Transcript Water Quality Testing Lab

Water Quality Test Lab
Testing Dissolved Oxygen, pH, Nitrate,
Nitrite, Ammonia, and Coliform Bacteria
Purpose
• This lab will enhance the
understanding of typical
water quality parameters in
different types of water
samples.
• After the lab is complete you
should have developed a
better understanding of how
the given water quality
parameters apply to the real
world.
Background
• We will testing some of all of the following types of water samples:
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Tap Water (from school water fountain)
Filtered Tap water (equivalent to bottled water)
Groundwater from private water well
Pond/Stream water
Aquarium water
Unknown source
• The water quality parameters we will be evaluating include some of all
of the following:
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Hardness (dissolved solids)
Dissolved Oxygen
pH
Nitrate
Nitrite
Ammonia
Coliform Bacteria
Hypothesis
• With consideration to the source of each water
quality parameter, order each water sample type
from highest to lowest with a brief explanation
for your reasoning
– For instance: pH: 1) aquarium, 2) pond, 3) tap, etc. I
think aquarium water will have the highest pH
because…
Procedure
• There will be five groups and five stations
– 1) test the samples for hardness
– 2) test for Ammonia and pH
– 3) test for Nitrite and dissolved oxygen
– 4) test for Nitrate
– 5) test for coliform bacteria (initial
only)
Hardness
Background: Several ion species contribute to water hardness.
These include calcium, magnesium, iron, zinc, and manganese. Control of
water hardness will prevent scaling and clogging of water pipes.
• High Range (0-300 mg/L)
– Rinse beaker with sample water, then fill to the 5 mL mark and cover with
plastic wrap
– Add 5 drops of hardness buffer and mix solution by swirling in small circles
– Add 1 drop of Calmagite Indictor and mix. The solution should turn a redviolet color.
– Using titration syringe, push syringe plunger completely into syringe.
– Insert syringe tip into HI 3812-0 EDTA solution then pull plunger out until
lower edge of seal is on the 0 mL mark of the syringe.
– Insert filled syringe into sample beaker and slowly add titration solution one
drop at a time until solution becomes purple.
– After solution turns purple, mix for 15 seconds prior to adding an additional
drop. Continue adding drops, mixing 15 seconds after each drop is added
until solution turns blue.
– Read off the amount of titration solution remaining in the syringe and
multiply by 300 to obtain the hardness value in mg/L
Hardness continued
• Low Range (0.0-30.0 mg/L)
– If the result indicated by the high range test is less than 30
mg/L, the precision of the test can be improved by the following
the low range procedures
– Rinse a 50 mL beaker (or larger) with the water sample, then fill
to the 50 mL line.
– Place plastic wrap over beaker.
– Follow the same titration steps as indicated in the high range
procedures.
– Read off the amount of titration solution remaining in the
syringe and multiply by 30 to obtain the hardness value in mg/L
Ammonia and pH
Background: Fish release ammonia through their gills, urine and solid
waste. Uneaten food and decaying organic matter are also sources of
ammonia in water
• Rinse a beaker with sample water, then fill with 5 mL of the water
sample
• pH
– Insert a pH paper strip into water sample.
– Allow 5 seconds for color development.
– Compare paper color when viewed against a white background with
pH reference chart
• Ammonia
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Add 5 drops of Ammonia Test solution #1
Add 8 drops of Ammonia Test solution #2
Cover beaker with plastic wrap and shake vigorously for 5 seconds.
Allow 5 minutes for reaction to occur.
Observe the color when viewed against a white background and
compare with color reference chart
– Record value
Nitrite and Dissolved Oxygen
Background: Ammonia, Nitrite, and Nitrate are all related as
they are part of the Nitrogen Cycle. Ammonia will convert to
nitrite which can be toxic to fish (since it prevents normal
respiration), prior to converting to nitrate. However, this
process can take several weeks. Any value of nitrite (>0 mg/L)
can begin to harm fish.
• Nitrite
– Rinse clean beaker with sample water then fill beaker to the 5
mL mark
– Add 5 drops of Nitrite test solution
– Place plastic wrap over beaker and shake vigorously for 5
seconds
– Wait 5 minutes for color to develop.
– Observe color against white background and compare with
nitrite indicator chart
Nitrite and Dissolved Oxygen
continued
• Dissolved Oxygen
– Rinse clean beaker with sample water then fill to the 25
mL mark
– Take one dissolved oxygen ampoule and place in beaker
– Press against beaker side until the tip breaks and fills with
water
– Remove ampoule and rotate top to bottom to allow
remaining air bubble to thoroughly mix solution.
– Allow color development for 2 minutes.
– Under a bright light compare sample color to color
indicator spectrum
– Record results
Nitrate
Background: High nitrate levels indicate a high level of organic
compounds such as wastes. In aquatic environments, this indicates
poor water quality and contributes to the likelihood of fish disease.
Excessive nitrates can also stimulate algal blooms which will
subsequently deplete dissolved oxygen. Healthy values are considered
to be less than 40 mg/L.
• Rinse a cleaned beaker with sample water then fill beaker with
sample to the 5 mL mark
• Add 10 drops of Nitrate test solution #1
• Place plastic wrap over beaker and invert to mix.
• Vigorously shake Nitrate Solution #2 for at least 30 seconds
• Remove plastic wrap over beaker
• Add 10 drops of Nitrate Solution #2 then replace plastic wrap and
shake vigorously
• Allow 5 minutes for color to develop
• Against white background, compare sample beaker color to nitrate
reference chart
Coliform bacteria
Background: Fecal coliform presence is a reliable indicator of sewage of
fecal contamination. Although coliform bacteria are not themselves
pathogenic, they occur along with intestinal tract pathogens which are
dangerous to human health.
• Possible dechlorination needed:
– *samples containing chlorine will suppress growth of coliform bacteria so
a dechlorinating agent must be used as one of the initial steps. These
would be for the tap water and possibly filtered tap water samples.
– Open the top of the water sampling bag (which includes a dichlorination
tablet) and fill to the 100 mL line
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Pour the sample into a coliform bacteria vial to the 10 mL line
Replace lid
Stand vial upright with tablet on the bottom of the vial
Move vials into prep room where it must incubate for 48 hours
After 48 hours, if coliform organisms are present in the sample, gas
will be generated as a result of the bacteria metabolizing the nutrients
in the sample. The gas will be trapped in the gel substance and cause
the gel to rise in the vial. The pH indicator may also change color from
red to yellow to further indicate the presence of coliform bacteria.
Results
• 1) What was the hardness value received for each
sample type? What hardness levels do these
correspond to?
• 2) Do the values for Ammonia (Nitrogen) and pH
obtained for each water sample meet the limits
established for in the Denton Pecan Creek WWTP
Permit (describe for each or provide a chart)? What
does this indicate (good, bad, etc.)?
• 3) What do the values received for each sample for
nitrite and D.O. indicate for fish? For humans?
• 4) Assuming each water sample type is water for fish
habitat, do the nitrate levels for each sample type
indicate a healthy aquatic environment?
• 5) Did any of the samples indicate the presence of
coliform bacteria? If so, would this be fecal coliform or
possibly another type? Explain your response
Thinking it Through
• Which type of water would be worst for
human consumption; explain your
reasoning based on results, not just what
type of sample it is
• Which type of water would be worst for a
fish habitat; explain your reasoning
• Which type of water would be best for a
fish habitat; explain your reasoning