Bacterial Water Quality Demonstration
These activities are meant for informal classroom settings, such as Boy or Girl Scouts. If you use this activity, we ask that you fill out this very short survey!
Water is essential to human life. However, more than 10% of the people on the earth still don’t have safe drinking water. Every day, about 2,000 persons die because their water is contaminated by bad microbes. Water treatment is important to protect human health. Developing cheap, effective, and reliable water treatment technologies is very meaningful and can potentially help many people in the world.
Objectives
This demonstration will measure the quality of the water in our environment and test the effectiveness of some commercially available water treatment products. After attending the demonstration, the audience will be aware of water safety and the need of water treatment, and will appreciate the value of clean water and understand the importance of water conservation.
Materials (Number of Materials will vary depending on the number of participants)
Water is essential to human life. However, more than 10% of the people on the earth still don’t have safe drinking water. Every day, about 2,000 persons die because their water is contaminated by bad microbes. Water treatment is important to protect human health. Developing cheap, effective, and reliable water treatment technologies is very meaningful and can potentially help many people in the world.
Objectives
This demonstration will measure the quality of the water in our environment and test the effectiveness of some commercially available water treatment products. After attending the demonstration, the audience will be aware of water safety and the need of water treatment, and will appreciate the value of clean water and understand the importance of water conservation.
Materials (Number of Materials will vary depending on the number of participants)
- Personal protection and other supplies
- Gloves, wipes, markers, tape
- Water sample collection and handling
- Bottles, tubes, pipettes
- Test the concentration of microbes
- Pre-prepared agar plates, spreading rods, incubators
- Water treatment
- Boiler, filter, chlorine pill
Day 1: 30 minutes to 1 hour
- Presentation (5-10 min)
- Introduce the necessary background on water quality
- This Ted-ED video is a good introductory video.
- Test the microbes on our hands (5-10 min, optional)
- Each audience may get one agar plate to test her/his own
- Touch the agar using fingers
- Have students tape the plates shut.
- These plates will be needed to be taken back to the lab to go into the incubator in order to see bacterial growth.
- Collect water samples (e.g., river, lake, spring, rain, tap, bottle, etc.) (5-10 min)
- Can be done before the demonstration if there is a time concern
- Can be done by parents if there is a safety concern
- Students will wear gloves and collect the water from a natural water source.
- Test the microbes in the collected water (5-10 min)
- This can be done in groups or individually depending on how many individuals there are.
- Put a drop of water on the prepared plates
- Use a rod to spread the water droplet
- This video can be used to demonstrate the proper technique.
- Make sure that students tape their prepared plates shut.
- These plates will be needed to be taken back to the lab to go into the incubator in order to see bacterial growth.
- Treat the water using different methods (5-10 min)
- Filtration, boiling, chlorine pills
- Audience can be separated to groups to do several treatments in parallel
- Students will treat water as directed
- Put a drop of treated water on the prepared plates
- Use a rod to spread the water droplet
- Make sure that students tape their prepared plates shut.
- These plates will be needed to be taken back to the lab to go into the incubator in order to see bacterial growth.
Day 2: 20-30 minutes
- Count the colonies on the agar plates after overnight growth (15-20 min)
- The growth of microbes on the agar plate takes about 16-24 hours if placed in the incubator.
- Microbes will form colonies on the agar plate allowing us to count the numbers
- Summary presentation and discuss which disinfection method worked the most effectively. (5 minutes)
- Students should not handle bleach, so this should be done by the supervising adult. Make sure that students do not open the plates!
- These plates can be cleaned in two ways, with an autoclave or with bleach.
- If using bleach, make a 1:10 dilution and soak the plates for 10 minutes.
- The plates can be thrown away in the trash after treated with bleach.
- If using the autoclave, follow all autoclave instructions to properly disinfect.