Water Testing
Alkalinity:
As shown in the diagram below, bicarbonate, and
sometimes carbonate, molecules act as hydrogen ion
absorbers. This causes the reactions of the bicarbonate
buffering system to shift left or right, but allows the
pH of the solution to remain relatively unchanged. If
hydrogen ions are added to the solution, they combine
with available bicarbonate or carbonate ions causing
the reactions to shift to the left and eventually
liberate carbon dioxide and water molecules. Addition
of carbonate to the solution causes the hydrogen ions
to be occupied and shifts the reaction to the left if
hydrogen ions are available. The addition of rainwater,
on the other hand, may shift the reactions to the
right. The normal pH of rainwater is about 5.6, a weak
carbonic acid solution resulting from the mixing of
water molecules with carbon dioxide molecules in the
atmosphere. Carbonic acid is weak, because some of the
carbonic acid molecules dissociate into hydrogen ions
and bicarbonate ions.
The alkalinity of surface water is primarily due to the
presence of hydroxide, OH–, carbonate, CO32–, and
bicarbonate, HCO3–, ions. These ions react with H+ ions
by means of the following chemical reactions:
OH– + H = H2O
CO3-2 + H = HCO3HCO3- + H = CO2 + H2O
Alkalinity is often related to hardness because the
main source of alkalinity is usually from carbonate
rocks (limestone), which are mostly CaCO3 (calcium
carbonate). So, generally, soft water is much more
susceptible to fluctuations in pH from acid rains or
acid contamination.
Alkalinity in streams is measured by its bicarbonate
content. The greater the alkalinity, the greater the
amount of bicarbonate, and thus the greater the
resistance to changes in pH. Alkalinity values of 20200 ppm are common in freshwater ecosystems. Alkalinity
levels below 10 ppm indicate poorly buffered streams,
which are the least capable of resisting changes in pH.
Streams with a pH of 6 or lower have very little
buffering capacity. The dominant form of inorganic
carbon in the bicarbonate buffering system is free
carbon dioxide, as shown in the diagram above.
The main sources of natural alkalinity are rocks, which
contain carbonate, bicarbonate, and hydroxide
compounds. Borates, silicates, and phosphates may also
contribute to alkalinity.
Limestone is rich in carbonates, so waters flowing
through limestone regions generally high alkalinity.
Conversely, granite does not have minerals that
contribute to alkalinity. Therefore, areas rich in
granite have low alkalinity and poor buffering
capacity.
Alkalinity:
Alkalinity is a measure of the buffering capacity of
water, or the capacity of bases to neutralize acids.
Measuring alkalinity is important in determining a
stream's ability to neutralize acidic pollution from
rainfall or wastewater. Alkalinity does not refer to
pH, but instead refers to the ability of water to
resist change in pH. The presence of buffering
materials help neutralize acids as they are added to
the water. These buffering materials are primarily the
bases bicarbonate (HCO3-), and carbonate (CO32-), and
occasionally hydroxide (OH-), borates, silicates,
phosphates, ammonium, sulfides, and organic ligands.
Waters with low alkalinity are very susceptible to
changes in pH. Waters with high alkalinity are able to
resist major shifts in pH. As increasing amounts of
acid are added to a water body, the pH of the water
decreases, and the buffering capacity of the water is
consumed. If natural buffering materials are present,
pH will drop slowly to around 6; then a rapid pH drop
occurs as the bicarbonate buffering capacity (CO32- and
HCO3-) is used up. At pH 5.5, only very weak buffering
ability remains, and the pH drops further with
additional acid. A solution having a pH below 4.5
contains no alkalinity, because there are no CO32- or
HCO3- ions left.
Alkalinity not only helps regulate the pH of a water
body, but also the metal content. Bicarbonate and
carbonate ions in water can remove toxic metals (such
as lead, arsenic, and cadmium) by precipitating the
metals out of solution.
Measurement of Alkalinity
Alkalinity is measured by titration. An acid of known
strength (the titrant) is added to a volume of a
treated sample of water. The volume of acid required to
bring the sample to a specific pH level reflects the
alkalinity of the sample. The pH end point is indicated
by a color change. Alkalinity is expressed in units of
milligrams per liter (mg/l) of CaCO3 (calcium
carbonate).
Factors Affecting Alkalinity
Geology and Soils
Carbonates are added to a water system if the water
passes through soil and rock that contain carbonate
minerals, such as calcite (CaCO3). Where limestone and
sedimentary rocks and carbonate-rich soils are
predominant, (such as the eastern part of the Boulder
Creek watershed) waters will often have high
alkalinity. Where igneous rocks (such as granite) and
carbonate-poor soils are predominant (such as the
western part of the Boulder Creek watershed) waters
will have low alkalinity.
Changes in pH
Because alkalinity and pH are so closely related,
changes in pH can also affect alkalinity, especially in
a poorly buffered stream. See the section on pH for
more information on factors affecting pH.
Sewage Outflow
The effluent from Wastewater Treatment Plants (WWTPs)
can add alkalinity to a stream. The wastewater from our
houses contains carbonate and bicarbonate from the
cleaning agents and food residue that we put down our
drains.
Because alkalinity varies greatly due to differences in
geology, there aren’t general standards for alkalinity.
Levels of 20-200 mg/L are
total alkalinity level of
the pH level in a stream.
that the system is poorly
susceptible to changes in
caused sources.
typical of fresh water. A
100-200 mg/L will stabilize
Levels below 10 mg/L indicate
buffered, and is very
pH from natural and human-
pH:
Living organisms, especially aquatic life, function
best in a pH range of 6.0 to 9.0. Acid shock may occur
in spring when acid snows melt, thunderstorms, natural
discharges of tannic waters, "acid rain", acidic
dryfall, and other discharges enter the stream.
One of the most significant environmental impacts of pH
is the affect that it has on the solubility and thus
the bioavailability of other substances. This process
is important in surface waters. Runoff from
agricultural, domestic, and industrial areas may
contain iron, lead, chromium, ammonia, mercury or other
elements. The pH of the water affects the toxicity of
these substances. As the pH falls (solution becomes
more acidic) many insoluble substances become more
soluble and thus available for absorption. For example,
4 mg/L of iron would not present a toxic effect at a pH
of 4.8. However, as little as 0.9 mg/L of iron at a pH
of 5.5 can cause fish to die.
Minimum Maximum
3.8
10.0
deformed
4.0
10.1
fish species
4.1
9.5
4.3
--4.5
9.0
normally
4.6
9.5
5.0
--5.0
9.0
--8.7
5.4
11.4
limits
6.0
7.2
1.0
--this pH
3.3
4.7
range
7.5
8.4
Effects
Fish eggs could be hatched, but
young were often produced
Limits for the most resistant
Range tolerated by trout
Carp died in five days
Trout eggs and larvae develop
Limits for perch
Limits for stickleback fish
Tolerable range for most fish
Upper limit for good fishing waters
Fish avoided waters beyond these
Optimum (best) range for fish eggs
Mosquito larvae were destroyed at
Mosquito larvae lived within this
Best range for the growth of algae
Nitrates:
People who use wells as a source of drinking water need
to monitor the level of nitrates in their well water.
If you drink water that is high in nitrates, it can
interfere with the ability of your red blood cells to
transport oxygen. Infants who drink water high in
nitrates may turn "bluish" and appear to have
difficulty in breathing since their bodies are not
receiving enough oxygen.
Unlike temperature and dissolved oxygen, the presence
of nitrates usually does not have a direct effect on
aquatic insects or fish. However, excess levels of
nitrates in water can create conditions that make it
difficult for aquatic insects or fish to survive.
Algae and other plants use nitrates as a source of
food. If algae have an unlimited source of nitrates,
their growth is unchecked.
Phosphates:
The element phosphorus is necessary for plant and
animal growth. Nearly all fertilizers contain
phosphates (chemical compounds containing the element,
phosphorous). When it rains, varying amounts of
phosphates wash from farm soils into nearby waterways.
Phosphates stimulate the growth of plankton and water
plants that provide food for fish. This may increase
the fish population and improve the waterway’s quality
of life. If too much phosphate is present, algae and
waterweeds grow wildly, choke the waterway, and use up
large amounts of oxygen. Many fish and aquatic
organisms may die.
The Phosphorus Cycle is said to be "imperfect" because
not all phosphates are recycled. Some simply drain off
into lakes and oceans and become lost in sediments.
Phosphate loss is not serious because new phosphates
continually enter the environment from other sources.
Phosphates come from fertilizers, pesticides, industry,
and cleaning compounds. Natural sources include
phosphate-containing rocks and solid or liquid wastes.
Phosphates enter waterways from human and animal wastes
(the human body releases about a pound of phosphorus
per year), phosphate-rich rocks, wastes from laundries,
cleaning and industrial processes, and farm
fertilizers. Phosphates also are used widely in power
plant boilers to prevent corrosion and the formation of
scale.
Effects on Humans
Phosphates won’t hurt people or animals unless they are
present in very high concentrations. Even then, they
will probably do little more than interfere with
digestion. It is doubtful that humans or animals will
encounter enough phosphate in natural waters to cause
any health problems.
Forms of Phosphate
Phosphates exist in three forms: orthophosphate,
metaphosphate (or polyphosphate) and organically bound
phosphate. Each compound contains phosphorus in a
different chemical formula. Ortho forms are produced by
natural processes and are found in wastewater. Poly
forms are used for treating boiler waters and in
detergents; they can change to the ortho form in water.
Organic phosphates are important in nature and also may
result from the breakdown of organic pesticides, which
contain phosphates.
Hach Company makes kits to test for the presence of
phosphate. You’ll probably use the cube kit that
measures the most common form—orthophosphate—or the
color disk that determines orthophosphate and
metaphosphate. A total phosphate kit measures all three
types of phosphates. Some values for total phosphatephosphorus are given below.
Table 7. Phosphate-phosphorus levels and effects
Total phosphate/
phosphorus*
Effects
0.01-0.03 mg/L
Amount of phosphatephosphorus in most
uncontaminated lakes
0.025 mg/L
Accelerates the
eutrophication process in
lakes
0.1 mg/L
Recommended maximum for
rivers and streams
DO and BOD
If water is too warm, there may not be enough oxygen in
it. When there are too many bacteria or aquatic animal
in the area, they may overpopulate, using DO in great
amounts.
Oxygen levels also can be reduced through over
fertilization of water plants by run-off from farm
fields containing phosphates and nitrates (the
ingredients in fertilizers). Under these conditions,
the numbers and size of water plants increase a great
deal. Then, if the weather becomes cloudy for several
days, respiring plants will use much of the available
DO. When these plants die, they become food for
bacteria, which in turn multiply and use large amounts
of oxygen.
How much DO an aquatic organism needs depends upon its
species, its physical state, water temperature,
pollutants present, and more. Consequently, it’s
impossible to accurately predict minimum DO levels for
specific fish and aquatic animals. For example, at 5 oC
(41 oF), trout use about 50-60 milligrams (mg) of
oxygen per hour; at 25 oC (77 oF), they may need five
or six times that amount. Fish are cold-blooded
animals,so they use more oxygen at higher temperatures
when their metabolic rate increases.
Numerous scientific studies suggest that 4-5 parts per
million (ppm) of DO is the minimum amount that will
support a large, diverse fish population. The DO level
in good fishing waters generally averages about 9.0
parts per million (ppm).
When DO levels drop below about 3.0 parts per million,
even the rough fish die. The table in this section
shows some representative comparisons.
Table 4. Effect of dissolved oxygen level on fish
Fish
Species
for:
Lowest DO level at which fish survive
24 hours (summer)
Northern Pike
6.0 mg/L
48 hours (winter)
3.1
Black Bass
5.5
4.7
Common Sunfish
4.2
1.4
Yellow Perch
Black Bullhead
4.2
4.7
3.3
1.1
Temperature
Variables that affect a waterway’s temperature
include:
1. The color of the water. Most heat warming surface
waters comes from the sun, so waterways with darkcolored water, or those with dark muddy bottoms, absorb
heat best.
2. The depth of the water. Deep waters usually are
colder than shallow waters simply because they require
more time to warm up.
3. The amount of shade received from shoreline
vegetation. Trees overhanging a lake shore or river
bank shade the water from sunlight. Some narrow creeks
and streams are almost completely covered with
overhanging vegetation during certain times of the
year. The shade prevents water temperatures from rising
too fast on bright sunny days.
4. The latitude of the waterway. Lakes and rivers in
cold climates are naturally colder than those in warm
climates.
5. The time of year. The temperature of waterways
varies with the seasons.
6. The temperature of the water supplying the
waterways: some lakes and rivers are fed by cold
mountain streams or underground springs. Others are
supplied by rain and/or surface run-off. The
temperature of the water flowing into a lake, river or
stream helps determine its temperature.
7. The volume of the water. the more water there is,
the longer it takes to heat up or cool down.
8. The temperature of effluents dumped into the
water. When people dump heated effluents into
waterways, the effluents raise the temperature of the
water.
Fish and most aquatic organisms are cold-blooded.
Consequently, their metabolism increases as the water
warms and decreases as it cools. Each species of
aquatic organism has its own optimum (best) water
temperature. If the water temperature shifts too far
from the optimum, the organism suffers. Cold-blooded
animals can’t survive temperatures below 0 oC (32 oF),
and only rough fish like carp can tolerate temperatures
much warmer than about 36 oC (97 oF).
Fish can regulate their environment somewhat by
swimming into water where temperatures are close to
their requirements. Fish usually are attracted to warm
water during the fall, winter and spring and to cool
water in the summer. Did you ever notice how fish swim
down to the cooler parts of the lake to escape the heat
of the noonday sun? Fish can sense very slight
temperature differences. When temperatures exceed what
they prefer by 1-3 oC, they move elsewhere!
Turbidity
Interference with sunlight penetration. Water plants
need light for photosynthesis. If suspended particles
block out light, photosynthesis—and the production of
oxygen for fish and aquatic life—will be reduced. If
light levels get too low, photosynthesis may stop
altogether and algae will die. It’s important to
realize conditions that reduce photosynthesis in plant
result in lower oxygen concentrations and large carbon
dioxide concentrations. Respiration is the opposite of
photosynthesis. (See Carbon Dioxide.
Large amounts of suspended matter may clog the gills of
fish and shellfish and kill them directly.
E Coli
Safe levels:
Australia: The recommended safe level for swimming and
water sports is 200 bacteria per 100ml.
Ohio – 235 bacteria per 100 ml
Suggests that total ammonia (NH3 + NH4) concentration
should be
between 160mg/L at pH of 6.0 and 0.06 mg/L at pH 9.0.
Assuming your measurements include both NH3 and NH4, it
seems that these readings are safe. If your testing
apparatus only measures NH3 however, the .2mg/L reading
is dangerously high. The site above should clarify this
matter.
As far as nitrates (NO3) are concerned, you have little
to worry
about. Dangerous levels of nitrates occur at
concentrations of 10mg/Lfor humans, which is many times
higher than your measurements.
In testing for e-coli, a safe range is 130 bacteria per
100
milliliters of water. Your current measurements are
well under this
level, but the site advises that a total of five tests
should be taken
over 30 days and the results averaged. I got this from
: