Bellingen Riverwatch Online Water Quality Monitoring Manual
Part 2. Can be done at the river or at home / school

2.5. Turbidity test

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Equipment:

  • 500ml water sample

  • Latex gloves

  • Safety glasses

  • Turbidity tube

1. Assemble the turbidity tube by sliding the two pieces together.

2. Put your back to the sun with the tube should be in the shadow.. The test must be conducted in the shade of your body.

3. Shake the 600ml plastic water sample bottle to disperse any sediment that has settled before beginning this test.

4. Holding the tube above and below the join, pour a little bit of water into the tube. Holding the tube vertically, look down into the tube.

Important - When looking into the tube, the top of the turbidity tube should be at least 15cm from your eye for safety and quality assurance

You may need to wait for the water to stop swirling to see if lines can be observed clearly. If you can still see them clearly, continue pouring a little at a time.  

5. Stop pouring when the three distinct black lines at the bottom of the tube cannot be seen clearly. Ask another person to verify your result.

6. Measure the turbidity by recording the last marked point on the tube below the level of the water.

Important - Do not estimate between the lines!

7. If you can still see the lines when the water has reached the top of the tube, RECORD THE RESULT AS 7 NTUs (means the result was <10NTUs).

8. Record your result.

Pack Up

  1. Rinse the tube and sample bottles with tap or deoinised water.

  2. Leave to drain and dry completely (preferably overnight) and then place back in the kit in their correct location.

Maintenance

Every 12 months, wash in warm soapy water and apply petroleum jelly lightly to the join for ease of assembly.

  • Turbidity in water is caused by suspended and colloidal matter such as clay, silt, finely divided organic and inorganic matter, and plankton and other microscopic organisms. Turbidity is a measure of the clarity of a water body and is an optical measurement that compares the intensity of light scattered by a water sample with the intensity of light scattered by a standard reference suspension.

    It is commonly recorded in nephelometric turbidity units (NTUs).