Water and Global Responsibility STEM Unit
LP14_Water Quality Testing
Lesson Plan 14: Water Quality Testing
Overview
This lesson exposes students to three forms of water quality testing to give them an
understanding of how we determine whether water is safe to drink.
Background Knowledge
Students should have an understanding of:
 Basic chemistry skills
 Difference between safe and unsafe water
 Where their water comes from and how it is treated
Educators may want to review the backgrounder at the end of the lesson plan on water
quality testing prior to the lesson.
Time Required: 1.5 hrs
Grade Level: Grades 5 and 6
Subject Area: Science, Social Studies, Math
Key Words: Turbidity
Alberta Curriculum Links: See curriculum link table
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Water and Global Responsibility STEM Unit
LP14_Water Quality Testing
Lesson Plan 14: Water Quality Testing
1 hr
Learning Expectations
1. Describe different forms of water quality testing.
2. Discuss the importance of water quality testing.
Materials
□
□
Power Point on Water Quality Testing
LCD Projector
Turbidity Test
□ Turbidity tube
□ 1 sample of tap water
□ 1 sample of dirty water
pH Test
□ Ph Strips
□ 1 labeled Beaker of each of the following:
a) Lemon Juice
b) Vinegar
c) Milk of Magnesia
d) Salt water
e) Tap water
f) Ammonia
g) Swamp or dirty water
Dissolved oxygen test
□ Dissolved oxygen tablets
□ 1 beaker of tap water
□ 1 beaker of dirty water
□ Refills of each type of sample water
Intro Demonstration
□ 1 glass of tap water
□ 1 glass of clear water with white vinegar
□ 1 glass of dirty water
□ Numbered cards to set beside the water classes.
More than one station for each type of test may be required depending on group
size.
Preparation
□
Prepare LCD Projector with Water Quality Testing PowerPoint.
□
Set up three glasses at the front of the class: 1 glass of tap water, 1 glass of
tap water with white vinegar, and 1 glass of dirty water.
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Water and Global Responsibility STEM Unit
LP14_Water Quality Testing
□
Number the glasses from 1 to 3. The numbers should be visible from the
back of the class.
□
Label beakers used for pH tests.
□
Set-up up at least one station for each test. You may want to do more
depending on class size.
Introduction
20 minutes
1. Direct students attention to the three glasses of water at the front of the room.
2. Ask student to vote on which of the glasses they would drink from and why.
Tabulate and record their results.
3. Ask three volunteers to come to the front of the room and examine the water
glasses.
4. Ask them what glass of water they would drink and tell them to explain why.
5. Draw students attention to the reasoning behind why the students chose a
particular glass of water: it’s clear, it has no smell, no taste etc.
6. Explain that there are many things that we can see, smell and taste in water
that can indicate if it might be safe to drink. This is called physical testing.
7. Tell students that to be certain that water is safe there are certain tests that
we need to perform to detect things in the water that we can’t always sense
8. Explain that today they are going to see three types of tests: turbidity, ph, and
dissolved oxygen.
Water Quality Testing Power Point
20 minutes
1. Go through the PowerPoint provided on water quality testing.
2. Do an example of each of the tests that they will conduct: turbidity, pH and
dissolved oxygen.
Testing
45 minutes
1. Divide students into groups of 3 to 4 and send each group to a testing station.
2. Ask each group to perform the test at the station and record their results on
the handout provided (see the end of the lesson).
3. When they have completed the test, ask them to rotate to the next station.
They will need to rotate three times to complete each test.
4. Ask groups to report their results for each test.
5. Discuss any differences between the groups.
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Water and Global Responsibility STEM Unit
Review
LP14_Water Quality Testing
30 minutes
1. Ask students to write down the procedures for each type of test, and then
respond to the following question in their journal. “With regards to water
quality testing I was surprised about. . . .”
Resources:




The Safe Drinking Water Foundation in Saskatchewan provides water quality
testing kits for students: http://www.safewater.org/education/order-kits.html
Kits can also be obtained from:
http://www.worldwatermonitoringday.org/Test_Kits/Kits_Main.html . At this site
you’ll also discover how your class can become involved in World Water
Monitoring Day.
You may also be able to purchase the materials required for these tests through
your science lead or school supplies.
Read the backgrounder provided on water quality testing
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Water and Global Responsibility STEM Unit
LP14_Water Quality Testing
Backgrounder on Water Quality Testing
Turbidity
Turbidity is a physical property of water. It is the ‘cloudiness’ caused by small particles
that are generally invisible to the naked eye. One can compare it to smoke in the air. In
rivers and other surface waters, turbidity usually increases after heavy rain as the water
picks up dirt particles.
The units for measuring turbidity are NTU (Nephelometric Turbidity Units) which are not
concentrations (mg per L), but rather values associated with how much light is reflected
due to the amount of particles in the water. The more particles, the higher the NTU
value.
Potential Health Effects
Turbidity doesn’t cause direct health impacts but is an indicator of biological
contamination, because viruses, parasites and bacteria like to attach themselves to
small particles. Turbidity also reduces the effectiveness of chlorination as chlorine. The
chlorine combines with the particles and leaves less chlorine available to kill pathogens.
WHO Guidelines
The WHO guideline for turbidity is less than 5 NTU, which, to the naked eye, looks like
clear water.
Turbidity Test Procedure
Turbidity tubes are an easy and cheap way to visually estimate NTU. There are small
turbidity tubes available in the World Water Monitoring Day Test kits. You may also be
able to order the tubes through your science head or school supply catalogue.
The readings on the turbidity tube will be significantly affected by the amount of light,
and the vision of the person doing the test. Some larger particles may settle directly to
the bottom, blocking the view. Give the tube a good shake before taking the reading.
pH
pH is a measure of the acidity or alkalinity of the water. The pH for drinking water is
generally between 6.5 and 8.0. Water at 25°C with a pH less than 7.0 is considered
acidic, while a pH greater than 7.0 is considered basic (alkaline). When a pH level is 7.0,
it is considered neutral.
The pH of the water in a stream, river, lake or aquifer will vary depending on a number of
conditions: the source of the water; the type of soil, bedrock and vegetation through
which it travels; the types of contaminants the water encounters in its path; and even the
amount of mixing and aeration due to turbulence in its flow. The effects of a specific type
of water pollution on living plants and animals can vary greatly.
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Water and Global Responsibility STEM Unit
LP14_Water Quality Testing
There are different methods for testing pH. Litmus paper will give you an indication of
whether a sample is acidic or basic. Other tests strips will give you a better indication of
the pH value of a sample. pH meters, although more expensive, can be useful in
obtaining the precise pH of a sample.
Dissolved Oxygen
Dissolved oxygen measures the presence of oxygen gas molecules in water. These
oxygen molecules keep organisms living and chemical process in the water occuring. A
high level of dissolved oxygen is generally considered good, while low levels can put
stress on fish and organic organisms.
Follow the procedure on the kit that you have for measuring the dissolved oxygen.
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Water and Global Responsibility STEM Unit
Water Quality Testing Student Handout
LP14_Water Quality Testing
Name __________________
Turbidity Test
1.
2.
3.
4.
5.
6.
Be sure you are in a place with good light.
Rinse the turbidity tube with sample water 2 to 3 times.
Place a sheet of white paper on the floor
Hold the tube vertically and pour your water sample into the tube bit by bit.
Look for the cross or circle at the bottom of the tube after each addition of water.
Keep on doing this until the black cross or circle at the bottom of the tube just
disappears or blurs completely.
Hold the tube vertically and read turbidity in NTU using the graduation on the side
of the tube. The result is the value of the line nearest the water level.
Record your results here:
What do your results mean?
pH
Place a test strip in each sample. Record your findings below.
a)
b)
c)
d)
e)
f)
g)
What do these results mean?
Dissolved Oxygen
Follow the instructions on the package for the dissolved oxygen test. Record your
answers below.
Results:
What might happen if there was a low level of dissolved oxygen in the water:
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