WATER CHEMISTRY Water Quality Testing

  

WATER CHEMISTRY

Water Quality Testing

Materials

Water samples

Green Standard LaMotte Water Monitoring Kit

Beakers

Thermometers

Transfer pipettes

Tests, Results and Interpretation

1. Water Appearance

• Collect a water sample in a clear, colorless, glass jar.
• Look at the sample against a white background.
• Record the appearance of water.

a. Green, Green-blue, Brown or Red: Indicates the growth of algae, which is caused by high levels of nutrient pollution.  Nutrient pollution can come from organic wastes, fertilizers or untreated sewage

b. Light to dark Brown: Indicates elevated levels of suspended sediments, giving the water a muddy or cloudy appearance.

c. Dark Red, Purple, Blue, Black: May indicate organic dye pollution from clothing manufacturers or textile mills

d. Orange-Red or Blue: May indicate the presence of copper, which can be both a pollutant and naturally occurring.  Copper is sometimes used a s a pesticide.  It can cause skin irritations and death of fish

e. Foam: Excessive foam is the result of soap and detergent pollution.

f. Multi-Colored (oily sheen): Indicates the presence of oil or gasoline floating on the water surface.

g. No unusual color: Not necessarily an indicator of clean water.  Many pesticides, herbicides, chemicals and other pollutants are colorless or produce no visible signs of contamination.

2. Water Odor

• Collect the water sample in a large mouthed container.
• Use your hand to wave the air above water sample toward you.
• Record the type and intensity (faint, distinct, or strong) of the water odor on the Data sheet.

a. Sulfur (rotten egg): May indicate organic pollution, such as domestic or industrial wastes

b. Musky: May indicate presence of sewage discharge, livestock waste, decaying algae, or decomposition of other organic material

c. Harsh: May indicate the presence of industrial or pesticide pollution

d. Chlorine: May indicate the presence of over-chlorinated effluent from a sewage treatment facility or a chemical industry

e. No unusual smell: Not necessarily an indicator of clean water.  Many pesticides and herbicides from agricultural and forestry run-off are colorless and odorless, as are many chemical discharged by industry.

3. Change in Temperature

Temperature is very important to water quality.  Temperature affects the amount of dissolved oxygen in the water, rate of photosynthesis by aquatic plants, and the sensitivity of organisms to toxic wastes.  Thermal pollution, the discharge of heated water from industrial operations, for example, can cause temperature changes that threaten the balance of aquatic systems.

• Select two sites where the physical conditions, current speed, amount of sunlight reaching the water and the depth of the stream are as similar as possible.  One site should be the sampling site and the second site should be approximately 1 kilometer upstream. 
• At each site, place the thermometer 4 inches below the surface for one minute.
• Remove the thermometer form the water.  Read the temperature and record the results as degrees Celsius. 
• Repeat the test with the second site as soon as possible.  The difference between the temperature upstream and the temperature at the sampling site is the change in temperature.

TEMPERATURE CHANGE (in ºC)	SCORE
0-2	4 (excellent)
3-5	3 (good)
6-10	2 (fair)
>10	1 (poor)

4. Turbidity

Turbidity is the measurement of the relative clarity of water.  Turbid water is caused by suspended and colloidal matter such as clay, silt, organic and inorganic matter, and microscopic organisms.  Turbidity should not be confused with color, since darkly colored water can still be clear and not turbid.  Turbid water may be the result of soil erosion, urban run-off, algal blooms, and bottom sediment disturbances. 

• Fill the turbidity tube to the line.
• Place the base of the tube on the outline on the Turbidity Chart.
• Look down through the sample water at the Secchi disk icon under the tube.
• Compare the appearance of the Secchi disk icon under the tube to the gray Secchi disks on the either side of the tube to determine the turbidity in Jackson Turbidity Units (JTU).

TURBIDITY (JTU)	SCORE
0	4 (excellent
> 0 to 40	3 (good)
>40 to 100	2 (fair)
>100	1 (poor)

5. Nitrate

Nitrogen is a nutrient that acts as a fertilizer for aquatic plants.  When nutrient levels are high, excessive plant and algae growth creates water quality problems.  Nitrogen enters the water from human and animal waste, decomposing organic matter, and run-off fertilizer from lawns and crops.  Nitrogen occurs in water as Nitrate, Nitrite and Ammonia.  Unpolluted waters usually have a nitrate level below 4 ppm.  Nitrate levels above 40 ppm are considered unsafe for drinking water. 

• Fill the test tube to the 5 mL line.
• Add one Nitrate #1 TesTab.
• Cap the tube and mix until the tablet has disintegrated.
• Add one Nitrate #2 TesTab.
• Cap the tube and mix until the tablet has disintegrated.
• Wait 5 minutes.
• Compare the color of the sample to the Nitrate Color Chart.
• Record the result as ppm Nitrate (If the reaction is yellow, record result as 0 ppm)

NITRATE (PPM)	SCORE
5	2 (fair)
20	1 (poor)
40	1 (poor)

6. Phosphate

Phosphate is a nutrient that acts as a fertilizer for aquatic plants.  When nutrient levels are high, excessive plant and algae growth creates water quality problems.  Phosphorous occurs in natural waters in the form of phosphate.  Over half of the phosphate in lakes, streams and rivers come from detergents.  Phosphate levels higher than 0.03 ppm contribute to increased plant growth.

• Fill the test tube to the 5 mL line.
• Add one Phosphorous TesTab.
• Cap the tube and mix until the tablet has disintegrated.
• Wait 5 minutes.
• Compare the color of the sample to the Phosphate Color Chart.
• Record result as ppm Phosphate.

PHOSPHATE (PPM)	SCORE
1	4 (excellent)
2	3 (good)
4	2 (fair)

7. Dissolved Oxygen

Aquatic animals need dissolved oxygen to live.  Fish, invertebrates, plants, and aerobic bacteria all require oxygen for respiration.  Oxygen can readily dissolve into the water from the atmosphere until the water is saturated.   Once dissolved in water, the oxygen diffuses very slowly and distribution depends on the movement of the aerated water.  Oxygen is also a by-product of photosynthesis.

Dissolved oxygen levels below 3 ppm are stressful to most aquatic organisms.  Dissolved oxygen levels below 2 or 1 ppm will not support fish.  Levels of 5 or 6 ppm are usually required for growth and activity.

Dissolved oxygen percent saturation is an important measurement of water quality.  Cold water can hold more dissolved oxygen that warm water.  High levels of bacteria from sewage pollution or large amounts of rotting plants can cause the percent saturation to decrease.  This can cause large fluctuations in dissolved oxygen levels throughout the day, which can affect the ability of plants and animals to thrive.

• Fill a small test tube to overflowing with sample water.
• Add two dissolved oxygen TesTabs to the test tube.
• Cap the tube.  Be sure no air bubbles are in the sample.
• Mix by inverting until the tablets have disintegrated (about 4 minutes).
• Wait 5 minutes.
• Compare the color of sample to the Dissolved Oxygen Color Chart.  Record the result as ppm dissolved oxygen.
• Determine the percent saturation from the chart given below.
• Locate the temperature of the water sample on the Percent Saturation chart.  Locate the Dissolved Oxygen result of the water sample at the top of the chart. 
• The Percent Saturation of the water sample is where the temperature row and the Dissolved Oxygen intersect.

     DISSOLVED OXYGEN

TEMPºC	0 ppm	4 ppm	8 ppm
2	0	29	58
4	0	31	61
6	0	32	64
8	0	34	68
10	0	35	71
12	0	37	74
14	0	39	78
16	0	41	81
18	0	42	84
20	0	44	88
22	0	46	92
24	0	48	95
26	0	49	99
28	0	51	102
30	0	53	106

Dissolved Oxygen (% saturation)	SCORE
91-110	4 (excellent)
71-90	3 (good)
51-70	2 (fair)
<50	1 (poor)

8. pH

The pH test is one of the most common analyses in water testing.  pH is a measurement of the activity of hydrogen ions in a water sample.  The pH scale ranges from 0 to 14.  Water samples with a pH below 7.0 are considered acidic; those above 7.0 are basic, with 7.0 considered neutral.  A pH range of 6.5 to 8.2 is optimal for most organisms.  Rapidly growing algae and vegetation remove carbon dioxide from the water during photosynthesis and this can result in a significant increase in pH.  Most natural waters have pH values from 5.0 to 8.5.  Sea water usually has a pH value close to 8.0

• Fill the test tube to the 10 mL line.
• Add one pH wide range TesTab.
• Cap the tube and mix until the tablet has disintegrated.
• Compare the color of the sample to the pH color chart.
• Record the result as pH.

pH	SCORE
4	1 (poor)
5	1 (poor)
6	3 (good)
7	4 (excellent)
8	3 (good)
9	1 (poor)
10	1 (poor)
11	1 (poor)

9. Coliform Bacteria

 Fecal coliform are naturally present in the human digestive tract but are rare or absent in polluted water.  Coliform bacteria should not be found in well water or other sources of drinking water.  Their presence in the water serves as a reliable indication of sewage or fecal contamination.  Although coliform bacteria themselves are not pathogenic, they occur with intestine al tract pathogens that are dangerous to human health.  This presence/absence total coliform test detects all coliform bacteria strains and may indicate fecal contamination.

Single Tube Test:

• Fill the tube to the 10 mL line.
• Replace cap.
• Stand the tube upright, with tablet flat on the bottom of the tube.
• Incubate the tube at room temperature for 48 hours.  Store out of direct sunlight.
• Compare the contents of the tube to the Coliform Bacteria Color Chart.

Coliform Reaction: The coliform tablet contains nutrients to support the growth of coliform bacteria, a gelling substance, and a pH indicator.  If coliform organisms are present, metabolism of nutrients by the bacteria produces gas, that will trapped in the gelling substance and cause the gel to rise in the tube.  The pH indicator may change form red to yellow as further evidence of coliform bacteria activity.

Negative Result:  Liquid above gel is clear, gel remains at bottom of tube, and indicator remains red or turns yellow with no gas bubbles.  This indicates less than 20 total coliform colonies per 100 mL of water when a single tube is used