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Wetlands: Nature's Water
Filters 
Grade level
2nd through 5th
Materials
- 8 celery stalks
- Red or blue food coloring
- Water
- Paring knife 2 glass jars or
beakers
- Paper towels for clean up
Discussion
The objective of this
activity is to simulate how wetland plants absorb pollution and serve as
"natural" water filters.
Background: Natural
wetlands are areas like marshes, swamps, bogs, sloughs, and floodplains that are covered
with water at least part of the year. Engineers often design constructed wetlands, which
are similar to natural wetlands, but are built to treat wastewater from domestic,
agricultural, industrial and mining processes. Roots and stems of wetland plants form a
dense mat where biological and physical processes occur to treat the wastewater. Wetland
plants vary across the United States, based on native plants and climate and thrive in
soil that is saturated for a significant portion of the time. Examples include grasses,
blueberry bushes, red maples, and silky dogwoods, among others.
As a means of treating
wastewater, constructed wetlands are fifty to ninety percent less expensive to build than
conventional chemical treatment systems. (In addition to treating wastewater, constructed
wetlands also create wildlife habitat and assist with flood control.)
Activity
Day 1
- In order to simulate how
wetland plants absorb pollution, put freshly cut celery stalks in colored water (divide
the stalks between 2 glass jars or beakers).
- Brainstorm the following
questions with students:
- What do the students think
the purpose of the experiment might be?
- What do they think will
happen to the celery, food coloring and water during the proceeding 24 hours?
- What do they think they'll
learn?
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Day 2
- Divide the class into eight
teams.
- Show the class the celery in
the colored water and give each team a stalk of celery.
- Cut the celery so each group
member has a piece.
- Have each student observe
how his/her piece of celery shows absorption of the "pollution."
- As a large group, discuss
the following questions:
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- Were the students correct
about what they thought the purpose of the experiment was?
- Were they correct in what
they thought would happen to the celery, food coloring and water?
- If the food coloring
represents pollutants, how does the celery represent a wetland plant? (It absorbs
pollutants in the water.)
- Did the celery absorb all
the food coloring (pollutants)? (No.) Explain why not. (Plants only absorb as much water
as they need.)
- When are constructed
wetlands most commonly used? (To treat mine run-off, for small communities that cannot
afford to build conventional water treatment plants, for industries and farm operations
that cannot use conventional wastewater treatment systems and to treat irrigation
run-off.)
- How do natural treatment
systems help protect the environment? (They replace the use of chemical treatment systems.
They are natural and existing, and subsequently have little impact on the environment.)
- Why will these types of
natural systems be increasingly important to us in the future? (As our world population
grows and our natural resources become increasingly limited, we will need to find more
ways to maintain our quality of life while protecting the environment. Natural treatment
systems help achieve this goal.)
- What role do engineers play
in developing constructed wetlands?
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For additional information,
visit the EPA Office of Wetlands, Oceans & Watersheds at: http://www.epa.gov/owow/wetlands.
This activity was
provided by CH2M HILL and the Water Environment Federation for National Engineers Week
2000. |
