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Middle School |
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You Want Me to Drink What?
(Water Supply Treatment and Technologies)
Description: Students will participate in class experiments in water purification.
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- Goals and Objectives
- Procedure and Teaching Suggestions
- Student Activity
- Extension
- Additional Resources
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Materials and Equipment
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- Gather samples of water from the supply in their local area (pond, lake, or river)
- Explore testing water quality of their own water supply
- Perform classroom experiments in water treatment
- Visit their local water treatment facility to observe local water treatment procedures
- Research treatments and water treatments they have experimented with and observed
- Work together to invent their own water purification system using objects from home and school
Water Scarcity
Evaporation from the seas and precipitation continually resupply that small percentage. Fresh water is a continually renewable resource. However, one can get no more water from a pipe than what flows through it. Natural supplies of fresh water are limited by amounts that move through the natural system. Precipitation patterns around the globe are far from even. Regions with abundant precipitation support lush forests ecosystems. Other regions have minimal rainfall and are deserts as a result. There are different volumes of flow through different regions. For example, there are over one million gallons of water per acre per year in a temperate forest region compared to 2500 gallons or less per acre per year in desert regions. Humans must draw on the same water for drinking, irrigating crops, and supplying industry. These many demands result in a depletion of water.
Water Quality
Numerous sources of fresh water might be safe to drink were it not for human pollution. The most serious threat to human health is contamination with disease causing organisms and parasites. The World Health Organization estimates that 80% of the sickness, disease, and deaths of infants and children in less developed countries can be attributed to contaminated water. In the US many water sources are overused and polluted, however many small towns cannot afford to construct new facilities. The greatest safe guard to human health is suitable protection and treatment of water supplies. The greatest step we can take toward improving world health would be to implement these services wherever they are not present.
The U.N. estimates that 1.2 billion people lack access to safe water. Over 3 million people in the world die each year as a result of water-related disease that could have been prevented. By 2025, it is likely that 3.5 billion people worldwide will experience water shortages. Nineteen countries in the world are labeled as "water stressed." More "water stressed" countries are in Africa than in any other region.
Many people in the world do not have access to enough fresh water. Some countries, states, and cities just don’t have enough water naturally like deserts in the Middle East, or they don’t have enough funds to make fresh water available. From Sandra Postel’s interview transcript in "Troubled Waters," she explains that in the recent United Nations conference in Johannesburg, a commitment was made to provide safe drinking water not for universal access but just trying to reduce by half the number of people that don’t have access by 2015. She explained that would be a major achievement, but we really need to move toward universal access for all to have safe drinking water.
Sandra Postel Interview (Microsoft Word document)
1. Ask students if they have ever wondered where our water supply originates and how it is cleaned. Accept any answers or ideas students offer. Present a sample of the water source to be studied. Have students observe the sample work as a whole class and create a KWL chart that contains 3 columns: K-what we know, W-what we want to learn, and L-what we learned. Have students fill in the K column with everything they know about where our water originates and how it is treated. Next, have students list all questions they have in the W column.
2. Give students some background information on water sources and water treatment; search the Internet for local water sources in your area. Also, allow students to go to www.waterhistory.org/ to gather information on the history of water treatment. Water in lakes, rivers, and swamps often contains impurities that make it look and smell bad. The water may also contain bacteria and other microbiological organisms that can cause disease. Water from surface sources must be treated before people can consume it. Polluted water is defined as water that contains one or more materials that make the water unsuitable for a given use. Water purification is any method that will remove one or more such materials.
Several methods of purification may be used in combination to obtain water that is sufficiently pure. Water treatment plants typically clean water by taking it through aeration, coagulation, sedimentation, filtration, and disinfection. Ask students if they are familiar with any of those terms. Study these terms with the students.
Explain to students that experiments and activities they will be involved in will help them answer questions from the W column of their chart to fill in the L column with what they have learned.
Have students search the "Troubled Waters" interview transcripts for detailed information from the following authorities:
- Courtney Hackney, Professor, Biological Studies, University of North Carolina at Wilmington
- Billy Ray Hall, President, North Carolina Rural Economic Development Center, Inc. (Rural Center)
- John Kime, Executive Director, Piedmont Triad Regional Water Authority
- Dr. David Moreau, Professor, Environment Quality Assessment and Water Resources, UNC-Chapel Hill
- John H. Morris, Director, Division of Water Resources, North Carolina Department of Environment and Natural Resources
- Robert W. Oreskovich, Utilities Director, Dare County, NC
- Paul Simon, Former Illinois State Senator, currently a Professor and Director of the Public Policy Institute at Southern Illinois University in Carbondale, IL
After filling out the database or copy of the form students will have a score for the water supply source. Have groups compare their scores of the water source.
Have a class discussion on water purification and fill in any information students learned in the L column of the KWL chart. Explain to students that they will use their water sample to perform water treatment simulation.
- Have groups gather all needed materials. Have them pour about 1.5
L of their water sample into a 2 L Bottle. Explain that aeration is
the addition of air to water. It allows gases trapped in the water to
escape and adds oxygen to the water. Air is a source of carbon, oxygen,
and nitrogen for all organisms. Place the cap on the bottle and shake
the water vigorously for 30 seconds. Continue the aeration process by
pouring the water into either one of the cut-off bottles, then pouring
the water back and forth between the cut-off bottles 10 times. Ask students
to describe any changes they observe in their science journals. Pour
the aerated water into a bottle with its top cut off.
- Explain that coagulation is the process by which dirt and other suspended
solid particles are chemically stuck together into floc (clumps of alum
and sediment) so that they can be removed from water. With the tablespoon,
add 20 g of aluminum crystals to the water. Slowly stir the mixture
for 5 minutes. Record observations in journal.
- Explain that sedimentation is the process that occurs when gravity
pulls the particles of floc to the bottom of the bottle. Allow the water
to stand undisturbed in the bottle. Ask students to observe the water
at 5-minute intervals for a total of 20 minutes and write their observations
with respect to changes in the water's appearance in their journals.
- Construct a filter from the bottle with its bottom cut off:
Attach the coffee filter to the outside neck of the bottle with a rubber band.
Turn the bottle upside down and pour a layer of pebbles into the bottle - the filter will prevent the pebbles from falling out of the neck.
- 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 5 L (or more) of clean tap water. Try not to disturb the top
layer of sand as you pour the water.
- Explain that filtration through a sand and pebble filter removes most
of the impurities remaining in water after coagulation and sedimentation
have taken place. After a large amount of sediment have settled on the
bottom of the bottle of water, carefully - without disturbing the sediment
- pour the top two-thirds of the water through the filter. Collect the
filtered water into a container. Pour the remaining (one-third bottle)
of water back into the collection container.
- Compare the treated and untreated water. Ask students whether treatment
has changed the appearance and smell of the water. Let students know
that the final step at the treatment plant is to add disinfectants to
the water to purify it and kill any organisms that may be harmful. Because
the disinfectants must be handled carefully, it is not presented in
this experiment. The water that was just filtered is not fit to drink.
- Take a field trip to the local water treatment plant so that students
may observe the process and gather more information on treatment and
technologies.
Students will work together to invent their own water purification system using objects from home and school.
Also have students evaluate the types of water purification systems people have in their homes. These should be shared and presented in class.
| “Water
should not be judged by its history, but by its quality. ” Dr. Lucas Van Vuuren National Institute of Water Research, South Africa |
What environmental issues are we creating by trying to create more fresh water? Have students search the Troubled Waters script for Sandra Postel’s, Director of Global Water Policy Project, interview to begin their research.
Have students research and do an assignment on point source and non-point source pollution. They can begin their research at:
http://creekconnections.allegheny.edu/NationalWaterMonitoringDay/PointvsNonpoint.html Web Sites
The Global Water Sampling Project: An Investigation of Water Quality
http://njnie.dl.stevens-tech.edu/curriculum/waterproj/index.shtml
The Global Water Sampling Project: An Investigation of Water Quality,
Language Arts Activities
http://k12science.ati.stevens-tech.edu/curriculum/waterproj/languageactivities.shtml
Quality Control
http://www.ourplanet.com/imgversn/94/ongley.html
Global Water Issues
http://www.freshwaters.org/info/issues.shtml
How Clean Water Reaches Your Home http://www.birdlife.org.za/resources/sustainable/water/34_35.htm
