"The Effect of Detergents on the Amount of
Oxygen in Pond Water"
by
Allison Burton
West Lake Jr. High Science Fair
February 7, 2003
9th Grade Biology
Mrs. Ramos
Table of Contents
Introduction...................................................................................................................3
Background Research....................................................................................................4
I. Hypothesis..................................................................................................................6
II. Experimental Procedure............................................................................................6
III. Results and Analysis................................................................................................7
IV. Conclusion.............................................................................................................10
Bibliography.................................................................................................................11
Acknowledgements......................................................................................................12
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Introduction
The purpose of this experiment was to test the effect of a phosphate on the oxygen level in pond
water. The hypothesis is that the phosphate will have an effect on the level of oxygen in the pond
water. The pond water with ten drops of the phosphate mixture will have less dissolved oxygen
than the pond water with fifty drops of the phosphate mixture.
For this experiment, eighteen jars were filled with tap water and one milliliter of algae was added
to each. The jars were labeled so that three were the constant, three had ten drops of the
phosphate mixture, and so on until the last three jars had fifty drops of the phosphate solution.
The jars were placed under a growth light. The amount of dissolved oxygen was measured daily
using a dissolved oxygen meter and the results were observed.
When averaged, this experiment proved that the jars containing the constant did have more
oxygen than the jars with the detergents because the constants had an average reading of 9.30.
When all the amounts were averaged, the jars with only ten drops of the detergent solution
proved to have more oxygen than the jars with twenty, thirty, forty, and fifty drops. Their
average was 9.25. The jars with twenty drops of the detergent solution had the third greatest
amount of oxygen than the jars with thirty, forty, and fifty drops. Their average was 9.17. The
jars with fifty drops of the detergent solution had the fourth greatest amount of oxygen and had
more oxygen than the jars with thirty and forty drops. Their average was 9.15. The jars with
thirty drops of the detergent solution had a total average of 9.11 and the jars with forty drops of
the solution had an average of 9.13.
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Background Research
Detergents have taken a toll on the environment. Old-fashioned soaps without phosphates were
slow to break down in water and created clouds of suds around sewage plants, private wells, and
waterways. As more and more detergents seeped into the underground water table, people found
their tap water polluted. The solution was a new detergent containing phosphates. Phosphates
were quick to break down, however, they had an effect with their fertilizing properties (6).
There are three chief sources of water pollution: industrial wastes, sewage, and agricultural
chemicals and wastes. About 10 percent of the sewage in the United States goes untreated
directly into waterways or the ocean. "Water pollution upsets various processes that occur
naturally in water. These processes, which use the oxygen dissolved in water, help to make
wastes harmless. In a process called mineralization, aerobic bacteria break down organic wastes
into simpler substances. Some of these substances, such as phosphates and nitrates, serve as
nutrients for plants. “… if the water contains too much organic wastes, the bacteria will use up
most or all of the oxygen in it" (2).
Bodies of water contain a natural cycle of life processes. Bacteria of decay break down the body
wastes of fish which releases such nutrients as carbon dioxide, nitrate, and phosphate. Tiny water
plants called algae feed on these nutrients. The fish then eat the algae. In this cycle each member
supports the others. Fish obtain food and oxygen from the plants. The bacteria use organic
matter from the fish and oxygen in the plants. The plants feed on the products of decay. When
people pollute the water with excess nutrients, they upset the cycle (5).
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The alga soon becomes too nourished and grows faster than the fish can eat it. "Thick layers of
algae, called algal blooms, soon spread over the surface of the water." The lower layers of algal
blooms cannot get the sunlight that they need for photosynthesis so they soon die and decay.
When they die and decay large quantities of oxygen are used up in the water. When the supply of
oxygen becomes too small, fish, and other water animals die. As they decay, they continue to use
up more oxygen. Without the oxygen, the bacteria of decay can no longer function and
foul-smelling wastes accumulate (5).
Reductions in seawater oxygen levels through increased plant abundance, attributable to
increased nutrients, decaying plants, or reduced herbivores, could result in further species
declines of marine snails and other oxygen-consuming animals (4). In 1990, more than 6,000
Mediterranean dolphins died from a virus scientists think was caused by pollution. In 1988, a
pollution-related virus killed nearly half of a population of North Sea seals (1). In the European
Union alone, consumers use 4 million tons of washing powder a year, which is emptied into their
drains. Scientists are trying to come up with a detergent that does not use phosphates to try to
help and save plant and animal life. They are now trying to use zeolites, made from bauxite, the
aluminum ore, and polycarboxylates, or PCA`s, which are petrochemicals to try and make
detergents more environmentally friendly (3).
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I.
Hypothesis
The hypothesis of this research project is that phosphate will have an effect on the level of
oxygen in the pond water.
II.
Experimental Procedure
First, eighteen mayonnaise jars were obtained and each filled with 500 mL of water using the
graduated cylinder. A balance was then used to measure 1.38g of Sodium Phosphate Monobasic
(NaH2PO4. H2O) and it was dissolved in 100 mL of water by placing a rubber stopper over a
flask and shaking it. The mixture would serve as a detergent solution. The jars, without tops, and
the detergent solution were left sitting overnight. Then, twenty mL of algae was obtained and by
using a pipette, one mL of algae was placed in each jar. The first three jars were used as a control
and did not receive any detergent solution. The next three jars received ten drops of the detergent
solution using an eyedropper. The next three received twenty drops of the detergent solution.
This process continued for thirty, forty, and fifty drops. The jars were then placed under a growth
light for the algae to grow. The amount of dissolved oxygen was measured each day using a
dissolved oxygen meter. All data and observations were recorded in a logbook.
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III.
Results and Analysis
Eighteen mayonnaise jars were obtained and each filled with 500 mL of water. A balance was
then used to measure 1.38g of Sodium Phosphate Monobasic (NaH2PO4. H2O) and it was
dissolved in 100 mL of water by placing a rubber stopper over a flask and shaking it. The
mixture would serve as a detergent or phosphate solution. The jars, without tops, and the
detergent solution were left sitting overnight. Then, 20mL of algae was obtained and by using a
pipette, 1mL of algae was placed in each jar. The first three jars were used as a control and did
not receive any detergent solution. The next three jars received ten drops of the detergent
solution using an eyedropper. The next three received twenty drops of the detergent solution.
This process continued for thirty, forty, and fifty drops. The jars were then placed under a growth
light for the algae to grow. The amount of oxygen inside the jars was measured each day using a
dissolved oxygen meter. All data and observations were recorded and the oxygen levels from the
jars with ten, twenty, thirty, forty, and fifty drops were compared with the constant.
The hypothesis did not support the results. The detergent solution did have an affect on the pond
water; however, the jars with fifty drops of the solution did not have less oxygen. Other studies
have shown that the pond water with the most detergent solutions, have less oxygen.
The amount of dissolved oxygen was recorded each day for all of the jars. The readings were
then averaged for the control, ten drops, twenty drops, thirty drops, forty drops, and fifty drops.
The averages for each day are as follows:
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Table 1
Date Control 10 drops 20 drops 30 drops 40 drops 50 drops
1/25
8.54
8.60
8.6
8.58
8.43
8.64
1/26
8.79
8.76
8.88
8.87
8.67
8.69
1/27
8.73
8.95
9.00
8.92
8.86
8.59
1/28
8.35
8.44
8.70
8.14
8.14
8.57
1/29
7.78
7.57
7.19
6.87
7.19
7.52
1/30
8.31
8.17
8.17
8.02
7.71
7.73
1/31
8.52
8.79
8.50
8.34
8.11
8.19
2/01
9.80
10.04
9.90
10.06
9.97
9.77
2/02
9.90
10.07
10.16
10.12
10.15
9.94
2/03
9.02
9.09
8.92
8.90
8.86
8.85
2/04
8.75
8.81
8.59
8.67
8.73
8.95
2/05
9.12
9.02
9.02
9.02
8.93
8.93
2/06
9.57
9.04
8.78
9.02
9.08
8.86
2/07
8.89
8.89
8.97
8.84
8.95
8.96
2/08
9.04
9.07
8.89
8.82
8.69
8.87
2/10
9.86
9.63
9.54
9.66
9.87
9.90
2/11
10.29
10.05
9.76
9.72
10.01
10.14
2/12
10.43
10.29
10.44
10.07
10.49
10.67
2/13
11.00
10.75
10.62
10.91
10.94
10.88
2/14
11.19
10.93
10.74
10.65
10.70
10.76
When all of the readings for the control were averaged the total average reading was 9.30. The
jars with ten drops of the detergent solution total average reading were 9.25. The average total
reading for the jars with twenty drops was 9.17. The average total reading for the jars with thirty
drops was 9.11. The total average for the jars with forty drops was 9.13 and the total average for
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the jars with fifty drops of the detergent solution was 9.15.
The results do not give a clear conclusion. Some problems and errors were; the evaporation of
the middle jars, stabilization of the dissolved oxygen meter, and letting the dissolved oxygen
meter warm-up longer for some jars than others . This made the data vary everyday. The jars
could have been rotated so that the middle jars would not have evaporated as fast. The data could
have also been taken at the same time for all the jars instead of at different times. For a different
experiment, other materials, such as pond plants, could have been added to the water for
observations.
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IV.
Conclusions
When averaged, this experiment proved that the jars containing the constant did have more
oxygen than the jars with the detergents. However, the experiment did not prove the hypothesis
correct. When all the amounts were averaged, the jars with only ten drops of the detergent
solution proved to have more oxygen than the jars with twenty, thirty, forty, and fifty drops. The
jars with twenty drops of the detergent solution had the third greatest amount of oxygen and had
more oxygen than the jars with thirty, forty, and fifty drops. The jars with fifty drops of the
detergent solution had the fourth greatest amount of oxygen and had more oxygen than the jars
with thirty and forty drops.
The total average of oxygen for the jars containing the constant was 9.30. The total average for
the jars with ten drops was 9.25. The total average for the jars with twenty drops was 9.17. The
total average of oxygen for the jars with thirty drops of the detergent solution was 9.11. The total
average of oxygen for the jars with forty drops was 9.13 and the total average for the jars with
fifty drops was 9.15.
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Bibliography
1. Bigham, Kennetha J. Bigham. "Watercide: Are We Killing Our Water?" Current Health.
November 1994: pgs. 19-21.
2. Likens, Gene E. "Water Pollution." The World Book Encylcopedia. 1991. Volume 21. pgs.
137-138.
3. Luesby, Jenny. "Lather over Laundry." Financial Times. England: London, June 7, 1995.
CD-ROM. SIRS, 1995.
4. McClanahan, T. R. "Snails Pace." Sea Frontiers. August 1994: pg. 49.
5. McGowan, Alan. "Eutrophication." The World Book Encyclopedia. 1991, Volume 6. pg. 430.
6. Vecchione, Glen. 100 Amazing Make-It-Yourself Science Fair Projects. New York: Sterling
Publishing Co., Inc., 1994,
pg. 192.
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Acknowledgements
I like to give thanks to my parents, my sister, all my friends that helped me, and Mrs. Ramos for
all her awesomeness.
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