Equipment:

60ml glass sample bottle
Latex gloves
Safety glasses

Important

Take the D.O. water sample from the bucket FIRST before the 500ml bottle sample, so there is less disturbance and oxygen getting into the water.

Collect the D.O. sample FIRST.

Try to test between 12noon and 2pm.

The recommended time for testing is between 10am and 2pm, and ideally, between 12noon and 2pm.

Collect from the same place each month.

Check your site guide sheet if you are unsure.

Collect the sample water from a flowing section of the water body in midstream (if possible). Do not collect sample water from backwater or stagnant pools.

Collect in flowing water in midstream (if possible).

1. Rinse collection bottle 3 times with the water to be tested.

2. Replace lid on sample bottle after rinsing.

3. Turn bottle on its side and lower into the water (lid closed).

4. Lower to half the depth of the stream.

5. Slowly remove lid and allow to fill with water.

6. Turn vertically up to completely fill and release all trapped air.

7. Recap bottle while underwater.

8. Remove from water.

9. Invert bottle to check that there are NO air bubbles.

If air bubbles are present, tip out water downstream of where you are collecting your sample and repeat steps 2 to 8.

The black lids have an inverted plastic cone inside which stops air bubbles being trapped within the water sample.

Dissolved oxygen (DO) is a measure of how much oxygen is dissolved in the water - the amount of oxygen available to living aquatic organisms. The amount of oxygen in the water regulates the distribution, activity, movement, and behaviour of all aquatic animals.
The amount of dissolved oxygen in water is dependent upon the water temperature; colder water can carry more dissolved oxygen that warmer water. When in equilibrium with the atmosphere, at this maximum concentration the water is said to be saturated or at 100% saturation of dissolved oxygen. DO is also affected by the presence of algae that can produce oxygen via photosynthesis during the day and consume oxygen via respiration at night. This is why it is important to always test at the same time of day.
DO analysis should be performed immediately and in situ. Therefore, this is test that should be performed on site where possible, however in some cases e. when raining or doing the test in a school room the sample can be fixed on site for further analysis at home or in the school room.