010. News Room: Drugs in Drinking Water-New Report Expl. Alliance for the Great Lakes. Accessed July 2, 2014. http://www.greatlakes.org/pharmareport
ContributorsTimothy S. Vaillancourt, Terri Camesano, Kristen Billiar, Jeanne Hubelbank
Copyright© 2015 by Regents of the University of Colorado; original © 2014 Worcester Polytechnic Institute
Supporting ProgramInquiry-Based Bioengineering Research and Design Experiences for Middle-School Teachers RET Program, Department of Biomedical Engineering, Worcester Polytechnic Institute
This activity was developed under National Science Foundation RET grant no. EEC 1132628. However, these contents do not necessarily represent the policies of the National Science Foundation, and you should not assume endorsement by the federal government.
Last modified: January 12, 2018