Water Testing Lab
Purpose: To determine the quality of a sample of water and compare it to other samples of water.
Background: You will be testing for the following indicators of water quality: fecal coliform bacteria, dissolved
oxygen levels, pH, iron, hardness, nitrates, phosphates, and copper. Depending on the levels you will be able to
determine how polluted a sample of water might be.
Procedures:
1.
2.
3.
4.
5.
When testing the samples of water for pH, iron, nitrates, phosphates, and copper, measure out 5 to 10 mL of
water into the vials according to the directions listed on the card at each station. Then add the appropriate Tes
Tab, shake to dissolve the tablet, and wait for the color to develop according to the time table on the card.
Compare the color of the water sample to the appropriate color chart and record the level indicated.
For hardness, measure out 50 mL of the water sample into the large vial and add hardness Tes Tabs one at a
time until the blue color develops. Record the number of tablets and multiply by 40 to get the results.
For the dissolved oxygen test, fill the glass vial with the water sample to the top, making sure that there are no
air bubbles and place the Tes Tab in. Shake and wait for any color to develop.
For the fecal coliform test, use the large glass vial with the agar at the bottom. Fill the sample to the indicated
line, but do not shake. This will need to be left for 48 hours to see if there is a change in color. When done,
give to your teacher for disposal.
Data: The data listed are for 5 different water samples – distilled, tap, spring water, lake water, fish tank water.
Distilled
water
Tap
water
Spring
Water
Lake
Water
Fish
tank
water
Fecal
Coliform
(yes/no)
No
pH
Copper
Iron
Nitrates
Phosphates Dissolved Hardness
Oxygen
7
0
0
0
0
1 ppm
0 ppm
No
7.5
0
0
0
0
4 ppm
80 ppm
No
7.5
0
0
0
0
1 ppm
280 ppm
Yes
8
0
0
5 ppm
2 ppm
8 ppm
240 ppm
Yes
6
0
0
40 ppm
4 ppm
7 ppm
280 ppm
Lab Analysis Directions
1.
2.
3.
4.
5.
6.
Title
Purpose
Hypothesis (predict which water sample would be most polluted)
Independent variable
Dependent variable
Control
7.
FOR THIS LAB ONLY, YOU MAY CUT AND PASTE IN THE DIRECTIONS AND THE DATA TABLE.
8.
Briefly describe each of the following water tests and how they indicate water quality. Be specific, don’t just
say they are bad or good, but what they actually tell you about what’s in the water.
a. pH
e. copper
b. iron
f. nitrates
c. phosphates
g. dissolved oxygen
d. hardness
h. fecal coliform bacteria
8. How would the presence of an oxygen demanding waste in the water affect the D.O. in the water? Give
an example of an oxygen demanding waste.
9. What is meant by the term “biological oxygen demand (B.O.D.)”? What is the relationship between B.O.D.
and D.O.? Give an example of a pollutant that would increase the B.O.D.
11. Which samples most closely resemble the control? Why do you think this is so? What are the
differences and why?
12. Why do you think the fish tank and lake samples were the only ones that tested positive for fecal
coliform bacteria?
13. Compare the fish tank and lake samples, why do you think the nitrates were so much higher in the fish
tank?
14. Sum up the results and state your conclusions based on your hypothesis.