Water Chemistry Project

In order to evaluate water

changes, we need access to reliable information on current and past conditions.

If changes are already taking place, comparing multiple sites at different areas can help us understand what is happening.

Some of the Factors that influence Water Quality are:

Source

Amount

Land use

Location

SourceFrom where?

underground

Or surface

How much?

Land Use

Location

Testing Water Quality

Water quality parametersoften tested are:

Dissolved oxygenWater temperaturepHphosphateNitrateTurbidityBOD

Water test kit

Dissolved Oxygen andPhotosynthesis/Respiration

6CO2 + 6H2O + light energy C6H12O6 + 6O2

photosynthesis

respiration

C6H12O6 + 6O2 6CO2 + 6H2O + heat energy

Dissolved Oxygen: • Oxygen can enter water directly from the

atmosphere and is produced during photosynthesis by plants and algae.

• It is removed from the water by plants and algae during respiration and by the decay of organic matter.

• Oxygen concentrations may be affected by water temperature, pressure, and salinity, as well as by the density of fish populations and by plant and algae photosynthesis, respiration, and decay.

Dissolved Oxygen:

• Cold water can dissolve more oxygen than warm water. For example, at 25˚ C, dissolved oxygen solubility is 8.3 mg/L, whereas at 4˚ C the solubility is 13.1 mg/L.

• As temperature goes up, water releases some of its oxygen into the air.

Water temperature

=

=

active

inactive

zz z

zzz

Temperature • Water temperatures have an effect on which

species are able to live in a particular area. • Temperatures may also affect animals’ feeding

and reproduction habits, as well as the water’s capacity to hold dissolved oxygen (cold water can dissolve more oxygen than warm water).

• Temperatures change naturally throughout the day and are also affected both by natural factors such as shade cover and snow melt and by human factors such as industrial discharge and surface runoff.

Dissolved oxygen and water temperature

dissolved oxygen and water temperature usually vary over a 24 hour cycle.

6 a.m. 6 a.m.midnight6 p.m.noon

0

15

10

5

Surface dissolved oxygen, mg/L

25

27

29

31

Surface water temperature, C

summer

Oxygen meter

pH = - log [ H+ ]

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

acid alkaline

pH

pH is a measure of acidity (hydrogen ion concentration) in water or soil.

neutral

pH

• Different species of aquatic life can tolerate different pH ranges; however most species prefer water that is relatively close to neutral pH, or 7.0.

• Extremes in pH can make water uninhabitable or may affect feeding and reproduction.

• pH levels may be affected by human factors such as mining drainage and industrial discharge.

Nitrite/Nitrate

feces

Bacterialdecomposition

NH4+ +1.5 O2 + Nitrosomonas NO2

- + 0.5 O2 + Nitrobacter

NO3- nitrite nitrate

Nutrients: • Nutrients such as nitrogen and phosphorous are

present in water naturally, from animal waste and decaying organic matter.

• These nutrients can sometimes build up in water both from natural sources and from human factors, including sewage, fertilizer runoff, detergents, and industrial discharge.

• This buildup of nutrients is called eutrophication. • High levels of nutrients may spur the growth of

algae and aquatic plants, which can lead to oxygen depletion due to respiration and decay by the plants or algae.

Phosphates

• The element phosphorus is necessary for plant and animal growth.

• 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 water weeds grow wildly, choke the waterway, and use up large amounts of oxygen. Many fish and aquatic organisms may die.

Phosphate levels

0.01-0.03 mg/L Amount of phosphate-phosphorus in most uncontaminated lakes

0.025 mg/L Accelerates the eutrophication process in lakes

0.1 mg/L Recommended maximum for rivers and streams

Turbidity Effects on Fish and Aquatic Life

• 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.

Biological Oxygen Demand (BOD)

• A measure of the oxygen used by microorganisms to decompose waste.

• If there is a large quantity of nutrients in the water supply, there will also be a lot of bacteria present working to decompose this waste.

• In this case, the demand for oxygen will be high (due to all the bacteria) so the BOD level will be high.

• When BOD levels are high, dissolved oxygen levels decrease because the oxygen that is available in the water is being consumed by the bacteria.

How water quality values are expressed as:

Parameter Value

Dissolved oxygen mg/L or ppm

Water temperature Degrees C or F

pH

Phosphate mg/L or ppm

Nitrate mg/L or ppm

Turbidity meters

BOD mg/L or ppm

Analysis of Test Results

• For each test performed research what an acceptable value would be for your water source.

• If any of your tests deviate from acceptable levels suggest reasons for this result and ways to correct them.

Determining the WQI

• http://www.indiana.edu/~bradwood/eagles/wqi.htm

• This site will help you calculate and overall WQI and interpret the results.