Water Quality Testing

Many factors can affect the water quality of a river system or lake etc. Conditions can fluctuate periodically, so we must measure water quality periodically to look for trends. Water is determined to be safe for one use but may be unacceptable for another purpose. Water quality is bested tested using the Water Quality Index( WQI)

What Does the WQI Mean?

The Water Quality Index uses a scale from 0 to 100 to rate the quality of the water, with 100 being the highest possible score. Once the overall WQI score is known, it can be compared against the following scale to determine how healthy the water is on a given day.

WQI Quality Scale
91-100: / Excellent water quality
71-90: / Good water quality
51-70: / Medium or average water quality
26-50: / Fair water quality
0-25: / Poor water quality

Water supplies with ratings falling in the good or excellent range would able to support a high diversity of aquatic life. In addition, the water would also be suitable for all forms of recreation, including those involving direct contact with the water. Water supplies achieving only an average rating generally have less diversity of aquatic organisms and frequently have increased algae growth.

Water supplies falling into the fair range are only able to support a low diversity of aquatic life and are probably experiencing problems with pollution. Water supplies that fall into the poor category may only be able to support a limited number of aquatic life forms, and it is expected that these waters have abundant quality problems. A water supply with a poor quality rating would not normally be considered acceptable for activities involving direct contact with the water, such as swimming.

Measuring Water Quality Index

To determine the Water Quality Index 9 tests are often performed.They are:

1. Temperature

2. Turbidity

3. Ph

4. Disolved oxygen

5. Phosphate

6. Total Solids (salt)

7. Faecal Coliform

8. Nitrate

9. BOD (Biochemical Oxygen Demand)

At St Mary’s we have the resources to do 1, 2,3, 4, 5, 6 and 8

Please refer to the following book on Mr Newman’s desk especially chapters 3 and 4 to get detailed instructions on conducting Water Quality tests and analysing the results. Alternatively, refer to the following pages to get a summarised version of the book.

Calculating the Overall Water Quality Index

After the water quality tests are completed and the results recorded, you can calculate the Water Quality Index (WQI) for the section of the water supply you monitored.

To calculate the overall WQI, you must first compute what are known as Q-values for the results you obtained for each of the tests and record them on the results sheet.

  1. Locate the chart for the appropriate test parameter.
  2. Plot your Result.
  3. Determine your Q-value for the test from the plot point
  4. Repeat each of these steps to find the Q-value for each of the remaining tests results.
  5. Insert data in the Excel spread sheet
  6. Look at the graphs.

WQI Quality Scale
91-100: / Excellent water quality
71-90: / Good water quality
51-70: / Medium or average water quality
26-50: / Fair water quality
0-25: / Poor water quality

Water Quality Results Sheet

Name: ______

Date: ______

Time: ______

Location: ______

Water Quality Test / Measurement Units / Result / Q-Value
1 / 2 / 3 / AVG
Temperature / ºC / n/a
TemperatureRange / ºC Site 1 / site1 – site 2 =
ºC Site 2
Dissolved Oxygen / mg per litre
% saturation
ph / Ph units
Sodium Chloride (salt) / ppm
Turbidity / NTUs
Faecal Coliforms / CFU/100ml
Nitrate
Phosphate

1. Water Quality- Temperature
Method 1

  1. Hold the thermometer in the water for at least 1 minute.
  2. Read the temperature while the thermometer’s bulb is still immersed in the water.
  3. Record the result.

Method 2

The water temperature of a river is very important, as many of the physical, biological, and chemical characteristics of a river are directly affected by temperature. Most waterborne animal and plant life survives within a certain range of water temperatures, and few of them can tolerate extreme changes in this parameter. Using the same thermometer, the water temperature should be checked at the test site and at a similar site further upstream. Care should be taken when taking the temperature upstream to ensure that the amount of sunlight and the depth of the river are similar to the original test site

Determine the Q- Value

2. Water Quality- Ph levels

Equipment

  • Vial (container)
  • Ph Test strip

Method

  1. Fill a vial with sample water.
  2. Take one pH strip Do not touch the coloured squares on the end of the strip.
  3. Immerse the coloured squares on the pH strip into the sample water for a few minutes.
  1. Match the colourof the centre square to the number it best matches on the strip.
  1. Record

Determine the Q VAlue


-

3. Water Quality- Dissolved Oxygen

Equipment

  • 1x Hannah Dissolved Oxygen Test Kit

Method

A sample needs to be prepared at the site, you can not take a sample and do this test later.

1) Take the temperature of the water you are testing (that is in the river or lake or pond etc). Then rinse the large glass bottle 3 times with your water sample and fill it until it overflows. Insert stopper and ensure that a small part of the sample spills over.

2) Remove the stopper and add 5 drops of Manganous Sulphate Solution and 5 drops of Alkali-Azide Reagent.

3) Add some more sample of your water to fill the bottle completely. Carefully stopper the bottle again and ensure that a part of the sample spills over. This is to make sure that no air bubbles have been trapped inside, which would corrupt the reading.Invert several times the bottle. The sample becomes orange-yellow and a flocculent precipitate (cloudy) will form if oxygen is present. Let the sample stand and the flocculent precipitate will start to settle.

4) After approximately 2 minutes, when the upper half of the bottle becomes limpid (transparent), add 10 drops of Sulphuric Acid Solution.Again stopper the bottle and invert it until all particulate material is dissolved. The sample is readyfor measurement when it is yellow and completely limpid (transparent).

This next section can be done on site or at home or the lab.

5) Remove the cap from the plastic container with the white lid. Rinse the plastic vessel with the solution in the bottle. Fill to the 5 ml mark and replace the cap.

6) Add 1 drop of Starch Indicator through the cap port and mix by carefully swirling the container in tight circles. The solution will turn a violet to blue colour.

7) Push and twist pipet tip onto tapered end of syringe ensuring an air tight-fit. Take the titration syringe and push the plunger completely into the syringe. Insert tip into HI 3810-0 Titrant Solution and pull the plunger out until the lower edge of the plunger seal is on the 0 ml markof the syringe.

8) Place the syringe tip into the hole of the plastic container and slowly add the titration solution dropwise, swirling to mix after each drop. Continue adding titration solution until the solution in the plastic vessel changes from blue to colorless.Read off the milliliters of titration solution from the syringe scale and multiply by 10 to obtain mg/1 (ppm) oxygen.

9) If results are lower than 5 mg/l. Add an amount of unused sample in the glass bottle to the 10 mL mark of the plastic containerl.Proceed with the test as described before and multiply the values on the syringe scale by 5 to obtain mg/L oxygen in the sample.

10) Use the graph below to determine the % saturation by using a straight edge from the temperature to the mg/L scale.

Determine the Q- Value

4. Water Quality- Dissolved Solids (Sodium Chloride SALT)

Equipment

  1. vial (container)
  2. Sodium Chloride Test Strip

Method

  1. Fill a small vial with about 2.5 cm deep water.
  2. Remove ONE sodium chloride test strip from bottle and replace cap immeaditely
  3. Insert lower end of strip into water up to yellow strip. DO NOT submerge strip past the yellow strip.
  1. Wait until Yellow line turns dark (usually 3-4 minutes)

Reading / Sodium Chloride (salt)ppm (mg/L)
0.2 / 70
0.4 / 120
0.6 / 160
0.8 / 210
1.0 / 260
1.2 / 320
1.4 / 380
1.6 / 460
1.8 / 540
2.0 / 620
2.2 / 720
2.4 / 820
2.6 / 930
2.8 / 1050
3.0 / 1180
3.2 / 1310
3.4 / 1460
3.6 / 1610
3.8 / 1780
4.0 / 1950
4.2 / 2130
4.4 / 2330
4.6 / 2540
4.8 / 2760
5.0 / 3000
5.2 / 3250
5.4 / 3520
5.6 / 3810
5.8 / 4110
6.0 / 4450
6.2 / 4810
6.4 / 5190
6.6 / 5620
6.8 / 6080
7.0 / 6580
7.2 / 7140
  1. Determine levels of Sodium Chloride by noting where the top of the white peak along the brown strip finishes on the number scale on the strip.
  2. Read top of white peak to the nearest 0.2 division and compare result to the table.

Determine the Q-Value

5. Water Quality- Turbidity

Equipment

  • Turbidity Tube
  • Sample bottle or bucket

Method

To collect a sample from the shore, use a bucket or samplebottle e. Scoop from below the surface in theupstream direction. Be careful not to stir up the sedimentupstream of your sample.

e.

1. Remove large objects from the water sample.(Filter through nylon stocking if necessary.)

2. Stir the sample for 15seconds to suspend all materials.

3. Stand out of direct sunlight. If you cannot getto a shady place, use your body to cast ashadow on the tube.

4. Slowly pour a small amount of sample into thetube.

5. Look for target disk on the bottom of tube. Ifdisk is visible, add water until it just

disappears.

6. If target disk is not visible, pour water off alittle at a time until disk is just visible.

7. Read the NTUs on side of tube.

8. Record measurement on data sheet.

9. Dump contents of tube on ground.

10. Repeat steps 2 through 9 twice

11. Record the second and third measurement on the datasheet.

12. Add the readings, divide by 3, and

record.

13. Use turbidity value conversion chart to

determine the turbidity value from the averagemeasurement (step 12).

14. Record the turbidity value for your averagemeasurement on the data sheet.


Making your own Tube
The following table will enable anyone who can obtain some straight transparent tubing of about the right size, a laboratory measuring cylinder, or any other long transparent tube, to make an accurate turbidity tube.

Depth / Turbidity
mm / ITUs
26 / 400
35 / 300
43 / 200
57 / 150
75 / 100
95 / 80
116 / 60
142 / 50
165 / 40
218 / 30
314 / 20
413 / 15
544 / 10

An even simpler alternative to the tube is to make a small 'Secchi' disk, paint it bright white, with some bold black lines across it.
Fasten the disk to one end of a strong piece of dowel, to look like a wheel on an axle.
Graduate the dowel using the distances given in the table.
In a good strong light push the disk vertically down into the water until it just becomes impossible to distinguish the white and black stripes as you rotate it (i.e. the disk just vanishes).
Read off the turbidity from the scale marked on the dowel.

Determine the Q-Value

6. Water Quality- Faecal Coliform colonies

See a Biology Teacher to organise this test

  • Colonies are seen as blue dots on the filter paper.
  • In some instances faecal coliform colonies may appear pink or red rather than blue
  • Ignore any other colours such as cream or grey - they are notfaecal coliforms.
  • Ignore any very tiny (pin point or smaller) blue dots as these arenot viable organisms.
  • Use grid paper as an aid to counting thecolonies by counting along the grid lines.

Recording results

Faecal coliforms are reported as colony forming units per 100mL of water (CFU/100mL).

  • If 0.1mL of sample water was filtered, multiply the resulting number of faecalcoliform colonies by 1000.For example, 21 colonies on a 0.1mL plate: 21 x 1000 = 21 000 CFU/100mL.
  • If 1mL of sample water was filtered, multiply the resulting number of colonies by100. For example, 21 colonies on a 1mL plate: 21 x 100 = 2 100 CFU/100mL.
  • If 10mL of sample water was filtered, multiply the resulting number of colonies by 10.For example, 21 colonies on a 10mL plate: 21 x 10 = 210 CFU/100mL.
  • If 100mL of sample water was filtered, you do not need to multiply the resultingnumber of colonies at all.For example, 21 colonies on a 100mL plate: 21 CFU/100mL.
  • If more than one volume of sample water has been tested from the one sample bottle do not average the results. Select the petri dish which has between 20 and 80 faecalcoliform colonies present to determine the result.

7 Phosphate


kits can be bought at an Aquarium supply place

8 Nitrate

kits can be bought at Aquarium supply places

Air Quality-Dust Particle Monitoring

Some airborne particles are large enough to be seen with the naked eye or under low power magnification. These dust particles are transported by the wind, and are also affected by gravity. You will collect these windblown particles with the following experimental procedures:

Equipment

  • Adhesive Labels
  • Ruler
  • Small box
  • Magnifying Glass
  • Scissors

Method

  1. Cut off the top of a box.
  2. With the sticky side of the label facing out, tape one label on each side of the box. Tape one label on the inside floor of the box.
  1. Tape a label on the ceiling of a closet, the underside of a shelf, or the ceiling of your room.
  2. Place the box in a location that is exposed to the open air, sheltered from rain and at least 1 meter off the ground.
  3. After 3-7 days carefully remove all the labels and tape onto a piece of paper.
  4. Next to each label, describe where it waslocated on the box and the orientation of the box. (For example: front of box, facing south, parking lot or left side, facing east, four foot from school building.)
  5. Look at the six labels and record any differences. Take a closer look with the magnifying glass. noteany differences among the appearance of the six labels.
  6. Do the four sides of the box receive equal amounts of particles? Where are most of the large particles and why?
  7. Do you find any evidence of materials from plants or animals, or of material that appears man-made?
  8. Draw three - one centimeter squares on the label from the floor of the box.
  9. Using the magnifying glass, count the particles within each of the three squares. If there are too many to count, estimate. An average count of the three boxes is your value.
  10. Counts over 500 per square centimeter indicate high particle pollution, between 100 to 500, mild particle pollution and any less than 100, low particle pollution.

Air Quality- Pollutants Dissolved in Rainwater

A variety of chemicals from the air dissolve in falling rain water. Some of these chemicals cause the rain to become very acidic. Acids are substances which can cause the corrosion or breakdown of a variety of metals and minerals. The rain falling near large industrial areas has become very acidic in recent years. -

There are three major types of gas that cause acidic rain. All three involve the oxides (oxygen- Containing compounds of an element. Nitrogen oxides, carbon oxides, and sulfur oxides all contribute to the acidity of the rain water. All three are produced by high temperature industrial processes, and by internal combustion engines.

Equipment

  • Test tube
  • Syringe
  • Bromthymol blue reagent
  • Distilled water

Method

Bromthymol blue is a chemical which changes colour depending on the acidity of the water. Acidity is measured in terms of a ph scale A pH of 7 is neutral. pH values above 7 are alkaline, and numbers below 7 are acidic. Bromthymol blue is blue in colour when the pH is above 7, and green to yellow at pH's below 7.

  1. Fill the test tube ½ full of distilled water.
  2. Add 30 drops of bromthymol blue solution to the water.
  3. To test the air in your region, fill the syringe with air to the 30 cc line.
  4. Blow the air through the water.
  5. Refill the syringe with air and repeat this procedure 5 times (total volume of air, 150 cc). Note any colour change during this time in the solution.
  6. If the solution changes colour to green or remains blue, then the air in your region has fairly low concentrations of acidic gases. A colour change to yellow indicates a high concentration of acid producing gases and a potential health and property hazard.
  7. Rinse the tube and syringe for later experiments