Hands-on Activity The Mystery of the Contaminated Water – An Engineering Challenge!

Quick Look

Grade Level: 11 (10-12)

Time Required: 2 hours 30 minutes

(three 50-minute periods)

Expendable Cost/Group: US $0.00

Group Size: 3

Activity Dependency: None

Subject Areas: Biology, Life Science, Problem Solving, Science and Technology

Two students in personal protective equipment (PPE) test a lab sample for contamination in a classroom setting.
Testing a potential contaminant in the lab.
Copyright © 2022 Mariana Quinn, Rice University RET


Students have a mystery to solve! At a remote research facility, a researcher has become gravely ill. Did someone contaminate their drinking water? Students must become water treatment sleuths to design a protocol to analyze the “contaminated water” and then implement that protocol to identify what was added to the water. Based on this knowledge, students just might be able to identify who poisoned Dr. Clearwater!
This engineering curriculum aligns to Next Generation Science Standards (NGSS).

Engineering Connection

Environmental and civil engineers develop new devices and systems for water resource management facilities. These engineered devices and systems ensure that citizens are provided with a continuous supply of clean, uncontaminated water for drinking, living, and recreational purposes. Before engineers treat the water, they need to figure out what they are treating the water for since water can be contaminated with specific bacteria, minerals, nutrients, and chemicals.

Learning Objectives

After this activity, students should be able to:

  • List the multiple types of containments and/or pollutants found in water
  • Describe different ways that water can be analyzed for the presence of contaminants and/or pollutants.
  • Discuss the importance of every step of their water analysis protocol.
  • Think and outline ways to improve testing methodology design.

Educational Standards

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.

  • SEP.1.9-12.3. Analyze data using computational models in order to make valid and reliable scientific claims. (Grades 9 - 12) More Details

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  • SEP.3.9-12.6. Construct an explanation based on valid and reliable evidence obtained from a variety of sources (including students' own investigations, models, theories, simulations, peer review) and the assumption that theories and laws that describe the natural world operate today as they did in the past and will continue to do so in the future. (Grades 9 - 12) More Details

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  • SEP.3.9-12.9. Design or refine a solution to a complex real-world problem, based on scientific knowledge, student-generated sources of evidence, prioritized criteria, and tradeoff considerations. (Grades 9 - 12) More Details

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Materials List

Each group needs:

To share with the entire class:

To make each water sample evidence:

Worksheets and Attachments

Visit [www.teachengineering.org/activities/view/rice-2646-contaminated-water-mystery-activity] to print or download.

Pre-Req Knowledge

Students should be familiar with different of types of contaminants (such as bacteria, minerals, nutrients, chemicals) that can be found in water. Students should also be familiar with different ways and/or equipment that can be used to analyze water for contaminants.


How do we approach a situation where someone has gotten sick from contaminated water? Engineers have been able to develop very clever ways to ensure the water we consume is safe, but sometimes their methods can have flaws, or these systems can encounter issues or problems the presence of something unexpected.

Through the years, engineers and scientists have come up with very clever ways to treat the water that we consume. But before developing ways to treat water, they must figure out why they are treating water and what potential substances need treatment. This can include specific bacteria, minerals, nutrients, or chemicals.

Our case takes place in a remote research facility. This research lab comprises six Principal Investigators (PIs). Dr. Noolan Courage, one the PIs, went to talk to Dr. Mystery Clearwater about one of the groups’ research projects. When Dr. Courage knocked Dr. Clearwater’s door, and no answer came from within, he proceeded to open the door, only to find Dr. Clearwater’s lifeless body on the floor! Dr. Courage ran out of the bedroom and alerted the other four PIs, including Dr. Kristeena Crowfurd, Dr. Leena Specktackle, Dr. Ripple Mistales, and Dr. Sheerluck Molmes.

Dr. Molmes began working the room like a crime scene. He instructed all the PIs to put on proper PPE and to walk around the room to see what could have caused the death of Dr. Clearwater. After a couple of minutes, Dr. Specktackle found a glass of what seemed to be water near the body. Could this mean that Dr. Clearwater was poisoned? The contents of the glass were put in a closed lid container to be analyzed later.

Dr. Mistales brings up an interesting fact. What if the whole water supply is compromised with whatever it is that killed Dr. Clearwater? The scientists started looking at each other. Lately everybody seemed to be on edge and seemed to be suffering from cabin fever. Could it be that there is a killer among them? Dr. Molmes instructed everybody to not drink the water until it could be properly examined.  Luckily, the lab has a couple of boxes of soda pop that we can drink, but eventually water will be needed.

Dr. Molmes has called you all to help in the case. He has requested for each team to take a sample of the water supply and create a protocol to analyze the contents of the water. Let’s see who can solve the mystery of the contaminated water. Could it be an accident, or could this be the nasty job of a killer among our researchers? Dr. Molmes also started investigating the relationship of Dr. Clearwater with all the other PIs, and he has discovered some disturbing facts:

  1. Dr. Kristeena Crowfurd: Specializes in bacteria research. She was very upset with Dr. Clearwater because one of his papers had been published before hers.
  2. Dr. Leena Specktackle: Specializes in microorganisms larger than bacteria. She had a couple of rough encounters with Dr. Clearwater because he kept stealing candy from her personal candy stash.
  3. Dr. Ripple Mistales: Specializes in chemicals- especially phosphates. Dr. Clearwater and Dr. Mistales went to the same university and apparently Dr. Clearwater had dated Dr. Mistales’ sister and had broken her heart.
  4. Dr. Sheerluck Molmes: Specializes in chemicals- especially nitrates. He is very open about not liking Dr. Clearwater. He shared that there is something annoying about how Dr. Clearwater chews his food.
  5. Dr. Noolan Courage: Specializes in aquatic plants. He doesn't seem to have a motive, but he has always felt intimidated by Dr. Clearwater, and by every person in the research team, including the research engineers.



Water is the basis of human life.  All living organisms, from plants to animals, need water to survive. Without water, life as we know it could not exist.

Humans have come very far in the realm of water treatment. Scientists have been able to develop different methods to ensure the safety of the water we consume in our day-to-day lives. Even though water treatment plants have developed better ways to treat our water, they still encounter certain issues, causing several individuals’ illness and sometimes death. Some of these include severe waterborne outbreaks such as the presence of Cryptosporidium, to large amounts of E.coli found in our water supply. When outbreaks like this occur, engineers must research the problem first to see what exactly they are encountering and then they can develop a way to solve the problem. Through this activity, students will be immersed in a problem of water pollution. Like scientists, they will have to develop a protocol to further research their problem of contaminated water, so they can then develop the best way to approach the problem and find a solution.

Before the Activity

  • Make copies of:
  • Prepare water samples - make different samples so students can have different results and can approach their individual problem (such as identifying what pollutant is in the water) in different ways. To conclude who the ‘killer’ is, students will have to look at their results for the water and compare it to each of the suspects.
    • If you want to make it trickier and have multiple killers, you can combine contaminants in some of the water samples.
    • Bacteria water:
      • Use a 12 oz. glass jar with a lid
      • Add 10 oz. of distilled water
      • Using an inoculation loop or a cotton swab, collect bacteria from the “Introductory Bacteria Set, Living Tube Cultures (Item #: 154755) from Carolina and swirl it in the 10 oz of distilled water
      • Mix thoroughly
    • Microorganisms water
      • Use a 12 oz. glass jar with a lid
      • Add 9 oz. of distilled water
      • Use the Mixed Protozoa Demoslide Set, Living (Item #: 130865) from Carolina. Collect 1 oz of the sample and mix it with the 10 oz distilled water.
      • Be aware that some of these organisms will need food to survive
      • You can make a higher concentration of microorganisms in the water by changing the ratio of distilled water to mixed protozoa sample
    • Aquatic Plants/algae sample
      • Use a 12 oz. glass jar with a lid
      • Add 9 oz. of distilled water
      • Use the Desmid Mixture, Living (Item #: 151261) from Carolina. Collect 1 oz of the sample and mix it with the 10 oz. distilled water
      • Be aware of the conditions to keep the sample viable
      • You can make a higher concentration of algae in the water by changing the ratio of distilled water to desmid mixture sample
    • Phosphate sample
      • Use a 12 oz. glass jar with a lid
      • Add 10 oz. of distilled water
      • Add one tablespoon of any pesticide/herbicide high in phosphate
      • Mix thoroughly
      • You can increase the concentration of phosphate in the sample by adding more of the chemical
    • Nitrate sample
      • Use a 12 oz. glass jar with a lid
      • Add 10 oz. of distilled water
      • Add one tablespoon of any fertilizer high in nitrate
      • Mix thoroughly
        • You can increase the concentration of nitrate in the sample by adding more of the chemical
    • NOTES:
      • You can mix samples to have multiple “killers” – This is particularly helpful to make sure students test each type of contaminant.
      • You can also use stagnant water from potted plants or collect rainwater
      • Keep in mind that in these types of samples, you don’t know what kind of contaminant you will get so it will make for an interesting result as far as the finding of the killer goes.
  • Using the Evidence Log and Chain of Custody Sheet, label each sample with an evidence log, seal it with evidence tape and attach chain of custody log.

With the Students

 Day 1: Ask, Research

  1. Divide the class into groups of three students.
  2. Hand each group a Case File Sheet with Suspect Cards.
  3. Give students 10 minutes to analyze contents of the case file, including the storyline, suspect list, and the Student Handout Part 1.
  4. Display the PowerPoint Presentation. As a class, read through slides 3-12 and reiterate the storyline and suspect list.  
  5. Explain the activity to the students: Students will design a protocol to follow for the analysis of their evidence (water sample).
  6. Show slide 13. Ask the students to try and define a protocol.
  7. Show slide 14.  Read through slide 14 to describe a protocol.
  8. Ask the students why they think it’s important to have a clear protocol. Probe students to answer why they think that having a protocol is important in a lab setting.
  9. Show slide 15. Explain how students will use the steps in the Engineering Design Process to solve their mystery.
  10. Show slide 16. Allow the students time (5-10 minutes) to complete Step A of the first portion of the student handout.
  11. Show slide 17. For the rest of the class period, have students research each of the types of water contaminants. Have them record their research on Step B of the student handout. (Note: If students need more time, have them finish the research step as homework.

Day 2: Research, Brainstorm, Plan

  1. Show slide 19. As a class, share out each team’s research findings. List the class’s findings on white board or poster board for everyone to see.
  2. Hand each group their “evidence” (water sample). Advise students to not touch the evidence unless they have PPE.
  3. Instruct students how to open the “Evidence seal” and how to fill out the Evidence Log and Chain of Custody Sheet for the water sample.
  4. Using just their eyes, have students pre-analyze their sample and write down their observations in the Student Handout Part 1.
  5. Show slide 20. Explain the constraints. Tell the students that they only have a specific set of materials on hand to analyze their water sample. These include pH tablets, phosphate tablets, nitrate tablets, coliform tablets and microscopes and petri dishes for bacterial growth and the identification of microorganisms (found in the Introductory Bacteria Set and Mixed Protozoa Demoslide Set; see Materials List.)

Notes for teachers:

    1. For pH testing: pH tablets can be used or pH strips (this will vary depending on which ones you want to provide for the students).
    2. For pH, nitrates, phosphates, coliform bacteria: If using the tablets, give students very vague instructions on how to use them. Let them know that they will have to elaborate on their protocol and be very specific about the type of container to be used, the use of a control when testing, etc.
    3. Microscope usage: One of the suspects specializes in microorganisms larger than bacteria and another one in aquatic plants. Probe the students to use the microscope to see if any of these are present in the water.
    4. Petri dishes: To be used for bacterial growth. Give students vague instructions on how to grow bacteria from their sample. Inform them that they will have to elaborate on the instructions of how to grow bacteria in their protocol.
    5. NOTE: This list of constraints can be modified according to the materials that you have in your class that you want the students to use.
  1. Show slide 21. Brainstorm: Have students use their research and the class compiled list to make a list of pollutants/contaminants that could be found in their water samples and how they could use the available materials to test. (Note: You can also tell the students that clues of what to look for are on the specialties of each of our suspects.)
  2. Show Slide 22. Go over things students should consider for their protocol. Make sure to discuss with the students the importance of having a control group within the experiment to compare results.
  3. Give students the rest of the class period to create an outline of their protocol. (Note: If students need more time, have them finish their protocol as homework.)

Day 3: Brainstorm, Plan

  1. Give students more time to finish their protocol outline (if needed).
  2. When students complete their protocol, have them get it approved by their “PI” (aka the teacher).
  3. Once the protocols have been approved, give students 20 minutes to write their protocol on the poster paper and post their poster around the room for a Gallery Walk.
  4. Hand each group the Student Handout Part 2.
  5. Gallery time! Have students walk around the room and analyze each other’s protocols. Students should make note on the Student Handout Part 2 of items that they like from other groups’ protocols that they want to include on their protocol. Hand students ‘stickers’ and have them place stickers on the protocols they believe are the most complete.

Day 4: Create, Test, Iterate

  1. Time to run the protocol and see if it works! Have each student team use their written protocol and the materials provided in class to test their water sample to check for its content
  2. (Note: Let the students know that they should include any notes or adjustments they want make while running through their protocol.)
    1. Share with the students some things to consider:
      1. How will you present your data?
      2. How will you ensure that you don't accidentally contaminate the sample during testing?

A student in personal protective equipment (PPE) checks the seal on a petri dish in a class laboratory.
Image 1: Sealing a petri dish to prevent further contamination.
Copyright © 2022 Mariana Quinn, Rice University RET

A group of three students in personal protective equipment (PPE) analyze a sample and take notes at a lab station.
Image 2: Students analyze their samples in the lab.
Copyright © 2022 Mariana Quinn, Rice University RET

  1. Students should record what happens in Step 5 of the Student Handout Part 2.
  2. Students should list what worked and what didn’t work in their protocol in Step 6 of the Student Handout Part 2.
  3. In Step 7 of the Student Handout Part 2, students should list what they would change in their protocol and then rewrite their protocol with their changes and updates.
  4. (optional) Using their updated written protocols and the materials provided in class, have students test their water sample again to check for its contents.
  5. (optional) Students should write down their results and who they think killed Dr. Clearwater in Step 7 of the Student Handout Part 2.
  6. Instruct the students to turn in the following:
    1. A final, clean copy of their protocol.
    2. An analysis of their results.
    3. And a conclusion of the experiment: Who could have contaminated the water?

NOTE: To identify who is the ‘killer’ is, students will have to cross-reference their results to the specialty of each one of the suspects. Have students back up their answer using their results from their water analysis.


biofilm: A biofilm is a film created when microorganisms stick to each other and often also to a surface.

constraint: Condition of an optimization problem that the solution must satisfy.

contamination: The presence of an undesirable element that spoils, corrupts, infects, makes unfit, or makes inferior a material, physical body, natural environment, workplace, etc.

pollutant: A substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. A pollutant may cause long- or short-term damage by changing the growth rate of plant or animal species, or by interfering with human amenities, comfort, health, or property values. Some pollutants are biodegradable and therefore will not persist in the environment in the long term.

protocol: A procedural method in the design and implementation of an experiment. Protocols are written whenever it is desirable to standardize a laboratory method to ensure successful replication of results by others in the same laboratory or by other laboratories.


Pre-Activity Assessment

Questions: Probe students with questions such as:

  • What is a protocol?
  • What are some of the common contaminants that are found in water?
  • What are constraints?

Activity Embedded (Formative) Assessment

Handouts: Students complete the Student Handout Part 1 and Student Handout Part 2.

Post-Activity (Summative) Assessment

Analysis: Students turn in a final copy their protocol, analysis of their results, and their conclusion (with reasoning) on “Who could have contaminated the water?”

Investigating Questions

  • What is the importance of having a clear protocol to follow?
  • Why would engineers need to approach a problem by researching it first?

Safety Issues

  • Use eye protection (goggles or safety glasses), gloves, and an apron when handling the water samples.
  • Water samples are safe to dispose of down the sink. If preferred, spray bleach solution on the water samples. This will kill the bacteria.
  • While the bacteria that occur naturally during the experiment are generally harmless, students should wash their hands after handling the water samples.

Activity Extensions

  • After students develop their protocol, you can provide them with a water analysis kit for them to analyze their water sample.
  • Students will provide a data table of their results.
  • Students will then develop a ‘water treatment’ apparatus to filter their water sample.


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© 2023 by Regents of the University of Colorado; original © 2022 University of Wyoming


Mariana Quinn; Christina Crawford; Xiaoyin Tian

Supporting Program

Engineering Research Center for Nanotechnology Enabled Water Treatment Systems (NEWT) RET, Rice University


This curriculum was based upon work supported by the National Science Foundation under Rice University Engineering Research Center for Nanotechnology Enabled Water Treatment Systems (NEWT) RET grant no.1449500. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.

Special thanks to Christina Crawford, Xiaoyin Tian, Dr. Jun Lou, and Dr. Carolyn Nichol.

Last modified: March 15, 2023

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