346
Exercise 28
c. Concentrations of Na+, NH4 +, Cl-, P0 4 - 3 , and N0 3 - (see Exercise 7).
d. Concentration and percent saturation of dissolved pxygen (see Exercise 6).
e. Concentrations of dissolved organic matter (see Exercise 9).
f. Concentrations of suspended solids (see Exercise 7).
g. Numbers and biomass of benthic fauna (see Exercises 12 and 13).
h. Visually, quantities of periphyton and 'sewage fungus" [see Exercise 22, and
Hynes (1963, p. 96)].
i. Colonies (clones) of coliform bacteria.
The following is a simple procedure for determining the presence and abundance of
coliform bacteria in water samples. Certain coliform bacteria, which commonly live
in the guts of warm-blooded animals, incorporate dye such as eosin or fuchsin and
then deposit the dye on the surface of the colony, leaving a metallic sheen.
Escherichia coli is a common coliform bacterium of humans. Colonies of E. coli
grown on a medium containing such dye may be distinguished from the majority of
bacteria that either do not take up the dye or simply become colored, without
forming the sheen. Further tests may be done to show that the colonies thus isolated
are, in fact, E. coli [see Rodina (1972) and American Public Health Association
(1989)].
4. A sample of the bacteria can be collected conveniently with a special stainless steel
syringe equipped with a two-way valve and a plastic filter holder containing a sterile,
gridded, white filter (e.g., Millipore; see "Apparatus and Supplies").
a. Obtain 10ml of water from the stream with a graduated cylinder.
b. Remove the blue cap from the filter holder and place the plastic connector on the
tube into the opening.
c. Remove the red cap from the filter holder and gently insert the side opening of the
valve on the syringe into the opening.
d. Place the plastic tube into the water in the graduated cylinder. Holding the filter
disc parallel to the ground, draw the water through the filter and into the syringe.
If the plunger pulls all the way before all the water has been filtered, press the
plunger back. Water will be forced out the end of the valve but should not flow
back into the filter holder.
e. When all of the water is drawn out of the graduated cylinder, turn the syringe and
filter holder so that the water lies above the filter. Expel the excess water and draw
the rest of the water down from the tube and through the filter. Be careful not to
get air into the filter before all of the water is expelled or the filter will become
clogged. Be sure to hold the filter horizontally so that filtration is even.
f. Pump the syringe until the filter is dry.
g. Replace the plastic stoppers with the red plug on the grid side and the blue plug on
the pad side. This procedure reverses the color positions and indicates that the
filter has been used.
h. Collect three water samples at each station. Be sure to label each chamber after it is
charged with station number, time, date, and collector's name. Do not reuse the
plastic tube.
Coliform bacteria will be retained on the filter and then can be visualized
readily by allowing each microorganism to multiply into a colony (clone). Such
colonies are referred to commonly as colony-forming unit (CFU), and each
CFU is assumed to have arisen from a single microbial cell in the original
sample. There are difficulties with this assumption but counting the number
of clones is easy and gives a relative index of the amount of bacterial contamination of water.
Exercise 28
c. Concentrations of Na+, NH4 +, Cl-, P0 4 - 3 , and N0 3 - (see Exercise 7).
d. Concentration and percent saturation of dissolved pxygen (see Exercise 6).
e. Concentrations of dissolved organic matter (see Exercise 9).
f. Concentrations of suspended solids (see Exercise 7).
g. Numbers and biomass of benthic fauna (see Exercises 12 and 13).
h. Visually, quantities of periphyton and 'sewage fungus" [see Exercise 22, and
Hynes (1963, p. 96)].
i. Colonies (clones) of coliform bacteria.
The following is a simple procedure for determining the presence and abundance of
coliform bacteria in water samples. Certain coliform bacteria, which commonly live
in the guts of warm-blooded animals, incorporate dye such as eosin or fuchsin and
then deposit the dye on the surface of the colony, leaving a metallic sheen.
Escherichia coli is a common coliform bacterium of humans. Colonies of E. coli
grown on a medium containing such dye may be distinguished from the majority of
bacteria that either do not take up the dye or simply become colored, without
forming the sheen. Further tests may be done to show that the colonies thus isolated
are, in fact, E. coli [see Rodina (1972) and American Public Health Association
(1989)].
4. A sample of the bacteria can be collected conveniently with a special stainless steel
syringe equipped with a two-way valve and a plastic filter holder containing a sterile,
gridded, white filter (e.g., Millipore; see "Apparatus and Supplies").
a. Obtain 10ml of water from the stream with a graduated cylinder.
b. Remove the blue cap from the filter holder and place the plastic connector on the
tube into the opening.
c. Remove the red cap from the filter holder and gently insert the side opening of the
valve on the syringe into the opening.
d. Place the plastic tube into the water in the graduated cylinder. Holding the filter
disc parallel to the ground, draw the water through the filter and into the syringe.
If the plunger pulls all the way before all the water has been filtered, press the
plunger back. Water will be forced out the end of the valve but should not flow
back into the filter holder.
e. When all of the water is drawn out of the graduated cylinder, turn the syringe and
filter holder so that the water lies above the filter. Expel the excess water and draw
the rest of the water down from the tube and through the filter. Be careful not to
get air into the filter before all of the water is expelled or the filter will become
clogged. Be sure to hold the filter horizontally so that filtration is even.
f. Pump the syringe until the filter is dry.
g. Replace the plastic stoppers with the red plug on the grid side and the blue plug on
the pad side. This procedure reverses the color positions and indicates that the
filter has been used.
h. Collect three water samples at each station. Be sure to label each chamber after it is
charged with station number, time, date, and collector's name. Do not reuse the
plastic tube.
Coliform bacteria will be retained on the filter and then can be visualized
readily by allowing each microorganism to multiply into a colony (clone). Such
colonies are referred to commonly as colony-forming unit (CFU), and each
CFU is assumed to have arisen from a single microbial cell in the original
sample. There are difficulties with this assumption but counting the number
of clones is easy and gives a relative index of the amount of bacterial contamination of water.