|
|
|
JUST IN TIME LECTURE SERIES:
Water Contamination in a Hurricane’s Aftermath
DESCRIPTION
Water contamination is a major health threat facing people in hurricane
struck areas. This activity explores contamination causes and demonstrates
the processes through which biological and chemical contaminants are
removed.
OBJECTIVES
At the end of this lesson, students will be able to:
- Name one negative health impact caused by a major natural disaster
on any given population.
- State the sources and health risks posed by biologic and chemical
hazards.
- Demonstrate the processes involved in removing contaminants from
water.
TIME
1 (50 minute) class period
PREPARATION
-
Visuals. Print and create overheads of images.
-
Materials. Gather materials for lab of demonstration
-
Background. To prepare the students combine this lesson with a
lesson on hurricanes (e.g., how and where they form and what are the
dangers). A sample lecture can be found at;
http://www.pitt.edu/~super1/lecture/lec20371/index.htm.
MATERIALS FOR DEMONSTRATION
- 500ml Beaker filled with water
- Flour
- Corn meal, grits or crisped rice cereal
- Food coloring
- Vegetable oil
|
- Fine screen
- Rubber tubing or turkey baster
- Filter paper
- Activated Charcoal
- Hot plate
- Pan with ice
|
PROCEDURE
Introduce the Topic with Discussion Questions.
On August 29, 2005 Hurricane Katrina, a category IV storm, struck the
Gulf Coast, resulting in what has been called the greatest natural
disaster in the history of the United States. The winds and storm surge
resulted in widespread death and destruction, flooding much of the coast
including approximately 80% of New Orleans, Louisiana.
- Ask: What sorts of problems did people in the area who
survived the initial storm face in the days immediately after the storm?
Possible answers: No power, rescue from roofs, no food, lack of
water, no communication, no transportation, pollution, mosquitoes,
fires, electrocution, cuts and other wounds, little police protection,
snakes, disease.
-
Show picture and ask why would people in the middle of a flood have
a problem finding water to drink?
 |
|
(from www.cnn.com photo gallery) |
Possible answers: The flood water was dirty, contaminated,
poisonous. Explain that flood water often contains potentially harmful
microbes and that these come from overflow of privies and septic systems
in rural areas; flooded sewage treatment plants in urban areas; animal
feces from pets, livestock and wild animals; natural bacteria in the
environment; human waste; and dead bodies of both humans and animals.
These are generally referred to as biological contaminants.
- Show picture of flooded trucks and cars and ask what sorts
of things in cars would make the water dangerous to drink?
 |
|
(from www.cnn.com photo gallery) |
Possible answers: Gasoline in gas tanks, oil in crank cases, lead
in batteries, asbestos in brake pads, brake and transmission fluids,
coolant.
- Ask: if these are biological or chemical contaminants?
Possible answers: Chemical
-
Ask: What other sources and types of chemicals are likely to be
present?
Possible answers: Poisons and sprays used in agriculture and around
the home. Industrial waste and cleaners from factories and businesses.
Point out that both biological and chemical contaminants can cause illness
and need to be removed from water before it is safe to drink
Demonstrate
Explain that now that you’ve discussed some of the possible sources and
types of contaminants in water you will show how some of these can be
removed. Explain that each household item represents a certain biological
or chemical contaminant.
- Show the class the beaker of clear water and explain that, although it
may contain dust and materials from the air, rainwater is generally
considered clean and drinkable as long as it is collected in a clean
container.
-
Show the corn meal or crisped rice cereal and explain that water in ponds,
streams, lakes, and rivers generally contains suspended organic and
inorganic material such as mud and silt. Flood water contains much higher
levels than found under normal circumstances — add 2–3 tablespoons of the
corn meal or cereal and stir well.
-
Show the flour and explain that it represents various sorts of germs and
bacteria suspended in the water. Add a tablespoon of the flour and explain
that bacteria are a normal part of the ecology of aquatic systems and that
runoff from fields carries bacteria from animal feces and other sources
into our water supply. Point out that floods often dump raw sewage into
the system and that levels of bacteria in flood waters are often greater
than normal. Add another 2–3 tablespoons of flour.
-
Show the food coloring and explain that water often contains chemicals
that are leached out of the soil or from contaminants. Explain that,
unlike the flour, that is in suspension, these chemicals are dissolved in
the water. Add a couple of drops of each color and stir well.
-
Show the vegetable oil and explain that it represents gasoline, motor oil,
and other petroleum products released into the water from flooded
vehicles, gas stations and other sources — add 1–2 tablespoons of the
vegetable oil and stir well.
-
You should now have a rather disgusting liquid mess of flour, food
coloring, cereal and vegetable oil that represents some of the problems
found in flood water. Ask the class how they would go about making this
safe to drink.
-
Help them by stating that each type of pollutant has its own
characteristics and students should address each contaminant one at a
time.
-
Start with the vegetable oil. The oil should rise to the top after a few
minutes. It can be skimmed off the surface using a piece of filter paper
or water can be siphoned off the bottom using the rubber tubing or turkey
baster.
-
Go next to the particulates (corn meal or cereal). Explain that much of
this material will settle out on its own and that water treatment
facilities often use a combination of settling and filtration through sand
filters to remove that which remains. Pour the water mixture from step 8
through the screen.
-
Explain that we need to get the germs out. The filtration used to remove
the particulates will take out some but not all of the microbes and
municipal systems often use finer filters and chemicals to destroy what is
left. Boiling will also kill most biological contaminants. It is not
usually used in municipal systems except under some circumstances when the
pressure drops in distribution lines — then authorities may issue a boil
order and recommend that water be boiled before being used for food or
drink. Filter the water mixture from step 9 through a filter paper. The
result should be relatively clear but colored water.
-
Explain to the class that we have removed the oil and the particulates and
have either removed or killed most of the germs but that our water still
contains the dissolved chemicals. Ask the class how they might remove
these.
-
After getting answers, explain that the government has established
standards for many dissolved substances such as lead and mercury. Water
with levels above these thresholds are considered unsafe for drinking.
Water with high levels of nontoxic materials are drinkable but considered
to be “hard.” Depending on the type of material and concentrations, water
can be treated using chemicals, activated charcoal or resins similar to
those found in home water purifiers or by distillation. Municipal systems
use a variety of these methods to ensure that water is safe.
-
If a distillation apparatus is available, use it to distill a sample of
the water from step 10. If not, bring a sample in a pan or beaker to a
boil and slant a baking dish of ice over the steam. The steam will
condense and run down the outside of the dish to the bottom were it can be
collected. You can also remove the dye by filtering through activated
charcoal.
Teacher Note: This activity is an excellent candidate for an
inquiry-based lab. Follow directions as given, but allow student groups to
devise their own water purification method given the materials. In a
post-lab discussion each group could present how clean they got their
water sample. In a lab report, students could compare their results to the
results of other groups in the class.
Additional information on CDC’s involvement in Hurricane Relief efforts
-
For general information related to Hurricane Katrina,
www.bt.cdc.gov/disasters/hurricanes/index.asp
-
More than 200 CDC employees have been directly involved in relief efforts.
These include laboratory, medical, epidemiology, health communications,
environmental health, and public information personnel.
-
CDC personnel have worked to prevent diarrheal illness in evacuation
centers by recommending vigorous and consistent handwashing.
-
Carbon monoxide poisoning has emerged as a major health threat. CDC
recommends that portable grills, generators, etc. not be used inside a
home, basement, garage, camper or near an open window.
-
CDC posts an update from the CDC Director’s Emergency Operation Center
during emergency situations. Most recent posts, including this
information, can be found at:
www.cdc.gov/od/katrina
* Links to
non-Federal organizations are provided solely as a service to our users. Links
do not constitute an endorsement of any organization by CDC or the Federal
Government, and none should be inferred. The CDC is not responsible for the
content of the individual organization Web pages found at these links.
|
|
