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Water Monitoring Testing

What is Dissolved Oxygen?

Dissolved Oxygen (DO) is important to the health of aquatic ecosystems. All aquatic animals need oxygen to survive. Natural waters with consistently high dissolved oxygen are most likely health and stable environments capable of supporting a wide variety of aquatic organisms.

Depletions in dissolved oxygen can cause major shifts in the kinds of aquatic organisms found in water bodies. As dissolved oxygen levels in water drop below 5.0 mg/l, aquatic life is put under stress. The lower the concentration, the greater the stress. Oxygen levels that remain below 1-2 mg/l for a few hours can result in the death of aquatic life.

DO Test

What You'll Need:

  • Small test tube from your test kit.
  • Two Oxygen TesTabs® - foil pack from your test kit that says "DO".
  • A watch for timing.
  • Protective gloves.
  • Color chart from your test kit for comparing against your sample.

Dissolved Oxygen Test Procedure:

  1. Submerge the small test tube from your kit into the water sample. Then, carefully remove the tube from the water sample, keeping the tube full to the top.
  2. Take two Dissolved Oxygen TesTabs from the foil packs that say "DO" and drop them into the tube. Water will overflow when the tables are added.
  3. Screw the cap on the tube. More water will overflow as the cap is tightened. Make sure no bubbles are present in the sample.
  4. Mix by turning the tube over and over until the tables have disintegrated. This will take about 4 minutes.
  5. Wait 5 more minutes for the color to develop.
  6. Compare the color of the sample to the Dissolved Oxygen color chart from your kit. Record the result as ppm Dissolved Oxygen.
  7. The Dissolved Oxygen (DO) test results are measured in ppm (parts per million), which is also called milligrams per liter (mg/L). 1 ppm is one part per million. Record your results in your field data sheet as ppm Dissolved Oxygen.
Comparing sample to the Dissolved Oxygen color chart.
Comparing sample to the Dissolved Oxygen color chart.

Next Test - % Saturation »


This full-featured set of instructions took an extremely technical and difficult-to-understand set of instructions and broke them down into layman terms that school teachers were able to understand. As a result two foreign schools in Uzbekistan and Warsaw, Poland were able to participate in the World Water Monitoring Day event. These instructions also served as the replacement for the on-site training that some of the local teachers missed.

If you need help writing or editing instruction content, contact me today. I'm also really good at testing the accuracy of procedures. I will actually go through the process of whatever the instructions cover and ask questions if I come across something unclear or inaccurate. Then, I rewrite what's unclear or inaccurate. I also include applicable computer screen shots for software instructions and other illustrations to help the user better understand the task they are performing.