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Lesson Plan Title: Water Purification Systems Lesson Plan
Subject: Chemistry
Teacher: Margaret Strowe, B.S., Morris Catholic High School, Denville, New Jersey
Description: Many people around the world don’t have ready access to water. When there’s a
drought, water becomes scarce, and women and children have to walk long distances to fetch it
for their families. When they do find water, it’s often not safe to drink. The lesson plan is
designed for a semester, but it can be modified to be completed in 1 week and/or portions can
be incorporated into a teacher’s existing curriculum. The lesson plan covers the following
activities:
1. Research papers and presentations
Students research and write papers on water purification systems and methods,
including the science behind the processes, the materials used, their relative
effectiveness, etc. Presentations will include the science behind the concept, the
advantages and disadvantages, diagrams/photos of the system, materials
needed to build the system, the cost of the system and the capacity of the
system.
2. Students discuss and vote on which systems would be feasible to build in the
classroom.
3. Class obtains necessary materials.
4. Class builds purification systems in classroom.
5. Class tests purification systems.
Objectives:
Through this project, students gain an appreciation of the properties of water, the means for
testing it and methods for purifying it. The project culminates with students building and testing
water purification systems.
Materials Needed:
Students will need access to print and online research materials to prepare their papers and
presentations, as well as computers with PowerPoint software. Materials can cost several hundred
dollars per system, so part of the challenge will be creating an affordable and reproducible purification
system.
For the phase of the project that includes the testing of the filtering devices and systems, the following
lab materials will be needed:
 Analytical balance
 Beakers
 Bunsen burners
 Commercial test strips
 Graduated cylinder
 Inoculating loop
 Nutrient agar plate
 Pipet suction device
 Sample bottles
 Watch glasses
Key Vocabulary and Definitions:
Opening Activity/Introduction:
Research Paper
1. Topics:
Paper topics must be about water purification systems/methods (not biographies of the people who
developed them, information about companies that make them, etc.). Possible research topics
include:
 Filtration
 Boiling
o Pump style filtration systems
 Camping water purification systems
o Gravity-fed filters
 Solar distillation
 Reverse osmosis
 Industrial/commercial water
 Distillation
purification
 Ultraviolet light purifiers
 Chemical purification pills
 Mixed-oxidant solution purifiers
 Ozone water treatment
Each topic should be covered by at least one class member. There are likely to be duplications, with
more than one person reporting on the same system/method. Students who share topics should
work independently and not duplicate each other’s work.
2. Length and Format:
Length should be two to three pages (not counting pictures, drawings, charts, works cited). Font size
should be no larger than 12 and line spacing should be 1.5. Papers should be in MLA format. As this
is a research paper, students must use text citations including a minimum of four reliable sources.
3. Requirements:
Paper must address the following issues:
 The science behind the chosen
method (this needs to be as
detailed as possible)
 Benefits and disadvantages of your
system of choice.
o What types of water systems
and sources is it best used for?
(for example, a household
system with water coming from
a well or public water supply, or
water coming from a stream or
other natural source)
o



Are there types of
contamination that your chosen
system will not remove?
(Boiling, for example, will kill
most but not all microorganisms.)
o What types of micro-organisms
won’t it kill?
Materials needed to purchase/build
a system
Estimated cost of a system
Estimated capacity in gallons per
day
Presentations
1. Topics
Presentations will describe a water purification system of the students’ own conception. They may
be created and presented individually or by teams of two students.
2. Length and Format
The presentation should be at least 10 minutes. Each presentation should contain the following
components:
 Introduction
 The science behind the proposed system
 Materials needed to build the system
 Steps to build the system (with enough details to build in class)
 Cost of materials
 Capacity of the system (gallons per hour, gallons per day, or similar units)
 Advantages of the system
 Disadvantages of the system
 Summary
Activities/Procedure
Lab Work: Testing the Filters
After viewing the presentations, the classes should review the different types of systems researched,
discuss them and vote on (or have the teacher choose) which filtering device(s) or system(s) they want
to build. They should consider cost and capacity as well as the purpose for which they envision the
filter(s) or system(s) being built.
Building the water filtering device or system can take place in the classroom lab over several periods. It
can involve different classes or different lab partners working on different parts of the filter. If there are
students to spread the work around, class(es) can build several filters—either multiple iterations of the
same filter or different filters from the class presentations. The idea is to create usable, durable, quality
devices or systems.
Below are the procedures used when students were prompted to work on aworking filtering devices and
systems:
o
Solar distillation
o
Soda bottle filter
o
Slow sand filtration
o
Birch bark filter
o
Gravity filtration (commercial vs.
o
Sock filter
homemade systems)
o
Frontier pro
o
Emergency/survival/camping
o
Ultra-violet treatment, chemical
filtration systems
treatment, boiling
Data to Be Collected
The following data should be collected for all systems:
a. Volume of water before treatment
b. Volume of water after treatment
c. Mass of treatment system before treatment, where practical (for emergency/survival/camping
systems, for example, where the system itself may absorb some of the water.)
d. Mass of the treatment system after treatment
e. Time needed for treatment

a.






The following physical tests will be run on all water samples:
Using commercial test strips:

nitrates
pH

nitrites
total hardness
b.
Testing in the lab:
total alkalinity

percent solids
total chlorine

bacterial growth (using nutrient
agar
plates)
iron
copper

Students will record the findings on data sheets and submit them to the teacher, who will
publish the data in an Excel spreadsheet on Moodle, so all classes can share the data.
Materials and Procedures for Sample Testing for All Filters
1.
Commercial test strip kits Record and follow all procedures described in the test strip
instructions.
a.
Test strip 1 (pH, total alkalinity, total chlorine and total hardness tests)
i.
Dip the strip in water sample for 5 seconds using a constant, gentle, back-and-forth motion.
ii.
Remove the test strip and shake once to remove excess water.
iii.
Wait 20 seconds, and then compare the strip to the color scale in the test kit
iv.
Complete within 10 seconds (going beyond these times may result in inaccurate data)>
v.
Record data.
b.
Test strip 2 (iron test)
i.
Dip test strip in the water sample for 5 seconds using a constant, gentle, back-and-forth motion.
ii.
Remove the test strip from the water and allow it to sit for 2 minutes to complete the reaction
with the test materials in the strip.
iii.
At 2 minutes, compare the strip with the color scale provided.
iv.
Record data.
c.
Test strip 3 (copper test)
i.
Dip the test strip in the water for 30 seconds using a constant, gentle, back-and-forth motion.
ii.
Remove the test strip from the water and allow it to sit for 2 minutes to complete the reaction
with the test chemicals in the strip.
iii.
At 2 minutes, compare with the color scale provided.
iv.
Record data.
d.
i.
ii.
iii.
iv.
Test strip 4 (nitrates and nitrites tests)
Dip the test strip in the water for 2 seconds without any motion.
Remove the test strip from the water sample. Do not shake.
Allow to sit for 1 minute, and then compare with the color scale provided.
Record data.
2.
Lab Tests
a.
Procedure for percent solids
Most public, private (well) and natural water sources contain some level of dissolved materials. in them.
These are usually carbonates that come from rocks and minerals in the ground. These materials also
contribute to the water’s pH, total alkalinity and hardness. When water is tested at a laboratory, these
materials would be listed as dissolved solids, or as percent solids.
Materials:



Beaker
Watch glass that will completely cover the beaker
Hot plate
i. Using an analytical balance, obtain the mass (in grams, to four decimal places, i.e., 0.0000) of your
empty watch glass.
ii. Fill your beaker approximately three-quarters full with water and bring to a boil.
iii. While your beaker of water is heating, take your watch glass and a small sample of your test solution
over to the analytical balance. Make sure that at least one member of your group remains with the hot
plate while it is in operation.
iv. On to the watch glass. Measure out approximately 10.0000 grams of sample. Record the mass of the
watch glass before you begin weighing and after to determine the actual mass of your sample.
v. Carefully take the watch glass with your water sample back to your station and place it on top of the
beaker with the now—hopefully—boiling water. Allow the watch glass to sit until all of the water has
evaporated. Add water to the beaker as needed to prevent all the water from evaporating from the hot
beaker.
vi. Remove the watch glass from on top of the beaker and allow it to cool.
vii. When your watch glass has cooled, measure the mass again with the analytical balance. The difference
between the mass of your watch glass obtained in step i and step vii is the mass of the solids.
To calculate the percent solids, use the following formula:
% solids
=
mass of solids (from step vii)
mass of initial sample (from step
iv)
viii. Record your results.
b.
Biological testing
You can use nutrient agar plates (petri dishes with a material inside that will grow bacteria when
incubated) to perform biological testing. Nutrient agar is very sensitive, so bacteria in the room can
easily contaminate samples. Before working with the dishes, students should learn the aseptic
procedure for proper inoculation of the medium to minimize contamination and provide the best
results.
The following tests will attempt to compare pretreated water and post-treatment samples for bacterial
growth.
Materials
i.



You will need:
loop
agar plate
water samples
ii.
Obtain one nutrient agar plate for each before-and-after sample (both will be tested on the
same plate).
iii.
Carefully (without allowing the plate to open) use a marker to draw a line down the center of
the plate. Clearly mark one side B, (for before treatment) and the other side A (for after treatment).
iv.
Obtain an inoculating loop.
v.
Using your Bunsen burner, heat the tip of the inoculating loop to red hot. Allow the loop to cool,
but do not allow it to touch the countertop, your hands, or any other object.
Make sure you have all of your supplies ready.
vi.
Ask one of your lab partners to carefully loosen—but not remove—the top of the untreated
water sample. Have them remove the lid and carefully place the inoculating loop in the water sample
without touching the sides of the bottle. After you remove the loop, they may recap the sample bottle.
vii.
Have another lab partner ready with the agar plate. They will gently tip the cover up to about a
30- to 45-degree angle, but will not completely uncover the plate. Then, carefully and gently stroke the
loop across the surface of the agar on the side labeled B, being careful not to dig into the agar.
viii.
Repeat procedures iv to vii for the after-treatment water sample.
ix.
Carefully tape the dish shut and make sure that you have labeled the plate with your name and
the information about the system you are testing (i.e., UV exposure, gravity filtration, commercial, etc.).
x.
Collected samples go into the incubator.
xi.
Note the time and date that the samples were prepared.
xii.
When the next class meets, check the petri dishes to see how much, if any, bacterial growth has
occurred. Rate them from 0 to 6 with 0 being “no obvious growth” and 6 being “large amount of
growth.”
xiii.
Be descriptive with your observations. Try to count the colonies, describe the color, texture and
any other features of the growth you can observe. Depending on the results, return plates to the
incubator to see if additional growth will occur.
Materials and Procedures for Sample Testing for Different Types of Filters
1.
Solar Distillation
a.
Take a small sample of the water you are going to use for testing and fill one of the bottles
labeled “before treatment.” Take a larger sample (approximately 250‒300 mL) and fill a beaker with
enough water to perform the before and after tests.
b.
Using a graduated cylinder, measure approximately 10 liters of water into the basin in the solar
still. Record the exact amount of water added.
c.
Set the still up for operation with a collection vessel under the downward end of the tube. Cover
the tube and the collection vessel with plastic wrap to prevent rainwater, bugs and other contaminants
from getting into the clean water. Secure the collection vessel to the table, if necessary, to prevent the
vessel from being blown away.
d.
Using the procedures outlined for previous tests above, test your sample of untreated water.
(The treated water will be tested later.) Use the commercial test strips provided and also test for
percent solids. Do not use the small bottles for these tests. They should be preserved for bacterial
growth testing.
e.
Check the collection vessel daily for water and record the amount. Use a graduated cylinder, if
possible.
f.
Keep a log of the amount of water (in milliliters) collected.
g.
Add water, if needed, to the basin. Record any amounts you add.
h.
When you’ve collected about 250 to 300 mLs, you should have sufficient water to test. At that
time, determine the volume of water remaining in the basin. (Remove the basin from the enclosure and
remove water one liter at a time.) Record this figure. These before and after numbers are very
important, as they will allow you to determine how much water is being lost to evaporation.
i.
Take a sample of the treated water and fill one of the bottles labeled “after treatment.”
j.
Using the procedures outlined for previous experiments, test your sample of treated water using
the commercial test strips provided, and test for percent solids. Do not use the small bottles for these
tests. The small bottles are for bacterial growth testing.
2. Slow Sand Filtration
a.
Take a small sample of the water you are going to use for testing and fill one of the bottles
labeled “before treatment.”
b.
Take another sample of about 500‒600 mL of untreated water and put it in a beaker, cover it
with plastic wrap and label it “untreated” for testing compared to the treated water.
c.
Secure a plastic ruler to the side of the tank with a spring clip. Use a marker to indicate the
starting water level in the filtration system.
d.
Measure the amount of water in the tank being used as the reservoir. Record the amount.
e.
Set up the system so that a small stream of water or slow drip from the reservoir falls into the
slow sand system. Make sure the water from the reservoir going in to the filtration system is equal to
the water coming out of the filter system. If the water leaves the filtration system too fast compared
with the water coming in, the sand will go dry and compromise the biological layer—so it is very
important to equalize the rate of water transfer.
f.
Place a small cork with a hole in it into the hole of the filter outlet so that a small amount drips
into the receiving tank. Secure the receiving tank to the bench with duct tape, and then cover the tank
with plastic so that rain or other contaminants won’t enter the treated water.
g.
Let a gallon or so of water run through the system to clean out some of the grit and sand and to
allow the water to run reasonably clean. Replace any water lost from the tank after this process.
h.
Record the volume of the water in the receiving tank on a daily basis. After you’ve collected a
liter of water, you may begin sampling.
i.
Fill one of the bottles labeled “after treatment” with water from the filtration system.
j.
Perform the tests outlined in previous experiments using the remaining water from the test
sample.
k.
Measure the amount of water in the container that is being used as the reservoir.
l.
Determine if the level of water in the filtration system is at the mark on the ruler.

If the level of the water in the filtration system is low, add water from the container until the
water is at the level of the ruler. Record the amount of water added.

If the level of the water in the system is high compared with the starting level marked on the
ruler, then remove the cork from the filtration system and let the water flow into the graduated cylinder
until the level in the tank matches the ruler. Record the amount of water removed.
3. Gravity Filtration
a.
Take a small sample of the water you are going to use for testing and fill one of the bottles
labeled “before treatment.”
b.
Set up the Brita water filter per the instructions in the box. Set up the homemade filter.
c.
Using the graduated cylinder, add 1 liter of water to the Brita filter. Record the exact
amount of water added. Start timing and determine the amount of time until the upper storage vessel is
empty.
d.
Take the water from the lower container and, using the graduated cylinder, record the
volume of water.
e.
Fill one of the bottles labeled “after treatment” with water filtered through the Brita filter.
f.
Repeat steps C through E for the homemade gravity filter.
g.
If you would like to repeat the test with a layer of activated charcoal on top of the filter
paper, you may do so; just be sure to record the starting and ending volumes.
h.
Using the procedures outlined above, test your samples of untreated water and treated
water using the commercial test strips provided, and test for percent solids. Do not use the small bottles
for these tests; keep them for the bacterial growth testing.
4. Soda Bottle Filter
a.
Clean some of the gravel of dirt and grit under
running water. Let the water run until it’s clear. Clean some
of the activated carbon the same way.
b.
Take a small sample of the water we will be
treating and fill one of the bottles labeled “before
treatment.”
c.
Set aside a beaker of approximately 400 mLs of
water for testing and cover it with plastic wrap.
d.
Remove the bottom of the soda bottle.
e.
Add a small amount of cheesecloth at the neck
of the soda bottle placing it on the top where the cap would rest and securing it with a rubber band.
This will stop the charcoal, sand, and gravel from spilling out while still allowing the water to flow.
f.
Add a layer of activated charcoal, followed by a layer of sand and a layer of gravel, until the
bottle looks like the bottle pictured.
g.
Using a beaker to hold the bottle upright, obtain the mass of the system with the electronic
balance. Do not use the analytical balance for this. This system is too large and too heavy and will
damage the analytical balance.
h.
Secure the filter to a stand.
i.
After securing the filter, position a beaker under the filter to collect the water being filtered.
j.
Take a 1-liter graduated cylinder and begin to add water to the filter system. If possible, add
the entire liter. Let the liter run through the system, collecting as much as possible in the collection
beaker. When the system is no longer dripping water into the collection beaker, it is ready to collect
final samples.
k.
Measure the volume of the water in the collection beaker. Record that figure. Make
observations as to the physical appearance of the water before and after treatment (color; sediment, if
any, etc.).
l.
Fill one of the bottles labeled “after treatment” with the filtered water.
m.
Take the remaining treated water and run the tests outlined above (test strips and percent
solids) on the sample as well as on the sample of the untreated water.
5. Birch Bark Filter
This filter will be somewhat improvised, as we will use a plastic funnel instead of one made out of birch
bark so as not to damage any birch trees for our experiment. To the best of my knowledge, there is
nothing chemical that the birch bark that contributes to the process; it simply acts as a means to hold all
the components together.
a.
Take a small sample of the water you will be treating and fill a bottle
labeled “before treatment.”
b.
To prevent the gravel and other parts of the filter from falling out of
the bottom, place a small piece of cheesecloth at the bottom of the funnel.
c.
Clean some of the gravel of dirt and grit under running water. Let
the water run until it’s clear. Clean some of the activated carbon
the same way.
d.
Prepare your filter by placing a layer of grass clippings at the bottom
of the funnel.
e.
Cover the layer of grass with a layer of sand.
f.
The next layer will be a layer of activated carbon.
g.
Repeat steps d to f, adding another layer of grass, sand and activated carbon.
h.
Cover the top layer of activated carbon with a very thin layer of sand.
i.
Do not use the analytical balance for this: use only the regular balance. Using a large beaker or
other container, obtain the mass of the completed filter (obtaining the mass of the empty beaker first).
Put the funnel in the beaker, making sure it will stay supported, and obtain the mass of the beaker plus
the funnel/filter. The difference between the two measurements is the mass of the filter.
j.
Using a graduated cylinder, measure out 1 liter of stream water. Pour the 1 liter of stream water
through the filter and let it settle into a recovery container (a beaker or other container large enough to
hold 1 liter of water).
k.
When the water stops running out of the funnel, obtain the volume of the water that has come
out (the water in the collection vessel).
l.
Take a small sample of the treated water and place it in one of the small bottles labeled “after
treatment.”
m.
Transfer the treated water to another container so you can obtain the mass of the filter
material. The difference in mass between the initial mass of the filter material and the final mass is
water, precipitates or other materials removed from the water.
6.
Sock Filter
a.
Take a small sample of the water you will be treating and fill a bottle labeled “before
treatment.”
b.
Wash some gravel under running water until the water runs clear. This will remove dust and
sediment from the gravel so it won’t end up in the water.
c.
Prepare your filter by placing a layer of sand at the toe of the sock.
d.
Cover the layer of sand with a layer of stone/gravel.
e.
The next layer will be a layer of cheesecloth.
f.
Cover the next layer with grass clippings.
g.
Using a regular balance (not an analytical
balance), obtain the mass of the completed filter.
i.Obtain the mass of an empty beaker.
ii.Put the sock in the beaker, making sure it will stay
supported, and obtain the mass of the beaker plus the
funnel/filter.
iii.The difference between the two measurements is the
mass of the filter.
h.
Using some string, secure the sock to a stand so
that it is suspended above a large beaker that will collect
the water as it’s filtered. If possible, use a Popsicle stick or
similar tool to hold the top of the sock open so you can
pour the water into the sock.
i.
Using a graduated cylinder, measure out 1 liter of
stream water. Pour the liter of stream water through the
filter and let it settle into a recovery container, such as a beaker or other container large enough to hold
the water.
j.
When the water stops running out of the funnel, obtain the volume of the water that came out.
This is the water that was in the collection vessel.
k.
Take a small sample of the treated water and place it in one of the small bottles labeled “after
treatment.”
l.
Transfer the treated water to another container so that you can obtain the mass of the filter
material. The difference in mass between the initial mass of the filter material and the final mass is
water, precipitates and other materials removed from the water.
m.
Using the procedures outlined in previous experiments, test your sample of untreated water
and your treated water using the commercial test strips provided and test for percent solids. Do not use
the small bottles for these tests. Those are for the bacterial growth testing.
7.
Frontier Pro: Portable water bottle filter
This system may not work in a manner that we can collect a sample as it uses suction.
a.
Take a small sample of water and fill one of the bottles labeled "before treatment” with the
stream water.
b.
Obtain the mass of the filter system on the lab balance.
c.
Take a graduated cylinder and pour 1 liter into the 1-liter water bottle.
d.
Secure the Frontier Pro system to the top of the bottle.
e.
Try applying gentle pressure to the water bottle and see if you can get water to flow out of the
filter and into a collection beaker.
f.
If you can get water out, continue to apply gentle pressure until the full liter has run through the
system. If you can’t get water to go through, go to step k.
g.
Collect the treated water and, using the graduated cylinder, determine the volume of the water
after treatment.
h.
Take a small volume of the treated water and place it in one of the bottles labeled “after
treatment.”
i.
Take the filter system and obtain the mass on the lab balance. The difference in masses
between the final mass and the initial mass is the water absorbed and any particulates filtered out.
j.
Using the procedures outlined in previous experiments, test your sample of untreated water
and your treated water using the commercial test strips, and test for percent solids. Do not use the small
bottles for these tests. Those are to be kept for the bacterial growth testing
k.
Perform this step only if you’re unable to get water to go through the filter by squeezing the
water bottle.
Obtain a pipet suction device. Apply suction to the filter while squeezing the filter in the spot where you
would use your teeth if you were actually drinking from the bottle. It will hopefully work with some
gentle squeezing. Once water is flowing under suction, allow a full liter of water to go through and then
return to step g.
8.
a.
UV treatment
Determine if you will prefilter your water sample.
b.
Take a sample of untreated water and place it in one of the sample bottles labeled “before
treatment.”
c.
Fill a smaller beaker (200 mL or so) with untreated water (this will serve as your control) and set
it aside, covering it if possible.
d.
From the directions on the package, determine the amount of sample that you will most
efficiently treat during a normal length lab period. Using a graduated cylinder, place this amount in a
beaker of sufficient size so the sample will fit in the beaker with some room above. Record the volume
of water.
e.
Treat the water with the UV light source.
f.
Measure the volume of water after treating.
g.
Take a small amount of the treated water and place it in a bottle labeled “after treatment.”
h.
Using the procedures outlined in previous experiments, test your sample of untreated water
and your treated water using the commercial test strips, and test for percent solids. Do not use the small
bottles for these tests. They are for bacterial growth testing.
i.
Record the results of your tests.
9.
a.
Chemical Treatment
Take a small sample of untreated water and fill one of the bottles labeled “before treatment.”
b.
Take an approximately 1,500 mL beaker (or other vessel) and, using a graduated cylinder, add
the amount of water indicated in the directions. Record the amount of water added.
c.
Treat the water according to the package directions. Record the directions in your lab journal.
d.
After treatment is completed using the graduated cylinder, record the volume of your sample.
e.
Take a small sample of the treated water and fill one of the bottles labeled “after treatment.”
f.
Using the procedures outlined above, test the samples of untreated water and treated water
using the commercial test strips provided, and test for percent solids. Do not use the small bottles for
these tests. They are for testing bacterial growth.
10.
a.
Boiling
Determine if you are going to prefilter your sample.
b.
Take a sample of water and fill a bottle labeled “before treatment.”
c.
Determine what volume of water you want to use for testing.
d.
Using a graduated cylinder, add the amount of water that you want to test to a beaker large
enough to hold that amount of water.
e.
Using a hot plate, bring the water to a boil. Boil for the amount of time—indicated in the various
presentations—that is sufficient to kill most organisms. Record the amount of time you boil the sample.
f.
Turn off the heater and allow the sample to cool.
g.
When cool, remeasure the volume of water using the graduated cylinder. Record this amount.
h.
Take a small sample of the treated water and place it in a bottle labeled “after treatment.” Using
the procedures outlined above, test your sample of untreated water and your treated water using the
commercial test strips provided and test for percent solids. Do not use the small bottles for these tests.
Review: Highlight terms and ideas you want to review with the students at the end of the
lesson.
Homework/Assessment/ Evaluation: Discuss any in-class assessments, projects and/or
homework that you will be assigning. Ideally, include the rubric for grading.
Required Handouts/Resources/Websites: Include any resources critical to the lesson plan (e.g.
handouts, charts, print resources) and any websites you have cited.
Enrichment Resources to Supplement: (optional)

“At home …” Include an activity that students can do with their families at home that
week.

Helpful Supplemental Resources—songs, books, poetry, art, websites that could enrich
the lesson plan