Yakima WATERS Mini Lesson
Fecal Coliform Assessment of Local Water Bodies
Targets and Assessment
WA Science Standards Addressed:
 9-12 INQA- question
 9-12 INQB-investigate
 9-12 INQC-explain
Lesson Parameters
Content Area: Biology, Chemistry, Geology
Overview: Investigating the fecal coliform
levels of water bodies and understanding the
concepts of pollutant accumulation and
movement in watersheds.
Grade Level: 10th
Assessments:
 Fecal coliform testing is just one component of
a larger unit on water quality. A final lab
report will be written detailing various
pollutants levels, stream velocity, and aquatic
invertebrate abundance (for example see
“Rubric for Peer Review”).
 In the fecal coliform section in the final report
students will be graded on their:
 Synthesis of how fecal coliform gets into the
water (unit).
 Deduction of what levels are safe in drinking
water.
 Graphical representation of fecal coliform
levels throughout the body of water.
 Short interpretation of if fecal coliform levels
are safe for drinking in the local body of water.
Suggested Time: Two 1:45 minute periods.
Special Materials: Per group per water sample
 15 sterilized large test tubes with caps
 15 duran tubes
 1 large size test tube holders (60 holes)
 159 ml Lauryl tryptose broth
 200 ml deionized water
 60 ml sample water
 1 incubator set to 35 degrees Celsius
Learning Outcomes:
Knowledge: Fecal coliform testing can be used to evaluate the effects of human impacts on a water
body. Students will be able to recognize how pollution accumulates and migrates within a
watershed if multiple water samples are taken from the same stream gradient.
Skill: In this lesson students gain exposure in:
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Following detailed instructions
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Performing experiments
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Handling and measuring chemicals
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Interpreting results
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Performing fecal coliform tests
In writing the final report (next two lessons) students gain exposure in:
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Compiling information into a formal lab report
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Creating and analyzing graphs using real data
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Peer evaluation
o
Disseminating information to interested parties
Science Concept Background:
Fecal coliform testing is part of a 6 day unit assessing pollution
levels in Cowiche Canyon watershed (http://www.cowichecanyon.org/). The
canyon is located six and a half miles northwest of Yakima, Washington.
Water samples were taken from four sites along Cowiche stream starting
at the base of the Cascades and ending just before Cowiche Stream joins
the Naches River.
Fecal coliform gets into the water table via agricultural and storm runoff, human sewage, or other animal
waste. In high agricultural areas such as the Yakima Valley, fecal coliform levels may be high. Several
waterborne pathogenic diseases such as dysentery and typhoid fever may coincide with fecal coliform
contamination. The minimum standard for fecal coliforms in drinking water is less than one part per billion
of fecal matter (less than one fecal coliform) per 100 ml of water. Environmental effects include a decrease
in dissolved oxygen levels which can eliminate aquatic organisms. Regular testing of waterways for fecal
coliform pollution is necessary to preserve biodiversity, monitor general health of water body, and protect
the health of the general public.
http://www.state.ky.us/nrepc/water/wcpfcol.htm
http://www.oasisdesign.net/water/quality/coliform.htm
http://www.epa.gov/
The attached document “How to test Fecal Coliform” is a step by step procedure; therefore, no previous
experience is necessary.
Materials: Per group (3-4 students) per water sample
– All supplies can be purchased from http://www.labdepotinc.com/?gclid=CMeBjr3dh6UCFRhCgwodGhdRPg
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15 sterilized large test tubes with caps
15 duran tubes
1 large test tube holders (60 holes)
159 mL Lauryl tryptose broth
60 ml sample water (collected from local water body)
200 ml deionized water
1 incubator set to 35 degrees Celsius
Teacher pre-lesson procedure per group per water sample:
1. Gather 5 test tubes with clear caps, 5 test tubes with blue caps, and 5 test tubes with yellow cap.
2. Place all test tubes in test tube rack.
3. Invert duran tubes into each test tube.
4. Thoroughly mix 8.12 g Lauryl tryptose broth in 100 ml deionized water.
5. Pipette 10ml of this solution into each of the five test tubes with clear caps.
6. Thoroughly mix 4.06 g Lauryl tryptose broth in 100 ml deionized water.
7. Pipette 10ml of this solution into each of the test tubes with blue and yellow caps.
8. Autoclave all test tubes for one hour.
Procedure:
DAY 1
Introduction:
Notify students of the number fecal coliforms in one human feces (10,000) so they have a concept of the size
and source of coliforms. Brainstorm with the students about how they think fecal coliforms get into the water
table, what they can do to humans, and the importance of regular water testing. Then inform them on the EPA
standards of fecal coliform in drinking water in their area. http://www.epa.gov/
Give a description and short demonstration of the procedure referencing the “how to test fecal coliform”
handout. Next, explain the purpose of using Lauryl tryptose as a media for bacteria to feed on. Then, address the
rational for multiple testing (ie. Why it is important to use 15 test tubes for a statistically significant result.)
Finally, instruct the students on proper measuring of the water sample and the handling of Lauryl tryptose broth
and glass test tubes. A safety discussion should remind students not to pick up test tube by caps, to use care in
handling glass instruments, and the proper disposal of broken glass.
Fecal Coliform Testing:
Student procedure per water sample (see attached sheet “How to test Fecal Coliform”:
1. Gather one test tube rack containing 5 large test tubes with clear lids, 5 test tubes with Blue lids, and 5
test tubes with Yellow lids.
2. Place 10 ml of sample water into each of the 5 test tubes with clear lids using a graduated cylinder.
3. Place 1 ml of sample water into each of the 5 test tubes with blue lids using a plastic pipette.
4. Place 0.1 ml of sample water into each of the 5 test tubes with yellow lids using the same plastic pipette.
5. Write on tape: One person’s name, sample water location, your period, and place on test tube holder.
6. Repeat procedure for other water samples.
All test tubes will be incubated at 35ºC for 24 hours.
DAY 2
Introduction:
Explain how to interpret fecal coliform growth, determine number present, and how to properly dispose of
samples. Fecal coliform is present in test tubes that have particulate and a gas bubble present in the duran tube.
Tally and record number of clear capped test tubes with fecal coliform. Repeat for blue and yellow capped test
tubes. This will give you a 3 number ratio. Consult the attached table to determine with a 95% confidence
interval the number of total fecal coliforms. See attached “Fecal Coliform Stats Table” and “Fecal Coliform
Quanitiy” sheet for an example on how to determine coliform number. Students should complete the questions
on the “Fecal Coliform” sheet to prepare for writing the field report.
To clean up simply dump all solutions into a 5 gallon bucket of 10% bleach to water and dump down drain.
Autoclave all test tubes to sterilize.
After the second period students should be able to answer the following key questions for their lab
report:
1. How many fecal coliforms are present in each water sample?
2. What are safe fecal coliform levels for drinking water according to the EPA?
3. Where does fecal coliform come from?
4. What do fecal coliforms do to the human body?
Conclusion:
Have students compile their data from each water sample on one graph at the front of the room so they can see
variation in sampling among groups. Encourage students to come up with errors in their experiment. Guide the
discussion in the interpretation of the graph looking for trends.
Extension(s):
The students are required to write a formal lab report compiling previous lessons testing for nitrates,
phosphates, water velocity, and aquatic invertebrate abundance in their water source. The students are
responsible to compiling an introduction, methods, results of each water quality test, discussion, and literature
cited. Their lab report will be reviewed by their peers and then submitted to the local land managers (in this case
Cowiche Canyon Conservancy).
Saftey: Lauryl tryptose broth should not be ingested. If spilled on hands simply wash with soap and water. Use
caution when handling glass test tubes. Instruction should be given on how to handle broken glass and spills.
For spills simply spray surface area with 10% bleach solution.
Supplements:
See attached “How to test fecal coliform”, “Fecal Coliform”, Stats Table, and “Rubric for Peer Review”.
References:
http://www.cowichecanyon.org/
http://www.state.ky.us/nrepc/water/wcpfcol.htm
http://www.oasisdesign.net/water/quality/coliform.htm
http://www.epa.gov/
http://www.labdepotinc.com/?gclid=CMeBjr3dh6UCFRhCgwodGhdRPg
Author: Melissa Reitz, Yakima WATERS Project, CWU, Fall 2010